Aquatic Insects of California: With Keys to North American Genera and California Species [4th printing, Reprint 2020 ed.] 9780520320390

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Aquatic Insects of California

Aquatic Insects of California W I T H KEYS T O

W. C. BENTINCK H. G. CHANDLER

N O R T H AMERICAN GENERA

W. C. DAY

AND C A L I F O R N I A

K. S. HAGEN

SPECIES

D. G. DENNING

S. G. JEWETT, JR. W. H. LANGE, JR. IRA LA RIVERS J. D. LATTIN

Edited by ROBERT L. USINGER

H. B. LEECH A. E. PRITCHARD D. B. SCOTT, JR. R. F. SMITH ALAN STONE R. L. USINGER W. W. WIRTH

U N I V E R S I T Y

O F

B E R K E L E Y ,

A N G E L E S ,

LOS

C A L I F O R N I A L O N D O N

P R E S S •

1971

University of C a l i f o r n i a

Press

Berkeley a n d Los A n g e l e s , C a l i f o r n i a

University of C a l i f o r n i a Press, Ltd. London,

England

Copyright

195(5

By The Regents of the University of C a l i f o r n i a Fourth ISBN:

Printing,

1971

0-520-01293-3

M a n u f a c t u r e d in the U n i t e d States of A m e r i c a

To Harry Phylander Chandler Whose untimely death during the preparation of this work deprived us of an esteemed colleague and close friend.

Preface Aquatic entomology is a large and diverse s c i e n c e . It partakes of many fields and, in its applied a s p e c t s , is pursued by persons with quite unrelated interests and o b j e c t i v e s . Specialists in mosquito control, for example, are not directly concerned with problems of stream and lake management for the production of fish, and limnologists generally are inclined to s t r e s s physical and chemical studies and plankton investigations rather than trying to deal with numerous and imperfectly known i n s e c t s . It is the purpose of this study to point out the central role of i n s e c t s in aquatic situations, to bring to bear on insects the basic concepts and tools of limnology, and to provide keys and illustrations to aid in the identification of aquatic i n s e c t s . It is probably this last aspect of the subject that has been the greatest stumbling block to progress in the p a s t . I n s e c t s comprise about four-fifths of the Animal Kingdom, and only time and intensive research can overcome the obstacle of such numbers of s p e c i e s . B e c a u s e of limitations of time, space, and s i z e it has been necessary to restrict the treatment at the s p e c i e s level to California and adjacent regions. However, the California fauna is fairly representative of much of the western United States because of the diverse elements that are included within the geographical boundaries of the state. At the generic level a more comprehensive treatment was f e a s i b l e , so keys are given to all the genera known from North America. Most books are the result of the work of many people, and this is particularly true of the present volume. It is a direct outgrowth of University of California Syllabus SS Biology of Aquatic and Littoral Insects (Entomology 133, by R. L. Usinger, Ira La Rivers, H. P . Chandler, and W. W. Wirth, University of California P r e s s , 1948), now out of print, which was tested in the laboratory and in the field and was used for several years in c l a s s e s at various institutions in the West. The syllabus was frankly a compilation of existing knowledge with comparatively little original work. It was meant to be a one-volume working " l i b r a r y . " Now, after eight years, it can be said that the objectives of the syllabus have been realized. Extensive collections have been gathered from all parts of the s t a t e , and s p e c i a l i s t s have devoted much time and effort to each group. The

results are offered at this time as original contributions, each chapter written by an authority who is most intimately acquainted with our fauna. Illustrations have been added to clarify the text, and a glossary explains the technical terms that are not understandable from the figures. Much remains to be done in every group, but it can now be said that we have a sound foundation on which to build.

Acknowledgments The editor is personally grateful to the group of distinguished collaborators, each of whom has given generously of his research time to make this volume p o s s i b l e . We are indebted a l s o to all those students who have contributed to the store of knowledge on aquatic i n s e c t s , a rich heritage from which we have drawn heavily. Detailed acknowledgments are given in each chapter and on nearly every page, but a few persons or institutions have contributed so extensively that they are deserving of special mention here. For advice and a s s i s t a n c e in the introductory s e c t i o n s , thanks are due to Paul R. Need ham (general principles, stream and lake management); F . R. Pitelka (ecology); R. F . P e t e r s , J . R. Walker, A. C. Smith, and T. D. Mulhern in the Bureau of Vector Control, State Department of Public Health (mosquito control); E. A. Smith and E. H. Pearl of the Santa Clara County Health Department (mosquito control); W. R. Kellen, Research Entomologist, U.S.P.H.S. grant for study of insects in relation to sewage disposal; and Dana Abell, National Science Foundation Fellow (stream classification). Many of the suggestions of the above-mentioned s p e c i a l i s t s have been incorporated, but it should be made clear that the author alone is responsible for the final version. Valuable a s s i s t a n c e was furnished in the final preparation of the manuscript by the following: J . D. Lattin (photographic copy of illustrations), W. C. Bentinck (glossary), and Jon Herring (index). For fundamental works in taxonomy, we are indebted to Dr. J . G. Needham and his colleagues and students at Cornell University, and to the late S. A. Forbes and T. H. Frison and to H. H. R o s s and others at the Illinois Natural History Survey who have done v¡¡

vi ü Preface so much to further our knowledge of the aquatic insects of North America. Taxonomic work represents the fruition of the labors of countless collectors and curators. In California, f i e l d work and collections are recent, as compared with many parts of the world, but are nonetheless impressive. T h i s work is based largely on the collections of the University of California Insect Survey ( B e r k e l e y ) , the University of California collections at D a v i s , L o s A n g e l e s , and Riverside, the California Academy of Sciences (San Francisco), the L o s A n g e l e s Museum, the San D i e g o Museum, and the personal collections of the authors. Thanks are due to the curators in charge of these collections, and e s p e c i a l l y to E. S. R o s s , J. N. Belkin, P . D. Hurd, and A . T . MacClay. The illustrations may very well prove to be the most useful part of this book. Acknowledgment is given for each borrowed figure by citation in the legend and by listing the original work in the bibliography at the end of each chapter. Original drawings are mostly by Mrs. C e l e s t e Green of the Department of Entomology and Parasitology, University of California, Berkeley (introduction and chapters 4, 10, 11, and 13) and by Arthur Smith, at the British Museum (Natural History) (chapter 7). Photographic work in connection with illustrations was done by J. D. Lattin and W. C. Bentinck. Several chapters have been read and improvements suggested by Jon Herring. For permission to use copyrighted figures we are indebted to the following publishers and authors: University of Toronto P r e s s , E. M. Walker, The Odonata of Canada and Alaska, 1953; Pennsylvania Fish Commission, K . F . L a g l e r , Freshwater Fishery Biology; John Wiley & Sons, Inc., G. C. Whipple, The Microscopy of Drinking Water, 4th ed., 1927; The Macmillan Company, E. 0 . E s s i g , College Entomology, 1942; Lane Publishing Company, Sunset Magazine; University of California P r e s s , E . S. R o s s , Insects Close Up, 1953; Institute for Fisheries Research, Michigan

Berkeley, California June 12, 1956

Department of Conservation, C. L . Hubbs and R . W. Eschmeyer, The Improvement of Lakes for Fishing. A Method of Fish Management, 1938; C. WesenbergLund, Biologie der Süsswasserinsekten; The Macmillan Company, E . 0 . E s s i g , Insects of Western North America, 1926; Entomológica Americana, A . G. Boving and F . C. Craighead, An Illustrated Synopsis of the Principal Larval Forms of the Order Coleoptera, 1931; Ohio State University, D. J. Borror and D. M. Delong, An Introduction to the Study of Insects, 1954; Ohio State University, Alvah Peterson, Larvae of Insects; University of Toronto P r e s s , F . Ruttner, Fundamentals of Limnology, 1953; A . S. Barnes and Company, J. Edson Leonard, Flies, 1950; Comstock Publishing Company, Inc., J. G. Needham, J. R . Traver, and Yin-Chi Hsu, The Biology of Mayflies, 1935; Comstock Publishing Company, Inc., R . Matheson, Handbook of the Mosquitoes of North America, 1944; The Ronald P r e s s Company, R. W. Pennak, Fresh-water Invertebrates of the United States, copyright. 1953; W. B . Saunders Company, E . P . Odum, Fundamentals of Ecology, 1953; American Museum of Natural History, C. H. Curran, The Families and Genera of North American Diptera; Ward's Natural Science Establishment, Inc., How to Make an Insect Collection; Scientific American, Inc., articles by E . S. D e e v e y , Jr. and Ralf E l i a s s e n ; McGraw-Hill Book C o . , Inc., R. E . Snodgrass, Principles of Insect Morphology, 1935; McGraw-Hill Book Company, Inc., P . S. Welch, Limnology, 1952; Methuen and Company L t d . , N. E . Hickin, Caddis, a short account of the biology of British Caddis flies with special reference to the immature stages, 1952; University of California P r e s s , J. G. Needham and M. J. Westfall, Jr., A Manual of the Dragonflies of North America, 1955; Charles C. Thomas, Publisher, P . W. C l a a s s e n , Plecoptera Nymphs of America (North of Mexico), 1931; Charles C. Thomas, Publisher, J. G. Needham and II. B. Heywood, A Manual of the Dragonflies of North America, 1929; University of Florida, F . N. Young, The Water Beetles of Florida, 1954.

Robert L . Usinger

Contents

INTRODUCTION A. Principles and Practices

Robert L. Usinger

B. Equipment and Technique

3

John D. Lattin

50

1. STRUCTURE AND CLASSIFICATION

William C. Bentinck

68

2. AQUATIC COLLEMBOLA

David B. Scott

74

3. EPHEMEROPTERA

Willis C. Day

79

4. ODONATA

A. Earl Pritchard and Ray F. Smith

106

5. AQUATIC ORTHOPTERA

Ira La Rivers

154

6. PLECOPTERA

Stanley G. Jewett, Jr.

155

7. AQUATIC HEMIPTERA

Robert L. Usinger

182

8. MEGALOPTERA

Harry P. Chandler

229

9. AQUATIC NEUROPTERA

Harry P . Chandler

234

10. TRICHOPTERA

Donald G. Denning

237

11. AQUATIC LEPIDOPTERA

W. Harry Lange, Jr.

271

12. AQUATIC HYMENOPTERA

Kenneth S. Hagen

289

13. AQUATIC COLEOPTERA

Hugh B. Leech and Harry P. Chandler

293

14. AQUATIC DIPTERA

Willis W. Wirth and Alan Stone

372

GLOSSARY

483

INDEX

489

Aquatic Insects of California

Introduction to Aquatic Entomology A.

Principles and Practices

By Robert L .

Usinger

U n i v e r s i t y of C a l i f o r n i a ,

Berkeley

the end of the Paleozoic era (200 million years), and all subsequent evolution was confined to modifications of these basic patterns of structure and development. At the end of the Paleozoic and during the Mesozoic and Cenozoic eras representatives of many modern groups of insects took to the water. The exact sequence is not known, but probably the stoneflies were among the earliest with dobsonflies, b e e t l e s , and true bugs not far behind (Permian, 220 million years). Caddisflies, true flies, and parasitic wasps first appear in the very fragmentary record much later ( J u r a s s i c , 160 million years), and the Lepidoptera not until early Tertiary (60 million years). (See Carpenter, 1953, for a summary of information on the geological history of i n s e c t s . ) Furthermore, it seems certain that each of the large orders (Coleóptera, Diptera, e t c . ) invaded the water not once but several times. As Miall (1895) puts it, " I think we can say with a considerable degree of probability that this change of habitat from terrestrial to aquatic has taken place in the c l a s s of insects at l e a s t a hundred times quite independently, It is thought that aquatic insects were derived from and the number may be very much higher than a hununknown terrestrial types which invaded the water on dred." As a result we have a most amazing variety several occasions during the course of their evolution. of insects occupying aquatic habitats, many with a The first record is of mayflylike insects of the now superficial similarity in form owing to the highly extinct order Paleodictyoptera. T h e s e appear suddenly selective environment but each group with unique in the geological record in rocks of the Upper Carbon- methods for performing essential life functions. iferous period. At this remote time, 250 million years At present, ten orders of insects have truly aquatic ago, the first winged insects had complete mastery forms, and several others may be described as semiof the air because no bird, bat, or flying reptile had aquatic, at l e a s t in part. All these except the beetles yet developed to challenge them. The subsequent and true bugs live on land or in the air as adults and history of aquatic insects (and terrestrial forms, as in the water only in their immature stages. In contrast well) was one of increasing diversity. F i r s t a wing- to this, most water bugs and beetles are aquatic folding device rendered all higher insects (Neoptera) throughout their lives but are directly dependent on more efficient in flight than the dragonfly and mayfly surface air for respiration a s adults. Thus it can be types (Paleoptera). Second, the direct method of said that despite their great numbers and remarkable development through s u c c e s s i v e instars with external diversity, insects are only secondarily and incomwing pads (stoneflies, true bugs) was improved by pletely adapted to aquatic life. This probably accounts the adoption of a more indirect series of stages with for their prevalence in shallow ponds and streams, larvae specialized for feeding, pupae for transforma- their scarcity in very large rivers and deep lakes, tion, and adults for reproduction. Wing pads develop and their virtual absence from the open waters of internally in such larvae. T h e s e advances came before the ocean.

Insects are generally the most conspicuous forms of life in ponds and streams and occur in tremendous numbers in such unlikely places as the bottoms of lakes. No other group of animals shows such diversity in structure and habits. And yet, aquatic insects fall into a pattern, each major group (order, family, or genus) occupying a particular habitat with s p e c i e s represented on each of the continents. Thus a stream in South Africa may resemble a stream in California, each having its own representatives from among the stoneflies, mayflies, caddisflies, and so on. Likewise, a pond in Sumatra and a lake in Sweden will resemble, in a general way, comparable bodies of water in North America. This same phenomenon is noted among the common genera of plankton organisms. However, many of the plankton species are cosmopolitan whereas aquatic insect species are usually limited in their distribution, with some species restricted to local oases in otherwise completely barren deserts. This leads to a multiplicity of insect species and, of course, provides the b a s i s for still greater diversity.

3

4 Usinger: Introduction R o l e of I n s e c t s in A q u a t i c C o m m u n i t i e s

In 1887 Stephan A. Forbes wrote an essay, " T h e Lake as a Microcosm," showing that a lake is essentially a self-contained or closed community. This concept is also applicable, though to a lesser extent, to ponds and even to larger streams. Each community of plants and animals is more or less attuned to its physical and biotic environment, and the various elements of which it is composed are integrated to form an ecosystem. Insects play an important but not a vital role in such systems. As dominant members of the littoral fauna, together with fishes, they are intermediate in position between the autotrophic or constructive elements (green plants) and such heterotrophic or destructive elements as the bacteria (intro, fig. 1.)

A

MW • 'Wsutoé mtrknH'

Fishes ' Littoral Fauna

Zooplankton

Heterotrophic Bacteria Autotrophic Littoral Flora

Autotrophic Phytoplankton

Iritro. f i g . 3. F o o d - c y c l e r e l a t i o n s h i p s in a lake ( L i n d e m a n , 1941).

Nutritive Substances in Solution or on the bottom Intro, f i g . 1. S i m p l i f i e d d i a g r a m of the d y n a m i c s of an a q u a t i c c o m m u n i t y . S o l i d a r r o w s r e p r e s e n t c o n s t r u c t i v e s t e p s ; dotted lines, reductive steps.

In the littoral fauna, insects such as mayfly nymphs and midge larvae serve as primary converters of plant materials into animal protoplasm. As pointed out by Elton (1947) such basic herbivores are "key indust r i e s " in a community and are usualLy small in size and large in numbers. Successive links in the food chains are larger and scarcer and are usually carnivorous. Essentially, the food chain concept is simple

I n t r o * . f i g . 2 . D i a g r a m of the f o o d c h a i n i n a p o n d . T h e c o n t i n u o u s a r r o w s s h o w t h e c o u r s e of i n o r g a n i c s a l t s a n d t h e b r o k e n l i n e s i n d i c a t e t h e i r c o u r s e after t h e y h a v e b e e n b u i l t up i n t o l i v i n g matter. a, p h y t o p l a n k t o n ; b, z o b p l a n k t o n ; c, w e e d - d w e l l i n g f a u n a ; d, bottom f a u n a ( M a c a n , M o r t i m e r , a n d W o r t h i n g t o n , 1 9 4 2 ) .

(intro. fig. 2) with relatively few links. In nature, however, the situation becomes much more complex, so much so that even in diagrammatic form it has been termed a food web or food cycle (intro. fig. 3). Insects enter into such a cycle as "browsers" and as "swimming predators" on plankton and on benthic organisms. Probably no two biotic communities are identical in every respect, but there are certain types that are characteristic of particular aquatic situations, and each of these types has a distinctive insect fauna. Three representative types are: 1. Lakes—with Chironomid larvae in the bottom ooze and Chaoborus larvae that prey on plankton and perform diurnal migrations from the bottom mud to or near the surface. A varied insect fauna also occurs in the shallow littoral waters of lakes but such forms, with few exceptions, are more characteristic of shallow ponds than of lakes. 2. Ponds—with a large and varied insect fauna including midge larvae in the bottom and mayfly nymphs, caddis larvae, and others as basic herbivores together with numerous predatory beetles, bugs, and odonatan nymphs. Although dependent on the plankton and rooted vegetation, it can truly be said that pond insects are dominant forms of life in their limited environment. Furthermore, they are admirably suited to the uncertain conditions of pond life, with short life histories and ready means of dispersal. 3. Streams—with stonefly nymphs, mayfly nymphs, caddisfly larvae, and various midge larvae as basic herbivores—sieve feeders or grazers—and a host of predaceous forms. Here again, insects predominate and form the staple diet of most fishes.

5 Usinger: Introduction Adaptations of Aquatic Insocts All l i v i n g organisms are variously adapted for survival in their respective environments. Many adaptations are so commonplace that they are taken for granted. However, the requirements for e x i s t e n c e in aquatic habitats are s o rigorous that the adaptations are usually striking. T h e stream-lined form, as seen in certain f i s h e s and mayfly naiads of s w i f t - f l o w i n g streams, and the flattened body with suction d i s c s seen in Psephenid l a r v a e (waterpennies) and certain fly larvae (Blepharoceratidae, Deuterophlebiidae, Maruina) that cling to surfaces in rapids, are examp l e s . Other common adaptations, e s p e c i a l l y among adult aquatics, are reduction in s i z e of antennae which are concealed to reduce water resistance, development of powerful l e g s with swimming hairs, and presence of hydrofuge hairs or waxy surfaces to prevent wetting. T h e latter are particularly important at critical periods such as time of hatching of the egg and time of emergence of the adult. Without such adaptations the emergence of a delicate simuliid f l y from its pupal c a s e attached to a rock in s w i f t - f l o w i n g water would be impossible. Surface film.—The nature of the surface film i s of greatest importance to aquatic insects because of their amphibious e x i s t e n c e . T o an organism of small s i z e this air-water interface can be an impenetrable barrier, a surface on which to rest, or a c e i l i n g from which to hang suspended. A t the surface the water molecules are arranged in such a way that a surface tension i s created. T h i s can be demonstrated by a drop of water on a waxy surface (intro. f i g . 4). T h e angle

In nature the angle of contact usually results in a n e g a t i v e meniscus when the water surface i s in contact with the waxy surfaces of green plants with stems or l e a v e s extending above the water (intro. f i g . 5). T h i s soon changes to a p o s i t i v e meniscus, however, owing to the accumulation of wettable gelatinous materials or to the death of the plants and consequent l o s s of wax at the surfaces. T h e line of intersection between the three interfaces, water-air, water-plant, and plant-air, has been termed the " I n t e r s e c t i o n L i n e " by H e s s and H a l l (1945), and the number of meters of intersection line per square meter of water surface is c a l l e d the " I n t e r s e c t i o n V a l u e . " Insects are variously adapted to the intersection line or meniscus. Anopheles mosquito larvae, for example, are drawn head first toward a negative menis^ cus from a distance of 0 mm. by forces independent o f their own efforts (intro. f i g . 6) (Renn, 1943); the larvae of Dixa midges spend most of the time in p o s i t i v e menisci where the water surface meets a wettable surface such as a stone. Other i n s e c t s , such as water striders, are adapted to l i f e on the surface film where their hydrofuge (non-wettable) tarsi bend but do not break the surface.

Intro, f i g . 6. Diagram showing the pull of positive menisci at a wettable surface ( A ) on the upward-bent tail of a model Anophe/es and the reverse action on the downward-bent head. The e f f e c t s with respect to non-wettable surfaces are shown in B. The pull extends for a distance of 9 mm. (Renn, 1943).

Agnatic respiration.—Possibly because of their origin as terrestrial air breathers, insects have d e v e l oped the most remarkable adaptations for aquatic respiration. T h e s e include: ( 1 ) blood g i l l s with hemoglobin (chironomid larvae or bloodworms), ( 2 ) cuticular respiration by simple diffusion into the tracheal system (immature stages of most aquatic i n s e c t s ) , Intro, f i g . 4. Diagram to show the angle of contact, made by a drop of fluid on a waxy surface, where yS is the solid-air tension, yLS the liquid-solid tension, and yL the liquid-air tension (Thorpe and Crisp, 1947).

of contact Q under these circumstances i s 105°110°. Addition of soap or some other wetting agent to the water changes the angle of contact so that the bubble spreads across the wax surface.

Intro, f i g . 5. Diagram showing positive and negative menisci with respect to various emergent and floating objects. Stems that are " w e t t a b l e " pull the surface about them into upward slopes, or positive menisci, and stems that do not wet readily (with waxy surfaces) bend it downward into negative menisci (Renn, 1943).

liSij);

Intro, f i g . 7. o, Dryops freshly submerged, crawling along stem enclosed in its bubble; b-d, Ochthebius, dorsal, ventral, and lateral v i e w s of submerged Insect. The extent of the air film i s indicated by dotted lines in b and c, and by stippling in d. Wetted areas are black (Thorpe, 1950, in part after Hase).

6 Usinger: Introduction

Intro, f i g . 9. D i a g r a m s to i l l u s t r a t e the w e t t i n g o f : a, a s y s t e m of s h o r t , s t i f f , e r e c t h a i r s ; a n d b, c, a s y s t e m o f l o n g e r h a i r s b e n t to form a more or l e s s h o r i z o n t a l a n d c o m p r e s s i b l e mat ( T h o r p e and C r i s p , 1947).

I n t r o , f i g . 8. S u r f a c e r e s p i r a t i o n by w a t e r b u g s , a, fifth i n s t a r n y m p h o f Belostoma flumineum S a y ; b, fifth i n s t a r n y m p h of Notonecta undulata S a y ; c, a d u l t Ranatra fuse a P. B. (Maloeuf, 1936).

(3) tracheal gills that depend upon diffusion of dissolved oxygen from the water directly into the tracheal system (many aquatic larvae, mayfly naiads, e t c . ) , (4) respiration (intro. fig. 7) by means of an air bubble from which oxygen diffuses into the i n s e c t ' s spiracles and into which oxygen diffuses from the surrounding water (adult bugs and beetles), (5) direct contact with air in plant tissues by inserting tubes into the roots and stems of aquatic plants (beetle larvae of the genus Donacia, mosquito larvae of the genus Mansonia), and (6) contact with atmospheric air by breaking the surface with hydrofuge hairs or surfaces (intro. fig. 8a, b) (adult beetles and bugs) or with breathing tubes (intro. fig. 8c) (water scorpions, mosquito larvae, etc). Of all these, the most remarkable is the silvery bubble of adult beetles and bugs that serves as a gill, holding approximately 80 percent N and 20 per cent 0 2 when first formed at the surface. When the insect submerges, the oxygen in the bubble begins to decrease as it is used up, thus lowering the volume of the bubble and reducing the ratio of 0 2 to N. To compensate for this lower oxygen tension, oxygen diffuses into the bubble from the surrounding water, and since the invasion coefficient of oxygen between water and air is three times as great as that of nitrogen, the insect is able to remain submerged much longer (thirteen times as long in one experiment) than if it were dependent on surface oxygen alone (Comstock, 1887). Theoretically it is only when all the nitrogen has diffused outward that the system breaks down and new surface air is required.

The bubble of changing volume is held by hydrofuge hairs which lie more or l e s s parallel to the body surface in a compressible mat. The system is illustrated (intro. fig. 96 and c), showing the angle of contact, of water on the waxy surfaces of the hairs (Thorpe and Crisp, 1947). A few beetles (Dryopidae) and an old-world water bug (Afhelocheirus) have a plastron of fixed volume, maintained by stiff hairs of a density up to 2 million per square millimeter (intro. fig. 9a). Unlike the larger bubbles described above, the plastron is virtually incompressible and hence can act as a permanent gill or avenue of diffusion of oxygen from the water to the tracheal system. T h e s e are among the very few permanently aquatic insects that do not need to come to the surface at any time during their life cycle (Thorpe, 1950). Osmoregulation.—The regulation of osmotic pressure of body fluids is another important type of adaptation in aquatic insects. Many marine animals have body fluids that are isotonic with s e a water. All fresh-water organisms have some method of regulating the concentration of their body fluids. In the

Intro, f i g . 10. T e r m i n a l s e g m e n t s o f Culex pìpiens L . larvae s h o w i n g t y p i c a l a p p e a r a n c e of a n a l p a p i l l a e w h e n r e a r e d in m e d i a of i n c r e a s i n g s a l t c o n c e n t r a t i o n , a, l a r v a r e a r e d i n d i s t i l l e d w a t e r w i t h m e a n l e n g t h o f p a p i l l a e 0 . 8 2 mm; b, t a p w a t e r ( 0 . 0 0 6 per c e n t N a C I ) — 0 . 3 6 mm.; c, m e d i u m w i t h 0 . 0 7 5 per c e n t N a C I — 0 . 3 3 mm.; d, m e d i u m w i t h 0 . 3 4 per c e n t N a C I — 0 . 2 2 mm.; e, m e d i u m w i t h 0 . 6 5 per c e n t N a C I — 0 . 2 0 mm.; f, m e d i u m w i t h 0 . 9 0 per cent N a C I — 0 . 2 0 mm. ( W i g g l e s w o r t h , 1 9 3 8 ) .

7 Usinger: Introduction s i m p l e s t c a s e s an impervious body w a l l p r o t e c t s the i n t e r n a l fluids, and e x c e s s water and s a l t s o b t a i n e d with the food are e x c r e t e d ( m o s t adult b e e t l e s and b u g s ) . Wigglesworth ( 1 9 3 8 ) showed t h a t there i s a c o r r e l a t i o n in mosquito l a r v a e b e t w e e n s a l t c o n c e n tration o f the surrounding medium and d e g r e e o f d e v e l opment of the anal p a p i l l a e (intro. fig. 1 0 ) . L a r v a e reared in d i s t i l l e d water had w e l l - d e v e l o p e d p a p i l l a e ( f u n c t i o n a l hypertrophy for c h l o r i d e uptake), w h e r e a s l a r v a e reared in a medium with 0 . 9 0 per c e n t N a C l had g r e a t l y reduced p a p i l l a e . T h i s same phenomenon i s o b s e r v e d in nature where saltrmarsh m o s q u i t o e s are a b l e to adapt to varying d e g r e e s o f s a l i n i t y .

A q u a t i c H a b i t a t s in C a l i f o r n i a P r o b a b l y no a r e a o f equal e x t e n t in the world c a n c l a i m a g r e a t e r v a r i e t y of a q u a t i c h a b i t a t s than C a l i fornia. Spanning ten d e g r e e s of l a t i t u d e and n e a r l y 15 thousand f e e t in a l t i t u d e , the s t a t e o f f e r s p r a c t i c a l l y e v e r y kind o f a q u a t i c s i t u a t i o n e x c e p t the a r c t i c tundra and t r o p i c a l j u n g l e . T h e a v e r a g e annual p r e c i p i t a t i o n r a n g e s from 109 i n c h e s or more in p a r t s o f D e l Norte County on the north c o a s t to l e s s than 2 i n c h e s in D e a t h V a l l e y , and the c l i m a t e v a r i e s from c o o l and uniform along the c o a s t to e x t r e m e s o f h e a t and cold in the interior mountains and d e s e r t s . T o understand the p r e s e n t c l i m a t e and topography it i s n e c e s s a r y to know something of the g e o l o g i c a l h i s t o r y o f the s t a t e . E v i d e n c e from f o s s i l s (Camp, 1 9 5 2 ) s h o w s t h a t m o i s t c l i m a t e s p r e v a i l e d throughout m o s t of t h e T e r t i a r y ( 7 0 million y e a r s ) and that the p r e s e n t period i s o n e o f r e l a t i v e aridity. In the Miocene and P l i o c e n e , inland s e a s o c c u p i e d s u c h present>day d e p r e s s i o n s a s the C e n t r a l V a l l e y , the G r e a t B a s i n , and the southern C a l i f o r n i a d e s e r t s . In k e e p i n g with t h i s kind o f c l i m a t e redwoods were widely distributed over the w e s t e r n United S t a t e s , and a b r o a d - l e a v e d d e c i d u o u s f o r e s t o c c u r r e d in many p l a c e s . More r e c e n t l y the P l e i s t o c e n e g l a c i a l and p l u v i a l p e r i o d s (the l a s t a s r e c e n t a s 10 thousand y e a r s ) r e s u l t e d in a southward e x t e n s i o n of boreal f a u n a s and floras and r e t r e a t of the southern b i o t a s . U n l i k e the g r e a t i c e s h e e t o f the northeastern s t a t e s , Sierran g l a c i e r s were l o c a l , cutting c i r q u e s and gouging U-shaped v a l l e y s with terminal or l a t e r a l m o r a i n e s . T h e s e p r o c e s s e s , which are s t i l l going on to a limited e x t e n t , s e t the s t a g e for the g r e a t v a r i e t y o f l a k e s and s t r e a m s that a r e now s o c h a r a c t e r i s t i c o f the S i e r r a Nevada. R e l i c t g l a c i e r s and i c e c a v e s now s e r v e a s r e f u g e s for more northern p l a n t s and a n i m a l s , most of which r e t r e a t e d with the a d v e n t o f warmer, more arid c o n d i t i o n s . During this same period " p l u v i a l " l a k e s e x t e n d e d over wide a r e a s in the S o u t h w e s t (Hubbs and Miller, 1 9 4 8 ) . L a k e L a h o n t a n (including p r e s e n t - d a y l a k e s s u c h a s P y r a m i d and Walker in Nevada and arms e x t e n d ing into C a l i f o r n i a and Oregon) and L a k e Manly (including D e a t h V a l l e y and p a r t s of Inyo and S a n B e r n a r d i n o c o u n t i e s ) are e x a m p l e s . T h e s e f l u c t u a t e d from large inland l a k e s to dry play a s . Most o f the p l u v i a l l a k e s a r e now g o n e , but a few l i k e Mono L a k e

s t i l l p e r s i s t and o t h e r s , l i k e O w e n s L a k e , come and g o , depending on s u r f a c e and ground water f l u c t u a t i o n s . One o f the b e s t known o f the d e s e r t b a s i n l a k e s i s the S a l t o n S e a . I t s e e m s c e r t a i n that a t one time the G u l f o f C a l i f o r n i a e x t e n d e d northward over m o s t o f the Imperial and C o a c h e l l a v a l l e y s (intro. fig. 1 1 a ) . S u b s e q u e n t l y the C o l o r a d o R i v e r b u i l t up a s i l t dam (intro. fig. 1 1 5 ) , c r e a t i n g an a n c i e n t s a l t - w a t e r l a k e . T h i s l a k e had no o u t l e t and, l i k e many other inland w a t e r s o f the W e s t , e v e n t u a l l y dried up. S t i l l l a t e r , p o s s i b l y during a p l u v i a l period, the C o l o r a d o R i v e r c h a n g e d i t s c o u r s e , emptying into the dry b a s i n rather than into the G u l f , thus c r e a t i n g p r e h i s t o r i c L a k e C a h u i l l a (or L a k e L e C o n t e a s it i s s o m e t i m e s c a l l e d ) (intro. fig. 1 1 c ) . T h i s may h a v e p e r s i s t e d until the time of the e a r l y C a h u i l l a I n d i a n s , judging by a l e g e n d handed down to the p r e s e n t ( B l a k e , fide, Hubbs and Miller, 1 9 4 8 ) . In the l a s t s t a g e but one in the s t o r y , the C o l o r a d o R i v e r again s h i f t e d i t s c o u r s e and L a k e C a h u i l l a dried up. T h e n , in 1 9 0 5 , t h e river poured water into the b a s i n for a two-year period, forming the S a l t o n S e a which w a s 17 by 4 3 m i l e s in e x t e n t , 84 f e e t in maximum depth, and w e l l b e l o w s e a l e v e l . S i n c e 1907 i t s a r e a a t f i r s t s l o w l y d e c r e a s e d by evaporation and i t s s a l i n i t y i n c r e a s e d (intro. f i g . lid). Now irrigation water i s r e v e r s i n g the p r o c e s s . S i n c e the l a s t p l u v i a l period g e o l o g i c a l p r o c e s s e s throughout the s t a t e c o n t i n u e d a s in the p a s t , including upfaulting and s u b s i d e n c e o f l a r g e a r e a s , e r o s i o n , and v o l c a n i c a c t i o n . A s a r e s u l t water c o u r s e s were formed, dammed a t v a r i o u s p o i n t s by m o r a i n e s , l a v a f l o w s , or alluvium, and f i n a l l y r e a c h e d the s e a or d i s a p p e a r e d i n t o the underground water t a b l e or were l o s t through e v a p o r a t i o n . T h i s happened r e p e a t e d l y through time, the p r o c e s s e s b e i n g c o n t i n u o u s , s o t h a t our p r e s e n t a q u a t i c h a b i t a t s and the i n s e c t s t h a t i n h a b i t them are but a momentary s t a g e in p h y s i o g r a p h i c and b i o t i c e v o l u t i o n .

Stream and L a k e

Classifications

T h e r e have b e e n s e v e r a l a t t e m p t s by l i m n o l o g i s t s to c l a s s i f y s t r e a m s , l a k e s , and other a q u a t i c h a b i t a t s for p u r p o s e s o f e c o l o g i c a l a n a l y s i s . S u c h c l a s s i f i c a t i o n s are doomed from the s t a r t b e c a u s e they a t t e m p t to fit c o n t i n u o u s l y v a r i a b l e and e n d l e s s l y d i v e r s e s i t u a t i o n s into s t e r e o t y p e d s y s t e m s . N e v e r t h e l e s s , the urge to c l a s s i f y runs deep in human n a t u r e , and useful generalizations and c l e a r e r understanding have r e s u l t e d from c e r t a i n b r o a d l y b a s e d e c o l o g i c a l classifications. In C a l i f o r n i a the s t r e a m s and l a k e s are profoundly i n f l u e n c e d in form and distribution by the topography o f the land. T h i s i s o f c o u r s e a truism, but i t i s e s p e c i a l l y striking in r e g i o n s o f high r e l i e f . F o r p u r p o s e s o f a n a l y s i s Meyer ( 1 9 5 1 ) h a s divided the s t a t e into s e v e n major hydrographic a r e a s and numerous drainage b a s i n s , s u b b a s i n s , and stream g r o u p s . T h e b i o t a , too, i s determined to a l a r g e e x t e n t by topography which h a s l a r g e l y i n f l u e n c e d the migration o f floras and f a u n a s . T h e r e f o r e any stream or l a k e c l a s s i f i c a t i o n must take into a c c o u n t both p h y s i c a l

8 Usinger:

Introduction

San Gargonio P a M

Present C h o c o l a t e M t n s .

C o l o r a d o River

a Intro, (reprinted

and biotic evidence. The principal topographic and aquatic features of the state are shown on the accompanying relief map (intro. fig. 12). Essential features, from the viewpoint of an aquatic biologist, are the high mountain ranges surrounding the Central Valley, with drainage through the Carquinez Straits to San Francisco Bay; the coastal slopes on the west; and the southern California deserts with isolated mountain ranges. Faunistically, the picture is, of course, very complex, but certain broad generalizations have crystallized out of recent analyses of the best-known group of animals—the birds (Miller, 1951) (intro. fig. 13). In general, the pattern derived from birds can be applied directly to aquatic insects, the minor deviations being attributable to the special nature of aquatic habitats. The dominant fauna of the northern part of California and of the higher mountains in the south is boreal. This includes the barren alpine regions and the evergreen coniferous forests. It is similar to, and more or less continuous with, the widespread coniferous forests of northern North America and of the Rocky Mountains. Minor differences in California

f i g . 11. D i a g r a m m a t i c r e p r e s e n t a t i o n from Sunset Magazine, February,

are due to the heavy snow pack in the winter and the virtual lack of summer rains with consequent arid conditions, especially in the south. Intruding from the east are the Great Basin faunal elements, with important sections in Modoc and Lassen counties, along the desert slopes of the Sierra, and in the Owens Valley and Mojave Desert. A striking feature of this region is the relict southern fauna of the hot springs of Death Valley and adjacent parts of Nevada in the Amargosa River system. Southern elements in the aquatic fauna are now confined (except for the Death Valley relicts) to the Colorado drainage system. The Colorado River itself, with its oxbows, sloughs, and reservoirs, is a rich source of Sonoran and Neotropical types, and streams on the California side are strictly comparable to those of the nearby Gila Mountains in Arizona. The rest of the state, including the Central Valley, the south and central Coast Range, and the western foothills of the Sierra can best be called Californian. It is a region of winter rains and summer drought. It is not rich in aquatics but, because of its isolation and presumably also its age, is unique in character.

9 Usinger: Introduction

of the probable history 1952, c o p y r i g h t Lane

of the Saiton Sea Publishing Company).

T h e distinctions between these faunas (and f l o r a s ) are striking to the f i e l d naturalist but are only evident to the taxonomist after careful analysis of distributional patterns in particular groups. Such analyses must be based on extensive collections from all parts of the state, and it is unfortunate that such c o l l e c tions of aquatic insects have not y e t been made, except in a. few groups like the mosquitoes.

Streams General faunistic relations apply equally to streams, lakes, and other aquatic situations, but many other features are distinctive for each type of water. Streams are e s p e c i a l l y susceptible to outside influences and hence are infinitely variable. A s a result, our knowledge of streams has lagged far behind that of lakes. N e v e r t h e l e s s , certain generalizations have emerged from extensive field investigations, and i t may be useful to summarize these and see if they apply to California streams. Stream

habitats.—Ricker

(1934)

speaks

of

the

"overwhelming variety of habitats presented in streams and r i v e r s . " A t the same time, certain habitats occur repeatedly within any short section of a stream. For example, there are f a l l s , r i f f l e s , runs, and pools in nearly every stream in the world, and bottom habitats including boulders, rubble, gravel, sand, and mud. A l s o there are endless microhabitats, where each aquatic organism occupies a unique e c o l o g i c a l niche with preference for a particular side of a rock, for example, or finds other special conditions different for each stage in its l i f e c y c l e . T h e accompanying figure (intro. fig. 14) shows an assemblage of stream organisms as they might appear on a submerged rock in any stream. T h e s p e c i e s would be different for each part of the world, but the main groups or their e c o l o g ical equivalents would be the same. Stream habitats for Y e l l o w s t o n e National Park and other regions of the northwest were c l a s s i f i e d by Muttkowski (1929) as f o l l o w s : 1. Permanent habitats, with native (endemic) biota a. White water h a b i t a t s — f a l l s , cascades, white rapids b. Clear rapids and stone bottoms—on and under rocks

10

Usinger: Introduction

LOWER KLAMATH L .

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REDWOOl Y LAKE

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NAVARRO RI GARCIA RP

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iLKER RIV.

RÍV • IV.-V ¡TON RH. ÍARD R E ^ J ^ P Q I iT>Ht?CAUS RI V . J . XBRLOCK LAKE

PESCADERO W SAN L< .KINGS VER SLOUGH CARMEL R|

SANTA MARIA b j

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SANTA INEZ

:mm

IMPERIAL RES J i IJWJI.a iiES. BARRETT RES.

Intro,

•ALL AMERICAN CANAi

MORENO RES.

f i g . 12. R e l i e f map of C a l i f o r n i a s h o w i n g , i n a d d i t i o n t o m o u n t a i n r a n g e s a n d v a l l e y s , p r i n c i p a l l a k e s , r e s e r v o i r s , and river s y s t e m s (original d r a w i n g by C e l e s t e G r e e n ) .

the

DRAFT 1955 ¿ajlvtu

I n t r o , f i g . 13. B i o t i c p r o v i n c e s o f C a l i f o r n i a b a s e d o n a n a n a l y s i s o f t h e a n d f a u n a l r e l a t i o n s h i p s of the b i r d s (after M i l l e r , 1 9 5 1 ) .

distribution

Intro, fig. 14. Stream o r g a n i s m s o n a s u b m e r g e d r o c k — d i a g r a m m a t i c . 1) R h y a c o p h i l idae ( T r i c h optera), l a r v a in a c a s e of s a n d g r a i n s ; 2) Ancylus ( G a s t r o p o d a ) ; 3) B l e p h a r o c e r a t i d a e ( D í p t e r a ) , a, p u p a e , b, l a r v a ; 4) E l m i d a e ( C o l e ó p t e r a ) , a, l a r v a , b, adult; 5) G o e r i d a e ( T r i c h o p t e r a ) , l a r v a ; 6) S i i n u l i i d a e ( D i p t e r a ) , a, pupa, b, larva; 7) B a e t i d a e ( E p h e m e r o p t e r a ) , n y m p h ; 8) H e p t a g e n i i d a e ( E p h e m e r o p t e r a ) , nymph; 9) P e r l o d i d a e ( P l e c o p t e r a ) , n y m p h ; 10) R h y a c o p h i l i d a e ( T r i c h o p t e r a ) , a, pupal c a s e , b, l a r v a ; 11) H e p t a g e n i i d a e ( E p h e m e r o p t e r a ) , nymph; 12) P l a n a r i a ( T u r b e l l o r i a ) ; 13) P h i l o p e t a m i d a e ( T r i c h o p t e r a ) , l a r v a in its c a t c h i n g net ( R u t t n e r , 1953).

c. Placid water habitats—pools and holes d. Marginal areas—on or under rocks, in soil 2. Interrupted habitats, with native biota e. Deposits—on rocks, bottoms, or shores f. Splash areas—on rocks 3. Temporary habitats—transient and transitional, with varied biota g. Marginal pools h. Recession areas These apply to mountain streams. Obviously other habitats should be mentioned including slow moving rivers of considerable depth with steep banks and mud bottoms. A l s o , springs are of various types (see below) and offer a variety of special habitats including basins, seepage areas, and the like. Stream classification.—Different classifications have been proposed for the streams of the European continent (Steinmann, 1907; Thienemann, 1912; Huet, 1948), the British Isles (Carpenter, 1928), Yellowstone National Park (Muttkowski, 1929), Ontario (Ricker, 1934), and other areas. These have been variously based on source of water, size, speed of current, slope, elevation, temperature, substrate, permanence, oxygen and carbon dioxide, pH, hardness of water, productivity, or combinations of several of the above factors. Actually, most of these are interdependent, and it may very well be that no classification can be devised that will reveal in a meaningful way all the

complicated interrelations. Therefore, each factor will be discussed separately and will be related, as far as possible, to California conditions. Source.—The sources of surface waters are glaciers, snow, springs, and surface run-off from rain. T h e latter results in very temporary storm courses and, in arid regions with little vegetation, in flash floods. Temporary storm courses have no real significance for stream ecology except in rare instances when aquatic organisms may be transported long distances and survive in new regions. Snow is also a temporary source of water but the Sierran snow pack is so great —20 feet or more in many places—that long-flow intermittent streams are numerous and support a special biota of short-lived organisms with adaptations for surviving the periodic dry periods. Glaciers are, of course, a permanent source of water but are so small and so few in number in California that they are a minor factor. Springs, on the other hand, are of major importance throughout the state and are the only source of perennial streams below snow line and throughout most of the southern part of the state. Muttkowski (1929) said of the springs of Yellowstone Park that " e v e r y conceivable type o c c u r s , " and this is equally true of California. Muttkowski says further that " O n e could employ a dozen different criteria for their classification and still not exhaust them. One might

13 Ustngw:

lntro

MITE (I. syhiorum)

?

J . BIRD (Sparrow-Finch)

CHICKEN

Intro, f i g . 26. I n f e c t i o n c h a i n f o r w e s t e r n e q u i n e e n c e p h a l i t i s (Mosquito Abatement in California, 1951).

Pest mosquitoes.—Long ignored in many parts of the world, pest mosquitoes have received attention mainly near large centers of population (New Jersey, Florida, the Chicago area, the San Francisco Bay area, and elsewhere). In California the most important pest mosquitoes are .salt-marsh species (Aedes dorsalis, Aedes squamiger, and Aedes taeniorhynchus); domestic mosquitoes (Culex pipiens, Culex quinquefasciatus); mosquitoes of irrigated areas (Aedes Aedes dorsalis, Culex tarsalis); treenigromaculis, hole mosquitoes in the deciduous forests of coast range and foothills (Aedes varipalpus); and snow mosquitoes (Aedes communis, Aedes hexodontus). The control of pest mosquitoes has lagged in some places because funds are usually earmarked for disease vectors. California is an exception to this, with an efficient and extensive organization for pestmosquito abatement. This is contributing in no small measure to the high land values, increased enjoyment of recreational areas, and increased efficiency of workers out-of-doors. Mosquito control.—In 1915 the Mosquito Abatement District Act was passed by the state legislature. In subsequent years this resulted in forty-three local areas (intro. f i g . 27) (counties or other areas) organizing for mosquito control and supporting the work with tax rates up to 40 cents on each $100 of assessed valuation. A l s o nine local health departments are active in mosquito control. Mosquito Abatement Districts are governed by boards of trustees which establish policies and employ a manager to carry out the program of the district. " T h e District has the power to enter upon and inspect lands for mosquito sources, and to take appropriate measures to abate mosquitoes thereon, whether such lands be within or outside of the district; to acquire land or rights of way for drains or other purposes; to purchase supplies and equipment for the work, e t c . " T h e technical staff of a district includes a manager and usually one or more entomologists, inspectors, foremen, and so on. Technical guidance and support is provided to the districts by the Bureau of Vector Control of the State Department of Public Health. The Bureau of Vector Control also conducts investigations of particular problems that are beyond the scope or facilities of th.e individual districts. Role of the entomologist in mosquito control programs.—Very early in the development of mosquito control programs it was realized that " s h o t - g u n " methods were expensive and not very e f f e c t i v e .

23

Usinger: Introduction

CALIFORNIA MOSQUITO

ABATEMENT

AGENCIES

19 5 5

Dismcn MtmtciPAL AID c o o m u n c u s

Intro, f i g . 2 7 . M o s q u i t o a b a t e m e n t d i s t r i c t s of C a l i f o r n i a . ( F r o m B u r e a u of V e c t o r C o n t r o l , C a l i f o r n i a D e p t . of P u b l i c H e a l t h . )

24 U s i n g e r : Introduction

Instead of spreading larvicides over thousands of acres of .water without regard to kinds or numbers of mosquitoes present, the concept of " s p e c i e s sanitation" was adopted. This required that trained entomologists sample potential breeding areas at regular intervals and report on the presence or absence and relative density of the various species encountered. For disease vectors, control measures were undertaken only when counts reached a predetermined level. By this means, Aedes aegypti was eliminated from Havana and other Latin American cities, Anopheles quadrimaculatus was controlled in the vicinity of war areas in the eastern United States during World War II, and Anopheles freebomi was reduced in and around military establishments in California and other western states. To control mosquitoes effectively and economically, then, requires the services of an entomologist and a crew of trained inspectors. The duties of an entomologist in a mosquito control program are outlined as follows (Bureau of Vector Control Memorandum, April 30, 1948): 1. Accurate appraisal of the existing and potential mosquito sources within and adjacent to the district, with such information systematically recorded on appropriate maps and records. This information to be obtained by: a. Surveys of mosquito occurrence such as (1) properly chosen and collected resting stations, light traps, and biting conditions; (2) systematic larval dipping collections; (3) field observations integrated to understand mosquito species ecology. b. Accurate identification and systematic recording of species distribution in the district. c. Observations of species habitats (aquatic and adult), applied to guide control operations. 2. Evaluation of adequacy and efficiency of control programs by: a. Coordination of the routine survey and section survey findings with the over-all control program. b. Coordination of the observations of the inspectors with operations of the control crews. 3. Training of organization personnel through: a. Casual daily conversations with staff. b. Organized training programs to acquaint the staff with mosquito species identification and with the vulnerability of species as determined by knowledge of their ecology. 4. Testing of control methods, materials, and techniques, to determine their reliability in obtaining control and the degree of control. This is accomplished by: a. Comparisons of methods, such as aerosol vs. spray; ground vs. aerial approach; adult control vs. larval control. b. Testing of materials and determining their capacities one against another, in fresh, foul, salt, brackish, sunlit, and shaded water; also their residual qualities, effects upon mosquito predators, and effects upon agricultural crops, livestock, beneficial insects.

5. Assisting in the planning, preparation, and carrying out of public relations and educational programs, which in the long run serve to document the district's activities by recording its history. This is done by: a. Preparation of visual education matter, such as graphs, maps, photographs, exhibits, educational pamphlets. b. Preparation of publicity releases for newspaper and magazine publication of the entomological aspects of the district's operations. c. Preparation and delivery of talks about mosquitoes, their life histories, and habits, to schools, service clubs, farm organizations, and professional groups. d. Personal contacts and professional associations which promote closer appreciation of the entomological problems and the scope and objectives of the entire control program. 6. Immediate application of new methods, materials, and techniques developed by contemporary entomological, chemical, medical, and veterinary workers through: a. Review and interpretation of the current literature concerning mosquito control. b. Personal contact with research workers at professional meetings and institutions of higher learning. 7. Investigation of encephalitis, encephalomyelitis and malaria cases, including epidemiological analyses of their occurrence by: a. Keeping of spot maps. b. Correlation of cases with mosquito populations. c. Gathering of case histories. 8. Assisting in district administration, particularly in decentralized districts. Survey methods are of several standard types. Adults may be caught while biting on the bare arms or legs, or counts may be made of the landing rates on trousers or dark cloth. However, counts in natural resting places are preferred because they can be standarized and visited at regular intervals. Favorite resting places include hollow trees (intro. fig. 28), sheds or barns (intro. fig. 29), the shaded undersides of bridges, chicken houses, porches, tank houses, and the like. Artificial resting places may be set up, including cages baited with live animals, or plain boxes (intro. fig. 30). The latter have proved to be effective for sampling Anopheles mosquitoes in many places. Another effective method for sampling the populations of some species of mosquitoes is the light trap. A very efficient and standardized type is the so-called "American light trap" (Mulhern, 1953), modified from the "New J e r s e y " type (intro. fig. 70). Unfortunately, the light-trap method is not uniformly effective for all apecies and varies in efficiency with changes in climate. Likewise, none of the methods mentioned above gives data that can be compared with other samples in the same or different regions because the factors that influence adult mosquitoes are extremely local and elusive. In spite of these difficulties,

25 Usinger: Introduction

Intro, f i g . 28. S a m p l i n g a d u l t m o s q u i t o e s in a h o l l o w trunk of a tree ( U . S . P . H . S . , C . D . C . photo).

sampling at a single station, properly chosen, can provide valuable data from week to week and year to year and is the best criterion we have for judging the relative abundance of most mosquitoes.

Intro, f i g . 30. R e d b o x s e r v i n g a s a n a r t i f i c i a l r e s t i n g p l a c e for adult A n o p h e l i n e s ( U . S . P . H . S . , C . D . C . photo).

and the counts recorded so that data will be comparable. Only experience in a particular area can determine at what l e v e l of adult or larval counts control measures should be undertaken. Control measures.—The various methods used in mosquito control are diverse and must be adapted to each situation. For adults, which should be the last line of defense, indoor space sprays are employed— using aerosol " b o m b s " or even the simple " F l i t - g u n . " A e r o s o l mists and sprays are designed for quick knockdown of mosquitoes and have been used for this purpose even over extensive outdoor areas with applications made by airplane or s p e c i a l i z e d equipment on the ground. Most adult sprays contain D D T , pyrethrum, or some other material which has a residual e f f e c t when sprayed on walls or other surfaces. R e s i d ual sprays are particularly e f f e c t i v e in malaria control because engorged females of some Anophelines rest on treated walls and are killed before they are Intro, f i g . - 2 9 . Anopheles m o s q u i t o e s r e s t i n g o n the c e i l i n g of a barn. I n s e t — m o s q u i t o in b i t i n g p o s i t i o n ( U . S . P . H . S . , C . D . C . photo).

Larval and pupal densities are in some ways easier to determine. A standard, white enamel dipper is commonly used as a sampler (intro. f i g . 31). T h e dipper is placed at the water surface and one edge is tipped so that water flows in, carrying larvae and pupae with it. Specimens can be seen, counted, and collected with a pipette if necessary. Hess (1941) d e v i s e d a straight-edged screen dipper that samples a standard area of surface, thus giving more meaningful results but this dipper has not come into general use. Dippers are totally inadequate under some circumstances. For example, the water in a weed-choked irrigated pasture is so shallow that other means must be used. A s a partial solution to this dilemma Yamaguchi (1949) devised a " s l e e v e sampler" consisting of a vertical cylinder from which larvae were removed by a hand-operated suction pump (intro. f i g . 32). A standard number of dips or samples should be taken

Intro, f i g . 3 1 . S a m p l i n g for m o s q u i t o l a r v a e w i t h a w h i t e e n a m e l d i p p e r ( U . S . P . H . S . , C . D . C . photo).

26 Usinger: Introduction

Intro, f i g . 32. breeding places are s u c k e d o u t ejected into the

Sleeve sampler used for s h a l l o w water mosquito in i r r i g a t e d pastures ( Y a m a g u c h i , 194$). L a r v a e o f t h e p l a s t i c c y l i n d e r by t h e " p u n i p " and t h e n enamel pan for c o u n t i n g .

Intro, f i g . 34. U s e of dynamite for c o n s t r u c t i o n of a drainage d i t c h for m o s q u i t o control ( U . S . P . H . S . , C . D . C . photo).

Intro, f i g . 33. Drainage one of the most e f f e c t i v e H.S., C . D . C . photo).

is the most permanent and therefore methods of mosquito control ( U . S . P .

able to incubate the malaria parasites and transmit the d i s e a s e . Other measures directed at adult mosquitoes include screening, nets of various kinds, and repellents such as " 6 1 2 , " dimethylphthalate", and the like. Most methods of mosquito control are directed against the immature forms—the larvae and pupae. One of the most important of all methods because it i s relatively permanent is the elimination of breeding p l a c e s by drainage (intro. fig. 33). Drainage ditches. Intro, fig. 35. Dragline d i t c h i n g at M a r y s v i l l e , C a l i f o r n i a (U.S. Army Signal Corps). may be blasted (intro. fig. 34) or dug by dragline (intro. fig. 35) or by hand labor. The cost of maintenance may be greatly reduced if drainage ditches are banks (intro. fig. 360, before concrete lining; 6, after). lined with concrete and sod planted on the upper Underground drainage is commonly used in seepage

27 Usinger: Introduction

Intro, f i g . 36. L i n i n g a d i t c h w i t h c o n c r e t e and s o d d i n g the upper b a n k s t o i n c r e a s e e f f e c t i v e n e s s and r e d u c e m a i n t e n a n c e c o s t s , o, before; b, after ( U . S . P . H . S . , C . D . C . photo).

areas using tile or buried poles. Breeding place's may also be eliminated by filling with a bulldozer or by diking and dewatering with pumps. In brackish waters such as are found in the salt marshes, drainage ditches may suffice, but more often tidal action requires that other measures be used. Dikes may be constructed with tide gates or automatic siphons to hold back the salt water at high tide and permit drainage outward at low tide. Biological control has long been a solution to mosquito breeding in local areas. The top minnow, Gambusia affinis, is ideal for this purpose and can be introduced into ornamental pools (intro. fig. 37) or even into cisterns and other unlikely bodies of water. Mosquito fish have been distributed so widely that they may be found in almost any body of water or a supply can usually be had by telephoning the nearest mosquito control agency. Gambusia are not needed in garden pools if goldfish are present and are not fed excessively. Mosquito larvicides are considered as emergency measures or temporary means of control, yet larviciding has and probably will continue to occupy a large part of the time of mosquito control crews. Progress in this field has been so rapid during and since World War II that generalizations are likely to be misleading and are certain to be dated. The principal materials in use at the present time are: oils, either alone or as solvents for organic poisons; chlorinated hydrocarbons such as DDT and related compounds; and organic phosphates. The toxicity of various chemicals was tested with colonized larvae of Culex quinquefasciatus Say by Isaak (1952) with results as shown in table 2.

Intro, f i g . 3 7 . S t o c k i n g a garden poo! w i t h m o s q u i t o f i s h , Gambusia affinis ( U . S . P . H . S . , C . D . C . photo).

Of the larvicides tested, EPN was the most effective followed by Parathion, Aldrin, colloidal Aldrin, Heptachlor, Dieldrin, DDD, DDT, Q- 1 37, chlordane, lindane, and toxaphene in that order. Field applications are made at concentrations that seem ridiculously low by prewar standards. Formerly, 20. gallons of fuel oil or 20 pounds of Paris green dust were applied per acre of water surface, at great expense and effort.

28 U s i n g e r : Introduction

TABLE 2 (Introduction) Toxicity Range and LD-50 of Various Insecticides Against Colonized Culex quinquefaaciatua Larvicide

EPN Parathion Aldrin Colloidal aldrin Heptachlor Dieldrin DDD DDT Q-137 Chlordane Lindane Toxaphene

1

.2

100 100

100

100 100 89

.1

.04

100 95 84 100 98 98 marsh mosquitoes occur as larvae in the winter and early spring. Therefore drainage and larviciding should be completed before midMarch. Flood water species such as Aedes vexans must be treated as soon as pools begin to form when the water recedes in spring or early summer. Control in irrigated pastures must be adjusted to water schedules during the spring and summer months. Tree-hole mosquitoes can be treated with wettable dusts during the breeding season, and filling with sand and asphalt or concrete may be done during the winter months.

Intro, f i g . 3 9 . H a n d d u s t e r for d i s t r i b u t i n g m o s q u i t o ( U . S . P . H . S . , C . D . C . photo).

larvicides

29 Usinger: Introduction

Intro, f i g . 4 0 . J e e p e q u i p p e d for p o w e r l a r v i c i d i n g (Consolidated Mosquito Abatement District).

Intro, f i g . 4 2 . A p p l i c a t i o n of l a r v i c i d e s by m e a n s of a n a i r p l a n e (Kern County Mosquito Abatement District).

Snow-pool mosquitoes may be treated in the spring when the snow is melting and the eggs are hatching or in the fall in anticipation of the spring hatch. For domestic mosquitoes such as Culex pipiens control measures should be continued throughout the year. Unfortunately, with the increase in potency of mosquito larvicides greater hazards have been introduced to fish and other aquatic organisms. Ordinarily this problem does not arise because it is considered bad mosquito control to introduce larvicides in areas where fish occur. Nevertheless, the danger e x i s t s and evidence is not yet entirely clear as to the limits of tolerance of various species under diverse conditions. However, certain generalizations can be made from the work of Tarzwell (1950) and his a s s o c i a t e s . F i e l d

experiments were conducted at weekly intervals by airplane using a standard rate of 0 . 1 pound per acre of DDT mosquito larvicide applied as a spray or aerosol. " S t u d i e s on the effect of DDT (dichlorodiphenyl-trichloroethane) and certain other new insecticides indicate that they are all toxic to fishes if used in large doses. With DDT the type of pond or water in which it is used greatly influences the onset and severity of toxic action on fishes. Vegetation, organic material, type of water, and silt or turbidity are all factors influencing this action. Crabs, crayfish, amphipods, isopods, and Palaemonetes are very sensitive to DDT, being considerably more so than fishes. Among the fishes, some of the Centrarchidae are the first to be affected, especially the bluegill . . . Although top minnows were among the first fish to be killed, they continued to be present during the period of treatment and were in evidence when most other fish had been eliminated. A few frogs and snakes were killed by routine dosages of 0 . 1 and 0.05 pound DDT per acre. At routine dosages of 0 . 1 pound per acre, DDD (dichloro-diphenyl-dichloroethane), chlordane, and DDT are toxic to fish and will significantly reduce the population of ponds. At dosages of 0.05 pound per acre, DDT appears to be somewhat more toxic than chlordane or DDD. Studies carried on in 1947 indicated that DDD was considerably l e s s toxic to fish than DDT. T h e s e three insecticides appear to have no significant effect on the fish population at dosages of 0.02.5 pound per acre. Toxaphene was found to be very toxic to fishes, giving complete kills at 0.2 and 0 . 1 pound per acre after two and three applications in deep ponds. Kills were obtained at dosages of l e s s than 1 part in 27 million, indicating that this material is as toxic or more toxic to fish than rotenone and may be useful as a substitute for it in fish management work." Doudoroff, Katz, and Tarzwell (1953) added data on other insecticides, stating that, "Aldrin appears to be l e s s toxic to goldfish than toxaphene, but much more toxic than DDT and BHC (benzene hexachloride)."

Intro, treating photo).

fig. 41. Hand sprayer mounted catch basins with larvicide

o n a m o t o r c y c l e for (U.S.P.H.S., C.D.C,

/

30 Usinger: Introduction

As regards invertebrates, Tarzwell (1947) reported that DDT is less toxic applied as a dust than in oil. He found that treatment at the rate of 1 to 2 pounds per acre in fuel oil killed Hemiptera, Coleoptera, Odonata, Ephemeroptera, and Chironomids. At 0.025 pound per acre in fuel oil Dytiscids, Gyrinids, Hydrophilids, and Corixids were killed. Seasonal effects after periodic treatment were: an increase in the number of Oligochaetes, nematodes and copepods; a decrease in the numbers of Chironomids, Hemiptera, Coleoptera, and Ephemeroptera. Insects as a group decreased, with the greatest effect of the treatment on the Chironomids. Repopulation after treatment with DDT was studied by Hoffmann, Townes, Sailer, and Swift (1946). As might be expected, the insect fauna of ponds, which is characterized by short life histories, came back to normal within a few weeks. Streams, on the other hand, required a year or more. Gnat control.—Gnat control is a peripheral activity of mosquito abatement districts in a few places. Chironomid gnats are the principal pests in Lake Elsinore (southern California) (Miller, 1951) and in Klamath Lake and nearby waters along the OregonCalifornia border. By far the worst pest, however, is the "Clear Lake gnat," Chaoborus astictopus D. and S. In 1940 it was estimated that the total seasonal emergence in the upper part of Clear Lake (44 sq. mi.) was 712 billion gnats or 356 tons (Lindquist and Deonier, 1942), and the "phantom larvae" were estimated on the basis of adequate samples to number 800 billion. One light trap captured 88% pounds of gnats in two hours. Eggs at a density of 10 million per square foot occurred near shore in drifts 20 feet wide and several miles in length. Fork-tail catfish, square-tail catfish, and split-tail were important feeders on all stages of the gnat; one 9-inch fish was found with more than 1,000 larvae in its stomach. In former years control seemed to be impossible but the advent of chlorinated hydrocarbon larvicides opened up new possibilities. Experiments had shown that DDD would kill larvae at a dilution of one part to 75 million parts of water whereas fish and other aquatic life in the lake were not killed unless the concentration was increased to 1 in 45 million. With this margin of safety, and after a preliminary trial in nearby Blue Lakes, Lake County organized a mosquito abatement district and, with state and federal help, treated the entire 41,600 acres of lake surface on September 15 and 16, 1949 (Lindquist, Roth, and Walker, 1950). The lake is eutrophic and relatively shallow (27 to 50 feet) without a thermocline so the wettable insecticide was thoroughly mixed by the wind. Control was complete and no gnats were found in the lake for several years, though they gradually increased until 1954 when, on September 25 and 26, a second treatment was carried out. It was a remarkable fact that the removal of so much fish food had no apparent effect on the over-all economy of the lake, probably because Chaoborus larvae are carnivorous and are an intermediate link in the food chain and hence were bypassed.

I «Md.

3 3 4 3

LECENO

C*oflc. M r Erad FU.imui Nalud Eract

i Cmr*

7 • 9 ID

F I M H I * khrt FlMtln« L M I SwbMT««! PUmlM

Intro, f i g . 4 3 . C l a s s i f i c a t i o n of p l a n t t y p e s a l o n g t h e l i n e o f a r e s e r v o i r in r e l a t i o n to w a t e r l e v e l m a n a g e m e n t and H a l l , 1945).

shore (Hess

M a n - M a d e Impoundments

Literally hundreds of dams have been built or are planned for California. The resulting impoundments vary in size from small stock ponds to local reservoirs and enormous multipurpose lakes. They do not differ fundamentally from naturally dammed lakes and ponds, but economic considerations are more likely to arise because of the effects on erosion, mosquito breeding, fish production, and recreation. Therefore, limnological studies have now become an important part of reservoir planning. Reservoirs.—Some important considerations in a preimpoundage entomological survey (Malaria Control on Impounded Water, 1947) are: 1. Location in relation to known pest or diseasebearing insects is a critical factor. For example, a mosquito survey should be made to determine the species present in the locality and their relative abundance, the present and potential breeding areas, and the flight range of potential pests. Periodic density observations should be made throughout the season and during a period of several seasons in order to provide a basis for comparing mosquito production before and after impoundage. 2. Soil and vegetation have a significant bearing on aquatic life. Therefore a reconnaissance survey should include: a study of the timber in the basin

MEDIUM Relativo Intersection V a l u e i

Intro, f i g . 4 4 . Anopheles quadrimaculatus p r o d u c t i o n of p l a n t t y p e s ( H e s s a n d H a l l , 1 9 4 5 ) .

potentials

31 U s i n g e r : Introduction

Intro, f i g . 4 5 . R e l a t i o n s h i p between intersection line and p r o d u c t i o n of e g g s a n d l a r v a e o f Anopheles quadrimaculatus (Malaria Control on Impounded Water, 1 9 4 7 ) .

(acreage to be cleared, density, predominating s p e c i e s , and tolerance to flooding); soil conditions and types; and the existence, location, and extent of marginal DEEPENING AND FILLING

and aquatic plants. Shore-line plants may be c l a s s i f i e d into ecological types (as was done by H e s s and Hall, 1945, for the southeastern United States) (intro. fig. 43) and then rated in terms of intersection line (airwater-plant-interface) values (Hess and Hall, 1943) (p. 5, intro. fig. 5). An accompanying figure (intro. fig. 44) shows the relative intersection values of each of the ecological types (woods, coppice, etc.) and gives the production in terms of eastern Anopheles quadrimaculatus larvae per square foot. The correlation between intersection line and numbers of eggs and larvae i s shown (intro. fig. 45). From the above, it i s evident that marginal vegetation is of primary importance to Anopheles mosquito production. It also influences other aquatic i n s e c t s . Therefore, shore-line filling (intro. fig. 46) and clearing (intro. fig. 47) are e s s e n t i a l operations both during the preparation of a reservoir and after the water has been impounded. On surveys it is useful to try to estimate the cost of such operations by dividing the reservoir into areas c l a s s i f i e d according to type of shore line. 3. Water level schedules are of great importance in reservoir management. They not only a f f e c t the A a

fliver «

Miles SjL_

MARGINAL DRAIHAGI

Intro, f i g . 4 6 . F i l l i n g o p e r a t i o n s u s e d in p r e p a r i n g r e s e r v o i r s o f the T e n n e s s e e V a l l e y A u t h o r i t y ( M a l a r i a Control on Impounded Water. 1 9 4 7 ) .

Intro, f i g . 4 7 . C l e a r i n g o p e r a t i o n s a s u s e d i n p r e p a r i n g r e s e r v o i r s o f t h e T e n n e s s e e V a l l e y A u t h o r i t y (Malaria Control on Impounded Water, 1 9 4 7 ) .

32 Usinger: Introduction

production of aquatic insects but also influence the growth of marginal vegetation and consequently the cost of maintenance. In planning a water level schedule for a reservoir it is necessary to consider: a. The primary purpose or purposes of the project— whether for flood control, power, navigation, water supply, irrigation, recreation, wildlife, or a combination of these. b. The stream flow and volume of storage in the fluctuation zone—the probability of filling each year, amount of fluctuation possible, and the seasonal recession are all functions of these two items. c. The design of the dam and the water level control facilities—the maximum pool level, flood surcharge, and rate and extent of recession, all depend upon the type of design, elevation, and capacity of the control facilities. d. The topography and vegetation in the fluctuation zone—a steep, rugged shore line exposed to wave action will require much less precise water level management than a shore line of extensive, flat, shallow areas; and water level fluctuation is sometimes ineffective for mosquito control where the shore line or margin is colonized with certain types of marginal or aquatic vegetation. The simplest schedule for high storage reservoirs with steep banks and little or no mosquito production is direct seasonal recession. For large reservoirs at low elevations a more complicated schedule may be required. The classical example of this is the combination of seasonal recession and cyclical fluctuation (intro. fig. 48) used on twenty-four of the large Tennessee Valley Authority impoundments involving 735,000 acres of water surface and 10,000 miles of shore line. This schedule, which is not directly applicable to California conditions, calls for maximum elevation for a short time before April 1 to strand the winter accumulation of drift and floatage. Then there follows a constant pool level during the spring growth period (April 1 to May 15). This prevents the invasion of marginal vegetation into the zone of fluctuation and delays the germination of annual Spring Growth Period

Winter Period Controlled Elevations not Necessary for Mosquito-Control

Malaria Mosquito Production Penod

Maximum Btiw-

Moderate

Heaviest

Control Elevation c 4 «

Cyclical Fluctuation Larvtcides

Seasonal Recession Cyclical Fluctuation Larvicide*

Fall Low Rainfall Period

Fall Shoreline Conditioning Operations

M a x i m u m Elevation — Ftax Surcharg S

iti.

/»Recession About 3.1 Foot per Week

Maximum Mosquito-Contro Elevation

Minimum Mosquito-Control Elevation.

Basic Clearing Line

tylMA

Mosquito-Control luctuation Zone 2'± —

¿ A n *

ym

^Cyclical Fluetuation Approximate 1-Foot at We« kly or 10-0ay Intervals 1

i

— "

~ Minimum lor Navigation and Power Minimum in Advance of Floods Apr 1

Mi» 1 M«» 15

Jul 1

Sep 1

Oct 1

Approximate Dates Vary with Location a n d from S e a s o n to Season

Intro, f i g . 4 8 . S c h e d u l e for w a t e r l e v e l m a n a g e m e n t o n m a i n river r e s e r v o i r s of the T e n n e s s e e V a l l e y A u t h o r i t y , c o m b i n i n g c y c l i c a l f l u c t u a t i o n a n d s e a s o n a l r e c e s s i o n (after H e s s a n d K i k e r , 1944).

plants, thus decreasing the cost of annual shore line conditioning. During the period of moderate mosquito production (May 15 to July 1) the water level is raised and lowered one foot at weekly or ten-day intervals. This alternately strands larvae and eggs on the shore or flushes them out of protective vegetation and exposes them to predators. During the period of heaviest mosquito breeding (July 1 to October 1) cyclical fluctuation is combined with an over-all recession of about 0.1 foot per week. Finally (after October 1) during the period of low rainfall the water level is lowered to or near the minimum required for navigation and power. This exposes broad expanses of shore line for the annual job of shore-line conditioning. 4. Preimpoundage studies should also be made of the productivity of lakes and reservoirs in the vicinity as an indication of the probable adequacy of fish-food organisms. In this connection a fish-stocking plan may be developed to ensure the best utilization of fisn-food organisms in the reservoir. 5. The productivity of the stream below the proposed dam should be determined as accurately as possible in order to predict the effects of periodic flooding or drying and to recommend the optimum flow for maintenance of adequate bottom food organisms for fish. Such figures are often used as a basis for legal action when adverse effects are noted after impoundage. Duck ponds.—The impoundment of water by clubs for duck hunting has become a common practice in parts of California. The subject was difficult in the past because the interests of sportsmen and mosquito control agencies appeared to be in conflict. More recently it has become evident that good practices for duck clubs are also good for mosquito control. After considerable study the Wildlife Committee of the California Mosquito Control Association made the following recommendations pertaining to the management of duck ponds: 1. If it is desired to hold ducks in a hunting area, a certain proportion of the area should be prepared as good sharp banked and properly maintained ponds, and permanently flooded rather than flooding the whole area early in the summer to achieve this purpose 2. An attempt should be made to adjust the duck hunting season by smaller regions allowing for a later season in the Central Valley. This is concurred in by many hunters; however, the setting of the season is done by the United States Fish and Wildlife Service and direct recommendations will have to be made by them. 3. Efforts should be made to control or eliminate cattails, tules, and other emergent vegetation, especially in permanently flooded ponds. 4. Where seepage areas occur outside of ponds a ditch should be dug around the pond to cut off this water and the water in the drain ditch should be disposed of by draining into an existing drainage system or pumping back into the pond. 5. Ponds should be drained immediately after the close of the season. 6. The planting of food grains in the ponds should be done in such a manner that no mosquito problems can be caused.

33 U s i n g e r : Introduction

7. When pond areas are used as cattle pasture between seasons the land should be so prepared that good and proper pasture irrigation practices can be used. Ponds created or influenced by faulty engineering practices.—Roadside ditches are found in many places where highways and railroad beds interrupt normal drainage and impound water because culverts are improperly placed. Borrow pits and quarries almost always hold water and provide breeding places for mosquitoes and other aquatic insects. Such conditions can be corrected only at considerable expense. Swimming pools.—Outdoor swimming pools are becoming a feature of suburban life. Most of them are easy to clean and are free from insect pests. However, biting insects such as backswimmers (Notonecta) and " t o e - b i t e r s " (Belostomatidae) sometimes fly in and annoy swimmers, usually in the heat of the summer when large flights of insects are attracted to nearby electric lights. The most practical method of control is to drain the pool and destroy the insects when they are concentrated at the deepest point. The mosquitoes, Culex pipiens and quinquefasciatus, occasionally breed in swimming pools. They may be controlled with emulsifiable pyrethrum or kerosene sprays.

Irrigation

In California most of the precipitation occurs in the north and only during the winter months. Therefore elaborate irrigation systems have been developed for transporting water to the arid south, and the underground water supply is tapped by thousands of irrigation pumps. According to Henderson (1951) California leads the nation in area under irrigation with 6 million acres. With the huge volume and extensive surface of water it is not surprising that insects intrude into the picture at several points. Caddisworms, for example, have been reported obstructing water in irrigation tunnels in southern California (Simmons, Barnes, Fisher, and Kaloostian, 1942) and many irrigation ditches and canals are inhabited by Simuliid larvae and other stream insects. In irrigated fields the insect fauna is determined largely by the nature of the crop and by the water schedule. Any irrigated crop can produce mosquitoes but in general, row crop irrigation is less troublesome than sheet irrigation. R i c e , for example, is constantly flooded over wide areas and presents ideal conditions for the development of aquatic insects. In 1954 more than 453,000 acres of rice were harvested in California, and most of this area was under water from April or May into September. Leaf- and stem-boring aquatic flies (Cricotopus, Hydrellia) are pests in the Sacramento Valley, and a host of pond-dwelling i n s e c t s commonly invade the fields. Hydrellia griseola var. scapularis Loew, in particular, built up to epidemic proportions in 1953, causing an estimated l o s s of 10 to 20 per cent of the crop (Lange, Ingebretsen, and Davis, 1953). The rice leaf miner, as it is called, belongs to the family Ephydridae. The eggs are laid on leaves lying prone in the water and hatch in about

four days. The larvae feed in the leaves. Control was achieved by lowering the water to a depth of about two inches and spraying with dieldrin or heptachlor. After forty-eight hours the water level was raised and the checks were blocked off so that no water was spilled from the fields for two weeks. Mosquitoes have long been a problem in rice fields. Culex tarsalis i s the most important of these. Anopheles freeborni is the malaria vector that caused the epidemics of former years (Herms, 1949) and was responsible for the recent outbreak initiated by a malaria carrier just returned from Korea (Brunetti, Fritz and Hollister, 1954; Fontaine, Gray and Aarons, 1954). A. freeborni is mainly a breeder in rice fields and outlying areas and can be reduced in numbers by good irrigation practices. Aedes dorsalis breeds in the rice fields early in the season in response to initial flooding (Portman and Williams, 1952). The eggs of this mosquito overwinter in the soil and may remain viable for several years. Soon after flooding, larvae appear in great numbers and produce myriads of adults unless controlled by application of insecticides such as wettable DDT powder mixed with the seed rice at the rate of one and one-half to two pounds of 50 per cent powder to the acre. Other aquatic pests in the rice fields (Portman and Williams, 1952) include fairy shrimps, Apus spp., which undergo a life history somewhat like Aedes dorsalis and chew off the tender leaves and dislodge the soil around the roots of the seedlings, and giant scavenger b e e t l e s , Hydrous triangularis (Say), the larvae of which dig in the bottom mud and uproot entire plants. Alfalfa fields and irrigated pastures provide extensive aquatic habitats, with more than a million acres of each in California. B e c a u s e of the increased availability of water in the past two decades, the practice of irrigating pasture lands has spread over much of the Central Valley. Coincident with this, Aedes nigromaculis and Culex tarsalis have extended their ranges and the former has now become the number one pest mosquito over a wide area. Culex tarsalis i s a known vector of encephalitis. In irrigated pastures a succession of generations is produced through the season, the larvae breeding in shallow water choked with grass and weeds at low points in the fields. Another method of using irrigation water that i s quite common in California is the spreading of water for percolation purposes. In such c a s e s individual pumps are used to replenish the water supply. The use of percolation beds creates mosquito problems. Also, of course, mosquitoes breed in irrigation structures of all kinds including canals, ditches, standpipes, and the like. From the above discussion it is obvious that mosquito breeding is intimately related to irrigation. The solution to the problem should therefore be sought in better irrigation practices. Henderson (1951) refers to the problem a s "conservation irrigation" or the use of "irrigated soils and irrigation water in a way that will insure high production without the waste of either water or soil . . . Generally, the direct economic benefits of conservation irrigation materially exceed

34 Usinger: Introduction

the cost. Under proper technical guidance, resultant freedom from nuisance mosquitoes and encephalitis hazard are dividends obtained at negligible cost to society." Water

Pollution

The disposal of domestic and industrial wastes is a major problem of modern civilization. The pollution of surface and underground waters threatens the 15 billion gallons of water used by cities in the United States each day. It also endangers recreational fishing, boating, and swimming and may lower land values. The enormity of the problem is difficult to grasp by mere citing of figures. For example, the City of Sacramento produces 45 million gallons of raw sewage per day, and a single river such as the Delaware (Eliassen, 1952) is estimated to receive each day 500 million gallons of domestic sewage and hundreds of millions of gallons of industrial wastes. Legal basis.—To control the undesirable consequences of water pollution (intro. fig. 49) California operated for many years under a statute of the State Health Department. In 1949 this was changed and the Water Pollution Control Act was passed. This law sets up a state board and nine regional boards. The regional boundaries, shown on the accompanying map (intro. fig. 5U), are based on the major watersheds of the state. The regional boards have four principal duties: prescribing regulations for waste discharges; obtaining coordinated action in controlling pollution; enforcing orders for correcting pollution by means of administrative hearings, followed, if necessary, by court action; and formulating and adopting long-range plans and policies for water pollution control (Water Pollution Control Board Publication No. 5, 1952). According to California law there are two basic aims of water pollution control: protection of public health and conservation of water quality for various beneficial uses. The first aim considers only the health aspects of waste treatment and disposal. The second considers the economic aspects and requires that the cost of waste disposal be balanced against the beneficial uses of the receiving waters. These two aspects are recognized and defined in California statutes as follows: Contamination is impairment of water quality by sewage or industrial waste causing an actual hazard to the public health. Primary responsibility for reducing contamination rests with the State Department of Public Health and the local health agencies, although the State Water Pollution Control Board may legally assume final responsibility in the case of an uncorrected contamination. Pollution

-WATER POLLUTION CONTROL WASTE DISCHARGE CLEAN WATER

Intro, f i g . 4 9 . T h r o u g h w a t e r p o l l u t i o n c o n t r o l d o m e s t i c a n d i n d u s t r i a l w a s t e s are t r e a t e d a n d c l e a n w a t e r i s maintained (Water P o l l . C o n t r . B o a r d P u b l . N o . 5 , 1 9 5 2 ) .

.

S

5

2.

N •

REGIONAL BOARD OFFICES 1. 2. 3. 4. 5. 6. 7. 8. 9.

Santa ROM Oakland S a n Luis O b i i p o Los Ang«l«s Sacromonto Bhhop Indio Santa Ana S a n Oiogo STATE BOARD OFFICE Socramonto

I n t r o . f i g . 5 0 . Water p o l l u t i o n c o n t r o l r e g i o n s a n d l o c a t i o n o f board o f f i c e s (Water P o l i . C o n t r . B o a r d P u b i . N o . 5, 1 9 5 2 ) .

adversely and unreasonably impairs the beneficial use of water even though no actual health hazard is involved. The regional and state water pollution control boards are the agencies primarily concerned with reducing pollution. (The regional boards also are responsible for controlling nuisance, such as odors or unsightliness caused by unreasonable waste disposal practices.) Since insects have little to do with the contamination of natural waters, the present discussion will be limited to pollution. Insects do play an important role at various stages in the treatment of polluted waters and are used as indicators of pollution. Types of wastes.—Wastes are of three principal types: physical, including silt and other erosive agents; chemical, including toxic materials from industry, and agricultural chemicals such as insecticides and weed killers; and organic, including domestic sewage, industrial wastes from canneries, and fertilizers. Effects of physical wastes.—The effects of physical agents are diverse and far-reaching. Silt, for example, may be abrasive and injure the gills of aquatic organisms; it may coat the gills and interfere with respiration; or it may settle out and cover natural habitats. It may also reduce light penetration and thus restrict the photosynthetic zone with consequent loss of oxygen and food supply for higher organisms. Excessive .silting is usually caused by faulty agricultural practices and by the deep cuts and exposed banks now so characteristic of our countryside along superhighways. Such uncontrolled erosion loads streams, fills lakes, and eliminates some of the best fish-food organisms (stonefly and mayfly nymphs,

35 Usinger: Introduction

etc.). The solution is well-known but too often neglected—roadside plantings to stabilize the soil and, in agricultural areas, contour plowing, and other soil conservation methods. Effects of chemical wastes.—Chemicals usually affect aquatic organisms by their direct toxic action, though there may be secondary effects such as extremes of pH or changes in osmotic pressure. Attempts have been made to establish precise tolerances for various chemical substances, based largely on their toxicity to fish. However, such figures have been shown to be extremely misleading (Doudoroff and Katz, 1950, 1953) because "the minimal harmful concentration of a toxic substance may vary greatly, depending on the duration of the test, the species and age of the test animals, the dissolved mineral content of the water used as a solvent or diluent, the concentration of other waste components having a pronounced synergetic or antagonistic effect, the temperature, and other factors." Under the circumstances, safe concentration limits of toxic wastes were not definitely prescribed. Doudoroff and Katz did conduct extensive tests, however, using the method of " b i o a s s a y " or exposure of known concentrations to fish. Their conclusions are too voluminous to repeat here but a few points may be listed: (1) pH values above 5.0 and ranging upward to 9.0, at least, are not lethal for most freshwater fishes; (2) none of the strong alkalies which are important as industrial wastes (NaOH, CA(OH)2, and KOH) has been clearly shown to be lethal to fully developed fish when its concentration is insufficient to raise the pH well above 9.0; (3) solutions of ammonia, ammonium hydroxide, or ammonium salts can be very toxic to fish even when the pH is not very high (that is, below pH 9.0); (4) the common strong mineral acids (that is, H 2 S0 4 , HC1, and HN03) and also phosphoric acid (H 3 P0 4 ) and some moderately weak organic acids apparently can be directly lethal to fully developed fish only when the pH is reduced thereby to about 5.0 or lower; (5) a number of weak inorganic acids (such as carbonic, tannic, etc.) can cause pronounced toxicity without lowering the pH as low as 5.0; (6) the susceptibility to free carbon dioxide varies greatly; for example, sensitive species may succumb rapidly at free C0 2 concentrations between 100 and 200 ppm in the presence of much dissolved oxygen; (7) solutions of hydrogen sulfide, free chlorine, cyanogen chloride, carbon monoxide, and ozone all are extremely toxic and have been reported as lethal to sensitive fish in concentrations near 1 ppm or less; (8) all metal cations can be toxic in rather dilute (less than 0.05 m) physiologically unbalanced solutions of single metal salts; (9) sodium, calcium, strontium, and magnesium ions are among the least harmful of the metallic cations; (10) silver, mercury, copper, lead, cadmium, aluminum, zinc, nickel, and trivalent chromium, and perhaps also tin and iron, can be classed as metals of high toxicity; (11) cupric, mercuric, and silver salts are extremely toxic.

other kinds of aquatic organisms including insects. In some cases insecticides are regarded as pollutants or toxic agents from the viewpoint of fish production. Either as mosquito larvicides applied directly to the water or as applications on agricultural crops that run off or are washed into streams or lakes, these materials are a threat to aquatic resources. Fortunately, the conflicting interests of agriculturists, mosquito control agencies, and sport fishermen can be resolved in most cases by judicious choice of materials, careful timing of applications, and adjustment of concentrations to fit the tolerances of fish and fish-food organisms. (See discussion under mosquito control.) Tolerances to chemicals (except insecticides) have not been studied for many insects but it has been observed that the copper sulfate treatment for reduction of algae in swimming pools has no apparent effect on insects. On the other hand, chlorine at the concentrations used for purification of drinking water may produce a residual that is toxic to aquatic insects and fish; hence treated water cannot be used safely for rearing insects in the laboratory unless it is detoxified by boiling, filtering, or by holding in a container for twenty-four hours. Effects of organic wastes,—The effects of organic pollutants are more complex than those of mechanical or chemical agents. In general, the action of bacteria on organic material causes a deficiency of oxygen. Patrick (1953) has described the process as follows: " T h e s e organisms use the complex wastes . . . as a source of energy in their metabolism. In so doing they break down the wastes into substances that can be used as a source of food by other organisms. These processes, which are often referred to as decay or decomposition, occur most rapidly when the bacterial population is of optimum size. When the bacteria become too numerous the processes are slowed down. The protozoa and other small invertebrates which feed on bacteria are instrumental in keeping the bacterial populations in check. The algae are also at the base of the food chain. They are able to utilize inorganic substances to make proteins and carbohydrates, which are used as a source of food by other organisms. Indeed, algae have often been referred to as the grasses of the sea. Upon them not only the many different invertebrates, but also some fish and other vertebrates, feed directly. Besides their value as a source of food they also replenish the oxygen supply . . . by photosynthesis."

Insects fit into this complex picture in diverse ways. When exposed to organic pollution in a stream they follow a typical pattern (intro. fig. 51). Immediately below a sewage outfall a septic zone develops with turbid water and noxious odors. The bottom is coated with zoogloea and inhabited by tubificid worms. Oxygen is low or absent. The bacterial count is high and and plankton organisms include Oscillatoria Sphaerotilus. Fish are absent. The insect fauna is limited to larvae which breathe surface air through tubes—Tubifera (Eristalis), Culex. Below the septic These are, of course, generalizations and would zone is the zone of recovery with clearer water, differ not only for each species of fish but also for cleaner bottom, and more dissolved oxygen. Here

36 Usinger: Introduction

P IS J

!N

dissolved OXYCfN

WATER

FISH

^

PLANKTON

INVERTEBRATES

N O R M A L FISH POPULATION! G A M E . P A N F O O D , FOftAGE FISH

C A D D I S FLY

M A Y FLY

OEDOGONHJM NAVICULA , „ , DINOWYON

TOIEIIANT FISHES: CARP, BUFFALO, O A R S . CATFISH

CHIRONOMUS

SIMULIUM

PARAMECIUM BEGGIATOA

CLEAR A N D FRESH

\

'«v. jiJ \ '"iv V ^M ' ' :

TURBID A N D

STENTOR

DARKER

CULEX

SEPTIC-NOXIOUS ODORS, FLOATING SLUDGE TOLERANT FISHES: CARP, BUFFALO, O A R S , C A T F I S H

ERISTAIIS \ TUBIFEX

CHIRONOMUS

*\

IMPROVING

N O R M A ! FISH P O P U L A T I O N : G A M t , P A N I O O D , F O R A G E FISH

C A D D I S FLY

__

SIMULIUM

\ S T O N E FLY

OSCILLATORIA MELOSIRA ^ SPHAEROTILUS

a

SPIROGYRA PANDORN I A t-Jt EUGL£NA

OFDOGONU IM NAVC IULA Kw DINOBRYON

CLEAR A N D FRESH

Intro, f i g . 5 1 . P o l l u t i o n a n d r e c o v e r y i n a s t r e a m . A s the o x y g e n d i s s o l v e d i n the w a t e r d e c r e a s e s ( c u r v e at left), s o d o c e r t a i n m i c r o b r g a n i s m s a n d , i n turn, t h e i n s e c t s a n d f i s h e s t h a t d e p e n d u p o n t h e m for f o o d ( E l i a s s e n , 1 9 5 2 ) .

the oxidation of organic matter by bacteria is hastened because sunlight can penetrate the clearer water and produce oxygen through the agency of the more numerous algae. Spirogyra and Euglena are often abundant in the plankton, and Chironomid larvae occur in enormous numbers on the bottom. Finally, and often within a surprisingly short distance, the stream returns to normal with clear water, clean bottom, abundant oxygen, and with the wide variety of organisms described elsewhere. A similar pattern is seen when organic matter is dumped into lakes, but the effect of water movement is less evident and in smaller bodies of water the chief agents for recovery of oxygen are the algae. Trickling filters.— The ability of natural waters to purify themselves is limited. For example, a stream loses its ability to absorb organic pollution if its microorganisms use up the dissolved oxygen faster than it can be replenished (Eliassen, 1952). The rate at which the micropopulation uses up oxygen depends primarily on the amount of organic matter in the water. This establishes what is known as the biochemical oxygen demand (B.O.D.). Various methods have been devised to reduce the B.O.D. to a level that a stream can absorb. Perhaps the commonest method is the trickling filter (intro. fig. 52). The various steps in the trickling filter process are as follows: After preliminary grease removal and chemical treatment, if necessary, the sewage is run through a primary settling tank. There, solids are taken out and pumped to a sludge digestion tank where anaerobic bacteria

act to reduce the material and methane gas is produced. After treatment the dried sludge is used as fertilizer. Meanwhile the fluid sewage is sprayed onto filter beds where it trickles between rocks of 1- to 3-inch diameter to a depth of 3 or 4 feet. The surfaces of the rocks soon become coated with zoogloea, an organic film containing millions of bacteria, algae, and other microscopic organisms. Oxidation (and hence treatment) of the sewage takes place as it passes over the zoogloea. For efficient operation the filter must be rich in zoogloea but still open enough so that the liquid can pass through at a high rate. Psychodid larvae play a decisive role in this process. They occur in enormous numbers in filter beds where they feed on the zoogloea. Too many larvae scour the rocks excessively and reduce the effectiveness of the treatment. On the other hand, too few larvae result in excessive growth of the zoogloea which clogs the filter and produces "ponds" of standing water that may halt the entire process. Larvae have been maintained at optimal levels in recent years by careful application of DDT in wettable form at dilutions of 5 parts per million. After treatment in the filter the effluent may be run through a secondary settling tank and chlorinated to kill pathogenic bacteria. Finally it is discharged into a stream or other body of water which has been found capable of carrying the reduced but nevertheless considerable organic load. Oxidation ponds or sewage treatment lagoons.— Another method for the treatment of domestic and

37 Usinger: Introduction

oxygen and nutrients between mud and water. In the biodynamics of oxygen pond treatment insects represent one of the end points of energy transfer—unless fish are introduced to eat the insects. Also insects are the only agents that actually remove part of the energy and organic load from the system as they emerge and fly away. The rest of the unsettled material is transformed into dead algal cells with a B.O.D. -, Gas Storage T a n k Operating Building feyj Grease R e m o v a l / that may not be very different from (he original sewage '\ i'C h e m i c a l i l - l^T" and hence creates a considerable load when disI ! ! ¡Treatment' charged into a stream. Detection of pollution.—Various tests have been SluJge devised to recognize the presence of pollution and to Digestion detect the effects of past exposure to wastes. The Tank simplest methods and therefore the ones most generally used are physical and chemical. It is relatively easy to take water samples from a stream, for example, and test for dissolved oxygen (DO), biochemical oxygen demand (B.O.D.), pH, turbidity, and the presence of toxic chemicals. However, such tests are not very revealing because pollutants are seldom discharged continuously and therefore their presence may be missed by sampling at the wrong time. What is needed is a method of determining the Glass Covered effects of pollution on the resident biota, and this Sludge B e d s is precisely where insects fit into the picture. "Specifically (as stated by Gaufin and Tarzwell, 1953), the degree and extent of pollution in a stream can be determined accurately by reference to the macroinvertebrate fauna, particularly that found in the riffles. A biological analysis of the pollutional ,,.'!> Final Effluent status of a stream can be obtained in the field through recognition of the orders, families, or genera in the Intro, fig. 52. Model sewage treatment plant showing the various processes including settling, filtration, and sludge invertebrate associations encountered. This type of digestion. The arms on the filter rotate s l o w l y , spraying f l u i d biological inventory is superior to chemical data, which t r i c k l e s over the zoogloeal surfaces and through the [because] the complex of such organisms which i n t e r s t i c e s o f t h e r o c k s ( E l i a s s e n , 1952). develops in a given area is . . . indicative of present, industrial wastes is by oxidation in shallow ponds. as well as past, environmental conditions . . . Bottom This is the procedure used in many suburban and organisms are more fixed in their habitat than are fish rural parts of California. Sewage is settled and or plankton and cannot move to more favorable surstrained to eliminate solid matter and then the fluid roundings when pollutional conditions are most is run through a series of shallow ponds several critical." acres in extent. Organic matter is acted on by bacBecause of the importance of the bottom fauna teria, first under virtually anaerobic conditions and and more particularly in streams, the insect fauna, later in the presence of oxygen supplied in large attempts have been made to set up criteria of abunpart through photosynthesis by symbiotic algae. dance or to fix upon the presence or absence of Insects play an important part in this system. Only certain indicator organisms as evidences of pollution. surface breathing Tubifera larvae and other Diptera Unfortunately, these efforts have failed because, as with respiratory tubes can live in the milky, anaerobic pointed out by Patrick (1953), it is the total spectrum water of the first ponds. Later, however, a rich insect of all groups of organisms that provides the best fauna develops with many beetles, true bugs, dragonfly criterion for judging the "health" of a river. In and mayfly nymphs, and mosquito larvae. general a normal stream will be rich in species with By far the most numerous forms, however, are no single group predominating, whereas a polluted Chironomid larvae (Glyptotendipes, etc.). Counts of stream is poor in number or variety of species but 1,500 or more per square foot of bottom surface have often rich in individuals. Therefore it has been sugbeen made, and the total dry weight of the annual gested (Needham and Usinger, 1954) that biological crop of larvae in a 4% acre pond at Concord has been sampling for detection of pollution be done by means calculated at 575 pounds (Kellen, 1955). The algal of bottom samples (Surber or drag-type samplers). blooms utilize end products of bacterial metabolism The organisms in the samples should be sorted out and form a high percentage of the final effluent. according to orders or other major taxonomic groups. However, the larvae extract algae by filter feeding; In this way the spectrum of organisms can be deteralso, they burrow at the mud-water interface, extend- mined with only two or three square-foot samples ing oxygen deeper and promoting the exchange of giving reliable evidence as to the presence or absence of main groups.

38

Usinger: Introduction

By -way of summary it should be emphasized that wastes are not intrinsically bad. In many cases they are legitimate by-products of man's civilization. Too often industrialists try to ignore pollution problems by "looking the other way" and conservationists would simply legislate them out of existence. The result is an impasse and the solution, of course, lies not in either extreme but requires that issues be faced squarely and dealt with on a continuing basis. Actually, substantial progress has been made in recent years by recovering useful chemical wastes, improving erosion control, and by increased knowledge of the processes involved in reduction of organic wastes by natural waters. It is now realized that organic wastes simply speed the process of eutrophication in a lake or stream. In limited or controlled amounts they increase the productivity of natural waters. It is only when an excessive load is dumped at a time or place which affects the interests of other people that trouble starts. At such times the limnologist is usually called upon to provide evidence for or against pollution. Pond F i s h Culture

Aquiculture has been practiced since the dawn of history and has been a source of protein in China and India for centuries. Strictly from the viewpoint of productivity in pounds per acre, carp are unsurpassed, yielding up to 3,000 pounds per annum in the Orient. However, in the United States carp are not considered desirable for human consumption, and fish ponds are not intended solely for food production. They may be purely aesthetic garden ponds, primarily practical farm ponds for watering stock, or recreational pools for fishermen. In California there has been increased interest in the multipurpose farm pond and in commercial "trout farm" ponds where fishermen are guaranteed results and pay for their catches by the linear inch or pound. Experiments in Alabama (Swingle and Smith, 1941) have shown that each pond has a normal carrying capacity for a particular species of fish, regardless of depth (18 to 54 inches) and regardless of number of fish stocked. If a pond is overstocked, the fish will be small, if understocked, they will be large; in either condition the pounds per acre will be the same. Phytoplankton feeders such as goldfish yielded up to 1,000 pounds per acre; insect feeders such as bluegill, 600 pounds per acre; and fish feeders such as large-mouthed black bass, 200 pounds per acre. Ideally, a pond should be stocked with a ratio of carnivorous and forage fish of approximately 1:10 or 1:15. The total productivity of a pond can be increased by addition of fertilizer. The following mixture is recommended: 40 pounds of sulfate of ammonia, 60 pounds of superphosphate (16 per cent), 5 pounds of muriate of potash, and 15 pounds of finely ground limestone per acre. The materials should be mixed before applying. Fertilizer was applied in Alabama (Swingle and Smith, 1951) beginning in April or May

and continuing every four weeks until September or October. Thus eight to fourteen applications were made at an annual cost per acre of $11.00 to $20.00 or 3 to 6 cents per pound of fish. The stocking policy of the U. S. Fish and Wildlife Service for new farm ponds in the southeastern states is: 50 bass and 500 bluegills per acre in unfertilized waters, and 100 bass and 1,000 bluegills per acre in fertilized waters (Holloway, 1951). Weeds are generally considered to be undesirable in fish ponds. They supply protection for mosquito larvae, hinder bass from their essential role in preventing an overpopulation of plankton and insectfeeding fish, utilize fertilizer without greatly increasing food for fish, and interfere with sport fishing. To prevent the rooting of weeds along shore lines, the edges of ponds should be deepened. Periodic clearing also may be necessary to remove volunteer plants before they become heavily rooted and spread (Davison and Johnson, 1943). The role of insects in farm ponds was studied intensively by Wilson (1923) in Iowa. It was found, as might be expected, that insects are an important element in the food of pond fishes and that they are, in turn, dependent on phytoplankton and other organic matter for their existence. However, a special situation exists for predatory insects in farm ponds. Immediately after stocking, all the fish are small and hence are at the mercy of the larger insects, with no fish yet large enough to eat them. The beetle genera Dytiscus, Hydrous, and Cybister, Belostomatids, and large nymphs of Odonata are especially troublesome in ponds with fish fry but seldom bother fish more than one year old and, in fact, are a valuable source of food for the larger fish. Therefore it is recommended to: screen small ponds for fish fry in areas where large predatory insects occur in abundance; remove strong lights from the immediate vicinity of ponds since the large predators are attracted to lights; remove fry from infested ponds and stock with larger fish; and remove fry and drain infested ponds, thus exposing large predators so that they may be destroyed by hand. Chemical control has been recommended by Meehean (1937), using oil film at the surface (1 part cod-liver oil to 3 parts kerosene, or straight kerosene at 10-12 gallons per acre), but this has no effect on the gill-breathing immature insects which take oxygen beneath the surface. A purely negative approach is not adequate for proper management of insects in pond fish culture. By far the majority of aquatic insects are desirable and should be maintained at high population levels. Fortunately, insects need not be stocked because they migrate readily from one pond to another. Wilson (1923) found eight species of beetles in a new pond twenty-four hours after it was filled with water and five more species invaded the pond after three days. In ponds where predation by fish is so intensive that insects cannot maintain themselves, fish-free side ponds or troughs may be used. In this way stocks of insects can be developed and washed into fish ponds periodically as needed.

39 Usinger: Introduction Stream and L a k e Management

Sport fishing has long been a means of recreation and, in recent years, has achieved the status of big b u s i n e s s . In addition to the large investments for the manufacture and s a l e of fishing gear, there i s enormous expenditure for hatchery production and stocking of fish. More recently attention has been directed to the improvement of natural waters in an attempt to provide more fish at l e s s c o s t than has been p o s s i b l e with hatchery methods. T h i s i s a complicated s u b j e c t with ramifications that have no place in a book on aquatic i n s e c t s ; therefore the present d i s c u s s i o n will be limited to the entomological a s p e c t s of stream and lake management. Analysis of food grades and preferences.—Hatcherybred fish have been stocked in California waters for more than half a century. Much of this was done without regard to the natural food supply and hence with no knowledge of the carrying capacity of the stream or lake, but in recent years this situation has changed. Pioneer studies by Embody (1927) provided the b a s i s for a stocking policy, and more recently investigations have been made of the fish-food organisms of many of our lakes and streams; stocking recommendations have been based on them. Unfortunately, most surveys of stream-bottom organisms have been made with a Surber Square F o o t Sampler. Although this i s undoubtedly the most practical sampler thus far devised for shallow r i f f l e s , Needham and Usinger (1955) showed that it does not give s t a t i s t i c a l l y significant data for total weights and numbers of organisms, even in a single relatively uniform riffle. It was found that 194 and 73 samples, respectively, would be required to give reliable figures at the 95 per cent level of s i g n i f i c a n c e . Hence all existing data on stream-bottom organisms is s t a t i s t i c a l l y inadequate, but it is the best we have and may be the best that can be obtained b e c a u s e of the extreme variability of stream habitats. Examples of this type of data are found in the unpublished reports of Needham and Hanson (1935), Smith and Needham (1935), and T a f t and Shapovalov ( 1 9 3 5 ) for the Klamath, S h a s t a , Sierra, Mono, and Inyo national forests. Some idea of average and extreme numbers of bottom food organisms for various streams (Surber samples) and l a k e s (Ekman samples) in California are given in table 3. TABLE

Klamath and Shasta Mono and Inyo Sierra

TABLE 4 (Introduction) S T A N D I N G C R O P S O F B O T T O M O R G A N I S M S IN P O U N D S P E R A C R E A T V A R I O U S S E A S O N S IN W A D D E L L C R E E K , C O N V I C T C R E E K , AND T H E M E R C E D R I V E R .

Waddell Creek

Standing crop l b s . per acre

Month

Location

February, 1933 May, 1933

Low Convict Creek Merced River

70 472

May to Sept., 1938

68

May to Sept., 1942 February August

197 103 85

High

Attempts have been made to improve the techniques for sampling fish-food organisms in order to obtain more meaningful r e s u l t s . Such efforts are of g r e a t e s t importance to the aquatic entomologist who has found himself too often in the p a s t expending great effort in the field to obtain data which are virtually meaningless. One attempt at increasing precision is the " f o r a g e r a t i o " (Hess and Swartz, 1941) proposed to aid in interpreting the results of stomach contents investigations. It was pointed out that the organisms found in the stomach of a fish reveal nothing a s to food preferences unless it is a l s o known what organisms occurred in the immediate environment of the fish a t the time it was feeding. T h e forage ratio ( F R ) is obtained by dividing the percentage of a given kind of organism in the stomachs by its percentage in the environment. T h e formula may be expressed a s follows:

3 (Introduction)

n

A V E R A G E NUMBERS OF B O T T O M F O O D ORGANISMS T A K E N B Y S Q U A R E F O O T S U R B E R S A M P L E R S IN S T R E A M S AND B Y I / 4 S Q U A R E F O O T E K M A N S A M P L E R S IN L A K E S O F C A L I F O R N I A IN 1 9 3 4 National forests

dwelling organisms. Therefore the total volume or " w e t w e i g h t " may be more s a t i s f a c t o r y . Wet weights are commonly taken after drying the samples for one minute on blotting paper. In a quantitative t e s t using 100 samples taken from a single riffle in P r o s s e r Creek near T r u c k e e , California, Needham and Usinger (1954) found a minimum of 2 and a maximum of 198 organisms per square foot with wet weights from 0 . 1 5 grams to 2 . 3 1 grams. F o r comparative purposes wet weights are sometimes calculated in pounds per acre. T a b l e 4 shows such figures for Waddell Creek near Santa Cruz, the Merced River in Yosemite National P a r k , and Convict Creek at the head of the Owens River (Needham, 1938, 1939; Maciolek and Needham, 1952).

N o . of stream organisms

N o . of lake organisms

380 370 143

150 66 26

Numbers of organisms can be quite misleading b e c a u s e of the great disparity in s i z e of bottom-

FR = N' where n = the number of any organism in the stomachs, N = the total number of organisms in the stomachs, n' = the number of the same organism in the environment inhabited by the fish, and N' = the total number of food organisms in the environment. Weight or volume may be substituted for number if desired. A forage ratio of 1 indicates that an organism is being taken at random according to i t s relative abundance in the environment; a forage ratio of more than

40 Usinger: Introduction MOUl/SCA NEMATHEIHINTHES IfYMEMOPTERA \\ HE MPVERA PISCES (OVAt •COLEOPTERA *JPLECOPTERA CRUSTACEA DIPTERA fj[. UMUMDAE

« o < ve

.TSKHOPTERA

LARVAL DENSfTY PER SQUARE FOOT Intro, (ig. 53. C o r r e l a t i o n b e t w e e n forage r a t i o and d e n s i t y of m o s q u i t o l a r v a e ( H e s s a n d T a r z w e l l , 1942).

1 indicates that an organism is either being selected in preference to other organisms, or that it is more a v a i l a b l e than others; and a forage ratio of l e s s than 1 indicates that an organism is either l e s s preferable or l e s s available. In a test using top minnows (Garnbusia affinis) and anopheline and culicine larvae, Hess and T a r z w e l l (1942) found that there was a direct correlation between forage ratio and population density (intro. f i g . 53).' " T h i s would seem to indicate that as Anopheles became more abundant, Gambusia became more accustomed to feeding upon them and began to s e l e c t them in preference to other food organisms p r e s e n t . " A knowledge of the biology of aquatic insects should be used in conjunction with forage ratio data in order to interpret the results correctly. For example, during one period of their development different spec i e s of food organisms may be of great value to the fish and at another period be of no value. Hess and Swartz c i t e emerging caddisfly pupae as a c a s e in point. Trichoptera larvae may be relatively unavailable to the fish owing to their stone c a s e s ; the pupal

.EPHEMEKOPTERA

Intro, fig. 55. C o m p o s i t i o n of food material from the s t o m a c h s of trout f e e d i n g in the s a m e area at the s a m e time a s Intro, fig. 5 4 ( N e i l I, 1938).

stage is quiescent and spent under a stone c a s e , but when the pupae emerge and make their way to the surface of the water, they are free of their cases and are readily available to all fish. The forage ratio may also be used to make more meaningful the calculation of food grades of streams ( H e s s and Swartz, 1941). F o o d grades have commonly been determined without regard to the value of the various organisms as food for the fish. T h e following method was proposed to correct this: The forage ratio for a given group multiplied by the mean density of the group per square foot will g i v e a measure of the " e f f e c t i v e food g r a d e " in terms of that group, in relation to the species of fish for which the forage ratio was determined. Only those organisms which

I

April

Intro, f i g . 5 4 . C o m p o s i t i o n of the bottom f a u n a area o f the R i v e r D o n ( S c o t l a n d ) d u r i n g s p r i n g ( N e i l l , 1938).

in a limited a n d summer

EPHÍME80PTERA

SlMl/VinAf-

May

June

Wm

BY WEIGHT

•

BY NUMBER

I July

Intro, f i g . 56. S e a s o n a l f l u c t u a t i o n s in a m o u n t of food t a k e n by trout ( b a s e d o n the a m o u n t of E p h e m e r o p t e r a , T r i c h o p t e r a , and S i m u l i i d a e f o u n d in the s t o m a c h s ) ( N e i l l , 1938).

41 Usinger: Introduction 12. C o l e o p t e r a , Hemiptera, Hymenoptera, A r a c h n i d a , M o l l u s c a , Nematoda, H i r u d i n e a , P i s c e s (ova). 11. C r u s t a c e a . 10. P l e c o p t e r a 9. D i p t e r a ( i m a g i n e s ) other t h a n S i m u liidae 8. D i p t e r a (larvae and pupae) other than Simuliidae.

100—

^

9,10,11,1|

—100

10,11,12

10,11,12 9 8

WO—

—

90

80—

—

80

70—

—

70

(»0—

—

60

fiO—

—

50

10—

—

40

30—

—

30

20—

—

20

—

10

—

0

7. S i m u l i i d a e ( i m a g i n e s ) . 6 . S i m u l i i d a e (pupae).

5. Simuliidae (larvae).

4. T r i c h o p t e r a ( i m a g i n e s ) . 3. T r i c h o p t e r a (larvae and pupae).

2. Ephemeroptera ( s u b - i m a g i n e s and imagines).

m 1. Ephemeroptera ( n y m p h s ) .

10—

m

m

1

(I— April

May

July

I n t r o , f i g . 5 7 . C o m p o s i t i o n of f o o d m a t e r i a l m o n t h b y m o n t h . T h e s e c t i o n s o f e a c h c o l u m n r e p r e s e n t , s u p e r i m p o s e d in the order s h o w n on the left, the p e r c e n t a g e of the m o n t h ' s food m a t e r i a l f o r m e d b y the d i f f e r e n t g r o u p s d r a w n o n ( N e i l l , 1 9 3 8 ) .

make up 1 per cent or more of the f i s h ' s d i e t w i l l be considered as food organisms. Sufficient numbers of both bottom samples and f i s h e s ' stomachs shall be taken to keep the standard error within 10 per cent of the mean. Another factor to consider in food preference studies is the rate of digestion of different organisms eaten by fish. Hess and Rainwater (1939) found that softbodied organisms, such as many dipterous larvae, are digested and passed through the alimentary tract much more rapidly than heavily chitinized forms such as stonefly nymphs. D i f f e r e n c e s in rates of digestion of various organisms and differences in time of exposure to digestion in different stomachs (owing to delays in dissecting stomachs, gathering fish from traps or g i l l nets, e t c . ) therefore should be considered in interpreting food preference data.

l i f e histories. However, N e i l l (1938) has conducted a comprehensive study on the R i v e r Don in Scotland that might w e l l serve as a model for future investigations: 1. T h e general characteristics of the site were recorded on a sketch map and summarized, including area, gradient, current v e l o c i t y , depth, nature of bottom, nature of banks, influence of pollution, and general nature of the biota, plant and animal, including fish, and, as far as p o s s i b l e , synchronous f i e l d observations were made both in regard to day and hour (noon); 2. Daily observations were made of air temperature, barometric pressure, light intensity, rainfall, wind, water temperature, depth, current speed, water samples for pH, alkali reserve, carbon dioxide content, oxygen content, bottom samples (using a cylindrical sampler somewhat like the Hess modification of the Surber sampler), plankton samples, surface It is probably too early in the development of the samples, and fish captures, and preservation of stoms c i e n c e of aquatic entomology to outline an ideal achs; 3. T h e bottom fauna for the limited area during procedure for the analysis of fish-food organisms spring and summer (intro. f i g . 54) was compared with because too many of the basic techniques are inade- the food material (intro. f i g . 55) taken from the stomquate and too little information is available on insect achs of fish feeding in the same area over the same

42 Usinger: Introduction WATER SURFACE

- IMAGO

-PUPA

-LARVA

EGG BAETIS

SIMULIUM

Intro, f i g . 58. Relative accessibility of Baetis and Simulium during the aquatic stages of the l i f e c y c l e . Degree of shelter— black. Degree of exposure—white (Neill, 1938).

period of time; 4. Seasonal variations in amount of food (intro. f i g . 56) and composition of food (intro. f i g . 57) were recorded; 5. The e f f e c t s of current, vegetation, type of bottom, and chemical character of the water were related to densities of food organisms; 6. F i s h were taken at a time to correspond to the end of a given d a y ' s feeding, thus ensuring adequate fresh material; they were captured mostly by angling rather than by seining,, (but no significant differences were found in amount and kinds of food in the stomachs of 496 fish whether taken with nets or by angling, Dimick and Mote, 1934); 7. A l l organisms were identified to the s p e c i e s l e v e l with notations as to developmental stages; 8. For each group the l i f e c y c l e s of the s p e c i e s present were described, so that the times of greatest abundance could be associated with the presence of various organisms in the food; 9. The relative a c c e s s i b i l i t y (intro. fig. 58) of each of the principal food organisms TABLE

was worked out by grouping the whole fauna into f i v e categories, to each of which a conservatively estimated " c o e f f i c i e n t of a c c e s s i b i l i t y " was assigned. A l l available bionomic data were taken into account in assigning these figures which ranged from 1.0 for freely exposed groups ( e . g . , Simulium) to 0.0 for comp l e t e l y secure groups (Oligochaeta) (table 5). T o t a l numbers in the bottom samples were multiplied by the appropriate c o e f f i c i e n t to bring out the a c c e s sible fauna. In spite of the somewhat arbitrary method of ranking, a high degree of correspondence was found when figures for the " a c c e s s i b l e " fauna were com-? pared with those for stomach contents. T h i s led N e i l l to the conclusion that " t h e predatory relationship between the brown trout and its organic environment therefore i s that the trout feeds on the whole range of animals present in whatever type of habitat it finds itself to an extent dependent on the degree of a c c e s s i b i l i t y and the extent of their representation in the fauna. T h i s is sufficient to account for the nature of its stomach contents without invoking discrimination on the part of the f i s h . " Summary of the methods of assessment of the food of fresh-water fish (after Hynes, 1950).—Most workers studying the food of fresh-water fish have based their conclusions on study of the contents of the stomach or, more rarely, of the entire gut of captured fish. Digestion is l e s s advanced in the stomach, and thus identification of the contents is usually more satisfactory. There has been great variety in the methods of analyzing and presenting the data. Some authors have merely listed the food organisms found in each fish, but this, without analysis, g i v e s no indication of the relative importance of each type of food organism, and most workers have analyzed their data by one or more of the following methods. ( a ) The occurrence method. The number of fish in which each food item occurs i s listed as a percentage of the total number of fish examined. Often the number of occurrences of all items is summed and scaled down to a percentage basis to show the percentage composition of the diet. (b) The number method. T h e total numbers of individuals of each food item are given, and are a l s o usually expressed as percentages of the total number of organisms found in all fish examined. ( c ) The dominance method. T h e number of fish in which each food item occurs as the dominant foodstuff is expressed in one of the two ways used in the occurrence method.

5 (Introduction)

" C O E F F I C I E N T OF A C C E S S I B I L I T Y " OF COMMON GROUPS OF AQUATIC ORGANISMS Freely exposed 1.0

Partly protected or hidden 0.78 0.5

Largely secure 0.25

Secure 0.0

Simulium (all stages)

Ephemerid nymphs

Trichoptera larvae and pupae

Coleoptera larvae

Oligochaeta

Coleoptera (adults)

Pleooptera nymphs

Hirudinea

Diptera larvae

Hydr acarina

Nematoda Díptera pupae Crustacea Mollusca

43 U s i n g e r : Introduction

(d) The volume and weight methods. The volume or weight of each food item, or of the total food of each fish, is given, and is usually expressed as a percentage of the total weight of the fish. Some authors calculate the weight of food eaten from the known average weight of each individual of each food item. Most workers use this method only to supplement some other method, and it is often used to show seasonal variation in food intake. Ricker, however, by counting and " w e i g h t i n g " each type of food organism according to its known average weight, has evolved a method similar to the points method (below). (e) The fullness method. Some workers wishing to demonstrate seasonal variation in food intake have used an arbitrary estimate of the fullness of the stomachs. This is only a special extension of the total volume method. (f) The points method. Swynnerton and Worthington used a method in which the food items in each fish were listed as common, frequent, etc., on the basis of rough counts and judgment by eye, due regard being taken of the size of the organisms as well as of their abundance (i.e., one large organism counted as much COMBINATION

WAVE-BREAKER

AND FISH

SHELTERS

as a large number of small ones). Each category was then allotted a number of points and all the points gained by each food item were summed and scaled down to percentages, to give percentage composition of the food of all the fish examined. This is essentially a volumetric method, and is similar in principle to that of Ricker above. However, until dietetic values of food s p e c i e s are known, volume would appear to be a satisfactory basis for assessment, and this method has the advantage of being rapid. The points system of Swynnerton and Worthington has been modified slightly by taking into account a l s o the degree of fullness of the stomach. Consideration of the various methods indicates that the points method is the most satisfactory. F a c t s in its favor are that it is rapid and e a s y , requires no special apparatus for measurement, is not influenced by frequent occurrence of a small organism in small numbers, nor of heavy bodies, like snail shells and caddis c a s e s , and does not involve trying to count large numbers of small and broken organisms. It a l s o does not give the spurious impression of accuracy which i s given by some other methods.

WEED-BED

SPAWNING

AND

FOOD PRODUCING SLAB

Ma.icn.als

: 0labs wire states

Oak or Material

s :

t ocs 6 to 10 inches Slabs4- to /Z inches

ROCK TYPES

WEED Square

or

BED

or recéanejuhzr Min.tm.um dimensions

TYPE in.

general zo ft

* 20

¿fia.f>a> ft.

elm.

short Ìocjì

I n t r o , f i g . 59. M e t h o d s of i m p r o v i n g s h e l t e r for a q u a t i c o r g a n i s m s a n d in l a k e s ( H u b b s a n d E s c h m e y e r , 1 9 3 8 ) .

DEVICES

TYPES

fish

+ te

/z

AT* 9 4'dieim.

inch«s yauyo so

tony

44 Usinger:

Introduction

Improvement of streams and, lakes.—Stream and lake management for the production of fish-food organisms was first developed in England (Mosely, 1926) where private trout streams have been maintained for centuries and close attention could be given to methods for the production of fish-food organisms. Many of the techniques advocated for British streams, such as collecting eggs of mayflies to introduce into a barren stream, are totally impractical here where miles of unimproved waters exist. However, some practical techniques have been developed in this country (Hubbs and Eschmeyer, 1938) and abroad, mainly applying to the fish alone but in some cases with definite advantages from the standpoint of fish-food production. Certain practices have been found to be effective in increasing fish food in lakes. These include: (1) management of water level by dams so as to maintain maximum littoral productivity and, in small lakes, to prevent drying up with consequent mortality; (2) stabilizing banks by plantings to avoid excessive silting; (3) regulating the abundance of fish and balance of kinds of fish so that fish populations can maintain themselves at optional densities in relation to food supplies; (4) improving the shelter for both, aquatic organisms and fish (intro. fig. 59); and (5) managing the growth of aquatic plants. Other measures such as fertilizing and dredging or filling have been done in small artificial impoundments but are not practical or .even desirable in most natural lakes of the state. In streams fish need pools for protection and riffles for food production and spawning. Therefore stream improvement seeks to provide both types of habitat in the proper proportions, usually in a ratio of about 1:1. Riffles are maintained by clearing trash and logs and by fencing to prevent trampling by stock. Pools are created by small dams or by deflectors strategically placed (intro. fig. 60). Banks are stabilized by plantings to prevent erosion. In burned-over areas shade is restored by reforestation so that water temperatures in trout streams can be maintained below 70°-75° F . It is very difficult to measure the results of stream improvement because of the lack of precise sampling methods. Tarzwell (1937) attempted an evaluation in Michigan by determining the average production for various types of bottom and then calculating the potential volume of food production on the basis of the area of each bottom type before and after improve-

Spring

Boulder

Stone

Retards

Deflector Br

Stone

Deflector Stake

Log

Cover

Planting —C^V

Section

C—C

of D e i b l e r

Dam

Intro, f i g . 6 0 . S u m m a r y of s o m e s t r e a m improvement t e c h n i q u e s ( L a g l e r , 1952).

ment (table 6). The results showed a threefold increase after improvement. More general methods for improving the health of streams include the following: 1. Pollution is prevented whenever possible. 2. Check dams are installed in large drainage areas primarily for flood control but also to maintain some flow throughout the year in otherwise intermittent streams (flow maintenance dams, Cronemiller, 1955) thus permitting the survival of organisms with long life cycles and creating a perennial population of fish food organisms; 8. Stream flow is equalized below large dams by judicious management to avoid the scouring effects of flash floods and the mortality caused by drying parts of the bed; 4. Finally, efforts are being made in a few places to control the ratio of predators to bottomfeeding fish so that optimum productivity of fish food

TABLE 6 (Introduction) V O L U M E OF POOD P R O D U C T I O N IN A S T R E A M B E F O R E AND A F T E R I M P R O V E M E N T , C A L C U L A T E D ON T H E BASIS OF A V E R A G E P R O D U C T I O N OF VARIOUS B O T T O M T Y P E S AND I N C R E A S E IN A R E A O F E A C H B O T T O M T Y P E

B o t t o m type

Sand Muck Gravel Gravel riffle Plant beds Total

A v e r a g e production oil 4 s q . f t . (in QO.)

0.27 3.99 22.76 12.48 5.32

Before

improvement T o t a l oaloulated production (in o o . )

A r e a of e a c h bottom type in s q . f t .

76,105 4,942 17,791

5,137 23,397 12,276

98,838

22,355

A f t e r improvement A r e a of e a c h bottom Total oaloulated type in s q . f t . production ( i n o o . )

48,995 23,397 14,719 7,142 4,585 98,838

3,307 23,397 10,156 22,283 6,098 65,241

45 Usinger: Introduction is permitted. Ultimately it is hoped that streams can be managed in such a way that they will produce maximum numbers of game fishes and at the same time be restored as nearly as possible to their natural condition. Artificial flies and the fisherman's entomology.— Whether entomology has a place in the art and lore of angling is a moot question. Leonard (1950) takes a p o s i t i v e position, stating that, " t h e fisherman with a knowledge of aquatic insects and the important relationship they bear to the fish he wants to catch is better equipped with a single fly than is the man who knows nothing of such things though he sports a j a c k e t full of fly-boxes stuffed with crisp, unmouthed f l i e s of every description. T h e man with an understanding of aquatic l i f e knows how and where to place his casts, fishing those places his knowledge tells him suit the lure and the fish, whereas the other fellow will c a s t at random, forever changing f l i e s , fondly hoping that eventually he will discover a f l y of some sort that w i l l catch a fish . . . T h e fly-dresser in particular is obliged to know as much as he possibly can about the l i f e c y c l e s of the insects his f l i e s are designed to represent. The more he knows about their aquatic and aerial stages, the more intelligently he will design, balance, and dress the c o p i e s . " That Leonard is not alone in his position is indicated by a literature that runs into hundreds of t i t l e s . One of the earliest accounts ( c a . 200 A . D . ) is by Aelianus in De Animalium Natura (1611) so the Macedonians are credited 'with the first use of artificial f l i e s in the river Astraeus. In England the subject came into its own with such c l a s s i c s as A Treatyse of Fysshynge With an Angle by Dame Juliana Berners (1496). Later c l a s s i c s include: Izaak Walton's The Compleat Angler, or the contemplative man's recreation, being a discourse of rivers, fishponds, fish and fishing (1653) (5th ed., 1676, with Cotton's Instructions how to angle for a Trout or Grayling in a clear stream, containing many entomological notes); R o n a l d s ' The Fly-Fisher's Entomology (1836); Halford's Dry-fly Entomology (1897); M o s e l y ' s The Dry-fly Fisherman's Entomology (1921); and Harris' An angler's Entomology (1952). A noteworthy American title of recent date is J. Edson Leonard's Flies, their origin, natural history, tying, hooks, patterns and selections of dry and wet flies, nymphs, etc. (1950). "Fundamentally [as stated by Leonard, 1950], artificial f l i e s are made according to two schools of thought. T h e first, the Impressionistic, b e l i e v e s that approximate s i z e , general appearance and color are sufficient to lure a trout under all conditions, while the second, the R e a l i s t i c , demands precise duplication of an i n s e c t . " In the books mentioned above and in literally hundreds of others, we find an astonishing amount of fact and fiction, of novelty and tradition, of superficiality and meticulous care. A s an illustration of the latter the following quote from " P i s c a t o r " in the P r e f a c e to the sixth edition of Ronalds (1862) i s typical, stating that, " h e has been induced to paint both the natural and artificial fly from nature, to etch them

with his own hand, and to colour, or superintend the colouring of each particular i m p r e s s i o n . " Scientific competence was added to the empirical observations of former times by the late Martin Mosely, deputy keeper of entomology in charge of the principal groups of aquatic insects at the British Museum (Natural History). Mosely was a c l o s e a s s o c i a t e of Halford and after his death controlled a length of the River T e s t at and below Mottisfont (England), for a joint period of about eighteen years. M o s e l y ' s contribution to dry-fly entomological literature was to supply at Halford's request " a series of plates, . . . based on modern s c i e n t i f i c ideas, and illustrating in color the insects which are of main importance to the dryfly fisherman." In setting out to accomplish this Mosely stated that " I am . . . inclined to regard such a task as this with the e y e of an entomologist rather than that of the fly-fisherman; and throwing aside such considerations as whether this f l y is acceptable to the trout, whether that fly has a bitter taste and i s allowed to float away unnoticed, I have attempted to describe the f l i e s which I myself have found in plenty, and which I think my brother anglers w i l l a l s o meet with by the river's b a n k . " " D r y f l i e s " are meant to imitate insects that f a l l onto the water surface and f l o a t without wetting. Actually, such " d r i f t f o o d " includes all sorts of terrestrial insects that f a l l onto the water from overhanging vegetation. In practice, however, most dry f l i e s are made to imitate adults of the aquatic groups — m a y f l i e s , s t o n e f l i e s , c a d d i s f l i e s , and true f l i e s . " W e t f l i e s " are those that are fished under water, including adult insects that have become w e t and immature nymphs and larvae of various kinds. B e c a u s e of the s k i l l s required to s e l e c t and c a s t f l i e s properly the dry-fly fisherman enjoys a higher status than those who employ other techniques and lures. In England, a s p e c i a l fisherman's nomenclature has been developed for the commonest s p e c i e s and higher groups of aquatic i n s e c t s . Since our own literature and culture has drawn s o heavily on British sources many of these names have been carried over, at times inappropriately, to our fauna. T h e resulting confusion is probably of little consequence to the fisherman but TABLE

7 (Introduction)

SCIENTIFIC AND ANGLER'S NAMES FOB SOME COMMON GROUPS OF AQUATIC INSECTS Scientific name Ephemeroptera

Plecoptera Trichoptera Diptera Megaloptera Corydalidae Sialidae Odonata

Angler's names Mayfly, drake, quill, Brown, Cahill Developmental stages: nymph, dun (subimago), spinner (imago), spent-wing (wet imago) stonefly, perl id, willow, sally caddisfly, caddicefly, sedge, grannom, fish moth, stickworm, caseworm crane fly, midge, punkie, gnat mosquito, bloodworm Dobsonfly, hellgrammite Alderfly Dragonfly, damselfly, snake feeder, devil's darning needle, mosquito hawk

Introduction

Dubb

Hackle

Each Turn Slightly Overlapped

F ibers

lers

Wind E v e n l y Toward Front

I n t r o , f i g . 6 1 . T o o l s u s e d for t y i n g (J. E d s o n L e o n a r d , 1950).

flies . 6 3 . T e c h n i q u e for t y i n g a w e t (J. E d s o n L e o n a r d , 1950).

is confusing to the entomologist. Hence the preceding list is given, not to explain common names of British s p e c i e s , but to show the common names of the principal groups of aquatic insects here and abroad with equivalent scientific name (table 7). Much has been made of the technique of fly-tying and of the skill required to achieve a close approximation to nature. The subject is too extensive for detailed treatment here but a few key illustrations are reproduced from the excellent book by Leonard (1950) with permission of the author and the publishers. T h e s e figures are largely self-explanatory but the original work should of course be consulted for d e t a i l s . The tools illustrated (intro. fig. 61) may be obtained from dealers in sporting goods. Materials such as hooks, feathers, silk, wax, and so on, may

Topping lorns7 /

fly

Stroke F i b e r s • T o w a r d Butt to

• over

Slightly Overlap to R e i n f o r c e F a s t e n Quill" B e h i n d Wing

Under Wing

Shoulder

Tail

Topping

D o Not H a l f - H i t c h

Front H a c k l e Wind H a c k l e B e t w e e n A & B a n d S e c u r e at A I n t r o , f i g . 6 2 . T e r m i n o l o g y a p p l i e d to t h e v a r i o u s p a r t s a fly (J. E d s o n L e o n a r d , 1950).

of

Intro, fig. 6 4 . T e c h n i q u e for t y i n g a dry (J.

Edson

Leonard,

1950).

fly

47 Usinger: Introduction Enlarge

Thorax

nd F a s t e n Hump

Hackle Stems Wind Working (Stripped) Silk to H o o k - e y e

Material

Add

Antennae

if R e q u i r e d

Intro f i g . 65. T e c h n i q u e for t y i n g a n y m p h (J. E d s o n L e o n a r d , 1950).

also be obtained commercially but many of the body materials are commonly available as quills, wool, kapok, tinsel, chenille, and chicken feathers. Special terminology (intro. fig. 62) is used for the various parts of a " f l y . " Techniques are shown (intro. figs. 63-65) for tying a wet fly, a dry fly, and a nymph, respectively. With sufficient skill it is possible to copy such standard fly patterns as the "Royal Coachman" or to imitate insects found flying at the stream side or discovered by dissecting fish stomachs. However, as pointed out by Neill (1938), it is not known whether dry flies and wet flies "are invariably accepted by trout for what they are intended to represent." In fact, evidence has been obtained indicating that fish take food strictly according to its accessibility without exercising fine discrimination or food preferences. From the preceding discussion it is evident that aquatic entomology is a large and complex subject. Cutting across many specialized fields, it includes much of general entomology and limnology and certain aspects of public health and wildlife management. The aquatic entomologist should be well grounded in these diverse fields and in addition should be able to use the technical keys and descriptions given or referred to in the following chapters and thus make the study of insects an integral part of his work.

REFERENCES

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HYNES, H. B . N. 1950. T h e food of f r e s h - w a t e r s t i c k l e b a c k s ( G a s t e r o s t e u s a c u l e a t u s and P y g o s t e u s p u n g i t i u s ) , w i t h a r e v i e w of methods u s e d in s t u d i e s of the food of f i s h e s . J o u r . Anim. E c o l . , 19:36-58. ISAAK, L . W. 1952. P r o g r e s s R e p o r t CMCA O p e r a t i o n a l I n v e s t i g a t i o n s P r o j e c t — I n s e c t i c i d e i n v e s t i g a t i o n s . P r o c . P a p . 20th Ann. C o n f . C a l i f . Mosq. C o n t r . A s s ' n . , p p . 31-36. JENKINS, D. W., and S. J . C A R P E N T E R 1946. E c o l o g y of the tree hole b r e e d i n g m o s q u i t o e s of n e a r c t i c North America. E c o l . Monog., 16:31-48. L A G L E R , K. F . 1952. F r e s h w a t e r f i s h e r y b i o l o g y . D u b u q u e , Iowa: W. C . Brown, pp. x + 3 6 0 . L E O N A R D , J . EDSON 1950. F l i e s , their o r i g i n , natural h i s t o r y , t y i n g , h o o k s , p a t t e r n s and s e l e c t i o n s of dry and wet f l i e s , nymphs, s t r e a m e r s , s a l m o n f l i e s for f r e s h and s a l t w a t e r in North America and the B r i t i s h I s l e s , i n c l u d i n g a d i c t i o n a r y of 2200 p a t t e r n s . New York: H. S. B a r n e s , p p . x i i + 340. LINDEMAN, R . L . 1941. S e a s o n a l f o o d - c y c l e d y n a m i c s in a s e n e s c e n t l a k e . Amer. Midi. N a t . , 26:636-673. LINDQUIST, A. W., and C . C . DEONIER 1942. E m e r g e n c e h a b i t s of the C l e a r L a k e G n a t . J o u r . K a n s a s E n t . S o c . , 15:109-120. LINDQUIST, A. W., A. R . R O T H , and J . R . WALKER 1950. R e p o r t on the c o n t r o l of the C l e a r L a k e G n a t , Chaoborus astictopus Dyar and Shannon, in C l e a r L a k e , C a l i f o r n i a . Unpubl. R e p . U.S.D.A. B u r . E n t . P I . Quar. Malaria Control on Impounded Water 1947. pp. x i i i + 422. U.S. P u b l i c H e a l t h S e r v i c e and T e n n e s s e e V a l l e y Authority. Washington, D . C . MACAN, T . T . , C . H . MORTIMER, and E . B . WORTHINGTON 1942. T h e p r o d u c t i o n of f r e s h w a t e r f i s h for f o o d . F r e s h w . B i o l . A s s n . B r i t . E m p . S c i . P u b l . No. 6, pp. 1-36. MACAN, T . T . , and E . B. WORTHINGTON 1951. L i f e in l a k e s and r i v e r s . T h e New N a t u r a l i s t S e r i e s . L o n d o n : C o l l i n s , pp. xvi + 2 7 2 . M A L O E U F , N . S. R . 1936. Q u a n t i t a t i v e s t u d i e s on the r e s p i r a t i o n of a q u a t i c a r t h r o p o d s and on the p e r m e a b i l i t y of their outer i n t e g u m e n t t o g a s e s . J o u r . E x p . Z o o l . , 74:323-351. MEEHEAN, O. L . 1937. Control of p r e d a c e o u s i n s e c t s and l a r v a e in p o n d s . P r o g r . F i s h - C u l t u r i s t , N o . 33, p p . 15-16. MEYER,C.B. 1951. Water r e s o u r c e s of C a l i f o r n i a . State Water R e s o u r c e s B o a r d , B u l l . 1, pp. 1-648. MIALL, L . C . 1895. T h e natural h i s t o r y of a q u a t i c i n s e c t s . L o n d o n : Macmillan. p p . ix + 395. M I L L E R , A. H. 1951. An a n a l y s i s of the d i s t r i b u t i o n of the b i r d s of C a l i f o r n i a . Univ. C a l i f . P u b l . Z o o l . , 50:531-644. MILLER, LEONARD 1951. T h e g n a t problem of E l s i n o r e . P r o c . P a p . 19th A n n . C o n f . C a l i f . Mosq. Contr. A s s ' n . , pp. .96-97. MOSELY, M. E . 1921. T h e dry f l y f i s h e r m a n ' s e n t o m o l o g y . L o n d o n , p p . xx + 109. 1926. I n s e c t l i f e and the management of a t r o u t f i s h e r y . L o n d o n , p p . 1-112. Mosquito a b a t e m e n t in C a l i f o r n i a 1951. State of C a l i f o r n i a , D e p t . P u b . H e a l t h , B u l l . V C - 1 , pp. 1-47. MULHERN, T . D. 1953. B e t t e r r e s u l t s w i t h m o s q u i t o light t r a p s through s t a n d a r d i z i n g m e c h a n i c a l p e r f o r m a n c e . Mosquito N e w s , 13:130-133. MUTTKOWSKI, R . A . 1929. T h e e c o l o g y of trout s t r e a m s in Y e l l o w s t o n e N a t i o n a l P a r k . B u l l . N.Y. St. C o l l . F o r . R o o s e v e l t Wild L i f e A n n a l s , V o l . 2, N o . 2 , p p . 151-240.

49 Usinger: Introduction NEEDHAM, P . R . 1 9 3 4 . Quantitative s t u d i e s of stream bottom f o o d s . T r a n s . Amer. F i s h . S o c . , 6 4 : 2 3 9 - 2 4 7 . 1938. Trout s t r e a m s . I t h a c a , New York: C o m s t o c k . pp. 233. 1 9 3 9 . Quantitative and qualitative observations on f i s h foods in Waddell C r e e k L a g o o n . T r a n s . Amer. F i s h . Soc., 69:178-186. NEEDHAM, P . R . , and R . L . USINGER 1 9 5 6 . V a r i a b i l i t y in the macrofauna of a s i n g l e riffle in P r o s s e r C r e e k , C a l i f o r n i a , a s indicated by the Suber sampler. Hilgardia, V o l . 2 4 , No. 14, pp. 3 8 3 - 4 1 0 . N E I L L , R . M. 1 9 3 8 . T h e food and feeding of the brown trout ( S a l m o trutta L . ) in relation to the organic environment. T r a n s . Roy. Soc. Edin., 59:481-520. ODUM, E . P . 1 9 5 3 . F u n d a m e n t a l s of e c o l o g y . P h i l a d e l p h i a : W. B . Saunders, pp. x i i + 3 8 4 . PATRICK, R. 1 9 5 3 . Aquatic organisms a s an aid in s o l v i n g w a s t e d i s p o s a l problems. Sewage and Ind. W a s t e s , 2 5 : 2 1 0 - 2 1 4 . P E N N A K , R . W., and E . D . VAN G E R P E N 1 9 4 7 . Bottom fauna production and p h y s i c a l nature of the s u b s t r a t e in a northern Colorado trout s t r e a m . Ecology, 28:42-48. PORTMAN, R . F . , and A. H. WILLIAMS 1952. T h e control of Aedes dorsalis and other a q u a t i c p e s t s in r i c e f i e l d s . P r o c . P a p . 20th Ann. C o n f . C a l i f . Mosq. Contr. A s s ' n . , pp. 8 8 - 8 9 . R E E V E S , W. C . 1 9 5 3 . The knowns and the unknowns in the natural history of e n c e p h a l i t i s . P r o c . P a p . 2 1 s t Ann. Conf. C a l i f . Mosq. Contr. A s s ' n . , pp. 5 3 - 5 5 . R E I M E R S , N., J . A. M A C I O L E K , and E . P . P I S T E R 1 9 5 5 . L i m n o l o g i c a l study of the l a k e s in C o n v i c t Creek B a s i n , Mono County, C a l i f o r n i a . U . S . D . I . , F i s h and Wildlife S e r v i c e , F i s h e r y B u l l . 103, pp. 4 3 7 - 5 0 3 . RENN, C. E . 1943. Emergent v e g e t a t i o n , mechanical properties of the water s u r f a c e , and distribution of Anopheles l a r v a e . J o u r . Nat. Malaria S o c . , 2 : 4 7 - 5 2 . R I C K E R , W. E . 1934. An e c o l o g i c a l c l a s s i f i c a t i o n of c e r t a i n Ontario s t r e a m s . Univ. Toronto S t u d i e s , B i o l . S e r . No. 3 7 , pp. 1 - 1 1 4 . R O N A L D S , A. 1 8 3 6 . T h e f l y - f i s h e r ' s entomology. London, pp. v i i i + 1 1 5 . RUTTNER, F. 1953. Fundamentals of limnology. T r a n s l . by D . G. F r e y and F . E . J . F r y . U n i v e r s i t y of Toronto P r e s s , pp. xi + 2 4 2 . SIMMONS, P . , D . F . B A R N E S , C . K . F I S H E R , and G. I I . KALOOSTIAN 1 9 4 2 . C a d d i s f l y larvae fouling a water tunnel. J o u r . E c o n . E n t . , 3 5 : 7 7 - 7 9 (Simmons, in litt., 1 9 5 5 ) . STEINMANN, P A U L 1907. Die T i e r w e l t der G e b i r g s b a c h e . E i n e f a u n i s t i s c h b i o l o g i s c h Studie. Ann. B i o l . L a c . , 2 : 1 - 1 3 7 . SWINGLE, H. S . , and E . V . SMITH 1941. T h e management of ponds for the production of

game and pan f i s h . In " A Symposium on H y d r o b i o l o g y " . U n i v e r s i t y W i s c o n s i n P r e s s , pp. ix + 4 0 5 ( 2 1 8 - 2 2 6 ) . T A R Z W E L L , C . M. 1 9 3 7 . E x p e r i m e n t a l e v i d e n c e on the value of trout stream improvement in Michigan. T r a n s . Amer. F i s h . S o c . , 66:177-187. 1947. E f f e c t s of D D T mosquito larviciding on w i l d l i f e . I . The e f f e c t s on s u r f a c e organisms of the routine hand a p p l i c a t i o n of D D T l a r v i c i d e s for mosquito c o n t r o l . P u b l i c Health R e p . , 6 2 : 5 2 5 - 5 5 4 . 1950. E f f e c t s of D D T mosquito larviciding on w i l d l i f e . V . E f f e c t s on f i s h e s of the routine manual and airplane a p p l i c a t i o n of D D T and of the mosquito l a r v i c i d e s . P u b l i c Health R e p . , 6 5 : 2 3 1 - 2 5 5 . TIHENEMANN, A. 1912. Der B e r g b a c h d e s S a u e r l a n d e s . Int. R e v . g e s . Hydrobiol. Hydrogr., B i o l . Suppl., 4 , pp. 1 - 1 2 5 . 1 9 2 6 . Die B i n n e n g e w ä s s e r Mitteleuropas. Die B i n n e n g e w ä s s e r , B d . 1. 2 2 5 pp, T H O R P E , W. H. 1950. P l a s t r o n r e s p i r a t i o n in aquatic i n s e c t s . B i o l . Rev., 25:344-390. T H O R P E , W. H . , and D. J . C R I S P 1 9 4 7 . S t u d i e s on plastron r e s p i r a t i o n . I . T h e biology of Aphelocheirus and the mechanism of plastron r e t e n t i o n . Jour. Exp. Biol., 24:227-269. U S I N G E R , R . L . , and W. R . K E L L E N 1955. T h e role of i n s e c t s in s e w a g e d i s p o s a l b e d s . Hilgardia, 2 3 : 2 6 3 - 3 2 1 . U S I N G E R , R . L . , and P . R . NEEDHAM 1 9 5 4 . A plan for the b i o l o g i c a l p h a s e s of the periodic stream sampling program. S t a t e Water Pollution Control B o a r d , Unpublished R e p o r t , 59 pp. 1 9 5 6 . A drag-type riffle-bottom s a m p l e r . T h e Progr. Fish-Culturist, 18:42-44. WALSHE, B . M. 1951. T h e feeding h a b i t s of certain chironomid larvae (subfamily T e n d i p e d i n a e ) . P r o c . Z o o l . S o c . London, 121:63-79. WALTON, IZAAK 1 6 5 3 . T h e c o m p l e a t angler or the comtemplative man's r e c r e a t i o n . B e i n g a d i s c o u r s e of fish and fishing, not unworthy the perusal of most a n g l e r s . London; Maxey. 2 4 6 pp. ( 1 6 7 6 , 5th e d . by C h a r l e s C o t t o n , I n s t r u c t i o n s how to a n g l e for a trout or grayling in a c l e a r stream, London.) Water P o l l u t i o n Control P r o g r e s s Report for 1950 through 1 9 5 2 . Water P o l l u t i o n Control Board P u b l i c a t i o n No. 5, S a c r a m e n t o , pp. 1 - 5 6 . WELCH, P . S. 1 9 5 2 . Limnology. 2d e d . McGraw-Hill. pp. ix + 5 3 8 . W H I P P L E , G. C . 1 9 2 7 . T h e m i c r o s c o p y of drinking water. 4th e d . r e v i s e d by G . M. F a i r and M. C . Whipple. New Y o r k . 5 8 6 pp. WIGGLESWORTH, V . B . 1 9 3 8 . T h e regulation of osmotic p r e s s u r e and chloride c o n c e n t r a t i o n in the haemolymph of mosquito l a r v a « . Jour. Exp. Biol., 15:235-247. WILSON, C . B . 1 9 2 3 . Water b e e t l e s in r e l a t i o n to pond fish culture, with life h i s t o r i e s of t h o s e found in fishponds at F a i r p o r t , Iowa. B u l l . U . S . B u r . F i s h e r i e s , 3 9 : 2 3 1 - 3 4 5 .

B.

Equipment and Technique

By John D, Lattin O r e g o n State C o l l e g e ,

Corvallis

F i e l d work in aquatic entomology i s carried out by many persons with diverse points of view. Some approach the s u b j e c t as taxonomists specializing in one or another of the groups of aquatic i n s e c t s ; others are primarily interested in life histories or e c o l o g i c a l relations. And there i s an increasing number of professional workers whose primary concern i s quantitative sampling of populations for mosquito control or stream and lake management. It is the o b j e c t of this chapter to describe the equipment and methods b e s t suited to each of these varied purposes. A fuller discussion of entomological equipment i s given in Peterson (1953), culture methods are described in the compendium edited by J . G. Needham (1937), and general limnological methods are treated in detail in Welch (1948).

GENERAL

of debris should be turned over and carefully examined. All types of vegetation growing near the water should be examined and the i n s e c t s dislodged by beating or " s w e e p i n g " into a net. Swarms of gnats and other aerial i n s e c t s should be swept with the net. Nets.— Although many different types of nets are used by collectors, the b a s i c design i s the same (intro. fig. 66). A light, strong handle is used with a ring of stout, spring-steel wire to which i s fastened a bag of nylon netting. Aerial n e t s , for catching i n s e c t s in flight, should be light enough to handle e a s i l y . The sweeping net, on the other hand, is of

COLLECTING

Terrestrial Most aquatic i n s e c t s are terrestrial or aerial a s adults and can be identified to the s p e c i e s level only a t this s t a g e . Therefore i t i s important to c o l l e c t generally in tile vicinity of water where adult i n s e c t s are most likely to occur. Stones, boards, and p i l e s

Intro, f i g . 6 6 . S p e c i f i c a t i o n s for c o n s t r u c t i o n of i n s e c t net ( R o s s , 1 9 5 3 ) .

50

Intro, f i g . 6 7 . S w e e p i n g net in a c t i o n ( R o s s , 1 9 5 3 ) .

51 L a t t i n : Introduction heavier material and may be made of heavy-duty muslin with canvas reinforcement along the leading edge. It is swept through heavy vegetation, jarring loose and capturing many small insects that would otherwise be overlooked (intro. fig. 67). Nets and other equipment may be homemade or obtained from biological supply houses such as Ward's Natural Science Establishment, Rochester, N . Y . ; Turtox (General B i o l o g i c a l Supply House, Chicago, 111.), and others. Specialized limnological equipment may be ordered from the equipment shop o f the California Academy of Sciences, San Francisco.

I n t r o , f i g . 6 8 . T h e c o r r e c t use of the b e a t i n g s h e e t ( R o s s ,

1953).

c

Beating sheet.—This d e v i c e consists of a sheet of canvas stretched over a wooden frame (intro. fig. 68). It is held under vegetation from which insects are jarred l o o s e with a stick. On a warm, sunny day considerable dexterity is needed to capture quickflying insects before they l e a v e the sheet. A hookhandled umbrella, used upside down, is a useful " b e a t i n g s h e e t " because the handle can be slipped around the neck, leaving both hands free to c o l l e c t the insects. Berlese funnel.—The B e r l e s e funnel is useful for collecting small insects living in duff or debris at or near the edge of the water. It consists of a large funnel with a screen inserted to hold the material (intro. fig. 69). The debris is brought back to the laboratory in sacks and dumped into the funnel. A strong light is placed above, and the heat and light drive the insects down the funnel, through the screen, and into a jar of 70 per cent alcohol. A sheet of aluminum foil placed on the debris increases the e f f e c t i v e n e s s of the funnel and prevents the possibility of fire. T h e B e r l e s e funnel is particularly useful for collecting springtails and many small b e e t l e s and bugs which are seldom seen or collected by any other method. Light traps.—Many different types of light traps have been designed. B r i e f l y , they consist of a light source that attracts insects, and some method of

I

I n t r o , f i g . 6 9 . D e t a i l s of t h e B e r l e s e F u n n e l ; a, l i g h t b u l b ; b, m e t a l c o v e r ; c, m e t a l c y l i n d e r t o h o l d d e b r i s ; d, s h e e t o f a l u m i n u m f o i l ; e, d e b r i s ; f , c i r c u l a r piece of 1 / 2 " hardware c l o t h w i t h m e t a l r i m ; g, o n e o f t h r e e m e t a l f l a n g e s f a s t e n e d t o i n s i d e o f c y l i n d e r t o s u p p o r t s c r e e n ; h , m e t a l f u n n e l ; /, s u p p o r t i n g s t a n d ; /', l i d o f m a s o n j a r ; k , m a s o n j a r ; I , 7 0 per c e n t e t h y l a l c o h o l (original).

Intro, f i g . 70. Structural d e t a i l s of New J e r s e y l i g h t trap (Malaria Contr. Imp. Waters).

52 Lattin: Introduction retaining and killing the specimens. Intro, figure 70 shows a common type, known as the New Jersey light trap, which can be constructed with comparative ease. It is desirable to have an electric outlet c l o s e to the trap although battery operated traps can be set up. A Coleman lantern on a white sheet makes an e f f i c i e n t " l i g h t t r a p " and frequently is the best way to c o l l e c t many of the adult stages of aquatic insects. Collecting at any light source near water usually y i e l d s many adult aquatic insects, and neon lights ( e s p e c i a l l y blue) in towns are sometimes productive. In general, insects fly to lights in greatest numbers on warm sultry nights when there is little or no wind and the moon is not too bright. methods.—The aspirator (intro. fig. Miscellaneous 71) is a d e v i c e used to c o l l e c t insects from the net, from resting places under bridges and on vegetation, and from microhabitats at the water's edge. The insects are sucked into a tube and are later transferred to a killing bottle. T h e insect fauna of sand or mud may be collected by splashing water on the bank and washing out individual specimens. The reverse can l i k e w i s e be done; that is, sand can be thrown into the water to float off sKore dwelling forms. T h i s type of collecting will produce larvae and adults of such beetle families as Omophronidae, Staphylinidae, Heteroceridae, and Carabidae and certain dipterous larvae. Rocks in the intertidal zone of the seashore are the special habitat of members of several families of beetles (Eurystethidae, Staphylinidae). A crow bar is useful to split such rocks and expose b e e t l e s that have retreated deep into cracks. Some flying insects, including large dragonflies, are practically inaccessible during the heat of the day but may be picked from resting places on vegetation in the early morning. Strong fliers which are otherwise unobtainable may be " f e l l e d " at c l o s e range with fine dust shot from a smooth-bore .22 caliber gun. A good collector does not rely s o l e l y on s p e c i a l i z e d equipment but examines every p o s s i b l e microhabitat—under stones, boards, grass, and mats of vegetation or debris.

AQUATIC C O L L E C T I N G T h e same intensive approach is necessary in aquatic as in terrestrial collecting. C l o s e attention should be paid to the seemingly endless microhabitats including surfaces of stones, aquatic vegetation, sunken logs, and accumulations of debris. If trash and plant materials are removed from the water and spread out

I n t r o , f i g . 7 1 . A s p i r a t o r ; o, t w o - h o l e r u b b e r s t o p p e r ; b, g l a s s or c o p p e r t u b i n g ; c, f i n e c o p p e r s c r e e n ; d, rubber t u b i n g ; e, g l a s s or p l a s t i c v i a l ( O m a n a n d C u s h m a n , 1 9 4 6 ) .

Intro, f i g . 7 2 . M e t h o d of u s i n g i n s e c t net for s t r e a m c o l l e c t i n g ( R o s s , 1953).

in the sun to dry, dozens or even hundreds of small insects will crawl out. Such trash may be raked from the bottom of a pond or stream, gathered in a net, or collected from snags after a flash flood. Small Dryopids and other beetles may continue to emerge from drying trash for one-half hour or more. Nets and screens.—Water nets should be sturdier than aerial nets. Nylon is desirable because of its strength; also it dries quickly and hence can be used for terrestrial collecting as w e l l . T h e s i z e mesh should be 24 to 32 strands per inch with mesh as open as is practicable to hold insects of the desired s i z e . Mesh of too fine gauge drags the net and hinders the capture of quick-moving insects. In streams, the net is held c l o s e to the bottom, and stones and trash are disturbed as the collector moves upstream (intro. fig. 72). Insects are dislodged and carried downstream into the net by the current. A p i e c e of window screen fastened to two strips of lath is particularly useful for this type of collecting (intro. fig. 73c). T h e screen is stretched across a narrow section of stream, or held with both hands, while the collector backs upstream scuffing the bottom with his boots. In a rich stream this method will yield enough specimens to occupy the collector for a half hour or more, picking from the drying screen in direct sunlight. Small dip

Intro, f i g . 7 3 . S p e c i a l i z e d s t r e a m c o l l e c t i n g e q u i p m e n t : a. N e e d h a m s c r a p e r ; b, N e e d h a m net; c, L a t h s c r e e n c o l l e c t o r ( T r o v e r , 1940).

53 Lattin: Introduction nets and even kitchen strainers make good collecting tools in streams and ponds. Intro, figure 736 shows a Needham net that can be used in areas where weeds are thick. The coarse screen on top permits the i n s e c t s to enter but keeps out most of the vegetation that would foul the net. The Needham scraper (intro. fig. 73 / genital pocket

107 Smith and Pritchard: Odonata

F i g . 4 : 2 . M a i n w i n g v e i n s of a n i s o p t e r o u s w i n g s . A , a n a l v e i n ; a l , a n a l l o o p , a r , a r c u l u s ; br, b r i d g e ; C , c o s t a ; C u , c u b i t u s ; M , m e d i a ; n, n o d u s ; o, o b l i q u e v e i n ; R , r a d i u s ; s , s u b t r i a n g l e ; S c , s u b c o s t a , s n , s u b n o d u s ; s t , s t i g m a ; t, t r i a n g l e ( N e e d h a m a n d H e y w o o d , 1929).

F i g . 4:5. Diagram principle interspaces a n d Westfall, 1955).

s h o w i n g paired in v e n a t i o n of

v e i n s , f u s e d v e i n s , and dragonfly wing (Needham

to the modifications of the thorax (fig. 4:1) and the special copulatory mechanism. The meso- and metathorax are greatly enlarged and fused to form a pterothorax. This pterothorax contains the large flight muscles. The legs are crowded together and moved forward on the thorax. They are not used for walking, but they are adapted for perching and for catching and handling the prey. In flight the legs act a s sort of a basket to catch prey. The front legs are also used to hold the prey, either at rest or in flight, while it is being chewed by the mandibles. The abdomen i s ten-segmented and carries the genital appendages at the distal end. The males of all Odonata have a pair of movable, unsegmented dorsolateral appendages F i g . 4 : 6 . C o m p a r a t i v e d i a g r a m s o f the b a s e s of a n i s o p t e r o u s w i n g s , a, f a m i l y G o m p h i d a e (Ophiogomphus carolus); b, f a m i l y L i b e t l u l i d a e (Erythcmis simplicicollis). Triangles striated, subt r i a n g l e s dotted, anal loops w a v y - l i n e d , b a s a l triangle c r o s s hatched ( N e e d h a m and Westfall, 1955).

their c o n n e c t i o n s , sup, supratriangle; a c , anal c r o s s i n g . lettering a s in fig. 4 : 2 ( N e e d h a m and Westfall, 1955).

Other

F i g . 4 : 4 . V e n a t i o n a l c h a r a c t e r s in a n i s o p t e r o u s w i n g (Comphus cavillaris). M i d d l e fork ( M F ) t h i c k e n e d for e a s i e r r e c o g n i t i o n ; A c , a n a l c r o s s i n g ; a n , a n t e n o d a l c r o s s v e i n s ; b, b r a c e v e i n ; p n , p o s t n o d a l c r o s s v e i n s . O t h e r l e t t e r i n g a s in f i g . 4 : 2 ( N e e d h a m and Westfall, 1955).

immediately behind the tenth segment. In the suborder Anisoptera there is an additional median inferior appendage (fig. 4:23), whereas in the Zygoptera there are two inferior appendages (fig. 4:68). T h e s e male appendages are adapted to grasp the head or thorax of the female in copulation. In addition, the males p o s s e s s a penis on the venter of the second and third abdominal segment. The female Odonata lack this penis on the second and third abdominal segments; however, the superior anal appendages are usually simpler and reduced or vestigial. In all Zygoptera and in the Aeshnidae and Petaluridae of the Anisoptera, a well-developed ovipositor consisting of three pairs of ventral p r o c e s s e s is present near the tip of the abdomen. In other families it is reduced or absent. The well-developed male naiads show the developing genitalia on the venter of abdominal segment two, and in the female the ovipositor may be seen on the venter of segments eight and nine. The male transfers sperm capsules from the genital aperture on the ninth segment to the penis vesicle on the second segment. In mating the male grasps the female either by the head (Anisoptera) or the prothorax (Zygoptera) with the terminal abdominal appendages. The female then curls her abdomen forward to reach

108 Smith and Pritchard: Odonata

are deposited in long gelatinous strings or m a s s e s . More often the eggs are inserted in s o f t plant t i s s u e beneath the water. In some c a s e s the females go beneath the water to reach suitable ovipositon s i t e s . A few oviposit in twigs above the water. The naiads of all Odonata are predaceous like the adults. They are attracted to their prey by sight and if it is not too large it will be seized by an extension of the labium. The climbing naiads, such a s most Zygoptera and Aeshnidae, hide in beds of submerged vegetation and actively pursue their prey. An aeshnid naiad may sometimes sight its prey at a distance of several inches and slowly stalk it until within striking distance. Other naiads, such as those of the Libellulidae that sprawl on the bottom, are very sluggish and do not strike until the prey comes within reach of the labium. T h e s e sprawlers are frequently covered with a camouflage of algae or a layer of s i l t . The naiads of the Gomphidae burrow into the bottom sand or mud so that only the tip of the abdomen r e a c h e s the water. After about ten to fifteen instars and a period from l e s s than one to five years the naiad is fully grown. It then crawls out of the water and attaches itself to some suitable object. The adult then

F i g . 4=7. G e n e r a l i z e d h a b i t a t o f Cordulegaster dorsalis: n a i a d w i t h p r o t e c t i v e c o a t of a l g a e o n s t r e a m bottom; e x u v i u m a n d f e m a l e o v i p o s i t i n g in s t r e a m bed ( K e n n e d y ,

Below, above, 1917).

the intromittent organ on the second abdominal segment of the male and to receive the sperm (fig. 4:9). The male frequently accompanies the female while she oviposits (fig. 4:8). The naiads (fig. 4:36) are strikingly different in appearance from the adults. They are short and compact as compared to the adults and have smaller heads. They are cryptically colored and breathe by means of gills. In the Zygoptera t h e s e c o n s i s t of three caudal lamellae; the Anisoptera have rectal gills. The most striking feature of the naiad is .the development of an extensile labium. It is long and jointed so that it can be extended quickly to capture prey. Most Odonata develop in permanent fresh water. A few are semiaquatic in that they occur in bogs; others occur in saline water, and some with short life cycles can develop in temporary waters. They are found in ponds, lakes, streams, tanks, rivers, and canals of all s i z e s and descriptions. Although the naiads are aquatic the adults sometimes range many miles from water. The eggs are laid in various ways (fig. 4:7). They may be simply dropped into the water, or they may be attached to o b j e c t s in the water. In a few c a s e s they

F i g . 4 : 8 . D o m s e l f l y p a i r s (Ischnura denticollis) ovipositing ( b e l o w ) a n d in r e s t i n g p o s i t i o n ( a b o v e ) ( K e n n e d y , 1 9 1 7 ) .

109 Smith and Pritchard: Odonata specimens. Rearing the adults from the naiads frequently gives the best specimens and, of course, associates the two stages. The adults should not be killed in cyanide but papered and allowed to die slowly. When handled in this manner the contents of the gut are excreted and the colors of the preserved specimens are at their best. Artificial drying is sometimes necessary to fix the colors properly. The adults may then be pinned, or better, placed with wings folded in transparent envelopes, or they may also be placed directly into 80 per cent alcohol. Naiads may be collected by any of the usual aquatic insect collecting methods. They should be preserved in 80 per cent alcohol. Key

to N e a r c t i c

Families

Adults

emerges through a slit in the dorsum of the head and thorax. The newly emerged adults are pale and without the darker markings. Within a few hours the pattern appears, but the full color does not develop until later. Blues and reds are especially slow to develop. Different kinds of Odonata have characteristic flight and habits. Details are given below under the special discussions. In general, the dragonflies have very few natural enemies. The teneral adults are especially vulnerable owing to their weak powers of flight. At this time and later they may be attacked by birds, lizards, frogs, spiders, and other Odonata. The naiads are eaten by fish, birds, frogs, and other aquatic insects. Of these the most important are the fish. A few hymenopterous egg parasites have been reported on some of the species that lay their eggs in plant tissue. The parasite goes beneath the water to oviposit in the eggs. Certain water mites are also occasionally abundant on the naiads. Adult dragonflies are usually collected with a standard insect net. The net opening should be fifteen inches or more in diameter and the handle at least three feet long. In netting a dragonfly, a quick following stroke from below and behind is better than a head-on stroke. Many species have regular habits of flight and their movements can be anticipated. In some cases sweeping vegetation in the early morning or at night will be very profitable. For damselflies a large fly swatter is helpful and for large, high-flying forms the finest dust shot in a .22 target pistol will yield a fair proportion of good

1. Fore and hind wings dissimilar in s i z e and shape, the proximal part of hind wing broader than that of fore wing; supratriangle and triangle present ( f i g . 4:2); male with 3 caudal a p p e n d a g e s — 2 superior and 1 inferior ( f i g . 4:32) ANISOPTERA 2 — Fore and hind wings similar in s i z e and shape, the proximal part of both fore and hind wings of about equal width ( f i g . 4:74); quadrangle present; male with 4 caudal appendages—2 superior and 2 inferior ( f i g . 4:60) ZYGOPTERA 6 2. T r i a n g l e s of fore and hind wings about equally distant from arculus and similarly shaped ( f i g . 4:6a) 3 — Triangle more distant from the arculus in fore wing than in hind wing and with its long axis at right angle to costa ( f i g . 4:66) LIBELLULIDAE 3. Stigma with a brace v e i n at its inner end ( f i g . 4 : 4 ) 4 — Stigma without a brace v e i n at inner end ( f i g . 4 : 2 ) CORDULEGASTRIDAE 4. E y e s w i d e l y separated on top of head 5 — E y e s meeting on top of head or nearly s o : AESHNIDAE 5. Stigma linear, not widened medially ( f i g . 4:15) P E T ALTJRID A E — Stigma rhomboid, widened medially ( f i g . 4:4) GOMPHIDAE 6. Wings distinctly petiolate, with 2 to 4 antenodal cross v e i n s ( f i g s . 4:616,c; 4:74) 7 — Wings not distinctly petiolate, with 5 or more antenodal cross v e i n s ( f i g . 4:61a) AGRIONIDAE 7. Wings with v e i n M3 arising nearer to arculus than to nodus; short intercalary v e i n s present between M s and principal adjacent v e i n s and running to wing margin ( f i g . 4:616) LESTIDAE — Wings with v e i n Ms arising nearer the nodus than to the arculus; no such intercalary veins present ( f i g . 4:61c) COEN AGRIONIDAE Naiads

1. Anus surrounded by 3 stiff pointed v a l v e s ( f i g . 4:13); head not markedly wider than thorax and abdomen ( f i g . 4: lOp) ANISOPTERA 2 — Three external g i l l s present at caudal end of abdomen; head wider than thorax and abdomen ( f i g s . 4:14; 4:72) ZYGOPTERA 6 2. Mentum of labium (including lateral l o b e s ) f l a t , or nearly s o , without stout setae 3 — Mentum of labium (including lateral l o b e s ) spoonshaped, covering f a c e to base of antennae ( f i g . 4 : 1 0 i ) , armed with stout setae ( f i g . 4:112) 5 3. Antenna 6- or 7-segmented ( f i g . 4:11a,6); tarsi 3-segmented, the fore tarsus 2-segmented in Gomphaeschna 4

110 Smith and Pritchard: Odonata — 4.

— 5. — 6. —

F i g . 4 : 1 0 . A n i s o p t e r o u s n a i a d s , a, Libellula; b, Plathemis; c, Paltothemis; d, Somotochlora; e, Platycordulia; f, N e u r o cordulia; g , Tramea; h, Pachydiplax; i, Leucorrhinia, /. Celithem/s; k, Basiaeschno; I, Naslaeschna; m, o, M o c r o m / a ; n, O c f o gomphus; p , q, Eplcordu/ia, d o r s a l a n d l a t e r a l v i e w s ; a-n, d o r s a l v i e w of h e a d ; o, l a t e r a l v i e w of h e a d ( W r i g h t a n d P e t e r s o n , 1 9 4 4 ) .

Antenna 4-segmented (fig. 4 : 1 1 c,d,e)\ fore and midtarsi 2-segmented, the hind tarsus 3-segmented GOMPHIDAE Antennal segments short, thick, heavily setiferous (fig. 4:116); abdominal segments 2 (or 3) to 9 with a pair of laterodorsal tufts of long black bristles (fig. 4:12i) PETAL, UR ID AE Antennal segments slender and bristlelike (fig. 4:11a); abdominal segments without laterodorsal tufts AESHNIDAE Labium with large irregular teeth on distal edge of lateral lobe (fig. 4:11A); mentum with a median cleft CORDULEGASTRIDAE Labium with distal edge of lateral lobe entire or with small, even-sized crenulations or teeth (fig. 4:111); mentum without a median cleft LIBELLULIDAE Antennal segments approximately equal in length (fig. 4:14a); mentum entire (fig. 4:14f) or with a closed median cleft 7 Antennal segments unequal in s i z e , 1st segment as

F i g . 4 : 1 1 . A n i s o p t e r o u s n a i a d s , a n t e n n a e a n d p a r t s of l a b i u m . a, p, Aeshna; b, Tachopteryx; c, n, Dromogomphus, d, O c t o g o m p h u s ; e, Progomphus; f, Boycria; g, Basiaeschna; h, Cordulegaster; i, Pantala; j, T r a m e o ; k, Libellula; I, Epicordulia; m, Plathemis; o, Coryphaeschna; q, Pachydiplax; o - e a n d q, a n t e n n a e ; f-/, l a t e r a l lobe of l a b i u m ; k - p , inner s u r f a c e of m e n t u m a n d l a t e r a l l o b e s of l a b i u m (Wright a n d P e t e r s o n , 1 9 4 4 ) .

Ill Smith and Pritchard: Odonata

F i g . 4:12. A n i s o p t e r o u s n a i a d s , a,b, Dromogomphus; crd,kr Gomphus; e, Aphylla; f,g, Basioeschno; h, Nasiaeschna; i, Tachopteryx; j, Progomphus; a-i, caudal segments of abdomen; j,k. ventral view of thorax (Wright and P e t e r s o n , 1944).

long a s 6 f o l l o w i n g t o g e t h e r ( f i g . 4:14«); mentum w i t h a d e e p , open, median c l e f t (fig. 4:14d) AGRIONIDAE 7. B a s a l half of labium g r e a t l y narrowed l i k e a s t a l k ; l a t e r a l l o b e s wi£h d i s t a l margin d e e p l y c u t b y 2 or 3 incisions; median cleft present, closed (fig. 4:146) LESTIDAE —

B a s a l half of labium not g r e a t l y n a r r o w e d ; l a t e r a l l o b e s not d e e p l y c l e f t ; m e d i a n c l e f t l a c k i n g ( f i g . 4 : 1 4 c , / ) COENAGRIONIDAE

ANISOPTERA Family P E T A L U R I D A E The petalurids comprise the most generalized group of living Anisoptera. A single s p e c i e s , Tachopteryx thoreyi Selys, occurs in the eastern United States, whereas the genus Tanypteryx is found in western North America and in Japan. The sluggish naiads

112 Smith and Pritchard: Odonata

Fig,

4:13.

Anisopterous

naiads,

caudal

segments

of

abdomen,

all

dorsal

views

except

g,

(lateral), a, Macromia; b, Didymops; c,d, Neurocordulia; e, Cannacria; f, S/mpetrum; g, Erythemis; h, Perithemis; i, Pachydlplax; j, Tramca; k, Partial a (Wright and Peterson, 1944). occur bogs.

in the muck of seepage

K e y to N e a r c t i c

waters

and in spring

Genera

Adults

1. Hind wing with triangle having a cross vein; thorax grayish, striped with black Tachopteryx Selys Hind wing with triangle lacking a cross vein ( f i g . 4:15);

thorax black, spotted with yellow

Tanypteryx

Kennedy

Naiads

1. Antenna with 7 segments ( f i g . 4:112>); no extra hooks present Tachopteryx Selys Antenna with 6 segments; lateral lobe of labium with minute extra hook on upper rim of base of movable hook Tanypteryx Kennedy

113 Smith and Pritchard: Odonata NYMPHS

F i g . 4 : 1 5 . W i n g s of Tanypteryx hageni (Needham and Westfall, 1955).

Genus Cordulegaster

F i g , 4 : 1 4 . Z y g o p t e r o u s n a i a d s . a,c,f, C o e n a g r i o n i d a e ; b, L e s t i d a e ; d, e, A g r i o n i d a e (Wright and P e t e r s o n , 1 9 4 4 ) .

Genus Tanypteryx

Kennedy, 1917

Adults of Tanypteryx have been taken in alpine meadows, from California to British Columbia, but very few specimens are known. The only naiads referable to this genus in North America were collected by Vincent Roth in a mountain bog in Oregon. His field notes state that he collected two naiads "on a moss covered bank at Parker Creek, about 3000 feet on Marys Peak, Benton County, Oregon. The bank is essentially a rock formation over which water seeps throughout the year. The moss forms a thin cover on the rocks, seldom being over an inch or two in depth. The specimens were collected in wet moss at the junction of one rock and another where a slight niche was formed." The habits of the adults have been described by Whitney (1947). A single species, Tanypteryx hageni (Selys) 1879, has been described from western North America. Family CORDULEGASTRIDAE The family Cordulegastridae contains a single genus in North America, although some workers split off Taeniogaster Selys and Zoraena Kirby.

Leach, 1815

A single species, Cordulegaster dorsalis Hagen 1858, is widespread in western North America, being known from Alaska to southern California along the Pacific Coast, and eastward to Wyoming and Utah. Another species, C. diadema Selys 1868, is known from Utah, the Southwest, and northern Mexico, but it has not been found in California. Adults of Cordulegaster dorsalis are very large and are strong fliers. Kennedy (1917, p. 517) observes that, "In the steep and narrow mountain gorges where the rushing torrents pour down through the shade of the redwoods and alders, this dragonfly adds a note of mystery to the scene, for the individuals with their strange ophidian coloration glide noiselessly upstream or down, never showing that curiosity toward strangers or unusual surroundings which is exhibited by the libellulines of the sunny valleys, but always moving straight ahead as though drawn irresistably onward. Only males are common on the streams, the females seldom resorting to the water except to oviposit. The males, as indicated above, fly on the longest beats I have observed for any dragonfly, for they fly continuously upstream or down until they come to the head of the stream or to the slow water below, or until some unusual obstruction turns them aside, when they face about and fly as steadily in the opposite direction. The course is usually a foot or two above the surface of the stream and goes through dense shade and any loose brush or foliage which may hang over the water. Because of this habit of flying in long beats this dragonfly is not easily taken, as the collector has but a single chance at each individual" (figs. 4:7). Regarding oviposition, Kennedy writes, " T h e female flew hurriedly up the creek and every few yards stopped, and with a sudden backing or downward stroke, while hovering with the body in a perpendicular position, stabbed her large ovipositor into the coarse sand beneath. Four to ten such perpendicular thrusts were made at each stop. Some stops were along the open beaches, but more were in quiet nooks between large rocks where she would

114 Smith and Pritchard: Odonata

have barely room enough for her wing expanse. She usually faced the center of the stream while ovipositing, though once she faced upstream and once toward the bank." The naiads are hairy and lie buried to their e y e s in the s o f t mud and sand of slowly moving woodland streams. They do not burrow with their fore feet but kick out the mud with their hind feet and movements of the body. The naiads may be carried downstream during the three or four years required to reach maturity. It i s for this reason, Kennedy observes, that oviposition i s farther upstream than where the exuviae are found. Family GOMPHIDAE Adult gomphids are clear winged, with yellow and brown or black bodies, and the caudal end of the male abdomen is more or l e s s enlarged. They spend much of their time perched on the ground or low objects, making short flights. The naiads are found buried shallowly in the sandy or muddy beds of streams or ponds. They do not usually climb stems of plants for transformation but move to the adjacent shore or objects on the shore. Key

to N e a r c t i c

Genera

Adult«

1. F o r e wing w i t h n o d u s l o c a t e d b e y o n d m i d d l e ( f i g . 4 : 1 6 ) ; basal subcostal cross vein usually present 2 — F o r e wing w i t h n o d u s a t middle ( f i g . 4:4); b a s a l s u b costal cross vein absent .' 5 2. A n a l loop w e l l d e f i n e d , w i t h 2 or 3 c e l l s 3 — A n a l loop i n d i s t i n c t " 4 3. A n a l loop w i t h 3 or more c e l l s ; male w i t h i n f e r i o r a p p e n d a g e w e l l d e v e l o p e d and d e e p l y f o r k e d Gomphoides Selys — A n a l loop w i t h 2 c e l l s ; male w i t h inferior a p p e n d a g e v e r y s m a l l or not e v i d e n t Phyllocycla Calvert 4. Supratriangle with c r o s s veins; triangle 3-sided . . . Aphylla Selys — Supratriangle without c r o s s v e i n s ; triangle 4-sided (fig. 4:16) Progomphus Selys 5. T r i a n g l e w i t h a c r o s s v e i n ; a n a l loop w i t h 4 c e l l s Hagenius Selys — T r i a n g l e w i t h o u t a c r o s s v e i n ; a n a l loop w i t h 3 c e l l s or l e s s , if p r e s e n t ( f i g s . 4:18; 4 : 6 ) 6 6. A n a l loop d i s t i n c t , w i t h 2 or 3 c e l l s ( f i g . 4 : 1 8 ) Ophiogomphus Selys — A n a l loop i n d i s t i n c t or a b s e n t ( f i g s . 4 : 4 ; 4 : 2 1 ) 7 7. Hind femur w i t h many s h o r t s p i n e s and a row of promin e n t long s p i n e s Dromogomphus Selys — Hind femur w i t h many s h o r t s p i n e s only ( f i g . 4 : 2 6 i ) 8 8. Hind w i n g w i t h c e l l s b e l o w s u b t r i a n g l e t w i c e a s long a s wide (fig. 4:21); thorax with middorsal stripe yellow and c o n t r a s t i n g Octogomphus Selys — Hind wing w i t h c e l l s b e l o w s u b t r i a n g l e l i t t l e l o n g e r than wide; thorax with middorsal stripe dark 9 9. S t i g m a d i s t i n c t l y w i d e r t h a n s u b t e n d e d c e l l s ( f i g . 4 : 2 2 ) ; m a l e w i t h f o r k s of i n f e r i o r a p p e n d a g e c o n t i g u o u s . . . . Erpetogomphus Selys — S t i g m a a p p r o x i m a t e l y a s wide a s s u b t e n d e d c e l l s ( f i g . 4:4) 10 10. A r c u l u s w i t h upper s e c t i o n much s h o r t e r t h a n lower s e c t i o n ; s t i g m a a b o u t t w i c e a s long a s w i d e Lanthus Needham

A r c u l u s w i t h upper s e c t i o n s i m i l a r i n . l e n g t h t o lower s e c t i o n ; s t i g m a more t h a n t w i c e a s long a s w i d e ( f i g . 4:4) Gomphus Leach Naiads

1. T e n t h a b d o m i n a l s e g m e n t s h o r t e r t h a n 8th and 9th abdominal s e g m e n t s combined 2 — T e n t h a b d o m i n a l s e g m e n t from a b o u t o n e - t h i r d t h e l e n g t h of t h e a b d o m e n t o n e a r l y a s long a s a l l t h e other s e g m e n t s c o m b i n e d ( f i g . 4 : 1 2 e ) 10 2 . M e s o c o x a e c l o s e r t o g e t h e r a t b a s e t h a n p r o c o x a e or m e t a c o x a e ( f i g . 4:12j)\ 4th a n t e n n a l s e g m e n t e l o n g a t e , a b o u t o n e - f o u r t h a s long a s t h e h a i r y 3rd a n t e n n a l s e g m e n t ( f i g . 4 : l l e ) ; burrow r a p i d l y in s a n d s of r i v e r s and l a k e b o t t o m s Progomphus Selys — P r o c o x a e and m e s o c o x a e a p p r o x i m a t e l y s a m e d i s t a n c e a p a r t a t t h e i r b a s e s ( f i g . 4:12k)\ 4th a n t e n n a l s e g m e n t never a s a b o v e , u s u a l l y a s m a l l r o u n d e d knob ( f i g . 4:11c,d) 3 3 . Wing c a s e s w i d e l y d i v e r g e n t 4 5 — Wing c a s e s p a r a l l e l a l o n g m i d - l i n e 4 . D o r s a l h o o k s p r e s e n t on a b d o m i n a l s e g m e n t s 2 or 3 t o 9, h o o k l i k e and curved on c a u d a l s e g m e n t s ; l a t e r a l a n a l a p p e n d a g e s a b o u t t h r e e - f o u r t h s or l e s s a s long a s inferiors Ophiogomphus Selys — D o r s a l h o o k s p r e s e n t o n l y on a b d o m i n a l s e g m e n t s 2 t o 4 , a t m o s t a s l i g h t t h i c k e n i n g on t h e m i d d o r s a l l i n e of s e g m e n t s -8 and 9; l a t e r a l a n a l a p p e n d a g e s a b o u t a s long a s i n f e r i o r s Erpetogomphus Selys 5. T h i r d a n t e n n a l s e g m e n t o v a t e , f l a t , n e a r l y a s w i d e a s long ( f i g . 4 : 1 Id); l a t e r a l a n a l a p p e n d a g e a b o u t half a s long a s i n f e r i o r s 6 — T h i r d a n t e n n a l s e g m e n t e l o n g a t e or l i n e a r , u s u a l l y cylindrical (fig. 4:11c) 8 6. Abdomen s u b c i r c u l a r , a l m o s t a s wide a s l o n g ; b o d y d e p r e s s e d ; p a i r e d t u b e r c l e s on t o p of h e a d Hagenius Selys — Abdomen a t l e a s t t w i c e a s long a s w i d e ; n o t u b e r c l e s on h e a d 7 7. Abdominal s e g m e n t s 7 t o 9 w i t h s h o r t l a t e r a l s p i n e s Octogomphus Selys — A b d o m i n a l s e g m e n t s 8 and 9 w i t h s h o r t l a t e r a l s p i n e s Lanthus Needham 8. A b d o m i n a l s e g m e n t 9 r o u n d e d d o r s a l l y and w i t h o u t a s h a r p d o r s a l h o o k , or, if d o r s a l hook p r e s e n t on a b d o m i n a l s e g m e n t 9, t h e n the s e g m e n t longer t h a n w i d e a t i t s base (fig. 4:27) Gomphus Leach — Abdominal segment 9 with an acute middorsal ridge w i t h a d o r s a l hook at i t s a p e x , t h i s s e g m e n t n e v e r a s long a s w i d e a t i t s b a s e 9 9. Mentum w i t h m e d i a n l o b e m o d e r a t e l y p r o d u c e d in a low r o u n d e d c u r v e d s p i n u l o s e b o r d e r ; a b d o m i n a l s e g m e n t 10 a little longer than 9 Gomphoides Selys — Mentum w i t h s t r a i g h t f r o n t b o r d e r ; a b d o m i n a l s e g m e n t 10 s h o r t e r t h a n 9 Dromogomphus Selys 10. Abdomen w i t h s h a r p l a t e r a l s p i n e s on s e g m e n t s 6 or 7 t o 9; l a b i u m w i t h inner margin of l a t e r a l l o b e e n t i r e l y s m o o t h , 3 t e e t h b e f o r e end hook of l a t e r a l l o b e Phyllocyola Calvert — Abdomen without lateral s p i n e s ; labium with inner margin of l a t e r a l l o b e a r m e d w i t h l a r g e s h a r p p o i n t e d r e c u r v e d t e e t h , 4 or 5 t e e t h b e f o r e end h o o k of l a t e r a l lobe ^ . Aphylla Selys

Genus Progomphus

S e l y s , 1854

The genus Progomphus (considered by Muttkowski, 1910, to be Gomphoides) i s primarily Neotropical in distribution. Two s p e c i e s are wide ranging in the United States. One s p e c i e s , P. obacurua (Rambur) 1842, i s a greenish, yellowish s p e c i e s striped with brown (fig. 4:16). It i s common in the eastern United

115 Smith and Pritchard: Odonata —

1917) morrisoni Selys 1879 Posterior hamule spatulate distally (western U.S. and Canada) ( f i g . 4:17d,e) ( = montanus ( S e l y s ) 1878) severus Hagen 1874 Females

1. Occipital spurs present 2 — Occipital spurs absent 3 2. Head with a pair of postoccipital spurs ocoidentis Hagen — Head without postoccipital spurs bison Selys 3. Humeral stripe usually double morrisoni Selys — Humeral stripe with anterior part reduced to an oval spot or absent severus Hagen F i g . 4:16. Wings of Progomphus obscurus (Needham and W e s t f a l l , 1955).

States. 1 Another s p e c i e s , P. borealis MacLachlan 1873, is widespread in the western United States and Mexico, having been recorded from Arizona, California, Colorado, New Mexico, Oklahoma, Oregon, T e x a s , and Utah. It is a grayish brown and dull yellow s p e c i e s . T h e naiads of Progomphus l i v e in the sandy beds of permanent streams and lakes. They are adept burrowers, and their colors match the sand in which they burrow. P. borealis is found in the sandy shallows of permanent desert streams and in sandy areas of intermittent streams in the Sierra Nevada foothills. Adults rest on the banks of the streams or on snags protruding from the water.

Genus Ophiogomphus

Selys, 1854

Ophiogomphus naiads are found in the gravelly beds of mountain lakes and streams. Adults rest on the g r a v e l l y shores when they are not in s a l l i e s of flight. Three of the f i v e s p e c i e s recognized from the western United States are subject to considerable variation in the development of the thoracic stripes ( f i g . 4:17). Names based on such differences in coloration are here considered to be synonyms, although subspeciation may be indicated.

K e y to C a l i f o r n i a

Species

Males

1. Inferior appendage broad near base and narrowing distally 2 — Inferior appendage slender proximally and enlarging distally, the dorsal margin concave ( f i g . 4:17^) (British Columbia to Utah and California) (= phaleratus Needham 1902; = ocoidentis californicus Kennedy 1917) ocoidentis Hagen 1882 2. Superior appendages with ventral angulation near distal end bearing tiny denticulations; tibiae usually with outer face pale 3 — Superior appendages slender, without ventral angulation and with large denticulations; tibiae black ( f i g . 4:17a) (California, Nevada) ( = sequoiarum Butler 1914) . . . bison Selys 1873 3. Posterior hamule acutely pointed (California, Oregon, Nevada) ( f i g . 4:176,c) ( = m o r r i s o n i nevadensis Kennedy 'Reports from the far West are undoubtedly misidentification or records before recognition of P. borealis as a distinct species.

Naiads

1. Lateral spines on abdominal segments 6-9 ( f i g . 4:19a) 2 — Lateral spines on abdominal segments 7-9 ( f i g . 4:196) 2. Lateral anal appendages about nine-tenths inferiors; lateral spines on abdominal segments 7 and 8 subequal ( f i g . 4:19a) bison Selys — Lateral anal appendages about seven-tenths inferiors; lateral spine on abdominal segment 8 longer than spine on segment 7 ( f i g . 4:19c) ocoidentis Hagen 3. Dorsal hooks on abdominal segments 8 and 9 weak, slender, flattened; tips of hooks on segments 2 and 3 tapered, erect ( f i g . 4:19c) severus Hagen — Dorsal hooks on abdominal segments 8 and 9 stout, erect; tips of hooks on segments 2 and 3 very blunt ( f i g . 4:196) morrisoni Selys

Genus Octogomphus

S e l y s , 1873

T h e genus Octogomphus is based on a single s p e c i e s , 0. specularis (Hagen) 1859. It is found along the P a c i f i c Coast, from Mexico to British Columbia. Adults of Octogomphus specularis ( f i g s . 4:20; 4:21) are found primarily along the upper reaches of densely shaded streams in the coastal mountains. T h e males perch on low objects in sunlit openings of the stream, but the females are seldom found near the water except for oviposition. Kennedy (1917) writes regarding an ovipositing female: " S h e came volplaning down through an opening in the canopy of alders and, while going through evolutions involving several figures, 8's and S's, she touched the surface of the pool lightly with the tip of her abdomen at intervals of two to six feet. A f t e r twenty seconds of this she airily spiraled up and out into the sunshine, where she alighted on a bush on the hillside above the c r e e k . " The naiads l i v e in the loose trash on the bottom of pools and eddies. Kennedy estimated that the naiads spend three years in the water, emergence occurring throughout the spring and summer.

Genus Erpetogomphus

S e l y s , 1858

Members of the genus Erpetogomphus are found along sandy streams in the western United States, Mexico, and Central America. T w o s p e c i e s are known to occur in California.

116 Smith and Pritchard: Odonata

Fig.

4:17. Adult characters

morn's on/ nevadensis;

in the g e n u s Ophiogomphus.

a,

O . bison;

b,

O. m o r n ' s o n i; c , O .

d, 0. severus montanus; e, 0. severus; f, 0. arizontcus;

g, O.

occidcntis;

h, O. o c c i ' d e n t / s c a / i f o r n i c u s ; 1, c o l o r p a t t e r n ; 2, h a m u l e s ; 3 , v a l v a ; 4 , o c c i p u t of f e m a l e ; 5 , d o r s a l v i e w of m a l e a b d o m i n a l a p p e n d a g e s ; 6, l a t e r a l v i e w of m a l e a b d o m i n a l a p p e n d a g e s ( K e n n e d y , 1917).

K e y to C a l i f o r n i a

Species

Males

1. Superior appendages with a dorsal angulation (California to T e x a s and Oklahoma) . . . lampropeltia Kennedy 1918 — Superior appendages without a dorsal angulation (Oregon and California to Wyoming and T e x a s ) compositus Hagen 1858

Females

1. Occiput with caudal margin emarginate medially lampropeltis Kennedy — Occiput with caudal margin trilobed compositus Hagen

117 Smith and Pritchard: Odonata

F i g . 4:18. Wings of Ophiogomphus carolus (Needham and Westfall, 1955). Naiads 1. D a - s a l hooks rudimentary or a b s e n t on abdominal s e g m e n t s from 4 t o 9; l a t e r a l s p i n e s on 6 and 9 s m a l l e r than on 7 and 8 lampropeltis Kennedy — D o r s a l hooks v e s t i g i a l on 7 t o 9; lateral s p i n e s about equal in s i z e on 6 to 9 oompositus Hagen

F i g . 4:20* Octogomphus specu/aris. a, second abdominal segment of male; b, dorsal v i e w of male abdominal appendages; c, ventral view of male abdominal appendages; d-e, male abdominal appendages applied to head of female; f , ventral view of female abdominal segments 9-10; g, female thoracic color pattern variation; h'k, color variation in male abdominal segment 9; /, male color pattern; m, female color pattern (Kennedy, 1917).

Genus Gomphus Leach, 1815

F i g . 4:19. Naiad characters in the genus Ophiogomphus. a, 0 . bison; b, 0. morrisoni; c, 0 . severus; d, 0 . morrisoni nevadensis; e, 0 . Occident is; 1, mentum; 2, teeth and setae on middle lobe of mentum; 3, dorsal view of abdominal segments 6-10 (Kennedy, 1917).

Gomphus is a very large Holarctic genus, the members of which breed in diverse aquatic environments. Although many species occur in the eastern United States, only three are known from California. The naiads have special hooks for burrowing in silt. Of the California species, Gomphus intricatus and G. olivaceous develop in warm and muddy streams or sometimes ponds. G. confraternus confratemus2 Selys 1873 (=sobrinus Selys 1873) is also found in sluggish streams of the valleys. However, G. confraternus donneri is found in clear mountain lakes. This subspecies differs from the nominate subspecies in that the yellow spot on the ninth abdominal segment is smaller. 2 Gloyd (1941) showed Gomphus confraternus to be a synonym of G. kurilis Hagen (1857). We prefer to use the better known name.

118 Smith and Pritchard: Odonata

F i g . 4:21. Wings of Octogomphus ( N e e d h a m and W e s t f a l l ,

specularis 1955).

K e n n e d y ( 1 9 1 7 ) w r i t e s with regard to Gomphus intricatus: " A s with most s p e c i e s of Gomphus this s p e c i e s s p e n d s much of i t s time s e a t e d on some bush or p i e c e of d r i f t w o o d , rarely a l i g h t i n g on the ground. H o w e v e r , when i t i s on the wing it i s v e r y e n e r g e t i c , and the m a l e s f l y rapidly back and forth in short b e a t s , about s i x i n c h e s a b o v e the s u r f a c e of the w a t e r . T h e f e m a l e s o v i p o s i t w h i l e f l y i n g in the same q u i c k , nervous manner. In copulation the male p i c k s the f e m a l e up e i t h e r from o v e r the water or from some bush, and a f t e r a v e r y short nuptial f l i g h t s e t t l e s for a v e r y l o n g p e r i o d of c o p u l a t i o n . " Key to California

Species

Males

1. Posterior hamule stout, sharply bent forward near distal end (Washington to California) ( f i g s . 4:23; 4:24) confraternus Selys 1876 — Posterior hamule slender, tapering distally 2 2. T i b i a yellow externally; club of abdomen bright orange

F i g . 4:23. Gomphus confraternus donneri. a, v u l v a ; b-c, lateral v i e w of male abdominal a p p e n d a g e s ; 6, second abdominal segment of male; e, dorsal v i e w of male abdominal a p p e n d a g e s ; f, f e m a l e occiput; g, ventral v i e w of male abdominal a p p e n d a g e s ; h t c o l o r pattern of male; /, c o l o r pattern of f e m a l e ( K e n n e d y , 1917).

—

(British Columbia to California, east to Nebraska and T e x a s ) ( f i g s . 4:25a; 4:26). intricatus Hagen 1858 T i b i a black; club of abdomen pale yellowish and largely black dorsally (British Columbia to Utah and California) (= olivaceous nevadensis Kennedy 1917) ( f i g . 4:25d,f) olivaceous Selys 1873 Females

1. Tibiae black — Tibiae with outer face yellow I

2

intricatus Hägen 2. Thorax with dark lateral stripe ( f i g s . 4:23; 4:24) confraternus Selys — Thorax without lateral stripe ( f i g . 4:25®,¡7) olivaceous Selys Naiads

Fiig. 4:22. Wings of Erpetogomphus coluber ( N e e d h a m and W e s t f a l l , 1955).

1. Dorsal groove present on segments 3-7; concave inner edge of lateral lobe of mentum with 1-3 rounded teeth ( f i g . 4:27o-6) 2 — Dorsal groove absent, but apex of segments 2-7 with low rounded middorsal tubercle; inner margin of lateral lobe of mentum with 6 or more low rounded teeth followed by smaller ones ( f i g . 4:27c-d) confraternus Selys 2. Segment 9 with no median spine; anal appendages

119 Smith and Pritchard: Odonata they can capture is eaten, even small fish, and they are a l s o notoriously cannibalistic. Many of the genera found in North America are indigenous to the eastern United States or e l s e they are primarily tropical in distribution. Only four genera are known to occur in California; a fifth genus, Oflonaeschna, occurs in the neighboring state of Arizona. Key

to

Nearctlc

Genera

Adults

1. Arculus with upper sector shorter than lower sector (fig. 4:28) Anax Leach — Arculus with upper sector as long as or longer than lower sector (figs. 4:29; 4:33) 2 2. Basal space with 2 or more cross veins Soyeria MacLachlan — Basal space with a single cross vein or cross veins lacking 3 3. Radial sector simple 4 — Radial sector forked; stigma surmounting 3 or more cross veins not counting brace vein (fig. 4:29) 6 4. Stigma surmounting 1 cross vein not counting brace vein; supratriangle without cross veins Gomphaeschna Selys

b Fig. 4:24. Gomphus confraternus confratcmus. a,c, vulva; bt lateral v i e w of male s e g m e n t of male; e, f, f e m a l e o c c i p u t ; g, kt color pattern of 1917).

abdominal a p p e n d a g e s ; d t second abdominal dorsal v i e w of mole abdominal a p p e n d a g e s ; ventral v i e w of male abdominal a p p e n d a g e s ; male; i, color pattern of f e m a l e ( K e n n e d y ,

twice the length of segment 10 (fig. 4:276) intricatus Hagen — Segment 9 with a minute middorsal spine at apex; anal appendages equal to segment 10 (fig. 4:27a)olivaceous Selys

Family AESHNIDAE Adults belonging to the family Aeshnidae are large, robust, and strong flying dragonflies. They are commonly seen over ponds or lakes, feeding on swarming insects, and many s p e c i e s roam far from water, even into c i t i e s and buildings. Most of the group are diurnal, but a few s p e c i e s are crepuscular in flight. T h e female has a well-developed ovipositor that she inserts into succulent stems of aquatic plants for oviposition. Most s p e c i e s breed in the quiet water of lakes or along the margins of slow flowing streams. T h e naiads p o s s e s s a smooth, elongate body with long thin l e g s . T h e y are a c t i v e and clamber over the aquatic vegetation and bottom trash, sometimes pausing to stalk their prey. Almost any living animal that

F i g . 4:25. Color patterns in the genus Gomphus, a - c , G. intricatus; d-gt G, olivaceous ( K e n n e d y , 1917).

120 Smith and Pritchard: Odonata Naiads

1. — . 2. — 3.

— 4. — 5. —

6. —

L a t e r a l l o b e s of l a b i u m w i t h s t o u t r a p t o r i a l s e t a e . . 2 L a t e r a l l o b e s of l a b i u m l a c k i n g r a p t o r i a l s e t a e ( f i g . 4: l l o - p ) 3 L a t e r a l s e t a e of l a b i u m n e a r l y u n i f o r m in l e n g t h . . . . Triacanthagyna Selys L a t e r a l s e t a e of l a b i u m v e r y u n e q u a l in l e n g t h , d i m i n i s h i n g t o v e r y s m a l l o n e s a t p r o x i m a l e n d of r o w . . . Gynacantha Rambur D i s t a l b o r d e r of m e n t u m w i t h a p a i r of s h a r p , p a r a l l e l s p i n e s , 1 on e a c h s i d e of t h e m e n t a l c l e f t ; h e a d f l a t t e n e d a n d e l o n g a t e - r e c t a n g u l a r s e e n from a b o v e ( f i g . Williamson 4 : 1 1 o) Coryphaeschna D i s t a l b o r d e r of m e n t u m not s o a r m e d ( f i g . 4 : l i p ) . . . 4 L a t e r a l s p i n e s p r e s e n t on a b d o m i n a l s e g m e n t s 7-9 . . 5 L a t e r a l s p i n e s p r e s e n t on a b d o m i n a l s e g m e n t s 4 , 5, or 6-9 7 S u p e r i o r a n a l a p p e n d a g e but s l i g h t l y s h o r t e r t h a n inferior 6 Superior anal appendage about three-fourths inferiors; i n f e r i o r s a b o u t s u b e q u a l in l e n g t h t o m i d d o r s u m of s e g m e n t s 9 a n d 10; m a l e a p p e n d a g e t r i a n g u l a r w i t h a blunt, rounded apex Aeshna Fabricius I n f e r i o r a n a l a p p e n d a g e a b o u t one and o n e - h a l f t i m e s a s long a s m i d d o r s a l l e n g t h of s e g m e n t 9 and 10; superior anal appendage c l e f t at apex Anax L e a c h I n f e r i o r a n a l a p p e n d a g e l e s s t h a n m i d d o r s a l l e n g t h of s e g m e n t 9 a n d 10; s u p e r i o r a n a l a p p e n d a g e b l u n t l y rounded at a p e x Gomphaeschna Selys

F i g , 4 : 2 6 . G o m p h u s intricotus. a, s e c o n d a b d o m i n a l s e g m e n t o f m a l e ; b, l a t e r a l v i e w of m a l e a b d o m i n a l a p p e n d a g e s ; c, v e n t r a l v i e w of f e m a l e a b d o m i n a l s e g m e n t s 9 - 1 0 ; d, d o r s a l v i e w of m a l e a b d o m i n a l a p p e n d a g e s ; e , f e m a l e o c c i p u t ; f , v e n t r a l v i e w of t e r m i n a l s e g m e n t s of m a l e a b d o m e n ; g - i , c o l o r p a t t e r n on m a l e legs ( K e n n e d y , 1917).

— 5. — 6. — 7. — 8. — 9. — 10.

—

S t i g m a s u r m o u n t i n g 2 or more c r o s s v e i n s not c o u n t i n g brace v e i n ; supratriangle with c r o s s v e i n s 5 B a s e of w i n g s w i t h l a r g e b r o w n s p o t ; 1 row of c e l l s between C u , and Cu, Basiaeschna Selys B a s e of w i n g s h y a l i n e ; 2 r o w s of c e l l s b e t w e e n C u , and Cua Oplonaeschna Selys R a d i a l s e c t o r w i t h fork s y m m e t r i c a l , and w i t h n o t more t h a n 2 r o w s of c e l l s b e t w e e n it and i t s p l a n a t e 7 R a d i a l s e c t o r w i t h fork u n s y m m e t r i c a l , a n d w i t h 3 or more r o w s of c e l l s b e t w e e n it and i t s p l a n a t e ( f i g . 4 : 3 3 ) 8 F r o n s strongly projecting, the dorsal margin a c u t e ; r a d i a l p l a n a t e s u b t e n d i n g 1 r o w of c e l l s Nasiaeschna Selys F r o n s not p r o j e c t i n g ; r a d i a l p l a n a t e s u b t e n d i n g 2 r o w s of c e l l s Epiaeschna Hagen R a d i a l s e c t o r forked under the stigma Coryphaeschna Williamson R a d i a l s e c t o r forked- p r o x i m a d t o t h e s t i g m a 9 Supratriangle no longer than m i d b a s a l s p a c e (fig. 4:29) Aeshna Fabricius S u p r a t r i a n g l e d i s t i n c t l y l o n g e r t h a n m i d b a s a l s p a c e . 10 Hind w i n g w i t h 2 r o w s of c e l l s b e t w e e n M j a n d Ma b e g i n n i n g d i s t a d t o b a s e of s t i g m a ; f e m a l e w i t h t r i f i d p r o c e s s on v e n t e r of 10th a b d o m i n a l s e g m e n t ( f i g . 4 : 3 4 ) Triacanthagyna Selys Hind w i n g w i t h 2 r o w s of c e l l s b e t w e e n M, a n d M 2 b e g i n n i n g a t b a s e or p r o x i m a l t o b a s e of s t i g m a ; f e m a l e w i t h b i f i d p r o c e s s on v e n t e r of 10th a b d o m i n a l s e g m e n t (fig. 4:33) Gynacantha Rambur

b3 Fig.

4:27.

olivaceous;

Naiad

characters

b, G. intricafus;

in

the

genus

Gomphus.

c, G. confraternus donneri;

c o n f r a t e r n u s c o n f r a t e r n u s ; 1, m e n t u m , 2 , d e t a i l of 3, t e r m i n a l a b d o m i n a l s e g m e n t s . ( K e n n e d y , 1 9 1 7 ) .

mental

a,

G.

d, G. lobe;

121 Smith and Pritchard: Odonata 7. Caudolateral margin of head from dorsal view with 2 large, well-developed tubercles (fig. 4:X0Z); e y e s small, occupying only one-third of the lateral margin of the head 8 — Caudolateral margin of head from dorsal view never with 2 tubercles as described above; e y e s large, occupying about half of the lateral margin of the head (fig. 4:10A) 9 8. Low but distinct dorsal hooks (best seen from lateral view) present on abdominal segments 7 to 9; apex of lateral lobe broadly rounded; lateral anal appendages l e s s than half the length of the superior (fig. 4:12A) Nasiaeschna Selys — Dorsal hooks absent on a l l abdominal segments; apex of lateral lobe truncate; lateral anal appendages more than half the length of the superior . Epiaeschna Hagen 9. Lateral s p i n e s present on abdominal segments 6-9 Aeshna F a b r i c i u s — Lateral spines present on abdominal segments 3, 4 , or 5-9 10 10. Hind angles of head strongly angulate (fig. 4:10&) . . 11 — Hind angles of head rounded or slightly angulate . . . 12 11. Lateral lobe of labium obtuse or subtruncate at tip; median border of lateral lobe with distinct, more or l e s s square-cut teeth (fig. 4:11 f) Boyeria MacLachlan — Lateral lobe of labium with a taper-pointed tip; median border of lateral lobe with indistinct denticulation (fig. 4 : 1 1 ^ ) Basiaeschna Selys 12. Superior anal appendage nine-tenths length of inferiors; inferiors strongly incurved at tips Oplonaeschna Selys — Superior anal appendage about three-fourths a s long as inferiors Aeshna F a b r i c i u s

Genus Anax Leach, 1815 Four species of the cosmopolitan genus Anax occur in the United States. One of these, A. junius (fig. 4:28), is widespread and common in North America, but the others are more southern in distribution. Adults are commonly known as green darners. They are large and very strong fliers. Anax walsinghami is the largest of our North American dragonflies, with a wing length up to five inches and a length up to nearly ten inches. Eggs are inserted beneath the water into the watersoaked stems of reeds or other plants or floating sticks. The slender, green and brown naiads are active climbers on submerged pond vegetation and also move by ejection of water from the respiratory chamber. They are notoriously cannibalistic.

F i g . 4 : 2 8 . W i n g s of A n a x junius

(Needham and Westfall,

1955).

K e y to C a l i f o r n i a

Species

Mates

1. Superior appendages not bifid; abdomen 4 7 - 5 8 mm. (North America, Central America, West Indies) junius (Drury) — Superior appendages bifid; abdomen 1 0 0 - 1 1 6 mm. (California, Utah, and T e x a s to Central America) . . walsinghami MacLachlan

long 1773 long . 1882

Females

1. Occiput with 2 blunt teeth on hind margin —

junius (Drury) walsinghami MacLachlan

Occiput without teeth Naiads

1. Lateral lobes of labium tapering to a hooked point; no teeth on mentum on either side of median c l e f t junius (Drury) — Lateral lobes of labium squarely truncate, a little rounded on the superior angle; mentum with small teeth on either side of the median cleft walsinghami MacLachlan

Genus Aeshna

Fabricius, 1775

The original spelling of Aeshna, rather than Aeschna, as used by many workers, is retained because of a ruling by the International Commission on Zoological Nomenclature. Adults are strong fliers, usually blue and brownish in color, and they are often commonly called blue darners. Features of the coloration are often indistinct in specimens that are not dried rapidly. They are found most abundantly near waters in which they breed, but they may wander far inland, particularly shortly after maturity. Generally, the imagoes follow no regular course but fly up and down over marshes and sluggish streams, shallow lakes, ponds, or bays containing vegetation. In hot weather the adults have a tendency to hang in the shade from the underside of leaves of trees. Two species of Aeshna have been recorded as swarming. Females oviposit soon after becoming fully mature and continue to do so from time to time throughout

F i g . 4 : 2 9 . W i n g s of Aeshna

juncea

(Needham and Westfall,

1955).

122 Smith and Pritchard: Odonata b a s a l plate l a t e r a l plate ovipositor g e n i t a l valve

stylus

abdominal appendage

F i g . 4 : 3 0 . V e n t r a l v i e w of f e m a l e Aeshna. a , A. clepsydra; Westfall, 1955).

t e r m i n a l a b d o m i n a l s e g m e n t s of b, A. s u b a r c t i c a ( N e e d h a m a n d

the- rest of their life. The eggs may be inserted in the stem of an aquatic plant every two or three seconds until the female is entirely submerged. Rarely, an immersed log or even the sand or mud may be used for egg deposition. Three years appear to represent the normal term of life of an Aeshna naiad, representing seven immature stages. Most naiads are found in fresh water that is rather shallow and harboring aquatic vegetation. However, A. californica has been recorded from brackish water. Naiads of smaller dragonflies, water beetles, mayflies, and aquatic bugs, as well as leeches, tadpoles, and small fish, all serve as food for the voracious naiads. Walker (1912) presented an excellent monograph of the genus Aeshna, but the later papers of Walker must also be consulted. The California species fall into four distinct species groups as far as the male terminalia are concerned, but it is rather difficult to determine some of the females with certainty. The following species are related to those recorded from California, but they are not yet known from this state:

B

C

D

S

F i g , 4 : 3 1 . T y p e s of l a t e r a l l o b e s o f n a i a d s in t h e g e n u s Aeshna. a, c o n s t r i c t a ; b, canadensis; c, californica, multicolor a n d verticalis; d, walkeri a n d interrupt a; e, palmata and umbrosa ( N e e d h a m and Westfall, 1955).

F i g . 4 : 3 2 . L a t e r a l v i e w s of m a l e a b d o m i n a l a p p e n d a g e s in t h e g e n u s Aeshna. a , californica; b, interrupta; c, palmata; d, multicolor (Celeste Green).

Aeshna dugesii C a l v e r t 1908, B a j a C a l i f o r n i a , Mexico, and T e x a s ( r e l a t e d t o A. multicolor). Aeshna mannt Williamson 1930, B a j a C a l i f o r n i a ( r e l a t e d t o A. californica and m i s i d e n t i f i e d by C a l v e r t 1908, a s A. cornigera Brauer 1865). Aeshna arida Kennedy 1918, Arizona and New Mexico ( r e l a t e d to A. palmata). Key

to C a l i f o r n i a

Species

Males

1. Abdominal s e g m e n t 1 w i t h a v e n t r a l t u b e r c l e 2 — Abdominal s e g m e n t 1 without a v e n t r a l t u b e r c l e . . . . 3 2. Superior a p p e n d a g e with a s h a r p v e n t r a l a n g u l a t i o n or s p i n e near d i s t a l end ( f i g . 4:32d) ( B r i t i s h C o l u m b i a t o Wyoming, s o u t h t o T e x a s and C a l i f o r n i a and P a n a m a ) multicolor H a g e n 1861 — Superior a p p e n d a g e without a v e n t r a l p r o j e c t i o n near d i s t a l end ( f i g . 4:32a) ( B r i t i s h Columbia and Idaho t o C a l i f o r n i a and A r i z o n a ) californica C a l v e r t 1895 3. Anal t r i a n g l e w i t h 2 c e l l s ; s u p e r i o r . a p p e n d a g e w i t h o u t a d i s t o v e n t r a l tooth ( f i g . 4:326) 4 — Anal t r i a n g l e with 3 c e l l s ; superior a p p e n d a g e w i t h a s h a r p , d i s t o v e n t r a l tooth ( f i g . 4:32c) 5 4. Mesothorax with d o r s a l p a l e s t r i p e s r e d u c e d t o s m a l l , i s o l a t e d s p o t s or narrow, incomplete l i n e s ( C a n a d a , w e s t e r n U.S.) interrupta1 Walker 1908 — Mesothorax with d o r s a l p a l e s t r i p e s c o m p l e t e , e x p a n d e d at upper e n d s (U.S.) verticalis H a g e n 1861 i A. interrupta interna Walker 1908 (British Columbia, Oregon to Colorado and New Mexico), a montane subspecies. A. interrupta nevadensis Walker 1908 (British Columbia, western Nevada, and California), a valley subspecies.

123 Smith and Pritchard: Odonata 5. Superior appendage with distal tooth short, not exceeding tip of appendage 6 — Superior appendage with distal tooth slender, reaching well beyond tip of appendage (fig. 4:32c) 7 6. Bear of head partly fuscous or yellowish (Canada and western U.S.) umbrosa* Walker 1908 — Rear of head black (California, Nevada, to Baja California) walkeri Kennedy 1917 7. Abdomen with venter entirely black (eastern U.S., British Columbia to Baja California) constricta Say 1839 — Abdomen with venter largely pale (Alaska to California and Colorado) palmata Hagen 1856 Feme les

1. Abdomen with a tubercle on the venter of segment 1 2 — Abdomen without a tubercle, on the venter of segment 1 3 2. Face with a brown or black line on frontoclypeal suture californica Calvert — Face without a black line on frontoclypeal suture multicolor Hagen 3. Styli as long as the dorsum of abdominal segment 10; appendages broadest before middle (fig. 4:30) constricta Say — Styli much shorter than dorsum of abdominal segment 10; appendages broadest beyond middle 4 4. Genital stylus with a tiny pencil of hairs; genital valves with apices not elevated 5 — Genital stylus without a tiny pencil of hairs; genital valves with apices elevated 7 5. Mesothorax with dorsal pale stripes absent or represented by a small spot; face with a black line on frontoclypeal suture interrupta Walker — Mesothorax with dorsal pale stripes present; face without a black line on frontoclypeal suture 6 6. Mesothorax with first lateral pale stripe having anterior margin sinuate verticalis Hagen — Mesothorax with first lateral pale stripe having anterior margin straight .walkeri Kennedy 7. Rear of head pale; face without a black line on frontoclypeal suture umbrosa Walker — Rear of head black; face with a black line on frontoclypeal suture palmata Hagen Naiads

1. Blade of lateral lobe of labium wider than in figure 4:3 la or b 2 — Blade of lateral lobe of labium shaped as in figure 4:31a; femora concolorous constricta Say 2. Blade about like figure 4:31c; mentum of labium about V/i times as long as greatest width 3 — Blade wider than figure 4:31c; mentum of labium about 1.3-1.6 times as long as greatest width 5 3. Blade with minute triangular tooth on innermost angle; femora concolorous verticalis Hagen — Blade merely sharply angulate at innermost angle; femora striped 4 4. Lateral spines of abdominal segment 8 shorter than 9, 6 rudimentary multicolor Hagen — Lateral spines of abdominal segment 8 longer than 9, 6 well developed calif ornica Calvert 5. Blade of lateral lobe of labium shaped as §hown in figure 4:3\d 6 — Blade of lateral lobe of labium shaped as shown in figure 4:31e 7 6. Blade of lateral lobe of labium with minute tooth on innermost angle interrupta Walker umbrosa umbrosa Walker 1908, a Canadian subspecies. A. umbrosa occidentalis Walker 1912, occurring from Alaska to Utah, Nevada and California. 4A,

F i g . 4:33. Wings of Gynacantha nervosa (Needham and W e s t f a l l , 1955).

— Blade of lateral lobe of labium sharply angulate at innermost angle walkeri Kennedy 7. Mentum about 1.3 times as long as greatest width; ovipositor of female about one and one-third times as long as segment 9 palmata Hagen — Mentum about 1.6 times as long as greatest width; ovipositor of female about one and one-tenth times as long as segment 9 umbrosa Walker

Genus Gynacantha

Rambur, 1842

Gynacantha represents a group of aeshnine genera of dragonflies that are found in the tropics. T h e only s p e c i e s found in the United States, G. nervosa Rambur, 1842 ( f i g . 4:33), ranges widely over Central and South America, and it has been found in southern Florida and southern California. T h i s i s a large, dusky brown s p e c i e s with green markings, particularly at the base of the abdomen. Adults f l y only for a short period in the evening and early morning. F e m a l e s lay eggs in soil near water. T h e type of the genus Gynacantha was first designated by Kirby 1890, as G. trífida. P r e v i o u s l y , however, S e l y s , 1857, made G. trífida the type of his genus Triacanthagyna, because the female is generi c a l l y recognizable by the triacanthagyne characteristics. It is true that Gynacantha, with seven originally included s p e c i e s , was without a type s p e c i e s until K i r b y ' s designation, which should be accepted under

F i g . 4:34. Wings of Triacanthagyna (Needham and W e s t f a l l , 1955).

trífida

124 Smith and Pritchard: Odonata

the present rules of zoological nomenclature. This interpretation would make Triacanthagyna a synonym of Gynacantha, and Gynacantha, in the sense of having biacanthagyne characteristics, would be replaced by Acanthogyna Kirby 1890 (with the type Gynacantha nervosa by designation of Cowley, 1934). However, we propose to use the well-established interpretations of these genera rather than make such a confusing switch. Family L I B E L L U L I D A E The members of the family Libellulidae are mostly showy dragonflies commonly seen hovering over the surface of still water. They vary greatly in size; in our fauna the smallest is about an inch in length, and the largest about four inches. The bodies of these dragonflies are in general stouter - and l e s s elongated than the Aeshnidae and Gomphidae. The females do not p o s s e s s a well-developed ovipositor but merely drop their eggs into the water or place them about plants at the surface of the water. The naiads are usually protectively colored and sprawl on the bottom in shallow water or clamber over fallen plant debris. They p o s s e s s a characteristic spoon-shaped, masklike labium. Many authors split this group into two or' three parts, each of family rank. Because of difficulties involved in characterizing the naiads at the family level, they are considered here as subfamilies. Key

to N e a r c t i e

Genera

s p o t s (fig. 4:37)

Tetragoneuria

Hagen

11. — 12. — 13.

Stigma with e n d s parallel (figs. 4:43; 4:45) 12 Stigma trapezoidal (figs. 4:41; 4:55; 4:57) . 33 A n a l l o o p c o m p l e t e , m o r e or l e s s f o o t - s h a p e d 13 A n a l l o o p o p e n a t w i n g m a r g i n . . . . Nannothemis Brauer Pronotum with caudal lobe e r e c t , a s wide a s pronotum and bilobulate 14 — Pronotum with caudal lobe directed c a u d a d , narrower t h a n the pronotum and u s u a l l y entire 23 14. B i s e c t o r of a n a l l o o p n e a r l y s t r a i g h t 15 — B i s e c t o r of a n a l l o o p d i s t i n c t l y a n g u l a t e b e y o n d m i d d l e (fig. 4:44) 16 15. F o r e w i n g w i t h t r i a n g l e a s b r o a d a s l o n g

—

Perithemis

Hagen

Celithemis

Hagen

F o r e wing with triangle longer than broad

16. H i n d w i n g w i t h C u , a r i s i n g from o u t e r f a c e of t r i a n g l e (fig. 4:40) 17 — H i n d w i n g w i t h C u , a r i s i n g f r o m p o s t e r i o r a n g l e of triangle (fig. 4:48) 20 17. F o r e w i n g w i t h d i s t a l a n t e n o d a l m a t c h e d ( f i g . 4 : 5 3 ) 18 — Fore wing with d i s t a l antenodal unmatched (fig. 4:52) 19 18. Wing w i t h 2 or m o r e c r o s s v e i n s u n d e r s t i g m a

Leucorrhinia

— Wing w i t h o n l y 1 c r o s s v e i n u n d e r s t i g m a

Brittinger

Erythemis

Hagen

R a d i a l p l a n a t e s u b t e n d i n g 2 r o w s of c e l l s , t i b i a l s p i n e s much longer t h a n i n t e r v a l s Lepthemis H a g e n 2 0 . Wing w i t h 2 or m o r e c r o s s v e i n s u n d e r s t i g m a 21 — Wing w i t h n o t m o r e t h a n 1 c r o s s v e i n u n d e r s t i g m a (figs. 4:48; 4:51) 22 2 1 . M e d i a n p l a n a t e s u b t e n d i n g 2 r o w s of c e l l s ; h i n d w i n g w i t h 7 or 8 a n t e n o d a l c r o s s v e i n s —

Cannacria Kirby

M e d i a n p l a n a t e s u b t e n d i n g 1 r o w of c e l l s ; with 6 antenodal c r o s s veins

hind wing

Brachymesia

Kirby

2 2 . A b d o m e n w i t h an e x t r a t r a n s v e r s e c a r i n a on 4th s e g m e n t —

Abdomen

segment

without

an

Tarnetrum Needham and F i s h e r

extra

transverse

carina

on

4th

Sympetrum Newman

Selys

Williamsonia

Davis

2 6 . Wing w i t h 1 b r i d g e c r o s s v e i n ( f i g . 4 : 4 3 )

at the b a s e , n o d u s ,

Epicordulia

and

Selys

Wing w i t h o u t d i s t a l m a r k i n g a n d w i t h o u t a s e p a r a t e nodal maculation 7 7. H i n d w i n g w i t h 2 c u b i t o - a n a l c r o s s v e i n s ; b i s e c t o r of anal loop c l o s e r t o Aa than t o A,; w i n g s without f u s c o u s Hind wing with

Helocordulia N e e d h a m H i n d w i n g w i t h 4 or 5 a n t e n o d a l c r o s s v e i n s ( f i g . 4 : 3 9 )

Neurocordulia

—

—

—

2 3 . Hind wing narrow at b a s e , with 2 c u b i t o - a n a l c r o s s v e i n s , a n d w i t h v e i n C u , a r i s i n g from o u t e r s i d e of triangle ( T e x a s and West I n d i e s ) Cannaphila K i r b y '— H i n d w i n g w i d e r a t b a s e ; v e i n s n o t a s a b o v e 24 24. Fore wing with distal antenodal matched 25 — Fore wing with distal antenodal unmatched (fig. 4:54) 30 2 5 . H i n d w i n g w i t h C u . a r i s i n g f r o m h i n d a n g l e of t r i a n g l e 26 — H i n d w i n g w i t h C u , a r i s i n g f r o m o u t e r f a c e of t r i a n g l e

F o r e wing w i t h triangle long and narrow

d i s t a l end

Cordulia Leach

—

1. A n a l l o o p m u c h l o n g e r t h a n w i d e , i t s c e l l s d i v i d e d i n t o 2 r o w s ; hind wing w i t h triangle c l o s e to a r c u l u s (fig. 4:40) 2 — Anal loop little longer than wide, its c e l l s not arranged in 2 r o w s ; h i n d w i n g w i t h t r i a n g l e r e m o t e from a r c u l u s (fig. 4:35) MACROMIINAE 3 2. Anal loop not b o o t - s h a p e d , d i s t a l a n g l e s similarly d e v e l o p e d ( f i g s . 4 : 3 7 ; 4 : 3 8 ; 4 : 3 9 ) ; p o s t e r i o r m a r g i n of e y e e m a r g i n a t e ; male with a u r i c l e s on s e c o n d a b d o m i n a l s e g m e n t a n d w i t h a n a l l o b e of h i n d w i n g n o t c h e d . . . CORDULIINAE 4 — Anal loop b o o t - s h a p e d , the toe rarely a b s e n t ; posterior m a r g i n of e y e r o u n d e d ( f i g . 4 : 4 0 ) ; m a l e w i t h o u t a u r i c l e s on s e c o n d a b d o m i n a l s e g m e n t a n d w i t h a n a l l o b e of hind wing s m o o t h L I B E L L U L I N A E 11 3. Occiput larger than vertex; s p a c e above bridge with 4 to 6 cross veins Didymops R a m b u r — Occiput smaller than vertex; s p a c e above bridge with 2 or 3 c r o s s v e i n s ( f i g . 4 : 3 5 ) Macromia R a m b u r 4 . F o r e w i n g w i t h M4 a n d C u , d i v e r g e n t 5 6 — F o r e w i n g w i t h M4 a n d C u , c o n v e r g e n t ( f i g . 4 : 3 7 ) . 5. F o r e wing w i t h t r i a n g l e e q u i l a t e r a l

6 . Wing w i t h l a r g e m a c u l a t i o n s

(fig. 4:38)

10. H i n d w i n g w i t h 6 a n t e n o d a l c r o s s v e i n s

P achydiplax B r a u e r 19. R a d i a l p l a n a t e s u b t e n d i n g 1 r o w of c e l l s ( f i g . 4 : 5 2 ) ; t i b i a l s p i n e s about a s long a s i n t e r v a l s

Adults

—

a n a l l o o p e q u i d i s t a n t f r o m A , a n d A2 ( f i g . 4 : 3 8 ) ) . . . . 8 8 . F o r e w i n g w i t h t r i a n g l e o p e n . . . Dorocordulia N e e d h a m — Fore wing with triangle having a c r o s s vein ( f i g s . 4:38; 4:39) 9 9. Hind wing with proximal i n f u s c a t i o n ( e x c e p t in one s p e c i e s from F l o r i d a ) 10 — Hind wing without i n f u s c a t i o n (northern U.S., C a n a d a )

Somatochlora

Selys

1 c u b i t o - a n a l c r o s s v e i n ; b i s e c t o r of

Erythrodivlax

—

Wing

with

2

or

more

bridge

cross

Brauer

Orthemis Hagen

veins

(fig.

4:44) 27 2 7 . F o r e w i n g t r i a n g l e w i t h 3 or m o r e c e l l s ( f i g . 4 : 4 4 ; 4 : 4 5 ) 28 — F o r e w i n g t r i a n g l e w i t h o n l y 2 c e l l s . . Ladona N e e d h a m 2 8 . A r c u l u s n e a r m i d d l e of d i s t a n c e b e t w e e n f i r s t a n d second antenodal c r o s s v e i n (fig. 4:45); male with a

125

Smith and Pritchard: Odonata pair of stout processes on venter of first abdominal segment; fore wing triangle distinctly convex on outer side Plathemis Hagen — Arculus at or very c l o s e to second antenodal cross vein ( f i g . 4:44); male without ventral processes of first abdominal segment; fore wing triangle straight or very s l i g h t l y convex on outer side 29 29. Wings marked with reddish Belonia Kirby — Wings marked with black, white, or hyaline Libellula Linnaeus 30. Wing with anal crossing directly opposite A 2 31 — Wing with anal crossing proximal to origin of A 2 . . . . 32 31. Fore wing subtriangle with 2 c e l l s Hagen Macrothemis — Fore wing subtriangle with 3 c e l l s ( f i g . 4:54) Brechmorhoga Kirby 32. Hind wing triangle with a cross vein ( f i g . 4:42) . . . . Pseudoleon Kirby — Hind wing triangle without a cross vein Micrathyria Kirby 33. Radial planate subtending 1 row of c e l l s 34 36 — Radial planate subtending 2 rows of c e l l s 34. V e i n M2 undulate Macrodiplax Brauer — V e i n Mj smoothly curved 35 35. Wing with one cross vein beneath stigma Miathyria Kirby — Wing with 2 cross v e i n s under stigma.. .Tauriphila Kirby 36. Abdominal segment 4 with a median transverse carina 37 — Abdominal segment 4 with only the transverse carina near caudal end of segment 38 37. V e i n M2 strongly undulate ( f i g . 4 : 5 7 ) . . . . Pantala Hagen — V e i n M2 evenly curved ( f i g . 4:56) Tramea Hagen 38. Hind wing with bisector of anal loop about t w i c e as far from A t as from A 2 at base of anal loop ( f i g . 4:58) JJythemis Hagen — Hind wing with bisector of anal loop at least 3 times as far from A , as from A 2 ( f i g . 4:55) Paltothemis Karsch Naiads5

1. Head with a prominent upturned frontal horn between the bases of the antennae ( f i g s . 4:10m,0; 4:36); l e g s very long MACROMIINAE 2 — Head without a prominent upturned frontal horn ( f i g . i-AOd-j) C O R D U L I I N A E and L I B E L L U L I N A E 3 2. Lateral spines of 9th abdominal segment reaching to apex of anal appendages ( f i g . 4:13ft); lateral setae of labium 3 or 5; dorsal hook on segment 10 absent Didymops — Lateral spines of 9th abdominal segment reaching l e s s than halfway to apex of anal appendages ( f i g . 4:13a); lateral setae of labium 6; small dorsal hook on segment 10 Macromia 3. Abdomen with dorsal hooks or knobs present on 1 or more segments (best seen in lateral v i e w s ) 4 — Abdomen with dorsal hooks or knobs absent on all segments, sometimes v e s t i g i a l tubercles or tufts of hair present 27 4. Dorsal hook or knob present on abdominal segment 9 5 — Dorsal hook or knob absent on abdominal segment 9 16 5. Lateral spines of abdominal segment 9 reaching to or beyond the tips of the anal appendages ( f i g s . 4:10; 4:13c) 6 — Lateral spines of abdominal segment 9 shorter, not reaching to tip of anal appendages ( f i g . 4:13e-h) . . . 8 6. Frontal shelf present between bases of the antennae, lateral setae 5 to 6 ( f i g . 4 : 1 0 f ) Neurocordulia — Frontal shelf not present between bases of the antennae, low and rounded, not produced into a f l a t triangle (fig-. 4:10p) 7 7. Distal half of dorsal surface of mentum heavily s e t o s e ; s Naiads

of Williams onia and Cannaphila are unknown.

lateral setae 4 to 5 ( f i g . 4:11Z) Epicordulia Distal half of dorsal surface of mentum with f e w or generally no setae; lateral setae 6 to 8 . .Tetragoneuria 8. Lateral anal appendages nearly as long as the superior appendage 9 — Lateral anal appendages one-half or l e s s the length of superior appendage . . .T 10 9. Dorsal hooks absent on segments 3 and 4, crenulations of the lateral lobes deep ( f i g . 4 : l i t ) Helocordulia — Dorsal hooks present on segments 3 and 4; crenulations of the lateral lobes shallow Somatochlora (in part) 10. Dorsal hooks cultriform, the s e r i e s in-lateral v i e w like teeth of a circular saw; lateral setae of labium 5 or 6 ( f i g . 4:13A) Perithemis — Dorsal hooks more spinelike "or low and blunt; lateral setae of labium 6 to 10 11 11. Dorsal hooks long and laterally flattened 12 — Dorsal hooks short and thick 14 12. Abdomen broadly depressed, little longer than w i d e ; lateral setae of labium 8 Tauriphila 13 — Abdomen about twice as long as wide 13. Superior anal appendage, seen from above, s l i g h t l y l e s s than half as long as its basal width Brachymesia — Superior anal appendage about twice as long as its basal width; tip of hind wing case extends posteriorly about halfway across abdominal segment 6 ( f i g . 4:13e) Cannacria 14. T e e t h on opposed e d g e s of lateral lobes of labium large 15 — T e e t h on opposed edges of lateral lobes of labium obsolete; lateral setae 6-7; mental setae 9 . . .Dythemis 15. Lateral setae of labium 6; mental setae 9-10 Macrothemis — Lateral setae of labium 7 to 9; mental setae 14-15 Brechmorhoga 16. Postocular distance less than the length of the e y e when v i e w e d from above; e y e s large and prominent on an usually triangular-shaped head ( f i g . i:10g-j) . . . . 17 — Postocular distance equal to or greater than the length of the e y e when v i e w e d from above; e y e s usually small and not very prominent ( f i g . 4:10a,b,c) 23 17. Lateral anal appendages nearly as long as superior appendage; lateral setae 6 or 7 18 — Lateral anal appendages usually about half the length of the superior appendage; lateral setae 7 to 14 19 18. Abdomen with lateral spines on segment 9 one-third as long as that segment; dorsal hooks present on segments 5 to 8, those on 7 and 8 not prominent . . . . Dorocordulia — Abdomen with lateral spines on segment 9 one and onehalf times as long as that segment; dorsal hooks present on segments 3 or 4 to 8 increasing in s i z e posteriorly Miathyria 19. Dorsal hook present on segment 3; inferior anal appendages subequal in length to superior appendage 20 — Dorsal hook absent on segment 3; inferior anal appendages markedly longer than superior appendage (except in Sympetrum costiferum) 22 20. Dorsal hook present on segments 2-6; lateral setae 7 to 9 Paltothemis — Dorsal hook absent on segment 2 21 21. Mental setae 10-15; lateral spine on segment 9 l e s s than middorsal length of segment 9; lateral setae 9-12 Leucorrhinia — Mental setae 16-17; lateral spine on segment 9 greater than middorsal length of segment 9; lateral setae 10; dorsal hooks present on abdominal segments 7 and 8 Macrodiplax 22. Lateral spines of abdomen long and straight, those of segment 9 extending to or beyond the tips of the inferior anal appendages Celithemis — Lateral spines of abdomen short, not reaching tips of anal appendages, curved toward meson ( f i g . 4:13/) Sympetrum (in part) 23. Inferior and superior anal appendages subequal in length 24 —

126 Smith and P r i t c h a r d : O d o n a t a — 24. — 25. — 26.

— 27. — 28. — 29. — 30. — 31.

— 32. — 33. — 34. — 35. — 36.

—

37.

—

Inferior anal appendages noticeably longer than the superior Sympetrum (in part) Mental setae 0 to 4 Ladona Mental setae 8 to 15 (fig. 4:11ft) 25 Margin of median lobe of labium crenulate on its distal margin; abdominal segments 7 to 9 with dark, shining middorsal ridges Plathemis Margin of median lobe of labium evenly contoured; abdominal segments 7 to 9 without such ridges 26 Abdomen with lateral spines present on segments 8 and 9; dorsal hooks normally present on abdominal segments 3 to 8, those on 7 and 8 rudimentary and hidden among scurfy hairs Libellula (in part) Abdomen with lateral spines vestigial on segments 8 and 9; dorsal hooks absent Belonia Apical third of inferior and lateral anal appendages strongly decurved (fig. 4:13^) 28 Apical third of all anal appendages straight, not decurved (fig. 4 : 1 3 i ) 29 Minute lateral spine on abdominal segment 9; lateral setae of labium 11 or 12 Lepthemis No lateral spines on abdomen; lateral setae of labium 7 to 9 Erythemis Postocular distance equal to or greater than the length of the eye when viewed from above; eyes usually small and not very prominent (fig. 4 : 1 0 a , b , d ) 30 Postocular distance l e s s than the length of the eye when viewed from above; eyes large and prominent on a somewhat triangularly shaped head (fig. 4:10^-i) . 36 Lateral anal appendages nearly as long a s the superior 31 Lateral anal appendages one-third to two-thirds as long as the superior; crenulations of lateral lobes shallow or absent (fig. 4:11/) 33 Crenulations of the distal margin of the lateral lobe obsolete, merely indicated by about 15 single spinules; abdomen abruptly rounded to tip; caudal appendages protruding but little beyond the ventral margin of segment 9 Pseudoleon Crenulations of the distal margin of the lateral lobe shallow to deep, with groups of 2-7 spinules on each tooth 32 Crenulations on lateral lobes deep and separated by rather wide notches; thorax unicolored Somatochlora (in part) Crenulations on lateral lobes shallow, teeth low; thorax with a dorsal longitudinal dark stripe Cordulia (in part) Lateral spines present on abdominal segments 8 and 9 34 A single small lateral spine present only on abdominal segment 9 or none 35 Mentum with distal margin crenulate; abdominal segments 4 to 7 with dorsal tufts of long hair (fig. 4:11m) Orthemis Mentum with distal margin entire, evenly contoured; abdominal segments 4 to 7 not a s above (fig. 4:11ft) Libellula (in part) Mental setae 5-11, lateral s e t a e 8 - 1 0 . . .Belonia (in part) Mental setae 12-16, lateral setae 10-12 Tarnetrum (in part) Anal appendages long, slender and needle-pointed; lateral spines of segments 8 and 9 long and curved toward meson, those on segment 8 at l e a s t as long a s middorsal length of segment 9 (fig. 4:13j-k) 37 Anal appendages short and heavy, not projected into a long needlepoint; lateral spines on segments 8 and 9 flat and straight, those on 8 not a s long as middorsal length of segment 9 ' 38 Lateral spines of abdominal segment 8 but slightly shorter than those of segment 9 (fig. 4:13;'); lateral spines of segment 9 reaching tips of anal appendages, crenulations of distal margin of lateral lobe shallow (fig. 4:11;') Tramea Lateral spines of abdominal segment 8 only one-third size of those of segment 9; lateral spines of segment 9 not reaching tips of anal appendages (fig. 4:13ft);

38. — 39. — 40. — 41. — 42. —

43.

—

crenulations of distal margin of lateral lobe deep (fig. 4:lli) Pantala Lateral setae 6 or 7; lateral anal appendages more than half as long as the inferiors 39 Lateral s e t a e usually 9 to 16, sometimes as few a s 6¿ lateral anal appendages half or l e s s than half a s long as inferiors 40 Lateral setae 6; mental setae 9 to 11; inferior and superior anal appendages subequal in length Nannothemis Lateral setae 7; mental s e t a e about 14; inferior anal appendages longer than superior appendage Cordulia (in part) Lateral spines absent or vestigial on abdominal segment 8 Tarnetrum (in part) Lateral spines present on abdominal segment 8 41 Superior anal appendages nearly as long as the inferiors (mainly northern North America) Leucorrhinia (in part) Superior anal appendages usually much shorter than the inferiors (mainly southern North America) 42 Lateral spines of abdominal segments 8 and 9 subequal in length 43 Lateral spines of abdominal segment 8 about half a s long as those of 9; lateral spine of 9 equal to or greater than the middorsal length of segment 9 (figs. 4 : 1 1 q\ 4:13i) Pachydiplax Lateral spines of abdominal segment 8 approximately half as long as segment. 9 middorsally; some s p e c i e s with prominent bunches of setae present on the dorsum of abdominal segments 4 to 9 Erythrodiplax Lateral spines of abdominal segment 8 nearly as long as segment 9 middorsally; without prominent bunches of s e t a e as described above Micrathyria

Subfamily

MACROMIINAE

T h i s i s a small group containing l a r g e , a c t i v e l y flying, brown or b l a c k i s h dragonflies marked with yellow. T h e y fly high, forage widely, and are very difficult to capture. T h e n a i a d s have a short, flat, a l m o s t c i r c u l a r abdomen, an e r e c t horn on the front of the head, and long l e g s with long simple c l a w s (fig. 4 : 3 6 ) . T h e y live sprawled in the s i l t of bare a r e a s awaiting their prey. Only two g e n e r a , Macromia and Didymops, o c c u r in the United S t a t e s ; the l a t t e r i s r e s t r i c t e d to the E a s t .

Genus Macromia

Rambur, 1 8 6 2

Most of the s p e c i e s of this group in the United S t a t e s o c c u r in the a r e a e a s t of the M i s s i s s i p p i R i v e r . However, two are found along the P a c i f i c C o a s t . Macromia magnifica M c L a c h l a n 1 8 7 4 , 'occurs from B r i t i s h Columbia south to California and A r i z o n a (fig. 4 : 3 5 ) . Kennedy ( 1 9 1 5 , pp. 3 1 3 - 3 2 2 ) studied t h i s s p e c i e s in Washington. He s t a t e s : . " t h e male Macromias were usually found patrolling the larger p o o l s or sometimes a patrol would include two or three of the shorter p o o l s . Seldom were more than three or four m a l e s s e e n a t any one time, and e a c h m a l e ' s b e a t w a s rarely over three hundred feet long. T h e flight w a s very swift, ordinarily about two feet above the s u r f a c e of the water and s t r a i g h t down the middle of the pools or, on the broader p o o l s , up one s i d e and down the other. F o r s p e e d few d r a g o n f l i e s c a n

127 S m i t h and P r i t c h a r d : Odonata

head with the abdominal appendages he would free his feet and she would bend her abdomen forward and copulate. The copulatory flight was ordinarily away from water over the surrounding trees, but ended in a long period of copulation while resting on some bush or tree. One pair, observed resting in copulation for fifteen minutes, on being disturbed flew away still in copulation." Kennedy (1915, pp. 318-319) also figures the naiads (fig. 4:36) which he found in a mass of fibrous alder roots in a pool about three feet deep. M. pacifica is largely restricted to the Midwest, and the California records of this species are doubtful. M. magnified can easily be separated from M. pacifica by the yellow markings which broadly cover the upper surface of the vertex in M. magnifica but are restricted to the summit in M. pacifica.

Subfamily

CORDULIINAE

This subfamily contains large, strong flying dragonflies often brilliantly colored with metallic green, blue, or purple. The hairy, dark-colored naiads sprawl on the bottom or climb through the bottom vegetation. Of the nine genera in the United States only three reach California.

F i g . 4 : 3 5 . M a l e o f M o c r o m i o magnifica

(Kennedy,

1915).

equal it . . . This species was found most commonly over the water on calm days between the morning hours of seven and ten. Few were found in the afternoons or on windy days. The flight over the water appeared to be controlled by the ovipositing females, who resorted to the water to oviposit early in the day in calm weather, where they were sought by the males. As the females oviposited by striking the end of the abdomen on the surface of the largest pools only, this could not be done except when the surface was smooth. At other times even until late twilight individuals of both sexes might be found patrolling glades and barnyards as much as a half mile from water. Here the flight varied from close over the ground to as high as the trees . . . In ovipositing the female would fly several times back and forth over a short beat of forty or fifty feet, striking her abdomen on the surface of the water at three to five foot intervals. This beating back and forth generally lasted until a male discovered her, when she would be taken away in copulation. At such times the male swooped and grasped the female's head with his feet, then bending the abdomen forward and grasping the female's

Fig. 4:36. Naiad

o f Macromia

magnifica

(Kennedy,

1915).

128 Smith and Pritchard: Odonata

Fig. 4:37. Wings of Somatochlora tenebrosa (Needham and Westfall, 1955).

Genus Cordulia

Fig. 4:39. Wings of Tetragoneuria sepia (Needham and Westfall, 1955).

L e a c h , 1815

T h i s genus contains one species in North America, C. shurtleffi Scudder 1866 ( f i g . 4:38). It is a bogloving s p e c i e s with a northern distribution. It occurs in Canada and northern United States, but ranges as far south as Utah and California in the West. T h e naiads are thick set and hairy and occur in shaded trashy areas at margins of ponds or bogs.

Genus Somatochlora

Selys, 1871

Somatochlora is a large circumpolar genus inhabitating the northern parts of the Palaearctic and Nearctic regions ( f i g . 4:37). One s p e c i e s , S. semicircularis ( S e l y s ) 1871, ranges from western Alaska south to the high mountains of California, Utah, and Colorado. T h e adults f l y in sunny openings in wooded mountain slopes or river v a l l e y s . The immature stages occur in swamps or spring bogs. While feeding they f l y at heights of thirty to f i f t y f e e t or more. In the breeding areas they fly back and forth low over the bog. E g g s are laid in masses on the surface of the water in the more open pools. T h e s e masses disintegrate and f a l l to the bottom. For more details on the habits of this

TL

and other Somatochlora (1913).

see Walker (1925) and Kennedy

Genus Tetragoneuria

Hagen, 1861

T h e genus Tetragoneuria contains brownish, nonmetallic dragonflies with the thorax heavily clothed with hairs ( f i g . 4:39). T h e adults are of a roving habit and most of the species are widely distributed. They are sometimes very abundant at long distances from water where in a clearing or along a road they may be seen patrolling a few f e e t above the ground. T w o wide ranging s p e c i e s occur on the P a c i f i c Coast. T h e naiads are smooth, hairless, and with a depressed abdomen. They are frequently very abundant along the e d g e s of ponds and streams where they crawl over the bottom and l o o s e trash. Key to C a l i f o r n i a S p e c i e s Ma les 1. D o r s a l appendages each with a strong dorsal tooth, the medioventral tooth on i n s i d e short and blunt ( C a n a d a , northern U . S . , Washington t o C a l i f o r n i a ) canis M a c L a c h l a n 1886 — D o r s a l appendages e a c h without a dorsal tooth, and the medioventral tooth on inside long and slender ( C a n a d a , northern U . S . , Washington t o C a l i f o r n i a ) . spinigera S e l y s 1871

T t l T T T r Females 1. Frons ( a s abdominal — Frons ( a s abdominal

s e e n from a b o v e ) with anterior margin p a l e , appendages 2.3-2.7 mm. in length canis s e e n from a b o v e ) w i t h anterior margin b l a c k , appendages 3.5 mm. in length spinigera Naiads

Fig. 4:38. Wings of Cordulia shurtleffi (Needham and Westfall, 1955).

1. L a t e r a l s p i n e s of the ninth abdominal segment v e r y s l i g h t l y or not at a l l d i v e r g e n t , six-tenths middorsal length of segment canis — L a t e r a l s p i n e s of the ninth abdominal s e g m e n t s t r o n g l y d i v e r g e n t longer than middorsal length of segment spinigera

129 Smith and Pritchard: Odonata

austratis, F i g . 4 : 4 1 . V e n a t i o n o f Tauriphita p i o n a t e s in r e l a t i o n to p r i n c i p a l v e i n s : A p R pi, r a d i a l planate; M pi, m e d i a n p l a n a t e .

fore w i n g , pi, apical

showing planate;

The naiads have squarish heads when viewed from above. They are usually active and climb through the aquatic vegetation. vesiculosa, male, F i g . 4 : 4 0 . B a s e o f h i n d w i n g of Lepthemis g, gaff; h, heel c e l l ; a, i n t e r p o l a t e d a n k l e c e l l s ; s i , s o l e ; n,o, p a r a n a J s ; m, m e m b r a n u l e ; A c , a n a l c r o s s i n g ; M f , m i d d l e f o r k ; mr, m i d r i b ; b r , b r i d g e ; m - p l , m e d i a n p l a n a t e ; o b , o b l i q u e c r o s s v e i n ; r, r e v e r s e c r o s s v e i n ( N e e d h a m a n d W e s t f a l l , 1 9 5 5 ) .

Subfamily

LIBELLULINAE

This group contains the commonest and b e s t known of the Odonata. The adults are common about every pond, ditch, and roadside. They are generally nonmetallic but often of brilliant coloration. In some c a s e s the color becomes obscured by pruinosity in old age. The s e x e s frequently differ in color and markings. This cosmopolitan subfamily is the largest and most dominant member of the order comprising about one-fourth of all known s p e c i e s . The majority of the s p e c i e s breed in still water, and adults rarely stray far from water.

Genus Pseudoleon

Kirby, 1889

A single ornate s p e c i e s , P . superbus (Hagen) 1861, is found in the Southwest and south to Guatemala. The adult is easily recognized by the heavy pattern of brown on the wings (fig. 4:42) and dull yellow oblique markings on the abdomen. T h e naiads occur in cooler parts of southwestern streams. The females prefer ovipositing in and about algae and other debris in slow moving pools. Genus Pachydiplax

Brauer, 1868

T h i s genus contains the single s p e c i e s , P . longipennis (Burmeister) 1839 (fig. 4:53). It is wide rang-; ing, occurring in southern Canada, the United States, West Indies, and northern Mexico.

F i g . 4 : 4 2 . W i n g s o f Pseudoleon (Needham and Westfall,

superbus 1955).

130 Smith and Pritchard: Odonata

F i g . 4 : 4 3 . W i n g s of Orthemis (Needham and Westfall,

ferruginea 1955).

The males are conspicuous and swift in flight. They hover near the surface of water or rest briefly on projecting twigs. They challenge all newcomers; when two males meet they face each other, then dart upward together to great heights. The females are less in evidence as they rest back from shore except when foraging or ovipositing. When ovipositing over open water they fly horizontally close to the surface and occasionally move the abdomen down to the water. Among vegetation, they fly up and down as do most Libellulidae. They are most common in the neighborhood of bushes and small trees at the edges of woods. The naiads crawl about the trash in the bottom of ponds and transform close to the margin of the water. They occur in static water with mud bottoms such as ponds, borrow pits, or creeks. Genus Erythemis

F i g . 4 : 4 4 . W i n g s of Libellula ( N e e d h a m and Westfall,

istically, the adults rest on the ground, floating logs, or other low objects. They wait for the appearance of suitable food and then dart out to take it. The female, unattended by the male, oviposits by touching her abdomen to the surface of the water at widely scattered points. As the adults age, they change in color. For example, Erythemis simplicicollis Say (fig. 4:52) is bright green with black when young and then becomes a pruinose blue gray in old age. In some places near the margins of ponds large numbers of these dragonflies may be found congregating. The thick-bodied naiads have bulging green eyes and usually occur in static water with a mud bottom. Bick (1941) gives details of the life history of E. simplicicollis. Key

Hägen, 1861

These are pond species of moderate size. Character-

incesta 1955).

to C a l i f o r n i a

Species

Adults

1. F a c e

green;

F i g . 4 : 4 5 . W i n g s of Plathemis lydia ( N e e d h a m and Westfall, 1955).

abdominal

appendages

yellow

(Canada,

131 Smith and Pritchard: Odonata — Lateral spines convergent

of

Genus Tarnetrum

abdominal

segment

9 distinctly glacialis

Needham and Fisher, 1936

T w o s p e c i e s of this genus, c l o s e l y related to Sympetrum, occur in the United States. T h e s e two s p e c i e s are probably the commonest dragonflies in our area. T h e adults can be found along roadsides, in f i e l d s , and near ditches ( f i g . 4:51). K e y to C a l i f o r n i a F i g . 4:46. Wings of Leucorrhinia Intacta (Needham and W e s t f a l l , 1955).

U.S. and Mexico, West Indies)

Simplicioollis (Say) 1839 — Face black across irons; abdominal appendages black (British Columbia to Utah, California and Mexico) . . . . collocata (Hagen) 1861

Species

Adults

1. Vertex with tip emarginate; wings with orange suffusion proximally and along costa; legs yellowish (British Columbia and Wyoming, south to California, Mexico, Argentina) illotum (Hägen) 1861 — Vertex with tip truncate; wings hyaline; legs black, (North America to British Honduras; Asia) corruptum (Hägen) 1861

Naiads

1. Lateral anal appendages not more than one-half as long as superior appendage Simplicio ollis — Lateral anal appendages two-thirds as long as superior appendage collocata

Genus Leucorrhinia

Naiads

1. Lateral anal appendages two-thirds as long as inferiors; lateral setae 9; mental seta« 13 illotum — Lateral anal appendages half as long as inferiors; lateral setae 13-14; mental setae 17 corruptum

Brittinger, 1850 Genus Sympetrum

T h i s is a northern group of small, white-faced dragonf l i e s . T h e y have red or tawny bodies with hyaline wings ( f i g . 4:46). T h e males are similar to the females except that they are somewhat larger. Of the seven species in the United States, three reach California. T h e green and brown slender naiads are climbers among green vegetation. T h e naiads and adults occur in and about sphagnum pools and boggy p l a c e s . T h e adults fly low near shore and are fond of bright sunlight. K e y to C a l i f o r n i a

Species

Adults

Newman, 1833

T h e species of this genus are mostly reddish in color and are most abundant in the autumn ( f i g . 4:48). They occur in or near ponds and wet meadows. T h e y are poor f l i e r s and easy to catch. T h e beautiful red colors fade in preserved specimens. Adults frequently congregate in large numbers in sunny locations. T h e slender naiads crawl over the bottom trash and vegetation in ponds. Key to C a l i f o r n i a

Species

Males

1. Tibia pale, at least on outer face

1. Abdomen with middorsal pale triangles on segments 4 to 7 or at least 6 and 7 (Canada, northern U.S., Oregon, California, Nevada, Utah) hudsonica (Selys) 1850 — Abdomen without pale spots on segments 4 to 6 . . . . 2 2. Abdomen with a pair of pale spots on segment 7 (Canada, northern U.S., British Columbia to California) intacta Hagen 1861 — Abdomen with ssgment 7 entirely black (Canada, northern U.S., British Columbia to California) glacialis Hagen 1890 Naiads

1. Dorsal hooks present on abdominal segments 7 and 8; no distinct band on under side of abdomen . . . . intacta — Dorsal hooks absent on abdominal segments 7 and 8; 3 wide longitudinal dark bands on underside of abdomen 2 2. Lateral spines of abdominal segment 9 pointing straight to rearward, with axes parallel hudsonica

F i g . 4:47. Wings of Erythrodiplax berenice (Needham and Westfall, 1955).

2

132 Smith and Pritchard: Odonata

—

4. — 5. —

6.

F i g . 4:48* Wings of Sympetrum vicinum (Needham and Westfall, 1955). — Tibia black 3 2 . Hamule broadly bifid on d i s t a l fifth (fig. 4:50