The Wild Silk Moths of North America: A Natural History of the Saturniidae of the United States and Canada 9781501738005

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THE OF

WILD NORTH

SILK

MOTHS

AMERICA

THE CORNELL SERIES IN ARTHROPOD BIOLOGY edited by

George C. Eickwort

Army Ants: The Biology of Social Predation by William H. Gotwald, Jr. The Tent Caterpillars by Terrence D. Fitzgerald The Wild Silk Moths of North America: A Natural History of the Saturniidae of the United States and Canada by Paul M. Tuskes, James P. Tuttle, and Michael M. Collins

THE WILD SILK MOTHS OF NORTH AMERICA A NATURAL HISTORY OF THE SATURNIIDAE OF THE UNITED STATES AND CANADA

Paul M. Tuskes, James P. Tuttle, and Michael M. Collins Drawings by Margaret A. Tuttle

Comstock Publishing Associates Cornell University Press I

a division of

ithaca and London

Copyright © 1996 by Cornell University All rights reserved. Except for brief quotations in a review, this book, or parts thereof, must not be reproduced in any form without permission in writing from the publisher. For information, address Cornell University Press, Sage House, 512 East State Street, Ithaca, New York 14850. First published 1996 by Cornell University Press.

Printed in the United States of America. Color plates printed in Hong Kong. © The paper in this book meets the minimum requirements of the American National Standard for Information Sciences—Permanence of Paper for Printed Library Materials, ANSI Z39.48-1984.

Library of Congress Cataloging-in-Publication Data Tuskes, Paul M. The wild silk moths of North America : a natural history of the Satumiidae of the United States and Canada / Paul M. Tuskes, James P. Tuttle, and Michael M. Collins ; drawings by Margaret A. Tuttle. p. cm. — (The Cornell series in arthropod biology) Includes bibliographical references (p. ) and indexes. ISBN 0-8014-3130-1 (cloth : alk. paper) 1. Saturniidae—United States. 2. Satumiidae—Canada. I. Tuttle, James P. II. Collins, Michael M. III. Title. IV. Series. QL561.S2T87 1996 95-32570 595.78'1—dc20

Contents

Publisher's Foreword Acknowledgments Introduction

4

vii

1

3

PART ONE I BEHAVIOR AND ECOLOGY 1

Life History Strategies

2

Parasitism

3

Diseases of Satumiidae

v

7

9

Metamorphosis and Development 10 Diapause 10 Adult Development 11 Voltinism 11 Adult Emergence 12 The Adult 13 Defensive Role of Wing Patterns and Behavior 13 Pheromone Mating System 13 Thermoregulation 16 Oviposition 16 Host Plants 17 Caterpillar Survival Strategies 18 Primary Defenses 18 Secondary Defenses: Response to Discovery 19 Behavioral Thermoregulation 20 Pupation 20 Underground and Soil Surface Pupation without Cocoons 21 Cocoon Spinning 21 24 28

30

The Genetic Structure of Populations 30 Speciation 32 Interpreting Phenotypic Variation in Nature 33 The Subspecies Problem 33 Phenotypic Blending in Zones of Sympatry 34 Polymorphism 34 Hybrid Zones 35 Allopatric Populations and Experimental Hybridization 35 Species Concepts and Their Application in Taxonomy 36 Summary 37

ix

Format and Organization 2 Distribution Maps 3 Taxonomy and the Species Problem Classification 4

Populations, Species, and Taxonomy

5

Collecting

6

Rearing 45 Host Plants Ova 46 Larvae 47 Pupae 49 Adults 50

7

39

45

Silk Moths and Human Culture Silk 52 Silk Moths as Food 53 Symbols in Art and Religion Pests 54

52

54

PART TWO I SPECIES ACCOUNTS Subfamily Ceratocampinae Citheronia

59

regalis 60 sepulcralis 62 splendens sinaloensis

63

59

57

vi

Contents

Eacles

64

imperialis imperialis imperialis pini 66 oslari 68

Anisota

her a marcata 147 hera magnifica 148

64

Automeris

69

stigma

70

manitobensis 71 consularis 73 virginiensis 74 senatoria 76 finlaysoni 77 peigleri 78 os/arz 79

Dtyocampa

80

rubicunda

80

Sphingicampa

Subfamily Satumiinae Saturnia

82

isara

Coloradia don's luski

93

Anther aea

176

polyphemus oculea 179

95

95

Actias

182

luna

182

Sflim'u

184

cynthia

184

187

lebeau forbesi 187 cz'ncta cmcffl 189

Eupackardia

103

calleta

tricolor 106 hualapai 107 oliviae 109

191

191

Callosamia

194

promethea 194 angulifera 197 securifera 198

111

maz'a peigleri 114 lucina 115 nevadensis 117 slosseri 119

Hyalophora

maia complex Great Lakes Region Populations 120 electra electra 122 electro clio 124 electra mojavensis 125 electra Lower Colorado Desert Population 126 juno 127 gro tei grotei 128 grotei diana 130 stonei 131 neumoegeni 132 burnsi 134 chinatiensis 135 griffini 137

200

cecropia 201 Columbia Columbia 205 Columbia gloveri 207 euryalus 211 "kasloensis" and Other Hybrid Populations in the Pacific Northwest 213

Appendix 1. Host-Parasitoid Records Appendix 2. Satumiid Hybrids Literature Cited Subject Index

227 241

Taxonomic Index

eglanterina eglanterina 138 eglanterina shastaensis 140 eglanterina annulata 141 Other Hemileuca eglanterina Populations nuttalli 143 hero her a 145

177

Rothschildia

pandora pandora 99 pandora davisi 101 oe/dfl 102

mow maw

169

galbina 170 anona anona 171 anona dyari 173 anona platensis 174 homogena 175

96 98

Hemileuca

162

Agapema

93

Subfamily Hemileucinae

162

mendocino 163 walterorum 166 albofasciata 168

bisecta 83 bicolor 85 heiligbrodti 86 hubbardi 87 blanchardi 88 montana 90 raspa 91 albolineata 92

Adeloneivaia

149

io io 150 io neomexicana 152 louisiana 153 patagoniensis 155 iris hesselorum 157 cecrops pamina 158 zephyr ia 159 randa 160

244

Index to Host Plants

247

143

The color plates follow page 58.

224

217

Publisher's Foreword

The field of entomology is undergoing a renaissance

interactions with the environment. Each volume can

as modem behavioral and ecological approaches are

thus serve as a primer for students and scholars wish¬

applied to the study of insects and their relatives. Rec¬

ing to study that group of animals.

ognizing the significance of this development and the

This particular volume contains more detailed cov¬

need for books that consider arthropods from a modem

erage of systematics than was intended for the series.

evolutionary viewpoint, the late George C. Eickwort in¬

Yet much of this information is new and unavailable in

itiated the Cornell Series in Arthropod Biology.

other monographs. Furthermore, the extensive discus¬

The volumes in the series focus on the behavior and

sion of taxonomic and evolutionary issues is appropri¬

ecology of a particular taxon, varying in rank from class

ate for the Satumiidae. In keeping with the intent of the

to genus. Written by scientists who are making the

series, the book also thoroughly describes the biology,

greatest advances in expanding our knowledge of ar¬

natural history, and behavioral ecology of the silk

thropod biology, the books are comprehensive in their scope, not only detailing the subject animals' behavioral

moths. The series, we hope, will engender the great enthu¬

ecology but also summarizing their evolutionary his¬

siasm for entomology that George Eickwort spread to

tory and classification, their development, important

all who knew him.

aspects of their morphology and physiology, and their

vii

Acknowledgments

We could not have done the extensive fieldwork, mu¬

signing studio equipment and for his expert photog¬

seum research, and literature searches necessary for this

raphy in producing the adult color plates. Ronald S.

book without the assistance of a number of individuals,

Wilkinson secured copies of hard to obtain antiquarian

institutions, and agencies. Throughout the text we

books. Steven J. Prchal (Plate 2, no. 9), Jane M. Ruffin

gratefully acknowledge those who provided assistance

(Figure 6), William D. Winter, Jr. (Figure 21), and the

during this effort. The following people made special

Denver Museum of Natural History (Figure 8) gener¬

contributions, and we believe they merit additional rec¬

ously shared photographs. The entire manuscript, or

ognition for their interest, enthusiasm, encouragement,

specific sections, were reviewed by Ring T. Carde,

and expertise in various fields. For extensive field as¬

Thomas W. Carr, Walter G. Goodman, Ann McGowan-

sistance we thank Thomas W. Carr, Jimmie Coleman,

Tuskes, Richard S. Peigler, John E. Rawlins, Michael J.

Brenda C. Collins, Rose Farmer, Nita Fuller, Hilton J.

Smith, Margaret A. Tuttle, and Robert D. Weast.

and Joyce T. Gaspard, Peter M. Jump, Michael T. Lefort,

Finally, we wish to express our appreciation for the

Steven J. McElfresh, Ann McGowan-Tuskes, David C.

guidance offered by George C. Eickwort as editor of the

and Karen M. Robacker, Jeffrey R. Slotten, and Brian G.

Cornell Series in Arthropod Biology. Dr. Eickwort

Scholtens. For the loan of specimens and the sharing of

made a difficult decision, early in the editing process,

collecting records we thank Thomas W. Carr, Boris C.

to include a lengthy systematic treatment in this vol¬

Kondratieff (Colorado

Steven J.

ume. This decision allowed us to present a more inte¬

McElfresh, Richard S. Peigler (Denver Museum of Nat¬

grated evolutionary account of the North American

ural History), Jeffrey E. Slosser (Texas Agricultural Ex¬

Satumiidae in what is a series devoted primarily to life

periment Station), Michael J. Smith, and Ralph E. Wells.

history adaptations. We share with his associates the

Technical assistance in preparing the distribution maps

sense of loss at his untimely passing.

State

University),

was provided by Richard D. Foley. Margaret A. Tuttle produced the many excellent line drawings. We thank Wilfried Wietstock for his skill and patience in de¬

P. M. T. J. P. T. M. M. C.

IX

%

THE OF

WILD

NORTH

SILK

MOTHS

AMERICA

Introduction

The moths in the worldwide family Satumiidae, in

history were written by women: Ida M. Eliot and Car¬

the insect order Lepidoptera, are commonly called giant

oline G. Soule (1902), Ellen Robertson-Miller (1912), and

silk moths or wild silk moths for the elaborate silken

Gene Stratton-Porter (1912). Their books helped estab¬

cocoons spun by the larvae of many species. There are

lish the Satumiidae as an important part of America's

about 70 species of Satumiidae in the region covered

natural history culture. Satumiids are often used in the

by this book, a small fraction of the nearly 11,000

classroom to teach insect life cycles, and most people

known species of moths in all families in North Amer¬

know the cecropia moth (Hyalophora cecropia) and the

ica north of Mexico. And so it is appropriate in intro¬

lima moth (Actias luna) as icons of natural beauty, if not

ducing a work of this scope to justify the intense study

by name. The splendor of the satumiids makes them

of a small group of insects such as the North American

valuable in drawing the public's attention to environ¬

Satumiidae, only a few of which are in any sense com¬ mercially or economically important. Part of the expla¬

mental issues. Sadly, since the 1960s the wild silk moths have declined in numbers, especially in the northeast¬

nation

and

ern United States, probably as a result of habitat de¬

taxonomic diversity, and the ease with which most spe¬

struction and control measures directed against the

cies can be bred and studied. Lepidopterists have always included satumiid enthu¬

gypsy moth (Holden, 1992; Schweitzer, 1988), and per¬ haps also because the increasingly widespread mercury

siasts, but we also hope to appeal to readers with a

vapor lights disrupt their mating. Some species, includ¬

general interest in natural history. Most of us who have

ing the imperial moth (Eacles imperialis) and the royal

collected and studied moths and butterflies were at¬

walnut moth (Citheronia regalis), have become rare and

tracted at a young age to the giant silk moths by their

possibly extinct in certain regions of the Northeast.

large size and great beauty, and for many this is justi¬

Now is a critical time to catalog the diversity of our

fication enough to pursue a long-term interest in the

native Lepidoptera species as part of a worldwide con¬

Satumiidae. Whether they are at rest or slowly fanning their wings to display intricate patterns and rich colors,

servation effort. Lepidoptera in general have proven to be excellent

these creatures fascinate all who notice them. Cloaked

subjects in ecology and evolutionary biology (Vane-

in velvety scales, often quite large compared with but¬

Wright & Ackery, 1984). The Satumiidae in particular

terflies, they almost resemble furry mammals, and in¬

have served science in studies of insect development

deed, those who rear adults from larvae often come to

and physiology and in research on ecology and life his¬

lies

in

their beauty,

their

ecological

regard them more as pets than as specimens. The larvae

tory adaptations. In his excellent monograph of North

are as interesting as the adults. Some species display

American Satumiidae, Ferguson (1971, 1972) expressed

colorful and complex markings, many are quite large,

surprise that such a popular group posed so many un¬

and all are variously adorned with often colorful tu¬

answered questions in taxonomy and speciation, ecol¬

bercles, sometimes modified as long "horns” or branch¬

ogy, and biogeography. His works plus the earlier

ing spines. The relative scarcity of the satumiids is also

amateur's guide by Collins and Weast (1961) and

a part of their fascination. The most influential early works on satumiid natural

the volumes by Lemaire (1971-1974, 1978, 1988) have

1

stimulated lepidopterists, many of them amateurs, to

2

Introduction

collect, rear, and document satumiids. This book ob¬

species, ranging from historical anecdotes to an over¬

viously has benefited from this recent work. Yet, even

view of current taxonomic controversy or justification

as we present new information, we also pose many

for taxonomic modification.

questions for study. Distribution. General distribution data are offered for all taxa. We list specific collection sites for species with

Format and Organization

limited ranges, for new range extensions, or when only a few records exist. The preferred habitats and plant

We attempt to present the North American Saturni-

communities are also discussed in this section.

idae in terms of natural populations, and it is our goal to direct the reader toward broader questions in biol¬ ogy rather than restricting the discussion to taxonomi-

Adult Diagnosis. This section lists other generally sim¬

cally specialized topics. To this end we include chapters

ilar species and identifies and discusses characters that

on the life history adaptations of the Satumiidae—their

will assist in distinguishing taxa.

population biology, parasitoids, and disease—and silk moths in human cultures, as well as practical sections on collecting and rearing. We do not include sections on making and maintaining a collection of preserved specimens; such information is available in many ex¬ cellent Lepidoptera field guides. Specific information on the preparation and study of genitalia can be found in Cribb, 1972. To promote further research we provide an extensive bibliography, including selected references outside the Lepidoptera literature. We offer new life history information obtained through correspondence and our own original research, and we attempt to cor¬ rect erroneous information. Although it is not a bound, permanent record, the "Season Summary of the News

Adult Variation. The adaptive significance of adult variation may be difficult to determine, but phenotypic variation certainly influences our understanding of tax¬ onomic relationships. For that reason, we discuss sev¬ eral categories of morphological variation within each taxon, including sexual dimorphism, individual varia¬ tion within populations, regional variation, and phe¬ notypic dines where appropriate. Hybrid zones are discussed under "Adult Biology" for specific cases. The size of the forewing from base to apex is given in mil¬ limeters for both sexes, along with the average and range values when these are known.

of the Lepidopterists' Society" is an excellent source of information, and we include data from there, cited as

Adult Biology. This section includes information about

(SS, year, p.). We acknowledge the contribution of data

adults' daily emergence times, mating times and be¬

from others by means of personal communication

havior, seasonal flight patterns, oviposition, and other

citations; and in a few cases our own unpublished ob¬

biological adaptations. We give special attention to iso¬

servations are denoted by the initials of the author—

lating mechanisms that allow species to maintain re¬

for example, (JPT).

productive integrity in areas of sympatry.

Our discussion of species is presented in a standard¬ ized format to help the reader locate information and compare taxa. We include the type locality of each

Immature Stages. Ova, larval behavior and defense

taxon and a partial list of synonymies. The synonymies

mechanisms, and host plants are addressed in this sec¬

listed include nomenclature published since the Fer¬

tion. We describe regional variation in common host

guson monograph and any older names specifically dis¬

plants, based on our own experience and reliable

cussed in the text. We do not include a list of

sources. Host plants are plants on which wild larvae

aberrations. Rare morphs, the result of developmental

have actually been found feeding. We sometimes also

mutations or environmental effects, were commonly

indicate plants on which cocoons or resting larvae were

named near the turn of the century, but they have no

collected. Pupation, overwintering adaptations, and, if

taxonomic significance and are not recognized in the

available, information on individual and regional mor¬

International Code of Zoological Nomenclature. Com¬

phological variation in larvae are discussed in this sec¬ tion as well.

plete listings of synonyms, including aberrations, can be found in the Ferguson monograph.

Rearing Notes. Our suggestions for successfully rear¬ General Comments. The introductory remarks in this section cover the characteristics that distinguish the

ing the species in captivity include optimal conditions and alternate host plants.

Taxonomy and the Species Problem

Distribution Maps

3

north of Mexico, with the exception of Anisota manitobensis, Adeloneivaia isara, and Agapema galbina. More¬

Distribution maps are provided for general guidance.

over, we have reared and studied various named and

The actual ranges of many satumiids have not been

unnamed populations whose taxonomic status is un¬

completely defined. In addition, the reader should not

certain. In our species accounts we draw on this infor¬

infer that a given species can be found throughout its

mation to discuss life histories, describe phenotypic

projected range on the map. The scale of reduction

variation within and among populations, and make tax¬

makes it impossible to designate appropriate plant communities and habitats. As an example, although the

onomic decisions. Satumiids are especially well suited to experimental

various Coloradia species are shown as broadly distrib¬

hybridization for taxonomic studies because they are

uted over the western United States, much of the

easy to mate and breed. The adults, which do not feed,

shaded area is not of sufficient elevation to maintain

require little special care. The males' response only to

the pine habitat that Coloradia requires. Given these lim¬

pheromones released at specific times makes satumiids

itations, and if the reader uses them in conjunction with

especially amenable to experimentation, unlike butter¬

the habitat discussion and specific records offered in

flies, which exhibit more complex courtship behavior.

the text, the maps can serve as a handy reference in

Unfortunately, these virtues have not been sufficiently

determining species distributions. Broad biogeographic

exploited in taxonomic studies.

relationships can be studied by comparing and con¬

We address taxonomic questions at the species and subspecies levels from the standpoint of reproductive

trasting the ranges of given species.

isolation rather than relying solely on morphological characters such as male genitalia. In many cases we of¬ fer new information on isolating mechanisms, such as

Taxonomy and the Species Problem

responses to pheromones or the results of experimental In Chapter 4 we briefly discuss the origin and main¬

hybridization.

tenance of genetic variation in populations and the

Population biologists have discovered that popu¬

process of speciation. This evolutionary view of the

lations of many Lepidoptera species are highly dif¬

species is especially useful in understanding patterns of

ferentiated both genetically and ecologically. Within

phenotypic variation in nature. We also discuss the dif¬

populations a measurement of individual variation can

ficulties in applying the subspecies category and justify

serve as a baseline reference in taxonomic comparisons

the use of reproductive isolation as a criterion for de¬

among populations or between taxa. Such information

fining species. Cladistics and phylogenetic analysis,

can only be acquired through the systematic rearing of

also discussed in Chapter 4, may be more suitable for determining monophyly (descent from a single ances¬

siblings and by sampling various populations. These

tor) and constructing phylogenetic trees. The informa¬

characters in some cases actually represent individual

tion in Chapter 4 should help the reader to understand

variation within a single population. The geographic

the evolution of life history traits and strategies (re¬

patterns of morphological variation in Lepidoptera are

viewed in Chapter 1) and to evaluate the taxonomic

often more complex than that represented by named

treatment of the species described in Part 2. Our classification and nomenclature follow that of

subspecies. We employ a conservative approach in ap¬

Ferguson (1971, 1972) in the Moths of North America fas¬

In general, we avoid applying subspecies names to ge¬

cicles. Where differences exist we offer detailed justifi¬

ographic variation that involves extensive phenotypic

cation.

of

blending between populations. Although we continue

priority for the subfamily name Ceratocampinae in

the use of current subspecies names for some distinct

place of Citheroniinae. The works of Ferguson and

allopatric populations, we try to cite relevant hybridi¬

Lemaire probably represent the last major systematic

zation or other biological data that shed light on genetic

revisions of the Satumiidae based primarily on mor¬

relationships among populations. In many cases we

phological criteria. Current taxonomic practice favors a

simply describe geographic variation, both morpholog¬

multidisciplinary approach, and powerful methods

ical and biological, without applying formal names to

such as multivariate analysis of phenotypic variation, phylogenetic analysis and cladistics, and molecular ge¬

the component populations. In a few instances we have reduced to subspecies rank recently described taxa that

netics are joining comparative morphology as routine

we feel do not merit full species rank based on current

taxonomic tools. We have collected and reared all the satumiids found

jective, and we suggest that the reader not become too

We

accept Lemaire's

(1988)

arguments

methods allow us to show that supposedly diagnostic

plying subspecies names in our taxonomic treatment.

data. Taxonomy at the subspecies level can be very sub¬

4

Introduction

immersed in nomenclature controversies. The biases of

scolus is present on the eighth abdominal segment in

a given author for or against the name applied to a

the Hemileucinae and Satumiinae, and on the eighth or

specific population should in no way reduce the bio¬

ninth abdominal segment in the Ceratocampinae, but

logical significance of the unique characteristics of that

may be reduced in the genus Anisota. The scoli of the

population.

Ceratocampinae are often well-developed hornlike tu¬ bercles. In all the subfamilies the scoli usually become reduced in proportion to the body as the larvae mature,

Classification

but those on the dorsum of the thoracic segments and the eighth abdominal segment are often pronounced.

The family Satumiidae comprises about 1200 species

Secondary setae are present, although the number and

worldwide, in more than 125 genera. Many of the spe¬

length may be reduced in some groups as larvae ma¬

cies are large and showy. The Asian Atlas moths (Attacus and Coscinocera spp.) are probably the largest

ture. Most authors place the saturniids into seven subfam¬

Lepidoptera in wing area. Although diverse in form

ilies. The Agliinae, Salassinae, and Ludiinae are found

and habit, the 70 or so species in 18 genera that occur

only in the Old World, and the primitive Arsenurinae

north of Mexico represent only a fraction of the more

is confined to the New World Tropics and subtropical

than 600 New World satumiid species. Packard's (1905,

Mexico.

1914) monographs of the bombycine moths of North

Hemileucinae are also found only in the Western

America are historically important in their scope of top¬

Hemisphere, where their greatest species diversity oc¬

The Ceratocampinae (=Citheroniinae) and

ics, the artistic quality of the color plates of the larvae,

curs in the Tropics. The distribution of the large genus

and the classification system they use, which is essen¬

Hemileuca, however, is centered in the North American

tially similar to that used by later authors. Michener

West and Southwest, and among saturniids these

(1952) constructed the first comprehensive phylogeny

moths have most successfully adapted to the desert and

for the Satumiidae of the Western Hemisphere, dis¬

Great Basin regions. The subfamily Satumiinae is found

cussed associated evolutionary trends, and presented a

in both the Old and the New World. Each subfamily is

classification based on a detailed analysis of compara¬

treated in detail in Part 2.

tive adult morphology. The monographs by Ferguson

Several lines of evidence indicate that the Satumi¬

(1971, 1972) and Lemaire (1971-1974, 1978, 1988) pre¬

idae first evolved in the American Tropics (Fergu¬

sent a species taxonomy of New World Satumiidae

son, 1971; Michener, 1952). The greatest taxonomic

with emphasis on genitalic structures. Peigler (1989) of¬

diversity within the Satumiidae occurs there, as do the

fered the only cladistic analysis of the Satumiidae—for

most primitive genera of Satumiidae and the primitive

the tribe Attacini—and included sections on ecology,

families most closely related to them. On the other

biogeography, and other related subjects in his mono¬

hand, the members of the New World subfamily Sa¬

graph of the Australasian genus Attacus. All serious

tumiinae appear to be most closely related to the more

students of the Satumiidae should consult these refer¬

diverse Old World fauna, and the North American

ences.

genera may have evolved from a few groups that rein¬

Saturniids are characterized by heavy bodies cloaked

vaded the New World by crossing the Bering land

in hairlike scales, small heads with vestigial mouth-

bridge, perhaps during the late Tertiary. The supposed

parts, and quadripectinate antennae (four branches per

fossil of an Attacus-like wing (Cockerell, in Packard,

segment; except for the bipectinate antennae of the ge¬

1914) from the Oligocene shales of Florissant, Colo¬

nus Hemileuca). The males' antennae are typically broad

rado, was reinterpreted by Peigler (1989) as being a

and featherlike; those of females are much narrower

leaf fossil, not an imprint of a moth wing. In any case,

and often more simply branched. The humeral angle of

the members of the tribe Attacini within the Satumi¬

the hindwing is pronounced so as to engage the anal

inae (Hyalophora, Callosamia, Eupackardia, Rothschildia)

margin of the forewing in flight, thus performing the

are thought to be more divergent from their Old

function of the frenulum present in most other Lepi¬ doptera.

World relatives than the American Satumiini are.

With few exceptions the larvae bear well-developed

genera Antheraea, Actias, and Saturnia closely resemble

spiny scoli, often called tubercles, that are diagnostic of

their congeners in the Old World, and American gen¬

the family with the exception of the moth family Limacodidae and the larvae of certain nymphalid butter¬

era such as the Copaxa are closely allied to the Asian Caligula.

flies. Larvae usually have enlarged dorsal or dorsal

In spite of saturniids' popularity and worldwide dis¬

thoracic scoli and reduced lateral scoli. A mid-dorsal

tribution, however, no one has applied modem meth-

Within the tribe Satumiini, American species in the

Classification

5

ods of cladistic analysis to perform a phylogenetic

tionships to allied genera. Future research on the Sa-

study of the entire family. Such methods should also

tumiidae should employ a wide range of characters,

be applied to large genera, such as Hemileuca and

including ecological and behavioral ones as well as bio¬

Anisota, to elucidate questions of monophyly and rela¬

chemical and morphological ones.

■

1

Life History Strategies

Those who first rear satumiids solely for their beauty soon begin to ponder how the various life cycle stages adapt each species to its natural surroundings. The con¬ cept of life history strategies states that through natural selection, evolution has coordinated the physiology, morphology, and behavior of each organism into an overall plan for survival. The term strategy is teleolog¬ ical because it implies that organisms plan their own adaptive evolution, but the concept is useful neverthe¬ less as a framework for discussion in a field that is increasingly specialized and quantitative (Denno & Dingle, 1981; Dingle & Hegmann, 1982). In phyloge¬ netic terms, adaptive traits at the family level—large adults that do not feed, for example—both present op¬ portunities and impose constraints for further evolution at the genus and species levels (see Janzen's [1984a] eloquent discussion of the tropical satumiids). In a broad sense, satumiids employ a strategy of overcoming losses to predators, parasitoids, and dis¬ ease and the effects of adverse environmental factors by synchronizing their reproductive effort as nonfeed¬ ing adults and producing large numbers of eggs. Adult females emerge with a full complement of mature ova, and both sexes live on stored lipids (fatty reserves). Adult behavior, then, is almost entirely devoted to re¬ production, which takes place within a few days, free from dependence on nectar sources. Only a small per¬ centage of the total ova laid survive to the adult stage. An average of two per breeding female must reach adulthood if a stable population size is to be main¬ tained. For a species that lays an average of 200 ova, this is a 1% survival rate. Because the adult males have the ability to locate fe¬ males by following wind-borne pheromone trails, satumiid populations can exist at relatively low densities

9

compared with many other Lepidoptera. Seemingly iso¬ lated, the virgin females remain inactive, conserving their stored food reserves and minimizing their expo¬ sure to predation while releasing an attractant phero¬ mone (“calling”) and awaiting the arrival of the wide-ranging males. Such widespread, low-density populations may be relatively immune to local and temporarily adverse conditions, both biological and physical. Should local extinction occur, satumiids' abil¬ ity to disperse and survive at low densities increases the likelihood of recolonization. Although it is difficult to accurately assess popula¬ tion size, our extensive cocoon- and larva-collecting ex¬ perience indicates that some species can survive at a density of a few tens of individual adults or cocoons per square mile (Collins & Weast, 1961; Ferguson, 1971; Weast, 1989). A more efficient method for determining population size involves collecting males that are at¬ tracted to calling females, marking them, and then re¬ leasing them at specified locations on a grid. The ratio of released to recaptured males gives an estimate of population size using a Lincoln Index (Cummins et al., 1965; Gall, 1985). This type of estimate is subject to var¬ ious sources of error, including movement of males into and out of the area. Surprisingly, no such study on sa¬ tumiids has been reported. Low-density populations may make it “unprofitable” for parasitoids and pred¬ ators to concentrate or attempt to specialize on saturniids. Through such protective strategies as crypsis, unpalatability, and defensive behavior, enough individuals mature to ensure the survival of the population. The female's oviposition habits, the host plant distribution and availability, and the distribution of predators and parasitoids in the environment all combine to produce

10

Life History Strategies

a patchy distribution of individuals. The offspring of

egy risks loss if the larvae cannot complete their growth

many females will all perish; a few females will pro¬

before the onset of intolerable conditions. Before the

duce many survivors that successfully reproduce.

end of the growing season the larvae must be able to

Populations often appear to undergo cyclic changes

enter the pupal stage in a state of reduced metabolism

in abundance. Some species, especially those in the gen¬

and cell activity called diapause. A neural-hormonal

era Anisota, Coloradia, and Hemileuca, may reach levels

system that responds to day length and temperature

of outbreak proportion during favorable years. Disease,

cues determines whether a larva enters diapause or

predators, and parasitoids subsequently take their toll,

continues to develop to the adult stage. Glandular

however,

crashes,

structures called the corpora allata produce juvenile

sometimes to such a low level that casual collect¬

and

the

population

eventually

hormone, which regulates the developmental expres¬

ing may fail to detect the species for a number of sea¬

sion of tissue type. High levels of juvenile hormone

sons.

maintain the synthesis of larval structures. When the

The females of many large species, including Hyalo¬

level of juvenile hormone decreases, the larva begins to

phora cecropia, Actias luna, and Eacles imperialis, use a

pupate. The timing of these developmental events is

general strategy of survival through dispersal by dis¬

regulated by the brain and the prothoracic gland, which

tributing their ova in small clutches over a wide area.

work in concert to produce the hormone ecdysone.

Many other species, especially in the Hemileucinae and

When converted

Ceratocampinae, literally lay all of their eggs in one

stimulates molting and the onset of adult development.

basket, as one or a few large clutches or egg rings. The

The brain integrates environmental and internal cues to

latter species are commonly smaller and are often

produce prothoracicotropic hormone, which regulates

brightly, perhaps wamingly, colored as adults, and

ecdysone synthesis.

to 20-hydroxyecdysone, ecdysone

their stinging or apparently distasteful larvae are often

Much of the early research on the physiology of de¬

gregarious. Many in this group are diurnal fliers. We

velopment and diapause was done using Hyalophora

explain the adaptive correlation of these various traits

cecropia and other satumiids (Schneiderman & Gilbert,

later in this chapter.

1964; Schneiderman & Williams, 1954; Williams, 1952,

In the following sections of this chapter we discuss

1956, 1959; Williams & Adkisson, 1964a,b; see Riddi-

selected life history adaptations for the successive

ford, 1985, for a review of current concepts of insect

stages of development, beginning with the adult. Our

development). Williams and his co-workers found a

examples are drawn largely from the Satumiidae, but

biological clock in the larval brain that measures the

the cited references cover Lepidoptera in general.

relative amounts of daylight and darkness (photophase

First, however, we describe the mechanisms that

and scotophase) to an accuracy of about 15 minutes

regulate growth and development in order to provide

per day. By appropriately responding to photoperiod

the background necessary for an appreciation of geo¬

in midsummer, the hormonal system of the larva in¬

graphic adaptation within species and life history dif¬

duces the proper physiological state, leading several

ferences among species. Different populations of many

weeks later to either pupa-to-adult development or to

insects, including satumiids, vary in the seasonal tim¬

diapause in anticipation of winter. A 16-hour photo¬

ing of their growth and development (their phenology)

phase experienced by fourth-instar Antheraea polyphe-

in response to climatic and other geographic variation

mus larvae leads to adult development, and a 12-hour

in their environment. The life history strategy of the

photophase produces the onset of pupal diapause.

genus Hemileuca, involving a fall flight and over¬

There is evidence that the critical photoperiod neces¬

wintering ova, probably evolved as an adaptation to

sary to produce a second brood in the univoltine (sin¬

the sharp seasonality of the southwestern deserts.

gle-brooded) Hyalophora is longer than any that the

Members of the Agapema anona species group appear

larvae normally experience in nature (Mansingh & Smallman, 1966).

to have independently evolved a similar phenology.

Members of the tribe Satumiini possess a clear patch of pupal cuticle that allows the underlying brain to per¬

Metamorphosis and Development Diapause

ceive photoperiod through the cocoon. Experiments have shown that a larva raised under long-day condi¬ tions, which normally leads to immediate adult devel¬

Lepidoptera in temperate climates are subject to two

opment, can be forced to enter diapause if the pupa is

opposing selective regimes. A population can increase

exposed to a short day length. The reciprocal experi¬

its numbers by producing more than one annual brood,

ment has also been performed (Williams & Adkisson, 1964a,b).

but for those species that overwinter as pupae this strat¬

Metamorphosis and Development

Adult Development

11

which emerge to produce a second brood, and slowgrowing larvae that pupate and enter diapause.

The onset of adult development following winter is regulated by temperature. Diapausing cecropia pupae

The phenotype of spring-brood adults of some spe¬ cies (e.g., A. luna and C. securifera) is different from that

require chilling for 8-10 weeks at a maximum of 6-15°C

of summer-brood adults. In this case, environmental

to condition the pupal brain to respond to rising spring

cues activate sets of genes controlling the expression of

temperatures and initiate adult development. The re¬

wing pattern. This phenomenon, called seasonal poly-

sumption of DNA synthesis is a key event in the ter¬

phenism, has been especially well studied in pierid but¬

mination of diapause and appears to be linked to the

terflies (Shapiro, 1984). Under experimental conditions,

presence of ecdysone (Berry, 1981). A similar temper¬

either phenotype may be produced within a brood

ature-sensitive system seems to operate in all temperate satumiids that overwinter as pupae.

ent temperatures, photoperiods, or other factors. Sea¬

from a single female if the larvae are exposed to differ¬

The clear pupal window found in the species of the

sonal polyphenism differs from genetic polymorphism,

tribe Satumiini may also play a role in breaking dia¬

in which different, discrete phenotypes result from ge¬

pause. Miyata (1974, 1986) showed that even dim light

netic differences among individuals in the same popu¬

stimulates the brain in Asian Actias, and that photope¬ riod as well as temperature plays a role in breaking di¬

lation (e.g., Automeris cecrops pamina, Eacles imperialis, E. oslari, and Hemileuca eglanterina).

apause. It is not known whether this mechanism

Genetic differences among populations do exist along

occurs generally in temperate satumines. If their co¬

north-south dines with regard to the critical day length

coons are disturbed, pupae of Actias luna and Anther-

that cues voltinism. The basis for these adaptations is

aea polyphemus orient themselves toward the light. This

the variation in the length of the growing season with

activity can be heard some distance away when the

respect to changing day length. For example, in the far

pupae are incubated in cages. The three species of

North the growing season is too short for a second

North American Saturnia emerge in especially well

brood, yet the midsummer days are longer than those

synchronized peak periods of a few days. To our

experienced farther south. Northern populations of a

knowledge no one has experimented with controlling

given speries are genetically programmed to ignore these long days and remain univoltine, while popula¬

temperature and photoperiod and masking the pupal window, although the phenomenon certainly invites investigation.

tions from southern latitudes produce a second brood in response to a certain minimum photoperiod.

The adults of the large moth fauna of southeastern

Another type of dine in natural selection for voltin¬

Arizona generally emerge during the late summer rainy

ism occurs with regard to altitude. Day length does not

season, and the onset of warm temperatures seems to

vary with elevation, of course, but dramatic changes in

play no role in their emergence, as it does in temperate

the length of the growing season may occur within rel¬

fauna. Nor does the environmental cue that interrupts

atively short distances. The populations of H. eglanter¬

diapause appear to be simply the onset of the rains. In

ina inhabiting California's Central Valley pupate in late

fact, the initiation of adult development must occur at

May and early June and develop immediately into

least three weeks before the flight period, in anticipation

adults, which emerge (eclose), mate, and lay egg

of much of the rainy season. Experiments in which tem¬

masses that overwinter. High-altitude populations in

perature, photoperiod, humidity, and moisture are con¬

the Sierra Nevada experience a much shorter growing

trolled are needed if we are to understand these moths'

season and overwinter as pupae. The adults emerge in

adaptations to their unique environment.

the summer or early fall, mate, and lay eggs that over¬ winter. The larvae that eclose in the spring overwinter

Voltinism

as pupae, thus producing a two-year life cycle. Foothill populations have split broods. Populations of these

The number of broods produced by each population

moths are adapted to their respective environments

(voltinism) is determined not by fixed genetic differ¬ ences but by a flexible or facultative mechanism that

through a genetic reprogramming of the developmental response to environmental cues.

allows each individual to assess its own state of devel¬

In light of these differences in developmental adap¬

opment in relation to the environment. In the middle

tations, it is not surprising to find that diapause and

latitudes, many species (e.g., Actias luna, Automeris io,

emergence patterns are often disrupted in crosses be¬

Callosamia promethea, and Antheraea polyphemus) pro¬

tween geographically distant populations of the same

duce a partial double brood. The progeny of a single

species, as well as in interspecific hybrids (Byers & La-

female may include both fast-developing individuals.

fontaine, 1982; Collins, 1984; Oliver, 1979a,b, 1980, 1983;

12

Life History Strategies

Rabb, 1966; Tuskes & McElfresh, 1995). These kinds of

in the central Midwest may be an adaptive strategy of

genetically based life history traits are part of the over¬

risk splitting. Moths with genotypes promoting early

all genetic differentiation of widely separated popula¬

emergence are favored in years with summer drought,

tions and are important in resolving questions of

and individuals in the delayed main flight are favored

speciation and taxonomy (see Chapter 4).

in years with cold spring weather. We discuss this be¬ havior in greater detail in the cecropia account in Part

Adult Emergence

2. It is possible that careful record keeping may reveal more examples of bimodal emergence among northern

portant to the reproductive effort of the population that

temperate satumiids. The Hemileuca life cycle may have evolved as an ad¬

they synchronize their emergence. We have already

aptation to the short growing season in the Great Basin

discussed how environmental cues such as temperature

and desert regions. The overwintering egg ring allows

and photoperiod stimulate a neurohormonal mecha¬

larvae to emerge and begin feeding early in the spring,

nism to initiate adult development. Microclimate dif¬

when host plant quality is highest, without any delay

ferences among pupation sites, genetic variation among

caused by the need for adults to emerge and mate. The

individuals, and changes in weather all act to disperse

larvae complete their growth before hot summer tem¬

the temporal emergence pattern of a population, yet the

peratures and low rainfall lower the leaves' water con¬

entire adult phase of a given population may last only

tent. The adults emerge late in summer or in early fall,

a few weeks. Eclosion in laboratory populations and

and most species fly diumally to avoid the colder night¬

wild adult capture data often show bell-shaped distri¬

time temperatures. The cooler fall temperatures are also

butions, suggesting that the adults of some species

required to suppress egg development in Hemileuca.

Because the adults live for only a few days, it is im¬

eclose within a narrow peak period of only a few days.

A biological clock regulates the approximate time of

Synchronized eclosion within a population increases

emergence (Truman & Riddiford, 1970), which tends to

mating efficiency by producing a high average density

be characteristic for a given species. Most species

of individuals. Males often begin emerging a few days

emerge during the day to give the adults adequate time

before females (protandry), a phenomenon common in

to spread and dry their wings, but tropical forms such

Lepidoptera. Although they may also be exposed to ad¬

as Sarnia and Rothschildia usually emerge in early eve¬

ditional predation, early-emerging males may on av¬

ning. Under the influence of this clock mechanism, the

erage mate with more females than later-emerging

brain controls the release of an eclosion hormone from

males. Selection may also have favored a slight devel¬

an associated structure, resulting in a stereotyped se¬

opmental delay in females relative to males because a

quence of behaviors: abdominal movement, escape

female that delays her emergence is more likely to at¬

from the cocoon, crawling to a suitable support (often

tract a mate from among the many males already on

the cocoon itself if it is attached to a branch), and wing

the wing.

spreading (Truman, 1971). The escape from the cocoon

In temperate climates, various factors favor emer¬

in species that lack a valve structure (at least as studied

gence in late spring or early summer, as soon as tem¬

in Antheraea) is aided by the release of cocoonase, a

perature and other weather conditions are conducive to

powerful proteolytic enzyme that attacks the sericin

adult development and flight. Although uncertain

binding the silk strands together (Kafatos & Williams,

spring weather may disrupt the emergence season, the

1964). After the end of the cocoon has been softened,

larvae's need for nutritious and abundant host plant

moths such as Actias and Antheraea use a hornlike pro¬

leaves opposes a delay until warmer summer temper¬

jection at the base of the wing to break the silk filaments

atures prevail. The quality of the host plant's leaves

with a heaving action. Moths of the tribe Attacini spin

often diminishes during summer as a result of desic¬

cocoons with escape valves and secrete a different, less

cation, especially in the Great Basin and in California,

strongly proteolytic fluid to facilitate eclosion. The

with its summer drought, and the growing season is

emergence activity of species that pupate underground

limited at high altitudes and in northern latitudes by

without spinning cocoons has not been well studied,

the early fall. If cold weather does interrupt the emer¬

but pupae adorned with spines probably first move to¬

gence period, the already eclosed adults remain inac¬

ward the surface by telescoping and retracting the ab¬

tive until warmer weather returns and stimulates the

dominal segments before the adults split the pupal

eclosion of their cohorts. As discussed below, adults are

case. The cremaster in Ceratocampinae such as Eacles

able to thermoregulate, and many species fly and mate

no doubt aids this behavior. Stratton-Porter's (1912) de¬

at relatively low temperatures.

scription of this behavior in Eacles imperialis, Citheronia

The bimodal emergence pattern of Hyalophora cecropia

regalis, and several sphingids is one of the few that have

The Adult

13

been published. We were once fortunate enough to find

tasteful, aposematic tropical satumiids and compared

a freshly emerged £. imperialis next to its empty pupal

them with the life spans of palatable species and pro¬

case, which was on the surface of the ground. On an¬

posed that selection has favored relative longevity in

other occasion several C. regalis we had reared were

the former group because the population benefits when

allowed to pupate in soil under natural conditions.

birds and other predators learn to avoid the species by

During eclosion the next summer the pupae moved

"sampling” post-reproductive individuals. In contrast,

head-first to just above the soil surface, and then the adults emerged from their pupal cases.

cryptic and palatable species are short-lived. Presuma¬ bly their crypsis decreases the probability that they will

Once a newly emerged moth has crawled to a sup¬

encounter a predator, which in turn lessens the likeli¬

port, it spreads its wings by pumping hemolymph into

hood that predators will form a search image for the

the wing veins and remains motionless while the wings

cryptic pattern of the moth. The temperate satumiids

harden. When first disturbed or during the first flight,

have not been studied in a similar fashion, nor have

the adult forcefully discharges the metabolic waste ac¬

palatability studies like Lincoln Brower's (1984) well-

cumulated during its pupal stage. This liquid dis¬

known work with the swallowtails and the monarch

charge, the meconium, may provide some protection

been performed on satumiids. Many of the Ceratocam-

from predators, although that appears never to have been tested. The adults of many species, and especially

pinae and Hemileucinae have brightly colored abdo¬ mens, often red, yellow, and black, and typically curl

the males, disperse in a brief flight at dusk. This habit,

and pulse their abdomens in a Hymenoptera-like man¬

combined with protandry, appears to be a mechanism

ner when attacked. Ferguson (1971) even suggested

to avoid inbreeding.

that the "Pseudohazis” species group in the Hemileuca (eglanterina, nuttalli, hera) are Mullerian mimics because they share a similar forewing pattern and all have

The Adult Defensive Role of Wing Patterns and Behavior

orange-and-black-striped abdomens. When disturbed they also curl their bodies as described above. The wing patterns of groups such as the Hyalophora

The large size and striking wing colors and patterns

are striking to the human eye but difficult to interpret

of satumiids both capture our interest and challenge us

as having a defensive role. The undersurface patterns

to interpret their adaptive role. Blest (1957a) was

of Hyalophora wings are dull, and resting adults may be

among the first to note that a pattern mimicking the

cryptic with their wings folded vertically. The small

vertebrate eye has evolved independently many times

eyespot at the wing apex seen in many Attacini has

in the Lepidoptera, including in the satumiids, and that

been likened to a snake's head (Peigler, 1989; Watson,

this image is effective in thwarting bird attacks. Wing

1910), which would seem to complement the wing-

spots that resemble vertebrate eyes are often revealed

fanning behavior of these moths. Janzen (1984b) be¬

in a characteristic display behavior that probably star¬

lieved this behavior in the Rothschildia, which have

tles predators (Sargent, 1990). Hindwing eyespots are

brown wings and transparent eyespots, mimics dead

widespread among the Automeris but are covered at

foliage swaying in the breeze.

rest by the forewings, which are cryptic against a back¬ ground of leaf litter. When the moth is disturbed, it

Pheromone Mating System

suddenly draws aside its forewings to display the

It was a memorable evening. I shall call it the Great

brightly colored hindwings. Antheraea polyphemus is

Peacock evening. Who does not know this magnificent

similarly camouflaged at rest, with its wings either

Moth [Saturnia pyri], the largest in Europe, clad in ma¬

spread horizontally or closed vertically over its thorax.

roon velvet with a necktie of white fur? ... a female

When attacked, these moths dramatically flap their

emerges from her cocoon in my presence, on the table

wings. Surprisingly, there have been no careful, quan¬

of my inseetory. I forthwith cloister her, still damp

titative studies of the effectiveness of such defenses in

with the humours of the hatching, under a wire-gauze

the North American satumiids. Blest (1957b) catego¬

bell-jar.... At nine o'clock in the evening, just as the

rized other wing patterns and associated protective dis¬

household is going to bed, there is a great stir in the

plays as well. Many satumiids (e.g., Actias, Automeris,

room next to mine. Little Paul, half undressed, is rush¬

Coloradia, Eacles) appear to mimic living and dead fo¬

ing about, jumping and stamping, knocking the chairs

liage and ground cover, and they obviously benefit

over like a mad thing.... "Come quick!" he screams.

from remaining motionless when they are not involved

"Come and see these Moths, big as birds! The room

in reproductive behavior. Blest (1963) determined the average life spans of dis¬

is full of them!" ... The Great Peacock, it would seem, has taken possession of pretty well every part of the

14

Life History Strategies

distant females and the specificity of the pheromones females use to attract them. Among the saturniids, as in many other moth fam¬ ilies, calling females release pheromone by protruding a special gland located at the tip of the abdomen (Fig¬ ure 1). Most moth pheromones are either alcohols, al¬ dehydes, or acetates 10-20 carbon atoms long. There are usually more species of moths, even within a lim¬ ited geographic area, than there are chemical species of pheromones. Satumiid congeners typically share a pheromone with the same basic chemical structure. Preisner (1968, 1973) and Schneider (1966, 1972) mea¬ sured the electrical depolarization of nerves in male antennae.

The

electroantennograms thus

produced

showed that specificity among saturniids is more of¬ ten at the genus than the species level, even when Old and New World congeners are tested together in the lab. The male's response is based on the ability of Figure 1. Female Callosamia promethea releasing pheromone (calling)

receptors in his antenna to respond optimally to as¬ pects of the structural chemistry of the pheromone molecule: the location of various side groups, the

house. What will it be around my prisoner, the cause

location of double bonds between carbon atoms, the

of this intrusion? Luckily, one of the two windows of

optical isomer (mirror image) form of the molecule,

the study had been left open. The approach is not

and often the ratios of molecules that differ in these

blocked. We enter the room, candle in hand. What we

characteristics. Closely related moths usually employ

see is unforgettable. With a soft flick-flack the great

the same pheromone mixtures, but the relative pro¬

moths fly around the bell-jar, alight, set off again,

portions of the molecular types are unique to each

come back, fly up to the ceiling and down. They rush

species (Carde,

at the candle, putting it out with a stroke of their

pheromones is not well known, but the pheromone

wings; they descend on our shoulders, clinging to our

used by Antheraea polyphemus has been determined to

clothes, grazing our faces. The scene suggests a wiz¬

be a 90:10 mixture of frans-6,ds-ll-hexadecadienyl ac¬

ard's cave, with its whirl of Bats. Little Paul holds my

etate and fnms-6,ds-l 1-hexadecadienal aldehyde (Kochansky et al., 1975).

hand tighter than usual, to keep up his courage. (J. Henri Fabre, in Teale, 1949, pp. 75-76)

1987).

The chemistry of satumiid

The male's highly branched, featherlike antenna con¬ tains minute, specialized hairlike structures called sen-

The ability of female saturniids to attract distant

silla, whose receptor cells bind with the pheromone

males has long been cited as a dramatic example of

molecule and then release a nerve impulse to the

chemical communication in insects (Kalmus, 1958; Rau

brain. The antenna of A. polyphemus males contains

& Rau, 1929; Stratton-Porter, 1912; Teale, 1949; E. O.

more than 60,000 sensilla with about 150,000 receptor

Wilson, 1963), and even experienced collectors enjoy re¬

cells (Schneider, 1969). Among these are specialized

calling their first observation of this event. Male moths

sensilla that apparently respond to various concentra¬

following the pheromone scent trail of the female are

tions and molecules within the pheromone blend, or

amazingly persistent and are undeterred by leaves,

"bouquet,” released by the female. Depending on the

branches, and other obstacles. They cover great dis¬

concentration and makeup of the pheromone blend,

tances in their search, and the northern and boreal spe¬

the male's brain processes these chemical signals and

cies, especially, fly through rain, wind, and cold to reach the female.

translates them into a sequence of behavioral re¬ sponses. The branched structure of the male antenna is

In the past three decades the chemistry, physiology,

a highly efficient molecular filter that substantially

and behavior of pheromone-regulated mating systems

slows the flow of air through it under experimental

have been intensively studied, mostly in pest Lepidop-

conditions (Vogel, 1983). Isolated polyphemus antennae

tera (see Bell and Carde, 1984; Birch, 1974; and Shorey

are capable of adsorbing up to 32% of radioactively la¬

and McKelvey, 1977, for reviews). Researchers have

beled pheromone molecules passed over them (Kanaujia & Kaissling, 1985).

sought to understand both the ability of males to locate

The

wind direction

f

Adult

15

calling female

zags at right angles to the wind; the flight becomes

9

more directly upwind as the male nears the female. If close-range search and mating

the pheromone source is experimentally interrupted, the male may continue to fly upwind for some time, but eventually he resumes the zigzag flight, casting about in crosswind flight until he again detects the pheromone (Figure 2). When he is within a few feet of

crosswind search

the female, the male may suddenly begin a distinctive mode of slow, deliberate flight. This close-range search behavior may be triggered when specific sensilla on the male's antenna detect pheromones that the female releases in very low concentrations and that are detect¬ able only at very close range. Meng et al. (1989) iden¬ tified three sensory cell types on the sensilla of Antheraea polyphemus and A. pernyi, each specifically sensitive to one of three pheromone components. The¬ oretically, the number, arrangement, and measured sensitivities of these cells should allow the male to es¬ timate the distance to a nearby calling female. The func¬ tional association of low-concentration pheromones with close-range search behavior is difficult to demon¬ strate experimentally at the level of the central nervous

anemotaxis

system, and the true basis of close-range search behav¬ ior is the subject of current debate (R. Carde, pers. comm.). An alternative hypothesis holds that males in¬ itiate close-range search behavior as a response to the pheromone plume's width, which is characteristically

Figure 2. Pheromone plume and male response

narrow near calling females. Most of what we know about male satumiids' ori¬ entation to pheromones is based on observations of di¬ urnal species (L. Brown, 1972a; Collins & Tuskes, 1979).

The efficiency of the pheromone mating system is in¬

The gypsy moth (Lymantria dispar) is probably the best

creased by the synchronization of mating activity in

studied of all moths (Charlton & Carde, 1990; Elkinton

each species. The female's release of pheromone is con¬

et al., 1987; M. A. Willis et al., 1991). Early estimates

trolled by a neurohormonal mechanism that is trig¬

(Bossert & Wilson, 1963; Wilson & Bossert, 1963) indi¬

gered by the interaction of an internal clock and specific

cated that males could detect a distant pheromone

light levels (Riddiford & Williams, 1971; Sasaki et al.,

source up to 1 km (0.6 mile) away, but more sophisti¬

1983). Likewise, males become active during one or

cated studies of the pheromone plume (Elkinton &

more specific periods in a 24-hour cycle, although they may take flight when experimentally stimulated with

Carde, 1984) suggest that pheromone density at that

pheromone. Marked male satumiids are often recovered several

experimentally difficult to determine the point at which

miles from the point of release and, probably with the

pheromone. For example, very few marked gypsy moth

aid of winds, may cover net distances of up to 20 miles

males released more than 1 km from a pheromone

over a period of a few days (Rau & Rau, 1929; Toliver

source were recovered (Elkinton & Carde, 1980). The

& Jeffords, 1981; Waldbauer & Stemburg, 1982a; Weast,

recovery of marked satumiid males from much great¬

1959). Wind tunnel and field experiments have shown

er distances than that may be due solely to their abil¬

that a male moth does not necessarily orient his flight

ity to fly farther during their search for pheromone

directly toward the calling female in response to a gra¬ a behavior

plumes. The periodicity and specificity of the pheromone

termed “anemotaxis," males judge the wind direction

mating system are often said to be reproductive iso¬

by measuring their drift in reference to landscape fea¬

lating mechanisms that act to separate closely related

tures. The male's initial flight pattern consists of zig¬

moth species (Carde, 1987; Carde & Baker, 1984; Roe-

dient in

pheromone concentration.

In

distance may be below the threshold of detection. It is a male in anemotaxis actually begins to respond to the

16

Life History Strategies

lofs & Carde, 1974). Theoretically, specific mating

and by hairlike insulating scales, which give these

times and pheromones could arise through natural se¬

moths their furry appearance.

lection favoring increased mating efficiency, and not

The ability to thermoregulate allows certain noctur¬

necessarily as an adaptation minimizing the produc¬

nal satumiids to live at high altitudes and in northern

tion of unfit hybrids (Chapter 4; Phelan & Baker,

latitudes. The montane species of Hyalophora, for ex¬

1987). A peak activity period or optimal pheromone

ample, maximize the short growing season by emerg¬

mixture might initially evolve in the context of maxi¬

ing in early summer; they are able to fly and mate when

mizing mating efficiency and then subsequently be¬

ambient temperatures are only a few degrees above

come an isolating mechanism on secondary sympatry

freezing. These are also some of our largest species,

of recently evolved species. In actual field tests, repro¬

perhaps because selection has favored a reduced sur¬

ductive isolation of closely related species is often

face-to-volume ratio. The expenditure of energy by cec¬

produced by a combination of differences in phero¬

ropia males during flight results in an average 20%

mone composition and behavioral traits, as in the Cal-

weight loss during the first night, and about a 40% loss

losamia (L. Brown, 1972a; Ferguson,

over the average life span of five to six days (Wald-

1972; Peigler,

1977a, 1981), Hemileuca eglanterina and H. nuttalli (Col¬ lins & Tuskes, 1979), and Hyalophora Columbia and H. cecropia (Tuttle, 1985).

bauer et al., 1985). Daytime flight has evolved independently in several satumiid genera (e.g., Anisota, Hemileuca, and Saturnia).

Female satumiids typically mate with the first male

The diurnal species are in general smaller than the noc¬

to reach them, without further courtship. Although

turnal ones, perhaps as a thermoregulatory adaptation

most Hemileucinae and the Saturnia pair for only about

allowing more efficient radiation of heat in the face of

an hour, the majority of nocturnal species, if undis¬

solar heating. They are also often rapid and erratic fli¬

turbed, remain in copula until the following evening,

ers, which may offer some protection from predators.

when the pair separates and the female seeks out host

Batesian mimicry, warning coloration, and unpalatabil-

plants on which to oviposit.

ity are common in diurnal moths (Brower, 1984), and we discuss possible examples of such defense mecha¬

Thermoregulation Flying requires a great expenditure of energy. Hein¬

nisms in our descriptions of the diurnal Anisota and Hemileuca in Part 2. Adults of the diurnal species of Callosamia and Eupackardia are an exception, but the

rich (1981) showed that thoracic wing muscles are only

adults may be mimics of the large, dark, unpalatable

about 20% efficient, so four-fifths of the work per¬

pipevine swallowtail (Battus philenor). As we discuss in

formed in flight is released as heat. Wing muscles are

the accounts of the various desert-dwelling Hemileuca

furnaces, and in order to fly insects must be able to

species, the white wings of burnsi and neumoegeni may

thermoregulate; that is, they must maintain their body

reflect heat. By contrast, the degree of melanism among

temperature within an optimum range, usually above

electra populations seems correlated with the regional

that of their surroundings. This is especially true for

variation in the fall flight season of these moths, prob¬

nocturnal species, both temperate and tropical. Wing

ably based on the relative benefit of solar heating to aid

muscles are most efficient at about 35-40°C, and many

flight.

insects, including satumiids, reach this temperature by vibrating their wings before flight to generate heat. Because they are small and have a large body

Oviposition

surface-to-volume ratio, insects tend to lose heat. In

Once a female has mated, the presence of sperm in

order to maintain a constant elevated temperature, they

the spermatheca stimulates her brain, which in turn

must either be metabolically more efficient at generat¬

causes a gland to release an oviposition hormone (Tru¬

ing heat, or they must be more efficient at controlling

man & Riddiford, 1971). This hormone stimulates her

heat loss. Researchers have found that the former is the

to fly and search out appropriate host plants for her

case; insect flight muscles are about 10 times more ef¬

eggs. Ironically, the strong stimulus to oviposit, even in

ficient in generating heat than those of flying birds or

the absence of the host plant, facilitates rearing but

mammals (Bartholomew, 1981). Excess heat is carried away from the wing muscles via the hemolymph

makes the experimental study of oviposition difficult. In captivity, most species lay clusters of 1-10 ova, the

(blood) to the abdomen, where it is released to the sur¬

majority of which are laid during the first two or three

rounding air. Excess cooling, in turn, is opposed by the

nights after mating. But one must be cautious about

thermal inertia of stored heat in body fat and tissues,

assuming that laboratory observations represent natu-

Host Plants ral oviposition behavior. Anyone studying the popu¬

17

expense of greater metabolic cost to the plant (Feeny,

lation biology of a species would want to know the

1976). Scriber and Feeny (1979) found that satumiids

distances flown by ovipositing females. Oviposition be¬

and certain papilionids grew more slowly on such hosts

havior largely determines the distribution and density

than papilionids that fed on herbaceous hosts. Large

(the demography) of the population. Females probably

host plants may convey the advantage of a reliable

do not range as far as males, but they may disperse as

quantity of foliage that supports and conceals the often

they become lighter after ovipositing the majority of

large satumiid caterpillars, but Janzen (1984a) noted

their ova. Even day-flying species are difficult to track,

that conspicuous hosts also allow rapid oviposition, a

and, unlike butterflies, adult females cannot be recov¬

benefit to large, nonfeeding females. Oviposition effi¬

ered at water or nectar sources. To help study female

ciency could also be the basis for generalists' (poly-

dispersal, Weast (1989) suggested the intriguing possi¬

phagous species) feeding strategy. As a corollary, many

bility of using microtransmitters now under develop¬

specialists (e.g., many western Hemileuca) feed on

ment in connection with Africanized (“killer") bee

widely distributed shrubby hosts. These plants are con¬

research.

spicuous not for their size but because they are preva¬ lent over wide areas. A species may feed on a wide range of host plants over its entire geographic range, and yet specialize on

Host Plants

a few hosts in a given region, and published lists of insect-host

hosts for a given species do not always reliably indicate

plant relations was greatly enhanced by the discovery

these geographic specializations. A study of larval pref¬

that plants produce secondary chemicals that can affect

erences found that local populations of Papilio glaucus

the feeding behavior and metabolism of insect herbi¬

fed a host plant not native to their area grew more

vores. Insect species in turn have evolved adaptations

slowly (Scriber, 1983). In contrast, in the same study the

to specific hosts; for example, enzymes that detoxify the

generalist Callosamia promethea performed as well on tu¬

plant compounds (Dethier, 1954, 1978; Seiber et al.,

lip tree as C. angulifera, which feeds solely on this host;

1980). This interaction—plant develops deterrent com¬

even populations of promethea from outside the range

pound; insect develops strategy to avoid it—is an ex¬

of tulip tree grew well on this host. Callosamia promethea

ample of coevolution (Futuyma, 1983). The phytogenies

and C. angulifera, however, showed decreased growth

of many Lepidoptera have been studied in relation to

rates and survival on sweetbay (Magnolia virginiana) in

their adaptations to host plants (Ehrlich & Raven, 1964;

comparison with C. securifera, a monophagous special¬

Feeny, 1975; Gilbert, 1979). Host plant specialization

ist on this tree (K. S. Johnson, 1993). Johnson identified

appears to be a highly adaptive strategy, and biologists

at least two chemicals in sweet bay as the basis of these

have sought to understand the physiological and eco¬

adaptive differences. Callosamia securifera possesses en¬

logical differences between host plant specialists and

zymes that detoxify and promote digestion of the com¬

generalists. Are there adaptive tradeoffs for generalist

pounds, but the enzymes are lacking in the other

feeders between decreased metabolic efficiency on a given host balanced by the benefits of increased host

Callosamia. Judging from the lists of alternate hosts used by am¬

availability? Obviously, adaptation to a host plant in¬

ateur breeders (Gardiner, 1982; Stone, 1991), it may be

volves many factors other than nutrition and meta¬ bolism. The host plant and its immediate environment

generally true that the range of hosts acceptable to lar¬ vae is greater than the oviposition preference of fe¬

constitute an ecological niche involving such varied

males, and that larvae may retain the ability to grow

components as predation, parasitoids, crypsis, micro¬

on ancestral hosts or hosts outside the range of a given

climate, and spatial distribution, and each of these par¬

population. The results of feeding trials indicate that

ameters may change seasonally. Published satumiid host plant records (Collins &

this lack of specialization is true for Callosamia promethea

The

understanding of phytophagous

Weast, 1961; Ferguson, 1971, 1972; Janzen, 1984a; Stone,

(Scriber et al., 1991), but not for Actias luna (Lindroth, 1989). Hyalophora cecropia is an example of an extreme

1991; Tietz, 1972; Tuskes, 1984) reveal that shrubs and

generalist with the ability to adapt to many cultivated

trees tend to be favored over forbs and herbs. The for¬

and exotic hosts in urban settings. By contrast, the Aga-

mer tend to be larger, more permanent members of plant communities, to have leaves with relatively low

pema anona group typically refuse all substitute Rham-

water content, and to possess secondary compounds

naceae after beginning on Condalia. The quality of the host plant may have a greater ef¬

that protect against a wide range of herbivores at the

fect on larval growth than genetically based metabolic

18

Life History Strategies

adaptations of larvae, however. Scriber (1984) and Scriber and Slansky (1981) found that leaf water and

reduced movement. But not all primary defenses are passive in nature.

nitrogen content, and their seasonal changes in concen¬ tration, were often more important factors affecting lar¬ val growth of C. promethea and other Lepidoptera than the host plant species itself. The probability of survival on a given host may be determined more by ecological factors than by meta¬ bolic factors such as growth rate and biomass at ma¬ turity (Fox & Morrow, 1981; Rhoades & Cates, 1976). This conclusion is suggested by the observation that the ranking of host use from field-collected data may differ from a ranking by growth performance in the lab on a given host (e.g., Collins, 1984). For example, larval sur¬ vival may be lower on a host high in nutrients than on apparently less desirable host plants. But on the latter hosts the larvae may be more cryptic, or may find more appropriate cocoon-spinning sites, or may share the plant with fewer Lepidoptera and thus suffer less pre¬ dation and parasitism.

Primary Defenses Active Avoidance. Although such behavior is not com¬ mon in satumiids, the larvae of some species rest away from their feeding sites, apparently to avoid detection. We have seen this behavior most often in Hemileuca, especially in the desert and Great Basin species, which often rest in the interior of their shrubby hosts. This behavior may help them avoid predators and parasi¬ toids, but it probably is also a way of avoiding extreme midday temperatures. The larvae of Automeris io build a molting shelter during the later instars by wrapping themselves in leaves loosely held together with silk. Heinrich and Collins (1983) showed that birds can learn to preferentially search tree species that predictably harbor large numbers of larvae. Birds can also learn to recognize characteristic caterpillar leaf damage. In an apparent effort to counter this ability, certain Lepidop¬

Caterpillar Survival Strategies

tera eliminate signs of their feeding by consuming the entire leaf or by cutting the petiole and allowing the

The caterpillar is the growth stage in the life cycle of a moth or butterfly. The larvae of satumiids must ac¬ cumulate sufficient metabolic stores to serve the non¬ feeding adult during its life as the reproductive and dispersal stage. A considerable portion of the adult

uneaten portion to fall, a behavior known as "stem¬ ming" (Heinrich, 1979). We have observed this feeding habit in some Callosamia species and in Antheraea polyphemus (see Chapter 5 for more details on this behav¬ ior).

female's biomass is allocated to the development of ova, and females whose larval growth was stunted lay

Cryptic Form and Coloration. Most satumiid larvae are

fewer than the normal number of ova. Caterpillars are

shades of green or brown and appear cryptic to varying

in essence highly efficient feeding machines capable of

degrees. The later instars of many groups (e.g., Hyalo-

increasing their mass, over a period of a few weeks,

phora) are reverse countershaded; that is, the dorsal sur¬

from a few thousandths of a gram at eclosure to up to

face, which faces downward in the resting position, is

20-30 g in the case of a large larva like Eacles imperialis.

lighter than the ventral surface. This pattern lessens the

In addition to converting plant nutrients into larval bio¬

darkening effect of shadow so that natural overhead

mass, the gut and its associated enzyme system must

lighting tends to create a featureless, uniform appear¬

also detoxify, sequester, or eliminate secondary plant

ance in a larva clinging to a twig or leaf petiole. Many

compounds (see Host Plants, above). Throughout its

larvae probably escape predation by means of cryptic

life the caterpillar must face a host of predators, par-

coloration combined with a general tendency to remain

asitoids, and pathogens. We will discuss defenses

relatively sedentary, as has been documented for sphin-

against insect and avian predators here. Parasitoids are

gid larvae (Schmidt, 1990). The convex body segments

treated separately in Chapter 2, and disease is covered in Chapter 3.

of Antheraea polyphemus and Actias luna closely resemble indented leaf margins and compound leaves. Callosamia

In his review of caterpillar defense mechanisms, Led-

angulifera and C. securifera larvae closely match the color

erhouse (1990) distinguished between primary de¬

of the undersurface of their host plant's leaves, and

fenses, which reduce the likelihood of detection, and

their lateral markings resemble the leaf petiole and

secondary defenses, which are used after the larva is aware of the presence of an enemy. Among the North

midrib. Often otherwise cryptic larvae, such as Hyalophora and Callosamia, are ornamented with brightly col¬

American satumiids the most common primary de¬

ored scoli (tubercles); the adaptive significance of these

fenses are inconspicuousness and wide spacing be¬

structures has not been systematically studied. The scoli

tween individuals, aided by cryptic coloration and

usually become smaller relative to body size as the lar-

Caterpillar Survival Strategies

vae grow from one instar to the next; on mature larvae they are apparent only on dose examination.

19

oration (Collins & Weast, 1961; Weast, 1989); when mechanically disturbed, the larvae release a bitter fluid from their scoli. The protective value of this fluid has

Disruptive Coloration. Caterpillars that exhibit disrup¬

been experimentally verified. The fluid secreted by lar¬

tive coloration break up the form of the body with con¬

vae of European Saturnia pavonia and S. pyri is more

trasting dark and light patterns. Examples of this

effective against ants than the defensive chemical of E.

strategy can be seen in many Automeris species, Rothschildia cincta, and R. lebeau forbesi. The silvery markings

calleta, but the latter species appears to be better pro¬

on Sphingicampa larvae and the pearl-colored scoli of

Duncan (1941) discovered a dead robin that had ap¬

Antheraea polyphemus suggest light shining through fo¬

parently choked on a mature larva of H. Columbia glov-

liage. The venter of the last two instars of Saturnia men-

eri lodged in its throat. The larvae of this species give

docino is a dark red-brown that closely matches the

off a camphorlike odor similar to that of E. calleta, and

color of manzanita twigs. The body of this species may

it is possible that a toxic reaction occurred. The larvae

be one of several colors (i.e., the species is polymor¬

of Agapema homogena feed openly and seem to adver¬

phic), but most of the larvae in a population are a green

tise their presence with their bold black-and-yellow coloration. Although these larvae lack the stinging

tected against bird attack (Demi & Dettner, 1990, 1993).

similar to the host's foliage. Manzanita has persistent foliage, and the older leaves die and are shed at about

spines of the related Saturnia, they may be distasteful

the same time the larvae mature, at the beginning of

to predators. It is possible, but difficult to demonstrate,

the hot California summer. The less common yellow

that the complex color patterns of E. calleta and A. hom¬

and mauve (salmon pink) forms resemble the colors of

ogena larvae may appear cryptic to a predator at a cer¬

these dead leaves before they fall. These larvae thus

tain distance but have an aposematic role at close range.

exhibit adaptations that integrate crypsis, disruptive coloration, and polymorphism. As a final defense, the larvae have stinging spines, but the larvae do not ap¬ pear to be aposematic, as is commonly the case in urticating larvae (see below).

Secondary Defenses: Response to Discovery The cryptic, nonurticating larvae typical of satumiids appear to be relatively defenseless once discovered by

Mimicry. First-instar larvae of Citheronia regalis and C.

their enemies. When ova or first-instar larvae are re¬

splendens resemble bird droppings, both in their color

leased and monitored in natural settings, the vast ma¬

and in their habit of curling back on themselves with

jority, typically over 75%, are lost in the early instars to

their long scoli pressed against their bodies. The first

birds, wasps, Hemiptera, spiders, and other predators

two instars of the West Coast species of Saturnia also

(Weast, 1989; MMC). The spiny scoli of the early instars

resemble bird droppings, although not to the degree

are much larger in proportion to body size than those

seen in many Papilio and Limenitis species. The false

of older larvae, yet the role and effectiveness of this

vertebrate eyes on larvae of certain sphingids and pa-

armament are not well understood. Perhaps the spines

pilionids are rare in the Satumiidae. Mimics of urticat-

offer some defense against parasitoids and smaller in¬

ing species occur in the Central American satumiid

sect predators. When disturbed, the larvae of cryptic

fauna (Jarvzen, 1984a), but we know of no North Amer¬

species cease feeding and remain motionless. Many

ican example of such mimicry.

species,

especially

the

Ceratocampinae,

assume

a

sphinxlike pose with the anterior raised and the first Aposematic Coloration. The interpretation of apose¬

set of prolegs detached from the plant. Such a posture

matic (warning) coloration is subjective because vivid,

may mimic the shape of leaves. The larvae of Antheraea

contrasting patterns that appear conspicuous outside

polyphemus click their mouthparts during this behavior,

the natural setting may resemble patterns of light and

but the possible defensive role of this is not understood.

shadow when larvae are viewed on their host plants.

If sufficiently provoked, many species will regurgitate

Warning coloration in insects is typically accompanied

partially digested food. This in itself may be offensive

by various chemical defenses (Whitmann et al., 1990).

to predators, but when the fluid contains plant toxins

The boldly marked stinging larvae of Hemileuca maia and H. nevadensis appear to be aposematic, although

it is an even more effective defense (Cornell et al., 1987; Whitmann et al., 1990).

their markings might also serve the role of disruptive

Among the North American satumiids, the larvae of

coloration. The larvae of Eupackardia calleta, which are

the Hemileucinae possess stinging scoli, and this de¬

striking in their boldly contrasting colors, have also

fense has evolved independently in Saturnia. Young

been mentioned as possible examples of warning col¬

hemileucine larvae are typically gregarious, and per-

20

Life History Strategies

clusters of H. lucina larvae is an effective defense against tachinid flies.

Behavioral Thermoregulation Larvae regulate their body temperature by modify¬ ing their behavior in response both to cool weather and to solar heating. The most common means of con¬ trolling body temperature is to adjust daily feeding periods to take advantage of favorable ambient tem¬ peratures. In the North, most species (e.g., Automeris io) feed primarily during the day. In the extremely hot Figure 3. Dead ants among scoli of Hemileuca eglanterina

Southwest, however, many species feed at night. The season is also a factor in determining feeding strategy. During the winter Eupackardia calleta from south Texas

haps the clusters of small, stinging larvae are better

and the Ajo area of Arizona take advantage of moder¬

protected against birds than individuals would be.

ate daytime temperatures and feed diumally. During

These larvae also appear to benefit from basking in sun¬

the cold nights, when temperatures occasionally drop

light, perhaps because the increase in body temperature

to freezing, the larvae cease all activity until daybreak.

speeds growth (Stamp & Bowers, 1990a). The majority

Yet, once the sun has risen the larvae do not passively

of Hemileuca species occur in the Great Basin and desert

wait for the ambient temperature to rise to acceptable

regions where the growing season is short. The larvae

levels before they resume feeding. Instead, they appear

emerge from their egg rings very early in the summer

to accelerate the rise in their body temperature by

when cold overnight temperatures restrict feeding to

openly basking to absorb radiant energy (JPT & PMT).

the warmer daytime period. Stamp and Bowers also

The summer-feeding larvae of Hemileuca oliviae ben¬

found that gregarious H. lucina larvae are able to ele¬

efit both from their light ground color and from an

vate their body temperatures as much as 5°C above am¬

adaptive resting orientation. The larvae feed in the

bient. The integrated adaptation of stinging larvae and

morning and late afternoon, but during the intense

gregariousness allows these species to complete growth

heat of midday the late-instar larva finds a vertical

early in the season before the hot summer dries out the

support and positions it between itself and the sun.

leaves of their host plants. Mature larvae may be

This shield, which is maintained by constant move¬

somewhat immune to attack by ants, as dead ants have

ment in relation to the sun, helps the larva keep its

been found among the spines of Hemileuca eglanterina

body temperature below the danger point (Capinera et

(Figure 3). Vespid wasps nevertheless successfully attack larvae

al., 1980). Feeding periods are not the only times that satumiid

in this group. Stamp and Bowers (1988) found that

larvae regulate their body temperature. Coloradia pan¬

when wasps attack the larvae of Hemileuca lucina, those

dora overwinters as partially grown larvae. The larvae

larvae not under direct attack drop to the ground or

form small clusters at the terminal ends of branches on

wander into the interior of their shrubby host plant.

the host plant, where they remain dormant throughout

Dropping from the host when disturbed is a common

the winter. Schmid and Bennett (1988) noted that most

behavior among the hemileucines. In the interior of the

C. pandora davisi aggregations they found were on the

plant the larvae are somewhat protected from wasps,

south side of trees at sufficient heights to avoid being

but they also experience cooler temperatures and are

in the shade, presumably to take advantage of the sun's

forced to feed on older, less nutritious leaves. Larvae

warming effect.

that have to spend much time in the host plant's inte¬ rior avoiding wasps grow significantly more slowly, which in turn prolongs their exposure to parasitoids

Pupation

and other enemies. We have found, at least in the west¬ ern species, that Hemileuca larvae are very subject to

On reaching maturity larvae cease feeding and

parasitism by braconid wasps, which appear undeter¬

empty their gut in preparation for pupation. All spe¬

red by the stinging scoli. Stamp and Bowers (1990d)

cies begin an apparently obligate wandering phase

reported, however, that the coordinated thrashing of

during which they may pass by appropriate pupation

Pupation

sites. The larvae of some species move only a short

21

fined to specific taxonomic groups. Some Satumiinae

distance from where they were feeding to pupate, but

(Eupackardia, Rothschildia, etc.) cocoons are suspended

others may travel 10 yards or more over a period of

from the host plant or an adjacent plant by a silk at¬

several hours. Just before this wandering phase, the

tachment known as a peduncle. The cocoons of other

larvae of certain species (e.g., Actias lutia and Saturnia

Satumiinae (Hyalophora, Saturnia, etc.) are attached

mendocino) become cryptic, often turning a shade of

along their length to branches or other supporting sub¬

brown that matches branches and leaf litter. Eventu¬

strates, or are placed in cracks and crevices that offer

ally the larva selects a site that is generally character¬

protection. The larvae of Actias luna often spin their co¬

istic

to

coons among the leaves of the food plant but do not

distinguish the shape and density of foliage and other

attach them to the twigs. When the leaves of the host

features by eyesight, but the final location is probably

plant drop in the fall, the cocoon also drops to the

of the

species.

Larvae

are

able

roughly

chosen using tactile cues (Scarbrough et al., 1977; Van

ground. This third cocoon-spinning strategy has a var¬

der Kloot & Williams, 1953a).

iation in which individuals may wander off the host plant and spin among the leaf litter. Interestingly, An-

Underground and Soil Surface Pupation without Cocoons

theraea polyphetnus uses all three strategies and varia¬ tions (Wagner & Mayfield, 1980). All North American Automeris larvae leave the host plant and search out a

All the Ceratocampinae and many Hemileucinae pu¬

protected location to spin their cocoons. Perhaps be¬

pate in underground chambers (see Stratton-Porter,

cause the cocoons are very fragile and offer minimal

1912, for a detailed discussion of underground pupa¬

protection from the elements, many individuals look for crevices in rocks and logs.

tion in satumiids). The backward-facing scoli of the Ceratocampinae probably help the larvae to burrow.

With the exception of the distantly related com¬

These larvae apparently use little or no silk to form the

mercial silkworm, little is known of spinning behavior

chamber, although the surface walls are formed using

or the physiology and ecology of cocoons. In a series

a larval secretion. The earthen chambers can be recov¬

of interesting papers Van der Kloot and Williams

ered intact if carefully handled. Within the Hemileuci¬

(1953a,b,c) portrayed cocoon spinning as a unique

nae, the species in the genus Automeris spin cocoons;

window through which to examine animal behavior:

some Hemileuca species spin very loose cocoons at ground level (e.g., H. oliviae), and others pupate under¬ ground with very little silk forming the chamber. In no case do pupating larvae appear to burrow beneath the frost line. We know little about a larva's abilities to as¬ sess variables such as soil moisture, soil density, or par¬ ticle size.

At a precise moment in its life cycle the Cecropia silk¬ worm transforms a silk thread, nearly a mile long, into an intricate cocoon of predictable form. It outlines in silk a program ... which, for experimental analysis ... is little short of optimal. The silken strands chart the movements of the head of the animal which placed them there; the cocoon itself becomes a permanent rec¬

Cocoon Spinning The satumiids are the master craftsmen of the Lepidoptera. Many species spend the majority of the life cycle as pupae, surrounded by an elaborate silken co¬ coon that must offer protection from weather, parasitoids, and predation. To this end, the larva devotes a

ord which can be weighed, unwound, or chemically analyzed. Here is a clear instance of behavior uncom¬ plicated by previous learning: the caterpillar has never seen a cocoon such as, with ease and certainty, it pro¬ ceeds to spin. (Van der Kloot & Williams, 1953a, p. 141)

considerable proportion of its biomass to the produc¬ tion of silk and may spend several days locating an

By experimentally manipulating the spinning envi¬

appropriate spinning site and constructing the cocoon.

ronment, Van der Kloot and Williams separated the

Most cocoons are brown, and often they are wrapped

innate behavior of the larva from more flexible adap¬

in leaves or spun among twigs. The color and texture

tive responses to structural features of its surround¬

of the silk and the attached plant matter disguise the

ings. Given a minimum requirement of supports in

cocoon as dead foliage or bark. The details of cocoon

three dimensions, the cecropia caterpillar spins the

construction are often species-specific and can serve

outer layer, intervening mesh, and inner cocoon in a

as taxonomic characters, especially in the Attacini.

stereotyped sequence, no stage of which can be re¬

There are three main strategies of cocoon construc¬

peated. In later experiments using similar techniques,

tion and placement, although these are not strictly con¬

Lounibos (1975, 1976) showed that Antheraea pernyi

22

Life History Strategies

The emergence valve in cecropia is positioned largely in response to gravity, as a function of the inclination of the cocoon on its support. If the spinning larva is inverted at a critical stage, it can be tricked into placing the valves of the outer and inner cocoons at opposite ends. The silk glands increase rapidly in size during the final instar and continue synthesizing silk during the early stages of spinning. Either directly or indirectly, spinning cecropia larvae allot a relatively constant frac¬ tion of their silk to the various layers of the cocoon. Near the end of cocoon construction the larva secretes a fluid (apparently from its gut through the anus) that in many species hardens to a chalk and seems to help waterproof the cocoon. The form and mass of the outer layer of cecropia co¬ coons are much more subject to environmental influ¬ ences than the intervening layer and inner cocoon. The “baggy" cocoon type is largely, but not entirely, de¬ pendent on the number and spatial array of potential attachment points available in the spinning site (Waldbauer & Stemburg, 1967a; Waldbauer et al., 1982). The heritability and ecological aspects of cocoon polymor¬ phism should be studied in more detail. Larvae of C. promethea can measure the diameter of twigs and mod¬ ify the cocoon attachment accordingly to ensure that the cocoon remains attached when the host sheds its Figure 4. Rothschildia cincta constructing a cocoon

leaves in the fall (Waldbauer & Stemburg, 1982b). Co¬ coon placement and color can vary in an apparently adaptive manner; A. luna from the first brood of the year spin light-colored cocoons in foliage, but the dia-

and A. polyphemus exhibit a similar stereotyped se¬

pausing brood construct dark brown cocoons near the

quence of behaviors during spinning, although the co¬

ground.

coons of these species lack an emergence valve and

Many questions concerning the adaptive role of co¬

are not double-walled. The initial phase of cocoon

coons remain unanswered. How effective is the cocoon

construction is fundamentally similar in most satumi-

in protecting against attack by specific predators? How

ids. The larva begins by constructing a superstructure

well do cocoons of various species resist submersion in

of widely spaced strands, often stretching its body

water? Does the placement of the cocoon of temperate

and swinging back and forth to survey potential at¬

species affect subsequent adult development as a func¬

tachment points. On this framework the larva then

tion of exposure to the sun? What are the ecological

begins to form the outermost envelope of the cocoon,

tradeoffs between risk of predation during spinning site

and the characteristic shape usually begins emerging

selection, placement to avoid subsequent predation,

within 12 hours (Figure 4). Layers of silk are spun by

and placement to facilitate wing spreading and mating?

means of a pattern of overlapping figure-eight mo¬

The biophysics of cocoon construction is an open

tions. During spinning the larva turns around in the

field of study. We know very little about the role the

cocoon at regularly timed intervals; this behavior

cocoon plays in regulating water loss, thermoregula¬

seems important for producing a cocoon with a sym¬

tion, and resistance to predation. Research opportuni¬

metrical shape and walls of uniform thickness. One of

ties in this area abound. For example, one could use the

the first features to emerge is the attachment to the

miniature computerized thermistors and other appa¬

branch. The larvae of some species construct an emer¬

ratus now available to study temperature regulation

gence valve by spinning parallel strands of silk in a

based on the reflectance or albedo of the whitish, ex¬

conical shape. The emerging moth can push these

posed cocoons of desert species such as Rothschildia

strands apart, but the valve resists forced entry from the outside.

cincta and Eupackardia calleta. Another desert species, Agapema anona, spins a puffy, open-mesh cocoon that

Pupation

23

may allow air circulation to cool the pupa, while its

tail of their life histories, documented through a long

nearby montane relative, A. homogena, spins a more

tradition of study by dedicated amateurs. In spite of the

conventional, denser cocoon.

popularity of the satumiids, many aspects of their bi¬

In Part 2 we discuss the unique adaptations for sur¬ vival of individual species and genera, and the rich de¬

ology are poorly understood, and we propose many topics for further study.

2

Parasitism

Parasites are organisms that live at the expense of a

levels, but anyone who collects late-instar caterpillars

host from which they derive food and shelter. True par¬

is sure to be impressed by the number that have been

asites do not kill the host. The negative effect of the

parasitized. The Hyalophora Columbia gloveri populations

relationship on the host is often correlated with the life

in Utah systematically sampled by Duncan (1941) over

cycle of the parasite. In cases in which the parasite re¬

a four-year period were heavily parasitized: 37.1% of

quires more than one host during its life cycle, the par¬

the 1629 cocoons collected contained parasites. Of 31

asite has traits that minimize deleterious effects on each

fifth-instar Hemileuca eglanterina larvae collected in

host, although the latter may be severely weakened be¬

Monitor Pass, Mono Co., California, by Collins (1974),

cause the parasite uses the host's metabolic resources

2 yielded the ichneumonid Enicospilus americanus, 28

for its own gain. The host, in turn, may have defenses

produced Cotesia braconids, and 1 developed into a live

against infection or may develop tolerance for the par¬

pupa; of 9 H. nuttalli, 5 were parasitized by Enicospilus,

asite. These types of complex relationships, in which

2 by Cotesia, 1 by an unidentified tachinid, and 1 pu¬

parasites and their hosts continually develop survival

pated normally; of 30 H. hera, 5 were parasitized by the

strategies and counterstrategies, are examples of co¬

ichneumonid, 24 by the Cotesia, and 1 pupated. These

evolution (May & Anderson, 1983). Parasite-host rela¬

high levels of parasitization make parasitoids ideal, and

tionships have been studied extensively, especially with

commonly employed, agents in the biological control of pest Lepidoptera.

respect to the parasitic species that affect humans. The term parasitoid is applied to organisms that rely

Most of the known satumiid parasitoids are wasps

on a single host and whose relationship with the host

(Hymenoptera) within the superfamilies Chalcidoidea

eventually results in the host's death. The families of

and Ichneumonoidea, and flies (Diptera) in the family

wasps and flies that attack the larvae of Lepidoptera

Tachinidae. Some parasitoids are generalists and attack

are typical examples of primary parasitoids. Parasitoids mate and disperse independently of their hosts, and the

several insect orders; others specialize at the family or even generic level.

free-flying adults are often seen feeding at flowers and

The larvae of most satumiid parasitoids live inside

at lights. The hosts' coevolutionary strategies to combat

the host (endoparasitism) and feed primarily on the vic¬

parasitoids are poorly understood. Weseloh (1993) in¬

tim's hemolymph and fatty tissues (Figure 5); some,

dicated that parasitoids tend to have narrower habitat

however, also feed on the surface of the host caterpillar

tolerances than their hosts and concluded that hosts

(ectoparasitism). Because of their more intimate rela¬

may be able to escape parasitization, at least temporar-

tionship with the host and its physiology, endoparasi-

ily, by colonizing a new plant species or microhabitat.

toids tend to be more host specific than ectoparasitoids (Godfray, 1994; Strand, 1986).

Although this has not been conclusively established, it seems reasonable to say that the host-parasitoid rela¬ tionship is an evolutionary game of hide-and-seek.

as occasionally happens, they may be stunted or may

The effect of parasitoids on host populations can be

even die. Two situations that can cause this state are

profound. It is difficult to estimate the impact of insect

multiple parasitism, in which more than one parasitoid

and vertebrate predators on Lepidoptera population

species attacks the same host larva, and superparasi-

24

When too many parasitoid larvae infest a single host,

Parasitism

25

providing additional food and an expanded environ¬ ment in which the parasitoids can develop. First-instar parasitoid larvae may suspend their own growth in an early-instar host larva to allow for the development of a larger food resource (Godfray, 1994). Depending on the larval instar at which the host is attacked, it may be counterproductive for the developing parasitoid larva to immediately kill the host by attacking vital or¬ gans. Parasitoids that attack earlier-instar larvae seem to concentrate their feeding on "nonessential” host tis¬ sue (Godfray, 1994). Although there are no reported ex¬ amples of parasitoid larvae

contributing chemical

stimuli that ensure their satumiid hosts' continued de¬ Figure 5. Parasitic wasp larvae (Cotesia) emerging through cuticle of mature Automeris io io larva

velopment, it has been demonstrated that braconids in the genus Cotesia, a group that also commonly attacks satumiids, do actively manipulate the endocrine system of the sphingid Manduca sexta. By suppressing the nor¬ mal drop in juvenile hormone levels necessary to stim¬

tism, in which too many eggs from a single parasitoid species are laid on a host larva. Superparasitism may result from either multiple attacks by different conspecific females or a mistake on the part of a single female who lays too many eggs on one host. The existing literature documents a number of parasitoid-satumiid relationships (see Appendix 1) but offers little specific information on these interactions. Inferences often must be drawn from similar relation¬

ulate the onset of pupation in its lepidopteran host, the parasitoid prolongs the host's larval stage, and its own use of the host (Beckage & Riddiford, 1983). After the parasitoid larva reaches maturity, the host larva soon dies. Different parasitoids attack at specific stages in the host's life cycle. Some species attack ova (Chalcidoidea, Proctotrupoidea), most use larvae (Tachinidae, Chalci¬ doidea, Ichneumonoidea), and a few attack prepupae

ships in other Lepidoptera and other insect orders. The

or pupae (Ichneumonoidea). Obviously, the parasitoids

parasitoid larva needs adequate time and food to reach

that feed on satumiid ova are very small, since a single

maturity, and it is important that the parasitized satur-

host ovum must support the complete larval develop¬

niid larva continues to feed, grow, and molt, thereby

ment of the attacker (Figure 6). The female parasitoid extends her ovipositor through the chorion of the host egg and deposits a single ovum, then she releases a chemical marker so that conspecific females do not ovi¬ posit in the same egg (Strand, 1986). Very little is known about the biology of the various egg parasitoids, but they are probably less host specific than other sa¬ tumiid parasitoids because they often also attack Hemiptera eggs. Most satumiids are attacked during the larval stage. Parasitoids that attack satumiid larvae oviposit by one of three methods: eggs are laid on the host larva (most flies), in the host larva (most wasps), or on host plant foliage (certain flies and wasps) (Godfray, 1994). In the latter case, the host larva ingests the parasitoid ova as it feeds on the host plant. Female parasitoids that oviposit directly on or in the host are drawn to a general area by olfactory cues given off by frass (feces) and by damaged leaves (Godfray, 1994). Once in the vicinity, they use their keen eyesight to locate the host. The female wasp penetrates the

Figure 6. Parasitic wasp (Anastatus sp.) emerging from Au¬ tomeris io io ova

host's cuticle with her ovipositor and lays one or more eggs in the soft tissue of the larva. Female flies lay eggs

26

Parasitism

by the host larvae in a timely fashion. Once ingested, the fly ova probably hatch very quickly, as the parasi¬ toid larvae must bore out of the host's intestinal tract before they are eliminated with the feces. Fly ova laid randomly on foliage may not be eaten for several days, if at all, and would be subject to premature hatching or desiccation. While unquestionably Leschenaultia fulvipes exploits the gregarious feeding habits of early-instar Hemileuca larvae in its oviposition strategy, what hap¬ pens next is unclear. Since the fly ova are so small, the resulting larvae may be able to pace their growth with that of the Hemileuca host. Another possibility is that the fly larvae are able to suspend their growth after hatching so as to allow the host larva to gain size. This interesting method of oviposition is used by several other tachinid genera and by all trigonalid wasps. If parasitoids are to be successful, they must be able to exit the host at the appropriate time. Many parasitoid Figure 7. Tachinid fly (Leschenaultia fulvipes) ovipositing near feeding larvae of Hemileuca maia complex

larvae emerge from the host (whether larva, prepupa, or pupa) and pupate in the ground. Other species pu¬ pate within, or on, the host. The parasitoid usually has very little difficulty exiting the cocoon through the es¬

on the outer cuticle of the host's skin, and the emerging

cape valve spun by the satumiine genera Callosamia,

parasitoid larvae burrow through the cuticle, usually

Hyalophora, and Sarnia; however, we have found a few

leaving behind a dark mark on the host's cuticle near

cocoons of Antheraea polyphemus, which lack an escape

the vacated egg. If such a mark is not visible, the fly

valve, containing dead puparia and adults of tachinids

larva has probably not yet hatched. In that case, the fly

that eclosed but were unable to escape.

egg can be removed from the cuticle of the host by

A few of the large ichneumonid wasps seem to spe¬

careful use of a fine-tipped needle or dull blade, and

cialize on prepupal larvae. Reliable field observations

the satumiid larva can be saved. Every fly egg must be

indicate that the wasps are attracted by the smell of

removed for this to be effective, however, and the sa¬

freshly spun silk. Marsh (1937) reported that a female

tumiid larva is not usually a cooperative participant.

ichneumonid in Illinois attacked a Hyalophora cecropia

Little has been published about indirect oviposition,

larva by extending her long ovipositor through the par¬

in which parasitoid eggs are laid on foliage and in¬

tially spun cocoon, laying her eggs, and then stinging

gested by host larvae. Although this may seem an in¬

the prepupal larva. J. B. Duncan (1941) reported that

effective method of ensuring the next generation of

the large ichneumonid Gambrus extrematis has only a

parasites, a closer look at the actual process shows oth¬

narrow window of opportunity in which to locate and

erwise. While monitoring a Hemileuca maia population

oviposit on spinning Hyalophora Columbia gloveri larvae.

in Lucas Co., Ohio, we noted a high rate of parasitism

Once the gloveri cocoon has hardened, the ovipositor of

on first- and second-instar larvae by the tachinid Les¬

the parasitoid female cannot penetrate it. Primary pu¬

chenaultia fulvipes. We watched a female fly as she in¬

pal parasitism has been reported in Hemileuca oliviae

spected each larval cluster. She quickly abandoned molting (nonfeeding) clusters, instead focusing her at¬

(Shaw et al., 1987) and Anisota senatoria (Hitchcock, 1958).

tention on clusters of feeding larvae. The larvae, which

Not much has been published about how satumiid

were able to sense her presence, often thrashed in uni¬

larvae respond to parasitoid attacks. Certainly the most

son, occasionally driving her away. In most instances,

effective defense is avoidance, which may be enhanced

however, the female fly successfully laid her ova on a

by their generally low population densities or by noc¬

leaf immediately in front of the rows of feeding satur-

turnal feeding. Passive defenses may include shelters,

niid larvae. After she flew away, the Hemileuca larvae

like those occasionally constructed by late-instar Auto-

resumed eating the leaf (Figure 7). We never saw a fe¬

meris larvae, and the technique of chewing off partially

male fly lay eggs on a leaf other than those actively

consumed leaves at the petiole, presumably to mini¬

being fed on by Hemileuca larvae. The female fly's ovi¬

mize the release of chemical cues, as is done by Callo¬

position technique ensures that her ova will be ingested

samia promethea. The tough cuticle on last-instar larvae

Parasitism

27

pel attacking parasitoids in this fashion (Godfray, 1994). Finally, the host larvae of some insects mount a cellular defense by encapsulating and asphyxiating the parasitoid (Godfray, 1994). Many parasitoid species are themselves potential hosts. In the complex interaction known as hyperpar¬ asitism, the species that attack primary parasitoids are known as secondary parasitoids, and the species that use secondary parasitoids as hosts are known as ter¬ tiary parasitoids. A facultative hyperparasitoid can succeed either as a primary or a secondary parasitoid, while an obligatory hyperparasitoid can reach matur¬ ity only as a secondary or tertiary parasitoid. All sec¬ ondary parasitoids are wasps, but they can use either Hymenoptera or Diptera as hosts. Parasitoid relation¬ ships can be difficult to sort out; a satumiid cocoon or larva from which small wasps emerge should be searched for evidence of hyperparasitism. A common example of hyperparasitism involves chalcid wasps, an ichneumonid wasp, and a Hyalophora cecropia pupa. Many small chalcids may be seen emerging from the cecropia cocoon, and when the cocoon is cut open and the pupa examined, the remains of the cecropia larva and a large ichneumonid cocoon with numerous small exit holes are revealed. Only when the ichneu¬ Figure 8. Parasitic wasp cocoons (Cotesia) on fourth-instar Hyalophora Columbia gloveri larva (photo by Gary D. Hall)

monid cocoon is cut open do the numerous chalcid cocoons that yielded the wasps appear. Marsh (1937) and J. B. Duncan (1941) wrote excellent accounts of hyperparasitism in satumiids, and these sources should be consulted for additional information. The

of many large Lepidoptera may be a passive defense.

data accompanying secondary parasitoids must in¬

Braconid females (Cotesia) cannot penetrate the cuticle

clude the primary parasitoid host and the satumiid

of last-instar Manduca sexta larvae, although they rou¬

host in addition to the usual collection data.

tinely attack fourth-instar larvae (Beckage & Riddiford,

Late-instar satumiid larvae often suffer heavy losses

1978). Interestingly, Cotesia females also routinely attack

to parasitoids. Anyone planning to collect larvae and

early instars of Hemileuca and Hyalophora, but not the

rear them to adulthood should collect the larvae as

last instar (Figure 8). Active defenses against parasitization involve violent

early as possible to reduce the probability of attack. Since so little is known about this interesting aspect of

wriggling, retreating to the center of the host plant, and

satumiid biology, parasitized larvae should not be dis¬

dropping from the host plant (Stamp & Bowers, 1990d).

carded. We encourage collectors to mount, carefully la¬

At least some host larvae use their mandibles to remove

bel, and photograph parasitoids in the field, and then

attached tachinid eggs (H. W. Allen, 1925). Lepidoptera

compare their records with the associations listed in

larvae that regurgitate digestive fluids occasionally re¬

Appendix 1.

3

Diseases of Saturniidae

The Saturniidae are subject to a number of bacterial,

dispersed. Dwyer (1991) demonstrated that transmis¬

fungal, viral, and protozoan infections. Diseases in

sion of NPV to late-instar Orgyia pseudotsugata larvae is

given populations are usually cyclic and appear to be

strongly influenced by the patchiness of their distribu¬

influenced by a number of factors. Seasonal environ¬

tion.

mental conditions play a significant role in determining

sometimes exhibit abnormal behavior that further as¬

the level of infection. Most pathogens of Lepidoptera

sists in the dispersal of the pathogen. Infected larvae

are affected by temperature, moisture, humidity, and

often climb to the highest point on the host plant before

the amount of available sunlight (Tanada & Fuxa, 1987).

hanging by their prolegs and dying. This elevated po¬

The experienced rearer, who knows that most livestock

sition enhances the spread of wind-borne diseases and

Lepidoptera

larvae

that have

been

infected

are lost during cool, damp seasons, may scoff at the

increases the chance of discovery by predators and par-

obvious, but the conditions that give rise to an epidemic

asitoids that investigate the dying larva and then trans¬

are subtle. While temperature, moisture, and humidity all affect the virulence of these pathogens to some de¬

mit the disease to new locales and hosts (Watanabe, 1987).

gree, lack of sunshine may be the key factor in creating

Poinar and Thomas (1984) offered a list of diagnostic

optimal conditions for pathogens. Nuclear polyhedrosis

symptoms for each of the four types of infection dis¬

viruses (NPV) in the Douglas-fir tussock moth (Orgyia

cussed below (bacterial, fungal, viral, and protozoan).

pseudotsugata: Lymantriidae), for example, have been

We fully credit them now to avoid undue redundancy.

rendered inactive by limited exposure to the ultraviolet

Most bacterial infections (bacteriosis) of Lepidoptera

wavelengths of sunlight (Griego et al., 1985). Yet, en¬

gain access to the internal organs through wounds or

vironmental conditions are not the sole determinants of infectious outbreaks.

lesions; the cuticle of the larva is otherwise resistant.

Watanabe (1987) addressed a number of factors that

cillus thuringiensis (Bt), that produce toxins that open

There are, however, true insect pathogens, such as Ba¬

increase the potential for epidemics. The density of the

the wall of the host's gut without relying on an already

host population, its reproductive and dispersal behav¬

existing injury. Mass applications of Bt, widely used to

ior, abnormal behavior resulting from infection, and the

suppress pest Lepidoptera, often cause high mortality

activity of vertebrate and invertebrate vectors all affect the level of the outbreak. As we stress in Chapter 6 and

in nontarget species, including satumiids (Peacock et

elsewhere in this volume, rearing larvae in crowded

early signs of infection include loss of appetite, diar¬

conditions greatly increases the potential for disease.

rhea, and regurgitation. The larva may become sluggish

Most outbreaks of disease occur during wet years that

and uncoordinated, and it may change color, suffer con¬

follow several successive “boom” years in which pop¬

vulsions, and eventually experience paralysis. Death

ulation levels have built up. The oviposition habits of

usually occurs within a few days of infection. Bacterial

each species influence larval density, which in turn af¬

infections are characterized by dissolution of all tissues,

al., 1993). Most bacterial infections begin in the gut, and

fects the potential for disease. Outbreaks are more fre¬

and the infected larva is often found hanging from the

quent in the Hemileucinae, which lay their eggs in

host plant by its anal claspers (see photograph of Sarnia

clusters, than in the Satumiinae, whose eggs are more

cynthia in Collins & Weast, 1961:102). Bacterial infec-

28

Diseases of Satumiidea

29

tions have been reported in Actias luna, Antheraea poly-

and cause the tissue to disintegrate and liquify. Death

phemus, Eacles imperialis, Hyalophora cecropia (Collins &

usually takes several weeks, and dead larvae are often

Weast, 1961), Hemileuca maia, H. oliviae, and Hyalophora

found hanging from the host plant in much the same

euryalus (Thomas & Poinar, 1973).

manner as larvae infected with bacteria. Both NPV and

Fungal infections (mycosis) often occur during hiber¬

granulosis viruses (GV) have been reported from Sa-

nation or quiescent periods such as molting. Moist soil

tumiidae. Specific records exist for Hemileuca maia

favors the growth of spores, and Lepidoptera that pu¬ pate in subterranean chambers are especially suscepti¬

(Mitchell et al., 1985), H. nuttalli (Collins, 1974), H. slosseri (Wangberg, 1983), H. tricolor, H. eglanterina, and Co¬

ble. The fungus usually attacks through the spiracles

lorado pandora pandora (Steinhaus & Marsh, 1962).

and can kill very quickly through suffocation. The ex¬

Attack by protozoans (microsporidioses), well known

terior cuticle and internal body cavity are often covered

in the domestic silkworm (Bombyx mori), is seldom re¬

with mycelia. Infected larvae almost immediately stop

ported in North American species, but the lack of re¬

feeding and become weakened. They often change

cords may be the result of inadequate sampling. The

color, develop dark spots, and die in species-specific

microsporidians may be present in the larval, pupal, or

poses (see photograph of Anisota senatoria in Steinhaus & Marsh, 1962:455). The dead host's body cavity may

adult stage. No specific symptoms of early infection have been identified, but there may be general lethargy,

become hollow or hardened. Species reported to have

loss of appetite, and difficulty in molting. The infection

been infected by fungi include Anisota senatoria, Hyalo¬

is not always fatal. Quite often the larva simply drops

phora euryalus (Steinhaus & Marsh, 1962), and H. cec¬

dead with no advance warning. The only records of

ropia (Thomas & Poinar, 1973).

microsporidian infection in a North American satumiid

Viral infections tend to have the greatest impact on

of which we are aware involve Hyalophora cecropia be¬

Lepidoptera populations. Again, the Hemileucinae are

ing infected by a Nosema species and a Thelohania spe¬

the most frequently affected. Viruses can lay dormant

cies (Thomas & Poinar, 1973).

for long periods and reach epidemic levels only when

Satumiidae are probably exposed to a number of

conditions are right. Infected larvae become inactive

pathogens that have little impact on the population in

and feed sporadically, and the integument usually

most years. Only when population and environmental

changes color. Stamp and Wilkens (1993) indicated that

conditions are favorable will disease symptoms appear

infected larvae may be able to resist or even overcome

at epidemic levels; however, these cyclic occurrences

early infection if they are kept warm enough. Late-

may have tremendous impacts on individual popula¬

instar larvae are more subject to infection and thus are more likely subsequently to infect other larvae (Dwyer,

tions. Collins (1974) reported an epidemic NPV infec¬ tion that decimated a population of Hemileuca nuttalli

1991). Viruses destroy the functions of individual cells

over several acres in the Sierra Nevada of California.

4

Populations, Species, and Taxonomy

In this chapter we outline recent advances that help

of each individual. During reproduction the process of

elucidate the nature of genetic variation in populations

meiosis recombines genes in each sex to produce a huge

and relate these concepts to species-level taxonomy of

number of genetic combinations among gametes (eggs

Lepidoptera, especially the Satumiidae. Authors of past

and sperm), which unite to form the next generation.

and current Lepidoptera field guides and reference

Even in a very large population, the progeny from one

books have, perhaps wisely, avoided discussing these

generation that survive to reproduce and form the next

complex topics. But taxonomy and systematics have

generation will express only a tiny fraction of this po¬

been subjects of great controversy in recent years (Ehr¬

tential range of variation. From a statistical viewpoint

lich & Murphy, 1982, 1983a,b,c; Hammond, 1991; L. D.

alone, the chance mating of genetically different indi¬

Miller & Brown, 1983; Murphy & Ehrlich, 1984; Sha¬

viduals will tend to cause separate populations of the

piro, 1983), and we feel that collectors and breeders of

same species to become gradually more and more dis¬

Lepidoptera would benefit from an introduction to the

tinct over time, but such random genetic change,

topics under debate. We encourage readers to go on to

known as genetic drift, is much more likely in very

more specialized references. A general discussion of

small populations.

population genetics and speciation can be found in

Each gene controlling a given trait exists in several

works by Dobzhansky (1970), Futuyma (1986), Ricklefs

forms called alleles. An individual that happens to in¬

(1990), and Stebbins (1982). Speciation theory is re¬

herit a combination of alleles that increases (through

viewed by Otte and Endler (1989), and by Collins (1991)

any means) its chance of survival and reproduction will

for the Lepidoptera.

tend to leave more progeny, and thus these favorable genes will increase in frequency in the population. This process, called natural selection, is an interaction be¬

The Genetic Structure of Populations

tween factors of the biotic and physical environments and the individual. Selection acts on the individual's

Over the range of a given species, individuals occur

phenotype, its physical traits, which is a product of

as interbreeding members of populations that are sep¬ arated from other such groups by unsuitable terrain,

both its genetic constitution (genotype) and the effects

lack of host plants, or other barriers. Stable populations

itable variation in a trait is subject to natural selection.

exist at some average density, which varies greatly over

Since genes interact in a complex manner during

time and from one species to another, and below which

growth and development, the probability of survival of

the population would be in danger of extinction if ad¬

a given individual depends on the collective effect of

verse conditions should overwhelm its reproductive ca¬

integrated gene action. Alternative alleles often differ

pacity. A population that is extirpated locally may

only slightly in their effect on the phenotype, yet when

subsequently be reestablished by individuals from nearby populations.

selection acts over long periods the frequency of the

The members of an interbreeding population share a gene pool encoded in the chromosome set, or genome, 30

of the environment during its development. Only her¬

more favorable allele will increase in a population and may eventually replace alternative, less favorable al¬ leles.

The Genetic Structure of Populations

31

In this way populations become adapted to their local

change. Similarly, many genes controlling growth, de¬

environments, and consequently become to varying de¬

velopment, metabolism, and life history traits interact

grees genetically distinct from other populations of the

in such a complex manner that major genetic change

same species. Examples of local adaptations in Lepi-

would likely be severely selected against. Many Lepi-

doptera include female oviposition preferences, varia¬ tion in the ability of larvae to metabolize nutrients and

doptera species have regional subspecies distinguished by wing pattern, size, or other morphological or eco¬

detoxify defensive chemicals in host plants, and hor¬

logical traits. Yet these populations retain the ability to

monal systems that adjust diapause, development, and

interbreed, and will form blend zones at adjoining sub¬

emergence in response to environmental cues. Viewed

species boundaries. In summary, species integrity is the

collectively, these life history traits define the ecological

product of internal constraints on gene expression as

niche of a population. Although regional populations

well as reproductive isolation from related taxa.

of a species may vary in their specific ecological traits,

Recent advances in population biology, especially in

each species as a whole typically occupies a unique ec¬

molecular genetics, have revealed unexpectedly high

ological niche. If two species with similar niche char¬

levels of genetic variation among populations of species

acteristics come into sympatry (occupy the same place),

in a large number of taxonomic groups, including Lep-

natural selection tends to favor any genetic variation that reduces competition between them for space and

idoptera. This finding has stimulated a spirited debate that calls into question important assumptions relating

resources. This theory, known as the competitive exclu¬

to the genetic integrity of species (Ehrlich & Raven,

sion principle, is one of the fundamental concepts in

1969; Ehrlich & White, 1980; McKechnie et al., 1975).

ecology, and it helps us understand the organization of

The new evidence suggests that gene flow between

biotic communities and the origin of biological diver¬

populations, which tends to reduce interpopulation

sity.

variation, has probably been overestimated for many

There are limits on the degree to which a population

species. Without the predominant homogenizing effect

can become genetically adapted to its environment. Re¬

of gene exchange, the component populations of a spe¬

combination during sexual reproduction and the intro¬

cies have the potential to diverge genetically, subject to

duction of genes from individuals immigrating from

the constraints outlined above. But there is controversy

other populations (gene flow) tend to prevent popula¬

concerning what factors are maintaining such high lev¬

tions from becoming homogeneous for only adaptively

els of allelic variation in a population. Some of this var¬

superior gene variants. Furthermore, the nature of se¬

iation may not be subject to selection because it is

lection in a given environment usually varies over time

adaptively neutral or equivalent in terms of the fitness

and distance and also acts to maintain genetic variation.

it bestows. By contrast, other alleles are maintained in

Biologists have long sought to define and understand

a population because they confer a distinct advantage

the factors that give species their integrity. In other

in a given environment.

words, given the tendency of populations to diverge

Population biologists now believe that populations of

genetically, why don't allopatric (geographically sepa¬

a given species are more or less independent units of

rate) populations always evolve into separate species

ecological adaptation and genetic change (Ehrlich &

(Felsenstein, 1981)? The biological species concept says

Murphy, 1983b). Species as an entity do not evolve, be¬

that species are defined as populations whose individ¬

cause the factors causing genetic change do not operate

uals can interbreed with members of related popula¬

uniformly over the entire range of a species. Rather, the

tions but are reproductively isolated from other such

populations that compose a species each evolve sepa¬

groups. Evolutionary biologists developed the species

rately and at different rates. The genetic makeup of a

concept to explain the origin and maintenance of

population is the result of natural selection, the degree

genetic cohesion within populations of species (Dob-

of gene exchange with related populations, mutations,

zhansky, 1970; Mayr, 1963). Reproduction in the Lepi-

genetic drift, and significant historical changes in these

doptera

and

factors (Slatkin, 1987). Consequently, no single popu¬

copulation resulting in successful insemination and fer¬

lation can adequately characterize the genetic variation

tilization. Since separate genes control reproductive

of the entire species. Many of the differences between

physiology and behavior in males and females, a ge¬

species may actually arise in populations before they

netic change with a major effect on one sex would be

become reproductively isolated.

disruptive unless it were accompanied by a simulta¬ neous and compatible change in the other sex, an un¬

Furthermore, various traits evolve at different rates. In practical taxonomic terms, this means that morpho¬

likely event. Reproduction is therefore under a kind of

logical differences, such as wing patterns or genitalic

stabilizing natural selection that tends to resist genetic

structure, may not be accurate indicators of reproduc-

requires

mate

location,

recognition,

32

Populations, Species, and Taxonomy

tive isolation among populations under study (for a re¬ view of genitalic analysis in systematics, see Shapiro & Porter, 1989). Modem taxonomic practice usually em¬ ploys a variety of techniques to assess relationships. An index of genetic relationship at various taxonomic lev¬ els can be derived using molecular genetics techniques such as electrophoresis of enzyme gene products or di¬ rect comparisons of DNA gene sequences. Morpholog¬ ical variation for many different traits can best be studied with computer analysis using multivariate sta¬ tistics. Differences in the genes controlling growth, de¬ velopment, and reproduction (genetic compatibility) can be studied by hybridization. As an expedient in classification and identification, most Lepidoptera field and identification guides treat species as discrete units of equal taxonomic rank, each with distinctive ecological and morphological charac¬ ters. This practice gives the impression that all the traits that characterize a species were acquired during the process of speciation, while in fact, “good species" may be evolutionarily old, and the observed differences may have arisen at various times both before and after re¬ productive isolation. Among the satumiids treated in this work are many examples of morphologically dis¬ tinct populations that are reproductively isolated to varying degrees. Hybridization is apparently rare in the Callosamia but common in the Hyalophora, although this genus in turn contains a hierarchy of poorly defined to well-defined species. Saturnia mendocino and S. walterorum appear to be distinct species, especially in terms of female morphology, yet they freely interbreed in the lab, sometimes producing fully fertile hybrids, and ap¬ pear to hybridize in nature where their ranges overlap. The genus Anisota, on the other hand, includes species that are very similar morphologically but maintain sympatry without interbreeding. Automeris io and A. louisiana do not interbreed in nature, but lab hybrids are viable and fertile. Some populations in the Hemileuca maia group seem to hybridize in nature, yet others, phenotypically and biochemically very similar, differ ecologically (and apparently also in their pheromone chemistry) and do not interbreed. The taxonomy of cer¬ tain other closely related allopatric taxa needs further study: the relationship of Eacles imperialis to E. oslari, various populations in the Agapema anona species group, and Automeris patagoniensis with respect to the Mexican A. colenon.

Speciation A consideration of the process of speciation is im¬ portant in order to understand the controversy over

what constitutes a species and what taxonomic rank should be assigned to a given population. Closely re¬ lated species usually exhibit obvious ecological, behav¬ ioral, morphological, and physiological differences. At one time it was thought that speciation must therefore be accompanied by a "genetic revolution" to account for the origin of these differences. Any theory of spe¬ ciation must explain the transition from one stable, har¬ monious system of interacting genes to another such system. We have discussed how part of this transition occurs when the populations that make up a single species genetically differentiate to produce many of the kinds of characteristics typically used to distinguish separate species. Much of the controversy in taxonomy arises because reproductive barriers are often lacking or in¬ effective in such highly differentiated populations. The evolutionary biologist is not surprised by this finding, given the continuous and relatively slow pace of evo¬ lution. Nevertheless, reproductive isolation is a useful criterion for assessing taxonomic status in sexual, rela¬ tively mobile organisms like the Lepidoptera because related populations can diverge toward separate evo¬ lutionary fates only after gene exchange is reduced be¬ low some critical level. Speciation events, the origin of reproductive iso¬ lation, are thought to occur most often in small and isolated populations, which may be formed by coloni¬ zation or perhaps as the result of redistribution in re¬ sponse to climatic change. In such populations the probability of inbreeding is increased. Inbreeding can produce novel genotypes through matings between in¬ dividuals carrying rare genes (genetic drift). Isolated populations may inhabit areas with unique natural se¬ lection regimes, and the new phenotypes may be better adapted to a particular habitat than are individuals from the main population. Extinction is probably the most common fate of small isolates, but cycles of selec¬ tion and the production of new gene combinations can lead to significant changes in traits affecting reproduc¬ tion. This model of speciation, known as the allopatric model, is widely accepted, partly because population genetics theory shows that even small amounts of gene flow can prevent genetic divergence. Biogeographic patterns of variation also support the allopatric speci¬ ation model. Oceanic islands and other geographically isolated communities often support novel species that are clearly related to mainland or central, apparently ancestral, species. Episodes of glacial advance and re¬ treat during the Pleistocene had a profound effect on the distribution and composition of natural communi¬ ties. Correlations between the distribution of speciation

Interpreting Phenotypic Variation in Nature

33

phenomena (such as hybrid zones, blend zones be¬

Selection cannot favor an increase in postzygotic iso¬

tween subspecies, and centers of species diversity) and

lation such as sterility, since unfit hybrids have inferior

the known effects of glaciation are common (Reming¬

reproductive fitness by definition. In other words, hy¬

ton, 1968). Examples among the North American satur-

brid unfitness should provide the selective basis for the

niids discussed in this work include the intergrade

origin of prezygotic reproductive isolation. But in fact,

populations in the Hemileuca main complex in the Great

this long-held concept of further improvement or re¬

Lakes region, which are roughly coincident with similar examples in Hyalophora Columbia, Limenitis, and Papilio

inforcement of reproductive isolation in zones of range overlap has not been substantiated generally by field or

(reviewed in Collins, 1991). Hybrid zones in Papilio

theoretical analysis (see Hybrid Zones, below).

(Sperling, 1987) and Hyalophora are found in roughly

In summary, the origin of a new species is a rare

the same area in the Northwest. In these cases one can

event promoted by special circumstances; it is not nec¬

infer that populations were temporarily isolated in re-

essarily the inevitable result of geographic isolation of

fugia and then brought together in sympatry as they

closely related populations. Reproductive isolation may

reinvaded previously glaciated terrain. The high spe¬

be the chance result of ecological or physiological

cies diversity of the Hemileuca in the West and South¬

change, or it may occur independently and at a differ¬

west may be the result of episodes of allopatric speciation brought about by range changes during the

ent rate of change than other traits such as morphology or specialized ecological adaptations.

Pleistocene when plant communities were displaced in both altitude and latitude (D. E. Brown, 1982; Van De¬ vender & Spalding, 1979). The characteristics that act to reproductively isolate two species living in sympatry, different flight seasons

Interpreting Phenotypic Variation in Nature The Subspecies Problem

or times of pheromone release, for example, are com¬

Subspecies are recognizably different geographic

monly called reproductive isolating mechanisms. Ac¬

populations or sets of populations assigned a formal

tually, this is a misleading term, as many of these traits

taxonomic name. The use of the subspecies category

probably first evolved in response to selection favoring

has proliferated in the taxonomy of Lepidoptera, partly

increased mating success and efficiency in small, iso¬

because it is a convenient catchall for difficult problems

lated populations as outlined above. Other character¬

in classification, but also because taxonomists have a

istics may have first evolved as ecological adaptations.

natural tendency to split and recognize intensely stud¬

When two closely related species later occur sympat-

ied groups. We tend to agree with the many evolution¬

rically, these reproductive and ecological traits then

ary biologists who feel that designating morphological

serve secondarily as isolating mechanisms. Typically no

subspecies is largely an arbitrary decision. On the one

one characteristic is effective in reproductive isolation,

hand, it may help catalog variation within a species, but

but the collective interaction of many characters pre¬

on the other hand, it may actually be misleading be¬

vents hybrid matings, as, for example, allochronic flight

cause it implies a specific genetic status and ignores

and pheromone differences in Hemileuca (Collins & Tuskes, 1979), temporal and seasonal isolation between Hy¬

other significant patterns of divergence (Gillham, 1956; E. O. Wilson & Brown, 1953).

alophora cecropia and H. Columbia (Tuttle, 1985), and

Four specific objections can be raised against the sub¬

allochronic flight periods in Callosamia (L. Brown,

species concept. First, there is no testable criterion of

1972a; Peigler, 1977a, 1981).

subspecies rank, such as reproductive isolation as a test

Natural selection has long been invoked as the mech¬

for species status. Just how different must a population

anism behind the origin of adaptations, and so it is log¬

be to be called a subspecies? Second, a subspecies may

ical to try to explain the origin of reproductive isolation

be a member of a dine or mosaic array of variable pop¬

as a direct, adaptive product of natural selection. If two

ulations. Geographic variation in several characters

populations are interbreeding in an area of sympatry

may not be congruent, making geographic limits for

and their hybrid offspring are sterile or subvital, selec¬

subspecies quite arbitrary. Third, other populations un¬

tion might be predicted to favor any trait that would

distinguished by phenotype may actually have di¬

reduce the reproductive waste of this hybridization. In

verged in more significant ways, such as adaptation to

this model, selection acts only on aspects of reproduc¬

unique hosts, shifts in mating times, and so on. Fourth,

tion that precede the formation of the embryo; such

traditional morphological subspecies are not necessar¬

prezygotic isolation includes differences in adult emer¬

ily undergoing indpient spedation, even when they are

gence season, diurnal mating rhythms, pheromone

isolated in unique environments.

structure and composition, and mate choice behavior.

The origin of reproductive isolation tends to be con-

34

Populations, Species, and Taxonomy

servative. Ecological and morphological characters may

notypic blend zone should produce fully vital and fer¬

evolve more rapidly. More detailed studies of compar¬ ative biology, experimental hybridization, and molec¬

tile offspring. Clines may be confused with areas of overlap in

ular genetics are required than have traditionally been

which morphologically similar forms (often called sib¬

applied to the subspecies problem. Such studies can be

ling species) do not interbreed. Breeding experiments

very engrossing and satisfying endeavors in which

and the examination of progeny from wild-caught fe¬

groups of amateurs and professional biologists can co¬

males can distinguish between the two phenomena.

operate. The very accumulation of this kind of infor¬ mation is a much more significant contribution than mere nomenclatural changes for their own sake.

Polymorphism Polymorphism is an adaptive response to selection

Phenotypic Blending in Zones of Sympatry

factors that vary in space or time. If alternate pheno¬ types are adapted to different features of the environ¬

Regions of phenotypic blending often connect the

ment, or if selection alternately favors one form and

ranges of adjoining geographic subspecies. The histor¬

then the other, populations may become polymorphic

ical causes and current factors maintaining such blend

for these discrete phenotypes. Populations of Hemileuca

zones are controversial. Secondary intergradation oc¬

eglanterina, Eacles imperialis, E. oslari, Anisota consularis,

curs as the result of interbreeding following a period

and Automeris io are often polymorphic for adult color

of geographic isolation. While they were isolated the

forms, and the larvae of Saturnia walterorum and S. men-

subspecies may have become phenotypically and eco¬

docino are usually polymorphic (see Primary Defenses,

logically distinct, but they remained reproductively

Chapter 1). Sexual dimorphism is a spedal case of pol¬

compatible so that the two populations freely interbred

ymorphism. With the exception of mimicry complexes,

on secondary contact.

many of which have been well studied, the adaptive

Blend zones may also be produced when patterns of

significance of most polymorphisms is not well under¬

selection form a gradient in intensity over geographic

stood. The adults of many polymorphic species appear

distance. This kind of selection produces a dine, a sit¬

to resemble leaf litter, which is composed of many

uation in which one or more characters vary gradually

shades of yellow and brown. It is possible that the ex¬

over distance. Because this pattern occurs over a por¬

istence of different cryptic color morphs interferes with

tion of a species' range without the intervention of

birds' ability to form a search image. If predation occurs

physical barriers, it is called primary intergradation.

most heavily on the most common color morph, the

Character dines are steep in situations in which the

relative frequencies of color morphs in a population

strength of selection increases rapidly over distance and

may shift over time. The phenomenon of industrial

gene exchange is weak. Clinal variation is minimal

melanism is one of the best-known examples of poly¬

where the selection gradient is gradual and gene

morphism in moths.

exchange is intensive. Clines for wing pattern traits of¬

the lichen-covered tree trunks where the normally

ten seem to be correlated with environmental gradients

light-colored, cryptic adults rested, the once-rare me-

such as temperature or aridity, but it is very difficult to

lanic form increased in frequency (Kettlewell, 1973).

experimentally establish the true adaptive basis main¬ taining dines.

As industrial soot darkened

Seasonal polyphenism is a special kind of polymor¬ phism. In this case, environmental cues such as pho¬

From the standpoint of population genetics, it is the¬

toperiod induce the expression of alternate genes

oretically impossible to distinguish primary from sec¬

encoded in the chromosomes of a given individual (see

ondary intergradation, especially when relatively few

Chapter 1). Actias luna and Callosamia securifera have

genes control the traits in question (Endler, 1977). If the

"spring” and "summer" forms, and Janzen (1984b) de¬

groups form specialized associations with host plants,

scribed the adaptive basis for wet- and dry-season

inferences can be made from fossil floras concerning

forms of Rothschildia lebeau. The adults of the latter spe¬

historical range changes and the likelihood of second¬

cies rest during the day on dead foliage. The light

ary contact (Sperling, 1987; Tuskes & Collins, 1981).

brown or rust-colored morph tends to match the color

Careful experiments are required to understand the

and hues of dead foliage during the dry season; adults

population genetics of subspecies blend zones and to

of the darker, chocolate-colored morph are more cryptic

distinguish them from hybrid zones (discussed below).

during the rainy season when moisture and mold turn

By definition, crosses between subspedes across a phe¬

dead leaves dark brown.

Interpreting Phenotypic Variation in Nature

35

els of speciation would predict (Dobzhansky, 1970).

Hybrid Zones

Most matings just outside the hybrid zone are be¬ Phenotypic intergradation also occurs when taxo-

tween “pure" parental genotypes, and so these pop¬

nomically distinct populations interbreed in areas of

ulations are not subject to selective pressure to avoid

contact called hybrid zones. In these cases, effective

hybrid matings (Bigelow, 1965). The increase in fre¬

mating barriers have not evolved, but complete fusion of the parental gene pools is prevented because hybrids

quency of compatible genotypes within the hybrid zone, which might lead to a fusion of the two hybrid¬

are to various degrees subvital, infertile (usually the fe¬

izing taxa, is opposed by continuing gene flow of pa¬

males in Lepidoptera), or ecologically unfit outside the

rental

hybrid zone. Many hybrid zones take the form of nar¬

Subsequent recombination would break up favorable

row bands that may be tens or hundreds of miles long

gene combinations as they arose.

genotypes

from

each

side

of

the

zone.

but are often less than one or only a few miles wide,

The structure of the hybrid zone is a measure of the

bounded by populations of the parental forms. The

similarities and differences between the two taxa for

width and the genetic structure of hybrid zones seem

genes controlling development and reproduction. Hy¬

to result from an equilibrium between gene flow from

brid zones are therefore natural laboratories for study¬

the parent populations and the opposing effect of se¬

ing speciation. The most effective studies of hybrid

lection on unfit genotypes within the zone that tends

zones employ multivariate analysis of phenotypic var¬

to prevent fusion of the two species. Within the hybrid

iation, with laboratory-reared parental and hybrid

zone a wide range of recombinant genotypes occurs,

groups used as standards for comparison. The degree

producing phenotypic variability usually exceeding

of genetic recombination and introgression in hybrid

that seen in first-generation (F,) laboratory hybrids. Of¬

zones is best determined using electrophoretic assays

ten, parental phenotypes are rare or absent in mid¬

of enzyme markers or other molecular genetic tech¬

hybrid zone; their presence in significant numbers

niques.

would indicate preferential mating among conspecifics or strong selection against hybrids. From this pool of variability, neutral or beneficial genes from one species may introgress by means of gene flow into the popu¬

Allopatric Populations and Experimental Hybridization

lation on the opposite side of the hybrid zone, as in the

One of the more vexing problems in systematics oc¬

hybrid zones of Hyalaphora (Collins, 1984, 1996) and the

curs when similar yet distinct populations occur allo-

various mimetic forms of Heliconius erato (Mallet et al.,

patrically, separated by great distance alone or as

1990).

isolated populations. Allopatry in itself tells us nothing

The distribution of hybrid zones and the topogra¬

about the potential for successful reproduction should

phy of the areas they occupy often suggest that they

these forms come into contact. In practice, if independ¬

resulted from contacts between previously isolated

ent measures of relationship such as multivariate anal¬

groups expanding outward from Ice Age refugia as

ysis of morphology and electrophoretic surveys of

the climate warmed following the Pleistocene. Bioge¬

enzymes both reveal significant differences, then the al¬

ographic considerations suggest that some hybrid zones may be as much as 8000-10,000 years old. The

lopatric populations are usually considered separate species.

apparent stability of hybrid zones intrigues popula¬

We also know very little about the degree of genetic

tion geneticists, who seek to explain why selection

divergence among distant populations within species.

has not favored either effective mating barriers or the

By the 1970s the data on genetic variability obtained

elimination of genetic incompatibility among hybrid

from electrophoretic surveys of populations and species

recombinants leading to fusion of the hybridizing pair

were being used to explore gene flow and population

(Barton & Hewitt, 1985; Bigelow, 1965; Harrison, 1990,

structures, but such data revealed little directly about

1993; Woodruff, 1981). Selection blocks the introgres-

the genetic changes that accompany speciation. Were

sion of deleterious genes, such as those producing

these differences between populations in genes that en¬

low fecundity or fertility. If there are many such in¬

code enzymes accompanied by differences in the genes

compatible loci, any closely linked alleles, even bene¬

that control reproduction and development? To answer

ficial ones, will also be retarded. In this manner,

this question Oliver (1979a,b, 1980, 1983) made test

hybrid zones can act as barriers to gene exchange.

crosses between geographically distant populations

This mechanism probably explains why reproductive

within species and between recognized species, pri¬

isolation

not

marily in the butterfly genus Phyciodes. In many cases

evolve in hybrid zones, contrary to what certain mod¬

the offspring from the intraspecific crosses exhibited

between

the

hybridizing

taxa

does

36

Populations, Species, and Taxonomy

prolonged larval growth, disrupted diapause, abnormal

in the lab, or the female of the species to be mated can

emergence schedules, and reduced fertility. Oliver in¬

be confined next to a calling female of the other species.

terpreted this genetic incompatibility as evidence of dif¬

Although amateur breeders have made many intra-

fering ecological adaptations among the populations.

and intergeneric crosses (Appendix 2), they almost

Interestingly, the abnormalities in interspecific hybrids

never record quantitative data on hybrid compatibility.

were similar in kind but more severe in degree. More¬

Careful records should be kept regarding the fertility

over, hybrid incompatibility was not necessarily well

of ova and viability of embryos, survival and growth

correlated with morphological differences, and a new

rates of larvae, survival and diapause of pupae, emer¬

species was subsequently described based on this work.

gence patterns, sex ratios, time of mating activity, fer¬

Much less disruption in interpopulation crosses within

tility of adults, and fecundity of females (e.g., Collins,

species is seen in Junonia (Hafemik, 1982) and Hyalo-

1984; Hafemik, 1982; Oliver, 1980, 1983; Scriber et al„

phora (Collins, 1984). Species with low dispersal rates

1990; Tuskes & McElfresh, 1995; West & Clarke, 1988).

and those that exist in small, isolated populations are

In our justification for elevating Antheraea oculea to spe¬

more subject to genetic differentiation than highly mo¬

cies status we give an example of the kind of data that

bile species. More surveys of this type need to be done.

can be obtained from experimental hybridization.

The degree of geographic variation within species in the genes that control mating and reproduction is es¬ pecially relevant to studies of speciation and to systematics. Regional variation in pheromone composition,

Species Concepts and Their Application in Taxonomy

and in corresponding male response, is known for cer¬ tain pest Lepidoptera (Carde & Baker, 1984; Klun &

Systematics is the study of relationships among or¬

Maini, 1979). Geographic variation in the time of pher¬

ganisms and the diversity of life. One of the goals of

omone release is known in Hyalophora cecropia, and ex¬

systematics is to determine the branching pattern of ev¬

periments within the Hemileuca maia group revealed

olutionary trees, in which each fork represents diver¬

apparent geographic variation in pheromones that is

gence from a common ancestor. Classifying biological

not closely correlated with adult phenotype. These ex¬

diversity into these schemes of relationships is the prac¬

amples are discussed more fully in the species accounts

tice of taxonomy. The natural groupings that the

in Part 2. Such variation in reproductive traits could

systematist and taxonomist recognize should be mon-

arise for several reasons: as an adaptive response to

ophyletic. In a correct classification, all members of a

interference from nonrelated, sympatric species; as re¬

genus share a single ancestral species, all genera in a

productive character displacement to avoid interbreed¬

family evolved from a common ancestor, and so on up

ing with closely related sympatric species; in response

to the higher levels of classification.

to environmental factors affecting mating success; in re¬

Taxonomy based on concepts of genetic divergence

sponse to predators exploiting mating behavior; or

within evolving populations infers relationships based

through genetic drift (Carde, 1987).

on measures of genetic similarity, indirectly through

Additional fieldwork and experimental hybridization

analysis of morphological variation, or more directly

studies will help to elucidate speciation and genetic dif¬

according to allozyme variation or comparisons of

ferentiation of populations. This is an area in which am¬

DNA composition. The evaluation of such measures of

ateur breeders can contribute a wealth of information.

genetic relatedness is often subjective, partly because

Artificially reared females from selected populations

variation detected by each methodology does not fall

can be used as bait in funnel traps to evaluate variation

necessarily into the discrete groupings of genera, fam¬

in the time of pheromone release and the degree of

ilies, and so on. The museum curator must often

male response, both between species and among re¬

deduce genetic relationships within and between pop¬

gional populations within nominal species. Experimen¬

ulations solely from locality data and the phenotypic

tal hybridization can be used to evaluate both pre- and

characters evident in spread specimens. The biological

postzygotic isolation. Satumiids are ideal subjects for

species concept, based on the potential of populations

studies of this kind. They are usually very easy to mate

to successfully interbreed, is especially difficult to apply

in cages or to hand-pair, they do not feed as adults,

to allopatric populations, as we have discussed above.

and they will generally oviposit in paper bags even in

Hybrid zones and laboratory hybridization have shown

the absence of leaves of their host plants. If the two

that reproductive isolation may be incomplete in oth¬

species to be hybridized release their sex pheromones

erwise recognizably different taxa. Even when experi¬

at different times, the photoperiod can be manipulated

mental crosses can be made, it is difficult to extrapolate

Summary

37

to what might occur in nature should allopatric popu¬

trends. Such reversals of polarity can lead to incorrect

lations somehow come into sympatry. Reproductive

inferences of derived versus ancestral states. Problems

isolation as a species criterion for allopatric populations

in classifying or encoding characters often lead to al¬

can be criticized on both practical and theoretical

ternative but equally plausible phylogenetic trees.

grounds.

Computer programs have been designed to lessen the

The phylogenetic species concept seeks to represent

effect of these errors, usually by employing the criterion

the process of speciation as well as to provide useful

of parsimony, which assumes the least number of cases

criteria for taxonomic classification (Cracraft, 1989; Fu-

of parallel evolution or character state reversal.

tuyma, 1986). Modem phylogenetic systematics, includ¬

In making taxonomic decisions in this volume we

ing cladistics, is based on the fact that various biological

have chosen to stress morphological variation in natu¬

characteristics evolve at different rates. All the mem¬

ral populations, life history traits, and reproductive

bers of a natural group should logically share certain

characters. This bias may be due partly to formal train¬

unique, derived traits, but they should also have in

ing, but it is also the result of our admitted fascination

common with related groups other, more conservative

with evolutionary processes in natural populations of

or ancestral traits. Phylogenetic species are irreducible

North

clusters of organisms distinguished from other such

uniquely amenable to such studies because they are so

groups by unique characteristics. Reproductive cohe¬

easy to mate and rear. The stability of Lepidoptera tax¬

sion is implicitly recognized as the process that gives

onomic nomenclature, especially that of the butterflies,

integrity to such clusters, but reproductive isolation is

has suffered from what many consider to be excessive

not invoked as a criterion to distinguish species. Phy¬

splitting of genera and naming of subspecies (Ehrlich

logenetic species and higher taxonomic groups are de¬

& Murphy, 1982; Murphy & Ehrlich, 1984). The outline

American silk

moths.

The

Satumiidae

are

fined in terms of ancestor-descendant lineages and are

of population genetic processes above is an attempt to

by definition monophyletic. Phylogenetic methods de¬ fine criteria to distinguish between ancestral and de¬

apply an evolutionary perspective to taxonomic ques¬ tions.

rived traits, quantify or encode variation in selected

We have not been able to apply a phylogenetic anal¬

characters, and then analyze the data to generate phy¬

ysis to evaluate species relationships or as a test of

logenetic trees or groupings. Systematists such as Mich-

monophyly within a group, although the large and

ener used similar methods (e.g., in his study of

highly variable genera Anisota and Hemileuca are obvi¬

satumiid phylogeny; Michener, 1952), but modem practice is more formal and less intuitive in that stan¬

ous candidates for such studies. It is interesting that none of the several new North American satumiid

dardized, computer-generated means are used to de¬

species named since Ferguson's monograph was pub¬

termine branching points in phylogenetic trees. Of

lished (1971, 1972) was described on the basis of phy¬

course, phylogenetic analysis can also use biochemical

logenetic study, multivariate analysis of morphology,

data as well as more traditional morphological charac¬

or allozyme variation or some other molecular genetics

ters.

technique. Satumiid taxonomy has fallen behind in

Problems arise, however, in determining which char¬

Lepidoptera taxonomy. Certainly the satumiid fauna,

acters are homologous; that is, which evolved, with

both regional and worldwide, deserves a modem phy¬

modification, from a character in a common ancestor.

logenetic reclassification, but such an effort is clearly

Very similar but genetically unrelated traits can evolve

outside the scope of this book.

by parallel evolution in two groups in response to sim¬ ilar selection pressures. The eye of the squid is very similar to the vertebrate eye, but it is obviously not a

Summary

homologous structure given the phylogeny of the two groups; in fact, it develops from a different tissue layer

Three important generalizations can be drawn from

in the embryo. Among related species, developmental genetic phe¬

the discussion in this chapter. First, species exist as pop¬

nomena can lead to misinterpretation regarding what

a variety of ways. No one population can typify the

is truly derived versus ancestral. Suites of seemingly

species because populations undergo independent evo¬

unrelated characters may be controlled in their expres¬

lutionary divergence. Second, while biogeographic pat¬

sion by specific developmental genes. The timing and

terns support the long-held concept of allopatric genetic

ulations, each of which may be genetically diverse in

effect of such genes may differ among closely related

divergence in many cases, strong selection can produce

species, causing reversals of apparent evolutionary

clinal variation in the absence of physical barriers. Sec-

38

Populations, Species, and Taxonomy

ondary intergradation resulting from rejoined popula¬

fail to reveal the true evolutionary picture. The degree

tions that diverged while they were separated is very

of morphological similarity is often poorly related to

difficult to distinguish from the primary intergradation

reproductive isolation, and many pairs of apparently

produced by selection gradients along clines. Third, ab¬

distinct taxa may nevertheless hybridize to varying ex¬

solute reproductive isolation is an impractical criterion

tents in nature or in the laboratory. The phylogenetic

in the taxonomy of many Lepidoptera. If the popula¬

species concept is an attempt to overcome the problems

tions have diverged at or near the species level, taxo¬

of defining and classifying taxa on the basis of repro¬

nomic decisions based on one or a few criteria often

ductive isolation.

Collecting

Success in field collecting depends largely on under¬

probably will not have access to the collection no matter

standing the biology of the species being sought, es¬

how far you have traveled to see it. A series of species

pecially on knowing its larval food plants and their

from a wide geographic area is not only a source of

habitats. Careful planning often determines the success

new collecting localities and dates, it is also an indicator

of a field trip. Do your research in the library and at

of the extent of phenotypic variation in the species.

the museum, correspond with other collectors, and then

Take notes from the information on the collecting la¬

design a trip based on the information you collect.

bels. Although reared specimens are often in better con¬

The best initial source of data may be the Season

dition, the emergence date on a reared specimen may

Summary published in the News of the Lepidopterists' So¬

not reflect the natural flight period and may be mis¬

ciety. The Season Summary includes yearly collecting

leading. Museum collections may have a separate lo¬

data (date, location, and collector) for hundreds of spe¬

cation for papered material, unidentified specimens,

cies of moths and butterflies, most from the New

and material recently curated but not incorporated into

World. If you need more data on a particular record,

the main collection. If appropriate, ask to examine each

you can call or write the collector. The addresses and

of these. Come prepared to take notes. We often use a

phone numbers (optional) of society members are pub¬

small hand-held tape recorder. It is faster than writing

lished every two years. Another good source is the

and allows you to include more information than you

annual index of publications that specialize on Lepi-

might normally take the trouble to record in written notes.

doptera. The index appears in the final issue of each year and is useful for finding articles about species and

In this era of environmental conservation and wild¬

topics of interest. Peruse the references cited in papers

life protection, it is important to consider the ethics of

and books for additional information.

field collecting and the accompanying legal implica¬

Visit the library and determine what journals or ref¬

tions. Many of us had our interest in Lepidoptera

erence books are available. College, university, and mu¬

piqued at an early age and fondly look back on sunny

seum libraries often have more technical publications

afternoons spent swinging a net in nearby fields or

than local city or county libraries. If your local library

woodlots. While those opportunities are still available,

does not have the publication you need, you may be

you should always be very conscious of the location

able to convince the person in charge of acquisitions to

and the species you are collecting.

start carrying it. If necessary, you can ask the librarian to borrow the publication through interlibrary loan.

In some areas, prime habitat has fallen victim to de¬ velopment or is under governmental protection, or ac¬

Museum collections are an excellent source of un¬

cess is restricted by private owners. Fieldwork in parks,

published collecting records. To gain access to most col¬

wildlife areas, and other types of public land may re¬

lections you will need to discuss your interest with the

quire permits for any type of collecting, and violators

curator of entomology or, if the collection is large, the

could be subject to severe penalties. Since ignorance of

curator of Lepidoptera. Explain what you are interested

the law is no excuse, it becomes the responsibility of

in doing and why, and then make an appointment to

the collector to determine the accessibility of a collect¬

see the collection. If the curator is not available, you

ing location. Contact the Department of Natural Re-

39

40

Collecting

sources in the state where you intend to collect and get

sist that copies of appropriate permits accompany pro¬

firm written answers on specific collecting locales. This

tected specimens when exchanging with others, and the

is especially important if the area is a park, preserve,

permits should be safely filed away.

sanctuary, or refuge. The property rights of landowners

Often, problems can be alleviated simply by taking

should be respected, and permission must always be

the time to obtain permits. Many park officials are gen¬

obtained to gain access to private property, once again,

uinely interested in helping researchers and can pro¬

preferably in writing. Many people, even those with no

vide

direct interest in natural history, are now very con¬

weather, and flora. Depending on the nature of the re¬

scious of conservation concerns and will not hesitate to report trespassers.

search, it may be necessary to collect a sizable series of individuals for statistical significance. If that is the case,

Even after you have obtained permission for general

carefully explain that need in the application process.

valuable

information

on

local

microhabitats,

collecting, you are still responsible for determining

With respect to field collecting, reasonable research

which species are collected. Some species may occur at

requests are usually granted but may require a detailed

low population levels, and every collector has an ethical

written proposal and field summary. Even though you

obligation to assess the need to actually take specimens.

have a permit, make every effort to conduct your activ¬

Careful field observations or photographs may negate

ities away from the general public, thereby reducing

the need to collect specimens, or a single female may

the

be taken and the resulting offspring reared in the lab.

intentioned, conservation-minded citizens. The collec¬

potential

for

misunderstandings

with

well-

Some species are formally recognized as threatened

tion and study of several of the species we discuss in

or endangered by the state or the federal government.

this book would not have been possible without per¬

Check with the state about the legal status of targeted

mits that allowed us to do fieldwork in the Santa Ana

Lepidoptera well in advance of your field trip. At the

National Wildlife Refuge (Hidalgo Co., Tex.), Laguna

present time no Satumiidae are protected under the En¬

Atascosa National Wildlife Refuge (Cameron Co., Tex.),

dangered Species Act of the United States, although

Sabal Palm Grove Sanctuary (Cameron Co., Tex.), Bent-

several Sphingicampa species would almost certainly

sen State Park (Hidalgo Co., Tex.), Huntsville State Park

qualify if the decision was based exclusively on their

(Walker Co., Tex.), Organ Pipe Cactus National Mon¬

extremely limited distributions in our region. This

ument (Pima Co., Ariz.), Schuk Toak District of the Pa-

brings up the broader philosophical issue of whether

pago Indian Reservation (Pima Co., Ariz.), Death

widely distributed species should be protected within

Valley National Monument (Inyo Co., Calif.), Lake

political boundaries that encompass only a small part

Hope State Park (Vinton Co., Ohio), Montague Barrens

of their geographic range. As an example, many species widespread in Mexico reach their northern limits in a

(Franklin Co., Mass.), and Bird's Hill Provincial Park (Winnipeg, Man.).

few counties in Arizona and Texas. Here they are

The importation of livestock is controlled by both

prized by collectors because of their restricted range in

federal and state regulations. Purchasing or returning

the United States. The same situation occurs within the

from foreign countries with live material without the

United States regarding Hemileuca main maia, a species

appropriate permits is a violation of U.S. Department

that is listed as threatened or endangered in several

of Agriculture regulations that are in place to prevent

New England states, although it can be extremely com¬

the introduction of pest species. Although most satur-

mon over much of the rest of its range, which extends

niids are unlikely to achieve pest status, many injurious

at least as far west as Texas. Regardless of your position

plants and animals have been introduced in the past.

on this debate, there is no justification for illegal or ir¬ responsible collecting. Trafficking in or possessing do¬

All inquiries should be directed to the U.S. Department of Agriculture.

mestic and foreign specimens illegally collected by

Do not ruin an otherwise enjoyable hobby or risk

others can also result in severe civil and criminal pen¬

your professional career by being overzealous. Obey all

alties. The importation of foreign specimens is con¬

local, state, federal, and foreign laws with respect to

trolled by the provisions of the Lacey Act, which

field collecting and building a collection. With these

requires that a permit from the country of origin, listing

warnings in mind, it should be obvious that choosing

species and number of individuals, accompany the specimens. This process ensures that the specimens

field collecting sites may require a great deal of advance preparation.

were collected legally. Inquiries and permits regarding

Once in the field it is important to be able to identify

threatened or endangered species should be directed to

larval food plants and the habitats that support them.

the U.S. Fish and Wildlife Service. Collectors should in¬

By recognizing suitable habitat the collector can more

Collecting

41

efficiently survey broad geographic areas and increase

mental "search image" of the targeted species. As dis¬

the potential for success. For example, it would be a

cussed in Chapter 1, birds appear to use a similar

waste of time to search for the various Coloradia species

search image to locate larvae. Focus your efforts on host

outside pine belts, or for Callosamia angulifera in areas where tulip tree does not grow. Although the distri¬

plants that are isolated or growing along the edge of a plant community. Later instars of some species, such as

bution of larval food plants may be the primary factor

Callosamia promethea and Antheraea polyphemus, eat part

restricting the range of many satumiid species, it is

of the leaf, then back down to the main branch and

probably never the only factor. Very few species inhabit

chew through the petiole until the remainder of the leaf

the entire range of their larval host plants. Soil type

drops to the ground. We believe this is an attempt by

appears to further restrict the distribution of the Color¬

the larvae to disguise leaf damage. This feeding pattern,

adia and Hemileuca species that pupate underground,

known as "stemming," usually occurs at the terminal

and species such as Rothschildia lebeau forbesi and Ani-

end of a branch and alerts the experienced collector to

sota consularis appear to be restricted by their inability

the presence of a large satumiid or sphingid larva.

to tolerate winter temperature extremes. There are un¬

Other species, such as Callosamia angulifera, almost

doubtedly a number of other, unidentified factors that

never eat the entire leaf or midvein. Half-eaten leaves

exclude satumiid species from habitats that appear suit¬

on a tulip tree almost certainly indicate feeding by an¬ gulifera.

able to us. The identification and impact of these factors on the various species offer almost unlimited oppor¬ tunities for study.

to begin searching for larvae by focusing on the

Depending on the habitat, it may be more productive

Even in known habitat for a given species, the prob¬

ground. In southern Michigan and much of the Great

ability of collecting success is dramatically increased by

Lakes region, for example, sassafras is preferred by Ea¬

determining which life stages are easiest to collect. Ova

cles imperialis. The tree usually grows in sandy soil and

on a small tree in full summer foliage are harder to

is often found growing in long rows adjacent to and

locate than a large cocoon attached to that same tree

overhanging roads. By searching the road for frass and

once it has dropped its leaves in the winter, even

then scanning the branches for feeding patterns, you

though the density of ova far exceeds that of the co¬

can greatly reduce your search time. Similar methods

coons spun by survivors. Searching for ova is almost

are successful with many western species.

always the least productive method of collecting, and

A few species are best collected as larvae by "beat¬

discoveries are often made fortuitously while searching

ing," a technique that involves placing a white back¬

for larvae. Anisota and Coloradia may occur at high den¬

ground (i.e., a sheet, lining paper, etc.) on the ground

sities, and the large clusters of ova they lay can occa¬

beneath a likely bush and then sharply striking the

sionally be found. Most Hemileuca overwinter as egg

branches in an attempt to dislodge larvae. We have

rings on or in close proximity to the host plant, and

been somewhat successful locating early-instar larvae

many of those plants drop their leaves in the winter,

of Saturnia albofasciata with this method, but the tech¬

which makes searching somewhat easier. We have had

nique is not routinely used.

success collecting ova of most Hemileuca species.

Occasionally the presence of leaf damage, frass, or

Larvae often feed gregariously or have characteristic

both indicates that a large larva is on a given plant, but

feeding habits that assist in locating them. Particularly

even diligent searching fails to uncover the culprit. The

in the early instars, gregarious larvae feed in large and

larva may be a nocturnal feeder that avoids the heat of

conspicuous clusters. The late-instar larvae of these spe¬ cies tend to disperse and frequently wander off the host

day by hiding in the center or at the base of the host plant. We often identify such plants during the day and

plant, making them more difficult to find. Gregarious

return at dawn, dusk, or nighttime to scan them with

feeding behavior is characteristic of all Hemileucinae

flashlights. Using this method and with an admitted

and the small Ceratocampinae (Anisota, Dryocampa),

degree of luck, we have found Sphingicampa blanchardi,

and collecting early-instar larvae is the most productive

Automeris io, Eacles oslari, and Citheronia sepulcralis.

method for obtaining this group.

Searching for larvae requires persistence and patience,

Many Satumiinae and the large Ceratocampinae

but it can be both a challenge and a pleasant diversion.

(Citheronia, Eacles, and Sphingicampa) feed as isolated in¬

Late-instar satumiid larvae suffer heavy losses to par-

dividuals in all instars and are more difficult to locate.

asitoids, and caterpillars should be collected in early

The best results are obtained by systematically search¬ ing the underside of the leaves, and success greatly im¬

instars to reduce the probability that they have been parasitized.

proves as the collector develops through experience a

Collecting underground pupae is difficult and not

42

Collecting

to coUect more than one species, it may be necessary to run the Ughts throughout the night. CoUecting at exist¬ ing Ughts on buildings just before dawn is often a more productive technique. Second, even within a single spe¬ cies, the range of response varies according to sex. The males of most Anisota and Callosamia are diurnal, and usually only females are taken at Ughts. Among other saturruid species, however, far fewer females are taken at Ughts than males. This should not automatically be interpreted as unresponsiveness on the part of females. We suspect that light placement has historically biased results in favor of coUecting males. Logic suggests that egg-laden females do not have the flight range of the more mobile males that seek them out, and females probably remain in areas of high host plant concentra¬ tions to increase their effectiveness in oviposition. Col¬ lectors routinely place portable Ughts in open areas in an attempt to maximize the effectiveness of the light, but this strategy may actuaUy reduce their chances of taking females. This interpretation is true with respect Figure 9. Collecting at a portable light, Santa Cruz County, Arizona

to at least one species in Pima Co., Arizona (T. Carr & JPT). During the early morning hours of 13 January 1990, the large floodUghts on a school in SeUs were checked and in excess of 100 male Hemileuca tricolor

very productive. Subterranean pupae are occasionally

were observed, but not a single female. The entire

excavated by random digging, and we occasionally find

schoolyard had been cleared of shrubbery, and the

Hemileuca pupae at the base of large clumps of grass

nearest larval host plant (Cercidium microphyllum) was

and among debris, but this method is time-consuming

several hundred yards away. We found a similar num¬

and yields very few pupae.

ber of H. tricolor adults within an hour sUghtly farther

The species that construct true cocoons use three

west at Quijotoa, under identical elevation and weather

main spinning strategies (see Pupation, Chapter 1). Sus¬

conditions, on a smaU store iUuminated by a single 60-

pended cocoons are fairly easy to locate once the leaves

watt incandescent bulb. The store was situated in the

of the host plant have dropped; cocoons attached

middle of a large concentration of the larval host plant,

lengthwise to branches or trunks tend to be less con¬

however, and there were almost as many females as

spicuous. With a little practice and a good search im¬

males at the storefront. Many of the females still carried

age, however, cocoons of both groups are fairly easy to

a complement of ova, and a desultory search turned up

locate, and collecting cocoons is actually the best

egg rings on several of the adjacent trees. These obser¬

method for obtaining livestock. Cocoons that drop to

vations suggest that the lack of females at the flood¬

the ground are most often found by chance, although

Ughts in Sells was a function of the distance from the

sifting through leaf Utter under isolated host plants oc¬

Ughts to suitable habitat, and not a general unrespon¬

casionally results in a few viable cocoons. Knowing the

siveness to light, since all other factors appeared to be

preference of Automeris species for protected spinning

the same at both locales. Such results suggest that port¬

sites has allowed us to collect cocoons of A. io and A.

able Ughts should be set up in close proximity to host plants if females are desired.

louisiana by systematically inspecting the underside of logs and wood debris. The most common way to sample a habitat is to col¬

The second method of taking adults exploits the at¬ traction of males to a caged, calling female, a process

lect adults at night. With the exception of the diurnal

explained in detail in Chapter 1, "Pheromone Mating

Hemileuca species, most satumiids are attracted to light,

System." If conditions are favorable, a large number of

and the results can be impressive (Figure 9). In addi¬

males will respond (Figure 10). Although setting out

tion, nearly aU females taken at Ughts have previously

calling females is the most effective method of survey¬

mated and will lay fertile ova. Two factors should be

ing a new locale or of collecting males in a known hab¬

considered when using Ughts to coUect adults. First,

itat, there are a few limitations to consider. Unlike Ught

each species has specific flight times. If you are trying

traps, which provide a sample of aU of the night-flying

Collecting

43

Figure 11. Tethered Antheraea polyphemus female (right) mating with a wild male

The cages into which the virgin females can be placed in the field range from simple coffee-can cages that al¬ low the female to mate through open mesh (T. A. Miller & Cooper, 1976), to portable funnel traps (Collins & Weast, 1961), to large walk-in cages (Stemburg & Waldbauer, 1969). The cages and traps protect the female and allow the collector to systematically sample a large number of males from a population. The traps have also proved extremely useful in mark-and-recapture studies of male dispersal, in studies of mating behavior and reproductive isolation, and in other population biology investigations (Collins, 1973, 1974; Collins & Figure 10. Wild Hyalophora males from the Sierra Nevada hybrid zone collected in a funnel trap baited with a virgin female

Tuskes, 1979; Stemburg & Waldbauer, 1969; Sweadner, 1937; Tuskes & Collins, 1981). Depending on their de¬ sign, some cages require continuous monitoring, and others need to be checked only periodically. If a coffeecan cage is used, only a single mating male will remain,

species present at a site, calling females generally at¬

and he may later fly away or be attacked by a bird. In

tract only males of the same species.

There are

contrast, funnel traps and walk-in cages confine the fe¬

exceptions, and the males of some genera will respond

male in a small cage so that she remains unmated and

to the female of any species if she is available during

continues to call during the entire flight period. Dozens

the proper time of the year and calls during the proper

of males can be collected without the need for contin¬

time of the day. The second consideration is the sea¬

uous monitoring. If pairings are desired, additional fe¬

sonal availability of virgin females. Pupae must be kept

males can be placed within the trap.

under conditions that closely duplicate those in nature

Another commonly employed method of attracting

so adults will emerge in synchrony with the wild pop¬

wild males involves tying out a virgin female in the

ulation. If captive females emerge before the natural

field without the protection of any type of cage. In this

flight period, they can be stored under humid condi¬

technique, a fine thread is tied around the female's

tions in a refrigerator for up to three weeks, and they

thorax between the forewings and hindwings or be¬

can be kept in an ice chest on collecting trips. Be

tween the abdomen and thorax. The female is then

warned, though, that the long-anticipated emergence of

hidden in a bush, and the other end of the thread is se¬

the most desirable females, whose nearest population

cured to the bush (Figure 11). The advantages of tying

is several hours away, almost always occurs on a hol¬

out are that the females do not have to be tended, and

iday weekend or during a previously planned family

a trapline of several females can easily be set out to

outing.

sample a large area. The disadvantage is that regard-

44

Collecting

less of the species involved, only a single male can be

should be checked as early as possible the following

taken with each female, and the mating male may not

morning.

always remain with her, making it difficult to tell if a

In spite of these limitations, calling females are the

mating has occurred. In addition, the potential exists

most effective way to obtain hard-to-get satumiid spe¬

for predation by ants, lizards, and birds before and

cies. Paired field tests with females of related taxa also

during mating. To minimize the risk of avian preda¬

offer the greatest opportunity to study mating biology

tion, females should be tied out at dusk, and the site

and reproductive isolation.

6

Rearing

Breeding Lepidoptera has long been a popular pas¬

encouraged to follow the proper procedures. In addi¬

time in Europe and Japan, and is increasingly so in

tion, species from other locales present a number of

North America. Collectors rear satumiids for the fas¬

rearing problems, perhaps the most common being

cination of observing and photographing the life

what to feed them.

stages, to obtain perfect specimens for their collections or to trade with other collectors, and for educational purposes. The satumiids are ideal subjects for both

Host Plants

laboratory and field research in ecology and popula¬ tion biology because they are large, they do not feed as

Some species (e.g., Callosamia angulifera and Agapema

adults, and they readily mate and oviposit in the lab¬

species) will probably not accept alternate host plants.

oratory. All breeders, however, regardless of their

Other species have regional larval host plant pref¬

goals, are faced with the same constraints and limita¬

erences, and the rearer should be aware of the natural

tions. We will discuss these factors in detail for each

food plants in the area where that particular stock

life stage following some general comments.

originated. For example, in Canada and the northern

First-time breeders should rear species that can be

border states, Actias luna is usually found on birch

collected locally. There are several advantages to this

(Betula), while throughout the rest of its range it feeds

approach. The availability of livestock is not dependent

primarily on members of the Juglandaceae. This dis¬

on the efforts of someone else. An appreciation of the

tinction is important: it has been our experience that

habitat gives the collector an understanding of the bi¬

the Juglandaceae-eating stock will not accept birch in

ology of the local species, and observing the moths in

captivity.

the field leads to a better understanding of the local

If the required food plant is not native to the area,

environment. Natural larval food plants in good con¬

look for locally accessible ornamental plantings. As an

dition are readily available. Local environmental con¬

example, sweetbay (Magnolia virginiana), the primary

ditions (e.g., humidity, temperature, light regimens,

food plant for Callosamia securifera, is not native to the

etc.) favor success with species that have evolved under

Midwest. It is occasionally used in commercial land¬

those conditions. In addition, access to the local wild

scaping, however, and in protected locations sweet bay

population allows the breeder to supplement labora¬

survives as far north as southern Michigan. Contact lo¬

tory stocks. This is especially important for researchers

cal colleges and universities as well; many of them

with long-term projects or breeders who maintain stock

have arboretums, greenhouses, and far-reaching botan¬

over several generations. Many states have regulations that restrict the impor¬

ical contacts. Such arrangements should always be

tation of normative insects from other regions of the

some food plants are not readily available. It may even

country. Federal law further restricts interstate ship¬

become necessary to rear some larvae on potted plants.

ment of live insects and the importation of live material

Regional nurseries can usually supply the necessary

from foreign countries. Permits can be obtained for le¬

seeds or plants. The most comprehensive list of native

gitimate research, however, and breeders are strongly

plant societies and nurseries is in the Wildflower Hand-

15

made before obtaining ova or larvae, however, since

46

Rearing

book published by Voyageur Press, Stillwater, Minne¬

temperature extremes should be avoided. We store

sota. Be sure to check the requirements for shipping

most ova in plastic dishes with tight-fitting tops and

live plants to your area before ordering. It should now

keep them out of direct sunlight to avoid lethal tem¬

be apparent that the rearing of some species may re¬

peratures. The plastic lid should also be removed for a

quire a great deal of planning and preparation.

short period each day to allow for the circulation of air

Fortunately, many satumiid species accept alternate

in the container. There is no need to add moisture to

hosts in captivity. When offering alternate hosts, al¬

ova of any North American species, and doing so may

ways try to use local members of the same plant gen¬

cause mold to grow on them. Additionally, be cautious

era used by the larvae in nature. The ornamental

about putting leaf material into the plastic container

buckthorns, Rhamnus frangula and R. cathartica, are ac¬

before the larvae hatch. We have put small amounts of

ceptable to the larvae of Agapema homogena. If a mem¬

host plant into the containers just before eclosion with¬

ber of the same genus is not available, substitute a

out any resulting difficulties; however, Gardiner (1982)

member of the same plant family.

reported significant losses of ova when plant material

The chemical

makeup of closely related plants may stimulate larval

was introduced into the plastic containers before the

feeding and make the substitute food plant easier to

larvae eclosed and suggested that carbon dioxide re¬

assimilate. Stone (1991) compiled a valuable list of lar¬

leased by the plants may have been the cause. As a

val food plants cited in the existing literature, but he

rule of thumb, when dealing with Ceratocampinae, Sa-

was unable to verify individual records. Unless stated

tumiinae, Automeris, and Coloradia ova, just patiently

otherwise, all the larval food plant records cited in this

watch and wait for them to hatch.

book are based on our personal observations or those

Most Hemileuca overwinter in the egg stage and re¬

of close associates we regard as knowledgeable and re¬ liable.

quire some degree of special attention. If the egg ring is not exposed to proper conditions, the ova may hatch

Even if acceptable ornamental host plants occur in

prematurely or the larvae may never eclose. While

your area, the timing of their availability may present

populations from farther south fly in September or Oc¬

a problem. Adults of many species from the Southeast

tober, an extremely cold-tolerant bog population of the

and Southwest fly early in the spring or late in the fall,

maia complex from Michigan's Upper Peninsula flies

and their larvae often become available before or after

as early as mid to late August, when the first frost can

foliage is available to breeders in other areas. Monitor

be expected. If egg rings from this population are re¬

potential host plants to determine when they come into

moved to southern Michigan in early September, when

leaf in the spring and when they drop their leaves in

temperatures can still be quite warm, they hatch and

the fall. We often force buds into leaf by bringing cut¬

the larvae eventually starve when the fall frosts kill the

tings indoors in order to feed first-instar larvae in the

host plant. Successful eclosion in the range caterpillar

spring, and we scour the countryside for the last green

(H. oliviae) is at least partially a function of rainfall and

leaves of fall to bring late-instar larvae to pupation in¬

relative humidity. Generally speaking, the egg rings of

doors. Plants in urban areas often come into leaf one or

Hemileuca (except those of hualapai and tricolor, which

two weeks earlier than their counterparts in rural areas.

do not overwinter) should be stored in cool, dry con¬

This may be just enough time to mean the difference between success or failure.

ditions. They should not be exposed to warm temper¬ atures and humidity until the next breeding season. If the adult pairing was not actually observed, then determining the fertility of ova is primarily a matter of

Ova

patience. The oviposition rate is an early indicator for

The ova of non-overwintering satumiids require very little care. Handling should be kept to a mini¬

Mated females tend to lay the bulk of their ova at the first opportunity. Infertile ova begin to shrink within a

mum, but the ova of most species are surprisingly re¬

week and by the end of the second week have almost

sistant to damage. Satumiid females readily oviposit

totally collapsed; ova containing embryos that fail to

when confined in a paper sack, and the clusters of

complete development turn dark but do not totally

eggs can simply be cut out of the sack. Always note

collapse. Although this distinction between fertility

the oviposition date when storing ova, and begin mon¬

and viability may be lost on the recreational breeder, it

determining whether or not mating actually occurred.

itoring them on a daily basis after three or four days.

is important to the researcher involved in hybridiza¬

Some species (e.g., Sphingicampa) may emerge in as lit¬

tion studies. Fertile ova may also show slight signs of

tle as five days. The development rate can be short¬

indentation, but they always maintain their general

ened by storing ova at higher temperatures, but

shape. Many species also give the breeder additional

Larvae

47

of the food plant can be misleading; plants that still look fresh may have lost their nutritive value. The var¬ ious pines (Pinus) are examples of this; regardless of the appearance of the needles, the food plant should be replaced every third day. It is important to remove all frass from the container and wipe it dry at least once a day to avoid the buildup of condensation and mold. The plastic container should never be placed in direct sunlight; a fatal increase in temperature can occur in just a few minutes. Rearing early-instar larvae in sealed containers prevents any loss to predators and wander¬ ing. On the negative side, container rearing requires constant maintenance and transferring of the larvae. The early-instar larvae of most species hold on to the food plant tenaciously, and attempts to forcibly remove them may lead to fatal injuries. It is best to cut around the larvae and transfer them along with the leaf or twig to a clean container. If a small larva wanders away and is located, it can be coaxed onto a leaf or transferred using a small artist's brush. Larvae are especially vul¬ Figure 12. Nylon mesh rearing sleeve on a maple tree

nerable to injury while molting and should not be han¬ dled at all during that time. A larva accidently removed from its silk molting pad should be transferred to a

clues regarding ova viability. The ova of all Cerato-

piece of muslin or cheesecloth, which usually offers an

campinae are clear initially and change color as larval

effective substitute holdfast.

development progresses. On the day before hatching,

Although larvae can be reared to maturity in sealed

the larva becomes clearly visible through the chorion

containers, this method becomes less desirable as the

of the egg. All Hemileucinae have a micropyle (the

larvae get larger. The increasing volume of frass ele¬

pore through which sperm enters) at the anterior end

vates the humidity in the airtight environment and

of the egg that turns darker than the rest of the cho¬

dramatically increases the potential for disease. In ad¬

rion if the ovum is fertile. This contrast is subtle in

dition, larvae reared under these conditions tend to

Hemileuca and Coloradia ova, but the micropyle of Au-

produce stunted adults. The second commonly used

tomeris eggs turns black. Fertility in the early develop¬

rearing method is "sleeving." A cylinder of fine-mesh

mental stages is more difficult to determine in the

netting is placed over a branch of the food plant, the

Satumiinae, and the breeder must simply monitor the

livestock is placed in the sleeve, and then both ends

ova for collapse.

are securely tied off (Figure 12). When possible, the sleeve should be examined and cleaned daily. Fre¬

Larvae

quently removing frass reduces the risk of disease. In addition, the potential for predation may be reduced, since we suspect that some predators and parasites use

So many variables can affect rearing larvae that suc¬

olfactory clues given off by the frass to locate the gen¬

cess is never a certainty, but a number of methods have proven largely successful. Many rearers start first-instar

eral area where larvae are feeding before initiating

larvae in airtight plastic containers. Some species, such

tages to sleeving larvae. It is an especially effective

as Antheraea polyphemus and Automeris, make their first

method for rearing local species, and it probably

meal of the eggshell, but many others (Hyalophora, Cal-

comes as close as possible to duplicating natural con¬

losamia, etc.) almost immediately begin feeding on

ditions while at the same time offering the larvae pro¬

leaves of the host plant. The food plant should be checked daily and replaced as needed. Some satumiid

tection from predators and parasites. Most late-instar

species are nocturnal feeders, and others are diurnal.

many into a sleeve increases the potential for disease.

Know each species' feeding pattern and replace food

As the larvae grow larger, the number of individuals

plants just before feeding time to maximize the fresh¬

per sleeve should be reduced. The second major ad¬

ness of the leaves. Also, remember that the appearance

vantage of sleeving is its convenience. Even the most

visual search patterns. There are a number of advan¬

satumiid larvae are solitary feeders, and crowding too

48

Rearing

dedicated breeder will not be able to attend sleeves

stinging spines. No matter how careful we are, it seems

every day as we recommend, and the ability to skip a day here and there keeps the task from becoming bur¬

that we are stung at least once during each changing session.

densome. Sleeving also reduces the number of times

Sleeves are not impervious to attack by ants and Pol-

that larvae must be handled, since the amount of foli¬

istes wasps, which may chew through the netting ma¬

age in a single sleeve is usually sufficient to allow

terial. Assassin bugs (Reduviidae) often swarm on

them to develop beyond the early instars. The final ad¬ vantage of sleeving involves the ability it gives the

sleeves and attack hapless larvae that come in contact with the netting.

breeder to manipulate the microenvironment. Within

Once species that pupate underground begin to wan¬

limits, placement of the sleeve can elevate or lower the

der, the sleeve should be checked daily and the pre-

temperature at which the larvae are reared. Eacles im-

pupal larvae should be removed to an appropriate

perialis pini being reared in sleeves in more southern

pupation site. This is especially true for Citheronia and

locales should always be placed in a shaded area on

Eacles, whose prepupal larvae are incredibly powerful

the north side of the tree. In contrast, larvae from

diggers and occasionally burrow right through the

southeastern Arizona being reared in northern states

sleeve. Sleeves containing these species must be care¬

should always be placed in sleeves on the south side

fully monitored and the prepupal larvae removed, or

of the tree in direct sunlight. Eupackardia calleta placed

the entire brood can be moved to a cage or other con¬

in sleeves with southern exposure mature two weeks

tainer. In spite of the few drawbacks to sleeving, it is

earlier than their sleeved siblings on the shaded side of

certainly the most widely used and effective larval rear¬ ing technique.

the same tree. Gaming two weeks is critical to rearing success in locales where fall comes early.

A third rearing alternative works best with seden¬

As is the case with all rearing techniques, there are a

tary species that feed on host plants that hold up well

few disadvantages to sleeving. No matter how well

as cut branches. These larvae can be successfully

camouflaged and hidden it is, once in a while a sleeve

reared indoors in cages or in small sleeves on cuttings

will fall victim to human vandalism. With that possi¬

in a free-standing bottle of water. The mouth of the

bility in mind, it is a good idea to split broods rather

bottle should always be plugged with a piece of foam

than risk putting all of the eggs in one basket (meant

rubber or cotton to prevent the larvae from wandering

to be interpreted quite literally!). In addition, it is a

down the stem and drowning, as most species seem to

good idea to surreptitiously mark each branch on

lack the instinct to avoid contact with water. Cut

which a sleeve has been placed. Vandals often remove

branches tend to lose water and can be misted period¬

the sleeve entirely, but, with luck, some larvae can be

ically. Misting is especially useful in regions with low

recovered on the marked branch. If the sleeves are

humidity, but it should never be done in closed con¬

placed in rural areas or on your own property there is

tainers. Indoor cages may actually be better than out¬

no problem in clipping off branches to transfer larvae

door sleeves for rearing desert species in regions with

to the new sleeve. Problems may arise when you ar¬

high humidity or during extended cold spells, espe¬

range to use a neighbor's tree or bush or a specialty

cially at the end of the growing season. We have suc¬

plant in an arboretum. Before "borrowing" these

cessfully

plants, carefully explain that, other than aesthetically,

cuttings of privet (Ligustrum), which remains green

late-season feeding will have little if any impact on the host plant.

reared

late

Rothschildia

lebeau forbesi

on

late into the fall, and we know of several species brought to maturity during late fall and in winter on

Changing sleeves can be time-consuming. Many spe¬ cies are difficult to locate even when they are confined

frozen cuttings of wild black cherry (Prunus serotina) (R. Weast, pers. comm.).

to a known branch, and it is amazing how many times

Some rearers use a method known as "setting out," in which ova or larvae are simply placed on a

a second check will reveal individuals missed during the first inspection. One method for searching is to lift

food plant and then periodically monitored. While this

the branch above eye level, thereby reducing the ef¬

maintenance-free technique may replicate natural con¬

fectiveness of the countershading of the larva and sil¬

ditions, larval wandering, predation, and parasitism

houetting it against the sky. Most late-instar Anisota

take a heavy toll. Results can be good on ornamental

and Automeris species routinely drop from the food

plantings in sterile shopping center parking lots. We

plant when disturbed, and the rearer should be pre¬

have had occasional success rearing Callosamia, Hyalo-

pared with a temporary collection container. Some lar¬

phora cecropia, and Antheraea polyphemus in this fashion,

vae, such as Automeris and Hemileuca species, have

but usually the losses are high. Since we can offer no

Pupae

49

width of antennae

origin and parentage of laboratory broods has become increasingly important in light of recent findings regarding the nature of genetic divergence among populations of a given species. In the past, insect phys¬ iologists often treated species in a "typological" man¬ ner, assuming that A. polyphemus, for example, would behave identically under experimental conditions, re¬ gardless of the source of the stock. We now know that various populations within a species differ in the un¬ derlying physiology of ecological adaptations such as their response to day length during development, their ability to feed on and metabolize various host plants, and even their mating behavior (see also Chapters 1 and 4). Both the supplier of stock and the laboratory that rears the stock should carefully document the ge¬ fourth abdominal segments

ographic origin and breeding pedigrees of their cul¬ tures.

Figure 13. Characters used to sex pupae of Hyalophora cecropia

Pupae explanation for our periodic successes, we view them

Many species spin their cocoons in folds of the

as aberrations and do not recommend setting out as a

sleeve. Automeris, Saturnia, and Actias cocoons are par¬

reliable rearing method. Normative species should

ticularly fragile, and great care is necessary in removing

never be set out.

them. Ideally, it is advisable not to handle newly spun

As satumiids became common subjects for research

cocoons for several weeks. Inverting a half-spun cocoon

in insect physiology and development, reliable methods

will cause the larva to improperly orient itself or to spin

for mass rearing the larvae had to be developed. Epi¬

an inverted inner cocoon (in species with double-

demic disease and the need for large quantities of suit¬

walled cocoons), making it impossible for the eclosing

able foliage for food are the two main problems encountered when large numbers of larvae are cultured

adult to escape. Clustered cocoons should be separated to facilitate later adult emergence.

in the laboratory. Artificial diets have been tried (Rid-

There are times when it may be advantageous to sex

diford, 1968), but placing large sleeves or cages on cul¬

pupae in anticipation of adult emergence. Some breed¬

tivated shrubs or small trees of the proper host plant is

ers claim that they can accurately determine sex by

a more reliable method (Taschenberg & Roelofs, 1970;

weight, because females are heavier than males. While

Telfer, 1967). Late-instar larvae can be sexed by exam¬

this method may give the breeder a general idea of the

ining the ventral surface of the eighth or ninth abdom¬

sex of an individual pupa, we prefer to examine the

inal segment with a hand lens; males have a single dark

pupae themselves. With the Satumiinae this requires

pit that is lacking in females. This technique is reliable

making a slit in the cocoon. If it becomes necessary to

for sexing Antheraea polyphemus, Eupackardia calleta, Cal-

sex Satumiinae pupae, we strongly suggest waiting un¬

losamia promethea, Hyalophora cecropia, and H. Columbia

til spring to slit the cocoons to avoid the risk of desic¬

gloveri, and may be advantageous if adults of only one

cation. Some species, such as those of the genera

sex are needed for research (T. A. Miller et al., 1977;

Antheraea and Hyalophora, can be reliably sexed by look¬

T. A. Miller & Machotka, 1980).

ing at the antennae on the pupal case; male antennae

Disease can be controlled by minimizing handling

are at least three times wider than those of the female

and avoiding rearing in containers; ova laid in paper

(Figure 13). The difference in antenna width is not al¬

bags can be set out directly in appropriate numbers into

ways a reliable character in Callosamia and Eupackardia

sleeves and allowed to develop and hatch under natu¬

species, however, and among Ceratocampinae pupae

ral conditions. Antibiotics are most successful for pre¬

the antennae are never a reliable indicator of the sex of

venting disease, but much less so for treating already

a pupa. An alternative that works with all satumiids

infected larvae (Riddiford, 1967). Finally, proper identification of the geographical

involves examining the abdominal segments. If the fourth segment below the one covered by the bottom

50

Rearing

of the wing case is intact, then the pupa is a male; if it

spray the pupae with water. We have had great success

is broken, notched, or marked in any way, the pupa is

using these techniques for overwintering cocoons and

a female (Figure 13). Admittedly, these characters can

subterranean pupae and synchronizing the emergence of the adults.

be difficult to interpret, but practice can yield reliable results (see Ehrlick et al., 1969; Mosher, 1914, 1916a,b; and Villiard, 1969, for more information about sexing satumiid pupae).

Adults

Many breeders experience significant losses during the pupal stage. The satumiines are fairly well pro¬

Satumiid adults have strong mating and oviposition

tected in their cocoons. Species that originated in the

instincts, and breeders usually experience no difficulty

North need to be subjected to freezing temperatures in

arranging pairings. Similar methods can be used for all

order to complete adult development. Breeders who

species. Females are compelled to call (release phero¬

live in cold climates can simply place the cocoons in a

mone) and almost always accept the first male that re¬

predator-proof cage outdoors. Breeders in warm cli¬

sponds, without any further courtship. Mated females

mates often refrigerate cocoons in plastic containers.

confined to a paper sack routinely begin laying eggs on

Unfortunately, frost-free refrigerators can desiccate the

the sides of the sack, even in the absence of host plant.

pupae, and spraying the cocoons to counteract drying

The need to oviposit extends to unmated females as

increases the risk of mold. There are no simple answers

well, and if pairing has not taken place in the first two

to this delicate balance, but we have found that a small

to four days (depending on the species), the female will

piece of dampened sponge is usually sufficient to main¬

begin to lay infertile ova. Males are capable of mating

tain an acceptable humidity level. The thin cocoons of

several times in captivity, and mark-and-recapture

Actias and Automeris offer far less protection from the

studies suggest that multiple matings also occur in na¬ ture.

weather and if kept outside should be covered with a layer of leaf litter.

The exploitation of calling females to attract wild

Storing subterranean pupae in northern locales is no

males is discussed in detail Chapter 5. It is not the tech¬

more difficult than overwintering cocoons outdoors.

nique of which we remind the reader here, but rather

Allow the prepupal larvae to burrow into a 5-gallon

its genetic implications. When rearing a species over

pail of sterilized potting soil and keep it under a pro¬

several generations, one can eliminate inbreeding and

tective roof for several weeks. (Sterilized potting soil

ensure that the laboratory population remains viable by

can be obtained from most nurseries and garden

mating wild males to laboratory-reared females. The

stores, and 5-gallon pails are often thrown away by

ease with which the pairings can be obtained and the

bakeries and ice cream stores.) Some pupae will prob¬ ably work their way back to the surface, and these

ability of a single male to fertilize several females offer great potential for further study.

should be covered with additional soil. The entire pail

Many breeders rely on cage matings, but just putting

can simply be stored for the winter in an unheated ga¬

adults of the opposite sex together in the same cage

rage or crawl space under the house where tempera¬

does not always guarantee success. In general, the

tures remain in the 0-5°C

Pupae can be

larger the moth, the larger the cage required. Large

examined in the fall, and dead and deformed pupae

moths such as Sarnia cynthia and Hyalcrphora cecropia

should be discarded and the healthy pupae re-covered

readily pair in very small cages, however, and many of

with fresh soil. In southern California we frequently

the ceratocampids frustrate us by failing to mate at all.

spray overwintering pupae with water. In cold cli¬

We suspect that more often than not success depends

range.

mates we never spray subterranean pupae with water

on the orientation of the female in the cage rather than

during the winter, but we usually replace the dried potting soil once each season.

the actual size of the cage. We have often watched Ea-

When spring arrives, place the cocoons in emergence

to the side of the cage and work their way to the top

cages and expose them to the natural weather condi¬

of the cage without ever encountering her. The number

tions. Dig up and examine subterranean pupae. Discard dead pupae and place the healthy pupae on top of the

of matings is increased if we design or manipulate the cage so that the female is at the top.

soil. The 5-gallon pails can now be converted to emer¬

The ability to mechanically manipulate pairing situ¬

gence chambers by inserting wire screening around the

ations also allows breeders to experiment with a num¬

inner wall of each pail and then placing the pail top on

ber of inter- and intrageneric hybrids. A number of

the screen. Keep the emergence cages out of direct sun¬

interesting combinations have been obtained by placing

light and rain in a protected area, and periodically

a calling female of one species in a cage and placing a

cles imperialis males flutter past a calling female clinging

Adults

51

calling female of a second species downwind in an ad¬

cess with this technique, we refer the reader to the

jacent cage with males of the first species. Crosses have

works by Carr and Peigler cited above. The known sa-

also been successfully obtained by hand-pairing (Carr,

tumiid crosses involving species from North America

1984; Peigler, 1977a). Since we have had very little suc¬

are presented in Appendix 2.

7

Silk Moths and Human Culture

Members of the family Satumiidae have been part of

larvae, collecting wild cocoons, spinning thread, and

human culture for several thousand years. Various sa-

manufacturing silk fabric are all parts of a cottage in¬

tumiid species and members of closely related families

dustry that provides supplemental income in many

have played an important role in human history as

countries in Europe, Africa, and Asia.

items of trade on several continents. The larvae and

Silk consists of a protein (fibroin) produced in glands

pupae are eaten even today, and valuable fabric is pro¬

that extend nearly the length of the larva. It is secreted

duced from their silk. Lepidoptera, including satumi-

as a viscous material by a pair of structures on the head

ids, had symbolic significance in many ancient cultures

of the larva called spinnerets, and it quickly dries in the

and were incorporated into their artworks and lore. To¬

air to form a long fiber. While spinning the cocoon,

day in the United States, the larvae of a few satumiids

some larvae add a gummy white substance called ser-

cause economic damage when their numbers reach pest

icin to the silk. This material is especially noticeable in

status in forests or rangelands, and larvae with urticat-

the cocoons of Rothschildia, Eupackardia, and Callosamia,

ing spines cause minor medical problems.

which tend to produce dangling cocoons, and the sericin may help bind the silk and smooth the cocoon. The Agapema and some Saturnia species use little sericin in

Silk

the construction of their meshlike cocoons. Some larvae spin an obvious opening in the cocoon

For millennia, silk has been associated with wealth

through which the adult exits, some construct an exit

and luxury. Silk has long been important in world com¬

valve but seal the exit with loose silk, and others, such

merce, and it helped link the East and the West in trade.

as Actias and Antheraea, produce a cocoon without an

The early overland trade route from Rome to China

obvious exit. In the latter two instances, the emerging

was called the Silk Road. For centuries, under penalty

adult splits open the pupal case and then secretes a

of death, the Chinese kept the secret of silk, until ap¬

silk-digesting liquid from the head. The adult often

proximately 300 a.d., when the Japanese acquired lar¬

wiggles in a circular motion, rubbing its head against

vae and the secret of silk production.

the silk. As the silk weakens, the adult is able to push

Commercial silk is produced by larvae of moths be¬

its head and front legs through the opening and then

longing to at least four families: Bombycidae, Satumi¬

pull itself out of the cocoon (see Pupation, Chapter 1).

idae, Lasiocampidae, and Notodontidae. Bombyx mori

The pupae produced in commercial silk operations are

(L.), a member of the Bombycidae, has been domesti¬

killed with boiling water to prevent them from hatch¬

cated in China for approximately 4000 years. It is esti¬ mated that in China alone there are 10 million silk

ing and damaging the silk during their exit from the cocoon.

farmers, and another half million are employed in silk

Currently, commercial silk is produced by three sa-

fabric production. In 1992, China produced more than

tumiid genera—Samia, Antheraea, and to a lesser extent

half of the world's silk from Bombyx and Antheraea (Sa¬

Attacus—all of which originated in Asia. The quality of

tumiidae). India also has a significant sericulture in¬

the silk is characteristic of the particular species of silk moth.

dustry, based on two species of Antheraea. Rearing 52

Silk

Moths as Food

53

Mulberry silk is produced by the well-known silk¬

per is most notable for the quality of Trouvelot's

worm, Bombyx mori, a species whose life history and

observations, illustrations, and conclusions. In Califor¬

physiology have been artificially altered over the cen¬

nia, efforts were also made to utilize the silk of Hyalo-

turies to serve the silk industry. The adult moths are

phora euryalus, but acquiring silk from the cocoon was

flightless and mate readily in confinement, having lost

impractical. Serious attempts at mulberry silk produc¬

the usual circadian rhythms of mating behavior. The

tion were made again around 1917 and 1928, but all

fine silk thread of Bombyx is easy to unwind from the

the efforts eventually failed (Essig, 1931). Samia cynthia,

cocoon and reel into fibers. Muga silk, produced by An-

a commercially important species, was imported to the

theraea assamensis (Westwood) in India, dates back at

northeastern United States in the 1860s. It is not clear if

least several centuries. The silk is a coarse golden

the interest in cynthia was part of a serious attempt at

brown or amber and is produced in the Assam region.

silk production or only a passing interest, but it re¬

Tasar silk comes from A. paphia (L.) (=A. mylitta

sulted in the introduction and eventual naturalization

(Drury)) in India and has been produced since approx¬

of Samia cynthia on the introduced tree-of-heaven (Ai-

imately 1590 B.c. The tusser (or tussah) silk moth, A.

lanthus altissima). Andrews (1869) provided notes on

pernyi (Guerin-Meneville), is from China and was first

rearing cynthia and extolled its virtues but did not in¬

used to produce silk between 206

In

dicate any commercial success with this species in the

Japan, A. yamamai (Guerin-Meneville), known as tensan,

United States. Trouvelot was optimistic about using

has been used to produce silk since at least 1000

a.d.

polyphemus, but Andrews doubted its economic value

Tasar silk is reeled or spun into thread by pulling loose

because he believed polyphemus to be single brooded,

silk fibers from the cocoon. Eri silk is produced by

whereas cynthia is capable of producing two broods.

b.c.

and 220

a.d.

Samia ricini (Boisduval) in India. The silk of S. cynthia (Drury) may be sold as eri silk but is also known as fagara silk. Eri silk is unreelable and must be spun (Peigler, 1993). Glossy silk gets its appearance from the shape and

Silk Moths as Food In many parts of the world humans exploit silk

texture of the fibers. The triangular fibers have a pris¬

moths as a food source. In the silk- producing countries

matic effect, and if the fibers are long and smooth, the

of Asia, the dried larvae and the pupae are eaten. In

material will appear shiny. The ways the thread is pro¬

Africa, the mature larvae of the satumiids Gonimbrasia

duced and the fabric is woven also influence the silk's texture.

belina (Westwood), Bunaea alcinoe (Stoll), Imbrasia ertli

Sericulture has been attempted many times in the

(Rebel), and Urota sinope (Westwood) are collected and sold live in the outdoor markets for human consump¬

United States. The first attempt, involving Bombyx

tion. They are eaten raw, dried, or powdered, or used

mori, took place in the early 1700s. By 1720 the Caroli-

as a garnish in stew (Pinhey, 1972). In the western

nas were granting land to settlers who agreed to plant

United States, the indigenous people of California and

100 mulberry trees per 10 acres. In 1732 a small silk¬

Oregon collected and consumed the prepupal larvae

reeling plant was established in Savannah, Georgia,

and pupae of Coloradia pandora (Aldrich, 1912, 1921).

and in 1739 more than 10,000 pounds of cocoons were

The Paiute Indians of California collected large num¬

reeled into thread (Leggett, 1949). In California, mul¬

bers of larvae by digging trenches around the bases of

berry culture was advocated as early as 1855, and the

pine trees, the host plant. Larvae descending in search

state legislature encouraged the production of silk by

of pupation sites were trapped in the trenches. The lar¬

offering $250 to anyone who started and maintained

vae were collected, mixed with hot soil, and left for

5000 mulberry trees, and a $300 bonus for each 100,000

about an hour, a process that dried and partly cooked

salable cocoons. By 1868 there were an estimated 4

them, then they were removed from the soil and dried

million mulberry trees in the state, and only two years

for a few additional days. The final product, called

later 12 million cocoons were produced. It soon be¬

pe-aggie by the Paiutes, is known by other tribes under

came evident, however, that silk production costs were

similar names. The dried larvae were most frequently

too high to compete with Asia and southern Europe.

used in stews. Aldrich (1921) stated that the Paiutes

Leopold Trouvelot, the French entomologist known

produced about 3000 pounds of pe-aggie just in the

for his accidental release of the gypsy moth, published

area of Mono Lake. The dried larvae he acquired in

an extensive paper (1868) on the biology of Antheraea

1911 were still in perfect condition in 1921, and he

polyphemus based on his attempt at commercial silk production with that species in the United States. Al¬

stated that their odor had improved as well (Aldrich,

though it implies some success at the venture, the pa¬

dians roasted and consumed pupae rather than dried

1921). Patterson (1929) observed that the Klamath In¬

54

Silk Moths and Human Culture

larvae. Sutton (1988) reviewed the collection, prepara¬

in Hopi weavings, as a symbol of fecundity. Satumiids

tion, and use of pandora larvae in more recent times

found in the historic lands of the Hopi and other

by the native inhabitants of Oregon, Nevada, and Cali¬ fornia.

Pueblo Indians include Hemileuca hera magnifica, H. griffini, H. nevadensis, H. neumoegeni, H. eglanterina, Co¬ loradia doris, C. luski, C. pandora, Antheraea oculea, and Hyalophora Columbia gloveri; many of these are day¬

Symbols in Art and Religion

flying species. The Navajos use the butterfly pattern as a symbol of

Peigler (1994) provided an excellent review of co¬ coon use by native African and North American cul¬

love, temptation, foolishness, and "moth madness," a

tures.

The indigenous people of Mexico and the

displays fainting, frenzy, spells, trembling, or seizures

southwestern United States have long made rattles out

(Capinera, 1993). A person with these symptoms is as¬

of the cocoons of Rothschildia. Hyalophora euryalus co¬

sumed to have come into contact with a moth. The

coons were used by California tribes to make ceremo¬

Navajo Mothway legend is about the butterfly people,

term the Navajos apply to any malady whose victim

nial hand rattles. In Arizona and Sonora, Mexico, the

who engaged in incest rather than marrying outsiders.

cocoons of Eupackardia calleta and Rothschildia cincta

This, in time, made the butterfly people go wild and

were also used as hand rattles. In Mexico, R. cincta, E.

become destructive. Moth madness is symbolized by

calleta, Antheraea montezuma, and Hyalophora Columbia

the tendency of moths to rush into flames.

gloveri cocoons, especially the first two, are used to make ankle rattles (Peigler, 1994). The latter two spe¬ cies have also been used for necklaces, and H. euryalus

Pests

cocoons have been incorporated into good-luck charms (Peigler, 1994). Moths and butterflies appear on pre¬

The larvae of many silk moths have stinging spines

historic and current pottery and in the weavings of

that can raise a painful welt. In the United States, the

various cultures from the American Southwest. A

larvae of Hemileuca, Automeris, Saturnia, and some

Hemileuca larva is clearly present in the pattern of

Coloradia are well known for their ability to inflict pain

Mimbres pottery (Capinera, 1993) that probably dates

on the unsuspecting passerby or careless collector. In

from 1100

Old pottery patterns of the Hopi, Zuni,

Houston, Texas, the larvae of Automeris io are some¬

and other groups also clearly show Lepidoptera. Much

times common on grass, shrubs, and hedges of thin¬

a.d.

of the older Hopi pottery dates from the polychrome

leaved privet, and gardeners and children are the most

period and from the ruins of Sikyatki (Fewkes, 1919).

common victims. The larvae of the range caterpillar,

The motif is called the butterfly pattern by archaeolo¬

Hemileuca oliviae, have reached pest status by damag¬

gists and anthropologists, even when it is actually a moth.

ing range grasses utilized by cattle (Ainslie, 1910; Watts & Everett, 1976). The urticating spines of the lar¬

Mimbres pots depict a butterfly at rest with the

vae may also injure the mouths of grazing livestock.

wings folded above its body (Fewkes, 1919), and a

Stinging larvae of A. io and H. eglanterina can be a nui¬

Zuni

wings, the proper type of antennae, and a curled pro¬

sance to agricultural workers, nurserymen, and the general public.

boscis (L. Frank & Francis, 1990), all details that indi¬

The scoli of stinging larvae may contain histamine,

polychrome

shows

a butterfly

with

striped

cate the artist's awareness of the animal's behavior and

histamine-releasing substances,

morphology. Although the potter may not have real¬

other proteins that cause cutaneous, neurologic, or car¬

ized the significance of these differences, they were of¬

diovascular symptoms (Rosen, 1990). A sting may

kinin

activators,

or

ten well depicted nevertheless. Lepidoptera depicted

cause an immediate localized reaction or, in some in¬

in Hopi pottery are drawn with thin, straight anten¬

stances, an allergic response. After the pain starts to

nae; some examples have a proboscis; others have

subside, erythema, swelling, and urticaria develop at

thick, curled antenna and lack a proboscis. Satumiids

the site and persist for hours or days, a reaction known

are the only large moths that lack a proboscis and

as Lepidoptera dermatitis or lepidopterism. A study at

have thick antennae. Many figures look like a moth at

the Regional Poison Center in Shreveport, Louisiana,

rest, with wings generally a solid color showing no

identified 112 cases of Lepidoptera dermatitis. The spe¬

identifying pattern but displayed lying flat and swept

cies most often involved were Hemileuca maia, Automeris

toward the rear. The pattern usually has the moth or

io (both satumiids), and larvae in the Megalopygidae

butterfly oriented toward the opening of the bowl, like

(Everson et al., 1990). Mild cases resolve spontaneously.

a moth attracted to a flame. A similar pattern appears

Ferguson (1972) reported that the long hairs that cover

Pests

the body of some tropical species cause irritation to the eyes and respiratory system. Only one species other than the range caterpillar causes cyclic but significant economic damage. In the western United States, the larvae of Coloradia have dev¬

55

astated vast areas of pine trees from California to Col¬ orado (Chamberlin, 1922; Tuskes, 1984; Wygant, 1941). Anisota, Antheraea, Citheronia, and Hyalcrphora have been reported as occasional pests in agricultural, forest, and residential settings.

A

Subfamily Ceratocampinae

This subfamily is characterized by the male antenna, which is quadripectinate for only the basal two-thirds and then simple to the end. The body is elongated and large relative to the wings, which are somewhat narrow and sphingiform. Species range in body mass from among the smallest satumiids to among the largest. The ova are large relative to other satumiids of comparable size and are translucent so that the developing embryo

Figure 14. Subterranean pupa of Eacles imperialis showing cremaster

can be seen within. Scoli in first-instar larvae are quite pronounced and typically forked. Mature larvae are of¬ ten covered with hairlike setae and often have dorsal

brown, and most species have prominent yellow or

thoracic scoli modified into hornlike processes. The

white markings. The forewings are elongated and

larvae pupate in underground chambers. The pupae

somewhat reminiscent of a sphinx moth. The presence

are typically spinose with a pronounced cremaster (Fig¬ ure 14).

hindwings are rounded and somewhat reduced in

In the United States and Canada the greatest number

size. The antennae of males are quadripectinate and

of species occur in the Southeast. Midsummer flight in

taper toward the end; females have simple filiform antennae.

warm, humid weather may be an adaptation related to the tropical affinities of the group; the southwestern

of discal spots varies from species to species. The

species are largely confined to the mountains of south¬

The large, yellowish ova are translucent and are usu¬ ally laid in groups of two to six on leaves of the host

eastern Arizona and fly during the summer monsoon

plant. Development of the larva is clearly visible

season. The wing patterns of adults typically resemble

through the eggshell. The newly emerged larvae of all

leaf litter, although some Anisota males are diurnal and appear to mimic Hymenoptera. Of the 27 genera and

species have disproportionately large dorsal scoli, hence the common name homed devils. They are

170 species in the New World, we recognize 23 species,

among the most spectacular Lepidoptera larvae in size

representing 6 genera (Citheronia, Eacles, Anisota, Dry-

and appearance; well-fed individuals can exceed 150

ocampa, Sphingicampa, and Adeloneivaia) in our area.

mm in length. All Citheronia undergo five larval instars. All species pupate in a subterranean chamber and over¬ winter in the pupal stage.

Genus Citheronia Htibner, [1819]

Citheronia is broadly distributed in the Americas, from the temperate regions of the northeastern United

Type species: Bombyx regalis Fabricius, 1793; designated by Grote & Robinson, 1866b

States, throughout Central America, and south through much of South America. Lemaire (1988) recognized 21

Members of the genus Citheronia are large, stout¬

species and several subspecies, most of which are Neo¬ tropical in distribution. Three species presently occur in

bodied moths. Adult coloration varies from orange to

the United States. Citheronia regalis and C. sepulcralis

59

60

Ceratocampinae

Distribution. The species is broadly distributed in heavily forested areas east of the Great Plains. Histor¬ ically, regalis was taken throughout much of the North¬ east. Although recent records are lacking from Rhode Island and Massachusetts, where the species previously was reported, regalis still occurs in parts of New York (R. Dirig, pers. comm.) and southern New Jersey (Worth et al., 1979). The species occurs throughout Ap¬ palachia and into the Ohio Valley, where it can be lo¬ cally common. It has recently been taken near Pittsford, Hillsdale Co., and Coldwater, Branch Co., in southern Michigan (SS, 1992, p. 23). The range extends through the lower Midwest and into eastern Kansas (Ferguson, 1971). Citheronia regalis is often encountered along the Atlantic Coast as far south as central Florida. Records extend westward from Florida through the Gulf States into eastern Texas. Map 1. Distribution of Citheronia regalis, C. sepulcralis, and C. splendens sinaloensis

Adult Diagnosis. The size and wing shape are the same in regalis and splendens sinaloensis, but there are several differences that immediately distinguish the two. The ground color of regalis is orange, and sinaloen¬

are found in heavily forested areas of the eastern

sis is reddish. Citheronia splendens sinaloensis is much

United States, and C. splendens sinaloensis occurs in

more prominently marked with off-white spots the en¬

southern Arizona. Holland (1903) reported a fourth

tire width of the postmedial area of the forewing than

species, identified as C. mexicana, from southern Ari¬

regalis, which is only sparingly marked with yellow

zona around the turn of the century. Ferguson (1971)

spots. The two species cannot be confused in the wild;

suggested that several old specimens identified as mex¬

regalis occurs in the eastern United States, and sinaloen¬

icana from Texas, New Mexico, and Cochise Co., Ari¬

sis is taken only in extreme southern Arizona and

zona, may be the product of fraudulent labeling, but

adjacent areas of Mexico.

Lemaire (1988) pointed out that while mexicana is an inhabitant of eastern Mexico, the closely related C. beledonon occurs along the west coast of northern Mexico. Since beledonon is taken in Sonora, Mexico, in associa¬ tion with several other satumiid species that extend their range into southern Arizona (Tuskes, 1985b), his¬ torical records of another Citheronia species should not be summarily dismissed.

Adult Variation. The maculation is similar in both sexes; however, the forewing of the male is narrower and more tapered at the apex. Forewing: male 55-62 mm; female 62-75 mm. Our experience indicates that regalis is extremely uni¬ form in appearance across its range. Aberrant speci¬ mens have been reared and have received "variety" names in the past, but natural individual variation ap¬

Citheronia regalis (Fabricius, 1793)

pears to be very rare.

Figures: Adults, Plate 7; Larva, Plate 1; Map 1 Type locality: America borealis (North America)

Adult Biology. Throughout most of its range from Michigan to Florida, regalis is a summer species that

General Comments. Citheronia regalis is probably best

emerges from late June through early August. In east¬

known for its spectacular larva, which was described

ern Texas, adults are on the wing from late August

in the literature almost 70 years before the adult was

through mid-September. Although J. R. Heitzman and

known. Sloane (1725) illustrated the last instar and

Heitzman (1987) stated that May-August records for

quite appropriately named it Eruca maxima cornuta. The

Missouri represent at least two annual generations, ma¬

"great homed catterpillar" [sic], later called the hickory

terial from Florida and Texas that we reared in the Mid¬

homed devil, was also illustrated by Catesby (1743).

west was univoltine.

Although impressive in its own right, the adult was not described by Fabricius until 1793.

Adults emerge during the late evening and remain quiescent until the following evening. Males become ac-

Citheronia regalis

61

Worth et al. (1979, 1982) found that the effectiveness of host plant assimilation varies from population to pop¬ ulation. A study of localized preferences in this species, with its broad array of natural host plants, would be an interesting topic for further investigation. Ova are usually laid singly or in groups of two or three on both surfaces of the leaf (leaflet) near the ter¬ minal end. Development is rapid, and larvae eclose within 6-10 days. As is the case with all Citheronia, the larva is visible through the eggshell just before hatching. The larvae are solitary feeders even in the early in¬ stars. In the first two instars the larvae rest fully ex¬ posed on the upper surface of the leaf (leaflet) with the head curled back on the tail and the scoli held close to the body (Figure 15). In this position the larva appears Figure 15. Second-instar larva of Citheronia regalis mimick¬ ing a bird dropping

to mimic a bird dropping, a defense mechanism shared with other members of the genus. In all instars the larva thrashes its head violently from side to side when dis¬ turbed.

five at dusk and are very strong fliers. Females call

It is hard to imagine a more spectacular larva. The

from approximately 2300 to 0200. Mated pairs remain

disproportionately large spines dominate its appear¬ ance in all instars. The mature larva can approach 150

in copula throughout the following day, and egg laying begins at dusk.

mm in length. The ground color is usually green,

Males are readily attracted to lights, but females are

brown, or a combination of those colors, with con¬

taken much less frequently. Old reports (Druce, 1882;

trasting black, white, or reddish markings. The late

Grote, 1886) of regalis adults responding to bait are

last-instar larva becomes a distinctive aqua blue. The

quite confusing and probably in error, since morpho¬

long thoracic horns are orange or reddish and are

logical studies indicate that satumiid mouthparts are nonfunctional.

tipped with varying amounts of black. Variability in ground color and markings is routinely observed

Citheronia regalis is sympatric with C. sepulcralis along most of the eastern seaboard and westward

iation in the larvae. The armature gives the larva an

where the latter species occurs. Our observations indi¬

intimidating appearance, and Villiard (1969) reported

among siblings. We have yet to find any regional var¬

cate that females of both species call at the same time.

that the scoli of regalis cause a severe sting. In our ex¬

Although we have noted seasonal variation in some

perience the scoli are not urticating, although careless

geographic populations, the lack of recognition re¬

handling of a last-instar larva may cause a spine to

sponse between regalis females and sepulcralis males in

pierce the tender skin on the back of the hand. The

captivity leads us to believe that reproductive isolation

pupa is stout, very smooth, and has a greatly reduced cremaster.

is probably achieved through effective pheromone dif¬ ferentiation.

Rearing Notes. Citheronia regalis can be fed a large Immature Stages. The larvae feed on a number of host

number of host plants in captivity with varying degrees

plants in nature. The most broadly utilized plant family

of success. In addition to the reported natural hosts,

is the Juglandaceae: hickories (Carya), pecan (C. illinoen-

privet (Ligustrum) and Prunus species have also been

sis), butternut (Juglans cinerea), and black walnut (/.

used. As we previously pointed out, most polyphagous

nigra) have all been reported as larval hosts. Sweet

species, including regalis, appear to have regional host

gum (Liquidambar styraciflua), persimmon (Diospyros

plant preferences that should be taken into account

virginiana), and the sumacs (Rhus) are common natural

whenever possible. The species is relatively free from disease in captivity and generally easy to rear.

host plants; less so are sourwood (Oxydendrum arboreum), ash (Fraxinus), sycamore (Platanus occidentalis),

We have experienced significant losses (20-25%)

and lilac (Syringa vulgaris). Citheronia regalis is occasion¬

during the prepupal transformation and have tried a

ally a pest on cultivated cotton (Gossypium) in Louisiana

number of methods to improve our results, including

and Florida (T. Powell, 1891; Riley, in Packard, 1905).

changing the consistency of the pupation medium (top-

62

Ceratocampinae

soil, peat, sand, and mixtures of those mediums) and

The maculation of sepulcralis does not vary signifi¬

controlling the humidity. We suspect that the failures

cantly either individually or regionally, but there is mi¬

are an artifact of rearing, despite our efforts, and doubt

nor individual variation in the amount of pink on the

that such large losses also occur in nature. We also have

hindwing. Specimens from the Deep South are half

experienced varying success in overwintering the pu¬

again as large as those from the rest of the range.

pae. Some seasons we have relatively high survival; in other seasons and under the same conditions we lose

Adult Biology. Citheronia sepulcralis produces a single

pupae to desiccation or mold. Adult emergences tend to be synchronized, and mat¬

brood throughout the northern part of its range. Spec¬

ings are relatively easy to achieve in cages. Mated fe¬

Atlantic States, and Appalachia from mid-June to late

males readily oviposit on the sides of a paper sack.

July. There are two emergence periods in the Carolinas:

imens have been captured in the Northeast, the Mid-

the spring brood emerges from late April to mid-June, and the summer brood from early August to midCitheronia sepulcralis Grote & Robinson, 1865 Figures: Adults, Plate 7; Larva, Plate 1; Map 1 Type locality: Andover, Massachusetts

September (Ferguson, 1971). Farther south, sepulcralis is probably also bivoltine, but the broad range of capture dates in Florida (March-October) makes it difficult to determine the number of annual generations with cer¬

ber of broad-leaved plant families, but sepulcralis is the

tainty. Adults emerge in the late morning. The males be¬

only species known to feed on pine (Pinus). Citheronia

come active at dusk of the first evening and are readily

sepulcralis also has a more divergent adult phenotype

attracted to light. They are among the strongest-flying

than any other member of the genus.

satumiids, in flight rather reminiscent of sphingids. Fe¬

General Comments. Citheronia larvae feed on a num¬

males call from late evening to early morning (2200Distribution. The species inhabits pine forests in coastal areas of the eastern United States. Citheronia se¬

0200). Mated pairs remain together until the following night, when oviposition begins.

pulcralis extends slightly farther north (to Norway, Ox¬ ford Co., Me.) and south (to Florida City, Dade Co.,

Immature Stages. Ova are laid singly or in groups of

Fla.) along the Atlantic Coast than regalis. Along the

two or three at the base of pine needles. Wild larvae

Gulf Coast, sepulcralis occurs at least as far west as

have been collected on pitch pine (Pinus rigida) (Horn,

Abita Springs, St. Tammany Par., Louisiana (V. Brou,

1969), eastern white pine (P. strobus), and Caribbean

pers. comm.). Lemaire (1988) suggested that sepulcralis

pine (P. caribaea) (Ferguson, 1971). The ova take 7-10

occurs in eastern Texas but did not offer specific rec¬

days to hatch, and the embryo is visible through the

ords to support that range extension. Inland, sepulcralis

eggshell. The larvae are solitary feeders in all stages.

occurs sporadically throughout the Appalachian region

Although sepulcralis is an impressive larva, its spines

of southeastern Ohio, West Virginia, eastern Kentucky,

are not as prominent as those of most Citheronia. As

and eastern Tennessee. It is considered uncommon to

with the adults, regional size variation in last-instar

rare throughout much of its range but can be common

larvae can be significant; larvae from the Appalachian

in southeastern Louisiana and throughout Florida.

region are 70-80 mm long; those from Florida are 90110 mm. Color contrast is reduced in sepulcralis, and

Adult Diagnosis. The wing shape is typical of the ge¬

the larvae's cryptic black and brown markings make

nus. Except for a dark discal spot, however, the fore¬

them blend with the pine branches. We have not ob¬

wings of sepulcralis are plain gray-brown and lack the

served significant individual larval variation, and ma¬

yellow or orange markings found on all other Cither¬

terial from West Virginia, North Carolina, and Florida

onia, and this character distinguishes sepulcralis from

does not show any regional variation in general ap¬

the other species. It may be that this plainness makes

pearance. The smooth pupa is elongated, and its broad cre¬

sepulcralis cryptic in the pine forests it inhabits.

master is shorter than that of regalis. Loose soil is ap¬ Adult Variation. Sexual differences in maculation are

parently required for successful pupation. In bivoltine

minimal in sepulcralis, although females may be almost

populations, midsummer pupation lasts only a few

twice as large as males. Females also have broader and

weeks.

more rounded forewings than males, and more pink on the hindwings. Forewing: male 34-42 mm; female 4560 mm.

Rearing Notes. Securing livestock of sepulcralis can be difficult, but once ova are obtained the species is very

Citheronia splendens sinaloensis

63

easy to rear in captivity. The larvae accept most native

little variation in forewing pattern except in the extent

and introduced pines. They appear resistant to disease

of the cream-colored markings through the antemedial

and, unlike regalis, readily pupate. Matings in cages can

area. The hindwing shows more variation than the fore¬

be difficult to obtain because males beat themselves

wing. Some specimens exhibit diffused white patches

into a flightless condition if females are not available

through the dark gray submarginal area. The basal area

the first night. Mated females readily oviposit in paper sacks in captivity.

of the hindwing can be cream or dark gray. Forewing:

Citheronia splendens sinaloensis Hoffmann, 1942b

male 48-56 mm, avg. 53 mm; female 59-70 mm, avg. 64 mm. Adult Biology. Adults have been taken at light from

Figures: Adults, Plate 7; Larva, Plate 1; Map 1

early July to the second week of August, with peak

Type locality: Sierra Madre, Sinaloa, Mexico

emergence in late July. Males are usually attracted to lights after 2300 and come sporadically until just before

General Comments. Citheronia splendens sinaloensis was

dawn. Females are far less commonly attracted to

relatively unknown in the United States until the early

lights. Adults eclose between 2100 and 2300. We ob¬

1970s, when Ferguson (1971) published color illustra¬

served a newly emerged female travel at least 15 feet

tions. Since that time much has been learned about its

across the ground and climb several feet up a tree be¬

distribution and larval food plant preferences in Ari¬

fore coming to rest on a small branch. Wing expansion

zona. Although slightly smaller than the eastern spe¬

began after about 10 minutes and required 35 minutes;

cies, Citheronia regalis, it is an equally attractive moth

another hour passed before the wings were hardened

and the only member of the genus known to occur in

and folded over the back. Mating occurs between 0100

Arizona. Citheronia beledonon occurs just to the south in

and 0330, and the pair remains together until early eve¬ ning of the next day.

Sonora, Mexico. Although beledonon was reported from Arizona (as mexicana) before the turn of the century, there are no confirmed U.S. records.

Immature Stages. Larvae are most commonly found on wild cotton (Gossypium thurberi) or manzanita (Arc-

Distribution. This is a Mexican species whose north¬

tostaphylos pungens) during late August, but they have

ern limit extends into extreme southern Arizona. In Ar¬

also been collected on New Mexico evergreen sumac

izona, sinaloensis has been taken from the Baboquivari

(Rhus choriophylla) and squawbush (Rhus

Mountains of Pima Co., east through Santa Cruz and

Some populations appear to be host specific and utilize

southern Cochise Cos., to Guadalupe Canyon in the Pe-

only one food plant even though others are present. In

loncillo Mountains, just a few miles from the ArizonaNew Mexico border. Adults and larvae are associated

the Huachuca Mountains, for example, sinaloensis eats manzanita, but wild cotton is the preferred host in the

with desert arroyos containing wild cotton and hillsides

Santa Rita Mountains. The light yellow ova measure

where manzanita is present.

about 2 mm and are deposited on both surfaces of the

trilobata).

Adult Diagnosis. Citheronia splendens sinaloensis most

leaf, either singly or in groups of up to four. Earlyinstar larvae are black with a reddish orange midbody

resembles C. beledonon, which Ferguson (1971) illus¬

band. The larva rests on the upper surface of the leaf

trated as C. mexicana. Both sinaloensis and beledonon oc¬

curled over in a J shape and resembles a bird dropping,

cur in Sonora, and it is possible that beledonon may on

just as regalis does (Figure 15). The early instars feed

occasion stray into southeastern Arizona. Citheronia be¬

mostly in the evening. As the larva matures, it rests on

ledonon has a yellow-and-brown thorax, the wings are

the petiole of the leaf or stem and feeds sporadically

brown with yellow markings, and there is a thin yellow

throughout the day. There are five instars, and devel¬

submarginal line on the forewing. The thorax of sinal¬

opment is rapid. In September the larva leaves the plant

oensis is white and dark red, the wings are dark gray

and burrows into the ground, where it constructs a pu¬

with white markings, and no submarginal line is pres¬

pation chamber. There is only one generation per year.

ent on the forewing. Citheronia splendens sinaloensis is

The immature stages and biology of sinaloensis were de¬ scribed by Tuskes (1986b).

the larger of the two species.

Mature larvae of sinaloensis and beledonon are easily Adult Variation. The forewing markings are similar in

distinguished. The former have a purplish brown

both sexes, but females' wings are broader and less

ground color; the dorsal and dorsolateral thoracic scoli

pointed,

the

are light brown at the base with black tips; there is a

hindwing are reduced to small patches. Males exhibit

trace of a cream-colored abdominal subspiracular line;

and

the

cream-colored markings

on

64

Ceratocampinae

and the ventral surface is brownish black. Citheronia be-

larvae. All the Eacles have five larval instars, and all

ledonon occurs in Sonora, Mexico, and has been re¬

overwinter as pupae in subterranean chambers. The

ported from Arizona. The mature larva of beledonon has

pupae are spinose and have fairly long cremasters.

a dark brown to black ground color and a prominent

Ferguson (1971) recognized four taxa from North

light yellow subspiracular line that extends the length

America: imperialis imperialis, imperialis nobilis, imperialis

of the abdomen; the dorsal and dorsolateral thoracic

pini, and oslari. Lemaire (1988) recognized the same four

scoli are light pink at the base with black tips. We have

taxa but relegated oslari to subspecies status under im¬

reared beledonon on wild cotton, one of the host plants

perialis. We recognize only three taxa: imperialis imperi¬

commonly used by sinaloensis in Arizona.

alis, imperialis pini, and oslari. We discuss our reasons for this in the species and subspecies treatments.

Rearing Notes. In some broods, larvae established on one host plant become reluctant to feed on other host species. Larvae transferred from wild cotton to man-

Eacles imperialis imperialis (Drury, 1773)

zanita or from Brazilian pepper tree (Schinus terebinthifolius) to wild cotton may refuse to feed or fail to achieve the size of wild specimens. In addition to the natural host plants, we have reared larvae on black and English walnuts (Juglans regia), Brazilian pepper tree,

Figures: Adults, Plate 8; Larva, Plate 1; Map 2 Type locality: New York Synonymies: Bombyx didyma Palisot de Beauvois, 1805

Eacles imperialis var. nobilis Neumoegen,

1891b,

REVISED SYNONYMY

laurel-leaf sumac (Rhus laurina), and sweet gum (Liquidambar styraciflua). Prepupal larvae should be placed

General Comments. Regional variation and polymor¬

in a deep container with at least 6 inches of relatively

phism of imperialis adults have led to the naming of

dry potting soil. Pupae should not be exposed to freez¬

several forms and to different opinions of the appro¬

ing temperatures during the winter. Beginning in June,

priate relationships among them. The name didyma has

sprinkle the pupae with water two or three times a week.

long been associated with adults whose wings are suf¬ fused with purple-brown at their outer margins. This form (Plate 8, no. 2) tends to be less frequently encoun¬ tered in the North, where yellow imperialis imperialis

Genus Eacles Hubner, 1819

(Plate 8, no. 3) predominates. Rearing of broods from West Virginia and Kentucky has shown that both forms

Type species: Phalaena imperialis Drury, 1773; designated by Grote & Robinson, 1866b

can be obtained from a single female (T. Carr, pers. comm.). Farther south, didyma is the dominant form, although yellow imperialis imperialis can also be taken

The large, stout-bodied moths of the genus Eacles are

in Louisiana, Texas, and Florida. These observations

primarily Neotropical in distribution. Lemaire (1988)

support the view of Ferguson (1971) and Lemaire (1988)

recognized 17 species and several subspecies ranging

that didyma is a color morph without taxonomic stand¬

from southern Canada to northern Argentina. Eacles is

ing. The status of the polymorphic Texas material has

the most widely distributed satumiid genus in the Americas.

been slightly more contested. Influenced by the pres¬

The genus contains some of the largest Satumiidae

urrected imperialis nobilis (Plate 8, nos. 4, 5). Lemaire

in the world; the wingspan of E. penelope reaches 185

(1988) questioned the validity of nobilis and maintained

ence of suffused morphs in Texas, Ferguson (1971) res¬

mm. The species are mostly yellow or brown, and all

that equal numbers of yellow imperialis imperialis, inter¬

have discal spots on both wings. Some species are poly¬

mediate forms, and fully suffused forms occur in these

morphic and polytypic. The degree of sexual dimor¬

populations. When we collected in Waller and Walker

phism varies from species to species. The wings are

Cos., Texas, we found the yellow form by far the most

broader in Eacles than in Citheronia, a characteristic

common; suffused adults represented only a small part

more evident in males than females. Males have quad-

of our sample. We believe that selective collecting of

ripectinate antennae that become simple at the apex;

the suffused morph may have skewed the samples

females have simple ciliate antennae.

available for examination. Vernon Brou (pers. comm.)

The known larvae have unusually long scoli in the

has also taken all three morphs at the Red Dirt Wildlife

early instars, although these become short and broad

Refuge, Natchitoches Par., in central Louisiana. Since

in later instars. The most diagnostic character, however,

nobilis appears to be one morph in a polymorphism sys¬

is the long, fine secondary hairs that cover last-instar

tem that has no reported genitalic or biological differ-

Eacles imperialis imperialis

65

margin and the antemedial area of the forewing that are usually lacking in females. In didyma, however, the outer wing margins of both wings are prominently marked in both sexes. Forewing: male 47-59 mm; fe¬

W

male 58-68 mm. Most of the variation between imperi¬ alis imperialis populations has already been addressed. As a broad generalization, the characters represented by the various forms tend to be regional, but examples of each can be found in most populations. Individual variation is most apparent in the Texas and Louisiana populations, where adults can vary from

Eacles imperialis imperialis \

A—L

\

distinctly marked yellow forms to obscurely marked and highly suffused purplish brown forms. Just as in¬ teresting is the presence or absence of postmedial lines

Eacles imperialis phn

\

[

-

on the ventral surface of both wings: irrespective of sex or geographical form, the lines can be completely lack¬ ing, partially developed, or strongly developed.

Eacles oslari

Map 2. Distribution of Eacles imperialis imperialis, E. imper¬ ialis pini, and E. oslari

Adult Biology. Eacles imperialis imperialis is a summer species. Adults emerge in New England and the Great Lakes region from mid-June through early August.

ences, it seems inadvisable to maintain nobilis as a

Based on capture dates of wild specimens and reared

subspecies, and we reduce it here to synonymy with imperialis imperialis.

material, we have found populations from at least as far south as Virginia and Kentucky to be clearly univoltine. Multiple generations have been reported far¬

Distribution. Nominate imperialis occurs primarily in

ther south and to the west (Covell, 1984; Ferguson,

the deciduous forests east of the Great Plains, but it has

1971; J. R. Heitzman & Heitzman, 1987). Heitzman and

disappeared from many urbanized areas in the North¬

Heitzman (1987) based their suggestion that two broods

east (Ferguson, 1971; Holden, 1992). The northern limit

occur in Missouri on the fact that capture dates range

appears to be near Naples, Cumberland Co., in south¬

from May through August. Ferguson (1971) identified

ern Maine (Patch, 1908). Westward, the species occurs

two broods in coastal South Carolina: the first flies from

in southern New York, the lower Niagara peninsula of

mid-May through mid-July, and the second from late

Ontario, Isabella Co. in central Michigan (Central Mich¬

July through mid-September. In the Deep South, imper¬

igan University collection), southwestern Wisconsin (SS, 1988, p. 34), and central Iowa (R. Weast, pers.

ialis imperialis flies from late July through late Septem¬ ber in Texas (Ferguson, 1971; PMT), and from April

comm.). At the edge of the Great Plains imperialis im¬

through October in Louisiana (V. Brou, pers. comm.).

perialis has been taken in eastern Nebraska (SS, 1980, p.

Kimball (1965) reported “a few from April through

18) and south through Missouri, Arkansas, and into

July" in Florida, but more from August through early

central Texas at least as far as Kerrville, Kerr Co. (Ken¬

November. Material we reared from Iowa, Texas, and

dall & Kendall, 1971). Brou (pers. comm.) reported that

Florida produced only single extended generations. We

the species is extremely common in southeastern Lou¬

believe that early and late emergence in conjunction

isiana. Nominate imperialis is also common in penin¬

with scattered sampling over several seasons may give

sular Florida and has been taken as far south as Big

the appearance of bivoltine populations, but we think

Pine Key (Rutkowski, 1971).

these records probably represent a single extended gen¬ eration.

Adult Diagnosis. The differences that distinguish im¬

Adults emerge in the hours immediately preceding

perialis imperialis from imperialis pini and oslari are dis¬

dawn and remain quiescent until the following night. We have observed females calling in the early morning

cussed under the latter taxa.

(0100-0300). The males are very strong fliers and rap¬ Adult Variation. Most imperialis forms show well-

idly approach calling females. Mated pairs may remain

developed sexual dimorphism. Yellow imperialis males

in copula until the next evening, but they often separate at the slightest provocation. Egg laying begins at dusk.

have prominent purplish patches along the outer wing

66

Ceratocampinae

and ova are laid singly or in small clusters of two to

ture and in captivity. This species should not be

five on both surfaces of the leaves of the host plant.

crowded since it is prone to disease. The larvae need loose soil in which to pupate and should be left undis¬

Immature Stages. The bright yellow ova are as large

turbed throughout the winter. Adults are reluctant to

as those of Citheronia regalis and take approximately

mate in cages, and a very large cage is usually required

two weeks to hatch. The developing larva can be seen

for successful mating. Mated females oviposit readily in captivity.

through the chorion of the egg just before eclosion. The early instars have exaggerated thoracic and caudal spines, which are proportionately reduced in later in¬ stars. Even in the early stages the larvae are solitary feeders, but the female's egg-laying pattern makes it fairly common to find several larvae feeding in close proximity.

Eacles imperialis pini Michener, 1950 Figures: Adults, Plates 7, 8; Larva, Plate 1; Map 2 Type locality: Cheboygan, Michigan

The species accepts not only a number of deciduous

General Comments. Although all previous works have

trees and shrubs but also several conifers. It would be

treated pini as a subspecies of imperialis (Ferguson, 1971;

pointless to list all the recorded natural hosts (see Stone,

Lemaire, 1988; Michener, 1950), Ferguson (1971) stated

1991), but pine (Pinus), oak (Quercus), box elder (Acer

that this northern taxon may represent a full species.

negundo) and other maples, sweet gum (Licjuidambar

He indicated that pini can always be separated from

styraciflua), and sassafras (Sassafras albidum) are among the most frequently reported.

nominate imperialis with confidence based on its north¬ ern distribution, adult characteristics, and exclusive ac¬

The last-instar larvae have a pair of enlarged thoracic

ceptance of conifers, but he hesitated to elevate pini to

horns and a middorsal horn, but these scoli are not as

species status without more knowledge about the tran¬

large as those on most Citheronia species. Although usu¬ ally lacking, there may be remnant rows of dorsal and

sition between the two taxa. The discovery of addi¬ tional material from Michigan and New York that

dorsolateral scoli on the abdominal segments. Charac¬

could be interpreted as intermediate combined with re¬

teristic of the genus, the larvae are covered with long,

cent hybridization results indicate that pini should be treated as a subspecies of imperialis.

fine, white or light brown hair. Eacles imperialis imperi¬ als also has prominent yellow spiracles encircled in dark blue. The impressive last instar is 95-115 mm long.

Distribution. Eacles imperialis pini occurs in pine for¬ ests across much of the northern Great Lakes Basin. In

Although they are not as variable as the adults, lastinstar larvae do exhibit color morphs and some varia¬

region near Montreal, Quebec. Records for the subspe¬

tion in armature. All populations have larvae that vary

cies continue across southern Quebec, through Sud¬

from green to brown, but dark morphs predominate in

bury, Ontario, and west along the north shore of Lake

most areas. Based on casual observations, we have not

Huron to the area of Sault St. Marie, Ontario. An ex¬

Canada, pini has been taken in the St. Lawrence River

been able to correlate these larval color morphs with

treme range extension based on a single specimen

specific adult forms. As previously mentioned, the ab¬

from the western edge of Lake Superior near Thunder

dominal armature of most individuals is greatly re¬ duced or absent, but Dominick (1972) provided an

Bay, Ontario, requires further investigation (Ferguson, 1971).

excellent photograph of a last-instar larva from South Carolina with fairly well developed dorsal and dorso¬

In the United States, pini occurs across the northern third of Michigan's Lower Peninsula. Michener (1950)

lateral scoli on the abdominal segments. The color of

reported a single adult taken near West Fort Ann,

the armature also seems to be variable; green larvae

Washington Co., New York. Ferguson (1971) viewed

usually have yellow scoli, and brownish larvae usually have darker scoli.

the occurrence of pini in upstate New York with skep¬

The large pupa is spinose with an exaggerated bifur¬ cate cremaster (Figure 14). The pupa is very active when handled, which makes it easy to determine the viability of overwintering material.

ticism, but we offer additional data from the region. A review of the old literature turned up what may be a second pini record from that area. Packard (1905), in comparing a larval variety from Brant (as "Brandt") Lake with Brooklyn imperialis imperialis, stated that the northern larva had longer and more prominent spines,

Rearing Notes. As previously indicated, imperialis im¬ perialis accepts a broad array of host plants, both in na¬

which were white. This brief description accurately de¬ scribes all the pini we have reared, and Brant Lake

Eacles imperialis pini

(Warren Co.) is very near West Fort Ann. In addition, we examined two pitii-like specimens in the State Mu¬

67

ilar intermediate specimens collected near Pittsburgh, Pennsylvania.

seum of New York at Albany. Howard Romack, Jr. (pers. comm.) advised us that pitii was encountered reg¬

Adult

Biology. The

subspecies

pini

is

univoltine

ularly in Cambridge, Washington Co., during the 1950s.

throughout its range. Although the records indicate

Agricultural development has eliminated many of the

that adults may eclose from mid-June to early August,

pine forests, however, and the subspecies has not been

most begin flying in early July. The adult biology of

recently collected in the area. In addition to these New

pini is otherwise very similar to that of imperialis imper¬

York records, there is an old specimen from Burlington,

ialis. Adults emerge in the early morning and wait until

Chittenden Co., Vermont, in the University of Vermont collection (J. Hedbor, pers. comm.).

males begin calling after midnight (0001-0230), and

the following evening to initiate mating activity. Fe¬ mated pairs often remain together until the next eve¬

Adult Diagnosis. The smaller size of Eacles imperialis pini, its tendency toward a heavier sprinkling of purple

ning. Egg laying begins at dusk and occurs as in im¬ perialis imperialis.

to black dots on both wings, and the well-defined post-

In spite of having mentioned the possibility of a

medial lines on the ventral surface of both wings usu¬

blend zone in Ontario, Ferguson (1971) inferred that

ally are enough to distinguish it from nominate imperialis.

pini and imperialis imperialis are allopatric. Our initial impression after examining major collections supported the notion of allopatric distribution in Michigan: pini in

Adult Variation. As is the case with nominate imper¬

the north, imperialis imperialis in the south, and no Eacles

ialis, sexual dimorphism is quite evident in pini. Most

at all in the middle of the state. While searching

males have strong purple shading along the outer wing

through student collections at Central Michigan Uni¬ versity, however, we found a female taken in Isabella

margin and basal area of the forewing that is lack¬ ing in females. Forewing: male 42-48 mm; female 4754 mm.

previously reported range limits for pini and imperialis

The maculation of all the pini females we have ex¬

imperialis. The discovery of this specimen suggests that

amined generally resembles that of yellow imperialis im¬

the lack of Eacles records from central Michigan may be

perialis-, the outer margins of both wings remain yellow

the result of limited collecting. The specimen is fully as

with only the basal areas having a hint of purple. In¬

large as nominate imperialis, but the ventral surface of

dividual variation in females is primarily limited to the

both wings shows traces of a postmedial line. We rec¬

degree of stippling with dark dots. The pini males, how¬

ognize that the presence or absence of postmedial lines

ever, exhibit even more variability in the amount of

is a variable trait in imperialis imperialis and would not

dark purple than nominate imperialis. The dorsal fore¬

base our belief that a dine exists on a single specimen.

wing of most pini males has prominent patches of dark

However, the intermediate appearance of the specimen

purple that extend from the basal area to the discal spot

certainly provides the impetus for further fieldwork in

and from the postmedial line to the outer wing margin.

central Michigan. The interaction between the two taxa

In some males the dorsal forewing has greatly reduced patches of purple in the basal area and completely lacks

in Ontario and New York is not clearly understood ei¬ ther.

purple along the outer wing margin. These yellow

Wild pini males have been attracted to, and have

Co., Michigan, a spot almost equidistant between the

males superficially resemble females; to our knowl¬

paired with, virgin imperialis imperialis females from

edge, similar forms have not been reported in nominate

Kalamazoo Co., Michigan, at the University of Michi¬

imperialis. As in the females, the degree of dark stip¬

gan Biological Research Station (the type locality) near

pling can be variable.

Pellston, Michigan (B. Scholtens, pers. comm.). Unfor¬

We observed intermediate specimens in upstate New

tunately, the resulting F, larvae were lost during rear¬

York that deviate from the diagnostic characters cited

ing. We subsequently obtained a pairing of the same

by Ferguson (1971). One male from Hudson Falls,

combination using stock from the same localities. The

Washington Co., is pini-like dorsally but lacks the ven¬

hatch rate was 96.3%, the resulting larvae appeared

tral postmedial lines. An otherwise "typical" pini male

fully viable, and 46 were reared to pupation on white

from Plattsburgh, Clinton Co., is very sparingly stip¬

pine and silver maple. The following season the adults

pled with dots. Both specimens are in the State Mu¬

were fully viable and the females contained a full com¬

seum of New York at Albany. John Rawlins (pers.

plement of ova. The Fj adults exhibited a range of phe¬

comm.) advised us that the Carnegie Museum has sim¬

notypes ranging from pini to nominate imperialis. An F2

68

Ceratocampinae

pairing yielded normal ova (in contrast to imperialis im-

previously published by Tuskes (1986b) supports the

perialis

oslari crosses), all ova produced embryos, and

species rank of oslari. Tuskes reported that a newly

79% (143 of 181) eclosed. This hatch rate is somewhat

emerged imperialis imperialis female from Waller Co.,

low, but it could be ascribed to inbreeding depression

Texas, was tied out in Box Canyon, Pima Co., Arizona.

resulting from the sibling-sibling mating. Based on

The female attracted and mated with a male oslari at

these results, we maintain subspecies status for pini.

0130, and the pair remained together until the follow¬

X

ing evening. Only 21 ova were deposited, of which 17 Immature Stages. The biology of immature pini is

were infertile and 4 developed embryos; only one larva

much like that of imperialis imperialis. The ova are in¬

eclosed, and it died in the first instar. The Texas pop¬

distinguishable, the larvae are solitary feeders, and the

ulation of imperialis imperialis is geographically the

pupae overwinter in subterranean chambers.

nearest to the Arizona population. Michael Wilson

The larvae are believed to be exclusively associated

(pers. comm.) made 11 crosses between Virginia and

with conifers. Most collections have been from red pine

West Virginia imperialis imperialis and oslari. Reciprocal

(Pinus resinosa) and eastern white pine (P. strobus), with

crosses were made using females of each species. Wil¬

occasional defoliations reported in south-central On¬

son found the eggs to be fully fertile (96-100%) with

tario (McGugan, 1958). Isolated records also exist for

high survival in the Fj hybrid larvae. When the hybrids

jack pine (P. banksiana), Scotch pine (P. sylvestris), and

were crossed to produce the F^ generation, however,

white spruce (Picea glauca).

the fertility of three different matings ranged from only

In general appearance pini larvae are similar to im¬

59 to 78%, and many of the eggs were deformed. Fur¬

perialis imperialis, but there are several differences be¬

ther, Wilson's field observations suggest a difference in

tween the two taxa. Nominate imperialis larvae often

pheromone response. In a paired study using females

lack, or have only remnant rows of, yellowish dorsal

of both species, set about 6 feet apart, 32 of 36 male

and dorsolateral scoli on the abdominal segments.

oslari attracted during 11 nights came to the female os¬

These scoli are large in pini, always present, and shiny

lari. The 4 males attracted to the female imperialis im¬

white. The spiracles are white in pini, yellow in imper¬

perialis bumped the cage and then moved on rather

ialis imperialis. Last-instar pini larvae exhibit several

than initiating the expected close-range search behav¬

color forms that vary from bright lime green to almost

ior. Taken together, these observations suggest that os¬

black. The last instar is 75-80 mm long.

lari

is

geographically,

biologically,

and

probably

reproductively distinct from imperialis imperialis and Rearing Notes. This northern subspecies is sensitive

merits species status.

to high temperatures, but we have successfully sleeved out larvae in highly shaded areas. We usually offer

Distribution. Eacles oslari has been collected with reg¬

eastern white pine (P. strobus), but captive larvae will

ularity only in the Santa Rita, Patagonia, Atascosa, and

accept most pine species. As is the case with nominate

Huachuca Mountains of Pima, Santa Cruz, and Cochise

imperialis, matings in cages can be difficult to achieve,

Cos., Arizona. It is also widespread in the states of So¬

but mated females oviposit freely in captivity. Light,

nora, Sinaloa, and Chihuahua, Mexico. Eacles oslari ap¬

airy soil should be offered as a pupation medium. Stock

pears to be primarily a Mexican species whose northern

of pini is difficult to obtain, and extra care should be taken with this subspecies.

limit extends into southern Arizona. Adult Diagnosis. The most diagnostic characteristic of adult oslari is the bold, continuous brown line on the

Eacles oslari Rothschild, 1907

undersurface of the wings. On the forewing it extends

Figures: Adults, Plates 8, 9; Larva, Plate 1; Map 2

from the apex to the inner margin; on the hindwing it

Type locality: Nogales, Arizona

crosses diagonally from the leading edge to the anal area of the wing. Although some populations of nom¬

General Comments. The Eacles in southern Arizona

inate imperialis may have a poorly developed line, most

was assumed to be a disjunct population of imperialis

lack any trace of these lines on the ventral surface. The

imperialis until Ferguson (1971) elevated it to species

two species are allopatric, and imperialis imperialis does not occur west of Texas.

status based on differences in distribution, adult mor¬ phology, coloration, and pattern. Lemaire (1988) treated oslari as a subspecies of imperialis based primarily on

Adult Variation. There are three distinct adult color

the similarity of the males' genitalia, but information

phases: yellow, orange-brown, and pale lavender or

Anisota

lavender tinged. Some specimens appear transitional

69

Genus Anisota Hiibner, 1820

between these forms, but yellow is the most common phenotype. Forewing: male 51-58 mm, avg. 56 mm; fe¬ male 64-68 mm, avg. 66 mm.

Type species: Bombyx stigma Fabricius, 1775; designated by Grote,

Adult Biology. The flight season of oslari in Arizona

The genus Anisota is a homogeneous group of small

extends from the first week of July to mid-August, but

to medium-sized brownish moths. Most of the species

the peak occurs from 20 July to 5 August. Both sexes

are found in the southeastern United States; only a few

are attracted to light, but males are more frequently

occur farther west and into Mexico. The species of An¬

captured than females. Captive adults usually mate af¬

isota and the closely related Dryocampa rubicunda are the

ter 2000, and the pair remains together until the follow¬

smallest U.S. satumiids. The adults have a characteristic

ing evening. Oviposition begins about an hour after

white discal spot on the forewing, and sexual dimor¬

sunset. Females deposit ova singly or in clusters of up

phism is strongly developed. The basis for this di¬

to six. The adults are extremely vulnerable to predation by bats (SS, 1949, p. 87).

morphism appears to be the males' mimicry of Hymen-

1874

optera. Males are predominantly diurnal, rapid fliers, and several species have large, transparent (hyaline) ar¬

clude Mexican blue oak (Quercus oblongifolia), Emory

eas on the forewing that give them a beelike appear¬ ance in flight.

oak (Q. emoryi), and western soapberry (Sapindus sapon-

The genitalia of males of all Anisota species are broad

aria drummondii), but other plants are probably also util¬

and generally uniform. Only virginiensis shows diver¬

ized. Early-instar larvae are brown and feed singly.

gence with its elongated and more curved aedeagus.

After the third instar, larvae may be either brown or

The males have quadripectinate antennae; the females

green. The spiracles are turquoise ringed with black.

have simple ciliate antennae. The females are consid¬

Mature larvae are 95-110 mm long. Pupation takes

erably larger than the males and have opaque wings,

place in an underground chamber. There is one gen¬

and they are generally nocturnal, although late after¬

eration per year. The immature stages were described

noon oviposition is occasionally reported (H. J. Brodie, 1929; Riotte, 1969).

Immature Stages. The confirmed larval food plants in¬

by Tuskes (1986b). Larvae of oslari resemble imperialis imperialis from the

The translucent yellow to orange ova are laid in clus¬

eastern United States. Larval variation among imperialis

ters of 15-150 on oaks (Quercus) and occasionally on

imperialis populations (from Mich., Va., Fla., Miss., and

Castanea (also a member of the Fagaceae) and hazel

Tex.) is extensive, and the characters that appear to

(Corylus:

make oslari larvae unique are also found here and there

through the chorion as the ovum matures. The Anisota

in populations of nominate imperialis. The larvae of os¬

species are best known for their larvae, which are col¬

lari tend to have fewer contrasts in ground color on the

lectively called oak worms. The larvae are highly gre¬

dorsal and lateral surfaces, and the spiracles are con¬

garious in the early instars and tend to remain together

sistently turquoise. Most populations of imperialis im¬

even in later instars. This habit and their characteristic

perialis have cream-colored to black spiracles and

feeding pattern make the larvae fairly easy to locate in

contrasting prominent light brown patches on the lat¬ eral surfaces.

the wild. Many Anisota species exhibit population ex¬

Betulaceae).

The

larva

becomes

visible

plosions and occasionally reach pest status. Several spe¬ cies appear to be aposematically colored and may use

Rearing Notes. We have reared larvae on various

tannins obtained from their host plants as protection

tree

against vertebrate predators. All Anisota larvae (except

(Schinus terebinthifolius), sweet gum (Liquidambar styra-

finlaysoni) have a pair of prominent horns on the second

ciflua), and manzanita (Arctostaphylos patula). The lar¬

thoracic segment, a characteristic shared with Dry¬

vae have also been reared on two species of sumac

ocampa. Last-instar larvae can usually be sexed by size;

(Rhus glabra and R. typhina) and on eastern white pine

the larger ones are females. Pupation occurs in a loosely

(Pinus strobus) (W. Winter, pers. comm.). Pupation is subterranean. Pupae should be exposed to cool but

constructed subterranean cell, and all species over¬ winter as pupae.

not freezing temperatures during the winter. Starting

The taxonomy of the genus was recently revised at

in June, the pupae should be sprinkled with water a

the species and subspecies levels. Ferguson (1971) rec¬

few times a week in order to encourage a July emer¬

ognized seven species (virginiensis, consularis, finlaysoni, senatoria, oslari, manitobensis, and stigma) and three sub-

species

gence.

of

oak

(Quercus),

Brazilian

pepper

70

Ceratocampinae

species (virginiensis pellucida, virginiensis discolor, and stigma fuscosa) based on adult and larval morphology. In 1975, Riotte described peigleri as a new species from North America. In their later revision of the genus, Riotte and Peigler (1980) recognized four species groups: the stigma group (stigma, fuscosa, consularis, and manitobensis); the pellucida group (pellucida, discolor, and virginiensis); the senatoria group (senatoria, finlaysoni, and peigleri); and the Mexican group (oslari). Riotte and Peigler elevated all these taxa to species status on the basis of minor morphological variation, even though neither Ferguson (1971) nor Lemaire (1988) found many of the characters diagnostically reliable; nor do we. Le¬ maire (1988) recognized only the virginiensis and stigma species groups and reduced several of the taxa elevated

Anisota stigma Anisota consularis

by Riotte and Peigler (1980) to subspecies, citing a lack of reliable genitalic characters (see the stigma and vir¬ giniensis accounts, below). We offer new data that identify pheromone differ¬

Anisota manitobensis

Map 3. Distribution of Anisota stigma, A. consularis, and A. manitobensis

entiation rather than allopatry as a primary reproduc¬ tive

isolating

mechanism

between

some

Anisota

and maculation remains constant across the range re¬

species, and in other cases we have found taxonomi-

gardless of ground color, we synonymize fuscosa with stigma.

cally significant phenotypic blend zones. Based on these findings, we adopt a conservative treatment of the genus and recognize the following taxa and species

Distribution. Anisota stigma occurs along the Atlantic

groups: the stigma group (stigma, manitobensis, and con¬

Coast from southern New England to central Florida.

sularis), the senatoria group (senatoria, finlaysoni, and

Old records (unconfirmed by recent collections) also ex¬

peigleri), virginiensis, and oslari. In the species accounts

ist from the Canadian Maritime Provinces. Westward

that follow we discuss the uncertain taxonomic status of peigleri, finlaysoni, and manitobensis. Where synon¬

the species occurs from southern Ontario to Minnesota and south through central Texas.

ymy is used, justification is given under the appropri¬ ate species.

Adult

Diagnosis. The

characters

that

distinguish

stigma from manitobensis, and stigma females from con¬ sularis females are discussed under the latter species.

Anisota stigma (Fabricius, 1775) Figures: Adults, Plate 9; Larva, Plate 2; Map 3

Adult

Variation. Unlike

most

North

American

Type locality: "America Meridionalis" (see explanation in Riotte & Peigler, 1980)

Anisota, stigma males lack the hyaline patch on the fore¬

Synonymy: Anisota stigma fuscosa Ferguson, 1971, new synonymy

reduced. Females are decidedly larger than males, how¬

wing, and sexual dimorphism is therefore somewhat ever; in southeastern populations they may be nearly

General Comments. The taxonomy of stigma was very simple until Ferguson (1971) described the brownish

twice as large. Forewing: male 18-25 mm; female 2634 mm.

Texas populations as stigma fuscosa. Riotte and Peigler

Regional variation has been reported. Specimens

(1980) elevated fuscosa to species status, but Lemaire

from the Southeast are much smaller than those from

(1988), citing the lack of reliable morphological char¬

elsewhere in the range of stigma. As previously men¬

acters, relegated fuscosa back to a subspecies. Al¬

tioned, the ground color of Texas material tends to have

though the ground color of Texas material does tend

a brown cast. It is interesting to note that Texas virgi¬

to be brown, we collected wild males in Waller Co.,

niensis also has a tendency toward brown. In addition.

Texas, with ground colors varying from reddish to

New England and Wisconsin populations often include

brown that are fully as large as nominate stigma. Sim¬

males with straight outer wing margins and acutely an¬ gled hindwings.

ilar males are routinely collected in Anderson and Or¬ ange Cos., Texas (Ferguson, 1971; E. Knudson, pers.

Individual variation exists in the degree of black

comm.). Since the two forms are sympatric in nature

spotting on the forewing, the intensity of purple along

Anisota manitobensis

the outer wing margins, and the degree to which the antemedial line is present.

71

differentiation is the primary mechanism restricting re¬ productive interaction.

Adult Biology. Anisota stigma is the only Anisota spe¬

Immature Stages. The yellowish ova are typical of the

cies whose males are frequently collected at lights. Over

genus. Development takes approximately two weeks.

time, and in part because the species is so well known

Early-instar larvae are gregarious, but the larval clus¬

in the literature, the fact that both sexes are attracted to light evolved into a belief that stigma is exclusively noc¬ turnal. Virtually every author who has discussed the

ters are usually small. Later instars become solitary feeders. The pupae overwinter in subterranean cham¬ bers.

biology of stigma has perpetuated this perception. On

The most striking feature of the last instar is the ex¬

11 June 1989, however, at 0845, we were fortunate to

aggerated elongation of the scoli. The heavy mottling

observe a wild male respond to a freshly emerged wild

of white, granular secondary setae is another charac¬

female near Yankee Springs, Barry Co., Michigan. The

teristic of the stigma group. In spite of these striking

mating took place in bright sunshine, and the pair re¬

features, the variable ground color can greatly alter the

mained in copula until dusk, when oviposition began. The female progeny of this mating also emerged during

general appearance of larvae. Populations in the North and in Texas vary from pinkish to various shades of

the morning hours and often began calling before their

brown, broken by black longitudinal spiracular stripes

wings had fully expanded. When males were available,

that are highlighted to varying degrees by white bands.

the caged females mated between 0630 and 0930. We

In southeastern populations the last instar tends to be

also observed midmoming mating in captive females

reddish and the longitudinal stripes are greatly reduced

from Kentucky and Florida. It is interesting that un¬

or even lacking.

mated caged females exhibited a second calling time, between 0100 and 0300, and Peigler (pers. comm.) saw a wild female calling "well after nightfall" in Clemson,

Rearing Notes. The combination of smaller larval clusters and solitary feeding habits in the late instars

South Carolina. The discovery of two such diverse call¬

make stigma larvae more difficult to collect than most

ing times is not clearly understood and deserves further

Anisota species. Material from Texas populations is re¬

attention. Ova are usually laid in smaller clusters (5-

portedly prone to disease (Riotte & Peigler, 1980), but

20) than are typical of most Anisota species.

we have been successful with these populations by

Throughout its range stigma maintains relatively sta¬

rearing indoors and avoiding crowding. The adults

ble population levels. Although adults of both sexes are

readily pair in small cages and females oviposit freely in captivity.

attracted to light, they are seldom taken in great num¬ bers. The range of recorded flight dates is very broad, but the species appears to be univoltine everywhere it occurs. Flight activity begins in June in the north, July in the middle states, July-August in the Southeast, and not until August-September in Texas. The long-standing belief that stigma was the only An¬ isota that mated at night made reproductive isolation

Anisota manitobensis McDunnough, 1921 Figures: Adults, Plate 9; Map 3 Type locality: Aweme, Manitoba, Canada (site no longer exists on provincial maps, approximately 3 miles north of Treesbank, Manitoba)

seem to be a simple matter. After the recent discovery of diurnal mating in stigma, however, we must com¬

General Comments. Anisota manitobensis is the least

pletely reevaluate our understanding of its reproduc¬

known Anisota, and it may eventually prove to be a

tive isolation from other Anisota.

mere clinal variation of A. stigma. Even though severe

Across various parts of its range stigma occurs sym-

larval infestations were reported in the past (McGugan,

patrically with senatoria, peigleri, consularis, and virgi-

1958), we have not been able to locate the species in the

niensis. In many areas stigma flies at the same time of

field. As a result, our knowledge of manitobensis is

the year as its congeners; flight times overlap with vir-

based on the small amount of information that has been

giniensis and senatoria in southern Michigan and north¬

published by others.

ern Ohio, and with consularis, virginiensis, and probably peigleri in northern Florida. The daytime flight period

Distribution. Most

manitobensis

records

are

from

of stigma is somewhat earlier than the flight times ob¬

southern Manitoba in the area of the Riding Mountains

served for senatoria, peigleri, consularis, and virginiensis,

National Park, Winnipeg, and various locations near

but we do not have enough data to determine whether

the North Dakota border. We have been unable to

a subtle variation in daily mating activity or pheromone

locate any records for manitobensis later than C. S.

72

Ceratocampinae

Quelch's (pers. comm.) collection east of Winnipeg in

area on the fore wing of males. Males are 20-30%

the mid-1970s, and have ourselves tried light trapping,

smaller and tend to have less of a pinkish tint than

searching for larvae, and using caged virgin stigma fe¬

females. The outer wing margins are rounded in fe¬

males in the same locales. Perhaps there is something

males but tend to be straight, or nearly so, in males. In

crucial missing from our knowledge about the biology

addition, the apical angle of the forewing is more acute

of the species. Most of the forests of southern Manitoba

in males. Forewing: male 19-22 mm; female 26-30 mm.

have been converted to farmland, but apparently suit¬

There is no reported variation in manitobensis macu-

able habitat still exists along streams and some road¬

lation. The only noticeable variation is an occasional

sides; the type locality, at the abandoned Criddle

darkening in the ground color of males, but even this

homestead near Treesbank, is one such location. We re¬

is not significant.

cently identified a male manitobensis collected near Ro¬ seau, Roseau Co., Minnesota, in the University of Minnesota collection. Based on our interpretation of

Adult Biology. Adults fly from early June through

manitobensis, this specimen represents the first U.S. rec¬

early July. H. J. Brodie (1929) observed a wild female

ord. The species should also be anticipated from North

ovipositing "in the sunshine, facing west, at about four

Dakota in the Turtle Mountains and along the Pembina River near Walhalla.

o'clock in the afternoon." Nothing has been reported

Riotte and Peigler (1980) identified spotted males

about manitobensis, but it seems reasonable that the bi¬

from Wisconsin as manitobensis and suggested that man¬ itobensis and stigma are sympatric in the extreme south¬

ology of this species would closely parallel the biology of stigma.

ern part of the state near Madison, Dane Co. Our

As previously discussed, an examination of manito¬

reexamination of many of the same specimens seem to

bensis in the northern border states would be of great

indicate that all the males are of the manitobensis

help in clarifying its status and distribution. Anisota

phenotype, while all the females in this area of pro¬

manitobensis is sympatric with virginiensis across its

posed sympatry appear to be stigma. That seems un¬

range, but it is impossible to speculate on interactions between the species.

likely, given the frequency with which stigma males are

concerning the time of mating. Little else is known

taken at lights. Based on this improbability and the sim¬ ilarity of the questionable males to atypical stigma males from New England, we believe that all the Wis¬ consin material examined to date represents stigma, not manitobensis. Further study may yet indicate that manitobensis is only a northern variation of stigma (a Lucas Co., Ohio, stigma female reared by Tom Carr was indistinguish¬ able from manitobensis). The limited amount of material available for examination and the lack of livestock pre¬ vent us from saying more at the present time.

Immature Stages. The following larval description and discussion are paraphrased from Brodie (1929, p. 100): Ground color pinkish brown. Brown subdorsal stripes and black dorsal stripe. Setae on second thoracic segment greatly elongated with many more spines present. Mottling of white granular secondary setae as in stigma. Spiracles black with pinkish border. The early-instar larvae are highly gregarious. The only reported wild larval cluster (100+) was much larger than any stigma cluster on record. McGugan (1958) described manitobensis as a solitary defoliator,

Adult Diagnosis. Anisota manitobensis can usually be separated from stigma by the lack of black spotting on the wings of the former (both sexes). Anisota manito¬ bensis females have a decidedly pinkish cast, and males also tend to have a more pinkish tint than stigma. The hindwing of manitobensis males tends to

but this is probably because he collected later instars, which, like stigma, abandon the gregarious feeding strategy. Bur oak (Quercus macrocarpa) appears to be the preferred larval host, but larvae were also collected on an undetermined hazel (Corylus). Pupation is reported to be the same as in other Anisota.

be more acutely angled than that of most stigma males, although stigma males from New England and

Rearing Notes. Brodie (1929) reported difficulty in

Wisconsin tend to have the acute wing shape of man¬ itobensis.

rearing one group of larvae but implied that his failure may have been the result of inexperience with the spe¬ cies. He reared a second group with almost total suc¬ cess. Virtually nothing else is reported in the literature

Adult Variation. Like stigma, sexual dimorphism is less obvious in manitobensis because there is no hyaline

about rearing manitobensis. It should treated like other Anisota species.

probably be

Anisota consularis Anisota consularis Dyar, 1896

73

Adult Variation. Like the other members of the genus,

Figures: Adults, Plate 9; Larva, Plate 2; Map 3

consularis exhibits extreme sexual dimorphism. The

Type locality: West Palm Beach, Florida

males have narrow forewings with a weak hyaline patch. The females are considerably larger than the

General Comments. Although once it was considered rare, consularis is common throughout much of Florida. Most of our knowledge of this species has been ob¬ tained in the past 15 years.

males (approximately 50%) and have broad, opaque wings. Forewing: male 18-21 mm; female 24-30 mm. Females are highly variable in appearance, and this has contributed to the long-standing confusion regard¬ ing the Anisota fauna of the Southeast. Careful rearing of a long series of adults from each of 13 females

Distribution. Anisota consularis was long believed to be restricted to Florida, but the collection of larvae in Long and Bulloch Cos. in coastal Georgia (Riotte & Peigler, 1980) and near Fountainebleau State Park, St. Tammany Par., Louisiana (JPT), greatly extended the range. Previous adult captures have also been con¬ firmed from Fluker, Tangipahoa Par., Louisiana, and Gulfport, Harrison Co., Mississippi (Tuttle, 1984). All

showed that individuals from a single female can rep¬ resent every recognized morph, ranging from unicolor bright reddish orange with a greatly reduced postme¬ dial line, to sepia brown with well-defined postmedial lines and strongly contrasting purple outer margins, to faint orange individuals that are almost impossible to distinguish from senatoria. Surprisingly, the males are fairly constant in appearance.

the records outside Florida are from coastal areas pro¬ tected from temperature extremes by the warming in¬ fluence of the Atlantic Ocean or the Gulf of Mexico. The species occurs along the Gulf Coast from Louisiana to Florida and up the Atlantic Coast at least to northern coastal Georgia.

Adult Biology. The species appears to be univoltine, and adults emerge from July through early September. The diurnal males are extremely fast fliers. Females be¬ gin calling at approximately 1000, and mated pairs re¬ main in copula for approximately two hours. Once the two have separated, the female remains concealed until

Adult Diagnosis. Males have a hyaline area and white discal spot on the forewing and the general appearance

dusk. The eggs are laid on the underside of oak leaves (Quercus) in clusters of up to 100.

of finlaysoni, peigleri, senatoria, and virginiensis. Anisota

The analysis of reproductive interactions among the

finlaysoni and senatoria cannot be confused with consu¬

Florida Anisota has historically been hindered by mis-

laris since, as far as we know, the species are not sym-

identification of the taxa. More recent discoveries of

patric. Anisota consularis can be reliably separated from

gaps in our knowledge of the biology of the Anisota

virginiensis by its light brown ground color and sprin¬

species have added an additional element of confusion.

kling of black dots; virginiensis is deep reddish brown,

Riotte and Peigler (1980) concluded that consularis

almost always lacks dots, and has a much larger hya¬

and peigleri are reproductively isolated by their allo-

line area on the forewing. Distinguishing between con¬

patric distributions, even though their own citations

sularis and peigleri is much more difficult, although the

indicated records of both species from Gainesville,

contrast between the light brown of the inner wing and

Florida. We examined preserved larvae of both species

the purplish ground color beyond the postmedial line

in the Florida State Collection of Arthropods that were

tends to be greater in consularis, and peigleri- is more

collected in Gainesville. Anisota consularis is common

uniformly reddish brown. The anal angle of the hind¬

throughout northern Florida and unquestionably is

wing also tends to be more rounded in consularis than in peigleri.

sympatric with peigleri in areas where the latter species

The females of consularis have often been confused

Riotte and Peigler (1980) reported that a consularis fe¬

also occurs. Since both species call in the morning, and

with senatoria, stigma, and, more recently, peigleri. Ani¬

male attracted peigleri males in South Carolina, there

sota consularis females are polymorphic, and individuals

must be subtle, as yet undetected, differences in daily

may be extremely difficult to identify with certainty. Most stigma from the Deep South are reddish orange

mating activity, secondary pheromone differentiation, seasonal isolation, or some combination of these fac¬

with prominent but fuzzy postmedial lines on both

tors that prevent hybridization in nature. Unfortu¬

wings. The postmedial lines are finer and sharper on

nately, Florida peigleri records are so limited that an

the forewing and are often lacking on the hindwing of the reddish orange consularis morph. Anisota peigleri fe¬

adequate site for testing these mechanisms has not been located.

males tend to have more acutely shaped wings and are

The mechanism that isolates consularis from stigma

more orange than consularis.

is also not well understood. We took adults of both

74

Ceratocampinae

species at the same light near Jennings, Hamilton Co., Florida, in late July, and we now know that both spe¬ cies begin

their mating

activity in

the

morning.

Therefore, unless subtle variations in circadian rhythm are discovered to be a factor, it would seem that pher¬ omone differentiation is involved in reproductive iso¬ lation between the two species. Anisota

consularis

and

virginiensis

are

sympatric

Anisota virginiensis (Drury, 1773) Figures: Adults, Plates 9, 10; Larva, Plate 2; Map 4 Type locality: Suffolk, Virginia (neotype designated by Riotte & Peigler, 1980) Synonymies: Phalaena pellucida J. E. Smith, 1797, revised SYNONYMY

Anisota virginiensis discolor Ferguson, 1971, REVISED SYNONYMY

throughout much of Florida. Contrary to previous reports (Riotte & Peigler, 1980), there is evidence of

General Comments. Ferguson (1971) recognized three

pheromone differentiation between virginiensis and

subspecies of virginiensis (virginiensis, pellucida, and dis¬

consularis. On 1 August 1980, a mass emergence of

color), but the three taxa have changed in status in each

virginiensis occurred at Tomoka State Park, Volusia

succeeding treatment. Riotte and Peigler (1980) elevated

Co., Florida. We observed caged consularis and wild

all three taxa to species on the basis of minor morpho¬

virginiensis females calling from 1000 to

1300. In

logical characters, perceived allopatry, and difficulty in

spite of the fact that literally thousands of virginiensis

rearing interbred larvae. Lemaire (1988) noted the lack

males were observed seeking mates, not a single vir¬

of reliable genitalic differences between the three taxa

giniensis male was attracted to the calling consularis fe¬ males.

and realigned discolor to subspecies status under pellu¬ cida. We synonymize all three taxa with virginiensis, based on the lack of diagnostic characters in genitalia, the con¬ sistency of maculation in adults, and the biology of the

Immature Stages. The ova are similar in general ap¬

taxa. Although it is true that specimens from the pel¬

pearance to most of our native Anisota eggs. We have

lucida populations of the Southeast are a deeper reddish

noted considerable variation in the size of larval clus¬

brown than northern virginiensis

ters. The larvae are gregarious in the early instars, but

seems to be a clinal trend. Material from Halifax Co.,

there is a tendency toward solitary feeding in the last

North Carolina, appears intermediate and is not easily

populations,

this

mstar. In Florida, live oak (Quercus virginiana) is the

attributable to either taxon. Females from discolor pop¬

most commonly used host plant, but Q. nigra, Q. falcata,

ulations in Texas generally have a slight brownish cast,

Q. laevis, and Q. myrtifolia have also been reported to

but earlier treatments agree that this character is highly

be hosts (Riotte and Peigler, 1980). Like the other Ani¬

variable (Ferguson, 1971; Riotte & Peigler, 1980). Fur¬

sota species, consularis pupae overwinter in shallow subterranean chambers.

ther, the discolor males that we examined are nearly im¬ possible to distinguish from pellucida. We interpret

The last-instar larvae are highly variable, and it was

pellucida and discolor from Louisiana parishes bordering

this fact that probably led Dyar (1896) to propose the

Texas, where no topographical or plant community bar¬

presence of stigma larvae in a cluster of consularis larvae

riers are apparent, as being examples of polymorphic

(Riotte and Peigler, 1980). Carefully reared consularis

populations. In addition, because rearing success can

larvae exhibit multiple color forms and even variation

vary even under the best of artificial conditions, we find

in armature among siblings. Last-instar larvae may be

it difficult to interpret losses of regionally interbred Fj

brown, tan, or pale green with prominent longitudinal

larvae as evidence of "hybrid inviability," as Riotte and

black stripes. The sublateral row of scoli is quite pro¬

Peigler (1980) did. Considering these factors, it seems

nounced in all the material we examined, but even

more appropriate to treat the named entities as mem¬ bers of a single variable species.

among siblings the dorsolateral scoli can vary from prominent to completely lacking.

Distribution. Anisota virginiensis is the most broadly distributed Anisota. It has been reported across Canada Rearing Notes. Anisota consularis larvae are relatively

from Nova Scotia to southeastern Manitoba, and huge

free from disease when reared in captivity. The larvae do well on cut host plant when late-season weather

population explosions occasionally occur in the north¬ western part of its range (D. Henne, pers. comm.). In

conditions do not allow sleeving. Care should be taken

the United States, virginiensis has been taken in the

to overwinter pupae at mild temperatures and high hu¬

states east of the Mississippi River, south to eastern

midity. The adults are easily mated in cages, and fe¬ males oviposit readily in captivity.

Texas, and across the Gulf States well into peninsular Florida. The unique appearance of the larvae and the

Anisota virginiensis

75

place in early June to mid-June, with stragglers ap¬ pearing until early July. Through the middle part of its range virginiensis is bivoltine, and in exceptionally warm years, partial second generations have been pro¬ duced as far north as Lucas Co., Ohio (T. Carr, pers. comm.). Adults emerge in May, and the larvae pupate

w

within six weeks. These summer pupae emerge in a very

short

time

(late July-early

September).

The

second-generation pupae overwinter until the follow¬ ing spring. According to Riotte and Peigler (1980), the spring brood of the east Texas population is only par¬ tial; the primary emergence is from late August through mid-September. The range of dates in Florida Anisota virginiensis Anisota oslari

l

\

f

\

is so broad that Riotte and Peigler (1980) and H. D.

y

Baggett (pers. comm.) suggested at least three genera¬ tions per year there.

Map 4. Distribution of Anisota virginiensis and A. oslari

Mating activity commences in midmoming and ex¬ tends to late morning (0930-1200). The males are ex¬ tremely

fast

fliers,

and

when

several

males

are

"buzzing” a cage of calling females, the effectiveness of the bee mimicry can be truly appreciated. Once the relative ease with which females can be separated from

male locates the female, coupling takes place with in¬

other Anisota females mean that most records for vir¬

credible speed. The pair remains together for the re¬

giniensis can be viewed as reliable.

mainder of the day; at dusk the female breaks away to begin laying eggs. Ova are laid in clusters (10-100) on

Adult Diagnosis. Males can usually be separated from other Anisota species by the more pronounced hyaline area on the forewing and the lack of secondary black spotting. Females are distinguished by reduced or ab¬

the underside of oak (Quercus) leaves. Throughout its range virginiensis is sympatric with other Anisota species, and it appears that there are sev¬

sent black spots and uniform purple coloration along

eral isolating mechanisms to prevent hybridization. In Canada and the northern Great Lakes region, virginien¬

the outer margin of both wings.

sis is generally reproductively isolated from its conge¬ ners by its earlier seasonal flight period.

Recent

Adult Variation. Sexual dimorphism is strongly de¬

observations of diurnal mating of stigma during early

veloped in this species. The males have the largest and

June in southern Michigan suggest that pheromone dif¬

best-developed hyaline area on the forewing of any An¬

ferentiation, subtle variation in daily mating activity, or

isota; the wings of the female are opaque. Like many

both probably also play a role in reproductively isolat¬

other Anisota, males have narrow,

wings, and females have broadly rounded wings. Fore¬

ing the two species. Pheromone differentiation appears to be the primary mechanism isolating virginiensis from

wing: male 18-21 mm; female 24-30 mm.

consularis in Florida (see the discussion under consu-

acutely angled

Maculation is fairly constant across the range, but the

laris).

color of both sexes darkens and intensifies from north to south. In addition, the postmedial line tends to be

Immature Stages. The ova of virginiensis are darker

weaker in northern populations and more strongly de¬

and more orange than yellow. The larvae are gregari¬

veloped in southern populations. As previously men¬

ous during the early instars. Even the later instars tend

tioned, these changes appear to be clinal. Females from

to feed together, but their clusters are generally smaller

east Texas tend to have a brownish cast, but the males

than those of most other Anisota species. Pupation lasts

are often indistinguishable from material from the

only a few weeks in the spring and summer genera¬

Southeast. The white discal spot on the forewing tends to be greatly enlarged in females from Wisconsin, Min¬

tions. Like all the Anisota species, virginiensis over¬

nesota, and Manitoba.

winters in the pupal stage. The species is immediately recognizable in the last instar by the broad, pink longitudinal dorsolateral and

Adult Biology. Anisota virginiensis is univoltine in the

sublateral stripes. Rows of sublateral and dorsal scoli

northern part of its range. The peak emergence takes

are evident but not nearly as pronounced as in other

76

Ceratocampinae

Anisota peigleri Anisota finlaysoni

Map 5. Distribution of Anisota senatoria, A. peigleri, and A. finlaysoni

Anisota. Individuals may have traces of the dorsolateral scoli, but they are lacking in most specimens. Riotte and Peigler (1980) cited regional color differences in popu¬ lations from the North, Southeast, and Texas; however, we have noted some individual variation within these populations and consequently question the diagnostic significance of color. Rearing Notes. Anisota virginiensis is very easy to rear in captivity. The larvae accept many oaks (Quercus) and do quite well on cut food. Pupae will not diapause if kept warm in the lab. Adults readily mate in even the smallest cages.

Anisota senatoria (J. E. Smith, 1797) Figures: Adults, Plate 10; Larva, Plate 2; Map 5 Type locality: Gibsland, Bienville Par., Louisiana (neotype desig¬ nated by Riotte & Peigler, 1980)

General Comments. Anisota senatoria is perhaps the best-known Anisota because of its periodic pest status. The species is the nominate form in the senatoria com¬ plex, which also includes finlaysoni and peigleri. Care¬ ful fieldwork is needed to sort out the validity and distributions of the various taxa within this complex. Distribution. The species occurs from the Great Lakes region to the eastern seaboard and then south along the edge of the Great Plains at least to eastern Texas. Before

finlaysoni and peigleri were described, Anisota senatoria records based on larval collections had always been ac¬ cepted with a degree of confidence. Now, however, re¬ cords from south-central Ontario and the Appalachian region are difficult to evaluate. Although the senatoria complex is broadly distributed, senatoria seems to be displaced by finlaysoni along the north shore of Lake Ontario. The distribution of senatoria in the Appala¬ chian region is even more difficult to evaluate because of confusion with peigleri. Based exclusively on records of larvae (the armature of fifth-instar larvae usually are distinctive), we know of no locales where the two taxa occur sympatrically. An intermediate population re¬ cently located in Luray, Virginia, is discussed under peigleri. Anisota senatoria is generally associated with lower elevations than peigleri, but the rolling hills of that part of Virginia do not appear to offer topograph¬ ical barriers that would isolate it from peigleri. Earlier authors reported senatoria as occurring spo¬ radically in Florida, but these records appear to be the result of confusion with other Anisota species (Fergu¬ son, 1971). We examined the specimen from Monticello, Florida, cited by Riotte and Peigler (1980) and the spec¬ imen from Spring Creek, Decatur Co., Georgia (Fergu¬ son, 1971), and are confident that both are consularis females. We are not aware of any recent records of sen¬ atoria from southern Georgia. Considering the previous confusion with consularis, it seems inappropriate to con¬ tinue reporting senatoria from Florida without new and convincing records. Adult Diagnosis. Anisota senatoria tends to be orange and can often be separated from finlaysoni by the brownish earth tone of the ground color of both sexes of the latter species. No reliable diagnostic characters have been identified in the genitalia of the two species. Separating adult senatoria from peigleri is very difficult. The lack of reliable adult characters is one more reason to take a closer look at the biology of these taxa to assist in determining their taxonomy. Adult Variation. Sexual dimorphism is extreme in all members of the senatoria complex. The females may be twice as large as the males. The males have narrow forewings with a small translucent patch; the females have broad, opaque, well-rounded wings. Forewing: male 15-20 mm; female 24-30 mm. Individual variation within populations is minimal, although the amount of spotting on females can be somewhat variable. Regional variation in ground color occurs to some degree in both sexes. In the North, males tend to be brownish orange and females are yel-

Anisota finlaysoni

lowish brown; in the South, males are reddish brown and females are brownish orange. One additional re¬ gional characteristic has been noted: the hyaline area

77

Anisota finlaysoni Riotte, 1969 Figures: Adults, Plate 10; Larva, Plate 2; Map 5 Type locality: Shartnonville, Ontario, Canada

on the forewing of males tends to be larger and more strongly developed in northern material.

General Comments. Riotte (1969) described finlaysoni as a species within the senatoria complex on the basis

Adult Biology. Anisota senatoria adults fly from late

of differences in adult and larval morphologies. Riotte

June through mid-July. Ova are laid in large clusters on

and Peigler (1980) stated that finlaysoni and senatoria are

the underside of oak leaves (Quercus). Oak is the most

sympatric in the Niagara peninsula of Ontario and said

common host, although we recently received a report of senatoria larvae on chinquapin (Castanea pumila) in

section. Although we are not certain of the reliability

West Virginia (J. Rawlins, pers. comm.). Population

of genitalic characters in these species, the dramatic re¬

densities tend to be cyclic over much of the range. An¬

duction of the thoracic horns on last-instar finlaysoni lar¬

isota senatoria is one of the few satumiids often reported as a pest. Serious defoliations have been reported in

vae is unique among the Anisota. We believe that finlaysoni and senatoria are sibling species, whose rela¬

Connecticut

tionship warants further study.

(Hitchcock,

1958,

1961a,b),

Minnesota

that the identity of their material was confirmed by dis¬

(Lugger, 1890), New York (Clarkson, 1883), and Ohio (T. Carr, pers. comm.). Mating occurs in late morning to early afternoon (1100-1400). Females either begin ovipositing in the late afternoon or wait until dusk. Anisota senatoria is sympatric with virginiensis and stigma throughout most of its range. Field observations in Lucas Co., Ohio, indicate that differences in seasonal emergence may play a role in reproductively isolating senatoria and virginiensis in that area; virginiensis flies in early June, and senatoria flights are delayed until late June or early July. Preliminary observations of wild males' response to females of the two species in adja¬ cent cages suggest that the two use different phero¬ mones (T. Carr, pers. comm.).

Distribution. Riotte and Peigler (1980) suggested that finlaysoni occurs across southern Ontario and in isolated populations in Minnesota and Wisconsin. Our exami¬ nation of the same material they used (in the Milwau¬ kee Public Museum, the American Museum of Natural History, and the Royal Ontario Museum) and our own fieldwork indicate that finlaysoni has a very limited dis¬ tribution in south-central Ontario along the north shore of Lake Ontario; reliable records extend from Trenton to Kingston. We believe that, based on wing coloration, records of finlaysoni from the Kitchener area of south¬ western Ontario actually represent senatoria. There is a dramatic geological shift from limestone to clay with an accompanying plant community change in the area

Immature Stages. The ova of senatoria are yellow and

of Cobourg that may offer a barrier to sympatry. Ad¬

take approximately two weeks to hatch. The larvae are

ditionally, our examination of the museum material in¬

highly gregarious in the early instars and are often

dicates that reports of finlaysoni from Minnesota and

found in close proximity in the late instars as well, mak¬

Wisconsin are the result of confusion with other spe¬

ing them quite easy to collect in the wild. Late-instar

cies. We have yet to locate what we consider a valid

larvae are extremely susceptible to dipterous parasi-

specimen of finlaysoni from the United States. Based on

toids. The fifth-instar larva is flat black with lateral yellow¬

existing records, however, it seems reasonable to as¬

ish orange stripes. There are two rows of dorsal scoli;

the southeastern shore of Lake Ontario.

sume that the species occurs in upstate New York along

those on the second thoracic segment are enlarged into prominent horns. There is also a row of sublateral scoli. The larvae appear fairly uniform in appearance across their range.

Adult Diagnosis. Characters distinguishing finlaysoni from senatoria are discussed under the latter species.

Rearing Notes. The larvae are easy to rear in captivity

Adult Variation. Sexual dimorphism is well devel¬

and are not prone to disease when crowded. The pu¬

oped, as in other members of the senatoria complex (see

pae are easy to overwinter as long as they are not sub¬ jected to extreme temperatures. The adults readily

variation in finlaysoni, although most of the material we

mate in confined spaces, and females oviposit quite

examined was reared from a limited number of broods.

freely.

Forewing: male 15-20 mm; female 24-30 mm.

the discussion under senatoria). We are unaware of any

78

Ceratocampinae

Adult Biology. Anisota finlaysoni is univoltine, and the

Distribution. Anisota peigleri

appears

to

maintain

adults emerge from mid-June to mid-July. Mating takes

large, stable populations at moderate elevations in the

place in the late morning (1000-1200). The pair may

Piedmont areas of the Carolinas and northern Georgia.

remain in copula until evening, or the female may

In addition, we collected larvae in eastern Tennessee

break away and begin ovipositing in the late afternoon

and extreme southern Kentucky. The Whitley Co., Ken¬

(Riotte, 1969). The eggs are laid in large clusters on the

tucky, records greatly extend the northern range of the

terminal tips of oaks (Quercus).

spedes and raise questions about the identity of pre¬

We believe that finlaysoni occurs as a geographic iso¬

viously reported material from that area. Surprisingly,

late from senatoria in south-central Ontario. Extensive

peigleri also occurs sparingly as far south as north-

fieldwork with calling females of both species might

central Florida (Gainesville) in flat, dry scrub oak hab¬

shed additional light on the species' distribution and status.

itat (records based on last-instar larvae we examined in the Florida State Collection of Arthropods).

Anisota finlaysoni does occur sympatrically with virginiensis within the range defined in the present work.

Adult Diagnosis. Both sexes of peigleri are extremely

Probable pheromone differentiation between the spe¬

similar to senatoria, and no reliable diagnostic character

cies was exhibited when calling finlaysoni females failed

has yet been identified. There is a tendency for the hy¬

to attract wild virginiensis males in Lucas Co., Ohio (T. Carr, pers. comm.).

aline area on the forewing of peigleri males to be re¬ duced and more opaque than in the other diurnal spedes. Orange consularis females may resemble peigleri

Immature Stages. The ova are indistinguishable from senatoria ova. The larvae are highly gregarious in the

females, but the acute angle of the apex of the hindwing of peigleri is usually enough to separate the two.

early instars and tend to remain together in later in¬ stars. Most collections have been on white oak (Quercus

Adult Variation. Sexual dimorphism is well devel¬

alba), but finlaysoni has also been collected on chestnut oak (Q. prinus).

oped, as in other members of the senatoria complex (see

Anisota finlaysoni is unique among the Anisota in that

variation is minimal, but we have taken melanic spec¬

the scoli on the second thoracic segment are greatly re¬ duced. The material we examined from several wild-

imens on occasion. Forewing: male 19-21 mm; female 26-32 mm.

collected larval clusters was extremely uniform in ap¬ pearance.

Adult Biology. Adults fly from mid-July to late Au¬

the discussion under senatoria). Individual and regional

gust throughout the range. The females are readily Rearing Notes. We have found finlaysoni easy to rear

attracted to light. The day-flying males are also occa¬

in captivity. The larvae readily accept most oaks and are free from disease. Riotte and Peigler (1980) reported

sionally seen at lights, either in copula or in close as¬ sociation with a female.

that many adults emerge shortly after pupation in the

Mating occurs from midmoming until midaftemoon

fall if kept in the lab, although it is not clear whether

(1000-1700). Daily flight periods may vary regionally.

the artificially warm temperature or the extended pho¬

We observed midmoming mating in material from

toperiod is responsible for these emergences.

North Carolina, and stock from South Carolina has been reported to mate in the afternoon (1600-1700) (R. Peigler, pers. comm.). The pair remains coupled for sev¬

Anisota peigleri Riotte, 1975 Figures: Adults, Plate 10; Larva, Plate 2; Map 5 Type locality: Clemson, Pickens Co., South Carolina

eral hours before separating. The female then remains quiescent until dusk, when she begins to lay her eggs. Historical records are difficult, if not impossible, to sort out with respect to peigleri and senatoria. This is especially true of identifications based on adults. It is

General Comments. The taxonomic relationship be¬

also difficult to interpret the intermediate-appearing

tween peigleri and senatoria remains uncertain. Recent

Luray, Virginia, larval material. The row of supraspi-

collections of larvae intermediate in armature between

racular spines is present in these specimens, but all spines are reduced on the fifth-instar larva.

peigleri and senatoria, peigleri range extensions, and the hybrid viability we report in this book suggest that peig¬ leri may not represent a fully divergent species but is rather the southern terminus of a dine.

Interestingly, peigleri females

(Whitley Co.,

Ky.)

mated to senatoria males (Lucas Co., Ohio) produced viable adults of both sexes. Females were also back-

Anisota oslari

79

crossed to senatoria males (Lucas Co.) with no apparent

Texas are much more spotty. The records that do exist

loss of viability or fertility. Obviously, the ranges of the

suggest that gaps in the reported distribution are the

two phenotypes and the status of peigleri need clarifi¬

result of insufficient collecting. The Colorado record is

cation.

of a single female collected in Mesa Verde National Park (Colorado State University). The species has also

Immature Stages. The general appearance—three sets

been taken in Chihuahua, Mexico.

of longitudinal yellow stripes and jet black ground color—is reminiscent of senatoria. The sublateral line is

Adult Diagnosis. Unlike the other Anisota species,

the most prominent, and the dorsal and dorsolateral

both sexes of oslari have nearly uniform brown fore¬

lines are reduced. This species can be separated from

wings that are free of stippling, and the hindwing is

senatoria throughout most of its range by its spiny ap¬

usually darker than the forewing. Adult oslari are 25-

pearance, which is more reminiscent of stigma; peigleri

35% larger than the other Anisota species found north

larvae have a pronounced row of dorsolateral scoli

of Mexico.

(lacking in senatoria and finlaysoni) and a general elon¬ gation of the dorsal and sublateral scoli. The species is

Adult Variation. Sexual dimorphism is somewhat less

uniform in appearance except in the previously dis¬

evident in oslari compared with other Anisota. The

cussed Luray, Virginia, population.

wings of the females are more acutely angled than

Large clusters of ova are preferentially laid on trees

those of other Anisota females, approaching the general

of the black oak group (Quercus). This preference be¬

appearance of oslari males. Females are larger than

came apparent when we observed black oaks being de¬

males (30-40%), and the ground color is mauve in fe¬

foliated at a North Carolina rest area while adjacent

males and usually more reddish in males. Forewing:

white oaks remained untouched. In addition, the larvae

male 22-29 mm; female 32-^40 mm.

can be especially destructive to ornamental plantings of

The males show some color variation and were re¬

pin oak (Q. palustris). The larvae are highly gregarious

ported by Riotte and Peigler (1980) to occasionally ap¬

throughout all stages and feed in tight groups. Larval development is very rapid, seldom taking more than 30

proach the mauve ground color of the females. Most of the specimens we examined for the present work were

days. The species overwinters as subterranean pupae.

dark red-wine. The females are very consistent in ap¬ pearance across their range.

Rearing Notes. The larvae are very hardy in captivity most Anisota, the pupae are easy to overwinter as long

Adult Biology. There is one generation per year, and, at least in southeastern Arizona, adult emergence is

as they are not exposed to freezing temperatures. Mat¬

closely tied to the monsoon rains of July and August.

ing in captivity is accomplished with very little diffi¬

The males are diurnal and quite active in the morning.

culty.

Anisota oslari females begin calling slightly earlier than

and are easy to rear on cut food. As is the case with

their eastern counterparts. In the Box Canyon, Pima Co., and Guadalupe Canyon, Cochise Co., Arizona, popula¬ Anisota oslari Rothschild, 1907 Figures: Adults, Plate 10; Larva, Plate 2; Map 4 Type locality: Nogales, Santa Cruz Co., Arizona

tions we examined, matings took place as early as 0830. Females called and males continued to respond until approximately 1130. Females temporarily quit calling when the sun went behind the clouds for any significant

General Comments. Anisota oslari is the largest mem¬ ber of the genus north of Mexico. In addition, through¬

time. Mated pairs remained in copula until dusk. Cap¬ tive females laid their eggs in the early evening.

out its range in the southwestern United States oslari is

As previously mentioned, oslari does not come into

the only Anisota; it cannot be confused with any other

contact with any other Anisota in the United States. In¬

species.

formation on the extent of its range in Mexico is very limited, and nothing is known about its interaction with

Distribution. In the United States oslari is known from

other Anisota species.

southeastern Arizona, New Mexico, southwestern Col¬ orado, and extreme west Texas (see Map 4). Although

Immature Stages. The ova are larger than those of the

oslari has been collected in suitable habitat across most

other Anisota but similar in appearance. The larvae feed

of southeastern Arizona (Cochise, Santa Cruz, and

on oaks (Quercus) in canyons and on hillsides of the

Pima Cos.), records from Colorado, New Mexico, and

various mountain ranges running north along the Si-

80

Ceratocampinae

erra Madre from Mexico. Throughout southeastern Ar¬

has the use of Dryocampa rubicunda stabilized, and

izona oslari is most often collected on Mexican blue oak

Riotte and Peigler, 1980, and Lemaire, 1988, maintain the relationship.

(Q. oblongifolia) and scrub live oak (Q. turbinella). The early mstars are gregarious, and their characteristic

Dryocampa adults can be distinguished from Anisota

feeding pattern of not eating the midvein of leaves

on the basis of several characters. The wings of Dry¬

makes colonies easy to locate in late August and early

ocampa are yellow to white with pink markings and lack

September (M. J. Smith, 1987). Last-instar larvae are sol¬

discal spots; Anisota species all have a brown ground

itary feeders. Pupation occurs in a subterranean cham¬ ber where the pupa overwinters.

color and a discal spot on the forewing. Ferguson (1971)

The ground color of the last instar is brick red. A

cited a number of reliable genitalia characters that also

broken black longitudinal spiracular stripe is present to

distinguish the two genera. In addition, adult rubicunda are strictly nocturnal.

varying degrees; some individuals are heavily marked

The armature of the larva, which includes a pair of

while others have almost no stripe. The markings on

prominent thoracic horns, is reminiscent of Anisota;

the pictured specimen (Plate 2) are intermediate. We

however, the green ground color of the larva differs

are not aware of any regional variation in oslari.

from the brown, black, and reddish ground colors of most Anisota.

In three years of collecting at Lake Pena Blanca, Santa Cruz Co., Arizona, we observed no adults the first sea¬ son, many the second season (oslari was the most com¬ mon satumiid), and only a few individuals during the

Dryocampa rubicunda (Fabricius, 1793)

third season. It is not clear whether these observations represent cyclic population fluctuations or a response to the weather conditions of a given year (e.g., early vs. late rains). Perhaps pupae hold over for one or more seasons and emerge in response to optimal amounts of rainfall.

Figures: Adults, Plate 10; Larva, Plate 2; Map 6 Type locality: Virginia Synonymy: Dryocampa

rubicunda

alba

Grote,

1874,

revised

SYNONYMY

General Comments. The variability exhibited by rubi¬ cunda adults has led to conjecture that there are sibling

Rearing Notes. The larvae are excellent subjects for

species rather than just one species. This matter was

sleeving out on most oaks (Quercus). They also readily

discussed in detail by Ferguson (1971), who recognized

accept cut food. Pupae are fairly easy to overwinter but

rubicunda and rubicunda alba but also speculated that the

should not be exposed to freezing temperatures. Adults mate readily in cages.

faintly marked, light-colored material that he illustrated (Ferguson, 1971:Plate 1, fig. 7) from the northeastern United States and the Canadian Maritime Provinces might represent a third taxon. Although Ferguson

Genus Dryocampa Harris, 1833

(1971) distinguished between alba and the light forms of the northeastern populations, we find no justification

Type species: Bombyx rubicunda Fabricius, 1793; designated by Grote, 1874

for this distinction. Munroe (SS, 1951, p. 109) observed

The single species in this genus, Dryocampa rubicunda,

by side with rubicunda and noted that the reddish

occurs throughout the eastern United States and Can¬

patches on the abdominal segments are reduced, or

ada. After the original description of rubicunda by Fa¬

even absent, in last-instar alba larvae. We agree with

bricius (1793), the first available generic association was

Ferguson (1971) that the genitalia of alba and rubicunda

made by Harris (1833). Because rubicunda shares a num¬

are indistinguishable. D. C. Allen (1976) showed that

ber of characters with the Anisota species, however,

alba-like adults occur in the polymorphic populations

Grote (1864) reassigned the species as Anisota rubicunda.

of the Northeast. Although the transition from rubi¬

In spite of Grote's (1874) later recognition of rubicunda

cunda to alba is not clearly understood, J. R. Heitzman

as the type species of Dryocampa, rubicunda continued

and Heitzman (1987,

to be assigned to Anisota in major works on the Saturniidae (McDunnough, 1938; Packard, 1905). Michener

forms plus an intermediate phenotype occur in Mis¬ souri: "The pale form, D. alba, occurs in western and

(1952) later made Dryocampa a subgenus of Anisota, but

most of northern Missouri. A slightly pinker form is

Ferguson (1971) reestablished Dryocampa as a mono-

found in central and northeastern Missouri, while the

typic genus based on differences in adult morphology

dark pink D. rubicunda is found in the Ozarks." Al¬

and genitalia. Only since Ferguson's (1971) monograph

though the authors discussed only variation in the

a mass emergence of rubicunda in Quebec, and all were of the white form. We reared alba from Missouri side

p. 229) demonstrated that both

Dryocampa rubicunda

81

and their hindwings are usually less rounded. Males have bipectinate antennae; females have simple anten¬ nae. Forewing: male 17-20 mm; female 23-25 mm. Dryocampa rubicunda is extremely variable in colora¬ tion. The ground color may vary from bright yellow to cream to white. The amount of pink can also vary from dominating the general appearance of the moth to be¬ ing completely absent. As we indicated in the discus¬ sion of taxonomy above, extremes of these variants have been interpreted as regional trends. D. C. Allen (1976), however, identified five clearly defined morphs that varied from unmarked white to yellow heavily marked with pink in large samples from two popula¬ tions in the Northeast. Adult Biology. Wild adults have been captured from mid-May through early August in Nova Scotia (Fer¬ Map 6. Distribution of Dryocampa rubicunda

guson, 1971), and similar dates have been reported from across Michigan's Upper Peninsula (based on material in the Northern Michigan University collec¬ tion). L. F. Wilson (1971) stated that a partial second

amount of pink, their color plates (p. 229) show a clear

brood occasionally occurs in the northern part of the

change in ground color from white (alba) to yellow (rub¬

range of rubicunda (location unspecified), and we ob¬

icunda). The two phenotypes also reportedly occur in

served isolated second-generation emergences in cap¬

close proximity in southwestern Missouri (R. Heitzman,

tivity while rearing stock from southern Michigan.

pers. comm.). Unless careful fieldwork in this area

Nevertheless, the broad range of dates from these

shows distinct allopatric distributions or subtle biolog¬

northern locales represents an extended univoltine

ical differences that reproductively isolate the forms in

emergence. This conclusion is consistent with the de¬

nature, the pale populations probably do not merit tax¬

tailed field observations of D. C. Allen (1976) in New

onomic recognition. We treat all populations as rubi¬

England, where the peak emergence is in early July

cunda.

but adults may be taken any time from late May through late July. Ferguson (1971) reported two well-

Distribution. Dryocampa rubicunda occurs throughout

defined generations in South Carolina. The first brood

the eastern United States and Canada to the edge of the

emerges from early April through late May, the sec¬

Great Plains. It has been taken from Nova Scotia in the

ond brood from late June through mid-September. It

Maritime Provinces, through Quebec, and westward to

is not clear whether there are two or three genera¬

at least Dryden in extreme southwestern Ontario (Fer¬

tions in the Deep South. Kimball (1965) cited adult

guson, 1971). In the United States the species is com¬

captures from January through September in Florida,

monly encountered along the entire length of the

and Vernon Brou (pers. comm.) has collected rubi¬

Atlantic Coast from Maine to Dade Co. in southern

cunda from March through October in Louisiana.

Florida (Kimball, 1965). Westward, the species has been

Adults emerge in the late afternoon (1600-2000). Mat¬

taken in Itasca State Park, Clearwater Co., Minnesota

ing occurs in the late evening of the same day (2200-

(University of Minnesota collection), Iowa, eastern Kan¬

2400), and the pair remains together throughout the fol¬

sas and Nebraska, Missouri, Arkansas, and south to at

lowing day. Egg laying begins at dusk, almost imme¬

least San Jacinto Co., Texas.

diately after the pair separates. Adults of both sexes readily come to light.

Adult Diagnosis. The yellow to white ground color and pink maculation make rubicunda unique among North American satumiids.

Immature Stages. Ova are laid in clusters of 10-30 on leaves of the host plant. The ova are translucent yellow when laid and indistinguishable from most Anisota

Adult Variation. Sexual dimorphism is minimal in

eggs. The developing larvae become visible through the

rubicunda. Maculation is the same in both sexes. Fe¬

eggshell, and eclosion occurs in approximately two

males tend to have slightly broader wings than males,

weeks.

82

Ceratocampinae

The early instars are gregarious and often feed in uni¬

of the other species that we commonly call Sphingi¬

son, but by the fourth instar the larvae have become

campa in the subgenus Bouvierina. Sphingicampa bicolor

solitary feeders. There are five larval instars, and the

was separated from Bouvierina based primarily on the

mature larva is 45-55 mm long. Dryocampa rubicunda

bipectinate antennae of females (simple in females of

occasionally reaches pest status during periodic popu¬

other species) and characters of the male genitalia. The

lation explosions. The species is closely associated with

subgenus Syssphinx under Michener's classification

maple trees (Acer) and is most often reported on red

contained only the species molina, which was distin¬

maple (A. rubrum), sugar maple (A. saccharum), and sil¬

guished by unique characters in the male genitalia and

ver maple (A. saccharinum). Larvae have been collected

a distinct postmedian band on the hindwing.

on turkey oak (Quercus laevis) in Florida (Ferguson,

Nearly 20 years later, Ferguson (1971) combined the

1971) and an unidentified oak (Quercus) in Missouri

subgenera Bouvierina and Sphingicampa as the genus

(J. R. Heitzman & Heitzman, 1987). Pupation occurs in

Sphingicampa based on the overlap among a variety of

shallow underground chambers. In populations with

morphological characters in adults. As a result, the ge¬

multiple generations, the pupae resulting from spring-

nus Syssphinx, represented only by the type species,

brood adults emerge in approximately three weeks. In

Syssphinx molina, became monotypic. This was not as

all populations, the species overwinters in the pupal stage.

pointed out that molina exhibits unique characters. Most

Both the literature and our own observations indicate

recently, Lemaire (1988) again synonymized Sphingi¬

subtle variations in rubicunda larvae. Ferguson (1971) noted that preserved larval material from Florida had

campa with Syssphinx based on what he described as a continuum of characters.

a dark spiracular stripe, a character we have not ob¬

Since the morphology of the moths has not changed

dramatic a change as it seems, since Michener (1952)

served in Florida larvae. We have noted, however, that

during the past century, it is obvious that the authors

Florida larvae tend to have a redder head, a more yel¬

mentioned above had differing opinions as to what

low ground color, and smaller spines than material

constitutes a genus. Having examined and reared Sys¬

from other regions. Ferguson (1971) also reported in¬

sphinx molina and members of the subgenera Bouvierina

dividuals that completely lacked the black lateral lines.

and Sphingicampa, we concur with Ferguson's (1971)

Until systematic rearing of geographically diverse pop¬

combining of the two subgenera under Sphingicampa

ulations is completed, we will not be able to distinguish

and believe that morphological and genitalic differ¬

regional differences from individual variation.

ences warrant generic status for Syssphinx. We therefore retain the use of Sphingicampa. There is no doubt that

Rearing Notes. Larvae are easy to rear if maple (Acer)

Sphingicampa bicolor has unique characters (e.g., the bi¬

is available. The larvae should always be sleeved be¬

pectinate female antennae), but we feel that the North

cause maple wilts rapidly when cut. Adults readily pair

American species are phylogenetically closer to each

in confined spaces, and females oviposit freely in cap¬ tivity.

other than they are to Syssphinx molina. The genus Sphingicampa is obviously closely related to Anisota and Dryocampa and to the tropical genus Adelocephala. In North America, Sphingicampa can be distinguished from

Genus Sphingicampa Walsh, 1864 Type species: Sphingicampa distigma Walsh = Dryocampa bicolor Harris, 1841

the first two genera by its differently colored fore wings and hind wings. Eight species of Sphingicampa occur north of Mexico, and one reaches southern Canada. The largest number of species is found in Texas and Arizona. Six of the

The taxonomic status of Sphingicampa has changed several times. At the turn of the century, Holland (1903)

species occur as closely related groups. Sphingicampa al-

placed one North American species, bicolor, in Adeloce-

ern Texas. Three similar species: S. raspa, S. montana,

phala and the remainder in Syssphinx. Packard (1905)

and S. hubbardi, occur farther west in Texas, New Mex¬

separated molina in Syssphinx and placed the other

ico, and Arizona. All are medium-sized moths. The

North American species in Adelocephala.

Michener

adults are nocturnal, and the larvae tend to feed on

(1952) treated Sphingicampa as a subgenus of Syssphinx

woody legumes. Males are more commonly attracted

and synonymized Adelocephala under Sphingicampa. The

to light than females. Before landing at the collecting

subgenus Sphingicampa contained S. bicolor, which had

light they often exhibit a sphingidlike flight pattern.

been placed in Dryocampa by Harris (1841) and in Ade¬

Once they land, they fold their wings over the back and often remain at the light until dawn.

locephala by Jewett (1882). Michener (1952) placed most

bolineata, S. blanchardi, and S. heiligbrodti occur in south¬

Sphingicampa bisecta

83

forward movement. In captivity larvae often pupate at the bottom of containers filled with 5-6 inches of soil. The pupation chamber itself consists of soil that is sometimes slightly compacted, perhaps by the move¬ ment of the larva. Packard (1905) speculated that the enlarged scoli may render the larvae inedible to avian predators, but such a conclusion does not explain the variability in the number of scoli. A more plausible explanation is that the reflective metallic scoli break up the larval outline and offer a degree of concealment. Tuskes (1985a) sug¬ gested that the spacing of the silver scoli makes larvae more difficult to see on the natural host and that the Sphingicampa bicolor

frequency of silver scoli may be related to the leaflet size of the natural food plant. Species that feed on

Sphingicampa bisecta

small-leaved Acacia, for example, may have more silver scoli than those that feed on honey locust, whose leaf¬ Map 7. Distribution of Sphingicampa bicolor and S. bisecta

lets are wider and spaced farther apart. We used this hypothesis to speculate on the food plants of three spe¬ cies whose natural hosts had been unknown. In spite of the fact that numerous legumes were present in each

The ova are green and dorsoventrally compressed to form flattened ovoids about 2.5

of the habitats we investigated, we were able to collect

2 mm in diameter.

wild larvae of two of those species on the predicted

The mature larva is green with a prominent whitish subspiracular lateral stripe often accompanied by a red

host plant. For specific examples and a more detailed discussion, see the S. bicolor, blanchardi, montana, and

to near black spiracular line, and the silver to white

raspa species accounts, below.

X

dorsal and lateral scoli are elongated and have a meta¬ llic luster. The larvae of many satumiids are attractive, but the mature larvae of some Sphingicampa are truly

Sphingicampa bisecta (Lintner, 1879)

spectacular. Within some species, individual variation is most evident in the number of lateral pairs of pearly

Figures: Adults, Plate 11; Larva, Plate 2; Map 7 Type locality: Racine, Wisconsin

white dorsal scoli. The larvae of certain South African legume-feeding species in the subfamily Satumiinae (Heniocha, Aurivillius, and Gynanisa) have striking con¬ vergent patterns of silvery scoli (Pinhey, 1972; R. Peigler, pers. comm.). Early-instar larvae cling to the underside of the pet¬

General Comments. Sphingicampa bisecta was named for the almost straight line that bisects the dorsal fore¬ wing as it passes from near the apex to the inner wing margin. This distinctive character separates bisecta from all other Sphingicampa in our region.

iole and feed at the base of the leaflets. The later instars notch the petiole and bend the leaf back, allowing them to consume the entire leaf without having to crawl out

Distribution. Sphingicampa bisecta is the only Sphingi¬

to the end of the petiole. At rest, the immature larvae

campa whose distribution is restricted to the United

of several species position their dorsal thoracic scoli to¬

States, where it is the second most widely distributed

gether in a cluster, breaking up the elongated outline

member of the genus. The species is best known from

of a typical caterpillar. The larvae of S. hubbardi, and

the Midwest, where it can be locally common in the

perhaps of all the species, fluoresce under ultraviolet

Ohio Valley. Its northern limit appears to be the south¬

light (Stahnke, 1972), making them easy to collect at

ern extremes of Wisconsin (Racine, Racine Co.) and

night. Larval development is rapid, and all the species

Michigan (Morenci, Lenawee Co.), where it is only

produce multiple broods over at least part of their

rarely collected. Along the western edge of its range,

range. Just before pupation, the larval ground color

bisecta is known from Ottawa, Franklin Co., Kansas,

darkens, the enlarged dorsal scoli curve backward, and

and the Engeling Wildlife Preserve, Anderson Co.,

the larvae leave the host plant and enter loose soil

Texas (E. Knudson, pers. comm.). The eastern distri¬

head-first. After the larva has burrowed in about a

bution of bisecta is not quite as clear. There were no

quarter of its body length, the curved scoli enhance its

records from east of the Appalachian Mountains when

84

Ceratocampinae

Ferguson's monograph, The Moths of North America

tine. The flight periods appear to shift from year to year

North of Mexico, was published in 1971; however, the

in response to weather conditions. The combination of

collection of adults near Jalapa, Newberry Co., South

broad flight periods and annual variation in flight com¬

Carolina (SS, 1974, p. 12), and Whitfield Co., Georgia

mencement has resulted in a wide range of natural cap¬

(J. Adams, 1992), indicates that the species occurs at

ture dates. Depending on location, the spring brood

least sporadically east of the Appalachians.

emerges from April through June, and the summer gen¬ eration emerges from July through September.

Adult Diagnosis. Sphingicampa bisecta is similar in size

Sphingicampa bisecta occurs sympatrically with bicolor

and general appearance to female bicolor and blanchardi.

throughout its range, but pheromone differentiation ap¬

It is distinguished from bicolor by the thin, well-defined

pears to prevent reproductive interaction between the

black antemedial line and the thin postmedial line that

species (this is discussed in greater detail under bicolor).

extends from near the apex of the dorsal forewing to the medial area of the inner wing margin, and by its slightly larger size and distinctly pointed wings. Adults of bicolor lack an antemedial line, and the postmedial line is wider, suffuse, and often concave. The forewing of bicolor is stouter and more rounded than that of bi¬ secta. Sphingicampa blanchardi occurs in south Texas, out¬ side the range of bisecta. Some males of blanchardi resemble bisecta, but they always have white spots at the discal cell of the dorsal forewing, and the forewing is more rounded than that of bisecta. The females of the two species are very similar, but again, the forewing of bisecta is distinctly pointed compared with that of blan¬ chardi.

Immature Stages. The greenish ova are laid singly or in pairs and are indistinguishable from those of bicolor. Development is rapid, and eclosion can occur in as little as five days. The larvae have been collected on honey locust (Gleditsia triacanthos) and Kentucky coffee tree (Gymnocladus dioicus). We collected larvae of bisecta and bicolor on the same tree in northern Kentucky. By Sphingicampa standards, bisecta larval develop¬ ment is somewhat protracted.

Depending on

the

weather conditions, the larvae reach maturity in ap¬ proximately 40-45 days. The last instar is 55-60 mm long. Pupation in the spring is relatively short; summer adults emerge within two to three weeks. Larvae from

Adult Variation. The males are smaller than the fe¬ males and have more acutely angled wings. Males usu¬

the summer brood overwinter in the pupal stage. Mature bisecta larvae can be easily distinguished from

ally lack the dark stippling of the females, which is

bicolor on the basis of several reliable characters. The

often concentrated in the discal cell of the forewing and

prominent thoracic and middorsal abdominal scoli are

appears as a dark spot. Individual variation in the

primarily green in bisecta and red in bicolor. The wide

ground color of females is minimal, but males can vary

longitudinal subspiracular stripe is bordered by a thin,

from yellowish to orange. The size of the pink area on

dark line in bisecta, but replaced by a prominent broad

the hindwing of both sexes is also quite variable. None

red stripe in bicolor. In addition, the abdominal seg¬

of this variation appears to be seasonal since these var¬

ments of bisecta have yellowish lateral stripes running

iants occur among siblings of each generation. Fore¬ wing: male 25-30 mm; female 32-36 mm.

from the spiracle to the dorsum. The lateral pearly white scoli characteristic of the genus are present in varying numbers in both species. Ferguson (1971) sug¬

and become active that evening. Mating occurs during

gested that bisecta has more lateral scoli than bicolor, but we have not always found this to be true.

the late evening and early morning (2200-0200). The

As suggested above, individual variation is most ev¬

mated pairs we have observed remained in copula

ident in the number of pearly white lateral scoli. R.

throughout the following day.

Mecky Furr (pers.

Heitzman (1961) indicated that even among siblings the

comm.), however, reported that tethered females are

number of lateral scoli in bisecta can vary from two to

seldom accompanied by males the following morning. Egg laying begins at dusk.

segment are occasionally bluish, and the dark high¬

Sphingicampa bisecta is rarely taken along the extreme

lighting of the white subspiracular stripe may be lack¬

northern edge of its range, and the flight period in the

ing. We have not examined enough systematically

upper Midwest is poorly understood. The only records

reared material to determine whether or not there is any regional larval variation.

Adult Biology. Adults emerge in the late afternoon

from Michigan are from mid-July through mid-August

six. In addition, the lateral stripes on each abdominal

(Newman & Nielsen, 1973), although the lack of springbrood records may be the result of limited collecting.

Rearing Notes. Sphingicampa bisecta is usually free

Throughout the rest of its range bisecta is clearly bivol-

from disease and very easy to rear in captivity. In ad-

Sphingicampa bicolor

85

dition to the natural host plants cited above, we often

out, however, these traits are variable even within pop¬

use cultivated honey locusts (Gleditsia); Lemaire (1988)

ulations. The degree of dark stippling on the forewing

cited black locust (Robinia pseudoacacia) as a host. It is

also varies greatly, much as it does in the Anisota spe¬

possible that bisecta will accept other leguminous trees

cies. The diffuse postmedial line on the dorsal forewing

and shrubs in captivity as well. The adults readily mate

may be pronounced or almost lacking, and individuals

in cages, and the resulting pupae are easy to over¬ winter.

may have one, two, or no white discal spots. All these potential combinations of characters make bicolor one of the most variable of the satumiids. There appears to be some regional variation in bicolor, as populations from

Sphingicampa bicolor (Harris, 1841)

the Gulf Coast have reduced white forewing discal

Figures: Adults, Plate 10; Larva, Plate 2; Map 7

spots or none at all. Our limited experience with ma¬

Type locality: North Carolina

terial from the lower Rio Grande valley of Texas sup¬ ports this observation. Males are smaller than females

General Comments. Sphingicampa bicolor is the smallest and most variable of the Sphingicampa found north of

by 15-20%. Forewing: male 23-29 mm; female 3034 mm.

Mexico. It is often overlooked by collectors, perhaps be¬ cause it is so common, but the wide range of seasonal

Adult Biology. Adults emerge in the evening and seek

phenotypes makes this an unusual and interesting spe¬ cies.

mates the same night. Mating occurs from 2200 to 0200. Mated pairs remain in copula for the rest of the evening

Distribution. Sphingicampa bicolor is the most broadly

and throughout the following day, until the female be¬ gins laying her eggs at dusk. Extreme northern popu¬

distributed Sphingicampa in North America. It has been

lations, including those in Wisconsin, Michigan, and

collected sporadically along the Atlantic Coast from

Ontario, are bivoltine. The spring generation emerges

New Jersey to northern Georgia. West of the Appala¬

from overwintering pupae in late May through early

chians, bicolor can be extremely common in the Ohio Valley. In the North, bicolor has been reported from

June, and the resulting summer generation emerges in late July or early August.

Brantford, Dunnville, and Woodbridge in southern

Packard (1905) stated that bicolor is trivoltine at least

Ontario (Riotte, 1967), across southern Michigan, and

as far north as Dayton, Montgomery Co., Ohio. While

into southwestern Wisconsin (Grant and Richland

discussing the Dayton population, he quoted Jewett as

Cos.). Along the western edge of its range, the species

follows (p. 73): "Although the large majority of each

occurs

and

brood follows the cycle of development as described

Oklahoma. In the Gulf States, bicolor has been collected

[three broods], yet a few of each brood are much slower

in Mississippi, Louisiana, and eastern Texas through

in making their changes.... This accounts for the fact

the lower Rio Grande valley. The species has also been

that larvae of all stages of development may be found

reported from Nuevo Leon, Mexico (Beutelspacher &

at any time throughout the summer." The species

de Maza, 1975).

appears to be trivoltine throughout most of its range,

in

eastern

Iowa,

Nebraska,

Kansas,

Adult Diagnosis. Summer females can be similar to

with localized emergence dates from April through September.

bisecta females, and the gray form of bicolor looks

The lack of summer records from the lower Rio

somewhat like S. heiligbrodti. The characters that distin¬

Grande valley suggests that the populations there may

guish the three species are discussed in the bisecta and

forgo the midsummer brood; or perhaps the absence

heiligbrodti accounts.

reflects collectors' reluctance to collect during the ex¬ treme heat at this time of the year. Because it is the most

Adult Variation. Sexual dimorphism is minimal in bi¬

broadly distributed Sphingicampa species, bicolor occurs

color, but there is a tremendous amount of individual

sympatrically with several of its congeners. Throughout

and seasonal variation. Stalling and Turner (1942) de¬

much of its range bicolor is sympatric with bisecta. Ex¬

scribed the seasonal color forms of a trivoltine popu¬

tensive collections in southwestern Tennessee indicate

lation in Kansas: the spring broods have grayish

that bicolor and bisecta fly during the same season (M.

forewings and bright red hindwings, early summer

Furr, pers. comm.), and we have observed captive fe¬

broods have yellowish forewings and the amount of

males of both species calling at the same time of the

red on the dorsal hindwings is reduced, and late sum¬ mer broods have brownish forewings and increased red

evening. Thus it appears that pheromone differentia¬ tion is the primary factor reproductively isolating bi¬

on the dorsal hindwings. As Ferguson (1971) pointed

color from bisecta. In the Sabal Palm Sanctuary near

86

Ceratocampinae

size variation in these scoli. As we indicated in the dis¬ cussion of the genus, the appearance of the scoli and their variable number may be related to crypsis. Larvae do not appear to show significant regional variation, although the few we examined from south Texas showed a tendency toward reduction in the amount of red on the large dorsal armature. Additional material from the Rio Grande valley should be exam¬ ined to determine the extent of this variation. Rearing Notes. In addition to the natural host plants, we have achieved excellent results feeding larvae cul¬ tivated honey locusts (Gleditsia). Stone (1991) cited sev¬ eral possible alternate hosts, at least two of which (Ligustrum and Quercus) are questionable. The species is easy to rear in captivity and, in our experience, usu¬ ally free from disease. The adults readily mate in cages, and females oviposit freely in captivity. Brownsville, Cameron Co., Texas, bicolor is sympatrical with albolineata, blanchardi, and heiligbrodti (E. Knudson, pers. comm.).

Sphingicampa heiligbrodti (Harvey, 1877) Figures: Adults, Plate 11; Larva, Plate 2; Map 8

Immature Stages. The light green ova are laid singly

Type locality: Bastrop Co., Texas

or in pairs on the leaflets of the food plant. The ova become darker as the larvae develop, and the larvae are

General Comments. Sphingicampa heiligbrodti is the

clearly visible through the chorion just before hatching.

easternmost representative of two closely related taxa

Depending on the ambient temperature, eclosion can occur in as little as five days.

that were once treated as a single species. Ferguson

Larvae and ova have been collected on honey locust

it to full species status. The material we examined from

(1971) separated hubbardi from heiligbrodti and elevated

(Gleditsia triacanthos) and Kentucky coffee tree (Gym-

the University of California at Davis collection suggests

nocladus dioicus). As indicated in the bisecta account, we

that the two species occur sympatrically in portions of

collected both species on the same tree. Although past

Mexico, and Michael Smith (pers. comm.) collected both

reports (Packard, 1905) hint at local food preferences,

species near Alamos, Sonora, Mexico. The status of the two taxa merits further investigation.

we have found that captive bicolor readily accept either host plant. As with ova, larval development is influ¬ enced by temperature and can be extremely rapid. In¬

Distribution. In the United States, heiligbrodti is most

dividuals of midsummer generations often reach their

frequently encountered in the lowland thorn scrub hab¬

full size in three weeks. Mature larvae enter the soil

itat of Texas from Port Lavaca, Calhoun Co., south

and construct shallow pupation chambers. The pupal

along the coastal bend to the Mexican border. There are

stage lasts approximately two weeks in the spring and

numerous records from Cameron, Hidalgo, and Willacy

midsummer generations. As the result of the rapid de¬

Cos. in the lower Rio Grande valley, and from Sinton,

velopment in all stages, the entire life cycle is often

San Patricio Co. Our understanding of the northern and

completed in six weeks. The late summer generation overwinters in the pupal stage.

western limits is based on a few scattered records. Pre¬

Mature larvae have two pairs of prominent red scoli

State Park, Palo Pinto Co., greatly extend the range to

on thoracic segments 2 and 3, a stout red middorsal

the north (A. Blanchard, pers. comm.). Ferguson (1971)

scolus on the ninth abdominal segment, and a pro¬

cited records from San Antonio west to Uvalde and Del

nounced red-and-white spiracular stripe. The combi¬

Rio that extend the range toward that of hubbardi. The

nation of these characters distinguishes bicolor from all

records from this area suggest a break between the two

of its congeners. The mature larva is 50-55 mm long.

species in west-central Texas, with heiligbrodti occurring

Individual variation is most evident in the number of

in Uvalde Co. but replaced by hubbardi 85 miles to the

enlarged pairs of pearly white dorsal and dorsolateral

north in Kimble Co. Careful fieldwork and rearing may

scoli. Ferguson (1971) summarized previous reports of

shed additional light on the status of the two taxa.

viously unpublished records from Possum Kingdom

Sphingicampa hubbardi

87

Adult Diagnosis. Sphingicatnpa heiligbrodti resembles

pers. comm.). If heiligbrodti shares the food preferences

hubbardi and some color forms of S. bicolor. The dorsal

of its closest relative, S. hubbardi, it may also feed on

forewing of heiligbrodti is light gray; that of hubbardi is

species of Acacia. Like all Sphingicampa, the larvae de¬

dark slate gray. Although the two species are very close

velop rapidly and pupate in shallow subterranean

in maculation, the darker ground color of hubbardi min¬

chambers. The larvae from the spring brood appear to

imizes the appearance of the postmedial and anteme-

remain in the pupal stage throughout the summer and

dial lines that are so apparent in heiligbrodti. Ferguson

emerge in the fall. The larvae from the fall brood over¬

(1971) cited the postmedial lines on the dorsal hindw¬ ing and the ventral surface of both wings in heiligbrodti

winter as pupae. The last instar of heiligbrodti is similar to raspa in gen¬

as characters usually lacking in hubbardi, but we have

eral appearance. Both species have prominent paired

not found this to be a reliable means of separating the

dorsal thoracic scoli tinted with varying degrees of blue and yellow, two longitudinal rows of pearly white

two species. He also noted differences between the male genitalia: the valve in heiligbrodti is distinctly

spines, a red-and-white spiracular stripe, and red spir¬

larger than in hubbardi, but the length of the medial

acles, but there are several reliable characters that can

process is reduced. Adult Variation. The species is fairly consistent in ap¬

be used to separate them. The back of the white spines and the prominent anal horn have varying amounts of red in heiligbrodti, and

pearance. The variation we have noted involves the oc¬

varying amounts of yellow in albolineata. The red stripe

casional reduction, or even absence, of the postmedial

is greatly reduced and only highlights the spiracular

line and the intensity of the pink on the dorsal hind¬

white stripe in heiligbrodti, but in albolineata the red

wing. Forewing: male 23-28 mm; female 32-37 mm.

stripe dominates the spiracular stripe. As is typical of most Sphingicampa, there is individual variation in the

Adult Biology. Adults responded to light shortly be¬

number of lateral silver spines. We have not reared

fore midnight near Encino, Brooks Co., Texas, and in

enough larvae from different locations to note any sig¬

Hidalgo Co., Texas, we collected females by 2100 in the

nificant regional variation. The last instar is 55-60 mm

spring. Captive males became active soon after dusk,

long.

and females called during late evening and early morn¬ ing (2200-0200). The mated pairs often remained to¬

Rearing Notes. Blanchard (1964) reported that captive

gether throughout the following day, and oviposition

heiligbrodti fed equally well on honey mesquite (Prosopis

began at dusk. The species appears to be bivoltine in Texas. The spring brood emerges from mid-March through mid-

glandulosa), huisache (Acacia farnesiana), and blackbrush

June, although most adults are taken in April. We are

When host plants are available, the species is very easy

not aware of records that suggest a summer brood;

to rear. The adults are easy to mate in cages, and fe¬

however, this may be a function of limited summer col¬

males readily oviposit in captivity.

acacia (A. rigidula). We found that heiligbrodti readily accepts alternate ornamental honey locusts (Gleditsia).

lecting. The second brood emerges during the rainy season, mid-September-mid-October. In the lower Rio Grande valley (Cameron Co.) hei¬ ligbrodti is

sympatric with albolineata,

bicolor,

and

blanchardi, and adults of all four species were taken on

Sphingicampa hubbardi (Dyar, 1902) Figures: Adults, Plate 11; Larva, Plate 2; Map 8 Type locality: Oracle, Arizona

the same night in late September (E. Knudson, pers. comm.). We found three of the species to be sympatric

General Comments. Sphingicampa hubbardi was treated

in Hidalgo Co. These observations suggest that phero¬

as a subspecies of heiligbrodti until Ferguson (1971) el¬

mone differentiation is the primary method of main¬

evated it to species status on the basis of differences in

taining reproductive isolation, especially since there

male genitalia and adult coloration. Sphingicampa hub¬

appear to be no interspecific differences in nocturnal

bardi is the most common and widespread member of

flight times.

the genus in the western United States.

Immature Stages. The ova are light green, and eclo-

Distribution. North of Mexico hubbardi occurs sporad¬

sion occurs in five to six days. Larvae have been col¬

ically from central Texas (Kimble Co.) west to the

(Prosopis glandulosa) at

mountain ranges of northeastern San Bernardino Co. in

Bentsen State Park, Hidalgo Co. (E. Knudson, pers.

southeastern California. In Arizona it is commonly

comm.), and at George West, Live Oak Co. (M. Rickard,

taken in Pima, Santa Cruz, and Cochise Cos., and it has

lected on honey

mesquite

88

Ceratocampinae

been reported from Yavapai, Maricopa, and Pinal Cos.

The larvae are similar to other western Sphingicampa

as well. A specimen was recently collected in Sedona,

species. Mature larvae measure 52-55 mm. The en¬

Coconino Co. (W. Harding, pers. comm.). Based on host

larged dorsal and dorsolateral mesothoracic and meta-

plant distribution, it probably also occurs in Graham

thoracic scoli are yellow-green, and the outer edges are

and Mohave Cos., Arizona. In New Mexico, Ferguson

often silver. The dorsal and dorsolateral abdominal

(1971) reported it from Hidalgo and Luna Cos. We col¬

scoli may be enlarged and silver or may appear as a

lected it recently in Dona Ana and Otero Cos. and ex¬

simple spine with only a few secondary scoli present.

pect that it also occurs in Grand and Sierra Cos., New Mexico.

The lateral line is predominantly yellow. The ground color is green, like all Sphingicampa larvae, but the area below the lateral line is often blue-green. In general, the

Adult Diagnosis. The dorsal forewing of both sexes is slate gray, and the dorsal hindwing is red to pink. The

mature larvae are similar to heiligbrodti, but most tend to have orange spiracles rather than black.

most closely related species, heiligbrodti, has similar maculation but is distinguished by its light gray dorsal

Rearing Notes. Larvae readily accept alternate host

forewing and more easterly geographic distribution.

plants in captivity, including, most commonly, honey

The material we examined also indicates that male hub-

locust (Gleditsia triacanthos), huisache/sweet acacia (A.

bardi are larger than male heiligbrodti. The forewings of

farnesiana), and black locust (Robinia pseudoacacia). The

female hubbardi are more angular than those of female heiligbrodti.

larvae are easy to rear on cut host plant. Exposure of the pupae to freezing temperatures is not recom¬ mended.

Adult Variation. Other than size, males and females are quite similar. The coloration of the dorsal hindwing varies from dark pink to red. The reddish color extends

Sphingicampa blanchardi Ferguson, 1971

nearly to the margin in some specimens, but in others

Figures: Adults, Plate 11; Larva, Plate 2; Map 9

it terminates midway between the black eyespot and

Type locality: Brownsville, Cameron Co., Texas

the margin. Males have a poorly developed medial line on the dorsal hindwing; this line is virtually nonexistent

General Comments. Sphingicampa blanchardi is one of

on most females. Forewing: male 25-31 mm, avg. 28

several Lepidoptera species that have been adversely

mm; female 30-35 mm, avg. 32 mm.

affected by loss of habitat to agriculture and commu¬ nity development in extreme southern Texas. At this

Adult Biology. Adults are attracted to lights from June

writing, less than 1% of the original thorn forest habitat

to September in California, Arizona, and New Mexico,

remains (Jahrsdoerfer & Leslie, 1988). Aerial views im¬

but most records are from late July and early August.

mediately south of the border indicate similar habitat

Records from Texas include May and July through No¬

destruction in Mexico. Most of the remaining thorn for¬

vember, suggesting multiple broods (Ferguson, 1971).

est is protected in national or state refuges, and col¬

The adults eclose at dusk, and mating usually occurs

lecting is not allowed without a research permit.

after 2300. The pair stays together until the following evening. The female deposits her eggs over the course

Distribution. In the United States blanchardi is re¬

of the next few evenings, although most are laid the

stricted to southernmost Texas; all records are from Hi¬

first evening. Males are more commonly collected at

dalgo and Cameron Cos. Adults are associated with the ebony woodland community.

lights after 2200, whereas previously mated females tend to come to light earlier.

Adult Diagnosis. The dorsal forewings are brown to Immature Stages. The larval host plants in Arizona in¬

light yellow and the medial area is usually lighter in

clude Wright's acacia (Acacia wrightii) and honey mes-

color than either the marginal or antemedial area. Three

quite (Prosopis glandulosa var. juliflora). In California the

other Sphingicampa species occur sympatrically with

larvae probably use both catclaw acacia (A. greggii) and

blanchardi, but it is easily distinguished from each of

mesquite. Ferguson (1971) cited one record of little-leaf

them. Sphingicampa bicolor and heiligbrodti have gray

paloverde (Cercidium microphyllum) as a larval host

forewings, and albolineata has brownish gray-green

plant. Steve McElfresh (pers. comm.) found mature lar¬

forewings with a distinctive diagonal white stripe. The

vae by searching the food plant at night with a flashlight.

but that species is larger and more intensely colored.

most similar species is montana from southern Arizona,

Sphingicampa blanchardi

89

lenta), brasil (Condalia hookeri=obovata), Barbados cherry (Malpighia glabra), and coma, or saffron plum (Bumelia angustifolia). All but the last three species are legumes. Immature Stages. Larval development is rapid; adults may be produced from ova in as little as 45 days. We collected last-instar larvae on Texas ebony (Pithecellob¬ ium flexicaule) at the Sabal Palm Sanctuary in Southmost. Adult flight records indicate that larvae are probably present nearly year-round. This in turn suggests that the host plant(s) does not lose its leaves during either winter or the summer drought. The var¬ iability of the silver dorsal and dorsolateral scoli indi¬ cates that the larvae probably feed on a legume with medium-sized leaflets. (See the S. montana account, be¬ low, for a discussion of scoli variability in relation to tana

host plants.) Though captive larvae do well on a wide variety of legume trees associated with the ebony thorn

Adult Variation. Sexual dimorphism is similar to that

forest, only Texas ebony meets all the criteria necessary

found in montana (see below), although the differences

for the natural host plant: it is restricted to Cameron

are even more pronounced in blanchardi. The ground

and Hidalgo Cos., is evergreen, and has medium-sized

color of most specimens is light brown, but some, es¬

leaflets. Since larvae feed on so many types of legumes

pecially males, may be yellowish or even brown. The

in captivity, it is likely that ovipositing females are very

antemedial and marginal portions of the male's fore¬

selective. For example, huisache is an excellent host for

wing vary from purple to brown. The dorsal forewing

captive larvae and is associated with drier areas in the

of either sex may be heavily spotted or free of brown

ebony thorn forest, but it also occurs in other commu¬

spots. The reddish pink on the dorsal hindwing varies

nities from Florida to California while blanchardi does not. Huisache would also be a poor candidate because

in intensity; in some specimens it extends to the wing margins; in others it is restricted to the anal area. Fore¬ wing: male 24-28 mm; female 31-36 mm.

it drops its leaves during the winter. It is likely that Texas ebony is the only natural host plant in the United

Adult Biology. Adults can be collected at lights from

States. Mature larvae measure 52-55 mm. The enlarged dor¬

March to November, but the flight season peaks in

sal and dorsolateral mesothoracic and metathoracic

March and April. The larger numbers present in early

scoli are yellow-green with some silver. The dorsal and

spring most likely reflect the emergence of holdover

dorsolateral abdominal scoli may be enlarged and sil¬

pupae and winter larvae. The offspring of females that

ver or may be reduced to a simple spine with a few

fly in November probably pupate in early January.

secondary lateral scoli. The lateral line is predominantly

Frosts occur during January and February, and adults

yellow. Like all Sphingicampa larvae, the ground color

have not been reported during the winter months. The

is green, but the area below the lateral line is blue-green

adults eclose at night, and mating usually occurs after

in blanchardi.

2200. The pair stays together until the following eve¬ ning. Females deposit eggs over the course of the next

Rearing Notes. Larvae readily accept honey locust

three evenings, with most laid the first evening. Males

(Gleditsia triacanthos), huisache (Acacia farnesiana), prai¬

are attracted to lights after 2200, whereas previously

rie acacia (A. angustissima), tepeguaje (Leucaena pulverulenta), and Texas ebony (Pithecellobium flexicaule).

mated females often come earlier in the evening. Our observations indicate that most blanchardi are

Other legumes that have been tried but found to be

collected in mature ebony woodland or ebony thorn

unsuitable include screwbean mesquite (Prosopis pubes-

forest. The prominent trees in this community include

cens), blue paloverde (Cercidium floridum), black locust

Wright's acacia (Acacia wrightii), blackbrush acacia (A.

(Robinia pseudoacacia), and Jerusalem thorn (Parkinsonia

rigidula),

soft-leaf mimosa

aculeata). Sphingicampa blanchardi seems to produce

(Mimosa malacophylla), Texas ebony (Pithecellobium flex-

broods continuously, and if the pupae are kept warm

icaule), tepeguaje, or giant lead tree (Leucaena pulveru-

they progress to the adult stage rapidly. Chilling the

guajillo

{A.

berlandieri),

90

Ceratocampinae

pupae causes them to hold over for four to six weeks.

the evening, and mating usually occurs before 2300.

The pupae should not be exposed to freezing temper¬ atures.

The pair stays together until the following evening. Fe¬ males deposit eggs over the course of the next three to four evenings, but most are laid the first evening. In

Sphingicampa montana (Packard, 1905) Figures: Adults, Plate 11; Larva, Plate 2; Map 9

Arizona, adults are associated with washes in thorn for¬ est dominated by low-growing Acacia and Mimosa. The forewings are cryptic and yellow to brown. The

Type locality: Among the mountains near Guadalajara, Mexico

reddish hindwings could be aposematic, but warning behavior has not been observed by us or report¬

General Comments. Sphingicampa montana is relatively

ed in the literature. We have not observed specimens

uncommon north of Mexico. In some years a dozen or

that show signs of bird attack, perhaps because the

more specimens may show up at lights, but frequently

moths are cryptically colored and emerge in the early evening.

less than a half dozen specimens are taken per year. Adults are quite variable, and reared specimens often appear darker than wild adults.

Immature Stages. The larval host plant(s) in Arizona is unknown. In Sonora, Mexico, Steve Prchal collected

Distribution. Within the United States montana has

larvae on Haematoxylon brasalita and a large-leaved cas¬

been collected only in Santa Cruz and Pima Cos. in

sia (Cassia emarginata) (Tuskes, 1985a). Captive larvae

southern Arizona. Most specimens have been collected

have been reared on a wide variety of related legumes.

at Lake Pena Blanca and Sycamore Canyon in the

We suspect the host in Arizona is one of several low-

Atasco Mountains, Josephine Canyon on the south side

growing acacias or mimosas that grow in or near

of the Santa Rita Mountains, the Patagonia Mountains

washes. An unidentified species resembling Mimosa

near Harshaw, and Nogales, all in Santa Cruz Co. The

biuncifera occurs in all locales where montana has been

Pima Co. records are from the north side of the Santa

taken, and we suspect it is one of the natural host plants in Arizona.

Rita Mountains and include lower Madera Canyon and Box Canyon.

Development is rapid; only one month is required to progress from egg to pupa. The appearance of the lar¬

Adult Diagnosis. The dorsal forewing is brown to yel¬

vae may be influenced by the host plant. Mature larvae

low, and the medial area is distinctly lighter in color

from Sonora, Mexico, collected on large-leaved hosts

than either the marginal or antemedial area. There is

had few enlarged silver dorsal and dorsolateral scoli,

no

similar

species

in

Arizona,

although

montana

somewhat resembles blanchardi from south Texas. Sphingicampa montana can be distinguished from blan¬ chardi by its more rounded wings, reduced or absent white forewing discal spots, large size, and more in¬ tense coloration. Adult Variation. The extent of sexual dimorphism and the variation exhibited by each sex are dramatic. The ground color is yellow, brown, or a combination of the two. The dorsal fore wing may be stippled with small dark brown spots, although these are lacking on some specimens. Females are larger than males and fre¬ quently lack white discal spots on the dorsal forewing and the dark gray discal spot on the dorsal hindwing, which is usually prominent in males. The margin of the hindwing of females is gold, but reddish pink fre¬ quently extends from the basal area to the margin on males. Forewing: male 28-31 mm; female 35-39 mm.

but most of their offspring, which were reared on the small-leaved Acacia smallii, had silver scoli on all seg¬ ments. Careful rearing experiments should determine whether this result is a statistical artifact or is in fact the result of the host plant's influence. Greene (1989) documented a similar larval phenotypic plasticity in re¬ sponse to host plant morphology for a geometrid from Arizona. The iridescent silver on the scoli breaks up the larva's outline into segments, an effect further enhanced by the individual leaflets of the host plant. Thus, phenotypic variability may be an adaption that makes the larva cryptic on the appropriate host. We have observed sim¬ ilar variation in other Sphingicampa larvae, but not to this extent. Steve Prchal (pers. comm.) collected montana larvae lacking silver scoli on Cassia emarginata, which has large leaves. Sphingicampa bicolor and bisecta com¬ monly feed on honey locust, a plant with moderate¬ sized leaflets, and often have only a few silver scoli. Sphingicampa hubbardi, heiligbrodti, and raspa feed on

Adult Biology. Specimens have been collected at lights from 18 July to 8 August. The adults eclose in

hosts with small leaflets, and their larvae usually have silver on their dorsal and dorsolateral scoli. It is pos-

Sphingicampa raspa

91

sible that polyphagous species are under greater evo¬ lutionary pressure to develop and retain flexibility in this character. Mature larvae measure 54-60 mm. The enlarged dor¬ sal and dorsolateral mesothoracic and metathoracic scoli are green at the base, red the length of the shaft, and yellow at the tip. These scoli are blue and yellowish green on the mature raspa larva, and on hubbardi larvae they are purplish red and green and yellowish green. Tuskes (1985a) described the life history and immature stages of montana. Field records indicate only one sum¬ mer brood in Arizona.

□ Sphingicampa raspa

H

Sphingicampa albolineata

Rearing Notes. Larvae readily accept huisache (Acacia farnesiana) and honey locust (Gleditsia triacanthos). Some broods we reared accepted Jerusalem thorn (Parkinsonia aculeata) and Albizia distachya, and others did not. Other

Map 10. Distribution of Sphingicampa raspa and S. alboli¬ neata

legumes that we have offered but found unsuitable in¬ clude screwbean mesquite (Prosopis pubescens), blue pa-

Distribution. Within the United States raspa is re¬

loverde (Cercidium floridum), Texas prairie acacia (A

stricted to areas bordering Mexico. In Arizona it has

texensis), prairie acacia (A angustissima), and black lo¬

been collected in the Huachuca Mountains of Cochise

cust (Robinia pseudoacacia). The larvae drink water

Co. at Copper, Miller, Garden, and Ash Canyons; in

sprinkled on the leaf surface.

Santa Cruz Co. in the Patagonia Mountains at Wash¬ ington Camp and near Harshaw; and in Pima Co. in Lower Madera and Box Canyons at the base of the

Sphingicampa raspa (Boisduval, 1872)

Santa Rita Mountains and at Lake Pena Blanca in the Atacosa Mountains. Records are infrequent from Pena

Figures: Adults, Plate 11; Larva, Plate 2; Map 10

Blanca, Lower Madera Canyon, and Box Canyon. In

Type locality: Oaxaca, Mexico

western Texas, we examined a specimen that had been

General Comments. Ferguson (1971) treated Sphingi¬

collected at Black Gap, Brewster Co., by David Hyatt (Tuskes, 1985a).

campa raspa as a junior synonym of albolineata, but Lemaire (1988) relied on genitalic differences to elevate

Adult Diagnosis. The dorsal forewing is yellow to

raspa to species status. We examined material from

olive green or gray with a prominent white line ex¬

southern and western Texas, Chihuahua and Coahuila,

tending from near the apex of the wing to the medial

Mexico, and Arizona. The specimens from southern

inner wing margin. The antemedial line and discal

Texas appear to be slightly smaller than those from

spot are also white. A white medial line is also pres¬

the Arizona and west Texas populations, and they dif¬

ent on the dorsal hindwing, which is red to pink. The

fer in color and markings. The male genitalia vary

dorsal forewing of albolineata is smaller and browner

between Texas and Arizona populations, but the sig¬

than that of raspa, and the antemedial and medial

nificance of this is not clear. Tuskes (1985a) examined

white lines are closer together, causing the diagonal

15 genitalia and determined a consistent pattern: the

line to terminate in the basal third of the wing rather

southern Texas and Coahuila specimens had a very

than in the medial area. The antemedial and diagonal

distinct long, thin spine on the valve of the male geni¬

lines may touch on the forewing of females. The di¬

talia; males from central Chihuahua had no spine

agonal white line on the forewing of raspa females

on the valve; those from Arizona and west Texas

may terminate near the basal third of the inner wing

had a short, stout spine. Given the current information,

margin, but it is well separated from the antemedial

we do not know if these differences between popula¬

line. Further, the white line on the dorsal hindwing

tions warrant species status for raspa, but we follow

tends to be postmedial in raspa and medial or nearly

Lemaire (1988) and call Arizona and west Texas pop¬

so in albolineata. Other species of Arizona Sphingi¬

ulations raspa and the south Texas population alboli¬ neata.

campa lack the white antemedial and diagonal fore¬ wing lines.

92

Ceratocampinae

Adult Variation. Males and females express little sex¬

instar from mostly yellow to only slightly yellow. The

ual dimorphism except in size. Females are larger and

life history and immature stages were described by

have slightly more rounded wings. Among the 17

Tuskes (1985a; at the time, raspa and albolineata were

males and 8 females we examined, we noted variation

believed to be a single species).

in the intensity and location of the white forewing lines and the amount of white scaling between the anteme-

Rearing Notes. Larvae readily accept prairie acacia

dial and diagonal medial white lines. A small white

(Acacia angustissima) and related subspecies such as

discal spot is usually, but not always, present on the

Texas prairie acacia (A. texensis). Some broods we

dorsal fore wing. In Arizona the ground color of the

reared accepted honey locust (Gleditsia triacanthos), but

male forewing is consistently yellow; the female's may

they developed more slowly, had high mortality, and

be yellow or olive green or gray. Forewing: male 30-34

frequently produced stunted adults. Michael Wilson

mm; female 34-38 mm.

(pers. comm.) found Albizia distachya to be a suitable host, but we were unable to successfully rear larvae on

Adult Biology. In Arizona, adults may be collected at

Albizia. Other legumes found to be unsuitable hosts

lights during late July and early August. Females often

include screwbean mesquite (Prosopis pubescens), Jeru¬

appear at lights between 2200 and 2350; males are at¬

salem thorn (Parkinsonia aculeata), blue paloverde (Cer-

tracted between 0100 and 0300. Until they land, the

cidium floridum), huisache (Acacia farnesiana), and black

males' size, light color, and rapid flight make them look

locust (Robinia pseudoacacia). Mature larvae burrow into

like sphingids.

dry, loose soil and construct a poorly defined pupation

A few mid to late September records from Cochise

chamber by tying debris together with silk. Captive pu¬

Co., Arizona, and Mexico suggest a second brood.

pae should not be exposed to freezing temperatures,

About 60% of captive pupae that we kept under

and the soil in which they are overwintering should be

warm, humid conditions emerged between 16 and 24

moistened every month or two. Beginning in July, in¬

September, supporting the possibility of a second

crease the frequency of watering to once a week. The

brood in some years in Arizona. The only Texas rec¬

soil should not stay moist for more than one or two

ord, from Brewster Co., is of a male captured on 29

days. Keeping the pupae wet for too long increases the

April 1982. This spring record also supports the idea

risk of fungal infections. Adults are easily mated in

that raspa produces multiple broods in some years.

moderate-sized screen cages.

Records from Mexico indicate two or more broods per year. The adults eclose in the evening and often remain

Sphingicampa albolineata (Grote & Robinson, 1866a)

quiescent until the next night. In captivity, mating usu¬

Figures: Adults, Plate 11; Larva, Plate 2; Map 10

ally occurs after 1900 and before 2300, after which the

Type locality: Mexico

pair stays together until the following evening. Females deposit their eggs over the course of the next four eve¬

General Comments. Like Sphingicampa raspa, montana,

nings; about 60-70% are deposited the first evening. Fe¬

and blanchardi, albolineata is a Mexican species whose

males sleeved on Acacia laid their eggs singly on the leaflets.

range extends just north of the border. It is the leastknown of our Sphingicampa, and only recently were we able to collect and rear this species. In appearance the

Immature Stages. Eggs held at 29°C hatch in 9-11

adult and larva are similar to raspa.

days. Development is rapid; from egg to adult takes only five to six weeks. We speculated that the larval

Distribution. This species is common in Mexico, but

host plant was Acacia angustissima based on habitat as¬

in the United States albolineata has been reported only

sociation and this genus's general requirement of a leg¬

from the Brownsville-"Southmost" area of Cameron

ume host, and eventually we found a fourth-instar

Co., Texas. Most records are from the Sabal Palm Sanc¬

larva on A. angustissima in Miller Canyon to lay spec¬

tuary, a humid, semitropical locale that supports a rem¬

ulation to rest. The larvae have a strong preference for

nant climax forest dominated by ebony and palms and

leaves of intermediate age, often avoiding both new

bordered by thorn forest. The sanctuary contains at

growth and older, discolored leaves. Mature larvae

least 14 different legume species, several of which reach

measure 54—60 mm and have long, thin dorsal scoli. In

their northern range limits in the lower Rio Grande val¬

Arizona raspa is the only Sphingicampa with blue-and-

ley. Records cited by Ferguson (1971) from Galveston,

yellow dorsal scoli and orange spiracles. The color of

Texas, probably represent mislabeled material, as the

the prominent anal and dorsal scoli can vary in the last

closest suitable habitat is several hundred miles south-

Adeloneivaia isara

west of there and quite different from the Galveston vegetation.

93

Genus Adeloneivaia Travassos, 1940 Type species: Adelocephala subangulata Herrich-Schaffer, 1855; des¬

Adult Diagnosis. In addition to albolineata, three other

ignated by Travassos, 1940

Sphingicampa species occur in Cameron Co., Texas: bi¬ color, blanchardi, and heiligbrodti. Sphingicampa albolineata

The moths of the genus Adeloneivaia are small to me¬

is easily separated from the others because it is the only

dium sized, and the adults are primarily yellowish or

one with a white antemedial and diagonal white line

brownish. The outer forewing margins of males tend to

that extends from near the apex of the forewing to the

be straight; those of females may be more rounded. The

inner wing margin. Sphingicampa raspa, a similar species

adults of all species have a prominent forewing discal

found in western Texas and Arizona, is larger than al¬

spot, but the hindwing discal spot is greatly reduced or

bolineata, has the antemedial and diagonal white lines

even lacking. Both sexes have quadripectinate antennae

spaced farther apart, is more variable in ground color,

and, unique among North American satumiids, retract¬

and has a slightly lighter pink hindwing. For additional

able tufts of anal hairs, which are shed after copulation

information, see the raspa account, above.

(Lemaire, 1988). The greenish ova are translucent and develop rap¬

Adult Variation. Relatively little variation has been

idly, and the developing embryo is clearly visible

observed in specimens from south Texas. Females are

through the eggshell just before hatching. The larvae

larger and have slightly more rounded forewings than

are highly ornate with rows of long tubercles; in some

males. The amount of white scaling between the diag¬

species the tubercles are iridescent silver and reflect

onal and antemedial lines of the forewing is variable,

light as in the Sphingicampa. Very little has been written

as is the size of the white discal spot, especially among

about the biology of Adeloneivaia. Pupation in the spe¬

females. Material from the east coast of Mexico looks

cies that have been reared is subterranean.

very similar to Texas specimens. Fore wing: male 25-30 mm; female 31-37 mm.

Lemaire (1988) recognized 15 species and four sub¬ species in his treatment of the genus. Adeloneivaia is dis¬ tributed from Arizona (based on a single record) south

Adult Biology. Adults are collected at lights from April to November. Recent records from Texas and

through Mexico, Central America, and South America to northern Argentina.

northern Mexico indicate two or possibly three gener¬ ations per year in those areas. We observed large num¬ bers of adults at lights in the Sabal Palm Sanctuary,

Adeloneivaia isara (Dognin, 1905)

Cameron Co., Texas, in late September 1993. Adult flight records from the Brownsville-"Southmost" area

Figures: Adults, Plate 11; Larva, Plate 2; Map 11 Type locality: San Salvador, Central America

of Cameron Co., compiled by Ed Knudson, are dated 18 April 1982, 2 June 1984, 20 September 1974, 27 Sep¬ tember 1988, 7 October 1982, and 20 October 1974. Fer¬ guson (1971) cited a record from Brownsville dated 10 November 1928. No information is available on emer¬ gence, mating, or oviposition. For general guidance, re¬ view the comments regarding raspa, a closely related species. Immature Stages. The natural host plant is unknown but is most likely an Acacia, Mimosa, or Leucaena. The single larva we reared was very similar to raspa. The

General Comments. The inclusion of isara as a member of our fauna is based on a single record. A female was collected on 3 July 1984 by John Palting in Guadalupe Canyon in the Peloncillo Mountains (Cochise Co.) of extreme southeastern Arizona (SS, 1985, p. 16). The oc¬ currence of this species within our region is not sur¬ prising; Guadalupe Canyon has produced many new Neotropical Lepidoptera records, including Automeris randa, and isara is commonly collected in adjacent So¬ nora, Mexico (M. Smith, pers. comm.).

anal horn was greenish and the thoracic horns were green and blue, whereas in raspa these horns may have a great deal of yellow. Additional rearing may prove that this character is just as variable in albolineata.

Distribution. The

species

occurs

throughout

the

length of Mexico south to at least Costa Rica in Central America. In Sonora, Mexico, isara occurs in dry thorn scrub, a habitat dominated by legumes. In Costa Rica

Rearing Notes. The larva illustrated here was reared

the species inhabits dry tropical forests.

on Leucaena pulverulenta. It thrived in a hot, humid greenhouse, in conditions similar to those in the lower Rio Grande valley in the fall.

Adult Diagnosis. Adeloneivaia isara should not be con¬ fused with any other species likely to be taken in the

94

Ceratocampinae

rounded in females. Forewing: male 18-27 mm; female 26-32 mm. Both sexes exhibit color polymorphism ranging from yellowish to dark orange. Janzen (1984a) found that the adults are light in color during dry periods and dark during rainy periods, and suggested that this may be an adaptation to seasonal changes in foliage coloration and appearance. The degree of dark stippling on the forewing can also be quite variable.

Adult Biology. Very little has been published about the biology of isara. Janzen (1984a) reported that mating takes place shortly after dusk, but since we have not reared the species we cannot offer any further infor¬ Map 11. Distribution of Adeloneivaia isara thorn scrub of the Arizona-New Mexico border with

mation.

Immature

Stages. The

larva

illustrated

here

was

Mexico. The only other yellowish species in the region

reared ex ova by Steve Prchal from a wild female col¬

is Sphingicampa montana, and there are several reliable

lected in Sonora, Mexico. Janzen (1984a, 1985) collected

characters that distinguish it from isara. Adeloneivaia is¬

larvae on Lysiloma auritum and L. divaricata (Faba-

ara is smaller with narrow, more sphingidlike fore¬

ceae=Leguminosae) in Costa Rica.

wings, and both the forewing and the hindwing have a postmedial line; in montana only the forewing has a postmedial line.

Rearing Notes. The only reported hosts are members of the genus Lysiloma. If Lysiloma is not available, offer the larvae other legumes. Since the species is Neotrop¬

Adult Variation. Males are slightly smaller than fe¬ males. The outer wing margin is straight in males.

ical in origin, larvae should be reared and pupae should be stored at warm temperatures.

Subfamily Hemileucinae

The moths of this subfamily are small to medium

A few old records of dubious authenticity report a

sized and have bipectinate or quadripectinate antennae.

fourth genus, Hylesia, from Arizona, but these records

The genera found in the United States tend to have

lack precise localities and dates (Ferguson, 1971). Al¬

hindwings that are more brightly colored than the

though we do not discount the possibility that Hylesia

forewings. This trait, in concert with the often black-

has occurred in Arizona, extensive collecting in the last

and-red or black-and-yellow-ringed abdomen, may

two decades has failed to confirm these records, and

represent a warning pattern. When disturbed, hemileu-

we do not treat Hylesia as a member of our satumiid fauna.

cines curl the abdomen and pulsate it in a Hymenoptera-like manner. The hindwings of some genera bear a large discal spot resembling a vertebrate eye. All members of the subfamily appear to share a behavior that may be unique among the satumiids. When set¬

Genus Coloradia Blake, 1863

tling down to rest, the adults often rock the thorax from side to side, pulling the wings inward and peaking

Type species: Coloradia pandora Blake, 1863

them over the body like a tent, with the antennae tucked under the wings and out of sight. This habit

The genus Coloradia ranges throughout the montane

appears to make the moth more cryptic against its back¬

coniferous forests of the western United States and

ground and helps to eliminate a telltale shadow. The

Mexico. At present, eight species and several subspe¬

exposed forewings of resting moths often resemble leaf

cies are thought to occur in the United States and Mex¬

litter, or at least are duller than the hindwings and

ico (Beutelspacher, 1978; Ferguson, 1971; J. W. Johnson

body.

& Walter, 1979; Lemaire & Smith, 1992). We recognize

The eggs are laid in clusters or rings. The micropyle

four species and one subspecies (doris, luski, pandora

is visible at one end and turns dark in fertilized eggs.

pandora, pandora davisi, and velda) as occurring north of

Early-instar larvae are gregarious, and larvae bear

Mexico. Coloradia is closely related to Hemileuca.

rows of branched, spiny scoli throughout their devel¬

The moths of this genus are medium sized, and their

opment. Many of these spines are urticating; that is,

forewings are cryptically colored black, gray, white,

they are hollow and release an irritant that has the ef¬

and occasionally brown to match the bark of pine trees.

fect of stinging nettles. The members of the genus Au-

The hindwings, which are concealed while the moth is

tomeris spin simple cocoons, but the remaining North

resting, are tinted to varying degrees with diffuse black,

American hemileucines pupate in leaf litter or under¬

white, and pink. The extent of sexual dimorphism var¬

ground. The Hemileucinae comprises several hundred

ies from species to species. Males have broad quadri¬

species belonging to more than 20 genera, but only 3

pectinate antennae; females have narrow bipectinate

genera (Coloradia, Hemileuca, and Automeris) and about

antennae.

30 species are found in North America north of Mex¬

The ova of the six taxa that we have reared (doris,

ico, and these occur primarily in the West and South¬

luski, pandora pandora, pandora davisi, prchali, and velda)

west.

are exceptionally large for a medium-sized moth. They

95

96

Hemileucinae

believed to feed on pine (Pinus). The early instars are gregarious, and three to five larvae feed in unison on a single pine needle (Figure 16). Each species has five larval instars, and the mature larvae range in size from 60 to 80 mm. The larvae of all known Coloradia bear urticating spines, although the size of their armature varies from species to species. The life histories of the different species are quite varied as well. The adults are primarily nocturnal, but diurnal activity has been re¬ ported in pandora subspecies during periodic popula¬ tion explosions. Pairing occurs in the evening and lasts only a short time. Most species produce one generation a year, but pandora subspecies are biennial; early-instar larvae overwinter the first season, and pupae over¬ winter the second year. All species pupate in a loose cocoon beneath the surface of the ground. Native Americans have long understood the biennial life cycle of pandora, and the larvae are regarded as a great del¬ Figure 16. Early-instar larvae of Coloradia velda in a feeding cluster

are usually laid in small clusters near the base of pine

icacy (Aldrich, 1912, 1921; E. A. Blake & Wagner, 1987; Engelhardt, 1924).

Coloradia doris Barnes, 1900

needles or on the bark of pine trees. The ova are light

Figures: Adults, Plate 12; Larva, Plate 4; Map 12

green at oviposition and bluish gray with a dark mi-

Type locality: Glenwood Springs, Colorado

cropyle at maturity. The larvae of all the species are General Comments. Coloradia doris is both the most ob¬ scurely marked Coloradia in our region and the most broadly distributed. Distribution. Coloradia

doris

is

widely

distributed

throughout the Rocky Mountain states from Montana and Idaho south to New Mexico and Arizona. The spe¬ cies has been reported from Miles City, Custer Co., Montana (Ferguson, 1971); Pebble Creek Canyon, Car¬ ibou Co., Idaho (G. Gier, pers. comm.); the Black Hills, Weston Co., Wyoming; the Bristol Mountains (Lincoln Co.), Toiyabe Mountains (Lander Co.), and Toquima Mountains (Nye Co.), of Nevada (G. Austin, pers. comm.); Carbon, Daggett, Garfield, and Juab Cos., Utah (M. J. Smith, 1988); Alamosa Co., Colorado (D. C. Fer¬ guson, pers. comm.); the Sandia Mountains, Bernalillo Co., New Mexico; and the Chiricahua Mountains, Co¬ chise Co., Arizona. During the flight season doris can be expected to occur in pine habitats throughout this large area. The species has not been reported from Mex¬ ico, but the proximity of the Chiricahua Mountains to the border suggests that doris will eventually be taken in Sonora. Adult Diagnosis. The differences between doris and luski are discussed under the latter species. Although Map 12. Distribution of Coloradia doris, C. luski, and C. velda

doris and velda have allopatric ranges and can be

Coloradia doris

97

distinguished on the basis of locality, there are several

under luski, most reproductive interaction between the

morphological characters that separate the two species

species is avoided through seasonal isolation, although

as well. The fore wing maculation of males is much

circumstantial evidence suggests that pheromone dif¬ ferentiation is also a factor (see luski).

less defined in doris than in velda. Even more di¬ agnostic in males is the difference in their hindwings: the hindwings of doris are faintly marked and almost

Immature Stages. The ova are laid in groups of 5-12

translucent; those of velda are boldly marked in black

around the base of pine needles. These clusters often

and bright pink. We have not found reliable char¬

look like small Hemileuca egg rings. The ova are typical

acters that separate females of the two species, al¬

in appearance for the genus and take approximately

though the antemedial line in doris tends to be less angulate.

wild collections and ova laid by captive females.

three weeks to hatch. These observations are based on Larvae and ova have been collected on ponderosa

Adult Variation. Sexual dimorphism is well devel¬ oped in doris; the hindwings are light and translucent

pine (Pinus ponderosa) near Upton, Wyoming (Ferguson, 1971); Horsetooth Ridge, Larimer Co., Colorado (S.

in males, dark and more opaque in females. Forewing: male 28-32 mm; female 34-38 mm.

Stone, pers. comm.); and Flagstaff, Coconino Co., Ari¬

The females appear to be fairly uniform in appear¬

hosts. Gary Gier (pers. comm.) reported that lodgepole

ance, but the males exhibit some variation in the degree

pine (P. contorta latifolia) is the only pine species near

of marking on the hindwing. Some individuals, espe¬

Pebble Creek Canyon, Caribou Co., Idaho, where he

cially from the Chiricahua Mountains of southern Ari¬ zona, completely lack any marking other than the fine

has taken doris adults. M. J. Smith (1988) found doris associated with pinyon pine (P. monophylla) in Utah.

black outer wing margin; others have varying degrees

The early instars are gregarious and characteristi¬

of faint black bands or hints of pink along the inner

cally feed in groups on a single pine needle. Late-

margin of the hind wing.

zona (JPT). Other pine species may also be natural

instar larvae are solitary feeders. The larvae pupate in loose cocoons just under the surface of the ground in

Adult Biology. The adults fly earlier in the year than

late summer. Like luski, doris overwinters in the pupal

any other Coloradia. There are records from April in

stage, and the adults emerge the following spring or summer.

southern Arizona, and from mid-July in more northern locales. While we have never taken doris in great num¬

The last instar has rows of sublateral, lateral, dorso¬

bers, the adults of both sexes are frequently attracted

lateral, and dorsal spines and enlarged scoli on the pro¬

to light. Except for the earlier seasonal flight, the biol¬

thorax, mesothorax, and ninth abdominal segment, just

ogy of doris is similar to that of luski. Larval develop¬ ment is completed in one season, and the adults emerge

as luski does. We have noted some last-instar variation that appears to be regional rather than individual, but

the following summer.

until a larger sample is obtained from across a broader

The adults emerge in the late morning (0900-1200),

area of distribution, we cannot state that conclusion

and females begin calling at dusk of the first evening;

with certainty. The larvae from Coconino Co., Arizona,

mated pairs remain in copula for about an hour. Ovi-

are faintly marked, and the purple ground color dom¬

position takes place shortly after the pair separates and

inates the general appearance; larvae from Larimer Co.,

may be completed the first night. Like most Coloradia,

Colorado, have vertical black bands between each

female doris produce large but relatively few ova. The

abdominal segment that give the larva a very distinct

female's strong urge to oviposit soon after mating com¬

appearance. The diagnostic characters that separate

bined with the small number of ova she produces

doris and luski larvae are discussed under the latter spe¬

means that "spent" females are rather frequently col¬

cies.

lected. Flight activity occurs soon after dusk, probably to

Rearing Notes. Coloradia doris readily accepts eastern

avoid the nighttime temperatures, which drop quickly

white pine (P. strobus) in captivity and almost certainly

after sunset throughout the species' range and even during midsummer may fall to freezing just before

will accept other pines. In our experience, the species is difficult to rear in the high humidity and tempera¬

dawn. We routinely collect torpid adults at lights in

tures of the East. Perhaps differences in altitude also

the early morning near Flagstaff, Coconino Co., Ari¬

play a role in rearing difficulties. Larvae should be al¬

zona.

lowed to pupate in light, airy soil. The pupae are easy

Coloradia doris is sympatric with luski and the pandora subspecies in several parts of its range. As we discuss

to overwinter. Adults readily pair in captivity, and freshly mated females oviposit freely.

98

Hemileucinae

Coloradia luski Barnes & Benjamin, 1926 Figures: Adults, Plate 12; Larva, Plate 4; Map 12 Type locality: White Mountains, Arizona

replacing the gray-black ground color of the forewing. This color form is seldom encountered, however, and we do not know if it is geographically restricted to northern Arizona.

General Comments. Coloradia luski is the smallest mem¬ ber of its genus and the most sexually dimorphic. Ex¬

Adult Biology. Coloradia luski is a midsummer species

cept for Comstock's (1958) brief description of newly

that flies from late June through early August. Material

hatched first-instar larvae, the biology of luski was vir¬ tually unknown until the present work.

habitat and also reared in the East completed larval de¬

Distribution. Coloradia luski is known from midlevel

velopment in one season and produced adults the next summer.

elevations (6000-7500 feet) of several mountain ranges

Adults emerge in the afternoon (1200-1600) and be¬

in Arizona, New Mexico, and Colorado. Recorded

come sexually active the first evening. Females begin

from Flagstaff, Coconino Co., Arizona, sleeved in native

collecting sites include the Chiricahua Mountains,

calling soon after dusk. Mated pairs remain together a

White Mountains, and the area of Flagstaff, in Arizona;

very short time, usually no more than an hour. Shortly

the Cibola National Forest (McKinley Co.), Manzano

after the two separate, the female begins ovipositing.

Mountains, and Magdelena Mountains, in New Mexico

The ova are large for a moth of this size, and females

(J. Coleman & R. Wells, pers. comms.); and Chaffee Co.,

seldom produce more than 60.

Colorado (D. C. Ferguson, pers. comm.). The species

Throughout its range luski is sympatric with doris and

probably occurs in most of the mountain ranges within

the pandora subspecies. Most reproductive interaction is

those states. Suitable habitat extends throughout much

prevented by seasonal isolation: doris is a late spring

of the Rocky Mountain chain, and luski may yet turn

species, luski is a midsummer species, and the pandora

up in adjacent states. Ferguson (1971) cited a possible

subspecies are late summer fliers. Yet there is a certain

record from near Escalante, Garfield Co., Utah, but be¬

amount of seasonal overlap, particularly with respect

lieved the specimen might represent doris. Coloradia lu¬

to luski and doris. In captivity, both species called just

ski has also been reported from near Yecora, Sonora,

after dark. Although this is not conclusive evidence, it

Mexico (M. Smith, pers. comm.).

does suggest that the two species use different phero¬ mones to avoid reproductive interaction. The interac¬

Adult Diagnosis. Coloradia luski males can usually be separated from doris by the combination of their smaller

tion of these taxa in nature is an interesting subject for further research.

size, the exaggerated extension of the midpoint of the antemedial line to the discal spot on the dorsal fore¬ wing, and the greater amount of black and pink on the hindwing. Females of luski cannot always be reliably separated from doris, but their smaller size, melanic ground color, and more opaque appearance usually separate the two.

Immature Stages. Captive females laid clusters of 512 ova around the base of pine needles. At oviposition the eggs are light green; they turn blue-gray and de¬ velop a dark micropyle as they mature. The ova take approximately three weeks to eclose. Although wild larvae have not yet been collected, and the natural host plant has thus not been conclu¬

Adult Variation. Sexual dimorphism is strongly de¬

sively determined, the Flagstaff area, where luski com¬

veloped in luski. The maculation of the forewing is the

monly occurs, is dominated by ponderosa pine (Pinus

same in both sexes, but the detail is lost in the females'

ponderosa). The early instars are gregarious and, char¬

darker ground color. The hindwing of males is trans¬

acteristic of the genus, feed in unison on a single pine

lucent and has contrasting black-and-white bands; fe¬

needle. This feeding pattern persists until the larvae

males have an opaque black hindwing. Forewing: male 23-28 mm; female 25-34 mm.

molt into the fourth instar, at which time they become solitary feeders. Larval development is fairly rapid, and

Individuals of both sexes vary in the degree of white

pupation occurs by mid-September. The larvae spin

along the postmedial line of the forewing and the

loose cocoons under the surface of the soil. Coloradia

amount of pink on the hindwing. The black bands on

luski overwinters in the pupal stage, and the adults emerge the following summer.

the hindwing are very weak in some males. The ground color of females may be grayish to black.

The last-instar larva has rows of sublateral, lateral,

A male figured by Ferguson (1971:Plate 6, Fig. 7)

dorsolateral, and dorsal scoli, and the scoli on the pro¬

from Coconino Co., Arizona, is very light, with brown

thorax, mesothorax, and ninth abdominal segment are

Coloradia pandora pandora

99

greatly enlarged. Four lots of more than 30 siblings showed no significant individual larval variation. The armature of last-instar luski larvae is almost iden¬ tical to that of doris, but the material we examined showed subtle differences between the two species. The ground color is grayish brown in luski and purple in doris. The lateral subspiracular white stripe in luski has a well-defined black band that is usually lacking in doris. The diffuse black-and-white vertical band runs through the center of each abdominal segment in luski, and is lacking or occurs between segments in doris. Rearing Notes. Larvae readily accept eastern white pine (Pinus strobus) in captivity. Although we tried no other alternate hosts, we suspect that luski will accept many different pines. The species is very sensitive to humidity when reared outside its native habitat. The larvae often succumb to disease in the high humidity of Michigan, but during one exceptionally dry summer virtually every larva matured. The species requires light, airy soil in which to pupate. The pupae over¬ winter without special care, and emerging adults read¬ ily pair in confinement. Map 13. Distribution of subspecies of Coloradia pandora Coloradia pandora pandora Blake, 1863 Figures: Adults, Plate 12; Larva, Plate 4; Map 13 Type locality: Pike's Peak, Colorado

found significant differences between the taxa in larval

Synonymy: Coloradia pandora lindseyi Barnes & Benjamin, 1926,

morphology. For all of these reasons we place lindseyi into

REVISED SYNONYMY

synonymy with pandora pandora. With some hesitation we maintain the status of the small, dark subspecies davisi.

General Comments. Coloradia pandora pandora is the

Our reasons are discussed under that taxon.

largest member of the genus in the United States and one of the few satumiids that achieves major pest status. Periodic population explosions damage large forest tracts in Oregon (Patterson, 1929), California (Richers, 1985; Tuskes, 1984), Colorado (Carolin & Knopf, 1968; Wygant, 1941), Utah, Wyoming (Carolin & Knopf, 1968), and Nebraska (R. Rosche, pers. comm.). Ferguson (1971) recognized three subspecies of pan¬ dora: pandora, lindseyi, and davisi. We examined newly emerged material from California, Colorado, Arizona, and Nebraska, including groups from reared larval lots, and concluded that lindseyi does not differ sufficiently to merit subspecies status. We agree that lindseyi is somewhat larger than nominate pandora from Colorado,

Distribution. Our treatment of pandora pandora ex¬ tends the nominate subspecies' range throughout the coniferous forests of the western United States. Nomi¬ nate pandora is common in the Nebraska National For¬ est, Dawes Co., Nebraska (R. Rosche, pers. comm.); the Black Hills of western South Dakota and west through the mountainous areas of Wyoming, Colorado, and northern Utah (Ferguson, 1971); the Spring Mountains of western Nevada (M. Smith, pers. comm.); and from Oregon south through the length of California. Nomi¬ nate pandora has also been reported in northern Baja California, Mexico.

but we found almost no size difference between lindseyi and pandora pandora from Nebraska. Although the fore¬

Adult Diagnosis. Its size, prominent discal spots on

wing maculation and the suffusion of pink on preserved

both wings, late seasonal flight, and distribution make

specimens of pandora pandora from Colorado are very

pandora pandora difficult to confuse with any other spe¬

faint, fresh specimens show much variation. Specimens

cies. The characters that distinguish pandora pandora

from Wyoming and Nebraska often exhibit nearly as

from pandora davisi are discussed below under the latter

much pink on the hind wings as lindseyi. Nor have we

subspecies.

100

Hemileucinae

Adult Variation. Sexual dimorphism is reduced in

Across most of the species' range, pandora subspecies

pandora pandora compared with most other Coloradia

are reproductively isolated from other Coloradia by their

species. The females tend to be slightly larger and their

late seasonal flight period. Nominate pandora flies 6-8

hindwings are more diffused with gray-black than

weeks after velda in California (Tuskes, 1984), and pan¬

those of males, but these differences are minimal. Fore-

dora davisi flies 10-12 weeks after doris in Arizona (JPT).

wing: male 36-42 mm; female 39^44 mm.

In the Pike's Peak area of Colorado, however, pandora

As previously mentioned, the amount of pink on the

pandora can be flying by late July (luski flies in early July)

hindwing can be somewhat variable. The only other

(D. Gring, pers. comm.). Although it may yet be estab¬

variable character that we have noted is the size of the

lished that subtle differences in seasonal flight time exist

discal spot, which is quite large in some individuals.

between pandora pandora and luski in that area, the lim¬ ited amount of luski material from Colorado keeps us

Adult Biology. Depending on the location, eclosion

from stating that conclusion with certainty.

peaks from early July to late September. Sorting through adult mating activity can be somewhat confus¬

Immature Stages. The ova are laid in clusters of 3-20

ing because field observations of these moths are so

on pine needles or on the trunk of the host tree. When

varied. Patterson (1929) reported that adults in Oregon

population numbers are exceptionally high, females

were strictly diurnal and unresponsive to light at night,

seem to oviposit almost indiscriminately on trees, un¬

but Tuskes (1984) and Richers (1985) both reported that

derbrush, and even rocks. The appearance of the ova is

flight activity in southern and north-central California,

typical for the genus. As is the case with many other

respectively, did not commence until at least 2000, and

aspects of pandora pandora biology, there are conflicting

that adults of both sexes were attracted to lights in great

reports in the literature regarding the fertility of ova.

numbers. We closely monitored pandora pandora from

Patterson (1929) reported at least 20% infertility in wild-

Nebraska in outdoor cages and consistently observed

collected ova, but Wygant (1941) said that "very few of

mating activity to begin shortly after dusk (2200-2400).

the eggs in the field failed to hatch." Depending on

Diurnal activity in both pandora subspecies may be den¬

elevation and the date of adult emergence, hatching

sity dependent, as it has been reported only during

takes from three to seven weeks. The larvae are gre¬

population explosions (Tuskes, 1984).

garious during the early instars but become solitary feeders in the late instars.

Pairing is brief in pandora pandora; the mated pairs we observed seldom remained in copula for more than

Unique among Coloradia species, both pandora sub¬

an hour. It should be noted, however, that our obser¬

species have a biennial life cycle. The newly emerged

vations were of captive pairs, which mated at night.

larvae begin feeding in the fall but have reached only

Our laboratory females began ovipositing soon after separating from the males.

the second or third instar by the onset of cold weather. Ova collected in San Diego Co., California, did not eclose until mid-October (PMT). The gregarious larvae overwinter in a tight cluster at the base of pine needles at the terminal end of the branch. When warm weather returns and the host plant resumes its growth, the lar¬ vae develop rapidly and pupate in late June or early July. Pupation is in a loose chamber of silk and debris that is formed just below the surface of the ground (Fig¬ ure 17). In southern California, the adults may emerge during the fall of the same year (Tuskes,

1984),

but throughout most of the range, pandora pandora pu¬ pae overwinter a second season, and many of the adults emerge the following year. Carolin (1971) re¬ ported that pupae may remain in diapause for up to five years. Nominate pandora has been collected in coniferous forests throughout the western United States, mostly on Figure 17. Pupa of Coloradia pandora pandora in its pupation chamber

Jeffrey pine (Pinus jeffreyi), ponderosa pine (P. ponderosa), and lodgepole pine (P. contorta); specimens have

Coloradia pandora davisi

also been collected on Coulter pine (P. coulteri) and sugar pine (P. lambertiana) (Carolin & Knopf, 1968). The armature of last-instar larvae appears to be con¬ sistent across the range of pandora pandora. Although the spines are urticating, their flexibility makes them very ineffective at inflicting a sting. Color morphs rang¬ ing from almost black to brown or green occur in most populations. Rearing Notes. Rearing the pandora subspecies in cap¬ tivity is very difficult because of the two-year life cycle. On one occasion we successfully overwintered earlyinstar larvae by sleeving them on an eastern white pine in a protected area, and Steve Stone (pers. comm.) suc¬ cessfully sleeved them on ponderosa pine. It may be that diapause in pandora larvae can be artificially bro¬ ken by exposing them to warm temperatures and ex¬ tending the photoperiod during the fall, but we are unaware of any attempts to do so. Late-instar larvae readily accept alternate pines in captivity, and we have finished pandora larvae on Scotch pine (P. sylvestris) and eastern white pine (P. strobus). Like most Coloradia that we have reared, the larvae are sensitive to high humid¬ ity. A light, airy medium is required for successful pu¬ pation. The pupae are very easy to overwinter. Adults readily pair and oviposit in captivity.

101

The darker ground color reduces the contrast in the postmedial and antemedial lines on davisi; the lines are obvious on pandora pandora. As reported by Ferguson (1971), the genitalia of the two subspecies appear to be identical. Adult Variation. Sexual dimorphism is somewhat more developed in davisi than in pandora pandora, since davisi males are usually darker than females. The an¬ tennae are the same in both sexes, as is the case with pandora pandora. Forewing: male 32-35 mm; female 3638 mm. The males from a single brood varied in the amount of pink on the ventral surface of both wings. The fore¬ wings were similar, but the hindwings were extremely variable. Some individuals had well-defined black wing margins and postmedial lines; others had faint postmedial lines, and the black along the outer wing mar¬ gins was greatly reduced (Plate 12, no. 5).

Distribution. Coloradia pandora davisi has been col¬ lected in Arizona, southern Utah, New Mexico, and the Davis Mountains of extreme west Texas (Ferguson, 1971). Like the other Coloradia species, davisi is associ¬ ated with montane pine habitats. Although davisi has not yet been reported from Mexico, the proximity of the Arizona and Texas records to the border suggests that the subspecies will eventually be taken in Sonora, Chihuahua, or both.

Adult Biology. Adults emerge from late August through early September. Seemingly insignificant changes in elevation (as little as 200 feet) can result in microenvironmental differences that shift eclosion dates by as much as two weeks (Schmid & Bennett, 1988). Larry Brown (1984) reported nocturnal attraction to light and diurnal flight activity in both sexes of davisi in northern Arizona; Schmid and Bennett (1988) also reported large numbers of adults attracted to light and observed diurnal matings during population explo¬ sions. Freshly emerged females often copulated in the daytime, before they had expanded their wings, but they seldom initiated flight until nightfall. We have closely monitored caged davisi females in their native habitat and have consistently observed calling in the late evening to early morning (2230-0100). The mated pairs often remained together for two to four hours, much longer than other Coloradia pairs. Our mated fe¬ males usually began ovipositing soon after breaking away from the male. Like pandora pandora, davisi is reproductively isolated from other Coloradia species by its late seasonal flight. In the Flagstaff, Coconino Co., Arizona, area, where we have collected extensively, davisi flies from late August to early September, luski from late June to early August, and doris from mid-May to mid-June. Similar flight per¬ iods probably also separate the three species in New Mexico.

Adult Diagnosis. Subspecies davisi is consistently smaller (by approximately 15-20%) than nominate pan¬ dora, and the forewings of the males are much darker.

Immature Stages. The biology of immature davisi is similar to that of pandora pandora, except that all known davisi populations are biennial; early-instar larvae over-

Coloradia pandora davisi Barnes & Benjamin, 1926 Figures: Adults, Plate 12; Map 13 Type locality: White Mountains, Arizona

General Comments. This small, dark moth appears to be sufficiently different from nominate pandora to be re¬ liably separated in collections. Based on its smaller size and darker color, plus the fact that the two subspecies are believed to be allopatric, we maintain Ferguson's (1971) treatment of davisi as a subspecies of pandora.

102

Hemileucinae

winter the first season, and pupae overwinter the sec¬

on the forewing and pink on the hindwing, but this

ond year.

individual variation is minimal.

Schmid and Bennett (1988) noted that

overwintering davisi larvae usually positioned them¬ selves on a protected branch with a southern exposure, apparently an attempt at spatial thermoregulation.

Adult Biology. The species flies primarily in late May and early June, but there are a few records extending

This subspecies has been reported as a pest of pon-

into July. Adults of both sexes are readily attracted to

derosa pine (Pinus ponderosa) on the Kaibab Plateau of

lights in the late evening (2200-2400). Like doris and

northern Arizona (L. Brown, 1984; Schmid & Bennett,

luski, velda completes the larval stage in a single season,

1988). The larva and pupa closely resemble those of

and the adults emerge each summer.

nominate pandora.

Eclosion takes place in the late morning (0900-1200) and the fresh adults are inactive for the remainder of

Rearing Notes. The same rearing problems experi¬

the day. Soon after dusk females begin calling and mat¬

enced with larvae of pandora pandora may be encoun¬

ing takes place. Pairings last approximately an hour,

tered with davisi. We have had success feeding the

and females begin ovipositing shortly after breaking

larvae eastern white pine (Pinus strobus) and Scotch

away from the males. The slightly larger velda females

pine (P. sylvestris), and the subspecies almost certainly

tend to produce more ova than either doris or luski.

will accept other pines in captivity. The pupae are easy

Within its limited range velda occurs sympatrically

to overwinter. Adults readily mate in cages, and fe¬

with pandora pandora, but the two species are reproduc-

males oviposit freely in captivity.

tively isolated by their seasonal flight periods. The main velda flight occurs approximately two months be¬ fore the pandora pandora adults eclose (Tuskes, 1984).

Coloradia velda Johnson & Walter, 1979(80) Figures: Adults, Plate 12; Larva, Plate 4; Map 12 Type locality: Coxie Meadow, San Bernardino Co., California

Immature Stages. Captive adults laid ova in clusters of 6-15 in typical Coloradia fashion at the base of pine needles. The ova are indistinguishable from other spe¬

General Comments. Although it had previously been recognized as distinctive (Ferguson, 1971), this Califor¬

cies within the genus and take approximately three weeks to develop.

nia endemic was only recently described as a new spe¬

Larvae have not been collected in the wild, but the

cies (J. W. Johnson & Walter, 1979). Coloradia velda is

close association of velda with pinyon pine (Pinus mon-

the most boldly marked Coloradia in the United States,

ophylla) strongly suggests that it is the natural host

and fresh males in particular can be quite striking.

plant. First- instar velda larvae refused Jeffrey pine (P. jeffreyi), the only other pine that occurs in the region

Distribution. Coloradia velda is presently known only

(Tuskes, 1984). The early instars feed gregariously in

from the San Bernardino Mountains, San Bernardino

typical Coloradia fashion and become solitary feeders in

Co., California. It has been collected in the pine belt that

the fourth instar. Captive velda pupated in late August

runs along the length of the mountain range, but most

or early September. The pupating larva spins a loose

records are from the northern edge of the range near

cocoon just under the surface of the ground, where the

the type locality. The species has not been found in any

pupa overwinters.

of the adjacent mountain ranges in spite of intensive searches.

The general armature of last-instar velda larvae is very similar to that of doris and luski except for two characters that differ to some degree. The ground color

Adult Diagnosis. The differences between velda and doris are discussed under doris, above.

of velda is usually chalky white, and the vertical black markings frequently found on the other two species are lacking. In addition, the long scoli on the prothorax,

Adult Variation. Sexual dimorphism is greatly re¬

mesothorax, and ninth abdominal segment appear

duced in velda, and the females are almost as boldly

slightly shorter in velda. The ground color may vary

marked as the males. The maculation is the same in

from chalky white to grayish purple, but we observed

both sexes, but males tend to have slightly more pink on the hindwing. The females are approximately 20%

little additional variation in the broods of velda larvae that we reared (Tuskes, 1984).

larger than the males. Forewing: male 28-32 mm; fe¬ male 38-41 mm.

Rearing Notes. We have reared captive velda on pin¬

Adults of both sexes are fairly consistent in appear¬

yon pine (P. monophylla) and eastern white pine (P. stro¬

ance. There is some variation in the amount of white

bus). Stone (1991) reported P. edulis, P. jeffreyi, P.

Hemileuca

103

sylvestris, and P. thunbergiana as hosts. Coloradia velda

shaft, unlike the related Automeris larvae. All mature

has not proven as difficult to rear as doris or luski, and

Hemileuca larvae have urticating spines that can cause

in our experience is not as prone to disease. Adults are

a welt lasting from a day to more than a week. Al¬

easily mated in cages, and females readily oviposit in captivity.

though the spines may deter some vertebrate predators (and collectors), they provide little or no defense against parasitic flies and wasps. At times more than 90% of the mature larvae we collected were parasitized,

Genus Hemileuca

although larvae collected in the first and second instars

Walker, 1855

were usually free of parasites. There is a minimum of Type species: Phalaena maia Drury, 1773; designated by Grote & Robinson, 1866b

five larval instars, and, depending on the species and condition of the host plant, there may be six to seven. All species will pupate in surface debris or clumps of

The moths of this large genus hold a special interest for collectors because of their variability in color and

grass, but if loose soil is available many will burrow to a depth of 4-8 inches.

wing pattern, their unusual life history traits, and their

The adults of most species emerge a few months after

geographic distribution. The majority of the two dozen

pupating, but a portion of the population may over¬

or so species are brightly colored day fliers with distri¬

winter as pupae. The desert species, especially, are

butions centered in the desert, chaparral, and montane

known to delay eclosion for two to four years in cap¬

habitats of the Southwest and Great Basin. Structurally,

tivity, and such delays probably occur in nature. Spe¬

the bipectinate male antennae are unique among the

cies in the eglanterina group have a two-year life cycle

Hemileucinae and nearly so among all the Satumiidae.

in localities with a short growing season; the eggs over¬

The genitalia are similar to those of the genus Coloradia.

winter the first year, and pupae overwinter the second.

Most Hemileuca adults fly in the summer or fall. The

Larvae collected in the early instars and reared in

high-altitude species tend to fly earlier in the season

warmer locations pupate earlier and often eclose the

and are diurnal. The few nocturnal species are found

same year. Thus, in at least some instances the two-year

primarily in desert regions and fly early in the fall

cycle of high-altitude populations is environmentally

when evening temperatures are still mild. All species

induced. A certain photophase experienced at a crucial

lay their eggs in rings that encircle a twig or flower

stage in development may alter hormone levels and in¬

stalk of the host plant. Some desert species that utilize

duce diapause.

small host plants deposit their eggs in clusters of less

The adults are variously colored in shades of white,

than 24; species that feed on trees, large shrubs, or her¬

black, yellow, and red. When disturbed, most adults

baceous plants that grow in dense stands lay from 50

assume a characteristic pose with the wings elevated

to more than 200 eggs in a ring. The eggs of most spe¬

over the back and the abdomen curled downward.

cies overwinter and hatch in March or April, but a few

Many species have red-tipped abdomens that may be

hatch with the onset of the winter rains in temperate

aposematic. In others the abdomen is marked with

southern California or at the beginning of the summer

yellow-and-black bands, and the moth pulsates it when

rains in southeastern Arizona. Early-instar larvae feed gregariously in tight clusters,

son (1971) suggested that the similarity of certain spe¬

and their black, dark red, or dark brown coloration

cies is evidence of a Mullerian mimicry complex, and

allows them to rapidly absorb solar energy. Thus the

certainly a careful study of this group's unpalatability

larvae are able to complete their growth early in

and mimicry would be interesting and worthwhile.

attacked, producing a Hymenoptera-like effect. Fergu¬

the season, even at high altitudes. The larvae develop

Although some members of the genus have been con¬

species-specific markings as they mature, and they typ¬

sidered rare, we have found all of the species to be very

ically

When

common in localized populations. The adults of most

disturbed, later-instar larvae curl up and drop to the

species are rapid, erratic fliers, forcing one to give chase

ground. Many species, especially those in the open

in the manner of a cartoon caricature of a butterfly col¬

spaces of the Great Basin and the southwestern deserts,

lector. A more dignified and efficient method is to col¬

exist in dense, widespread populations, and the larvae feed on the dominant members of the shrubby plant

lect the conspicuous larvae, either as they feed in clusters or as they wander in search of a pupation site.

community. Other aspects of the Hemileuca life cycle are

Careful searching can also reveal egg rings after the

discussed in Chapter 1. The dorsal abdominal scoli of the larva are formed

leaves have fallen. Reared virgin females can be tied

as short tufts or clusters of spines without a central

be netted or trapped. This technique is an excellent way

feed

singly

after

the

fourth

instar.

out to call in males; sometimes hundreds of males can

104

Hemileucirtae

Table 1. Relationships among Hemileuca in the United States and Canada

Species group

Primary host plant

Time of oviposition

Female much larger than male

Larval pinaculum concolorous

Pupation in soil or leaf litter

tricolor group hualapai oliviae tricolor

Poaceae Poaceae Fabaceae

night day night

yes yes yes

no no no

no no no

maia group lucina maia nevadensis slosseri

Rosaceae Fagaceae Salicaceae Fagaceae

day day day day

yes yes yes yes

no no no no

yes yes yes yes

electra group electra juno

Polygonaceae Fabaceae

day day

yes yes

no no

yes yes

grotei group grotei stonei

Fagaceae Fagaceae

day day

yes yes

no no

yes yes

burnsi group burnsi neumoegeni

Asteraceae, Rosaceae Rosaceae, Anacardiaceae

night night

yes yes

no no

yes yes

chinatiensis group chinatiensis griffini

Anacardiaceae, Fabaceae Rosaceae

day day

yes yes

yes some

yes yes

eglanterina group eglanterina hero nuttalli

Rosaceae, Salicaceae, Rhamnaceae Asteraceae Rosaceae, Caprifoliaceae

day day day

no no no

yes yes yes

yes yes yes

to survey large areas and find new colonies. The fe¬

ral pheromones and developed synthetic pheromone

males of electra attract males of many different species

blends to attract a wide range of species. Table 2 de¬

and have been useful in such surveys. Nocturnal spe¬

scribes the response of male Hemileuca to females of the

cies can be collected at light.

different Hemileuca species (the table is from Tuskes,

Michener (1952) recognized four subgenera of Hemi¬

1984, modified to include data from McElfresh and Pat¬

leuca: Euleucophaeus, Pseudohazis, Argyrauges, and Hem¬

rick Savage). Interspecific male response to the different

ileuca. Ferguson (1971) and Tuskes (1984) did not apply

pheromones does not correlate well with morphologi¬

Michener's subgenera in their discussions of Hemileuca,

cal groupings. The question of whether the Hemileuca

however, because subsequent to Michener's work two

species are truly monophyletic will probably persist un¬

important species, chinatiensis and griffini, were discov¬

til it is answered by a cladistic analysis incorporating

ered whose male genitalia, wing shape, wingspan, sex¬

morphological and molecular data.

ual dimorphism, and larval characters place them

The tricolor group includes tricolor, oliviae, and huala-

between Michener's subgenera Hemileuca and Pseudo¬

pai. Hemileuca tricolor larvae feed on Fabaceae (=Leg-

hazis (Tuskes, 1984). Stone and Smith (1990) placed all

uminosae), and the other species feed on grasses

the species within Hemileuca and resurrected the origi¬

(Poaceae=Gramineae). Larvae often pupate above the

nal four subgenera. Although they characterized the

soil, at the base of dense grass clumps or low-growing

subgenera in detail, they were unable to place several

bushes. The pupa has white, chalklike material on the

taxa within this classification. In this book we recognize

surface that gives it a mottled appearance. The adults

distinct species groups, which we feel more closely rep¬

are usually nocturnal, but when populations reach high

resent true phylogenetic relationships. Table 1 sum¬

densities diurnal activity is common. The forewing

marizes some of the trends that characterize the species

ground colors tend to be light brown or gray, and the

groups. Steve McElfresh (pers. comm.) analyzed natu¬

hindwing of the male often has little or no maculation.

Hemileuca

105

Table 2. Intrageneric response of male Hemileuca to females of various species Calling 9 nevadensis nevadensis electra electra mojavensis electra electra electra electra electra electra electra electra electra juno burnsi burnsi chinatiensis chinatiensis chinatiensis chinatiensis chinatiensis eglanterina eglanterina eglanterina eglanterina hera hera nuttalli nuttalli

Male tested

Wild