The entire text is referenced to an extensive bibliography.
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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