The Odonata of Canada and Alaska: Volume One, Part I: General, Part II: The Zygoptera–Damselflies 9781442654181

Table of contents :
Preface
Contents
Part I. General
A. External Structure
B. Life History and Habits
Part II. The Zygoptera of Canada and Alaska
The Zygoptera-Damselflies
Family Agriidae
Family Lestidae
Family Coenagriidae
Bibliography
Index

Citation preview

THE ODONATA OF CANADA AND ALASKA

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The O D O N A T A of Canada and Alaska By E D M U N D M. W A L K E R Professor Emeritus of Zoology, University of Toronto Honorary Curator of Zoology, Royal Ontario Museum of Zoology and Palaeontology

VOLUME ONE PART I: GENERAL PART II: THE ZYGOPTERA—DAMSELFUES

UNIVERSITY

OF TORONTO

PRESS:1953

Copyright, Canada, 1953, and printed in Canada by University of Toronto Press SCHOLARLY REPRINT SERIES

ISBN 0-8020-7074-4 LC A 54-4344

T O M Y WIFE, N O R M A WHOSE CO-OPERATION AND ENCOURAGEMENT HAVE MADE THIS TASK A JOY

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PREFACE VERY few faunistic studies of a major group of insects have as yet been made for the whole of Canada or even a single province. Dr. G. P. Holland's recent treatise on the Canadian Siphonaptera is a notable exception, and more works of this type are much needed for the exact determination of species and for definite information on their geographical distribution. Having collected and studied Odonata for more than fifty years in every province of Canada, we feel that it is now time to assemble the available knowledge of this order and make it more accessible to others. There is also need of more precise descriptions of the females of many of the species, particularly of the Zygoptera, and of the nymphs of the majority of this suborder. We have therefore decided to deal first with the order as a whole and next with the Zygoptera, leaving the Anisoptera for a future volume. The treatment is not confined to taxonomy and geographical distribution, but includes data on habitats, season of adult life, and brief notes on habits, when these are available. The material for this study was chiefly the collection of the Royal Ontario Museum of Zoology and Palaeontology, formerly belonging for the most part to the writer. Our collection is adequate in adult material, except in a few species, and in the nymphs of the Anisoptera, but is deficient in zygopterous nymphs, to which until recently we had given relatively little attention. Consequently it has been necessary to borrow material from others to fill some of the gaps, as indicated in the acknowledgments. The published sources of data are given in the Bibliography. As a general source book on Odonata Tillyard's The Biology of Dragonflies was indispensable and so was Calvert's classic of 1893 (Catalogue of the Odonata (Dragonflies) of the Vicinity of Philadelphia, with an Introduction to the Study of this Group of Insects). Needham's studies on venation were also invaluable, especially his early paper of 1903 ("A Genealogic Study of Dragonfly Wing Venation") and his latest paper of 1951 ("Prodrome for a Manual of the Dragonflies of North America, with Extended Comments on Wing Venation Systems"). The two papers by Kennedy on western Odonata (1915 and 1917) were particularly valuable, not only because of the careful descriptions and illustrations, but also for the detailed ecological observations, which have rarely been equalled by other writers on this continent. For information on many of the eastern Zygoptera Carman's two papers The Zygoptera of Illinois and The Odonata of Connecticut were frequently consulted. Several European publications were very helpful, namely, Wesenberg-Lund's Odonaten-Studien (1913-14) and his monumental Biologie der Susswasserinsekten (1943), Erich Schmidt's Ordnung Libellen vii

Viii

PREFACE

in Die Tierwelt Mitteleuropas, a model of careful treatment; and the detailed descriptions of nymphs by Ander, Gardner, and MacNeill. For distributional data from south of our border the numerous state lists and local lists, cited in the Bibliography, have been indispensable, and for data of this kind from Canada the writer's provincial and local lists have been the chief source, together with Whitehouse's and Buckell's papers on the British Columbian and Albertan faunas. Mrs. Gloyd's Synopsis of the Odonata of Alaska covers the needed references to that territory. Without the assistance that has been so freely given by my colleagues this study would have been very incomplete. First of all I wish to thank my good friend, Dr. F. A. Urquhart, Director of the Royal Ontario Museum of Zoology and Palaeontology and Curator of the Division of Insects, for placing at my disposal the facilities of the Museum, for making possible the publication of my study, and also for personal contributions which he has made to the collections on which the study is based. Next, I would express my gratitude to those from whom I have borrowed material, this having been seriously needed to fill the gaps in our collection of damselfly nymphs. I am indebted to Mrs. L. K. Gloyd for the loan of material from the collections of the Illinois State Natural History Survey, particularly material collected and reared by the late Dr. Philip Carman; to Professor J. G. Needham and Dr. Minter J. Westfall, Jr., for nymphs and reared specimens of Argfa and Enallagma; to Dr. J. Speed Rogers, Director of the Museum of Zoology, University of Michigan; Dr. T. H. Hubbell, Curator of Insects at the same Museum; and Dr. D. J. Borror, Ohio State University, for the loan of rare specimens. For the gift of specimens my thanks are due to many friends and colleagues, particularly to Drs. C. E. Atwood, E. L. Bousfield, J. R. Dymond, A. G. Huntsman, F. P. Ide, B. E. Montgomery, J. G. Oughton, D. S. Rawson, J. G. Rempel, W. E. Ricker, and Norma Ford Walker; Messrs. A. G. Edmund, C. E. Hope, T. B. Kurata, E. B. S. Logier, G. M. Neal, Eric Thorn, W. Y. Watson, H. C. White, F. C. Whitehouse, and G. B. Wiggins, and Mrs. W. DeBel; and to Mr. Paul D. Harwood, of Ashland, Ohio, for a number of Kodachrome slides of living Zygoptera, some of which were used for the drawings on Plate 7. Lastly I should like to express my appreciation of the remarkably efficient work of Miss Barbara Plewman of the University of Toronto Press in the final preparation of this study for publication. As to the illustrations: Plate 8 is from a photograph by Mr. Wm. Carrick; the figures of wings illustrating venation are also by Mr. Carrick, but all except fig. 1, Plate 2 and fig. 1, Plate 3 have been reinforced by drawing. The remaining figures are all from drawings by the author, except figs. 2 and 3 on Plate 3, which are copies from Needham and Tillyard. E.M.W.

CONTENTS PREFACE PART I. GENERAL A. EXTERNAL STRUCTURE—The Order Odonata External Features of the Adult Dragonfly The Head The Thorax Prothorax—Pterothorax: Legs, Wings, Venation (nymphal tracheae, veins of the adult wing, the discoidal cell and structures derived from it, special features of the Zygoptera) The Abdomen General features—Anal appendages—Male genitalia—Female genitalia External Features of the Full-grown Nymph General features—Nymphs of Anisoptera—Nymphs of Zygoptera

vii 1 3 5 5 7

B. LIFE HISTORY AND HABITS Habitats Ponds—Lakes—Streams—Saline habitats Habits of Adults The Teneral Flight Activity in sunshine—Crepuscular forms—Migration Food Reproductive Period Mating—Pruinosity—Oviposition (endophytic oviposition, exophytic oviposition) Developmental Stages The egg—Incubation period—Hatching or eclosion—First nymphal instar—Nymphal changes during growth—Number of nymphal instars—Length of nymphal life—Food and feeding habits of nymphs—Emergence of the adult Enemies of Dragonflies Enemies of adults—Enemies of nymphs Parasites Egg parasites—Parasitism by water-mites—Other parasites

32 32

PART II. THE ZYGOPTERA OF CANADA AND ALASKA Abbreviations Key to the Suborders of Odonata ix

17 23

35 35 36 38 39 45

52 55 59 61 61

x

CONTENTS

Key to the Families of Zygoptera Distribution of the Zygoptera of Canada and Alaska FAMILY AGRIIDAE

Key to the Genera Genus Agrion Fabricius Key to the species of Agrion Agrion maculatum Beauvois Agrion aequabile (Say) Agrion amatum (Hagen) Genus Hetaerina Hagen Hetaerina americana (Fabricius)

FAMILY LESTTDAE

Genus Lestes Leach Key to the Species of Lestes Lestes eurinus Say Lestes vigilax Hagen Lestes inequalis Walsh Lestes congener Hagen Lestes unguiculatus Hagen Lestes dryas Kirby Lestes disjunctus Selys L. disjunctus disjunctus Selys L. disjunctus australis Walker Lestes forcipatus Rambur Lestes rectangularis Say

FAMILY COENAGRIIDAE

Key to the Genera Genus Argia Rambur Key to the Species of Argia Argia moesta (Hagen) Argia apicalis (Say) Argia tlbialis (Rambur) Argia translata Hagen Argia sedula (Hagen) Argia violacea (Hagen) Aroia vivida Hagen Argia emma Kennedy Genus Chromagrion Needham Chromagrion conditum (Hagen) Genus Amphiagrion (Selys) Key to the Species of Amphiagrion Amphiagrion saucium (Burmeister) Amphiagrion abbreviatum (Selys) Genus Nehalennia Selys Key to the Species of Nehalennia Nehalennia Irene (Hagen)

62 62 65

67 67 68 68 72 75 76 77 80

81 83 87 89 92 93 96 100 104 105 109 111 113 117

117 121 123 128 132 136 140 143 145 149 153 157 157 160 161 161 165 167 167 168

CONTENTS

Nehalennia gracilis Morse Genus Coenagrion Kirby Key to the Species of Coenagrion Coenagrion resolutum (Hagen) Coenagrion interrogation (Hagen) Coenagrion angulatum Walker Genus Enallagma Selys Key to the Species of Enallagma Enallagma carunculatum Morse Enallagma civile (Hagen) Enallagma clausum Morse Enallagma boreale Selys Enallagma cyathigerum (Charpentier) Enallagma vernale Gloyd Enallagma hageni (Walsh) Enallagma ebrium (Hagen) Enallagma minusculum Morse Enallagma geminatum Kellicott Enallagma exsulans (Hagen) Enallagma antennatum (Say) Enallagma aspersum (Hagen) Enallagma vesperum Calvert Enallagma signatum (Hagen) Genus Ischnura Charpentier Key to the Species of Ischnura Ischnura posita (Hagen) Ischnura verticalis (Say) Ischnura perparva Selys Ischnura cervula Selys Ischnura damula Calvert Ischnura erratica Calvert Genus Anomalagrion Selys Anomalagrion hastatum (Say) Addenda

Xi

171 173 173 175 180 183 187 191 200 205 209 213 217 221 225 228 232 233 236 240 242 245 248 251 253 255 257 261 264 268 272 274 275 278

BIBLIOGRAPHY

279

INDEX

287

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PART I

GENERAL

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A. E X T E R N A L S T R U C T U R E THE ORDER ODONATA

THESE are the dragonflies and all species of the order are properly so called. There are, however, two suborders of Odonata of strikingly different appearance, namely, the Zygoptera and the Anisoptera. The Zygoptera are slender insects of delicate appearance and relatively feeble flight, while the Anisoptera are usually larger and more sturdily built, swift and bold of flight, with an appearance calculated to inspire fear in the minds of most people. The name damselfly has for many years been applied to the Zygoptera in America, and its use has spread so rapidly as to give it a place in the vocabulary of both the general entomologist and the limnologist. It has even been accepted by some leading British entomologists. As a result one frequently hears of "dragonflies and damselflies," occasionally with unfortunate results to the collector. On one occasion, for example, we received a collection of Odonata from a little-known region without a single specimen of Zygoptera. This was because we were known to be interested in dragonflies; damselflies were something else. The name damselfly was doubtless suggested by the French word demoiselle, but this name is applied to the entire Order Odonata, as is also the German name Wasserjungfer. It would thus appear that, if damselfly is to be retained, dragonfly will need to be restricted to the Anisoptera, or some other name must be found for the Anisoptera alone.* Dragonflies (pi. 1, fig. 1) are elongate insects of large or medium size, with a freely movable head, whose outer surface is largely occupied by the enormous compound eyes; with three closely placed ocelli, extremely short setaceous antennae, and biting mouth-parts. The prothorax is small, neck-like, and free; the mesothorax and metathorax are large and fused to form the pterothorax (synthorax); the legs are all crowded forward and adapted *Darning-needle is the most common of the vernacular names for dragonflies heard in Canada and is equally familiar in the United States. Mosquito-hawk and snake doctor we have also heard, the latter from boys in Pennsylvania; and there are various other names, such as snake feeder and horse stinger, with their associated superstitions, which have been handed on by generations of children. Although attempts have been made to give common names to genera and species of dragonflies with a view to popularizing the study of these insects, such names are not needed. When an insect becomes a notorious pest like the Japanese beetle or the European corn-borer, or when it is conspicuous enough to arouse the interest of the layman, as in the case of the monarch butterfly or the praying mantis, a common name arises naturally. But dragonflies can scarcely be regarded as pests and most of the species can be identified only by a "key," so that the scientific name must be learned first in any case. To the student, the generic names soon become the common names. He soon begins to speak of enallagmas, libellulas, and sympetrums and he does it as easily and naturally as the gardener discourses of primulas, petunias, and chrysanthemums. (For further discussion of this question see Williamson (1931).) 3

PLATE 1 FIG. 1. Aeshna constricta Say, $, a typical example of the Anisoptera. (ab 1, ab 2 . . . ab 10—abdominal segments; ac—anteclypeus; air—ante-alar carina or ridge; antantenna; bp—basal plate of ovipositor; c—"cercoid" or superior anal appendage; ex 1, ex 2, ex 3—coxae; em 2—mesepimeron, em 3—metepimeron; es 2—mesepisternum; es 3-metepisternum; fe-femur; fr-frons; hu-humeral suture; ieps 2-mesinfraepisternum, ieps 3-metinfraepisternum; int-intersegmental annulus or region; lea—lateral carina of abdomen; li—labium; lo—lateral ocellus; lr—labrum; Is 1, Is 2— first and second lateral sutures; md—mandible; oc—compound eye; pa—paraproct; pc— postclypeus; pr-prothorax; sp 2, sp 3-spiracles (mesostigma, metastigma); sty-stylus; ti—tibia; tr 2—middle trochanter; trc—transverse carina of abdomen; ts—tarsus) FIG. 2. Aeshna, anterior view of head, (mo—median ocellus; v—vertex. Other lettering as in fig. 1)

FIGS. 3-5. Cordulegaster maculatus Say: 3. left mandible; 4. left maxilla; 5. labium, ventral view, (cd—cardo; eh—end-hook; g—inner lobe (united galea and lacinia); inc—incisors; Ib—lateral lobe; m—mentum; mh—movable hook; mp—molar process; mxp-maxillary palp; pm-ligula; sm-submentum; sq-squame; stp-stipes) FIGS. 6 and 7. Agrion aequabile Say: 6. left view of head and thorax with middle leg and bases of wings; 7. anterior view of head. (Lettering as in figs. 1 and 2) FIGS. 8 and 9. Aeshna, fourth abdominal segment: 8. ventral view; 9. outline of crosssection, (dc—dorsal carina; lea—lateral carina; pea—posterior carina; st—sternum; tg— tergum; vc—ventral carina)

GENERAL—EXTERNAL STRUCTURE

5

for perching; there are two pairs of subequal, net-veined wings, which are shifted backward and held when at rest in the horizontal (Anisoptera) or vertical (Zygoptera) plane; each wing has a nodus (pi. 2, figs. 1, 4) and nearly always a pterostigma. The elongate abdomen is of ten segments, each having a very large tergum and a very narrow sternum; the terminalia consisting of a pair of unjointed superior appendages, and, in the male, single or paired inferior appendages; the male also has highly specialized accessory genitalia on the ventral side of the second and third abdominal segments; the female may or may not have an ovipositor. Metamorphosis is incomplete, the immature insect after eclosion being known as a larva or nymph; the nymph is shorter and more compactly built than the adult, with cryptic coloration, a relatively smaller head, prehensile labium, a flatter thorax, more widely separated and thickset legs, wing-buds that become inverted in the later stages, and an abdomen with three caudal lamellae (Zygoptera) or anal valves and rectal gills (Anisoptera). The nymph undergoes 8 to 15 moults before transforming into an adult. EXTERNAL FEATURES OF THE ADULT DRAGONFLY The Head (PI. 1, figs. 1-7) The head is wider than long, the huge compound eyes occupying the sides; hypognathous, the face vertical, projecting in front of the eyes; posterior surface concave for the reception of the slender neck and prothorax, and the venter occupied by the somewhat prominent mouth-parts.

6

THE ODONATA OF CANADA AND ALASKA

Above the posterior cavity is the occiput, which is extensive when the eyes are wide apart (Zygoptera) or reduced to a small triangle, when the eyes meet in the mid-dorsal line (most Anisoptera). In Anisoptera with more widely separated eyes, such as Gomphidae, the occiput is broader and shelflike, and is continuous in front with the vertex. This is the area that bears the three ocelli in a small triangle, the median ocellus in front. The size of the vertex varies with the distance between the eyes, being broadest in the Zygoptera, fairly broad and flat in the Gomphidae, and small, convex, and separated from the occiput in those groups in which the compound eyes meet. Immediately before the vertex and set widely apart, are the very short, setaceous antennae, composed usually of six or seven segments, although the number may be reduced to four or three (Gomphidae). In front of the antennae and vertex is the jrons, forming the shelf-like front margin of the dorsum and the uppermost sclerite of the face, the two surfaces, dorsal and anterior, often meeting at a sharp angle. The lower part of the face consists of the clypeus, which is divided transversely into the large postclypeus above, extending from eye to eye, and the much smaller and often differently coloured anteclypeus, to whose lower margin the labrum is articulated. The mouth-parts (figs. 2-5) are of the biting type, but differ rather strikingly from the basic or orthopteroid type, found in most mandibulate insects. The labrum (fig. 2) is a short, broad flap, separated from the anteclypeus by a transverse suture, and having a broadly arcuate front margin. The mandibles (fig. 3) are stout, wedge-shaped, and heavily sclerotized, the outer surface convexly curved, the inner surface more or less irregularly concave, with a number of strong, sharp teeth disposed in two groups, a proximal group of four raised on a Z-shaped ridge, the molar process, and a distal or apical group of three incisors. The maxillae (fig. 4) are much smaller and more slender than the mandibles. They are typical in their basal sclerites, cardo and stipes, but there is only one terminal lobe, which is generally considered to represent the fused galea and lacinia. Its mesal margin is produced into six long, curved, spine-like teeth. The maxillary palp is relatively short and composed of a single segment. The labium (fig. 5) is a large, scoop-shaped structure, consisting of (1) a short basal sclerite, the submentum, articulated with the head capsule; (2) the mentum, a still shorter segment, movably articulated with the submentum, and from which lateral sclerites, known as the squamae are more or less distinctly demarcated; (3) the lateral lobes, which are anatomically the labial palpi, two-segmented structures articulated with the squamae, the first segment greatly expanded and terminating in the endhook, and a much smaller second segment, the movable hook, which is absent in the Libellulidae and Corduliidae; and (4) the middle lobe or ligula, which is bilobed in the Zygoptera and usually entire in the Anisoptera.

GENERAL—EXTERNAL STRUCTURE

7

In feeding, the dragonfly holds the prey in the hollow of the labium probably with the maxillae, while it is being masticated by the mandibles. The labrum functions as an upper lip, as it does in other mandibulate insects. The Thorax (PL 1, figs. 1,6) The thorax is divided into a small, movable prothorax and a large, compact pterothorax, composed of the fused mesothorax and metathorax. Prothorax The prothorax is narrowest in front, where it is joined to the head by a very slender neck. The prothorax itself is neck-like in contrast to the large pterothorax behind it. Its dorsal sclerite, the pronotum, is collar-like and is the only part of the segment that is important taxonomically, the pleura and sterna being much reduced. The pronotum is divided by transverse grooves into three lobes, anterior, middle, and posterior. The middle lobe is the largest and folded downward on each side to meet the pleura. The anterior and posterior lobes are bent upward from the middle lobe. In pairing, the posterior lobe of the female pronotum in the Zygoptera is usually grasped by the inferior appendages of the male and hence shows many structural modifications correlated with the specific forms of the male appendages. Pterothorax The pterothorax (or synthorax) of Odonata is widely different from that of other insects. The pleura are greatly elongated dorsoventrally but, instead of sloping backward and downward, as in the orthopteroid insects, they slope backward and upward. This results in the backward displacement of the tergal region (meso- and metanotum), and the forward displacement, of the thoracic sterna, together with the legs. The npta and sterna are much reduced; the so-called thoracic dorsum and venter are formed mainly by the pleura, the dorsum from the mesepisterna and the venter chiefly from the metepimera, although there is a posterior area immediately anterior to the first abdominal sternum, known as the intersternum, which appears to represent a resclerotization of the expanded intersternal membrane.* This peculiar shifting of the pterothoracic pleura is correlated with the perching habits of dragonflies, adapting them particularly for perching in a vertical or oblique position, although they also rest in a horizontal position, and many of them, e.g. Gomphidae, habitually so. *Actually the line of fusion between the right and left mesepisterna is derived from the intersegmental membrane between pronotum and mesonotum, and the corresponding line between the fused metepimera from the intersegmental membrane between metasternum and first abdominal sternum, the posterior part of the latter forming the intersternum.

8

THE ODONATA OF CANADA AND ALASKA

Certain other details of structure and terms used in classification should be added to the above general description. The sides of the pterothorax are marked by the pleural and intersegmental sutures, the latter being usually obliterated except posteriorly toward the wing-bases. The sutures known to morphologists as the mesopleural, the intersegmental (between meso- and metathorax), and the metapleural are known to taxonomists as the humeral, first lateral, and second lateral sutures, respectively. From each of the two episterna a small sclerite is separated by a suture above the corresponding coxa, known as the cross-suture. These small sclerites are the infraepisterna, namely, the mesinfraepisternum and the metinfraepisternum (ieps 2 and 3). At the anterior end of the thoracic dorsum (mesepisterna) is a pair of small, transverse plates, known as the mesostigmal laminae (pi. 31, fig. 9) because each is connected in front with one of the mesostigmata or anterior spiracles, which lie in the intersegmental membrane, concealed by the posterior lobe of the pronotum. Their mesal ends are separated by the expanded anterior end of the median carina, known as the base, which is typically bifid, the two rami forming the posterior wall of a space that encloses the median pit. The anterior wall of this space is formed by a transverse ridge, the anterior carina, the lateral walls by similar ridges, the lateral carinae. The ridges together may be known as the frame* In the females of Zygoptera the mesostigmal laminae are part of the coupling mechanism used in pairing, being engaged by the inferior appendages of the male. They are thus subject to specific variation and, in certain genera, they provide reliable characters for separating nearly related species. The posterior spiracle or metastigma lies in the metepisternum, just above the cross-suture, near its junction with the first lateral suture. The median carina runs the entire length of the thoracic dorsum, joining at its posterior or dorsal end the ante-alar ridge, a sclerotized ridge that encloses the wing-bases on three sides, anteriorly and laterally. LEGS (pi. 1, figs. 1,7) The legs of dragonflies serve for support and orientation of the body but very little for walking. They possibly also function during flight as a net for trapping their prey, which consists of flying insects of various kinds. The forward position of the legs and the presence of spines or long, stiff setae on the femora and tibiae suggest this function, but it has not been proven. Ordinarily the legs are tightly flexed during flight. When feeding, dragonflies usually hang from a branch by their middle and hind legs, and use the front pair to hold the prey while it is being chewed by the mandibles. When the food is more finely divided this function is taken over by the maxillae. Although the legs are very variable in structural details, they are less so than in most insect orders, since they are not specialized for a variety of functions. The coxae are of moderate size, subvertical in position, set very *This terminology is based on that of Kennedy (1902), but a few changes were found necessary for descriptive purposes.

GENERAL—EXTERNAL STRUCTURE

9

close together, and have the form of an inverted and truncated cone. The trochanters are slender, curved upward, and divided by a transverse groove, so as to appear two-segmented. The femora and the tibiae are elongated and together form the arches that raise the body above its support. The femora are moderately slender, somewhat compressed, and are armed with two or more rows of stiff setae, spines, or tubercles. The two principal series arise from the flexor surface, anteriorly and posteriorly. They vary greatly in length, often forming in the Zygoptera a graded series, the shortest setae at the proximal end. The tibiae are more slender than the femora and less compressed. They are generally slightly longer or about the same length, but in the Gomphidae the hind tibiae are much shorter than the hind femora, a peculiarity that is doubtless correlated with the habit, in this family, of resting on the bare ground. The tibiae are armed with two rows of spines or stiff setae on the flexor surfaces, often in a graded series, the longest at the proximal end. The tarsi are three-segmented, the first segment shortest, the third longest. The third segment terminates in a pair of tarsal claws, each usually bearing on the underside a distinct tooth. Only the vestige of a terminal pad or plantula is present. The double rows of spines borne by the tibiae are continued on the underside of the tarsal segments, or the latter may be covered with hairs. All of the leg segments are subject to great variation in their armature, but it would be beyond the scope of this study to consider these variations. WINGS (pi. 2, figs. 1,4) The two pairs of wings are always functional in the Odonata and are approximately equal in length and similar, though not identical, in form. In the Zygoptera (fig. 4) they are closely similar, the wings of both pairs being narrowed toward the base and usually petiolate or stalked, i.e. there is a proximally narrowed portion and a distally expanded part, like a paddle, except that the expansion is only on the posterior side. In the Anisoptera (fig. 1), on the other hand, the hind wings are much broader at base than the front wings, there being a more or less distinct anal margin, which either meets the hind margin of the wing at a distinct angle, the anal angle (males of most of the families), or passes into the hind margin in a broad curve (females of all the groups and males of Libellulidae). In all Anisoptera there is an opaque membrane bordering the anal margin of the hind wings, known as the membranule. The wings arise from the sides of the terga of the pterothorax and, when expanded, lie in a plane at a distinct angle with the longitudinal axis of the body. In this position the downward beat of the wings is actually downward and forward. When at rest the wings of Odonata are held either horizontally (Anisoptera) or in the vertical plane above the body (most Zygoptera and in Anisoptera just after the first expansion of the wings following emergence). Some Zygoptera such as Lestes, Chromagrion, and Ischnura cervula, rest

PLATE 2 FIG. 1. Cordulegaster maculatus, $, wings. (A—anal vein; Ax, A2> A3—branches of A; Ac—anal crossing; al—anal loop; anx—antenodal cross-veins; ar—arculus; br—bridge; C—costal vein; Cu—cubital vein; M—median vein; M x , M2, . . . M4—branches of M; n—nodus; o—oblique vein; pnx—postnodal cross-veins; pt—pterostigma; R—radial vein; Rs—radial sector; s—subtriangle; Sc—subcostal PLATE 2 vein; sn—subnodus; spt—supratriangle; t—triangle) FIG. 2. Tracheation of wing-bud of young Gomphus nymph (after Needham). (C—costal trachea; Sc—subcostal trachea; R—radial trachea; Rs—radial sector; M—median trachea; Cu—cubital trachea; A—anal trachea) FIG. 3. Wing-buds of an older nymph, apical parts omitted, showing relation of tracheae to principal longitudinal veins (after Tillyard). (mspl—median supplement. Other lettering as in fig. 1) FIG. 4. Wings of Argia apicalis, illustrating venation of the Zygoptera. (q—quadrangle. Other lettering as in fig. 1)

GENERAL—EXTERNAL STRUCTURE

11

with the wings partly spread, whereas many Libellulidae, resting on a rush or herb, bend the wings downward so that the tips are below the level of the body. The wings of dragonflies are transparent even when heavily pigmented, being devoid of scales or hairs. In the majority of species they are clear or only faintly tinted, except at the pterostigmata ("wing spots") and along the veins. Nearly all dragonflies have a pterostigma on each wing. It is primarily a single wing cell in the costal space near the apex, generally larger and often wider than the neighbouring cells, and differing also in the heavy pigmentation which makes it more or less opaque, though it is often pale in reflected light. Occasionally the pterostigma is subdivided by a secondary reticulum, as in the females of Agrion. (See Plate 3.) VENATION

The wing venation provides the most reliable characters for distinguishing the major groups of Odonata, down to the genera. These characters are stable and clear-cut and are the only satisfactory ones in the study of fossil dragonflies. Hence it is chiefly on the venation that we depend for a knowledge of the interrelationships of dragonflies. For the separation of species other characters are more important, as will be shown later. For our purpose a brief sketch of the subject of venation will be sufficient. For a more thorough study the reader is referred to Needham (1903, 1951), Tillyard (1917), and Munz (1919). The so-called veins are of two kinds, longitudinal and cross-veins. The longitudinal veins are cuticular structures, which first appear at an early stage in the growth of the larva or nymph, generally along the course of the tracheae of the developing wings. The cross-veins are likewise cuticular structures, but appear only in the last nymphal instar and have no relation to the tracheae. They are much more variable and less constant than the longitudinal veins but there are certain cross-veins that have taken on important mechanical functions and have become well-established structures.

12

THE ODONATA OF CANADA AND ALASKA

The main longitudinal veins are those which are typical of all orders of insects: the costa or costal vein (C), subcosta or subcostal vein (Sc), radius or radial vein (R), media or median vein (M), cubitus or cubital vein (Cu), and anal vein (A). Some of the longitudinal veins are unbranched, others have primary branches, formed along the course of the tracheae and there may also be secondary branches formed by a series of cross-veins, which have become shifted into alignment and have acquired the appearance of a typical longitudinal vein. The primary branches are numbered from before backward by placing a small numeral after the letter or symbol for the vein. Thus the four branches of the median vein are MI, M2, M3, and M4. If MI appears to be branched again, as is sometimes the case, the posterior branch is a secondary one and is known as Mi a , In the case of the radius there are typically five branches in generalized insects, and at the first dichotomy the anterior branch gives rise only to RI, while the posterior branch is the common trunk of the remaining branches and is known as the radial sector (Rs). In the Odonata Rs has no main primary branches, although it sometimes appears to be bifurcated, owing to the development of an anterior secondary branch. In this case the two branches are designated Rst and Rs2. Two other venational terms may be mentioned here: supplement and bridge. Where two primary veins or branches are widely divergent, additional support is sometimes given to the intervening space by the development of secondary veins of considerable size, which may or may not appear to have any direct connection with one of the primary veins. These are known as supplements. Examples are the radial and median supplements in the wings of many Libellulidae and many Aeshnidae. Supplements may also appear occasionally in relatively narrow spaces, e.g. the "mid-rib" of the anal loop in Libellulidae. A bridge is a supplement that continues the course of a vein backwards, in such a way as to add to its original length as a primary vein. Nymphal tracheae. Before considering the venation further it is desirable to examine the nymphal tracheae along which the longitudinal veins are formed. On Plate 2, fig. 2, which represents an early stage of a wing-bud, the tracheae are all separate branches of the thoracic trunk from which they arise. They are six in number and receive the same names as those already given for the six main longitudinal veins in the adult wing. The costal trachea is the only one that has no definite relation to the vein of like name or any of the veins. The subcosta is primarily two-branched, but Sci is abortive and the subcostal vein is formed along 802. The radius is twobranched, the anterior branch being RI and the posterior branch the radial sector, Rs. The latter is peculiar in that it crosses a part of the media. The media has four branches, the fourth leaving the main trunk first, then the third, while the remaining stem, Mi-2, finally bifurcates into MI and M2. It is the basal parts of these two tracheae, or their common stem, that are crossed by Rs.

GENERAL—EXTERNAL STRUCTURE

13

Behind the media is the cubitus, which has two branches, GUI and Cu2. Lastly is the anal trachea, which is relatively short and typically curves backward and divides into three widely spread branches, AI, A2, and A3. In later instars, with the contraction of the wing-bases, the tracheae become crowded at their bases and the resulting effect on the basal trunks of the veins is to cause fusion between the main trunks of the radial and median veins. These and various other unions and fusions, which can be seen at this stage, serve to explain the venation of the adult as described further. Veins of the adult wing (pi. 2, fig. 1). The costa (C) occupies the anterior margin of the wing from base to apex. It is not a genuine "vein," not being formed along any trachea of the developing wing of the nymph, but is a mere thickening of the anterior margin of the wing. Immediately behind the costa is the subcosta (Sc), an unbranched vein,* which follows a course parallel to C for a varying distance from the base, usually nearly halfway toward the apex in the Anisoptera, but often not nearly so far in the Zygoptera. Here it terminates abruptly in the nodus (n), which is a crossvein thickened by fusion with the distal end of Sc and united with C in a joint-like structure. The radius is proximally fused with the media (R + M) but, at a point not far from the base, and proximal to the nodus, R and M separate, the base of M appearing like an oblique cross-vein, which is joined behind by a true cross-vein, the two together forming the arculus (ar). The arculus forms the outer boundary of a clear space, the median space, whose other boundaries are R -f- M in front and the cubitus (Cu) behind. The cubitus runs out a little beyond the arculus, then bends sharply backward, forming the proximal side of the triangle, an important Anisopteran character, which will be considered later. At the posterior angle of the triangle the cubital vein divides into GUI and Cu2. These pass outward and curve backward to the hind margin of the wing, the course of GUI being usually a long curve, whereas that of Cu2 is somewhat sinuate. The anal vein runs straight out from the wing-base, joining the cubitus at or close to the point of bifurcation of Cu. Its terminal branch, AI, is fused for a limited distance with Cu2, forming a short vein that runs straight back and then divides again into its two components. Cu2 swings outward, thus making its first bend, while AI in the hind wing bends inward and, bridging the gap with cross-veins, joins A2, thus enclosing an area that is known as the anal loop (see below). A3 runs straight back to the wing margin, forming in the hind wing the distal side of the anal triangle, where this is present. The further course of the longitudinal veins and their branches is best understood by comparing the adult wing with a late nymphal wing. •Strictly speaking Sc is a branched vein, since the cross-veins between C and Sc, known as the antenodals, develop along a series of small branches of the subcostal trachea.

14

THE ODONATA OF CANADA AND ALASKA

The radial vein, after separation of the median at the arculus, continues a course parallel to the subcostal and costal veins as far as the nodus, where it divides into HI and Rs. RI continues the course of R, parallel to C, to the apex of the wing. (The pterostigma occupies a portion of the space between C and RI.) The extreme base of Rs, as it leaves the nodus, is a short, oblique vein called the subnodus. But at this point we must leave the course of the radial sector and turn to the median vein, since Rs, as can be seen in the nymphal wing, crosses a part of the median vein. It has already been noted that the arculus consists of the basal part of the median vein and a cross-vein, which joins it from behind. From the distal side two veins arise close together, or sometimes united for a short distance. These veins, known as the sectors of the arculus, are actually formed by the bifurcation of the media, as can be seen in the nymphal wing (pi. 2, fig. 3). The anterior branch divides into Mi-8, while the posterior branch, M4, passes obliquely to the hind margin of the wing. From the anterior branch, which follows a close parallel to the veins in front of it, M3 first separates and pursues a course to the hind margin more or less parallel and close to that of M4. Mi-2 is left to continue its former course, dividing, in the Anisoptera, into MI and M2 at the point where it is joined by the subnodus. M! continues the course parallel to the wing margin, while M2 usually runs more obliquely across the wing. An extremely short part of the course of M2, from its base, is shared by Rs, which thus leaves it as the oblique vein (o), Rs having then crossed from the anterior to the posterior side of M2. The oblique vein has the appearance of a cross-vein, but the longitudinal vein, which it joins behind, is really its continuation distal to the point of union. This part of Rs, which terminates a little behind the apex of the wing, is usually simple but sometimes apparently forked. When this is the case, one of the branches, generally the anterior, is a secondary structure made up of a series of cross-veins that have come into alignment. What appears to be the proximal part of Rs is really another secondary vein, formed in the same way. It is known as the bridge (br). In the Zygoptera the bridge is presently only in the Lestidae, in which Rs is fused with M2 for some distance, leaving it via an oblique vein, and the bridge extends from the latter back to near the separation of M3 from Mi-2. In the Coenagriidae there is no bridge nor oblique vein and M3 leaves M^ far distant of the nodus. The discoidal cell and structures derived from it. In the space between M and Cu there is an area which, in its primitive state, is a quadrilateral bounded by two thickened cross-veins, one of which is the lower part of the arculus, the other a similar cross-vein from M to the bifurcation of Cu into GUI and Cu2. This space, known as the discoidal cell, probably at one time contained other cross-veins, these being numerous in primitive dragonflies. But only one of these persisted in the Anisoptera, and this one acquired an oblique position as one of the results of a tendency of the wings of Anisoptera, particularly the hind wings, to expand analward.

GENERAL—EXTERNAL STRUCTURE

15

Tillyard (1917) gives a series of diagrams showing the evolution of the discoidal cell, in the Anisoptera, into the triangle and the supratriangle, these being separated by the oblique cross-vein, which has become still more oblique until, in the most specialized forms, it comes into alignment with Cu and then appears to be a part of that vein. Meanwhile the posterior boundary of the discoidal cell, distal to the attachment of the cross-vein, becomes bent backward to form the proximal side of the triangle, while the cross-vein forming the distal side of the original discoidal cell is now much longer and more oblique and forms the distal side of the triangle. The two cross-veins in the more specialized Anisoptera meet one another at an angle, thus completing the triangle. The space between the triangle and M is more or less narrowly triangular and is known as the supratriangle. In many Anisoptera a part of the cubital space adjoining the triangle is separated by a cross-vein as a more or less triangular area known as the subtriangle or internal triangle. In its more primitive form it is trapezoidal rather than triangular (Gomphidae), but in the majority of modern Anisoptera it is definitely triangular. Both triangle and subtriangle may be divided by cross-veins into two or three cells, or even more. In the Libellulidae the subtriangle of the fore wings becomes highly specialized and constantly divided into three cells, while in the hind wings it is usually undivided. The proximal cubito-anal cross-vein, in contrast to the other cross-veins in this space, is a constant character of the entire Order Odonata and, in fact, is no ordinary cross-vein at all. Because of the part it plays in the course of the anal trachea it is known as the anal crossing (Ac). The course of the anal trachea is very different from that of the anal vein, as described above. During the development of the wing it is swung forward until the basal part of its trunk is crowded against the cubital trachea. Distally it remains free and turns back by way of the anal crossing to its original level, where it typically divides into its three branches, AI, A2, and A3. Since the anal vein in the course of its ontogeny does not deviate from the straight course seen in the adult wing, nor does the fossil record give any evidence of a different course, we believe that this view, so ably defended by Needham, (1951) is sound, although it was opposed by Tillyard (1917). Mention has been made of the anal loop in dealing with the course of the branches of the cubital and anal veins in the hind wings of the Anisoptera. The anal loop is a closed area of wing cells that becomes of increasing importance with the expansion of the anal area in groups that have specialized in this direction. In its most primitive form the anal loop is short and broad and not as clearly defined as in some of the more specialized groups, such as the Libellulidae, in which the hind wings reach their greatest breadth and the anal loop its greatest length. Here it is a long, narrow, curved area, shaped somewhat like a bent human leg and foot, and consisting of two regular rows of cells separated by a supplement known as the midrib. The anal loop probably serves to give support to the expanding area of wing membrane in the anal region.

PLATE 3 3 PLATE

FIG. 1. Agrion aequabile, base of hind wing. (q—quadrangle. Other lettering as in Plate 2, fig. 1) FIGS. 2-4. Pterostigrnata of Agrion: 2. A. amatum; 3. A. aequabile; 4. A. maculatum.

GENERAL—EXTERNAL STRUCTURE

17

Special features of the Zygoptera. In the Zygoptera there is no triangle and the primitive discoidal cell persists in a more or less modified form and is known as the quadrangle or quadrilateral. In the Agriidae it is a long, narrow rectangle with the original cross-veins retained, whereas in the Lestidae, Coenagriidae, and other specialized groups the cross-veins have disappeared, the distal side has become more and more oblique, and the costal side shorter, with increasing specialization. These changes are associated in most of the Zygoptera with the narrowing of the wing-bases, the tendency in this suborder being the opposite of that which is found in the Anisoptera. The two branches of Cu, arising at the posterior angle of the quadrilateral, usually run side by side in a straight and almost longitudinal course, often separated for the greater part of their length by a single row of cells. GUI usually keeps a straight course farther than Cu2, which often breaks up soon into a zigzag row of cell walls. The reduction of the base of the wings brings about the disappearance of the branches of the anal vein, the trunk of which, except in the Agriidae, remains as the marginal vein of the petiole. Another peculiarity of the Zygoptera is that the trachea Rs in the nymphal wing fails to cross Mi-2, being replaced beyond the crossing by a branch of the media. For this reason Tillyard (1917) changed the name of Rs in the adult wing to median sector (Ms). In this view he has not been generally followed. There is a decided tendency in the Zygoptera for the cross-veins to become arranged in parallel lines across the wing. Generally speaking this tendency is greatest anteriorly, beginning as an alignment between the veins of the costal space and the next space beyond (Sc or RI) and decreasing toward the hind margin. It is obviously an arrangement that gives strength to the cross-veins. In the more primitive types of venation, in which crossveins are numerous, e.g. the Agriidae, there is comparatively little indication of this pattern but, in the Coenagriidae, in which the cross-veins are relatively few, they often form lines extending across seven or eight spaces or, in certain situations, across the entire wing. Such rectangular cells have been derived from hexagonal cells (Tillyard, 1917). The Abdomen

General Features (pi. 1) The abdomen of the adult dragonfly is always more or less elongate, as compared with most other insects, although it varies considerably in relative length. It is usually a little longer than the hind wings, sometimes consider-

18

THE ODONATA OF CANADA AND ALASKA

ably longer. It is composed of ten distinct segments, which increase in length up to segment 3, then remain nearly equal to the end of segment 6, decreasing thereafter until the end. In many dragonflies, including all the Zygoptera, the abdomen is subcylindrical, but in others, such as the Libellulidae and some Corduliidae, it is more or less depressed. The exoskeleton of each segment consists of two sclerites, tergum and sternum (often inaccurately called tergite and sternite). The tergum constitutes by far the greater part of the segment wall, in fact all but a midventral groove, in which lies the narrow sternum. This is, in fact, usually scarcely noticed, owing to the overlapping of the tergal margins. The sternum is connected with the tergum on each side by a very narrow pleural membrane, in which the spiracles open not far from the front margin. Along each tergal margin is a slight longitudinal ridge, known as the ventral carina and, in the mid-dorsal line of Libellulidae and Aeshnidae, there is a distinct dorsal carina. There is also, in all Odonata, a transverse ridge at each end of the tergum, the anterior and posterior transverse carinae. The former is inconspicuous and is not usually referred to by taxonomists, but the posterior carina is a distinct ridge bearing a row of small tubercles or denticles. It marks the end of the segment, and the space between it and the anterior carina of the next segment is considered to be an intersegmental area or "suture." It is often distinctively coloured or marked. In those groups with a cylindrical abdomen the tergum of a typical or unspecialized segment, such as segment 4, 5, or 6, is like a short tube, slit along the midventral line and slightly gaping. The gap is filled by the extremely narrow sternum and pleural membranes. Such are the middle segments in the Zygoptera, and the Gomphidae and Cordulegastridae of the Anisoptera. In the Aeshnidae, Libellulidae, and Corduliidae the generalized segments are transversely arched or tectate above but flattened beneath, and the tergum, even in these groups, makes up most of the segment wall, being sharply bent under along the angle where the dorsal or dorsolateral passes into the ventral wall. Along this angle is another ridge, known as the supplementary lateral carina or simply the lateral carina. A supplementary transverse carina is also found in the Aeshnidae, Libellulidae, and a few other forms. It is usually present on some of the anterior segments only, and its position is somewhat in front of the middle of the segment, often near the base. The first and second segments and the last three or four differ from the middle segments in having relatively large sternal areas. That of segment 2 and the anterior end of 3 are occupied by the secondary genitalia, which will be considered later. The sterna of segments 8 and 9 in the female are involved in the formation of the ovipositor, when it exists, and even when it is absent the sternum of 8 is widened distally and more or less modified in front of the genital opening at the end of the segment in the formation of the vulvar lamina.

GENERAL—EXTERNAL STRUCTURE

19

On the sternum of segment 9 in the male is the genital aperture, flanked by a pair of small flaps, the genital valves, which are vestigial coxopodites and are homologous with the outer valves of the ovipositor in the female.

Anal Appendages In the males of all Odonata there is a pair of movable, unsegmented appendages, situated dorsolaterally, immediately behind the tergum of segment 10. These are variously known as cercoids, cerci, or superior anal appendages but, since their morphological nature is unsettled, we prefer the last term, abbreviating it to superior appendages. In the Anisoptera there is a single median inferior appendage, projecting backward just above the anus and below the superior pair. It serves with the latter to grasp the head, or the prothorax of the female, or both, during copulation, or when the pair is flying in tandem. In the males of Zygoptera there is a pair of inferior appendages that takes the place of the single appendage of the Anisoptera, but it is not homologous with the latter but with the divided sternum of the eleventh segment (paraprocts). In the mating of Anisoptera the head is held between the superior and inferior appendages, the former usually pressing on the rear of the head, the latter on the occiput. In the Zygoptera it is the posterior lobe of the pronotum that is held between the two pairs of appendages, the inferior pair in front and the superior pair behind, engaging also the mesostigmal laminae. In the females of both suborders representatives of the male superior appendages are found. In the Anisoptera they are often comparable in length with those of the male, but are simple, styliform, or foliaceous structures having no obvious function. In the Zygoptera they are almost vestigial. The homologues of the male inferior appendages in this group look like ordinary paraprocts, as they do in the males of Anisoptera, but here again is a subject on which opinion is divided. The anal appendages of the males of both suborders are adapted to engage the parts of the female that are held in mating, and the engagement of parts is so accurate that attempts to mate between different species are generally unsuccessful, although occasionally a male and a female of different, though related, species are found in tandem. As might therefore be expected, the anal appendages present excellent specific characters, in some genera much better than in others. Species of a genus that differ little from one another in appearance are likely to show conspicuous differences in the anal appendages or the genitalia, while those that are easily recognizable in flight are relatively uniform in the appendages. When the appendages are similar the genitalia may differ greatly. Successful mating between different species seldom takes place and hybridization is therefore rare.

Male Genitalia (pi. 4) Although the genital aperture of the male occupies the usual position in insects, namely, the sternum of segment 9, the external genitalia are situ-

PLATE 4 FIGS. 1-3. Cordulegaster maculatus, genitalia: 1. penis; 2. ventral view of genitalia with penis removed; 3. ventrolateral view with penis in situ, (ha—anterior hamule; hp— posterior hamule; Ig—ligula; p—penis; pv—penis vesicle) FIG. 4, Argia moesta, genitalia, part of left side of anterior lamina removed. (anl— anterior lamina; f—fenestra; sp—spiracle. Other lettering as before) FIG. 5. Lestes forcipatus, apical part of penis, (gp—glans penis) FIG. 6. Enallagma boreale, penis, (a) median view of apical part, (b) lateral view of entire organ. (Lettering as before) FIG. 7. E. signatum, apical part of penis. FIGS. 8-10. Coenagnon, penis, (a) median view, (b) lateral view: 8. C. resolution; 9. C. interrogatum; 10. C. angulatum.

GENERAL—EXTERNAL STRUCTURE

21

ated on the venter of segment 2 and the anterior part of segment 3. This position is correlated with the habit, peculiar to Odonata, of forming a loop in pairing, the head or thorax of the female being held by the anal appendages of the male, while the abdomen of the female is bent upward under the body of the male, so that the ovipositor or vulvar lamina can be engaged by the male accessory genitalia. It will be convenient first to describe the general structure of the genitalia as found in the Anisoptera. For a detailed treatment of this subject see Schmidt (1915). The sternal region of segment 2 is deeply grooved, forming a cavity known as the genital fossa, and within this cavity are found the penis and accessory genitalia: the sheath of the penis or ligula, the hamuli, and the anterior lamina. The penis is attached to the front margin of the sternum of segment 3. It is a tubular structure consisting of three segments, the first of which is the vesicle, a broad saccular structure lying at the posterior end of the enital fossa. Its ventral wall is convex and mostly sclerotized, while its orsal wall is flattened and membranous. The vesicle is narrowed in front, where it is joined to the second segment of the penis. This is cylindrical and proximally bent dorsad and then cephalad. Its wall is strongly sclerotized and bears a dorsal spur by which it is easily identified. The convex dorsal surface also bears a slit-like opening, the orifice, from which a duct passes into the vesicle and widens into a sac for the storage of sperm capsules. Another duct leads from the orifice into the third segment and opens on the glans, which is the largely membranous terminal part of the segment. The glans is ventrally sclerotized but bears a great variety of flexible outgrowths, which may take the form of long filamentous processes. The penis in the resting position is folded upon itself so that its convex surface (segment 2), bearing the orifice, faces forward and the third segment downward and backward, resting in a depression on the front of the vesicle. The wall of the genital fossa, the fenestra, is partly membranous and partly sclerotized on each side to form the framework from which arises the penis sheath and the hamuli. The two lateral sclerites of the framework terminate anteriorly in a plate known as the anterior lamina which, in the

f

22

THE ODONATA OF CANADA AND ALASKA

Aeshnidae and other more primitive groups, is bifid and may bear a pair of spines. In the Corduliidae and the Libellulidae it is much reduced and is entire or only slightly bilobed. The posterior lamina is a smaller, bar-like structure, which completes the framework at the posterior end. The penis sheath is a transverse arch, arising from both sides of the framework, the median part often expanded into a sort of hood, and serving to support the penis. The hamuli are used in copulation for engaging the female genitalia. The anterior hamuli are best developed in the Aeshnidae, in which they are the more important pair and offer many useful systematic characters. The posterior hamuli are present in all Odonata and, in the Libellulidae, exhibit a great variety of forms and characters of systematic value. Besides the genitalia there are other structures, closely associated with these organs, which are secondary sexual characters, being peculiar to the males. These are the auricles and the genital lobes. The auricles are somewhat ear-like outgrowths from the sides of segment 2, with the distal margin bent downward and often denticulated. They are found only in the Anisoptera and almost exclusively in males that have angulated hind wings. Genital lobes are found only in the Libellulidae and Corduliidae. They are extensions of the posterolateral angles of the tergum of segment 2. Although they occur normally only in the male, vestigial lobes are sometimes found in the females of certain Corduliidae. The male genitalia of the Zygoptera are similar to those of the Anisoptera and are formed in the same segments but differ in some important respects. The penis is not connected with the vesicle nor with any part of segment 3. It is attached to the fenestra and its lumen opens into the haemocoele. It consists of a long, unsegmented stalk, strongly curved at base, and the terminal glans, which is supported proximally by a sclerotized area; the distal and lateral parts are membranous and usually prolonged into one or more pairs of lobes or filamentous appendages. It is not known how the penis functions in conveying the sperm capsules to the female genital aperture, but Kennedy (1917, p. 296) remarks of Ischnura cervula that "The heavy penis seems to be the sole clasping organ as the anterior Tiamules' fold upward during copulation (figs. 90 and 91) when the penis is exserted." (The "hamules" referred to here are the two divisions of the anterior lamina.) Female Genitalia The female genital aperture occupies the usual position at the end of the eighth sternum. In the Zygoptera and some of the Anisoptera there is a wellformed ovipositor, homologous with that of the Orthoptera, Hemiptera, and other insect orders. It consists of three pairs of processes, the anterior, posterior, and lateral gonapophyses. The anterior gonapophyses arise from the posterior margin of the eighth abdominal sternum, close to the middle line. At the base of each is a transverse sclerite, known as the basal plate. The posterior gonapophyses arise from the ninth sternum, immediately be-

GENERAL—EXTERNAL STRUCTURE

23

hind the anterior pair, with which they are serially homologous. The members of both pairs are curved, firmly sclerotized processes, tapering to a sharp point, with a short, serrated edge near the apex. These four gonapophyses form the terebra, which functions in piercing the tissues of plants for the insertion of the eggs. The lateral gonapophyses or genital valves arise from the ninth sternum laterad of the posterior gonapophyses. They form a sheath for the terebra, most of which is concealed from view except during oviposition. Each genital valve bears at its distal end a ventrolateral stylus, which, in the Aeshnidae, bears a tuft of hairs. The ovipositor is well developed in all Zygoptera and in the families Aeshnidae and Petaluridae of the Anisoptera. In the other families it is either simplified, reduced, or absent and is not used for piercing plant tissues. In the Cordulegastridae the ovipositor is elongate and horizontal but simplified, the valves being vestigial, while the terebra is enlarged, though blunt and lacking the saw-edge of the Aeshnidae. These insects oviposit in an upright position over shallow water, striking the bottom of the stream with the ovipositor and releasing the eggs at the same time. In the Gomphidae, Corduliidae, and Libellulidae, which release the eggs by tapping the surface of the water (exophytic oviposition), the ovipositor has undergone still further reduction. The genital valves are absent, the posterior gonapophyses extremely reduced or absent, and the anterior gonapophyses either are reduced to small lobes or may become united into a single bilobed or entire flap, known as the vulvar lamina. In some genera the vulvar lamina has again become enlarged, so that it may cover the whole of the ninth sternum and, in certain exotic Libellulidae, even extend beyond the end of the abdomen, simulating the Cordulegastridae. In some species, both of Corduliidae and Libellulidae, the vulvar lamina has taken the form of a triangular scoop in a position oblique or perpendicular to the axis of the body. Such ovipositors are fitted for laying the eggs in the wet sand or mud of a stream bed, or the wet bank of the stream above the water line. EXTERNAL FEATURES OF THE FULL-GROWN NYMPH (PL 5, figs. 1-8) General Features As the descriptions of the larva or nymph are based on the final instar only, we shall describe this stage first and treat the other stages very briefly in a later section. We may take as a convenient and easily obtainable example one of the common, large aeshnid nymphs, such as Aeshna umbrosa or Anax junius. The nymph differs strikingly from the adult in both form and colour. It is always more stockily built, with a smaller head, and smaller thorax, with legs not yet shifted far forward and still used for walking, and an abdomen much shorter and stouter than in the adult stage. The coloration is of the cryptic type, entirely lacking the bright hues of the adult. The eyes are

PLATE 5 FIGS. 1-3. Aeshna, nymphal structures: 1. mandible; 2. maxilla; 3. labium, dorsal view. (Lettering as in Plate 1, figs. 3-5) FIG. 4. Sympetrum nymph, dorsal view of labium. (1st—lateral setae; mst—mental setae. Other lettering as in Plate 1, figs. 3-5) FIG. 5. Sympetrum nymph, terminal segments and anal appendages, (c—lateral appendage ("cercoid"); dh—dorsal hook; ep—superior appendage (epiproct); Isp—lateral spine; pa—inferior appendage (paraproct)) FIG. 6. Gomphus furcifer, nymph, terminal segments and anal appendages, (ap—anal pyramid. Other lettering as in fig. 5) FIG. 7. Lestes nymph, $, ventral view of abdominal segments 9 and 10, showing ovipositor, (ga-anterior gonapophysis; gl-lateral gonapophysis; la 1-base of lateral lamella; pa-basal segment of lateral lamella (paraproct); sty-stylus) FIG. 8. Enallagma boreale, nymph, median caudal lamella and associated parts, (axaxis; ep-epiproct (basal segment of median lamella); la 1-lateral lamella; la m— median lamella; nd-nodus; pa-paraproct (basal segment of lateral lamella); stm d —dorsal setose margin of median lamella; stm v—ventral setose margin of median lamella) FIGS. 9-11. Eggs of Odonata: 9. elongate egg of Enallagma carunculatum; 10. elongate egg of Aeshna constrict a; 11. ovoid egg of Somatochlora kennedyi with gelatinous envelope.

GENERAL—EXTERNAL STRUCTURE

25

much smaller and more forwardly placed. The dorsum of the head is consequently much larger than in the adult, especially the occiput, which is produced behind and often somewhat bilobed (postocular lobes). The region that becomes the vertex in the adult is also wide and flat and passes without demarcation into the frons. Upon this region, near the margin of the eyes, are the antennae, which are relatively larger and more distinctly separated. There are six or seven segments in the antennae of the aeshnid nymph, this being the usual number in the Anisoptera, but in the Gomphidae the number of segments is reduced to four or even three. Below the frons, the ridge of which is present but lacks the prominence of the adult, is the undivided clypeus, followed by the labrum. On the underside of the head are the mandibles and maxillae, which are similar to those of the adult. These are covered by the labial mask, one of the most remarkable of odonate structures. The submentum and the so-called mentum (anatomically the prementum or united labiostipites) form, with the two labial palpi, a large prehensile arm which in the position of rest lies folded upon itself, with the submentum directed backward and concealed by the mentum, which is turned forward, covering the jaws and meeting the labrum at the mouth.* Hinged to the distal margin of the mentum at its lateral angles, are the two lateral lobes or labial palpi. Each is two-segmented, the larger first segment being prolonged mesad to meet its fellow of the opposite side and terminating in the apical or distal margin, at the posterior (mesal) angle of which is commonly the end-hook. This is but slightly *The mentum in the Aeshnidae is elongate and of the flat type, in which there is little development of the middle lobe, this being merely an obtusangular projection of the distal margin. Although primarily bifid there is, in this group, only a small, closed, median cleft.

26

THE ODONATA OF CANADA AND ALASKA

indicated in Aeshna umbrosa, but in Anax the whole apex forms the hook. The second segment is a slender, curved or sharp-pointed hook, articulated with the first segment on its lateral margin, and overlapping its fellow of the opposite side. It is generally known as the movable hook and is an important instrument in seizing the prey. The dragonfly nymph seizes its prey by a sudden extension of the labium, the submentum being swung forward, carrying with it the mentum, whose two lateral lobes act like the two arms of a pair of forceps. These lobes with their sharp, movable hooks are directed forward, when the labium is extended, and serve to seize the prey, which is immediately drawn back within reach of the jaws. The return of the extended labium to the folded position automatically closes the lateral lobes, so that the prey is firmly held while it is being acted upon by the mandibles. The prothorax is freely movable as in the adult, but is relatively larger and less contracted. The propleura are sometimes raised into a pair of processes, known as the supracoxal armature (or prothoracic processes), which sometimes offer useful systematic characters. The meso- and metathorax are already firmly united to form a pterothorax, but the skewness seen in the adult is still incomplete. The wing-bases are shifted caudad, and the mesepisterna meet in front of them, but the segments are relatively flat and the legs are still in a position to permit of walking and climbing, not being thrust so far forward nor so close together as in the adult. The legs are also shorter and more robust than in the adult and lack the armature of setae or spines that are characteristic of the mature insect. The wing-cases occupy a position like that of a grasshopper but unlike that of most immature insects, in that the front wings are the inner pair, the hind wings the outer pair, and it is the under side of the latter that is exposed. The longitudinal veins can be clearly seen at this stage and frequently also the cross-veins to some extent. The abdomen in the Anisoptera is always much shorter and stouter than in the adult, although its form varies greatly and has little or no relation to the form of the imaginal abdomen. In Anax and Aeshna it is longer than in most families and is somewhat spindle-shaped. Dorsally it is transversely convex, ventrally flattened, the two regions meeting in a well-marked angle or carina, which is interrupted by the intersegmental annuli. On some of the more posterior segments, such as segments 6 to 9 in Aeshna umbrosa and 7 to 9 in Anax junius, the lateral carina terminates behind in an angular projection, known as a lateral spine. These spines are always longest on segment 9 and are successively smaller anteriorly. They are constantly referred to in descriptions because of their taxonomic value. The nymphs of many Anisoptera also have a series of mid-dorsal segmental hooks, which likewise furnish useful systematic features. The terga do not overlap the pleura and sterna, as they do in the adult, but join the pleura at the lateral margins. The somewhat flat ventral surface of the abdomen is divided into

GENERAL—EXTERNAL STRUCTURE

27

three regions, separated by longitudinal sutures, namely, two narrower lateral regions, the pleura, and a wider median region, composed of the sterna. The pleura are identified as such by the presence of the rudimentary abdominal spiracles on segments 1 to 8, these being as yet closed. Upon the sternum of segment 2 of the male the rudiments of the genitalia may be seen and in the female the developing ovipositor occupies the sternal region of segment 9, with the anterior gonapophyses arising from the hind margin of segment 8. In the Anisoptera, respiration is wholly rectal. Regular movements of expansion and contraction of the rectal walls cause an inflow of water through the anus into the branchial chamber, alternating with its expulsion. Sudden expulsion of water serves also in locomotion, which is by the method of jet propulsion, and the elongation of the anal appendages serves to concentrate the stream in a backward direction. There are three main wedge-shaped appendages, which spread apart during the intake of water, and when closed come together in a pyramidal group, known as the anal pyramid. One of these appendages is above the anus and is known as the superior appendage or appendix dorsalis; the other two are lateroventral to the anus and are the inferior appendages. They are often called the cerci, but opinion is divided as to what constitute the true cerci. Anatomically they appear to be paraprocts or laminae subanales, while the superior appendage is the epiproct or lamina supra-analis. The two small, dorsolateral appendages, termed by Heymons (1904) cercoids, are probably the true cerci, even though they are developed postembryonally, such events in development being by no means unusual in metamorphosis. Since we are not concerned, however, with morphological matters here, we prefer the term lateral appendages for these small structures. From the superior appendage of the male is derived the inferior appendage of the adult, and the contour of the developing adult appendage may be seen in the last nymphal instar, occupying the basal part of the larval appendage. In the female the latter is wholly a larval structure. The ventral appendages of the anisopteran nymph become reduced in the adult to what have all the appearance of typical paraprocts. The lateral appendages are the rudiments of the superior appendages of the adult. Enclosed within the anal pyramid and immediately surrounding the anus are three very small processes having relative positions similar to the three main appendages described above. These have been regarded by followers of Heymons as the vestige of a twelfth segment, the dorsal process being the epiproct or tergum, and the ventral parts the paraprocts or divided sternum. The segmental nature of these structures, however, is open to doubt. They are so wholly different from anything found in other insect orders that we hesitate to regard them as primitive structures, particularly as they are associated with the opening and closing of a rectal chamber, highly specialized for respiration and locomotion.

28

THE ODONATA OF CANADA AND ALASKA

Nymphs of Anisoptera (pi. 5, figs, 1-6) Nymphs of Anisoptera vary greatly in general form and in many details of structure, of which only a few can be mentioned here. Aeshna and Anax are relatively elongate nymphs of subcylindrical form. Many of the Gomphidae are also elongate but are more depressed, being modified for a burrowing habit in the superficial layers of sand or mud at the bottom of a pond, lake, or stream. This burrowing habit, together with the needs of rectal respiration, is associated with more or less elongation of the terminal abdominal segments, although there are no very striking examples of this type of variation in the Canadian fauna. In our largest gomphid, Hagenius brevistylus, which is not a true burrower, the abdomen is strikingly different from the usual gomphid type, very flat, broad, and almost circular in outline, and in the corduliid genera Macromia and Didymops the abdomen is likewise short and rounded in outline, even though it is long and cylindrical in the adults of all of these genera. In fact, the form of the nymphal abdomen seems to have no relation to that of the adult, but to be a strictly larval adaptation. Difference of habitat is also expressed in the length and form of the legs. In the actively clambering aeshnids, which are usually found in water with immersed or standing aquatic vegetation, the nymphs may rest in either a horizontal or a vertical position, and will stalk their prey for a short distance, clambering over the vegetation in order to come within striking distance of the moving object. Their legs are of average size and show no special modifications, In the burrowing nymphs of the Gomphidae the legs are sprawling and generally shorter than in the Aeshnidae. The femora and tibiae bear strong longitudinal ridges; the front and middle femora are short, thick, and curved, and the tips of the front tibiae are more or less flattened and hooked for burrowing. Both front and middle tarsi are reduced to two segments. The longest legs in the Anisoptera of our fauna are found in the Macromiinae, a subfamily of Corduliidae. These nymphs clamber among the roots of trees along the banks of streams and lakes and have a very characteristic spider-like appearance. The antennae of anisopterous nymphs are most frequently seven-jointed and tapering, but six-jointed antennae are commonly found and are due to failure of the sixth segment to divide at the penultimate moult. Nymphs of Gomphidae never have more than four antennal segments and sometimes have only three. The third is greatly enlarged and sometimes broad and rounded, and the fourth segment is usually vestigial. Among the most important nymphal variations are those of the labium. The flat type described for the Aeshnidae is also found in the Gomphidae, in which it is shorter with even less development of the middle lobe, which is usually slightly arcuate with a fringe of scurfy setae, and lacks the cleft altogether. In this flat type of labial mask there are no mental setae, i.e. the mentum is without a transverse row of setae on the upper surface. The

GENERAL—EXTERNAL STRUCTURE

29

lateral lobes are narrow and parallel-sided and terminate usually in an end-hook, which is sometimes slender but usually very blunt or even absent, the lateral lobe being merely truncate. Lateral setae, i.e. a submarginal row of setae on the upper surface, are generally lacking in this type of labium, and always so in the species of our fauna. In other families of Anisoptera, except Petaluridae, the labial mask is a scoop-shaped structure, the mentum being dorsally concave with a much more prominent middle lobe and the broad, triangular, and likewise concave lateral lobes form the front wall of the scoop by contact of their lower margins with the edges of the middle lobe, and by engaging one another in the median line by their distal margins. When in use the lateral lobes open like a pair of doors. There is a submarginal row of setae, born by the lateral lobes, known as the lateral setae (also raptorial setae), and these, with the mental setae, help to cover the hollow of the scoop when the labium is projected. The distal margins of the lateral lobes are more or less crenulate, sometimes deeply scalloped, and each crenulation or scallop usually bears a group of stiff setae. In the Corduliidae and Libellulidae the scallops are regular and even, while in the Cordulegastridae they are strikingly irregular. The movable hook is greatly reduced in all nymphs with the scoop-shaped labium, being no longer an important structure in prehension. The wing-pads are important taxonomically since, in the last instar, the generic position may often be recognizable from the developing venation. They show few other variations of systematic value, however, except their position with relation to the middle line. In the great majority of genera the wing-cases of opposite sides are parallel, their costal margins nearly meeting in the middle line, but in some genera, such as Ophiogomphus and Cordulegaster, they are divergent. In the exuviae, or cast skins, they always assume this divergent position. The most important abdominal characters, apart from general form and proportion of segments, are found in the number, size, and form of dorsal hooks and lateral spines or their absence. Dorsal hooks are typically falciform or cultriform but may be reduced to small knobs. They are common in the Corduliidae and Libellulidae, but are generally absent or but little developed in the other families. Laterial spines are projections of the rarely present anterior to segment 5 and are often confined to segments 8 and 9. They are often quite conspicuous on these two segments, or on segment 9 only, even when absent from all the other segments. Complete absence of lateral spines is also common.

Nymphs of Zygoptera (pi. 5, figs. 7, 8; pi. 6, figs. 1-9; pis. 32-44) The nymphs of the Zygoptera are more slender than those of the Anisoptera; the head is wider than the thorax or abdomen, with relatively longer antennae; the abdomen is generally cylindrical, tapering slightly to the last segment. It terminates in three caudal lamellae, commonly called gills,

PLATE 6

o>

FIGS. 1-9. Nymphal structures: 1. Agrion maculatum, head; 2. A. aequabile, head; 3. Hetaerina americana, head; 4. Agrion maculatum, labium; 5. Hetaerina americana, labium; 6. Lestes, right lateral lobe of labium; 7. Argia moesta, right lateral lobe of labium; 8. Enallagma boreale, distal margin of lateral lobe of labium; 9. Coenagrion angulatum, labium from above, showing the usual form in the Coenagriidae. FIG. 10. Hetaerina americana, $, anal appendages, dorsal view on left, ventral on right.

GENERAL—EXTERNAL STRUCTURE

31

although functioning principally, if not entirely, as fins. Bodine (1918) has shown that respiration is rectal in the Zygoptera as in the Anisoptera and that oxygen is carried by the blood, not by the tracheae. He found no evidence that the caudal lamellae had a respiratory function. The head is usually much wider than long, the eyes moderately prominent, the ocelli easily seen in the final instar. The antennae are setaceous, as long as the head or longer, rarely shorter. The labium is of various types, usually more or less flattened and with both mental and lateral setae. The thorax and wing-cases are similar to those of the Anisoptera in general features, though relatively narrower and more cylindrical as a rule. The legs are variable, generally slender and fitted for climbing over submerged vegetation. The abdomen is without dorsal hooks and with lateral spines inconspicuous or absent. Low lateral carinae are present on all the segments except the first and last. The superior and inferior anal appendages are specialized to form the caudal lamellae. Each has a stout base from which arises a lamella, which is delimited by a transverse suture. The caudal lamellae are usually compressed, the only exceptions in our fauna being the lateral lamellae of the Agriidae, which are triquetral. The lamellae are penetrated by two main tracheae, which occupy the longitudinal axis, and from these, numerous branches pass toward the dorsal and ventral margins. Great variety exists in the number and arrangement of both the main and secondary branches and the finer twigs. In the Coenagriidae the caudal lamellae are usually of the nodate type. The nodus (pi. 5, fig. 8, nd) is a point on the edge of the lamella where there is a change in the marginal setae. The antenodal setae are short and stiff, whereas the postnodal setae are fine hairs, often of considerable length. The setose margins, or margins bearing the stiff antenodal setae, are stronger on one side of the lamella than on the other. On the median lamella the stronger setae are dorsal, whereas on the lateral lamellae they are ventral. The line joining the nodal points of the two margins is termed the nodal line and may be either transverse or oblique. The lateral appendages are very small, but their exact dimensions are sometimes useful in separating otherwise nearly identical nymphs of closely related species.

B. LIFE HISTORY AND HABITS Habitats ALL dragonflies develop normally in fresh water. Only some of the primitive family Petaluridae are subaquatic, e.g. Petalura gigantea of Australia, which "forms burrows or canals in the peat or mud of small mountain swamps" (Tillyard, 1917). The majority of dragonflies require permanent waters for the development of the nymphs, since the cycle of most species takes at least a year, and may take two to four years, probably even longer in the far north. In relatively few species the postembryonic period has been reduced to five months or less, so that they can develop in temporary ponds that do not dry up before July or August. Of the Canadian fauna all such species belong to the genera Lestes and Sympetrwn. The most productive localities of dragonflies in our territory, except in the far north, are small lakes, large permanent ponds, or the lower reaches of slow streams, that are clear enough and shallow enough over a large part of their extent to produce an abundance of vegetation, submersed, floating, and emergent, and warm enough during summer for the normal activities of the nymphs. Calcareous soils, on the whole, make the most productive bottoms. The aquatic vegetation provides an abundance of dissolved oxygen, food for numerous organisms, which in turn are fed upon by predators, including dragonfly nymphs; and also shelter for the nymphs, particularly those of damselflies, from fish and other predators. Only in the mountainous or subarctic regions would the question of low temperatures arise. Lakes fed by glacial streams may never become warm enough for the activities of dragonfly nymphs. In the Bow Valley at Banff, Alberta, in the Canadian Rocky Mountains, there are three lakes fed by a glacial stream, known as the Vermilion Lakes. Two of these lakes are too cold for dragonfly nymphs, but the third is fed also by hot springs and consequently has an abundant invertebrate fauna, including numerous dragonflies. Habitats of dragonfly nymphs may be roughly divided into ponds, lakes, and streams, but there is no sharp distinction between any two of these. Ponds According to Chapman (1931), "Ponds are characterized by having shallow depths, and have, as a consequence, a relatively large ratio of surface and bottom in proportion to volume as compared with lakes." There are various other definitions of pond that "involve the idea of depth whereas the general feeling is that a lake is large and a pond is small" (Macan and Worthington, 1951). Except for this difference in size there seem to be no 32

GENERAL—LIFE HISTORY

33

definite data on which a satisfactory distinction between pond and lake can be made. Nevertheless, most ponds are easily recognized as such. Slough is a western term for any kind of marshy hollow or reedy pond. Ponds are of many kinds. Those of recent origin, such as many quarry ponds, often produce an interesting temporary fauna, since there is little competition between species in the early ecological stages and relatively slight danger from predators. Species that are usually rare may thus flourish for a short time, but as the pond matures the fauna eventually acquires the typical characteristics of the region. There are some types of pond that deserve special mention. Northern Canada is the land of muskeg and muskeg ponds or sphagnum pools are common throughout the precambrian region and are occasional farther south. These ponds are deficient in minerals and nitrogen and have an acid reaction. They are surrounded by a zone of sphagnum moss intermingled with a variety of peculiar plants, such as sundew, cranberries, and other ericacaeous shrubs, that generally form a floating margin. The odonate fauna is scanty but includes some characteristic species, such as Nehalennia gracilis, Nannothemis bella, and Leucorrhinia frigida. These species, however, are found only in the Eastern Provinces. Sphagnum ponds and sphagnum lakes are indistinguishable except in size. Another type of pond is often seen on the wide sandy beaches and dunes in the immediate vicinity of large lakes. We have termed these beach lagoons. They are shallow, have a firm bottom, and the vegetation is usually somewhat scanty, although there is sometimes a dense growth of spikerushes. Being often without shade and very shallow, they sometimes become overheated, causing mortality among the nymphs. They are frequented by many species of dragonflies, among which Sympetrum costiferum is commonly seen. We have found Pantala hymenea flying in some numbers over such a pond at Victoria Beach, Lake Winnipeg, a somewhat remarkable record for this southern species. Lakes Except at the mouths of streams, in channels, or other sheltered places, the larger lakes have a meagre odonate fauna, which consists of species that are mainly inhabitants of streams. Wave action on a large lake provides a plentiful supply of dissolved oxygen in the region where dragonfly nymphs occur, which is wholly in the epilimnion, but is generally too irregular and at times too violent to meet the needs of dragonflies. The boulder-strewn shore of Lake Simcoe, Ontario, at DeGrassi Point, is an example of a shore that is exposed at times to heavy winds, but a few dragonflies manage to breed here. Under the smaller boulders along shore are found the nymphs of Boyeria grafiana, and adults of this species patrol the shore in August and September. Beyond the boulder zone, which is only a few yards wide, is a muddy bottom from which, here and there, at depths of five or six feet, arise patches of bulrushes (Scirpus). Nymphs of Dromo-

34

THE ODONATA OF CANADA AND ALASKA

gomphus spinosus, which are not uncommon where the shore is lower and more sheltered, emerge occasionally, and rarely nymphs of Macromia fflinoiensis also. The only damselfly is Enallagma carunculatum, which breeds in the Scirpus beds. These species are all commoner in large rivers and channels of the precambrian region, where Argia moesta abounds. Streams Quiet, marsh-bordered streams in deep soils are similar in their dragonfly fauna to the smaller marshy lakes, except when the flow is disturbed by clearing the forests, especially from the headwaters, or by pollution. Undisturbed forest streams in the Eastern Provinces are usually characterized by intermittent rapids and pools and have a considerable dragonfly fauna in the south, which decreases somewhat rapidly northward. Of the Zygoptera the conspicuous genus is Agrion, A. maculatum being the common species in the south, A. aequabile northward to the latitude of Hudson Bay. In the well-settled parts of the Eastern Provinces Argia moesta and A. violacea are common inhabitants of rocky streams, moesta frequenting the larger and more rapid streams and lakes, violacea gentler brooks, not always rocky, Other argias appear in the southernmost parts of Ontario and two in the west. Enallagma exsulans is a widely distributed eastern species of streams, and E. antennatum is abundant in southern Ontario and Quebec on quiet streams. Chromagrion appears usually about the mouths of spring runs, again in the East. The Aeshnidae are represented principally by Boyeria vinosa, Basiaeschna Janata, and Aeshna umbrosa, the Gomphidae by several species of Ophiogomphus, Gomphus, Hagenius, and Lanthus in the East and the first two with Octogomphus in the West; the Corduliidae by Macromia and Didymops, Somatochlora, and other genera. The Libellulidae are almost absent from forest streams, but are abundant in all quiet, marshy places, streams as well as lakes and ponds. A few peculiar species are found on wet springy slopes or spring bogs, usually supporting a growth of short spike-rushes (Eleocharis). In the East Amphiagtion saucium is particularly characteristic. Anomalagrion hastatum, which barely enters Canada but is common farther south, may also be found in such habitats but is hardly peculiar to them in regions where it is really abundant. Chromagrion conditum, already referred to, is closely associated with springs, but is usually found about their mouths, in more or less shaded places. The western Argia vivida is particularly characteristic of springs and has a very wide distribution from Mexico northward to Field, B.C., and Banff, Alberta. Of this species Kennedy (1915) writes: "Argia vivida has a special preference for springs and the boggy streamlets flowing from them. Now springs do not freeze, as their waters originating deep in the ground, maintain a fairly uniform temperature throughout the year, so that the springs in western Canada, in which Argia t;it;ida has been taken, are probably the warmest waters in that region, comparing not unfavourably in warmth with springs of California and even Mexico." Argia vivida was

GENERAL—LIFE HISTORY

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taken near the hot springs at Banff but whether it was actually associated with them or not is not known. Saline Habitats Many of the normally freshwater species of both Zygoptera and Anisoptera have been found breeding in brackish water, the nymphs tolerating a salinity up to a specific gravity of 1.010 (Osburn, 1906). At this density the eggs hatched and the nymphs developed as usual, but at a density of 1.015 they died within less than a day. Osburn found a number of species breeding in a slightly brackish pond near Victoria, B.C., namely Enallagma carunculatum, Ischnura perparva, I. cervula, Aeshna californica, Sympetrum madidum, Erythemis simplicicollis collocata, Libellula quadrimaculata, and L. forensis. Kennedy (1917) found E. carunculatum and E. clausum breeding abundantly in Pyramid Lake, Nevada, the water of which has a density of 1.0034 (about one-ninth that of sea water). Both of these species and E. boreale breed in some of the saline lakes of Saskatchewan (Walker, 1940), the salinity of which varies greatly (from .05 to 2.0). While adults of E. clausum and boreale were taken at Big Manitou Lake, which has a salinity of 2.0, there is no proof that the nymphs breed there and, in the light of the observations of Osburn (1906) and Pearse (1932), we must regard this as very improbable. Nevertheless there are Odonata that will tolerate a salinity higher than that of sea water. Pearse (1932) found Erythrodiplax berenice in ponds with a salinity up to 170 per cent of sea water and Wright (1941) found the same species exclusively in salt marshes, both on the central Gulf Coast and the Mississippi River Delta. In fact he states that its abundance increases with the salinity. Habits of Adults The Teneral The newly emerged dragonfly is pale yellowish and without darker markings. When the wings are fully expanded they are first held in the vertical plane, a position that is only temporary in the Anisoptera. The characteristic pattern appears within an hour or less, but the full development of colour is usually later. The black, yellow, and green pigments appear early but the blue and red not until the colour-pattern is complete. During the dragonfly's first flight the wings are very shimmery and the body still somewhat soft, the exoskeleton being still thin. At this stage the insect is known as a teneral. Flight is feeble and the period is one of danger. The teneral falls an easy prey to birds and the smaller forms also to larger dragonflies. Young dragonflies soon scatter and occupy themselves for a time entirely with the pursuit of their prey. Some drift a long way from their place of emergence, the strong-flying Aeshnidae often many miles. Others, like the weak-flying agrions, tend to remain in the valley of the stream where they develop.

36

THE ODONATA OF CANADA AND ALASKA

Flight During the period of feeding that continues after the teneral stage, many peculiarities of habit may be noted. Gomphidae, for the most part, fly short distances and light on the ground in the sun. Some species of Gomphus, on hot, sunny days, fly in a series of concave loops, like inverted arches. Many Corduliidae fly at considerable heights, well out of range of the net and not infrequently about the tree-tops. Tetragoneuria and Epicordulia fly back and forth in sunny glades, showing strong territorial instincts. They are among the most skilful and tireless of aeronauts. Libellulidae usually fly nearer the ground and come to rest more frequently, often returning to the same twig. Libellula julia, in contrast to most species, resembles Gomphus in settling on the ground. The broad-winged Tramea and Pantala are also unlike our other Libellulidae in their tireless flight, displaying an apparent laziness that is deceptive, as it gives the novice the false impression that they are easy to catch. Some of these habits are paralleled in the Zygoptera. The Agriidae flit about like satyrid butterflies, resting frequently on foliage in sheltered, sunny places, closing their wings in the typical zygopteran manner, all four wings being held together in the vertical plane, so as to appear like a single wing. The species of Lestes fly mostly in open places—marshes and meadows or the edges of woods—coming to rest on low vegetation within two or three feet of the ground or the water. They usually select vertical supports and rest with the body inclined and the wings half spread. This manner of holding the wings is unusual in the other Zygoptera of our fauna, but there are at least two species of Coenagriidae that practise it, namely, Chromagrion conditum and Ischnura cervula. Argia rests on the bare ground or on rocks like the Gomphidae, except that the wings are closed in the usual manner of the Zygoptera. Enallagma clausum also has this habit, whereas the other species of Enallagma perch on foliage, usually within a few feet of the ground, although we have found both E. vesperum and E. signatum resting on trees, the latter species on the foliage in shelter from a high wind. The small damselflies of the genera Nehalennia, Amphiagrion, and Anomalagrion fly among low-growing plants, close to the water or bog moss, and our tiniest libellulid, Nannothemis bella, likewise rarely rises more than a few inches above the sphagnum of its bog habitat. ACTIVITY IN SUNSHINE

Most Odonata are active only in sunshine, except during the teneral stage, when various species of Zygoptera (Lestes disjunctus, L. rectangularis, Enallagma carunculatum, Ischnura verticdis, etc.) are found in the deep shade of woods, where they are probably safer from insectivorous birds and other enemies than in the open. When the feeding period is in full swing dragonflies are very sensitive to changes in the intensity of sunlight. When

GENERAL—LIFE HISTORY

37

the sun is momentarily overcast they seem to disappear as though by magic. The Zygoptera simply come to rest in the grass or sedges and are easily found, but many Anisoptera fly into the trees and are then safe from the prying eyes of the collector. On the whole, dragonflies are most active in the afternoon and come to rest when the shadows overtake them, but some of the high-flying Corduliidae (Somatochlora spp.) rise to steadily greater heights, keeping in the sunshine as the lengthening shadows creep up the trees. CREPUSCULAR FORMS

A few species of both suborders fly until dusk or later. Of the Zygoptera, two species of Enallagma (E. vesperum and signatum) are active after sundown and so also, of the Anisoptera, are various Aeshnidae (Boyeria, Basiaeschna, and various species of Aeshna, particularly A. umbrosa) and certain Corduliidae, such as species of Somatochlora and Neurocordulia. All but the last of these, however, fly also in the afternoon, although some of them favour partly shaded places, flying in and out of the sunshine. Only Neurocordulia yamaskanensis is exclusively crepuscular, flying for about half an hour only during dusk. This peculiarity seems to be correlated with the feeding habits, the chief prey of this species being apparently the large mayflies of the genus Hexagenia, which fly at this same season and hour. MIGRATION

Many reports have appeared of vast numbers of dragonflies of one or more species moving in a steady stream, in a definite direction, and continuing for hours at a stretch. Such flights are said to be most common in the warmer parts of the world, although most of the reports have come from middle Europe, doubtless because of the larger number of observers there than elsewhere. The species most frequently reported is our common Libellula quadrimaculata, a circumboreal insect, abundant both in the Old World and the New, and known as a migratory species in both Europe and North America. It was this species that comprised the swarms observed by Federley (1908) in Finland, the most northerly migration that has yet been observed. Federley suggests overcrowding as a primary factor in the origin of migratory swarms of dragonflies, as of some other insects. Certainly there appear to be unusual numbers of individuals where such swarms gather. Dragonfly nymphs that are ready for emergence tend to wait for favourable weather, which should be warm, dry, and sunny. Thus it may happen after a period of cold or wet weather, when there is a sudden rise in the air temperature, that immense numbers of dragonflies emerge on the same day from the ponds or marshes in a particular locality. The air seems filled with dragonflies, all teneral and recently emerged. It is under such conditions that migrations begin, but what determines the direction of flight is still unknown. The flights observed by Federley in Finland followed the sea-

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THE ODONATA OF CANADA AND ALASKA

coast closely, in a nearly west-east direction, but in other cases swarms have crossed parts of the sea, such as those that have invaded the British Isles. Neither food nor the reproductive impulse plays a part in the development of these flights. Federley noted that, although the insects were plentiful on the route followed by the dragonflies, the latter did not stop to feed, but pursued an uninterrupted course. They had not reached sexual maturity, being still tenerals. The British Isles have been invaded many times by migratory dragonflies. Longfield (1948) describes in detail an invasion of the south coast of Ireland (Co. Cork) by immense numbers of dragonflies between mid-August and mid-September, 1947. Quoting from her summary, "They were seen flying steadily or drifting with the wind, all in one direction, mostly north, in five different localities and, in some cases, on several days in succession. They were also seen in countless thousands spread over localities several miles inland, for at least six weeks. These swarms came in from the sea in the form of narrow columns, the insects flying roughly a foot apart, but they were inclined to spread out more on reaching land/' The swarms were composed of one species, Sympetrum striolatum, and all the individuals were mature, pairs flying per collum having been commonly seen. Although this is a common British species, the immigrants were not of the typical British subspecies, but were nearer the subspecies nigrifemur, and probably came from the coast of Spain or Portugal, a distance of 500 to 600 miles. Two other species of Sympetrum, S. fonscolombii and S. flaveolum, occasionally invade Britain and become established for a few years but eventually die out (Macan and Worthington, 1951). The two genera mentioned both belong to the Libellulidae, but representatives of three other families are known to take part in migratory flights, namely, the Agriidae, Coenagriidae, and Aeshnidae (Calvert, 1893). We know of no reports of dragonfly migrations in Canada, although the occurrence of swarms of certain species is no rarity. We know of one occasion when Libellula quadrimaculata appeared in large numbers in Parkdale, a western section of Toronto on the lake front. In one back yard a forty-foot clothesline was covered from end to end by resting dragonflies. There were no breeding places in the immediate vicinity of this part of the city, but within a mile there are marshy ponds in High Park. Swarms of Tetragoneuria cynosura and T. spinigera, separate or mixed, are a not uncommon sight in early summer, and other members of the Corduliidae, e.g. Cordulia shurtleffi and Somatochlora franklini, sometimes appear in great numbers in the north. Food Most dragonflies feed on any small insects they can capture, particularly caddis-flies, small moths, midges, and other nematocerous Diptera. The larger species include in their diet smaller members of their own order,

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especially Zygoptera, and we have seen Basiaeschna Janata carry off a teneral Gomphus spicatus, almost as large as itself, although relatively helpless. Specialized feeding habits, such as that of Neurocordulia, mentioned above, are not common among dragonflies. The only other case that we have observed is that of Hagenius brevistylus, a huge gomphid that habitually preys upon other smaller dragonflies, such as Tetragoneuria and Gomphus. Reproductive Period After a period of feeding, which may last a week or more, the dragonfly returns to its characteristic habitat in the vicinity of water. Then follows the time when the male dragonflies may be seen coursing over ponds and lagoons or patrolling the shores of lakes and streams. The females seldom appear over the water, except when pairing or ovipositing. They are generally to be found at a considerable distance from the water, in sheltered glades and clearings, or in open woods. The males are often so aggressive that, for their own safety, the females must lead a more secretive life. Hence the collector first receives the impression that there are far more males than females, although the sex ratio is actually about equal, as may be readily determined of any common species during the teneral stage. Males of some species patrol very limited territories along the banks of ponds or streams, a few rods or sometimes only a few yards. Others like Cordulegaster follow the course of a stream, apparently for the entire length of that section which belongs to its type of habitat. Boyeria also examines long stretches of lake shore or streams. A male does not restrict himself entirely to a single beat but ventures forth to other regions from time to time. When engaged in the regular patrol, however, a dragonfly will immediately pounce upon an intruder, even of his own kind, and the two soar aloft, until they disappear from sight. But in a few minutes, back comes the original occupant to his beat and carries on as before. A patrolling male is also watchful for females that may stray into his territory while ovipositing. A male aeshna will seize a female of any species that appears in his beat, although copulation between different species does not often follow. MATING (pi. 7, fig. 3) Pairing takes place most frequently in the vicinity of water, in open marshes, or sometimes at a distance from water in fields or on the borders of woods. When the male seizes the female the pair usually flies to some neighbouring bush or tree and comes to rest on a branch. Aeshna constricta commonly mates at a distance from water and is remarkable for the wild nuptial flight the pair takes before coming to rest. Among our fauna only the Agriidae appear to perform courtship antics. Those of Agrion maculatum have been most frequently noted. The male has been seen to hover in front of the female with the wings spread in the form of a cross, and the female has been observed to respond by opening and closing the wings suddenly.

PLATE 7 FIG. 1. Lestes congener Hagen, pair ovipositing above water. FIG. 2. Enallagma geminatum Kellicott, pair in copula. FIG. 3. Argia violacea (Hagen), pair ovipositing. FIGS. 4-6. A. moesta (Hagen): 4. ovipositing pair descending into water; 5. same, female submerged; 6. same, pair far under water. (Figs. 2 and 3 are drawn from Kodachrome slides by Paul D. Harwood, the others from Kodachrome films by Norma Ford Walker)

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We have also seen a male hover in front of a female immediately before copulation. Before mating the male stores the penis vesicle with sperm capsules and copulation may be interrupted several times by the male, in order to refill the vesicle. The male seizes the female during flight and often while she is engaged in oviposition. In the Anisoptera the head is seized by the anal appendages, which act like a pair of forceps in the vertical plane, the superior appendages together forming the upper jaw of the forceps, the inferior appendage the lower jaw. The upper jaw is applied to the rear of the head, the lower jaw to the occiput and sometimes the interocular region between occiput and vertex. In the Aeshnidae the superior appendages, besides opposing the lower jaw in this way, also hold the prothorax between them (Walker, 1912), while in Petalura they hold the pterothorax (Tillyard, 1917). This seizure of the female appears to cause, by a reflex action, a forward and upward bending of the female's abdomen, thus bringing the ovipositor, or vulvar lamina, in contact with the male genitalia and effecting its engagement with the genital hamuli. The sperm capsules can then be transferred from the vesicle to the female genital aperture. During this rocess, in the Anisoptera, the female holds the abdomen of the male with er legs. This double union, whereby the bodies of the mating pair form a complete loop, is unique in the Class Insecta. The copulatory position in the Zygoptera is quite similar to that of the Anisoptera, except in the manner in which the male holds the female with his anal appendages and in the way the female holds her legs. In this group the posterior lobe of the pronotum is held as in a vise between the inferior appendages in front and the superior appendages behind. In such genera as Agrion and Lestes, in which the superior appendages are forcipate, an additional grip on each side of the mesothorax is obtained, whereas in the Coenagriidae, in which the superior appendages are generally short, they engage the mesostigmal laminae, each species having its own particular combination of grooves, pits, ridges, and knobs, which are adapted to fit accurately only the superior appendages of their own species. The head of the female is usually not held by the male but, according to Tillyard, it is only touched when the inferior appendages are long enough to pass forward and press against it from behind (as in some Lestidae). In Zygoptera the legs of the female, instead of grasping the abdomen of the male, hang freely or may rest upon the ground.

E

42

THE ODONATA OF CANADA AND ALASKA PRUINOSITY

With the advent of sexual maturity many species of Odonata become more or less pruinose, i.e. the colour-pattern becomes obscured by a whitish or bluish white exudate, which in some species is confined to certain regions, while in others it covers almost the entire body. It is usually preceded by a dark pigmentation of the parts to be affected. While generally much more pronounced in the male, as in Lestes and various Libellulidae, pruinosity is a strictly female feature in Ischnura. In most of our species of this genus almost the entire body is affected and the colour-pattern is completely obscured. Both sexes of Argia moesta are somewhat affected, although only the male becomes heavily pruinose. Its teneral pattern is very soon altered by the spread of a dark pigment, which is simultaneously obscured by the pruinose exudate. OVIPOSITION (pi. 7, figs. 1,3-6) After copulation the sexes may separate before oviposition takes place, or the connection between the head or thorax of the female is retained and the pair flies about in tandem. The females of most of our Zygoptera and some of the Anisoptera may oviposit in tandem. In other species the male may take no part in the process. One or two males may hover over the female while she is ovipositing (see under exophytic oviposition). Oviposition is performed by two methods, endophytic and exophytic. The former is the more primitive, although the more complex, method and is practised by all Odonata possessing a fully developed ovipositor. These comprise all the Zygoptera and two families of Anisoptera, the Aeshnidae and the Petaluridae. Exophytic oviposition is practised by the remaining families of Anisoptera. Endophytic oviposition. In endophytic oviposition the eggs are deposited in the tissues of aquatic plants, either below or above the surface of the water, occasionally in wet wood or moss. In most species of Aeshna the female supports herself on the stem of an emergent aquatic plant, just above the water, lowers her abdomen below the surface, and makes a number of thrusts here and there against the stem, apparently searching for suitable spots in which to introduce the ovipositor. In this action it is probably the styli on the apices of the genital valves that guide the insect in selecting the proper places. Using the spiny posteroventral surface of the tenth segment as a fulcrum, the terebra is exserted from the valves and pushed into the tissue of the plant like a can-opener. Sometimes a little sawing is done with the serrated edge of the gonapophyses. The punctures are arranged by many of the Aeshnidae somewhat irregularly in oblique or concentric rows, while in the Zygoptera they are generally quite irregular. Most species place a single egg in each pit, but some deposit several. Aeshna constricta Say deposits its eggs in the stem of the sweet-flag (Acorus calamus Say) two feet above the water. It is the only species of Anisoptera in our fauna known to oviposit above the water. Anax junius

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Drury, another aeshnid, oviposits in spring in a horizontal position in dead floating stems of Typha, and sometimes also in standing stems. It is usually accompanied by the male and is our only Anisopteran known to practise endophytic oviposition in tandem. Females of Zygoptera oviposit with or without the male, more frequently the former. Females of Agn'on, however, seem always to oviposit alone. Our two common species of this genus both oviposit in bur-reed (Sparganium spp.), A. maculatum choosing the floating leaves and depositing the eggs just beneath the surface, while A. aequabile uses the submerged parts of the plant, backing down to depths of a foot or more and remaining there sometimes over half an hour, finally floating to the surface farther downstream. Several of our Coenagriidae descend under the water this way, but usually in tandem. We have observed a pair of Argia moesta descend the side of a wooden diving float, the female puncturing the wood as she went down and pulling her mate after her. This pair came out together after more than half an hour's submergence, but often the male emerges after a few minutes under water. In these descents the supply of oxygen comes from the film of air that adheres to the hairs of the body surface and between the wings. Most Coenagriidae, while ovipositing, rest on floating leaves of hydrophytes at the surface of the water or just beneath it. The female generally keeps the horizontal position, while the male stands upright or obliquely, supported only by his hold on the prothorax of his mate. The abdomen of the female enters the water and may be thrust in various directions, eggs being introduced often quite irregularly into the slender stems and leaves of aquatic plants; or it may be curved around the edge of a water-lily leaf and the punctures made on the lower side of the leaf. Sometimes the body of the female may enter the water through a hole in the leaf, the eggs being deposited in concentric arcs. Our species of Lestes oviposit high above the water in various emergent plants or even in willow branches. Needham (1900) has reported considerable damage to the stems of the blue flag (Iris versicolor L.) by ovipositing females of Lestes. The female is usually accompanied by the male in oviposition, but not always. Exophytic oviposition. Exophytic oviposition is practised by the Cordulegastridae, Gomphidae, Corduliidae, and Libellulidae. It is always associated with a reduced ovipositor or the absence of one. Many species of all these families, except the first, oviposit by flying low over the water and striking the surface here and there with the end of the abdomen, a cluster of eggs being dropped at each dip. It is a more familiar sight, however, to see one of the common pond libellulas performing this function in a somewhat different way. Libellula pulchella, for example, taps the water with the abdomen rhythmically, about four times per second, and always rising between strokes to the same height, about five inches. With each stroke the abdomen is swept downward and forward in a graceful curve. Twenty or thirty dips may be taxen over the same spot, but the position is varied

44

THE ODONATA OF CANADA AND ALASKA

from time to time. The rounded eggs are exuded in a constant stream, and many are released at every stroke and sink upon the algae or other aquatic plants below. Eggs dropped freely into the water by this method are sometimes quite dry as they come from the genital opening; in other cases they are surrounded by a gelatinous envelope of varying thickness. In Cordulia and Somatochlora each egg has at first a separate envelope, which is inconspicuous until it comes into contact with water, when it swells to many times its original volume. When many eggs are deposited in one spot over algae or other plants, the swollen envelope becomes fused into a single mass, suggestive of the spawn of some amphibian on a small scale. The most remarkable egg-masses of this type, however, belong to the corduliid genera Tetragoneuria and Epicordulia and the closely related Eurasian genus Epitheca. The eggs of Tetragoneuria, for example, pass out of the oviducts in long, gelatinous strings which, on entering water, swell into rope-like clusters. They are often found at the surface of a weedy lake or bay, sometimes floating free, more often entangled upon aquatic vegetation or submerged sticks. Since more than one female may oviposit in the same spot, these egg-clusters may represent the work of several individuals, although a single rope is always produced by one female. Occasionally we have seen females of Tetragoneuria canis with a string of eggs several inches long trailing from the end of the abdomen. Many species of Libellulidae oviposit in tandem, and females of other species engage in this operation with one or two males hovering overhead. The former habit is seen in various species of Sympetrum, e.g. S. costiferum and S. danae. In these species the process is otherwise much as in Libellula, but in S. vicinum, in which the vulvar lamina projects like a spout, the female accompanied by the male strikes the wet bank and the water alternately. It is believed that the eggs are deposited in the bank and the vulvar lamina is then washed free of mud or slime by dipping in the water. The same method is practised by certain species of Somatochlora and, in the case of the European S. metallica, it has been shown definitely (Miinchberg, 1932a) that the eggs are driven into the mud of the bank. Several of our native species of Somatochlora oviposit in the same way, and all of them have projecting, spout-like vulvar laminae. We have watched the female of S. williamsonii strike the bank or a wet knoll seven or eight times before touching the water, and we believe the latter movement is merely to clear the cavity of the lamina from debris, although this is contrary to the view that we formerly held (Walker, 1925). One other variation of exophytic oviposition should be mentioned, that of Cordulegaster. The species are black and yellow dragonflies, the males of which course up and down long stretches of a stream, whereas the secretive females are rarely seen. Their manner of egg-laying is most peculiar. The ovipositor is degenerate but the anterior gonapophyses are hypertrophied and form a sort of trough leading back from the genital orifice, beyond the

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end of the abdomen. The female, while ovipositing, flies up and down in a vertical position over a shallow water or wet sand, driving the ovipositor into the stream bed into which the eggs are deposited. Developmental Stages

The Egg (pi. 5, figs. 9-11) The eggs of Odonata fall into two general categories: elongate eggs and ovoid eggs. Elongate eggs are characteristic of those species which practise endophytic oviposition, whereas ovoid eggs are similarly related to exophytic oviposition. The elongate eggs are somewhat cigar-shaped and are three to more than six times as long as their transverse diameter. The outer ends are pointed and surmounted by a small cap or operculum. This end is anterior, according to the position of the full-grown embryo. The inner ends are rounded. Dorsal and ventral surfaces can also be distinguished, the dorsal being more convex, the ventral somewhat flattened. The shell is thin and often quite transparent. Anisopterous eggs of this type, whose measurements have been recorded, range in length from about one millimetre to nearly two millimetres. Zygopterous nymphs are usually about a millimetre in length or somewhat shorter. The ovoid eggs are not more than twice as long as their transverse diameters, but vary considerably, sometimes being almost subspherical. Like the elongate eggs, they bear a cap at the anterior end, and their dorsal surface is somewhat more convex than the ventral. They differ in having a much thicker shell, which is brown and opaque. Such eggs may be dry or enclosed in a gelatinous envelope of varying thickness (see Oviposition). The range in length of ovoid eggs is at least .4 to .66 mm. The average number of eggs deposited by dragonflies is about 200 to 300 (Calvert, 1893), but the number varies greatly, being in general greater in those species which drop their eggs at random in the water than in those which practise endophytic oviposition. Sometimes they are much more numerous than the above. Needham (Needham and Heywood, 1929) "obtained 5,200 eggs from an ovipositing female of Gomphus externus that had already deposited a part of her stock/' Incubation Period The incubation period also varies greatly, not only in different species, but in the same species. The temperature of the water is an important factor, but variation occurs in the time of hatching even among eggs of a single mass kept under like conditions. In those species whose eggs hatch during the season in which they are deposited, the period varies in different species from five days to more than a month. Bick (1951) gives five to seven days for Tramea lacerata, without subjecting them to varying temperatures. Balfour-Browne (1909) found that eggs of Ischnura elegans and

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THE ODONATA OF CANADA AND ALASKA

Coenagrion pulchellum, deposited about the beginning of August, hatched for the most part in slightly less than four weeks, while those laid later in the year required more than five weeks before hatching. Grieve (1937), who reared nymphs of Ischnura verticalis from more than 500 eggs, found that the great majority hatched from 12 to 20 days after they were laid, depending partly on differences of temperature, the range of which she did not state. Martin (1939), who reared Agrion maculatum and A. aequabile in numbers, found the incubation period to range from 18 to 29 days, and this appears to be about the average length for many species. Even under like conditions eggs of many species hatch irregularly. Lamb (1925) found that the eggs of Pantala flavescens, from a single egg-mass, laid by one individual, hatched over a period of more than a month (from September 1 to October 5). Even longer was the period during which eggs of Sympetrum obtrusum, collected on August 14 and 15, 1928, and kept at room temperature, continued to hatch (Krull, 1929). Hatching began on October 9 and continued until January 30, 1929. These eggs could be kept from hatching if placed in a cold room at 45°F., but would resume the process if again put in a warm room for a few days. Eggs of Lestes spp., which are deposited high above water in the stems or leaves of Typha, Iris, Sparganium, and Salix, develop to the stage when the eyes are visible (Needham, 1900). Then development ceases until the following spring, when the stems in which the eggs have been deposited have become submerged. Some dragonflies pass the winter in the egg stage, notably certain Aeshnidae, e.g. Boyeria and Aeshna, We kept pieces of wood containing eggs of B. vinosa over winter at room temperature and, though deposited in September, they hatched in April of the following year. Eggs of Somatochlora kennedyi laid in August also hatched in the following spring. It is possible that there is a winter diapause in the egg stage of many, if not most, of far-northern species, but this has not been determined, at least for our native fauna. Hatching or Eclosion The process of hatching has been observed by various authors, notably Balfour-Browne (1909) and Grieve (1937) in Ischnura, Tillyard (1917) and Shafer (1923) in Anax, and Gardner (1951b) in Sympetrum. The main steps in the process, as we understand it, appear to be the following: Preparation for hatching is initiated by peristaltic movements of the stomodaeum, which pass from the mouth backwards and are synchronous with rhythmical contractions of the dilator muscles of the pharynx (Grieve, 1937). Fluid from the amniotic cavity is swallowed but is apparently accumulated within the stomodaeum, causing a swelling of the head region. The resulting pressure upon the front of the head causes a rupture of the thin egg-shell, thus exposing the lining membrane (serosa) to the water. Osmosis follows, and water accumulates in the amniotic cavity in front of the head and

GENERALrr-LIFE HISTORY

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forms the "vesicle." Water continues to be swallowed, resulting in further expansion of the head, which pushes forward until it fills the vesicle. Up till now there has been no forward movement of the embryo as a whole, but the vesicle protrudes from the pit in which the egg lies and is soon followed by the head. The pressure of the head ruptures the enclosing membranes (amnion and serosa) and the embryo slips out. It is not yet a nymph, but is known as the pronymph. It is somewhat pupiform, since the antennae and limbs are all folded back under the body. First Nymphal Instar After the pronymph has escaped from the egg, the swallowing movements, which have meanwhile decreased in rate, become more rapid again and produce the pressure necessary to split the cuticle of the pronymph and permit the emergence of the first nymphal instar. In this stage the insect has already something of the form of the full-grown nymph, the larval specializations being already present in part. The head is proportionally larger and the thorax smaller than in the older nymph, but the family to which it belongs is already recognizable, as a rule. The compound eyes are relatively smaller, there are only three (sometimes four) antennal segments, the tarsi are only one-segmented, and there are no rudiments of wings. The three thoracic segments are much alike in size and form. They lack the pleural ridges; and the obliquity or "skewness" that characterizes the meso- and metathorax of the adult has not yet begun to show. There are three prominent anal appendages, the superior (appendix dorsalis) and paired inferior appendages, and surrounded by these are the three small appendages that are said to belong to the twelfth segment, the so-called supra-anal and subanal laminae. In the Zygoptera the superior and inferior appendages are long, slender, tubular, and hairy, but do not have the appearance of tracheal gills at this stage. In the Anisoptera the branchial basket is already well developed and functional. Other features not characteristic of the entire order or of either suborder but of lesser groups may or may not be present at this stage. Such features as the teeth or the crenulations of the lateral lobes of the labium may be strikingly different at this stage, or even later, and in both Anisoptera and Zygoptera, species which have a series of mental and lateral setae at a later stage may have no mental setae in the first instar and only one lateral seta (Balfour-Browne, 1909; Lamb, 1925; Bick, 1951), or they may have one of each (Gardner, 1951a). Nymphal Changes during Growth The principal changes in the external features of the nymph during its growth are: (1) Increase in the size of the compound eyes, involving an increase in the number of facets at each moult.

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THE ODONATA OF CANADA AND ALASKA

(2) Increase in the number of antennal segments from three (more rarely two or four) to six or seven (in Gomphidae four or three). The first two segments, scape and pedicel, remain throughout life without further division. The third segment divides into two at the second moult, while the seventh may appear as early as the sixth or seventh stage, but more frequently later, up to the last moult. (3) Changes in the labium: more complete fusion of parts; strengthening of movable hook; and, when present, increase in the number of mental and lateral setae, and in setae of margins of lateral lobes with decrease in relative size of their teeth. (4) Changes in the shape of the thorax and development of the wings: the pleural ridges appear in about the fourth or fifth instar and, at the next stage, the wing-buds first show as minute ridges. In each succeeding stage the pleural ridges lengthen and become more oblique, the pterothorax increases in size, while the prothorax remains relatively small. The wings lengthen at each moult and become shifted to a more oblique plane, as the mesepisterna grow forward to meet each other in front of the wing-bases. The hind wing-buds gradually overlap the front pair until they cover all but their costal margins. (5) Appearance and development of the lateral anal appendages ("cercoids"), which are first recognizable from the fourth to the eigbJi stage. (6) Growth of the female gonapophyses (in Agrion from the sixth to the seventh instar) and the male gonapophyses (in Agrion in the eighth instar). (7) In the Zygoptera the change in the caudal lamellae from the linear to the triquetral and then, as a rule, to the lamellate form, with its richer supply of tracheae. "Number of Nymphal Instars Balfour-Browne (1909) found that in four species of Coenagriidae the number of nymphal instars, not including the pronymph, varied from 10 to 12 in each species (rarely 13 in one species). In all of the species of Odonata hitherto reared, including representatives of several families, the usual number was found to be 11 or 12 and the total range is 10 to 15. Length of Nymphal Life The duration of the nymphal period varies greatly throughout the order and considerably among individuals of the same species. Temperature and food are important factors in determining both the length of the nymphal period and the number of moults. Low temperature and insufficient food will greatly prolong development and may increase the number of moults, whereas keeping nymphs under optimal conditions may reduce to a minimum the number of moults and the length of the nymphal period. The few species that develop in temporary ponds overwinter in the egg stage and hatch generally in early spring. Lestes unguiculatus and L. dryas,

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which are common in such ponds provided they contain water as late as June or July, appear to go through their larval development in a few weeks. Wesenberg-Lund (1943) gives three to four weeks for European species of Lestes of this habit. Sympetrum internum and S. obtrusum also develop in such ponds, the former emerging in late June (in southern Ontario) and the latter in July. Most of our Zygoptera develop in permanent waters, although some of them visit temporary ponds casually. Ischnura verticalis, the most nearly ubiquitous species in the Eastern Provinces, develops under optimum laboratory conditions in 57 to 64 days (Grieve, 1937), but in its natural habitat it may go through its entire developmental period between spring and late summer, or the nymphs may overwinter, producing adults in the spring. The majority of our Coenagriidae appear to have one generation a year and one period of emergence of two or three weeks. There are, however, a few marked exceptions besides I. verticalis, e.g. I. cervula and Enallagma boreale on the west coast of British Columbia, which Whitehouse (1941) states are on the wing from the end of April to mid-October. Many Anisoptera likewise develop from egg to adult in a year, particularly in the family Libellulidae. Pantala flavescens has been reared through all its stages in 65 to 101 days by Warren (1915) and 80 days by Lamb (1925); Sympetrum vicinum and Erythemis simplicicollis, both libellulids of permanent waters, in 113 and 97 to 100 days, respectively, by Nevin (1929). At least one of our Aeshnidae, Anax junius, has a nymphal life of 11 months, as determined by Calvert (1929), but in Canada, where this species emerges in late summer instead of spring or early summer and then migrates southward without mating, nymphal development apparently requires about 14 months, eggs being deposited in late May or June by the return migrants and the nymphs maturing in the late summer of the following year.* Species of Aeshna pass the winter in the egg stage and require two to four years to develop (Miinchberg, 1930). Three years is probably the usual length of the nymphal period in southern Canada, but farther north it is apparently a year longer, full-grown nymphs being found in late summer, after the time of emergence is over. Our observations bearing on this question, however, are too few to be of much value. Judging from Miinchberg's (1932a) observations of European Gomphidae, it appears that the length of nymphal life is decidedly long, being at least three or four years in the species of Gomphus and Ophiogomphus which he investigated. The more abundant North American fauna may be expected to vary more than the European in this regard, but our species of Ophiogomphus and the fluviatile species of Gomphus will probably agree closely with Miinchberg's findings. Some of the Corduliidae are also slow in development, e.g. the genera Cordulia and Somatochlora. The Eurasian C. aenea develops in two to three *On June 27, 1953, we found two exuviae of this species on the margin of a pond at Snelgrove, Ontario, while spring adults were still flying. This is our first evidence of June emergence of Anax in Canada.

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THE ODONATA OF CANADA AND ALASKA

years (Miinchberg, 1932b), and it is probable that the closely related but more boreal C. shurtleffi of North America takes about the same time, if not longer. We have reared S. kennedyi in three years from eggs that had overwintered, but it is probable that conditions were unfavourable, since the mortality was very high and the single adult obtained was undersized. One libeUulid, Nannothemis bella, the smallest of our fauna, is exceptional in its family in its slow development, Calvert (1929) having reared it in 674 days (August 5,1925 to June 10,1927) and 1,037 days (August 5,1925 to June 7, 1928). Food and Feeding Habits of Nymphs Like the adults, the nymphs of all Odonata are carnivorous and are attracted to their prey by sight. Any moving object, if not too large, is likely to be seized by the prehensile labium. The lateral lobes serve as a pair of tongs and, in those forms that possess raptorial setae, these probably help to prevent the escape of small captive organisms from the concavity of the labial mask. The climbing nymphs, such as most Zygoptera and the Aeshnidae, which lurk in beds of submersed vegetation or rest on the stems of standing aquatic plants, actively pursue their prey. Aeshnid nymphs perceive the movements of animals much smaller than themselves at a distance of several inches, and stalk their prey with stealthy, cat-like motions, stopping whenever the movement ceases, and thus advancing gradually until within striking distance. We have seen Aeshna nymphs in a jar, placed upon a window sill, evidently attracted to the movements of waving white clothes on a line, a hundred or more feet away. We have also known an Aeshna nymph, which we had been feeding for several months, to move to the top of the aquarium and approach us as we entered the room. This nymph seemed to associate our presence with food. Other nymphs, e.g. those that sprawl on the bottom, are much more sluggish and, even when hungry, will make no attempt to strike at their prey until it comes within reach of the extended labium. We found this Behaviour to be particularly marked in nymphs of Somatochlora kennedyi, which we had under observation for several years. Such sprawling nymphs are usually covered with a layer of silt, which renders them very inconspicuous. The burrowing nymphs of the family Gomphidae also wait until their prey is within reach, but they are even better concealed as they burrow slightly beneath the bottom sand or mud, only the upturned end of the abdomen reaching the water for respiration. The Cordulegastridae are somewhat intermediate between sprawlers and burrowers. First-stage nymphs are usually too small to feed on anything larger than ciliates or rotifers. Several workers have used Paramoecium cultures to feed these tiny nymphs. We used a species of Euglena to feed first-instar somatochloras, nothing else being available at the time when they began to hatch.

GENERAL—LIFE HISTORY

51

Small mosquito larvae were used by Lamb (1925) along with Paramoecium, for young Pantala nymphs. Very soon the young nymphs turn to larger animals. Small Crustacea become the chief item on their diet, such as Cyclops, Diaptomus, and other copepods, ostracods, and Cladocera. Daphnia, being easily obtained and cultivated, is perhaps the most useful of all the smaller Crustacea. Larvae of midges (Chironomidae) and other Nematocera and larvae of mayflies (Ephemeroptera) and of Zygoptera are among the organisms most often taken by odonate nymphs, especially the smaller ones. The larger nymphs of Aeshna and Anax will readily attack tadpoles or even small fish. In fact, dragonfly nymphs are well known to fish culturists, since they sometimes consume considerable numbers of fry. Young fish with the yolk-sac still attached are readily preyed upon by dragonfly nymphs. One case came to our notice of nymphs of Leucorrhinia sp. causing some damage to salmon in this stage in a British Columbia hatchery. All dragonfly larvae are cannibalistic, and when rearing them care should be taken to keep them in separate jars. Damselfly nymphs, if kept together, are likely to devour each other's caudal lamellae, and it is particularly necessary to keep them apart, as the caudal lamellae are most important for identification. Emergence of the Adult For some days prior to emergence the dragonfly nymph becomes darker in colour, more sluggish, resting with the anal opening at the surface, and taking no food. If the nymph is examined more closely it will be apparent that the tissues of the labial mask are undergoing histolysis, and within a day or two of emergence nothing is left of the nymphal labium except the shell. The eyes of the developing adult have grown rapidly and can be seen beneath the nymphal cuticle to occupy most of the dorsum of the head. At this time the nymph may sometimes be seen to rest at the surface of the water with the head and part of the thorax exposed. The mesothoracic spiracles have opened and the nymph is breathing through them. The nymph is now almost ready to emerge. Most dragonflies of both suborders climb upon standing aquatic plants a few inches or more above the water and emerge in the upright position. Species of Argia, particularly A. moesta, and most of the Gomphidae, transform on rocks, logs, or tree trunks in either a horizontal or a vertical position. Some species of Gomphus, e.g. G. furcifer and villosipes, scarcely leave the water, the nymphs being supported merely by a tangle of aquatic plants, or the same species may crawl out upon the floating leaf of a spatterdock or water-lily. Many Corduliidae (Macromia, Didymops, Epicordulia, Tetragoneuria) climb upon trunks of trees, boathouses, cottages on lake shores, etc., often to distances of more than fifty feet from the water's edge and six or seven feet from the ground. After securing a firm grip upon the support with the tarsal claws, the nymph remains quiescent for a few minutes while the outer surface is dry-

52

THE ODONATA OF CANADA AND ALASKA

ing, and then the thorax begins to bulge dorsally. Pressure from within is due to the increased bulk of the wing muscles and the great enlargement of the compound eyes, but is augmented by the rhythmical exertions of the insect. A longitudinal split follows, first on the thorax; then running forward, it joins a transverse rent across the dorsum of the head, including the compound eyes; while posteriorly it divides into two, below the wing-bases. The protrusion of the thorax is followed immediately by that of the head; next the legs and wines are withdrawn from their sheaths, the front legs being freed first, then the other legs in succession, and lastly the wings. The head and thorax, now being free, hang backward for some minutes while the new exoskeleton is hardening. Then, suddenly, the insect bends forward and, grasping the support above the exuvia, or the exuvia itself, pulls out the abdomen, As long as the abdomen is within the nymphal cuticle it is soft and somewhat flat, but soon after it has been freed by emergence it has become cylindrical and tense, owing to the pressure of air in the digestive tract, which is generally believed to have been swallowed. Associated with the pressure of air from within is an increase in the pressure and rate of pulsation of the blood, which is rapidly pumped into the wings. These are sometimes fully expanded in half an hour or less. Similarly, the abdomen elongates and becomes more slender. Expansion of the wings may be completed either before or after the abdomen has attained its full length. In other cases the abdomen is well extended before the wings have begun to expand, e.g. in Petalura (Tillyard, 1917). The newly emerged dragonfly is pale yellowish in colour, but acquires its pigmentation rapidly, as described in the section on the adult stage (p. 35). The cast skin or exuvia retains the form of the nymph very well, except for the gaping thorax and divergent wing-sheaths. The long white strands that project from the thoracic opening are the cuticular linings of the large tracheae that open upon the two pairs of thoracic spiracles. Emergence most frequently takes place at night or in the early morning, a habit that may be regarded as an adjustment against the dangers that beset these insects at this stage when they are most helpless. Damselflies, however, may often be seen emerging at later hours. Their smaller size and larger numbers render them individually less conspicuous than the Anisoptera, and they are usually better concealed among the sedges and tall grasses which they frequent. Enemies of Dragonflies Enemies of Adults The most dangerous period for the dragonfly after leaving the water is the period of emergence and the first day or two of flight Dragonflies that emerge on the ground are sometimes attacked and destroyed by ants during the act. Newly emerged dragonflies may be devoured in large numbers by

GENERAL—LIFE HISTORY

53

birds. Calvert (1893) quotes Fisher (U.S. Dept Agric., Div. Ornith. and Mam., Bull. 3, 1893), who records seven species of Falconidae (including Accipitridae, as now understood), as feeding on Odonata in the United States. Six of these are well known also in Canada, namely, the sharpshinned hawk (Accipiter striatus), red-shouldered hawk (Buteo lineatus), broad-winged hawk (Buteo platypterus), duck hawk (Falco peregrinus anatum), pigeon hawk (Falco columbarius), and sparrow hawk (Falco sparverius). Lyon (1915) describes the destruction of hundreds of tenerals of Gomphus on the day of their emergence by sandpipers, grackles, redwing blackbirds, and other birds that frequent the water's edge. Swallows and swifts habitually catch damselflies on the wing, as they sweep over the marshes and borders of streams. Of other birds, the kingbird (Tyrannus tyrannus) is most often seen to watch dragonflies from a perch and, selecting a particular individual, pounce upon it when the opportunity comes. We once saw a kingbird catch a male Gomphus scudderi, a fairly large and stout species. Frogs are possibly even more destructive to dragonflies than birds. Needham and Heywood (1929) instance the finding of Pachydiplax longipennis in the stomachs of six out of 100 Carolina tree-frogs, and Carman (1927) mentions the cricket frog as feeding on damselflies. Among insects, we have already referred to dragonflies themselves as feeding on smaller species of the same order, the large gomphid, Hagenius brevistylus, being a habitual enemy of other dragonflies of smaller size. Even dragonfly nymphs are not exempt from capturing the adults of their own kind, for we once found an ovipositing female of Aeshna eremita, whose submerged abdomen had been seized by a full-grown nymph of its own species. Wasps (Vespidae) occasionally seize and carry away damselflies to their nests, doubtless to be prepared into food for their larvae. Damselflies are also preyed upon by robber flies (Asilidae) and dragonflies of both suborders are frequently caught in spiders' webs. Even the large aeshnas are sometimes ensnared in the webs of large orbweaving spiders. The only insectivorous plants in our territory that capture Odonata are the sundews (Drosera), by whose sticky leaves enallagmas and doubtless other damselflies are sometimes captured. More destructive to dragonflies than any living creatures are adverse weather conditions. As most dragonflies feed only in sunny weather, a prolonged period of dull, cold, or rainy weather may almost wipe out the entire local population of these insects. Severe windstorms may drive them out to sea or over the larger lakes, where they perish and are washed ashore in hundreds or thousands. Enemies of Nymphs The chief enemies of dragonfly nymphs are fish, aquatic birds, and probably frogs and the larger predaceous aquatic insects. Fish are undoubtedly the most important of these. Perch, sunfish, crappie, and other small or medium-sized fish of weedy waters devour large numbers of

54

THE ODONATA OF CANADA AND ALASKA

zygopterous nymphs (Carman, 1917), and sturgeon, pike, speckled trout, and even sometimes suckers often feed on the nymphs of Anisoptera. From stomachs of lake sturgeon we have identified nymphs of Gomphus (three spp.), Aeshna (two spp,), Macromia illinoiensis, and Somatochlora cingulata. The last named has also been taken from pike (Esox lucius) and speckled trout (Salvelinus fontinalis). Aquatic and semi-aquatic birds of five distinct orders are known to feed on dragonfly nymphs and sometimes also on the adults. Much information on this subject may be found in various United States Government bulletins, particularly those of the Department of Agriculture and The Wildlife Research Bulletins of the Bureau of Biological Survey, which are listed in our Bibliography. Because of our necessarily brief treatment of these birds, it will be sufficient to consider them in two groups only: (1) swimmers, and (2) waders and shore birds. Two distinct groups of swimmers, namely grebes and ducks, are known to feed on dragonfly nymphs and sometimes on the adults. A detailed analysis of the food of three species of North American grebes (Wetmore, 1926) shows that all utilize dragonfly nymphs as food, the largest number in proportion to the total food taken being consumed by the pied-billed grebe (Podilymbus podiceps). Among the numerous ducks reported as feeding on dragonflies, the river and pond ducks probably take the heaviest toll of nymphs. The gizzard of one mallard (Anas platyrhynchos) contained no fewer than 100 nymphs of Anisoptera, and two others contained 30 and 40 nymphs, respectively (McAtee, 1918). The black duck (Anas rubripes) and the wood duck (Aix sponsa) also consume a large number of dragonfly nymphs, 2.5 per cent of the wood duck's food consisting of nymphs of both suborders (Mabbott, 1920). Some of the sea or diving ducks also stand high on the list of swimming birds that feed on nymphs. The most noteworthy of these are probably the lesser scaup duck (Ay thy a affinis) and the common golden-eye (Bucephala clangula). Of 1,021 stomachs of the lesser scaup, 126 contained dragonfly nymphs and 26 contained adults (Kubichek, 1933). No less than 11.6 per cent of the food of the golden-eye, consumed in August, consisted of dragonfly nymphs. In the stomach of one individual, collected at Lake Nipigon, we found remains of nymphs of Libellula Julia and Aeshna eremita. Although belonging to the Rallidae, which are not typical swimmers, the American coot (Fulica americana) may be mentioned here in concluding the group of swimming birds. Dragonflies are an important ingredient of its diet, since they make up the second largest percentage of its insect food (Jones, 1940). The deep-wading birds, comprising the herons, bitterns, and ibises, are well known to feed on dragonfly nymphs, although we have no precise data on this group. Most of the shore birds would not be expected, from the

GENERAL—LIFE HISTORY

55

nature of their habitats, to use many dragonfly nymphs as food. In a study of the food of the woodcock, snipe, knot, and two species of dowitchers (Sperry, 1940) only the common (or Wilson's) snipe was found to eat many dragonfly nymphs. Both nymphs and adults of several groups of dragonflies belonging to both suborders were identified in the stomach contents examined. The chief predaceous insects that feed on dragonfly nymphs are the aquatic Hemiptera of the families Belostomatidae and Nepidae, the larvae of the larger diving beetles (Dytiscidae), and, most destructive of all, dragonfly nymphs themselves. According to Tillyard (1917), the nymphs of Zygoptera are the favourite food of the larger Anisoptera, and this is probably true in our territory as elsewhere. Parasites Egg Parasites Hymenopterous egg parasites of Odonata confine their operations to those host species which practise endophytic oviposition. The European parasites, which have been more intensively studied than those of North America, belong to the chalcidoid families Trichogrammidae and Mymaridae. For the following notes we have relied chiefly on Miinchberg (1953), who has given a critical survey of the literature of this subject. He claims that there have been many errors and much confusion in the identification of the species of these parasites. There is apparently only one species of Trichogrammidae in Europe that is known with certainty as an egg parasite of Odonata, namely, Prestwichia solitaria Ruschka. This species infects both Coenagriidae and Aeshnidae. Its specific name refers to the fact that, as a parasite of the small eggs of Coenagriidae, it is solitary in habit, only one of its eggs being inserted in the host egg, but when it oviposits in the relatively large egg of an Aeshna, two or three eggs are introduced. Several species of Anagrus, of the family Mymaridae, have been reported as parasites of dragonfly eggs, but Miinchberg regards it as probable that there is but one species known, A. subfuscus Forst. (=A. incarnatus Haliday). The oft-quoted reference to Polynema natans Lubbock as an egg parasite of Calopteryx (=Agrion as here used) is apparently an error, the parasite referred to being Anagrus subfuscus, and the host not Calopteryx but one of the Coenagriidae. The species of both Anagrus and Polyema are truly aquatic insects, which oviposit under water and swim by means of their wings. Of the odonate parasites of this family, Tillyard (1917) states that the grub hatches within the host egg and feeds upon its contents, which are devoured completely within a few days. Pupation follows and the adult emerges ten or twelve days later. Several North American species of Hymenoptera have been reared from eggs of Lestes and were described by Ashmead (1900). These are the

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THE ODONATA OF CANADA AND ALASKA

following: Centrodea odonatae and Brachista pallida of the family Trichogrammidae, and Hyperteles polynemae and Tetrastichus polynemae of the family Eulophidae. More recently another American egg parasite, Hydrophylax aquivolans, of the family Mymaridae, was described by Matheson and Crosby (1912) from specimens reared from eggs of Ischnura. Parasitism by Water-mites Dragonflies of still waters, especially of eutrophic ponds and lakes, are often observed to carry around egg-like bodies, generally of a red or reddish brown colour, attached to the membranous infoldings of the integument, usually on the underside of the thorax (between the coxae, on the metasternum, etc.) or the sternal region of the abdomen; or, more rarely, on the ventral sides of the wings, along the main longitudinal veins. These bodies represent an immature stage in the life cycle of certain water-mites or Hydracarina. In Europe these mites are well known and, during the last two decades, their life histories have been carefully studied by the German investigator Paul Miinchberg. They belong chiefly to the genus Arrenurus, of which there are at least 24 species in Europe that parasitize Odonata. This genus is world-wide in distribution but in our territory, until recently, has received little attention. Now, however, the taxonomy of the North American species is being actively studied by Dr. Ruth Marshall of Dell, Wisconsin, but their life histories have been scarcely touched. As in Europe, most of our species of Arrenurus that infect Odonata in early summer appear in the parasitic stage attached chiefly to the abdominal sterna of coenagriid damselflies, such as species of Enallagma and Ischnura. Other species parasitize the midsummer dragonflies, e.g. species of Letfes, Sympetrum, and Pachydiplax, and are most often attached to the metapleura and metasternum of their host or the bases of the legs. Dr. Miinchberg (1937, 1952) has contributed much to our knowledge of the life history of A. planus Marshall, a parasite of midsummer dragonflies, e.g. Lestes (L. dryas, disjunctus, and forcipatus) and Sympetrum (rubicundulum and obtrusum). It is the North American representative of A. papttlator of Eurasia. He has also identified the parasitic larval stage of A. americanus var. major Marshall, taken from Ischnura posita, and has described both larval and adult stages of a new species, A. platy-rotundo-cuspidator, which is parasitic on Pachydiplax longipennis. The life history of Arrenurus can be only briefly sketched here. There are three resting stages, each followed by an active stage. Each resting stage is passed within a closed envelope, termed an apoderm. The first apoderm is formed within the egg membrane and encloses the embryo. When this apoderm is cast off, the six-legged larva is set free in the water. It is this larva that settles on a dragonfly nymph and is carried into the air at the time of emergence.

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The larval mite now migrates from the exuvia to the young dragonfly and soon settles on one of the soft infoldings of the body wall, such as the pleural or sternal folds of the thorax or abdomen. Thus begins the parasitic stage, which generally lasts three or four weeks, often longer. During this stage the mite sucks the blood of its host and grows to many times its original size. At the end of this growing period, the longest in the life history, feeding ceases, histolysis of the appendages takes place, and a new apoderm is formed. This is the first pupal stage, known as the nymphochrysalis, and lasts usually from two to ten days. During this time the mite regenerates its appendages and becomes an eight-legged nymph. The nymph breaks through the apoderm and drops or crawls off the dragonfly. It must reach water, however, in order to complete its life history. If successful in being liberated in a pond, it leads an active life for a short time and then settles on some water plant. Here it changes into the second pupal stage or teleiochrysalis, which is essentially like the nymphochrysalis, the new apoderm being formed in the same way. From this third quiescent stage, which is of variable length but usually lasts from five to seven days, the free-swimming adult mite emerges. Its round eggs are deposited in a flat layer, held together by a network of gelatinous strands. Other Parasites Among other parasites of dragonflies, mention may be made of the minute flies of the family Ceratopogonidae that are found on the bases of the wings of dragonflies in some of the warmer parts of the world, such as Liberia and Indonesia. These flies suck blood from the wings, as do some of the mites mentioned above. Although there are flies in our territory of the same family and same habit found on certain species of Chrysopa, Tipulidae, and various moths, they have not been found on any of our Odonata and therefore do not come under our consideration. Internal parasites, such as Sporozoa, Trematoda, Nematoda, and Gordiacea we shall also omit, since our study is not concerned with the internal organs, either anatomically or ecologically.

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PART II

THE ZYGOPTERA OF C A N A D A AND ALASKA

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THE ZYGOPTERA-DAMSELFLIES ABBREVIATIONS

In the keys, descriptions, and measurements that follow, the following abbreviations are used: abd. — abdomen, abdominal n. — northern, northward ant. — antenna ov. — ovipositor apps. — appendages pnx. — postnodal cross-vein caud. lam. — caudal lamella pt. — pterostigma (pi. -mata) d. — dorsal s. — southern, southward e. — eastern, eastward seg. — segment h. f. — hind femur sup. — superior h. w. — hind wing v. — ventral inf. — inferior w. — western, westward lat. — lateral w. hd. — width of head All measurements are in millimetres. Length of abdomen is exclusive of appendages. KEY TO THE S U B O R D E R S OF O D O N A T A

Head compact; eyes never separated by a space greater than their own width, often meeting mid-dorsally; wings held horizontally in repose, the hind wings considerably wider at base than the front wings, with a triangle and supratriangle, and a membranule; males with a single inferior appendage; females with or without an ovipositor; relatively robust and usually larger forms. Nymphs relatively stout, the abdomen never cylindrical but widening from base to middle or beyond; without caudal lamellae, the anus surrounded by three stiff pointed valves, forming the anal pyramid ANISOPTERA

Head transversely elongate; eyes separated by more than their own width, very prominent; wings in repose meeting above the body in the sagittal plane, or only partly expanded, the two pairs nearly alike, the hind wings being no wider at base than the front wings; triangle and supratriangle represented by a quadrangle, which may be crossed or free; membranule absent; male with two inferior appendages; females with a fully developed ovipositor, bearing styli; slender forms, usually relatively small. Nymphs slender, abdomen cylindrical (rarely slightly flattened), not widening behind die base; with three caudal lamellae in place of the anal pyramid ZYGOPTERA 61

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KEY TO THE F A M I L I E S OF Z Y G O P T E R A

ADULTS 1. Wings not petiolate; antenodal veins numerous; quadrangle with several cross-veins. Larger forms with wings partly or wholly darkened or coloured Agriidae Wings petiolate; antenodal veins 2; quadrangle free. Mostly smaller forms with wings hyaline, at most slightly yellowish 2 2. MS separating from Mi-2 nearer the arculus than the nodus; base of Rs (properly the base of the bridge to Rs) arising nearer the arculus than the nodus; between MS and the adjacent primary veins there are short intercalary sectors running to the wing margin; pt. more than twice as long as wide Lestidae MS separating from Mi-2 nearer the nodus than the arculus; base of Rs arising nearer the nodus than the arculus; no intercalary sectors between M3 and the adjacent primary veins; pt. not more, generally less, than twice as long as wide Coenagriidae NYMPHS 1. First antennal segment longer than the others combined; middle lobe of labium deeply cleft; lateral lobes terminating in 3 curved spines; lateral caudal lamellae triquetral Agriidae First antennal segment much shorter than the others combined, mostly shorter than the 3rd; middle lobe of labium with only a small closed cleft or none; lateral lobe not terminating in 3 spines; lateral 2 caudal lamellae flat 2 2. Proximal half, or more, of labial mask narrowed like a stalk; lateral lobe widened distally, with distal margin deeply cut by 2 or 3 incisions, the innermost incision separating a huge end-hook, which is more than half as long as the entire lobe; caudal lamellae with the main tracheal branches parallel, unbranched except toward the margins, leaving the axis at an angle approaching a right angle Lestidae Proximal half of labial mask not greatly narrowed, the margins diverging gradually from the base; lateral lobes not widened distally, with not more than 2 main divisions, exclusive of the movable hook; end-hook small; caudal lamellae with the main tracheal branches (not obscured by pigment) freely branched and leaving the axis at an angle much less than a right angle Coenagriidae D I S T R I B U T I O N OF THE ZYGOPTERA OF CANADA AND ALASKA

The known Zygoptera of Canada and Alaska comprise 51 species, a number that is somewhat less than half the total number known from North America, north of Mexico. These species belong to three families, Agriidae,

PLATE 8

PLATE 8 Canadian Agriidae (males left, females right): TOP PAIR, Agrion maculatum, $ French River, Ontario, $ York Co., Ontario; £ND PAIR, A. aequabfle, $ Waskesiu Lake, Saskatchewan, $ Silver Islet, Lake Superior, Ontario; SRD PAIR, A. amatum, $ Knowlton, Quebec, $ Petitcodiac River, N.B.; BOTTOM PAIR, Hetaerina americana, $ and $ from Credit River, Erindale, Ontario (photograph by Wm. Carrick).

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Lestidae and Coenagriidae, and the 11 genera are distributed as follows: Agriidae 2, Agrion and Hetaerina; Lestidae 1, Lestes; Coenagriidae 8, Argia, Amphiagrion, Chromagrion, Nehalennia, Coenagrion, Enallagma, Ischnura, and Anomalagrion. Of these genera five belong strictly to the New World, and of the latter, three are represented in both North and South America, namely, Hetaerina, Argia, and Anomalagrion; and two are North American only, Amphiagrion and Chromagrion. Of the remaining six genera, three are cosmopolitan, Lestes, Enallagma, and Ischnura, and three are holarctic, Agrion, Nehalennia, and Coenagrion. The American genera occupy only the more southern parts of Canada, being scarcely, if at all, represented north of about lat. 50°N. At the latitude of James Bay, Great Slave Lake, or even Prince Albert, Saskatchewan, and Edmonton, Alberta, the Zygoptera all belong to holarctic and cosmopolitan genera. Most of the 51 species have a wider range in the United States than in Canada. In fact, more than 50 per cent are limited in Canada to the southern parts of the Eastern Provinces, particularly the Lake Erie counties of Ontario, and a few are restricted to southern British Columbia. On the other hand, there is a small number of boreal species, whose main areas of distribution are north of the United States. 'All of these, however, enter some parts of the States, chiefly along the mountains of the 'west. The distributional ranges of the species are imperfectly known, but they may be provisionally grouped as follows: A. Austral or southern species, confined or almost confined, to the Carolinian strip of Ontario, i.e. the Lake Erie counties between the Niagara and St. Glair rivers: 1. Hetaerina americana (Fabr.) 2. Argia apicalis (Say) 3. Argia translata Hagen

4. Argia tibialis (Rambur) 5. Argia sedula (Hagen) 6. Anomalagrion hastatum (Say)

Lestes disjunctus australis Walk, which barely reaches the southernmost border of Ontario, could be included in the group, although the species disjunctus ranges far northward. Nos. 1 and 2 range to the vicinity of Toronto, No. 1 having been once recorded from Montreal.

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B. Restricted eastern species belonging chiefly to the Atlantic Seaboard: 1. Agrion amatum (Hagen) 2. Enallagma minusculum Morse No. 1 ranges westward locally to southern Quebec, north of Vermont No. 2 is restricted in Canada to the Maritime Provinces. C. United States and Canadian provinces east of the Great Plains: 1. Agrion maculatum Beauv. 10. Nehalennia gracilis Morse 2. Lestes eurinus Say 11. Enallagma geminatum Kell. 3. Lestesvigilax Hagen 12. Enallagma exsulans (Hagen) 4. Lestesinequalis Walsh 13. Enallagmaantennatum (Say) 5. LestesrectangularisSay 14. Enallagmaaspersum (Hagen) 6. Argia moesta (Hagen) 15. Enallagma vesperum Calvert 7. Argia violacea (Hagen) 16. Enallagma signatum (Hagen) 8. Chromagrion conditum (Hagen) 17. Ischnuraverticalis (Say) 9. Amphiagrionsanctum (Burm.) 18. Ischnura posita (Hagen) All of the above species are more widely distributed in the United States than in Canada. No. 17 ranges into eastern Manitoba. D. Atlantic to Saskatchewan or foothills of the Rocky Mountains: 1. Agrion aequabile (Say) 4. Enallagma civile (Hagen) 2. Lestes forcipatus Rambur 5. Enallagma hageni (Walsh) 3. Coenagrioninterrogatum (Hagen) No. 1 is transcontinental, but the range is discontinuous and, as far as our territory is concerned, it is unknown west of Saskatchewan. A. aequabile yakima (Hagen) occurs in Washington State but apparently does not reach Canada. No. 3 is strictly boreal and probably belongs to the transcontinental group, but has not been reported west of the Rocky Mountains. No. 4 is widely distributed in the United States and even farther south, but its range in Canada is discontinuous. No. 5 has actually penetrated British Columbia, but is still extremely local there. It is essentially an eastern species, and seems to fit into this group better than any other. E. Transcontinental species: Lestes congener Hagen 6. Coenagrion resolutum (Hagen) Lestes unguiculatus Hagen 7. Enallagma carunculatum Morse Lestes dryas Kirby 8. Enallagma boreale Selys Lestes d. disjunctus Selys 9. Enallagma cyathigerum (Charp.) Nehalennia Irene Hagen 10. Enallagma ebrium (Hagen) Most of these are distributed far northward, Nos. 3, 4, 6, 8, and 9 being essentially boreal. Nos. 3 and 9 are circumpolar.

1. 2. 3. 4. 5.

F. British Columbia and Western States, eastward to Saskatchewan and Manitoba: 1. Amphiagrion abbreviatum (Selys) 2. Enallagmaclausum Morse

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No. 2 ranges sporadically much farther east, having been taken on Lake Nipissing, Ontario, and at Lachine, Quebec. G. Species restricted in Canada to the interior, particularly the Great Plains: 1. Coenagrion angulatum Walk. 3. Ischnura damulaCalvert 2. Enallagma vernale Gloyd This is a somewhat unnatural group. No. 1 is one of the boreal species, ranging northward to Alaska, the Mackenzie District, N.W.T., and extreme northeastern British Columbia. No. 2 is insufficiently known, but occurs from Quebec to Saskatchewan, while No. 3 is found in Canada in Manitoba, Saskatchewan, and northeastern British Columbia, but, south of the Canadian boundary, ranges southward to New Mexico and Nevada. H. Southern British Columbia: 1. Argia vivida Hagen 4. Ischnura perparva Selys 2. Argia emma Kennedy! 5. Ischnura erratica Calvert 3. Ischnura cervula Selys A. vivida and /. cervula both occur at Banff, Alberta, in the vicinity of thermal springs. All are distributed southward at least to California, Nos. 3 and 5 to Lower California and Nos. 1, 3, and 4 to Texas or New Mexico.

FAMILY AGRIIDAE

These are large damselflies, chiefly tropical in distribution and but poorly represented in our territory. They are easily distinguished from other native Zygoptera by the broader wings, which are not petiolate, by the close venation, in which cross-veins are very numerous and there are many secondary sectors alternating with the primary longitudinal veins towards the wing margin. There are also many antenodal veins, instead of two only. The quadrangle is long, narrow, and parallel-sided, and is traversed by many cross-veins. The wings are variously pigmented. The pterothorax has the first lateral or intersegmental suture complete. Body coloration is decidedly metallic. The nymphs develop in streams. They are slender, long-legged, stifflooking creatures, with pentagonal heads, and antennae with the first segment longer than all the others combined, and sometimes considerably longer than the head. The labial mask is not very long, but has the middle lobe considerably produced and deeply cleft, each division bearing a single small dorsal seta. The lateral lobes terminate in three curved and acute processes, the middle one longest and representing the end-hook. Mental and lateral setae are absent. The lateral caudal lamellae are stiff, triquetral, longer and narrower than the middle lamella, which is flat and thin-walled.

PLATE 9 Wings of Zygoptera: 1. Hetaerina americana; 2. Lestes vigflax; 3. Argia apicalis.

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FAMILY AGRIIDAE—KEY TO THE GENERA ADULTS Median space without cross-veins; arculus bent where its sectors arise; sectors of arculus proximally straight; wings without a basal red spot; pt. absent in male, in female white, often divided into several cells; body coloration dark metallic green, with pale markings, if present, very much reduced Agrion Median space with many cross-veins; arculus not bent, its sectors proximally curved, wings of male with large red basal spot, those of female more or less reddish; thorax, legs, and abdomen with extensive pale areas on a dull metallic ground colour; pt. present in both sexes, onecelled Hetaerina NYMPHS Median cleft of the labial mask extending halfway to the base and well beyond the articulation of the lateral lobe; posterolateral angles of abd. segs. 9 and 10 without spines Agrion Median cleft of labial mask extending much less than halfway to the base, not beyond the articulation of the lateral lobe; posterolateral angles of abd. segs. 9 and 10 with small spines Hetaerina Genus Agrion Fabricius The species of this genus are our largest Zygoptera. They all have metallic green bodies, with blue reflections and very few pale markings. The legs are long, slender, and black, with long stiff setae. The wings are broad, and may be wholly dark or the apical parts only dark. Those of the female, especially young individuals, are more lightly and uniformly coloured than in the males, except on the pterostigmata, which are white in the females and absent in the males. The anterior branch of the median vein (Mi- 2 ), on leaving the arculus, curves strongly forward and fuses with R. Our three species are very distinct, yet the superior appendages of the males are so much alike that they do not offer good specific characters. "The nymphs cling to roots and stems swaying in the current. They are long legged, stiff, awkward creatures that move but little from place to place" (Needham and Heywood, 1929). The species of Agrion all develop in streams and, in the teneral stage, do not usually drift very far from the place of their emergence. Young adults may be seen flying over bushes in sunlight or resting on foliage, with

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the wings closed in the vertical plane. The older adults fly along the banks of small streams, with a beautiful dancing flight, like that of the meadowbrown butterflies (Satyridae). As usual with dragonflies, the females are relatively sedentary but are not particularly secretive. They may be seen resting on foliage or branches on the bank of a stream while the males hover in front of them, performing various acts of courtship (see A. maculatum). Oviposition takes place without the accompaniment of the male. Key to the Species of Agrion Adults 1. Wings one-third as broad as long, almost uniformly dark in both sexes, deep brown in mature male, smoky in female, except the white pt, which are nearly half as broad as long, divided irregularly into many cells, and followed for a short distance by more than one row of cells maculatum Wings less than one-third as broad as long, basally clear ( 3 ) or diffusely coloured to beyond the nodus ( 9 ); pt. distinctly less than half as broad as long, composed chiefly of one large cell, but usually with one or more small cells at the ends, and followed by a single row of cells 2 2. Wings about four times as long as broad, in $ nearly hyaline, with the apices of both pairs dark brown; in 9 diffuse brown, more or less deepened apically; pt. two-fifths as broad as long, and more than twice as broad as the cells immediately behind aequabile Wings about four and one-half times as long as broad, in $ nearly hyaline, only the hind wings somewhat darkened apically; those of 9 uniformly pale brownish; pt. small, one-third or one-fourth as broad as long and less than twice as broad as the cells immediately behind amatum Nymphs Length of seg. 1 of antennae (2.8) slightly less than width of head (2.95); hind wing-cases nearly one-third as broad as long maculatum Length of seg. 1 of antenna (3.8) equal to, or greater than, width of head (3.2); hind wing-cases about one-fourth as broad as long or slightly less aequabile Unknown amatum Agrion maculatum Beauvois. (PI. 3, fig. 4; pi. 8, top pair) Agrion maculatum Beauv., Ins. rec. Afr. et Amer., 1805, p. 85. Calopteryx maculata Burm., Handb. Ent, 2: 829,1839.

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Male. Almost uniformly dark metallic green, with blue reflections; thorax without pale markings; abdomen with sterna of segs. 9 and 10, the distal part of 8, and the inferior apps. pale brownish. Wings about three times as long as their greatest width, in mature males either uniformly deep brown or with small basal areas subhyaline. Female. Similar to $, but with abd. segs. 8-10 brownish dorsally as well as ventrally; a pale mid-dorsal yellowish stripe on 9, sometimes obscure; wings dusky, more or less deepened apically in old individuals; the white pt. nearly half as broad as long and divided irregularly into a dozen or more cells; the costal row of cells, distal to pt. divided for a short distance into a double row. Measurements. Total length $ 42-47, $ 41-44; abd. $ 32-36, $33-36; h. w. $ 26-31, $ 30-32; h. f. $ $ 7; width h. w. $ $ 10. Nymph (pi. 6, figs. 1, 4). A slender long-legged nymph with a flat pentagonal head and long antennae, with the 1st seg. long and stiff. Head flat, length about five-sevenths of width; eyes small, lateral, not very prominent; occiput and postocular lobes very short, angles of latter raised into distinct tubercles exceeding the eyes in height. First seg. of antenna shorter than width of head, about equal to its length, and about one-fifth longer than the remaining segments. Prothorax about three-fifths as long as head and three-fifths as long as wide; pterothorax one-fifth wider than prothorax. Wingcases about as long as distance from front of head to base of front wings, each about one-third as wide as long, similar in shape to adult wings. Legs bearing only soft hairs; hind femora extending somewhat beyond hind wing-cases and slightly longer than these. Abd. segs. subcylindrical, with margins nearly parallel but slightly divergent distally; lateral carinae low, gently arcuate, clothed sparsely with soft hairs. Lateral caudal lamellae one-third longer than hind femora and seven times as long as wide, apices bluntly pointed; median lamella decidedly shorter, widest in distal third or fourth, bluntly pointed. Colour light brown, marked with darker brown. Head pale with a dark dorsolateral stripe from base of each antenna to eye, and another from eye to posterolateral angle of head; eyes blackish, antennae uniform brown. Thorax light on dorsum, deepening on sides, with a dark stripe along sides of pronotum. Legs light yellow-brown or orange; femora pale, somewhat darkened at base, and extreme apex with median and anteapical dark annuli, pale between latter and apex; tibiae pale, sometimes slightly darkened at base and apex, with a median dark annulus, not always apparent in preserved specimens. Wing-cases uniform brown, with two laterodorsal longitudinal marks on each side of the intersegmental membrane of segs. 2-6. Caudal lamellae dark brown with a pale crossband about the middle. Total length 31-32; h. w. 5.7-6.0; width h. w. 1.6-2.0; h. f. 7-9; lat. caud. lam. 9-10; seg. 1 of ant. 2.6; pt. 2.0-2.4; width pt. .8-1.0.

Habitat and range. Small streams with intermittent rapids, more or less shaded, mainly a forest species. Florida to Texas, n. to N.S., N.B., n. shore of lower St. Lawrence R. and the Laurentides, Que., to Nipissing and Algoma districts, Ont, the extreme s.e. of Man. and Minn. Distribution in Canada. N.S.-Cape Breton Is., Annapolis, Digby, Halifax, and Pictou counties. N.B.-Carlton, Charlotte, Northumberland, Queens, Sunbury, and Westmoreland counties. Que.—St. Honore, Knowlton, Hemmingford, Covey Hill, Wakefield, and other stations in the Gatineau Valley, n. to Godbout on the n. shore, lower St. Lawrence R., and Nominingue, Labelle Co. Onf.-General throughout s. Ont. from shores of Lakes Erie and Ontario, n. to Muskoka, Parry Sound, Nipissing, and Algoma districts. Man.—Waugh.

PLATE 10 Wings of Zygoptera: 1. Chromagrion conditum; 2. Amphiagrion saucium; 3. Nehalennia irene.

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In Florida this species attains a larger size than in the Middle and Northern States and has been described as a different subspecies, A. maculatum floridanum Huggins. Specimens from Cape Breton Island, N.S., are a little smaller than the average for Ontario, but there appears to be no evidence of a gradual diminution in size northward through the geographical range of the species. Field notes. This is the common black-winged damselfly that flits along our smaller forest streams during the summer months. In southern Ontario, where it is very abundant, emergence begins usually a little before the end of May, reaching a peak early in June. It is still common throughout July, although the numbers are decreasing. A few are found until late in August in such cool habitats as the mouth of a brook or the nearby shore of a lake. The earliest and latest dates on which we have observed adults in Ontario are May 27 and September 10, but we have only two September records of this species, both in the year 1945. The young adults wander from the stream where they emerged, but usually not far, remaining for the most part in sunny glades in the stream valley. Their flight is remarkably like that of the satyrid butterflies and suggests an aerial dance. Where there are alternate rapids and smooth reaches on the stream, they tend to congregate at the rapids. The courtship antics of this insect are varied. According to Williamson (1904) the male possesses a shining white spot at the tip of the abdomen* which it displays by curving the abdomen upward and forward, the fore wings being held motionless, the hind wings fluttering rapidly. We observed a male hovering before a female, which was resting on foliage over a stream. The four wings were spread apart like a cross and vibrating rapidly. The male was within a few inches of the female and, in less than a minute, the male seized the female per collum and copulation ensued. The pair remained on the leaf, the abdomen of the female bending downward, but about half a minute passed before the female finally bent the abdomen forward to engage the genitalia of the male. We also have a motion picture record showing a male in the presence of a female, opening his wings deliberately and then closing them with a snap. This movement was followed by a similar one on the part of the female, which looked like a response. The female of A. maculatum oviposits alone but, as Nevin (1930) observes, "her mate is close at hand to ward off any other suitor. I have noted five of these males at one time each guarding a particular spot along the stream. If his neighbour flies too close to this region a fight results and in nearly every case the encroacher is driven back to his own stronghold." *The pale brownish area on the underside of segs. 9 and 10 and part of 8 and the underside of the inferior appendages.

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The eggs are deposited in almost any kind of plant tissue. Nevin observed many females ovipositing in watercress, others in moneywort (Lysimachia nummularia), in stems of grasses, in moss covering an old wheel under water, and in the side of a decaying log. Martin (1939) found the bur-reed (Sparganium) to be a favourite plant, stating that the eggs "are deposited just beneath the surface of the water in leaves floating horizontally in a brisk current." A female that has oviposited is often recognizable by the muddy tip of her abdomen. Eggs that had been deposited on July 18 hatched in from 26 to 29 days. There are 11 or 12 instars, exclusive of the pronymph, in the development of this species before the adult stage is reached and, in general, the duration of the stadium tends to increase with successive moults. Maturity is reached in one year or less. For further information on the nymphal development the reader is referred to Nevin (1930) and Martin (1939). Agrion aequabile (Say). (PI. 1, figs. 6, 7; pi. 3, figs. 1, 3; pi. 8, 2nd pair) Cdopteryx aequabilis Say, J. Acad. Nat. Sci. Phila., 8: 33,1839. Agrion aequabile Muttk., Cat. Odon. N. Amer., p. 27, 1910. Calopteryx hudsonica Hagen, Proc. Boston Soc. Nat. Hist, 18: 22, 1875. Male. Metallic green with blue reflections. Head dull dark bronze-brown above; labrum metallic green, anteclypeus with a small pale yellow spot; median and proximal parts of labrum aull greyish brown, distal parts snining brown. Pterothorax wholly dark metallic green above; pleura sometimes with parts of ventral margins pale yellowish; legs blackish, the posterior margins of the metacoxae sometimes pale. Wings about four times as long as broad, nearly hyaline, the apices darkened to a variable extent, the darkened area of the hind wings occupying approximately the apical two-fifths, that of the fore wings half or less than half that area. Abdomen wholly dark blue-green above; venter of seg. 1, in mature males, whitish pruinose. Genitalia and venter of seg. 10, with basal parts of inf. apps., light brownish. Female. Labium and basal sees, of antennae pale. Fterothorax as in male, but with the following parts pale yellowish: sterna and margins of pleura, including a streak on lower half of second lateral suture and small spots at upper ends of episterna. Wings diffuse yellow-brown, deepened apically in mature specimens, the extent of the dark areas similar to those of tne male. Ft. somewhat less than one-third as broad as long, composed chiefly of one large cell, but usually with a few small cells at each end, followed by a single row of cells. Abdomen with last three segs. pale yellowish on the sides and with a mid-dorsal pale stripe; ovipositor pale yellowish. Measurements. Total length $ 47.0-51.5, $ 44.5-48.5; abd. $ $ 34-41; h. w. $ 30-36, $ 31-37; width h. w. $ 9 8.9; h. f. 8.0. Nymph (pi. 6, fig. 2). Similar to A. maculatum except in certain dimensions, in general larger. Head flat, three-fourths as long as wide, postocular tubercle less pronounced than in maculatum, not raised above the eye; seg. 1 of antennae equal in length to the width of the head or slightly longer, nearly twice as long as the remaining segments. Labium reaching middle coxae, sides of mentum subparallel in basal half, strongly divergent distally, width about two-thirds of the length, median cleft extending about halfway to base. Prothorax and pterothorax as in maculatwn\ wing-cases about one-fourth as wide as long, similar in shape to adult wings; hind femora extending beyond hind wing-case to a distance equal to about one-fourth the length of the wingcase; legs long and slender; tibiae about one-fifth bnger than femora. Abdomen with

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sides subparallel, slightly divergent on segs. 8-10; margins of segments faintly arcuate, but lateral carinae little developed, with only a sparse fringe of soft hairs. Lateral caudal lamellae similar to those of maculatum but longer; median lamella flat, about threefourths as long as lateral lamellae, all the lamellae bluntly pointed, with rounded apical margins. Colour-pattern similar to that of maculatum, somewhat indistinct in the scanty material at hand, but evidently distinct in live specimens, as seen in photographs of living nymphs (see Martin, pi. 4, fig. 1) and drawings by Kennedy (1915) of the western subspecies yakima, whicn is probably inseparable in the early stages from the typical form. Head and thorax brown above, darkening on the sides as in maculatum; femora pale, with the following parts dark: distal fourth, a submedian annulus, and sometimes a short basal annulus; or the entire femur may be more or less dark, except the pale annulus at the distal third, with the darkest areas bounding the pale annulus. Total length 35-40; h. w. 7; width h. w. 1.6; h. f. 7.0-7.6; lat. caud. lam. 13-15; seg. 1 of ant. 4; pt. 2.0-3.2, width pt. .6-.8.

Variations. The so-called race or subspecies hudsonicum Hagen is merely an example of the tendency of northern species to be more robust in the northern part of their range. The somewhat larger dark apical areas of the wings also parallel the increase in dark pigmentation seen in other boreal Zygoptera. In the Maritime Provinces the dark areas of the two pairs of wings are more nearly equal than in southern Quebec and Ontario, where the dark area of the front wings is generally much smaller than that of the hind wings. Habitat and range. Small to medium-sized streams, averaging larger than those frequented by A. maculatum. The typical subspecies, including hudsonicum Hagen, ranges from N.S. to James Bay, Que., and n. Ont.; w. to Prince Albert Park, Sask., s. to N.J., n. O., n. Ind., and n. 111. The other three subspecies occupy isolated areas of distribution: yakima Hagen, Washington; coloradicum Ckll., Colorado; and californicum Kndy., California. A. aequabile yakima may possibly occur locally in southern British Columbia. Distribution in Canada. N.S.—Annapolis, Kings, Hants, Halifax, and Pictou counties. N.B.—Charlotte, Carlton, York, Sunbury, Kings, and Westmoreland counties. Que.—Covey Hill; Knowlton; Potton Springs; Vaudreuil; Hull; Wakefield and other stations in the Gatineau Valley; Nominingue, Labelle Co.; Laurentides Park and La Ferine, Abitibi Co. On*.—Middlesex, Oxford, Brant, Waterloo, Wellington, Peel, York, Huron, Grey, Dufferin, Simcoe, Hastings, Prince Edward, Frontenac, Leeds, Lanark, Renfrew, and Carlton counties, n. to Nipissing, Cochrane, Thunder Bay, Kenora, and Rainy River districts. Man.—Treesbank, Sandilands, Winnipeg. Sask.—Waskesiu Lake, Prince Albert National Park. Field notes. Although we have not recorded A. aequabile earlier than June 3, individuals taken on that date were fully mature, whereas those of A. maculatum were still teneral. We therefore believe that aequabile emerges somewhat earlier than maculatum. Its seasonal range as actually recorded is June 3 to September 2.

PLATE 11 Wings of Zygoptera: 1. Coenagrion resolutum; 2. Enallagma boreale; 3. Ischnura perparva; 4. Anomalagrion hastatum.

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While often flying with maculatum in the southern part of its range, A. aequabile shows a preference for larger streams than its congener. It is considerably swifter and warier in flight than maculatum. We have not observed the courtship behaviour of this species, except to note, on one occasion, a male in flight, facing a resting female and swinging from side to side in a wide inverted arc. Unfortunately we did not watch this performance long enough to know what followed. As with A. maculatum, the female oviposits unaccompanied by the male and appears indifferent to the males that flutter above her. Like A. maculatum, she prefers Sparganium, but according to Martin (1939) "the eggs are inserted in the submerged parts of the plant, the female descending a foot or more below the surface in quieter parts of the streams, sometimes remaining there for half an hour or more." We can confirm this account, but have watched A. aequabile descend to oviposit in a brisk current. We watched her for about twenty minutes, when she floated to the surface about two yards downstream, and appeared to fly away directly from the water. The incubation period, as determined by Martin, varied from 18 to 29 days. Water temperatures were not taken during this period, except that 27.2 °C. was the highest temperature to which any of die eggs were subjected. The number of instars was 12 or 13, usually 12. The developmental period of the nymph is distinctly longer for A. aequabile than for A. maculatum. Martin's data were not quite complete, but the indications were clear that the nymphal life of aequabile is of two or three years' duration, as compared with one year or less for maculatum. Agrion amatum (Hagen). (PI. 3, fig. 2; pi. 8,3rd pair) Calopteryx amata Hagen, Psyche, 5: 244,1890. Agrion amatum Muttk., Cat. Odon. N. Amer., p. 28,1910. Male. Metallic green with slight blue reflections. Head dark coppery or green; labium, exposed parts of mandibles, labrum, and a median spot on anteclypeus dull light brownish or yellowish; frons with a pale lateral ridge on each side, meeting base of antenna. Pterothorax metallic green, with ventral margins of pleura, especially the metepimera and areas adjacent to the middle and hind coxae, orange-brown. Legs black, the posterior parts of the coxae orange-brown. Wings about four and one-half times as long as wide, slightly stained with brownish, the apices of the hind pair, about halfway to nodus, smoky. Female with abdomen somewhat shorter and stouter than in male. Pterothorax with extensive pale areas adjacent to the meso- and metacoxae, a wider pale ventrolateral margin of the metepimera, and with pale streaks extending dorsad along the pleural sutures and below the ante-alar ridge. Coxae largely pale behind. Wings uniformly dull yellowish brown, the white pt. each consisting mainly of a single cell, about four times

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as long as wide, with one or two small cells often marked off at the ends. Abdomen uniform metallic green above, except on the last two or three segments, where it is brown; 9 and 10 with a pale median line. Sides and venter of segs. 8-10, including ovipositor, pale brownish, Measurements. Total length $ 52-55, 9 49-53; abd. 8 40-41, $ 37.0-41.5; h. w. & 32.5-36.0, $ 37.0-41.5; width h. w. $ 7.5-8.0, $7.8-8.5; h. f. $ $ 8.5-10.0; pt. 1.3-1.7, rarely 2.0; width pt. .4-.5. Nymph. Unknown.

Habitat and range. Clear cold streams, N.B. w. to s. Que. and n. N.Y., s. to Mass., Conn., and N.C. Distribution in Canada. N.B.—Sunbury Co. and stream near Fredericton, St. Margaret's; Petitcodiac River, near Petitcodiac. Que.—Knowlton, South Bolton, St. David de L£vis. Field notes. Little is known of the habits of this species. Some difference in habitat preference between A. amatum and A. aequabile was apparent when we met these two species together on a branch of the Kennebecasis River, N.B., on July 13,1932. We found amatum abundant over a stretch of rapids flowing over small boulders at a rate of about three feet per second, while farther downstream, where the current was slower (one foot per second) and the water deeper, with a coarse sandy or gravelly bottom, A. aequabile was the commoner species. This was a cold stream, too cold for A. maculatum, but on the Rockwell, a warmer stream near Fredericton, we found all three species of Agrion. Here A. amatum was very scarce, the other two abundant. Mr. Harley C. White, who has made a close study of the salmon in the Petitcodiac River, N.B., for many years, recently found adults of A. amatum in the stomachs of young salmon on the upper reaches of the Petitcodiac near its source. Mr. White has sent us a fine series of all three species of Agrion from the Petitcodiac, A. maculatum being the rarest species there, and A. aequabile the commonest. Woodruff (1914) describes the flight of amatum, as compared with those of our other two species of Agrion, as "peculiar, not after the manner of A. maculatum, slowly fluttering in an aimless way among the verdure along the banks, nor even of the more active A. aequabile . . . but suggesting more the hunting tactics of a Gomphine, even to the frequent alighting for rest on the mid-stream stones." On one occasion we saw for a few seconds an aerial duel between males of this species, similar to that mentioned under A. maculatum. Genus Hetaerina Hagen Syn. Calopt, p. 30,1885. Type-ca/a (Drury). Hetaerina is a large genus of stream damselflies, most abundant in central and South America, but represented in the United States by four species, only two of which range north of Texas and Arizona. These are H. ameri-

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cana (Fabr.) and H. titia (Drury), both found as far north as Illinois, Indiana, and Pennsylvania, but only the former reaching Canada. The species of Hetaerina are more slender than those of Agrion and have narrower wings, which are usually clear, with ruby or carmine basal spots in the male and a more diffuse reddish or amber colour in the female. Small simple pterostigmata are present in both sexes. The body coloration is bronzy or coppery, with pale lines and stripes on the thoracic sutures, and pale below. Venational characters other than those given in the key are a strongly slanting arculus, the sectors of which arise behind the middle; the forward curvature of the quadrangle; and the reverse bending of Cu2 near its base. The nymphs are much like those of Agrion, differing in the much shallower cleft of the middle lobe of the labium, which extends proximad only to the level of the articulations of the lateral lobes, and in the presence of short lateral spines or acute angles on abdominal segments 8 and 9. Hetaerina americana (Fabricius). (PI. 6, fig. 10; pi. 8, bottom pair; pi. 9, fig.l) Agrion americanum Fabr., Ent. Syst., Suppl., p. 287,1788. Calopteryx americana Burm., Handb. Ent. 2: 826,1839. Hetaerina americana Hagen, Syn. Galop., p. 30,1853. A large reddish bronze damselfly that flits along the banks of rapid streams, easily distinguished from all other Canadian Zygoptera by the clear wings with bright carmine ( $ ) or amber ( $ ) bases. The possibility of another species (H. titia) in southern Ontario should be kept in mind, and the identity of males of our species should be checked by a comparison of the anal appendages with the figures. Male. Dorsum of head dark reddish brown, with clear red, but not brilliant, reflections. Basal segment of antennae nearly as long as the others together, directed posteriorly; second joint dark, more or less erect, more than half as long as the first. Postclypeus bright coppery, labrum pale reddish yellow, with a small dark median spot, labium pale brownish; rear of head dull dark brown. Prothorax pale laterally and ventrally, where it becomes slightly pruinose; pterothorax dark brown with a metallic red lustre, and with pale yellow lines and stripes on the sutures and pale yellow below. Dorsum and sides above the first lateral suture dark, with pale lines on dorsal carina and humeral sutures (obscure in old specimens); sides and venter yellow, with broad dark stripes on the metepisterna and metepimera; legs dark brown anterodorsally, paler behind; tibiae with extensor surfaces yellowish. Wings reaching middle of seg. 7, their greatest width about 21 per cent of their length, bases of both pairs to about the proximal fourth bright red, elsewhere slightly tinted with brownish; venation beyond the red area dark brown, pt. one-celled, dark brown. Abdomen dull dark brown above, with very little lustre, ventrolateral margins of terga and basal annuli on segs. 3-7 interrupted mid-dorsally and often a pale middorsal line on some of the anterior segments; a spot at the posterior margin and venter of seg. 10, and the anal appendages, yellow or orange. Sup. apps. wide apart at base; inner margins concave at base, with a large convex lobe about the middle, directed

PLATE 12 Thoracic pattern of Lestes9 females: 1. L. eurinus; 2. L. vigilax; 3. L. inequalis; 4. L. congener; 5. L. unguiculatus-, 6. L. dryas; 7. L. d. disjunctus; 8. L. d. australis; 9. L. forcipatus-, 10. L. rectangularis. All figs. X approx. 6.

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mesoventrad, and a small one distal to this; apices slightly expanded, bluntly rounded; inf. apps. mostly hidden in dorsal view, consisting or stout bases, which meet in the middle line in a straight edge, and slender distal processes, slightly incurved and fitting on the underside of the sup. apps. In profile the apps. appear very flat and strictly horizontal. Female. Shorter, with relatively longer wings, the hind wings lacking the bright red basal patches, being generally suffused with reddish brown, which is deepened toward the bases; costal margins of wings dark brown. Head as in male; thorax and abdomen metallic greenish or bronze, without the red lustre; mid-dorsal thoracic carina pale, except in old individuals. Abdomen with mid-dorsal yellow line wider than in male, extending from base to end of seg. 7; 8 and 9 with mid-dorsal spots; black spots on 2-7 much more conspicuous than in male, often elongated below into streaks. Measurements. Total length $ 40-46, $ 38-40; abd. $ 31.0-35.5, 9 29-32; h. w. £25.5-27.5, $ 28.0-29.5; h. f. £5.2-6.0, $ 5-6. Nymph (pi. 6, figs. 3, 5). Head small, pentagonal, about two-thirds as long as broad; irons prominent, clypeus very short and inconspicuous, labrum projecting slightly from behind frons; seg. 1 of antennae about one-fourth longer than the others combined and about equal to the median sagittal length of the head; labium extending back slightly behind the fore coxae; margins of mask subparallel in proximal half, then strongly divergent to the articulations of the lateral lobes; median lobe obtusangularly produced, median cleft reaching only to level of articulation; lateral lobes with first joint terminating in three curved hooks, shorter than the movable hook, the middle hook longest, the mesal shortest. Inner surface of mask with a seta at the base of each bifurcation of the median lobe, and a few setae on the first joint of the lateral lobe, close to the articulation of the movable hook. Prothorax with front margin nearly straight, upturned, hind margin rounded obtusangulate, lateral margin with two angles, the anterior more prominent and upturned; pterothorax stout, the hind wing-cases extending back as far as hind femora, their width about two-ninths of the length; legs long, fore femora not quite as long as width of head, hind tibiae of about same length as hind femora. Abdomen with lateral carinae not distinct on segs. 1 and 2, becoming gradually more prominent on 3-9, on 8 terminating in a blunt angle and on 9 and 10 in a short spine. Lat. apps. near mid-dorsal line, somewhat more than half as long as seg. 10. Ovipositor reaching middle of seg. 10. Lateral caudal lamellae about a third longer than hind wing-cases, their sides subparallel, width two-ninths of length; middle lamella slightly shorter, thin and flat, narrowing somewhat at both ends, bluntly pointed. Brown or greenish, the few specimens before us without distinct markings. Total length 30; h. w. 6; h. f. 5.5; lat. caud. lam. 9; seg. 1 of ant. 2.6.

Habitat and range. Borders of gently flowing streams, flying close to the banks. Calif, and Ariz., N. Mex. and Tex., e. to Fla., n. to Kans., la., and s. Minn., thence e. through s. Wis., s. Mich., s. Ont, s.w. Que. to s. Me. Also Mex. to Guatemala. Needham and Heywood's (1929) citation of "N. A. generally" as the range of this species is grossly inaccurate. Not only is it absent from nearly all of Canada, but also from northwestern U.S. and a part of all of the northernmost tier of states. Distribution in Canada. Qwe.-Montreal. Onf.—Essex, Kent, Lambton,

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Elgin, Middlesex, Oxford, Brant, Haldimand, Perth, Huron, Peel, and York counties. Field notes. The seasonal range of H. americana is long and rather late, our records extending from July 1 to September 24. Although this range appears shorter than in Illinois, namely, June 19 to October 22 (Carman, 1917), this may be only apparent. We have no emergence records, since H. americana is much more local in Ontario, and it is quite probable that it emerges soon after mid-June and we believe that, in occasional seasons, it flies into October. While it frequents the edges of streams with a noticeable flow, it does not actually occur where the banks of the streams are bare. It flits over the ripples as they flow over pebbles and small boulders, where the banks are covered with overhanging vegetation, and especially where there are overhanging willows. The adults wander little from their favourite situation along the banks of the stream. They fly low, chiefly within a foot or two of the water, and more rapidly than Agrion maculatwn. They come to rest upon foliage, a stick, a projecting boulder, or a patch of wet sand. We have not observed the habit of congregating described by Kellicott (1899) of this species in Ohio. The Canadian populations are probably too small to produce even a fraction of the swarms found in many parts of the United States. Kellicott states that "these assemblies commence in the afternoon and do not disperse until the warmth of the following day awakens them to activity. Both sexes assemble and they rest so compactly that I have captured seventy-five by one sweep of the net." Kellicott also describes the process of oviposition of this species as follows: "I have seen the female, unattended by the male, resting on a half-submerged log or alga-laden rock or water-weed, and thrusting the abdomen beneath the water, place her eggs, one by one, in the soft substance."

FAMILY LESTIDAE

In the Lestidae the nodus is at about one-third of the wing length, or a little farther distad; the arculus is about halfway between base and nodus, the sectors of the arculus arising far forward of the middle, separate from their origin; Rs apparently arises from Mi-2 a little distad of M3, but actually is fused with M2 for some distance, then separates from it by way of an oblique vein, its apparent proximal continuation to Mi-2 being a long "bridge"; M4 and distal part of Rs are broken; the quadrangle is relatively narrow, obliquely placed, its distal angle very narrow; the pterostigmata have a strong brace. The first lateral suture of the pterothorax is distinct only toward the wing-bases. The superior appendages of the male are forci-

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pate, as long as segment 10, usually longer, their mesal margins toothed. Nymph: see under Lestes. There is only one genus, Lestes, in our fauna. Genus Lestes Leach These are rather large damselflies, usually elongate, although the females are sometimes of sturdy build; the legs are slender, with the femoral and tibial setae much longer than the spaces that separate them; the wings are moderately narrow, strongly petiolate; the pterostigmata are generally two and a half to three times as long as broad, surmounting two or more cells. Coloration is dorsally metallic green, bronze, or brownish, usually rather dull pale yellowish or greenish below, the pale colour extending along some of the thoracic sutures, but with no pale antehumeral stripes. The colour pattern often becomes obscured in old individuals by pruinosity, especially in the males, in which the rear of the head, most of the thorax, and the base and segments 8 and 9 of the abdomen often become bluish white. The nymphs are long and slender: the mentum of the labium is narrowed proximally into a kind of stalk, its lateral lobes widened distally, with a long, movable hook arising relatively near the base and bearing two or three lateral setae, also one or two setae proximad of movable hook; the distal margin is deeply and irregularly incised, with a very large end-hook, and two smaller hooks with a toothed margin between them; there are usually six or seven mental setae. The abdomen is cylindrical, the more posterior segments having small posterolateral spines. The caudal lamellae are large, without stiff marginal setae or nodus; the tracheae are numerous, close-set, and almost perpendicular to the axis, branched only near the margins, marked with dark brown, usually in several transverse bars or blotches. The species of Lestes frequent still marshy or bog-margined waters, usually ponds or small sheltered lakes. Several of our species develop frequently in temporary waters and probably all have a one-year cycle. They fly rather low over the water and come to rest on emergent vegetation usually within two or three feet of the water, with the body somewhat inclined and the wings half spread. Their flight is not swift and they are generally easily captured. All of the species, so far as known, oviposit in standing aquatic plants, such as Typha, Scirpus, Sparganium, and Eleocharis, or even on willow branches and grass culms. They oviposit, as a rule, well above the waterline, and generally in tandem, although the female sometimes performs alone. Needham (1903) states that the eggs of L. dryas and unguiculatus develop during the first two or three weeks after deposition, almost to the stage of hatching, but then estivate through the remainder of the summer and autumn until the pools are refilled by the late rains "and the stems and leaves, now dead, fall into the water." Eggs gathered in mid-October and placed in a bowl of water in the laboratory hatched within a week.

PLATE 13 Terminal segments (7-10) of Lestes, females: 1. L. eurinus; 2. L. vigilax; 3. L. inequalis; 4. L. congener; 5. L. unguiculatus; 6. L. dryas. All figs. X 9.

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Key to the Species of Lestes Males 1. Inf. apps. less than half as long as sup. apps. Inf. apps. more than half as long as sup. apps.

2 3

2. Thorax metallic green, wings yellowish, length of hind wing 28 mm.; sup. apps, with a toothed prominence near middle of inner margin; postnodal cross-veins rarely less than 13 eurinus Thorax nearly black; wings colourless; length of hind wing less than 25 mm.; sup. apps. without a toothed prominence near middle of inner margin; postnodal cross-veins rarely more than 12 congener 3. Inf. apps. longer than sup. apps., their apices incurved; total length about 50 mm. inequalis Inf. apps. shorter than sup. apps., their apices not incurved; total length usually less than 50 mm. 4 4. Inf. apps. sigmoid, with divergent apices Inf. apps. not sigmoid, nor with divergent apices

unguiculatus 5

5. Sup. apps. meeting at an acute angle, their inner margins with only one tooth, near the base; inf. apps. straight and linear; postnodal crossveins of either wing generally 15-17 vigilax Sup. apps. meeting at an obtuse angle or an arc, their inner margins with two teeth, a basal and an ante-apical; postnodals of either wing generally fewer than 15 6 6. Abdomen very long and slender, the hind wings less than two-thirds of its length, including apps.; inf. apps. sharply decurved rectangularis Abdomen of moderate length, stouter; hind wing about two-thirds of its length, including apps.; inf. apps. not decurved 7 7. Thorax above metallic green, pale humeral stripe extremely narrow or, in fully mature individuals, absent; inf. apps. broadly expanded distally dryas Thorax above dull bronze to brownish or blackish, becoming more or less pruinose; inf. apps. slender and straight, scarcely expanded distally 8 8. Abd. seg. 2 three-fifths as long as seg. 3; anterior lamina more than 2.5 mm. long, about 2.5 times as long as abd. sternum 1; white shieldshaped cavity on vesicle of penis widest at front margin; median

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V-shaped incision on seg. 10 more than one-third the width of the segment at hind margin; distal tooth of sup. apps. much smaller than proximal tooth, nearly always blunt forcipatus Abd. seg. 2 half as long as seg. 3; anterior lamina less than 1.5 mm. long, about twice as long as abd. sternum 1; white shield-shaped cavity on vesicle of penis widest behind or at the middle; median V-shaped incision of seg. 10 one-third or less of the segment width; distal tooth of sup. apps. variable (in our territory nearly always acute and almost as large as the proximal tooth) disjunctus Females 1. Wings flavescent; posterolateral margins of basal plate of ovipositor rounded; large species (abd. 35, h. w. 32) eurinus Wings colourless; posterolateral margins of basal plate of ovipositor angulate, the angle generally produced into an acute process; mostly smaller species 2 2. Ovipositor shorter than abd. seg. 7, the valves usually not reaching as far back as the extreme end of the abdomen Ovipositor as long as abd. seg. 7, the valves reaching as far back as the extreme end of the abdomen 8 3. General form elongate (abd. 30-38); abd. seg. 7 twice as long as ovipositor or nearly so 4 Shorter species (abd. 25-27); abd. seg. 7 distinctly less than twice as long as ovipositor 6 4. Hind wing 22-24 mm.; postnodals of fore wings usually 11-12; dorsum of thorax dark brown, scarcely metallic; median carina and humeral stripes grey, the latter more than half as wide as the dark mesepisternal area; extensor surfaces of tibiae pale yellow rectangularis Hind wing 24-29; postnodals of fore wing usually 15-16; dorsum of thorax metallic green; median carina and humeral stripes reddish or yellowish 5 5. Humeral stripe one-third to more than one-half as wide as the metallic area on each side of the median carina, reddish brown; tibiae dark brown; hind wing 24-26 vigilax Humeral stripe linear, less than one-fourth as wide as the metallic area on each side of the median carina, yellowish; extensor surfaces of tibiae yellow; hind wing 27-29 inequalis 6. Dorsum of thorax and abdomen dark brown, with a dull metallic lustre; humeral stripe pale yellowish, linear; a dark spot above and below the metapleural carina congener

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Dorsum of thorax and abdomen paler bronze-brown, pale humeral stripe one-third to one-half as broad as the dark area on each side of median carina, dull yellow; without a black spot above and below the metapleural carina 7 7. Length of abd. segs. 8-10 (with paraprocts) 2 mm.; seg. 9, measured mid-dorsally, slightly less than half as long as seg. 7; ovipositor 2 mm.; dark areas of abdomen bronzy disjunctus Length of abd. segs. 8-10 (with paraprocts) 2.75 mm.; seg. 9 barely more than half as long as seg. 7; ovipositor 2.5 mm.; dark areas of abdomen greenish unguiculatus 8. Dorsum of thorax and abdomen metallic green; humeral stripe clear yellow, linear, much narrower than mesepisternal dark area dryas Dorsum of thorax and abdomen dull bronze-brown, humeral stripe dull yellowish, its greatest width half that of the mesepisternal dark area forcipatus Nymphs 1. Lateral spines present on abd. segs. 4 or 5 to 9; median caudal lamella with dorsal margin arcuate, ventral margin more or less sinuate; all lamellae tapering distally 2 Lateral spines present on abd. segs. 2 or 3 to 9; caudal lamellae with margins nearly straight and parallel throughout most of their length vigilax 2. Labial mask with proximal part very slender, its least width being not more than one-fifth that of the expanded part at the distal margin; lateral setae normally 3 3 Labial mask with proximal part relatively stout, its least width being about one-third that of the expanded distal parts; lateral setae 4 or 5 congener 3. Slender proximal part of labial mask at least twice as long as expanded distal part 4 Slender proximal part of labial mask 1.5 times as long as distal part 6 4. Length, including caudal lamellae, less than 30 mm.; outer wing-pad less than 6 mm.; hind femur 5 or less; ovipositor reaching end of seg. 10 or beyond 5 Length, including caudal lamellae, about 35 mm., outer wing-pad 6.8; hind femur 6; ovipositor not reaching hind margin of seg. 10 eurinus 5. Ovipositor 3 mm. long, or more, reaching basal suture of lateral caudal lamellae dryas Ovipositor 2 mm. long, not reaching as far back as basal suture of lateral lamellae disjunctus

PLATE 14 FIGS. 1-3. Terminal segments (7-10) of Lestes, females: 1. L. d. disjunctus; 2. L. forcipatus; 3. L. rectangularis. FIGS. 4-10. Terminal segments (8-10) of Lestes nymphs: 4. L. eurinus; 5. L. congener; 6. L. unguiculatus; 7. L. d. disjunctus; 8. L. dryas; 9. L. rectangularis; 10. L. vigtiax. All figs, x 9.

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6. End-hook of lateral lobes of labium about three times as long as its middle width; venter of abdomen without a median row of black spots; caudal lamellae indistinctly banded, only the margins showing alternate dark and pale markings, apices bluntly pointed unguiculatus End-hook of lateral lobes of labium about four times as long as its middle width; venter of abdomen with a median row of black spots; caudal lamellae rather conspicuously banded, their apices more rounded rectangularis Unknown

forcipatus and inequalis

Lestes eurinus Say. (PL 12, fig. 1; pi. 13, fig. 1; pi. 22, fig. 1) Lestes eurinus Say, J. Acad. Nat. Sci. Phila., 8: 36, 1839. A large, sturdy species with yellowish wings, the general colour in the adult dark metallic green with a whitish pruinescence; the thorax in the teneral stage with median and lateral longitudinal stripes, orange-brown. Male. Dark metallic green, the thorax, first and last 2 or 3 segs. of the abdomen becoming somewhat whitish pruinose with age. Head above black, pruinose behind the ocelli; genae, anteclypeus, labrum, and exposed surfaces of mandibles pale greenish, labrum pale yellow; rear of head black. Median carina of thorax and ante-alar ridges black; humeral suture without a pale line; lower parts of pleura with the yellow area more or less subdivided by dark streaks and blotches, the principal dark areas being a streak extending to mesocoxae and a blotch on the metepimera. Abdomen with sides of segs. 2-7 pale yellowish, including interrupted basal annuli. Legs yellow and black; coxae yellow, femora streaked with black and yellow, tibiae black with extensor surfaces yellow, tarsi black. Wings a little more than three-fourths as long as the abdomen, lightly stained with yellow; pt. dark brown. Sup. apps. longer than seg. 10, strongly bowed, apices broad and expanded, meeting at nearly a right angle; mesal margins with a proximal tooth and a blunt spiny process near the middle; inf. apps. less than half the length of the sup. apps., each with an angular incision on the mesal margin. Female. Wings slightly longer than in male, abdomen shorter, the wings being about four-fifths the length of the abdomen. Seg. 8 a little more than half as long as 7, hind margin very oblique; seg. 9 slightly longer than 8, somewhat tumid above dorsum of 10, prominent apically; ovipositor about two-thirds as long as seg. 7, the valves barely or not quite reaching the end of seg. 10, rather finely toothed. Postnodal cross-veins, f. w. $ 12-17, $ .14; h. w. $ 12-17, 9 12-14. Measurements. Total length $ 50, $ 46; abd. £37-38, $ 34-35; h. w. $ 29-30, $ 30; pt. 2.5-2.8; w. hd. 6. Nymph (pi. 14, fig. 4; pi. 36, fig. 1; pi. 38, fig. 1). Very large, pale green to light brown, with little pattern. Head twice as wide as long, of die usual Lestes form; postocular lobes almost devoid of setae; length of antennae four-fifths of the head width;

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relative lengths of antennal segs., 15:28:58:36:26:18:14; labium very long, extending to apices of metacoxae, the slender proximal part comprising about three-fourths of the total length; apical width about equal to one-third of the total length; mental setae 7, rarely 6 or 8, the innermost one often very small; marginal labial setae 10-12; lateral setae 3 (2 on movable hook). Wing-cases generally reaching base of seg. 4, sometimes not quite to end of 3; the hind femora extending about the same distance. Abdomen subcylindrical, with terga and sterna smooth, thinly clothed with minute setae; with moderate lateral carinae, on segs. 2-9 bearing 8-15 low serrations; seg. 10 with a comb of rather small posterolateral spines. Dorsum of head with an ill-defined, dark transverse, interocular stripe; antennae with segs. 1 and 2 slightly darker than the others. Femora with ante-apical dusky annuli, their extreme tips and those of the tibiae darkened; first tarsal segment, tip of second, and distal halt of third also darkened; longitudinal veins of wing-cases delicately marked with brown. Abdomen with dorsum slightly darker than venter, with a mid-dorsal pale line; intersegmental annuli darkened mesally, with pale longitudinal lines and a dark lateral spot on each side, near the lateral spine. Caudal lamellae light brown, axis very dark, and tracheae less conspicuously darkened; with two more or less distinct cross-bars, one in basal third and the other at about three-fourths of the length, apex also somewhat darkened. Total length 34.5-38.0; h. w. 6.0-6.7; h. f. 6.2-6.5; caud. lam. 10.6-11.3; labium 5.5-6.5; ant. 4.5-5.0.

Habitat and range. Small lakes and ponds. N.E. States, N.Y. and Pa., w. through s. Que., s. Ont., and Mich, to Wis., and s. to N.J., O., Ind., la., and Mo.; everywhere local. Distribution in Canada. Extremely local, having been reported only from Nominingue, Labelle Co., Que.; Snelgrove, Peel Co.; Lake of Bays, Muskoka Dist., and Algonquin Park, Ont. Field notes. Although rare, this large Lestes seems to occur in a wide variety of habitats. Needham (1903) found it common at Saranac Inn, N.Y., about the edges of all sphagnum-bordered pools. McDunnough (1921) took it in the Lake of Bays district, Ontario, at a small forest pond near the roadside. This pond was not at all of the bog-margined type but had a firm bottom. The next Canadian record was from the vicinity of Nominingue, Labelle Co., Quebec. Here on July 8, 1936, Fr. Adrien Robert (1938) took a pair at Lac Lafleche, a small spring-fed lake with sandy shores and a rich aquatic vegetation. He saw another female on July 10, but it was evidently not common. When we finally discovered L. eurinus after more than forty years collecting, it was at one of the many small ponds near Snelgrove, Ontario, in the morainic district east of the village. We first found eurinus emerging here on May 27, 1944. This pond is evidently not a normal habitat for L. eurinus, being a temporary one, shallow and trampled by cattle. We found eurinus here only in 1944, but in 1951 we found it at another pond in the vicinity which, although in an open pasture like the first pond and frequented by cattle, is too deep to be trampled except at the edge, and has a considerable stand of Typha along the margin. Here we found eurinus emerging on May 28, 1951; and on June 17 adults were present, chiefly in the cat-tail patch.

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In 1952 we made several visits to the same pond, both before and after emergence of L. eurinus. On June 28 we found a fair number of these Lestes at the pond, but there were few among the cat-tails, a larger number being on the opposite side of the pond which was the sunnier side. We saw as many pairs as single individuals but, since they flew out towards the middle of the pond, they were not easy to catch. We saw two pairs oviposit, or attempt to do so, on short rushes that projected only a few inches above the water, and one of these pairs alighted on a water-lily leaf, the female thrusting her abdomen under water around the edge of the leaf. On the same afternoon we made a short examination of Gordon Lake, a small lake surrounded by dense woods and only a few minutes walk from the pond. This lake is an old familiar spot and we expected little of it. But almost immediately we found that Lestes eurinus was here too. In fact this lake appeared to be the centre of the population. In a few minutes we had two pairs and one more of each sex, in spite of our extremely precarious position on the boggy margin. The interesting fact, however, was that the insects were ovipositing in typical Lestes fashion in Typha, two to three feet above the water. We took a single female ovipositing and two pairs. We saw others beyond reach. Our days for emergence were May 27,1944, and May 28, 1951. Needham's (1903) dates for emergence were June 12 at Lake Forest, Illinois, and June 20 at Saranac Inn, in the Adirondacks, N.Y. We observed couples in tandem June 17 to June 28 and ovipositing on June 28 only. Lestes vigilax Hagen. (PI. 9, fig. 2; pi. 12, fig. 2; pi. 13, fig. 2; pi. 22, fig. 2) Lestes vigilax Hagen, Bull. Acad. Belg., (2), 13: 306, 1862. A long, slender, dark metallic species, with inconspicuous pale markings, flying chiefly in the second half of summer. Male. Dark metallic green to nearly black, with a lustre that is fairly bright in the young adult, but becomes obscured on the thorax and terminal abdominal segments by a greyish bloom. Mouth-parts and genae pale yellow to greenish; rear of head black, becoming dusky greyish. Pterothorax in juveniles showing three orange-brown bands, median and dorsolateral, which become reduced with age to fine lines or disappear. Sterna and lower parts of pleura pale fawn or yellowish in juveniles, later obscured by heavy bluish pruinosity, which extends to the pronotum, sclerites at bases of wings, and coxae. Legs dark brown to black, coxae at first yellowish. Abdomen dark metallic green above, with narrow basal annuli and venter dull ochraceous. Segs. 1, 9, and 10 becoming bluish to grey-pruinose above; 8 also more or less dulled; anal apps. black. Abdomen long and slender, narrowest from segs. 3—5, expanding on 8. Hind wing about five-ninths as long as abdomen, pt. short, yellow to brown. Sup. apps. meeting at a somewhat acute angle, with a rather blunt basal tooth and two other prominences on the mesal margin, apices somewhat dilated. Inf. apps. about three-fourths as long as sup. apps., nearly straight, extremely slender. Female. Similar to male, but with a slightly shorter and stouter abdomen, the wings a little longer, about three-fourths as long as abdomen. Similar in colour to male, but not becoming pruinose. Mid-dorsal and humeral pale bands variable in width but

PLATE 15 Colour-pattern of Argta, females, lateral view: 1. A. moesta; 2. A. apicalis; 3. A. translate, 4. A. tibialis; 5. A. violacea; 6. A. vivida; 7. A. emma. All figs. X 3.

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becoming linear in old individuals. Abdomen green to bronze-green, the pale venter and basal annuli sometimes very inconspicuous. Pt. paler than in male. Ovipositor reaching end of 10th sternum but not end of abdomen; seg. 8 half as long as 7; seg. 9 three-fourths as long as 8, or very nearly. Postnodal cross-veins, f. w. £ $ 13-17; h. w. $ 11-14, $ 12-16. Measurements. Total length $ 45.5-47.0, $ 42.0-44.5; abd. £37.0-38.5, $ 32-34; h. w. £24-25, $ 24-26; pt. 2.25; w. hd. $ $5.2. Nymph (pi. 14, fig. 10; pi. 36, fig. 4; pi. 38, fig. 3). Head nearly one-half as long as wide; postocular lobes almost devoid of setae; antennae long, their length about eightninths of head width, relative length of segs., 20:28:37:30:23:18:12. Labium extending to middle of mesocoxae or nearly to metacoxae, length of slender proximal part of mentum nearly two-thirds of total length, its minimal width one-sixth of the width at distal margin; mental setae 5; marginal labial setae very few (2-3) or absent; lateral setae 3, one on movable hook. Wing-cases extending to about basal fourth of seg. 4, the outer pair barely beyond apices of hind femora. Abd. segs. with numerous setae, dorsal and ventral, and a close-set comb of stout setae along the posterodorsal margin of 10, abdominal carinae of average prominence, with low setigerous serrations; seg. 1 with 6 setae, 2 to 9 with 6-8 setae each, 3 to 9 with slender lateral spines; ovipositor not quite reaching hind margin of 10th sternum. Caudal lamellae twice as long as hind femora, nearly parallel-sided, apices bluntly rounded, but with a slight point at the extreme tip; width of median lamella nearly one-fifth of its length, or lateral lamellae about one-seventh of their length. Light brown to green with little pattern; femora pale, with an ill-defined ante-apical dusky annulus; tips of tibiae and distal half of third tarsal segment dark; longitudinal veins of wing-cases slightly darkened. Abdomen almost uniform, but with a fine middorsal pale line; intersegmental areas appearing darker in exuvia, with a few paler longitudinal streaks. Caudal lamellae pale, with axis darker and three dark cross-bars, one at about the proximal third, the second slightly beyond the middle, and a third at about the apical fourth; apices clear. Total length 30.3; h. w. 5.4; h. f. 5.0; caud. lam. 10.2; ov. 2. Carman gives the length as 21-30 and that of the caud. lam. as 13.

Habitat and range. Marshy or bog-margined lakes, usually abundant where it occurs. Fla. and Ala. to Tenn. and la., n. to N.S., Me., s.w. Que., s. Ont., Mich., and Minn. Distribution in Canada. N.S.—South Milford, Annapolis Co. Que.—Ottawa Valley; Hull, Fairy Lake, and Gatineau Valley. Ont.—Locally in s. Ont., Essex, Lambton, Middlesex, York, Simcoe and Carlton counties, n. to Muskoka, Manitoulin, and Nipissing districts. Field notes. L. vigilax was formerly very abundant at Grenadier Pond, High Park, Toronto. This is not a pond, but a small lake with a spring-fed inlet and an outlet into Lake Ontario. It was formerly the habitat of many species of Odonata but, being now virtually enclosed by the city, it is polluted and nearly stagnant, and the rarer and more interesting dragonflies have disappeared, among them L. vigttax.

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In the numerous bog-margined ponds and small lakes in the vicinity of Go Home Bay, Georgian Bay, Ontario, we found vigilax in abundance. In its general distribution, however, it is far from being a common species in Canada, but becomes more general south of our border. Its size is comparable to that which it attains in the northern United States, but Florida specimens are much larger. Byers' (1930) measurements give an over-all length of 51-53 mm. for Florida material, which is slightly beyond that of our longest species, L. inequalis. The season of flight of L. vigilax, as recorded in Ontario, is June 16 to August 27. It is, however, undoubtedly somewhat longer than this. The few records from Quebec and Nova Scotia fall within this range. Lestes inequalis Walsh. (PL 12, fig. 3; pi. 13, fig. 3; pi. 22, fig. 3) Lestes inequalis Walsh, Proc. Acad. Nat. Sci. Phila., p. 385, 1862. A large, elongate species of metallic green coloration, which flies early in the season, chiefly in June and July. Male. Dark metallic green above, including head and pronotum, almost without dorsal markings; ventral regions mostly pale yellow, except in old individuals, in which the following parts become more or less bluish or greyish pruinose: rear of head, thoracic sterna, and lower parts of pleura, sclerites at bases of wings, and dorsa of abd. segs. 1, 9, and 10. Mouth-parts and cenae light greenish yellow, anteclypeus darker greenish, postclypeus black, rear of head dull ochraceous. Dorsum of thorax in tenerals with a fine fine on the mid-carina and on humeral sutures orange-brown. Thoracic sterna, lower parts of pleura, and coxae light yellow, the yellow area of the thorax separated from the dark area above by a line that is only slightly wavy. Femora black, streaked with light yellow; tibiae black, with extensor surfaces yellow; tarsi black; wings colourless, pt. dark brown. Abdomen with lower halves of segs. yellow, the basal annuli reduced, distinct only on the sides; apps. black. Abdomen long, somewhat stouter than in vigilax, widening slightly on seg. 7, more rapidly on 8; hind wing about two-thirds as long as abdomen. Sup. apps. meeting almost in an arc, their outer margins with rather coarse spines in distal half, inner margins with a strong proximal tooth, followed by a spinose edge which terminates distally in a small blunt tooth; inf. apps. slightly longer than sup. apps., stout at base but narrowing distally, their apices sharply hooked mesad so that they meet or overlap. Female. Coloration similar to that of male, except that the median thoracic carina and the humeral sutures are marked with distinct though very narrow yellow streaks. In tenerals there are broad median and humeral orange-brown bands, as in L. eurinus and vigilax. Similar to male in linear proportions, abdomen stouter; ovipositor reaching end of 10th sternum, but not end of abdomen; seg. 9 three-fourths as long as 8; seg. 8 slightly more than half as long as 7. Postnodal cross-veins, f. w. 8 13-19, $ 14-18; h. w. $ 14-18, $ 12-16. Measurements. Total length $ 46-50, $ 47.5-48.5; abd. $ 36-39, $ 37-38; h. w. 8 25-28, 9 27-29; h. f. 89 6.7; pt. 1.6-2.1; w. hd. 5.2-5.6. Nymph. Unknown.

Habitat and range. Marshy lagoons, permanent ponds, slow streams, and bog-margined lakes. Me. to w. Ont. and Minn., s. to N.C., Tenn., and Okla.

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Distribution in Canada. Que.-Hull and Fairy Lake, Ottawa Co. Ont.— Essex, Kent, York, Victoria, Prince Edward, Simcoe, Hastings, Carlton, and Renfrew counties; Muskoka and southern part of Kenora districts. Field notes. This large, striking species is more generally distributed in Ontario than L. vigilax but is always found in small numbers. It flies over open water more frequently than do our other species of Lestes except L. eurinus, and is therefore not so easy to capture. It is an early species, our dates of collection ranging from May 30 to August 8, but only two specimens have been taken in August. We have observed nothing of its habits of mating, nor oviposition. Lestes congener Hagen. (PI. 7, fig. 1; pi. 12, fig. 4; pi. 13, fig. 4; pi. 22, fig. 4) Lestes congener Hagen, Syn. Neur. N. Amer., p. 67, 1861. A very dark species of rather small to medium size, flying late in the season. Male. Nearly black above, with a dull bronze lustre; last two segs. of the abdomen becoming greyish. Mouth-parts pale yellowish, rear of head pale above, dark below, the dark area becoming whitish pruinose with age. Median carina of thorax and antealar ridges dull yellowish; humeral stripe yellowish, narrow, and constricted behind the middle to a fine line. Thorax below the dark area yellow, with a dark spot on mesinfraepisternum, and two dark spots on metapleura; metasternum with dark lateral streaks, pale areas and areas at bases of wings becoming whitish pruinose with age; coxae, femora, and tibiae pale, streaked lengthwise with black; tarsi black. Wings hyaline, their length five-sevenths that of the abdomen; pt. dark brown, nearly black. Abdomen with pale yellow basal annuli on segs. 3-7, the dark dorsal areas expanding on the sides in the posterior fourth, ventral half of segs. yellowish, dorsum of segs. 1 or 1 and 2 becoming whitish pruinose; segs. 9 and 10 and rear part of 8 greyish blue with age. Anal apps. black, sup. apps. meeting in an arc, their outer margins armed with a variable number of short spines; their inner margins with a row of fine, close-set spines and a small sub-basal tooth; inf. apps. about half as long as sup. apps., their apices bent inwards. Female. Similar in colour to male, but not quite so dark, humeral thoracic stripe and median carina more clearly marked, pale basal annuli of abdomen wider; pruinosity restricted to sides and venter of pterothorax, and areas around bases of wings. Wings relatively longer than in male, about four-fifths as long as abdomen; pt. brown. Postnodal cross-veins, f. w. $ 9, $ 10-12 (15); h. w. $ $ 8-11. Measurements. Eastern: total length $ 34-36, $ 32-34; abd. $ 26-29, 9 25.5-28.0; h. w. $ 19-21, $ 18.5-23.0; w. hd. $ $ 4.5; pt. $ 1.5-1.6, $ 1.5-2.0. Western (B.C.): total length 3 38-42, $ 39; abd. $ 29.0-33.5, $ 30; h. w. $ 21.0-23.5, $ 25. Nymph (pi. 14, fig. 5; pi. 36, fig. 6; pi. 38, fig. 2). Antennae about one-fourth longer than median length of head; relative length of segs., 13:23:31:22:15:12:8; labium extending to bases of hind coxae, narrowest about the middle, the width here being about one-third of the distal width; mental setae 6 or 7; lateral setae 4 or 5. Lateral carinae of abd. segs., particularly 7-9, with minute setae; lat. apps. of male about as long as seg. 10; ovipositor extending slightly beyond the hind margin of 10. Median lamella very slightly shorter than lateral lamella, its dorsal margin arcuate, especially in basal third, ventral margin slightly sinuate; greatest width in basal fourth slightly more

PLATE 16 Colour-pattern of Argia and Amphiagrion, lateral view: 1. Argia sedula $; 2. A. sedula 9; 3. Amphiagrion abbreviatum $; 4. A. abbreviatum 9; 5. A. saucium #; 6. A. saucium 9. All figs. X 3.8.

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than one-fourth of the length; lateral lamellae slightly narrower, ventral margin somewhat convex in basal fourth, dorsal margin nearly straight, except towards the ends, apices bluntly pointed with curved margins. Light brown, varied with bone yellow and dark brown. Head brown above, with pale streaks behind the antennae; a large spot between them and in front of the median ocellus, smaller pale spots on sides of lateral ocelli; antennae pale, with dorsal surfaces of segs. 1-3 darker; postocular lobes brown, sometimes streaked with pale yellow; rear and venter of head, with labium, pale. Prothorax brown, darkened along hind margin; pterothorax dark along mid-dorsal carina and wing-bases, paler on the sides; coxae and distal margins of trochanters darkened; femora with longitudinal carinae, apices, and an ante-apical annulus dark brown; tibiae pale, with carinae and apices somewhat darker; tarsi with third joint dark on apical half; wing-pads pale or smoky with the longitudinal veins darker. Abdomen brown, variegated with darker brown and pale yellow; most of the segs. with dark brown mid-dorsal and lateral spots at the hind margin, the dorsal spots divided by a continuous median pale line. Lateral carinae mostly pale yellow, with a dark edge on segs. 1-3, venter pale; ovipositor pale; caudal lamellae light yellowish, with bases and three cross-bands dark brown. Total length 22.0-26.5; h. w. 4.5-5.0; h. f. 4.0-5.5; caud. lam. 8.3-9.0; lab. mask 2.8-3.0.

Habitat and range. Permanent and semi-permanent ponds or pond-like expansions of slow streams. N.S. to n. Ont, s. Mackenzie Dist., N.W.T., and B.C., s. to N.J., O., Ind., Mo., N. Mex., and Calif. Distribution in Canada. N.S.-Annapolis Co. P.EJ.-Souris. N.B.-St Andrews, Charlotte Co. Que.—Island of Orleans, St. Chrysostom, and Gatineau Valley, Ottawa Co. Ont.—Welland, Peel, York, Ontario, Carleton, Simcoe, and Renfrew counties; Muskoka, Parry Sound, Nipissing, Algoma, Thunder Bay, and Kenora districts; northernmost station Attawapiskat Lake (52° N.). Man.—Treesbank, Westbourne. Sask.—Hamton, Kinley, Prince Albert, Polworth, Jackfish Lake. Alta.—Red Deer; "general in southern Alberta" (Whitehouse). B.C.—General throughout the southern half of the province; representative stations: Sooke and Wellington, Vane. Is., Hope, Harrison Bay, Similkameen, Princeton, Aspen Grove, Kamloops, Osoyoos, Vaseaux Lake, Okanagan Landing, Salmon Arm, Nelson, Revelstoke, Invermere, Briscoe, Golden, Prince George. N.W.T.—Great Slave Lake, Mackenzie Dist. Field notes. This is the latest of all our species of Lestes to reach the adult stage. The published records from Ontario give a seasonal range from August 9 to October 13, barring a single record of July 18 (Walker, 1950), and emergence or teneral records from British Columbia are chiefly in August: Nanaimo District, Vancouver Island, August 7-13 (Walker, 1927); Golden, August 14, and Tete Jaune, August 10 (Whitehouse, 1941). Whitehouse also records a teneral from Sooke taken on June 13, which he regarded as premature, but gives the flight period for British Columbia as July 10 to

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November 10. In eastern Canada L. congener is rarely seen before August, but in 1953 we found it emerging on June 27 from a pond near Snelgrove, Ontario, and again on July 4 from another pond near Aurora, Ontario. Although in both cases the insects were emerging in numbers, such occurrences must be regarded as exceptional. The most northerly Ontario record, that of Attawapiskat Lake, August 13, is also an emergence record, and we have one from Clementsport, N.S., where a male emerged on August 3 from a small pond formed by damming the outlet of a springy bog. This pond was nearly covered by a dense stand of sedges and was the haunt of numerous green frogs, swamp tree frogs (Pseudacris), and Hyla crucifer, in our experience a somewhat strange nabitat for L. congener. The eggs are deposited in various plants, usually high above the water. Kennedy (1915) records a pair ovipositing in a small willow stem about two inches above the surface of the water. Montgomery (1925) and Williamson "observed a pair ovipositing on a stem of Scirpus fluviatilis. The pair moved down the stem depositing eggs at short intervals. The female was observed to straighten out her abdomen after each egg was inserted in the tissues of the plant. After the pair had moved down the stem several inches in this manner, they walked up the stem about a foot and began the process over again. This movement was carried out in perfect unison . . . The eggs were inserted at intervals of 1.5 to 4 mm. and pointed downward at an angle of about 45° with the surface of the stem. Most of them were inclined slightly either to right or to left, from the plane passing thru the line of punctures and the centre of the stem." We may add the following from notes made on August 23, 1939: "Visited the cut-off pond in the Don Valley . . . Here there were innumerable pairs of Lestes congener flying in tandem and ovipositing. They were constantly alighting on the cat-tail leaves and other vegetation, including willow, whereupon the female would immediately proceed to oviposit. Sometimes two or three pairs were close together on the same leaf or stem. They were apparently indifferent as to the condition of the foliage, whether dead or alive, and many were seen ovipositing on dead, dried cat-tail leaves as well as green ones. The females throw the abdomen in a high loop so that it descends between the hind femora and is apparently held in place by this means/' We have observed L. congener ovipositing in large numbers as late as September 16, when they were still very abundant. Lestes unguiculatus Hagen. (PI. 12, fig. 5; pi. 13, fig. 5; pi. 22, fig. 5) Lestes unguicalutus Hagen, Syn. Neur. N. Amer., p. 7, 1861. A somewhat robust species of average size, flying chiefly in July and August, usually about temporary ponds, the mature males easily recognizable by their blue eyes, general pruinosity, and sigmoid inferior appendages.

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Male (young). Dorsum of head and thorax bronze-brown, with a slight lustre, brighter and more greenish on the mesepimera and abdomen. Mouth-parts, anteclypeus, and genae greenish yellow, rear of head blackish, with a light yellow transverse bar above; median carina of thorax and humeral stripes pale brownish or fawn; thoracic sterna, lower parts of pleura, lateral lobes of pronotum, and coxae light yellow; a dark spot above the middle coxae; the dark metallic pleural area divided behind by a pale 7-shaped mark. Femora pale yellow, with a dark streak on the anterior and another on the flexor surface; tibiae dark, with extensor surfaces pale; tarsi black. Pale areas of abdominal surfaces occupying two-thirds of the circumference of the segments, the pale basal annuli only slightly interrupted mid-dorsally; anal appendages brown. In mature males the humeral stripes are narrower than in the teneral, being only one-fourth or one-fifth as wide as the dark mesepisternal area, and are more clear-cut and more greenish than in the teneral. A large dark brown spot appears on the metepimera and often spreads and unites with the metallic areas, restricting the original pale colour of the pleura to a single oblique stripe. Similar spots appear on the sides of abd. segs. 1 and 2. Following these changes, the thorax, rear of head, and segs. 1, 2, 9, and 10 of abdomen become bluish pruinose. The pruinosity of the thorax is most marked on the sides and venter, and the interalar area, but includes also the pronotum and mesepisterna. Hind wings about two-thirds as long as abdomen, including anal apps. Abdomen narrowest from segs. 3-6, rapidly widening beyond middle of 7, widest at distal end of 8. Sup. apps. meeting in an arc, their outer margins armed with moderately coarse spines, especially in the distal half; inner margins with a sharp basal spine, followed by a slightly sinuate edge which bears a row of minute spines and terminates in a blunt angle. Inf. apps. shorter than sup. apps., slender, sigmoid, with divergent tips. Female. Colour-pattern similar to that of teneral male; dorsum of thorax brown, with a dull lustre; humeral stripes dull yellowish and about half as wide as the bright bronze mesepimeral area immediately below them, suddenly narrowed in their posterodorsal fourth; light pleural areas yellow or greenish yellow. Abdomen dark metallic green above, light yellow on the sides, the basal annuli a little wider than in male; anal apps. pale. Ft. lighter brown than in male. Nearly the same as the male in linear measurements but much stouter, with the abdomen slightly shorter and the wings a little longer, the relation of wing length to length of abdomen being nearly seven-ninths. Ovipositor reaching beyond 10th sternum but not quite to end of abdomen; seg. 9 about as long as 8, slightly tumid anterodorsally; seg. 8 more than half as long as 7. Basal plate of ovipositor with the outer angle prolonged into an acute process. Postnodal cross-veins, f. w. $ 11-12 (8-15), $ 9-11 (8-13); h. w. $ 11-12 (8-12), $ 9-11 (8-11). Measurements. Total length $ 34.5-36.4 (1$ 41.0), $ 31-38 (30.5-39.0); abd. $ 25.5-30.0, $ 24.5-27.5 (29.5); h. w. $ 18-19 (20.5), $ 20.5-22.0 (18.0-22.5); pt. 1.2-1.4; h. f. £ 9 4.5-5.5; w. hd. 4.5-5.0. Nymph (pi. 14, fig. 6; pi. 36, fig. 5; pi. 38, fig. 5). Length of antennae four-fifths of head width; relative lengths of antennal segs., 13:25:33:23:20:19:12. Labium reaching base of hind coxae; length of narrow proximal part of mask about five-ninths of total length, the narrowest part two-ninths of distal width, widening to two-fifths at base; mental setae 6 or 7, marginal setae about 6 or 7; lateral setae 3-5. Abd. carinae moderately prominent, most of the segs. with 10-13 low serrations, each bearing a minute seta; lat. spines on segs. 5 or 6 to 9; ovipositor extending slightly beyond 10th sternum. Caudal lamellae a little more than one-half longer than wing-bases; median lamella with dorsal margin strongly arcuate, ventral margin sinuate, convex near base then broadly concave on distal two-thirds, greatest width in proximal third three-tenths of the length; lateral lamella with dorsal margin strongly convex at extreme base, thence gently sinuate; ventral margin broadly convex, more distinctly so towards base; apices of lamellae moderately acute, being more so than in disjunctus and rectangularis but less so than in dryas.

PLATE 17 Colour-pattern of Enallagma, (a) males, dorsolateral view, (b) abdomen of females, dorsal view: 1. E. carunculatum; 2. E. civile; 3. E. clausum; 4. E. boreale; 5. E. cyathigerum; 6. E. vernale; 7. E. minusculwn. All figs. X 3.

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Medium to dark brown, paler beneath. Dorsum of head without distinct darker markings, except the eyes and the three black crescents of the developing ocelli; antenna with segs. 1 and 2 a little darker than the others. Thorax and wing-cases nearly uniform brown above, except the darkening of the longitudinal veins of the latter. Femora with inconspicuous darker streaks along the ridges and lines of setae, and an ante-apical dusky annulus; extreme apices of femora and tibiae somewhat darkened; tibiae otherwise nearly plain; tarsi pale, except seg. 3, which is mostly dark. Abdomen moderately dark above, deepening into a marginal stripe near the lateral carina; sterna pale with a usually conspicuous dark lateral stripe bordering the pleura, which in extended specimens appears as a light stripe between two dark ones. Caudal lamellae light to moderately dark brown, darkened along the axis and tracheae, the three dark bands usually indicated chiefly along the margins, one at the proximal fourth, another just beyond the middle, and a third at the distal fourth and around the apex. Total length 27-28; h. w. 5.0-5.5; h. f. 4.5-5.0; caud. lam. 9.0-9.5; ov. 2.1-2.2; labium 3.8-4.5.

Habitat and range. Chiefly temporary or semi-permanent ponds in the open; prairie sloughs. N.S. to B.C., s. to N.J., Tenn., Mo., Okla., and Calif. Distribution in Canada. N.S.—Colchester and Pictou counties; C.B. N.B.— Charlotte Co. Que.—Island of Orleans, Montreal, and Ottawa Co. Out.—Essex, Kent, Lambton, Elgin, Oxford, Waterloo, Halton, Huron, Wellington, Peel, York, Northumberland, Bruce, Grey, Simcoe, Hastings, and Carlton counties; Muskoka, Parry Sound, Algoma, Thunder Bay, Kenora, and Rainy River districts. Man.—Winnipeg, Stony Mountain, Treesbank, Onah, Westbourne. Sask.—Regina, Bredin, Markinch, Moose Jaw, Swift Current, Maple Creek, Madison, Glidden, Snipe Lake, Burstall, Hamton, Lac Vert, Liberty, Saskatoon, Elbow, Prince Albert, and Waskesiu Lake (Prince Albert National Park). Alta—Red Deer. B.C.—Vancouver Is. (Sooke n. to Nanaimo Dist.), Hat Creek, Chilliwack, Cultus and Chaperon lakes, Osoyoos, Similkameen, Vaseau Lake, Penticton n. through the Okanagan Valley to Okanagan Landing and Armstrong, West Kootenay, Wasa, Premier Lake, and Canal Flats. Field notes. L. unguiculatus is definitely more southern than any of the other transcontinental species. It is the most local Lestes in British Columbia, where it appears to be unknown anywhere north of about 50°30'N, but is by far the most abundant species in the Prairie Provinces, south of the wooded regions. Small prairie sloughs swarm with them, and they are equally abundant in the Eastern Provinces wherever there are small ponds in the open. Oxbow ponds in an open valley are a favourite type of habitat, even when they dry up soon after midsummer. Gravel-pit ponds or any kind of pond in the open appear to suit their needs. They are much less frequent in slow streams or spring-fed ponds, but they are not entirely absent from such habitats. We have not found them in shady situations such as those preferred by L. rectangularis.

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In southern Ontario L. unguiculatus generally begins to emerge about the middle of June and continues to emerge until approximately the end of the month, by which time many individuals are mature. In some years, however, they appear well before the middle of June; for example in 1942, when they emerged in large numbers on June 8 and 9 from oxbow ponds in the Don Valley, near Toronto, and on June 10 and 11 from another temporary pond near the city. After emergence the tenerals scatter freely, and during the first few days they may be flushed in numbers from the grass. Only females appear on the first day or two of emergence. Pairing commences before the middle of July, our earliest record being July 12, although we believe that the two sexes begin to fly in tandem well before this date. At a small gravel-pit pond near our summer cottage on Lake Simcoe they were recorded from July 12 to August 3 as "abundant, flying in tandem and ovipositing," being especially numerous at the beginning of August. They were observed to oviposit in any available kind of vegetation, most frequently bulrushes (Scirpus), spike-rushes (Eleocharis), and sometimes on grass culms (Agrostis stolonifera). As many as five or six pairs were observed on a single stem of Scirpus, all close together. They have also been reported by Needham (1900) as ovipositing in the stems of the blue flag (Iris versicolor) in company with L. dryas, their punctures being numerous enough to kill a large proportion of the fruiting stalks. Our latest record for pairing is August 31, 1940, but this was in a cool spring-fed pond, in which kind of habitat the life cycle is longer. The period of flight in Ontario and Quebec may be from June 8 to September 9, but is more often shorter; in Manitoba and Saskatchewan the earliest and latest dates reported are June 19 and October 7; in British Columbia, June 12 and August 24. The single October record from Onah, southern Manitoba, is probably unusual for any part of the range of L. unguiculatus in Canada. Lestes dryas Kirby. (PL 12, fig. 6; pi. 13, fig. 6; pi. 22, fig. 6) Lestes dryas Kirby, Syn. Cat. Od., p. 160, 1890; Cowley, The Entomologist, 68:155,1935. Lestes uncatus Kirby, Syn. Cat. Od., p. 160,1890. This is our stockiest Lestes, being similar in build to L. unguiculatus but with a slightly shorter abdomen, which is most noticeable in the female. It is easily recognized by its relatively bright metallic green colour. It is one of the earliest species to appear in the adult state. Male. Metallic green, tenerals drying to a deep blue; pale markings inconspicuous in dorsal view. Mouth-parts, anteclypeus, and genae pale yellow or greenish yellow. Thorax of tenerals with a pale mid-dorsal line and linear yellow streaks on the humeral sutures, those markings disappearing with maturity. Lower parts of thoracic pleura, sterna, and coxae pale yellowish or brownish, the line dividing the pale and dark areas

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with only slight irregularities. In older individuals a dark blotch appears on the metapleura and similar ones on abd. segs. 1 and 2. The thoracic blotch tends to spread until it replaces most or all of the pale colour. Femora with external faces black, extensor and flexor surfaces yellow; tibiae black, with extensor surface yellow; tarsi black. Abdomen dark green above, with narrow interrupted basal annuli, and somewhat less than the ventral half of each segment light yellow or brownish. Anal appendages black, partly brown. Pruinosity in old males not extensive, covering pronotum, thoracic sterna, and lower parts of pleura, interalar region, abd. seg. 1 and usually part of 2. Segs. 8-10 or 9-10 become thinly pruinose, giving them a greyish appearance. Hind wings about three-fourths as long as abdomen (excl. apps.). Abdomen narrowest from seg. 3 to seg. 6, rapidly widening beyond middle of seg. 7 and reaching its greatest width at distal end of 8. Sup. apps. broad, strongly curved mesad, meeting in an arc, their outer margins bearing a few coarse spines particularly at about threefourths of the length; inner margin with a strong proximal tooth near the base, followed by a slightly concave setose margin which terminates in a distinct tooth that is decidedly shorter than the proximal tooth; apices broad and rounded. Inf. apps. about three-fourths as long as sup. apps.; inner margins excavate; distal third expanded, particularly on the inner side, the distal margin oblique. Female. Colour-pattern similar to that of male, except that it is nowhere dulled by pruinosity, the pale linear streaks on mid-dorsal thoracic carina and humeral sutures clear-cut, the latter a little wider than in the teneral male; pale basal annuli on abd. segs. also a little wider than in male. Similar to male in linear proportions but much stouter, the wings averaging a little longer. Ovipositor extending slightly beyond end of abdomen, as long as seg. 7; seg. 9 distinctly longer than 8 and about two-thirds as long as 7. Basal plate of ovipositor prolonged into an acute process. Postnodd cross-veins, f. w. 8 10-12 (9-13), $ 12-13 (10-14); h. w. $ 10-11 (9-13), $ 11-12 (10-14). Measurements. Total length $ 36-38 (31), 9 32-37; abd. $ 27-29, $ 23.5-27.5; h. w. 8 19.5-21.5 (18), $ 21-24; h. f. # $ 5.0-5.5 (4.5); pt. 1.0-1.6; w. hd. 4.4-5.0; ov. 3.0-3.3. Nymph (pi. 14, fig. 8; pi. 36, fig. 2; pi. 38, fig. 4). Head about two-fifths as long as wide, of the usual Lestes form; length of antennae equal to about four-fifths of the head-width, the relative lengths of their segs., 13:25:32:25:20:18:12. Labium long, extending to apices of hind coxae, the slender proximal part of the mentum about twice as long as the expanded distal part, the width near the base one-third of the distal width; mental setae usually 7 in a graded series, the shortest at the mesal end sometimes absent; lateral setae 3-4, with one on the basal segment of the lateral lobe; marginal setae about 12 but variable. Lateral carinae of abdomen with low serrations bearing minute setae, 3 or 4 on seg. 1; 11 or 12 on segs. 2 and 3; 13 on 4; 12 on 6, 7, 8, and 9; lat. spines on segs. 5-9. Ovipositor extending well beyond seg. 10, about to basal joint of lamellae. Caudal lamellae four-fifths longer than outer wing-cases; median lamella with dorsal margin strongly arcuate, ventral margin sinuate, widest at about proximal third, the width being slightly more than one-fourth of the length, tapering to long acute apices; lateral lamellae with ventral margin gently arched, dorsal margin feebly sinuate or nearly straight, except in basal fifth and very near the apex; greatest width at proximal third, one-fifth of the length. The lamellae may be of equal length, or the median slightly shorter, or sometimes much longer, than the lateral lamellae. Light to dark brown with little pattern; femora with apices and an ante-apical annulus dark brown, separated by a pale space; tibiae uniform, except the darkened apices; 3rd tarsal seg. darkened on the distal half or more. Venter of abdomen apparently without dark spots or stripes. Caudal lamellae in average specimens light brown, with the following areas dark brown: extreme bases, a cross-band at proximal third, another at the middle, and a third at the apices, the markings not clear-cut owing to pigmentation of the tracheae in the paler areas. In very dark specimens the pattern would be

PLATE 18 Colour-pattern of Enallagma, (a) males, dorsolateral view, (b) abdomen of females, dorsal view: 1. Enallagma hageni; 2. E. ebrium; 3. E. geminatum; 4. E. exsulans; 5. E. antennatum; 6. E. aspersum; 7. E. signatum; 8. E. vesperum. All figs. X 3.

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better described as dark brown, with three pale areas: near the base and before and after the middle. Total length 23-25; h. w. 4.5-5.2; h. f. 4.2-4.8; caud. lam. &-9; ov. 2.5; labium 4.5-5.0. All the nymphal stages are described by Gardner (1952) from British material.

Habitat and range. Ponds, permanent or temporary, or pond-like expansions of slow streams, less frequently in distinctly marshy waters. N.S. and n. shore of Gulf of St. Lawrence, Que., to James Bay; Mackenzie Dist., N.W.T.; Yukon T. and Alaska s. to N.J., Tenn., Mo., Okla., and Calif. Also in Europe and Asia. Distribution in Canada and Alaska. N.S.—Annapolis, Lunenburg, Halifax, and Pictou counties, C.B. P.E.I.—Charlottetown. N.B.—Charlotte, Gloucester, Sunbury, and York counties. Que.—Covey Hill, Hemmingford, St. Chrysostom, Vaudreuil, Montreal, Island of Orleans, Natashquan, Fort Coulonge, Hull, Wakefield and other stations in the Gatineau Valley, n. to Nominingue, Labelle Co., and La Ferme, Abitibi Co. Ont.—Throughout s. Ont.; from the counties bordering on Lakes Erie and Ontario northward to Muskoka, Parry Sound, Nipissing, Manitoulin, Algoma, Timiskaming, Thunder Bay, Cochrane, and Kenora districts. Man.—Stockton, Treesbank, Westbourne, Portage la Prairie, Winnipeg, Victoria Beach, Riding Mts. Park, The Pas. Sask.—Burrows, Indian Head, Regina, Bredin, Caron, Maple Creek, Alsack, Loverna, Madison, Snipe Lake, Yorkton, Lashburn, Prince Albert, Waskesiu Lake. Alta.—Red Deer, Banff; doubtless general throughout the province. B.C.—Vancouver Is. (Sooke, Florence Lake, Wellington); Chilliwack, Hope, Hat Creek, Lillouet, Canim Lake, Chilcotin, Horsefly; Penticton, Salmon Arm, Kamloops, Robson, Shuswap Falls, Revelstoke, Boswell, Kaslo, Moyie, Canal Flats, Invermere, Mt. Robson, Vanderhoof; probably general throughout the province. N.W.T., Mackenzie Dist.—Fort Smith, Fort Simpson, Norman Wells, Fort Resolution, and Yellowknife, Great Slave Lake. Yukon T.—Dawson. Alaska—Chitina. Field notes. The nymphs of Lestes dryas often develop in small ponds or pools that may dry up before the summer is over. They also breed in permanent waters, particularly those that are partly shaded, such as ponds at the margin of woods, or cat-tail marshes. Emergence begins usually more than a week before that of L. unguiculatus; in British Columbia it is two weeks earlier (Whitehouse, 1941). Our earliest record of emergence is May 30, from Rondeau Park, Ontario, but we have also taken dryas in the vicinity of Toronto on June 1 and 2. There were at this time considerable numbers of tenerals present about the oxbow ponds in the Don Valley, and all of them were females, an indication that

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the period of emergence had just begun. A week later, at the same ponds, both sexes were present, and one pair was seen. Emergence continues locally until about the end of June or even later, for we have a record of tenerals, all females, at a small pond near Toronto on July 5. Meanwhile other individuals have been mature since the third week of June, pairing having been observed in southern Ontario as early as June 23; and we noted a pair at Victoria Beach, Manitoba, on June 29. Pairs are more commonly seen, however, in July, at least in the Eastern Provinces, and we have one record of a pair on August 8» L. dnjas oviposits usually in tandem in Typha and other emergent plants, high above water. It was one of the two species reported by Needham (1900) as ovipositing in stems of the blue flag (Iris versicolor) and causing considerable damage to the fruit. The maximum length of the adult season, as indicated by the earliest and latest dates of observation is nearly three months: from May 30 to August 25 for Ontario; June 14 to August 30 for the Prairie Provinces; and June 7 to September 6 for British Columbia. The records from the Prairie Provinces are, however, too incomplete to be significant. Lestes disjunctus Selys

Lestesdisjunct™ Selys, Bull. Acad. Belg., (2), 13: 302,1862. L. forcipatus Osburn, Od. B. C., 1905 (see also under subsp. australis). This widely distributed species is composed of two subspecies, disjunctus and australis, the former inhabiting almost all of Canada south of the limit of trees, the latter barely entering Canada in extreme southern Ontario. The males of these two subspecies may be separated as follows: Generally smaller (abd. usually 25.5-28.0 mm., h. w. 18-20); distal tooth of sup. apps. about as sharp and often nearly as large as proximal tooth; pale humeral stripe narrow, not encroaching on the mesepimeron and not confluent with the pale lateroventral area along the cross-suture, the dark area of the mesinfraepisternum being broadly confluent with that of the mesepisternum disjunctus Generally larger (abd. usually 31-32, h. w. 21-23); distal tooth of sup. apps. much smaller and typically blunter than proximal tooth, often rectangular; pale humeral stripe typically encroaching more or less on mesepimeron and confluent with the pale lateroventral area along the cross-suture, thus isolating a dark spot on the mesinfraepisternum australis The females are distinguishable only by differences in size, although australis is typically paler, with wider pale markings. The two subspecies are not difficult to separate, however, except in the zone where their geographical ranges overlap and intergradation sometimes occurs. The only part of Canada in which L. d. australis is known is a narrow strip along the

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north shore of Lake Erie, including Rondeau Park, Kent Co., and Point Pelee, Essex Co. This zone of intergradation in the United States occupies northern Ohio and northern Indiana, and probably parts of southern New England, New York, Pennsylvania, and Iowa. Lestes disjunctus disjunctus Selys. (PL 12, fig. 7; pi. 14, fig. 1; pi. 22, fig. 7) Walker, Trans. Amer. Ent. Soc., 78: 62,1952. Of rather small to average size throughout most of its range, and more slender than either L. unguiculatus or L. dryas, flying chiefly in the latter half of summer and frequenting permanent marshy or boggy waters; the commonest Lestes of the north. In western British Columbia it reaches a larger size than elsewhere in Canada. Male. Tenerals bronze, with a mild greenish lustre, the pale areas dull yellowish. As they mature the bronze areas become very dark, the dorsa of the head and thorax almost black, with a slight bronzy lustre that disappears when pruinosity develops; abdomen very dark bronze, often with a greenish tinge. Mouth-parts, anteclypeus, and genae pale yellowish to greenish; rear of head black. Pterothorax with a light yellow mid-dorsal line and a pale yellow stripe on the humeral suture, which is less than onethird as broad as the dark mesepisternal area, and which narrows behind and does not reach the ante-alar ridges. Thoracic sterna and lower parts of pleura light yellow, the metepimera showing a large dark blotch before becoming pruinose, the whole pleural region sometimes becoming dark though usually an oblique yellow stripe remains, bordering the original bronzy area. Coxae pale; femora yellowish, with the outer face and a ventral line dark; tibiae black, with a yellow extensor stripe; tarsi black. In old specimens the yellow is sometimes so dark that the legs appear to be almost entirely black. Abdomen with the light areas dull ochreous, narrowed behind on most of the segments by the encroachment of the dark dorsal area. Anal apps. black. In old males the following parts become bluish pruinose: rear of head (slightly); pronotum, sterna and lower parts of pleura of pterotnorax, interalar area, and first two segs. of abdomen (heavily); and segs. 8, 9, and 10 (moderately, appearing usually greyish). The pale humeral stripes of the thorax are clear and distinct, except in very old males, in which they may become entirely obliterated. This seems to be a feature of specimens from high latitudes or altitudes. The dorsum of the thorax in these old males becomes a dull grey-black, entirely without lustre. Wings about seven-tenths as long as abdomen (excluding apps.); abdomen narrowest from seg. 3 to seg. 6, expanding from base of 7 to end of 8. Sup. apps. meeting at a wide obtuse angle, inner margin with two sharp teeth, of nearly equal size, or the proximal one somewhat larger; inf. apps. about three-fourths as long as sup. apps., slender and nearly equal in width from near the base to near the rounded apices, straight or very slightly bent inward from the base. Female. Coloration similar to that of male before pruinosity begins, the general appearance of the female being thus lighter than the male; mid-thoracic and humeral streaks broader than in male and the pale areas of the abdomen likewise more conspicuous. The yellowish area occupying the ventral parts of most segments is more or less interrupted by a dark blotch, which meets the dark metallic area above. Pt. dark brown. Stouter than male, the wings a little longer, being about three-fourths as long as the abdomen. Ovipositor extending beyond the sternum of seg. 10, but not quite reaching the end of the abdomen; basal plate with posterolateral angle produced into an acute

PLATE 19 Colour-pattern of Coenagrion and Ischnura, (a) males, dorsolateral view, (b) abdomen of females, dorsal view: 1. Coenagrion resolutum; 2. C. interrogatum; 3. C. angulatum; 4. Ischnura verticalis; 5.1. perparva. All figs. X 3.8.

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process; segs. 8 and 9 about equal in length, each a little more than half the length of 7. Postnodal cross-veins, f. w. $ 11-13 (9-14), $ 10-12 (9-15); h. w. £ $ 9-13. Measurements. Total length $ 33.5-57.0 (west B.C. 37-41), 9 32.5-36.0 (w. B.C. 38.0-38.5); abd. 425.5-28.0 (w. B.C. 29-32), $ 24.5-28.0 (w. B.C. 29-30); h. w. 3 18-20 (w. B.C. 20-22), $ 20.4-20.5 (w. B.C. 22-25); h. f. 3 $ 4.75-5.0; pt. 1.1-1.5; w. hd. $ $ 4.25-4.6; ov. 2.0-2.7. Nymph (pi. 14, fig. 7; pi. 32; pi. 36, fig. 7; pi. 38, fig. 6; pi. 44, fig. 11). Antennae five-sixths as long as the head is wide, relative lengths of segs., 13:23:39:25:19:18:12. Labial mask extending to middle or apices of hind coxae, sometimes a little farther; the slender proximal part comprising about five-eighths of its length, its least width about one-fifth of the distal width; mental setae 5 or 6, the innermost small; lateral setae 3, two of which are borne by the second segment. Lateral carinae of abd. segs. 2-9 with 12-14 minute setiferous serrations; lateral spines on segs. 5-9, very small on 5; ovipositor extending to about the end of seg. 10. Median caudal lamella slightly shorter than lateral lamella, dorsal margin strongly arcuate, ventral margin sinuate, greatest width at proximal fourth, about one-fifth to one-fourth of the length; lateral lamella with margins straighter, the ventral margin slightly convex, the dorsal very slightly sinuate, widest about one-sixth of the length, apices of all lamellae narrowed but bluntly pointed. Pale brown, variegated with bone yellow and dark brown. Dorsum of head moderately dark brown, eyes blackish, with a narrow pale border; ill-defined light patches behind bases of antennae and a pale spot at each ocellus; antennae pale, seg. 1 brown above, seg. 2 with a touch of brown dorsally at apex; labium and venter of head pale yellowish to buflF.^ Prothorax moderately dark brown, deepening on front and hind margins to nearly black; pterothorax brown, very dark along mid-dorsal ridge and wingbases, paler on the sides, and very pale ventrally. Coxae, trochanters, and femora light brown, the femora with the immediate apices darkened, a broader ante-apical dark brown annulus, and a pale ivory space between the dark markings; longitudinal carinae also more or less darkened; tibiae light brown, deepened at apices; tarsi pale, with the three segments darkened apically, particularly the third, which is mostly dark brown above. Wing-cases light brown, the longitudinal veins darker brown, and the costal margins nearly black. Abdomen moderately light brown, the intersegmental areas appearing like dark annuli; a pale yellow marginal stripe along the lateral carinae; venter of abdomen pale, with a dark stripe bordering the pale carinal stripe, and with segmental pairs of submedian dark spots at the hind margins of most of the segments, sometimes fusing on the posterior segments into stripes. Ovipositor pale yellow and brown. Caudal lamellae dark brown, with three pale, often broken cross-bars, a basal, a median, and a post-median, the axes wholly dark; or, in pale specimens, light yellowish, with a dark band just distad of the pale base, another beginning about the middle and separated from the apical band by a narrow pale space; tracheae brown; margins darkened at the bands, axes interrupted at the pale bands. Total length 22.5-29.0; h. w. 4.5-5.0; h. f. 4.1-5.0; caud. lam. 6.7-10.8; ov. 2.25-2.4; labium 3.5-4.5 (w. B.C. 5.0).

Habitat and range. Permanent ponds with marshy or boggy margins and rich aquatic vegetation; marshy bays and slow weedy streams. Nfld. and Lab. to Mackenzie Dist., N.W.T., Yukon T., and Alaska, s. to Mass., Pa.,

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n. O,, n. Ind., Mich., and Minn,, w. to Wash, and Or., and s. along the mts. to Col., Ariz,, and probably Calif. Distribution in Canada and Alaska. Nfld.—Whitbourne, Spruce Brook, Gander. Lab.—Goose Bay. N.S.—Digby, Annapolis, Kings, Colchester, and Halifax counties; Aspy Bay, Victoria Co., C.B. N.B.-St. Andrews, Youghall, Nelson, and s. Miramichi River. Que.—Island of Orleans; Eastman; Montreal region; Hull; and the Gatineau Valley; Nominingue, Labelle Co.; La Ferme, Abitibi Co.; and n. to the Moisie River, Gulf of St. Lawrence and East Main, James Bay. On*.—General throughout s. Ont. from the counties bordering Lakes Erie and Ontario northward to Lake Abitibi, Cochrane Dist.; Timmins and Latchford, Timiskaming Dist.; Lake Nipigon and Gull River, Thunder Bay Dist.; Favourable Lake (53°l(yN) and Attawapiskat Lake (52°l(yN), Patricia section of Kenora Dist.; Rainy River Dist. Man.Treesbank, Westbourne, Winnipeg, Victoria Beach, Riding Mts. Park, The Pas, Wabowden, Gillam (56°N). Stwfc.-Regina, Swift Current, Duck Lake, Clearwater Lake, Lac Vert, Big Manitou Lake, Jackfish Lake, Prince Albert, Wapus, Reindeer Lake (56°23'N). AZte.-Red Deer, Banff, Jasper Park. B.C. —General throughout s. B.C. from Vancouver Is. eastward to the Rocky Mts. (Field, Mt. Robson) and northward to the Queen Charlotte Islands (Masset Dist), Prince Rupert, Hazelton, Prince George, Palling, and Atlin (60°N). Numerous localities are cited by Whitehouse (1941) and Buckell (1938). N.W.r.-Mackenzie Dist.-Fort Smith, Fort Simpson, Great Slave Lake, Norman Wells. Ywfcon T.—Dawson. Alaska—Admiralty Island, Anchorage, Gulcana, Juneau, Palmer. Field notes. This is the most widely distributed Lestes in Canada and, except in the Prairies and the most southerly counties in Ontario, it is also the most abundant species. It is one of the latest of the genus to emerge, rarely appearing before the last week of June and, in most parts of the country, not often before the middle of July. In British Columbia, Whitehouse reports it as emerging from Thetis Lake, Vancouver Island, on June 24, and from Kaslo, far eastward on Kootenay Lake, on the same date. He also found it emerging before the end of June at Beaver Lake, Vancouver, but in most of British Columbia the usual time for adults to appear is some time in July, as it is throughout the greater part of Canada. Thus Whitehouse found tenerals at Florence Lake, Vancouver Island, on July 2 and 5; at Atlin (60°N) on July 17; and on the Queen Charlotte Islands he found them "emerging from lakes, sloughs and muskeg potholes July 20th on." From every other part of the country-the Northwest and Yukon Territories, the Prairie Provinces, and across the Maritimes, the usual time for L. d. disjunctus to emerge is near the middle of July, a little later in the far north perhaps, and a little earlier in the extreme south. July 2 is our earliest date for southern Ontario, but we found myriads of young adults on July 5,1952, near Gananoque, Ontario (headwaters of the St. Lawrence River), and we have one record for July 5 from the Favourable Lake district in northern Ontario (5305(XN).

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Pairing begins about a week after emergence. Whitehouse observed L. disjunctus on the Queen Charlotte Islands pairing on July 26, just six days after he first saw them emerging. At Atlin, a northern locality on the mainland of British Columbia, he observed pairs of disjunctus on July 22, and at Wellington, Vancouver Island, where emergence is earlier, he notes this species on July 14 "adult and in cop/' In southern Ontario the usual time for pairing is apparently later, since our observations were all made in August and September. We have seen pairs in tandem, however, early in the season. Among the myriads of young adults mentioned above as having been observed near Gananoque on July 5, 1952, there were occasional pairs in tandem. Three pairs, however, examined in succession, consisted of males only. It would seem probable, therefore, that these individuals were not yet quite sexually mature. On August 7 many pairs were noted at the creek near De Grassi Point, Lake Simcoe, and some were ovipositing. Oviposition was observed on several occasions after this date, during various years, up to September 10. They oviposit in various emergent plants, including grass culms and Sparganium. A pair was seen on September 10 ovipositing in Sparganium from one to about 12 inches above the water. The female moved from plant to plant, sometimes depositing three or four eggs, sometimes apparently none. We have no later record of its oviposition, but have seen it in flight as late as September 21. We have reason to believe that it flies several weeks later than this. In British Columbia the latest recorded date is September 24, but in Saskatchewan it has been taken up to October 16, a surprisingly late date. Lestes disjunctus australis Walker. (PI. 12, fig. 8; pi. 22, fig. 8) Walker, Trans. Amer. Ent. Soc., 78: 64,1952. Larger than L. d. disjunctus, the metallic areas somewhat duller and the pale markings more extensive. The humeral stripes extend the entire length of the suture, although narrowed at both extremities. They resemble those of L. forcipatus in their dull colour and in their slight encroachment on the mesepimeron. The small distal tooth of the superior appendages, as compared with that of subsp. disjunctus, appears to be a constant character except where the ranges of the two subspecies overlap. In general appearance the males of australis resemble those of forcipatus, but may be separated by the characters given in the key. The females of australis differ from those of subsp. disjunctus only in the larger size, paler coloration, and more extensive pale markings. Measurements. Total length $ 37.0-44.0, $ 38.5-44.0; abd. $ 28.5-38.5, $ 29.5-34.0; h. w. $ 20.3-23.3, $ 22.0-25.5. Nymph (pi. 38, fig. 7). The nymph was reared by Carman (1917, 1927), who described it as that of L. forcipatus. We have seen the exuviae, which do not appear to differ from those of disjunctus, except in the somewhat larger size. Our figure of the caudal lamellae was drawn from one of these exuviae. Carman's measurements are as

PLATE 20 Colour-pattern of Chromagrion and Ischnura: 1. Chromagrion conditum, (a) #, lateral view, (fc)abdomen of 9, dorsal view; 2. Ischnura erratica, (a) #, dorsolateral view, (b) abdomen of 9, dorsal view; 3. I. damula, (a) $, dorsolateral view, (b) abdomen of 9 (homoeochromatic), dorsal view, (c) 9 (heterochromatic), dorsal view; 4. I. cervula, (a) $, dorsolateral view, (b) abdomen of 9 (homoeochromatic). All figs. X 3.3.

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follows: length 19-20; abd. 14; caud. lam. 8.5-9; width caud. lam. 2-3; med. lobe 2.4; width med. lobe .5-1.5. (The length of the body excludes the caudal lamellae. The median lobe, as termed by Carman, is the part usually called the mentum.)

Distribution. Pa., n. O. and Ind., la., Neb., and Kans., s. to Fla. and w. to Tex. and Okla.; barely entering Canada at Rondeau Park, Kent Co. and Point Pelee, Essex Co., Ont. It will certainly be found in southern New England and New York State. Field notes. The season of flight is very different from that of subsp. disjunctus. It is very early, beginning in Indiana in mid-April (Montgomery, 1948) and continuing until the third week in September. The few specimens from Ontario were all taken in July. Lestes forcipatus Rambur. (PL 12, fig. 9; pi. 14, fig. 2; pi. 22, fig. 9) Lestes forcipatus Rambur, Hist. Nat. des Insectes. Nevropteres, p. 246, 1842. Lestes hamatus Hagen, Syn. Neur. N. Amer., p. 70, 1861. A medium-sized species, becoming smaller toward the northern boundary of its range, flying from spring to late summer about permanent and temporary waters. Male. Juveniles bronze-black above, pale yellow to yellowish grey below. Labium pale brownish yellow; labrum, anteclypeus, and genae darker, dull olivaceous; rear of head dull blackish. Median line of thorax and humeral stripes dull yellowish or greenish grey, the former very fine, the latter broader in the middle than the adjoining mesepisternal area of one side, but suddenly narrowed towards the ends. Sterna and lower parts of pleura, and coxae greenish or dull yellow, creamy along the edge of the dark mesepimeral stripe, which has only slight angular irregularities. Legs greenish yellow, longitudinally striped with black as in disjunctus; tarsi black. Abdomen bronze-black above, with a greenish lustre; under parts dingy yellow of lighter and darker shades; a dark blotch on the sides of segs. 1 and 2, and a dark spot near the posterior end of most of the segments, joining the metallic stripe above. Anal apps. black. Pt. very dark brown. Wings about three-fourths as long as abdomen (excl. apps.); seg. 2 of abdomen three-fifths as long as seg. 3, which is relatively somewhat shorter and stouter than in L. disjunctus. V-shaped emargination of seg. 10 slightly more than one-third of the width of the segment at the hind margin. Sup. apps. similar to those of L. disjunctus australis, with differences given in the key. Inf. apps. as in disjunctus. Female. Colour a lighter bronze than in male; median thoracic line and humeral stripes greenish grey, broader than in male, the humeral stripes being about as wide

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as the dark mesepisternal area, but suddenly narrowed in the posterior fourth. The other pale markings much as in male, but broader, particularly on sides of abdomen. Stouter than male, with wings about four-fifths as long as abdomen; ovipositor about as long as seg. 7, extending well beyond end of abdomen, basal plate with outer distal angle produced into an acute process; seg. 0 longer than 8, tumid above; seg. 8 a little more than half as long as 7. Postnodd cross-veins, f. w. 3 9 10-13 (9-14); h. w. $ 10-11 (8-14), $ 10-11 (9-13). Measurements. Total length 8 36-41, $33-39; abd. $ 27-31, $ 26-30; h. w. $ 20.0-22.5, $ 22.0-24.5; h. f. $ 4.6-5.0, $ 4.7-5.4; w. hd. $ 9 4.7-5.2; pt. 1.2-1.5; ov. 3.5-4.0. Nymph. Unknown; Carman's description applying to L. disjunctus australis.

Habitat and range. Ponds, both temporary and permanent, marshy lakes, and slow weedy streams. N.S. to n. Que. and Ont., Sask., s. to Mass., Pa., O., Ind., Ill, Tenn., and Mo. Distribution in Canada. N.S.-Annapolis Co. N.B.-Fredericton, Petitcodiac. Que.—Island of Orleans, Montreal, Hull, Gatineau Valley, n. to Nominingue and La Ferme, Abitibi Co. (48°50'N). Ont.-Counties bordering Lakes Erie and Ontario, n. to Smoky Falls, Cochrane Dist. (50°N), and Fort Frances, Rainy River Dist. (48°N). Sasfc.-Waskesiu Lake, Prince Albert National Park. The wide distribution formerly accredited to this species was based on the misidentification of L. disjunctus australis, as first pointed out by Montgomery (1941). As indicated above, its range is much more restricted than that of L. disjunctus, or either of its subspecies. L. forcipatus is also much more local than disjunctus. Field notes. L. forcipatus emerges somewhat irregularly. It appears much earlier than L. d. disjunctus but, according to Montgomery (1948), a month later than L. d. australis in Indiana, i.e. the first of June. Our earliest date is a little later than this, as would be expected. On June 6, 1942, we found a few males flying over a small and temporary pond in a vacant grassy area just north of Toronto. This is our earliest record, but some of the individuals were already pruinose and had therefore emerged some days before we saw them. Others were still teneral and scattered over the adjoining grass. Anxious to secure nymphs, we visited the pond with a sieve a few days later, but, although we obtained a number of Lestes nymphs, the adults emerged much later and all were unguiculatus. Other occasions when we found tenerals in considerable numbers were June 16, 1937, at Gibson Lake, Peel Co., Ontario, and July 9, 1932, at a small pond near Fredericton, N.B. On both occasions the tenerals were resting on the emergent vegetation of an open marsh. We have observed L. forcipatus in copula several times during August, but individuals that emerge in June must begin pairing at a much earlier date. We noted several pairs on August 8,1937, near Latchford, Ontario, which is near the northern limit of this species, as far as known; and on August 16, near

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the mouth of a quiet Lake Simcoe stream, we noted many pairs ovipositing in the sweet-flag (Acorus calamus L.), all above the water-line. We noted five pairs on a single blade of sweet-flag, all close together and high above the water. The earliest and latest dates on which we have recorded adults are June 6 and September 21, and the records from other provinces do not extend this period. It is similar to Montgomery's flight period of this species for Indiana. The peak of abundance in Indiana comes about the middle of July and is probably not very different from that of southern Ontario. Lestes rectangularis Say. (PL 12, fig. 10; pi. 14, fig. 3; pi. 22, fig. 10) Lestes rectangularis Say, J. Acad. Nat. Sc. Phila., 8: 34, 1839. A long-bodied, short-winged species; the dark areas brown with little lustre, the pale markings extensive, greenish grey to pale yellow; flying in more or less shady places. Male. Dorsum of head including postclypeus black; labium pale dull yellowish; labrum, anteclypeus, and genae deeper yellow to light green, polished; rear of head black, becoming bluish pruinose with maturity. Thoracic dorsum dark brown, with a slight bronzy lustre of varying intensity; median line and humeral stripes dull greenish grey, much darker than the ventral parts of the thorax; the humeral stripes as wide as the mesepisternal dark area, but suddenly narrowed in the posterior fourth, continuous in front with the pale area of the pleura; mesepimeral dark stripe usually divided near the posterior end oy a pale 7-shaped mark; a separate spot in front on the mesinfraepisternum; lower parts of pleura, sterna, and coxae pale yellow; femora also pale yellow, with a dark streak on the outer face; tibiae yellow; tarsi dorsally partly yellow, ventrally dusky. Wings hyaline; pt. dark brown. Abdomen of juveniles a dull greyish brown with pale basal annuli ana dark annuli at posterior ends of segments, connected on segs. 3-7 with a dark subapical blotch. In mature individuals a dorsal greenish bronzy stripe develops, which widens and darkens posteriorly; segs. 9 and 10 without lustre; venter dull drab yellowish. This species is almost free from pruinosity, the only parts distinctly affected being the rear of the head and the interalar area. The two last segments of the abdomen become dull and greenish, but the effect is very slight. Hind wings about three-sevenths as long as abdomen. Abdomen extremely elongate, narrowest from seg. 3 to base of 6, thence widening gradually beyond to base of 8, then more rapidly to end of 9. Sup. apps. strongly bowed, their rounded apices meeting in an arc; inner margin with proximal and distal teeth, the proximal tooth very small, the distal tooth large and acute, separated from the apical portion of the appendage by a deep sinus; inf. apps. about two-thirds as long as sup. apps., distinctly bent downward, narrowing somewhat irregularly from bases to apices, slightly contracted before and after the middle. Female. Much shorter than male, the differences being mainly in the abdomen, which is also stouter. Length of wings about 69 per cent of the body length. Ovipositor about five-ninths as long as seg. 7, seg. 9 shorter than 8; seg. 8 a little less than half as long as 7. Postnodal cross-veins, f. w. £ 10-13, $ 9-13; h. w. $ $ 9-12. Measurements. Total length $ 44-47 (42-51), $ 37-42; abd. $ 34-40, 9 29.0-34.5; h. w. $ 20.0-21.5, $ 21-24; h. f. $ $ 4.5-5.0; w. hd. $ 4.5-4.8, $ 4.0-4.8; pt. £ $ 1.4-1.5; ov. 2.3-2.5.

PLATE 21 Colour-pattern of Nehalennia, Ischnura, and Anomalagrion: 1. Nehalennia irene, (a) #, lateral view, (b) S, terminal segments from above, (c) $, terminal segments from above, (d) same, left lateral view; 2. N. gracilis, (a) $, lateral view; (b) $, terminal segments from above, (c) $, terminal segments from above; (d) same, left lateral view; 3. Ischnura posita, (a) $, dorsolateral view, (b) $, abdomen, dorsal view; 4. Anomalagrion hastatum, (a) $, dorsolateral view, (b) $, dorsal view; 5. Ischnura verticalis, $ (heterochromatic), dorsal view. Figs. 1, 2, and 3, X 3.8; figs. 4 and 5, X 4.

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Nymph (pi. 14, fig. 9; pi. 36, fig. 3; pi. 38, fig. 8). Antennae slightly more than twothirds as long as the head is wide, relative lengths of segs., 13:22:28:21:16:16:12. Labium extending to bases of hind coxae, slender basal part of mentum making about fiveninths of the length, its minimum width scarcely one-seventh of the distal width; mental setae usually 7 (4-7); marginal setae about 5 or 6 but variable; lateral setae 3, 2 on movable hook. Abdomen with lateral carinae moderately prominent, most of the segments with 10-13 low serrations, each with a minute seta, none on seg. 1; lateral spines on segs. 5-9; hind margin of seg. 10 strongly spinose dorsally, and with a few shorter spines laterally and ventrally. Ovipositor reaching end of seg. 10, but not tip of abdomen. Caudal lamellae about two-thirds longer than hind wing-cases; median lamella nearly as long as lateral lamella, its dorsal margin slightly to moderately arcuate, ventral margin sinuate as in L. dryas, widest about the proximal fourth, width here being twosevenths of the length; lateral lamellae with dorsal margin well rounded at base, sinuate beyond basal fourth, widest at basal fifth, width here being one-fifth of the length; all the lamellae tapering to bluntly pointed apices. Light brown to pale green; head and thorax slightly darker above than below, without darker markings except the ocellar crescents and about the mesostigmata and wingbases. Femora pale, dark only at the extreme apices, each with an inconspicuous longitudinal darker streak and an ante-apical annulus; tibiae and tarsi pale, except distal half of third tarsal segment, which is darkened. Wing-cases with longitudinal veins marked with darker brown. Abdomen light brown or green above, with a pale mid-dorsal line, and darker spots at the posterolateral articulations, pleural and sternal regions pale, the latter with a narrow dark longitudinal streak on each side, parallel to the lateral margin, often faint except on the more posterior segments. Caudal lamellae rather pale, marked with dark brown as follows: the axis; edges of proximal third, just beyond middle, apical sixth including apex, and parts of the tracheae, particularly those connecting the darkened edges across the lamella, thus forming three more or less distinct dark cross-bands. The lateral lamellae are usually more distinctly banded than the median, which is often unmarked along the dorsal margin. Total length 23-24; h. w. 4.6-5.6; h. f. 4.0-5.4; caud. lam. 8.0-8.5; ov. 2.0-2.2.

Habitat and range. Partly shaded ponds or backwaters of quiet streams, more generally distributed in marshy waters southward. N.S. to w. Ont. and N. Dak., s. to Conn., S.C., Fla., and Ala., w. to Kans. and Okla. Distribution in Canada. N.S.—Digby, Annapolis, Lunenburg, Halifax, and Colchester counties. N.B.—Chamcook Lake, near St. Andrews. Que.— Vaudreuil, St. Paul, Otter Lake, Hull, Gatineau Pte. Onf.-Generally distributed throughout s. Ont., the most abundant Lestes in the Lake Erie counties, somewhat less common northward in the Muskoka, Parry Sound, and Manitoulin districts, also in the Kenora and Rainy River districts. Our most northern record is from Minaki, but Mr. Morley Neal, who collected Odonata in the vicinity of Favourable Lake (5305(XN), described

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a damselfly which he had seen but failed to capture, and from his description I was satisfied he had seen L. rectangularis. The records from western Ontario indicate that rectangularis will certainly be found in eastern Manitoba. Field notes. Although breeding in a variety of still waters, sometimes freuenting ponds in the open, L. rectangularis shows a decided preference )r somewhat shady situations. The difference in this respect between L. rectangularis and L. disjunctus, the two commonest late-summer Lestes in southern Ontario, is well illustrated by their distribution on two small streams that discharge into Lake Simcoe near our summer residence. These streams are mere brooks, less than a mile long, but each widens out within a hundred yards of its mouth into a pond-like basin, rich in aquatic vegetation and bordered by cat-tail marsh. Just above this expansion is an intermediate zone, which is narrower, shadier, and much less weedy, and the marginal vegetation has a smaller proportion of cat-tails (Typha), and more bur-reeds (Sparganium), with a background of alders and a variety of shrubs and deciduous trees. Year after year we have noticed that the common Lestes of the open pond is L. d. disjunctus, whereas at the narrower shadier part it is L. rectangularis. The areas frequented by the two species overlap a little, but this overlapping takes place just where the types of habitat intergrade. Adults of rectangularis of both sexes are often found resting in the woods in complete shade, in the vicinity of a quiet stream, pond, or ditch. This is one of the later Lestes to emerge. In the extreme south of Ontario, e.g. at Niagara-on-the-Lake and Jordan, we have seen tenerals on June 18, and found them in abundance, though still teneral, on June 20 and 21. We have one Lake Simcoe record for June 15, but this is an unusually early date. We found two rectangularis at a temporary pond just north of Toronto, on June 26, 1943, where L. unguiculatus had recently emerged, and this appears to be our earliest date for the Toronto region. There seem, in fact, to be two peaks of emergence in southern Ontario, and this is suggested by Montgomery's graph (1948) for Indiana, where emergence begins about the first of June. During 1952 we found great numbers of tenerals and exuviae at an oxbow pond in the Don Valley on June 30, and on other occasions we have found similar numbers of both in early August; e.g. on August 5, 1941, at the stream near DeGrassi Point, Lake Simcoe. According to Montgomery's graph, July is the month of greatest abundance of rectangularis in Indiana. In Ontario, August seems to be the month when it is most in evidence, although we have no exact date to support this impression. We have witnessed the oviposition of L. rectangularis only in September, but attach no particular significance to this fact. On September 5, 1945, we saw several pairs ovipositing in Sparganium and other emergent water plants in the creek at DeGrassi Point, Lake Simcoe. They performed at a height of one to two feet above the water. We noted a similar performance on the same creek on September 10.

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FAMILYC O E N A G R I I D A E

In this family the radial sector arises from Mi-3 at the subnodus; M8 separates from Mi-2 a little before the subnodus; there are no intercalary sectors in the spaces on either side of M3; the pterostigmata are shorter than in Lestidae, less than twice as long as wide, only rarely surmounting more than one cell and part of another; the wings in our species are clear, nearly always closed when at rest in the sagittal plane; the legs are shorter than in the other families; the superior appendages of the male are shorter than segment 10, not forcipate; colours are often clear and bright, frequently blue but sometimes green, yellow, orange, red, or purple, marked with black or dark brown. Nymphs are green or brown; the labial mask is shorter than in Lestidae, not extending back much beyond the front coxae, and not conspicuously narrowed proximally; the middle lobe is closed, the lateral lobes parallelsided, terminating in not more than two hook-like processes, the movable hook arises nearer the middle line than in the Lestidae; mental setae are present or absent; lateral setae are present, although sometimes reduced to one; the caudal lamellae have tracheae branching from near the base, leaving the axis at an acute angle. The small brightly coloured damselflies of our fauna all belong to this family. The females are often dichromatic, the homoeochromatic form being like the male in colour and often also in markings, while the heterochromatic form differs from the male not only in colour but often also in the pattern of the markings.

FAMILY COENAGRIIDAE—KEY TO THE GENERA ADULTS 1. Tibiae with setae of anterior row generally twice as long as the intervening spaces; wings stalked only to the level of the 1st antenodal cross-vein Argia Tibiae with setae of anterior row hardly longer than the intervening spaces; wings stalked usually to a level between the 1st and 2nd antenodal cross-veins 2 2. No pale postocular spots on head With pale postocular spots on head

3 5

3. Body black and red, rather short and thick-set, intersternum of male with a hairy prominence Amphiagrion Body not black and red, more slender, intersternum of male without a distinct hairy prominence 4

PLATE 22 Lestes, anal appendages of males, dorsal view: 1. L. eurinus; 2. L. vigilax; 3. L. inequalis; 4. L. congener; 5. L. unguiculatus; 6. L. dryas; 7. L. d. disjunctus; 8. L. d. australis-, 9. L. forcipatus-, 10. L. rectangularis.

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4. Body metallic green above, the last two segments usually pale blue; frons angular in profile; small slender species about an inch long Nehalennia Body blue or green and black, thorax yellow below; frons rounded in profile; larger species, about 1.5 inch long Chromagrion 5. M2 separating from Mi-2 near the 5th postnodal on the fore wing, 4th on the hind wing or beyond; pt. in front and hind wings of male similar; seg. 10 of male not usually elevated (except in E. exsulans); females not distinctly dichromatic, their markings not becoming obscured with age 6 M2 separating from Mi-2 near the 4th postnodal on the fore wing, nearest the 3rd (or 2nd) on the hind wing; pt. in fore and hind wings of male usually different in colour or size, or both; seg. 10 of male elevated, generally bifid; females generally dichromatic, their markings becoming obscured with age 7 6. Sternum of seg. 8 of female without a vulvar spine; penis bearing long apical or subapical membranous processes; inf. apps. of male in profile not distinctly triangular or, if so, with apex ventral, consisting of a stout base and a slender terminal part, which is sometimes concealed in profile view Coenagrion Sternum of seg. 8 of female with a vulvar spine; penis without long apical or subapical processes; inf. apps. of male triangular with apex uppermost and usually somewhat curved dorsad Enallagma 7. Male with ,pt. in front wing not separated from costal margin; seg. 10 raised into a bifid process; female usually with an external black stripe on middle and hind tibiae; fore wings with usually more than 7 postnodals Ischnura Male with pt. in front wing removed from costal margin; seg. 10 with a slender cylindrical process; female with no external stripe on middle and hind tibiae; fore wings with usually less than 7 postnodals Anomalagrion NYMPHS The main difficulty in constructing a key to the genera of this family, based on nymphal characters, is that the characters that appear to be generic do not always correspond to those based on adult features. This is the case in the related genera Enallagma, Coenagrion, and Ischnura. Considering the Canadian species of Enallagma alone, there are four welldefined groups of nymphs apparently deserving of generic rank. One of

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these groups, the cyathigerum group, is inseparable from Coenagrion and Ischnura* and, if we knew these forms only as nymphs, we would certainly class them as one genus. E. exsulans and antennatum would each stand alone, although exsulans has near relatives in the United States which would make a second group, and aspersum, whose nymph is unknown, would possibly be one of this group; a third group would be represented by antennatum and a fourth by E. vesperum and signatum. The last two have a number of close relatives in the United States. Hence a key to the recognized genera based on nymphal characters becomes highly artificial and, in some places, breaks down altogether. 1. Elongate cylindrical forms; labium with usually 3 or 4 mental setae (only one in Nehalennia); lateral setae 5 or 6 (rarely 4 or 7); lateral lobes truncate, with a denticulate margin, the largest denticle next the short end-hook; caudal lamellae not more than one-third as wide as long, more or less lanceolate, usually with pointed apices; tracheae of lamellae plainly visible 2 Short, thick-set, somewhat depressed forms; labium without mental setae; lateral setae 1-3 (rarely 4); lateral lobes bifid, the mesal branch being the end-hook; caudal lamellae ovate or obovate, one-third to more than half as wide as long; apical ends usually blunt, often terminating in a minute filamentous tip; lamellar tracheae only partly visible because of dense pigmentation Argia 2. Posterolateral margins of head angulate Posterolateral margins of head rounded

3 4

3. Caudal lamellae oblanceolate, widest at distal fourth, darkly pigmented except on apical margin Chromagrion Caudal lamellae ovate-lanceolate, widest about the middle, with little or no pigmentation Amphiagrion 4. Labium with 5 or 6 (rarely 4 or 7) mental setae; main lamellar tracheae usually evenly spaced 5 Labium with one mental seta only; main lamellar tracheae proximally sparse, distally closer together Nehalennia 5. Caudal lamellae bluntly pointed, pigmentation variable or absent (Coenagrion \Enallagma Caudal lamellae tapering to slender apices; pigmentation absent or confined to tracheae, or with 1-3 dark transverse bands (Ischnura [Anomalagrion •The known nymphs of Canadian species of Coenagrion and Ischnura have sevensegmented antennae, those of Enallagma six-segmented.

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Genus Argia Rambur These are damselflies of medium build and moderate to rather large size. The wings are petiolate to about the level of the first antenodal cross-veins; in the fore wing there are 12-18 postnodal cross-veins, in the hind wing 10-16; M2 arises between the fifth and ninth postnodal cross-veins; the pterostigmata surmount one to two cells. The superior appendages in the male are very short; the inferior appendages longer, their posteroventral surfaces usually sloping dorsad and flaring toward the posterior margin, which is often somewhat bifurcate; the sternum of segment 8 of the female is without a vulvar spine. Colour-pattern is varied, the North American species exhibiting two trends, (1) toward blue and purple, marked with comparatively little black, and (2) toward brown and yellow, with the black predominating. A. moesta is somewhat neutral, and is the only Canadian species to become heavily pruinose. The nymphs are the shortest, stockiest, and most depressed of our Zygoptera, presenting a characteristic appearance, which is easily recognized. The head is subpentagonal, longer in comparison with its width than in other Coenagriid genera of our fauna; the eyes are moderately large but not very prominent; the postocular lobes are decidedly prominent, although well rounded and more or less setose. The antennae are seven-jointed, usually about as long as the head, the segments increasing in length from 1 to 3, then decreasing to the end, the last two segments not very distinctly defined; the labial mask, when folded, does not reach the mesocoxae; mental setae are wanting, but a row of 12-20 short spinose marginal setae is resent; there are 1-4 lateral setae, occasionally none; the lateral lobes, eyond the base of the movable hook, are divided into two pointed branches, of which the mesal one is the longer and is the end-hook. The wing-cases are as long, or nearly as long, as head and thorax; the legs are sprawling and somewhat flattened. The ovipositor is depressed, usually extending just beyond the end of segment 10. The caudal lamellae are rarely less than two-fifths as broad as long, ovate or obovate, bluntly angulate or rounded distally, but usually terminating in a minute filament; they are heavily pigmented, sometimes uniformly dark, more frequently banded or blotched, the tracheae being more or less obscured; the margins of the lamellae are fringed with a mixture of stiff bristles and soft hairs or the latter only. One soon learns to recognize adult argias from their habits of flight, which are very different from those of most of our Zygoptera. They all show a preference for bare sunny places on which to alight, and are thus to be found flying low over roads or hard paths, clay banks, logs, or rocks, according to the nature of their special habitat. They are mostly stream species and, as such, often settle on boulders projecting from the water or rocks along shore. Even A. violacea, which frequents small gentle streams or lakes, often with grassy banks, prefers to settle on bare places if they are available. Argias are very alert insects and do not rest long in one spot.

E

PLATE 23 Argia, anal appendages of males, (a) lateral and (b) dorsal views: 1. A. moesta; 2. A. apicalis; 3. A. translata; 4. A. tibialis; 5. A. sedula; 6. A. violacea; 7. A. vivida; 8. A. emma.

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They must be approached with caution in order to be caught in the net. The females oviposit in wet wood, which may take the form of logs, boards or, according to Byers (1930), floating chips. The females may oviposit in tandem or unattended by the male. Pairs of A. moesta become completely submerged while ovipositing, and may remain under water for half an hour or more. The nymphs usually inhabit gently moving water, being particularly characteristic of streams, although A. moesta frequents rock-margined lakes in their most exposed shores. This species is also found under stones in rapids, while others live in the mud at the bottom of quiet streams or lakes. Argia is mainly a neotropical genus, the greater number of species being found in South and Central America. Eighteen species are known from the United States and, of these, eight enter Canada, most of them for a short distance only. Six species inhabit the Eastern Provinces and two others occur in southern British Columbia and the Alberta Rockies. Key to the Species of Argia Males 1. Abdominal segs. 3-6 dorsally black or brown (juv.), with pale basal annuli and often a pale mid-dorsal line on the anterior segments 2 Abdominal segs. 3-6 dorsally violet or blue, with black apical spots divided or constricted mesally 6 2. Length under 40 (33-38) mm.; pt. surmounting one cell (rarely 1.5 cells); inf. apps. more or less distinctly bifid; dorsum of head and thorax with little or no pruinosity 3 Length rarely under 40 mm.; pt. surmounting 1.5 to 2 cells; inf. apps. not bifid; dorsum of head and thorax, except in tenerals, heavily bluish white pruinose moesta 3. Mid-dorsal thoracic stripe at least half as wide as the pale antehumeral stripes; humeral stripes extending the entire length of the thoracic pleura, usually as wide as the antehumerals or wider; a black streak on the second lateral suture; sup. apps., viewed from behind, without a mesally decurved hook 4 Mid-dorsal thoracic stripe a mere hair-line; humeral stripes obsolete except in the anterior fourth and at the posterior end, where there is a short narrow spur, otherwise without a black line; sup. apps., viewed from behind, terminating mesally in a decurved hook apicalis

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4. Dark areas of abd. segs. 3-6, in lateral view, not constricted by encroachment of pale area from below; dorsum of abd. seg. 8 black or partly black; basal annuli of abd. segs. 3-6 very narrow, being ordinarily less than .33 mm. long and not more than one-fifteenth of the segmental length 5 Dark areas of abd. segs. 3-6, in lateral view, constricted by the encroachment of the pale area from below; dorsum of abd. seg, 8 wholly pale; basal annuli of abd. segs. 3-6 usually about .5 mm. long and one-eighth or one-seventh of the segmental length sedula 5. Pale antehumeral stripes broader than the dark median thoracic stripe; abd. segs. 9 and 10 wholly pale; sup. apps. short, scarcely or not at all arched; inf. apps. with the lower branch not prominent tibialis Pale antehumeral stripes narrower than the dark median stripe, disappearing in old individuals; abd. segs. 9 and 10 partly or entirely black; sup. apps. distinctly arcuate, as viewed in profile; inf. apps. with lower branch prominent, projecting well behind upper branch translate, 6. Sup. apps. in profile decurved or slightly hooked at tip; inf. apps. in profile distinctly bifid; humeral thoracic stripe usually not forked (sometimes in vivida); western species 7 Sup. apps. in profile bluntly rounded, not at all hooked; inf. apps. not distinctly bifid, as seen in profile, although bidentate; humeral thoracic stripe forked posteriorly; eastern species violacea 7. Mid-dorsal thoracic stripe about as broad as the antehumeral stripes; abd. segs. 3-6 with an anterior dark lateral blotch, often narrowly connected with the posterior apical spots; segs. 8-10 pale without black margins; sup. apps. decurved vivida Mid-dorsal thoracic stripe about one-third as broad as the antehumeral stripes; abd. segs. 3-6 without an anterior dark lateral blotch; segs. 8-10 pale, with black ventral margins; sup. apps. slightly hooked at the tips but not decurved emma Females 1, Dorsum of abdomen mostly black, with pale basal annuli on most of the segments; median pale area, if present, a mere line on the more anterior segments; humeral thoracic stripes extending the entire length of the mesopleuron, as broad as the antehumeral stripes and not narrowed posteriorly; second lateral suture marked by a heavy black line 2 Dorsum of abdomen mostly pale, segs. 3-6 with black or dark brown confined to lateral, dorsolateral, or apical markings; humeral thoracic stripe, if present, more or less undeveloped posteriorly 3

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2. Mid-dorsal thoracic stripe at least three times as wide as one of the antehumeral stripes; hind margins of mesostigmal laminae projecting freely in a pair of lobes translata Mid-dorsal thoracic stripe about half as wide as one of the antehumeral stripes; hind margins of the mesostigmal laminae not at all projecting in the form of lobes tibialis 3. Pterothorax without conspicuous dark markings, both mid-dorsal and humeral stripes being either reduced to a fine line or an ill-defined blotch, or absent altogether; dark dorsolateral or lateral markings on segs. 3-6, when definite, consisting chiefly of longitudinal stripes of even width, not constricted nor divided into postbasal and apical spots 4 Pterothorax with well-defined dark markings, the mid-dorsal stripe, even when reduced, being distinctly wider than the carina, and the humeral stripes well developed anteriorly, although reduced to a line posteriorly; dorsal or dorsolateral markings on segs. 3-6 consisting of postbasal and apical spots, which are usually separate on some of the more anterior of these segments, and, even when confluent, are constricted behind the middle 6 4. Dark abdominal markings consisting of longitudinal stripes of nearly constant width, one on each side of each segment, except the first and last two or three, and beneath the stripe a small lateral apical spot; wings colourless; ovipositor not extending at all beyond end of abdomen 5 Without distinct dark abdominal markings, except the small lateral apical spots, although the dorsum of each segment, except the last three, is somewhat darker than the sides; wings slightly tinted; ovipositor projecting slightly beyond end of abdomen sedula 5. Pt. usually surmounting more than one cell; mesostigmal laminae projecting posteriorly in the form of raised lobes, a large robust species moesta Pt. usually surmounting one cell only; mesostigmal laminae not projecting posteriorly in the form of raised lobes; a slender species apicalis 6. Mid-dorsal thoracic stripe wider than one of the antehumerals; humeral stripe generally bifid; mesostigmal laminae produced into a pair of lobes, overhanging the posterolateral depressions, which lack a marginal ridge; dorsal carina terminating in a large triangular expansion 7 Mid-dorsal thoracic stripe less than half as wide as one of the antehumerals; humeral stripe not bifid; mesostigmal laminae not produced over the posterolateral depressions, which are margined by a definite ridge; dorsal carina terminating in a small expansion emma 7. Dorsal pale area on segs. 3 and 4 constricted near the posterior end by slender mesal protrusions of the apical black spots; projecting lobes of

PLATE 24 Enallagma, anal appendages of males, (a) lateral and (b) dorsal views: 1. E. carunculatum; 2. E. civile; 3. E. clausum; 4. E. boreale; 5. E. cyathigerwn; 6. E. vernale; 7. E. hageni; 8. E. ebrium; 9. E. minusculum-, 10. E. geminatum.

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mesostigmal laminae ovoid and basally constricted; range in Canada eastern violacea Apical black spots on segs. 3 and 4 without mesal protrusions, usually close together or confluent; projecting lobes of mesostigmal laminae broad and not at all constricted at base; range western vivida Nymphs 1. Caudal lamellae with a marginal fringe of stiff bristles mixed with fine long hairs toward the apex 2 Caudal lamellae without stiff marginal setae or with only a few near the base 5 2. Caudal lamellae broadest at or before the middle, rounded at base; western species 3 Caudal lamellae broadest beyond the middle, narrowed toward the base; eastern species 4 3. Antennae shorter than head; lateral setae 4; caudal lamellae with apices acute vivida Antennae slightly longer than head; one lateral seta; caudal lamellae with round-angulate apices and a fine filament at tip emma 4. Lateral setae 3; caudal lamellae with coarse dark blotches on a pale background and a dark cross-band immediately beyond the middle sedula Lateral setae 2; caudal lamellae dark and nearly uniform, except near the apices, where they are crossed by a pale V-shaped mark violacea 5. Caudal lamellae broadly rounded distally, with a minute filament at tip, uniformly dark except along the apical margin, which is paler; labium with one lateral seta; lateral carinae of lateral lamellae with numerous long tapering setae moesta Caudal lamellae with acute or subacute apices; lateral carinae of lateral lamellae with short blunt setae or none 6 6. Lateral carinae of lateral lamellae without setae, except a very few minute ones at base0; lateral lobes of labium with one seta each or none translata Lateral carinae of lateral lamellae with a series of short stiff setae on the proximal third or more of the lamella 7 *This character based on a single exuvia mounted in balsam.

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7. Lateral setae 2-4; caudal lamellae with short stiff setae only along the lateral carinae of the lateral lamellae, forming here a crowded series on about the proximal two-thirds of the lamellar length; both median and lateral lamellae widest in the middle region, lateral lamellae about two-fifths as wide as long apicalis Lateral seta 1; caudal lamellae with a very few short stiff setae near the base of the median, as well as the lateral lamellae (dorsal edge of median, ventral edge of lateral, and a short row on each side of median) and a longer series, about 20, on the lateral carinae of the lateral lamellae; lateral lamellae widest beyond the middle, a third as wide as long or even narrower tibialis Argia moesta (Hagen). (PL 4, fig. 4; pi. 7, figs. 4, 5, 6; pi. 15, fig. 1; pi. 27, fig. 1) Agrion moestum Hagen, Syn. Neur, N. Amer., p. 94,1861. Argia moesta Selys, Bull. Acad. Belg., (2), 20: 385,1865. Agrion putridum Hagen, Syn. Neur. N. Amer., p. 96,1861. Argia putrida Selys, Bull. Acad. Belg., (2), 20: 385,1865. This is our largest and most abundant eastern Argia, which flies about rocky streams and lakes throughout the summer. It is remarkable for the dense whitish pruinosity of the male, which begins to appear as soon as the teneral stage is passed. Even the female becomes somewhat pruinose. Male. In the teneral stage the general colour is tan and dark brown. Dorsum of head dark brown, paler on the frons, reddish about the ocelli. Labrum, clypeus, and genae shining tan; labium pale yellowish; rear of head smoky brown. Pronotum dark brown in the middle, sides paler. Mid-dorsal thoracic stripe smoky brown, somewhat wider than the tan antehumeral stripes; dark humeral stripe extending from mesinfraepisternum nearly to ante-alar ridges; metapleura pale dull brownish, slightly darkened on mesepimera; a fine dark line on the second lateral suture, enlarging into a spot near the ante-alar ridge. Legs mostly pale buff, with black spines; femora with a darker streak on the outer face; tarsi black. Abdomen dark smoky brown; dorsum of segs. 1 and 2, a mid-dorsal line on 3 and on some of the more posterior segments light reddish brown or tan; pale basal annuli in most of the segments. Wings hyaline, pt. light brown. In mature males most of the pattern is obliterated by the dense white or grey pruinosity, which covers the dorsum and rear of the head, most of the prothorax, the entire pterothorax (usually except upper part of sides), coxae and femora, and basal segments of abdomen, on which the pruinosity gradually thins out caudad. Where not thus concealed, the abdominal segments are dull black with narrow pale annuli. Female. Tenerals dull ochraceous to tan, with darker longitudinal stripes on the abdominal segments. Dorsum of head reddish brown, paler on the face; labium pale buff. Rear of head pale, with one or two dark blotches on each side. Pronotum pale brown, variegated with darker brown, a dark spot on each side of the hind lobe. Pterothorax pale dull ochraceous; dorsal carina marked with a dark hair-line, which widens on the mesostigmal laminae; an ill-defined darker stripe on each side of the carina and a darker cloud on the mesepimera. Pleural sutures unmarked, or only with an extremely thin hair-line and a spot near the ante-alar ridge. Legs pale brownish,

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with black setae, marked as in the young male. Wings hyaline, pt. pale brown. Abdomen pale and dark brown; dorsum with a light tan stripe extending the entire length, constricted or divided near the posterior end of most of the segments and bordered by dark dorsolateral stripes, which are interrupted by pale yellowish basal annuli. Below there is a pale ventrolateral stripe, which narrows behind as far as seg. 7; it is bordered below by a dark ventral stripe. Segs. 8-10 pale, 8 and 9 with dark dorsolateral and lateral markings. In old females the pale areas become everywhere more or less darkened, and a grey pruinosity appears on the same areas as on the male, although less marked. The thorax in old females appears blue, but not a clear blue as in A. apicalis. Pt. normally surmounting more than one cell, frequently two cells. Seg. 10 of male with a posterior incision, whose margins are somewhat elevated. Sup. apps. short, bluntly rounded; inf. apps. scarcely projecting behind the sup. apps., neither bifid, nor flaring, the posterior surface almost vertical. Postnodal cross-veins, f. w. $ 15-17, $ 14-18; h. w. $ 13-15, $ 12-15. Measurements. Total length $ 38-42, $ 39.0-42.5; abd. $ 30.0-33.5, 9 30-34; h. w. $ 24-25, $ 25.0-27.5; h. f. 8 $ 4.3-4.5; pt. 1.2-1.4; w. hd. 4.5; ov. 1.5. Nymph (pi. 6, fig. 7; pi. 33, fig. 1; pi. 37, fig. 1; pi. 39, fig. 1). Eyes not very prominent, posterolateral margins of head rounded, spinose; hind margin excavate. Antennae as long as head, very slender beyond seg. 2; ratio of seg. lengths, 7:10:15: 11:7:4:2. Labium, when closed, reaching front margin of mesosternum; greatest width of mask five-sixths of its length; width at base three-fifths of distal width; middle lobe produced to a distance almost half the length of first seg. of lateral lobe, with one small lateral seta arising near the articulation of second segment; lateral margin of mask nearly straight, with 13-19 short setae; end-hook of lateral lobe separated from inner margin by a distinct notch. Wing-cases as long as head with thoracic segs. 1 and 2, usually reaching end of seg. 5; hind femora not quite reaching end of wingcases. Caudal lamellae a little longer than hind femora, broadly elliptical, widest at middle; apices rounded, with a minute slender point, which is often missing, the width here one-half (lat. lam.) to three-fifths (med. lam.) of the length; margins and lateral carinae densely fringed with soft hairs, but without spinose setae. Colour generally dark brown (often buff in preserved specimens); pattern of markings not usually conspicuous. Femora dark, with a pale ante-apical annulus; in pale individuals a dusky annulus may sometimes be seen just beyond the middle; tibiae somewhat darkened at base and apex and with a median dusky annulus. Caudal lamellae very dark, except a narrow apical margin which is whitish. Total length (extended) 20-23; f. w. 5.5; h. f. 4; w. hd. 3.5-4.0; caud. lam. 5-6.

Habitat and range. Rocky shores of streams and lakes. Mex. and Calif, e. through Ariz., Utah, Col., Tex., and Okla. to Fla., and from Kans. and Mo. n. to Minn, and w. Ont., e. through the middle and northern states and eastern provinces to Me. and N.S. Distribution in Canada. Onf.-Lake of the Woods, s. Kenora Dist, and probably eastward through the Rainy River Dist., but absent from the n. shore of Lake Superior; appearing in abundance on Georgian Bay, thence n. to Lake Timagami, Nipissing Dist, and s. throughout southern and eastern Ont. S. Kenora, Nipissing, Parry Sound, and Muskoka districts; Essex, Kent, Middlesex, Oxford, v Brant, Haldimand, Huron, Wellington, Peel, York, Bruce, Grey, Simcoe, Peterborough, Hastings, Leeds, Lanark, Addington, Prescott, Carleton, and Renfrew counties. Que.—Southern Counties, St. Lawrence Valley to Lanoraie, Ottawa, and Gatineau valleys;

PLATE 25 Enallagma, Amphiagrion, Nehalennia and Chromagrion, anal appendages of males, (a) lateral and (b) dorsal views: 1. Enallagma exsulans; 2. E. antennatum; 3. E. aspersum; 4. E. vesperum; 5. E. signatum; 6. Amphiagrion saucium; 7. A. abbreviatum; 8. Nehalennia irene (lateral view); 9. N. gracilis (lateral view); 10. Chromagrion conditum.

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Laurentides to Lac Mercier and Nominingue; Vaudreuil, St. Chrysostom, Hemmingford, St. Johns, Knowlton, Fulford, Wakefield and other localities in the Gatineau Valley. N.B.—Chamcook Lake, near St. Andrews; Gibson Lake; S.W. Miramichi R. N.S.—Near Annapolis and South Milford, Annapolis Co., Lunenburg Co., Bras d'Or Lakes, C.B. Field notes. This is the largest of the Canadian Coenagriidae and is common throughout southern Ontario wherever there are rapid streams or channels with rockbound shores or projecting boulders. It is abundant both in the regions underlain by sedimentary rocks and in those of the Precambrian. The nymphs lurk under stones and bottom debris and, when emergence takes place, the exuviae are generally left adhering to stones or logs, well above the water-line. The tenerals wander away from the stream and may be seen in sunny places in open woods, roads, or clearings, usually within a few hundred yards of the place of emergence. From experiments conducted by Borror (1934) on an Ohio stream with marked individuals of A. moesta, it was found that there was relatively little movement of the insects up and down stream but considerable movement to and from the river, occasionally to distances of over 200 yards, although usually much less than this. The river was wooded on the side where the damselflies were liberated, but there were two cleared passages (air drains) from the orchards and field behind the woods, and it was chiefly in these passages that the insects were recaptured. Some were taken as much as 24 days after liberation. Each individual could be recognized by the pattern of spots by which its wings were marked with india ink. The period of flight is a long one, beginning early in June in southern Ontario and southwestern Quebec, and lasting until some time in September. Our earliest record is June 7, the locality being the Credit River at Erindale, Ontario; but even on this date there were already mature individuals among the larger number of tenerals. Some young adults had strayed up the slope of the wide glaciated river valley and had nearly reached the top, having travelled about a quarter of a mile. From about this time on, in average seasons, for more than a month later, tenerals continue to appear, flying up the slopes of the valley to the top. But by the middle of July the majority of individuals are pruinose and flying in abundance all along the river. Borror found that adults returned to the stream to mate when about 14 days old. Farther north and in the Maritime Provinces A. moesta appears some-

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what later in the season, Thus we noted of this species at South Bay, Lake Nipissing, Ontario, that on July 10 "tenerals were beginning to be common," and at Sandy Bottom Lake, N.S., on July 5, that there were "many in the open woods within a hundred yards of the lake, all more or less juvenile." The records of pairing extend from June 21 (La PSche River, Gatineau Valley, Quebec) to September 12 (Erindale, Ontario). Pairing seems to be most active between late June and mid-August. We have observed oviposition in July and August, but it probably continues into September, since mating has been observed in that month. In this process, the female descends alga-covered rocks or wooden structures into which the eggs are thrust. She becomes completely submerged, often remaining under water for half an hour or more. She is very frequently but not always accompanied by the male. Kellicott (1899) made observations on five pairs that were ovipositing on the timbers of a wharf. They descended to depths varying from "barely covered" to six inches. The male in most cases abandoned the female sooner or later, while the female remained under water from 30 minutes to an hour. At Buckshot Lake, Addington Co., Ontario, in the late afternoon of July 9, 1945, we watched two unaccompanied females and a pair ovipositing on the sides of a diving raft. The female member of the pair was already below the surface of the water when we first noticed her, and gradually descending. The male, which was only partly submerged, was quiescent until closely approached, when he vibrated his wings as though attempting to escape, but became quiet again when we withdrew. We watched this pair for over half an hour. By this time they had reached the bottom of the raft, the female being now on the underside. We did not observe this pair come out, but in the case of another pair, the male still held the female as they emerged, although they separated almost immediately afterwards. Usually the male is freed soon after the pair becomes submerged. Argia apicalis (Say). (PI. 2, fig. 4; pi. 9, fig. 3; pi. 15, fig. 2; pi. 23, fig. 2; pi. 27, fig. 2) Agrion apicale Say, J. Acad. Nat. Sci. Phila., 8: 40, 1839. Argia apicalis Selys, Bull, Acad. Belg., (2), 20: 414, 1865. A slender species restricted in Canada to southern Ontario, where it frequents rivers through most of the summer. The clear blue of the thorax of the adult male distinguishes it from all other Canadian species of Argia. Male. Dorsum of head in front of ocelli pale greenish, partly divided by black streaks extending forward to base of antennae; behind the ocelli black, with large pale occipital spots; frons, clypeus, labrum, and genae greenish, labium greenish grey, rear of head light yellowish. Pronotum black, with front margin, lateral lobes, and a pair of dorsolateraf spots pale. Pterothorax clear light blue in living mature males, pale greenish in preserved material; light yellowish beneath and on lower parts of pleura. Dorsal carina a black hair-line; mesostigmal laminae and ante-alar ridges black; dark humeral stripe short and rectangular, covering upper half of mesinfraepisternum

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and a small part of the mesepimeron in front of the metastigma. There is also a short narrow streak extending from ante-alar ridge to the pits on the two pleural sutures. Legs pale greenish marked with brown; coxae pale, femora with outer surfaces mostly dark, tibiae pale with flexor surfaces dark, tarsi and spines dark. Wings about four-fifths the length of the abdomen, hyaline; pt. dark brown, surmounting one cell. Abdomen slender, black above, or dark brown, deepening to black towards the posterior ends of the segments, interrupted only by the short pale basal annuli, and extending on the posterior fifth to the ventral edges of the terga, so that the ventrolateral pale areas do not reach the posterior ends of the segments; sees. 8-10 light blue, with black ventrolateral margins; seg. 2 with a pale mid-dorsal streak, or 2 and 3 with a pale middorsal line. Sup. apps. of male in profile appear short and bluntly rounded, but viewed from behind they are seen to Dear two decurved hooks, a long mesal and a short caudal one. Inf. apps. shorter than seg. 10, projecting well behind sup. apps., distinctly bifid, outer branch stout, erect, rounded, inner branch slender and horizontal. Female. Dorsum of head light greenish, with a dark transverse occipital area or sometimes dark as far forward as the ocelli, with a pair of pale occipital spots and a transverse bar between them; face, including clypeus and labrum pale olivaceous to ochraceous, or grey, paler beneath, marked as in male, except that the short humeral stripe is not so well defined and is more variable; being sometimes a mere smudge and sometimes a distinct dark stripe on the mesepimeron, bordering the anterior half of the suture, including the mesinfraepisternum. Legs pale, outer surfaces of fore femora with a dark stripe and usually narrower dark streaks on middle and hind pairs; tibiae mostly pale but fore pair with a dark streak on under surface; tarsi with tips of last segment and claws black. Wings about four-fifths as long as abdomen, hyaline, pt. light brown. Abdomen dark brown above, with pale markings much as in male, except that segs. 8-10 are dark with a dorsolateral pale stripe, the pale basal annuli on most of the segments are wider, as are also the pale ventromarginal areas, because of the greater size of the segments. Ovipositor extending to end of seg. 10 but not beyond. Postnodal cross-veins, f. w. $ 13-17, 9 14-17; h. w. # 12-14, $ 13-14. Measurements. Total length $ 36-37 (33-38), $ 36-38; abd. $ 28-29 (26-30), $ 28.5-29.5; h. w. $ 22-23 (20.5-24.5), $ 23-24; h. f. $ $ 3.5-4.0; w. hd. 4.0-4.6; pt. .7-.8; ov. 1.6. Nymph (pi. 37, fig. 2; pi. 39, fig. 2; pi. 43, fig. 1). Posterolateral margins of head forming a well-rounded rectangle, bearing numerous short setae; antennae about as long as head, ratio of seg. lengths, 7:10:12:7:6:4.5:2. Folded labium reaching slightly beyond fore coxae, greatest width of mentum about equal to its length and more than twice its width at base; lateral margins gently convex, except at extreme base, with 10 or 12 short marginal setae; middle lobe subangularly produced to a distance equal to about one-third of its width; lateral lobes bearing each 2-4 lateral setae; end-hook marked off from mesal surface by a distinct notch. Caudal lamellae widest about the middle, the median lamella about half as wide, the lateral lamellae two-fifths as wide as long, with very short pointed apices and fringed with fine hairs; an irregularly double row of very short, stiff setae on the basal two-thirds of the lateral carinae of the lateral lamellae; median lamella without stiff setae near the base. Colour brown, inconspicuously marked; femora pale at base and apex, with two wide darker annuli, which may unite into a single very wide annulus; tibiae with a median dark annulus, sometimes indistinct, apices dusky. Abdomen with a pale median stripe, which widens caudad as far as seg. 9. Caudal lamellae smoky, with numerous small dark spots or blotches, often with a pale cross-band at two-thirds of their length. Total length 20; abd. 9.5; h. w. 4.5; h. f. 3.7; w. hd. 4; caud. lam., med. 4.5; lat. 5.5. Described from nymphs and exuviae of reared specimens taken at Galesbure, 111., bv Dr. J. G. Needham.

PLATE 26 Coenagrion and Ischnura, anal appendages of males: 1. Coenagrion resolutum, (a) lateral and (b) dorsal views; 2. C. interrogatum, (a) lateral and (b) dorsal views; 3. C. angulatum, (a) lateral and (b) posterolateral views; 4. Ischnura verticalis, (a) lateral, (b) posterior, and (c) dorsal views; 5. I. damula, (a) lateral and (b) posterior views; 6. J. cervula, (a) lateral and (b) posterior views; 7. I. perparva, (a) lateral and (b) posterior views; 8. /. posita, (a) lateral and (b) posterior views; 9. I. erratica, (a) lateral and (b) posterior views; 10. Anomalagrion hastatum, (a) and (b) posterior views.

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Habitat and range. Smaller rivers with a gentle current; occasionally on ponds. Fla. to Tex., n. to s. Me., N.Y., s. Ont, s. Mich., Wis., s. Minn., N. Dak., Kans. Distribution in Canada. Carolinian Zone, its northern limit being in the vicinity of London and Toronto; abundant on the lower reaches of the Grand and Thames rivers. On£.—Kent, Elgin, Middlesex, Oxford, Haldimand, and York counties. The Humber River at Weston, in the Toronto area, is at the extreme northeastern limit of this species' range. Only a few specimens have been taken here. Field notes. Although limited in Canada to a comparatively small part of Ontario in the extreme south, this species is quite abundant on the larger streams of this area; in fact, on the lower reaches of the Thames and the Grand rivers it is decidedly the most abundant Argia. In Indiana it has been taken also at ponds and gravel pits (Montgomery, 1944), but it is essentially a stream species. It flies with a dancing movement over the vegetation of the stream banks, frequently coming to rest on foliage, although always in the horizontal position. It exhibits, however, the characteristic habit of the genus of alighting on bare ground, a habit that is particularly noticeable when the tenerals spread along roads and fields nearby. According to Carman (1917), the nymphs "live in the mud at the bottom but when mature approach the bank and hide among dead, submerged weeds or rubbish. The eggs are deposited below the water in driftwood and large numbers of females may sometimes be seen congregated about an old log at the water's edge, depositing eggs." According to Needham and Heywood (1929), "Transformation takes place early in the forenoon, a few inches from the edge of the water." We have taken A. apicalis from June 24 to August 18, but this probably does not represent the entire length of the flight period. Montgomery (1944) gives a seasonal range in Indiana of about three and one-half months, i.e. from the first of June to the third week of September, while Needham (1929) found it at Galesburg, Illinois, as early as the middle of May. The season in Ontario, even of the southernmost counties, is shorter than in Indiana, and we can therefore postulate that, in the case of A. apicalis, it probably begins about the middle of June and lasts until early September.

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On June 24,1934, we found this species on the Thames River at Chatham. It was not yet abundant, and most of the population were tenerals and were flying over the vegetation of the river bank. Only a few mature individuals were noticed. Next day, four or five miles upstream from Chatham, we found tenerals in the fields skirting the river and scattered along the vines and shrubbery of the banks. There was a considerable number in full colour, although the tenerals predominated. We found one individual just emerged with its exuvia. On July 9, 1950, we found apicalis flying at Caledonia on the Grand River. It was abundant and for the most part mature, and a few pairs in copula were seen. Two days later we found it on the Thames, near Wardsville, in the same general territory in which we collected it on June 24. We also collected it along the margin of a pond-like expansion of a small stream formed by a dam. In both localities we noted mature males and females, together with younger females of various stages. At the second locality most of the individuals seen were pairing. On the later occasions, during August, when we have observed or collected this species, we have found it in abundance and still showing the tendency to fly up the banks to the flat ground above, where it would fly along a road close to the bank, tending to collect about the rain puddles. Argia tibialis (Rambur). (PI. 15, fig. 4; pi. 23, fig. 4; pi. 27, fig. 4) Platycnemis tibialis Rambur, Nat. Hist. Ins., Neur., p. 241, 1842. Trichocnemis tibialis Hagen, Syn. Neur. N. Amer., p. 72, 1861. Argia tibialis Selys, in Sagra, Hist. Cuba, Ins., p. 164, 1865. A dark southern species of average dimensions, reported from only one Canadian locality in southernmost Ontario. Male. Head dorsally brown or blue anteriorly, black behind, with a very irregular boundary between the two areas. The pale colour extends caudad along the margins of the compound eyes about as far as the front of the lateral ocelli, but is partly divided by three forward extensions of the black, all three to the level of the antennal bases, a oroad median extension enclosing median ocellus and narrow ones to the antennal bases. A pale spot in front of each lateral ocellus often joins the pale area in front, and one or two small pale spots are sometimes present behind the ocellar triangle. Face pale, with a dark line on the frontoclypeal suture; mouth-parts buff; rear of head black. Prothorax black; lateral margins and a pair of dorsolateral spots tawny, obscure or absent in old individuals. Mid-dorsal thoracic stripe black, about half as wide as the tawny antehumeral stripes; humeral stripes about as wide as antehumerals, covering most of mesinfraepisternum and mesepimeron, extending to the ante-alar ridge and enclosing at their posterior ends a small tawny spot which may disappear with age. Metapleuron pale, with a heavy black line on the second lateral suture; sterna chiefly pale yellowish at first, but becoming whitish pruinose at maturity, the pruinosity extending over the pale pleural areas ana basal parts of the legs. Coxae pale, trochanters and femora black, with a fine dorsal pale line; tibiae with flexor surface black, extensor surface yellow; tarsi black. Abdomen black above; seg. 1 with a small dorsal yellow spot and a larger lateral one; seg. 2 with an elongated middorsal and a larger lateral spot, constricted about the middle; 3-7 with narrow basal

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yellow annuli, uninterrupted mid-dorsally and confluent below with a long ventromarginal streak, which stops short at about three-fourths of the segment length, these streaks becoming narrower and less distinct caudad; seg. 8 wholly black, 9-10 yellow or blue, with a wide black ventral margin. Wings about four-fifths as long as abdomen; pt. surmounting one cell. Anal apps. shorter than seg. 10; sup. apps. in profile short and straight; inf. apps. bifid, outer branch stout and bulbous, inner branch bluntly conical, extending back scarcely beyond the outer branch. Female. Similar to male in size and colour-pattern. Head in northern specimens with a larger area of pale colour than in males, most of the dorsum appearing pale, with a few isolated spots and streaks of black, the main black area being reduced by further extension along the eye margin of the pale colour, the enlargement of the postocular spots, which are confluent, and the presence of a pale transverse bar between them. Prothorax with tawny lateral margins and dorsolateral spots larger than in male, and sometimes with an additional median spot. Pterothorax as in male, but the humeral stripe sometimes appearing bifid posteriorly, owing to the confluence of the enclosed pale spot with the pale area of the pleura. Legs pale yellow; femora with dorsal and lateral dark streaks; tibiae yellow; tarsi dusky. Wings sometimes proportionally longer than in male, but as a rule the ratio is the same; pt. only slightly paler than in male. Abdomen with the yellow markings more extensive than in male; segs. 8 and 9 black; 9 with a median pale stripe or spot; 10 pale above, black beneath. Ovipositor black, reaching end of abdomen or barely farther. Postnodal cross-veins, f. w. $ 12-15, $ 13-17; h. w. £ $ 11-14. Measurements. Total length $ 30-38, 9 30-36; abd. $ 24-29, $ 23-38; h. w. $ 18-24, $ 19-23; h. f. $ $ 3.5-4.5; w. hd. & 3.7-4.2, $ 4-5; pt. $ .7-.9, $ .8-1.0; ov. 1.5. 'Nymph (pi. 37, fig. 3; pi. 39, fig. 3; pi. 43, fig. 2). Posterolateral margins of head forming a rounded rectangle, coarsely setose; antennae scarcely as long as head, ratio of seg. lengths, 11:17:25:15:8:7:5. Folded labium reaching posterior ends of fore coxae, greatest width of mentum nearly equal to its length and slightly more than twice its basal width; lateral margins gently convex except at base, with 12 or 13 short marginal setae; middle lobe produced to a distance equal to about one-third of its width, forming a rounded angle; lateral seta one; end-hook separated from mesal margin of lateral lobe by a minute notch. Caudal lamellae widest about the middle (med. lam.) or at two-thirds of the length (lat. lam.), greatest width of median lamella being about half the length, that of lateral lamella one-third of the length, apices somewhat acutangulate, with small pointed tips and fringed with fine hairs; lateral lamellae with a single series of short blunt setae on the proximal third or more of the lateral carinae and a very few on the ventral edge near the base; median lamella with a few setae of the same kind near the base on each side and on the dorsal edge. Colour dark brown; dorsum of head with pale ocellar spots; femora with two narrow dark annuli, alternating with pale areas, apices dusky; tibiae with a small narrow dark median annulus, sometimes obscure, darkened at extreme base and apex. Abdomen with dark colour deepened above and below the lateral margins and bordering the pale median stripe, which widens caudad, reaching its greatest width on segs. 8 and 9. Caudal lamellae "sometimes wholly dark and smoky" (Carman), but usually marked with dark and pale areas arranged in somewhat irregular cross-bars, the pale areas broken by dark spots. Typically there is a wide, slightly postmedian dark band between two pale cross-bars, a wider proximal one, and a narrow, often somewhat zigzag, distal one; apices, axis, and usually a basal area dark. Total length 17-18; abd. 8.5; h. w. 4.0-4.4; h. f. 3.8; w. hd. 3.5; caud. lam., med. 4.3, lat. 5. Described from specimens taken by M. J. Westfall in Alachua Co., Fla.

PLATE 27 Argfa, mesostigmal laminae of females: 1. A. moesta; 2. A. apicalis; 3. A. translata; 4. A. tibialis; 5. A. sedula; 6. A. violacea; 7. A. vivida; 8. A. emma.

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Habitat and range. Small to medium-sized streams, with rapids or riffles and pools, and more or less shaded banks. Fla. to Tex., n. to N.J., N.Y., s. Ont, s. Mich., s. Wis., s. Minn., Kans., and Okla. Distribution in Canada. On a small tributary of the Thames River in Kent Co., near Wardsville (Middlesex Co.), June 19, 1922, 1 male, 2 females. This species is common in much of the eastern and middle U.S. and its occurrence in the extreme south of Ontario is not surprising. It is apparently very local, however, probably owing to the lack of favourable habitats in that very flat and overcleared district. Field notes. The stream where the above-mentioned specimens were taken is a small brook that winds through pastures and woods, being partly shaded and partly in the open. We visited it for a few minutes only, but noted that A. tibialis was associated with A. violacea and Enallagma antennatum. The only other occasions when we have taken A. tibialis were on July 20 and 22, 1951, near Richmond, Virginia. Behind the Richmond Autocourt, a short distance north of the city, is a small stream, two or three yards wide, flowing in a shallow gully in the shade of fair-sized trees. The banks were mostly shaded, but there were bare sunny spots here and there where both A. tibialis and A. violacea came to rest. A. tibialis frequented the vicinity of the quiet reaches, while A. violacea apparently preferred the gentle rapids. At a larger stream, which crosses the highway some 25 miles farther north, we found tibialis more plentiful. Below a dam on the east side of the highway the stream flows in a series of rapids and pools between rocky banks, and here we found tibialis, resting on the rocks but very wary. It was also common on the road, which follows a steep course uphill from the stream to the highway. According to Wilson (1912), A. tibialis in the Cumberland Valley, Kentucky and Tennessee, shows a greater tendency to frequent vegetation than the other two argias associated with it, A. apicalis and moesta, and was less constant in settling on the open sunny spots. Williamson (1900) also remarks on the same relative tendency of tibialis to frequent vegetation. Judging from Williamson's (1932) descriptions of the stations where he collected this species in Missouri, it would seem to be found under a great variety of conditions, from clear cold spring-fed streams, with a succession of pools and rapids, to river sloughs, without current and with an abundant growth of spatterdock or lizard's tails. Such sloughs, however, at times of high water, are on a river cut-off. The season of flight in Indiana, as shown in Montgomery's (1944) chart, is from the beginning of June until the second week in September. In Ontario it should be approximately from the middle of June until late in August

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Argia translata Hagcn. (PI. 15, fig, 3; pi. 23, fig. 3; pi. 27, fig. 3) Argia translata Hagen, Bull. Acad. Belg., (2), 20: 410, 1865. A slender, very dark species of average size, known in Canada only from the Thames River in southern Ontario, but very widely distributed southward. Male. Head black above, with a pair of small postocular pale spots, a minute yellowish spot in front of each lateral ocellus; face dark; gcnae, front margin of postclypeus, and labrum greenish to yellowish; labium light brownish or fawn, dusted with bluish grey pruinescence in old individuals; rear of head black, becoming pruinose bluish grey; all pale markings darkening with age. Prothorax and pterothorax black above, covered with soft hairs; pronotum with sides pale and a very small pair of dorsolateral pale spots. Pterothorax with median dorsal stripe at least three times as broad as the blue antehumeral stripes, which taper posteriorly and do not quite reach the ante-alar ridge, these stripes becoming narrow with age and finally disappearing. Humeral stripes very broad, covering nearly all the mesepimeron and enclosing, just before the ante-alar ridge, a pale triangular spot, which in young individuals is prolonged into a streak, closely paralleling the humeral suture and nearly dividing the stripe lengthwise. Sides of pleura, below the humeral stripe, pale yellowish or greenish, often with a reddish brown stripe next to the humeral stripe, the pale portion, together with the sterna and interalar area, becoming somewhat bluish pruinose with age; second lateral suture with a heavy black line. Coxae pale, femora dark brown, or greyish when pruinose; tibiae dark, with extensor surfaces pale; tarsi black. Abdomen black, sides of seg. 1 with a large pale spot; seg. 2 with two small pale markings below the middle, 3-7 with very narrow pale basal annuli, which are interrupted mid-dorsally; ventrolateral pale areas reduced to very narrow lateral and marginal streaks which disappear entirely with age; anal apps. black. Wings about two-thirds as long as abdomen, hyaline; pt. surmounting one cell, sometimes part of second cell. Sup. apps. somewhat arched; inf. apps. projecting back about as far as the length of seg. 10, bifid, the outer branch erect and conical, inner branch more slender, horizontal. Female. Similar to male in proportions, except in the stouter abdomen. Head above black, with a broad pale anterior margin, extending back along margins of compound eyes as far as bases of antennae; other pale spots as in male; face mostly brownish grey (greenish in life ?); anteclypeus and upper part of postclypeus black; labium pale yellowish. Prothorax, pterothorax, and legs marked essentially as in male, without the pruinosity and obliteration of pale markings in old individuals. Abdomen black or deep brown, marked with light yellow as follows: seg. 1 with a large triangular lateral yellow spot; 2 with mid-dorsal, lateral, and ventrolateral streaks; 3-7 with narrow dorsally interrupted yellow basal annuli; 3 also with a longitudinal lateral yellow streak and a fine mid-dorsal yellow line; 8-10 dark brown with ill-defined lateral and ventrolateral streaks. Mesostigmal laminae with a broad rounded lobe on each side of the large triangular base of the median carina. Ovipositor reaching end of seg. 10 but not beyond. Postnodal cross-veins, f. w. $ 13-16, $ 12-16; h. w. j 10-15, $ 10-14. Measurements. Total length $ 32.0-38.5, $ 34-36; abd. $ 26-30, $ 26.5-28.0; h. w. $ 19-22, $ 21-22; h. f. $ $ 3.6-3.7; w. hd. $ 9 4.0-4.8; pt 1; ov. 1.7. Nymph. We had for description only the exuvia of a reared female, received through the Kindness of Dr. M. J. Westfall, Jr. It is mounted in balsam, with the mouth-parts removed and mounted separately. In general appearance and markings the exuvia is similar to that of A. tibialis, although, being flattened, the form of most of the parts cannot be exactly determined.

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Posterolateral regions of head with few and inconspicuous setae. Antennae slightly longer than fore femur; ratio of seg. lengths, 10:16:33:23:13:9:6. Lateral lobes of labium described as having one lateral seta or none; none is visible in the mounted exuvia. Caudal lamellae apparently widest about the middle and, although both (only one lateral lamella is present) are slightly crumpled, the median lamella appears to be three times as long as wide, the lateral lamella a little longer and relatively slightly narrower; apices somewhat acutangulate. The lamellar margins are apparently almost devoid of hairs, even very fine ones, and there are no spinose setae. Even the lateral carinae of the lateral lamellae lack stiff setae, and only a few very minute setae are scattered over the basal part of the lateral lamellae. Colour-pattern similar to that of tibidis. Basal segment of antennae pale, the others darker; femora pale, with two distinct dark annuli; tibiae with three annuli, a basal, a median, and an ante-apical. Abdomen dark, with a pale median dorsal stripe (Carman, 1927). Caudal lamellae darkly pigmented, with a pale area or band about the proximal third and another just beyond the middle, apices pale. Total length approx. 18; abd. 7; h. w. 4.2; h. f. 3.5; caud. lam., med. 4, lat. 5; ov. 7. Described from an exuvia of a reared female, Cobb's Creek, between Penficld and Beechwood Park, Pa., June 1, 1916 (P. P. Calvert), received from M. J. Westfall, Jr.

Habitat and range. Ponds, lakes, and slow streams with shady banks. Calif, to Fla., s. to Colombia, Venezuela, and Trinidad, and n. from Tex. and Okla. to Ind., s. Ont., Pa., N.Y., and Conn. Distribution in Canada. One record from the Thames River at Chatham, Ont. Field notes. A pair was taken on June 25, 1934, while ovipositing in a bed of Myriophyllum or similar aquatic plant just above Chatham. Another pair was flying nearby but was not captured. Prolonged search was made for more specimens but without success. In the field they were easily distinguished from A. apicalis, the only other Argia present, by the much darker coloration. This species, although very widely distributed southward, is rare as far north as Indiana and was therefore not expected in Ontario. The fact that the only specimens seen were paired is of some interest, since Argia apicalis had not yet reached the pairing stage. The few records we have of A. translata from localities comparable in latitude with southernmost Ontario are all dated much later in the season. Thus the Indiana records of Williamson (1917) and Montgomery (1944) are from August 11 to 20; Leonard's (1928) from New York is also for August; Carman's (1927) two from Connecticut are dated July 8 and 29, and we ourselves took two males from York, Pennsylvania, on July 29. There is also a record for September from New Jersey (Calvert, 1900). There are some records dated as early as June 25 and 26 from Maryland and North Carolina, and as late as September 22 (Tennessee), but apparently not for the more northern parts of the range of A. translata. In general the period of flight is similar to those of other species of Argia, which in Indiana are much alike, as indicated by Montgomery's seasonal chart. Both of our captures of A. translata were on large streams with steep banks, clothed with rank vegetation. The current was gentle where the argias were taken, and the stream was without projecting boulders. The

PLATE 28 Enallagma, mesostigmal laminae of females: 1. E. carunculatum; 2. E. civile; 3. E. clausum; 4. E. boreale; 5. E. cyathigerum; 6. E. vernale; 7. E. hageni; 8. E. ebrium; 9. E. minusculum; 10. E. geminatum.

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characteristic haunts of tramlata as described by others, however, indicate a much greater variety of conditions. Wilson (1912) found this species in the Cumberland Valley, Kentucky and Tennessee, "in company with moesta, apicalis and tibialis, but preferring shade and spots amongst dense vegetation rather than the sunny open. None were seen ovipositing in company with the other species but always in secluded places by themselves." Williamson (1934) took translate, on the little Tennessee River, Tennessee, which he described as "a river 100-150 ft. wide, mostly ripples, in full sun with only scanty bordering rapids." Argia sedula (Hagen). (PI. 16, figs. 1, 2; pi. 23, fig. 5; pi. 27, fig. 5) Agrion sedulum Hagen, Syn. Neur. N. Amer., p. 94,1861. Argia sedula Selys, Bull. Acad. Belg., (2), 20: 411,1865. A small to medium-sized species, the males black and blue, the females dull olivaceous, with dark markings ill-defined or reduced. Male. Dorsum of head black, with the following parts blue or greenish: an irregular anterior area extending back halfway along the ocular margin, enclosing bases of antennae; a median transverse spot between the antennae and touching the median ocellus behind; and a pair of large occipital spots touching margins of eyes, just behind the level of the lateral ocelli; antennae black, first two segs. with pale apices; front of head and mouth-parts pale yellowish or greenish, postclypeus with a transverse black spot; rear of head light yellowish. Prothorax black, with sides and a pair of dorsolateral spots blue; dorsum of pterothorax black, with the blue antehumeral stripes slightly bowed, each about half as wide as the median black area; humeral stripe wider than the blue stripes, extending from prothorax to ante-alar ridge and enclosing at the posterior end a triangular blue spot; lateral walls of pterothorax greenish to pale yellowish below; second lateral suture marked by a black line. Legs pale; outer surfaces of femora with a dark stripe; tibiae with flexor surfaces dark; tarsi mostly pale, tarsal claws and spines black. Wings about three-fourths as long as abdomen, slightly tinted smoky yellowish; pt. brown, not very dark, surmounting one cell. Abdomen black above, black of seg. 2 enclosing a small blue spot, close to the base; segs. 3-7 with blue basal annuli, one-eighth or more of the seg. length, not interrupted mid-dorsally, and broadly confluent with the pale greenish ventrolateral areas. Black median areas on 3-6 constricted behind the middle and widened toward the posterior ends, where they extend to the mid-ventral line. Segs. 8-10 blue, with black ventrolateral margins. Sup. apps. with a straight lower margin and rounded apices; inf. apps. as long as seg. 10, bifid, outer branch erect, inner branch stout horizontal. Female. Olivaceous, not very dark; dorsum of head nearly devoid of dark markings; antennae dark brown; labrum pale olivaceous; labium and rear of head pale yellow. Prothorax without well-defined dark markings; dorsum of pterothorax almost uniformly pale; a black hairline on the dorsal carina; humeral stripes absent or reduced to a fine brown line on the humeral suture and sometimes an ill-defined dark spot on the upper part of the mesinfraepisternum and adjacent part of mesepimeron. Venter and legs pale;

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femora with a dark streak on the outer or extensor surface, widest on the front pair; tibiae pale; tarsi dusky at tips; tarsal claws and spines black. Abdomen dark brown above, with ill-defined pale basal annul!; interscgmental areas dark; venter pale yellow, with dark apical scgmental spots; segs. 8-10 almost uniform dull yellowish brown. Wings as in male; pt. light brown. Mesostigmal laminae with posterior margin raised into a projecting rim which is highest at the mesal end. Here it terminates abruptly, tapering laterally to the level of the general surface. Ovipositor extending a little beyond end of abdomen. Postnodal cross-veins, f. w. £ 12-13, $ 11-15; h. w. 3 10-11, $ 10-12. Measurements. Total length 3 29.5-32.5, $ 29-31; abd. $ 22.5-25.0, $ 22-24; h. w. $ 17.5-19.0, 9 18-19; h. f. 3 3.0-3.4, $ 3.6-3.7; w. hd. $ $ 3.7-4.0; pt. .7-.8; ov. 1.6. Nymph (pi. 37, fig. 4; pi. 39, fig. 4). Eyes somewhat prominent; posterolateral margins of head rounded and spinose; antennae about 1.5 times as long as head; ratio of seg. lengths, 6:10:14:10:6:3:2. Folded labium reaching hind margins of fore coxae; greatest width seven-eighths of length; width at base five-ninths of distal width; lateral margins slightly convex in distal half, with about 12 short setae; median lobe produced to a distance less than one-fourth the length of the first segment of the lateral lobe, which bears 3 lateral setae; no distinct notch separating end-hook from inner margin. Wingcases about as long as head and thorax, extending nearly as far back as hind femora. Caudal lamellae about one-half longer than hind femora, widest at three-fourths of their length, with a short angular apex, terminating in a slender point. Colour very dark brown; dorsum of head behind eyes with paler patches, lateral margins dark; ocellar spots pale; antennae with first two segs. pale, 3-5 darker, with pale apices. Prothorax dark, with pale sublateral bands; pterothorax and wing-cases mostly dark brown; legs conspicuously banded; femora pale, with two dark annuli, a median and an ante-apical; tibiae with a dark annulus at the proximal third or fourth; tarsi pale. Abdomen with a conspicuous pale mid-dorsal stripe, which is widest on segs. 9 and 10. Caudal lamellae heavily mottled, darkened along the tracheal axis, with a transverse dark stripe just beyond the middle and with spots and blotches of pigment in subapical area; apices pale. Underside of abdomen brown, darkened along posterior margins of segments; ovipositor paler. Total length (abd. contracted) 16; h. w. 4.3-4.5; h. f. 4; w. hd. 3.

Habitat and range. Streams with a gentle current and rich vegetation on the banks. Fla. to Ariz, and Calif., n. to Ohio, s. Ont, s. Mich., 111., Mo., and Kans. Also in northern Mexico. Distribution in Canada. Known only from the Thames River in Kent Co., very close to the boundary of Elgin Co. Field notes. We have taken this species on but two occasions, June 28, 1934, and August 12, 1935, and at approximately the same station, the Thames River near Bothwell, Ontario. On the former date it was not uncommon on the north side of the river, where we noted five or six males flying along the edge of the bank, very near the water. A pair was taken on the shore of a low island a few yards from the shore. On the second occasion, A. sedula was again found on the north side of the river, where the water was several feet deep and the bank very steep with overhanging willows at the water's edge. The current was comparatively gentle. These damselflies were quite numerous here, but it was difficult to approach them, owing to the depth of the water. On the south side of the river where the

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water was shallow, Argia apicalis and A. moesta were common, but A. sedula was entirely absent. Williamson (1900) writes that "with violacea this species prefers a life among the rank vegetation along ditches, streams and lakes"; and Kellicott (1899) that "A. sedula, the handsomest of our Argias [in Ohio] is rather common along larger streams in the southern part of the State/' Our two records, of course, give little idea of the seasonal distribution of the adult. In Indiana (Montgomery, 1944), A. sedula flies from the beginning of June to the end of September, with the main peak of numbers in mid-August and a lower peak in July. The season in extreme southern Ontario is in general a little shorter than in Indiana, about a week later in beginning and a week or more earlier at the close. Argia violacea (Hagen). (PL 7, fig. 3; pi. 15, fig. 5; pi. 23, fig. 6; pi. 27, fig. 6) Agrion violaceum Hagen, Syn. Neur. N. Amer., p. 90,1861. Argia violacea Selys, Bull. Acad. Belg., (2), 20; 404,1865. A rather small to medium-sized species, the male purple and blue, the female brownish, frequenting small streams in the Eastern Provinces. Male. Head dorsally purple, with a large transverse median area, enclosing the ocellar triangle together with a few pale spots, and narrowing laterad to the compound eyes; behind this area a pair of very large postocular spots contiguous with the eyes and margined behind with black; between the postocular spots a transverse stripe which sometimes connects them; face including genae, clypeus, and labrum purplish; labium and rear of head pale yellowish. Prothorax black, with anterior lobe and lateral margins pale, middle lobe with two large purple spots and a median pale one, hind lobe with median and lateral pale spots. Pterothorax purple above, venter and sides paler and yellowish, becoming somewhat pruinose with age. Mid-dorsal dark stripe about threefourths as wide as the purple antehumeral stripes; humeral stripe about half as wide as antehumerals, covering upper fourth of mesinfraepisternum and extending along mesepimeron for about three-fifths of its length, where it bifurcates, the larger branch running obliquely into the mesepimeron, while the smaller branch, in the humeral suture, is a mere hair-line, except in the pit near the posterior end, where it is somewhat enlarged; a dark line on the second lateral suture. Legs pale, with dark markings; anterior surfaces of femora with a dark stripe widened distally; tibiae pale, with flexor surfaces and parts of anterior surfaces dark; tarsi dusky, with most of upper surface pale. Wings three-fourths as long as abdomen, hyaline; pt. surmounting one cell, moderately dark brown. Abdomen in mature adults clear purple, except segs. 8-10, which are blue; marked with black as follows: seg. 1 with a transverse dorsal spot, 2 with a large lateral spot whose dorsal margin is broadly convex and hind margin sharply excavate, the spots of opposite side nearly meeting dorsoposteriorly; segs. 3 to 6 each with a pair of subtriangular or rhomboid spots just before the black intersegmental annulus, with which they are confluent on the more posterior segments, each spot having dorsal and anterior prolongations, the latter particularly on the posterior segments; seg. 7, except a purple basal annulus and small pale lateral spots near the posterior end; segs. 8-10 ventrally, and the inf. apps.; sup. apps. pale. Seg. 10 with a pair of distinct dorsolateral tubercles at the posterior end; sup. apps. declivent above, rounded behind; inf. apps. somewhat prolonged, although shorter than seg. 10; bifid but with short branches.

PLATE 29 Enallagma, Coenagrion, and Nehalennia, mesostigmal laminae of females (figs. 6-10 show also the rear part of the pronotum): 1. Enallagma exsulans; 2. E. antennatum; 3. E. aspersum; 4. E. signatum; 5. E. vesperum; 6. Coenagrion resolutum; 7. C. interrogatum; 8. C. angulatum; 9. Nehalennia irene; 10. N. gracilis.

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Female. Dull purple or brown; head and thorax with the same general pattern as in male, abdomen considerably different. Head dorsally similar to that of male, dark markings brown rather than blaek and with some slight extension and confluence of pale areas; face and mouth-parts pale brownish, rear of head pale buff. Prothorax pale buff, with two broad longitudinal dark bands separated by a narrow median space; markings of pterothorax as in male but slightly more reduced, i.e. humeral band occupies only upper sixth or less of mesinfraepisternum and the line on the second lateral suture is extremely fine. Legs as in male, with dark markings somewhat reduced. Wings four-fifths as long as body; pt. orange-brown. Abdomen dull purple or brown, paler on the sides; seg. 1 with a very narrow basal transverse black spot; seg. 2 with parallel dorsolateral dark spots, constricted or separated in the middle, with distomesal ends approximated; 3-6 with elongate parallel dorsolateral postbasal spots, and shorter, wider, paired apical spots, which on the more posterior segments are confluent with the intersegmental annuli, members of the same pair approaching one another mesally by angular extensions. On seg. 6 the postbasal and apical spots are confluent, and on seg. 7 they are represented by a pair of black stripes extending the length of the segment. Below the dark markings these segments are pale, with faint indications of distolateral spots on some of the segments; 8 and 10 pale, with ill-defined indications of dorsolateral black spots on 8 in some individuals. Ovipositor reaching end of sternum of seg. 10 but not quite to end of body. Postnodal cross-veins, f. w. $ 9 13-15; h. w. $ 11-13, 9 11-14. Measurements. Total length $ 29.0-32.5, 9 32.0-33.5; abd. $ 22.5-25.0, 9 25.026.0; h. w. $ 18-20, 9 20-22; h. f. $ 3.3-3.6, 9 3.75; pt. $ 9 .8-.9; w. hd. $ 9 4.0-4.3; ov. 1.5-1.75. Nymph (pi. 37, fig. 5; pi. 39, fig. 5). Eyes somewhat prominent, posterolateral margins of head rounded, spinose; antennae scarcely as long as head; ratio of seg. lengths, 5:8:10.5:5:5.5:3.5:2. Folded labium reaching front margin of mesosternum; distal width of mentum four-fifths of length; width at base half of distal width; lateral margins nearly straight, slightly convex in distal half, which bears about 12 marginal setae; distal margin well rounded, produced to a distance of much less than one-third the length of the first seg. of the lateral lobe; lateral setae 2, no notch separating end-hook from inner margin of lobe. Wing-cases slightly longer than the head together with the first two thoracic segments, or than hind femora, which project a little beyond them. Caudal lamellae about as long as front wing-cases, gradually widening from base to about the second third, where the width is about four-ninths of the length, apices bluntly angulate; margins of lamellae and lateral carinae densely fringed with stout setae, the margins mixed with much longer, fine hairs, especially toward the apices. Colour very dark brown, inconspicuously marked; femora with base and apex dusky and two dusky annuli, one proximal and the other distal to the middle; tibiae darkened at base, with a dusky annulus just before the middle. Abdomen with a pale mid-dorsal stripe, widest on the last three segments, sometimes indistinct. Caudal lamellae dark, often with a transverse pale band, more or less V-shaped, a little beyond the middle, and numerous scattered spots of pigment. Total length 16.0-16.5; h. w. 4; h. f. 3.0-3.6; caud. lam. 4.0-4.5; w. hd. 3.1.

Habitat and range. Streams and small lakes, chiefly the smaller, shallower streams with a gentle current, preferably with some exposed rocks and a

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clay or stony bed, commonest in calcareous regions. S.C. and Ala. to Ariz, (subsp. pallens), n.e. through Okla. and Kans. to Minn., Wis., Mich., Ont., Que., Me., N.B., and N.S.; also s. of U.S.—Mex. to Guatemala (pattens). Distribution in Canada. N.S.—Annapolis, Hants, Halifax, and Pictou counties. N.B.—Chamcook Lake, St. Andrews; Rockwell Stream, near Fredericton. Que.—Covey Hill, Hemmingford, St. Chrysostom, Vaudreuil, Hull, Wakefield and other stations in the Gatineau Valley, Lac Mercier, Labelle Co. Ont.—General throughout s. Ont.; Essex, Kent, Elgin, Middlesex, Oxford, Brant, Haldimand, Lincoln, Waterloo, Huron, Peel, York, Grey, Simcoe, Leeds, Carleton, and Renfrew counties; Muskoka, Parry Sound, and Nipissing districts. Northernmost station, Ko-ko-ko Lake, Timagami Forest Reserve. Field notes. Although generally absent from the large rivers and lakes where A. moesta is often common, and also from stagnant weedy streams, A. violacea frequents a great variety of habitats. It shows a preference for small shallow streams with a moderate current and exposed rocks, on which the adult males settle horizontally. The stream bed may be hard or soft, rock, clay, sand, or mud. Even a small brook without stones above the size of gravel, flowing through a lush meadow, may be inhabited by violacea. On one occasion we found it flying along a roadside ditch which was supplied with water from a spring bog. Small lakes on the course of a little stream, especially those formed by a dam, are favourable localities for violacea. On one such miniature lake, formed by a concrete dam across a small forest brook, violacea was very common. There were many pairs in tandem, and it was noticed that these pairs often rested on low herbs rising above the water, but single males almost always settled on the ground or on the concrete dam at the outlet. Single individuals do, however, frequently settle on foliage, particularly when in the teneral stage. When the adult males are flying over the stream and settling on bare ground, the females may usually be found at a considerable distance, often high up on the slope of the valley or on the top. In Ontario the flight period begins much later than in Indiana. For this state Montgomery (1944) gives a period extending from the third week in May till October 7, whereas Ontario records range only from June 19 to August 19. We believe, however, that violacea flies well into September in Ontario, the absence of records being due to insufficient observations in the latter part of the season. It is also probable that in the Lake Erie counties the adult season begins earlier than our scanty data indicate, little collecting having been done there before the third week in June. Throughout most of eastern Canada, including all but the southernmost counties of Ontario, violacea does not develop its adult coloration before the first week in July. Most of our observations on pairing were made from July 8 to August 12, but we have recorded pairing in southern Ontario on June 28 and 29 on various stations on the Thames River. Kellicott (1899) states that oviposition takes place, often in pairs, on submerged plants and rubbish. We observed

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a pair on Chamcook Lake, N.B., ovipositing on a log that was lying at the water's edge. A. violacea never descends below the surface of the water, as is the habit of A. moesta. Argia vivida Hagen. (PL 15, fig. 6; pi. 23, fig. 7; pi. 27, fig. 7) Argia vivida Hagen, Bull. Acad. Belg, (2), 20: 406, 1865. A robust species of average linear dimensions resembling violacea but blue rather than purple in colour. It is found in Canada only west of the Great Plains. Male. Head dorsally blue; postocular spots large, subtriangular, widely contiguous with the compound eyes, nearly joined by a cross-bar, narrowly black behind; median black area enclosing ocellar triangle and two triangular pale spots, narrowing laterad to ths eye margins and extending forward to bases of antennae; with median T-spot expanding on the frons; face including labrum blue, with a black line on the frontoclypeal suture; labium and rear of head buff. Prothorax black, with broad lateral margins and dorsolateral spots blue; dorsum of pterothorax blue, with a broad black median stripe whoss width is about 1.75 times the maximum width of one of the blue antehumsral stripes; humeral stripe covering upper half of mesinfraepisternum, continuing on the mesepimeron to the posterior half, where it is usually bifid, the lower and wider branch oblique, the upper very narrow, following the suture; second lateral suture marked with a heavy black line. Legs bluish or greenish; femora with upper and outer surfaces mostly blackish; tibiae dark, with extensor surfaces pale; tarsi dark. Wings about four-fifths as long as abdomen, hyaline; pt. surmounting one cell and frequently part of another. Abdomen blue, marked with black as follows: seg. 1 with a small dorsal spot, 2 with a longitudinal streak on each side, expanding into a pair of ante-apical dorsolateral triangles, nearly meeting mid-dorsally; 3-6 with elongated postbasal spots on each side, smallest and sometimes absent on 3, tapering posteriorly, and on 5 and 6 generally joining the ante-apical spots. These, on 3, are usually divided mid-dorsally and not confluent with the black intersegmental annuli; seg. 7 mostly black, but with a pals basal spot and pale ventral margin; 8-10 blue, usually almost without black markings. Declivity of seg. 10 with distinct dorsolateral tubercles; sup. apps. long and decurved; inf. apps. about as long as 10, bifid; upper branch short, conical, and erect; lower branch of about same length, horizontal. Female. Slightly longer winged than male, yellowish or greenish grey to pale brownish or sometimes bluish. Head marked as in male, with somewhat larger pale areas. Prothorax pale, with a dark median area, continuous with the mid-dorsal stripe on the pterothorax, the latter about half as wide as one of the antehumeral stripes, or slightly wider; humeral stripe crossing upper third or less of mesinfraepisternum, otherwise as in male, except that the lower branch of the fork is often represented by a separate spot or may disappear. Second lateral suture with a black line. Legs marked as in male, but with the dark areas narrower; tibiae pale except the flexor surfaces; tarsi pale above. Wings nearly nine-tenths as long as abdomen; pt. slightly paler than in male. Abdomen stout, marked with black as in male, except as follows: spots of seg. 2 appear more dorsal, their forward prolongations separated as a pair of postbasal spots; ante-apical dorsal spots on 3-6 joined mid-dorsally; postbasal spots on 3-5 may all be separated from the ante-apical spots or all joined; similarly the distolateral spots may be separated or joined with the dorsal ante-apical spots; all these spots usually confluent on 6; 7 as in male; 8-10 pale, 9 and sometimes also 10 each with a pair of dorsal black spots of very variable size, or there may be no definite dark areas.

PLATE 30 Ischnura, Chromagrion, and Amphiagrion, mesostigmal laminae of females (figs. 1-7 and 10 show also the rear part of pronotum): 1, Ischnura verticalis; 2. L perparva; 3. I. damula; 4. /. cervula; 5. L erratica; 6. /. posita; 7. Anomalagrion hastatum; 8. Chromagrion conditum-, 9. Amphiagrion abbreviatum; 10. A. saucium.

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Base of mid-dorsal thoracic carina broad and fan-shaped; mesostigmal laminae with hind margins produced into obtusangular lobes, which project over a pair of depressions on the mesepisterna, these depressions without a sharply defined margin. Ovipositor barely reaching end of abdomen. Postnodal cross-veins, f. w. $ 13-18, $ 12-16; h. w. $ 12-16, $ 12-14. Measurements. Total length $ 29.5-33.5, 9 30-35; abd. $ 23.5-25.5, $ 23-27; h. w. $ 18.5-21.0; $ 21-24; h. f. $ $ 3.0-3.7; w. hd. $ 4.5-4.8, $ 4.8-5.0; pt. .75-1.0; ov. 2. (From specimens taken at Banff, Alta. Those from localities in the United States vary considerably from the above.) Nymph (pi. 37, figs. 6, 8). Eyes moderately prominent; postocular lobes obtusangulate, posterior margins broadly convex; antennae shorter than head, the last seg. very short and easily overlooked, ratio of seg. lengths, 10:16:22:12:7:4:2. Folded labium reaching front border of mesosternum; distal width of mentum a little less than the length (100-115) and about twice the basal width, sides nearly straight but slightly constricted at base and midway of the length; marginal setae about 10-13; median lobe reduced to a distance somewhat less than one-third of the basal width, rounded; iteral setae 4. Legs somewhat short and flat, the hind femora being distinctly shorter than width of head. Caudal lamellae rounded at base, widest before the middle, tapering distally to acute apices, lateral carinae of lateral lamellae very prominent, with numerous stout taper-pointed setae, margins of lamellae also with similar stout setae, mixed distally with long slender hairs. Colour dark, pattern somewhat obscure, except on the legs, caudal lamellae, and the broad pale mid-dorsal stripe of the abdomen, which is edged with black and is widest on seg. 9. Femora with two broad dusky annuli, proximal and distal to the middle; tibiae with a dusky annulus a little before the middle. Caudal lamellae heavily spotted and blotched with dark pigment on a paler background, with an irregular dark band across the middle and extending along the axis. Total length (exuv.) 17; h. w. 4.5; h. f. 4; caud. lam. 5.5; ov. 1.3. Described from the exuvia of a reared female taken by C. H. Kennedy at Palo Alto, Calif. (Mus. Zoology, Univ. Mich.). Further details are given by Kennedy (1915) with a number of figures. In his fig. 38, a dorsal view of the nymph, the eyes are too prominent and the antennae too short. The figure of the labium (fig. 71) is too wide proximally, if drawn from a full-grown individual.

E

Habitat and range. Small spring-fed streams or pools. Mex. and Tex. to Calif., n. to Montana, w. Alta., e. B.C. and Wash. Distribution in Canada. Known in Canada only from Banff, Alta., Field and Glacier, B.C.; locally abundant on Sulphur Mountain, Banff, and at Field, both stations in the Rocky Mountains, one record from Glacier. Field notes. Argia vivida flies in the vicinity of spring pools and spring-fed streams, where the nymphs develop. Kennedy (1915) gives an interesting account of its haunts and habits at three such stations in Washington and Oregon, and states in a footnote that he later found it about all permanent springs in California and Nevada. The following extracts from his description of the first station will suffice to give an idea of its habitat. This was

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one of three stations on the course of Satus Creek and its tributaries, Yakima Valley, Washington. It was at the bottom of a canyon on a flat area, not more than an acre in extent, and the observations were made on June 15, 1913. "At one end of this flat a spring oozed out at the base of a cliff and its stream, trickling down through the alder thicket, contained many vivida nymphs. The shade, as usual in an alder thicket, was dense, but Argia vivida in couple were resting in profusion on the bushes, dead brush and rocks, which filled this stream. Tenerals were numerous as well as males in high color and a few females in full color, but I saw none copulating or ovipositing. This spring stream was not over 100 feet long, and its bed and sides were of black muck, from the leaves which fall into it annually. Scattered over the bed were rounded stones up to 12 inches in diameter, to the under sides of which the vivida nymphs were clinging. The spring was cold and the nymphs were sluggish, Exuviae were found clinging to the stones but an inch or two above the surface of the water. Argia vivida is a comparatively sluggish insect and seemingly very local or restricted to its choice of environment. Argias were very abundant on the ground in the open spaces of the flat near this spring stream, but were not found farther than 150 feet from it. In couple they hung to bushes when hovering about the stream, because the bushes overhung the water, giving them little choice, but outside in the sunshine they sat mostly on the bank or on stones or sticks lying on the ground." Williamson (1932) also discusses vivida as a species frequenting springs and small spring brooks, "preferring sunny spots near the water of hard bottomed pools or streams in shaded areas. It reaches the highest points in spring-fed streams attained by any species . . . so dependent is it on springs that its presence anywhere may be taken as positive proof of adjacent spring water." When we met with vivida at Banff, we found it in two distinct localities (Walker, 1927) both in the vicinity of hot springs. As observed by Kennedy, it was quite local but abundant over a limited area. We believed that the nymphs would probably be found in the warm streams issuing from the baths, but had no proof of this supposition. The Odonata of Banff are typically boreal, except for three species, Argia vivida, Amphiagrion abbreviatum, and Ischnura cervula, and the last-named species is known to breed only in a lake that is warmed by hot springs. Mr. E. R. Buckell, however, took a large series of vivida at Field, B.C. (Whitehouse, 1941) where there are no hot springs and, in view of what is known of its type of breeding place, we are ready to admit that the association of vivida with hot springs may be merely a coincidence. Kennedy's dates of collection in Washington are June 15 and August 24; Williamson's in Missouri are June 6 to August 26, and ours from Banff, Alberta, are June 12 to August 3. Whitehouse gives the period in British Columbia as June 12 to August 27. The last date is probably Buckell's from Field.

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Argia emma Kennedy. (PI. 15, fig. 7; pi. 23, fig. 8; pi. 27, fig. 8) Argia emma Kennedy, Proc. U.S. Nat. Mus., 40: 271, 1915. A large western species, violet in the male, variously coloured in the female, found in Canada only in southern British Columbia. Male. Head dorsally violet and black; postocular spots very large, widely contiguous with the compound eyes, narrowly joined by a cross-bar, and margined behind with black; median black area enclosing ocellar triangle and a pair of small pale spots connected with the eye margins and the antennal bases by slender offshoots, and a small T-spot forward from the median ocellus, but not expanding on the frons as in A. vivida; face violet, paler on the genae, black only on anteclypeus; labium buff; rear of head pale brownish. Prothorax violet, with a median pair of dark stripes and dark lines in the grooves bounding the three lobes and the lateral margin. Pterothorax violet, paler and brownish below, where it becomes whitish pruinose with maturity, the pruinosity encroaching upon the legs and including the interalar area; black mid-dorsal stripe at half length not more than half as wide as one of the antehumeral stripes, usually less; humeral stripe covering upper third of mesinfraepisternum, continuing below the suture to the posterior half, where it narrows to a hair-line on the suture, without any bifurcation; second lateral suture marked by a black line, which is never very heavy. Legs pale yellowish before becoming pruinose, fore femora largely dark grey or blackish on outer side, middle and hind femora with a dark longitudinal streak, tibiae with flexor surfaces dusky, extensor surfaces pale; tarsi dusky. Wings fivesevenths as long as abdomen, hyaline; pt. surmounting one cell, dark brown. Abdomen violet (often red-brown in dried specimens), marked with black as follows: seg. 1 with transverse spot; 2 with a pair or ante-apical spots narrowly connected mid-dorsally; 3-6 with apical fourth blackish; anteroventral angles of the dark spots more or less prolonged forward, and with a small pale lateral spot just before the apex on some or all of the segments; seg. 7, except a pale basal annulus; a ventral marginal stripe on 8-10, which are otherwise pale. Posterior declivity of 10 narrow and without lateral tubercles; sup. apps. shorter than in vivida, slightly arched, with pointed apices directed ventrad; inf. apps. slightly shorter than 10, bifid, with short branches, proximal branch rounded, distal branch conical, horizontal. Female. Colour variable, "tenerals as in male ... a light tan or creamy white, changing then through darker shades of brown to olive, and in some specimens . . . to a further stage of slate blue" (Kennedy, 1915). Head marked as in male, with the black area somewhat more reduced; prothorax almost entirely pale, without dark spots; middorsal thoracic stripe and humeral stripes as in male, or more reduced; second lateral suture with a very thin line or none. Legs as in male or with black markings reduced to a streak on outer surfaces of femora, heaviest on fore pair. Pruinosity over same areas as in male. Pt. pale yellowish brown. Abdomen with the following dark brown markings: a pair of dark spots on 2; 3-6 with postbasal and ante-apical dorsal spots, and lateral spots beneath them; postbasal spots on seg. 3 small, confined to anterior half of segment; spots on 3-6 successively larger, on 6 generally confluent with the ante-apical spot; the ante-apical spots may be mesially divided on 3, but are usually fused on 4-6; 7 with two long parallel spots, representing the postbasal series, ante-apical and distolateral spots absent or the latter vestigial; 8-10 without definite dark markings. Mesostigmal laminae bounded behind by a low ridge but not produced into a lobe; a pair of distinct concavities behind the median pit, each bounded by a curved ridge bearing a rounded tubercle at its outer end, where it meets the lamina. Ovipositor not quite reaching the end of seg. 10. Postnodal cross-veins, f. w. $ 13-17, 9 13-16; h. w. $ 12-14, $ 11-14.

PLATE 31 FIGS. 1-6. Ischnura females, pronotum from above: 1. I. posita; 2. I. verticalis; 3. I. cervula; 4. /. damula; 5.1. perparva; 6.1. erratica. FIG. 7. Enallagma hageni, $, oblique view from above of the mesostigmal laminae and anterior port of pterothoracic dorsum, showing raised edge of right mesostigmal lamina. FIG. 8. E. ebrium, $, same view, showing edge of right mesothoracic lamina scarcely raised above pterothoracic dorsum. FIG. 9. E. exsulans, $, mesostigmal laminae, showing parts referred to in descriptions. (acf—anterior carina of frame; fm—frame; Icf—lateral carina of frame; me—median carina of pterothorax; mpt—median pit; msl—mesostigmal lamina; rm—ramus of median carina; sp 2—mesostigma (mesothoracic spiracle))

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Measurements. Total length $ 33.5-39.0, $ 34-38; abd. $ 26.5-30.5, $ 27.5-30.0; h. w. $ 20-24, 9 22-25; h. f. $ 3.5-4.7, 9 4.4-4.8; w. hd. $ $ 4-5; pt. .7-.9; ov. 1.8-2.0. Nymph (pi. 37, fig. 7; pi. 39, fig. 6; pi. 44, fig. 10). Eyes moderate, postocular lobes rounded obtusangulate; antennae slightly longer than head, relative lengths of segs. 10:23:30:20:17:10:7. Labial mask reaching the posterior margin of the prosternum; distal width of mentum five-sixths of length, width at base two-fifths of distal width; lateral margins nearly straight, being very slightly convex proximally and distally and slightly contracted in the middle; marginal setae 12 or 13; middle lobe rounded obtusangulate, produced to a distance almost half the length of the first segment of the lateral lobe; one lateral seta arising near the articulation of the movable hook; end-hook separated from inner margin by a distinct notch. Legs of usual length, rather hairy; hind femora about as long as width of head; many hairs of tibiae twice as long as tibial width. Wing-cases about as long as head and first two thoracic segments. Caudal lamellae about as long as head and thorax, a little more than twice as long as broad, widest about the middle or a little beyond, rounded at apices; lateral carinae strong; margins densely fringed with short spinose setae, mixed with fine long hairs, especially towards the apices. Colour light brown, conspicuously marked with darker brown. Head with bases of antennae, ocellar spots, and broad margins of postocular lobes pale. Thorax, with pleural furrows, dark brown. Legs with dark areas as follows: femora with two dark annuli, one before and the other behind the middle; tibiae with darkened bases and a single dark annulus; abdomen dark, except a pale mid-dorsal stripe, which is narrowest in front and widest on the last two segments, and a broken whitish line along the lateral margins of the terga. Both mid-dorsal and lateral pale stripes edged with very dark brown or blackish. Caudal lamellae with median axes, and usually a wide transverse dark band across the middle or a little beyond; apices and also scattered spots darkened. Total length 20-21; h. w. 5.5; h. f. 4.0-4.5; w. hd. 3.6-4.0; caud. lam. 5.0-5.5.

Habitat and range. Clear rapid mountain streams. Calif, and Nev., n. through Or. and Wash, to s. B.C. Distribution in Canada. B.C.—Cultus Lake, s. of Chilliwack; outlet of Kawakawa Lake into the Coquihalla River (Hope); Christina Lake; Okanagan River at Penticton; Oliver; Lillooet and Mabel Lake. Field notes. Argia emma is essentially a species of rapid streams. Kennedy (1915) found it "on the gravelly reaches and stony riffles of lower Satus Creek," Yakima Co., Washington. This is a mountain stream, "which is

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dependent for its water on the mountain snows from the Klickitat Mountains, which give it a flood in May, while it becomes almost dry from July to October." At Cultus Lake, B.C., where it was observed throughout its flight period by Ricker (Walker and Ricker, 1938) its main habitat was Sweltzer Creek, the outlet of Cultus Lake, but it was also common along the shore of the lake itself. "Cultus Lake lies in a glaciated U-valley between two mountain ranges. It is three miles long and one-half mile broad, mostly deep, clear, and with the epilimnion quite warm in summer (20-22°C.)." Sweltzer Creek is "a warm stream of moderate current in summer. Its upper end is muddy and overgrown with Salix; below this is a short open stretch with Lysichiton kamtschatcense on exposed gravel bars; then a more rapid section with stony bottom, margined by dense forest." Argia emma "is extremely abundant along every part of the stream throughout summer and early autumn." The earliest date recorded in this locality is June 18 and the latest August 26, although A. emma is stated to fly well into September. Whitehouse (1941) found it emerging at Cultus Lake in the afternoon of June 18, and observed the first mature insects on June 25, when many were already in couple. According to Kennedy "emergence takes place any hour of sunlight after the middle of the morning. When about to emerge the nymph usually crawls up on a stone seldom more than one inch above the water." The teneral stage probably lasts a day or two, and during this stage they are usually found on the bushes along the banks. During adult life "the Argias, while spending all day close to the water, seldom leaving the riffles and bars, leave the water just before sundown and spend the night among the shrubs along the creek, where they are to be found early in the morning." Pairing has been noted at Cultus Lake by Ricker, Whitehouse, and others from June 25 to August 19. Kennedy observes that "the adults spend many hours in couple, the male holding the female by the prothorax and both seated on some sunny stone." Oviposition was observed by Kennedy at a single spot on Satus Creek, where it took place frequently, "This was among the pink roots of willows which hung in a shallow side pool through which a small stream flows. Oviposition is a lengthy process, the female sometimes working alone, but usually held by the male, who supports himself solely by his hold on the female and, scorning other support, stands stiffly out of the water with his wings folded and his legs drawn tightly against his thorax until the female, backing down into the water, submerges him with her." Ricker also mentions the "long clumps of red willow roots" as being the preferred site for oviposition by this species. Whitehouse noted "as many as six couples, side by side, within a space of several inches" ovipositing, a habit that appears to be common to many species of Argia. "The nymphs of this species are not easily found, as they roam over the

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whole creek bed and so are never numerous in any single place. They are found on the roots and brush of the larger pools and under large stones on the riffles" (Kennedy, 1915). Genus Chromagrion Needham Bull. 48, N.Y. State Mus., p. 246, 1903 Type-conditum (Hagen). This is a monotypical genus of eastern North America, most nearly related to the Palaearctic Erythromma, to which our species was formerly referred. The anterior side of the triangle is twice (fore wing) to three or four times (hind wing) as long as the proximal side; the anal vein separates from the hind margin in both fore and hind wings just before or opposite the cubito-anal cross-vein; M4 beginning to be angulate (fore wing) four or five cells beyond the level of the origin of M2; the areoles behind Cu are longer, in the axis of the wing, than wide; the vertex and the occipital region of the head are wholly black; the superior appendages of the male are subforcipate, being slightly incurved, but shorter than segment 10 and without teeth. Chromagrion conditum (Hagen). (PL 10, fig. 1; pi. 20, fig. 1; pi. 25, fig. 10; pi. 30, fig. 8) Erythromma conditum Hagen, Bull. Acad. Belg., (2), 41: 1305, 1876. Chromagrion conditum Needham, Bull. 68, N. Y. State Mus., p. 246, 1903. A slender species of early summer, found about spring-fed streams, and easily recognized in life by the bright sulphur yellow of the metapleura in a colour-pattern otherwise blue and black. Male. Face pale bluish, with postclypeus and a line across base of labrum black; labium pale yellowish; dorsum and rear of head black, without pale markings except the frontal margin. Prothorax black, anterior lobe and broad lateral margins pale blue. Pterothorax with a broad mid-dorsal black stripe, which is widened about the middle and notched on the sides above; pleura light blue, passing into sulphur yellow on the metapleura, almost devoid of black markings, except along the ante-alar ridge from which short spurs extend along the pleural sutures. Sterna and bases of legs whitish pruinose. Legs moderately long; outer faces of femora blackish; extensor surfaces of tibiae light yellow, flexor surfaces dusky; tarsi black. Wings hyaline; pt. greyish brown, surmounting a single cell. Abdomen long and slender, black above with blue basal annuli on segs. 3-7, which are interrupted mid-dorsally and are confluent with the blue of the ventral half; segs. 1 and 2 blue, 1 with a black dorsal spot, 2 with a black dorsal stripe, which is widened posteriorly and connected with a marginal black annulus; 8 and 9 blue, one or both with a pair of black dots above and black spots on the sides; seg. 10 and anal apps. black. Sup. apps. nearly as long as 10, horizontal, slightly arched, incurved, rounded at apices; inf. apps. two-thirds as long as sup. apps., horizontal with rounded apices. Female. Coloration either similar to that of male (homoeochromatic) or with the blue areas replaced by a more or less decided green (heterochromatic), the extreme in this direction being yellow-green. The black dorsal abdominal stripe is continuous, segs.

PLATE 32 Lestes disjunctus disjunctus Selys, nymph. X approx. 6.

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8 and 9 being unlike those of the male in this respect. Ovipositor short, not reaching hind margin of seg. 10. Postnodal cross-veins, f. w. $ 12-14, 9 13-15; h. w. $ 11-12, 9 10-13. Measurements. Total length $ 33-35, 9 32-38; abd. $ 27-29, 9 25.5-31.0; h. w. 3 20-23, 9 20.5-26.0; h. f. £ 9 3.5-4.0; w. hd. $ 9 4.0-4.2; pt. 1; ov. 1.5. Nymph (pi. 34, fig. 1; pi. 43, fig. 13). A very dark nymph with noticeably angular postocular lobes and dark white-tipped caudal lamellae. Head pentagonal, half as long as wide, front and eyes somewhat prominent; postocular margin of head almost rectangular; occipital margin strongly excavate in middle; antennae slightly longer than head, measured along the middle line, ratio of seg. lengths, 11:18:24:20:15:12:8; seg. 1 cylindrical, 2 elliptical, a little more slender than 1, 3 cylindrical and much more slender than 2, the remainder successively more slender. Labial mask reaching front of mesosternum, lateral margins nearly straight, diverging at an angle of about 34°, the distal width of mentum somewhat more than three times the basal width; middle lobe obtusangulate, about as in Enallagma; mental setae 3, marginal setae about 5-7, relatively coarse; one or two more setae at the articulation of the lateral lobes; lateral setae 5; distal margin of lateral lobe with about 7 denticles, successively smaller laterad, the first much the largest; movable hook short and strongly curved. Abdominal terga and sterna without stiff setae, except on the hind margin of seg. 10, on which there is a fringe all around; abdominal carinae low and without setae, except soft inconspicuous hairs which clothe both dorsal and ventral surfaces. Lateral appendages of male very short and rounded; ovipositor extending beyond middle of 10th sternum but not to the end. Caudal lamellae somewhat more than one-half longer than hind wing-cases; slender oblanceolate, widening with straight margins from base to about four-fifths of their length, where the width is one-fifth to one-fourth of their length (med. lam.) or onesixth to one-fifth of the length (lat. lam.), narrowing rapidly with curved margins, and tapering to slender acuminate tips; margins bearing 9-12 widely spaced and somewhat coarse setae, corresponding in position with the dark marginal spots; ventral margin of lateral lamellae proximally with a close-set fringe of setae; all the margins also with soft hairs, which are longest about the apex. Head almost uniformly dark above, with 3 pale spots over the developing ocelli; eyes blackish; antennae pale, with a very dark annulus at the articulation of segs. 1 and 2; annuli also encircling 4 and 6; 2 and 3 with apices brown, 5 and 7 entirely pale; labrum, labium, and underside of head light yellowish brown. Entire thorax dark brown above, light yellowish brown beneath; wing-cases moderately dark, with both longitudinal and cross-veins clearly marked with darker brown. Legs pale yellowish brown, strongly banded with dark brown, mostly paler below; femora moderately pale at base, but with most of the proximal half dark, deepening to a median band, and an ante-apical dark annulus between two pale areas, the distal one short, apices brown; tibiae pale, with a short dark annulus near the base and the apices also darkened; third tarsal segment darkened apically. Abdomen dark brown above, deepened along the lateral margin above the carinae, and with small paired dorsal black spots on segs. 1 or 2 to 9; with a pale longitudinal lateral stripe; venter somewhat pale, with a dark lateral margin. Caudal lamellae reddish brown, more or less mottled with whitish, and darkening distally before the whitish apices; with whitish marginal spots, alternating with black ones. Total length 21-22, h. w. 4.4-5.0, h. f. 4.0-4.3, caud. lam. 7.8-8.3.

Habitat and range. Shady spring-fed brooks and pools. N.S. to Wis., s. to S.C., Tenn., and Mo.

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Distribution in Canada. N.S.—Annapolis and Halifax counties. N.B.— Charlotte and Kings counties. {)uc.—Covey Hill; St. Chrysostom; Hull, Wakefield and other stations in the Galincau Valley; Nominingue, Labelle Co. Ont.—Elgin, Oxford, Waterloo, Pool, York, Simcoe, Carleton, and Renfrew counties; Mnskoka, Parry Sound, Nipissing, Algoma, and Cochrane districts. Long Point, Lake Abitihi, is the most northerly station from which this species has been reported. Field notes. This beautiful insect frequents partly shaded spring pools, sometimes among cat-tails (Tijpha), or spring runs and the mouths of small tributary spring-fed streams. Where a clear rapid brook is dammed to form a small artificial lake in a wooded ravine, C, conditum is likely to be found along the margin of the lake, especially where the soil is mucky. It may also occur about cut-off ponds close to rapids and in ditches dug through cold swamps. The adults do not often wander far from their breeding places and are not particularly active, although they are occasionally found about ponds or pools that are evidently not their usual haunts. They are commonly seen resting on foliage with their wings slightly spread, somewhat after the manner of a lestes. "The nymphs are climbers amid the submerged vegetation of sheltered pools" (Needham and Heywood, 1929). The full-grown nymphs, which we have collected in May, are found "on the bottom near the shore, in dead leaves and trash, well shaded" (Carman, 1927). We have observed emergence at Lake Sirneoe from May 30 to June 28. Pairing begins early in June, our first record being on June 7 on the Credit River, near Erindale, Ontario, and we have seen pairs as late as July 24. Ovipositing takes place in June and July, but we have rarely witnessed the act. We have, however, a Kodachrome motion picture showing a large number of C. conditum ovipositing in a widened part of a shady spring-fed stream, near Campbellville, Ontario, in which there is a dense growth of white water crowfoot (Ranunculus trichophyllus) in bloom. Numerous pairs can be seen over the surface, ovipositing apparently on the stems or leaves of aquatic plants just beneath the surface of the water. The position of the pairs is typical of most coenagriids, the female horizontal, the male vertical or oblique and supported only by his hold on the female's prothorax by his anal appendages. Our latest record for C. conditum is August 4, at DeGrassi Point, Lake Simcoe, Ontario. Genus Amphiagrion (Selys) Bull. Acad. Belg,, (2), 41: 284, 1876. Type-sawcwm Burm. This is a nearctic genus of small thickset red and black damselflies, with short legs and a ventral thoracic tubercle on the intersternum, and the

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tenth segment of the abdomen in the male raised into a conical elevation; the superior appendages of the male are slender and steeply declivent, the inferior appendages long and horizontal, pointed at the apices. The quadrangle is not widened distally, its proximal side is not longer than the anterior side and not longer than the anterior part of the arculus; M Ja arises between postnodal cross-veins 3 and 4. These insects appear never to stray far from their breeding places, which, owing to their special nature, are widely scattered; yet the genus is widespread in North America. In Canada there is a wide gap in their known distribution, no species being known north of the Great Lakes. This is probably mainly due to lack of collecting, but a narrower gap is to be expected north of Lake Superior. Key to the Species of Amphiagrion—Adults Smaller and less robust eastern species; length of thorax ( $ 3.6-4.0, $ 4.0-4.25) about one-fifth that of abdomen; length of hind femur 2 mm., width of head 3.5 mm.; ventral thoracic tubercle relatively low saucium Larger and more robust western species; length of thorax (5-6 mm.) one-fourth or more than a fourth that of abdomen; length of hind femur 2.5-3.0 mm., width of head 4 mm., ventral thoracic tubercle prominent abbreviatum Amphiagrion saucium (Burmeister). (PI. 10, fig. 2; pi. 16, figs. 5, 6; pi. 25, fig. 6; pi. 30, fig. 10) Agrion saucium Burm., Handb. Ent., 2: 819, 1839. Amphiagrion saucium Selys, Bull. Acad. Belg., (2), 41: 285,1876. A small red damselfly with a blackish thorax, found about springy bogs and pools. Male. Head, thorax, and first two abdominal segments clothed with soft pale hairs, which also extend over the legs. Head black above; labrum and jaws reddish brown; labium and rear of head pale. Prothorax and pterothorax blackish above, including in fully mature individuals the entire mesopleuron, except the lower half or more of the mesinfraepisternum; metapleuron mostly light orange-brown; venter paler and more or less whitish pruinose; interstermim raised into a round tubercle; legs rather short, the hind femora barely reaching base of abd. seg. 1; middle and hind coxae externally flattened, with a rounded margin; colour of legs pale reddish, femora and tibiae with a darker streak along the outer surface. Wings hyaline, venation reddish, pt. reddish, with anterior margin distinctly longc;r than posterior. Abdomen red, in dried specimens often brownish red; segs. 2-5 with ill-defined and indistinct posterodorsal and posterolateral dusky blotches; seg. 6 with a pair of more distinct posterolateral black spots; 7-10 mostly black; 7 red in the basal third or more, with black partly divided middorsally; 8 and 9 almost entirely black; 10 usually paler. Female. Usually a little longer than the male, the abdomen stouter and the coloration paler and less vivid, with less black. Dorsum of head varying from almost uniform

PLATE 33 Nymphs of Zygoptera: 1. Argia moesta (Hagen), X 5; 2. Amphiagrion saucium (Burmeister), X 6; 3. Nehalennia Irene (Hagen), X 7.

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deep orange to brownish black, with only the margin of the frons and a pair of postocular spots reddish; rear of head pale. Dorsum of thorax varying from almost uniform orange-brown to brownish black, as in male; intermediate forms sometimes showing an ill-defined mid-dorsal stripe, and a brownish stripe just behind the humeral suture. Legs generally uniform pale, with black setae. Abdomen sometimes almost uniform brownish red, but generally with a segmental series of median posterodorsal dark spots, increasing in size caudad and finally, on 7 to 9, covering most or all of the dorsal surface of the segments; 10 usually paler above. The spots on segs. 3-7 tend to be V-shaped, the apices on 6 and 7 prolonged in the mid-dorsal line far forward toward the front margin of the segment. Postnodal cross-veins, i. w. $ 8-10, $ 9-10; h. w. $ 7-8, $ 7-9; usually in both sexes, f. w. 9, h. w. 7. Measurements. Total length $ 23-25, 9 24.0-26.3; thor. $ 3.6-4.0, $ 4.0-4.25; abd. $ 18.0-19.5, $ 18.5- 21.0; h. w. 3 14, $ 15-16; h. f. £ $ 2; w. hd. $ 3.3-3.5, $ 3.5-3.6; pt. .5-.7. Nymph (pi. 33, fig. 2; pi. 40, fig. 1). A small dumpy short-legged nymph of nearly uniform olivaceous colour and with angular postocular lobes. Head nearly three-fifths as long as wide (17:30); front and eyes prominent; postocular lobes strongly angulate and turned slightly outward, with a patch of short close-set setae; median excavation of hind margin somewhat wider than the lobes; antennae short, about as long as head, six-segmented; relative lengths of segs., 7:12:11:8:7:8; labial mask extending to bases of mesocoxae, about one-third as broad at base as at distal margin; the latter measuring nearly three-fourths of the length; median lobe prominent; mental setae 3 ( 4 ) ; marginal setae in a rather close row of 6-8 on the distal half of the margins; lateral setae 5; distal margin of lateral lobes with two large denticles next to the end-hook, followed by a few very minute teeth. Pterothorax about as broad as long; wing-cases extending beyond the hind femora; legs very short, the length of the hind femora being about equal to the distance between the angles of the postocular lobes; tibiae somewhat shorter; femora and tibiae both with numerous short setae, the tibiae also with longer setae toward the apices. Dorsal and ventral surfaces of abdomen thickly studded with small dark raised spots, bearing minute setae; abdominal carinae not distinct and without special marginal setae, except on the hind margin of seg. 10, on which they are present but smaller than usual. Ovipositor extending beyond middle of 10th sternum, valves with a few ordinary setae in a patch. Caudal lamellae subelliptical, dorsal margins all somewhat arcuate, especially that of median lamella; lateral carinae prominent with about 20 short setae; dorsal margin of median lamella with 18-20 scattered setae among numerous slender hairs, which are longest and most numerous distally. These setae and hairs are distributed all along the margins, there being no hint of a nodus. Ventral margin of median lamella with about 30 setae or soft hairs; lateral lamellae with the coarse setae more numerous on dorsal margin (26) than on ventral margin (12), on which there are, however, numerous fine setae; lateral carina with some 22 stoutish setae. Lamellae widest about the middle, narrowing with curved margins toward both ends; apices bluntly pointed. Head above olivaceous; antennae of same general colour, with segs. 1 and 2 a little darker than the others, 2 with an ill-defined darker apical annulus. Pronotum with broad median and lateral dark stripes, separated by a broad paler dorsolateral area; pterothorax nearly uniform above and on the sides, slightly paler beneath; legs uniform (except when the black setae of the developing adult show through); wing-cases of same colour, darkened slightly along the costal border. Abdomen with indistinct pairs of dark submedian dorsal spots and dark median intersegmental spots, divided by a

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pale line; also dark anterolateral spots just above and below tlio pale lateral area. Caudal lamellae greenish yellow, the tracheae and setiferous serrations delicately pigmentcd. Total length 13 (extended 15, contracted 11); h. w. 3.0-3.2; h. f. 2.0-2.2; caud. lam. 3.0-3.2.

Habitat and range. Spring bogs and spring runs. N.S. to Wis. and Minn. (?),s.toS.C,,O.,Ind.,andIll. Distribution in Canada. N.S.—Bucklaw, C.B. Que.—Knowlton, Hemmingford, Covey Hill, Hull, Ironside, Broadview. Ont.—Kent, Elgin, Norfolk, Oxford, Brant, Lincoln, Waterloo, Wellington, Peel, York, Dufferin, Ontario, Bruce, Simcoe, and Carleton counties, Field notes. This attractive little damselfly is restricted to a type of habitat that is becoming rarer in the more intensively cultivated parts of its range, where the land has been overcleared, with the result that the springs have been dried up and the water-table has been lowered. It is found in springy bogs, often on the slope of a ravine or cutting, or at the base of a hill. Near Penetang, Ontario, we found A. saucium on the beach of Georgian Bay, where a spring run issued from the forest floor, seeping through the sand to the open lake. The area occupied by a local population of saucium is often very small but may produce a surprisingly large number of individuals. Whedon (1914) found thousands of them along a very small stream near Mankato, Minnesota, where their distribution was limited to an area of 200 yards along this little rivulet, so narrow that one could easily leap across it anywhere, and but a few inches deep.* In fact they are often much more localized than this, the colony being sometimes limited to a few square yards. The adults fly close to the ground among the club rushes, sedges, or horsetails, never over open water. The nymphs inhabit the small puddles or pockets of water in the bog. Sometimes they are found in the small running stream. We have found them to be all full grown in May, and most of the adults emerge in early June. Our earliest record is June 1, from a specimen collected at Tillsonljurg, Oxford Co., Ontario. Usually, however, they appear a little later than this, at least north of Toronto. We found them pairing in numbers on June 10, 1933, on a Lake Simcoe stream (Gilford), and have noted pairs on various dates during June and less frequently thereafter, until July 8. Our latest date of collection for both Ontario and Quebec is August 8, at Summerville, Ontario, and Broadview, Quebec. Our single record from Nova Scotia, however, is still later, namely, August 11, from Bucklaw, Cape Breton, where 3 males and 2 females were taken. The season of insect activity and plant growth is, however, much later in the Maritime Provinces than in Quebec and Ontario. We have not observed oviposition in this species. *It is possible that Whedon's specimens belonged to another species, as yet undescribed.

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Amphiagrion abbreviatum (Selys). (PL 16, figs. 3, 4; pi. 25, fig. 7; pi. 30, fig. 9) Pyrrhosoma abbreviatum Selys, Bull. Acad. Belg., (2), 41: 1299,1876. Amphiagrion abbreviatum Walker and Ricker, Can. Ent., 70: 148,1938. Amphiagrion saucium (Selys) Kennedy, Proc. U. S. Nat. Mus., 49: 326. Male. Robust and very hairy. Dorsum of head and greater part of pleura black, only the infraepisterna being largely pale reddish. Sterna and legs light reddish brown. Intersternum raised into a prominent knob. Femora, and sometimes tibiae, with a longitudinal dark streak on the outer surfaces. Wings hyaline, with reddish venation and pt. Abdomen red with intersegmental areas following segs. 3-6 dark, and a series of dark dorsolateral spots, often ill-defined, on 2 or 3 to 10, increasing in size caudad, generally absent from 2, sometimes obscure on 3 and 4, much larger on 6 and 7, and covering the entire dorsum of 8-10, except along the median line, where it is more or less divided by a red streak. Anal appendages similar to those of A. saucium. Female. Varying from a nearly uniform light brownish red to a darker diffuse reddish brown, sometimes without distinct spots, except the small lateral ones on the intersegmental membranes of some of the abdominal segments. In the more distinctly marked specimens the pterothorax has broad dark areas on the episterna, and a diffuse darkening of the whole thoracic dorsum is sometimes found; dorsum of head varying from pale to dark brown; rear of head pale. Abdomen brownish red, usually with a segmental series of paired oblique posterodorsal spots on segs. 3-7, with larger spots on 8 and 9. Postnodal cross-veim, f. w. $ 9 10-13; h. w. $ 9 8-10. Measurements. Total length $ 26.0-27.5, 9 27.0-28.5; thor. $ 9 5-6; abd. $ 20.0-20.5, $ 21.0-21.5; h. w. $ 17.0-17.5. 9 17.5; h. f. $ 9 2.5-3.0; w. hd. $ 9 4.0-4.3; pt. .7-.9. Nymph. Unknown.

Habitat and range. Marshy ponds with emergent vegetation, preferably shallow and hard-bottomed. S. B.C. to Sask., s. to Calif., Nev., Ut., Okla., and Kans. Distribution in Canada. B.C.—Victoria and Florence Lake district on Vancouver Is.; Vancouver, Cultus Lake, Kaleden, Penticton, Peachland, Vernon, Lumby, Hat Creek, Salmon Arm, Canoe, Kaslo, Vedder Crossing. Alta.—Banff. Sask.—Maple Creek, Cypress Park. Field notes. Although until recently regarded merely as a robust western form of A. saucium, this form has been separated from the type species of Amphiagrion on the authority of Mrs. Gloyd, who is engaged on a revision of this genus. The habitat of A. abbreviatum is strikingly different from that of the eastern species. Whitehouse (1941) states that "it likes shallow, sunlit, hard-bottomed reedy marsh or runways, as favoured by Ischnura erratica and this type of breeding place is by no means common." Both Whitehouse and Ricker collected abbreviatum at the Indian Reserve Sloughs, near Vedder Crossing, B.C. These are described by Ricker (Walker and Ricker, 1938) as "several small sloughs . . . about a mile and a half north of Cultus Lake, lying mostly in open fields. Their vegetation is principally Carex and areas of open water are very limited. Two small spring creeks are in the immediate vicinity and also the lower part of Sweltzer Creek," Our only personal encounters with this species were at Banff, Alberta. We

PLATE 34 Nymphs of Zygoptera: 1. Chromagrion conditum (Hagen); 2. Coenagrion resolutum (Hagen). X 5.5.

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first found it on July 2, 1913, but obtained only a single teneral female. We visited Banff in 1921 and on July 7 we took 4 males and 1 female, including a pair in couple, in a shallow slough close to the Bow River Falls. But, although we searched carefully for more specimens over the entire slough, which was not a large one, we could find no others. This slough was clear, rather cold, and only a few inches deep, with a firm bottom. It supported a somewhat sparse stand of emergent aquatic plants. We visited the same slough in 1926 but found no amphiagrions there. The flight period in British Columbia, as noted by Whitehouse, is May 16 to August 1. As we took a teneral at Banff on July 2, it is probable that the season begins later there. The two Saskatchewan records are dated June 1 (Cypress Park) and July 5 (Maple Creek). Genus Nehalennia Selys Rev. Odon., p. 172, 1850. Bull. Acad. Belg., (2), 46: 1235, 1876. Typespeciosa (Charpentier). These are small slender fragile insects with predominantly metallic green colour above, pale greenish or yellow below; the head is without pale postocular spots; the frons in profile is rectangular, the dark dorsal surface being separated from the pale anterior surface by a sharp angle; the pterothorax is uniform above, without antehumeral stripes. The legs are slender, moderately long. The wings are hyaline, with a narrow quadrangle, not widening distally, whose proximal end is longer than the upper part of the arculus; the pterostigmata are pale, surmounting one cell; there are 9-12 postnodal cross-veins in the fore wing, 8-11 in the hind wing; M2 arises between the third and fifth postnodals in the fore wing. The anal appendages of the male are extremely short; the eighth abdominal sternum of female is without an apical spine. Key to the Species of Nehalennia Adults Abd. segs. 9 and 10 of $ blue, with paired dark spots; seg. 8 dark above, with broad hind and lower margins blue; seg. 10 of $ with dark dorsal spots; pronotum of $ with hind margin trilobate, the mesostigmal laminae with hind margins strongly reflected irene Abd. segs. 9 and 10 of $ entirely blue or without small basal black spots; seg. 10 of 9 wholly pale; pronotum of $ with hind margin bilobate, the mesostigmal laminae without reflected margins gracilis

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Nymphs Caudal lamellae with numerous small marginal spots; posterolateral surface of head with about a dozen short spines, which are darker at base irene Caudal lamellae unspotted or nearly so; posterolateral surface with 4-6 small colourless spines gracilis Nehalennia irene (Hageri). (PI. 10, fig. 3; pi. 21, fig. 1; pi. 25, fig. 8; pi. 29, fig. 9) Agrion (Nehalennia) irene Hagen, Syn. Neur. N. Amer., p. 74, 1861. Nehalennia irene Selys, Bull. Acad. Belg., (2), 41: 1240,1876. Male. Dorsum of head greenish black, finely granulate with a soft metallic lustre, a pale transverse line on the occipital margin; antennae black, with tip of seg. 1 and an annulus on seg. 2 white; face pale, including vertical part of frons, most of the anteclypeus, and distal part of labrum; postclypeus and base of labrum black; labium pale; rear of head black, with wide pale lateral margins. Dorsurn of prothorax and pterothorax metallic green with a soft lustre; sides of pronotum and fore coxae pale yellowish. Sides of pteromorax, including lower half of mesinfraepisternum and the metapleura, except a triangular posterosuperior area, pale bluish green, yellowish green below. Legs pale yellowish, the anterodorsal surfaces of femora and anterior (outer) surfaces of tibiae each with a longitudinal black line; tarsi pale, with apices of segments dark. Abdomen, from segs. 3 to 6, very slender, the middle depth of sng. 3 being about one-tenth of the length, enlarging distally on seg. 7, stoutest at segs. 8 and 9. Sup. apps. in profile largely hidden by the inf. apps. Segs. 1-7 metallic green, 1-2 pale bluish on the sides, 3-7 ventrolaterally pale yellowish and with narrow, interrupted, pale basal annuli; seg. 8 bronze-green above, with the distal fourth or third blue; 9 and 10 blue, with paired basal dark spots. Female. Similar to male, with stouter abdomen, which widens on seg. 8 and narrows again on 10. Hind margin of pronotum trilobate, the lateral lobes fitting into concavities in the reflected mesostigmal laminae. Colour pattern nearly as in male, but metallic dorsal areas on 8 and 9 with a terminal angular blue cmargination. Postnodal cross-veins, f. w. $ 9-11, 9 9-12; h. w. $ 9 8-10. Measurements. Total length $ 20-27, 9 25-28; abd. $ 21.5, 9 21.0-23.5; h. w. $ 14-15, 9 15-17; h. f. $ 2.4-2.5, 9 2.4-3.0; w. hd. $ 3.2, 9 3.0-3.4; pt. .6-.7. Nymph (pi. 33, fig. 2; pi. 40, fig. 3). A slender green or brown nymph without conspicuous markings. Head about twice as broad as long, with postocular margins well rounded, having about the same curvature as the median excavation, and bearing about a dozen short spines on each side. Eyes moderately prominent; antennae nearly as long as the head; segs. 6 and 7 imperfectly separated; ratio of seg. lengths, 10:20:25:17:14:12:7. Labium reaching to front margin of mcsosternum, basal width of mentum about onethird of the distal width, sides slightly sinuate, diverging from the base at an angle of about 40°; mental setae one on each side, with sometimes a vestigial second; proximal seg. of lateral lobes widening distally and bearing 6 lateral setae, the truncated distal margin separated from the short end-hook by a distinct notch and bearing 3 or 4 denticles in a graded series. Wing-cases extending a little beyond apices of hind femora. Legs very slender, the femora and tibiae with double rows of very short, widely spaced setae. Caudal lamellae about as long as the last six segments, lanceolate, widest at about the distal fourth, tapering to slender pointed apices, with small, more or

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](3ss distinct, dark marginal spots and sometimes an arcuate crossband just beyond the middle. Stout setae: im;cl. lam., d. 9-12, v. 6-7; lat. lam., d. 5-6, v. 19-27. Total length 14.0-16.5; abd. 8; caud. lam. 4.0-4.5; h. w. 3.4; h. f. 3.0; w. hd. 2.5-2.8.

Habitat and range. Still marshy or boggy waters. N.S. and N.B., n.w. to James Bay, s. Mackenzie, and B.C., s. to Md., n. O., n. Ind., n. 111., Minn., Sask., and Alta. Distribution in Canada. N.S.—Annapolis, Halifax, and Pictou counties; Cape Breton Is. N.B.—Charlotte, Kent, York, and Gloucester counties. Que.— Eastman, Waterloo, St. John's, Hemmingford, St. Chrysostom, Vaudreuil, Lachine, Hull, Gatineau Valley, Nominingue, Lac Temiscouata. Out.— General throughout s. Ont., Essex to Welland; Wentworth to Prescott; n. to L. Abitibi, Cochrane Dist; Orient Bay, L. Nipigon; and Gull River, Thunder Bay Dist.; Favourable Lake region, Kenora Dist.; Rainy River Dist. Man.— Treesbank, Onah, Westbourne, Winnipeg, Winnipeg Beach, Victoria Beach, Dauphin, The Pas. Sasfc.—Burrows, Zealandia, Prince Albert. Alta.—Red Deer. B.C.—Nelson, Revelstoke, Williamson's Lake, Chase, Salmon Arm, Vanderhoof, Summit Lake (Prince George). Field notes. Except in the far north, this is probably the most abundant damselfly in eastern Canada and is by no means rare in the western provinces, although it does not quite reach the Pacific coast. It inhabits almost all still waters that support a stand of emergent vegetation, e.g. spring-fed ponds among cat-tails; shallow clay-bottomed sloughs amidst rushes, sedges, and horse-tails; oxbow ponds with any or all of these types of standing aquatic plants; or the marginal zone of slow streams, dominated by cat-tails and Acorus or Sparganium, with many other aquatic plants, such as Iris versicolor, Sium suave, and Calla palustris; and bog ponds of all sorts, although it is not always present in the typical sphagnum-bog pond with floating margin, N. gracilis being the characteristic Nehalennia of such ponds in eastern Canada. In all these situations N. Irene abounds in summer, flying close to the water among the rushes or other emergent plants, and in the grass and sedge along the shore, but usually not venturing over the open water. The nymphs may be found in the dense aquatic vegetation of their habitats and are full-grown in early spring. The adults begin to emerge in southern Ontario during the last few days of May or early June, and continue to emerge until the middle of the latter month or even later. In southern Ontario they are often abundant by the third or even the first day of June, many individuals being already full-coloured. By the middle or the third week of June, N. Irene has reached the peak of its abundance. On June 22, 1939, we calculated that the number of individuals of Irene at Grenadier Pond, a small lake west of Toronto, was more than fifty per cent of all the Odonata present. They continue to be abundant, although in less degree, until about the end of July, after which their numbers diminish somewhat rapidly, although they have been recorded as late as August 28 in Quebec (Robert, 1944). The fact that we have no Ontario records after

PLATE 35 Nymphs of Zygoptera: 1. Enallagma ebrium (Hagen); 2. Ischnura verticalis (Say).

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August 19 may be due merely to the incompleteness of our observations. We have observed pairing from June 10 to August 8, but this is probably also short of the actual period. Oviposition has been noted from July 18 to August 1. The female is generally accompanied by the male and oviposits in floating bits of dead rushes or sweet-flag (Acorus calamus) and doubtless on any similar dead plant material. While thus engaged, the female rests in a horizontal position, while the male is raised at an angle, often about 45°, supported only by his grip on the female's prothorax. Nehalennia gracilis Morse. (PL 21, fig. 2; pi. 25, fig. 9; pi. 29, fig. 10) Nehalennia gracilis Morse, Psyche, 7: 274,1895. Similar in size and coloration to N. irene but even more slender, a typical inhabitant of sphagnum bogs. Male. Head similar to that of N. irene; general coloration of thorax and abdomen also similar, but the sternal areas somewhat less yellowish; a fine pale line on the humeral suture. Sides of thorax and abdominal segs. 1-2 pale bluish green; 3-6 pale yellowish; metallic pattern as in irene; segs. 8-10 light blue, 8 with or without a dark bilobed spot on the basal half or less of the segment; 3-6 more slender than in irene, the middle depth of 3 (.36) being about one-eleventh of the length of the segment; 7 enlarging distally, greatest width of abdomen at end of 8 and 9. Sup. apps. rounded, the ventral outline not hidden in profile view as in irene; inf. apps. ending above in a black spinelike process; spines on the dorsal transverse arch of seg. 10 smaller than in irene. Female. Marked like 9 of irene, except on segs. 9 and 10 and sometimes 8, on which the blue of the apical annulus may extend forward up to one-third of the distance toward the front margin; 9 blue, with a bilobed basal dorsal spot or a pair of spots on the anterior half; 10 wholly blue. Pronotum bilobed, with a small process in the median notch; mesostigmal laminae not reflected, but bearing a pair of slender processes that converge over the base of the dorsal carina. Postnodal cross-veins, f. w. £ 9-11, $ 9-12; h. w. $ 8-11, $ 8-10. Measurements. Total length $ 25-27, $ 24-26; abd. $ 19.5-22.5, $ 19-21; h. w. $ 12-15, $ 14.0-16.5; w. hd. 4 $ 2.8-3.0. Nymph (pi. 40, fig. 3). Similar to that of N. irene, differing in the following features: the posterolateral surfaces of the head have each only 4—6 inconspicuous colourless spines, whereas in irene there are a dozen or more spines, which are somewhat coarser and blackish at base; caudal lamellae more slender, widest in the distal third, tapering somewhat more gradually than in irene, and with little or no indications of spots; proximal half of median caudal lamella with 8-11 coarse setae on both dorsal and ventral edges; lateral lamellae with 3-7 on the dorsal edge and 11-16 on the ventral edge, these extending a little beyond the proximal half. Total length 11.5-13.0; abd. 4.5-6.0; h. w. 2.2-2.7; h. f. 2.0-2.3; caud. lam. 3.5-4.0; w. hd. 2.3-2.4.

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Habitat and range. Sphagnum-bog ponds, N.S. to Wis., s. to N.J., O., Ind., and Mo. The record of a single specimen from Florida (Byers, 1930) would seem to need verification. Distribution in Canada. Annapolis and Queens counties; Cape Breton Is. N.B.—Near Bathurst. On*.—Peel and Addington counties; Muskoka and Parry Sound districts. Field notes. In contrast to N. irene, N. gracilis is almost entirely restricted to one type of habitat, the sphagrium-bog pond. It is true that it is occasionally found in open marshes among low sedges and grasses, but these occurrences are so rare that they may be regarded as probably transient. We first met with N. gracilis at Go Home Bay, Muskoka, on the coast of Georgian Bay. We found it in all sphagnous bogs bordering lakes and ponds. "It was first noted on June 18, 1907, and was found in abundance throughout July." In 1912, in the same region, "it was still common on Aug. 6, but had about disappeared by Aug. 25. Some imagoes emerged in the laboratory during July" (Walker, 1915). The nymphs are found in the floating margins of such bog ponds and climb a very short distance up the stems of the small cranberry (Vacciniwn oxycoccos) or other emergent plants in order to transform. Although N. irene was absent from these ponds on the Georgian Bay coast, we found the two species together in a very small, but typical, quaking bog pond near Snelgrove, Peel Co., Ontario, in the region of morainic hills. We have visited this pond for many years and have marked a gradual diminution of N. gracilis and an increase of N. irene. In another similar pond near London, Ontario, which we visited in 1925, only N. irene was present. In more recent years we have found N. gracilis in so many sphagnumbordered ponds that we would not hesitate to affirm that they are almost invariably present in any well-developed pond of this nature within their geographical range. They may be replaced by N. irene in small isolated ponds, but this absence is exceptional. Our earliest record for gracilis is May 30, 1933, when we found a single teneral female at the Snelgrove bog pond, but we have no further records until June 16, at the same pond. June 19 was the earliest date at Go Home Bay, the spring being here a little later than in Peel Co. N. gracilis continues to be abundant throughout July, and our latest definite records are August 11, when we found a few individuals in a bog on Cape Breton Island, N.S., and August 12 for Go Home Bay (although apparently it was casually noticed there as late as August 25). Like N. irene, gracilis flies close to the bog over the wet sphagnum moss and among the slender branches of cranberry and other bog plants. They skirt the edge of the floating marginal plants of such ponds but avoid the open water. We observed a great many pairs in copula on July 5, 1946, on a large bog pond near Buckshot Lake, Addington Co., Ontario, but have made no observations as to the length of its mating period, nor on oviposition.

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Genus Coenagrion Kirby Syn. Cat. Neur. Oclon., p. 148, 1890; new name for Agrion, preoccupied. Agrion Fabr., Syst. Ent., p. 425, 1775; in part. This genus is still known as Agrion by most European odonatists. These are moderate-sized damselflies, the males chiefly blue and black in colour, the females either blue or grey-blue (homoeochromatic) or of various shades of green to brownish (heterochromatic). Although it is difBcult to find good generic characters to separate this genus from Endlagma, the females are readily distinguished by the lack of a ventral spine on segment 8, while the males differ in the terminal segment of the penis. In Coenagrion this segment is prolonged into a pair of membranous appendages which may be either apical or lateral, whereas in Enallagma there are only very short angular projections. The superior appendages of the male, viewed in profile, tend to be partly concealed by the overlapping inferior appendages (cf. Ischnura), while those of Enallagma are completely exposed. The inferior appendages consist of a stout base, more or less prominent behind, and a slender apical process, usually spine-like, which may arise either posteriorly or more or less dorsally. The latter represents the apex of the more triangular inferior appendages of Enallagma. The nymphs resemble those of the northern species of Enallagma (boreale, cyathigerum, etc.), but have seven instead of only six antennal segments. The caudal lamellae are lacking in pigment and are characterized by a transverse nodal line, usually with a distinct nodal notch on each of the margins. Well-developed antenodal setae are present on both margins of each lamella. Coenagrion is mainly a Palaearctic genus, but includes three boreal species in North America. All of these have near relatives in Eurasia.

Key to the Species of Coenagrion Males 1. Abdomen narrowing slightly beyond seg. 8; sup. apps. with an inferior process, visible in profile view, directed posteroventrad; inf. apps. with a slender process arising from a stout base and having a terminal or nearly terminal position; seg. 2 with a pair of lateral black spots in addition to the median one, with which they are often joined; blue colour very pale 2 Abdomen expanding somewhat beyond seg. 8; sup. apps. with an inferior process largely concealed in profile view, directed anteroventrad; inf. apps. with a very short spine arising dorsally near the base; seg. 2 with a median black spot, not accompanied by lateral ones; blue colour azure angulatum

PLATE 36 Labia of Lestes nymphs: 1. L. eurinus; 2. L. dry as; 3. L. rectangularis; 4. L. vigilax; 5. L. unguiculatus; 6. L. congener; 7. L. disjunctus disjunctus. All figs, approx. X 15.

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2. Pale antehumeral stripes narrower than the black humeral stripes and, when divided, resembling an exclamation mark; the longer anterior spot tapering caudad to a point; venter of metathorax without dark markings resolutum Pale antehumeral stripes wider (in the middle) than the black humeral stripe, nearly always divided, the long anterior spot not tapering caudad; venter of metathorax heavily marked with black, the pattern including a median Y-shaped figure interrogatum Females 1. Hind margin of pronotum with a median notch, hence bilobate; seg. 8 of abdomen broadly black at base 2 Hind margin of pronotum trilobate; seg. 8 of abdomen with a broad pale basal area angulatum 2. Venter of thorax wholly pale; second lateral suture with black spot only in the pit; abd. segs. 3-7 black above, except small laterobasal pale areas, without ventrolateral longitudinal dark streaks resolutum Venter of thorax heavily marked with black; second lateral suture marked with black in front of the pit; abd. segs. 3-7 with pale basal annuli; most of the abd. segs. with long ventrolateral dark streaks interrogatum A key to the known nymphs of Coenagrion is incorporated with that of Enallagma. Coenagrion resolutum (Hagen). (PI. 4, fig. 8; pi. 11, fig. 1; pi. 19, fig. 1; pi. 26, fig. 1; pi. 29, fig. 6) Agrion resolutum Hagen, in Selys, Bull. Acad. Belg., (2), 41: 1263, 1876. Coenagrion resolutum Muttk., Cat. Odon. N. Amer., p. 66, 1910. A moderate-sized damselfly, of average build, resembling an enallagma in markings, but of a pale blue colour, passing into yellowish green below. Male. Head black above, with a pair of large subtriangular postocular spots and a narrow transverse marginal line between them blue; postclypeus and extreme base of labrum black, face and labium otherwise green, including a broad transverse band in front of the antennal bases; rear of head pale yellowish green. Prothorax black above, the following parts pale: narrow front and posterolateral margins, broad lateral margins, and a pair of minute spots on the middle lobe. Pterothorax black above, with pale green antehumeral stripes, which are narrower than the humeral stripes, slightly sinuate, broadest near the anterior end, tapering behind and usually more or less constricted at

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nearly three-fourths of their length by a lateral indentation, the posterior part being often separated, giving the form of an exclamation mark. There is also a small pale dot just in front of the antehumeral stripe. Humeral stripe widest behind mesinfraepisternum. Sides of pterothorax pale green, more yellowish ventrad; venter wholly pale; ante-alar ridge ana upper parts of lateral sutures 1 and 2 marked with a black line, a longer often broken line on the first suture and a shorter line or spot on the second. Legs yellowish green, anterodorsal surfaces of femora, anterior surfaces of tibiae, and apices of tarsal segments black. Abdomen pale blue, ventrally yellowish green; seg. 1 with a small basal dorsal and a pair of minute distolateral spots black; seg. 2 with a median black spot connected by a "neck" with the apical annulus; and usually with a pair of lateral "arms" extending forward. These arms are often separated and sometimes absent; segs. 3 and 4 with posterior half or more black above; 6 and 7 dorsally black, with a narrowly interrupted basal pale annulus; 8 and 9 blue, sometimes marked laterally with black in northern specimens; 10 with dorsum black. Sup. apps. of $ composed of short broad bluntly angular knobs, and a longer flat process with expanded apices, arising from the base beneath, and directed ventroposteriorly. Inf. apps. stout, horizontal, shelf-like, bearing a hook-like process on the laterodistal margin. Female. Pale colours like those of male (homoeochromatic) or yellowish green to brownish (heterochromatic). Sometimes the thorax is yellowish green and the abdomen blue. Black markings of head and thorax as in male. Abd. seg. 1 with a small basal dorsal spot; 2 with a dorsal median black band, laterally expanded and connected with the apical annulus by a short neck. Remaining segs. chiefly black above, the black area of 3 narrowed in front and expanded before the apical annulus; those of 4—7 with narrowly interrupted pale basal annuli; 7 and 10 with pale apical annuli. Sternum of 8 truncate; ovipositor reaching barely beyond the sternal margin of 10. Mesostigmal laminae triangular, enclosing a small rounded median pit, with the margin little raised; median carina crossing the posterior suture, its basal rami not divergent. Postnodal cross-veins, f. w. $ 9 9-13; h. w. $ 8-11, 9 8-10. Measurements. Total length, 8 27-30, 9 28-31; abd. $ 22-25, 9 22.5-24.5; h. w. 8 15-18, 9 18-20; h. f. $ 3, 9 3.0-3.8; w. hd. i 3.7-4.0, 9 4.0-4.5; pt. 4 .6-.7, 9 .8. Nymph (pi. 34, fig. 2; pi 40, fig. 9; pi. 43, fig. 4; pi. 44, fig. 8). Of average size and form, pale yellowish brown with numerous dark dots which mark the position of short setae, most abundant on the abdomen. Form of head as in Ischnura verticalis or Enallagma hageni, etc.; Antennae one-fourth longer than median length of head, ratio of seg. lengths, 13:25:27:15:13:10:8. Eyes moderate; the rounded postocular contours of head with a group of setae, the more central of which are similar to those of the legs. Labial mask extending to base of mesosternum, greatest width of mentum fourfifths of the length, slightly flaring distally, with or without 1-3 small marginal setae on distal third and 2 or 3 at the articulation of the lateral lobe; mental setae 4, one of them sometimes vestigial or lacking; lateral setae 6, rarelv 7; distal margin of lateral lobes with 6 angular denticles, the largest next the end-nook, the others successively smaller. Lateral margins of abd. segs. with a series of about 11-13 small spinules, not forming a definite single row and not sharply separable from the general clothing of setae but longer than most of these. Hind margin of 10 with an obtusangular emargination, bordered by longer setae than those of the general tergal surface, those of the ventrolateral part of the margin still larger. Caudal lamellae nearly one-half longer than the outer wing-cases, lanceolate, widest about the middle, the width here being a little more than one-fifth of the length; nodus slightly beyond the middle, nodal line transverse, slightly arcuate; no definite constriction at nodus, although the lamella is somewhat narrowed immediately beyond it; apices acute, with slightly convex margins; antenodal setae: med. lam., d. 23-30, v. 17-21; lat. lam., d. 17-21, v. 29-33. Lamellar tracheae slightly pigmented, the pigment broken here and there; many of the main

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branches coming off die axial trunks at a very acute angle, the more distal branches following an almost longitudinal course. Lateral apps. of male bluntly angulate in profile, in dorsal view broadly rounded, not at all concave mesally. Ovipositor projecting very slightly beyond the sternum of seg. 10. Head without distinct markings or, in dark specimens, with an irregular darker area between the eyes, which is transversely divided by a pale trilobed spot. Thorax almost uniformly pale, except for the dark dots already mentioned, and small black spots at the coxopleural articulations and the metastigma. Pronotum sometimes also with ill-defined lateral stripes and the mesostigma sometimes darkened. Legs pale, with a fairly distinct ante-apical dark annulus, followed by a pale apical annulus. Wing-cases with the longitudinal veins darkened. Abdomen brown, deepened slightly on each side of the pale mid-dorsal line; lateral margins pale with small dark dots at the tergal articulations, scarcely noticeable except in dark specimens. Caudal lamellae pale, darkened along the tracheae but without spots or bands. Total length (extended) 21-22; wing-cases 6.5-7.0; h. f. 3.0-3.3; caud. lam. 5.2-7.0.

Variations. In the southern part of its range, e.g. at Toronto, the build of C. resolutum is more slender and the black markings less heavy than in the far north, e.g. at Port Severn or Churchill, Hudson's Bay. Here the antehumeral stripes are frequently divided, the black lines on the lateral thoracic sutures are heavier, the coxae, as well as the trochanters, are marked in front with a black spot, and the paired lateral spots on abd. seg. 2 are heavier and joined with the median spot. The black spots of the abdomen also tend to be larger and spots appear on the sides of segs. 8 and 9, where they are absent in more southern specimens. Individuals from far north, however, are not always distinguishable in markings from southern ones. Habitat and range. Still marshy waters, more or less shaded in the southern part of its range. Nfld. to Hudson Bay and Alaska, s. to N.B., Me., n. N.Y., s. Ont, Mich., la., Sask., Alta., and at higher altitudes to Nev. and Calif. Distribution in Canada and Alaska. Nfld.—Spruce Brook, St. John. N.B.— Fredericton, Little Southwest Miramichi R., near Nelson; Bathurst. Que.— Magdalen Is.; Lake Temiscouata; Eastman; Cascapedia; Covey Hill; Gatineau Valley; Nominingue, Labelle Co.; La Ferme, Abitibi Co.; Natashquan; Knob Lake; East Main, James Bay. Ont.—Throughout s. Ont, commonest in calcareous regions; n. shore of Lakes Erie and Ontario, from Essex to Prescott counties, n. through Muskoka, Nipissing, Algoma, Cochrane, Thunder Bay, Kenora, and Rainy River districts, reaching Hudson Bay in the Patricia section of Kenora. Man.—Treesbank; Portage la Prairie; Winnipeg; Victoria Beach, Lake Winnipeg; Virden; Dauphin; Lake Winnipegosis; Riding Mts. Park; the Pas; and northward (Wabowden, Gillam) to Churchill. Sask.—Burrows, Regina, Yorkton, Hamton, Lac Verte, Prince Albert, Waskesiu Lake. Alta.—Calgary; Red Deer; Nordegg; Banff; Fort Chipewyan, Lake Athabaska. B.C.—Most of the records are from southcentral B.C., the most southerly being Nelson; representative localities from south to north are Hat Creek, Revelstoke, Chilcotin, Canim and Bridge Lakes, Tatla Lake, Horsefly, Prince George, Burns Lake, and Smithers, and, near the northern boundary of the province, Atlin (60°N). It appears

PLATE 37 FIGS. 1-7. Mentum of labium of Argia nymphs: 1. Argia moesta; 2. A. apicalis; 3. A. tibialis; 4. A. sedula; 5. A. violacea; 6. A. vivida; 7. A. emma. FIG. 8. Caudal lamellae of A. vivida. Figs. 1-7 are approx. same scale. Fig. 8, X 9.

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to be absent from the Pacific coastal region, even in the north, the most westerly localities from which it has been recorded being Tatla Lake, Smithers, and Atlin. N.W.T., Mackenzie Dist.-Fort Smith; Great Slave Lake region (Fort Resolution, Resdelta, Yellowknife River); Norman Wells; Reindeer Depot, Mackenzie Delta. Yukon T.—Whitehorse; Alaska Highway, m. 1143. Alaska—Anchorage, Gulcana, Palmer. The northern boundary of the range of C. resolutum is of some interest, since it probably represents the northern limit in the New World of the Zygoptera in general. From Spruce Brook, Nfld. (which is certainly far south of its actual northern limit on the Atlantic coast) to Knob Lake, Que. (54° 47'N), west to Port Severn, Hudson Bay (56°N); Churchill, Man. (59°N), also on Hudson Bay; Yellowknife, N.W.T. (62° Sff) and down the Mackenzie River to Reindeer Depot (68° 30') and Gulcana, Alaska (62° 30'). Field notes. This small, pale blue damselfly is one of the most widely distributed damselflies in Canada. It is the common damselfly of the north, and can probably tolerate a colder climate than any other species, with the possible exception of C. interrogatum. Yet it also ranges to our southern boundary and, in the west, far southward along the mountains, although at increasing altitudes. It is also widely distributed ecologically, inhabiting almost any small permanent or subpermanent body of still water. It may be found in ordinary ponds and prairie sloughs with marshy borders; in grassy or sedgy roadside ditches; in springy cat-tail marshes; in dark calla ponds; in sphagnum pools, in cool northern spruce or tamarack swamps, and in the marginal vegetation of slow weedy streams. C. resolutum flies low among the emergent plants and, in the southern part of its range, it shows a distinct preference for partly shaded waters. As to its flight period, it will be convenient to consider this first in southern Ontario where it is best known, and secondly in the more northern and typical parts of its range. In the vicinity of Toronto and other localities near the north shore of Lake Ontario, C. resolutum begins to emerge about the middle of May or soon after. In 1949 a number of nymphs were collected on May 6 and 7 from the morainic ponds near Snelgrove, Ontario, and from these nymphs adults emerged on the 16th and 17th. Individuals kept alive after emergence acquired their full colour in less than 24 hours, without having fed. The first full-coloured adults observed in the field were noted on May 23 but, until the end of this month, most of the insects were tenerals. But the time

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for tenerals is short and, after the first of June, full-coloured adults are generally in the majority. Our earliest date for both pairing and ovipositing is June 6, at a Lake Simcoe stream. As usual with coenagriids, C. resolutum usually oviposits in pairs, the male in an oblique or vertical position. On one occasion we noted pairs ovipositing in a narrow-leaved potamogeton, on another occasion floating Typha was chosen and, in the Riding Mountains Park, Manitoba, we saw a pair ovipositing in rushes and other standing aquatic plants. In Ontario, from Lake Simcoe southward, we have no records of C. resolutum after the first of July. From Algonquin Park we have a single record of July 12. The very few records from the Maritime Provinces are from July 1 to 12, but may represent the end of the flight period. The numerous records from northern and western Ontario, ranging from June 3 to August 1, indicate a season that begins two or three weeks later and lasts three or four weeks longer than in southern Ontario. This series of records includes those from Port Severn, a region bordering on the Arctic and comparable to that of Churchill, Manitoba, and parts of Great Slave Lake. From the last region the dates recorded range from June 12 to July 29, but probably the entire season of flight is not represented. Southern Manitoba and Saskatchewan apparently have a season only a little later than southern Ontario, the dates ranging from May 31 (Regina) to July 18, while at Red Deer, Alberta, Whitehouse (1917) gives May 26 as the date of the first appearance of resolutum in 1916, and July 19 as a date after which the flight period soon comes to a close. He noted numbers in copula from June 25 to July 19. Finally, in British Columbia the adult season is decidedly late, Whitehouse's (1941) range of dates being June 14 to August 18. A study of the flight period of this species throughout its range, combined with its entire life cycle, might yield interesting results. Coenagrion interrogatum (Hagen). (PI. 4, fig. 9; pi. 19, fig. 2; pi. 26, fig. 2; pi. 29, fig. 7) Agrion interrogatum Hagen, in Selys, Bull. Acad. Belg., (2), 41: 1254, 1876; translated from Hagen MS. Coenagrion interrogatum Walker, Can. Ent, 47: 174-181, 1915. Similar in size and proportions to C. resolutum, but more heavily marked with black, the markings including the venter of the thorax. Male. Dorsum of head black, with posterior margin and postocular spots pale blue and smaller than in resolutum, rounded laterally, with mesal angles and a fine transverse line between them; postclypeus and base of labrum black; face otherwise blue above, shading into greenish below; rear of head black, with pale lateral margins. Prothorax black, the following parts blue: most of anterior lobe, a narrow but continuous margin on hind lobe, and a oroad lateral margin. Pterothorax pale blue, heavily marked with black; dorsum black, with antehumeral stripes usually as broad in front as the median black area and the median width greater than that of the humeral stripe, sharply divided near the posterior three-fourths (very rarely entire or partly divided);

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humeral stripe widening in front and encircling the mesinfraepisternum. Sides of pterothorax with a short black streak on the upper part of the first lateral suture, with a black dot in front of it; second lateral suture marked with two black dots, usually connected and continuous with a heavy black stripe surrounding the metinfraepisternum, and bounding the anterior end of metepimeron; venter heavily marked with black; coxae all marked with basal black spots. Legs greenish, marked with black as in C. resolutum. Abdomen pale blue, sides of segs. 6 and 7 and a part of 5 green. Seg. 1 margined ventrolaterally with black; 2 with a transverse black bar at the middle third and a pair of large lateral black blotches, which may be connected with the transverse bar; 3 with posterior fifth to third black, enclosing on each side a pale posterolateral spot and extending forward in a long streak; 4 with more than the posterior half black; 5 and 6 with the posterior three-fourths or more black, the lateral streaks partly isolated or absent; 7 very narrowly blue at base, but with a larger apical blue area; 8 and 9 blue, usually with a few small black spots; 10 black above, blue on the sides. Legs a little shorter than in C. resolutum; sup. apps. with a much shorter ventral process; inf. apps. stout, each with a slender straight process, their extreme apices bent mesad. Pt. smoky brown, their costal margins one-fourth longer than the radial. Apices of penis prolonged, recurved, and deeply bifurcate. Female. Usually homoeochromatic or nearly so, but sometimes the pale areas are greenish throughout; a little longer-bodied than the male and proportionally longer than C. resolutum. Head, thorax, and legs marked as in male. Abdomen marked with black as follows: seg. 1 as in male; 2 with a mid-dorsal stripe from end to end, very narrow in front, abruptly widening a short distance from base, and in distal third laterally expanded, but connected with the apical annulus by a short neck; sides with a heavy longitudinal streak, widening toward the expanded part of the middle stripe, but usually not connected with it; dorsa of 3-6, except a basal blue area of variable length, usually about a fifth or sixth of the segment length; sides of 3-6 with a longitudinal streak, widened caudad, where it fuses with the expansion of the dorsal stripe, thus isolating a pale spot at the posterior end of the segment; the lateral streaks becoming narrower caudad, and on 7 and 8 sometimes reduced to ill-defined lines; 7 with basal blue area shorter than on the segments in front and often narrowly divided into paired spots. Distal margin of 7 and 8 pale, 8 otherwise black above; 9 blue, with a large median basal black spot; 10 pale, with the extreme base black. Hind margin of pronotum simple; mesostigmal laminae triangular, with posterior margin straight, median pit bounded in front and laterally by an arcuate margin, behind by the ends of the divergent basal arms of the median carina. Pt. slightly larger and paler than in male. Postnodal cross-veins, f. w. $ $ 9-12; h. w. $ 7-10, $ 8-10. Measurements. Total length $ 28.0-30.5, $ 30-32; abd. $ 22.5-25.0, $ 24-25; h. w. $ 17-18, $ 18.3-20.0; h. f. $ $ 2.5-3.0; w. hd. $ $ 3.5-4.0; pt. $ .5-.6, $ .6-.7. Nymph. Unknown.

Habitat and range. Cold swamps and open bogs. Nfld. to Hudson Bay and the Mackenzie Dist, N.W.T., s. to N.B., Me., n. shore of the Gulf of St. Lawrence and Nominingue, Que., n. shore of Lake Superior, Ont., n. Man., and Nordegg, Alta. Distribution in Canada. Nfld.—Spruce Brook. N.B.—Northumberland Co. Que.—Thunder River; Godbout; La Ferme, Abitibi Co.; Nominingue, Labelle Co. Ont.—Muskoka, Cochrane, Thunder Bay and Kenora districts. Man.-The Pas; miles 256 and 332, Hudson Bay Ry. Sask.-"Saskatchewan" (Selys). A/to.-Nordegg. N.W.T.-Fort Smith; Great Slave Lake. The most northerly localities from which it has been taken are Cape Henrietta Maria,

PLATE 38 Caudal lamellae of Lestes nymphs: 1. L. eurinus; 2. L. congener; 3. L. vigilax; 4. L. dryas; 5. L. unguiculatus; 6. L. d. disjunctus; 7. L. d. australis; 8. L. rectangularis. All figs, approx. X 5.

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Hudson Bay, Ont. (55°N) and Gros Cap, Great Slave Lake, N.W.T. (61°N). Its northern limit, however, may well be as far north as that of C. resolutum, but our records are too incomplete for us even to hazard a guess. Its southern limit is, however, definitely farther north than that of any other North American species of Zygoptera. Field notes. This species is more restricted in its choice of habitat than C. resolutum, being more partial to areas of open bog or marsh. Its most typical haunt is probably the quaking bog that surrounds a sphagnum pond, but it occurs also in the boggy margins of shallow ponds, and we have several times found it in the open bog or marsh at the outlet of a lake. Near Lowbush, Lake Abitibi, we found C. interrogatum in some numbers flying low over the still water of one of the many drainage ditches dug into the peaty soil along each side of the railway right of way. This section of the railway runs through a black spruce swamp and the ditches were well supplied with water drained from the swamp. It was only in a very restricted spot that C. interrogatum was found, and this particular ditch was somewhat deeper and narrower than usual, and was grown over with more standing vegetation than most of them. Undoubtedly our dates fail to indicate the complete period of adult life, since most of the collecting was done in July. The dates range from June 3 (Favourable Lake, Ontario) to July 25 (Lake Abitibi). The entire period of flight will probably prove to be similar to that of C. resolutum. Pairing was noted on almost every day on which we have collected this species, namely from July 8 to 24. We have not observed it ovipositing. Coenagrion angulatum Walker. (PI. 4, fig. 10; pi. 19, fig. 3; pi. 26, fig. 3; pi. 29, fig. 8) Coenagrion angulatum Walker, Can. Ent., 44: 256,1912. Enallagma lunifera Muttk., Bull. Wis. Nat. Hist. Soc., 10: 164-170, 1913. A more robust insect than the other two species of Coenagrion; the male of a darker blue with the dark abdominal areas more extensive, the female easily distinguished by the larger pale areas on abd. seg. 8 and the trilobate hind margin of the pronotum. Male. Dorsum of head black, with front margin pale; postocular spots subtriangular, without a pale occipital line between them; postclypeus and base of labrum black, face otherwise pale greenish, labium pale straw yellowish; rear of head centrally black, with a broad pale margin bordering the eyes, becoming partly whitish pruinose. Prothorax black above, with narrow anterior and broad lateral margins blue. Dorsum of pterothorax black; antehumeral stripes blue, nearly straight, narrowing slightly behind or

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nearly parallel-sided, slightly expanded at the anterior ends, half or less than half as wide as the median black area, and slightly narrower than the humeral stripes; the latter crossing the upper third or less of the mesinfraepisternum, widening just behind it and tapering somewhat to the posterior end; sides of pterothorax blue, shading into green below, with two short black streaks arising from the black ante-alar ridge and extending forward along the first and second lateral sutures; venter pale. Coxae with small anterolateral basal black spots; femora with extensor and tibiae with flexor surfaces black; tarsi black. Abdomen blue, with the following parts black: a small basal spot and short lateral margins on seg. 1; a transverse obtusangulate spot on dorsum of 2, without lateral stripes; dorsa of 3-7, except a basal blue area on each, continuous with the pale ventrolateral margins, these basal blue areas diminishing in length caudad, that of 3 one-fourth, and of 4 one-fifth as long as its segment, on 7 a very narrow annulus; 8 and 9 blue; 10 black above, blue on the sides. Legs slightly longer than in either C. resolutum or interrogatum, the hind femora reaching the middle of seg. 2. Abdomen expanding beyond seg. 8, being wider at the intersegmental line between 9 and 10 than at any point farther forward, not narrowing appreciably on 10. Sup. apps. black, terminating behind in a pale rounded tubercle, produced below into a black wedge-like projection, which is partly concealed in profile view; inf. apps. bluntly rounded, bearing a short, upwardly directed spine from the outer rim near the base. Female, Stouter and often larger than the male, usually heterochromatic, yellow-green to pale brown, the black markings of head and thorax as in male. Abdomen with brassy black markings as follows: sec. 1 with a small anterodorsal spot; 2 with dorsal spot of usual form, extending the length of the segment, very narrow in front, expanding toward the middle, and widening again abruptly toward the end, where it is connected by a short neck with the apical annulus; dorsa of 3-10; except the following pale areas: wide basal and lateral areas on 8, intersegmental annuli following 7-9; successively narrower interrupted basal annuli on 3-6, and apical margin of 10; ventrolateral areas of segments wholly pale, i.e. without black streaks. Posterior margin of pronotum trilobate, the median lobe slightly projecting and truncate. Mesostigmal laminae triangular, posterior margin raised into a low ridge; median pit transverse, occupying the anterior part of a square space formed by the low anterior and lateral walls. Sternum of 8 truncate; ovipositor reaching end of abdomen. Postnodal cross-veins, f. w. $ 10-13, $ 10-14; h. w. i 9-12, $ 9-13. Measurements. Total length t 28-30, $ 29.0-33.5; abd. $ 21.5-23.5, $ 22,5-26.5; h. w. $ 16.0-17.5, 9 18-22; h. f. $ 3.2-4.0, $ 3.5-4.1; w. hd. 3 $ 4.0-4.5; pt. $ .5-.6, $ .7-,9. Nymph (pi. 6, fig. 9; pi. 40, fig. 8; pi. 43, fig. 3; pi. 44, fig. 9). Of average build, the general form being like that of Iscnnura verticalis or Enauagma ebrium. Antennae longer than the head; relative lengths of segs., 10:20:25:12:10:8:5; eyes not very prominent; posterolateral contours or head rounded, with only the general covering of setae, which tend to be slightly longer than elsewhere on the head; labial mask extending to base of mesosternum, greatest width of mentum four-fifths of its length, lateral margins slightly flaring distally, with 3 or sometimes 4 inconspicuous setae; mental setae 4 or 5, lateral setae 6; distal margin of lateral lobes with 5 angular denticles, decreasing laterad, the last bifid. Lateral margins of abd. segs. with a single series of usually 5-7 small setae, chiefly in the posterior half; hind margin of 10 with a rounded emargination, the marginal setae very small but increasing in length lateroventrad, becoming much longer at the lateroventral margin. Caudal lamellae about one-third longer than the inner wing-cases, broad lanceolate, somewhat abruptly expanding from the bases, rounded angulate at apices, widest just beyond or sometimes just before the nodus, where there is a definite constriction; nodal line transverse and usually somewhat beyond the middle of the lamella, often at about three-fifths of the

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length. Antenodal setae: med. lam., d. 22-30, v. 14-23; lat. lam., d. 16-25, v. 25-30. The antenodal serrations bearing these setae become rapidly shortened near the nodus, but the setae they bear are longer and overlap one another as they approach the nodus. The postnodal margins are broadly arcuate and are thickened and pigmented for a short distance beyond the nodus. Lateral apps. in profile bluntly subangulate above, in ventral view somewhat convex laterally and slightly concave mesally. Ovipositor projecting barely beyond the sternum of seg. 10. General colour of exuvia brown, darkened at the bases of the numerous short setae, which are distributed over most of the integument. Dorsum of head with a median and two pairs of lateral clear areas, dark stains around bases of antennae and on first segment, especially at distal end. Thorax almost uniformly brown, except at the coxopleural articulations, at which there is a small dark spot. Legs without dark annuli. Wing-cases with veins somewhat darkened. Abdomen with dark spots at the tergal articulations and a pale mid-dorsal line. Caudal lamellae with no suggestion of bands or spots, uniformly pale brown, somewhat darkened along the tracheae. Total length 17-19; wing-cases 4.5; h. f. 3.5-4.0; caud. lam. 5-6. Described from eight final exuviae, all from specimens reared by Dr. J. G. Rempel, Department of Zoology, University of Saskatchewan. The nymph is extremely like that of the Eurasian C. lunulatum Charp. (v. Ander, 1926).

Habitat and range. Prairie sloughs and slow streams. Extreme western Ont. to the foothills of the Rocky Mts., Alberta, s. to Minn, and la., and n. to Great Slave Lake, N.W.T., and n.e. British Columbia. Distribution in Canada. Ont.—Minaki and Sioux Lookout, Kenora Dist. Man.—Treesbank; Onah; Portage la Prairie; Virden; Winnipeg; Victoria Beach and Winnipeg Beach, Lake Winnipeg; Dauphin; The Pas. Sask.— Carlyle; Burrows; Indian Head; Katepwa Lake; Balgonie; Regina; Pasqua; Caron; between Herbert and Waldeck; Swift Current; Hamton; Plunkett; Prince Albert; Waskesiu Lake; Lashburn. Alberta— Claresholm (F. A. Urquhart) Strathcona; Red Deer; vicinity of Calgary; Nordegg. N.W.T. Mackenzie Dist.-Fort Smith; Fort Resolution and Resdelta, Great Slave Lake. B.C.-Dawson Creek (56°N). Field notes. Although the east-west distribution of angulatum is much less than those of the other two coenagrions, it occurs in larger numbers than either of them. In fact, it is one of the most abundant of Zygoptera on the Canadian prairies. Stagnant prairie sloughs, permanent or semipermanent, are perhaps its most typical habitat, but it occurs on slow streams as well as ponds or sloughs. We have taken it, for example, in the beds of low emergent vegetation along the banks of the Red River at Kildonan Park, Winnipeg, and we have a considerable number of specimens from Wascana Creek, Regina, Saskatchewan. We also found it near Virden, Manitoba, on a pond-like expanse of water formed by damming a small stream. As far as our limited observations indicate, C. angulatum would appear to reach its greatest numbers farther north than the localities just mentioned. Seldom have we seen any species of Zygoptera equal the numbers of C. angulatum at The Pas, Manitoba, when we visited this town in early July, 1931. The Pas lies well beyond the prairie country, although there are large areas of marsh that have a prairie-like appearance, and in these marshes are numerous shallow lakes and ponds. Many of these lakes are

PLATE 39

g

Caudal lamellae of Argia nymphs: 1. A. moesta ( X 10); 2. A. apicalis ( X 10); 3. A. tibialis ( X 11); 4. A. sedula ( x 9); 5. A. violacea ( x 10); 6. A. emma ( X 10).

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surrounded by a tall fringe of reed grass (Phragmites communis Trin.), and the mud around the margins is deep and treacherous. The large numbers of C. angulatum seen at The Pas must have emerged from these ponds and lakes, although they were, at the time of our visit, well scattered over the marsh and hence had probably not reached the stage of pairing and ovipositing. The flight period of this species begins early, before the end of May in the south. A number of specimens from Regina, taken on May 26, 1936, are all teneral, but others, taken there May 31, 1936, are full-coloured and mature. A few tenerals were taken at Prince Albert, Saskatchewan, on June 16. Specimens reared by Professor J. G. Rempel from full-grown nymphs at Saskatoon, emerged from June 14 to 18, 1950. It appears to reach its peak of numbers in June in the southern part of its range. Even at Great Slave Lake, specimens taken from June 6 to 15, 1946, and on June 19, 1947, were all mature. On the other hand, the large number of angulatum seen at The Pas on July 4, 1931, flying over land, suggested a more recent emergence. This was perhaps due to a second peak of numbers, a common occurrence among various Coenagriidae. Pairing has been observed as early as June 9 at Regina.

Genus Enallagma Selys Bull. Acad. Belg., (2), 41: 496, 1876. Cowley (1934) has shown that this genus should be accredited to Selys, not to Charpentier (Lib. Eur., p. 21, 1840) as was formerly done. Enallagma is a genus of about 70 species, represented in all the continents except Australia, but much more abundant in North America than elsewhere. Only one species is known from Europe, this being the type species E. cyathigerum Charp., which is circumpolar. About two-thirds of the known species are from the Americas, most of them from North America, and of these, 15 have been recorded from our territory. Kennedy (1920) has subdivided the genus on the basis of penis structure, having erected six new genera, but these have not been generally recognized by other odonatists. Nevertheless a study of the larval characters of relatively few species, together with those of the adults, has confirmed our impression that Enallagma is a composite group that will eventually be subdivided into several genera. Until the nymphs of a great many more species are known, however, it would be unwise to attempt a general revision of the genus. To Enallagma belong nearly all of the small, bright blue damselflies

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that abound in the grass and sedges along the margins of ponds and quiet streams in early summer and are collectively among the most familiar insects of the entire Order Odonata. These strikingly blue damselflies are the males. The females are generally green or yellow-green or, if blue, are less conspicuous than the males because most of the abdomen is dorsally black, The genus, as defined at present, includes also species of other colour-patterns, the light areas being yellow or orange in place of blue, or a mixture of various colours, or, if blue is the only pale colour, it may be so reduced by the increase in the black areas as to give the insect a very different appearance. The head in all our forms is mostly black above; and the pale postocular spots are large or moderate in size and often connected by a pale occipital line, The pterothorax is always marked with a median dark stripe, pale antehumeral, and dark humeral stripes. The sides and venter of the pterothorax are pale, with the dark markings reduced to a minimum. The abdominal pattern is variable and will be treated under "Groups." In the wings of Enallagma the basal or petiolate part does not extend to the level of Ac; the second antenodals are not distinctly before the arculus; M2 usually arises between the fourth and fifth postnodal crossveins of the fore wings and between the third and fourth of the hind wings. The pterostigmata of fore and hind wings arc similar. The tenth abdominal segment of the male is not, or little, elevated; the penis has a rounded apical margin and a pair of short recurved lateral angles or points and another pair at the base of the membranous apical section. The superior appendages are typically shorter than the inferior appendages, but very variable and often longer; the inferior appendages, viewed in profile, are triangular, with the apex usually hooked or curved upward. The eighth abdominal sternum of the female terminates in a strong spine. The females are not sharply dichromatic but usually range in colour from the homoeochromatic to the extreme heterochromatic, the usual colour being more or less intermediate and the black markings remaining constant in type. Pruinosity is slight, there being little or none in the males, but sometimes considerable in the females, which may become more or less dull and greyish, though the pattern is never obliterated as in old females of Ischnura. The nymphs of Enallagma vary so greatly that it is impossible to distinguish the genus from such nearly related genera as Coenagrion and Ischnura. In fact there are greater differences between the nymphs of different groups of Enallagma than between those of typical Enallagma and Coenagrion or Ischnura. The nymphs of comparatively few species are known, but the group characters appear to be sharper in the nymphs than in the adults, All our species have six-segmented antennae. We have made a tentative division of the species found in Canada into three main groups, of which Group T ic composed of the most typical and also the most primitive species. It is the most northerly in distribution. The nymphs are inseparable by good generic characters from Coenagrion and

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Ischnura. Groups 2 and 3 are derivative in their characteristics and the nymphs have diverged considerably from those of the primitive stock. Group I. Male adults blue and black, the blue generally predominating on the abdomen; antehumeral stripes generally broad, being usually about half as wide as the median stripe and often wider than the humeral stripe; sup. apps. of male with a pale tubercle on the mesal surface at the apex, which sometimes encroaches on the lateral surface, thus appearing in profile view (absent in clausum). Nymphs with head as in Coenagrion, the posterolateral outlines and the eyes broadly rounded, neither being very prominent (pi. 44, fig. 1). Antennal seg. 2 longer than 1, cylindrical; seg. 3 about twice as long as 1 (pi. 44, fig. 4, 5) Lateral carinae of most of the abd. segs. bearing a series of 9-12 short stiff setae. Caudal lamellae often broad at base and widest near the middle; pigmentation confined to the tracheae, or with 1-3 transverse or oblique bands, the proximal one at the nodal line; dorsal antenodal serrations of median caudal lamella rarely fewer than 20, usually 25 to 40 or more, bearing stout setae, which tend to increase in size distad toward the nodus, beyond which there are only fine soft hairs; ventral antenodal serrations of lateral lamellae similar to the dorsal series of the median lamella, but normally somewhat greater in number, being rarely fewer than 30, more often 30-50. The number of serrations or stiff setae in the ventral series of the median lamella is usually much smaller than those of the dorsal series and vice versa in the case of the lateral lamellae, and the setae they bear are smaller. When the series are nearly equal in length on the two margins of the same lamella the nodal line is transverse, and when one series is much shorter than the other the nodal line is oblique. There are no soft hairs among the stiff setae of the antenodal series. This is a northern group, to which most of the Canadian species belong, including all the species found west of Ontario. They all develop in more or less quiet waters. Group II. Postocular spots narrow and usually connected by a pale occipital bar; antehumeral stripes narrower than the numerals and much less than half as wide as the median stripe. Abdomen of male mostly black above, the black dorsal areas on segs. 1 and 2 percurrent; segs. 2-7 black, with the pale areas mostly reduced to basal annuli; 8 blue on the sides, 9 wholly blue, 10 black above; pale coloration otherwise variable. Sup. apps. of male bifid, the branches divergent as viewed from above. Nymphs with eyes prominent, subangular (pi. 44, fig. 2), the posterolateral contours produced into lobes; 2nd seg. of antennae no longer than 1st, often shorter, elliptical, seg. 3 less than twice as long as seg. 1 (fig. 6). Lateral carinae of abdomen with only a few stiff curved setae, limited to the posterolateral angles. Caudal lamellae darkly pigmented basally and apically, with a pale intervening area divided lengthwise by a dark axial stripe connecting the two dark areas; tracheae with groups of closely crowded branches, which are darkly pigmented and give the appearance of

PLATE 40 Caudal lamellae of nymphs of Amphiagrion, Nehalennia, Ischnura, Coenagrion, and Anomalagrion: 1. Amphiagrion saucium ( X 9); 2. Nehalennia Irene ( X 10); 3. N. gracilis ( x 10); 4. Ischnura cervula ( X 10); 5. /. damula ( x 9); 6. I. verticalis ( X 8); 7. /. posita ( X 9); 8. Coenagrion angulatum ( X 10); 9. Coenagrion resolutum ( X 10); 10. Anomalagrion hastatum ( X 9).

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spots. Dorsal margin of median lamella with soft hairs along its entire length, with or without stiff setae forming an antenodal series; lateral lamellae with a similar mixed series of setae on the ventral margin. The characters of the nymphs as given above are based on those of E. exsulans, antennatum, and traviatum, the last from Carman's description and figure. Judged by adult characters, many other species probably belong to this group, but the nymphs are for the most part unknown and no others are available for study. E. aspersum is the only other species found in Canada of this group. Our two common species are both mainly inhabitants of streams. Group HI. Slender species of a yellow and black colour-pattern, the yellow predominating and varying in depth in different species. Postocular spots in our two species moderate or narrow, connected by a well-marked occipital bar. Pronotum largely yellow; pterothorax with antehumeral stripes of variable size, wide in our two species. Abdomen mostly dark above, segs. 3-7 having yellow interrupted basal annuli. Sup. apps. of male as long as seg. 10, not bifid, somewhat triangular in profile view, tubercle elongated or absent; inf. apps. small, apices upturned. Nymph slender; head (pi. 44, fig. 3) shorter than in group 2, slightly more than twice as wide as long, the posterolateral margins broadly rounded; eyes prominent, subangular; antennae (fig. 7) with seg. 2 no longer than seg. 1, elliptical, seg. 3 less than twice as long as seg. 1; lateral carinae of abdomen very prominent at the hind margins of most of the segments, the prominent parts bearing 4-5 or 6-8 short curved setae in a crowded group. Caudal lamellae oblanceolate, transversely banded; median lamella with dorsal stout setae absent near the base, most of them, if present, crowded near the nodus. A southern group of many species, only two of which enter our territory, E. vesperum and signatum. They frequent lakes and slow streams and are the only enallagmas in our territory that fly after sundown. Key to the Species of Enallagma Males 1. Black areas of abd. segs. 3 and 4 rarely more than two-thirds as long as the segment, measured along the mid-dorsal line, usually much less; pale colour of mature insect blue 2 Black areas of abd. segs. 3 and 4 more than four-fifths as long as the segment, measured along the mid-dorsal line; pale colours variable 10

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THE ODONATA OF CANADA AND ALASKA

2. Sup, apps. in profile riot bifurcate, at most with a shallow notch 3 Sup, apps, in profile deeply bifurcate, the two arms of nearly the same length ebrium 3. Sup. apps. shorter than inf. apps., not at all massive in appearance, pale tubercle when present not clearly seen in profile view 4 Sup. apps, as long as inf. apps. or longer, massive in appearance, the pale tubercle seen clearly in profile view 8 4. Sup. apps., viewed dorsally, not approximated at base nor alate, a pale tubercle appearing mesad and ventrad of the dark dorsal portion, or, if not distinct in this view, appearing in profile at the distal end 5 Sup. apps., viewed dorsally, approximated at base, alate, and without a pale tubercle clausum 5. Sup. apps., viewed in profile, show a more or less upturned or dorsally curved apex, which in dorsal view is seen to bear the pale tubercle at its extremity 6 Sup. apps., in profile, short and rounded, without an upturned extremity; viewed dorsally, the pale tubercle appears on the ventromesal margin boreale 6. Sup. apps. appearing in profile short and stumpy, with the apex very short and upturned, the pale tubercle not lacing directly posteriorly 7 Sup. apps. appearing in profile slender and gently curved upward but, viewed dorsally, they appear much wider and with the pale tubercles terminal hageni 7. Sup. apps., viewed obliquely from above, show a smooth dorsomesal surface without a ridge or tooth-like prominence; pale tubercle directed mesocaudad (pi. 43, fig. 15) cyathigerum Sup. apps., viewed obliquely from above, show a prominent ridge, separated from the pale tubercle by a concavity, the tubercle directed dorsad and somewhat mesocaudad (pi. 43, fig. 14) vernale 8. Sup. apps. longer than inf. apps., the pale tubercle appearing in profile to fit closely in a cavity at the distal end; no distinct notch between tubercle and the part of the appendage above it 9 Sup. apps. about as long as inf. apps., the pale tubercle forming a posterior rounded prominence with a distinct notch between it and the projecting part above it minusculum 9. Black areas of segs. 3 and 4 more than half as long as their respective segments; sup. apps., in profile, scarcely more prominent at the posterodorsal end than at the posteroventral end carunculatum Black areas of segs. 3 and 4 much less than half as long as their respective segments; sup. apps., in profile, much more prominent at the posterodorsal end than at the posteroventral end civile

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10. Sup. apps. longer than inf. apps..., never tapering to slender upturned apices 11 Sup. apps. slightly shorter than inf. apps., tapering to slender upturned apices geminatum 11. Sup. apps. shorter than seg. 10, bifid in profile Sup. apps. longer than seg. 10, subtriangular in profile, not bifid

12 14

12. Sup. apps. with dorsal branch longer than ventral, the two branches appearing widely divergent both in profile and dorsal view 13 Sup. apps. with dorsal branch shorter than ventral, the two branches not appearing divergent in dorsal view; body blue, extensively marked with black; seg. 8 with blue and black areas obliquely divided exsulans 13. Sup. apps., viewed in profile, with the two branches nearly equal; colour greenish yellow, deepening to orange on ventral surface of eyes and antennae; antehumeral stripe linear, much narrower than humeral stripe; seg. 8 black above, 9 blue antennatum Sup. apps., viewed in profile, with the branches very unequal, the dorsal branch much the longer; colour blue; antehumeral stripes as wide as humeral stripes or wider; segs. 8 and 9 both blue. aspersum 14. Greatest height of sup. apps. more than half their length; when seen from above, an elongate tubercle appears on the mesal side; humeral stripe much narrower than antehumeral, generally reduced to a hairline; seg. 9 blue vesperum Greatest height of sup. apps. less than half their length; when seen from above, no tubercle appears on the mesal side; humeral stripe as wide as antehumeral or wider; abd. seg. 9 yellow signatum Females 1. Mesostigmal laminae more than half as broad (anteroposterior dimension) as long, the hind margin ridged and posteriorly arcuate; abd. segs. 8-10 entirely black above. 2 Mesostigmal laminae at least twice as long as broad, the hind margin straight or nearly so; abd. segs. 8-10 usually partly pale 3 2. Posterolateral margins of mesostigmal laminae raised above the general surface of the dorsum, this feature seen in an oblique view from above (pi. 31, fig. 7) hageni Posterolateral margins of mesostigmal laminae not raised above the general surface of the dorsum (pi. 31, fig. 8) ebrium 3. Abd. seg. 8 partly pale Abd. seg. 8 dorsally wholly black

4 12

PLATE 41 i-H

^

s

Caudal lamellae of Enallagma nymphs: 1. E. clausum ( x 8); 2. E. carunculatum (X 7); 3. E. civile (X 8); 4. E. ebrium (x 8); 5. E. boreale (X 8); 6. E. cyathigerum (X 7); 7. E. vernale ( X 8); 8. E. geminatum ( X 8).

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4. Abd. segs. 3-6 black above, except for the small pale basal spots or divided annuli, the black areas abruptly rounded off in front and not constricted before the posterior expansion 5 Abd. segs. 3-6 with larger pale basal areas, the black stripes more or less acute in front and slightly constricted before the posterior expansion 6 5. Abd. seg. 7 entirely black, 8 with a pair of large blue spots geminatum Abd. seg. 7 blue, with an irregular median black stripe; seg. 8 with a pair of blue basal spots aspersum 6. Seg. 8 with the black, if present, chiefly on the posterior half or in the form of a posterior triangle with the apex forward, the pale area, which may be divided, larger than the pale area on seg. 7 or 6 7 Seg. 8 with a black dorsal stripe extending its entire length, the pale areas on the sides similar to those on 7 and not larger dorsally 10 7. Seg. 8 dorsally entirely pale or with only a trace of black 8 Seg. 8 pale at base, apically black, the pale area entire or divided partly or completely by a median extension, which may be either linear or acutangular 9 8. Mesostigmal laminae defined along their entire length by a posterior suture; divergent basal rami of median carina wholly within the frame clausum Mesostigmal laminae with a distinct posterior suture only on the lateral half: basal rami of median carina beginning to diverge behind the frame boreale 9. Mesostigmal laminae traversed by an oblique groove between frame and lateral extremity; posterior suture distinct only on the lateral half boreale Mesostigmal laminae nearly flat, not traversed by an oblique groove, posterior suture defined along its entire length cyaihigerum 10. Humeral stripe half as wide as antehumeral, mesostigmal laminae as wide in the lateral as in the mesal fourth; lateral carinae of frame unbroken, not convergent forward 11 Humeral stripe much less than half as wide as antehumeral, usually a mere line in the middle; mesostigmal laminae tapering laterad, much narrower in the lateral than in the mesal fourth; lateral carinae of frame broken and strongly convergent forward vernale 11. Black dorsal areas on abd. segs. 4-7 measuring about 80 or 90 per cent

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of the segment length, bluntly angular in front; mesostigmal laminae without an oblique ridge civile Black dorsal areas on abd. segs. 4-7 measuring about three-fourths to five-sixths of the segment length, acutangular in front; mesostigmal laminae traversed by an oblique ridge carunculaium 12. Abd. segs. 9 and 10 black above, mesostigmal laminae constricted in the middle, their outer ends strongly elevated; total length 25-26 mm., hind wing 14.3-15.4 minusculurn Abd. segs. 9 and 10 partly pale, mesostigmal laminae not constricted in the middle, their outer ends not strongly elevated; total length 29.0-36.5 mm., hind wing 17.0-21.5 13 13. Antehumeral stripes much narrower than humerals; hind margin of pronotum with a small median lobe marked with a yellow spot; mesostigmal laminae without prominent pale tubercles at the posterolateral angles of the frame 14 Antehumeral stripes as wide as the humerals or wider; mesostigmal laminae with a prominent pale tubercle at the posterolateral angle of the frame 15 14. Antehumeral stripes linear, less than half as wide as humerals; humeral stripes not longitudinally divided by a paler stripe; median carina clear yellow; mesostigmal laminae with a yellow slightly raised spot at the posterolateral angles of the frame antennatum Antehumeral stripes half as wide as humerals; humeral stripes usually divided by a brownish stripe, producing a double line; median carina dark; mesostigmal laminae without a yellow spot at the posterolateral angles of the frame exsulans 15. Humeral stripe wanting in the middle or at most (in eastern specimens) a somewhat ill-defined stripe not more than half as wide as the antehumeral stripe; mesostigmal laminae with lateral ends definite, rounded vesperum Humeral stripe about as wide as antehumeral, clearly defined; mesostigmal laminae with lateral ends not distinctly demarcated from the adjacent part of the dorsum signatum Nymphs of Enallagma and Coenagrion 1. Second seg. of antenna distinctly longer than 1st seg.; 3rd seg. at least twice as long as 1st (except in C. resolutum); caud. lam. usually without pigment except in tracheal walls, pigment elsewhere, if present, confined to 1-3 transverse stripes and rarely an ill-defined axial stripe; dorsal antenodal setae of med. lam. all stiff and forming a complete series, although sometimes proximally very minute 2

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Second seg. of antenna no longer than 1st seg.; 3rd seg. much less than twice as long as 1st seg.; caud. lain, with membrane extensively pigmented; dorsal antenodal setae of med. lam. partly or wholly reduced to slender hairs or confined to the vicinity of the nodus 12 2. Caud. lam. with patches of closely branched and deeply pigmented tracheae, the intervening areas with mostly unpigmented and much less branched tracheae, appearing pale 3 Caud. lam. without patches of closely branched and deeply pigmented tracheae, the branching uniform, the pigment general, but often interrupted by clear areas 4 3. Lateral apps. of male, in dorsal view, with an evenly curved margin and without a ridge, bluntly angular in profile (pi. 43, fig. 11); female apparently indistinguishable from the next species hageni Lateral apps. of male, in dorsal view, bluntly angular, the outer edge nearly straight and with an oblique ridge, seen as a line; in profile bluntly rounded (pi. 43, fig. 12) ebrium 4. Dorsal antenodal setae of med. lam. less than 20; caud. lam. 4 to 4.5 mm. long, the tracheal branches passing towards the margin at an average angle of more than 45 degrees geminatum Dorsal antenodal setae of med. lam. more than 20, nearly always exceeding 25; normal lamellae nearly always more than 4.5 mm. long 5 5. Nodal line oblique and indistinct, the dorsal antenodal series of setae of med. lam. being much longer than the ventral series and composed of usually twice as many setae, these features being reversed in lat. lam., the shorter series in each case composed of very small setae, widely and irregularly spaced 6 Nodal line transverse, suggesting a joint, with dorsal and ventral series of antenodal setae of about equal length and consisting of closeset setae, gradually increasing in size distad 8 6. Tracheae of caud. lam. with numerous branches, which tend to curve (pi. 41, fig. 2); dorsal nodus of med. lam. before the middle; lat. apps. of male about half as long as seg. 10, measured at the same level 7 Tracheae of caud. lam. larger, with fewer and straighter branches (pi. 41, fig. 1), dorsal nodus of med. lam. usually about the middle, though sometimes a little before; lat. apps. of male scarcely more than one-third as long as seg. 10 (pi. 43, fig. 7) clausum 7. Lateral carina of seg. 1 with a few spinose setae; dorsal nodus of med. lam. usually at about the proximal three-sevenths of the lamellar length; lat. apps. of male slightly longer than wide, their dorsal outline, viewed in profile, only gently convex (pi. 43, fig. 5) carunculatum

PLATE 42 Caudal lamellae of Enallagma nymphs: 1. E. exsulans; 2. E. antennatum; 3. E. vesperum\ 4. E. signatwn. All figs. X 10.

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Lateral carina of seg. 1 without spinose setae, dorsal nodus of med. lam. usually at about the proximal one-third of the lamellar length; lat. apps. of male about as high as long, their dorsal outline, viewed in profile, more strongly convex (pi. 43, fig. 6) civile 8. Seg. 2 of antenna nearly twice as long as seg. 1, segs. 2 and 3 of nearly equal length; caud. lam. with tracheal branches very long and tending to run longitudinally C. resolutum Seg. 2 of antenna less than twice as long as seg. 1, seg. 3 much longer than seg. 2; caud. lam. with tracheal branches of usual length and following an average course of an angle of about 45° with the axis (except in E. vernale) 9 9. Caud. lam. constricted at nodus or with a distinct notch on both dorsal and ventral margins; main tracheae scarcely branched except near margin of lamella, the main branches not overlapping one another C. angulatum Caud. lam. not constricted or, if notched, only on one side (dorsal on med. lam., ventral on lat. lam.); main tracheae extensively branched, often from near the base, or long and overlapping one another frequently 10 10. Antenodal setae of caud. lam. and setae of lat. carinae of abdomen relatively coarse; lamellae rather long and narrow, three-fourths longer than hind wing-cases (3.5 to 4 times as long as wide), tracheal branches tending to be distally more or less longitudinal and winding, overlapping each other often vernale Antenodal setae of caud. lam. and setae of lat. carinae of abdomen of moderate size (pi. 41, fig. 5); caud. lam. one-fifth to one-half longer than hind wing-cases; tracheal branches not tending to follow a longitudinal course, much branched 11 11. Caud. lam. one-fourth to one-half longer than outer wing-cases; greatest width of med. lam. about one-fourth of its length, of lat. lam. one-fifth of its length boreale Caud. lam. one-fifth longer than outer wing-cases; greatest width of med. lam. about one-third of its length, of lat. lam. one-fourth to threeeighths of the lamellar length cyathigerum 12. Posterolateral margins of head produced into prominent lobes (pi. 44, fig. 2), the distance from base of antenna to hindmost part of margin about equal to half the width of the head across the compound eyes;

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THE ODONATA OF CANADA AND ALASKA

lat. carinae of abdomen prominent but not projecting abruptly from end of segment, and bearing many slender hairs but few stiff setae; caud. lam. with patches of closely branched and deeply pigmented tracheae 13 Posterolateral margins of head rounded but not prominent (pi. 44, fig. 3), the distance from base of antenna to hindmost part of margin distinctly less than half of the width of the head across the compound eyes; lat. carinae of abdomen projecting abruptly from posterior part of segment but riot prominent in front, with a group of stiff curved setae on the prominence, but otherwise nearly bare; caud. lam. without patches of closely branched and deeply pigrnented tracheae 14 13. Caud. lam. oblanceolate, their greatest width, about the distal fourth, a fifth or a fourth of the length; the more setose margins notched at the nodus exsulans Caud. lam. narrowly lanceolate, scarcely widening beyond the middle, their greatest width one-sixth to one-eighth of the length, their margins without a notch and with no definite nodus antennatum 14. Dorsal margin of med. lam. without a group of stiff setae just proximal to the first dark cross-band and without a definite nodus; proximal cross-band much darker than the more distal ones; venter of abdomen with a segmental series of median black spots, not forming a line; posterior marginal setae of abdominal terga very coarse vesperum Dorsal margin of med. lam. with a group of stout setae just before the nodus or the first dark cross-band, the nodus marked by a distinct notch; cross-bands all equally dark; venter of abdomen with a dark median line; abdominal terga with a posterior marginal row of minute tubercles in place of stiff setae, except on last two segments signatum Enallagma caruneulatum Morse. (PL 17, fig. 1; pi. 24, fig. 1; pi. 28, fig. 1) Enallagma caruneulatum Morse, Psyche, 7: 208,1895. A rather large species, being similar in size to boreale and cyathigerum but a little more slender and easily distinguished in both sexes by the pattern of the abdomen. Male. Blue, with black markings of abdomen more extensive than in the other species of Group I.* Head black above, with a narrow to fairly wide blue front margin; postocular spots usually of moderate si/e, often isolated and rounded, in other specimens almost contiguous with the eyes and nearly confluent with one another by a well-marked transverse occipital bar; face pale up to bases of antennae, except the upper surface of the postclypeus; mouth-parts and rear of head pale greenish or yellowish. Pronotum black, with front and hind lobes narrowly edged with blue; middle lobe pale on the sides and with dorsolateral spots sometimes very small, but generally about as in boreale, cyaililgerum, etc. Pterothorax with pale markings blue above, venter greenish *Except E. geminatum.

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to yellow; antehumeral stripes straight, subequal, the middle width usually about equal to that of the median black stripe or a little wider; humeral stripe usually about half as wide in the middle as the antehumeral, but variable, being sometimes as wide or even a little wider, tapering gradually caudad; sides of pterothorax almost without markings. Legs yellowish to greenish, coxae and trochanters wholly pale, femora with the anterodorsal surface black, except the base which is pale with a small black dot, tibiae pale with a longitudinal black streak on the anterior surface, tarsi pale. Pt. brown, with a pale peripheral line. Abdomen blue; seg. 1 with basal dorsal black spot; 2 with dorsal spot on posterior half, constricted just before junction with apical transverse bar; black areas on 3-7 in the following proportions of the seg. length along the median line: 3 slightly more than half; 4 and 5 three-fifths to two-thirds; 6 two-thirds to threefourths; 7 all except a narrow basal blue half-ring, which is usually divided mid-dorsally into two spots; 8 and 9 bine above; 10 black on the dorsal half, pale yellow beneath; inf. apps. also pale yellow. Sup. apps. distinctly longer than inf. apps. and about two-thirds as long as seg. 10, in profile ovate, with dorsal and ventral margins about equal in length, the black proximal part excavated to receive the pale rounded tubercle; viewed from above, the black dorsal hooks are strongly divergent, rounded apically, with a prominent mesodistal tooth, the pale tubercle extending beyond the hooks and now seen to occupy the inner as well as the outer surface of the appendage. Inf. apps. in profile broadly triangular, the depth being greater than the length, the dorsal margin concave; viewed from above, their mesodistal angles are nearly rectangular, their mesal surfaces subparallel. Female. Blue to yellowish green, differing from boreale in colour pattern as follows: black abdominal stripes somewhat wider, more parallel-sided and less expanded toward their posterior ends, without a definite notch before the expansion; black area on 8 never absent, nor greatly reduced as in boreale, being more abruptly narrowed at base, so that the blue basal part of the segment is not larger than the blue area of 7, as it is in borcale and cyathigerum, in fact it is typically smaller on 8. In boreale the blue areas of 8 are frequently confluent, occupying the basal half or more of the dorsum; in carunculatum this is never the case. Mesostigmal laminae about twice as long as wide, almost parallel-sided, except at the lateral ends, where they are rather abruptly rounded and very prominent. The most distinctive features are a longitudinal concavity and an oblique ridge, crossing the lamina from the convex anterolateral margin to the posterolateral angle of the frame. The laminae are demarcated posteriorly by a slight groove but the suture is distinct only towards the lateral end; frame unbroken, the basal rami of the median carina diverging at first slightly, then abruptly, to form its posterior wall. Postnodal cross-veins, f. w. $ 10-12, 9 10-13; h. w. $ 9-11, 9 8-10. Measurements. Total length $ 30.0-35.5, 9 32.5-36.5; abd. $ 23.0-28.5, 9 25.528.0; h. w. $ 17.0-21.0, 9 19.5-21.0; h. f. $ 3.0-3.6, 9 3.0-3.8; w. hd. $ 9 4.0-4.5; pt. $ 9 .6-.8. Nymph (pi. 41, fig. 2; pi. 43, figs. 5, 8; pi. 44, figs. 4, 12). A large green or brownish nymph with no definite pattern and with usually plain caudal lamellae. Eyes moderate; antennae about a third longer than median length of head, relative lengths of segs., 12:18:27-32:18:10:5; posterolateral contours of head moderately convex, with a patch of short setae as in other related species; labial mask reaching base of mesosternum, greatest width of mentum about four-fifths of its length, margins flaring in distal twofifths; mental setae 3-4; marginal setae 7-9, small; lateral setae 6; distal margin of lateral lobes with 6 denticles, the last three so small that they appear as one unless very highly magnified. Ovipositor extending a little beyond the middle of seg. 10. Caudal lamellae plain or, rarely, with an ill-defined median stripe, chiefly distal to the nodal line, which may be more deeply marked by an oblique streak; broad lanceolate, rounded at bases; median lamella widest a little before the middle, the greatest width being about one-third of the length, lateral lamellae about one-fourth as wide as long, apices

PLATE 43

I

6

FIGS. 1-13. Details of nymphal structures: 1. Argia apicalis, hind margin of seg. 10 from below, showing basal parts of median and left lateral caudal lamellae; 2. A. tibialis, same view as fig. 1; 3. Coenagrion angulatum, end of seg. 10 from above, showing form of lateral appendages; 4. Coenagrion resolutum, same view as fig. 3, showing form of lateral appendages; 5, Enallagma carunculatum, $, lateral view of seg. 10, showing bases of caudal lamellae and form of lateral appendages; 6. E. civile, $, same view as fig. 5, showing form of lateral appendages; 7. E. clausum, $, same view as fig. 5, showing form of lateral appendages; 8. E. carunculatum, $, lateral appendages from above; 9. E. civile, $, lateral appendages from above; 10. E. clausum, $, lateral appendages from above; 11. E. hageni, $, lateral appendages, d—dorsal view, 1—lateral view; 12. E. ebrium, $, lateral appendages, d—dorsal view, 1—lateral view; 13. Chromagrion conditum, caudal lamellae. X 8.5. FIG. 14. Enallagma vernale, anal appendages of adult S, left dorsolateral view. FIG. 15. E. cyathigerum, anal appendages of adult $, left dorsolateral view.

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bluntly pointed with rounded margins. Dorsal nodus of median lamella and ventral nodus of lateral lamellae a little before the middle, or in the case of the lateral lamellae, sometimes just at the middle; the opposite nodus in each case definitely shorter, at about the proximal third of the lamellar length. The nodal lines are thus somewhat oblique. Antenodal setae: med. lam., d. 24-30, v. 10-17; Lit. lam., d. 11-22, v. 33-35. The longer series in each case is composed of small well-spaced setae proximally, becoming closer and much larger toward the nodus; the shorter series are likewise similar in that all the setae are small and somewhat widely spaced, being easily overlooked. Total length 19-23; h. w. 4-5; h. f. 3-5; caud. lam. 4.5-6.5. Described from numerous exuviae from Lake Simcoe, Ont, and nymphs from Saskatchewan lakes.

Habitat and range. Lakes and rivers, occasionally ponds; the nymphs often emerging from deeper water than is inhabited by other species of Enallagma; sometimes in saline or brackish water. N.S. to Sask., B.C., s. to N.J., Pa., O., Ind, 111, Mo, Okl, Ut, Nev, Calif, and Baja Calif, Mex. Distribution in Canada. N.S.— Annapolis and Halifax counties. N.B.— Bocabec Lake, St. Andrew's. Que.—St. John's; Vaudreuil; Hull; Ironside; Wakefield; Nominingue, Labelle Co. Ont—General in s. Ont; Essex, Kent, Lambton, Huron, Norfolk, Haldimand, Welland, Wentworth, Peel, York, Ontario, Bruce, Simcoe, Peterborough, Hastings, and Carleton counties; Muskoka, Parry Sound, s. Nipissing and s. Kenora districts. Sask.—Echo Lake, Last Mountain Lake (both saline lakes). B.C.—Vancouver Is. n. to Campbell R, Vancouver e. through the Cascades, Okanagan, and Kootenay valleys and n. to Canim Lake, Bridge Lake, with a record from Burns Lake in the Central Hinterland at about 54°15/N. Field notes. While this is a transcontinental species, its distributional range, so far as known, is not continuous in Canada, being broken by the Rocky Mountain range and in Manitoba and Alberta. The breaks in the Prairie Provinces are probably only apparent and due to insufficient collecting, although the occurrence of E. carunculatum in these provinces may be

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THE ODONATA OF CANADA AM) ALASKA

very local and confined lo the south. Jt will quite certainly be found in eastern Manitoba. In the more southern parts of the Eastern Provinces carunculatum is the common lake Enallagma of tin; hitler half of summer. In the larger lakes, such as Lake Simeoe, it is found wherever there are beds of bulrushes (Scirpus spp., especially S. flitviatilia), particularly in sheltered bays but also in fairly exposed places, when; no other species of Zygoptera will venture. In such situations the nymphs may emerge from depths of several feet and transform on the rushes a foot or more above the water. Exuviae and newly transformed tenerals clinging to the rushes are a familiar sight. In genera] the favourite haunts of E. carunculatum are the beds of tall rushes, cat-tails, or other emergent plants that border lakes and rivers. It is, however, by no means confined to such situations. On the shore of Lake Ontario, near Belleville, we found a number of tenerals on June 20, which had emerged, not from the lake itself, but from a series of shallow ponds in limestone rock, which had become heated by the sun, some having dried up completely. Possibly metamorphosis had been hastened by the unusual heat, for the record is a very early one for Ontario. We have also found carunculatum at the Lake of the Mountain, Prince Edward Co., and at Kelly Lake, York Co., Ontario, both of which are small soft-bottomed lakes lacking an outlet and scarcely more than large ponds. At Penticton, B.C., on July 22, 1926, we found this species common along the banks of the Okanagan River, flying close to the water and apparently filling an ecological niche like that of JE. exsulans in the east. E. carunculatum is also one of the few dragonflies that can develop in brackish water (Osburn, 1906) and sometimes breeds in saline lakes. Its nymph was among those collected from such lakes in southern Saskatchewan, associated with E. clausum, but only the adults were recognized at the time these species were recorded (Walker, 1940). These same two species were associated in Pyramid Lake, a saline lake in Nevada (Kennedy, 1917). Their nymphs are strangely alike for species not very closely related as judged by the adults. The young adults wander, as usual, far afield, and are often found in pastures or other open country and on the borders of woods. Tenerals will make their way to clearings through woods bordering a lake. At Lake Simcoe they may be found anywhere along the shore, independently of its character. Wherever there are Scirpus beds off shore, carunculatum may be seen resting on moored boats, rafts, or wharves. This is a relatively late species but has a long adult season. Our records in Ontario range from June 19 to September 20, but July and the first half of August cover the period of maximum abundance. Along Lakes Erie and Ontario, and in the Gatineau Valley, Quebec, we have many records from the latter half of June. At Franklin Bay, Parry Sound District, we found the earliest emergence in 1946 on July 3. At Lake Simcoe we found many tenerals, mostly females, in a field near Gilford, on July 12, yet we have seen adults in numbers on this lake as early as July 10. In fact they continue

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to emerge from time to time until about the first week in August, if not later. At Three Rivers, Quebec, we found many just emerged, with one mature male, on July 27; and at DeGrassi Point, Lake Simcoe, as late as August 7, we found a number of tenerals, although the majority were mature. By the first of September their numbers are much reduced, but we have seen them as late as September 20 (near Toronto). The flight period in British Columbia (Whitehouse, 1941) is even longer than in Ontario, being June 4 to September 29. In this province Whitehouse notes emergence at Thetis Lake, Vancouver Island, on June 22 and at Florence Lake, also on Vancouver Island, on July 5. Pairs flying per collum or in copula have been noted in Ontario only in the latter half of July and in August, namely from July 22 (Minaki) until August 23 (Lake Simcoe). Oviposition has been observed at Kelly Lake on July 30 and as late as August 20 at Southampton. We have seen them on Cook's Bay, Lake Simcoe, ovipositing in pairs on bulrushes (Scirpus fluviatilis) about a foot above the water. Enallagma civile (Hagen). (PI. 17, fig. 2; pi. 24, fig. 2; pi. 28, fig. 2) Agrion civile Hagen, Syn. Neur. N. Amer., p. 88,1861. Enallagma civile Selys, Bull. Acad. Belg., (2), 41: 514,1876. Similar in size and form to E. carunculatum, but with black of male much less extensive, resembling that of boreale, hageni, etc.; the females resembling carunculatum very closely, but differing slightly in the abdominal pattern. Male. Long and slender, as compared with other enallagmas that are predominantly blue. Head as in carunculatum, the face blue or bluish green, postocular spots small and rounded to fairly large, and mesally angular, sometimes nearly connected by the pale occipital bar; rear of head light greenish to buff. Pronotum as usual; pale area of sides large; dorsolateral spots small and narrow or absent, pale margins of front and hind lobes very narrow. Pterothorax blue above, grading below into a paler and more greenish colour; antehumeral stripes straight, subequal, generally more than half as wide in the middle as the median stripe, but varying from half to three-fourths of this width, usually about twice as wide as the humeral stripe; sides as in carunculatum. Coxae and trochanters pale; femora black with flexor surfaces pale; tibiae pale or brownish, with a black stripe on the anterior surface; tarsi brown. Legs in mature specimens heavily whitish pruinose towards the bases. Abdomen blue, with the general arrangement of black spots as follows: seg. 1 with basal dorsal spot; 2 with dorsal spot on posterior half; black areas on segs. 3-7 in the following proportions of the segment length along the middle line, 3, 4, and usually 5 one-fifth to one-fourth, that on 5 often a little longer than the others, occasionally reaching half of the segment length, that of 6 commonly one-half to three-fourths and that of 7 covering most of the dorsum, except a narrow basal annulus; 8 and 9 blue; dorsum of 10 and the sup. apps. (except the tubercle) black; inf. apps. pale, black-tipped. Sup. apps. similar to those of carunculatum but, viewed in profile, the dorsal surface is longer than the ventral, and somewhat elevated, the distal depth is about equal to the length and the tubercle is larger and more completely concealed by the overhanging dorsal part of the appendage.

PLATE 44 Details of nymphal structure FIGS. 1-3. Dorsal views of the three types of head in Enallagma: 1. E. boreale; 2. E. exsulans; 3. E. signatum. FIGS. 4-11. Antennae of various Zygoptera, showing form and relative lengths of segments: 4. Enallagma carunculatum; 5. E. clausum; 6. E. exsulans; 7. E. signatum; 8. Coenagrion resolutum; 9. C. angulatum; 10. Argia emma; 11. Lestes d. disjunctus. FIGS. 12-19. Lateral margins of seg. 7 in Enallagma: 12. E. carunculatum; 13. E. civile; 14. E. boreale; 15. E. vernale; 16. E. hageni; 17. E. exsulans; 18. E. antennatum; 19. E. signatum.

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Female. Very similar to carunculatum, somewhat more slender, usually greenish; head and thorax marked as in male. Markings of abdomen possibly not always distinguishable from those of carunculatum, but typically the anterior ends of the black dorsal spots on segs. 3-7 are more bluntly angular or rounded and approximate more closely the bases of the segments. The dorsa of segs. 1 and 2, and of 8-10 are almost completely black. The more reliable differences between the females of these two species are found in the mesostigmal laminae. In both species the laminae are subparallel-sicled with the anterior margins slightly concave in the middle but broadly rounded and prominent laterally, and the laminae, laterad of the frame, are decidedly concave. E. civile, however, lacks the oblique ridge, which in carunculatum extends from the posterolateral angle of the frame to the anterolateral margin, and in E. civile the laminae are more distinctly delimited by the posterior suture. Postnodal cross-veins, f. w. $ 10-12, $ 10-11; h. w. $ $ 9-10. Measurements. Total length $ 31.5-39.0, $ 31-34; abd. $ 24-30, $ 24-27; h. w. 3 18.0-20.5, $ 19.0-21.5; h. f. $ $ 3.0-3.7; w. hd. $ 3.6-4.5, $ 3.8-4.0; pt. $ $ .6-.8. Nymph (pi. 41, fig. 3; pi. 43, figs. 6, 9; pi. 44, fig. 13). Head as in carunculatum or other species of Group I; antennae barely longer than head, measured along median line, relative lengths of segs,, 12:17:32:16:10:8; labial mask reaching base of mesosternum, greatest width of mentum three-fourths of length; mental setae 3, with sometimes a small fourth; marginal setae 6-8; lateral setae 6; distal margin of lateral lobes as in carunculatum. Abd. segs. with well-developed but not strongly projecting lateral carinae; that of seg. 1 without setae; those of middle segments with a long series of setae on the posterior three-fourths or thereabouts, that of 7 with setae along almost the entire length. Abd. terga with short setae, rather sparsely and irregularly distributed. Lat. apps. of male (pi. 43) large, strongly convex above, as viewed in profile; seen from above the sides appear convex, the mesal contour nearly straight. Ovipositor reaching about the middle of seg. 10. Caudal lamellae plain, nearly one-half longer than the outer wing-cases, broadly lanceolate, rounded at base, widest a little behind the middle, tapering rather abruptly, but the immediate apices somewhat acute; greatest width of lateral lamella somewhat more than one-fourth of the lamellar length; dorsal nodus of median lamella well before the middle, sometimes at the proximal third; ventral nodus of lateral lamella a little farther distad, generally but not always before the middle; setae on these margins well developed, increasing in size distad; nodus on the other margins very short, with few and small setae at wider intervals. Antenodal setae: med. lam., d. 30-35, v. 6-12; lat. lam., d. 10-16, v. 31-47. Very similar to E. carunculatum; green or buff; antennae with segs. 1 and 2 and the base of 3 dark brown, the rest pale; femora with inconspicuous ante-apical dusky annuli; abdomen with a median series of pale spear-shaped spots, pointed behind, the last one on seg. 9 broadest, elliptical, the entire series enclosed in a dark brown stripe; a submarginal streak of brown on each side, deepened at the tergal articulations. Caudal

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lamellae; with the tracheae deeply pigmented, except at the basis, where they join the axis. Total length 22; h. w. 4.0-4.4; h. f. 3,3-3.5; caud. lam. 5,3-6.0. Described from nymphs and exuviae of reared material from Urbaria, 111., and nymphs from Raleigh, N.C. (W. J. Gehweiler).

Variations. E. civile, being a species of very wide distribution, varies greatly in size and considerably in the extent of the dark markings. Canadian specimens are larger than those from Indiana and much larger than material from New Mexico and Arizona. The black spots of the male abdomen are fairly uniform in Canadian specimens but, in occasional individuals, they are much larger than usual. In one from Chatham, N.B., for example, the spots on segs. 4, 5, and 6 are two-fifths, three-fifths, and six-sevenths as long as their respective segments, and seg. 7 is entirely black. As a general rule, however, E. civile differs from the other species of Enallagma that are predominantly blue in having the spots on 3, 4, and 5 nearly alike in size, whereas in other species there is generally a marked increase in size on seg. 5. Habitat and range. Ponds, lakes, and slow streams. Fla. to Tex., Ariz., and Utah, s. to W. Indies, Mcx., Guatemala, and Colombia, and n. to N.S., N.B., Me., s. and w. Ont, Mich., Minn., Man., and Sask. Distributions in Canada. This species has apparently entered Canada from U.S. by two or three routes: (a) from the New England states to the Maritime Provinces, where it is by no means uncommon; (b) from the Lake Erie states into southern Ontario, where its distribution is limited to the counties along the north shore of Lake Eric and the western part of Lake Ontario; (c) from Minnesota into western Ontario, Manitoba, and Saskatchewan. N.S.—Annapolis, Queen's and Halifax counties, Cape Breton Is. N.B.-Scotch Lake, Bocabec Lake. Onf.-Kent, Elgin, Haldimand, Welland, and York counties; Kenora (Minaki) arid Rainy River (near Fort Frances) districts. Man.—Emerson, Winnipeg, Selkirk, Victoria Beach, Lepelletier. Sask.— Wascana Lake, Regina; Swift Current district. Field notes. The only locality where we have found E. civile in abundance is Victoria Beach on Lake Winnipeg. From June 27 to 30, 1931, it was the commonest damselfly in the district. It flew over the sandy beach and the neighbouring dunes in company with other species, particularly E. clausum. There was a fairly large lagoon or shallow pond, surrounded by open marsh, adjacent to the dunes where civile was also plentiful, and several other smaller ponds where it occurred in smaller numbers, and it seems probable that these ponds were the breeding places, although at the time of our visit the dragonflies were more abundant on the beach itself and over the dunes. We also found E. civile on the banks of the Red River, near Winnipeg, and at Minaki, Ontario, on the Winnipeg River, but it was much less abundant at either of these localities than at Victoria Beach. In southern Ontario it has been found only in the Lake Erie counties and on the shore of Lake Ontario at Toronto. We have found it most frequently

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along the lower reaehes of the Thames, near Chatham, where there are patches of Scirpus, no perceptible current, and a muddy bottom. East of Toronto E. civile is unknown in Ontario, nor has it been found in any part of Quebec. But in the Maritime Provinces it appears again as a common species. At Bocabec Lake, a small lake near St. Andrews and close to Passamaquoddy Bay, into which it debouches by a short outlet, we found civile at the upper end of the lake, where it is very shallow and marshy and supports a considerable belt of emergent plants, especially Equisetum ftuviatile. It was associated here with a number of other Odonata, including Enallagma hageni, E. minusculum, and E. carunculatum. On Cape Breton Island, N.S., we found civile at several stations where there appeared to be no bodies of fresh water except small marshy puddles and ditches, but these individuals may have wandered some distance. E. civile is known to breed to some extent in brackish water (Osburn, 1906). Like its near ally E. carunculatum, E. civile has a long period of flight. Our Ontario records, which are meagre, range from June 6 (Point Pelee) to September 12 (Toronto), but these records certainly do not cover the entire adult season. Specimens found on September 12 were quite recently emerged. Montgomery (1942) gives the Indiana season as from the second week in May to the fourth week in October; Howe (1917) gives the season in New England as May to September 5; Whedon, for Minnesota, June 14 to October; while Carman (1917) states that at Urbana, Illinois, civile emerges "as early as June 13 and apparently continues to emerge throughout the season . . . Nymphs taken late in July emerged shortly after and another lot, collected at Lexington, Ky., emerged as late as August 18, 1915." Montgomery's (1942) graph for Indiana suggests that there may be two peaks of emergence, namely, in early July and in early September, We have no observations on the mating, nor the oviposition, of E. civile. Enallagma clausurn Morse. (PI. 17, fig. 3; pi. 24, fig. 3; pi. 28, fig. 3) Enallagma clausum Morse, Psyche, 7: 209,1895. Very similar to E. boreale and cyathigerum in general appearance. As found in the Prairie Provinces and Ontario, it averages slightly larger and more slender than these species, but specimens from British Columbia may be no larger than hageni and ebrium. The form of the anal appendages distinguishes the males readily, while the females may be known as a rule by the fact that seg. 8 is generally entirely blue, having at most only a trace of black. Identification of females, however, should always be checked by an examination of the mesostigmal laminae. Male. Blue, marked with black, the blue greatly predominating. Head marked as in civile, the postocular spots rather small, rounded, or subangular, not approaching the ocular margin as closely as in boreale and not connected by the occipital bar. Pronotum as in boreale, the pale margin of the anterior lobe not always present. Pterothorax blue; antehumeral stripes nearly straight with subparallel sides, each about as wide as the

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median stripe at half length; humeral stripes widest just behind the rnesinfraepisternum, narrowing in the middle- section often to a hairline and generally widening a little near the posterior end; sides of pterothontx otherwise unmarked with blaek or nearly so. Coxae pale; femora with extensor surfaces black, flexor surfaces more narrowly pale; tibiae pale, their anterior surfaces with a longitudinal black stripe; tarsi pale, with black intersegmental lines and black setae. Abdomen blue, with the following parts black: a median dorsal spot on anterior half of seg. 1; a transverse dorsal spot on the posterior half of 2, which may be confluent with the black apical semi-annulus; posterior dorsal spots on 3-6, expanding on the sides, each spot increasing in length caudad, from onefourth to one-third of the segment length on 3 (not including the angular dorsal prolongation) to half or more on 5 and three-fifths to two-thirds on 6; 7 except the anterior eighth or sixth; and the dorsum of 10, with the sup. apps.; 8 and 9 entirely blue or nearly so. Most of the dark spots are notched along their ventrolateral margins, in front of the apical annulus. Pt. smoky brown. Sup. apps. short, decurved, appearing in profile somewhat like those of E. cyathigerum and vernale, being upturned at the apices, out ventrally slightly concave; in dorsal view strikingly different from those of any of the species mentioned, being basally contiguous and having alate lateral expansions, without any trace of the pale tubercle seen in all the other comparable species. Inf. apps. scarcely longer than the sup. apps., appearing in profile as a somewhat abruptly upturned hook, being dorsally more concave and ventrally more convex than in boreale or cyathigerum. Female. Pale blue to yellowish green. Head marked as in male, the postocular spots sometimes smaller; thorax as in male, but dorsal carina with a pale line and humeral stripes tending to disappear in the middle section, with a distinct spot in front of the ante-alar ridge, which is pale; legs as in male but with black areas somewhat more reduced. Abdomen marked with black much as in boreale, but the black dorsal stripes do not extend quite so far ventrad on the sides and are somewhat more distinctly constricted behind the middle, the notches being thus more apparent in dorsal view; seg. 8 usually entirely blue, sometimes with a trace of a median dark line or a few minute black dots near the posterior end. Mesostigmal laminae delimited posteriorly by a complete suture, rather broad, with a somewhat sinuate front margin; frame laterally closed; basal rami of median carina abruptly divergent entirely within the frame and in front of the posterior suture; the median pit being thus crowded forward. Postnodal cross-veins, f. w. £ 9 11-13; h. w. $ 9 9-11. In a male from Lake Nipissing there are 15 postnodals on one fore wing, 12 on the other; and in a female from the same locality there are 17 on one forewing and 14 on the other. These counts appear to be too unusual to be included in the general range (based on counts of 20 wings of each sex). Measurements. Total length $ 31-37, 9 33-36; abd. $ 24.7-29.0, 9 26-29; h. w. $ 18-23, 9 20-23; h. f. $ 2.8-4.0, 9 3.8-4.0; w. hd. $ 3.8-5.0; 9 4.2-4.5; pt. $ .70-.75, 9 .75-.80. Nymph (pi. 41, fig. 1; pi. 43, figs. 7, 10; pi. 44, fig. 5). A large nymph, similar to that of E. carunculatuni in form and often in pattern. Antennae scarcely longer than head; relative lengths of segs., 13:18:27:14:10:12; labium extending to base of mesosternum; mentnm three-fourths as wide as long; mental setae 3-4; lateral setae 5-6; marginal setae 7-10, rather close-set; lateral lobes with distal margins bearing a stout end-hook separated by a deep incision from a series of five denticles, which are successively smaller laterad. Abdominal terga with minute setae somewhat irregularly distributed, particularly on the terminal segments; lateral carinae bearing regular series of slightly longer setae. Ovipositor reaching about the middle of seg. 10. Lat. apps. scarcely more than one-third as long as seg. 10, in dorsal view bluntly angular, outer margin convex, inner margin straight. Caudal lamellae nearly one-half longer than outer wing-cases, lanceolate, bluntly rounded at base on one side (ventral on median,

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dorsal on lateral lamellae), widest a little beyond mid-length, the greatest width being one-fourth to five-sixteenths of the length; apices bluntly aeutangulate or nearly reetangular, with rounded margins. Dorsal nodus of median lamella a little before the middle; ventral nodus very short, scarcely one-fifth of the lamellar length; dorsal nodus of lateral lamellae similar, very little longer; ventral nodus of lateral lamellae slightly beyond mid-length; nodal lines thus very oblique. Antenodal setae: med. lam., d. 30-41, v. 8-12; lat. lam., d. 12-19, v. 40-48; Setae of the longer series small at base, regularly increasing in length distad, the last ones often overlapping somewhat and, towards the end of the series, becoming elevated on prominent bases; setae of the shorter series very minute and far apart. Tracheal branches of lamellae rather regular, most of the main branches following a course at an angle of about 45° to the axis. Head and thorax of nymphs preserved in alcohol light brown with few definite markings; a pair of dark dots between the compound eyes; pronotum outlined in darker brown, sometimes with a squarish spot in the middle, sutures of pterothorax a little darkened; legs plain, without the usual ante-apical femoral annuli. Abdomen with segmentally arranged brown dorsal spots, deepened on the anterior half of each segment, where they are squarish and divided by a pale median line of varying width, very narrow in front but widening on segs. 8 and 9. Caudal lamellae either with only the tracheal branches pigmented or with a more or less distinct dark median stripe, and sometimes also with an oblique nodal crescent and one or two distal expansions. Total length 21-24; h. w. 4.0-4.6; h. f. 3.0-3.6; caud. lam. 5.5-6.0. Described from exuviae of reared specimens from Redberry Lake, Sask., and nymphs from various Saskatchewan lakes (J. E. Moore and D. S. Rawson).

Habitat and range. Lakes, fresh to saline. Nev. and Ut. n. to Wash, and s. B.C.; w. Kans., s. Sask. n. to Lac La Ronge (55°N), and e. through Man., and locally in Ont. and Que. Distribution in Canada. B.C.—Penticton, Soyoos, and, in the Cariboo district, Jesmond, Quesnel. Sask.—Antelope Lake, Edwards Lake, Fishing Lake, Lake Lenore, Margo Lake, Big Manitou Lake, Namekus Lake, Redberry Lake, Stony Lake, Lake La Ronge. Man.—Onah; Husavick; Victoria Beach, Lake Winnipeg; Dauphin Lake. Ont.—Nipissing Dist., islands in Lake Nipissing. Que.—Lachine. Field notes. As indicated above, this species has a peculiar distribution, which is discontinuous in Canada and possibly so in the United States. It was first found at Franktown, Nevada, where it was associated with saline lakes or ponds, but it has long been known to develop also in freshwater lakes. Kennedy (1917) found E. clausum in abundance at Pyramid Lake, Nevada, and gives an interesting account of its habits there. This lake lies in an extremely arid region in the Nevada Basin, at an elevation of 3,880 ft. It is a saline lake, with a density of 1.0034, or about one-ninth that of sea water. E. clausum "bred in large numbers in the shallow edge of the lake. A species of Potamogeton grows sparingly along the shore of the lake and to this are attached masses of filamentous algae. These masses break loose and are washed along the beach in quantity. In this litter two species of Odonata breed freely, Enallagma clausum and Sympetrum corruptum. Through the wave action the beach at the edge of the water is built into a

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low dyke over which storms force high waves that make a series of algaefilled pools from which both species emerge freely. Probably these individuals are washed into these pools from the lake when the pools are formed. On fence posts 50 feet from shore I found exuviae of both species. "Enallagma clausum has habits of alighting on the beach and flying quickly over the surface of the ground which are much like those of an Argia. Because of their nervous alertness and this habit of hugging the ground they are very difficult to capture, though they occur in large numbers. Copulation is on the wing or when seated on the beach or on the masses of algae. Emergence is at all hours, as I saw fresh tenerals at 3 o'clock in the afternoon. The male holds the female during oviposition while she places the eggs on the masses of algae." In Canada E. clausum inhabits a few widely separated regions. In British Columbia it was first found at Penticton in the Okanagan Valley in late July 1926. It flew over grassy, weedy flats, near the outlet of Okanagan Lake, in company with E. borcale, cyathigerum, and carunculatum. There were several dried-up sloughs in this area in which were deposits of a white saline material. The specimens taken here were of small size, as were also those of the other species. More recently clausum has been recorded by Whitehouse (1941) as far north as Jesmond and Qucsnel in the Caribou district. Another population of clausum occurs in the Prairie Provinces, and this is doubtless the largest in Canada. Specimens were first received by us from Dauphin Lake, Manitoba, and later we found it in abundance at Victoria Beach, Lake Winnipeg, during the last four days of July 1931. It was associated with E. civile and both species flew over the beach or rested along the edges of the dunes. These Manitoba specimens were distinctly larger than those from Penticton, B.C. A single specimen taken at a sphagnumbordered lake at Onah, Manitoba, may have been a stray. In 1940 clausum was first reported from Saskatchewan (Walker, 1940). In connection with an ecological survey of the saline lakes of southern Saskatchewan by J. E. Moore, it was collected at a number of lakes, both nymphs and adults having been taken. The salinity of the lakes where adults of clausum were collected varied from .04 to 2 per cent and the pH from 8,3 to 9.4, but it has not been proven that the nymphs can live in water above a specific gravity of 1.0034 (see above). Recently two large females of this species were received, through Dr. D. S. Rawson of the University of Saskatchewan, from Lac Ronge, Saskatchewan, which is far north of the previously known range of E. clausum. East of Manitoba, E. clausum is extremely local, having been found only on Lake Nipissing, Ontario, and at Lachine, Quebec. At Lake Nipissing we found it only on some of the outer, more exposed islands, on July 11-20, 1929. It was first noticed because of its large size, which was fully equal to Manitoba specimens, and its habit of alighting on the rocks after the manner of an argia, as observed by Kennedy. On these islands E. clausum was associated with E. carunculatum, and the only situations near the islands

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that looked at all possible as nymphal habitats for clausum were the beds of Scirpus whieh grew here and there within 50 to 100 feet of the shore. E. carunculatum is known to develop in sueh beds, although such a habitat is admittedly very different from that of clausum described by Kennedy. Numerous nyrnphs from lledberry Lake, Saskatchewan, were reared by Dr. D. S. Rawson and Mr. J. E. Moore from June 27 to July 11, 1941. The flight period appears to be long and rather late, although one record from Namekus Lake is dated May 20. The single specimen from Lachine, Quebec, was taken on June 16, 1925, and is the next in order of time, while the numerous specimens that we took at Victoria Beach, Manitoba, are dated June 27-30, 1931. The bulk of the adult material that we have seen, including the specimens from Lake Nipissing, Ontario, and those from the lakes of southern Saskatchewan, was taken throughout July, chiefly in the first three weeks. Specimens from Big Manitou Lake, however, are dated August 16 and 17. Whitehouse gives July 2 to August 22 as the flight period in British Columbia. Enallagma boreale Selys. (PI. 4, fig. 6; pi. 11, fig. 2; pi. 17, fig. 4; pi. 24, fig. 4; pi. 28, fig. 4) Aenallagma boreale Selys, Ent. M. Mag., 11: 242,1875. Enallagma boreale Selys, Bull. Acad. Belg., (2), 41: 509,1876. Enallagma calverti Morse, Psyche, 7: 208,1895. A robust species, usually above the average size but very variable, predominantly blue in the male, blue to green in the female. Male. Dorsum of head black, with a narrow to fairly wide blue front margin, postocular spots of usually large size, nearly touching the ocular margins, mesally acutangulate with a narrow occipital line between them; postclypeus black, with blue margin; face, mouth-parts, and rear of head pale greenish blue, the concavity surrounding the neck black. Pronotum black, with front and hind lobes narrowly edged with blue, middle lobe pale on the sides, and with a pair of dorsal blue spots. Pterothorax blue or bluish green; antehumeral stripes straight, typically more than half as wide as the median black stripe, and wider than the black humeral stripe, except sometimes in the anterior third; humeral stripes narrowly triangular, crossing upper part of mesinfraepisternum, bent ventrad and expanding behind, the width here being usually twice the middle width; second lateral suture with a black spot in the pit and the suture itself sometimes marked with a black line. Coxae pale blue or greenish, marked in front with black basal spots; femora and tibiae mostly black, but with yellowish or greenish longitudinal stripes on the flexor side of the femora and the extensor side of the tibiae; tarsi mostly black. Abdomen blue, with the following parts black: on seg. 1 small posterolateral spots and the usual dorsal one; on 2 a dorsal transverse subcrescentic spot and an apical annulus; on 3 and 4 a dorsal spot on the apical fifth or fourth, confluent with the apical annulus and sometimes expanding along the ventrolateral margins; 5 similar or with black area increased to two-fifths or more of the length; the apical threefifths to three-fourths of 6, the black area drawn out in front to a point; 7 except a narrow basal annulus; and the dorsum of 10; 8 and 9 wholly blue. Sup. apps. black; inf. apps. pale except their upper margins. Pt. dark brown, with paler submarginal lines. Sup. apps. in profile blunt and rounded, with a slight posteroventral notch, somewhat contracted basally when fully extended; in dorsal view appearing rounded distally, with

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a pale tubercle on the nicsul margin near the apices; viewed obliquely from above, the pale tubercle appears to be ventromesal in position, with a short oblique black ridge overhanging it, Inf. apps. tapering from a stout base dorsoposteriorly to slender apices, which project a little beyond the sup, apps. and are turned somewhat mesad. Female. Pale areas light blue to yellowish green. Head and thorax typically marked as in male. Abd. seg. 1 with dorsal black spot on anterior half, narrow in front, wide and diamond-shaped behind the middle, and connected with the apical annulus; 3 with broad rnid-dorsal stripe, tapering in front to a point and narrowing slightly again just before the sudden expansion on the apical fourth, this expanded area sometimes connected by a slight constriction with the apical annulus and often extending to the ventrolateral margin; 4-7 similarly marked, but with the black areas more obtuse in front, or even truncate, and tending to invade the sides more extensively, the blue basal areas frequently interrupted by a narrow black median line; 8 with the basal blue area enlarged to about half or more than half the length of the segment and generally bilobed or completely divided into two spots by a narrow median line, or the blue area may, rarely, cover the entire dorsum of the segment; 9 and 10 dark above, pale on the sides. Mesostigmal laminae with an oblique depression or groove just laterad of the frame, the posterior suture being obsolete where the groove crosses it; basal rami of median carina beginning to diverge behind the frame, lateral carinae of frame broken. Postnodal cross-veins, f. w. $ 10-16, $ 11-15; h. w. $ 9-13, 9 10-12. Measurements. Total length $ 28.0-36.5, $ 30.0-34.5; abd. $ 22-29, $ 23.0-26.5; h. w, $ 17-23, 9 19-22; h. f. 6 4-5, 9 4.0-4.4; w. hd. $ 4.5, $ 4.0-4.5; pt.

a $ .6-1.0.

Nymph (pi. 5, fig. 8; pi. 6, fig. 8; pi. 41, fig. 5; pi. 44, figs. 1, 14). Form of head and eyes as in the preceding species, the setae of the posterolateral surfaces short and inconspicuous; antennae one-fifth longer than head, measured along the middle line, ratio of seg. lengths, 10:18:26:16:11:13; labial mask extending to anterior end of mesosternum, mcntum four-fifths as wide as long, flaring distally as usual; mental setae 4 or 5; marginal setae 5 or 6; lateral setae 6; distal margin of lateral lobes with a stout end-hook, followed laterad with 6 denticles in a regularly diminishing series. Length of hind femora slightly less than width of head. Abd. terga with minute setae sometimes densely and regularly distributed, sometimes sparsely and irregularly. Ovipositor reaching middle of 10th abd. sternum; lat. apps. of male, viewed from above, broader than long, bluntly angular, outer margin straight, in profile angular, slightly longer than broad. Caudal lamellae two-fifths to one-half longer than the outer wing-cases, broadly lanceolate, rounded at base on one side, bluntly pointed at apices, with rounded margins; widest about the nodal line, which is transverse and situated at a little less to a little more than half the length of the lamella; greatest width of median lamella at about one-fourth the length; that of lateral lamellae at about one-fifth the lamellar length, but varying considerably. Antenodal setae: med. lain., d. 31-38, v. 26-30; lat. lam., d. 23-33, v. 37-56. Both of the longer series consist of crowded setae, which increase in size gradually from base to nodus, and the shorter series, although composed of weaker setae than the longer ones, are much better developed than in the three preceding species, besides being much more numerous. Similar in size to E. carunculatnm, clausum, cyathigerum, etc., without definite markings except on the caudal lamellae, on which there is usually a transverse, slightly crescentic stripe on the nodal line and often one or rarely two others, somewhat less distinct, a little distal to the nodal stripe, pigment of axial tracheae interrupted here and there, and many of the main branches also clear at the base but otherwise pigmented. Total length 20-22; h. w. 3.8-4.5; h. f. 3,5-4.0; eaud. lam. 5.5-7.0.

Variations. Like Coenagrion resolutum of similar north-south distribution, E. boreale is more slender towards its southern limit, more robust in the far north. The smallest specimens come from the dry interior of British

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Columbia, e.g. Pentictori, but almost anywhere there is considerable variation in size. Specimens from northern Manitoba, Mackenzie District, N.W.T., and Yukon Territory have the dark areas greatly increased, giving them the appearance of a different species. The antehumeral stripes are narrowed and divided as in C. resolutum, the humeral stripe is greatly widened, the second lateral suture is marked by a black line, and the dark lateral streaks of the abdomen are extended, suggesting the pattern of Coenagrion interrogatum. Habitat and range. Ponds and boggy or marshy lakes. Nfld. and the northern shore of the lower St. Lawrence, Que., to Hudson Bay, Great Slave Lake, Yukon T., and Alaska, s. to Mass., N.Y., O., Ind., 111., Man., Sask., Alta., B.C., and along the mountains to Ut, Nev., and Calif. Distribution in Canada and Alaska. Nfld.—White Bay (type loc.); Bay of Islands; Spruce Brook. N.S.—Annapolis and Halifax counties. N.B.—Bocabec Lake, St. Andrews; Little Southwest Miramichi R. ()we.—Magdalen Islands; Lake Temiscouata; Godbout; Laurentides Park; La Ferme, Abitibi Co.; Ste. Anne; Knowlton; Covey Hill; La Trappe; Gatineau Valley; Nominingue, Labelle Co. Out— Doubtless throughout the entire province but not known from the Lake Erie counties; reported from Welland, Waterloo, Wellington, Halton, and Peel, e. to Prescott and Carleton and n., through Muskoka, Manitouliri, Nipissing, Thunder Bay, Cochrane, Kenora, and Rainy River districts, to Pludson Bay at Fort Severn. Man.—Treesbank; Onah; Stockton; Strathclair; Winnipeg; Winnipeg Beach, L. Winnipeg; Wabowden; Gillam; Herchmer. Sask.—Little Fish Lake, Echo Lake, Regina, Last Mountain Lake, Caron, between Herbert and Waldeck, Swift Current, Antelope Lake, Maple Creek, Lake Lenore, Basin Lake, Margo Lake, Vonda, Prince Albert, Waskesiu Lake, Namekus Lake, Manito Lake, Soda Lake, Duck Lake. AZta.—Red Deer, Nordegg, Banff, Laggan, Jasper Park. B.C.—General throughout the southern half of the province from Vancouver Is. e. to the Rocky Mts. (Field) and n. to the Queen Charlotte Islands (Massett district), Prince Rupert, and Prince George. Many localities are given by Whitehouse (1941) and Buckell (1938), chiefly from the region between the Fraser and Columbia valleys. In the northern half of the province E. boreale is known from Atlin (60°N), Fort Nelson, and Power Post, N.W.T.-Mackenzie Dist., Fort Smith; Norman Wells; Fort Resolution and Resdelta, Great Slave Lake. Yukon T.-Whitehorse, Dawson, and Watson Lake. Alaska—Kukak Bay; Admiralty Island; Juneau; Gulcana; Matamiska; Palmer; Cook Inlet. Field notes. This is the most widely distributed species of Enallagma in Canada and is the commonest species in the far north. Its abundance is doubtless associated with a wide tolerance of habitat. Still fresh waters of almost any description and even somewhat saline waters seem to be acceptable as breeding places. And yet it is not always present when conditions appear to be favourable. It was not found, for example, at Cultus Lake, B.C., where careful collecting was done by Dr. W. E. Ricker and Mr. F. C.

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Whitehouse; neither did we find it at The Pas, Manitoba (although incorrectly reported from there). The very similar E. cyathigerum was very abundant at both of these localities, but for some unknown reason the two species do not often occur together in the same lake or pond. In the region of morainic lakes and ponds between Lakes Ontario and Simcoe, boreale is common in a great variety of bodies of water, ranging from relatively undisturbed forest-bordered lakes and sphagnum-bog ponds to shallow semi-permanent sloughs in treeless pastures. One of these pasture ponds, near Snelgrove, Ontario, which is permanent and much visited by cattle, supports the largest population of boreale for its size of any pond we have seen. Except for some patches of Typha, it has only a thin scattering of emergent plants, chiefly small submarginal rushes. Its submersed vegetation is rich and its bottom soft and sticky. Its outlet is dry except in early spring. In spite of the enormous population of boreale that flies about this pond, we were able to find only very few nymphs at the time when emergence had begun. Transformation takes place on emergent plants of any available kind, usually a few inches above the water. Other kinds of habitat of E. boreale are prairie sloughs, oxbow ponds, quarry ponds, marshy coves in rock-margined lakes, ponds in wooded swamps, and slow weedy streams. In southern Ontario this is the first Enallagma to emerge in the spring, according to our records, May 16 being our earliest date, although the height of emergence is not reached until the end of the month. In western British Columbia, however, it is much earlier, the flight period there, according to Whitehouse (1941), being sometimes as early as April 29, As with most northern species, its season in the southern part of the Eastern Provinces is brief. Although it is sometimes very abundant in June, even as far south as Toronto, its numbers are already dwindling before the end of this month, being rapidly replaced by E. hageni and ebrium. By the beginning of July or the first week, boreale has virtually disappeared in southern Ontario, although, at the latitude of northern Muskoka and Lake Nipissing it may be found occasionally until the middle or third week in July. Close proximity to a large lake may prolong the adult season of this species and many other Odonata. Farther east and north the season is later, in conformity with the delay in the opening of spring. When we visited Godbout on the north shore of the lower St. Lawrence, boreale was emerging on July 12 and there were numerous tenerals, although some fully coloured insects were present. From the relatively large number of tenerals it appeared as though emergence had not been long in progress, perhaps only a week or two, and the season of flight was thus fully a month later than in southern Ontario. And yet by July 24 boreale was already diminishing in numbers and being replaced by E. ebrium. In the far north, e.g. in the Yukon and Northwest Territories, most of the dates of our records are in July, but there are June records from Fort Smith and even Great Slave Lake as early as the 13th.

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In general, as far as the Eastern Provinces, Central Plains, and Boreal Region are concerned, the records, though meagre, give a fairly consistent picture. The season of adult activity is somewhat brief, its beginning varying with the coming of spring and its duration being a month to a month and a half. A different picture, however, confronts us in coastal British Columbia. Here the long growing season, with its comparative absence of high temperature, produces conditions that are favourable for the adult life of this species. Emergence continues throughout the summer, and the season of adult life is extended to about five and a half months (end of April to middle of October). Pairing begins early in adult life—May 30 is our earliest date in southern Ontario—and it continues throughout most or all of June, couples being most often observed during the second and third weeks. It varies, of course, with the time of emergence and the general course of the season of adult life. Oviposition is sometimes performed by the female alone, but more frequently with the male. It has been observed on Tijpha, always a little above the water-level, but doubtless many other emergent plants are used in this act, Typha being very frequently absent from the breeding places of E. boreale. Enallagma cyathigerum (Charpentier). (PI. 17, fig. 5; pi. 24, fig. 5; pi. 28, fig. 5; pi. 43, fig. 15). Agrion cyathigerum Charpentier, Lib. Eur., p. 163, 1840. Enallagma cyathigerum Selys, Bull. Acad. Belg., (2), 41: 505, 1876. Agrion annexum Hagen, Syn. Neur. N. Amer., p. 87, 1861. Enallagma annexum Selys, Bull. Acad. Belg., (2), 41: 506, 1876, race of cyathigerum? Extremely like E. boreale in form, size, and coloration, and showing similar variations in each of these categories, although not in all (see below). Male. Blue marked with black, the blue predominating. Dorsum of head black, with a broad to moderate anterior blue margin, usually covering the area in front of the antennal bases; postocular spots large to moderate, usually nearly touching the ocular margin and connected with a narrow blue occipital line; face, mouth-parts, and rear of head as in boreale. Pronotum black, with front and hind lobes margined with blue, middle lobe pale on the sides and with a pair of dorsolateral blue spots. Pterothorax marked as in boreale; antehumeral stripes slightly curved; in the middle usually about three-fourths as wide as the median black stripe; humeral stripes elongate triangular, the middle width usually less than half the width of the antehumerals at the same level; second lateral suture with a black spot at the pit. Legs as in boreale. Abdomen generally marked as in boreale, with similar variations (but with certain exceptions discussed under "Variations"). Pt. dark sooty brown, with pale marginal lines. Sup. apps. blunt and rounded above, showing in profile a very short upturned ventroapical hook; viewed from above, this hook appears as the small incurved apical part of the sup. app., which is sharply divided by a transverse ridge into a shining black proximal part and a paler brown distal tubercle. In this view the ridge projects a little mesad, like a small beak. The stout basal part of the appendage has no prominent

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ridge such as appears in E. boreale and varnale. Inf. apps. tapering from a stout base dorsoposteriorly to slander hook-like apices, which are bent slightly incsacl. Female. Marked as in borcmle, with a similar widening of the blue area on seg. 8, which as in borcale includes the sides and a variable part of the dorsum, the black area usually tapering eephalad to a pointed apex, which may appear as a hair-line or disappear altogether; or this area may be either widened or narrowed at the posterior end; rarely, it may almost disappear. Mesostigmal laminae rounded laterally, not crossed obliquely by a groove; posterior suture distinct from frame to lateral end; lateral carinae of frame unbroken; basal rami of median carina beginning to diverge behind the frame. Postnodal cross-veins, $ 10-14, $ 12-14; h. w. A 9-13, $ 10-12. Measurements. Total length $ 30.0-36.5, $ 29.0-34.0; abd. $ 23.0-28.5, $ 23.026.5; h. w. 3 17.5-21.0, $ 19.0-21.0; h. f. $ 3.5-4.2, $ 3-4; w. hd. $ 4-5, $ 4.0-4.5; pt. .7-.9. Only one male in our collection reaches the maximal length of 36.5, the second largest measuring 33.5. The very large male comes from the Athabasca delta. Nymph (from Ireland) (pi. 41, fig. 6). Very similar in size and form to that of boreale. Form of head indistinguishable; antennae about one-fourth longer than head, measured along median line; relative lengths of antennal segs., 12:21:38:19:10:13. Labial mask slightly longer than in boreale; greatest width of mentum about threefourths of its length; mental setae 3-5; marginal setae 6-9; lateral setae 6 or 7; distal margin of lat. lobe with denticles in two groups, 3 larger ones nearest the end-hook and 4 very minute ones at the lateral margin. Abdominal terga rather densely clothed with very short setae, those of hind margins of segments also short, except those of seg. 10, on which the dorsal fringe is well developed; lateral carinae of abdomen with setae similar in size and number to those of boreale. Caudal lamellae about one-fifth longer than the outer wing-cases, broadly lanceolate, widening rapidly from the base, with convexo-acute apices, median lamella widest about the nodus, where it is about one-third as wide as long; lateral lamella one-fourth to three-eights as wide as long, nodus transverse, situated about the middle; antenodal setae: med. lam., d. 28-42, v. 24-31; lat. lam., d. 28-36, v. 42-56. Colour-pattern variable but, as a rule, much more distinctly marked than in boreale or other similar species with brown, sometimes very dark against a paler background. Whether this heavy pattern, however, will be found in American nymphs of this species is as yet unknown. Dorsum of head generally with a dark zigzag marking, sometimes represented by a simple line; the sites of the ocelli appearing as pale spots, and another pale spot appearing at the base of each antenna; antennal segs. 1-3 darkened, the others pale. Pronotum dark, with a posterior pale border. Pterothorax dark, with a pale median stripe and a pale patch on each side in front; femora brown, with pale apices and a dark ante-apical annulus; tibiae and tarsi variable in colour, but without definite annuli. Abdomen with a scgmental scries of pale, somewhat diamond-shaped, mid-dorsal spots, each enclosed in a dark area, flanked by pale dorsolateral stripes, more or less distinctly margined with darker. Caudal lamellae with axial tracheae and branches darkened, but the latter with pale areas about their bases, giving them the appearance of being separated from the main tracheae; usually with a transverse stripe at the nodus and often one or two similar but less distinct stripes beyond the nodal stripe. Total length 24.3-26.5; h.w. 5; h. f. 4.3; caud. lam. 5.5-6.0. Described from specimens received from Col. Niall MacNeill, Dublin.

Variations. The ordinary range of variation in colour-pattern is much the same as in boreale. We have seen no subarctic specimens with such extensive dark areas as are sometimes found in boreale, although those from the Yukon Territory show a considerable forward widening of the humeral

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stripes, with a reduction of the pale spot on the mesinfraepisternum. Mrs. Gloyd (1938) describes a series of males from Admiralty Island, Alaska, in which the dark areas approach those of subarctic boreale. "On the thorax the mid-dorsal black stripe covers half of the mesepisternum, the humeral is almost as wide as the pale antehumeral, a black line is present on the second lateral suture and the metinfraepisternum is outlined in black." The black areas of abd. segs. 3 to 6 in these specimens cover the posterior third, half, two-thirds, and four-fifths of their respective segments. Whitehouse (1941) mentions a colony that he found near Terrace, B.C., in which the males showed an enlargement of the dark areas of the abdomen, giving the appearance of E. carunculatum. We have two of these males, both showing a slightly greater extent of dark abdominal markings than Mrs. Gloyd's specimens. In the darker of the two specimens, for example, the black areas of segs. 3 to 6 occupy, respectively, the posterior two-fifths, two-thirds, fivesixths, and all of seg. 6, except a narrow basal annulus like that of seg. 7, which is almost entirely black even in the ordinary colour-pattern. None of these cases, however, is comparable in the degree of melanism to those described by two European workers, M'Lachlan (1900)* and Fudakowski (1928). In these cases, both males, the black of the middle abdominal segments is not only more extensive but is prolonged forward as a median streak to the segment base. They were, however, apparently only individual mutants. Habitat and range. Ponds, marshy shores of lakes, and other quiet waters. Circumboreal: Eurasia, s. Alaska to Hudson Bay and Nfld., s. to Calif., Nev., Ut., Sask., Man., Mich., n. Ind., n. O., N.Y., Conn., and N.S. The known northern boundary of its range is approximately as follows: Palmer, Alaska (61° 30'); Dawson, Yukon (64°N); Fort Norman, N.W.T. (61°N); Fort Resolution, N.W.T. (61°N); Gillam, Man. (56°N); Favourable Lake, Ont. (54°N); Amos, Que. (48°N) and Bay of Islands, Nfld. (49°N). Distribution in Canada and Alaska. Alaska—Sitka; Admiralty Island; Juneau; Palmer. Yukon T.—Whitehorse; Dawson. N.W.T.—Mackenzie Dist, Fort Smith; Fort Norman; Fort Resolution and Resdelta, Great Slave Lake. B.C.—General throughout the southern half of the province from Victoria, Vane. Is., e. to the western trench of the Rocky Mts., and n., especially in the Okanagan Valley and the central hinterland, to Terrace and Prince George. In the northern half of the province known only from Atlin. Alia.— Macleod, High River, Red Deer, Calgary, Claresholm, Nordegg, Betty Lake, near L. Louise, Athabasca delta. Sask.—Kenosee Lake, Little Fish Lake, Regina (Wascana L.); Caron, between Herbert and Waldeck, Maple Creek, Lac Vert, Edward Lake, Vonda, Saskatoon, Prince Albert, Cream Lake. Man.-Assiniboine R. near Treesbank; Onah; Strathclair; Stockton; Winnipeg; Selkirk; Victoria Beach; Lepelletier; Virden; The Pas; mile 214, Hudson Bay Ry.; Wabowden; Gillam. Onf.-Peel, York, and Simcoe counties; Mus*M'Lachlan, Ent. Mo. Mag., (2), 9: 10. (Not seen by us but referred to by Fudakowski (1928) and Schmidt (1929).)

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koka, Cochrane, Thunder Bay, and Kenora districts. Que.—Lac St. Viateur, Abitibi Co., Magdalen Islands. N.B.-Little Southwest Miramichi R,, near Nelson. N.S.-Halifax Co.; Cape Breton Is. N/Id.-Bay of Islands, Grand Entry, Ocean Pond. Field notes. This species, so similar to E. boreale in appearance and in its North American distribution, appears later in the season, generally some time in June, but varying in different parts of its range. In all our records across the continent we have only two before June 1, both from Wascana Lake, Regina, Saskatchewan, May 26 and 31, 1936. Since there are four males and two females, taken on May 26, all very teneral, this was evidently the day of emergence. The single male taken May 31 is nearly mature. While these are very early for most parts of the country, they would not be unusual for the coast of British Columbia, for Whitehouse (1941) gives May 17 to October 8 as the flight period. Both of these extremes are far removed from those of any other province, according to the available data, with the single exception given from Regina, Saskatchewan. Thus, for the Prairie Provinces the range of dates is (May 17) June 9 to August 27; that of the Eastern Provinces, June 5 to August 11, and that of Alaska, Yukon, and Northwest Territories, June 22 to August 26. The great majority of records from both the Prairie and Eastern Provinces is, however, within these extremes. Whitehouse's (1917) notes on the seasonal range in the Red Deer district of Alberta are typical "On the wing early in June and adult by 24th of that month . . . By the fourth week in July the principal flight was over, but belated individuals appeared later . . . I took a £ as late as Aug. 27." In general the season of flight appears to be over by the beginning of August, except in the far north, the Atlantic seaboard, where the coming of summer is delayed, and of course the Pacific coast of British Columbia. Even Whitehouse's latest date, October 8, is not the latest on record, since Ricker (Walker and Ricker, 1938) states that cyathigerum "is on the wing at Cultus Lake until early November." E. cyathigerum appears to be more abundant in the west of North America than in the east. Yet Robert (1944) reports it as the dominant species of Zygoptera at Lac St. Viateur, Abitibi Co., Quebec, in late June and early July; and we have never seen it so abundant as it was in Manitoba, particularly at The Pas, in the first week of July, 1931. It was in the marshy lowlands and adjacent woods near The Pas that we found these damselflies in such large numbers. Apparently they had been blown from the lakes and sloughs nearby by strong winds, but we were unable to approach these bodies of water closely as the shores were muddy and very treacherous, and the margins screened by dense belts of tall reeds (Phragmites communis Trin.). At the time, we were surprised at the absence of E. boreale, but perhaps the adult season for the latter was over in this particular locality. It has been noted by Whitehouse and the writer that these two species are seldom found together on the same lake or pond. This may be due in some localities

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to seasonal differences, but in coastal British Columbia, where both species fly from spring to fall, some other reason must be found. There may be differences in the habitat preferences of the two species, but this is a subject upon which little can as yet be said. E. cyathigerum appears generally to avoid ponds in acid soils, such as the typical muskeg pools which boreale frequents, yet we found plenty of cyathigerum at a sphagnumbordered lake in southern Manitoba. It is noteworthy that at Cultus Lake (southwestern mainland of British Columbia) where Dr. W. E. Ricker collected Odonata for several seasons, E. cyathigerum was common in both the lake and its outlet, Sweltzer Creek, whereas boreale was not collected. This lake, according to Dr. Ricker (Walker and Ricker, 1938), has an epilimnion that is quite warm in summer (20°-22°C), and Sweltzer Creek is a "warm stream of moderate current and volume of flow of about one cubic foot per second in summer." E. boreale in our experience is found only in very slow streams with much submersed vegetation. Whitehouse found cyathigerum pairing at Sooke, Vancouver Island, on June 12; at Harrison Bay, August 15-19, "flying in hundreds in cop." The same author (1917) took pairs of this species at Red Deer, Alberta, on June 25 and July 15-16. We have also found it pairing on June 9 at Long Lake, Vancouver Island; July 1 at Kildonan Park, Winnipeg, Manitoba; and July 16 at Onah, Manitoba. In each case the insects were abundant and many pairs were noted. No observations on oviposition appear to have been made on this species in North America. Enallagma vernale Gloyd. (PL 17, fig. 6; pi. 24, fig. 6; pi. 28, fig. 6; pi. 43, fig. 14) Enallagma vernale Gloyd, Occas. Papers Mus. Zool., Univ. Mich., 479: 1-8, 1943. Enallagma cyathigerum Walker, Can. Ent, 48: 192-196, 1916. Smaller than the average size of E. boreale or cyathigerum, the male likely to be confused with the latter, the female with carunculatum or civile. ^ Male. Blue, with black markings very similar to those of boreale, hageni, etc. Dorsum of head black, with wide blue frontal margin, which sometimes extends behind the antennal bases; postocular spots moderate to large, not quite reaching the ocular margins, sometimes connected by a pale occipital bar; face, mouth-parts, and rear of head as in boreale or cyathteerum, pale green. Pronotum black, front lobe with pale margin or median spot; hind lobe with a very fine pale margin; middle lobe laterally pale and with a pair of large dorsolateral pale spots. Pterothorax blue; antehumeral stripes nearly straight, their middle width two-thirds to four-fifths that of the median stripe; humeral stripes narrower than in boreale and the other species of Group I (except clausum), which it resembles in colour-pattern, widest in anterior half, narrowing caudad in the posterior half, where it may be reduced to a hair-line, but widening again slightly at the pit; sides of thorax otherwise without black markings, except a small streak at the nind end of the second lateral suture. Legs greyish pruinose, with a broad black

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stripe on outer surface of femora and on the tibiae; tarsi light brown, darkened at the articulations; claws brown, black-tipped. Abdomen blue, marked with black as in boreale, hageni, etc. Dorsal black spot on seg. 2 either isolated and transverse or confluent with the apical annulus and more or less mushroom-shaped; black spots on 3, 4, and 5 a fifth to a fourth as long as their respective segments, or the spot on 5 a little longer and sometimes prolonged on the middle line, all somewhat expanded toward the posterior end, where they are confluent with the apical annulus; spot on 6 half to two-thirds of the segment length, generally acute in front; 7 black above with a basal blue annulus, narrowly interrupted; 8 and 9 blue; 10 black on dorsal half; sup. apps. and inf. apps. in part black; pt. dark brown, with extreme edges lightened. Sup. apps. half as long as 10, similar to those of cyathigerum, but a little shorter, with the apices more abruptly upturned, so that the pale tubercle is directed dorsad; viewed from above, a deep groove appears in front of the apical tubercle and is bounded proximally by a prominent riage, which is not present in cyathigerum. Both groove and ridge appear most distinctly when viewed obliquely from above (pi. 43). Inf. apps. longer than sup. apps., tapering to pointed apices directed dorsoposteriorly, the inferior margin straight. Female. Greyish blue to yellowish green (buff in dried specimens). Head and thorax marked much as in male, but with pale areas tending to be more extensive. Pale frontal margin of head tending to be broader than in male; postocular spots large, but not reaching ocular margin, connected by a pale occipital line; rear of head and mouthparts pale yellowish. Median thoracic carina with a pale line; antehumcral stripes sometimes as wide as the median dark stripe, usually narrower, nearly straight, and varying little in width; humeral stripe narrower than in male, often reduced behind the middle to a hair-line or vanishing altogether here, reappearing towards the posterior end. Legs pale; femora and tibiae with the dark stripes narrower than in the male. Seg. 2 of abdomen with the dark median stripe entire or broken in the middle, narrowing gradually from base to beyond middle, then expanding again into a diamond-shaped figure, confluent with the apical annulus. Sometimes the stripe is divided into basal and apical spots, with a wide gap between. Segs. 3-6 with the dorsal stripe of each seg. percurrent and divided by a constriction into a lanceolate anterior part occupying about three-fourths to four-fifths of the length, and an expanded posterior part which is joined with the apical annulus. There is considerable variation in the width of these stripes, but their outline is entirely visible from above. Seg. 7 with a similar but wider stripe with a less marked constriction; dorsal stripe of 8 not or scarcely constricted, with a pair of short spurs behind the middle; dorsal stripe of 9 broadest in front, somewhat narrowed apically; 10 with a relatively narrow stripe. Mesostigmal laminae narrowing more rapidly than in boreale or cyathigerum, the apices smaller; posterior suture distinct for more than half the distance from the apices to the median carina; lateral carinae strongly divergent caudad and continuous with an oblique ridge, which is subparallel with the anterior margin. Postnodal cross-veins, f. w. $ $ 11-12; h. w. $ $ 9-10. M2 arising on f. w. $ $ nearest pnx. 5 or 6; h. w. # $ pnx. 4 or 5. Measurements. Total length i 28.0-32.5, $ 28.8-33.0; abd. $ 22.0-25.5, $ 22.026.0; h. w. $ 17-19, 9 17.8-21.0; h. f. $ 3.0-4.0, $ 4; w. hd. $ $ 3.7-4.3; pt. $ $ .6-.8. Nymph (pi. 41, fig. 7; pi. 44, fig. 15). Moderately slender with large plain caudal lamellae and very little colour-pattern in basal half, distally; very like C. resolutum in general appearance. Head with eyes and posterolateral margins a little more prominent than in the preceding four species, the posterolateral surfaces with a small patch of short stout setae; antennae about one-third longer than head, the relative lengths of the segs. as follows, 15:23:30:17:14:14. Labial mask reaching just behind fore coxae, greatest width of mentum about four-fifths of the length, distal two-fifths distinctly flaring; mental setae 4 or 5; lateral setae 5 or 6; distal margin of lateral lobe with three larger

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denticles following the end-hook and decreasing in size laterad, followed by three or four minute ones, which are difficult to see. Abdominal terga fairly evenly covered with very short setae; lateral carinae prominent, bearing much larger setae, which increase in size caudad on each segment. On seg. 1 there are 4 on each carina; on 2, 7; on 3-8 each 10 or 11; on 9, 5; and on 10, 2 or 3 smaller setae. The setae on the hind margins of the segments are somewhat smaller than the largest of those on the lateral carinae. Ovipositor not quite reaching the middle of the 10th sternum. Caudal lamellae three-fourths longer than the outer wing-case, widest just before the nodus, which is about mid-length of the lamella or a very little beyond; greatest width of median lamella one-fourth of the length; of lateral lamellae just over one-fifth of the length; form lanceolate, rounded at the extreme base on one side; narrowing gradually beyond the nodus to apices that are rounded or convexo-acute; antenodal setae: med. lam., d. 29-31, v. 24-30; lat. lam., d. 24, v. 38-44. Dorsal antenodal setae of median lamella small at base but enlarging distally, the last 7 or 8 particularly large and crowded, and raised on a sort of crest at the nodus, at which there is a slight notch; ventral setae of lateral lamella similar, more numerous, the basal ones not so reduced; setae of the remaining edges much smaller and more widely separated; tracheal branches leaving the axis at a very small angle, especially distally, the branches long and rather irregularly placed, without many small twigs. Total length 25-27; h. w. 4.5; h. f. 3.75; caud. lam. 7.3-7.6.

Variations. Mrs. Gloyd (1943) states that specimens from southern Michigan (Washtenaw Co.) are smaller than those from northern counties (Emmet, Cheboygan). Ontario specimens, as hitherto found, are nearly uniform, and similar in dimensions to the larger specimens from Michigan. On the other hand specimens from the Laurentian Highlands, Quebec, average distinctly smaller than those from Ontario. Habitat and range. "Woodland pools, ponds and small lakes" (Gloyd); marshy inlets on the shores of large lakes. Laurentian Highlands of w. Quebec; shores of upper St. Lawrence R., Ont., w. along shores of Lakes Ontario and Erie to Washtenaw Co., Mich., n. rarely to Georgian Bay and through the Upper Peninsula of Mich, to w. Ont. and Sask. Distribution in Canada. Que.—St. Marguerite, Terrebonne Co. Ont.— Leeds, Prince Edward, Simcoe, York, Peel, and Norfolk counties; s. Muskoka and s. Kenora districts. Sask.—Big Quill Lake (nymphs). Field notes. The flight period of E. vernale is early and brief. Mrs. Gloyd's Michigan records date from May 29 to June 8. Ours have a similar beginning, May 29, 1914, when we found it emerging on Toronto Island and mistook it for E. cyathigerum, E. vernale being at that time undescribed. We collected a few nymphs, several of which transformed the following clay. Since then we have found vernale to be distributed in Ontario principally along Lakes Erie and Ontario and the headwaters of the St. Lawrence River in marshes along the shore. Since we found it emerging, all our records have been for June, but they range from the 8th to the 27th. We have several times visited Prince Edward Co. along the shore of Lake Ontario, and the marshes of the St. Lawrence River near Ivy Lea (a few miles east of Gananoque) in the effort to find E. vernale. On June 8, 1953, we found it in limited numbers, all mature and a few in couple. E. ebrium was already present in larger numbers but, as yet, nearly all

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THE ODONATA OF CANADA AND ALASKA

teneral, so that the bright blue males of vernale were easy to detect. On June 14 and 15 of the same year, we again paid two short visits to this station, but found only five males and no female in two half-hours' search. Ebrium was flying in hundreds, but most of them were now mature, the males blue and very similar in appearance to those of vernale. But it was evident that the season of the latter was drawing to a close. Sometimes, however, vernale remains in flight in southern Ontario until the third or fourth week in June, our latest date being June 27, 1925, at Picton, Prince Edward Co. But we have no record for July. We made a special search for this insect on July 5, 6, and 7, 1952, both on the St. Lawrence River and in Prince Edward Co., and not a single specimen was found; ebrium had completely replaced vernale. In western Ontario near Manitoba, however, vernale was taken by Mr. W. Y. Watson at Malachi and Sioux Lookout (approx, 50° N) from June 23 to July 18, and full-grown nymphs were collected from Big Quill Lake, Saskatchewan (approx. 52° N) on July 3, 1939. At the higher latitudes of these stations a later season would be expected. E. vernale has been hitherto unknown east of Ontario but, in 1953, we visited Ste. Marguerite, Quebec, from June 9 to 13, and found vernale in abundance in the vicinity of a small lake, known as Lake Lucerne. The males flew chiefly over the roads leading from the lake up the wooded hills, but were also found along the shore. Three mating pairs were taken on June 12, but only one unmated female was found. They averaged a little smaller than those from southern Ontario but slightly larger than specimens from Washtenaw Co., Michigan, as indicated by Mrs. Gloyd's measurements. Judging from our experience, E. vernale must be regarded as a lake rather than a pond species. Lake Lucerne, although less than a mile long, is fed by a stream of considerable volume and is far from being a pond. The other localities where we have found vernale in numbers are all in proximity to one of the two Great Lakes, Ontario or Erie, or the St. Lawrence River. Sometimes they were found on the marshy border of a pond, but the pond was close to the lake or river and in most cases it appeared that the breeding place, though sheltered from wind and waves, was connected with the main body of water. The contrary opinion is expressed by Mrs. Gloyd (1943), who states that "At Douglas Lake, a rather large inland lake, approximately four miles long and two miles wide, it was taken at two small ponds, a few yards from the lake shore at Sedge Point and Fairy Island, a narrow strip of land, about three-fourths of a mile long, extending into the lake and connected with the southwest shore at times of low water level. It is quite probable that the specimen from Fairy Lake came from one of its offshore or inland pools and not from Douglas Lake itself/' We have observed mating pairs on but three occasions: June 8, 1953, near Ivy Lea, Ontario (three pairs); June 12, 1953, at Lake Lucerne, Quebec (two pairs); and June 19, 1948, in Prince Edward Co., Ontario (one pair).

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Enallagma hageni (Walsh). (PL 18, fig. 1; pi. 24, fig. 7; pi. 28, fig. 7; pi. 31, fig. 7) Agrion hageni Walsh, Proc. Ent. Soc. Phila., 2: 234, 1863, named and figured; Proc. Acad. Phila., p. 386, 1862, descr. Enallagma hageni Selys, Bull. Acad. Belg., (2), 41: 512,1876. Smaller and more slender than average-sized E. boreale or cyathigerum, the males nearly identical in colour-pattern, but the females having the pale areas of the abdomen much more reduced. Both sexes are identical in size, general form, and colour-pattern with E. ebrium. Male. Rather small for Group I, blue and black, the blue predominating. Dorsum of head and postclypeus black, the front margin, as in boreale, blue; postocular spots smaller than in boreale, not nearly touching the eye margin and remote from the occipital bar; rear of head pale bluish green. Pronotum black, margins of front and hind lobes blue, variable in width; middle lobes with sides blue; dorsolateral spots often minute or absent, sometimes moderately large. Pterothorax much as in boreale; median black stripe widest near the front, gradually narrowed caudad; antehumeral stripes nearly straight and subparallel-sided, their middle width about three-fourths or four-fifths that of the median stripe; humeral stripes widest above the middle coxae, narrowing caudad very little, their middle width half to three-fourths that of the antehumeral stripe. Ante-alar ridges black on the mesothorax, pale on metathorax; sides of thorax otherwise pale except for a black spot on the second lateral suture at the posterior end. Coxae and trochanters pale, femora black, with flexor surface pale; tilbiae with extensor surfaces pale; tarsi reddish brown, sometimes very dark. Abdomen blue, marked with black as follows: a dorsal spot on front half of seg. 1; a large dorsal spot on rear half of 2, connected by a neck with the apical annulus; similar spots on 3 and 4, covering usually one-fifth to one-third of the segmental length, not including the slender median streak into which these spots are often prolonged; a usually longer spot on 5, occupying the hind third or half of the segment, sometimes more; 6 and 7 mostly black, with ventrolateral blue margins and with short basal blue areas, on 6 generally about one-sixth of the segment length but variable, on 7 a short interrupted annulus; 8 and 9 blue or with only minute posterolateral black spots; 10 black above, pale below. Sup. apps. black; inf. apps. pale, black-tipped, or entirely black. Pt. very dark brown. Sup. apps. about three-fourths as long as inf. apps., in profile slender and tapering from base to apex, the upper surface gently concave, apices slightly upturned, longer than in cyathigerum, with the tubercle terminal and sharply delimited by a transverse ridge; inner margins convex at extreme base, concave beyond; inf. apps. in profile triangular, dorsal surface straight or slightly concave, apices acute, incurved as seen from above. Female. Usually heterochromatic, although partly homoeochromatic individuals with greenish thorax and bluish abdomen are sometimes found. The heterochromatic females are greenish yellow or ochraceous, with extensive black areas. Head and thorax marked as in male; legs pale, with the anterodorsal surfaces of the femora black; tibiae pale, with a long black streak on the outer surface; tarsi pale, with articulations black. Pt. yellowish. Abdomen chiefly black above, greenish yellow or bluish on the sides. Seg. 1 with dorsal spot and posterolateral marginal lines black; 2 with broad black dorsal stripe, narrowest on the anterior half, widening behind the middle, but not so much as in boreale, cyathigerum, etc., notched on the sides just before the apical annulus; 3-10 mainly black above, the dark areas narrowed at base of each segment, except 9 and 10, but continuous along the median line, very slightly expanded before the posterior end of each segment, with a very slight notch before the apical annulus.

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Mesostigmal laminae divided into a very broad proximal part, boundr.d by a raised and strongly curved margin, arid a much smaller distal part. The posterolateral margin of the proximal part is curled up so that, when viewed obliquely from above, it is seen to project from the surface somewhat after the manner of the pronotal margin (pi. 31, fig. 7).* Anterior carina of frame very broad, the median pit much contracted; basal rami of median carina beginning to diverge behind the mesostigmal laminae, much thickened. Postnodal cross-veins, f. w. $ 9 9-12 (usually 10 or 11); h. w. 8-10. M2 arising on f. w. $ 9 between pnx. 4 and 5, or at 5; h. w. $ 9 between pnx. 3 and 4, or at 4. Measurements. Total length $ 26.3-32.0, 9 29.0-33.0; abd. $ 21-25; 9 23-26; h. w. £ 15.2-17.5, 9 18-20; h. f. $ 2.7-3.5, 9 3.0-3.5; w. hd. $ 3.3^3.8, 9 3.7-3.9; pt. $ 9 .5-.7. Nymph (pi. 43, fig. 11; pi. 44, fig. 16). Similar in form to all the preceding species, but smaller and easily distinguished from any of them by the spotted caudal lamellae. Head nearly as in boreale, etc., but with eyes and postocular lobes slightly more prominent, the constriction behind the eyes barely deeper; antennae about one-third longer than head, measured along median line; relative lengths of segs., 11:17:23:16: 12:12. Labial mask just reaching base of mesocoxae, about seven-tenths as wide as long; mental setae 3 or 4; marginal setae 0-4; lateral setae 5 or 6; distal edge of lateral lobe with about 6 denticles between end-hook and movable hook, diminishing laterad, three larger and three very minute. Inner wing-cases extending caudad a little beyond apices of hind femora, the length of which is about equal to the width of the head. Lateral carinae of abd. segs. prominent, that of seg. 1 with only 2 or 3 minute setae; 3-8 with 11 or 12 setae in a graded series, the first very small, the List 4 or 5 stout and somewhat curved. Posterior margins of terga with moderate setae, larger on seg. 10 ventrolaterally. Ovipositor reaching a little beyond middle of seg. 10; lat. apps. of male in dorsal view broadly rounded, smooth, and without a ridge, in profile narrowing distad. Caudal lamellae about three-eights longer than outer wing-cases, oblanceolate, widening gradually from base, usually somewhat beyond the middle, greatest width of median lamella being about four-elevenths of the length, that of lateral lamellae three-tenths of the length, the edges curving to bluntly pointed apices. Antenodal setae: med. lain., d. 20-26, v. 7-9; lat. lam., d. 7-9, v. 29-32. Dorsal setae of median lamella minute arid feeble in proximal half of the series but increasing rapidly in size distally, the last 10 or 12 becoming particularly well developed and stout; ventral setae of same lamella extremely small and few, the nodus scarcely apparent; nodal line curved and oblique; margins of lateral lamellae similar but reversed, with this difference, that the ventral series of setae is somewhat longer than the dorsal of the median lamella, the nodus being at about three-fifths instead of one-half (or less) of the lamellar length, and the setae are not degenerate but increase in size evenly and regularly from base to nodus. Specimens preserved in alcohol are light brown or buff, with some darker markings. Dorsum of head without definite markings, posterolateral regions somewhat darker than elsewhere; antennae with seg. 1 and basal third of 2 and 3 dark, remaining segs. also a little darker basally, otherwise pale. Thorax plain with dark spots at the pleurocoxal articulations and the metastigma; wing-cases with the longitudinal veins clearly marked in brown and the cross-veins also slightly so in dark specimens. Femora pale brownish with paler apices and a dusky ante-apical annul us; usually also with a number of short dark dorsomesal streaks. Abdomen brown, finely speckled with darker where the minute setae arise; with a pale median line, bordered by ill-defined darker brown, and with basal lateral dark spots at the tergal articulations. Caudal lamellae pale, with a variable number (usually 3-5) of dark patches on each side of the axis, each patch consisting of a somewhat compact group or closely branched and darkly pigmented tracheal twigs. Total length 17.5-22.0; h. w. 3.6-4.4; h. f. 3.0-3.5; caud. lam. 5.4-6.0. *This character was pointed out to me by Mrs. Gloyd. It is the only character by which the females of E. hageni and ebrium can be distinguished in the field.

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Habitat and range. Marshy and boggy ponds, lake shores, and slow streams, tolerant of acid waters. N.S. to eastern B.C., s. to N.C., Pa., n. O., n. I rid., n. 111., la., and e. Kans. Distribution in Canada. N.S.—Annapolis and Halifax counties; Dingwall and Aspy Bay, C.B. N.B.—Charlotte, Sunbury, and Gloucester counties. P.E.L—Charlottetown, Souris. Que.—Magdalen Is.; Knowlton; St. John's; Hemmingford; Waterloo; Vaudreuil; Lachine; Hull; Wakefield and other stations in the Gatineau Valley; Lac Mercier; Nominingue; La Ferme, Abitibi Co. Ont.—General throughout s. Ont., from Essex e. to Prescott Co., n. to Muskoka, Parry Sound, Nipissing, Manitoulin, Algoma, Sudbury, Cochrane, Thunder Bay, s. Kenora and Rainy River districts. Man.—Westbourne, Winnipeg, Stockton, Treesbank, Onah, Selkirk, Victoria Beach, Lake Winnipeg, Virden, Dauphin, Fork River, Winnipegosis, The Pas. Sask.— Indian Head, Regina, between Herbert and Waldeck, Swift Current, Maple Creek, Bredin. A/to.-Red Deer. B.C.—Stanley, near Barkerville (53°N). The northern boundary of the range of E. hageni is not well known. As recorded, it runs through the following stations: Magdalen Is. (47°N), La Ferme, Que. (48°35'N), Lowbush, Lake Abitibi, Ont. (49°N), The Pas, Man. (53°50'N), Red Deer, Alta. (52°N), and Stanley, B.C. (53°N). Field notes. This is one of the most abundant of summer damselflies in the more settled parts of eastern Canada, its rivals for such a distinction being Nehalennia Irene, Ischnura verticalis, and Enallagma ebrium. N. Irene is perhaps first in numbers of individuals, with E. hageni a close second, I. verticalis the most generally distributed, with the longest seasonal range, and E. ebrium as abundant or more abundant than hageni in calcareous regions. E. ebrium diminishes in numbers as soon as the Precambrian Region is entered, while hageni remains and is undoubtedly the commonest of Zygoptera in the acid waters of that region, south of the Hudson Bay watershed. When that latitude is reached, e.g. at Lake Abitibi, or at The Pas, Manitoba, hageni is local and other species, such as E. cyathigerum, replace it. In southern Ontario hageni usually appears first in early June when E. boreale and Coenagrion resolutum have reached their maximum numbers. Together with other species, such as E. ebrium, they soon replace the earlier species, which have nearly disappeared by the end of the month. Our earliest records for Jiageni are May 30, 1930, at Kelly Lake, Ontario, and June 1, 1929, at High Park, Toronto, both in York County. On both occasions only tenerals were seen, but they were abundant, particularly at Kelly Lake, where they appeared to have all emerged on the day on which they were seen. Generally, however, hageni is not much in evidence before the first week in June. Even on June 12, 1930, at Grenadier Pond, Toronto, although they were abundant and many in full colour, the majority were still tenerals. In fact the tenerals may be still numerous as late as June 22. Throughout the second half of June and the whole of July, E. hageni flies abundantly in the more southerly parts of Quebec, Ontario, and Mani-

228

THE ODONATA OF CANADA AND ALASKA

toba. It is also common in the Maritime Provinces at this season, but we have not found it there in the numbers that occur farther west, perhaps owing to the limited amount of collecting that has been done there. In southern Manitoba, for example at Victoria Beach, and stations on the Red and Assiniboine Rivers near Winnipeg, we found it common but generally less so than other species, such as cyathigerum; and at The Pas it was decidedly local, having been discovered only at one of the many small lakes and ponds that we visited. It was, however, the commonest species at this lake. About June 20, pairs in tandem begin to appear and may be seen thereafter as late as August 1. Our earliest date of oviposition is June 22, 1947, at the creek near DeGrassi Point, Lake Simcoe, where several couples were ovipositing on floating stems of last year's Typha. On the same creek on July 9, 1948, hageni was very abundant and a great many pairs were flying per collum and ovipositing. The females thus engaged were accompanied by males, which stand obliquely while the females oviposit in slender water plants just below the surface. We have never seen the female of hageni become submerged as that of ebrium sometimes does. Our latest date for oviposition is August 8, on the same stream. Although in southern Ontario E. hageni has nearly replaced boreale by the end of June, on the north shore of Lake Superior, at Silver Islet, we found hageni on July 13,1939, apparently only beginning to replace boreale, being not yet really abundant and not all mature. The adult season is about over by the middle of August, although occasional individuals are sometimes seen at Lake Simcoe as late as August 21. The flight period, as recorded for southern Ontario, is thus May 30 to August 21. This is almost identical with the period in New England, which according to Carman (1927) is from May 30 to August 10. In Indiana (Montgomery, 1942) it begins earlier, about the third week in May, whereas the latest record is about the end of August, although only a single collection was made after the end of July. Enallagma ebrium (Hagen). (PL 18, fig. 2; pi. 24, fig. 8; pi. 28, fig. 8; pi. 31, fig. 8) Agrion ebrium Hagen, Syn. Neur. N. Amer., p. 89,1861. Enallagma ebrium Selys, Bull. Acad. Belg., (2), 41: 513,1876. Practically indistinguishable from E. hageni, except in the form of the anal appendages of the male and the mesostigmal laminae of the female. Male. The description of the colour-pattern of E. hageni applies equally well to E. ebriwn, but we nave not found males with the maximum development of the black abdominal areas as represented in hageni, and in general the pattern of ebrium is nearest the paler phase of hageni. The anal appendages are so different from those of hageni as to suggest that the two species are not so closely related as they appear to be at first sight. Against this view, however, are important points of resemblance in the females and the extreme similarity of the nymphs. Sup. apps. nearly as long as inf. apps., in profile bifid, the upper branch

THE ZYGOPTTSRA—DAMSELFLIES

229

horizontal, bluntly rounded; lower branch bent downward and curved backward; viewed dorsally the bases of the sup. apps. are strongly divergent, but, continuing as the dorsal branches, are curved backward, ending bluntly, with a distomesal tooth or angle. The dorsal branch of each app. is black but the ventral branch appears pale brown, this part being a much enlarged tubercle. It is much broader and more rounded than the dorsal branch and projects far mesad. Inf. apps. pale, triangular, with the upper margin horizontal, except toward the base, where it is decurved; apices black, appearing incurved when viewed from above. Female. Identical in general appearance with hageni, the colour-pattern being precisely similar; usually heterochromatic (greenish yellow) but sometimes homoeochromatic (greyish blue). Mesostigmal laminae similar to those of hageni, the main part of each lamina being a very broad shallow basin, with a strongly elevated hind margin and with the small apices flat and deflexed. These apices are not sharply demarcated from the basin by a raised wall, as in hageni, and the posterolateral margins, when viewed obliquely from above, do not project freely as in the latter species (pi. 31, fig. 7). Postnodal cross-veins, f. w. $ 9-12, 9 10-13; h. w. $ 8-10, 9 8-11. M2 arising on f. w. # 9 at or near pnx. 5; h. w. # 9 between pnx. 3 and 4, or at 4. Measurements. Total length $ 26.5-31.0, 9 28-33; abd. £ 20.5-24.0, 9 22-25; h. w. $ 15.5-17.5, 9 16.5-19.5; h. f. $ 2.6-3.2, 9 3.3-3.5; w. hd. $ 2.6-3.2, 9 3.5-4.0; pt. $ 9 .5-.6. Nymph (pi. 35, fig. 1; pi. 41, fig. 4; pi. 43, fig. 12). Apparently indistinguishable from E. hageni except in the form of the lateral appendages of the male. Form of head, including eyes, as in E. hageni, the posterolateral surfaces with a dozen or slightly more fairly stout setae, a few of them longer than the others; antennae about one-sixth longer than the head, measured along the middle line; relative lengths of antennal segs., 13:19:27:16:8:11. Labial mask just reaching base of mesocoxae, greatest width fourfifths of length; mental setae 3, marginal setae 3-5, longer than in boreale and cyathigerum; lateral setae 5-6; distal edge of lateral lobes with 6 denticles, decreasing laterad, the first 3 much larger than the others and relatively wide apart, the last 3 minute. Wing-cases extending back a little farther than hind femora, the latter about as long as width of head. Lateral carinae of abdomen prominent, that of seg. 1 with only 2 or 3 very small setae; 2 with about 11 on the posterior three-fourths, the last 2 or 3 stout and curved; segs. 3-8 each with 11 or 12 setae similarly distributed, forming a graded series with the last 3 or 4 much larger and stouter. Posterior margins of terga with moderately large setae, those of 10, however, much stronger. Ovipositor reaching middle of 10th sternum, lat. apps. of male, viewed from above, bluntly angular, the lateral margin nearly straight, mesal margin convex, dorsally with an oblique ridge bounding a slight mesal concavity. Caudal lamellae lanceolate or somewhat oblanceolate, the bases, like those of hageni, narrower than in any of the other preceding species, the apices rather bluntly pointed, with rounded edges, or sometimes rounded; widest a little beyond the middle, the greatest width of the median lamella nearly one-third of the length, that of the lateral lamellae about one-fourth of the length. Antenodal setae: med. lam., d. 17-27, v. 6-12; lat. lam. d. 6-8, v. 31-38. Dorsal setae of median lamella small and weak at base, but becoming steadily stronger and more crowded toward the nodus; ventral setae of same lamella very small and widely separated, the nodal line somewhat oblique; setae of lateral lamellae similar but reversed, with the same differences as described for hageni; dorsal nodus of median lamella at about half the length, ventral nodus of lateral lamellae at about three-fifths of the length of the lamella. Light and dark brown, dorsum of head somewhat darkened about the posterolateral margins and sometimes with an ill-defined and broken transverse stripe between the eyes; antennae with 1st and basal third of 2nd and 3rd segs. dark, with a less distinct

230

THE ODONATA OF CANADA AND ALASKA

annulus on distal half of 3rd, entire 4th scg. darkened, the remaining parts pale. Thorax brown, with darker points where the minute setae arise and blackish spots at the pleurocoxal articulations; wing-eases with longitudinal veins clearly marked with brown; cross-veins also marked, but less distinctly; legs pule, banded and spotted with brown as follows: femora with an ante-apical annulus and the setae darkened, particularly on the fore femora; tibiae with an indistinct sub-basal spot on the flexor side. Abdomen brown, darkened about the bases of the setae, giving a finely speckled effect; a pale mid-dorsal line, margined with brown of a darker shade than the background; intersegmental areas with a row of dark spots alternating with pale spaces, the spots darkest nearest the mid-dorsal line; small very dark spots at the tergal articulations. Caudal lamellae pale, with large dark spots formed by the deeply pigmented and closely branched tracheae. Total length 16.5-19.5; h. w. 3.5-3.8; h. f. 3.0-3.5; caud. lam. 5.0-5.8.

Variations. It will be seen from a comparison of the measurements of ebrium and hageni that there are probably no significant differences between these two species in this regard. E. ebrium sometimes exhibits variation in the extent of the black areas, particularly of the abdomen, comparable to those of hageni, but such variations appear to be less frequent in Ontario than in hageni. Undersized individuals are sometimes found in peat bogs but, as a rule ebrium is absent from such habitats, while hageni is common there. Habitat and range. Marshy ponds, lake shores, and quiet marsh-bordered streams, most abundant on calcareous soils. Nfld. to central B.C., s. to Md., O., Ind., 111., la., and Utah. Distribution in Canada. Nfld.-St. John's, Spruce Brook. N.S.-Pictou, Hants, Halifax, Digby, and Annapolis counties. N.B.—Chamcook Lake, near St. Andrews; Notre Dame. Que.—Knowlton; St. John's; St. Chrysostom; Hemmingford; Vaudrcuil; Lachine; Montreal; Hull; Wakefield and other stations in the Catincau Valley; Lac Mercicr; Nominingue; Godbout; La Ferine, near Amos; Rupert House, James Bay. Ont.—General throughout s. Ont.: counties along Lakes Erie and Ontario, Essex to Lincoln and Weiland, Wentworth to Prescott, and n. to Muskoka, Parry Sound, Nipissing, Sudbury, Thunder Bay, Cochrane, s. Kenora, and Rainy River districts. Man.—Westbourne; Assiniboine R. near Treesbank; Onah, Stockton; Winnipeg; Selkirk; Victoria Beach, Lake Winnipeg; Dauphin; Virden; Winnipegosis; Fork River; The Pas. Sask.—Indian Head, Regina, Pasqua Lake, between Herbert and Waldeck, Swift Current, Maple Creek, La Verte, Waskesiu Lake. Alta.—Red Deer. B.C.—Chaperon Lake, Oliver, Penticton, Vernon, Falkland, Tappen, Kamloops, Crawford Bay, Boswell, Wasa, Bridge Lake, Stanley, Summit Lake, near Prince George. The distribution of E. ebrium across Canada is not quite continuous, since it is interrupted by the Rocky Mountains and its presence in central British Columbia appears to be due to a northward extension from the United States. Field notes. Enallagma ebrium is one of those midsummer damselflies

THE ZYGOPTERA—DAMSELFLIES

231

that fly in myriads in the marshes during June and early July. While it is sometimes found in company with E. hageni, the two species are usually found in separate populations. In general ebrium is the more abundant on calcareous soils while hageni is the common species in Precambrian regions. Ebrium is found in all sorts of still waters from lake marshes to quarry ponds. We have found it now and then in sphagnum-bog ponds but such ponds are, as we have already mentioned, unfavourable to this species. The flight period of the two species appears to be identical. Our earliest records of ebrium, as of hageni, are dated May 30, one from Kelly Lake, York Co., Ontario, in 1936, another from Snelgrove, Peel Co., in 1948. On both occasions ebrium was very abundant, but only tenerals were seen, those from Kelly Lake having apparently all emerged on the same day. Most of the individuals seen in the first nine or ten days of June are also teneral and, in southern Ontario, they continue to appear in smaller numbers until the end of June or even later farther north. Meanwhile the earlier individuals have matured, and we have seen fully coloured specimens in the Toronto district as early as June 2. By the middle of June they have reached their first peak of numbers, and we have noted another peak of emergence near the middle of July, following which they are still common until the end of the month. In August their numbers fall off rapidly, our last record from southern Ontario being dated August 24. Montgomery's (1942) chart for Indiana gives an earlier but not longer adult period than in Ontario. Thus in Indiana the period begins about a week earlier than in Ontario, but is over by the end of July instead of the third or fourth week in August. For New England, Carman (1927) gives May 26 to August 20, which is much the same as in southern Ontario. Farther north, e.g. at The Pas, Manitoba, or Godbout, Quebec, the flight period is much later in beginning. Thus at The Pas, in 1931, we found ebrium on July 3 not fully mature, and at Godbout, in 1918, where we collected from July 12, we found our first ebrium on July 19 and only tenerals were seen. In British Columbia the flight period is recorded by Whitehouse (1941) as from June 8 to September 3. We have no records of pairing before June 19, but it certainly takes place earlier than this, and we have seen pairs in couple at Lake Simcoe as late as August 6. We have seen ebrium ovipositing on the same day as it was first seen pairing, i.e. June 19. On this occasion a pair was observed to oviposit on a floating piece of last year's Typha on one of the Snelgrove ponds. Kellicott (1899) states that "the female oviposits among floating Utricularia, algae and stems of aquatics." On one occasion we saw a female on a small quiet stream near Toronto descend the stem of some standing aquatic plant, ovipositing as she went down, until she was a foot or more below the surface. After a few minutes of submersion she came to the surface again, but was unable to free her wings from the surface film. We recall watching two individual females, neither accompanied by a male, oviposit in this fashion, but apparently have no record of the event.

232

THE ODONATA OF CANADA AND ALASKA

Enallagma minusculum Morse. (PI. 17, fig. 7; pi. 24, fig. 9; pi. 28, fig. 9) Enallagma minusculum Morse, Psyche, 7:207, 1895 ( $ ); Carman, Bull. 39, Conn. Geol. and Nat. Hist. Surv., p. 77 ( $ $ ). A small species of the Atlantic seaboard, very limited in range, resembling the species hitherto described in colour-pattern. Male. Similar to ebrium and hageni in appearance, but smaller, readily distinguished from either by the form of the sup. apps,, which are neither deeply bifid nor tapering, as seen in profile. Blue and black, the blue predominating and the pattern very similar to that of the species just mentioned. Head hairy, particularly on the frons and face; black above, with the postocular spots rather small, subtriangular or rounded, isolated, the occipital cross-bar being absent in the specimens at hand; face below bases of antennae pale (blue in life ?), except the postclypeus, which is black, pale-margined; labrum, labium, and rear of head pale yellowish. Pronotum black, pale on the sides, and with a rather pale spot on the anterior lobe; middle lobe without dorsolateral spots, and posterior lobe wholly black, very narrow. Ptcrothorax marked as in hageni', median width of antehumeral stripes hardly more than half that of the median stripe; humeral stripes widest just behind the mesocoxae, tapering evenly caudad, their middle width about equal to that of the antehumeral stripes; sides of pterothorax pale blue, without black markings, except a short spur at the posterior end or the second lateral suture, and the ante-alar ridges in part. Venter of thorax and bases of legs more or less whitish pruinose in adults. Coxae pale, with one or two darker smudges at base; troehanters and femoral bases with a dark spot on each articulation; femora with anterior and dorsal surfaces black or dark grey except at extreme base; tibiae pale, with ventral surface black; tarsi pale, darkened at the articulation, and tips of claws. Abdomen blue, with the black spots averaging a little larger than in hageni and ebrium, their front margins truncate or even slightly concave but often slightly angulate on segs. 6 and 7; the spot on 2 usually covering the posterior half of the dorsum and confluent with the apical annulus; on 3-7 occupying the following proportions of the seg. length: 3-two-fifths to one-half, 4—one-half to three-fifths, 5—one-half plus to two-thirds, 6—two-thirds to fourfifths, 7—four-fifths to seven-eighths; segs. 8 and 9 blue, 8 sometimes with obscure dark smudges; 10 black, with venter sometimes pale. Pt. dark smoky brown. Sup. apps. about as long as inf. apps., very massive, in profile twice as high as long, divided into a large black flaring proximal part, terminating dorsally in an angle, and a paler rounded distal part, the very large tubercle, which is marked off by a notch from the dorsal angle. Viewed from above, the sup. apps. resemble those of ebrium, but the black dorsal portion is now seen to terminate in a smaller and much more sharply hooked distal extremity, while the tubercles extend beyond the tips of the dorsal portion and, mesad of them, the projecting tips of the ventral part may be seen. Female. Of various shades of greenish, greenish grey, greyish olivaceous, or pale buff, the colours of dried specimens appearing like those of heterochromatic specimens of E. hageni or ebrium, the greenish tones being doubtless much more distinct in the living insect. Carman (1927) states that the female is coloured like the male, and homocochromatic females probably exist, but none of the specimens we have seen are definitely of this type. Dorsum of head black, postocular spots variable, sometimes small and rounded, sometimes subtriangular or comma-shaped, with a very narrow occipital crossbar; face below bases of antennae pale, except the black postclypeus; rear and underside of head pale yellowish. Prothorax black, anterior lobe largely white, posterior lobe narrowly edged with white; sides below level of humeral line pale. Pterothorax dorsally green-black, including median carina; ante-alar stripes nearly uniform in width, narrower than the black humeral stripe; mesostigmal laminae black, with a light spot at the lateral ends; humeral stripe about half as wide as the median dorsal stripe, somewhat expanded above the cross-suture and at the extreme anterior end, narrowed at the posterior end.

THE ZYGOPTERA—DAMSELFLIES

233

Sides of ptcrothorax pale, almost without dark markings; ante-alar ridge black in front of the first lateral suture. Legs pale, femora marked as in male, but the black areas sometimes very narrow; .'interior surfaces of tibiae with a black stripe; tarsi brownish, with tips of segments black. Abdomen chiefly green-black above, pale on the sides; seg. 1 with black spot covering dorsum and widely connected with the black intersegmcntal line, which extends somewhat farther ventrud; seg. 2 with a broad black stripe covering dorsum, widening often angularly just behind the middle, and notched laterally in front of the apical cross-bar; segs. 3-10 black above, pale lateroventrally, the black continuous along median line and narrowed only at the extreme bases of segs. 3-8 by the dorsal extensions of the pale lateral areas, with slight ante-apical expansions on segs. 3-7. Mesostigmal laminae delimited posteriorly by a well-marked suture, contracted in the middle and somewhat expanded and rounded at the lateral ends, which in oblique dorsal view appear prominent, being bent upward; base of median carina not fused with lateral carinae of frame, which arc posteriorly divergent; median pit small, at the bottom of a broad concavity. Legs short, hind femora extending back only to the middle of seg. 1. Described from numerous specimens received from Dr. D. J. Borror. Poslnodal cross-veins, f. w. $ 9-11, 9 10-11; h. w. , ss£££±S£,M

"TSrJrtS.'VK.-S £MS±±raftJU

caudal lamellae, 29, 48, 62, 81, 117, 121, ECLOSION, 46 189, 191, 253 egg parasites of Odonata, 55 Centrodea odonatae, 56 eggs, hatching, 46 Ceratopogonidae, 57 number deposited, 45 cercoid, 27 overwintering, 46 Chapman, R. N., 32 emergence of adult dragonflies, 51 Chromagrion, generic characters, 157 Enallagma, generic characters, 187 species, conditum, 34, 36,157 key to species, females, 193 nymph, 159 males, 191 clypeus, of adult, 6 nymphal characters, 188, 189, 191 of nymph, 25 nymphs (with Coenagrion), 196 Coenagriidae, characters, 117 parasitized by Arrenurus, 56 key to genera, adults, 117 species, antennatum, 34, 240 nymphs, 119 nymph, 241 oviposition, 43 aspersum, 242 Coenagrion, generic characters, 173 boreale, 213 key to species, females, 175 nymph, 214 males, 173 carunculatum, 34, 35, 200 nymphs (with Enallagma), 196 nymph, 201 species, angulatum, 183 civile, 205 nymph, 184 nymph, 207 interrogatum, 180 clausum, 209 resolution, 175 36 nymph, 176 nymph, 210 compound eyes, changes during growth in, cyathigerum, 217 47 nymph, 218 coot, as enemy of nymphs, 54 ebrium, 228 copulation of Odonata, 19, 41 nymph, 229 Cordulegaster, 29, 39 exsulans, 34, 236 oviposition, 44 nymph, 237 ovipositor, 44 geminatum, 233 Cordulia, 38 nymph, 234 egg envelope of, 44 hageni, 225 nymphal period, 49 nymph, 226 Corduliidae, 29, 38 minusculum, 232 emergence, 51 signatum, 36, 248 high flight, 36 nymph, 249 costa, 13 vernale, 221 coxae, 8 nymph, 222

INDEX vesperum, 36, 245 nymph, 246 end-hook, 6, 25 enemies of dragonflies, adults, 52 nymphs, 53 Epteordulia, flight, 36 epiproct, 27 Erythemis simplicicollis, length of Me cycle, 49 Erythrodiplax berenice, in saline waters, 35 Eulophidae, parasitic on Odonata, 56 exuvia, exuviae, 52 FEDERLEY, H., 37, 38 femur, femora, 9 fenestra, 21 fish, as enemies of nymphs, 53 fish fry, devoured by nymphs, 51 flight of Odonata, 36 food, influence on length of nymphal life, 48 of Odonata, 38 frame, 8 frogs, as enemies of Odonata, 53 frons, 6, 25 Fudakowski, J., 219 GARDNER, A. E., 46, 47 Carman, P., 54, 135, 141, 160, 191, 209, 228, 231, 236, 247, 251, 256, 257, 261, 278 genital fossa, 21 genital valves, 23 genitalia, accessory, 21 female, 22 male, 19 gills, 29 glans, 21, 22 Gloyd, L. K., 165, 219, 223, 224, 226 Gomphidae, antennae, 6, 28 nymphs, 28, 29 Gomphus, devoured by Hagenius, 39 emergence, 51 flight, 36 nymphal period, 49 gonapophyses, anterior, 22 lateral, 23 posterior^ 23 grebes, as enemies of nymphs, 54 Grieve, E. G., 46, 49, 261 HABITATS, 32

saline, 35

289

Hagenius brevistylus, 28, 34, 39, 53 hamules, 22 hamuli, anterior, 21 posterior, 22 hawks, as enemies of Odonata, 53 head, external features, 5 Hemiptera, enemies of nymphs, 55 Hetaerina, generic characters, 76 nymphs, 77 species, Hetaerina americanay 62, 77 nymph, 30, 79 Heymons, R., 27 hook, movable, 6, 26, 29 hooks, dorsal, 26, 29 Hydrophylax aquivolens, 56 Hyperteles polynemae, 56 INCUBATION PERIOD, 45 instars, number, 48 intersternal membrane, 7 intersternum, 7 Iris versicolor, damaged by Lestes, 43 Ischnura, generic characters, 251 key to species, females, 254 males, 253 nymphs, 252 parasitized by Arrenurus, 56 species, cervula, 35, 36, 264 nymph, 266 damula, 268 nymph, 270 erratica, 272 perparva, 35, 261 nymph, 263 posita, 255 nymph, 256 verticalis, 257 developmental period, 49 nymph, 259 JONES, J. C., 54 KELLICOTT, D. S., 80, 132, 145, 148, 231, 236, 250 Kennedy, C. H., 8, 34, 35, 96, 151-3, 155-7, 187, 204, 211, 212, 250, 251, 263-5, 267, 268, 272-74 Klugh, A. B., and E. G. McDougall, 267 Krufi, W. H., 46 Kubichek, W. F., 54 LABIAL MASK, 25, 28

labial nalni. 25

290

INDEX

labium, 6, 28 changes during growth, 48 function of nymphal, 26 lateral lobes of, 25 labrum, 6, 25 lagoon, beach, 33 Lamb, L., 46, 47,49, 50 Lanthus, 34 lakes, as dragonfly habitats, 33 lamina, anterior, 21 posterior, 22 supra-analis, 27 laminae subanales, 27 lateral anal appendages, first appearance of, 48 legs, 8 Leonard, M. D., 141 Lestes, diapause in embryos, 46 flight, 36 generic characters, 81 habits, 81 key to species, females, 84 males, 83 nymphs, 85 parasitized by Arrenurus, 56 species, congener, 93 nymph, 93 disjunctus, 104 australis, 109 disjunctus, 104, 105 nymph, 107 dryas, 48, 100 nymph, 101 eurinus, 87 nymph, 87 forcipatus, 111 inequalis, 92 rectangularis, 113 nymph, 115 unguiculatus, 96 nymph, 97 vigilax, 89 nymph, 91 Lestidae, characters, 80 Leucorrhinia, nymphs feeding on salmon

MABBOTT, D. C., 54 Macan, T. T., and E. B. Worthington, 32, 38 McAtee, W. L., 54 McDunnough, J., 88, 244, 245 M'Lachlan, R., 219 Macromia, 34 Macromia illinoiensis, 34, 54 Macromiinae, nymphs, 28 mandibles, 6, 25 Marshall, Ruth, 56 Martin, R. D. C., 46, 72, 75 Matheson, R., and C. R. Crosby, 56 mating of Odonata, 39 maxillae, 6, 25 media, 13 median space, 13 membranule, 9 mentum, 6, 25, 28 Merriam, C. H., 267 mesepisternum, 7 mesinfraepisternum, 8 inesonotum, 7 mesostigma, 8 mesostigmal laminae, 8, 19 mesothorax, 3 metanotum, 7 mctastigma, 8 metathorax, 3 metinfraepisternum, 8 migration, 37 molar process, 6 Montgomery, B. E., 96, 111, 112, 116, 135, 139, 141, 145, 148, 209, 228, 231, 236, 239, 242, 245, 247, 251, 257, 277, 278 Moore, J. E., 211-13 Morgan, A. H., 245 Munchberg, P., 44, 49, 55, 56 Munz, P., 11

Leucorrhinia frigida, 33 Libellula pukhetta, oviposition, 43 Libellula quadrimaculata, in migration, 37 Libellulidae, 29, 34 ligula, of labium, 7 of penis, 21 lobe of labium, lateral, 6, 25, 29 middle, 7

Nannothemis bella, 33 nymphal period, 50 Neal, Morley, 115 Needham, J. G., 11, 15, 43, 46, 81, 88, 89,100,104,135,276, 277 Needham, J. G., and A. B. Heywood, 45, 53, 67, 79, 135, 160, 245, 272, 276, 277

fry, 51

lobes, genital, 22 postocular, 25 Longfield, C., 38 Lyon, M. B., 53

INDEX Nehalennia, generic characters, 167 key to species, adults, 167 nymphs, 168 species, irene, 168 nymph, 168, 169 gracilis, 33, 171 nymph, 171 Nepidae, as enemies of nymphs, 55 Neurocordulia, 37, 39 Nevin, F. R., 49, 71, 72 nodal line, 31 nodus of caudal lamella, 31 of wings, 5 nymph, of Anisoptera, 28 of Odonata, 23 of Zygoptera, 29 nymphal instar, first, 47 nymphal instars, characters of, 47 nymphal life, length of, 48, 49 nymphs, enemies, 53 food and feeding habits, 50 general features, 23 OCCIPUT, 6 Octogomphus, 34 Odonata, definition, 3 key to suborders, 61 Ophiogomphus, 29, 34 Osburn, R. C., 35, 204, 209 oviposition, endophytic, 42 exophytic, 43 ovipositor, 22, 23 Pachydiplax longipennis, parasitized by Arrenurus, 56 Pantala, flight, 36 Pantala flavescens, life cycle, 49 Pantala hymenea, 33 Paramoecium, as food for young nymphs, 50 paraproct, 27 parasites of Odonata, 55 patrolling of dragonflies, 39 Petalura gigantea, nymphal habitat, 32 Pearse, A. S., 35 penis, 21, 22 petiolate wings, 9 pit, median, 8 pleura of nymph, 26 shifting of pterothoracic, 7 ponds, 32 postclypeus, 6 Prestwichia solitaria, 55 pronotum, 7

291

pronymph, 47 prothoracic processes, 26 prothorax, 7, 26 pruinosity, 42 pterostigma, 5, 11 pterothorax, adult, 3, 7 nymph, 26 pyramid, anal, 27 QUADRANGLE, 17 quadrilateral, 17 RADIUS, 12, 13 rami, of median carina, 8 Rawson, D. S., 211-13 Rempel, J. G., 213 respiration, rectal, 27, 31 Ricker, W. E., 156,165, 215, 220 robber-flies, as enemies of damselflies, 53 Robert, Adrien, 88, 169, 220, 247, 248 SALINE HABITATS, 35 Schmidt, E., 21, 219 sector, of arculus, 14 median, 17 radial, 12, 14 setae, lateral, 29 mental, 28 setose margin, 31 Shafer, G. D., 46 slough, 33 Smith, M. E., 271 shore birds, as enemies of nymphs, 54 Somatochlora, egg envelope, 44 species, franklini, 38 kennedyi, nymphal period, 49 winter diapause of egg, 60 metallica, oviposition, 44 williamsoni, oviposition, 44 Sperry, C. G., 55 spiders, as enemies of Odonata, 53 spine, lateral, 26, 29 spring bogs, as habitats, 34 squamae, 6 stalked wings, 9 sterna, nymphal, 26 thoracic, 7 sternum, 18 streams, as habitats, 34 stylus, 23 subcosta, 12,13 submentum, 6, 25 subnodus, 14 subtriangle, 15

292

INDEX

sundew, as enemy of damselflies, 53 sunshine, activity of Odonata in, 36 supplement, 12 supracoxal armature, 28 supratriangle, 15 sutures (cross, humeral, intersegmental, lateral, mesopleural, metapleural, pleural),7-8 Sympetrum, parasitized by Arrenurus, 56 species, costiferum, opposition, 44 flaveolum, immigrant to Britain, 38 fonscolombei, immigrant, 38 internum, 49 obtrusum, 49 irregular incubation, 46 striolatum, in migration, 38 vicinum, life cycle, 49 oviposition, 44 synthorax, 3, 7 TEMPERATURE, influence on nymphal development, 48 temporary ponds, as habitats, 32 teneral stage, 35 tenerals, destruction by birds, 52 terebra, 23 terga, thoracic, displacement in nymph, 26 tergum, 18 Tetragoneuria, egg-masses, 44 flight, 36 species, canis, 44 cynosura, 38 spinigera,3S thorax, 7 changes during growth, 48 tibiae, 9 Tillyard, R. J., 11, 15, 17, 32, 41, 46, 52, 55 tracheae, nymphal (anal, costal, cubital, median, radial, subcostal), 12-13 Tramea, flight, 36 triangle, 13,15 anal, 13 internal, 15 Trichogrammidae, parasitic on Odonata, 55, 56 trochanter, 9

VEINS, of adult wing (anal, costal, cubital, median, oblique, radial, subcostal), 12, 13-14 cross-, 11 longitudinal, 11 venation, 11 venter, thoracic, 7 vertex, 6 vesicle, of penis, 21 vulvar lamina, 23 WADING BIRDS, as enemies of nymphs, 54 Walker, E. M., 35, 41, 44, 95, 152, 172, 204, 251 Walker, E. M., and W. E. Ricker, 156, 165, 221, 264, 274 Wallis, J. B., 270 Warren, A., 49 wasps, as enemies of damselflies, 53 water-mites, parasitic on Odonata, 56 Watson, W. Y., 224 weather conditions, destruction of dragones by, 53 Wesenberg-Lund, C., 49 Westfall, M. J., 137,140 Wetmore, A., 54 Whedon, A. D., 164, 209 White, H. C., 76 Whitehouse, F. C., 49, 95, 103, 108, 152, 156, 165, 167, 180, 205, 212, 213, 216, 219, 220, 221, 231, 264, 272, 274 Williamson, E. B., 3, 71, 96, 139, 141, 143, 145, 152, 236, 244, 250, 251 Wilson, C. B., 139, 143 wing-cases, wing-pads, 26 wings, 9 changes during development, 48 Woodruff, L. B., 76 Wright, M., 35 ZYGOPTERA, definition, 3 distribution in Canada and Alaska, 62 key to families, adults, 62 nymphs, 62 nymphs, 29