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ENTOMOLOGY

FOLSOM

BLAKISTON'S SCIENCE SERIES

ENTOMOLOGY

WITH SPECIAL REFERENCE TO

ITS BIOLOGICAL AND ECONOMIC ASPECTS

JUSTUS WATSON FOLSOM, SC.D. (Harvard)

ASSISTANT PROFESSOR OF ENTOMOLOGY AT THE UNIVERSITY OF ILLINOIS

Second IRevuseo JEoition
lUitb ffour flMates ano 304 Ceit-tficuires

PHILADELPHIA:

P. BLAKISTOX'S SOX & CO.
1012 WALNUT STREET
1914

Copyright, 1913. by P. Blakistox's Son & Co.

72 rt*

9L

<

PREFACE

This book gives a comprehensive and concise account of insects.
Though planned primarily for the student, it is intended also for the
general reader.

The book was written in an effort to meet the growing demand for a
biological treatment of entomology.

The existence of several excellent works on the classification of insects
(notably Comstock's Manual, Kellogg's American Insects and Sharp's
Insects) has enabled the author to omit the multitudinous details of
classification and to introduce much material that hitherto has not
appeared in text-books.

As a rule, only the commonest kinds of insects are referred to in the
text, in order that the reader may easily use the text as a guide to personal
observation.

All the illustrations have been prepared by the author, and such as
have been copied from other works are duly credited.

To Dr. S. A. Forbes the author is especially indebted for the use of
literature, specimens and drawings belonging to the Illinois State Labora-
tory of Natural History.

Permission to copy several illustrations from Government publica-
tions was received from Dr. L. O. Howard, Chief of the Bureau of Ento-
mology; Dr. C. Hart Merriam, Chief of the Division of Biological
Survey, and Dr. Charles D. Walcott, Director of the U. S. Geological
Survey. Several desired books were obtained from F. M. Webster, of
the Bureau of Entomology.

Acknowledgments for the use of figures are due also to Dr. E. P.
Felt, State Entomologist of New York; Dr. E. A. Birge, Director of the
Wisconsin Geological and Natural History Survey; Prof. E. L. Mark
and Prof. Roland Thaxter, of Harvard University; Prof. J. H. Comstock
of Cornell University; Prof. C. W. Woodworth of the University of
California; Prof. G. Macloskie of Princeton University; Prof. W. A.
Locy of Northwestern University; Prof. J. G. Needham of Cornell Uni-
versity; Di. George Dimmock of Springfield, Mass.; Dr. Howard Avers
of Cincinnati, Ohio; Dr. W. M. Wheeler of the American Museum of
Natural History, New York City; Dr. W. L. Tower of the University

vi

PREFACE

of Chicago; Dr. A. G. Mayer, Director of the Marine Biological Lab-
oratory, Tortugas, Fla.; James H. Emerton of Boston, Mass.; Dr. and
Mrs. G. W. Peckham of Milwaukee, Wis. ; Dr. William Trelease, Director
of the Missouri Botanical Garden; Dr. Henry Skinner, as editor of " En-
tomological News"; and the editors of "The American Naturalist."

Acknowledgments are further due to the Boston Society of Natural
History, the American Philosophical Society and the Academy of Science
of St. Louis.

Courteous permission to use certain figures was given also by The
Macmillan Co.; Henry Holt & Co.; Ginn & Co.; Prof. Carl Chun of
Leipzig; F. Dummler of Berlin, publisher of Kolbe's Einfiihrung; and
Gustav Fischer of Jena, publisher of Hertwig's Lehrbuch and Lang's
Lehrbuch.

In the revised edition much newT matter has been added; particularly,
an entire chapter on the transmission of diseases by insects. A few new
illustrations have been introduced and several of the old figures improved.
The bibliography has been increased by the addition of about one hun-
dred titles of important works.

CONTENTS

Chapter Page

I. Classification i

II. Anatomy and Physiology 21

III. Development 118

IV. Adaptations of Aquatic Insects 152

V. Color and Coloration 159

VI. Adaptive Coloration 178

VII. Insects in Relation to Plants 195

VIII. Insects in Relation to Other Animals 215

IX. Transmission of Diseases by Insects 234

X. Interrelations of Insects 253

XI. Insect Behavior 283

XII. Distribution 300

Xin. Insects in Relation to Man 325

Literature 339

Index 387

vii

ENTOMOLOGY

CHAPTER I
CLASSIFICATION

At the outset it is essential to know where insects stand in relation to
other animals.

Arthropoda. — Comparing an insect, a centipede and a crayfish
with one another, they are found to have certain fundamental characters
in common. All are bilaterally symmetrical, are composed of a linear
series of rings, or segments, bearing paired, jointed appendages, and have
an external skeleton, consisting largely of a peculiar substance known as
chitin.

If the necessary dissections are made, it can be seen that in each of
these types the alimentary canal is axial in position; above it extends the

d al

Fig. i. — Diagram to express the fundamental structure of an arthropod, a, Antenna; al,
alimentary canal; b, brain; d. dorsal vessel; cx, exoskeleton; /, limb; n, nerve chain; s,
suboesophageal ganglion. — After Schmeil.

dorsal blood vessel and below lies the ventral ladder-like series of seg-
mental ganglia and paired nerve cords, or commissures; between the
commissures that connect the brain and the suboesophageal ganglion
passes the oesophagus. These relations appear in Figs, i and 163.
Furthermore, the sexes are almost invariably separate and the primary
sexual organs consist of a single pair.

No animals but arthropods have all these characters, though the
segmented worms, or annelids, have some of them — for example the
segmentation, dorsal heart and ventral nervous chain. On account of

these correspondences and for other weighty reasons it is believed that

2 • 1

2

ENTOMOLOGY

arthropods have descended from annelid-like ancestors. Annelids,
however, as contrasted with arthropods, have segments that are essen-
tially alike, have no external skeleton and never have paired limbs that
are jointed.

Classes of Arthropoda.— Excepting the king-crab, trilobites and a

few other aberrant forms of uncertain
position, the members of the series, or
phylum, Arthropoda fall into six dis-
tinct classes, namely, Crustacea, Arach-
nida, Malacopoda, Diplopoda, Chi-
lopoda and Insecta. These classes are
characterized as follows:

Crustacea. — Aquatic, as a rule.
Head and thorax often united into a
cephalothorax. Numerous paired
appendages, typically biramous (Y-
shaped); abdominal limbs often pres-
ent. Two pairs of antennae. Res-
piration branchial (by means of gills)
or cutaneous (directly through the
skin). The exoskeleton contains car-
bonate and phosphate of lime in addi-
tion to chitin. Example, cray-rish.

Arachnida. — Terrestrial. Usually
two regions, cephalothorax and abdo-
men; though various Acarina have but
one and Solpugida have all three —
Fig. 2.-A scorpion, Buthus. Natural head? thomx and abdomen> Cephalo-
thorax unsegmented, bearing two pairs
of oral appendages and four pairs of legs. Abdomen segmented or
not, limbless. Respiration tracheal, by means of book-leaf tracheae,
tubular tracheae, or both; stigmata almost always abdominal, at most
four pairs. Heart abdominal in position. Example, Buthus (Fig. 2).

Malacopoda. — Terrestrial. Vermiform (worm-like), unsegmented
externally. One pair of antennae, a pair of jaws and a pair of oral slime
papillae. Legs numerous, paired, imperfectly segmented. Respiration
by means of tubular tracheae, the stigmata of which are scattered over the
surface of the body. Numerous nephridia (excretory) are present and
these are •arranged segmentary in pairs. Two separate longitudinal

CLASSIFICATION

3

nerve cords, connected by transverse commissures. Integument delicate.
A single genus, Peripatus (Fig. 3), comprising many species.

Diplopoda. — Terrestrial. Two regions, head and body. Body
usually cylindrical, with numerous segments, most of which are double
and bear two pairs of short limbs, which are inserted near the median
ventral line. Eyes simple, antennae short, mouth parts consisting of a

Fig. 3. — Peripatus capensis.^ Natural size. — After Moseley.

pair of mandibles and a compound plate, or gnathochilarium. Genital
openings separate, anterior in position (on the second segment of the
body). Example, Spirobolus (Fig. 4).

Chilopoda. — Terrestrial. Two regions, head and body. Body long
and flattened, with numerous segments, each of which bears a pair of
long six- or seven-jointed limbs, which are not inserted near the median
line. Eyes simple and numerous (agglomerate in Scutigera), antennae
long. A pair of mandibles and two pairs
of maxillae. A single genital opening, on
the preanal segment. Example, Scolo-
pendra (Fig. 5).

Insecta (Hexapoda). — Primarily ter-
restrial. Three distinct regions — head,
thorax and abdomen. Head with a pair
of compound eyes in most adults, one pair
of antennae and three pairs of mouth parts
— mandibles, maxillae and labium— besides
which a hypopharynx, or tongue, is pres-
ent. Thorax with a pair of legs on each

r . , . „ . Fig. 4. — A diplopod, Spirobolus

ot its three segments and usually a pair marginatus. Natural size.

of wings on each of the posterior two seg-
ments; though there may be only one pair of wings (as in Diptera and
male Coccidae); the prothorax never bears wings. Abdomen typically
with ten segments (seldom more) and without legs, excepting in some
larvae (as those of Lepidoptera, Tenthredinidae and Panorpidae). Stig-
mata paired and segmentally arranged. A metamorphosis (direct or
indirect) occurs except in Thysanura and Collembola.

4

F.XTOMOLOGY

Relationships. —The interrelationships of the classes of Arthropoda
form an obscure and highly debatable subject.

Crustacea and Insecta agree in so many morphological details that
their resemblances can no longer be dismissed, as results of a vague
"parallelism/' or "convergence'' of development, but are inexplicable
except in terms of community of origin, as Carpenter has insisted.

Arachnida are extremely unlike other
arthropods but find their nearest allies
among Crustacea, particularly the fossil
forms known as trilobites.

Malacopoda. as represented by Pcrip-
atus, are often spoken of as bridging the
gulf that separates Insecta. Chilopoda and
Diplopoda from Annelida. Peripatus in-
deed resembles the chaetopod annelids in
its segmentally arranged nephridia, dermo-
muscular tube, coxal glands and soft integu-
ment, and resembles the three other classes
in its tracheae, dorsal vessel, lacunar circu-
lation, mouth parts and salivary glands.
These resemblances, however, are by no
means close, and Peripatus does not form
a direct link between the other tracheate
arthropods and the annelid stock, but is
best regarded as an offshoot from the base
of the arthropodan stem.

In speaking of annelid ancestors, none
of the recent annelids are meant, of course,
but reference is made to the primordial
stock from which recent annelids themselves
have been derived.

Though Diplopoda and Chilopoda have
long been grouped together under the name
Myriopoda, they really have so little in common, beyond the numerous
limb-bearing segments and the characters that are possessed by all tra-
cheate arthropods, that their differences entitle them to rank as separate
classes. Chilopoda as a whole are more nearly related to Insecta than
are Diplopoda. as regards segmentation, mouth parts, tracheae, genital
openings and other characters.

Scolopendrella, now placed either among Diplopoda or else in a class

Fig. 5. — A centipede, Scolo-
pendra heros. About two-thirds
the maximum length.

CLASSIFICATION

5

by itself, Symphyla, presents a remarkable combination of diplopodan
and insectean characters. Scolopendrella (Fig. 6) and the thysanuran
Campodea have the same kind of head, with its long moniliform antennae,
and agree in the general structure of the mouth parts; the number of

Fig. 6. — Section of Scolopendrella immaculata. b, Brain; c, coxal gland; /, fore intestine;
h, hind intestine; m, mid-intestine; n, nerve chain; o. opening of silk gland; od, oviduct; ov,
ovary; s, silk gland; u, urinary tube. — After Packard.

body segments is nearly the same, the legs and claws are essentially
alike, and cerci and paired abdominal stylets are present in the two
genera, not to mention the correspondences of internal organization.
Indeed, it is highly probable, as Packard maintained, that the most
primitive insects, Thysanura (and consequently all
other insects), originated from a form much like
Scolopendrella. A singular thysanuran, Anajapyx
vesiculosus (Fig. 7), has been discovered by Silvestri,
who regards it as being in many respects the most
primitive insect known, combining as it does char-
acters of Symphyla, Diplopoda and Campodea.

Silvestri discovered a peculiar arthropod, Acer-
cntomon doderoi for which he made a new order — -
Protura. Berlese added two genera to this order,
namely, Eosentomon and Acer entulus; and according
to good authority Protapteron indicum Schepotieff
belongs to the former genus. Silvestri, followed
by Borner, put Protura among Apterygota; but
Berlese, who grouped these forms under the name
of Myrientomata, found that they had myriopodan Fig. 7.— Anajapyx

. rr ' ' . . Tr vesiculosus. Length, 2

as well as msectean amnities; and Rimsky-Kor- mm.— After Silvestri.
sakow argues that Myrientomata cannot be rightly
regarded as insects, but logically constitute a class by themselves; and
that this class does not form a direct link between myriopods and
insects, but that all these groups came from the same ancestral stock.

6

ENTOMOLOGY

The following diagram (Fig. 8) expresses very crudely one view as
to the annelid origin of the chief classes of Arthropoda.

The naturalness of the phylum Arthropoda has been questioned by
Kingsley and Packard. The latter author divided Arthropoda into
five independent phyla, holding that "there was no common ancestor
of the Arthropoda as a whole, and that the group is a polyphyletic one."
This iconoclastic view, however, by emphasizing unduly the structural
differences among arthropods, tends to conceal the many deep-seated
resemblances that exist between the classes of Arthropoda.

Carpenter, in a most sagacious summary of the whole subject
of arthropod relationships, has brought together no little evidence in

favor of a revised form of the

INSECT*

CH1L0PODA

CRUSTACEA

ARACHNIDA

DIPLOPODA

Fig. S.-

ANNELIDA

-Diagram to indicate the origin of Ar-
thropoda.

old Mtillerian theory of crus-
tacean origins. He traces all
the classes of Arthropoda back
to common arthropodan ances-
tors with a definite number of
segments and distinctly crus-
tacean in character; then traces
these primitive arthropods back
to forms hke the nauplius larva
of Crustacea, and these in turn
to a hypothetical form like the
trochosphere larva of recent
polychaete annelids.

Orders of Insects. — Lin-
naeus arranged insects in seven

orders, namely, Coleoptera,
Hemiptera, Lepidoptera, Neuroptera, Hymenoptera, Diptera and Aptera.
The wingless insects termed Aptera wrere soon found to belong to diverse
orders and the name has now become so ambiguous as to meet with little
approbation.

From the Linnaean group Hemiptera, the Orthoptera were set apart;
the old order Neuroptera, a heterogeneous and unnatural group, has been
split into several distinct orders, and many other changes in the classifica-
tion have been necessary.

Without entering any further into the history of the subject, it is
sufficient to say that increasing discrimination on the part of entomolo-
gists has been followed by a gradual increase in the number of orders,
until our present system has been attained.

CLASSIFICATION

7

Owing to the incomplete condition of entomological knowledge, how-
ever, the best system as yet proposed is but tentative and more or less
open to objection. The most competent and widely approved classifica-
tions are those of Brauer and Packard, and the system here adopted is
essentially that of Brauer, with certain important modifications made by
Packard.

In the course of the following synopsis of the orders of insects it is
necessary to use some terms, as metamorphosis and thysanuriform, in
anticipation of their subsequent definition.

i. Thysanura. — No metamorphosis. Mouth parts mandibulate,
either free (ectognathous) or enclosed in the head (entognathous) .

Fig. 9. — Campodea. Length, 3 mm. Fig. 10. — Lepisma. Length, 10 mm.

Wings invariably absent. Thoracic segments simple and similar. Ab-
dominal segments ten, with two to eight pairs of rudimentary limbs
and two or three anal cerci. Eyes aggregate, compound or absent.
Antennae multiarticulate. Integument thin. Examples, Campodea (Fig.
9), Japyx, Machilis, Lepisma (Fig. 10). Some one hundred and seventy-
five species are known.

2. Collembola. — No metamorphosis. Mouth parts entognathous
and typically mandibulate, with occasional secondary suctorial modifica-
tions. Wings invariably absent. Thoracic segments simple and similar

8

i.N H »M< >!.< >(.\

or prothorax reduced. Body cylindrical or globular; abdomen with six
segments. Ventral tube and furcula usually present, rarely rudimentary.
Eyes ocelliform or absent. Antennae of four segments in most genera;

th e or six in a few genera. Integument delicate.
Examples, Achorutes (Fig. n), Sminthurus (Fig.
12). About seven hundred species have been de-
scribed.

Under the term A pterygoid (Apterygogenea,
Brauer; Synaptera, Packard) the Thysanura and
Collembola, as primitively wingless insects, are
conveniently distinguished from air other insects,
or Pterygota (Pterygogenea, Brauer).

3. Orthoptera. — Metamorphosis direct.
Mouth parts mandibulate. Wings two pairs as a
rule, though not infrequently reduced or absent;
front wings coriaceous (tegmina) ; hind pair mem-
branous, ample, closely reticulate, plicate along the
numerous radiating principal veins. Abdomen
with ten or eleven segments. Eight families : For-
ficulidae, Hemimeridae (Fig. 13), Blattidae, Mantidae,

Fig. 11.— The snow Phasmidae (Fig. 241), Acridiidae (Fig. 14), Locusti-
flea, Achorutes nivicola. \ J/ . , .

Length, 2 mm. dae, Gryllidae. Over ten thousand species are

known.

Some authors prefer to separate Forficulidae from Orthoptera as
a distinct order, for which Brauer and Packard preserve the old term
Derma ptera of Leach, while Comstock uses Westwood's term Euplexoptera.

Hemimeridae consist at pres-
ent of two African species whose
affinities appear to lie with For-
ficulidae, but deserve further
study.

4. Platyptera. — Metamor-
phosis direct. Mouth parts man-
dibulate. Wings, if present, two
pairs, delicate, membranous, equal
or hind pair smaller, and with the
principal veins few and simple. Integument usually thin. Nymphs
thysanuriform. Two suborders.

Suborder Corrodentia. — Including three families, as follows:

CLASSIFICATION

9

membranous, delicate, with indefinite reticulation and with a character-
istic basal suture. Abdomen elongate, with ten segments and a pair of
short, two-jointed anal cerci. In-
tegument delicate. Social in
habit. Example, Termes (Fig.
277). Over one hundred species
are known.

Comstock places Termitidae in
an order by themselves, Isoptera.

Embiidce. — Eyes facetted. An-
tennae 15-32 jointed. Mouth
parts prognathous. Thorax elon-
gate, prothorax reduced. Wings

N Fig. 15. — OUgotoma michaeli. Length, 10.5

(sometimes absent) elongate, mm.— After McLachlax.

membranous, delicate, with few

and feebly developed longitudinal and cross veins. Abdomen elongate,
with ten or possibly eleven segments, and a pair of stout Particu-
late cerci. Integument delicate. Not social in habit. Examples,

1 Prognathous, directed forward; hypognathous, directed downward.

10

ENTOMOLOGY

Fig. io. — Psocus venosus. Length. 5 mm.

Embia, Oligotoma (Fig. 15). Some twenty species, all from warm
climates.

These insects are most nearly related to Termitidae and Psocidae.
Psocida. — Eyes facetted. Antennae 13-50 jointed. Mouth parts
hypognathous. Prothorax reduced. Wings present, rudimentary or

absent; front pair the larger;
veins few and irregular. Abdomen
with nine or ten segments and no
cerci. Integument delicate. Ex-
ample. Psocus (Fig. 16). About
two hundred species.

Comstock raises Psocidae to the
rank of an order, for which he em-
ploys, in a new sense. Brauers term Corrodentia.

Suborder Mallophaga. — Wingless flattened insects, of parasitic
habit. Head large. Eyes consisting of a few isolated ocelli or else ab-
sent. Antennae 3-5 jointed. Mouth parts prognathous. Prothorax dis-
tinct; mesothorax often and metathorax usually transferred to the ab-
dominal region. Abdominal segments eight to
ten in number; no cerci. Parasitic upon birds
and a few mammals. Example, Menopon (Fig.
17). More than fifteen hundred species have
been described.

Packard's order Platyptera originally included
Perlidae. Brauers order Corrodentia consisted
of Termitidae, Psocidae and Mallophaga ; Perlidae
being set apart as an order (Plecoptera) and Em-
biidae being transferred doubtfully to Orthop-
tera.

Enderlein's thorough studies confirm the
view that Termitidae, Embiidae. Psocidae and
Mallophaga constitute a single order.

5. Plecoptera. — Metamorphosis direct.
Antennae long, multiarticulate. Mouth parts
mandibulate. Prothorax large. Wings two

pairs, membranous, coarsely and complexly reticulate; equal or else hind
wings larger and with an ample plicate anal area. Abdomen with ten
segments and usually a pair of long multiarticulate cerci. Nymphs thy-
sanuriform. aquatic; adults unique in having tracheal gills. Example,
Pteronarcys (Fig. 18). A single family, Perlidae, comprising two hundred
species.

Fig. 17. — A chicken
louse, Menopon. Length,
2 mm.

CLASSIFICATION

II

6. Ephemerida. — Metamorphosis direct. Antennae bristle-like.
Mouth parts mandibulate, but atrophied in the adult. Prothorax small.
Wings membranous, minutely reticulate; hind pair much the smaller,

A B

Fig. 18. — Pteronarcys regalis. A, nymph (after Newport); B, imago. Slightly reduced.

B

Fig. 19. — Hexagenia variabilis. A, nymph; B, imago. Natural size.

12

ENTOMOLOGY

rarely absent. Abdomen slender, with ten segments and three or two
very long multiarticulate cerci. Integument delicate. Nymphs thysa-

. -4 B
FlG. 20. — LibMtda pulchella. A, Last nymphal skin; B, imago. Slightly reduced.

nunform, aquatic,
species.

Fig. 21. — Euthrips tritici.

Example, Hexagenia (Fig. 19). Three hundred

7. Odonata. — Metamor-
phosis direct. Antennas in-
conspicuous, bristle-shaped.
Mouth parts mandibulate.
Prothorax small. Wings
four, elongate, subequal, simi-
lar, membranous, minutely
reticulate, with a costal joint,
or nodus. Abdomen slender,
with ten segments'. Xymphs
thysanuriform, aquatic. Ex-
ample, Libellula (Fig. 20).
About two thousand species
have been described.

8. Thysanoptera (Phy-
including a subpupa stage.

Length. 1.2 mm.

sopoda). — Metamorphosis direct, but
Mouth parts suctorial. Prothorax long. Tarsus terminating in a
bladder-like organ. Wings present, rudimentary or absent, the two pairs
narrow, equal, similar, with few or no veins and fringed with long hairs.
Abdomen with ten segments. Minute insects. Example, Euthrips
(Fig. 21). About one hundred and fifty species have been des-
cribed.

9. Hemiptera. — Metamorphosis direct (excepting male Coccidae).

CLASSIFICATION 1 3

Antennae usually few-jointed. Mouth parts suctorial. Prothorax usu-

Fig. 24. — Chrysopa
plorabunda. Slightly
reduced.

ally large. Wings usually present, except in the parasitic forms. Eigh-
teen thousand species. Three suborders:

Suborder Heteroptera. Wings four, folded
flat; front wings thickened basally, membranous
apically (hemelytra), overlapping obliquely; hind
wings membranous. Head not deflexed. Ex-
ample, Benacus (Fig. 22). About twelve thou-
sand species.

Suborder Homoptera. Wings four, sloping
roof-like, similar and membranous or front pair somewhat coriaceous

throughout. Head deflexed. Example.
Cicada (Fig. 207). Six thousand species.

Suborder Parasita.— Wingless. Eyes
simple or none. Thoracic segments inti-
mately united; tarsus with a single claw.
Integument thin. Parasites upon mammals.
Example. Pediculus (Fig. 23). Some fifty
species are known.

10. Neuroptera. — Metamorphosis in-
direct. Antennae conspicuous. Mouth
parts mandibulate. Prothorax large.
Wings almost always four, membranous, subequal or else hind pair

Fig. 2

5. — Bittacus strigosus.
tural size.

Xa

14

KNTOMOU ICY

smaller, complexly reticulate, not plicate. Larvae thysanuriform or in
some cases eruciform, and aquatic or terrestrial. Example, Chrysopa
(Fig. 24). About six hundred species have been named.

11. Mecoptera. — Metamorphosis indirect. Mouth parts mandib-
ulate, at the end of a deflexed rostrum, or beak. Prothorax small.
Wings four, elongate, membranous, naked, coarsely reticulate, or else
rudimentary or absent. Larvae eruciform, caterpillar-like, with numer-
ous prolegs, carnivorous. Example, Bittacus (Fig. 25). A single family,
Panorpidae, comprising but few known species.

12. Trichoptera. — Metamorphosis indirect. Antennae filiform.
Mouth parts of imago rudimentary or imperfectly suctorial; mandibles

Fig. 26. — Molanna cinerea. A, Larva; B, imago. X 4 diameters. — After Felt.

rudimentary or absent. Prothorax small. Wings four, membranous,
hairy, veins moderate in number, cross veins few; hind pair almost
always the larger, with plicate anal area. Larvae suberuciform, aquatic,
usually case-forming. Example, Molanna (Fig. 26). Between five and
six hundred species are known.

13. Lepidoptera. — Metamorphosis indirect. Mouth parts suctorial,
mandibles absent or rudimentary (except in a few generalized species).
Prothorax small. Wings four, similar, membranous, clothed with scales,
veins moderate in number, cross veins few. Larvae eruciform (caterpil-
lars), phytophagous (almost never carnivorous), mandibulate. Some
fifty thousand species have been described. Two suborders, not sharply
separated from each other.

Suborder Heterocera. — Antennae of various forms, but not ter-

CLASSIFICATION

15

minating in a distinct knob or club. Frenulum usually present. Chiefly
nocturnal in habit. Example, Callosamia (Fig. 237).

Suborder Rhopalocera. — Antennae simple, terminating in a dis-
tinct club and without conspicuous lateral processes. Frenulum absent.
Diurnal normally. Examples, Papilio (Fig. 27), Anosia (Fig. 244, A).

14. Coleoptera. — Metamorphosis indirect. Mouth parts mandibu-
late. Pro thorax large, as a rule. Wings four; front pair horny (elytra),
meeting in a straight line ; hind pair membranous, often folded. Larvae
thysanuriform or eruciform. Example, Hydrophihis (Fig. 28). About
one hundred and fifty thousand species.

15. Diptera. — Metamorphosis indirect. Mouth parts typically suc-
torial, but modified for piercing, lapping, rasping, etc. Prothorax small.

Fig. 27. — Papilio troilus. A, Larva; B, larva suspended for pupation; C, chrysalis. Nat-
ural size.

One pair of wings (mesothoracic), membranous, transparent, with few
veins; wings rudimentary or absent, however, in most of the parasitic
species; hind wings represented by a pair of knobbed threads, or balan-
cers. Larvae eruciform, with the head frequently reduced to a mere
vestige with or without a pair of mandibles, and usually without true
legs, though pseudopods may be present. Example, Tipula (Fig. 29).
About forty thousand described species.

16. Siphonaptera (Aphaniptera).— Metamorphosis indirect. Head
small. Eyes simple or absent. Mouth parts suctorial. Body laterally
compressed. Thoracic segments subequal. Wings absent or at most
quite rudimentary. Larvae with a head, mandibulate, apodous. Para-

1 6 ENTOMOLOGY

sitic insects. Example, Ctenoce phalus (Fig. 30). One hundred and fifty

species.

17. Hymenoptera. -Metamorphosis indirect. Mouth parts at the
same time mandibulate and suctorial. Prothorax usually small. Wings

Fig. 28. — Hydrophilus triangularis. Natural size.

four, similar, membranous, transparent, with a few irregular veins and
cells; hind pair the smaller. Females with an ovipositor, modified for
sawing, boring or stinging. Larvae eruciform, mandibulate, caterpillar-

Fig. 29. — Tipiria. A, larva; B, cast pupal skin; C, imago. Slightly reduced.

like, with head and legs, or else maggot-like and apodous. Twenty-five
or thirty thousand species. Two suborders.

Suborder Terebrantia (Phytophaga, Sessiliventres). — Abdomen
broadly attached to the thorax. Ovipositor modified for boring, sawing

CLASSIFICATION

17

or cutting. • Larvae with complex mouth parts and frequently abdominal
legs. Phytophagous. Example, Tremex (Fig. 31).

Suborder Aculeata (Heterophaga, Petiolata).— Abdomen petio-
late or subpetiolate; first abdominal segment transferred to the thorax.
Ovipositor often modified to form a sting. Larvae apodous. Example,
Apis (Fig. 281).

Interrelations of the Orders.— The modern classification aims to
express relationships, and these are most clearly to be ascertained by a
comparative study of the facts of anatomy and development.

Fig. 30. — Cat and dog flea, Ctcnocephalus amis. Fig. 31. — Tremex columba. A,

A, Larva (after Kunckel d'Herculais); B, adult. Imago; B, larva (with parasitic larva
Length of adult. 2 mm. of Thalessa attached). Natural size.

— After Riley.

The most generalized, or primitive, insects are the Thysanura. Sub-
tracting their special, or adaptive, peculiarities, their remaining characters
may properly be regarded as inheritances from some vanished ancestral
type of arthropod. This primordial type, then, probably had three
simple and equal thoracic segments differing but slightly from the ten
abdominal segments; three pairs of legs and no wings; three pairs of
exposed biting mouth parts; a pair of long, many-jointed antennae and a
pair of cerci of the same description; a thin naked integument; a simple
straight alimentary canal distinctly divided into three primary regions;
a ganglion and a pair of spiracles for each of the three thoracic and the
first eight abdominal segments, if not all the latter; no metamorphosis;
functional abdominal legs and active terrestrial habits.

The existing form that best meets these requirements is Scolopendrella,
which is not an insect, however, but belongs among or near the diplopods.
The most primitive of known insects are Anajapyx and Campodea,
3

i8

ENTOMOLOGY

through which other insects trace their origin to the stock from which
Symphyla and Diplopoda arose.

Collembola, though specialized in several important ways, all have
the same peculiar kind of entognathous mouth parts as Campodea and
Japyw for which reason and many others it is believed that Collembola
are an offshoot from the thysanuran stem. Collembola, however, are
not nearly so primitive as Thysanura, for the former have fewer ab-
dominal segments than the latter, exhibit much greater concentration of
the nervous system, and are uniquely specialized in several respects,
notably as regards the ventral tube and the furcula, or springing organ.

Returning to Thysanura — the genera Machilis and Lepisma show de-
cided orthopteran affinities; thus their eyes are compound and their
mouth parts strongly orthopteran; indeed, the likeness of Lepisma to a
young cockroach is striking, as is also that of Japyx to a young forfkulid.

In short, as Hyatt and Arms express it, "The generalized form of
Thysanura, and the manner in wrhich it reappears in the larvae of other
insects, is the natural key of the classification."

Orthoptera probably arose directly from the original thysanuriform
stem.

Platyptera, as a whole, are most nearly related to Orthoptera on the
one hand and to Plecoptera on the other. Termitidae have strong orthop-
teran affinities and Embiidae have even been placed in the order Orthop-
tera, though the latter family is most nearly allied to Termitidae and
Psocidae. These two are approached rather closely by Mallophaga and
exhibit, by the way, some collembolan characters, as Enderlein has
pointed out.

Plecoptera, which Packard placed in his group Platyptera, are better
regarded as a distinct order with some orthopteran and many ephemerid
and odonate affinities. The strong resemblance between nymphs of
Plecoptera, Ephemerida and Odonata indicates community of origin.

Ephemerida and Odonata are well circumscribed orders, most nearly
related to each other, but sharply separated, nevertheless, by differences
in the wings, mouth parts and other organs. Ephemerida are almost
unique among insects in having a pair of genital openings — a primitive
condition.

Thysanoptera form a distinct order, which is usually placed next to
Hemiptera, chiefly on account of the suctorial mouth parts, though even
in this respect there is no close agreement between the two orders.

Hemiptera stand alone and give few hints of their ancestry. They
are least unlike Orthoptera and possibly originated with Thysanoptera

CLASSIFICATION

19

from some mandibulate and winged form. The conversion of rnandibu-
late into suctorial organs may be seen within the order Collembola. but it
is highly improbable that Hemiptera arose from forms like Collembola.
Hemiptera are exceptional among insects with a direct metamorphosis in
their highly developed type of suctorial mouth parts.

Metamorphosis offers, upon the whole, the broadest criteria for the
separation of insects into primary groups. All the orders considered thus
far are characterized either by no metamorphosis or by a slight, or so-
called u direct," or "incomplete," transformation. The following orders,
on the contrary, are distinguished by an u indirect," or ''complete,"
metamorphosis, which appears in Xeuroptera and attains its maximum
development in Diptera and Hymenoptera.

With Xeuroptera the eruciform type of larva appears, as a derivative
of the earlier thysanuriform type. The larva of Mantispa, as Packard
has shown, actually passes, during its individual development, from the
primary, thysanuriform stage to the secondary, eruciform condition.

Mecoptera form an isolated order, though their caterpillar-like larvae,
with eleven or twelve pairs of legs, suggest affinities with Lepidoptera
and, more remotely, with the tenthredinid Hymenoptera.

Trichoptera, while much like Mecoptera in structure and metamor-
phosis, are undoubtedly closely related to Lepidoptera; in view of the ex-
tensive and deep-seated resemblances between caddis flies and the most
generalized moths (Micropterygidae) there is little doubt that Trichoptera
and Lepidoptera originated from the same stock.

The origin of the coherent group Coleoptera is by no means clear, al-
though thysanuriform larvae occur frequently in this order. Packard
suggests that both beetles and earwigs arose from some thysanuroid form
or that the primitive coleopterous larva sprang from some metabolous
neuropteroid form. In any linear arrangement of the orders the position
of Coleoptera is largely arbitrary, and here the order is intruded between
Lepidoptera and Diptera simply for want of a more satisfactory place.

Lepidoptera, Trichoptera and Mecoptera are probably branches from
one stem. Lepidoptera, Diptera and Hymenoptera are regarded by
Packard as having had a common origin from metabolic Xeuroptera.

Among Diptera, such larvae as those of Culicidae are comparatively
primitive, according to Packard, and larvae of Muscidae are secondary, or
adaptive, forms.

Siphonaptera used to be regarded as Diptera and are probably an off-
shoot from the dipteran stem.

The most primitive hymenopterous larvae are those of the sawflies

20

EXTONK >L< >GY

(Tenthredinidae), judging from their resemblance to mecopterous and
lepidopterous larvae; and the simple, maggot-like form of the larvae of
ants, bees, wasps and parasitic Hymenoptera is due to secondary modi-
fications in correlation with their sedentary mode of life.

In Diptera and Hymenoptera the phenomenon of metamorphosis
attains its greatest complexity, as was remarked. Opinions differ as to
which of these two orders is the more specialized. Hymenoptera are
commonly called the ''highest" insects, when their remarkable psycho-
logical development is taken into account; but from a purely structural
standpoint it is hard to say which order is the more complex — indeed, the
two orders are specialized in so many different ways that no precise com-
parison can be made between them.

The following diagram (Fig. 32) is a graphic summary of what has
just been said in regard to the genealogy of the orders of insects. The

Fig. 32. — Genealogical diagram of the orders of insects.

positions of Hemiptera and Coleoptera are most open to criticism. The
central group (T) is the hypothetical thysanuroid source of all insects,
including Thysanura themselves. Though Thysanura and Collembola
show no traces of wings, even in the embryo, it should be borne in mind
that all the other insects probably had winged ancestors and that it is
more reasonable to assume a single winged group as a starting point than
to suppose that wings originated independently in several different
groups of insects.

CHAPTER II

ANATOMY AXD PHYSIOLOGY

i. Skeleton

Number and Size of Insects. — The number of insect species al-
ready known is about 300,000 and it is safe to estimate the total number
of existing species as at least one million.

Among the largest living species are the Venezuelan beetle. Dynastes
hercules, which is 155 mm. long, and the Venezuelan grasshopper, A cri-
dium latreillei, which has a length of 166 mm. and an alar expanse of 240
mm. Among Lepidoptera, Attacus atlas of Indo-China spreads 240 mm. ;
Attacus ccEsar of the Philippines, 255 mm.; and the Brazilian noctuid
Erebus agrippina, 280 mm. Some of the exotic wood-boring larvae attain
a length of 1 50 mm.

The giants among insects have been found in the Carboniferous, from
which Brongniart described a phasmid (Titanophasma) as being one-fourth
of a meter long.

At the other extreme are beetles of the family Trichopterygidae, some
of which are only 0.25 mm. in length, as are also certain hymenopterous
egg-parasites of the families Chalcididae and Proctotrypidae.

Thus, as regards size, insects occupy an intermediate place among
animals; though some insects are smaller than the largest protozoans and
others are larger than the smallest vertebrates.

Segmentation. — One of the fundamental characteristics of arthro-
pods is their linear segmentation. The subject of the origin of this seg-
mentation is far from simple, as it involves some of the most difficult
questions of heredity and variation. As arthropod segmentation is
usually regarded as an inheritance from annelid-like ancestors, the sub-
ject resolves itself into the question of the origin of the segmented from
the unsegmented "worms." Cope, Packard and others give the me-
chanical explanation which is here summarized. In a thin-skinned, un-
segmented worm, the flexures of the body initiated by the muscular sys-
tem would throw the integument into folds, much as in the leech, and
with the thickening of the integument, segmentation would appear from
the fact that the deposit of chitin would be least at the places of greatest
flexure, i. e., the valleys of the folds, and greatest at the places of least

21

22

ENTOMOLOGY

flexure, i. e., the crests of the folds. This explanation, which has been
elaborated in some detail by the Neo-Lamarckians, applies also to the
segmentation of the limbs, as well as the body.

Head. — In an insect several of the most anterior pairs of primary
appendages have been brought together to co-operate as mouth parts and
sense organs, and the segments to which they belong have become com-
pacted into a single mass — the head — in which the original segmentation
is difficult to trace. The thickened cuticula of the head forms a skull,
which serves as a fulcrum for the mouth parts, furnishes a base of attach-
ment for muscles and protects the brain and other organs.

While the jaws of most insects can only open and shut, transversely,
their range of action is enlarged by movements of the entire head, which
are permitted by the articulation between the head and thorax.

As a rule, one segment overlaps the one next behind; but the head,
though not a single segment of course, never overlaps the prothorax in the
typical manner, but is usually received into that segment. This condi-
tion, which may possibly have been brought about simply by the back-
ward pull of the muscles that move the head, has certain mechanical
advantages over the alternative condition, in securing, most economically,
freedom of movement of the head and protection for the articulation itself.

The size and strength of the skull are usually proportionate to the
size and power of the mouth parts. In some insects almost the entire
surface of the head is occupied by the eyes, as in Odonata (Fig. 20, B)
and Diptera (Fig. 39). In muscid and many other dipterous larvae, or
"maggots," the head is reduced to the merest rudiment.

Though commonly more or less globose or ovate, the head presents
innumerable forms; it often bears unarticulated outgrowths of various
kinds, some of which are plainly adaptive, while others are apparently
purposeless and often fantastic.

Sclerites and Regions of the Skull. — The dorsal part of the skull
(Fig. 33) consists almost entirely of the epicranium, which bears the com-
pound eyes; it is usually a single piece, or sclerite, though in some of the
simpler insects it is divided by a Y-shaped suture. The middle of the
face, where the median ocellus often occurs, is termed the front; ordinarily
this is simply a region, though a frontal sclerite exists in some insects.
Just above the front, and forming the summit of the head, is the region
known as the vertex; it often bears ocelli. The clypeus is easily recog-
nized as being the sclerite to which the upper lip, or labrum, is hinged,
though the clypeus is not invariably delimited as a distinct sclerite.
The cheeks of an insect are known as the gence, and post-gam sometimes

AXATOMY AND PHYSIOLOGY

23

occur. Oh the under side of the head is the gula, which bears the under
lip, or labium. That part of the skull nearest the prothorax is termed
the occiput; usually it is not delimited from the epicranium, though in
some insects it is continuous with the post-genae to form a distinct sclerite.
The occiput surrounds the opening known as the occipital foramen,
through which the oesophagus and other organs pass into the thorax.
The membrane of the neck in Orthoptera and some other insects contains
small cervical sclerites, dorsal, lateral or ventral in position; these, in the
opinion of Comstock, pertain to the last segment of the head. Besides

Fig. 33. — Skull of a grasshopper, Mdanoplus difcrcntialis. a, Antenna; c, clypeus; e,
compound eye; /, front; g, gena; /, labrum; Ip, labial palpus; m, mandible; mp, maxillary
palpus; 0, ocelli; oc, occiput; pg, post-gena; v, vertex.

those described, a few other cephalic sclerites may occur, small and in-
conspicuous, but nevertheless of considerable morphological importance.

Tentorium. — In the head is a chitinous supporting structure known
as the tentorium. This consists of a central plate from which diverge two
pairs of arms extending to the skull (Fig. 34). The central plate lies
between the brain and the subcesophageal ganglion and under the oeso-
phagus, which passes between the anterior pair of arms. The tentorium
braces the skull, affords muscular attachments and holds the cephalic
ganglia and the oesophagus in place. It is not a true internal skeleton,
but arises from the same ectodermal layer which produces the external

'■oc

A

B

24

ENTOMOLOGY

cuticula; though authors are not agreed as to the details of the develop-
ment.

Eyes. — The eyes are of two kinds — simple and compound. The latter,
or eyes proper, conspicuous on each side of the head, are of common
occurrence except in the larvae of most holometabolous insects, in some

Fig. 34. — Skull of a grasshopper, Dissos- Fig. 35. — Head of a gyrinid beetle, Dineutus,
tcira Carolina. 0, occipital foramen; /, /, to show divided eye.

anterior arms of tentorium.

generalized forms (as Collembola) and in parasitic insects. The com-
pound eyes (Fig. 40) are convex and often hemispherical, though their
outline varies greatly; thus it may be oval (Orthoptera) or triangular
(Notonecta), while in the aquatic beetles of the family Gyrinidae (Fig. 35)
each eye has a dorsal and a ventral lobe, enabling the insect to see upward

Fig. 36. — Agglomerate eyes of a male coccid, Fig. 37. — Facets of a compound eye of

Leachia fuscipennis. — After Sigxoret. Mdanoplus. Highly magnified.

and downward at the same time; so also in Oberea and other terrestrial
beetles of the same family. Superficially, a compound eye is divided
into minute areas, or facets, which though circular in the agglomerate
type of eye (Fig. 36) are commonly more or less hexagonal (Fig. 37), as
the result of mutual pressure. These facets are not necessarily equal in

ANATOMY AND PHYSIOLOGY

25

size, for in dragon flies the dorsal facets are frequently larger than the
ventral. In diameter the facets range from .016 mm. (Lyccena) to .094
mm. (Cerambyx). Their number is often enormous; thus the house fly
(Musca domestica) has 4,000 to each eye, a butterfly (Papilio) 17,000, a
beetle (Mor delta) 25,000 and a spjiingid moth
27,000; on the other hand, ants have from 400
down, the worker ant of Eciton having at most
a single facet on each side of the head.

Ocelli. — The simple eyes, or ocelli, appear
as small polished lenses, either lateral or dorsal
in position. Lateral ocelli (Fig. 38) occur in
the larvae of most holometabolous insects and
in parasitic forms. Dorsal ocelli, supplemen-
tary to the compound eyes, occur on or near
the vertex, and are more commonly three in
number, arranged in a triangle, as in Odonata,
Diptera (Fig. 39) and Hymenoptera (Fig. 40)
as well as many Orthoptera and Hemiptera.
Few beetles have ocelli and almost no butter-
flies (Leretna accius with its one ocellus being the only exception known),
though not a few moths have two ocelli.

As explained beyond, the compound eyes are adapted to perceive
form and movements and the ocelli to form images of objects at close
range or simply to distinguish between light and darkness.

Fig. 38. — Head of a cater-
pillar, Samia cecropia, to show
lateral ocelli.

A

Fig. 30. — Ocelli and compound eyes of a fly, Phormia regina. A, male; B, female.

Sexual Differences in Eyes. — In most Diptera (Fig. 39) and in
Hymenoptera (Fig. 40) and Ephemeridae as well, the eyes of the male are
larger and closer together (holoptic) than those of the female (dichoptic).
This difference is attributed to the fact that the male is more active than
the female, especially in the matter of seeking out the opposite sex.
Among ants of the same species the different forms may differ greatly

26

ENTOMOLOGY

in the number of lateral facets. Thus in Formica pratensis, according to
Forel. the worker has about 600 facets in each eye, the queen 800-900
and the male 1.200.

Fig. 40. — Ocelli and compound eyes of the honey bee, Apis melHfera. A, queen; B, drone. —

After Cheshire.

Fig. 41. — Various forms of antennae. A, filiform, Eusckistus; B, setaceous, Plathemis; C,
moniliform, Catogcnus; D, geniculate, Bombus; f, flagellum; p, pedicel; s, scape; E, irregular,
Phormia; a, arista; F, setaceous, Galerita; G. clavate, Anosia; H. pectinate, male Ptilodactyla;
I, lamellate, Lachnosterna; /, capitate, Megalodacnc; K. irregular, Dineutus.

ANATOMY AND PHYSIOLOGY

27

Blind Insects. — Many larvae, surrounded by an abundance of food
and living often in darkness, need no eyes and have none; this is true of
the dipterous "maggots" and many other sedentary larvae, particularly
such as are internal parasites (Tachinidae, Ichneumonidae) , or such as
feed within the tissues of plants (many Buprestidae, Cerambycidae and
Curculionidae) . Subterranean or cavernicolous insects are either eyeless
or else their eyes are more or less degenerate, according to the amount of
light to which they have access. The statement is made that blind in-
sects never have functional wings.

Antennae. — The antennae, never more than a single pair (though
embryonic " second antennae" occur in Thysanura and Collembola), are
situated near the compound eyes and frequently between them. With
rare exceptions the antennae have always several and usually many seg-
ments. In form these organs are exceedingly varied, though many of
them may be referred to the types represented in Figs. 41-43.

Though homologous in all insects, the antennae are by no means equiv-
alent in function. They are commonly tactile (grasshoppers, etc.) or
olfactory (beetles, moths) and occasionally auditory (mosquito), as
described beyond, hut may be adapted for other than sensory functions.
Thus the antennae of the aquatic beetle Hydro phi! us are used in connection
with respiration and those of the male
Meloe to hold the female.

Sexual Differences in Anten-
nae.— In moths of the family Saturnii-
dae (S. cecropia, C. promethea, etc.) the
pectinate antennae of the male are
larger and more feathered than those
of the female, and differ also in having
more segments (Fig. 42). Here the
antennae are chiefly olfactory, and the
reason for their greater development in
the male appears from the fact that the
male seeks out the female by means of
the sense of smell and depends upon
his antennae to perceive the odor ema-
nating from the opposite sex.

The plumose antennae of the male mosquito (Fig. 43) are highly de-
veloped organs of hearing, and are used to locate the female; they have
delicate ribrillae of various lengths, some of which are thrown into sym-
pathetic vibration by the note of the female (p. 85).

Fig. 42. — Antennae of a moth, Samia
cecropia. A, male; B, female.

28

ENTOMOLOGY

Mcloc has just been mentioned. In Sminthurus malmgrenii (Collem-
bola) the antenna} of the male are provided with hooks and otherwise
adapted to grasp those of the female at copulation.

Though systematists have recorded many instances of antennal
antigcny, the interpretation of these sexual differences has received very
little attention; though a beginning in the subject has been made by
Schenk, whose results wTill be referred to in connection with the sense
organs.

Mouth Parts. — On account of their great range of differentiation,
the mouth parts are of fundamental importance to the systematise par-
ticularly for the separation of insects into orders. Most of the orders fall

Fig. 43. — Antennae of mosquito, Cidex pipicns. A, male; B, female.

into two groups according as the mouth parts are either biting {mandibu-
late) or sucking {suctorial). Collembola and Hymenoptera, however,
combine both functions; Diptera, though suctorial, exhibit various modi-
fications for piercing, lapping or rasping; Thysanoptera are partly man-
dibulate but chiefly suctorial; and adult Ephemerida and Trichoptera
have but rudimentary mouth parts.

The mandibulate orders are Thysanura, Collembola (primarily),
Orthoptera, Platyptera, Plecoptera, Ephemerida (rudimentarily in adult),
Odonata, Xeuroptera, Mecoptera and Coleoptera.

The mouth parts of an insect consist typically of labrum, mandibles,
maxilla, labium and hypo pharynx (Fig. 44), though these organs differ
greatly in different orders of insects. The mandibulate, or primary type,

ANATOMY AND PHYSIOLOGY

29

from which the suctorial, or secondary type, has been, derived, will be
considered first.

Mandibulate Type. — The labrum, or upper lip, in biting insects is a
simple plate, hinged to the clypeus and moving up and down; though
capable of protrusion and retraction to some extent. It covers the man-
dibles in front and pulls food back to these organs. On the roof of the
pharynx, under the labrum and clypeus, is the epipharynx; this consists
of teeth, tubercles or bristles, which serve in some insects merely to hold
food, though as a rule the epipharynx in mandibulate insects bears end-
organs of taste (Packard).

Fig. 44. — Mouth parts of a cockroach, Ischnoptera pennsyhanica. A, labrum; B, mandi-
ble; C, hypopharynx; D, maxilla; E, labium; c, cardo; g (of maxilla), galea; g (of labium),
glossa; /, lacinia; Ip, labial palpus; m, mentum; ?np, maxillary palpus; p, paraglossa; pf,
palpifer; pg, palpiger; s, stipes; sm, submentum. B, D and E are in ventral aspect.

The mandibles, or jaws proper, move in a transverse plane, being
closed by a pair of strong adductor muscles and opened by a pair of weaker
abductors. The mandible is almost always a single solid piece. In
herbivorous insects (Fig. 45,-4) it is compact, bluntly toothed, and often
bears a molar, or crushing, surface behind the incisive teeth. In car-
nivorous species (B) the mandible is usually long, slender and sharply
toothed, without a molar surface. Often, as in soldier ants, the man-
dibles are used as piercing weapons ; in bees (C) they are used for various
industrial purposes; in some beetles they are large, grotesque in form and

3°

ENTOMOLOGY

apparently purposeless. The mandibles of Onthophagus (D) and many
other dung beetles consist chiefly of a flexible lamella, admirably adapted
for its special purpose. In Euphoria (Fig. 262), which feeds on pollen

Fig. 45. — Various forms of mandibles. A, Mclanoplus; B, Cicindela; CApis; D, Onthoph-
agus; E, Chrysopa; F-I, soldier termites (after Ha gen).

and the juices of fruits, the mandibles, and the other mouth parts as
well, are densely clothed with hairs. In the larva of Chrysopa, the inner
face of the mandible (Fig. 45, E) has a longitudinal groove against which
the maxilla fits to form a canal, through which the blood of plant lice is
sucked into the oesophagus. In termites (F-I)

Qthe mandibles assume curious and often inexpli-
cable forms.

Next in order are the maxillcB, or under jaws,
which are less powerful than the mandibles and
more complex, consisting as they do of several
sclerites (Figs. 44, 46). Essentially, the maxilla
/ consists of three lobes, namely, palpus, galea and
lacinia, which are borne by a stipes, and hinged to
the skull by means of a car do. The palpus, always
lateral in position, is usually four- or five-jointed
and is tactile, olfactory or gustatory in function.
The lacinia is commonly provided with teeth or
spines. The maxillae supplement the mandibles
by holding the food when the latter open, and help
to comminute the food. Additional maxillary
sclerites, of minor importance, often occur.

The labium, or under lip, may properly be lik-
ened to a united pair of maxillae, for both are formed
on the same three-lobed plan. This correspondence
is evident in the cockroach, among other generalized insects. Thus, in
this insect (Fig. 44) :

Fig. 46. — Maxilla of
Harpdlus caliginosus,
ventral aspect. c,
cardo; g, galea; I,
lacinia; p, palpus; pf,
palpifer; s, stipes; sg,
subgalea.

ANATOMY AND PHYSIOLOGY

31

Labium = Maxillae
palpus = palpus
paraglossa = galea
glossa = lacinia
palpiger = palpifer
mentum = stipites
submentum with gula = car dines

In most mandibulate orders the glossae unite to form a single me-
dian organ, as in Harpalus (Fig. 47, g). The
labium forms the floor of the pharynx and
assists in carrying food to the mandibles and
maxillae.

The use of the term " second maxillae " for the ^ ^ , ( V / ■
labium of an insect is open to objection, as it im-
plies an equivalence with the second maxillae of
Crustacea — wrhich is by no means established.

The tongue, or hypo pharynx, is a median
fleshy organ (Fig. 44) which is usually united
more or less with the base of the labium. In
insects in general, the salivary glands open at
the base of the hypopharynx. In the most gen- pdJG' tali&nosm™ "ventral
eralized insects, Thysanura and Collembola, the asPect; 7 8, united glossae,

J termed the glossa; m, men-

hypopharynx is a compound organ, consisting of turn; p, palpus; pg, palpiger;
a median ventral lobe, or lingua, and two dorso- mriL pt

lateral lobes, termed superlinguce by the author, tion of the labium beyond

0 ,. - , ... - the mentum is termed the

buperlinguae occur in a few other mandibulate uguia.
orders (Orthoptera, Fig. 48; Ephemerida, Fig.

49), but have not yet been recognized in the more
specialized orders of insects.

Suctorial Types. — Owing to their greater com-
plexity, suctorial mouth parts are not nearly so well
understood as the mandibulate organs, but enough
has been learned to enable us to homologize the two
types, even though morphologists still disagree in
regard to minor details of interpretation.

The suctorial, or haustellate, orders are Collem-
bola (in part), Thysanoptera (in part), Hemiptera,
Trichoptera (imperfectly), Lepidoptera, Diptera,
Siphonaptera and Hymenoptera (wThich have func-
tional mandibles, however).

Fig. 48. — Hypo-
pharynx of Hcmimcrus
talpoides. I, lingua; s,
superlingua. — After
Hansen.

32

ENTOMOLOGY

Hemiptera. — The beak, or rostrum, in Hemiptera consists (Fig. 50)
of a conspicuous, one- to four-jointed labium, which ensheathes hair-like
mandibles and maxillae and is covered above at its base by a short

labrum. The mandibles and maxillae
are sharply-pointed, piercing organs
and the former frequently bear retrorse
barbs just behind the tip; the two
maxillae lock together to form a suck-
ing tube. Though primarily a sheath,
the labium bears at its extremity sen-
sory hairs, which are doubtless used to
test the food. This general description
applies to all Hemiptera except the
parasitic forms, which present special modifications. A pharyngeal
pumping apparatus is present, which is similar in its general plan to that

Fig. 49. — Hypopharynx of an ephe-
merid, Heptagcnia. I, lingua; si, si,
superlinguae. — After Vayssiere.

Fig.

-Mouth parts of a hemipteron. Benacus griseus. A, dorsal aspect; B, transverse

section; C, extremity of mandible; D. transverse section of mandibles and maxillae; c, canal;
/, labrum; li, labium; m, mandible; mx, maxillae.

of Lepidoptera and Diptera, as presently described, though it differs as
regards the smaller details of construction.

ANATOMY AND PHYSIOLOGY

33

Fig. 51. — Head of a sphingid moth, Phlege-
thontius scxta. a, antenna; c, clypeus; e, eye;
/, labrum; m, mandible; p, pilifer; pr, pro-
boscis.

Lepidoptera. — In Lepidoptera, excepting Eriocephala, the labrum is
reduced (Fig. 51) and the mandibles are either rudimentary or absent
(Rhopalocera) . The two maxillae
are represented by their galeae,
which form a conspicuous pro-
boscis; the grooved inner faces
of -the galeae (or laciniae, according
to Kellogg) form the sucking tube,
which opens into the oesophagus.
The labium is reduced, though
the labial palpi (Fig. 52) are well
developed. The so-called rudi-
mentary mandibles of Anosia and
other forms have been shown by
Kellogg to be lateral projections
of the labrum (Fig. 51) and he
terms them pilifer s.

The exceptional structure of
the mouth parts in the generalized genus Eriocephala (Micropteryx) sheds

much light on the morphology of these organs
in other Lepidoptera, as Walter and Kellogg
have shown. In this genus there are func-
tional mandibles; the maxilla presents palpus,
galea, lacinia, stipes and cardo, though there
is no proboscis; the labium has well developed
submentum, mentum and palpi; a hypo-
pharynx is present.

The sucking apparatus, as described by
Burgess, is essentially like that of Diptera.
Five muscles, originating at the skull and in-
serted on the wall of a pharyngeal bulb, serve
to dilate the bulb that it may suck in fluids,
while numerous circular muscles serve by con-
tracting successively to squeeze the contents
of the bulb back into the stomach; a hypo-
pharyngeal valve prevents their return forward.

Diptera. — In the female mosquito the
mouth parts (Fig. 53) are long and slender.
As Dimmock has found, the labrum and epipharynx combine1 to form a

Fig. 52. — Head of a but-
terfly, Vanessa, a, antennae;
I, labial palpus; p, proboscis.

^ulagin, however, describes them as remaining separate.

34

ENTOMOLOGY

sucking tube; the mandibles and maxillae are delicate, linear, piercing
organs, the latter being barbed distally; maxillary palpi are present; the
hypopharvnx is linear also and serves to conduct saliva; the labium forms
a sheath, enclosing the other mouth parts when they are not in use; a
pair of sensory lobes, termed labella. occur at the extremity of the labium.

The oesophagus is dilated to form a bulb, or sucking organ, from which
muscles pass outward to the skull ; when these contract, the bulb dilates
and can suck in fluids, as blood or water, which are forced back into the

Fig. 53. — Mouth parts of female mosquito, Culcx pipicns. A , dorsal aspect; B, transverse
section; C, extremity of maxilla; D, extremity of labrum-epipharynx; a, antenna; e, com-
pound eye; A, hypopharvnx; I, labrum-epipharynx ; //, labium; m, mandible; mx, maxilla;
p, maxillary palpus. — B, after Dimmock.

stomach by the elasticity of the bulb itself, according to Dimmock; the
regurgitation of the food is prevented by a valve.

The male mosquito rarely if ever sucks blood, and its mouth parts
differ from those of the female in that the mandibles are aborted and the
maxillae slightly developed, but with long palpi, while the hypopharvnx
coalesces with the labium and there is no oesophageal bulb.

Hymenoptera. — In the honey bee, which will serve as a type, the
labrum (Fig. 54) is simple ; the mandibles are well developed instruments
for cutting and other purposes and the remaining mouth parts form a

ANATOMY AND PHYSIOLOGY

35

highly complex suctorial apparatus, as follows. The tongue is a long
flexible organ, terminating in a "spoon" (Fig. 127) and clothed with hairs
of various kinds, for gathering nectar or for sensory or mechanical pur-
poses. The maxillae and labial palpi form a tube embracing the tongue,
while the epipharynx fits into the space between the bases of the maxillae
to complete this tube. Through this canal nectar is driven, by the ex-
pansion and contraction of the tube itself, according to Cheshire, except
that when only a small quantity of nectar is taken, this passes from the
spoon into a fine "central duct," or also into the "side ducts," which are
specially fitted to convey quantities of fluid too small for the main tube.
For a detailed account of the highly complex and exquisitely adapted
mouth parts of the honey bee, the reader is referred to Cheshire's admir-
able work or to Packard's Text-Book.

Fig. 54. — Mouth parts of the honey bee, A pis mcllifera. a, base of antenna; br, brain; c,
clypeus; h, hypopharynx; Mabrum; Ip, labial palpus; m, mentum; wo, mouth; mx, maxilla;
sm, submentum. — After Cheshire.

Segmentation of the Head. — The determination of the number of
segments entering into the composition of the insect head has been a
difficult problem. As no segment bears more than one pair of primary
appendages, there are at least as many segments in the head as there are
pairs of primary appendages. On this basis, then, the antennae, man-
dibles, maxillae and labium may be taken to indicate so many segments;
but in order to decide whether the eyes, labrum and hypopharynx repre-
sent segments, other than purely anatomical evidence is necessary. The
key to the subject is furnished by embryology. At an early stage of
development the future segments are marked off by transverse grooves
on the ventral surface of the embryo, and the pairs of segmental appen-
dages are all alike (Fig. 195), or equivalent, though later they differen-
tiate into antennae, mouth parts, legs, etc. Moreover, the nervous sys-
tem exhibits a segmentation which corresponds to that of the entire in-

36

KXTOUHI, (M,Y

OvoO 0 0£> ft 00P<

sect; in other words, each pair of primitive ganglia, constituting a
romerc, indicates a segment. Now in front of the oesophagus three primi-
tive segments appear, each with its neuromere (Fig. 55) : first in position,
an ocular segment, destined to bear the compound eyes; second, an anten-
nal segment; third, an intercalary (premandibular) segment, which in
the generalized orders Thysanura and Collembola bears a transient pair
of appendages that are probably homologous with the second antennae of
Crustacea. In the adult, the ganglia of these three segments have united

to form the brain, and
the original simplicity
and distinctness have
been lost. The labrum,
by the way, does not rep-
resent a pair of append-
ages, but arises as a single
median lobe. Behind the
oesophagus, three embry-
onic segments are clearly
distinguishable, each
with its pair of appen-
dages, namely, mandibu-
lar, maxillary and labial.
Finally, the hypo-
pharynx, or rather a
part of it, claims a place
in the series of segmental
appendages, as the
author has maintained;
for in Collembola its two
dorsal constituents, or
super lingua? , develop

essentially as do the other paired appendages and, moreover, a super-
lingual neuromere (Fig. 55) exists. The four primitive ganglia immedi-
ately behind the mouth eventually combine to form the suboesophageal
ganglion.

To summarize — the head of an insect is composed of at least six seg-
ments, namely, ocular, antennal, intercalary, mandibular, maxillary and
labial; and at most seven, since a superlingual segment occurs between
the mandibular and maxillary segments in Collembola and probably
Thysanura, though it has not yet been discovered in the more specialized
insects.

Fig. 55. — Paramedian section of an embryo of the col-
lembolan Anurida maritima, to show the primitive cephalic
ganglia. 1, ocular neuromere; 2, antennal; 3, intercalary;
4, mandibular; 5, superlingual; 6, maxillary; 7, labial; 8,
prothoracic; 9, mesothoracic; a, antenna; /, labrum; li,
labium; I1, 12, 13, thoracic legs; m, mandible; mx, maxilla.
— After Folsom.

ANATOMY AND PHYSIOLOGY

37

Thorax.— The thorax, or middle region, comprises the three segments
next behind the head, which are termed, respectively, pro-, meso- and
metathorax. In aculeate Hymenoptera, however, the thoracic mass in-
cludes also the first abdominal segment, then known as the propodeum, or
median segment. Each of the three thoracic segments bears a pair of
legs in almost all adult insects, but only the meso- and metathorax may
bear wings.

The differentiation of the thorax as a distinct region is an incidental
result of the development of the organs of locomotion, particularly the
wings. Thus in legless (apodous) larvae the thoracic and abdominal seg-
ments are alike; when legs are present, but no wings, the thoracic seg-
ments are somewhat enlarged ; and when wings occur, the size of a wing-
bearing segment depends on the volume of the wing muscles, which in
turn is proportionate to the size of the wings
(as in Thysanura and Collembola) or the two
pairs equal in area (as in Termitidae, Odonata,
Trichoptera and most Lepidoptera) the meso-
and metathorax are equal. If the fore wings
exceed the hind ones (Ephemeridae, Hymenop-
tera) the mesothorax is proportionately larger
than the metathorax; as also in Diptera, where
no hind wings occur. If the fore wings are
small (Coleoptera) or almost absent (Stylopidae)
the mesothorax is correspondingly smaller than
the metathorax. The prothorax, which never
bears wings, may be enlarged dorsally to form
a protective shield, as in Orthoptera, Hemip-
tera and Coleoptera; or, on the contrary, may be greatly reduced, as in
Ephemerida, Odonata, Lepidoptera and Hymenoptera. In the primitive
Apterygota the prothorax may become reduced (many Collembola) or
slightly enlarged (Lepisma).

The dorsal wall of a thoracic segment is termed the notum, or tergum;
the ventral wall, the sternum; and each lateral wall, a pleuron; the re-
striction of these terms to particular segments of the thorax being indi-
cated by the prefixes pro-, meso- or meta-. These parts are usually divided
by sutures into distinct pieces, or sclerites, as represented diagrammati-
cally in Fig. 56. Thus the tergum of a wing-bearing segment is regarded
as being composed of four sclerites (tergites, Fig. 57), namely and in order,
prcBscutum, scutum, scutellum and postscutellum. The scutum and
scutellum are commonly evident, but the two other sclerites are usually

When wings are absent

p s si ps

Fig. 56. — Diagram of the
principal sclerites of a thoracic
segment, em, epimeron; es,
episternum; p, praescutum; pr,
parapteron; ps, postscutellum;
s, scutum; si, scutellum; st,
sternum. — After Comstock.

38

ENTOMOLOGY

small and may be absent. Each pleuron consists chiefly of two sclerites
( plcuritcs. Fig. 58), separated from each other by a more or less oblique
suture. The anterior of these two, which joins the sternum, is termed
the cpistcrnum; the other, the epimeron. The former is divided into two
sclerites in Odonata and both are so divided in Xeuroptera.

The sternum, though usually a single plate, is in some instances divided
into halves, as in the cockroach, or even into five sclerites (Forriculidae)-
To these should be added the patagia of Lepidoptera — a pair of erec-
tile appendages of the prothorax; and the paraptera, or tegulce, of Lepi-
doptera and Hymenoptera — a pair of small
sclerites at the bases of the front wings.

Each thoracic segment bears a pair of
spiracles in the embryo and in some adults
as well (Campodea, Heteroptera), but in
most imagines there are only two pairs of
thoracic spiracles, the suppressed pair
being usually the prothoracic.

The sclerites of the thorax owe their
origin probably to local strains on the in-
tegument, brought about by the muscles
of the thorax. Thus the primitively wing-
less Thysanura and Collembola have no
hard thoracic sclerites, though certain
creases about the bases of the legs may
be regarded as incipient sutures, produced
mechanically by the movements of the
legs. In soft nymphs and larvae, the
sclerites do not form until the wings
develop; and in forms that have nearly or quite lost their wings, as
Pediculidae, Mallophaga, Siphonaptera and some parasitic Diptera, the
sclerites of the thorax tend to disappear. Furthermore, the absence of
sclerites in the prothorax is probably due to the lack of prothoracic
wings, notwithstanding the so-called obsolete sutures of the pronotum
in grasshoppers.

Endoskeleton. — An insect has no internal skeleton, strictly speaking,
though the term endoskeleton is used in reference to certain ingrowths of
the external cuticula which serve as mechanical supports or as protections
for some of the internal organs. The tentorium of the head has already
been referred to. In the thorax three kinds of chitinous ingrowths may
be distinguished according to their positions: (1) pkragmas, or dorsal

Fig. 57. — Dorsal aspect of the
thorax of a beetle, Hydrous piceus.
j, pronotum; 2, mesopraescutum; 3,
mesoscutum; 4, mesoscutellum; 5,
mesopostscutellum; 6, metaprae-
scutum; 7, metascutum; 8, meta-
scutellum; g, metapostscutellum.
— After Newport.

ANATOMY AND PHYSIOLOGY

39

projections ; (2) apodemes, lateral ; (3) apophyses, ventral. The
phragmas (Fig. 59) are commonly three large plates, pertaining to the
meso- and metathorax, and serving for the origin of indirect muscles of
flight in Lepidoptera, Diptera, Hymenoptera and other strong-winged

Fig. 58. — Ventral aspect of a carabid beetle, Galerita janus. i, prosternum; 2, proepi-
sternum; 3, proepimeron; 4, coxal cavity; 5, inflexed side of pronotum; 6, mesosternum; 7,
mesoepisternum; 8, mesoepimeron ; p, metasternum; 10, antecoxal piece; 11, metaepi-
sternum; 12, metaepimeron; 13, inflexed side of elytron; a. sternum of an abdominal segment;
an, antenna; c, coxa; /, femur; Ip, labial palpus; md, mandible; mp, maxillary palpus; /,
trochanter; tb, tibia; ts, tarsus.

orders. The apodemes are comparatively small ingrowths, occurring
sometimes in all three thoracic segments, though usually absent in the
prothorax. The apophyses occur in each thoracic segment as a pair of
conspicuous processes, which either remain separate or else unite more or
less; leaving, however, a passage for the ventral nerve cord.

40

ENTOMOLOGY

These endoskeletal processes serve chiefly for the origin of muscles
concerned with the wings or legs, and are absent in such wingless forms as
Thysanura, Pediculidae and Mallophaga.

Some ambiguity attends the use of these terms. Thus some writers
use the term apodemes for apophyses and others apply the term apo-
deme to any of the three kinds of ingrowths.

Legs. — In almost all adult insects and in most larvae each of the three
thoracic segments bears a pair of legs. The leg is articulated to the

sternum, episternum and epimeron and consists
of live segments (Fig. 60) , in the following order:
coxa, trochanter, femur, tibia, tarsus. The coxa,
or basal segment, often has a posterior sclerite,
the trochantine.1 The trochanter is small, and
in parasitic Hymenoptera consists of two sub-
segments. The femur is usually stout and con-
spicuous, the tibia commonly slender. The
tarsus, rarely single- join ted, consists usually of
five segments, the last of which bears a pair of
claws in the adults of most orders of insects and
a single claw in larvae; between the claws in
most imagines is a pad, usually termed the
pulvillus, or em podium.

Adaptations of Legs. — The legs exhibit
a great variety of adaptive modifications. A
walking or running insect, as a carabid or cicin-
delid beetle (Fig. 62, A) presents an average
condition as regards the legs. In leaping in-
sects (grasshoppers, crickets, Haltica) the hind
femora are enlarged (B) to accommodate the
powerful extensor muscles. In insects that make
little use of their legs, as May flies and Tipulidae,
these appendages are but weakly developed. The spinous legs of dragon
flies form a basket for catching the prey on the wing. Modifications of the
front legs for the purpose of grasping occur in many insects, as the terres-
trial families Mantidae (C) and Reduviidae and the aquatic families Belos-
tomidae and Xaucoridae (D). Swimming species present special adapta-
tions of the legs (Fig. 229), as described in the chapter on aquatic insects.
In digging insects, the fore legs are expanded to form shovel-like organs,

Fig. 59. — Transverse sec-
tions of the thoracic segments
of a beetle, Goliathus, to show
the endoskeletal processes.
A, prothorax; B, mesothorax;
C, metathorax; a, a, apoph-
yses; ad, apodeme; p,
phragma. — After Kolbe.

1 But on account of the ambiguous use of this last term, the name meron (Fig. 6i), pro-
posed by Walton, is to be preferred.

ANATOMY AND PHYSIOLOGY

41

tb

notably in the mole-cricket (Fig. 62, E), in which the fore tibia has some
resemblance to the human hand, while the tarsus and tibia are remarkably
adapted for cutting roots, after the manner of shears.
The Scarabaeidae have f ossorial legs, the anterior tarsi of
which are in some genera reduced (F) or absent; they
are rudimentary in the female (G) of Phanceus carnifex
and absent in the male (H), and absent in both sexes
of Deltochilum. Though females of Phanczus lose their
front tarsi by digging, the degenerate condition of
these organs cannot be attributed to the inheritance
of a mutilation, but may have been brought about by
disuse ; though no one has explained why the two sexes
should differ in this respect. Many insects use the
legs to clean the antennae, head, mouth parts, wings
or legs; the honey bee (with other bees, also ants,
Carabidae, etc.) has a special antenna-cleaner on the
front legs (Fig. 264, D), which is described, with
other interesting modifications of the legs, on page 211.

Indeed, the legs serve many such minor purposes
in addition to locomotion. They are generally used
to hold the female during coition, and in several genera
of Dytiscidae (Dytiscus, Cybister) the male (Fig. 62, /)
has tarsal disks and cupules chiefly on the front tarsi,
for this purpose. Among other secondary sexual pecu-
liarities of the legs may be mentioned the tibial brushes
of the male Catocala concumbens, regarded as scent
organs, and the queer appendages of male Dolicho-
podidae that dangle in the air as these flies perform their dances.

The pulvillus is commonly an adhe-
sive organ. In flies it has glandular hairs
that enable the insects to walk on smooth
surfaces and to walk upside down; so
also in many beetles and notably in the
honey bee (Fig. 63) ; in this insect the
pulvillus is released rapidly from the sur-
face to which it has been applied, by
rolling up from the edges inward.

Sense organs occur on the legs.
Thus tactile hairs are almost always
present on these appendages, while auditory organs occur on the front

Fig. 60. — Leg of a
beetle, Calosoma cali-
dum. c, coxa; cl,
claws; /, femur; s,
spur; Z1-/5, tarsal seg-
ments; tb, tibia; tr,
trochanter.

es

Fig. 61— Left hind leg of Bittacus
c, coxa genuina; m,epimeron; es, epi-
sternum; /, femur; m, meron; /, tro-
chanter.

42

ENTOMOLOGY

tibia? of Locustida?, Gryllidae and some ants. Finally, the legs may be
used to produce sound, as in Stenobothrus and such other Acridiidae as
stridulate by rubbing the femora against the tegmina.

Fig. 62. — Adaptive modifications of the legs. .4, Cicindda scxguttata; B. Nemobius
vittatus, hind leg; C. Stagmomantis Carolina, left fore leg; D. Pelocoris femorata. right foreleg;
E, Gryllotalpa borealis, left fore leg; F, Canthon Icrcis, right fore leg; G, Phanaus carnifcx, fore
tibia and tarsus of female; H. P. carnifex, fore tibia of male; /, Dytiscus fasciventris, right fore
leg of male; c, coxa; /, femur; s, spur; /, trochanter; tb, tibia; ts, tarsus.

Legs of Larvae. — Thoracic legs, terminating in a single claw, are
present in most larvae. Caterpillars have, in addition, fleshy abdominal
legs (Fig. 64) ending in a circlet of hooks. Most caterpillars have rive

ANATOMY AND PHYSIOLOGY

43

pairs of these legs (on abdominal segments 3, 4, 5, 6, and 10), but the rest
vary in this respect. Thus Lagoa has seven pairs (segments 2-7 and 10)
and Geometridae two (segments 6, and 10),
while a few caterpillars (Tischeria, Limacodes)
have none. Larvae of saw flies (Tenthre-
dinidae) have seven or eight pairs of abdominal
legs and larvae of most Panorpidae, eight pairs.
Not a few coleopterous larvae (some Ceram-
bycidae, Phytonomus) also have abdominal legs,
which are incompletely developed, however, as
compared with those of Lepidoptera.

The legless, or apodous, condition occurs
frequently among larvae and always in correla-
tion with a sedentary mode of life; as in
the larvae of many Cerambycidae, almost all
Rhynchophora, a few Lepidoptera, all Dir>
tera, and all Hymenoptera except Tenthre-
dinidae, Siricidae, and other Terebrantia.

Among adult insects, female scale insects are exceptional in being
legless.

Walking. — An adult insect, when walking, normally uses its legs in
two sets of three each; thus the front and hind legs of one side and the

Fig. 63. — Foot of honey
bee, Apis mcllifera. c, c,
claws; p, pulvillus; t3-fi, tarsal
segments. — After Cheshire.

middle leg of the other move forward almost simultaneously — though not
quite, for the front leg moves a little before the middle one, which, in
turn, precedes the hind leg. During these movements the body is sup-

44

ENTOMOLOGY

ported by the other three legs, as on a tripod. The front leg, having been
extended and its claws fixed, pulls the body forward by means of the con-
traction of the tibial flexors; the hind leg, on the contrary, pushes the
body, by the shortening of the tibial extensors, against the resistance
afforded by the tibial spurs; the middle leg acts much like the hind one,
but helps mainly to steady the body. Different species show different
peculiarities of gait. In its analysis, the walking of an insect is rather
intricate, as Graber and Marey have shown.

The mode of action of the principal leg muscles may be gathered from
Fig. 65. Here the flexion of the tibia would cause the tibial spur (5)
to describe the line s 1; and the backward movement of the leg due to the

Fig. 65. — Mechanics of an insect's leg. a, axis of coxa; c, coxa; d, claw; e, extensor of
tibia; ec, extensor of claw; et, extensor of tarsus; /, flexor of tibia; fc, flexor of claw; ft, flexor
of tarsus; r, r, rotators of coxa; s, spur; t, trochanter muscle (elevator of femur); ti, tibia. —
After Graber.

upper coxal rotator r would cause the spur to follow the arc 5 5. As the
resultant of both these movements, the path actually described by the
tibial spur is 5 2; then, as the leg moves forward, the curve is continued
into a loop.

Caterpillars use their legs successively in pairs, and when the pairs of
legs are few and widely separated, as in Geometridae, a curious looping
gait results.

The leg muscles of a cockroach are shown in Fig. 66.

Leaping. — The hind legs, inserted nearest the center of gravity, are
the ones employed in leaping, and they act together. A grasshopper
prepares to jump by bending the femur back against the tibia; to make
the jump, the tibia is jerked back against the ground, into which the tibial

ANATOMY AND PHYSIOLOGY

45

spurs are driven, and the straightening of the leg by means of the power-
ful extensors throws the insect into the air. At the distal end of the femur
are two lobes, one on each side of the tibia, which prevent wobbling move-
ments of the tibia.

Wings. — The success of insects as a class is to be attributed largely
to their possession of wings. These and the mouth parts, surpassing all
the other organs as regards range of differentiation, have furnished the
best criteria for the purposes of classification. The
wings of insects present such countless differences
that an expert can usually refer a detached wing
to its proper genus and often to its species, though
no less than three hundred thousand species of in-
sects are already known.

Typically, there are two pairs of wings, attached
respectively to the mesothorax and the metathorax,
the prothorax never bearing wings, as was said.
When only one pair is present it is almost invariably
the anterior pair, as in Diptera and male Coccidae,
though in male Stylopidse it is the posterior pair,
the fore wings being rudimentary.

In bird lice, fleas and most other parasitic in-
sects, the wings have degenerated through disuse.
In Thysanura and Collembola there are no traces
of wings even in the embryo ; whence it is inferred
that wings originated later than these orders of
insects.

Miiller and Packard have regarded the wings as
tergal outgrowths; Tower, however, has recently
shown that the wings of Coleoptera, Orthoptera
and Lepidoptera are pleural in origin, arising just
below the line where later the suture between the
pleuron and tergum will originate, though the wings
may subsequently shift to a more dorsal position.

Modifications of Wings. — Being commonly more or less triangular,
a wing presents three margins: front (costal), outer (apical) and inner
(anal). Various modifications occur in the front wings, which are in
many orders more useful for protection than for flight. Thus, in Orthop-
tera, they are leathery, and are known as tegmina; in Coleoptera they are
usually horny, and are termed elytra; in Heteroptera, the base of the front
wing is thickened and the apex remains membranous, forming a hemely-

Fig. 66. — Muscles of
left mid leg of a cock-
roach, posterior aspect.
abc, abductor of coxa;
adc, adductor of coxa;
ef, extensor of femur;
et, extensor of tibia; Jf,
flexor of femur; //,
flexor of tibia; fta,
flexor of tarsus; rt,
retractor of tarsus. —
After Miall and
Denny.

46

ENTOMOLOGY

iron. Diptera have, in place of the hind wings, a pair of clubbed threads,
known as balancers, or haltcrcs, and male Coccidae have on each side a
bristle that hooks into a pocket on the wing and serves to support the
latter. In many muscid flies a doubly lobed membranous squama occurs
at the base of the wing.

In Hymenoptera the front and hind wings of the same side are held
together by a row of hooks (hamuli)] these are situated on the costal
margin of the hind wing and clutch a rod-like fold of the fore wing. In
very many moths, the two wings are enabled to act as one by means of a
frenulum, consisting of a spine or a bunch of bristles near the base of the
hind wing, which, in some forms, engage a membranous loop on the fore

3d A 2dA

IstA

Cu2

Fig. 67. — Hypothetical type of venation. .4 , anal vein; C,
costa; Cu, cubitus; M, media; R. radius; Sc, subcosta. — Figs.
67-71 after Comstock and Needham.

Venation, or Neuration. — A wing is divided by its veins, or ner-
vures. into spaces, or cells. The distribution of the veins is of great sys-
tematic importance,
but. unfortunately,
the homologies of the
veins in the different
orders of insects have
not been fixed until
recently, so that no
little confusion has
existed upon the sub-
ject. For example,
the term discal cell,
used in descriptions of Lepidoptera, Diptera, Trichoptera and Psocidae,
has in no two of these groups been applied to the same cell. The
admirable work of Comstock and Xeedham, however, seems to settle
this disputed subject. By a study of the tracheae which precede and, in a
broad way, determine the positions of the veins, these authors have ar-
rived at a primitive type of tracheation (Fig. 67) to which the more com-
plex types of tracheation and venation may be referred.

In general, the following principal longitudinal veins may be distin-
guished, in the following order: costa. subcosta, radius, media, cubitus, and
anal (Figs. 67-71).

The costa (C) strengthens the front margin of the wing and is essen-
tially unbranched.

The subcosta (Sc) is close behind the costa and is unbranched in the
imagines of many orders in which there are few wing veins, though it is
typically a forked vein.

ANATOMY AND PHYSIOLOGY

47

The radius (R), though subject to much modification, is typically five-
branched, as in Fig. 67. The second principal branch of the radius is
termed the radial sector (Rs).

The media (M) is often three-branched and is typically four-branched,
according to Comstock and Xeedham.

The cubitus (Cu) has two branches.

nt A Cu2 1

Fig. 68. — Wing of a fly, Rhyphus. Lettering as before.

The anal veins (A) are typically three, of which the first is generally
simple, while the second and third are many-branched in wings that have
an expanded anal area.

The Plecoptera, as a whole, show the least departure from the primi-
tive type of venation; which is well preserved, also, in the more general-
ized of the Trichoptera.

Starting from the primitive type, specialization has occurred in two
ways: by reduction and by
addition. Reduction occurs
either by the atrophy of veins
or by the coalescence of two
or more adjacent veins.
Atrophy explains the lack
of all but one anal vein in
Rhyphus (Fig. 68) and other
Diptera, and the absence of
the base of the media in FlG- 69-Wing of a butterfly, Anosia. Lettering as

Anosia (Fig. 69) and many

other Lepidoptera; in the pupa of Anosia, the media may be found com-
plete. Coalescence "takes places in two ways: first, the point at which
two veins separate occurs nearer and nearer the margin of the wing,
until finally, when the margin is reached, a single vein remains where
there were two before; second, the tips of two veins may approach each
other on the margin of the wing until they unite, and then the coales-

43

ENTOMOLOGY

cence proceeds towards the base of the wing." (Comstock and Needham.)
The former, or outward, kind of coalescence is common in most orders of
insects; the latter, or inward, kind is especially prevalent in Diptera.

Specialization by addition occurs by a multiplication of the branches
of the principal veins.

Comstock and Needham have succeeded in homologizing practically
all the types of neuration, including such perplexing types as those

of Ephemerida (Fig. 70),

Odonata (Fig. 20, B) and
Hymenoptera (Fig. 71),
and their thorough work
affords a sound basis for a
rational terminology of the
wing veins; there is no
longer any excuse for the
lamentable confusion that
has hitherto attended the
study of venation.

Fig. 70. — Wings of a May fly. Lettering as before. Folding of Wing. — In

some beetles (as Chrysobo-
thris) the wings are no larger than the elytra and are not folded; in others,
however, the wings exceed the elytra in size, and when not in use are folded
under the elytra in ways that are simple but efhcient, as described by
Kolbe and by Tower. To be understood, the process of folding should
be observed in the living insect. As described by Tower for the Colorado

Fig. 71. — A typical hymenopterous wing. Lettering as before.

potato beetle, the folded wing (Fig. 72, B) exhibits a costal joint (a), &
fold parallel to the transverse vein (b), and a complex joint at d. The
wing rotates upon the articular head (ah) and when folded back beneath
the wing-covers the inner end of the cotyla (c) is brought into contact
with a chitinous sclerite of the thorax, which stops the further movement

ANATOMY AND PHYSIOLOGY

49

of the cotyla medianward, and as the wing swings farther back the middle
system of veins (m) is pushed outward and anteriorly. This motion,
combined with the backward movement of the wing as a whole, produces
the folding of the distal end of the wing. There are no traces of muscles
or elastic ligaments in the wing which could aid in the folding.

Mechanics of Flight. — The mechanism of insect flight is much less
complex than one might anticipate. Indeed, owing to the structure of
the wing itself, simple up and down movements are sufficient for the
simplest kind of flight. During oscillation, the plane of the wing changes,
as may be demonstrated by
holding a detached wing by
its base and blowing at right
angles to its surface; the
membrane of the wing then
yields to the pressure of the
air while the rigid anterior
margin does not, to any
great extent. Similarly, as
the wing moves downward
the membrane is inclined
upward by the resistance of
the air, and as the wing
moves upward the mem-
brane bends downward.
Therefore, by becoming de-
flected, the wing encounters
a certain amount of resist-
ance from behind, which is
sufficient to propel the insect.
The faster the wings vibrate,

the greater the deflection, the greater the resistance from behind, and
the faster the flight of the insect.

The path traced in the air by a rapidly vibrating wing may be deter-
mined by fastening a bit of gold leaf to the tip of the wing and allowing the
insect— a wasp, for example — to vibrate its wings in the sunlight, against
a dark background. Under these conditions, the trajectory of the wing
appears as a luminous elongate figure 8. During flight, the trajectory
consists of a continuous series of these figures, as in Fig. 73.

Marey, the chief authority on animal locomotion, used chronopho-
tography, among other methods, in studying the process of flight, and
5

Fig. 72. — Wing of Leptinotarsa dccemlineata. A
spread; B, folded; a, costal joint; ah, articular head;
an, anterior system of veins; b, transverse vein; c,
cotyla; d, joint; m, middle system of veins; p, poste-
rior system of veins. — After Tower.

5°

ENTOMOLOGY

obtained at first twenty, and later one hundred and ten, successive photo-
graphs per second of a bee in flight. As the wings were vibrating 190
times per second, however, the images evidently represented isolated and
not consecutive phases of wing movement. Nevertheless, the images
could be interpreted without difficulty, in the light of the results ob-
tained by other methods. At length he ob-
tained sharp but isolated images of vibrating
wings with an exposure of only $ ^-J-^ of a
second.

The frequency of wing vibration may be
ascertained from the note made by the wing
jrIG 73 —Trajectory of the " — ^ ^ vibrates rapidly enough to make one;
wing of an insect. jn anv casej may De determined graphic-

ally by means of a kymograph, which, in
one of its forms, consists of a cylinder covered with smoked paper and
revolved by clockwork at a uniform rate. The insect is held in such
a position that each stroke of the wing makes a record on the smoked
paper, as in Fig. 74. Comparing this record with one made on the same
paper by a tuning-fork of known vibration period, the frequency of wing

Fig. 74. — Records of wing vibration. A, mosquito, Anopheles. Above is the wing record
and below is the record of a tuning-fork which vibrated 264.6 times per second. B, wasp.
Polistes. The tuning-fork in this instance had a vibration frequency of 97.6.

vibration can be determined with great accuracy. As the wing moves in
the arc of a circle, the radius of which is the length of the wing, the ex-
treme tip of the wing records only a short mark; if, however, the wing is
pressed against the smoked cylinder, a large part of the figure-8 trajectory
may be obtained, as in Fig. 74, B. The wings of the two sides move syn-
chronously, as Marey found.

ANATOMY AND PHYSIOLOGY

5*

The smaller the wings are, the more rapidly they vibrate. Thus a
butterfly (P. rapes) makes 9 strokes per second, a dragon fly 28, a sphin-
gid moth 72, a bee 190 and a house-fly 330.

Wing Muscles. — The base of a wing projects into the thoracic cavity
and serves for the insertion of the direct muscles of flight. Regarding the
wing as a lever (Fig. 75, A), with the fulcrum at p, it is easy to understand
how the contraction of muscle e raises the wing and that of muscle d low-
ers it. These muscles are shown
diagrammatically in Fig. 75. B.
Besides these, there are certain
muscles of flight which act in-
directly upon the wings, by
altering the form of the thoracic
wall. Thus the muscle ie (Fig.
75. B) elevates the wing by
pulling the tergum toward the
sternum; and the longitudinal
muscle id depresses the wing
indirectly by arching the ter-
gum of the thorax.

Though up and down move-
ments are all that are necessary
for the simplest kind of insect
flight, the process becomes com-
plex in proportion to the effi-
ciency of the flight. Thus in
dragon flies there are nine
muscles to each wing: live de-
pressors, three elevators and
one adductor. The earlier ac-
counts ofthe mechanics of flight
by Marey and others have been
recently modified and improved upon by Stellwaag and by Ritter, whose
modern methods of investigation have added considerably to our knowl-
edge of the subject. They show, particularly, the parts played by the
thoracic sclerites during flight.

Abdomen. — The chief functions of the abdomen are respiration and
reproduction, to which should be added digestion. The abdomen as a
whole has undergone less differentiation than the thorax and presents a
simpler and more primitive segmentation.

s

Fig. 75. — .4, diagram to illustrate the action
of the wing muscles of an insect. B, diagram of
wing muscles, a, alimentary canal; cn, muscle
for contracting the thorax, to depress the wings;
d, depressor of wing; e, elevator of wing; ex,
muscle for expanding the thorax, to elevate the
wings; id, indirect depressor; ie, indirect ele-
vator; /, leg muscle; p, pivot, or fulcrum; s,
sternum; /, tergum; wg, wing. — After Graber.

52

ENTOMOLOGY

Segments. — A typical abdominal segment bears a dorsal plate, or
tergum, and a ventral plate, or sternum, the two being connected by a pair
of pleural membranes, which facilitate the respiratory movements of the
tergum and sternum. Most of the abdominal segments have spiracles,
one on each side, situated in or near the pleural membranes of the first
seven or eight segments. The total number of pairs of spiracles is as
follows :

Thoracic. Abdominal. Total.

Campodea 3 o 3

Japyx 4 7 11

Machilis 2 7 9

Lepisma 2 8 10

Blattidae, Acridiidae 2 8 10

Odonata 2 8 10

Heteroptera 3 7 .10

Lepidoptera 2 7 9

Diptera 2 7 • 9

In most embryo insects there are eleven pairs of spiracles (three thora-
cic and eight abdominal); in adults, however, two pairs are commonly
suppressed — the prothoracic and the eighth abdominal.

Number of Abdominal Segments. — Though consisting typically
of ten segments — the number evident in such generalized insects as Thy-
sanura and Ephemerida — eleven occur in various adult Orthoptera, with
traces of a twelfth, while Heymons has detected twelve abdominal seg-
ments in embryos of Orthoptera and Odonata. In the more specialized
orders, ten may usually be distinguished, with more or less difficulty,
though the number is apparently, and in some cases actually, less owing
to modifications of the base of the abdomen in relation to the thorax,
but especially to modifications of the extremity of the abdomen, for
sexual purposes.

Modifications. — In aculeate Hymenoptera the first segment of the
abdomen has been transferred to the thorax, where it is known as the
propodeum, or median segment; in other words, what appears to be the
first abdominal segment is actually the second; this, as in bees and wasps,
often forms a petiole, which enables the sting to be applied in almost any
direction. In Cynipidae the tergum of segment two or three occupies
most of the abdominal mass, the remaining segments being reduced and
inconspicuous. The terminal segments of the abdomen often telescope
into one another, as in many Coleoptera and Hymenoptera (Chrysididae) ,
or undergo other modifications of form and position which obscure the

ANATOMY AND PHYSIOLOGY

53

— - a

segmentation. As to the number of evident (not actual) abdominal seg-
ments, Coleoptera show five or six ventrally and seven or eight dorsally;
Lepidoptera, seven in the female and eight in the male; Diptera, nine
(male Tipulidae) or only four or five; and Hymenoptera, nine (Tenthre-
dinidae) or as few as three (Chrysididae) . In the larvae of these insects,
however, nine or ten abdominal segments are usually distinguishable,
though the tenth is frequently modified,
being in caterpillars united with the ninth.

Appendages. — Foidimentary abdom-
inal limbs occur in Thysanura (Machilis,
Fig. 76). Functional abdominal legs do
not occur in adult insects, but in larvae the
abdominal pro-legs (often called " false legs,"
Fig. 64) are homologous with the thoracic
legs and the other paired segmental appen-
dages, as the embryology shows. The em-
bryo of (Ecanthus, according to Ayers, has
ten pairs of abdominal appendages (Fig.
197), equivalent to the thoracic legs. Most
of these embryonic abdominal appendages
are only transitory, but the last three pairs
frequently persist to form the genitalia, as
in Orthoptera (to which order (Ecanthus
belongs). In Collembola, the embryo has
paired abdominal limbs, and those of the
first abdominal segment eventually unite
to form the peculiar ventral tube (Fig. 12)
of these insects, while those of the fourth
segment form the characteristic leaping
organ, or furcula.

Cerci.— In many of the more generalized
insects the abdomen bears at its extremity
two or three appendages termed cerci. These

occur in both sexes and are frequently long and multiarticulate, as in Thy-
sanura (Figs. 76, 9, 10) and Ephemerida (Figs. 19, B.; 84), though shorter
in cockroaches and reduced to a single sclerite in Acridiidae (Fig. 87) . The
paired cerci, or cercopoda of Packard, are usually though not always as-
sociated with the tenth abdominal segment and are homologous with
legs, as Ayers has found in (Ecanthus and Wheeler in Xiphidium. As to
their function, the cerci of Thysanura are tactile, and those of the cock-

Fig. 76. — Ventral aspect of the
abdomen of a female Machilis
maritima, to show rudimentary
limbs (a) of segments two to nine.
(The left appendage of the eighth
segment is omitted.) c, c, c, cerci.
— After Oudemans.

54

ENTOMOLOGY

roach olfactory, while the cerci of male Acridiidae often serve to hold the
female during copulation.

Extremity of Abdomen. — Various modifications of the terminal
segments of the abdomen occur for the purposes of defalcation and es-
pecially reproduction. The anus, dorsal in position, opens always through
the last segment and is often shielded above by a suranal plate and on each
side by a lateral plate. The genital orifice is always ventral in position
and occurs commonly on the ninth abdominal segment, though there is
some variation in this respect. The external, or accessory, organs of re-
production are termed the genitalia.

Female Genitalia. — In Xeuroptera, Coleoptera, Lepidoptera and
Diptera the vagina simply opens to the exterior or else with the anus into
a common chamber, or cloaca. Often, as in Cerambyx (Fig. 77) and
Cecidomyia (Fig. 78) the attenuated distal segments of the abdomen serve

the purpose of an ovipositor;

Fig. 77. — Abdomen of female beetle, Cer- Fig. 78. — Abdomen of a female midge,

ambyx, in which the last three segments are Dasyneura legnminicola, to show the
used as an ovipositor. — After Kolbe. pseudo-ovipositor.

one another when not in use, form when extruded a lash-like organ ex-
ceeding frequently the remainder of the body in length.

A true ovipositor occurs in Thysanura, Orthoptera, Odonata, Hemip-
tera, Hymenoptera and some other orders of insects. The ovipositor con-
sists essentially of three pairs of valves, or gonapophyses — a dorsal, a
ventral and an inner pair. The two inner valves form a channel through
which the eggs are conveyed. In Locus tidae (Fig. 79) the three valves of
each side are held together by tongues and grooves, which, however,
permit sliding movements to take place. Most authorities have found
that the gonapophyses belong to the segmental series of paired appen-
dages— are homodynamous with limbs — and pertain commonly to ab-
dominal segments seven, eight and nine.

The ovipositor attains its greatest complexity in Hymenoptera, in
which it becomes modified for sawing, boring or stinging. In Sirex (Fig.
80) the inner valves are united; in Apis the dorsal valves are repre-
sented by a pair of palpi, the inner valves unite to form the sheath

ANATOMY AND PHYSIOLOGY

55

(Fig. 81, B), and the ventral two form the darts, each of which has ten
barbed teeth behind its apex, which tend to prevent the withdrawal of
the sting from a wound. The action of the sting, as described by Che-

Fig. 79. — Ovipositor of Locusta. A, lateral aspect; B, ventral aspect; C, transverse sec-
tion; c, cerci; d, dorsal valve; i, inner valve; v, ventral valve. The numbers refer to ab-
dominal segments. — After Kolbe and Dewitz.

shire, is rather complex. Briefly, the sheath serves to open a wound and
to guide the darts; these strike in alternately, interrupted at intervals
by the deeper plunging of the sheath (Fig. 81 , A). The poison of the
honey bee is secreted by two glands, one acid and
the other alkaline. The former (Fig. 82) consists
of a glandular region which secretes formic acid, of
a reservoir, and a duct that empties its contents
into the channel of the sheath. The alkaline gland
also opens into the reservoir. It is said that both
fluids are necessary for a deadly effect; and that in
insects which simply paralyze their prey, as the
solitary wasps, the alkaline glands are functionless.

Male Genitalia. — The penis may be hollow or
else solid, and in the latter case the contents of
the ejaculatory duct are spread upon its surface.
Morphologically, the male gonapophyses correspond to those of the
female. The penis (Fig. 83) represents the two inner valves of. the ovi-

Fig. 80. — Cross-sec-
tion of the ovipositor of
Sirex. c, channel; d,
d, dorsal valves; i,
united inner valves; v,
v, ventral valves. — After
Taschexberg.

56

ENTOMOLOGY

positor and is frequently enclosed by one or two pairs of valves. In
Ephemerida the two inner valves are partly or entirely separate from each
other, forming two intromittent organs (Fig. 84).

In male Odonata, the ejaculatory duct opens on the ninth abdominal
segment, but the copulatory organ is placed on the under side of the sec-
ond segment, to which the spermatozoa are transferred by the bending
of the abdomen. At copulation, the abdominal claspers of the male
grasp the neck of the female, and the latter bends her abdomen forward
until the tip reaches the peculiar copulatory apparatus of the male.

The claspers of the male consist of a single pair, variously formed.
They are present in Ephemerida, Xeuroptera, Trichoptera, Lepidoptera
(Fig. 85), Diptera and some Hymenop-
tera, though not in Coleoptera. and
often afford good specific characters, as

Fig. 81. — Sting of honey bee. A, 1, 2, 3, posi-
tions in three successive thrusts; s, sheath. B,
cross-section; c, channel; i, united inner valves,
forming the sheath; v, v, ventral valves, or darts.
— .4, after Cheshire; B, after Fexger.

Fig. 82. — Sting and poison appara-
tus of honey bee. ag, accessory gland;
p, palpus; pg. poison gland (formic
acid); r, reservoir; s, sting. — After
Kraepelin.

in Odonata. In butterflies of the genus Thanaos, the claspers are peculiar
in being strongly asymmetrical. In Odonata (Fig. 86, .4) and Orthoptera
(Fig. 87, A) the superior appendages of the male often serve as claspers.

In many insects the tergum of the last abdominal segment forms a
small suranal plate (Fig. 87, B, sp) ; this sometimes supplements the clasp-
ers of the male in their function, as in Lepidoptera (Fig. 85, A, s).

2. Integument

Insects excel all other animals in respect to adaptive modifications of
the integument. Xo longer a simple limiting membrane, the integument

ANATOMY AND PHYSIOLOGY

57

has become hardened into an external skeleton, evaginated to form mani-
fold adaptive structures, such as hairs and scales, and invaginated, along
with the underlying cellular layer, to make glands of various kinds.

Fig. 83. — Extremity of abdomen of a
male beetle, Hydro philus, ventral aspect, g,
genitalia; p, penis; vlt v2, pairs of valves
enclosing the penis; 6-g, sterna of abdom-
inal segments. — After Kolbe.

Fig. 84. — Extremity of abdomen of a
male May fly, Hexagenia variabilis, ventral
aspect, c, c, c, cerci; cl, cl, claspers; i, i,
intromittent organs.

Chitin. — The skin, or cuticula,1 of an insect differs from that of a
worm, for example, in being thoroughly permeated with a peculiar sub-

Fig. 85. — Genitalia of a moth, Samia cecropia. A, male; B, female; a, anus; c, c, claspers;
0, opening of common oviduct; p, penis; s, uncus (the doubly hooked organ); v, vestibule,
into which the vagina opens. The numbers refer to abdominal segments.

stance known as chitin — the basis of the arthropod skeleton. This is a
substance of remarkable stability, for it is unaffected by almost all ordi-
nary acids and alkalies, though it is soluble in sodic or potassic hypo-

xThe cuticula of an insect should be distinguished from the cuticle of a vertebrate, the
former being a hardened fluid, while the latter consists of cells themselves, in a dead and
flattened condition.

ENTOMOLOGY

chlorite (respectively, Eau de Labarraque and Eau de Javelle) and yields
to boiling sulphuric acid. If kept for a year or so under water, however,
chitin undergoes a slow dissolution, possibly a putrefaction, which ac-
counts in a measure for the rapid disappearance of insect skeletons in the
soil (Miall and Denny). By boiling the skin of an insect in potassic hy-
droxide it is possible to dissolve away the cuticular framework, leaving

Fig. 86. — Terminal abdominal appendages of a dragon fly, Plathemis trimaculata. A,
male; B, female, i, inferior appendage; s, s, superior appendages. The numbers refer to
abdominal segments.

fairly pure chitin, without destroying the organized form of the integu-
ment, though less than half the weight of the integument is due to chitin.
The formula of chitin is given as C9Hi5X06 or Ci8Hi5NOi2 byKruken-
berg. and Packard adopts the formula C15H06X0O10; though no two chem-
ists agree as to the exact proportions of these elements, owing probably
to variations in the substance itself in different insects or even in the same

Fig. 87. — Extremity of the abdomen of a grasshopper, Melanoplus differential is. A, male;
B, female. The terga and sterna are numbered, c, cercus; d, dorsal valves of ovipositor; e,
egg guide; p, podical plate; s, spiracle; sp. suranal plate; v, ventral valves of ovipositor.

species of insect. Iron, manganese and certain pigments also enter into
the composition of the integument.

Chitin is not peculiar to arthropods, for it has been detected in the
setae and pharyngeal teeth of annelid worms, the shell of Lingula and the
pen of the cuttle fish (Krukenberg) .

The chitinous integument (Fig. 88) of most insects consists of two
layers: (1) an outer layer, homogeneous, dense, without lamellae or pore

ANATOMY AND PHYSIOLOGY

59

canals, and being the seat of the cuticular colors; (2) an inner layer,
"thickly pierced with pore canals, and always in layers of different re-
fractiYe indices and different stainability." (Tower.) These two layers,
respectively primary and secondary cuticula, are radically different in
chemical and physical properties. The chitinous cuticula is secreted, as
a fluid, from the hypodermis cells. Each layer arises as a fluid secretion
from the hypodermis cells, the primary cuticula being the first to form and
harden.

The fluid that separates the old from the new cuticula at ecdysis is
poured over the hypodermis by certain large special cells, which, accord-
ing to Tower, "are not true glands, but the setigerous cells which, in early
life, are chiefly concerned with the formation of the hairs upon the body;
but upon the loss of these, the cell takes on the function of secreting the
exuvial fluid, which is most copious at
pupation. These cells degenerate in the
pupa, and take no part in the formation
of the imaginal ornamentation."

Histology. — The chitinous cuticula
owes its existence to the activity of the
underlying layer of hypodermis cells (Fig.
88). These cells, distinct in embryonic
and often in early larval life, subse-
quently become confluent by the disap-
pearance of the intervening cell walls,
though each cell is still indicated by its
nucleus. The cells are limited outwardly
by the cuticula and inwardly by a deli-
cate, hyaline basement membrane; they contain pigment granules, fat-
drops, etc.

Externally the cuticula may be smooth, wrinkled, striate, granulate,
tuberculate, or sculptured in numberless other ways; it may be shaped
into all manner of structures, some of which are clearly adaptive, while
others are unintelligible.

Hairs, Setae and Spines. — These occur universally, serving a great
variety of purposes; they are not always simple in form, but are often
toothed, branched or otherwise modified (Fig. 89). Hairs and bristles
are frequently tactile in function, over the general integument or else
locally; or olfactory, as on the antennae of moths; or occasionally audi-
tory, as on the antennae of the male mosquito; these and other sensory
modifications are described beyond. The hairy clothing of some hiber-

Fig. 88. — Section through integu-
ment of a- beetle, Chrysobothris. b,
basement membrane; c1, primary
cuticula; c2, secondary cuticula; h,
hypodermis cell; n, nucleus. — After
Tower.

6o

ENTOMOLOGY

nating caterpillars (as Isia Isabella) probably protects them from sudden
changes of temperature. Hairs and spines frequently protect an insect

Fig. 89. — Modifications of the hairs of bees. A , B, Megachile; C, E, F, Colletes; D, Chelos-

toma. — After Saunders.

from its enemies, especially when these structures are glandular and emit
a malodorous, nauseous or irritant fluid. Glandular hairs on the pulvilli

Fig. 90. — Section of antenna of a moth, Fig. 91. — Radial section through the

Satumia, to show developing hairs, c, cutic- base of a hair of a caterpillar, Pier is rapce.
ula; /, formative cell of hair; h, hypodermis; c, cuticula; /, formative cell; //, hair; hyt
t, trachea. — After Semper. hypodermis.

of many flies, beetles, etc., enable these insects to walk on slippery sur-
faces. The twisted or branched hairs of bees serve to gather and hold

ANATOMY AND PHYSIOLOGY

61

pollen grains; in short, these simple structures exhibit a surprising va-
riety of adaptive modifications, many of which will be described in con-
nection with other subjects.

A hair arises from a modified hypodermis cell (Fig. 90), the contents of
which extend through a pore canal into the
interior of the hair (Fig. 91); sometimes, to
be sure, as in glandular or sensory hairs, the
hair cell is multinucleate, representing, there-
fore, as many cells as there are nuclei. The
wall of a hair is continuous with the general
cuticula and at moulting each hair is stripped
off with the rest of the cuticula, leaving in
its place a new hair, which has been forming
inside the old one.

Scales. — Besides occurring throughout the
order Lepidoptera and in numerous Trichop-
tera, scales are found in many Thysanura and
Collembola, several families of Coleoptera
(including Dermestidae and Curculionidae), a
few Diptera and a few Psocidae.

Though diverse in form (Fig. 92), scales
are essentially flattened sacs having at one
end a short pedicel for attachment to the
integument. The scales usually bear mark-
ings, which are more or less characteristic of
the species; these markings, always minute,

are in some species so exquisitely fine as to test the highest powers of
the microscope; the scales of certain Collembola (Lcpidocyrtus, etc.) have
long been used, under the name of "Podura" scales, to test the resolving
power of objectives, for which purpose they are excelled only by some of

the diatoms. Butterfly scales are
marked with parallel longitudinal
ridges (Fig. 92, C), which are confined
almost entirely to the upper, or ex-
posed, surface of the scale (Fig. 93)
and number from 33 or less (Anosia)
the striae being from .002 mm. to .0007
these longitudinal ridges may be dis-
cerned delicate transverse markings. Internally, scales are hollow and
often contain pigments derived from the blood.

Fig. 92-
scales. A,
Machilis; B,
C, butterfly,
Limacodes.

Various forms of
E, thysanura n,
beetle, Anthrenus,
Picris; D, moth,

Fig

93. — Cross-section of scale
Anosia. — After Mayer.

of

to 1,400 (Morpho) to each scale,
mm. apart (Kellogg); between

62

ENTOMOLOGY

On the wing of a butterfly the scales are arranged in regular rows and
overlap one another, as in Fig. 94; in the more primitive moths and in
Trichoptera, however, their distribution is rather irregular.

A scale is the equivalent of a hair, for (1) a complete series of transi-
tions from hairs to scales may be

found on a single individual (Fig. 95) ;
and (2) hairs and scales agree in their
manner of development, as shown by
Semper, Schaffer, Spuler, Mayer and
others. Both hairs and scales arise
as processes from enlarged hypo-
dermis cells, or formative cells (Fig.
96) . The scale at first contains pro-
toplasm, which gradually withdraws,
leaving short chitinous strands to
hold the two membranes of the scale
together.

Uses of Scales. — Among Thy-

sanura and Collembola, scales occur

Fig. 94. — Arrangement of scales on the , , .

wing of a butterfly, Papilio. only on such species as live in com-

paratively dry situations, from which
it may be inferred that the scales serve to retard the evaporation of mois-
ture through the delicate integument of these insects. This inference is
supported by the fact that none of the scaleless Collembola can live long
in a dry atmosphere; they soon shrivel and die even under conditions
of dryness which the scaled species are able to withstand. In Lepidop-

Fig. 95. — Hairs and scales of a moth, Samia cecropia.

tera the scales are possibly of some value as a mechanical protection;
they have no influence upon flight, as Mayer has proved, and appear to
be useful chiefly as a basis for the development of color and color patterns
— which are not infrequently adaptive.

ANATOMY AND PHYSIOLOGY

03

Androconia. — The males of many butterflies, and the males only,
have peculiarly shaped scales known as androconia (Fig. 97) ; these are
commonly confined to the upper surfaces of the front wings, where they
are mingled with the ordinary scales or else are disposed in special patches
or under a fold of the costal margin of the wing (Thanaos). The char-
acteristic odors of male butterflies have long been attributed to these
androconia, and M. B. Thomas has found that the scales arise from glan-

Fig. 96. — Development of butterfly scales.
A. Vanessa; B, Aiwsia. b, basement mem-
brane; /, formative cell; h, hypodermis; s,
scale. — After Mayer.

Fig. 97. — Androconia of butterflies. A,
Pier is rapaz; B, Everes corny ntas.

dular cells, which doubtless secrete a fluid that emanates from the scale
as an odorous vapor, the evaporation of the fluid being facilitated by the
spreading or branching form of the androconium. Similar scales occur
also on the wings of various moths and some Trichoptera (Mystacides).

Glands. — A great many glands of various form and function have
been found in insects. Most of these, being formed from the hypoder-
mis, may logically be considered here, excepting some which are inti-
mately concerned with digestion or reproduction.

(-4

ENTOMOLOGY

Glandular Hairs and Spines. — The presence of adhesive hairs on
the empodium of the foot of a fly enables the insect to walk on a smooth
surface and to walk upside down; these tenent hairs emit a transparent
sticky fluid through minute pore canals in their apices. The tenent
hairs of Hylobius (Fig. 98) are each supplied with a flask-shaped unicellu-
lar gland, the glutinous secretion of which issues from the bulbous ex-
tremity of the hair. Bulbous tenent hairs occur also on the tarsi of Col-
lembola, Aphididae and other insects.

Nettling hairs or spines clothe the caterpillars of certain Saturniidae
(Automeris), Liparidae, etc. These spines (Fig. 99), which are sharp,
brittle and filled with poison, break to pieces when the insect is handled
and cause a cutaneous irritation much like that made by nettles. In

Fig. 98. — Section across tarsus of a beetle, Fig. 99. — Stinging hair of a caterpillar,

Hylobius, to show bulbous glandular hairs. — Gastropacha. c, cuticula; g, gland cell; h,
After SnniERUACHER. hair; hy, hypoderrnis. — After Claus.

Lagoa crispata (Fig. 100) the irritating fluid is secreted, as is usual, by
several large hypodermal cells at the base of each spine. These irritating
hairs protect their possessors from almost all birds except cuckoos.

Repellent Glands. — The various offensive fluids emitted by insects
are also a highly effective means of defence against birds and other in-
sectivorous vertebrates as well as against predaceous insects. The blood
itself serves as a repellent fluid in the oil-beetles (Meloidae) and Coccinel-
lidae, issuing as a yellow fluid from a pore at the end of the femur. The
blood of Meloidae (one species of which is still used medicinally under the
name of " Spanish Fly") contains cantharidine, an extremely caustic sub-
stance, which is an almost perfect protection against birds, reptiles and
predaceous insects. Coccinellidae and Lampyridae are similarly exempt

ANATOMY AND PHYSIOLOGY

65

from attack. Larvae of Cimbex when disturbed squirt jets of a watery
fluid from glands opening above the spiracles. Many Carabidae eject a
pungent and often corrosive fluid from a pair of anal glands (Fig. 146) ;
this fluid in Brachinus, and occasionally in Galerita janus and a few other
carabids, volatilizes explosively upon contact with the
air. When one of these "bombardier-beetles'' is
molested it discharges a puff of vapor, accompanied
by a distinct report, reminding one of a miniature
cannon, and this performance may be repeated several
times in rapid succession; the vapor is acid and corro-
sive, staining the human skin a rust-red color. Indi-
viduals of a large South American Brachinus when
seized "immediately began to play off their artillery,
burning and staining the flesh to such a degree that
only a few specimens could be captured with the naked
hand, leaving a mark which remained for a consider-
able time." (Westwood.)

As malodorous insects, Hemiptera are notorious,
though not a few hemipterous odors are (apart from their associations)
rather agreeable to the human olfactory sense. Commonly the odor is
due to a fluid from a mesothoracic gland or glands, opening between the
hind coxae.

Eversible hypodermal glands of many kinds are common in larvae of

Fig. 100. — Sting-
ing spines of a cater-
pillar. Lagoa crispata.
— After Packard.

Fig.

1 o 1 . — Osmeterium
polyxenes.

of Papilio

Fig. 102. — Ventral aspect of worker honey bee, show-
ing the four pairs of wax scales. — After Cheshire.

Coleoptera and Lepidoptera. The larvae of Melasoma lapponica, among
other Chrysomelidae, evert numerous paired vesicles which emit a peculiar
odor. The caterpillars of our Papilio butterflies, upon being irritated,
evert from the prothorax a yellow Y-shaped osmeterium (Fig. 101) which

66

ENTOMOLOGY

diffuses a characteristic but indescribable odor that is probably repellent.
The larva of C crura everts a curious spraying apparatus from the under
side of the neck.

Alluring Glands. — Odors are largely used among insects to attract
the opposite sex. The androconia of male butterflies have already been
spoken of. Males of Catocala concumbens disseminate an alluring odor
from scent tufts on the middle legs. Female saturniid moths (as cecro-
pia and promethea) entice the males by means of a characteristic odor
emanating from the extremity of the abdomen. In lycaenid caterpillars,
an eversible sac on the dorsum of the seventh abdominal segment secretes
a sweet fluid, for the sake of which these larvae are sought out by ants.

Wax Glands. — Wax is secreted by insects of several orders, but es-
pecially Hymenoptera and Hemiptera. In the worker honey bee the

wax exudes from unicellular hypo-
dermal glands and appears on the
under side of the abdomen as four
pairs of wax scales (Fig. 102).
Plant lice of the genus Schizoneura
owe their woolly appearance to
dense white filaments of wax,
which arise from glandular hypo-
dermal cells. In scale insects,
waxen threads, emerging from
cuticular pores, become matted
together to form a continuous
shield over and often under the
insect itself, the cast skins often
being incorporated into this waxen
scale. The wax glands in Coccidae are simply enlarged hypodermis
cells.

Silk Glands. — Larvae of very diverse orders spin silk, for the purpose
of making cocoons, webs, cases, and supports of one kind or another.
Silk glands, though most characteristic of Lepidoptera and Trichoptera,
occur also in the cocoon-spinning larvae of not a few Hymenoptera (saw
flies, ichneumons, wasps, bees, etc.), in Diptera (Cecidomyiidae), Neurop-
tera (Chrysopidae, Myrmeleonidae) , and in various larvae whose pupae are
suspended from a silken support, as in the coleopterous families Coccinel-
lidae and Chrysomelidae (in part) and the dipterous family Syrphidae, as
well as most diurnal Lepidoptera.

The silk glands of caterpillars are homologous with the true salivary

Fig. 103. — Head of caterpillar of Samia
cecropia. a, antenna; c, clypeus; /, labrum;
.lp, labial palpus; m, mandible; mp, maxillary
palpi; 0, ocelli; s, spinneret.

ANATOMY AND PHYSIOLOGY

67

glands of other insects, opening as usual through the hypopharynx,
which is modified to form a spinning organ, or spinneret (Fig. 103). The
silk glands of Lepidoptera are a pair of long tubes, one on each side of the
body, but often much longer than the body and consequently convoluted.
Thus in the silk worm {Bombyx mori) they are from four to five times as
long as the body and in Telea polyphemus, seven times as long. In the

silk worm the convoluted glandular portion

Fig. 104. — Silk glands of the Fig. 105. — Sections of silk gland of the silk worm,
silk worm, Bombyx mori. cd, A, radial; B, transverse, b. basement membrane; i,
common duct; d, one of the intima; s, glandular cell with branched nucleus. —
paired ducts; g, g, Filippi's After Helm.
glands; gl, gland proper; p,
thread press; r, reservoir.

into a short common duct, which passes through the tubular spinneret.
Two divisions of the spinning tube are distinguished: (1) a posterior
muscular portion, or thread-press and (2) an anterior directing tube. The
thread-press combines the two streams of silk fluid into one, determines
the form of the silken thread and arrests the emission of the thread at
times, besides having other functions. The silk fluid hardens rapidly
upon exposure to the air; about fifty per cent, of the fluid is actual silk

68

ENTOMOLOGY

substance and the remainder consists of protoplasm and gum, with traces
of wax, pigment, fat and resin.

A transverse or radial section of a silk gland shows a layer of glandu-
lar epithelial cells, with the usual intima and basement membrane (Fig.
105); the cells are remarkably large and their nuclei are often branched;
the intima is distinctly striated, from the presence of pore-canals. The
glands arise as evaginations of the pharynx (ectodermal) and the chi-
tinous intima of each gland is cast at each moult, along with the general
integument.

The silk glands of Trichoptera are essentially like those of Lepidop-
tera, but the glands of Chrysopa, Myrmelcon. Coccinellidae, Chrysomeli-
dae and Syrphidae, which open into the rectum, are morphologically quite
different from those of Lepidoptera.

3. Muscular System
The number of muscles possessed by an insect is surprisingly large.
A caterpillar, for example, has about two thousand.

The muscles of the trunk are segmentally arranged — most evidently

Fig. 106. Fig. 107. Fig. 108.

Muscles of cockroach; of ventral, dorsal and lateral walls, respectively, a, alary muscle;
abc, abductor of coxa; adc, adductor of coxa; ef, extensor of femur; h, head muscles; Is,
longitudinal sternal; //, longitudinal tergal; Ith, lateral thoracic; os, oblique sternal; ot,
oblique tergal; is, tergo-sternal; ts1, first tergo-sternal. — After MlAlX and Dexxy.

so in the body of a larva or the abdomen of an imago, where the muscu-
lature is essentially the same in several successive segments. In the
thoracic segments of an imago, however, the musculature is, at first sight.

ANATOMY AND PHYSIOLOGY

69

Fig. 109. —
Striated muscle
fiber of an insect.

unlike that of the abdomen, and in the head it is decidedly different;
though future studies will doubtless show that the thoracic and cephalic
kinds of musculature are only modifications of the simpler abdominal
type — modifications brought about in relation to the
needs of the legs, wings, mouth parts, antennae and other
movable structures.

The muscular system has been generally neglected
by students of insect anatomy; the only comprehensive
studies upon the subject being those of Straus-Diirckheim
(1828) on the beetle Melolontha; Lyonet (1762), New-
port (1834) and Lubbock (1859) on caterpillars; and
the more recent studies of Lubbock and Janet on Hy-
menoptera.

The more important muscles in the body of a cock-
roach are represented in Figs. 106-108, from Miall and
Denny. The longitudinal stemals with the longitudinal tergals act to
telescope the abdominal segments; the oblique stemals bend the abdomen
laterally; the ter -go- stemals, or vertical expiratory muscles, draw the

tergum and sternum together. The
muscles of the legs and the wings have
already been referred to.

Structure of Muscles. — The mus-
cles of insects differ greatly in form and
are inserted frequently by means of
chitinous tendons. A muscle is a
bundle of long fibers, each of which
has an outer elastic membrane, or
sarcolemma , within which are several
nuclei; thus the fiber represents several
cells, which have become confluent.
With rare exceptions (" alary" muscles
and possibly a few thoracic muscles)
the muscle fibers of an insect present a
striated appearance, owing to alternate
light and dark bands (Fig. 109), the former being singly refracting, or
isotropic, and the latter doubly refracting, or anisotropic.

The minute structure of these fibers, being extremely difficult of
interpretation, has given rise to much difference of opinion. The most
plausible view is that of van Gehuchten, Janet and others, who hold that
both kinds of dark bands (Fig. no) consist of highly elastic threads of

Fig. 1 10. — Minute structure of a
striated muscle fiber. A, longitudinal
section; B, transverse section in the
region of /; C, transverse section in the
region of n. I, longitudinal fibrillar ;
n, Krause's membrane; nl, nucleus;
r, radial fibrillar; s, sarcolemma. — After
Janet.

70

ENTOMOLOGY

spongio plasm (anisotropic) embedded in a matrix of clear, semi-fluid,
nutritive hyaloplasm (isotropic). The spongioplasmic threads of the
long bands extend longitudinally and those of the short bands (" Krause's
membrane") radially, in respect to the form of the fiber. Moreover, the
attenuated extremities of the longitudinal fibrillar connect with the radial
fibrillar, the points of connection being marked by slight thickenings, or
nodes, which go to make up Krause's membrane.

Under nervous stimulus a muscle shortens and thickens because its
component fibers do, and this in turn is attributed to the shortening and
thickening of the longitudinal fibrillar. When the stimulus ceases, the
radial fibrillae, by their elasticity, possibly pull the longitudinal ones back
into place. The last word has not been said, however, upon this per-
plexing subject.

Muscular Power. — The muscular exploits of insects appear to be
marvellous beside those of larger animals, though they are often exag-
gerated in popular writings. The weakest insects, according to Plateau,
can pull five times their own weight and the average insect, over twenty
times its weight, while Donacia (Chrysomelidae) can pull 42.7 times its
weight. As contrasted with these feats, a man can pull in the same fash-
ion but .86 of his weight and a horse from .5 to .83. How are these dif-
ferences explained?

It is incorrect to say that the muscles of insects are stronger than those
of vertebrates, for, as a matter of fact, the contractile force of a vertebrate
muscle is greater than that of an insect muscle, other things being equal.
The apparently greater strength of an insect in proportion to its weight is
accounted for in several ways. The specific gravity of chitin is less than
that of bone, though it varies greatly in both substances. Furthermore,
the external skeleton permits muscular attachments of the most advan-
tageous kind as compared with the internal skeleton, so that the muscles
of insects surpass those of vertebrates as regards leverage. These reasons
are only of minor importance, however. Small animals in general appear
to be stronger than larger animals (allowing for the differences in weight)
for the same reason that a smaller insect has more conspicuous strength
than a larger one, when the two are similar in everything except weight.
For example: where a bumble bee can pull 16. 1 times its own weight, a
honey bee can pull 20.2; and where the same bumble bee can carry while
flying a load 0.63 of its own weight, the honey bee can carry 0.78. Al-
ways, as Plateau has shown, the fighter of two insects is the stronger in
respect to external manifestations of muscular force — in the ratio of this
muscular strength to its own weight.

ANATOMY AXD PHYSIOLOGY

71

To understand this, let us assume that a beetle continues to grow (as
never happens, of course). As its weight is increasing so is its strength —
but not in the same proportion. For while the weight — say that of a
muscle — increases as the cube of a single dimension, the strength of the
muscle (depending solely upon the area of its cross-section) is increasing
only as the square of one dimension — its diameter. Therefore the in-
crease in strength lags behind that of weight more and more; consequently
more and more strength is required simply to move the insect itself, and
less and less surplus strength remains for carrying additional weight.
Thus the larger insect is apparently the weaker, though it is actually the
stronger, in that its total muscular force is greater.

The writer uses this explanation to account also for the inability of
certain large beetles and other insects to use their wings, though these
organs are well developed. Increasing weight (due to a larger supply of
reserve food accumulated by the larva) has made such demands upon the
muscular power that insufficient strength remains for the purpose of flight.

Statements such as this are often seen — a flea can jump a meter, or
six hundred times its own length. Almost needless to say, the length of
the body is no criterion of the muscular power of an animal.

4. Nervous System

The central nervous system extends along the median line of the floor
of the body as a series of ganglia connected by nerve cords. Typically,
there is a ganglion (double in origin) for each primary segment, and the
connecting cords, or commissures, are paired; these conditions are most
nearly realized in embryos and in the most generalized insects — Thysa-
nura (Fig. 111). In all adult insects, however, the originally separate
ganglia consolidate more or less (Fig. 112) and the commissures frequently
unite to form single cords. Thus in Tabanus (Fig. 112, C) the three
thoracic ganglia have united into a single compound ganglion and the
abdominal ganglia are concentrated in the anterior part of the abdomen;
in the grasshopper, the nerve cord, double in the thorax, is single in the
abdomen. Various other modifications of the same nature occur.

Cephalic Ganglia. — In the head the primitive ganglia always unite
to form two compound ganglia, namely, the brain and the sub oesophageal
ganglion (disregarding a few anomalous cases in which the latter is said
to be absent).

The brain, or supraoesophageal ganglion (Fig. 113), is formed by the
union of three primitive ganglia, or neuromeres (Fig. 55), namely, (1)
the proto cerebrum, which gives off the pair of optic nerves; (2) the deuto-

72

Fig. hi. — Central
nervous system of a thy-
sanuran, Machilis. The
thoracic and abdominal
ganglia are numbered in
succession. a, antennal
nerve; b, brain; e, com-
pound eye; /, labial nerve;
m, mandibular nerve;
mx, maxillary nerve; o,
oesophagus ; ol, optic lobe ;
s, subcesophageal gang-
lion ; sy, sympathetic
nerve. — After Oudemans.

ENTOMOLOGY

cerebrum, which innervates the antennae; and (3)
the tritocerebrum, which in Apterygota bears a pair
of rudimentary appendages that are regarded as
traces of a second pair of antennae.

The subcesophageal ganglion (Fig. 113) is
always connected with the brain by a pair of
nerve cords {oesophageal commissures) between
which tlie oesophagus passes. This compound
ganglion represents at most four neuromeres: (1)
mandibular, innervating the mandibles; (2) super-
lingual, found by the author in Collembola, but
not yet reported in the less generalized insects;
(3) maxillary, innervating the maxillae; (4) labial,
which sends a pair of nerves to the labium.

The minute structure of the brain, though
highly complex, has received considerable study,
but will not be described here for the reason that
the anatomical facts are of no general interest so
long as their physiological interpretation remains
obscure.

Sympathetic System. — Lying along the me-
dian dorsal line of the oesophagus is a recurrent,
or stomato gastric, nerve (Fig. 114), which arises
anteriorly in a frontal ganglion and terminates
posteriorly in a stomachic ganglion situated at the
anterior end of the mid intestine. Connected
with the recurrent nerve are two pairs of lateral
ganglia, the anterior of which innervate the dorsal
vessel and the posterior, the tracheae of the head.
The ventral nerve cord may include also a median
nerve thread (Fig. in) which gives off paired
transverse nerves to the muscles of the spiracles.

Structure of Ganglia and Nerves. — A gang-
lion consists of (1) a dense cortex, composed of
ganglion cells (Fig. 115), each of which has a
large rounded nucleus and gives off usually a
single nerve liber; and (2) a clear medullary
portion (Punktsubstanz) derived from the pro-
cesses of the cortical ganglion cells and serving as
the place of origin of nerve nbrillae. There are,

ANATOMY AND PHYSIOLOGY 73

however, ganglion cells from which processes may pass directly into
nerve fibrillae.

A nerve-fiber, in an insect, consists of an axis-cylinder, composed of

Fig. 112. — Successive stages in the concentration of the central nervous system of Diptera.
A, Chironomus; B, Empis; C, Tabanus; D, Sarcophaga. — After Brandt.

fibrillae, and an enveloping membrane, or sheath. The axis-cylinder is
the transmitting portion and the ganglia are the trophic centers, i. e.,
they regulate nutrition. A nerve is always either sensory, transmitting

Fig. 113. — Nervous system of the head of a cockroach, a, antennal nerve; ag, anterior
lateral ganglion of sympathetic system; b, brain; d, salivary duct; /, frontal ganglion; h,
hypopharynx; /, labrum; //, labium; m, mandibular nerve; mx, maxillary nerve; nl, nerve to
labrum; nli, nerve to labium; 0, optic nerve; oc, oesophageal commissure; oe, oesophagus;
pg, posterior lateral ganglion of sympathetic system; r, recurrent nerve of sympathetic system;
s, subcesophageal ganglion. — After Hofer.

impulses inward from a sense organ ; or else motor, conveying stimuli from
the central nervous system outward to muscles, glands, or other organs.
Functions. — The brain innervates the chief sensory organs (eyes and

74

ENTOMOLOGY

r -

antennae) and converts the sensory stimuli that it receives into motor

stimuli, which effect co-ordinated muscular
or other movements in response to particular
sensations from the environment. The brain
is the seat of the will, using the term "will" in
O ^mk""^ Lr, a loose sense; it directs locomotor movements

of the legs and wings. An insect deprived of
its brain cannot go to its food, though it is
able to eat if food be placed in contact with
the end-organs of taste, as those of the palpi;
furthermore, it walks or flies in an erratic
manner, indicating a lack of co-ordination of
muscular action.

The subcesophageal ganglion controls the
mouth parts, co-ordinating their movements
as well as some of the bodily movements.

The thoracic ganglia govern the appen-
dages of their respective segments. These
ganglia and those of the abdomen are to a
great extent independent of brain control,
each of these ganglia being an individual
motor center for its particular segment.
Thus decapitated insects are still able to
breathe, walk or fly, and often retain for
several days some power of movement.

In regard to the sympathetic system, it
has been shown experimentally that the frontal
ganglion controls the swallowing movements
and exerts through the stomatogastric nerve
a regulative action upon digestion. The
dorsal sympathetic system controls the dorsal vessel and the salivary

Fig. 114. — Sympathetic
nervous system of an in-
sect, diagrammatically repre-
sented, a, antennal nerve;
b, brain; /, frontal ganglion;
7, 1, paired lateral ganglia; m,
nerves to upper mouth parts;
0, optic nerve; r, recurrent
nerve; s, nerve to salivary
glands; st, stomachic gang-
lion.— After Kolbe.

Fig. 115. — Transverse section of an abdominal ganglion of a caterpillar. /, nerve-fibers; gt
ganglion cells; n, nerve-sheath; p, Punktsubstanz.

ANATOMY AND PHYSIOLOGY

75

glands, while the ventral sympathetic system is concerned with the spi-
racular muscles.

5. Sense Organs

For the reception of sensory impressions from the external world,
the armor-like integument of insects is modified in a great variety of
ways. Though sense organs of one kind or another may occur on almost
any part of an insect, they are most numerous and varied upon the head
and its appendages, particularly the antennae.

Antennal Sensilla. — Some idea of the diversity of form in antennal
sense organs may be obtained from Figs. 1 16-125, taken from a paper
by Schenk, whose useful classification of antennal sensilla, or sense
organs, is here outlined:

1. Sensillum cceloconicum — a conical or peg-like projection immersed
in a pit (Figs. 11 6-1 17). In all probability olfactory.

2. S. basiconicum — a cone projecting above the general surface (Fig.
118). Probably olfactory.

3. S. styloconicum — a terminal tooth or peg seated upon a more or less
conical base (Fig. 119). Olfactory.

4. 5. chceticum — a bristle-like sense organ (Fig. 120). Tactile.

5. S. trichodeuni — a hair-like sense organ (Figs. 121, 122). Tactile.

6. S. placodeum — a membranous plate, its outer surface continuous
with the general integument (Fig. 123). Function doubtful; not audi-
tory and probably not olfactory*, though the function is doubtless a
mechanical one; Schenk suggests that this organ is affected by air
pressure, as when a bee or wasp is moving about in a confined space.

7. S. ampullaceum — a more or less flask-shaped cavity with an axial
rod (Figs. 124, 125). Probably auditory.

These types of sensilla will be referred to in physiological order.

Touch. — The tactile sense is highly developed in insects, and end-
organs of touch, unlike those of other senses, are commonly distributed
over the entire integument, though the antennae, palpi and cerci are es-
pecially sensitive to tactile impressions.

The end-organs of touch are bristles (sensilla chaetica) or hairs (sensilla
trichodea), each arising from a special hypodermis cell and having con-
nection with a nerve. Sensilla chaetica doubtless receive impressions
from foreign bodies, while sensilla trichodea, being best developed in the
swiftest flying insects and least so in the sedentary forms, may be affected
by the resistance of the air, when the insect or the air itself is in motion.

7 6 ENTOMOLOGY

Not all the hairs of an insect are sensory, however, for many .of them
have no nerve connections.

Figs, i 16-125. — Types of antennal sensilla, in longitudinal section (excepting Figs. 119
and 120). Fig. 116, sensillum cceloconicum; 117, cceloconicum; 118, basiconicum; 119,
styloconicum; 120, chaeticum; 121, trichodeum; 122. trichodeum; 123. placodeum; 124,
ampullaceum; 125, ampullaceum; c, cuticula; //, h\podermis; n, nerve; s, sensory cell.
Figs. 116, 118, 121, 123, 124, honeybee, Apis mellifera; 117, 119, 122, moth, Fidonia piniaria;
120, moth, I no pruni; 125, wasp, Vespa crabro. — After Schexk.

In blind cave insects the antennae are very long and are exquisitely
sensitive to tactile impressions.

Taste. — The gustatory sense is unquestionably present in insects, as
is shown both by common observation and by precise experimentation.

ANATOMY AND PHYSIOLOGY

77

Will fed wasps with sugar and then replaced it with powdered alum,
which the wasps unsuspectingly tried but soon rejected, cleaning the
tongue with the fore feet in a comical manner and manifesting other signs
of what we may call disgust. Forel offered ants honey mixed with mor-
phine or strychnine; the ants began to feed but at once rejected the mix-
ture. In its range, however, the gustatory sense of insects differs often
from that of man. Thus Will found that Hymenoptera refused honey
with which a very little glycerine had been mixed (though Muscidae did
not object to the glycerine) and Forel found that ants ate unsuspectingly
a mixture of honey and phosphorus until some of them were killed by it.
Under the same circumstances, man would be able to detect the phos-
phorus but not the glycerine.

Location of Gustatory Organs. — As would be expected, the end-
organs of taste are situated near the mouth, commonly on the hypo-

Fig. 126. — Section through tongue of wasp, Vespa vul-
garis, c, cuticula; g, gland cell; h, hypodermis; 11, nerve;
ob, gustatory bristle; ph, protecting hair; sc, sensory cell;
lb, tactile bristle. — After Will.

Fig. 127. — Tongue of honey
bee, Apis mellifera. p, protect-
ing bristles; 5, terminal spoon;
/, taste setae. — After Will.

pharynx (Fig. 126), epipharynx and maxillary palpi. On the tongue of
the honey bee the taste organs appear externally as short setae (Fig. 127)
and on the maxillae of a wasp as pits, each with a cone, or peg, projecting
from its base (Figs. 128, 129). Similar taste pits and pegs have been
found by Packard on the epipharynx in most of the mandibulate orders of
insects.

Histology. — The end-organs of taste arise from special hypodermis
cells, as minute setae or, more commonly, pegs, each seated in a pit, or
cup, and connected with a nerve fiber (Figs. 129, 130). In some cases,
however, it is difficult to decide whether a given organ is gustatory or
olfactory, owing to the similarity between these two kinds of structures.

78

ENTOMOLOGY

In aquatic insects, indeed, the senses of taste and smell are not differen-
tiated, these forms having with other of the lower animals simply a
" chemical" sense.

Smell.- In most insects the sense of smell is highly efficient and in
many species it is inconceivably acute. Hosts of insects depend chiefly
on their olfactory powers to rind food, for example many beetles, the flesh
flies and the flower- visiting moths; or else to discover the opposite sex,
as is notably the case in saturniid moths. In dragon flies, however, this
sense is relied upon far less than that of sight.

Organs of Smell. — By means of simple but conclusive experiments,

Hauser and others have shown that
the antennae are frequently olfactory
— though not to the exclusion of tac-
tile or auditory functions, of course.
Hauser found that ants, wasps, vari-
ous flies, moths, beetles and larvae,
which react violently toward the vapor
of turpentine, acetic acid and other

Fig. 128. — Under side of left maxilla
of wasp, Vespa vulgaris, p, palpus; pr,
protecting hairs; tc, taste cup; th, tactile
hair. — After Will.

Fig. 129. — Longitudinal section of gustatory
end-organ (tc, of Fig. 128). c, cuticula; //, hypo-
dermis; sc, sensory cell; tc, taste cup. — After Will.

pungent fluids, no longer respond to the same stimuli after their antennae
have been amputated or else covered writh paraffine to exclude the air.
His experiments were conducted under conditions such that the results
could not be ascribed to the shock of the operation or to effects upon the
gustatory or respiratory systems; except for having lost the sense of
smell, the insects experimented upon behaved in a normal manner. It
should be said, however, that Carabus, Melolontha and Silpha still re-
acted to some extent toward strong vapors even after the extirpation of
the antennae; while in Hemiptera the loss of the antennae did not lessen
the response to the odors used. These facts indicate that the sense of

ANATOMY AND PHYSIOLOGY

79

smell is not always confined to the antennae; indeed the maxillary palpi
are frequently olfactory, as in Silpha and Hydaticus; also the cerci, as in
the cockroach and other Orthoptera. Experiments indicate that an
insect perceives some odors by means of the antennae and others by the
palpi or other organs. Hauser found that the flies Sarcophaga and Cal-
liphora, after the amputation of their antennae, became quite indifferent
toward decayed meat, to which they had previously swarmed with great
persistence, though their actions in all other respects remained normal.
Males of many moths and a few beetles are unable to find the females
(see beyond) when the former are deprived of the use of their antennae.

End-Organs. — Structures which are regarded as olfactory end-organs
occur commonly on the antennae, often on the maxillary and labial palpi
and sometimes on the cerci. These end-organs are hypodermal in origin
and consist, generally speaking, of a multinucleate cell (Fig. 131) pene-
trated by a nerve and prolonged into a chitinous bristle or peg, which is
more or less enclosed in a pit, as in Tabanus (Fig. 132). In many in-
stances, however, the end-organs take the form of teeth or cones project-
ing from the general surface of the antenna, as in Vespa (Fig. 133).
These cones are usually less numerous than the pits; in Vespa crabro,
for example, the teeth number 700 and the pits from 13,000 to 14,000
on each antenna. The pits are even more numerous in some other in-
sects; thus there are as many as 17,000 on each antenna of a blow fly

cSo

ENTOMOLOGY

(Hicks). The male of Melolontha vulgaris, which seeks out the female by
the sense of smell, has according to Hauser 39,000 pits on each antenna,
and the female only 35,000. Pits presumably olfactory in function have
been found by Packard on the maxillary and labial palpi of Perla and
on the cerci of the cockroach, Periplaneta americana. Vom Rath has de-
scribed four kinds of sense hairs from the two larger of the four caudal
appendages of a cricket, Gryllus; some of these (Fig. 134) may be olfac-
tory, though possibly tactile. The same author found on the terminal
palpal segment in various Lepidoptera a large flask-shaped invagina-
tion (Fig. 135) into which project numer-
ous chitinous rods, each a process of a
sensory cell, which is supplied by a
branch of the principal palpal nerve:
these peculiar organs are inferred to be
olfactory.

Fig. 132. — Section through antennal olfactory
pit of fly, Tabamis. c. cuticula; p. pit with peg;
pb, protecting bristles; s, sensory cell. — After
Hauser.

Fig. 133. — Longitudinal section of
antennal olfactory organ of wasp,
Vespa. c, olfactory cell; cn, olfactory
cone; ct, cuticula; h, hypodermis cells ;
11, nerve; r, rod. — After Hauser.

The chief reason for regarding these various end-organs as olfactory is
that they appear from their structure to be better adapted to receive that
kind of an impression than any other, so far as we can judge from our own
experience. Though it is easy to demonstrate that the antennas, for
example, are olfactory, it frequently happens that the antennae bear sev-
eral distinct forms of sensory end-organs, so minute and intermingled
that their physiological differences can scarcely be ascertained by experi-
ment but must be inferred from their peculiarities of structure. Schenk,
however, has arrived at precise results by comparing the antennal sen-
silla in the two sexes, selecting species in which the antennas exhibit a pro-
nounced sexual dimorphism, in correlation with sexual differences of be-
havior. Taking Xotolophus (Orgyia) antiqua. in which the male seeks out

ANATOMY AND PHYSIOLOGY

Si

the female by means of antennal organs of smell, he finds that the male
has on each antenna about 600 sensilla cceloconica and the female only
75; similarly in the geometrid Fidonia, in which the ratio is 350 to 100.
The sensilla styloconica, also, of these two genera are regarded as olfac-
tory organs. These two kinds of end-organs are not only structurally
adapted for the reception of olfactory stimuli, but their numerical dif-
ferences accord with the observed differences in the olfactory powers of
the two sexes, there being no other antennal end-organs to enter into the
consideration.

Assembling. — It is a fact, well known to entomologists, that the
females of many moths and some beetles are able by exhaling an odor to

Fig. 134. — Longitudinal section of a por-
tion of a caudal appendage of a cricket.
Gryllus domesticus. b, bladderlike hair; c,
cuticula; h, hypodermis; 11, nerve; ns, non-
sensory setae; sc, sense cell; sh, sensory hair.
— After vom Rath.

After vo.m Rath.

attract the opposite sex, often in considerable numbers. Under favor-
able conditions, a freshly emerged female of the promethea moth, exposed
out of doors in the latter part of the afternoon, will attract scores of the
males. A breeze is essential and the males come up against the wind;
if they pass the female, they turn back and try again until she is located,
vibrating the antennae rapidly as they near her. The female, meanwhile,
exhales an appreciable odor, chiefly from the region of the ovipositor, and
males will congregate on the ground at a spot where a female has been.
If one of these males is deprived of the use of his antennae, however.

82

ENTOMOLOGY

he flutters about in an aimless way and is no longer able to find the
female.

Among beetles, males of Polyphylla gather and scratch at places where
females are about to emerge from the ground. Prionus also assembles,
as Mrs. Dimmock observed in Massachusetts. In this instance many
males, with palpitating antennae, ran and flew to the female; moreover, a
number of females were attracted to the scene.

Sounds of Insects. — Before considering the sense of hearing, some
account of the sounds of insects is desirable. Most of these are made by
the vibrations of a membrane or by the friction of one part against another.

The wings of many Diptera and Hymenoptera vibrate with sufficient
speed and regularity to give a definite note. The wing tone of a honey
bee is A ' and that of a common house fly is F' '. From the pitch the num-
ber of vibrations may be determined; thus A' means 4401 vibrations per
second and F' , 352. The numbers thus ascertained may be verified by
Marey's graphic method (Fig. 74) ; he found that the fly referred to ac-
tually made 330 strokes per second against the smoked surface of a re-
volving cylinder.

Flies, bees, dragon flies and some beetles make buzzing or humming
sounds by means of the spiracles, there being behind each spiracle a mem-
brane or chitinous projection which vibrates during respiration. This
"voice" should be distinguished from the wing tone when both are pres-
ent, as in bees and flies. A fly will buzz when held by the wings, and some
gnats continue to buzz after losing wings, legs and head. The wing tone
is the more .constant of the two; in the honey bee it is A' , falling to F'
if the insect is tired, while the spiracular tone of the same insect is at least
an octave higher (A ") and often rises to B" or C", according to the state of
the nervous system; in fact, it is possible and even probable that various
spiracular tones express different emotions, as is indicated by the effects
produced by the voice of the old queen bee upon the young queens and
the males.

The well-known "shrilling" of the male cicada is produced by the
rapid vibration of a pair of membranes, or drums, situated on the basal
abdominal segment, and vibrated each by means of a special muscle.

Frictional sounds are made by beetles in a great variety of ways : by
the rubbing of the pronotum against the mesonotum (many Cerambyci-
dae); or of abdominal ridges against elytral rasps (Flaphrus, Cychrus);
or two dorsal abdominal rasps against specialized portions of the wing

1 Upon the basis of C as 264 vibrations per second. The C of the physicist has 256 as its
frequency of vibration.

ANATOMY AND PHYSIOLOGY

83

folds (Passalus cornutus), not to mention other methods. In most cases
one part forms a rasp and the other a scraper, for the production of sound.

In many of these instances the sound serves to bring the two sexes
together and is not necessarily confined to one sex; thus in Passalus cor-
nutus both sexes stridulate.

A few moths (Sphingidse) and a few butterflies make sounds; the South
American butterfly Ageronia feronia emits a sharp crackling noise as it
flies. A rasp and a scraper have been found in several ants, though ants
very seldom make any sounds that can be distinguished by the human
ear; Mutilla, however, makes a distinct squeaking sound by means of a
stridulating organ similar to those of ants.

Stridulating organs attain their best development in Orthoptera, in
which group the ability to stridulate is often restricted to the male, though
not so often as is commonly supposed. Among Acridiidae, Stenobothrus
rubs the hind femora against the tegmina to make a sound, the femur
bearing a series of teeth, which scrape across the elevated veins of the
wing-cover; while the male of Dissosteira makes a crackling sound during
flight or while poising, by means of friction between the front and hind
wings, where the two overlap.

Locustidae and Gryllidae stridulate by rubbing the bases of the teg-
mina against each other. Thus in the male Microcentrum laurifolium the
left tegmen, which overlaps the right, bears a file-like organ of about fifty-
five teeth (Fig. 136), while the opposite tegmen bears a scraper, at right
angles to the file. The tegmina are first spread a little; then, as they close
gradually, the scraper clicks across the teeth, making from twenty to
thirty sharp "tic" -like sounds in rapid succession. This call guides the
female to the male and when they are a few inches apart she makes now
and then a short, soft chirp, to which he responds with a similar chirp,
which is quite unlike the first call and, moreover, is made by the opening
of the tegmina. These and other details of the courtship may readily be
observed in twilight and even under artificial fight, as the latter, if not
too strong, does not disturb the pair. Something similar may be ob-
served in the daytime in Orchelimum, Xiphidium and the tree crickets,
(Ecanthus. The stridulating areas are usually membranous and the rasp-
ing organs are modified veins. Frequently the wing-covers bulge out to
form a resonant chamber that reinforces the sound.

The naturalist can recognize many a species of grasshopper by its
song; Scudder has expressed some of these songs in musical notation.
The usual song of the common meadow-grasshopper, Orchelimum vul-

34

ENTOMOLOGY

gore, may be represented by a prolonged zr . . . sound, followed by
a staccato jip-jip-jip-jip. . . .

In Orthoptera, the frequency of stridulation increases with the tem-
perature; and the correlation between the two is so close that it is easy to

Fig. 136. — Stridulating organs of Microccntrum laurifolium. A. dorsal aspect of file (st)
when the tegmina are closed; B. ventral aspect of left tegmen to show file; C, dorsal aspect
of right tegmen to show sera per (s) .

compute the temperature from the number of calls per minute, by means
of formulae. The formula for a common cricket [probably a tree-cricket,
(Ecanthus niveus], as given by Professor Dolbear, is

T = 50 + *^ ^4°. which simplified is J = 40 + ~-

Here T stands for temperature and N, the rate per minute.

A similar formula for the katydid (Cyrtophyllus perspicillatus) , based
upon observations made by R. Hay ward, would be

vr-

Here, in computing N, either the ''katy-did" or the " she-did " is taken
as a single call.

ANATOMY AND PHYSIOLOGY

85

A. F. Shull, who has made precise observations on the stridulation of
(Ecanthus, finds that there are numerous variations of rate that cannot be
accounted for by differences of temperature; that Dolbear's formula
cannot be applied without a possible error of 6. 65° F.; that humidity
seems to affect the rate of chirping and that crickets show a certain in-
dividuality in their manner of chirping under the same external condi-
tions.

Hearing. — There is no doubt that insects can hear. The presence
of sound-making organs is strong presumptive evidence that the sense of
hearing is present. Female grasshoppers and beetles make locomotor
and other responses to the sounds of the males, and male grasshoppers will
answer the counterfeit chirping made with a quill and a file.

Auditory organs are not restricted to any one region of an insect, but
occur, according to the species, on antennae, abdomen, legs, or elsewhere.

The antennae of some insects are evidently stimulated by certain notes,
particularly those made by their own kind. Thus the antennae of the
male mosquito are auditory, as proved by the well-known experiments of
Mayer. He fastened a male Cidex to a microscope slide and sounded
various tuning forks. Certain tones caused certain of the antennal hairs
to vibrate sympathetically, and the greatest amount of vibration oc-
curred in response to 512 vibrations per second, or the note C", which is
approximately the note upon which the female hums. The male prob-
ably turns his head until the two antennae are equally affected by the note
of the female, when, by going straight ahead, he is able to locate her with
great precision.

In the lack of experimental evidence, other organs are inferred to be
auditory on account of their structure. Acridiidae bear on each side of
the first abdominal segment a tympanal sense organ — the subject of
Graber's well-known figure (Fig. 137). This organ is admirably adapted
to receive and transmit sound-waves. The tympanum, or membrane,
is tense, and can vibrate freely, as the air pressure against the two sur-
faces of the membrane is equalized by means of an adjacent spiracle,
which admits air to the inner surface. Resting against the inner face of
the tympanum are two processes (Fig. 137, p, p), which serve probably
to transfer the vibrations, and there is also a delicate vesicle connected
by means of an intervening ganglion with the auditory nerve, which in
this case comes from the metathoracic ganglion. The nerve terminations
consist of delicate bristle-like processes which are probably affected by the
oscillations of the fluid contained in the vesicle just referred to.

Other tympanal organs, doubtless auditory, are found on the fore

86

ENTOMOLOGY

tibia? of Locusticke, ants, termites and Perlidae, on the femora of Pedicu-
lidae and the tarsi of some Coleoptera.

Several types of chordotonal organs have been described, of which
those of the transparent Corethra larva may serve as an example. These
organs, situated on each side of abdominal segments 4-10, inclusive, con-
sist each (Fig. 138) of a tense cord, probably capable of vibration, which
is attached at its posterior end to the integument and at its anterior end
to a ligament. Between the cord and the supporting ligament is a small

Fig. 137. — Inner aspect of right tympanal sense
organ of a grasshopper. Caloptenus italicus. b, chitin-
ous border; c, closing muscle of spiracle; gn, gan-
glion; m, tympanum; n, nerve; o, opening muscle
of spiracle; p, p. processes resting against tympanum;
s, spiracle; tm, tensor muscle of tympanum; v, vesicle.
— After Graber.

Fig. 138. — Chordotonal sense
organ of aquatic dipterous larva,
Corethra plumicornis. cd, cord; eg.
chordotonal ganglion; f, fibers of an
in tegumental nerve; g, ganglion of
ventral chain; /, ligament; m, lon-
gitudinal muscles; n, chordotonal
nerve; r, rods (nerve terminations);
t, tactile setae. — After Graber.

ganglion, which receives a nerve from the principal ganglion of the seg-
ment.

Vision. — The external characters of the two kinds of eyes — ocelli and
compound eyes — have already been described. While the lateral ocelli
are comparatively simple in structure, consisting of a small number of
cells, the dorsal ocelli almost rival the compound eyes in complexity.

Dorsal Ocelli. — These consist (Fig. 139) of (1) lens, (2) vitreous

ANATOMY AXD PHYSIOLOGY

87

body, (3) retina, (4) nerve fibers, (5) pigmented hypodermis cells, and (6)
accessory cells, between the retinal cells and the nerve fibers. The lens,
usually biconvex in form, is a local thickening of the general cuticula;
it is supplemented in its function by the vitreous body, consisting of a
layer of transparent hypodermis cells; these in many insects are elongate,
constituting a vitreous layer of rather more impor-
tance than the one represented in Fig. 139. The
retina consists of cells more or less spindle-shaped
and associated in pairs or in groups of two or three,
each group being termed a retinula. The basal end
of each retinal cell is continuous with a nerve fiber

Fig. 139. — Median ocellus of honey bee. Apis mellifera, in
sagittal section. hypodermis; /.lens; ;/. nerve; p. iris pigment;
r, retinal cells; V. vitreous bodv. — After Redikorzew.

Fig. 140. — An ocel-
lar retinula of the honey
bee, composed of two
retinal cells. A , longi-
tudinal section; B,
transverse section; n,
n, nerves; p, pigment;
r, rhabdom. — After Red-
ikorzew.

(Fig. 140), according to Redikorzew and others,
and in some instances (Calopteryx) a nerve fiber
enters the cell. Each retinula contains a longi-
tudinal rod, or rhabdom, in the secretion of which
all the cells of the retinula are concerned. Between the retinal cells and
nerve fibers are indifferent, or accessory cells. Pigment granules, usually
black, are contained in these cells, also in the retinal cells and around the
lens, in the last instance forming the iris.

Vision by Ocelli.

-Though the ocellus is constructed on somewhat

88

ENTOMOLOGY

the same plan as the human eye. its capacity for forming images must be
extremely limited; for since the form of the lens is fixed and also the dis-
tance between the lens and the retina, there is no power of accommodation,
and most external objects are out of focus; to make an image, then, the
object must be at one definite distance from the lens, and as the lens is
usually strongly convex, this distance must be small; in other words,
insects, like spiders, are very near-sighted, so far as the ocelli are con-
cerned; furthermore, the small number of retinal rods implies an image
of only the coarsest kind.

If the compound eyes of a grasshopper are covered with an opaque
varnish and the insect is placed in a box with only a single opening, it

readily finds its way out by means of its
ocelli; if all three ocelli are also covered,
however, it no longer does so, except by
accident, though it can make its escape
when only one of the ocelli is left uncovered.
The ocelli, then, can distinguish light from
darkness — and they are probably more
serviceable to the insect in this wav than

n c

Fig. 141. — Portion of compound
eye of fly, CaJUphora vomitoria.
radial section, c. cornea; i, iris
pigment; n, nerve fibers; nc, nerve
cells; r, retinal pigment; /.trachea.
— After Hickson.

Compound Eyes. — As regards delicacy
and intricacy of structure, the compound
eye of an insect is scarcely if at all inferior
to the eye of a vertebrate. In radial sec-
tion (Fig. 141), a compound eye appears
as an aggregation of similar elongate ele-
ments, or ommatidia. each of which ends
externally in a facet. The following struc-
tures compose, or are concerned with, each
ommatidium: (1) cornea, (2) crystalline lens, or cone. (3) rhabdom and
retinula, (4) pigment (iris and retinal), (5) fenestrate membrane, (6) fibers
of the optic nerve, (7) trachea.

The cornea (Fig. 142) is a biconvex transparent portion of the exter-
nal chitinous cuticula. Immediately beneath it are the cone cells, which
may contain a clear fluid or else, as in most insects, solid transparent
cones. The rhabdom is a transparent chitinous rod or a group of rods
(rhabdomeres) situated in the long axis of the ommatidium and surrounded
by greatly elongated cells, which constitute the retinula. Two zones of
pigment are present: an outer zone, of iris pigment, in which the pig-
ment in the form of fine black granules is contained chiefly in short cells

ANATOMY AND PHYSIOLOGY

89

that surround the retinula distally; and an
inner zone of retinal pigment, in which the
pigment cells are long and slender, and en-
close the retinula proximally. All these parts
are hypodermal in origin, as is also the fenes-
trate basement membrane, through which pass
tracheae and nerve fibers. The nerve fibrillae,
which are ultimate branches of the optic nerve,
pass into the retinal cells — the end-organs of
vision. Under the basement membrane is a
fibrous optic tract of complex structure.

Physiology. — After much experimenta-
tion and discussion upon the physiology of the
compound eye — the subject of the monumental
works of Grenacher and Exner — Miiller's
" mosaic" theory is still generally accepted,
though it was proposed early in the last cen-
tury. It is thought that an image is formed
by thousands of separate points of light, each
of which corresponds to a distinct field of vision
in the external world. Each ommatidium is
adapted to transmit light along its axis only
(Fig. 143), as oblique rays are lost by absorp-
tion in the black pigment which surrounds the
crystalline cone and the axial rhabdom. Along
the rhabdom, then, light can reach and affect
the terminations of the optic nerve. Each
ommatidium does not itself form a picture; it
simply preserves the intensity and color of the
light from one particular portion of the field of
vision ; and when this is done by hundreds or
thousands of contiguous ommatidia, an image
results. All that the painter does, who copies
an object, is to put together patches of light
in the same relations of quality and position
that he finds in the object itself — and this is
essentially what the compound eye does, so far
as can be inferred from its structure.

Exner, removing the cones with the corneal
cuticula (in Lampyris), looked through them from behind with the aid of

Fig. 142.-
ommatidium
vomitoria.
(chiefly); B,

-Structure of an
of Calliphora

A, radial section
transverse sec-

tion through middle region;
C, transverse section through
basal region; bm, basement
membrane; c, cornea; »,
nucleus; nv, nerve fibrillae;
pc, pseudocone; pg1, pg2, cells
containing iris pigment; pg3,
cell containing retinal pigment ;
r, one of the six retinal cells
which compose the retinula; rh,
rhabdom, composed of six rhab-
domeres; t, trachea; tv, tracheal
vesicle. — After Hicksox.

go

ENTOMOLOGY

a microscope and found that the images made by the separate ommatidia
were either very close together or else overlapped one another, and that
in the latter case the details corresponded; in other words, as many as
twenty or thirty ommatidia may co-operate to form an image of the same
portion of the field of vision; this " superposition" image being corres-
pondingly bright — an advantage, probably, in the case of nocturnal insects.

Large convex eyes indicate a wide field of vision, while small numerous
facets mean distinctness of vision, as Lubbock has pointed out. The

closer the object the better the sight, for the
greater will be the number of lenses employed to
produce the impression, as Mollock says. If
M tiller's theory is true, an image may be formed
of an object at any reasonable distance, no power
of accommodation being necessary; while if, on
the other hand, each cornea with its crystalline
cones had to form an image after the manner of
an ordinary hand-lens, only objects at a definite
distance could be imaged.

The limit of the perception of form by insects
is placed at about two meters for Lampyris, 1.50
meters for Lepidoptera, 68 cm. for Diptera and
58 cm. for Hymenoptera.

It is generally agreed, however, that the com-
pound eyes are specially adapted to perceive
movements of objects. The sensitiveness of in-
sects to even slight movements is a matter of
common observation; often, however, these in-
sects can be picked up with the fingers, if the
operation is performed slowly until the insect is
within the grasp. A moving object affects different facets in succession,
without necessitating any turning of the eyes or the head, as in verte-
brates. Furthermore, on the same principle, the compound eyes are
serviceable for the perception of form when the insect itself is moving
rapidly.

The arrangement of the pigment depends adaptively upon the quality
of the light, as Stefanowska and Exner have shown; thus, when the light
is too strong, the iris and retinal pigment cells elongate around the om-
matidium and their pigment granules absorb from the cone cells and rhab-
dom the excess of fight. If the light is weak, they shorten, and absorb
but a minimum amount of fight.

Fig. 143. — Diagram of
outer transparent portion
of an ommatidium to illus-
trate the transmission of an
axial ray {A) and the re-
peated reflection and ab-
sorption of an oblique ray
(B) , which at length emerges
at C. p, iris pigment.

ANATOMY AND PHYSIOLOGY

91

Origin of Compound Eye. — The compound eye is often said to
represent a group of ocelli, chiefly for the reason that externally there
appears to be a transition from simple eyes, through agglomerate eyes,
to the facetted type. This plausible view, however, is probably incor-
rect, for these reasons among others. In the ocellus, a single lens serves
for all the retinulae, while in the compound eye there are as many lenses
as there are retinulas. Moreover, ocelli do not pass directly into com-
pound eyes, but disappear, and the latter arise independently of the for-
mer.

Probably, as Grenacher holds, both the ocellus and the compound
eye are derived from a common and simpler type of eye — are "sisters,"
so to speak, derived from the same parentage.

Perception of Light through the Integument. — In various in-
sects, as also in earthworms, blind chilopods and some other animals,
light affects the nervous system through the general integument. Thus
eyeless dipterous larvae avoid the light, or, more precisely, they retreat
from the rays of shorter wave-length (as the blue), but come to rest in
the rays of longer wave-length (red) , as if they were in darkness (see page
286). The blind cave-beetles of the genus Anophthalmia react to the
light of a candle (Packard). Graber found that a cockroach deprived
of its eyesight could still perceive light, but Lubbock found that an ant
whose eyes had been covered with an opaque varnish became indifferent
to light.

Color Sense. — Insects undoubtedly distinguish certain colors, though
their color sense differs in range from our own. Thus ants avoid violet
light as they do sunlight, but probably cannot distinguish red or orange
light from darkness; on the other hand, they are extremely sensitive to
the ultra-violet rays. Honey bees frequently select blue flowers: white
butterflies (Pieris) prefer white flowers, and yellow butterflies (Colias)
appear to alight on yellow flowers in preference to white ones (Packard).
In fact, the color sense is largely relied upon by insects to find particular
flowers and by butterflies to a large extent to find their mates. To be
sure, insects will visit flowers after the brightly colored petals have been
removed or concealed, as Plateau found, but this does not prove that
the colors are of no assistance to the insect, though it does show that
they are not the sole attraction — the odor also being an important
guide. The honey bee is able to distinguish color patterns, according
to the experiments of C. H. Turner.

Problematical Sense Organs. — As all our ideas in regard to the

02

ENTOMOLOGY

sensations of insects are necessarily inferences from our own sensory ex-
periences, they are inevitably inadequate. While it is certain that in-
sects have at least the senses of touch, taste, smell, hearing and sight, it is
also certain that these senses of theirs differ remarkably in range from
our own, as we have shown. We can form no accurate conception of
these ordinary senses in insects, to say nothing of others that insects have,
some of which are probably peculiar to insects. Thus they have many
curious integumentary organs which from their structure and nerve con-
nections are probably sensory end-organs, though their functions are
either doubtful or unknown. Such an organ is the sensillum placodeum
(p. 76), the use of which is very doubtful, though the organ is possibly
affected by air pressure. Insects are extremely sensitive to variations of
wind, temperature, moisture and atmospheric pressure, and very likely
have special end-organs for the perception of these variations; indeed,
the sensilla trichodea are probably affected by the wind, as we have said.

The halteres of Diptera, representing the hind wings, contain sensory
organs of some sort. They have been variously regarded as olfactory
(Lee), auditory (Graber), and as organs of equilibration. When one or
both halteres are removed, the fly can no longer maintain its equilibrium
in the air, and Weinland holds that the direction of flight is affected by
the movements of these " balancers."

6. Digestive System
The alimentary tract in its simplest form is to be seen in Thysanura,
Collembola and most larvae, in which (Fig. 144) it is a simple tube ex-
tending along the axis of the body and consisting of three regions, namely,

Fig. 144. — Alimentary tract of a collembolan, Orchcsella. F, fore gut; H, hind gut; M,
mid gut; c, cardiac valve; cm, circular muscle; Im, longitudinal muscle; p, pharynx; py,
pyloric valve.

ore, mid and hind gut. These regional distinctions are fundamental, as
the embryology shows, for the middle region is entodermal in origin and
the two others are ectodermal, as appears beyond.

There are many departures from this primitive condition, and the

AXATOMY AND PHYSIOLOGY

93

most specialized insects exhibit the following modifications (Figs. 145.
146) of the three primary regions:

Fore intestine (stomodceum) : mouth, pharynx, oesophagus, crop, pro-
Yentriculus (gizzard), cardiac valve.

Mid intestine imesenteron) : ventriculus (stomach) .

Hind intestine (proctodceum) : pyloric valve, ileum, colon, rectum,
anus.

Stomodaeum. — The mouth, the anterior opening of the food canal, is
to be distinguished from the pharynx, a dilatation for reception of food.
In the pharynx of mandibulate insects the food is acted upon by the
saliva; in suctorial forms the pharynx acts as a pumping organ, in the
manner already described.

The oesophagus is commonly a simple tube of small and uniform caliber,
varying greatly in length according to the kind of insect. Passing be-
tween the commissures that connect the brain with the subcesophageal

Fig. 145. — Alimentary tract of a grasshopper. Melanoplus dijfcrenlialis. c, colon; cr,
crop; gc, gc, gastric caeca; /, iieum; m, mid intestine, or stomach; mt. Malpighian. or kidney,
tubes; 0, oesophagus; p, pharynx; r, rectum; s, salivary gland of left side.

ganglion (Fig. 113), the oesophagus leads gradually or else abruptly into
the crop or gizzard, or when these are absent, directly into the stomach.
In addition to its function of conducting food, the oesophagus is sometimes
glandular, as in the "grasshopper, in which it is said to secrete the ''mo-
lasses'' which these insects emit.

The crop is conspicuous in most Orthoptera (Fig. 145) and Cole-
optera (Fig. 146) as a simple dilatation. In Xeuroptera (Fig. 147) its
capacity is increased by means of a lateral pocket — the food reservoir;
this in Lepidoptera, Hymenoptera and Diptera is a sac (Fig. 148, c)
communicating with the oesophagus by means of a short neck or a long
tube, and serving as a temporary receptacle for food. In herbivorous
insects the crop contains glucose formed from starch by the action of
saliva or by the secretion of the crop itself; in carnivorous insects this se-
cretion converts albuminoids into assimilable peptone-like substances.

Next comes the enlargement known as the proventriculus, or gizzard.

94

ENTOMOLOGY

which is present in many insects, especially Orthoptera and Coleoptera
(Fig. 146), and is usually found in such mandibulate insects as feed upon
hard substances. The proventriculus is lined with chitinous teeth or
ridges for straining the food, and has powerful circular muscles to squeeze
the food back into the stomach, as well as longitudinal muscles for re-
laxing, or opening, the gizzard.
Some authors maintain that the
proventriculus not only serves as
a strainer, but also helps to com-
minute the food, like the gizzard
of a bird.

Fig. 146. — Digestive system of a beetle,
Carabus. a, anal gland; c (of fore gut), crop;
c (of hind gut), colon, merging into rectum;
d, evacuating duct of anal gland; g, gastric
caeca; i, ileum; m, mid intestine; mt, Mal-
pighian tubes; 0, oesophagus; p, proventricu-
lus; r, reservoir. — After Kolbe.

Fig. 147. — Digestive system of Myrme-
leon larva, c, caecum; cr, crop; m, mid
intestine; mt, Malpighian tubes; s, spin-
neret.— After Meixert.

In most insects a cardiac valve guards the entrance to the stomach,
preventing the return of food to the gullet. This valve (Figs. 144, 149)
is an intrusion of the stomodaeum into the mesenteron, forming a circular
lip which permits food to pass backward, but closes upon pressure from
behind.

ANATOMY AND PHYSIOLOGY

95

Mesenteron. — The ventriculus, otherwise known as the mid intes-
tine, or stomach, is usually a simple tube of large caliber, as compared with

Fig. 148. — Alimentary tract of a moth, Sphinx, c, food reservoir; cl, colon; cm, caecum;
i, ileum; m, mid intestine; mi, Malpighian tubes; 0, oesophagus; r, rectum; s, salivary
gland. — After Wagner.

the oesophagus or intestine, and into the ventriculus may open glandular
blind tubes, or gastric cceca (Figs. 145, 146); these, though numerous in
some insects, are commonly few in number and restricted to the anterior
region of the stomach. The gastric caeca of Orthop-
tera secrete a weak acid which emulsifies fats, or
one which passes forward into the crop, there to
act upon albuminoid substances. In the stomach
the food may be acted upon by a fluid secreted by
specialized cells of the epithelial wall. In various
insects, certain cells project periodically into the
lumen of the stomach as papillae, which by a process
of constriction become separated from the parent
cells and mix bodily with the food. This phenom-
enon takes place in the larva of Pty diopter a (van
Gehuchten), also in nymphs of Odonata (Xeedham),
and is probably of widespread occurrence among
insects. The chief function of the stomach, how-
ever, is absorption, which is effected by the general
epithelium. Physiologically, the so-called stomach
of an insect is quite unlike the stomach of a verte-
brate, being more like an intestine.

Proctodaeum. — At the anterior end of the kind
intestine there is usually a pyloric valve, which pre-
vents the contents of the intestine from returning into the stomach.
This valve may operate by means of a sphincter, or constricting,
muscle, or may, as in Collembola (Fig. 144), consist of a back-

Fig. 149. — Cardiac
valve of young muscid
larva. 0, oesophagus;
/>, proven triculus; v,
valve. In an older
larva the valve pro-
jects into the mid in-
testine.— After Kowa-

LEVSKY.

96

ENTOMOLOGY

ward-projecting circular ridge, or lip, which closes upon pressure from
behind.

In its primitive condition the hind intestine is a simple tube (Fig. 144).
Usually, however, it presents two or even three specialized regions,
namely and in order, ileum, colon and rectum (Fig. 145). The hind in-
testine varies greatly in length and is frequently so long as to be thrown
into convolutions (Fig. 150). The ileum is short and stout in grass-
hoppers (Fig. 145); long, slender and convoluted in many carnivorous
beetles; and quite short in caterpillars and most other larvae; its func-
tion is absorption. The colon, often absent, is evident in Orthoptera and

Fig. 150. — Digestive system of Belos-
toma. c, caecum; i, ileum; m, mid intestine;
mt. Malpighian tubes; r, salivary reservoir;
5, salivary gland. — After Locv, from the
American Naturalist.

. i

Fig. 151. — Wall of mid intestine of silk
worm, transverse section, b, basement mem-
brane; c, circular muscle; i, intima; /, longi-
tudinal muscle; n. n, nuclei of epithelial
cells; s, secretory cell.

Lepidoptera and may bear (Benacus. Dytiscus, Silphidae. Lepidoptera) a
conspicuous caecal appendage (Figs. 148, 150) of doubtful function,
though possibly a reservoir for excretions. The colon contains indigest-
ible matter and the waste products of digestion, including the excretions
of the Malpighian tubes. The rectum (Fig. 145) is thick- walled, strongly
muscular and often folded internally. Its office is to expel excrementi-
tious matter, consisting largely of the indigestible substances chitin,
cellulose and chlorophyll. The rectum terminates in the anus, which
opens through the last segment of the abdomen, always above the genital
aperture.

ANATOMY AND PHYSIOLOGY

07

g'

c --■

7

Histology. — The epithelial wall of the alimentary tract is a single
layer of cells (Fig. 151), which secretes the intima, or lining layer, and the
basement membrane — a delicate, structureless enveloping layer. The
intima, which is continuous with the external cuticula, is chitinous in the
fore and hind gut (which are ectodermal in origin) , but not in the mid gut
(entodermal) , and usually exhibits extremely fine transverse striae, which
are due probably to minute pore canals. Surrounding the basement
membrane is a series of circular muscles and outside these is a layer of
longitudinal muscles. The circular muscles serve to
constrict the pharynx in sucking insects and. in general,
to squeeze backward the contents of the alimentary
canal by successively reducing its caliber. The longi-
tudinal muscles, restricted almost entirely to the mid
intestine, act in opposition to the constricting muscles
to enlarge the lumen of the food canal and in addition
to effect peristaltic movements of the stomach.

The intima of the crop is sometimes shaped into
teeth, and that of the proventriculus is heavily chiti-
nized and variously modified to form spines, teeth or
ridges.

Salivary Glands. — In their simplest condition,
the salivary glands are a pair of blind tubes (Fig. 152),
one on each side of the oesophagus and opening separ-
ately at the base of the hypopharynx. Commonly,
however, the glands open through two salivary ducts
into a common, or evacuating, duct; a pair of salivary
reservoirs (Fig. 153) may be present and the glands
are frequently branched or lobed, and, though usually
confined to the head, may extend into the thorax or
even into the abdomen.

Many insects have more than one pair of glands
opening into the pharynx or oesophagus; thus the
honey bee has six pairs and Hymenoptera as a whole have as many as
ten different pairs. Though all these are loosely spoken of as salivary
glands, it is better to restrict that term to the pair of glands that open
at the hypopharynx.

All these cephalic glands are evaginations of the stomodaeum (ecto-
dermal in origin) and consist of an epithelial layer with the customary
intima and basement membrane (Fig. 154). The nuclei are large, as is
usually the case in glandular cells, and the cytoplasm consists of a dense

pie salivary gland of
Ccccilius. c, canal; J,
duct; g, g, glandular
cells. — After Kolbe.

98

ENTOMOLOGY

framework (appearing in sections as a network) enclosing vacuoles of a
clear substance — the secretion; the chitinous intima is penetrated by .fine
pore canals through which the secretion passes. In many insects, no-
tably the cockroach, the common duct is held distended by spiral threads
which give the duct much the appearance of a trachea.

Fig. 153. — Right salivary gland of cockroach, ventral
aspect, c, common duct; g, gland; h, hypopharynx; r,
reservoir. — After Miall and Denny.

Fig. 154. — Histology of
salivary gland of CcBcilius,
radial section. b, basement
membrane; c, canal; g, glandu-
lar cell; i, intima; n, nucleus.
— After Kolbe.

In herbivorous insects the saliva changes starch into glucose, as in
vertebrates; in carnivorous forms it acts on proteids and is often used
to poison the prey, as in the larva of Dytiscus. In the mosquito each
gland is three-lobed (Fig. 155) ; the middle lobe is different in appearance
from the two others and secretes a poisonous fluid which is carried out

along the hypopharynx. Though this
poison is said to facilitate the process
of blood-sucking by preventing the
coagulation of the blood, its primary
use was perhaps to act upon proteids
in the juices of plants.

Malpighian Tubes.— The kid-
ney, or Malpighian, tubes, present in
nearly all insects, are long, slender, blind tubes opening into the intestine
immediately behind the stomach as a rule (Figs. 145, 146), but always
into the intestine. The number of kidney tubes is very different in dif-
ferent insects; Collembola have none, while Odonata have fifty or more
and Acridiidae as many as one hundred and fifty; commonly, however,
there are four or six, as in Coleoptera, Lepidoptera and many other orders.

Fig.

-One of the three-lobed

salivary glands of a mosquito. The
middle lobe secretes the poison. — After
Macloskie, from the American Nat-
uralist.

ANATOMY AND PHYSIOLOGY

99

Not more than six and frequently only four occur in the embryo (Wheeler ) ,
though these few embryonic tubes may subsequently branch into many.

The Malpighian tubes (Fig. 156) are evaginations of the proctodeum
and are consequently ectodermal. A cross-section of a tube shows a
ring of from one to six or more large polygonal cells (Fig. 157), which
often project into the lumen of the tube; the nuclei are usually large and
may be branched, as in Lepidoptera. A chitinous
intima, traversed by pore-canals, lines the tube,
and a delicate basement membrane is present, sur-
rounded by a peritoneal layer of connective tissue.
Furthermore, the urinary tubes are richly supplied
with tracheae. In function, the Malpighian tubes
are analogous to the vertebrate kidneys and con-

Fig. 156. — Portion
of Malpighian tube of
caterpillar, Samia ce-
cropia, surface view.

Fig. 157. — Cross-section of Malpighian tube of silkworm,
Bombyx mori. b, basement membrane; c, crystals; i, intima;
/, lumen; n, nucleus; p, peritoneal layer. Greatly magnified.

tain a great variety of substances, chief among which are uric acid and its
derivatives (such as urate of sodium and of ammonium), calcium oxalate
and calcium carbonate.

Parts of the fat-body may also be concerned in excretion; thus the
fat-body in Collembola and Orthoptera serves for the permanent storage
of urates.

7. Circulatory System
Insects, unlike vertebrates, have no system of closed blood-vessels,
but the blood wanders freely through the body cavity to enter eventually
the dorsal vessel, which resembles a heart merely in being a propulsatory
organ.

Dorsal Vessel. — The dorsal vessel (Figs. 158, 162) is a delicate tube
extending along the median dorsal line immediately under the integu-

IOO

KMOMOLOGY

ment. A simple tube in some larvae, it consists in most adults chiefly

of a series of chambers, each of which has on each
side a valvular opening, or ostium (Fig. 159),
which permits the ingress of blood but opposes
its egress; within the chambers occur other val-
vular folds that allow the blood to move forward
only. With few exceptions (Ephemeridae) the
dorsal vessel is blind behind and the blood can
enter it only through the lateral ostia.

Aorta. — The posterior, or pulsating portion
(heart) of the dorsal vessel is confined for the
most part to the abdomen; the anterior portion,
or aorta, extends as a simple attenuated tube
through the thorax and into the head, where it
passes under the brain and usually divides into
two branches (Fig. 162), each of which may
again branch. In the head the blood leaves the
aorta abruptly and enters the general body cavity.

Alary Muscles. — Extending outward from
the " heart." or propulsatory portion, and making
with the dorsal wall of the body a pericardial
chamber, is a loose diaphragm, formed largely by
paired fan-like muscles — the alary muscles (Figs.
158, 160). These are thought to assist the heart
in its propulsatory action.

Structure of the Heart. — The dorsal vessel
has a delicate lining-membrane, or intima. and a thin enveloping mem-

Fig. 15

-Dorsal ves-

sel of beetle, Lucanus. a
aorta; al. alary muscle; 0
ostium.- — After Straus

DURCKHEM.

Fig. 159. — Diagram of a portion of the
heart of a dragon fly nymph, Epitheca.
0, ostium; v, valve; the arrows indicate
the course of the blood. — After Kolbe.

Fig. 160. — Diagrammatic cross-section of
pericardial region of a grasshopper. (Edipoda.
a, alary muscle; d, dorsal vessel; s. suspensory
muscles; sp, septum. — After Graber.

ANATOMY AND PHYSIOLOGY

IOI

brane; between these, in the heart, is a layer of fine muscle fibers, circular
or spiral in direction, which effect the contractions of the organ.

Ventral Sinus. — In many if not most insects a pulsatory septum
(Fig. 178, v) extends across the floor of the body cavity to form a sinus,

Fig. 161. — Blood corpuscles of a grasshopper, Stcnobothrus. a-f, corpuscles covered with fat-
globules; g, corpuscle after treatment with glycerine, showing nucleus. — After Graber.

in which the blood flows backward, bathing the ventral nerve cord as it
goes. This ventral sinus supplements the heart in a minor way, as do
also the local pulsatory sacs which have been discovered in the legs
of aquatic Hemiptera and the head of Orthoptera.

Blood. — The blood, or hcemolymph,
of an insect consists chiefly of a watery
fluid, or plasma, which contains cor-
puscles, or leucocytes. Though usually
colorless, the plasma is sometimes yellow
(Coccinellidae, Meloidae), often greenish
in herbivorous insects from the pres-
ence of chlorophyll, and sometimes of
other colors; often the blood owes its
hue to yellow or red drops of fat on the
surface of the blood corpuscles (Fig.
161).

Leucocytes. — The corpuscles, or
leucocytes, are minute nucleated cells,
6 to 30 n in diameter, variable in form
even in the same species, but commonly
(Fig. 161) round, oval or ovate in pro-
file, though often disk-shaped, elongate
or amoeboid in form.

Function of the Blood. — The blood
of insects contains many substances,
including egg albumin, globulin, fibrin, iron, potassium and sodium
(Mayer) , and especially such a large amount of fatty material that its
principal function is probably one of nutrition; the blood of an insect
contains no red corpuscles and has little or nothing to do with the

Fig. 162. — Diagram to indicate the
course of the blood in the nymph of a
dragon fly, Epitheca. a, aorta; h,
heart; the arrows show directions taken
by currents of blood. — After Kolbe.

102

ENTOMOLOGY

aeration of tissues, that function being relegated to the tracheal sys-
tem.

Circulation. — The course of the circulation is evident in trans-
parent aquatic nymphs or larvae. In odonate or ephemerid nymphs,
currents of blood may be seen (Fig. 162) flowing through the spaces
between muscles, 'trachea?, nerves, etc.. and bathing all the tissues;
separate outgoing and incoming streams may be distinguished in the
antennae and legs; the returning blood flows along the sides of the body
and through the ventral sinus and the pericardial chamber, eventually to
enter the lateral ostia of the dorsal vessel. A circulation of blood occurs
in the wings of freshly emerged Odonata. Ephemerida, Coleoptera,
Lepidoptera, etc., the currents trending along the tracheae; this circula-
tion ceases, however, with the drying of the wings.

The chambers of the dorsal vessel expand and contract successively
from behind forward. At the expansion (diastole) of a chamber its ostia
open and admit blood; at contraction (systole) the ostia close, as well as
the valve of the chamber next behind, while the chamber next in front
expands, affording the only exit for the blood. The valves close partly
through blood-pressure and partly by muscular action.

The rate of pulsation depends to a great extent upon the activity of
the insect and upon the temperature and the amount of oxygen or car-
bonic acid gas in the surrounding atmosphere. Oxygen accelerates the
action of the heart and carbonic acid gas retards it. A decrease of 8° or
io° C. in the case of the silkworm lowers the number of beats from 30 or 40
to 6 or 8 per minute. The more active an insect, the faster its heart beats.

The rate of pulsation is very different in the different stages of the
same insect. Thus in Sphinx ligustri, according to Newport, the mean
number of pulsations in a moderately active larva before the first moult
is about 82 or 83 per minute; before the second moult. 89. sinking to 63
before the third moult, to 45 before the fourth, and to 39 in the final larval
stage; the force of the circulation, however, increases as the pulsations
decrease in number. During the quiescent period immediately preceding
each moult, the number of beats is about 30. In the pupal stage the
number sinks to 22, and then lowers until, during winter, the pulsations
almost cease. The moth in repose shows 41 to 50 per minute, and after
flight as many as 139.

8. Fat-Body

The fat-body appears (Fig. 163) as many-lobed masses of tissue filling
in spaces between to her organs and occupying a large part of the body

ANATOMY AND PHYSIOLOGY

IO3

cavity. The distribution of the fat-body is to a certain extent definite,
however, for the fat-tissue conforms to the general segmentation and is
arranged in each segment with an approach to symmetry. Much of this
tissue forms a distinct peripheral layer in each segment, and masses of
fat-body occur constantly on each side of the alimentary tract and also at

Fig. 163. — Transverse section of the abdomen of a caterpillar, Pieris rapes, b, blood cor-
puscles; c, cuticula; <f, dorsal vessel; /, fat-body; g, ganglion; h, hypodermis; /, leg; m,
muscle; mi, mid intestine, containing fragments of cabbage leaves; mt, Malpighian tube; s,
silk gland; sp, spiracle; tr, trachea.

the sides of the dorsal vessel, in the latter case forming the pericardial
fat-body.

Fat-Cells. — The fat-cells (Fig. 164) are large and at first more or less
spherical, with a single nucleus (though there are said to be two in Apis
and several in Musca), but the cellular structure of the fat- tissue is often
difficult to make out because the cells are usually filled with globules of
fat (Fig. 165), while old cells break down, leaving only a disorderly net-
work. The fat-cells sometimes contain an albuminoid substance, and

104

EXTOMOLOCY

Fig. 164. — Fat-cells of a cater-
pillar, Picris. A, cells filled with
drops of fat; B, cell freed of fat-drops,
showing nucleus. — After Kolbe.

usually the fat-body includes considerable quantities of uric acid or its
derivatives, frequently in the form of conspicuous concretions.

Functions. — The physiology of the fat-system is still obscure. Prob-
ably the fat-body combines several functions. In caterpillars and other
larvae it furnishes a reserve supply of nutriment, at the expense of which

the metamorphosis takes place; the
amount of fat increases as the larva
grows, and diminishes in the pupal stage,
though some of it lasts over to furnish
nourishment for the imago and its germ
cells. The gradual accumulation of uric
acid and urates in the fat-body indicates
an excretory function, particularly in
Collembola, which have no Malpighian
tubes. The intimate association between the ultimate tracheal branches
and the fat-body has led some authorities to ascribe a respiratory func-
tion to the latter. A close relation of some sort exists also between the
fat-system and the blood-system; fat-cells are found free in the blood,
and the blood corpuscles originate in the thorax and abdomen from tis-
sues that can scarcely be distinguished
from fat-tissues. The corpuscles (leu-
cocytes, or phagocytes) which in some
insects absorb effete larval tissues
during metamorphosis have been by
some authors regarded as wandering
fat-cells. Cells constituting the peri-
cardial fat-body are attached to the
lateral muscles (alary muscles) of the
dorsal vessel, but almost nothing is
known as to their function.

(Enocytes. — Associated with the
fat-body proper and with tracheae as
well are the peculiar yellow cells
known as oenocytes (Fig. 166), that

occur in abdominal segments of larvae. These cells are enormous in size
as compared with all other insect-cells excepting ova, and are essentially
isolated from one another, though grouped among tracheal branches into
loose clusters, one on each side of a spiracle-bearing segment.

After arising from the primitive ectoderm the cenocytes never divide.

Fig. 165. — Section through fat-body
of a silkworm, showing nucleated cells,
loaded with drops of fat.

ANATOMY AND PHYSIOLOGY

Fig. 166. — CEno-
cytes and accom-
panying tracheae,
from abdomen of a
silkworm.

but gradually increase in size (Wheeler) , and their size is in a general way
proportional to that of the fat-body.

Their function has been problematical until recently. Many ob-
servers have regarded them as ductless glands, having seen "microscop-
ical exudations around the periphery of the cytoplasm,
especially at times when the nucleus is greatly ramified,
and therefore manifesting its great activity" (Glaser).

R. W. Glaser has recently thrown light upon the
nature of the cenocytic fluid. By using three-year-old
caterpillars of Zeuzera pyrina. which have a great
amount of fatty tissue and correspondingly large
cenocytes, he was able to extract enough of the fluid
for chemical experiments. He found by carefully con-
ducted tests that the fluid had the power of oxidizing
fats, by means of enzymes known as oxidases (though
no fat-splitting enzyme, or lipase, was present), and
concluded that the secretion of the cenocytes is used
to oxidize the reserve food stored up by the larva in the form of fat.

Photogeny. — This phenomenon appears sporadically and by various
means in protozoans, worms, insects, fishes and other animals. Lumi-
nosity in insects, though sometimes merely an incidental and pathological

effect of bacteria, is usually pro-
C*}m — — duced by special organs in which
light is generated probably by
the oxidation of a fatty substance.

There are not many luminous
insects. Those best known are
the Mexican and West Indian
beetles of the genus Pyrophoms
(Elateridae), in which the pro-
notum bears a pair of luminous
spots, and the common fire-flies
(Lampyridae). In Lampyridae
the light is emitted from the
ventral side of the posterior ab-
dominal segments, and the struc-
ture of the photogenic organ is essentially the same throughout the family.
In Photinus this organ ( Fig. 167) consists of two layers : a ventral photogenic
layer and a dorsal reflecting layer.. The latter, white and opaque, consists
of polygonal cells containing large quantities of crystals of urates; the

Fig. 167. — Transverse section of portion of
photogenic organ of Photinus. c. cylinder; p,
photogenic layer; r. reflecting layer; /, trachea.
— After TOWNSEND.

io6

ENTOMOLOGY

former layer is composed of tracheal structures and intervening paren-
chyma cells. The tracheae branch profusely in the photogenic layer,
where the larger air-tubes are each surrounded by a more or less cylin-
drical mass of cells; tracheal branches penetrate between the cells of each
cylinder, at the edge of which they pass into tracheoles which penetrate
the photogenic tissue and anastomose with those of adjacent cylinders;
in the meshes of the tracheolar network is a granular substance of fatty
nature ("differentiated fat-body"), the oxidation of which is the source
of the luminosity, it is inferred. The photogenic tissues of Photinus,
after being dried and kept in sealed tubes, have retained their photogenic
power for more than eighteen months, glowing after this interval upon
the "application of water in the presence of air or oxygen" (McDermott).
Three factors are involved in the production of the light : a substance to
be oxidized, oxygen and water.

The rays emitted by the common fire-flies are remarkable in being
almost entirely light rays. According to Young and Langley, the radia-
tions of an ordinary gas-flame contain less than three per cent, of visible
rays, the remainder being heat or chemical rays, of no value for illumina-
ting purposes ; while the light-giving efficiency of the electric arc is only
ten per cent, and that of sunlight only thirty-five per cent. The luminous
efficiency of the fire-fly, however, is not much under one hundred per
cent. ; in Photuris pennsylvanica it is about ninety- two per cent. , according
to Coblentz — an efficiency as yet unapproached by artificial means. The
actinic power of the light is so slight that it affects a photographic plate
only after a long exposure. Coblentz, who has recently applied most re-
fined methods of measurement to the radiation of fire-flies, found that
exposures of one to five hours were necessary with the spectograph. He
was unable to detect any infra-red radiation; the thermal radiation, if
present, being immeasurably small as yet. The intensity of the glow
averages ^'o.i'o'o candle power in our common fire-flies, according to
Coblentz.

This luminosity serves to bring the sexes together. "The male flies
over the tops of the grasses, weeds, etc., dropping down between them
and flashing; any females that come within the range of his flash, answer
by their slower flash; if the male sees this answering flash from one, he
approaches her, flashes again, to which she answers, and he then finally
locates her definitely by means of subsequent flashes," as McDermott
says. He found that he could get responses from the females by imi-
tating the flash of the male with a small electric bulb or even with a com-
mon safety match, and that he could deceive the males also by flashing the
tiny electric light after the manner of the female.

ANATOMY AXD PHYSIOLOGY

107

9. Respiratory System

In insects, as contrasted with vertebrates, the air itself is conveyed to
the remotest tissues by means of an elaborate system of branching air-
tubes, or trachea, which receive air through paired segmentally-arranged
spiracles. Each spiracle is commonly the mouth of a short tube which
opens into a main tracheal trunk (Fig.
168) extending along the side of the
body. From the two main trunks
branches are sent which divide and
subdivide until they become extremely
delicate tubes, which penetrate even
between muscle fibers, between the
ommatidia of the compound eyes and
possibly enter cells. In most cases
each main longitudinal trunk gives off
in each segment (Fig. 169) three large
branches: (1) an upper, or dorsal,
branch, which goes to the dorsal mus-
cles; (2) a middle, or visceral, branch,
which supplies the alimentary tract and
the reproductive organs; (3) a lower, or
ventral, branch, which pertains to the
ventral ganglia and muscles.

In many swiftly flying insects (dra-
gon flies, beetles, moths, flies and bees)
there occur tracheal pockets, or air-sacs,
which were formerly and erroneously
supposed to diminish the weight of the
insect, but are now regarded as simply
air-reservoirs.

Types of Tracheation. — Two
types of tracheal system are distin-
guished for convenience: (1) The pri-
mary, open, or holopneustic type described above, in which the spiracles
are functional; (2) the secondary, closed, or apneustic type, in which the
spiracles are either functionless or absent. This type is illustrated in
Collembola and such aquatic nymphs and larvae as breathe either directly
through the skin or else by means of gills. The two types, however, are
connected by all sorts of intermediate stages.

Fig. 168. — Tracheal system of an
insect. a, antenna; b, brain; /, leg;
n, nerve cord; p, palpus; s, spiracle;
spiracular, or stigmatal, branch; /,

si

main tracheal trunk; v, ventral branch;
vs, visceral branch. — After Kolbe.

io8

ENTOMOLOGY

Tracheal Gills. — In many aquatic nymphs and larvae the spiracles
are suppressed (though they become functional in the imago) and res-

Fig. 169. — Diagrammatic cross-section of the thorax of an insect. (7, alimentary canal;
d, dorsal vessel; g, ganglion; s, spiracle; w, wing; 1, dorsal tracheal branch; 2, visceral
branch; 3, ventral branch.

piration is effected by means of gills; these are cuticular outgrowths
which usually, though not invariably, contain tracheae, and are commonly

lateral or caudal in position. Lateral
tracheal gills are highly developed in
ephemerid nymphs (Fig. 170), in which
a pair occurs on some or all of the first
seven segments of the abdomen ; a few gen-
era, however, have cephalic or thoracic
gills. Larvae of Trichoptera have paired
abdominal gills varying greatly in form
and position, and Perlidae often have
paired thoracic gills. Caudal tracheal gills
are conspicuous in nymphs of Agrionidae
(Fig. 171) as three foliaceous appendages.
A few coleopterous larvae of aquatic habit,
as Gyrinus and Cnemidotus, possess tracheal
gills, as do also caterpillars of the genus
Paraponyx (Fig. 172), which feed on the
leaves of several kinds of water plants.

Though manifold in form, tracheal gills are generally more or less
foliaceous or filamentous, presenting always an extensive respiratory

Fig. 170. — Lateral gill from ab
domen of a May fly nymph, Hexa
genia variabilis. Enlarged.

ANATOMY AND PHYSIOLOGY

Fig. 171. — Caudal
gills of an agrionid
nymph, enlarged.

surface; their integument is thin and the tracheae spread closely beneath
it. These adaptations are often supplemented by waving movements of
the gills, as in May fly nymphs, and by frequent movements of the insect
from one place to another.

Especially noteworthy are the rectal tracheal gills of odonate nymphs.
In these insects the lining of the rectum forms nu-
merous papillae or lamellae, which contain a profusion
of delicate tracheal branches; these are bathed by
water drawn into the rectum and then expelled, at
rather irregular intervals. A similar rectal respira-
tion occurs also in ephemerid nymphs and mosquito
larvae.

A few forms, chiefly Perlidae, are exceptional in
retaining tracheal gills in the adult stage ; in some imagines they are merely
vestiges of the nymphal gills, but in others, such as Pteronarcys (Fig. 18),
which habitually dips into the water and rests in moist situations, the
gills probably supplement the spiracles. Further
details on the respiration of aquatic insects are
given in Chapter IV.

Spiracles. — The paired external openings of the
tracheae occur on the sides of the thorax and ab-
domen, there being never more than one pair to a
segment. Though the thysanuran J a pyx has n
pairs, no winged insect has more than 10; although
there are in all 1 2 segments which may bear spira-
cles— the three thoracic and the first nine abdominal
segments. (Additional details are given on page p. 52.)

The spiracles, or stigmata, are usually provided
with bristles, hairs or other processes to exclude
dust ; or the hairs of the body may serve the same
purpose, as in Lepidoptera and Diptera; in many
beetles the spiracles are protected by the elytra; in
other beetles, however, and in many Hemiptera and
Diptera the spiracles are unprotected externally.
Larvae that live in water or mud may have spiracles
at the end of a long tube, which can be thrust up
into the pure air; this is true of the dipterous larvae of Eristalis, Bitta-
comorpha (Fig. 173) and Culex (Fig. 230).

Closure of Spiracles. — As a rule, a spiracle is opened and closed
periodically by means of a valve, operated by a special occlusor muscle.

Fig. 172. — Cater-
pillar of Paraponyx
obscuralis, to show tra-
cheal gills. Length, 1 5
mm. — After Hart.

no

ENTOMOLOGY

In dipterous larvae the closure is effected by the contraction of a circular
muscle, but Coleoptera and Lepidoptera, among other insects, have a
somewhat complex apparatus for closing the trachea immediately behind
the spiracle. Thus, in the stag-beetle, a crescentic
bow (Fig. 174, b) extends half around the trachea, and
the rest of the circumference is spanned by a lever (I)
and a band (bd) ; these three chitinous parts, articulated
together, form a ring- around the trachea. Further-
more, a muscle (m) connects the lever and the band.
As the muscle shortens, the lever turning upon the
end of the band as a fulcrum, pulls the bow toward
the lever and band until the enclosed trachea is pinched
together. When the muscle relaxes, the trachea opens
by its own elasticity.

Structure of Tracheae. — The tracheae originate
in the embryo as simple in-pocketings of the outer
Fig. 173— Larva germ layer, or ectoderm, and from these the countless

of Bittacomor pha , , , , , . , , -

davipcs showing res- tracheal branches are derived by the same process of
piratory tube.— Nat- invagination. The lining membrane of a trachea is,

ural size. — After 0 0

Hart. then, continuous with the external cuticula, and the

cellular wall of a trachea is continuous with the rest
of the hypodermis. This wall consists of a layer of polygonal cells (Fig.
175) fitting closely together as a pavement epithelium. The chitinous

lining, or intima, is thickened at regular intervals to form thread-like
ridges, which course around the inner circumference in essentially a
spiral manner, though the continuity of the so-called spiral thread is

ANATOMY AND PHYSIOLOGY III

frequently interrupted. These elastic threads, or tcenidia, serve to keep
the trachea open without affecting its flexibility.

The ultimate tracheal branches (Fig. 176) are extremely delicate
tubes, which do not end blindly, but anastomose with one another, form-

Fig. 175. — Structure of a Fig. 176. — Tracheal capillary end-network from

trachea. h, tracheal hypodermis; silk gland of Porthetria dispat. p, peritracheal mem-

i, intima; t, taenidium. brane; t, tracheal capillary. — After Wistixghausen.

ing a capillary network of confluent tubes. Some authors have held that
the finest tracheal filaments penetrate epithelial or other cells.

Fig. 177. — Transverse sections of abdominal segments, to illustrate respiratory movements.
A, cockroach (Blatta); B, bee (Bombus); s, sternum; /, tergum. The dotted lines indicate
positions of terga and sterna after expiration; the continuous lines, after inspiration. — After
Plateau.

Respiration. — The external signs of respiration are the regular open-
ing and closing movements of some of the spiracles and the rhythmic con-
traction and expansion of the abdomen. During contraction, the dorsal
and ventral walls approach each other (Fig. 177) and during expansion
they separate. The tergum moves more than the sternum in Cole-

112

ENTOMOLOGY

optera and Heteroptera, and vice versa in Acridiidae, Odonata, Diptera
and aculeate Hymenoptera. The width of the abdomen usually changes
but little during respiration, for the tergal and sternal movements are
taken up by the pleural membranes which, as in the grasshopper, infold at
contraction and straighten out at expansion. Other respiratory move-
ments occur, but they are of minor importance.

The rate of respiration increases or diminishes with the activity of the
insect and with temperature and other conditions. In six specimens of
Melanoplus dijferentialis, held between the fingers, the thoracic spiracles

opened and closed respectively 34, 43,
45, 54, 60 and 61 times per minute.
Four individuals of M. femur-rubrum
under the same circumstances, gave
70, 78, 90 and 92.

At expansion inspiration takes
place, and at contraction expiration
occurs. In the grasshopper, the tho-
racic spiracles open almost simulta-
neously with the expansion of the ab-
domen. Contraction is effected by
special vertical expiratory muscles
(Fig. 178), but expansion is due to
the elasticity of the abdominal wall,
as a rule; this is the reverse of what
occurs in mammals, where expiration
is passive and inspiration active.
Inspiratory muscles are found, how-
ever, in Acridiidae, Trichoptera and
Hymenoptera.

Though the respiratory move-
ments of an insect may be studied with a hand-lens, a more precise
method is that of Plateau — the chief authority on insect physiology —
who made use of the stereopticon to project an enlarged profile of the
insect upon a screen, on which could be marked the different contours
of the abdomen at its phases of inspiration and expiration.

The way in which the air reaches the finest tracheal branches is not
clearly ascertained, but it is thought that air is forced into these tubes
by pressure from the abdominal muscles, while its escape through the
spiracles is being prevented by the compression of the stigmatal tracheae.

The respiratory movements are entirely reflex and are independent of
the brain or subcesophageal ganglion, for they continue after decapitation

s

Fig. 178. — Diagrammatic cross-sec-
tion of abdomen of a grasshopper, Acrid-
ium. d, dorsal septum, or diaphragm;
ex, expiratory muscle; /, fat-body; g,
ganglion; h, heart; in, inspiratory mus-
cle; v, ventral septum, below which is
the ventral sinus. The dorsal and
ventral septa rise and fall periodically.
— After Graber.

ANATOMY AND PHYSIOLOGY

and even in the detached abdomen of a grasshopper or dragon fly. Each
ventral ganglion of the body is an independent respiratory center for its
particular segment.

10. Reproductive System
The sexes are always separate in insects, hermaphroditism occurring
only as an abnormal condition. The sexual organs, situated in the ab-
domen, consist essentially of a pair of ovaries or testes and a pair of ducts
(oviducts or seminal ducts, respectively). Primitively, the ducts open
separately, as they still do in Ephemeridae, but in almost all other insects
the two ducts enter a common evacuating duct (vagina or ejaculatory

Fig. 179. — Reproductive system of male Fig. 180. — Reproductive system of

beetle, Melolontha. a, accessory gland; c, copu- male Lepidoptera. a, accessory gland;

latory organ; d, ejaculatory duct; s, seminal d, ejaculatory duct; /, united testes; v,

vesicle; /, testis; v, vas deferens. — After Kolbe. vas deferens. — After Kolbe.

duct); this opens ordinarily between the penultimate and antepenulti-
mate segments of the abdomen, i. e.. usually the ninth and eighth, at any
rate never through the last abdominal segment.

Homologies. — As in other animals, the reproductive organs are
homologous in the two sexes. Thus:

Male. Female

Testes = Ovaries
Seminal ducts = Oviducts
Ejaculatory duct= Vagina

Seminal vesicle = Seminal receptacle
Accessory glands = Accessory glands
Penis and accessories = Ovipositor

Male Organs. — Each testis, though sometimes a single blind tube, is
usually a group of tubes or sacs (Fig. 179), testicular follicles, which open
9

H4

ENTOMOLOGY*

into a seminal duct (vas deferens). In most Lepidoptera the testes are
secondarily united into a single mass (Fig. 180) as also in Acridiida?.
The two seminal ducts enter the common ejaculatory duct, which termin-
ates in the intromittent organ, or penis. Often each vas deferens is di-
lated near its mouth into a seminal vesicle, or reservoir; or there may be
only a single seminal vesicle, arising from the common duct. One or
more pairs of glands opening into the vasa deferentia or the ductus ejac-
ulatorius secrete a fluid which mixes with the spermatozoa and oftentimes

unites them into packets, known as spermato-
A I phores.

|X All these parts are subservient to the forma-

tion, preservation and emission of the 5 permatozoa.
These minute, thread-like bodies (Fig. 181) arise
in the testicular follicles from a germinal epithe-
lium, and consist, as in vertebrates, of a head,
middle-piece and a vibratile tail — without enter-
ing into the finer structure.

Female Organs. — Each ovary (Fig. 182) con-
sists of one or more tubes opening into an oviduct.
The two oviducts enter a common duct, the
vagina, which opens to the exterior, often through
an ovipositor. Frequently the vagina is expanded
as a pouch, or bursa copulatrix, though in Lepidop-
tera the bursa and the vagina are distinct from
each other and open separately (Fig. 183). In
most insects a dorsal evagination of the vagina
forms a seminal receptacle, or spermatheca, from
which spermatozoa emerge to fertilize the eggs.
The accessory glands, either paired or single,
provide a secretion for attaching the eggs to
foreign objects, cementing the eggs together, forming an egg-capsule, etc.

In each ovarian tube, or ovariole, are found ova in successive stages of
growth, the largest and oldest ovum being nearest the oviduct. In the
primitive type of egg-tube, as in Thysanura and Orthoptera (Fig. 184,
A) every chamber contains an ovum; in more specialized types, every
other chamber contains a nutritive cell instead of a germ cell, the nutri-
tive cells serving as food for the adjacent ova (B) ; or the nutritive cells,
instead of alternating with the ova, may be collected in a special chamber,
beyond the ovarian chambers (C). An egg-tube is usually prolonged dis-
tally as a terminal filament or suspensor, the free end of which is attached
near the dorsal vessel.

Fig. 181. — Sperma-
tozoa. A, locustid grass-
hopper; B, cockroach,
Blatta; C, beetle, Copris.
— After Butschli and Bal-
lowitz.

ANATOMY AND PHYSIOLOGY

Ovaries and testes arise from indifferent cells, or primitive germ cells,
which are at first exactly alike in the two sexes. In the female, certain
of these cells form ova and others form a follicle around each ovum (Fig.
185). In the male, the primary germ cells form cells termed spermato-
gonia; each of these forms a spermatocyte, and this gives rise to four sper-
matozoa.

Hermaphroditism. — The phenomenon of hermaphroditism, or the
combination of male and female characters in the same individual, occurs

Fig. 182. — Reproductive system of queen
honey bee. a, accessory sac of vagina; b,
bulb of stinging apparatus; c, colleterial, or
cement, gland; 0, ovary; od, oviduct; p,
poison glands; pr, poison reservoir; r, re-
ceptaculum seminis; rc, rectum; v, vagina.
— After Leuckart.

Fig. 183. — Reproductive system of fe-
male Lepidoptera. b, bursa copulatrix; /,
terminal filament; g, cement glands; 0, 0,
ovaries; od. oviduct; r, receptaculum seminis;
v, vagina; vs, vestibule, or entrance to bursa.
— After Kolbe.

only as an extremely rare abnormality among insects. Speyer estimated
that in Lepidoptera only one individual in thirty thousand is hermaphro-
ditic. Bertkau (1889) listed 335 hermaphroditic arthropods, of which 8
were crustaceans, 2 spiders, 2 Orthoptera, 8 Diptera, 9 Coleoptera, 51
Hymenoptera and 255 Lepidoptera. The large proportion of Lepidoptera
is due in great measure to the fact that they are collected oftener than
other insects (excepting possibly Coleoptera) and that sexual dimorph-
ism is so prevalent in the order that hermaphrodites are easily recognized.

The most common kind of hermaphroditism is that in which one side
is male and the other female, as in Fig. 186. Bertkau found this right-

n6

ENTOMOLOGY

and-left hermaphroditism in 153 individuals. In other instances the
antero-posterior kind may occur, as when the fore wings are of one sex
and the hind wings of the other; rarely, the characters of the two sexes
are intermingled.

Hermaphroditic insects are such rarities that very few of them have
been sacrificed to the dissecting needle in order to determine whether the

phenomenon involves the primary organs
as well as the secondary sexual characters.
Where dissections have been made it has
been found usually that hermaphroditism
does extend to the reproductive organs them-

Fig. 184. — Types of ovarian
tubes. A. without nutritive cells;
B. with alternating nutritive and

Fig. 185. — Ovum of a butterfly. Vanessa, in its
follicle, e. follicle epithelium; g, germinal vesicle;
n, branching nucleus of nutritive cell; 0, ovum. —
After Woodworth.

tive chamber; c. terminal cham-
ber; e, egg-cell; ep. follicle epi-
thelium; /, terminal filament; s,
strands connecting ova with nutri-
tive chamber; y, yolk, or nutritive
cells. — From Lang's Lehrbuch.

selves. Thus a butterfly with male wings
on the right side and female wings on the
left would have a testis on the right side of
the abdomen and an ovary on the left side.
Parthenogenesis. — Reproduction without fertilization is a normal
phenomenon in not a few insects. This parthenogenesis may easily be
observed in plant lice. In these insects there are many successive broods
consisting of females only, which bring forth living young; at definite
intervals, however, and usually in autumn, males appear also, and ferti-
lized eggs are laid which last over winter. This cyclic reproduction, by
the way, is known as heterogeny. Among Hymenoptera, parthenogenesis
is prevalent, usually alternating with sexual reproduction, as in many

ANATOMY AND PHYSIOLOGY

117

Cynipidae. In some Cynipidae. however, males are unknown; such is
the case also in some Tenthredinidae. The statement has long been made
that the unfertilized eggs of worker ants, bees and wasps produce invari-
ably males; it has been found, however, that the parthenogenetic
worker eggs of the ant La-
sius niger may produce normal
workers (Reichenbach, Mrs. A.
B. Comstock). Males may, of
course, result from fertilized eggs,
as in the honey bee, according to
Dickel. who maintains, indeed,
that all the eggs laid by the queen
bee are fertilized. Partheno-
genesis has been recorded as oc-
curring also in a few moths, some
Coccidae and many Thysanoptera.

Paedogenesis. — In Miastor
and a few other genera of Cecidomyiidce young are produced by the larva.
This extraordinary form of parthenogenesis is termed pedogenesis, and is
limited apparently to the family Cecidomyiidae. The paedogenetic larvae
of Miastor (Fig. 187) develop before the oviducts have appeared and

escape by the rupture of the
mother. After several suc-
cessive generations of this
kind the resulting larvae pu-

Fig. 187. Young paedogenetic larvae of Miastor pate ancJ form n0rmal male
in the bodv of the mother larva. Greatly enlarged. A

—After Pagenstecher. and lemale flies.

An excellent account of
Miastor has been given by Dr. Felt, who has discovered this remarkable
genus in New York State.

The pupa of a species of Chironomus occasionally deposits unfertilized
eggs, which develop, however, in the same manner as the fertilized eggs
of the species.

Fig. 186. — Hermaphrodite gypsy moth,
Porthctria dispar; right side, male; left,
female. Natural size. — After Taschexberg
from Hert wig's Lehrbuch.

CHAPTER III

DEVELOPMENT

i. Embryology

Ovum. — The ovum of an insect, as of any other animal is a single
cell (Fig. 188), with a large nucleus {germinal vesicle), a large nucleolus,
nutritive matter, or yolk {deuto plasm), contained in the cytoplasm, and a
cell wall {vitelline membrane) secreted by the ovum;
the egg-shell, or chorion, is secreted around the
ovum by surrounding ovarian cells.

Maturation. — As a preparation for fertilization
the germinal vesicle divides twice, forming two polar
bodies, and as the first of these bodies may itself
divide, there result four cells; three of these, how-
ever— the polar bodies — are minute and rudimen-
tary.

These phenomena of ovogenesis are paralleled in
the development of the spermatozoa, or spermato-
genesis; for the primary spermatocyte gives rise to
two secondary spermatocytes, and these to four sper-
matids, each of which forms a spermatozoon.

By means of this maturation process the number
of chromosomes in the egg-nucleus is reduced to half
the number normal for somatic cells (body cells as
distinguished from germ cells) . A similar reduction
occurs also during the development of the sperma-
tozoon, and when sperm-nucleus and egg-nude us
unite, the resulting nucleus contains the normal
number of chromosomes. The meaning of these
reduction phenomena — highly important from the
standpoint of heredity — is a much debated subject.

Fertilization. — As the eggs pass through the
vagina, they are capable of being fertilized by sper-
matozoa, previously stored in the seminal recep-
tacle. Through the micro pyle of the chorion one or more spermatozoa
enter and a sperm nucleus unites with the egg-nucleus to form what is

118

-pr

Fig. 188. — Sagittal
section of egg of fly,
Musca, in process of
fertilization. c, cho-
rion; d, dorsal; m, mi-
cropyle. with gelatinous
exudation; p, male and
female pronuclei, before
union; pb, polar bodies;
pr, peripheral proto-
plasm; v, ventral; vt,
vitelline membrane; y,
yolk. — After Hexkixg
and Blochmann.

DEVELOPMENT

HQ

Fig. 189. — Equatorial section of egg of a
beetle, ClytraJarciuscula. b, blastoderm; g. germ
band; y, yolk granule; yc, yolk cell. — After
Lecaillox.

known as the segmentation nucleus. Through this union of nuclear sub-
stances the qualities of the two parents are combined in the offspring.
Needless to say, the minute details of the process of fertilization are of
the highest biological impor-
tance.

Blastoderm.— In an arthro-
pod ovum the yolk occupies a
central position (centrolecithal
type), being enclosed in a thin
layer of protoplasm. From the
segmentation nucleus just men-
tioned are derived many nuclei,
some of which migrate outward
with their attendant protoplasm
to form with the original peri-
pheral protoplasm a continuous
cellular layer, the blastoderm (Fig.
189).

Germ Band. — The blasto-
derm, at first of uniform thick-
ness, becomes thicker in one re-
gion, by cell multiplication, forming the genu band {primitive streak, etc.) ;
this appears in surface view as an oval or elongate area, denser than the
remaining blastoderm, with which it is, of course, continuous.

Gastrulation. — The germ band next infolds along the median line,

appearing in cross-
section as in Fig. 190;
the two lips of the
median groove close
together over the in-
vaginated portion and
form an outer layer,
or ectoderm (Fig. 191),
while the invaginated
portion spreads out

as an inner layer, which is destined to form two layers, known respectively
as entoderm and mesoderm. This formation of two primary germ layers
by invagination or otherwise is termed gastrulation; it is an important
stage in the development of all eggs, and among insects several variations
of the process occur.

Fig. 190. — Transverse section of germ band of Clytra at gas
trulation. g, germ band; /, inner layer. — After Lecaillox.

120

1 . \ 1 « >MOU >GY

Amnion and Serosa.— Meanwhile, the blastoderm has been folding
over the germ band from either side, as shown in Fig. 190, and at length
the two folds meet and unite to form two membranes (f ig. 192), namely,
an inner one, or amnion, and an outer one, or serosa.

Fig. 191. — Transverse section of germ
layers and amnion folds of Clytra. a, am-
nion; e, ectoderm; i, inner layer (meso-ento-
derm); s, serosa. — Original, based on Lec-
aillon's figures.

Fig. 192. — Transverse section of germ
layers and embryonal membranes of Clytra.
a, amnion; ac, amnion cavity; e, ectoderm;
i, inner layer (meso-entoderm) ; s, serosa. —
After Lecaillox.

Segmentation and Appendages. — On the germ band, which repre-
sents the ventral part of the future insect, the body segments are marked
off by transverse grooves (Figs. 193, 195); this segmentation beginning

i

11
%\

if

B

<•••• •

33 $k

Fig. 193. — Germ band of a beetle, Melasoma, in three successive stages. A , unsegmented;
B, with oral segments demarkated; C, with three oral, three thoracic and two abdominal
segments. — After Graber.

usually at the anterior end of the germ band and progressing backward.
Furthermore, an anterior infolding occurs (Fig. 194), forming the stomo-
dceum, from which the mouth, pharynx, oesophagus and other parts of the
fore gut are to arise; a similar but posterior invagination, or proctodeum
(Fig. 194), is the beginning, or fundament, of the hind gut.

DEVELOPMENT

121

At the anterior end of the germ band is a pair of large procephalic
lobes (Figs. 193, 195), which eventually bear the lateral eyes, and im-
mediately behind these are the funda-
ments of the antennae. The funda-
ments of the primary paired append-
ages are out-pocketings of the ecto-
dermal germ band, and at first an-
tennae, mouth parts and legs are all
alike, except in their relative positions.
Behind the antennae (in Thysanura
and Collembola at least) appears a
pair of rudimentary appendages (Fig.
195, i) which are thought to represent

the second antennae of Crustacea; instead of developing, they disappear in
the embryo or else persist in the adult as mere rudiments. In front of
these transitory intercalary appendages is the mouth-opening, above which

Fig. 194. — Diagrammatic sagittal
section of hymenopterous egg to show
stomadaeal \s) and proctodaeal (p) in-
vaginations of the germ band (g). — After
Graber.

-pr

Fig. 195. — Ventral aspect of germ
band of a collembolan, Anurida marit-
ima. a, antenna; a1- a5, abdominal ap-
pendages; i, intercalary appendage;
/, labrum; li, left labial appendage;
m, mandible; mx, maxilla; p, pro-
cephalic lobe; pr, proctodeum; tl-l3,
thoracic legs.

Si I

-mx

Fig. 196. — Anterior aspect of embryonal mouth
parts of a collembolan, Anurida mar Uinta, a, an-
tenna; /, labrum; Ig, prothoracic leg; li, left funda-
ment of labium; In, lingua; m, mandible; mx, max-
illa; p, maxillary palpus; si, superlingua. — After
Folsom.

the labrum and clypeus are already indicated by a single, median evagina-
tion. Behind the mouth the mandibles, maxillae and labium are repre-

122

ENTOMOLOGY

sented by three pairs of fundaments, and in Thysanura and Collembola a
fourth pair is present to form the superlinguae (Fig. 196, si), already re-
ferred to. Next in order are the three pairs of thoracic legs (Fig. 195)
and then, in many cases, paired abdominal appendages (Figs. 195, 197),
indicating an ancestral myriopod-like condition; some of these abdom-
inal limbs disappear in the embryo but others develop into abdominal

prolegs (Lepidoptera and Tenthredinidae),
external genital organs (Orthoptera, Hy-
menoptera, etc.) or other structures. The
study of these embryonic fundaments sheds
much light upon the morphology of the ap-
pendages and the subject of segmentation.

Two Types of Germ Bands. — The germ
band described above belongs to the simple
overgrown type, exemplified in Clytra . in which
the germ band retains its original position
and the amnion and serosa arise by a pro-
cess of overgrowth (Figs. 191, 192), as dis-
tinguished from the invaginated type, illus-
trated in Odonata, in which the germ band
invaginates into the egg, as in Fig. 198, until
the ventral surface of the embryo becomes
turned around and faces the dorsal side of
the egg. In this event, a subsequent process
of revolution occurs, by means of which the
ventral surface of the embryo resumes its
original position (Fig. 199).

Dorsal Closure. — As was said, the germ
band forms the ventral part of the insect.
To complete the general form of the body the
margins of the germ band extend outward
and upward (Fig. 200) until they finally close
over to form the dorsal wall of the insect.
Besides this simple method, however, there
are several other ways in which the dorsal closure may be effected.

Nervous System. — Soon after gastrulation, the ventral nervous
system arises as a pair of parallel cords from cells (Fig. 201, n) which have
been derived by direct proliferation from those of the germ band, and are
therefore ectodermal in origin. This primitive double nerve cord be-
comes constricted at intervals into segments, or nenromeres, which cor-

Fig. 197. — Embryo of GLcan-
thus, ventral aspect, a, antenna;
al-a'°: abdominal appendages; e,
end of abdomen; /. labrum; li,
left fundament of labium; Ip,
labial palpus; I1-!3, thoracic legs;
m, mandible; mp, maxillary
palpus; mx, maxilla; p, pro-
cephalic lobe; pr, proctodeum.
— After Ayers.

DEVELOPMENT I 23

respond to the segments of the germ band. Each neuromere consists of
a pair of primitive ganglia, and these are connected together by paired

P

Fig. 198. — Diagrammatic sagittal sections to illustrate invagination of germ band in
Calopteryx. a, anterior pole; ac, amnion cavity; am, amnion; b, blastoderm; d, dorsal;
g, germ band; h, head end of germ band; p, posterior pole; s, serosa; v, ventral; y, yolk. —
After Brandt.

nerve cords, which later may or may not unite into single cords; more-
over, some of the ganglia finally unite to form compound ganglia, such

I24

ENTOMOLOGY

as the brain and the subocsophageal ganglion. In front of the oesophagus
(Fig. 55) are three neuromeres: (1) proto cerebrum, which is to bear the
compound eyes; (2) dcutocerebrum, or antennal neuromere; (3) tritocere-
brum, which belongs to the segment which bears the rudimentary inter-
calary appendages spoken of above. Behind the oesophagus are, at
most, four neuromeres, namely and in order, mandibular, superlingual

Fig. 200. — Diagrammatic transverse sections to illustrate formation of dorsal wall in
the beetle, Lcptinotarsa. a. amnion (breaking up in C); g, germ band; s, serosa. — After
Wheeler, from the Journal of Morphology.

(found only in Collembola as yet), maxillary and labial. Then follow the
three thoracic ganglia and ten (usually) abdominal ganglia. The first
three neuromeres always unite to form the brain, and the next four
(always three; but four in Collembola and perhaps other insects), to
form the subcesophageal ganglion. Compound ganglia are frequently
formed also in the thorax and abdomen by the union of primitive ganglia.

Tracheae. — The tracheae begin as paired invaginations of the ecto-
derm (Fig. 202. /); these simple pockets elongate and unite to form the

main lateral trunks, from which
arise the countless branches of
the tracheal system.

M e soderm . — From the inner
layer which was derived from the
germ band by gastrulation (Figs.
190-192) are formed the impor-
tant germ layers known as meso-
derm and entoderm. Most of the
layer becomes mesoderm, and this splits on either side into chambers,
or ccelom sacs (Fig. 201. c), a pair to each segment. In Orthoptera these
ccelom sacs are large and extend into the embryonic appendages, but in
Coleoptera, Lepidoptera and Hymenoptera they are small. These sacs
may share in the formation of the definite body-cavity, though the last
arises independently, from spaces that form between the yolk and the

Fig. 201. — Transverse section of germ layers
of Clytra. c, ccelom sac; n, neuroblasts (primi-
tive nervous cells). — After Lecaillox.

DEVELOPMENT

I25

mesodermal tissues. From the ccelom sacs develop the muscles, fat-
body, dorsal vessel, blood corpuscles, ovaries and testes; the external
sexual organs, however, as well as the vagina and ejaculatory duct, are
ectodermal in origin.

Entoderm.— At its anterior and posterior ends, the inner layer just
referred to gives rise to a mass of cells which are destined to form the
mesenteron, from which the mid intestine develops. One mass is ad-
jacent to the blind end of the stomodaeal invagination and the other to
that of the proctodaeal in-folding. The two masses become U-shaped
(Fig. 203), and the lateral arms of the two elongate and join so that the
entodermal masses become connected by two lateral strands of cells;

Fig. 202. — Transverse section of abdomen of Clytra embryo at Fig. 203. — Dia-
an advanced stage of development, a, appendage; e, epithelium of gram of formation
mid intestine; g, ganglion; m, Malpighian tube; mi, muscular layer of entoderm in Lep-
of mid intestine; ms, muscle elements; my, mesenchyme (source of tinotarsa. e, e, en-
fat-body); s, sexual organ; /, tracheal invagination. — After Lecail- todermal masses; tn,
lox. mesoderm . — After

Wheeler.

by overgrowth and undergrowth from these lateral strands a tube is
formed which is destined to become the stomach, and by the disappear-
ance of the partitions that separate the mesenteron from the stomodaeum
at one end and from the proctodaeum at the other end, the continuity of
the alimentary canal is established. The fore and the hind gut, then,
are ectodermal in origin, and the mid gut entodermal.

Polyembryony. — In certain Hymenoptera a single egg may give
rise to many individuals. Thus in some Chalcididae and Proctotrypidae,
according to Marchal, the fertilized ovum segments into many (12-100)
embryos, which develop into as many adults, all the individuals from the
same ovum being of the same sex.

126

ENTOMOLOGY

2. External Metamorphosis
Metamorphosis. — One of the most striking phenomena of insect
life is expressed by the term metamorphosis, which means conspicuous
change of form after birth. The egg of a butterfly produces a larva;
this eats and grows and at length becomes a pupa; which, in turn, de-
velops into an imago. These stages are so different (Fig. 27) that with-
out experience one could not know that they pertained to the same in-
dividual.

Holometabola. — The more specialized insects, namely, Neuroptera,
Mecoptera, Trichoptera, Lepidoptera, Coleoptera (Fig. 204), Diptera

Fig. 204. — Cyllene carycB. A, larva; B, pupa; C, imago. X 3.

(Figs. 205, 29), Siphonaptera (Fig. 30) and Hymenoptera (Fig. 284),
undergo this indirect, or complete,1 metamorphosis, involving profound
changes of form and distinguished by an inactive pupal stage. These
insects are grouped together as Holometabola.

Larvae receive such popular names as " caterpillar " (Lepidoptera),
"grub" (Coleoptera), and "maggot" (Diptera), while the pupa of a
moth or butterfly (especially the latter) is called a "chrysalis."

Heterometabola. — In a grasshopper, as contrasted with a butterfly,
the imago, or adult, is essentially like the young at birth, except in hav-
ing wings and mature reproductive organs, and the insect is active
throughout life; hence the metamorphosis is termed direct, or incomplete.

1 These terms, though somewhat misleading in implication, are currently used.

DEVELOPMENT

127

This type of transformation, without a true pupal period, is character-
istic of the more generalized of the metamorphic insects, namely, Orthop-
tera, Platyptera, Plecoptera, Ephemerida (Fig. 19), Odonata (Fig. 20),
Thysanoptera and Hemiptera (Fig. 206). These orders constitute the
group Heterometabola. Within the limits of the group, however, various
degrees of metamorphosis occur;
thus Plecoptera, Ephemerida and
Odonata undergo considerable
change of form; a resting, or
quiescent, period may precede the
imaginal stage, as in Cicada (Fig.
207); while male Coccidae have
what is essentially a complete
metamorphosis. In fact, the vari-
ous kinds of metamorphosis grade
into one another in such a way as
to make their classification to some
extent arbitrary and inadequate.

As there is no distinction be-
tween larva and pupa in most

heterometabolous insects, it is customary to use the term nymph during
the interval between egg and imago.

Fig.

205. — Phormia
puparium; C

regina.
, imago.

A, larv

X s.

Fig. 206. — Six successive instars of the squash bug, Anasa tristis. X 2.

Ametabola. — The most generalized insects, Thysanura and Collem-
bola, develop to sexual maturity without a metamorphosis; the form

128

ENTOMOLOGY

at hatching is retained essentially throughout life, there are no traces of
wings even in the embryo, and there is no change of habit. These two
orders form the group Amctabola. All other insects have a metamor-

Fig. 207. — Cicada tibicen. A, imago emerging from nymphal skin; B, the cast skin; C,

imago. Natural size.

phosis in the broad sense of the term, and are therefore spoken of as
Metabola. In this we follow Packard, rather than Brauer, who uses a
somewhat different set of terms to express the same ideas.

Fig. 208. — Eggs of various insects. A, butterfly, Polygonia interrogationis; B, house fly,
Musca domes tica; C, chalcid, Bruchophagus funebris; D, butterfly, Papilio troilus; E, midge.
Dasyneura trifolii; F, hemipteron. Triphleps insidiosus; G. hemipteron, Podisus spinosus;
H, fly, Drosophila ampclophila. Greatly magnified.

Stadium and Instar. — During the growth of every insect, the skin
is shed periodically, and with each moult, or ecdysis, the appearance of
the insect changes more or less. The intervals between the moults are
termed stages, or stadia. To designate the insect at any particular stage,
the term instar has been proposed and is growing in favor; thus the

DEVELOPMENT

129

Fig. 209. — Three eggs of the cabbage butter-
fly, Pier is rapes. Greatly magnified, but all
drawn to same scale.

insect at hatching is the first instar, after the first moult the second instar,
and so on.

Egg. — The eggs of insects are exceedingly diverse in form. Com-
monly they are more or less spherical, oval, or elongate, but there are
innumerable special forms, some
of which are quite fantastic.
Something of the variety of form
is shown in Fig. 208. As regards
size, most insect eggs can be dis-
tinguished by the naked eye;
many of them tax the vision,
however, for example, the ellip-
tical eggs of Dasyneura legu-
minicola, which are but .300 mm.
in length and .075 mm. in width;

the oval eggs of the cecropia moth, on the other hand, are as long as 3
mm.

The egg-shell, or chorion, secreted around the ovum by cells of the
ovarian follicle, may be smooth but is usually sculptured, frequently with

ridges which, as in lepidopterous eggs, may serve
to strengthen the shell. The ornamentation of
the egg-shell is often exquisitely beautiful, though
the particular patterns displayed are probably of
no use, being incidentally produced as impressions
from the cells which secrete the chorion. Varia-
tions of form, size and pattern are frequent in eggs
of the same species, as appears in Fig. 209.

Always the chorion is penetrated by one or
more openings, constituting the micro pyle, for the
entrance of spermatozoa.

As a rule, the eggs when laid are accompanied
by a fluid of some sort, which is secreted usually
by a cement gland or glands, opening into the
vagina. This fluid commonly serves to fasten
the eggs to appropriate objects, such as food
plants, the skin of other insects, the hairs of
mammals, etc.; it may form a pedicel, or stalk,
for the egg, as in Chrysopa (Fig. 210); may surround the eggs as a gelat-
inous envelope, as in caddis flies, dragon flies, etc.; or may form a cap-
sule enclosing the eggs, as in the cockroach.

Fig. 210. — Chrysopa, laying
eggs. Slightly enlarged.

130

ENTOMOLOGY

The number of eggs laid by one female differs greatly in different
species and varies considerably in different individuals of the same species.
Some of the fossorial wasps and bees lay only a dozen or so and some
grasshoppers two or three dozen, while a queen honey bee may lay a
million. Two females of the beetle Prionus laticollis had, respectively,
332 and 597 eggs in the abdomen (Mann). A. A. Girault gives the fol-
lowing numbers of eggs per female, from an examination of twenty egg-
masses of each species :

Hatching. — Many larvae, caterpillars for example, simply eat their
way out of the egg-shell. Some maggots rupture the shell by contortions
of the body. Some larvae have special organs for opening the shell;
thus the grub of the Colorado potato beetle has three pairs of hatching
spines on its body (Wheeler) and the larval flea has on its head a tempo-
rary knife-like egg-opener (Packard). The process of hatching varies
greatly according to the species, but has received very little attention.

Larva. — Although larvae, generally speaking, differ from one another
much less than their imagines do, they are easily referable to their orders
and usually present specific differences. Larvae that display individual
adaptive characters of a positive kind (Lepidoptera, for example) are
easy to place, but larvae with negative adaptive characters (many Dip-
tera and Hymenoptera) are often hard to identify.

Thysanuriform Larvae. — Two types of larvae have been recognized
by Brauer, Packard and other authorities: thysanuriform and erucijorm;
respectively generalized and specialized in their organization. The
former term is applied to many larvae and nymphs (Fig. 211, C, D) on
account of their resemblance to Thysanura, of which Camp odea and
Lepisma are types. The resemblance lies chiefly in the flattened form,
hard plates, long legs and antennae, caudal cerci, well-developed mandib-
ulate mouth parts, and active habits, with the accompanying sensory
specializations. These characteristics are permanent in Thysanura. but
only temporary in metamorphic insects, and their occurrence in the latter
forms may properly be taken to indicate that these insects have been
derived from ancestors which were much like Thysanura.

Thysanuriform characters are most pronounced in nymphs of Blat-
tidae, Forficulidae, Perlidae, Ephemeridae and Odonata, but occur also in
the larvae of some Xeuroptera {Mantis pa) and Coleoptera (Carabidae

Thyridoptcryx c phcmcrcrform is

Clisiocampa americana

Chionaspis furfura

DEVELOPMENT

and Meloidae). These primitive characters are gradually overpowered,
in the course of larval evolution, by secondary, or adaptive, features.

Fig. 211. — Types of larvae. A, B, Thysanura; C, D, thysanuriform nymphs; E-I, eruci-
form larvae. A, Campodea; B, Lepisma; C, perlid nymph (Plecoptera) ; D, Libcllula (Odo
nata); E, Tenthrcdopsis (Hymenoptera) ; F, Lachnosterna (Coleoptera) ; G, Mclanotus
(Coleoptera); H, Bombus (Hymenoptera); /, Hypodcrma (Diptera).

Eruciform Larvae. — The prevalent type of larva among holometab-
olous insects is the eruciform (Fig. 211, E-I), illustrated by a caterpillar

Fig. 212. — Mantis pa. A, larva at hatching — thysanuriform; B, same larva just before
first moult — now becoming eruciform. C, imago, the wings omitted; D, winged imago,
slightly enlarged. — .4 and B after Brauer; C and D after Emertox, from Packard's Text-
Book of Entomology, by permission of the Macmillan Co.

or a maggot. Here the body is cylindrical and often fleshy; the integ-
ument weak; the legs, antenna?, cerci, and mouth parts reduced, often
to disappearance; the habits sedentary and the sense organs correspond-

ENTOMOLOGY

ingly reduced. These characteristics are interpreted as being results of
partial or entire disuse, the amount of reduction being proportional to
the degree of inactivity. Extreme reduction is seen in the maggots of
parasitic and such other Diptera as, securing their food with almost no
exertion, are simple in form, thin-skinned, legless, with only a mere
vestige of a head and with sensory powers of but the simplest kind.

Transitional Forms. — The eruciform is clearly derived from the
thysanuriform type, as Brauer and Packard have shown, the continuity
between the two types being established by means of a complete series
of intermediate stages. The beginning of the eruciform type is found
in Xeuroptera. where the campodeoid sialid larva assumes a quiescent
pupal condition. The key to the origin of the complete metamorphosis,
involving the eruciform condition, Packard finds in the neuropterous
genus Mantis pa (Fig. 212), the first larva of which is truly campodea-
form and active. Beginning a sedentary life, however, in the egg-sac of
a spider, it loses the use of its legs and the antennae become partly aborted,
before the first moult. In Packard's words. "Owing to this change of
habits and surroundings from those of its active ancestors, it changes its
form, and the fully grown larva becomes cylindrical, with small slender
legs, and, owing to the partial disuse of its jaws, acquires a small, round
head." Meloidae (Fig. 218) afford other excellent examples of the tran-
sition from the thysanuriform to the eruciform condition during the life
of the individual.

Thysanuriform characters become gradually suppressed in favor of
the eruciform, until, in most of the highly developed orders (Mecoptera.
Trichoptera, Lepidoptera, Diptera, Siphonaptera and HymenopteraK
they cease to appear, except for a few embryonic traces — an illustration
of the principle of "acceleration in development."

Growth. — The larval period is pre-eminently one of growth. In
He'terometabola, growth is continuous during the nymphal stage, but
in Holometabola this important function becomes relegated to the larval
stage, and pupal development takes place at the expense of a reserve sup-
ply of food accumulated by the larva.

The rapidity of larval growth is remarkable. Trouvelot found that
the caterpillar of Telea polyphemus attains in 56 days 4.140 times its
original weight (TV grain), and has eaten an amount of food 86,000
times its primitive weight. Other larvae exceed even these figures; thus
the maggot of a common flesh fly attains 200 times its original weight in
24 hours.

Ecdysis. — The exoskeleton, unfitted for accommodating itself to the

DEVELOPMENT

X33

growth of the insect, is periodically shed, and along with it go not only
such integumentary structures as hairs and scales, but also the chitinous
lining, or intima, of the stomodaeum, proctodeum, tracheae, integumen-
tary glands, etc. The process of moulting, or ecdysis, in caterpillars is
briefly as follows. The old skin becomes detached from the body by an
intervening fluid of hypodermal origin; the skin dries, shrinks, is pushed
backward by the contractions of the larva, and at length splits near the
head, frequently under the neck; through this split appear the new head
and thorax, and the old skin is worked back toward the tail until the
larva is freed of its exuvicz. The details of the process, however, are by
no means simple. Ecdysis is probably something besides a provision
for growth, for Collembola continue to moult long after growth has
ceased, and the winged May fly sheds its skin once after emergence.
The meaning of this is not known, though perhaps ecdysis has an excre-
tory importance in the case of Collembola, which are exceptional among
insects in having no Malpighian tubes.

Number of Moults. — The frequency of moulting differs greatly in
different orders of insects. Acridiidae have live moults; Lepidoptera
usually four or rive, but often more, as in Isia (Pyrrharctia) Isabella,
which moults as many as ten times (Dyar); Musca domestica has three
(Packard) ; the honey bee probably six (Cheshire) ; and the seventeen-
year locust about twenty-live or thirty (Riley). Packard suggests that
cold and lack of food during hibernation in arctians (as /. isabella) and
partial starvation in the case of some beetles, cause a great number of
moults by preventing growth, the hypodermis cells meanwhile retaining
their activity.

The appearance of the insect often changes greatly with each moult,
particularly in caterpillars, in which the changes of coloration and
armature may have some phylogenetic significance, as Weismann has
attempted to show in the case of sphingid larvae.

Adaptations of Larvae. — Larvae exhibit innumerable conformities
of structure to environment. The greatest variety of adaptive structures
occurs in the most active larvae, such as predaceous forms, terrestrial or
aquatic. These have well-developed sense organs, excellent powers of
locomotion, special protective and aggressive devices, etc. In insects
as a whole, the environment of the larva or nymph and that of the adult
are very different, as in the dragon fly or the butterfly, and the larvae are
modified in a thousand ways for their own immediate advantage, with-
out any direct reference to the needs of the imago.

The chief purpose, so to speak, of the larva is to feed and grow, and

134

ENTOMOLOGY

the largest modifications of the larva depend upon nutrition. Take as
one extreme, the legless, headless, fleshy and sluggish maggot, embedded
in an abundance of food, and as the other extreme the active and " wide-
awake" larva of a carabid beetle, dependent for food upon its own powers
of sensation, locomotion, prehension, etc., and obliged meanwhile to
protect or defend itself. Between these extremes come such forms as
caterpillars, active to a moderate degree. The great majority of larval
characters, indeed, are correlated with food habits, directly or indirectly;
directly in the case of the mouth parts, sensory and locomotor organs,
and special structures for obtaining special food; indirectly, as in re-
spiratory adaptations and protective structures, these latter being numer-
ous and varied.

Larvae that live in concealment, as those that burrow in the ground
or in plants, have few if any special protective structures; active larvae,
as those of Carabidae, have an armor-like integument, but owe their pro-
tection from enemies chiefly to their powers of locomotion and their
aversion to light (negative phototropisni) ; various aquatic nymphs (Zaitha,
Odonata) are often coated with mud and therefore difficult to distin-
guish so long as they do not move; caddis worms are concealed in their
cases, and caterpillars are often sheltered in a leafy nest. There is no
reason to suppose that insects conceal themselves consciously, however,
and one is not warranted in speaking of an instinct for concealment in the
case of insects — since everything goes to show that the propensity to
hide, though advantageous indeed, is simply a reflex, inevitable, negative
reaction to light (negative phototropisni) or a positive reaction to contact
(positive thigmotropism) .

Exposed, sedentary larvae, as those of many Lepidoptera and Cole-
optera, often exhibit highly developed protective adaptations. Cater-
pillars may be colored to match their surroundings and may
resemble twigs, bird-dung, etc.; or larvae may possess a disagreeable
taste or repellent fluids or spines, these odious qualities being frequently
associated with warning colors.

Larvae need protection also against adverse climatal conditions,
especially low temperature and excessive moisture. The thick hairy
clothing of some hibernating caterpillars, as Isia (Pyrrharctia) Isabella,
doubtless serves to mollify sudden changes of temperature. Naked
cutworms hibernate in well-sheltered situations, and the grubs of the
common "May beetles," or "June bugs," burrow down into the ground
below the reach of frost. Ordinary high temperatures have little effect
upon larvae, except to accelerate their growth. Excessive moisture is
fatal to immature insects in general — conspicuously fatal to the chinch

DEVELOPMENT

135

Fig.

213.

Obtect

pupa of milkweed but-
terfly, Anosia plexippus,
natural size.

bug, Rocky Mountain locust, aphids and sawfly larvae. The effect of
moisture may be an indirect one, however; thus moisture may favor the
development of bacteria and fungi, or a heavy rain may be disastrous
not only by drowning larvae, but also by washing them off their food
plants.

As a result of secondary adaptive modifications, larvae may differ

far more than their imagines. Thus Platygaster in

its extraordinary first larval form (Fig. 219) is en-
tirely unlike the larvae of other parasitic Hymenop-
tera, reminding one, indeed, of the crustacean
Cyclops rather than the larva of an insect. As
Lubbock has said, the characters of a larva depend
(1) upon the group of insects to which the larva
belongs and (2) upon the special environment of
the larva.

Pupa. — The term pupa is strictly applicable to
holometabolous insects only. Most Lepidoptera
and many Diptera have an obtect pupa (Fig. 213),
or one in which the appendages and body are com-
pactly united; as distinguished from the free pupa of Xeuroptera, Trichop-
tera, Coleoptera and others, in which the appendages are free (Fig. 204).
This distinction, however, cannot always be drawn sharply. Diptera
present also the coar elate type of pupa (Fig. 205), in which the pupa re-
mains enclosed in the old larval skin, or pu pari urn.

Pupal characters, though doubtless of great adaptive and phylogenetic
significance, have received but little attention. Lepi-
dopterous pupae present many puzzling characters, for
example, an eye-like structure (Fig. 214) suggesting
an ancestral active condition, such as still occurs
among heterometabolous insects.

Pupation of a Caterpillar. — The process of pupa-
tion in a caterpillar has been carefully observed by
Riley. The caterpillar of the milkweed butterfly
(Pl. I, A) spins a mass of silk in which it entangles
its suranal plate and anal prolegsand then hangs down-
ward, bending up the anterior part of the body (B), which gradually
becomes swollen. The skin of the caterpillar splits dorsally from the
head backward, and is worked back toward the tail (C and D) by the
contortions of the larva.

The way in which the pupa becomes attached to its silken support

Fig. 214. — Head
of chrysalis of Pa-
pilio polyxcncs, to
show eye-like struc-
ture. Enlarged.

i3°

ENTOMOLOGY

is rather complex. Briefly, while the larval skin still retains its hold on
the support, the posterior end of the pupa is withdrawn from the old
integument and by the vigorous whirling and twisting of the body the
hooks of the terminal cremaster of the pupa are entangled in the silken
support. At rirst the pupa is elongate (F) and soft, but in an hour or so
it has contracted, hardened, and assumed its characteristic form and
coloration (F).

Pupal Respiration.— Except under special conditions, pupae breathe
by means of ordinary abdominal spiracles. Aquatic pupae have special
respiratory organs, such as the tracheal filaments of Simulium (Fig. 231),
and the respiratory tubes of Culex (Fig. 230).

Pupal Protection. — Inactive and helpless, most pupae are concealed
in one way or another from the observation of enemies
and are protected from moisture, sudden changes of
temperature, mechanical shock and other adverse in-
fluences. The larvae of many moths burrow into the
ground and make an earthen cell in which to pupate;
a large number of coleopterous larvae {Lachno sterna,
Osmoderma, Passalus, Lucanus, etc.) make a chamber
in earth or wood, the walls of the cell being strength-
ened with a cementing fluid or more or less silk, form-
ing a rude cocoon. Silken cocoons are spun by some
Xeuroptera (Chrysopidae, Fig. 215), by Trichoptera
(whose cases are essentially cocoons), Lepidoptera,
a few Coleoptera (as Curculionidae, Donatio), some
Diptera (as Cecidomyiidae) , Siphonaptera, and many
Hymenoptera (for example. Tenthredinidae, Ichneu-
monidae, wasps, bees and some ants).
The cocoon-making instinct is most highly developed in Lepidoptera
and the most elaborate cocoons are those of Saturniidae. The cocoon
of Samia cecropia is a tough, water-proof structure and is double (Fig.
216), there being two air spaces around the pupa; thus the pupa is pro-
tected against moisture and sudden changes of temperature and from
most birds as well, though the downy woodpecker not infrequently punc-
tures the cocoon. 5. cecropia binds its cocoon firmly to a twig; Tropcea
luna and Telea polyphenols spin among leaves, and their cocoons (with
some exceptions) fall to the ground; Callosamia promethea, whose cocoon
is covered with a curved leaf, fastens the leaf to the twig with a wrapping
of silk, so that the leaf with its burden hangs to the twig throughout the
wTinter. The leaves surrounding cocoons may render them inconspicuous

Fig. 215. — Co-
coon of Chrysopa,
after emergence of
imago. Slightly en-
larged.

Plate I.

F

Successive stages in the pupation of the milkweed caterpillar. Anosia plcxippus.

Natural size.

DEVELOPMENT

139

or may serve merely as a foundation for the cocoon. While silk and
often a water-proof gum or cement form the basis of a cocoon, much
foreign material, such as bits of soil or wood, is often mixed in; the cocoons
of many common Arctiidae, as Diacrisia virginica and Isia Isabella, con-
sist principally of hairs, stripped from the body of the larva.

Butterflies have discarded the cocoon, the last traces of which occur
in Hesperiidae, which draw together a few leaves with a scanty supply of
silk to make a flimsy substitute for a cocoon. Papilionid and pierid pupae
are supported by a silken girdle (Fig. 27), and nymphalid chrysalides
hang freely suspended by the tail (Fig. 213).

Cocoon-Spinning. — The caterpillar of Telea polyphemus "feels
with its head in all directions, to discover any leaves to which to attach

Fig. 216. — Cocoon of Samia cccropia, cut open to show the two silken layers and the enclosed

pupa. Natural size.

the fibres that are to give form to the cocoon. If it finds the place suit-
able, it begins to wind a layer of silk around a twig, then a fibre is attached
to a leaf near by, and by many times doubling this fibre and making it
shorter every time, the leaf is made to approach the twig at the distance
necessary to build the cocoon; two or three leaves are disposed like this
one, and then fibres are spread between them in all directions, and soon
the ovoid form of the cocoon distinctly appears. This seems to be the
most difficult feat for the worm to accomplish, as after this the work is
simply mechanical, the cocoon being made of regular layers of silk united
by a gummy substance. The silk is distributed in zigzag lines about
one-eighth of an inch long. When the cocoon is made, the worm will
have moved his head to and fro, in order to distribute the silk, about two
hundred and fifty-four thousand times. After about half a day's work,
the cocoon is so far completed that the worm can hardly be distinguished

ENTOMOLOGY

through the fine texture of the wall; then a gummy resinous substance,
sometimes of a light brown color, is spread over all the inside of the cocoon.
The larva continues to work for four or five days, hardly taking a few
minutes of rest, and finally another coating is spun in the interior, when
the cocoon is all finished and completely air tight. The fibre diminishes
in thickness as the completion of the cocoon advances, so that the last
internal coating is not half so thick and so strong as the outside ones."
(Trouvelot.)

Emergence of Pupa. — Subterranean pupae wriggle their way to the
surface of the ground, often by the aid of spines (Fig. 217), that catch
successively into the surrounding soil. These locomotor spines may occur
on almost any part of the pupa, but occur commonly on the abdominal
segments, as in lepidopterous pupae; the extremity of the abdomen, also,
bears frequently one or more spinous projections, as in Tipulidae, Cara-
bidae and Lepidoptera, to assist the escape of the pupa.
These structures are found also in pupae, as those of
Sesiidae, that force their way out of the stems of plants
in which the larvae have lived. The emergence from
the cocoon is accomplished in some cases by the pupa,
in others by the imago. Hemerobiidae, Trichoptera
and the primitive lepidopteron Eriocephala use the
pupal mandibles to cut an opening in the cocoon;
wThile many lepidopterous pupae have on the head a
beak for piercing the cocoon, or teeth for rending or

Fig. 217.-S11D- cuUing the silk,
terranean pupa of b

Anisota. Enlarged. Eclosion. — During the last few hours before the
emergence of a butterfly the colors of the imago develop
and may be seen through the transparent skin of the chrysalis (PL II A).
Xo movement occurs, however, until several seconds before emergence;
then, after a few convulsive movements of the legs and thorax of the
imprisoned insect, the pupa skin breaks in the region of the tongue and
legs (B), a secondary split often occurs at the back of the thorax, and
the butterfly emerges (C-E) with moist body, elongated abdomen and
miniature wings. Hanging to the empty pupa case (F), or to some other
available support, the insect dries and its wings gradually expand (G, H)
through the pressure of the blood. At regular intervals the abdomen
contracts and the wings fan the air, and sooner or later a drop or two of
a dull greenish fluid (the meconium) is emitted from the alimentary canal.
The expansion of the wings takes place rapidly, and in less than an hour,
as a rule, they have attained their full size (/).

Plate II.

Successive stages in the emergence of the milkweed butterfly, Anosia plexippus,
from the chrysalis. Natural size.

DEVELOPMENT

H3

T. polyphemus is "provided with two glands opening into the mouth,
which secrete during the last few days of the pupa state, a fluid which is
a dissolvent for the gum so firmly uniting the fibres of the cocoon. This
liquid is composed in great part of bombycic acid. When the insect has
accomplished the work of transformation which is going on under the
pupa skin, it manifests a great activity, and soon the chrysalis covering
bursts open longitudinally upon the thorax; the head and legs are soon
disengaged, and the acid fluid flows from its mouth, wetting the inside of
the cocoon. The process of exclusion from the cocoon lasts for as much
as half an hour. The insect seems to be instinctively aware [?] that
some time is required to dissolve the gum, as it does not make any at-
tempt to open the fibres, and seems to wait with patience this event.
When the liquid has fully penetrated the cocoon, the pupa contracts its
body, and pressing the hinder end, which is furnished with little hooks,
against the inside of the cocoon, forcibly extends its body; at the same
time the head pushes hard upon the fibres and a little swelling is observed
on the outside. These contractions and extensions of the body are re-
peated many times, and more fluid is added to soften the gum, until
under these efforts the cocoon swells, and finally the fibres separate, and
out comes the head of the moth. In an instant the legs are thrust out,
and then the whole body appears; not a fibre has been broken, they have
only been separated.

"To observe these phenomena, I had cut open with a razor a small
portion of a cocoon in which was a living chrysalis nearly ready to trans-
form. The opening made was covered with a piece of mica, of the same
shape as the aperture, and fixed to the cocoon with mastic so as to make
it solid and air-tight; through the transparent mica I could see the move-
ments of the chrysalis perfectly well.

"When the insect is out of the cocoon, it immediately seeks for a
suitable place to attach its claws, so that the wings may hang down, and
by their own weight aid the action of the fluids in developing and un-
folding the very short and small pad-like wings. Every part of the in-
sect on leaving the cocoon, is perfect and with the form and size of ma-
turity, except the pad-like wings and swollen and elongated abdomen,
which still gives the insect a worm-like appearance; the abdomen con-
tains the fluids which flow to the wings.

"When the still immature moth has found a suitable place, it re-
mains quiet for a few minutes, and then the wings are seen to grow very
rapidly by the afflux of the fluid from the abdomen. In about twenty
minutes the wings attain their full size, but they are still like a piece of

144

ENTOMOLOGY

wet cloth, without consistency and firmness, and as yet entirely unfit for
flight, but after one or two hours they become sufficiently stiff, assuming
the beautiful form characteristic of the species." (Trouvelot.) The
expansion of the wing is due to blood-pressure brought about chiefly by
the abdominal muscles. In the freshly-emerged insect, the two mem-
branes of the wing are corrugated, and expansion consists in the flattening
out of these folds. The wing is a sac, which would tend to enlarge into
a balloon-shaped bag, were it not for hypodermal fibers which hold the
wing-membranes closely together (Mayer). Samia cecropia also uses
a dissolvent fluid; Tropaza luna. Philosamia cynthia and others cut and
force an opening through the cocoon by means of a pair of saw-like organs,
one at the base of each front wing.

Hypermetamorphosis. — In a few remarkable instances, metamor-
phosis involves more than three stages, owing to the existence of super-
numerary larval forms. This phenomenon of hypermetamorphosis occurs
notably in the coleopterous genera Meloe, Epicauta, Sitaris. Rhi pi phorns
and Stylo ps, in male Coccidae and several parasitic Hymenoptera.

In Meloe, as described by Riley, the newly-hatched larva (triungulin I
form) is active and campodea-form. It climbs upon a flower and thence
upon the body of a bee (Anthophora), which carries it to the nest, where
it eats the egg of the bee. After a moult, the larva though still six-
legged, has become cylindrical, fleshy and less active, resembling a lamel-
licorn larva; it now appropriates the honey of the bee. With plenty
of rich food at hand the larva becomes sluggish, and after another moult
appears as a pseudo-pupa, with functionless mouth parts and atrophied
legs. From this pseudo-pupa emerges a third larval form, of the pure
eruciform type, fat and apodous like the bee-larvae themselves. After
these four distinct stages the larva becomes a pupa and then a beetle.

Epicauta, another meloid, has a similar history. The triungtdin
(Fig. 218, A) of E. vittata burrows into an egg-pod of Melanoplus differen-
tial is and eats the eggs of that grasshopper. After a moult the second
larva (carabidoid form) appears; this (B) is soft, with reduced legs and
mouth parts and less active than the triungulin. A second moult and
the scarabazidoid form of the second larva is assumed; the legs and
mouth parts are now rudimentary and the body more compact than
before. A third and a fourth moult occur with little change in the form
of the second larva, which is now in its ultimate stage (C). After the
fifth moult, however, the coarctate larva, or pseudo-pupa, appears; this
(D) hibernates and in spring sheds its skin and becomes the third lan a.
which soon transforms to a true pupa (E), from which the beetle (F)

DEVELOPMENT

145

shortly emerges. Thus the pupal stage is preceded by at least three
distinct larval stages.

In the anomalous beetle Stylo ps, the males are winged, but the fe-
males are maggot-like and sedentary, living in the bodies of bees and
wasps. Packard found as many as three hundred triungulin larvae
issuing from a female Stylo ps in the body of an Andrena. The further
life history of Stylops is but imperfectly known ; probably the triungulin
climbs upon a bee or a wasp and enters its body, after the manner of the
European Rhipiphorus paradoxus, whose life history is much better
understood.

Fig. 218. — Stages in the hypermetamorphosis of Epicauta. A. triungulin; B, carabidoid
stage of second larva; C, ultimate stage of second larva; D, coarctate larva; E, pupa; F,
imago. E is species cinerea; the others are vittata. All enlarged except F. — After Riley,
from Trans. St. Louis Acad. Science.

The most extraordinary metamorphoses have been found among
parasitic Hymenoptera, as in Platygaster, a proctotrypid which infests
the larva of Cecidomyia. The egg of Platygaster, according to Ganin,
hatches into a larva of bizarre form (Fig. 219, A), suggesting the crusta-
cean Cyclops, rather than an insect. This first larva has a blind food
canal and no nervous, circulatory or respiratory systems. After a moult
the outline is oval (B), and there are no appendages as yet, though the
nervous system is partially developed. Another moult, and the third
larva appears (C), elliptical in contour, externally segmented, with
tracheae and a pair of mandibles. From now on, the development is
essentially like that of other parasitic Hymenoptera.
11

146

ENTOMOLOGY

Equally anomalous are the changes undergone by Polynema, a proc-
totrypid parasite in the eggs of dragon flies, and by the proctotrypid
Teleas, which affects the eggs of the tree cricket (CEcanthus). In all
these cases the larvae go through changes which in most other insects are
confined to the egg stage. In other words, the larva hatches before its
embryonic development is completed, so to speak.

Significance of Metamorphosis. — "The essential features of meta-
morphosis," says Sharp," appear to be the separation in time of growth
and development and the limitation of the reproductive processes to a
short period at the end of the individual life."

Fig. 219. — Stages in the hypermetamorphosis of Platygastcr. A, first larva; B. second
larva; C, third larva; a, antenna; b, brain; /, fat-tissue; //. hind intestine; ;;/, mandible;
mo, mouth; ms, muscle; n, nerve cord; r, reproductive organ of one side; s, salivary gland;
/, trachea. — After Ganin.

The simplest insects, Thysanura, have no metamorphosis, and showr
no traces of ever having had one. Hence it is inferred that the first
insects had none; in other words, the phenomenon of metamorphosis
originated later than insects themselves. Successive stages in the evolu-
tion of metamorphosis are illustrated in the various orders of insects.

The distinctive mark of the simplest metamorphosis, as in Orthop-
tera and Hemiptera, is the acquisition of wings; growth and sexual
development proceeding essentially as in the non-metamorphic insects
(Thysanura and Collembola) . Here the development of wings does not
interfere with the activity of the insect; its food habits remain unaltered;
throughout life the environment of the individual is practically the same.

mo

DEVELOPMENT

147

Even when considerable difference exists between the nymphal and
imaginal environments, as in Ephemerida and Odonata, the activity of
the individual may still be continuous, even if somewThat lessened as the
period of transformation approaches.

With Neuroptera, the pupal stage appears. In these and all other
holometabolous insects the larva accumulates a surplus of nutriment
sufficient for the further development, which becomes condensed into
a single pupal stage, during which external activity ceases temporarily.

With the increasing contrast between the organization of the larva
and that of the imago, the pupal stage gradually becomes a necessity.
Metamorphosis now means more than the mere acquisition of wings, for
the larva and the imago have become adapted to widely different en-
vironments, chiefly as regards food. The caterpillar has biting mouth
parts for eating leaves, while the adult has sucking organs for obtaining
liquid nourishment; the maggot, surrounded by food that may be ob-
tained almost without exertion, has but minimum sensory and locomotor
powers and for mouth parts only a pair of simple jaws; as contrasted
with the fly, which has wings, highly developed mouth parts and sense
organs, and many other adaptations for an environment which is strik-
ingly unlike that of the larva; so also in the case of the higher Hymen-
optera, where maternal or family care is responsible for the helpless con-
dition of the larva.

Thus it is evident that the change from larval to imaginal adapta-
tions is no longer congruous with continuous external activity; a quies-
cent period of reconstruction becomes inevitable.

As was said, the eruciform type of larva has been derived from the
thysanuriform type, the strongest evidence of this being the fact that
among hypermetamorphic insects, the change from the one to the other
takes place during the lifetime of the individual. Furthermore, the
eruciform condition is plainly an adaptive one, brought about by an
abundant and easily obtainable supply of food. The lack of a thysanuri-
form stage in the development of the most specialized eruciform larvae,
as those of flies and bees, is regarded by Hyatt and Arms as an illustra-
tion of the general principle known as " acceleration of development,"
according to which newer and useful adaptive characters tend to appear
earlier and earlier in the development, gradually crowding upon and
forcing out older and useless characters. In connection with this sub-
ject, the appearance of temporary abdominal legs in embryo bees is
significant, as indicating an ancestral active condition. In accounting for

148

ENTOMOLOGY

the evolution of metamorphosis, the theory of natural selection finds
one of its most important applications.

3. Internal Metamorphoses
In Heterometabola, the internal post-embryonic changes are as di-
rect as the external changes of form; in Holometabola, on the contrary,
not all the larval organs pass directly into imaginal organs, for certain
larval tissues are demolished and their substance reconstructed into
imaginal tissues. When indirect, however, the internal metamorphosis

Fig. 220. — Diagram- Fig. 221. — Diagrammatic transverse sections of muscid

matic transverse section of larvae, to show imaginal buds. //, larval hypodermis; /.larval
Corethra larva, to show integument; ih. imaginal hypodermis; /. imaginal bud of leg;
imaginal buds of wings (w) w, imaginal bud of wing. — Modified from Lang's Lehrbuch.
and legs (/); h, hypoder-
mis; i, integument. — Modi-
fied from Lang's Lehrbuch.

is nevertheless continuous and gradual, without the abruptness that
characterizes the external transformation. In the larval stage imaginal
organs arise and grow; in the pupa stage the purely larval organs grad-
ually disappear while the imaginal organs are continuing their develop-
ment.

Phagocytes. — The destruction of larval tissues, or histolysis, is due
often to the amoeboid blood corpuscles, known as leucocytes or phago-

DEVELOPMENT

149

cytes, which attack some tissues and absorb their material, but later are
themselves food for the developing imaginal tissues. The construction
of tissues is termed histogenesis.

In Coleoptera, however, the degeneration of the larval muscles is entire-
ly chemical, there being no evidence of phagocytosis, according to Dr. R.
S. Breed. Berlese, indeed, goes so far as to deny in general the destruc-
tive action of leucocytes on larval tissues.

Imaginal Buds. — The wings and legs
of a fly originate in the larva in the form
of cellular masses, or imaginal buds, as
Weismann discovered. Thus in the larva
of Corethra, there are in each thoracic seg-
ment a pair of dorsal buds and a pair of
ventral buds (Fig. 220), each bud being
clearly an evagination of the hypodermis
at the bottom of a previous invagination.
The six ventral buds form the legs eventu-
ally; of the dorsal buds, the middle and
posterior pairs form, respectively, the
wings and the halteres, and the anterior
pair form the pupal respiratory processes.
Each imaginal bud is situated in a peri-
podal cavity, the wall of which (peripodal
membrane) is continuous with the general
hypodermis; as the legs and wings develop,
they emerge from their peripodal sacs and
become free.

In Corethra but little histolysis occurs,
most of the larval structures passing direct-
ly into the corresponding structures of the
adult. Corethra, indeed, is in many re-
spects intermediate between heterome-
tabolous and holometabolous insects as
regards its internal changes.

Muscidae. — In Muscidae, as compared with Corethra the imaginal
buds are more deeply situated, the peripodal membrane forming a stalk
(Fig. 221), and the processes of histolysis and histogenesis become ex-
tremely complicated. The hypodermis, muscles, alimentary canal and
fat-body are gradually broken down and remodeled, and part of the
respiratory system is reorganized, though the dorsal vessel and the central

Fig. 222. — Imaginal buds of full
grown larva of Pieris, dorsal aspect.
b, brain; m, mid intestine; s1, pro-
thoracic spiracle; 54, first abdominal
spiracle; sg, silk gland; I, pro-
thoracic bud; 77, bud of fore wing;
7/7, bud of hind wing. — After
Goxix.

ENTOMOLOGY

Fig. 224. — Internal transformations of Sphinx ligustri. A, larva; B. pupa; C, moth;
a, aorta; an, antenna; b, brain; /, fore intestine; fr, food reservoir; h, hind intestine; hi,
heart; m, mid intestine; ml, Malpighian tubes; p, proboscis; s, subcesophageal ganglion;
t} testis; tg, thoracic ganglia; v, ventral nerve cord. — After Newfort.

DEVELOPMENT

nervous system, uninterrupted in their functions, undergo comparatively
b'ttle alteration.

The imaginal hypodermis of the thorax arises from thickenings of
the peripodal membrane which spread over the larval hypodermis, while
the latter is gradually being broken down by the leucocytes; in the head
and abdomen the process is essentially the same as in the thorax, the
new hypodermis arising from imaginal buds.

Most of the larval muscles, excepting the three pairs of respiratory
muscles, undergo dissolution. The imaginal muscles have been traced
back to mesodermal cells such as are always associated with imaginal
buds.

Hymenoptera and Lepidoptera. — The internal transformation in
Hymenoptera, according to Bugnion, is less profound than in Muscidae
and more extensive than in Coleoptera and Lepidoptera. . The internal
metamorphosis in Lepidoptera resembles in many respects that of Core- ,
thra. In both these orders the dorsal pair of prothoracic buds is absent.
In a full-grown caterpillar the fundaments of the imaginal legs and wings
(Fig. 222) may be seen, the wings in a frontal section of the larva ap-
pearing as in Fig. 223. Many of the details of the internal metamorphosis
in Lepidoptera have been described by Newport and Gonin. Figure 224,
after Newport, shows some of the more evident internal differences in
the larva, pupa and imago of a lepidopterous insect.

Significance of Pupal Stage. — To repeat — among holometabolous
insects the function of nutrition becomes relegated to the larval stage
and that of reproduction to the imaginal stage. Larva and imago be-
come adapted to widely different environments. So dissimilar are the
two environments that a gradual change from the one to the other is no
longer possible; the revolutionary changes in structure necessitate a
temporary cessation of external activity.

CHAPTER IV

ADAPTATIONS OF AQUATIC INSECTS

Ease, versatility and perfection of adaptation are beautifully exempli-
fied in aquatic insects.

Systematic Position. — Aquatic insects do not form a separate group
in the system of classification, but are distributed among many orders, of
which Plecoptera. Ephemerida, Odonata and Trichoptera are pre-emi-
nently aquatic. One third of the families of Heteroptera and less than
one fourth those of Diptera are more or less aquatic. One tenth of the
families of Coleoptera frequent the water at one stage or another, but
only half a dozen genera of Lepidoptera. A few Collembola live upon
the surface of water; and several Hymenoptera, though not strictly
aquatic, are known to parasitize the eggs and larvae of aquatic insects.

The change from the terrestrial to the aquatic habit has been a gradual
change of adaptation, not an abrupt one. Thus at present there are some
tipulid larvae that inhabit comparatively dry soil; others live in earth
that is moist; many require a saturated soil near a body of water and
many, at length, are strictly aquatic. Among beetles, also, similar transi-
tional stages are to be found.

Food. — Insects have become adapted to utilize with remarkable
success the immense and varied supply of food that the water affords.
Hosts of them attack such parts of plants as project above the surface of
the water, and the caterpillar of Paraponyx (Fig. 172) feeds on submerged
leaves, especially of Vallisncria. being in this respect almost unique
among Lepidoptera. Hydrophilid beetles and many other aquatic in-
sects devour submerged vegetation. The larvae of the chrysomelid genus
Donacia find both nourishment and air in the roots of aquatic plants.
Various Collembola subsist on floating algae, and larvae of mosquitoes and
black-flies on microscopic organisms near the surface, while larvae of
Chironomns hnd food in the sediment that accumulates at the bottom of a
body of water.

Predaceous species abound in the water. Xotonecta (Fig. 225) ap-
proaches its prey from beneath, clasps it with the front pair of legs and
pierces it. Nepa and Ranatra likewise have prehensile front legs along

152

ADAPTATIONS OF AQUATIC INSECTS

!53

with powerful piercing organs. Belostoma and Benacus (Fig. 22) even
kill small fishes by their poisonous punctures. Some other kinds, as the
water-skaters (Gerridae, Fig. 226), depend on dead or disabled insects.
The species of Hydro philus (Fig. 227) are to some extent carnivorous as
larvae but phytophagous as imagines, while Dytiscidae are carnivorous

Fig. 225. — Backswimmer, Xotonecta insulata,
natural size.

Fig. 226.

-Water-skater, Gerris rcmigis,
natural size.

throughout life. Aquatic insects eat not only other insects, but also
worms, crustaceans, mollusks or any other available animal matter.

Even aquatic insects are not exempt from the attacks of parasitic
species. A few Hymenoptera actually enter the water to find their
victims, for example, the ichneumon Agriotypus,
which lays its eggs on the larvae of caddis flies.

Locomotion. — Excellent adaptations for aquat-
ic locomotion are found in the common Hydro phi-
lus triangularis (Fig. 227). Its general form re-
minds one of a boat, and its long legs resemble
oars. The smoothly elliptical contour and the
polished surface serve to lessen resistance. Owing
to the form of the body (Fig. 228, A) and the pres-
ence of a dorsal air-chamber under the elytra, the
back of the insect tends to remain uppermost, while
in Notonecta (Fig. 228, B), on the other hand, the
conditions are reversed, and the insect swims with
its back downward. The legs of Hydro philus, ex-
cepting the first pair, are broad and thin (Fig. 229, A )

and the tarsi are fringed with long hairs. When swimming, the "stroke "
is made by the flat surface, aided by the spreading hairs; but on the
"recover," the leg is turned so as to cut the water, while the hairs fall
back against the tarsus from the resistance of the water, as the leg is
being drawn forward. The hind legs, being nearest the center of gravitv,

Fig. 227. — Hydro ph-
ilus triangularis, nat-
ural size.

154

ENTOMOLOGY

are of most use in swimming, though the second pair also are used for
this purpose; indeed, a terrestrial insect, finding itself in the water,

Fig. 228

— Transverse sections of (A) Hydrophilns and (B) Notonecta.

tron; /, metathoracic leg.

e, elytron; h, hemely

instinctively relies upon the third pair of legs for locomotion. Hydroph-
ilns uses its oar-like legs alternately, in much the same sequence

as land insects, but Cybister
and other Dytiscidae, which
are even better adapted
than Hydro philus for aquatic
locomotion, move the hind
legs simultaneously, and
therefore can swim in a
straight line, without the
wobbling and less econom-
ical movements that charac-
terize Hydro philus.

Larvae of mosquitoes pro-
pel themselves by means of
lashing, or undulatory , move-
ments of the abdomen. A
peculiar mode of locomo-
tion is found in dragon fly
nymphs, which project them-
selves by forcibly ejecting a
stream of water from the
anus.

On account of the large
amount of air that they carry
about, most aquatic imagines are lighter than the water in which they live,
and therefore can rise without effort, but can descend only by exertion, and
can remain below only by clinging to chance stationary objects. The mos-

Fig. 229. — Left hind legs of aquatic beetles. A,
Hydrophilns triangularis; B, Cybister fimbriolatus; c,
coxa; /, femur; s, spur; /, tarsus; ti, tibia; tr, tro-
chanter.

ADAPTATIONS OF AQUATIC INSECTS

155

quito larva (Fig. 230, A) is often heavier than water, but the pupa (Fig.
230, B) is lighter, and remains clinging to the surface film.

The tension of this surface film is sufficient to support the weight of
an insect up to a certain limit, provided
the insect has some means of keeping its
body dry. This is accomplished usually by
hairs, set together so thickly that water
cannot penetrate between them. As the
legs and body of Gerris are rendered water-
proof by a velvety clothing of hairs, the in-
sect, though heavier than water, is able to
skate about on the surface. Gyrinus, by
means of a similar adaptation, can circle
about on the surface film, and minute col-
lembolans leap about on the surface as
readily as on land.

The modifications of the legs for swim-
ming have often impaired their usefulness
for walking, so that many aquatic Coleop-
tera and Hemiptera can move but awk-
wardly on land. When walking, it is inter-
esting to note, Cybister and some other
aquatic forms no longer move their hind
legs simultaneously as they do in swimming,
but use them alternately, like terrestrial
species.

The adaptations for swimming do not
necessarily affect the power of flight. Dy-
tiscus, Hydro philus, Gyrinus, Notonecta,
Benacus and many other Coleoptera and
Hemiptera leave the water at night and fly
around, often being found about electric
lights.

Respiration. — Aquatic insects have not
only retained the primitive, or open (holo-
pneustic), type of respiration, characterized by the presence of spiracles,
but have also developed an adaptive, or closed (apneustic), type, for
utilizing air that is mixed with water.

Through minor modifications of structure and habit, many holo-
pneustic insects have become fitted for an aquatic life. In these in-

Fig. 230. — Larva (.4) and pupa
(B) of mosquito, Culex pipiens. r,
respiratory tube; /, tracheal gills.

156

ENTOMOLOGY

stances the insects have some means of carrying down a supply of air
from the surface of the water. Thus Xotonecta bears on its body a
silvery film of air entangled in closely set hairs, which exclude the water.
Gyrinus descends with a bubble of air at the end of the abdomen. Dy-
tisciis and Hydro philus have each a capacious air-space between the
elytra and the abdomen, into which space the spiracles open. Xepa
and Ranatra have each a long respiratory organ composed of two valves,
which lock together to form a tube that communicates with the single
pair of spiracles situated near the end of the abdomen. The mosquito
larva, hanging from the surface film, breathes through a cylindrical tube
(Fig. 230, A, r) projecting from the penultimate abdominal segment;
the pupa, however, bears a pair of respiratory tubes on the back of the
thorax (Fig. 230, B, r, r), which is now upward, probably in order to
facilitate the escape of the fly. The rat-tailed maggot (Eristalis), three
quarters of an inch long, has an extensile caudal tube seven times that
length, containing two tracheae terminating in spiracles, through which
air is brought down from above the mud in which the larva lives. Sim-
ilarly, in the dipterous larva, Bittacomor pha clavipes (Fig. 173), the
posterior segments of the abdomen are attenuated to form a long re-
spiratory tube. The larva of Donacia appears to have no special ad-
aptations for aquatic respiration except a pair of spines near the end of
the body, for piercing air chambers in the roots of the aquatic plants
in which it dwells.

The simplest kind of apneustic respiration occurs in aquatic nymphs
such as those of Ephemerida and Agrionidae, whose skin at first is thin
enough to allow a direct aeration of the blood. This cutaneous res-
piration is possible during the early life of many aquatic species.

Branchial respiration, however, is the prevalent type among aquatic
nymphs and is perhaps the most important of their adaptive character-
istics. Thin-walled and extensive outgrowths of the integument, con-
taining tracheal branches or, rarely, only blood, enable these forms to
obtain- air from the water. May fly nymphs (Figs. 19, A; 170), with
their ample waving gills, offer familiar examples of branchial respiration.
Tracheal gills are very diverse in form and situation, occurring in a few
species of May fly nymphs on the thorax or head, though commonly re-
stricted to the sides of the abdomen, where they occur in pairs or in
paired clusters (Fig. 19, A). Caudal gills are found in agrionid nymphs
(Fig. 171). The aquatic caterpillars of Paraponyx (Fig. 172) are unique
among Lepidoptera in having gills, which are filamentous in this instance.

Caddis worms, enclosed in their cases, maintain a current of water by

ADAPTATIONS OF AQUATIC INSECTS

157

means of undulatory movements of the body, and the larvae and pupae
of most black flies (Simuliidae, Fig. 231) secure a continuous supply of
fresh air simply by fastening themselves to rocks in swiftly flowing
streams.

Rectal respiration is highly developed in odonate nymphs. In these,
the rectum is lined with thousands of tracheal branches, which are bathed
by water drawn in from behind, and then expelled.

All these kinds of respiration — cutaneous, branchial and rectal—
occur in young ephemerid nymphs; while mosquito larvae have in ad-
dition spiracular respiration.

With the arrival of imaginal life, tracheal gills disappear, except in
Perlidae, and even in these insects the gills are of
little, if any, use.

Marine Insects. — Except along the shore, the
sea is almost devoid of insect life, the exceptions
being a few chironomid larvae which have been
dredged in deep water, and fifteen species of Halo-
bates (belonging to the same family as our familiar
pond-skaters), which are found on warm smooth
seas, where they subsist on floating animal re-
mains.

Between tide-marks maybe found various beetles
and collembolans, which feed upon organic debris;
as the tide rises, the former retreat, but the latter
commonly burrow in the sand or under stones and
become submerged, for example the common A n urida
maritima.

Insect Drift. — Seaweed or other refuse cast upon the shore harbors
a great variety of insects, especially dipterous larvae, staphylinid scaven-
gers and predaceous Carabidae. On the shores of inland ponds and lakes
a similar assemblage of insects may be found feeding for the most part
on the remains of plants or animals, or else on one another. During a
strong wind, the leeward shore of a lake is an excellent collecting ground,
as many insects are driven against it. On the shores of the Great Lakes
insects are occasionally cast up in immense numbers, forming a broad
windrow, fifty or perhaps a hundred miles long. Xeedham has described
such an occurrence on the west shore of Lake Michigan, following a gale
from the northeast. In this instance, a liter of the drift contained nearly
four thousand insects, of which 66 per cent, were crickets (Xemobius),
20 per cent. Acridiidae, and the remainder mostly beetles (Carabidae,

Fig. 231. — Simu-
lium; A, larva; B.
pupa, showing respira-
tory filaments.

ENTOMOLOGY

Scarabaeida?, Chrysomelidae, Coccinellidae, etc.), dragon flies, moths,
butterflies (Anosia, Pieris, etc.) and various Hemiptera, Hymenoptera
and Diptera. A large proportion of the insects were aquatic forms, such
as Hydro philus, Cybister, Zaitha, and a species of caddis fly; these had
doubtless been carried out by freshets, while the butterflies and dragon
flies had been borne out by a strong wind from the northwest, after which
all were driven back to the coast by a northeast wind. While some of
these insects survived, notably Coccinellidae, Trichoptera, Asilidae,
Acridiidae and Gryllidae, nearly all the rest were dead or dying, in-
cluding the dragon flies, flies, bumble bees and wasps. Foraging Cara-
bidae were observed in large numbers, also scavengers of the families
Staphylinidae, Silphidae and Dermestidae.

On the seashore and on the shores of the Great Lakes, the salient
features of insect life are essentially the same. Similar species occur in
the two places with similar biological relations, on account of the general
similarity of environment.

Origin of the Aquatic Habit. — The theory that terrestrial insects
have arisen from aquatic species is no longer tenable, for the evidence
shows that the terrestrial type is the more primitive. Aquatic insects
still retain the terrestrial type of organization, which remains unob-
scured by the temporary and comparatively slight adaptations for an
aquatic life. Thus, the development of tracheal gills has involved no
important modification of the fundamental plan of tracheal respiration.
It is significant, moreover, that the most generalized, or most primitive,
insects — Thysanura — are without exception terrestrial. Aquatic in-
sects do not constitute a phylogenetic unit, but represent various orders,
which are for the most part undoubtedly terrestrial, notwithstanding the
fact that a few of these orders (Plecoptera, Ephemerida, Odonata, Tri-
choptera) are now wholly aquatic in habit. Adaptations for an aquatic
existence have arisen independently and often in the most diverse
orders of insects.

CHAPTER V

COLOR AND COLORATION

The naturalist distinguishes between the terms color and coloration.
A color is a single hue, while coloration refers to the arrangement of colors.

Sources of Color. — The colors of insects are classed as (i) pigmental
{chemical), those due to internal pigments; (2) structural (physical),
those due to structures that cause interference or reflection of light;
and (3) combination colors (chemico- physical) , which are produced in both
ways at once.

Structural Colors. — The iridescence of a fly's wing and that of a
soap bubble are produced in essentially the same way. The wing, how-
ever, consists of two thin, transparent, slightly separated lamellae, which
diffract white light into prismatic rays, the color differences depending
upon differences in the distance between the two membranes.

The brilliant iridescent hues of many butterfly scales are due to the
diffraction of light by fine, closely parallel striae (Fig. 92) just as in the
case of the " diffraction gratings" used by the physicist, which consist of
a glass or metallic plate with parallel diamond rulings of microscopic
fineness. The particular color produced depends in both cases upon the
distance between the striae. Though almost all lepidopterous scales are
striated, it is only now and then that the striae are sufficiently close to-
gether to give diffraction colors. In a Brazilian species of A patura the
iridescent scales have 1050 striae to the millimeter, and in a species of
Morpho, according to Kellogg, the iridescent pigmented scales have 1400
striae per millimeter, the striae being only .0007 mm. apart; while in some
of the finest Rowland gratings they number only 700 per millimeter.

These interference colors of butterfly scales may be due, not only to
surface markings, but also to the lamination of the scale and to the over-
lapping of two or more scales. In beetles the metallic blues and greens,
and iridescence in general, are often produced by minute fines or pits that
diffract the fight. Purely structural colors, however, are not so common
/ as might be supposed, according to Tower, who says, "The pits alone,
however, are powerless to produce any color; it is only when they are
combined with a highly reflecting and refractive surface lamella and a
pigmented layer below that the iridescent color appears. The action of

159

i6o

ENTOMOLOGY

light is in this case the same as in the plain metallic coloring, excepting
that each pit acts as a revolving prism to disperse different wave-lengths
of light in different directions, and the combined result is iridescence.
The existence of minute pits over the body surface is of common occur-
rence, but it is only when they are combined as above that iridescent
colors occur."

Silvery white effects are usually caused by the total reflection of light
from scales or other sacs that are filled with air; the same silvery appear-
ance is given also by air-filled tracheae and by the air bubbles that many
aquatic insects carry about under water.

Violet, blue-green, coppery,, silver and gold colors are, with few excep-
tions, structural colors. (Mayer.)

Pigmental Colors. — These are either cuticular or hypodermal. The
predominant brown and black colors of insects are made by pigment dif-
fused in the outer layer of the cuticula (Fig. 88) . Cockroaches are almost
white just after a moult, but soon become brown, and many beetles change
gradually from brown to black. In these cases it is apparently significant
that the cuticular pigments lie close to the surface of the skin, i. e., where
they are most exposed to atmospheric influences. Tower holds that
cuticular colors "are not due to drying, oxidation, secretion, or like pro-
cesses,'' but are due to ''some katalytic agent or enzyme [formed by the
hypodermis] which, passing out through the pore canals, comes in con-
tact with the primary cuticula and there becomes the active factor in the
production of cuticular colors." Gortner finds, however, that the black
cuticular pigment in Leptinotarsa belongs to the group of melanins and
is produced by oxidation, induced by an oxidase; that when all oxygen is
absent no pigmentation takes place.

The cuticular pigments are derived, of course, from the underlying
hypodermis cells, and these cells themselves, moreover, usually contain
(i) colored granules or fatty drops which give red, yellow, orange and
sometimes white or gold colors as seen through the skin; (2) diffused
chlorophyll (green) or xanthophyll (yellow), taken from the food plant.
Unlike the structural colors, which are persistent, these hypodermal
colors often change after death, though less rapidly when the pigments are
tightly enclosed, as in scales or hairs. Though white and green are
structural colors as a rule, they are due to pigments in Pieridae, Lycaeni-
dae and some Geometridae.

Frequently a color pattern consists partly of cuticular and partly of
hypodermal colors, the hypodermal or sub-hypodermal color forming "a
groundwork upon which the pattern is cut out by the cuticular color/'

COLOR AND COLORATION

161

(Tower.) Thus in Leptinotarsa decemlineata the pattern "is composed
of a dark cuticular pigment upon a yellow hypodermal background."

Combination Colors. — The splendid changeable hues of Apatura,
Euplcea and other tropical butterflies depend upon the fact that their
scales are both pigmented and striated. Under the microscope, certain
Apatura scales are brown by transmitted light and violet by reflected
light, and to the unaided eye the color of the wing is either brown or
violet, according as the light is received respectively from the pigment
or from the striated surfaces of the scales. According to Tower, chemico-
physical colors "which are of exceedingly wide occurrence, are also the
most brilliant and varied of all those found in insects. To this class be-
long all metallic iridescent, pearly, and translucent colors, as well as blue,
green, and violet in almost every case."

Nature of Pigments. — Some pigments are taken bodily from the
food; others are manufactured indirectly from the food, and some of
these are excretory products.

The green color of many caterpillars and grasshoppers is due to chloro-
phyll, which tinges the blood and shows through the transparent integu-
ment. Mayer has found that scales of Lepidoptera contain only blood
while the pigment is forming; that the first color to appear upon the pupal
wings is a dull ochre or drab — the same color that the blood assumes when
it is removed from the pupa and exposed to the air; also that pigments
like those of the wings may be manufactured artificially from pupal
blood. Pieridae are peculiar in the nature of their pigments, as Hopkins
has shown. The white pigment of this family is uric acid and the reds
and yellows of Pieris, Colias and Papilio are due to derivatives of uric
acid; the yellow pigment, termed lepidotic acid, precedes the red in time
of appearance, the latter being probably a derivative of the former. The
green pigments of some Papilionidae, Noctuidae, Geometridae and Sphin-
gidae are also said by some investigators to be products of uric acid, which
in insects as in other animals is primarily an excretory, or waste, product.

Effects of Food on Color. — -Besides chlorophyll, to which various
caterpillars, aphids and other forms owe their green color, the yellow con-
stituent of chlorophyll, namely xanthophyll, frequently imparts its color
to plant-eating insects, while some phytophagous species are dull yellow
or brown from the presence of tannin, taken from the food plant. Most
pigments, however, are elaborated from the food by chemical processes
that are not well understood.

Many who have reared Lepidoptera extensively know that the color
of the imago is influenced by the character of the larval food, other con-

12

162

ENTOMOLOGY

ditions being equal, and are able at will to effect certain color changes
simply by feeding the larvae from birth upon particular kinds of plants.
In this country we have few observations upon the subject, but in Europe
the effects of food upon coloration have been ascertained in the case of
many species of Lepidoptera. According to Gregson, Hybernia dejoliaria
is richly colored when fed upon birch, but is dull colored and almost un-
marked when fed on elm. Pictet, by feeding larvae of Vanessa urticce on
the flowers instead of the leaves of the nettle obtained the variety known
as urticoides. Food affects the color of the larva also, as Poulton found
in the case of caterpillars of Tryphazna pronuba, all from the same batch
of eggs. When fed with only the white midribs of cabbage leaves, the
larvae remained almost white for a time, but afterward showed a moderate
amount of black pigment; when fed with the yellow etiolated heart-leaves
or the dark green external leaves, however, the larvae all became bright
green or brown — the same pigment being derived indifferently from etio-
lin (probably the same substance as xanthophyll) or chlorophyll.

Though the pigments may differ in color or amount according to the
kind of food, the color patterns vary without regard to food. Thus
Callosamia promethea, Leptinotarsa decemlineata (Colorado potato beetle),
Coccinellidae (lady-bird beetles) and a host of other insects exhibit ex-
tensive individual variations in coloration under precisely the same food
conditions. Caterpillars of the same kind and age are often very dif-
ferently marked when feeding upon the same plant; for example, Helio-
this obsoleta (corn worm) and the sphingid Deilephila lineata. Further-
more, striking changes of coloration accompany each moult in most cater-
pillars, but particularly those of butterflies, and these changes may prove
to have an important phylogenetic significance. Individual differences
of coloration apart from those due to the direct action of food, light,
temperature and other environmental conditions are to be explained by
heredity.

Effects of Light and Darkness. — Sunlight is an important factor in
the development of most animal pigments, as they will not develop in its
absence. The collembolan Anurida maritima is white at hatching, but
soon becomes indigo blue, unless shielded from sunlight, in which event
it remains white until exposed to the sunlight, when it assume the blue
color. Subterranean or wood-boring larvae are commonly white or yel-
low, but never highly colored. The most notable instances, however,
are furnished by cave insects. These, like other cavernicolous animals,
are characteristically white or pale from the absence of pigment, if they
live in regions of continual darkness, but have more or less pigmentation

COLOR AND COLORATION

163

in proportion respectively to the greater or less amount of sunlight to
which they have access.

Curiously enough, light often hastens the destruction of pigment in
insects that are no longer alive, for which reason it is necessary to keep
cabinet specimens in the dark as much as possible. Life is evidently es-
sential for the sustention or renewal of the pigments.

A chrysalis not infrequently matches its surroundings in color. This
phenomenon has been investigated by Poulton, who has proved that the
color of the chrysalis is determined largely by the prevalent color of the
surroundings during the last few days of larval life. Larvae of Pieris rapes,
raised upon the same food plant (all other conditions being made as nearly
equal as possible) produced dark pupae if kept in darkness for a few days
just before pupation; yellow light arrested the formation of the dark
pigment and gave green pupae; while light colors in general gave light-
colored pupae. This color resemblance is commonly assumed to be of
protective value, and perhaps it is. Nevertheless, it is a direct effect of
light, and does not need to be explained by natural selection, even though
it cannot be denied that natural selection may have helped in its produc-
tion.

Poulton extended his studies to the adaptive coloration of caterpillars
and has published the results of an extensive series of experiments which
prove that the colors of certain caterpillars also are directly produced by
the same colors in the surrounding light. Gastro pacha quercifolia, which
always rests by day on the older wood of its food plant, was given black
twigs, reddish brown sticks, lichens, etc., to rest upon, and though all the
larvae were from the same cluster of eggs, and had been fed in the same
way, each larva gradually assumed the color or colors of its resting place,
resulting in exquisite examples of protective resemblance, the most re-
markable of which were those in which the larvae assumed the variegated
coloration of lichens. Only the younger larvae, however, proved to be
susceptible to the colors of the environment; unlike those of Amphidasis
betularia, in which the older larvae also were sensitive to the surrounding
light. Here again, natural selection is unnecessary, even if not superfluous,
as an explanation of this kind of protective coloration.

Effects of Temperature. — The amount of a pigment in the wing of a
butterfly depends in great measure upon the surrounding temperature
during the pupal stage, when the pigments are forming. Black or brown
spots have been enlarged artificially by subjecting chrysalides to cold;
hence it is probable that the characteristically large black spots on the
under side of the wings of the spring brood of our Cyaniris pseudargiolus

164

ENTOMOLOGY

are simply a direct effect of cold upon the wintering chrysalides. Simi-
larly the spring brood (Variety marcia) of Phyciodes tharos owes its dis-
tinctive coloration to cold, as Edwards has proved experimentally.
Lepidoptera have been the subject of very many temperature experi-
ments, some of which will be mentioned presently in the consideration of
seasonal coloration.

Speaking generally, warmth (except in melanism) tends to induce a
brightening and cold a darkening of coloration, the darkening being due
to an increased amount of black or brown pigment. Temperature,
whether high or low, seldom if ever produces new pigments, but simply
alters the amount and distribution of pigments that are present already.

Effects of Moisture. — Very little is known as to the effects of mois-
ture upon coloration. The dark colors of insular or coastal insects as
contrasted with inland forms, and the predominance of dull or suffused
species in mountainous regions of Tiigh humidity, have led observers oc-
casionally to ascribe melanism and suffusion to humidity. In these cases,
however, the possible influence of low temperature and other factors must
be taken into consideration. The experiments of Merrirield and of
Standfuss showed no effect of moisture upon lepidopterous pupae.

Pictet has found, however, that humidity acting on the cater-
pillars of Vanessa urticce and V. polychloros has a conspicuous effect on
the coloration of the butterflies. Thus when the caterpillars were fed
for ten days with moist leaves, the resulting butterflies had abnormal
black markings on the wTings, and the same results followed when the
larvae were kept in an atmosphere saturated with moisture.

Climatal Coloration. — The brilliant and varied colors of tropical
insects are popularly ascribed to intense heat, light and moisture; and
the dull monotonous colors of arctic insects, similarly, to the surrounding
climatal conditions. Climate undoubtedly exerts a strong influence upon
coloration, but the precise nature of this influence is obscure and will re-
main so until more is known about the effects separately produced by each
of the several factors that go to make up what is called climate.

The prevalence of intense and varied colors among tropical insects is
doubtless somewhat exaggerated, for the reason that the highly colored
species naturally attract the eye to the exclusion of the less conspicuous
forms. Indeed, Wallace assures us that, although tropical insects present
some of the most gorgeous colors in the whole realm of nature, there are
thousands of tropical species that are as dull colored as any of the tem-
perate regions. Carabidae, in fact, attain their greatest brilliancy in the
temperate zone, according to Wallace, though butterflies certainly show

COLOR AND COLORATION

a larger proportion ot vivid and varied colors in the tropics. Mayer
finds, in the widely distributed genus Papilio, that 200 South American
species display but 36 colors, while 22 North American species show 17.
While the number of species in South America is nine times as great as in
North America, the number of colors displayed is only a little more than
twice as great; hence Mayer concludes that the richer display of colors in
the tropics may be due to the far greater number of species, which gives
a better opportunity for color sports to arise; and not to any direct in-
fluence of the climate. Furthermore, the number of broods which occur
in a year is much greater in the tropics than in the temperate zones, so
that the tropical species must possess a correspondingly greater oppor-
tunity to vary.

Albinism and Melanism. — These interesting phenomena, wide-
spread among the higher animals, are little understood, but have often
been attributed to temperature.

Albinism is exceptional whiteness or paleness of coloration, and is due
usually to lack or deficiency of pigment, but in some instances (Pieridae)
to the presence of a white pigment.

The common yellow butterfly, Colias philodice, and its relatives, are
frequently albinic. Scudder observed that albinism among butterflies in
America appears to be confined to a few Pieridae, and to be restricted to
the female sex; is more common in subarctic and subalpine regions than
in lower latitudes and altitudes, and only in the former places includes all
the females. At low altitudes, however, instead of appearing early in
the year as might be expected, the albinic forms appear during the warmer
months.

The experiments made by Gerould on C. philodice show that the
number of albinic female offspring from white females crossed with yellow
males is in accordance with Mendelian law. Albinism is not entirely
confined to the female as Scudder thought, for white males occur, though
they are extremely rare. "They may be expected in regions where the
white female is especially abundant" (Gerould).

In Europe there are many albinic species of butterflies, and they are
by no means confined to the family Pieridae.

Melanism is unusual blackness or darkness of coloration. As to how
it is produced little is known, though warmth is probably the most po-
tent influence, and some attribute it to moisture, as was mentioned.
Pictet obtained partial melanism in Vanessa nrticce and V. polychloros by
subjecting the larvae to moisture.

In warm latitudes, some females of our Papilio glaucus are blackish

ENTOMOLOGY

brown with black markings, instead of being, as usual, yellow with black
markings. In the South, some males of the spring brood of Cyaniris
pseudargiolus are partly or wholly brown instead of blue. A melanic
male of Colias philodice occurs as an extremely rare mutation.

Seasonal Coloration. — When butterflies have more than one brood
in a year, the broods usually differ in aspect, sometimes so much that their
specific identity is revealed only by rearing one brood from another.
The same species may exist under two or more distinct forms during the
same season — in other words, may be seasonally dimorphic, trimorphic
or polymorphic.

Thus Polygonia inter rogationis has two forms, fabricii and umbrosa,
which differ not only in coloration, but even in the form of the wings and
the genitalia. In New England fabricii hibernates and produces um-
brosa. as a rule, while umbrosa usually yields fabricii.

Fig. 232. — Cyaniris pseudargiolus; A. form lucia; B, violacea; C, pseudargiolus proper.

Natural size.

The little blue butterfly. Cyaniris pseudargiolus (Fig. 232), is poly-
morphic to a remarkable degree. In the high latitudes of Canada a
single brood {lucia) occurs. About Boston the same spring brood ap-
pears, but under two forms: an earlier variety {lucia), which is small,
with large black markings beneath; and a later variety (violacea). which
is typically larger, with smaller black spots, though it varies into the form
lucia. Finally, in summer, a third form {pseudargiolus proper) appears,
as the product of lucia or else the joint product of lucia and violacea, and
this is still larger, but the black spots are now faint. In the warm South
the spring form is violacea, but while some of the males are blue, others are
melanic, as just mentioned— a dimorphic condition which does not occur
in the North. Violacea then produces pseudargiolus, in which, however,
all the males are blue.

Iphiclides ajax (Fig. 233) is another polymorphic butterfly whose
life history is complex. The three principal varieties of this species,
known respectively as marcellus, telamonides and ajax, differ not only in

COLOR AND COLORATION

l67

coloration, but also in size and form; marcellus appears first, in spring;
telamonides appears a little later (though before marcellus has disappeared) ;
and ajax is the summer form; as the season advances the varieties be-
come successively larger, with longer tails to the hind wings.

Now Edwards submitted chrysalides of the summer form ajax to
cold and thereby obtained, in

the same summer, butterflies
with the form of ajax but the
markings of the spring form
telamonides. Some of the
chrysalides, however, lasted
over until the next spring and
then gave telamonides.

In Phyciodes tharos (Fig.
234) the spring and summer
broods, termed respectively
marcia and morpheus, were
at first regarded as distinct
species. In marcia the hind

wings are heavily and diffusely * „ • ,

& - Fig. 233. — Iphichdes ajax, form telamonides. on

marked beneath with Strongly flower or button bush. Reduced.

contrasting colors, while in

morpheas they are plain and but faintly marked. Edwards placed upon
ice eighteen chrysalides that normally would have produced morpheus;
but instead of this, the fifteen imagines that emerged were all of the
spring form marcia and were smaller than usual. Pupae derived from eggs

Fig. 234. — Phyciodes tharos; A, spring form, marcia; B. summer form, morpheus; under

surfaces. Natural size.

of marcia gave, after artificial cooling, not morpheus. but marcia again.
The evident conclusion is that the distinctive coloration of the spring
variety is brought about by low temperature. In Labrador, only one

i68

ENTOMOLOGY

brood occurs — marcia; in New York, the species is digoncntic (two-
brooded) and in West Virginia polygoncutic (several-brooded).

Extensive temperature experiments upon seasonal dimorphism in
Lepidoptera have been conducted in Europe by some of the most com-
petent biologists. Weismann found that pupae of the summer form of
Picris napij if placed on ice, disclosed the darker winter form, usually
in the same season, though sometimes not until the next spring. It was
found impossible, however, to change the winter variety into the sum-
mer one by the application of heat. Similar results have attended the
important and much-discussed experiments of Dorfmeister, Weismann
and others upon Vanessa levana-prorsa and other species, from which it
has been inferred by Weismann that the winter form is the primary, older,
and more stable of the two forms, and the summer form a secondary,
newer, and less stable variety; since the latter form only, as a rule, re-
sponds much to thermal influences. Weismann argues that, in addition
to the direct effect of temperature, alternative inheritance also plays an
important part in the production of seasonal varieties. He tries to show,
moreover, that each seasonal variety is colored in adaptation to its
particular environment and that this adaptation may have been brought
about by natural selection — though he does not succeed in this respect.

In several instances, local varieties have been artificially produced
as results of temperature control. Thus Standfuss produced in Germany,
by the application of cold, individuals of Vanessa urticce which were
indistinguishable from the northern variety polar is; and from pupae of
Vanessa cardui, by warmth, a very pale form like that found in the
tropics; and, by cold, a dark variety similar to one found in Lapland.

These investigators and others, notably Merrifield and Fischer, have
accumulated a considerable mass of experimental evidence, the inter-
pretation of which is in many respects difficult, involving as it does, not
merely the direct effect of temperature upon the organism, but also deep
questions of heredity, including reversion, individual variation, and the
inheritance of acquired characters.

The seasonal increase in size that is noticeable, as in C. psendargiolus
and /. ajax, is doubtless an expression of increasing metabolism due to
increasing temperature. Warmth, as is well known, stimulates growth,
and cold has a dwarfing effect. While this is true as a rule, there are
some apparent exceptions, however. Thus Standfuss found that some
caterpillars were so much stimulated by unusual warmth that they
pupated before they were sufficiently fed, and gave, therefore, under-

COLOR AND COLORATION 1 69

sized imagines. A moderate degree of warmth, however, undoubtedly
hastens growth.

Sexual Coloration. — The sexes are often distinguished by colora-
tional as well as structural differences. Colorational antigeny (this

word signifying secondary sexual differences of whatever sort) is most
prevalent among butterflies, in which it is the extreme phase of that
differentiation of ornamentation for which Lepidoptera are unrivaled.

The male of Pieris protodice (Fig. 235) has a few brown spots on the
front wings; the female is checkered with
brown on both wings. In Colias philodicc
(Fig. 236) and C. eurytheme the marginal
black band of the front wings is sharp and
uninterrupted in the male, but diffuse and
interrupted by yellow spots in the female.
In the genus Pa pilio the sexes are often dis-
tinguished by colorational differences and in
Hesperiidae the males often have an oblique
black dash across the middle of each front
wing. Callosamia promethca (Fig. 237), the
gypsy moth and many other Lepidoptera
exhibit colorational antigeny. In not a few
Sesiidse the sexes differ greatly in coloration.
Thus in the male of the peach tree borer
(Sanninoidea exitiosa) all the wings are color-
less and transparent; while in the female the front wings are violet and
opaque and the fourth abdominal segment is orange above. The same
sex may present two types of coloration, as in males of Cyaniris pseudar-
giolns and females of Pa pilio glaucus, already mentioned. Pa pilio merope,

Fig. 236. — Colias philodice;
right fore wing of male (above)
and of female (below). Nat-
ural size.

ENTOMOLOGY

of South Africa, is remarkable in having three females, which are entirely
different in coloration from one another and from the male. There
is no longer any doubt, it may be added, as to the specific identity of
these forms.

Next to Lepidoptera, Odonata most frequently show colorational
antigenv. The male of Calopteryx maculata is velvety black; the female

smoky, with a white ptero-
stigmatal spot. Among
Coleoptera, the male of
Hoplia trifasciata is grayish
and the female reddish
brown; a few more ex-
amples might be given,
though sexual differences in
coloration are comparative-
ly rare among beetles. Of
Hymenoptera. some of the
Tenthredinidae exhibit col-
orational antigenv.

Among tropical butter-
flies there are not a few in-
stances in which the special
coloration of the female is
a d a p t i v e — harmonizing
with the surroundings or
else imitating with remark-
able precision the colora-
tion of another species
which is known to be im-
mune from the attacks of
birds — as described beyond.
In this way. as Wallace sug-
gests, the egg-laden females
may escape destruction, as they sluggishly seek the proper plants upon
which to lay their eggs. Here would be a fair field for the operation of
natural selection.

In most insects, however, sexual differences in coloration are ap-
parently of no protective value and are usually so trivial and variable
as probably to be of no use for recognition purposes. The usual state-
ment that these differences facilitate sexual recognition is a pure as-

Fig. 237. — Callosamia promcthca; A. male, clinging to
cocoon; B, female. Reduced.

COLOR AND COLORATION

I7I

sumption, in the case of insects, and one that is inadequate in spite of
its plausibility, for (1) it is extremely improbable from our present knowl-
edge of insect vision that insects are able to perceive colors except in
the broadest way, namely, as masses; (2) the great majority of insect
species show no sexual differences in coloration; (3) when colorational
antigeny is present it is probably unnecessary, to say the least, for sexual
recognition. Thus, notwithstanding the marked dissimilarity of colora-
tion in the two sexes of C. promethea, the males, guided by an odor, seek
out their mates even when the wings of the female have been amputated
and male wings glued in their place, as Mayer found.

Hence, when useless, colorational antigeny cannot have been de-
veloped by natural selection and may be due simply to the extended
action of the same forces that have produced variety of coloration in
general.

Origin of Color Patterns. — Tower, who has written an important
work on the colors and color patterns of Coleoptera, finds that each of
the black spots on the pronotum of the Colorado potato beetle (Fig. 238)
"is developed in connection with a muscle, and marks the point of at-
tachment of its fibers to the cuticula." Thus the color pattern, in its
origin, is not necessarily useful. This point is so important that we
quote Tower's conclusions in full. "The most important and widely
disseminated of insect colors are those of the cuticula . . . these
colors develop as the cuticula hardens, and appear first, as a rule, upon
sclerites to which muscles are attached. In one of the earlier sections of
this paper I showed that the pigment develops from before backward
and, approximately, by segments, excepting that it may appear upon
the head and most posterior segments simultaneously.

"In ontogeny color appears first, as a rule, over the muscles which
become active first, or upon certain sclerites of the body. These are
usually the head muscles, although exceptions are not infrequent. It
should be remembered that as the color appears the cuticula hardens,
and, considering that muscles must have fixed ends for their action, it
seems that there is a definite relation between the development of color,
the hardening of the cuticula, and the beginning of muscular activity;
the last being dependent upon the second, and, incidentally, accompanied
by the first. As muscular activity spreads over the animal the cuticula
hardens and color appears, so that color is nearly, if not wholly, seg-
mentally developed.

"The relation which exists between cuticular color and the stiffening
of the cuticula is thus a physiological one, the cuticula not being able to

172

ENTOMOLOGY

harden without becoming yellow or brown. What bearing has this
upon the origin of color patterns? In the lower forms of tracheates,
such as the Myriapods, colors appear as segmental repetitions of spots
or pigmented areas which mark either important sclerites or muscle
attachments. On the abdomens of insects, where segmentation is best
observed, color appears as well-defined, segmentally arranged spots,
but on the thorax segmentation is obscured and lost upon the head. Of
what importance, then, is pigmentation? And how did it arise? If the
ontogenetic stages offer any basis for phylogenetic generalization, we
may conclude that cuticula color originated in connection with the
hardening of the integument of the ancestral tracheates as necessary to
the muscular activity of terrestrial life. The primitive colors were yellows,
browns and blacks, corresponding well with the surroundings in which
the first terrestrial insects are supposed to have lived. The color pattern
was a segmental one, showing repetition of the same spots upon suc-
cessive segments, as upon the abdomen of Coleoptera.

"So firmly have these characters become ingrained in the tracheate
series, and so important is this relation of the hardening of the cuticula
to the musculature and to the formation of body sclerites, that even the
most specialized forms show this primitive system of coloration; and,
although there may be spots and markings which have no connection
with it, still the chief color areas are thus closely associated. "

Development of Color Patterns. — Although the causes of colora-
tion are, for the most part; obscure, it is possible, nevertheless, to point
out certain paths along which coloration appears to have developed.
These paths have been determined by the comparison of color patterns
in kindred groups of insects and the study of colorational variations in
adults of the same species. The development of coloration in the in-
dividual, however, has as yet received but little attention — excepting
the excellent studies of Mayer and of Tower. Butterflies, moths and
beetles have naturally been preferred by most students of the subject.

The most primitive colors among moths are uniform dull yellows,
browns and drabs — the same colors that the pupal blood assumes when
it is dried in the air. These simple colors prevail on the hind wings of
most moths and on the less exposed parts of the wings of highly colored
butterflies. The hind wings of moths are, as a rule, more primitively
colored than the front ones because, as Scudder says, "all differentiation
in coloring has been greatly retarded by their almost universal conceal-
ment by day beneath the overlapping front wings." Exceptions to
this statement are found in Geometridae and such other moths as rest

COLOR AND COLORATION

173

with all the wings spread. " In such hind wings we find that the simplest
departure from uniformity consists in a deepening of the tint next the
outer margin of the wing; next we have an intensification of the deeper
tint along a line parallel to the margin; it is but a step from this condi-
tion to a distinct fine or band of dark color parallel to the margin. Or the
marginal shade may, in a similar way, break up into two or more trans-
verse and parallel submarginal lines, a very common style of ornamenta-
tion, especially in moths. Or, again, starting with the submarginal
shade, this may send shoots or tongues of dark color a short distance
toward the base, giving a serrate inner border to the marginal shade;
when now this breaks up into one, two, or more lines or narrow stripes,
these stripes become zigzag, or the inner ones may be zigzag, while the
outer ones are plain — a very common phenomenon.

" A basis such as this is sufficient to account for all the modifications
of simple transverse markings which adorn the wings of Lepidoptera."

Briefly, one or more bands may break up into spots or bars, the
breaks occurring either between the veins or, more commonly, at the
veins; and in the latter event, short bars or more or less quadrate or
rounded spots arise in the interspaces. From simple round spots there
may develop, as Darwin and others have shown, many-colored eye-like
spots, or ocelli.

Mayer gives the following laws of color pattern: "(a) Any spot
found upon the wing of a butterfly or moth tends to be bilaterally sym-
metrical, botn as regards form and color; and the axis of symmetry is a
line passing through the center of the interspace in which the spot is
found, parallel to the longitudinal nervures. (b) Spots tend to appear
not in one interspace only, but in homologous places in a row of adjacent
interspaces, (c) Bands of color are often made by the fusion of a row
of adjacent spots, and. conversely, chains of spots are often formed by
the breaking up of bands, (d) When in process of disappearance, bands
of color usually shrink away at one end. (e) The ends of a series of spots
are more variable than the middle, (f ) The position of spots situated
near the outer edges of the wing is largely controlled by the wing folds
or creases. "

These results have been arrived at chiefly by the study of the varia-
tions presented by color patterns.

Variation in Coloration. — It is safe to say that no two insects are
colored exactly alike. Some species, however, are far more variable
than others. Catocala ilia, for example, occurs under more than fifty
varieties, each of which might be given a distinctive name, were it not

174

ENTOMOLOGY

for the fact that these varieties run into one another. One may examine
hundreds of potato beetles (L. deccmlincata) without finding any two
that have precisely the same pattern on the pronotum. The range of
this variation in this species is partially indicated in Fig. 238, and that
of Cicindela in Fig. 239.

Individuals of Cicindela vary in pattern in a few definite directions,
and the patterns that characterize the various species appear to be
fixations of individual variations. In the words of Dr. Horn: "(1)
The type of marking is the same in all our species. (2) Assuming a well-
marked species {vulgaris. Fig. 239, 7) as a central type, the markings of
other species vary from that type, (a) by a progressive spreading of the
white, (6) by a gradual thinning or absorption of the white, (c) by a
fragmentation of the markings, (d) by linear supplementary extension.
(3) Many species are practically invariable (i. e., the individual varia-
tions are small in amount as compared with those in other species).
These fall into two series: (a) those of the normal type, as vulgaris,
kirticollis and tenuisignata; (b) those in which some modification of the
type has become permanent, probably through isolation, as margini-
pennis, togata and lemniscata. (4) Those species which vary do so in
one direction only." New types of pattern, of specific value, appear
to have arisen by the isolation and perpetuation of individual variations.

Variations in general fall into two classes: continuous (individual
variations) and discontinuous mutations. The former are always present,
are slight in extent and intergrade with one another; they are distributed
symmetrically about a mean condition. The latter are occasional, of
considerable extent and sharply separated from the normal condition.

R. H. Johnson has published an important statistical study on evo-
lution in the color pattern of the lady-beetles. He finds both con-
tinuous and discontinuous variations present; that the color pattern is
capable of modification by the environment; that some modifications
are hereditary characters and others not.

Replacements. — Examples of the replacement of one color by
another are familiar to all collectors. The red of Vanessa atalanta and
Coccinellidae may be replaced by yellow. These two colors in many
butterflies and beetles are due to pigments that are closely related to
each other chemically. Thus in the chrysomelid Melasoma lapponica
the beetle at emergence is pale but soon becomes yellow with black
markings, and after several hours, under the influence of sunlight, the
yellow changes to red; the change may be prevented, however, by keep-
ing the beetle in the dark. After death, the red fades back through

COLOR AND COLORATION 1 75

/ 2 3

^••t*vV xH4#W

4 J . 6

••••l**J (*fU>*)

7 5 ^ 9

&iM«%)

%Vw

13 14 15

uuw «;w;» *«ir*

16 17 ^ ^ 18

Fig. 238. — Colorational variations of the pronotum of the Colorado potato beetle, Lcptinotarsa

decemlineata.

1 76

K.vn )MoLo(;v

Fig. 239. — Elytral color patterns of species of Cicindela. 1-8 illustrate reduction of dark
area; 9-14, extension of dark area; 15, 16, formation of longitudinal vitta; 17, 18, linear ex-
tension of markings. /, C. vulgaris; 2, generosa; 3, generosa; 4, pamphila; 5, limbata; 6,
togata; 7, gratiosa; 8, canosa; g, tenuisignata; 10, marginipennis; 11, hcntzii; 12, sexguttata;
1 j, hemorrhagica; 14, splendida; 15, imperfecta; 16, lemniscata; ij, gabbii; 18, saulcyi. —
After Horn, from Entomological News.

COLOR AXD COLORATION

177

orange to yellow, especially as the result of exposure to sunlight. Yellow
in place of red, then, may be attributed to an arrested development of
pigment in the living insect and to a process of reduction in the dead
insect, metabolism having ceased.

Yellow and green are similarly related. The stripes of Pcecilocapsus
lineatus are yellow before they become green, and after death fade back
to yellow. As the green pigment in most, if not all, phytophagous in-
sects is chlorophyll, these color changes are probably similar to those
that occur in leaves. Leaves grown in darkness are yellow, from the
presence of etiolin, and do not turn green until they are exposed to sun-
light (or electric light), without which chlorophyll does not develop;
and as metabolism ceases, chlorophyll disintegrates, as in autumn,
leaving its yellow constituent, xanthophyll, which is very likely the
same substance as etiolin.

Cicindela sexguttata and Calosoma scrutator are often blue in place of
green. Here, however, these colors are structural, and their variations
are to be attributed to slight differences in the spacing of the surface
elevations or depressions.

Green grasshoppers occasionally become pink toward the close of
summer. No explanation has been offered for this phenomenon, though
it may be remarked that when grasshoppers are killed in hot water the
normal green pigment turns to pink.

These changes of color are apparently of no use to the insect, being
merely incidental effects of light, temperature or other inorganic in-
fluences.

13

CHAPTER VI

ADAPTIVE COLORATION

Protective Resemblance. — Every naturalist knows of many ani-
mals that tend to escape detection by resembling their surroundings.
This phenomenon of protective resemblance is richly exemplified by in-
sects, among which one of the most remarkable cases is furnished by the
KaUima butterflies, especially K. inachis of India and K. paralekta of the
Malay Archipelago. The former species (Fig. 240) is conspicuous when on
the wing; its bright colors, however, are confined to the upper surfaces
of the wings, and when these are folded together, as in repose, the insect

Fig. 240. — KaUima inachis; A, upper surface; B, with wings closed,, showing resemblance to

a leaf. X %.

resembles to perfection one of the dead leaves among which it is accus-
tomed to hide. The form, size and color of the leaf are accurately re-
produced, the petiole being simulated by the tails of the wings. Two
parallel shades, one light and one dark, represent, respectively, the
illuminated and the shaded side of a mid-rib, and the side-veins as well
are imitated; there are even small scattered black spots resembling
those made on the leaf by a species of fungus. Furthermore, the butterfly
habitually rests, not among green leaves, where it would be conspicu-
ous, but among leaves with which it harmonizes in coloration. Not-

178

ADAPTIVE COLORATION

179

withstanding some discussion as to whether it usually rests in pre-
cisely the same position as a leaf, this insect certainly deceives experi-
enced entomologists and presumably eludes birds and other enemies by
means of its deceptive coloration.

Some of the tropical Phasmidae counterfeit sticks, green leaves, or
dead leaves with minute accuracy. Our common phasmids, Diaphero-

FiG. 241. — Manomera blalchleyi, on a twig.
Natural size.

Fig. 242. — Catocala lacrymosa; A , upper surface;
B, with wings closed, and resting on bark. Re-
duced.

mera femorata and Manomera blatchleyi (Fig. 241); are well known as
u stick insects"; indeed, it is not necessary to go beyond the temperate
zone to find plenty of examples of protective resemblance. Geometrid
caterpillars imitate twigs, holding the body stiffly from a branch and
frequently reproducing the form and coloration of a twig with striking
exactitude; and the moths of the same family are often colored like the
bark against which they spread their wings. Even more perfectly do the
Catocala moths resemble the bark upon which they rest (Fig. 242), with

i8o

k\tom()L()(;y

their conspicuous and usually showy hind wings concealed under the pro-
tectively colored front wings. The caterpillars of Basilarchia archippus
and Papilio thoas, as well as other larvae and not a few moths, resemble
closely the excrements of birds. Numerous grass-eating caterpillars are
striped with green, as is also a sphingid species (Ellema harrisii) that lives
among pine needles. The large green sphinx caterpillars perhaps owe
their inconspicuousness partly to their oblique lateral stripes, which cut a
mass of green into smaller areas. The caterpillar of Schizura ipomoece
(Fig. 243), which is green with brown patches, rests for hours along the
eaten or torn edge of a basswood leaf, in which position it bears an ex-

FlG. 243. — Caterpillar of Schizura ipomcece clinging to a torn leaf. Natural size.

tremely deceptive resemblance to the partially dead border of a leaf.
The weevils that drop to the ground and remain immovable are often
indistinguishable to the collector on account of their likeness to bits of
soil or little pebbles*. Everyone has noticed the extent to which some
of the grasshoppers resemble the soil in color; Trimerotropis maritima
is practically invisible against the gray sand of the seashore or other
places to which it restricts itself; and Dissosteira Carolina, which varies
greatly in color, ranging from ashy gray to yellowish or to reddish brown,
is commonly found on soil of its own color.

Adventitious Resemblance. — If, instead of hastily ascribing all
cases apparently of protective resemblance to the action of natural

ADAPTIVE COLORATION

181

selection, one inquires into the structural basis of the resemblance in
each instance, it is found that some cases can be explained, without the
aid of natural selection, as being direct effects of food, light or other
primary factors. Such cases, then, are in a sense accidental. For ex-
ample, many inconspicuous green insects are green merely because
chlorophyll from the food-plant tinges the blood and shows through the
skin. If it be argued that natural selection has brought about a thin
and transparent skin, it may be replied that the skin of a green cater-
pillar is by no means exceptional in thinness or transparency. More-
over, many leaf-mining caterpillars are green, simply because their food
is green; for, living as they do within the tissues of leaves, and surrounded
by chlorophyll, their own green color is of no advantage, but is merely
incidental.

Again, in the " protectively " colored chrysalides experimented upon
by Poulton, the color was directly influenced by the prevailing color
of the light that surrounded the larva during the last few days before
pupation. Of course, it is conceivable that natural selection may have
preserved such individuals as were most responsive to the stimulus of
the surrounding light; nevertheless the fact remains that these resem-
blances do not demand such an explanation, which is, in other words,
superfluous.

Indeed, a great many of the assumed examples of " protective re-
semblance" are very far-fetched. On the other hand, when the re-
semblance is as specific and minutely detailed as it is in the Kallima
butterflies — where, moreover, special instincts are involved — the phe-
nomenon can scarcely be due to chance; the direct and uncombined
action of such factors as food or light is no longer sufficient to explain
the facts — although these and other factors are undoubtedly important
in a primary, or fundamental, way. Here natural selection becomes
useful, as enabling us to understand how original variations of structure
and instinct in favorable directions may have been preserved and ac-
cumulated until an extraordinary degree of adaptation has been attained.

Value of Protective Resemblance. — The popular opinion as to
the efficiency of protective resemblances in undoubtedly an exaggerated
one, owing mainly to the false assumption that the senses of the lower ani-
mals are co-extensive in range with our own. As a matter of fact, birds
detect insects with a facility far superior to that of man, and destroy them
by the wholesale, in spite of protective coloration. Thus, as Judd has
ascertained, no less than three hundred species of birds feed upon pro-
tectively colored grasshoppers, which they destioy in immense numbers,

182

ENTOMOLOGY

and more than twenty species prey upon the twig-like geometric! larvae;
while the weevils that look like particles of soil, and the green-striped
caterpillars that assimilate with the surrounding foliage are constantly
to be found in the stomachs of birds.

After all, however, protective resemblance may be regarded as ad-
vantageous upon the whole, even if it is ineffectual in thousands of in-
stances. An adaptation may be successful even if it does fall short of
perfection; and it should be borne in mind that the evolution of protect-
ive resemblances among insects has probably been accompanied on the
part of birds by an increasing ability to discriminate these insects from
their surroundings.

Warning Coloration. — In strong contrast to the protectively
colored species, there are many insects which are so vividly colored as
to be extremely conspicuous amid their natural surroundings. Such
are many Hemiptera (Lygceus, Murgantia), Coleoptera (Xecrophorus,
Lampyridae, Coccinellidae, Chrysomelidae ) , Hymenoptera (Mutillidae,
Vespidae), and numerous caterpillars and butterflies. Conspicuous col-
ors, being frequently — though not always — associated with qualities
that render their possessors unpalatable or offensive to birds or other
enemies, are advantageous if, by insuring ready recognition, they ex-
empt their owners from attack.

Efficiency of Warning Colors. — Owing to much disagreement as
to the actual value of "warning" colors, several investigators have made
many observations and experiments upon the subject. Tests made by
offering various conspicuous insects to birds, lizards, frogs, monkeys and
other insectivorous animals have given diverse results, according to
circumstances. Thus, one gaudy caterpillar is refused by a certain bird,
at once, or else after being tasted, but another and equally showy cater-
pillar is eaten without hesitation. Or, an insect at first rejected may at
length be accepted under stress of hunger; or a warningly colored form
disregarded by some animals is accepted by others. Moreover, some
of the experiments with captive insectivorous animals are open to ob-
jection on the score of artificiality.

Nevertheless, from the data now accumulated, there emerge some
conclusions of definite value. Frank Finn, whose conclusions are quoted
beyond, has found in India that the conspicuous colors of some butter-
flies (Danainae, Acrcea violce, Delias eucharis, Papilio aristolochice) are
probably effective as "warning" colors. Marshall found in South
Africa that mantids, which would devour most kinds of butterflies, in-
cluding warningly colored species, refused Acrcea, wThich appeared to be

ADAPTIVE COLORATION

183

not only distasteful but even unwholesome; Acrcea is eaten, however,
by the predaceous Asilidse, which feed indiscriminately upon insects —
for example, beetles, dragon flies and even stinging Hymenoptera. The
masterly studies of Marshall and Poulton strongly support the general
theory of warning coloration.

In this country, much important evidence upon the subject has been
obtained by Dr. Judd from an extensive examination of the stomach-
contents of birds, supplemented by experiments and field observations.
Judd says that Murgantia histrionica and other large showy bugs are
usually avoided by birds; that the showy, ill-flavored Coccinellidae, and
Chrysomelidae such as the elm leaf beetle, Diabrotica, and Leptinotarsa
(Doryphora), possess comparative immunity from birds; and that
Macrodactylus, Chauliognathus and Cyllene are highly exempt from
attack. Such cases, he adds, are comparatively few among insects,
however, and in general, warning colors are effective against some ene-
mies but ineffective against others.

Generally speaking, hairs, stings and other protective devices are
accompanied by conspicuous colors — though there are many exceptions
to this rule. These warning colors, however, fail to accomplish their
supposed purpose in the following instances, given by Judd. Taking in-
sects that are thought to be protected by an offensive odor or a dis-
agreeable taste: Heteroptera in general are eaten by all insectivorous
birds, the squash bug by hawks and the pentatomids by many birds;
among Carabidae with their irritating fluids, Harpalus caliginosus and
pennsylvanicus are food for the crow, catbird, robin and six others;
Carabus and Calosoma are relished by crows and blackbirds; Silphidae
are taken by the crow, loggerhead shrike and kingbird; and Leptinotarsa
decemlineata is eaten by at least six kinds of birds: wood thrush, rose-
breasted grosbeak, quail, crow, cuckoo and catbird. Of hairy and spiny
caterpillars, Arctiidae are eaten by the robin, bluebird, catbird, cuckoo
and others; the larvae of the gypsy moth are food for the blue-jay, robin,
chickadee, Baltimore oriole and many others [thirty-one birds, in Massa-
chusetts]; and the spiny caterpillars of Vanessa antiopa are taken by
cuckoos and orioles. Of stinging Hymenoptera, bumble bees are eaten
by the bluebird, blue-jay and two flycatchers; the honey bee, by the
wood pewee, phcebe, olive-sided flycatcher and kingbird; Andrena by
many birds, and Vespa and Polistes by the red-bellied woodpecker, king-
bird, and yellow-bellied flycatcher.

These facts by no means invalidate the general theory, but they do
show that u disagreeable " qualities and their associated color signals

F.NTOMOLOCY

are of little or no avail against some enemies. The weight of evidence
favors the theory of warning coloration in a qualified form. While con-
spicuous colors do not always exempt their owners from destruction,
they frequently do so, by advertising disagreeable attributes of one sort
or another.

The evolution of warning coloration is explained by natural selec-
tion; in fact, we have no other theory to account for it. The colors

A

Fig. 244. — ,4, Anosia plexippus, the "model"; B, Basilarchia archippus, the "mimic."

Natural size.

themselves, however, must have been present before natural selection
could begin to operate; their origin is a question quite distinct from that
of their subsequent preservation.

Protective Mimicry. — This interesting and highly involved phe-
nomenon is a special form of protective resemblance in which one species
imitates the appearance of another and better protected species, there-

ADAPTIVE COLORATION

by sharing its immunity from destruction. Though it attains its highest
development in the tropics, mimicry is well illustrated in temperate
regions. A familiar example is furnished by Basilarchia archippus
(Fig. 244, B), which departs widely from the prevailing dark coloration
of its genus to imitate the milkweed butterfly, Anosia plexippus. The
latter species, or "model," appears to be unmolested by birds, and the
former species, or " mimic," is thought to secure the same exemption
from attack by being mistaken for its unpalatable model. The common
drone-fly, Eristalis tenax (Fig. 245, B) mimics a honey bee in form, size,
coloration and the manner in which it buzzes about flowers, in company
with its model; it does not deceive the kingbird and the flicker, however.
Some Asilidae are remarkably like bumble bees in superficial appearance
and certain Syrphus flies mimic wasps with more or less success. The

A B

Fig. 245. — Protective mimicry. A, drone bee, Apis mcllifcra; B, drone fly, Eristalis tenax.

Natural size.

beetle Casnonia bears a remarkable resemblance to the ants with
which it lives.

The classic cases are those of the Amazonian Heliconiidae and Pieridae,
in which mimicry was first detected by Bates. The Heliconiidae are
abundant, vividly colored and eminently fiee from the attacks of birds
and other enemies of butterflies, on account of their disagreeable odor
and taste. Some of the Pieridae — a family fundamentally different from
Heliconiidae — imitate the protected Heliconiidae so successfully, in
coloration, form and flight, that while other Pieridae are preyed upon by
many foes, the mimicking species tend to escape attack.

The family Heliconiidae, referred to by Bates, comprised what are
now known as the subfamilies Heliconiinae, Ithomiinae and Danainae;
similarly, Pieridae and Papilionidae are now often termed respectively
Pierinae and Papilioninae. Ithomiinae are mimicked also by Papilio-
ninae and by moths of the families Castniidae and Pericopidae.

ENTOMOLOGY

The discoveries of Bates in tropical South America were paralleled
and supported by those of Wallace in India and the Malay Archipelago
(where Danainae are the chief ''models"), and of Trimen in South Africa
(where Acraeinae and Danainae serve as models). Trimen discovered a
most remarkable case, in which three species of Danais are mimicked,
each by a distinct variety of the female of Papilio cenea (merope).

So much for that kind of mimicry — but how is the following kind to
be explained? The Ithomiinae of the Amazon valley have the same form
and coloration as the Heliconiinae, but the Ithomiinae themselves are
already highly protected. The answer is that this resemblance is of
advantage to both groups, as it minimizes their destruction by birds —
these having to learn but one set of warning signals instead of two. This
is the essence of Mullers famous explanation, which will presently be
stated with more precision. There are two kinds of mimicry, then: (i) the
kind described by Bates, in which an edible species obtains security by
counterfeiting the appearance of an inedible species; (2) that observed
by Bates and interpreted by Miiller, in which both species are inedible.
These two kinds are known respectively as Batesian and Mullerian
mimicry, though some writers prefer to limit the term mimicry to the
Batesian type.

Wallace's Rules. — The chief conditions under which mimicry
occurs have been stated by Wallace as follows:

" 1. That the imitative species occur in the same area and occupy the
very same station as the imitated.

"2. That the imitators are always the more defenceless.

''3. That the imitators are always less numerous in individuals.

"4. That the imitators differ from the bulk of their allies.

"5. That the imitation, however minute, is external and visible
only, never extending to internal characters or to such as do not affect
the external appearance."

These rules relate chiefly to the Batesian form of mimicry and need
to be altered to apply to the Mullerian kind.

The first criterion given by Wallace is evidently an essential one and
it is sustained by the facts. It is also true that mimic and model occur
usually at the same time of year; Marshall found many new instances
of this in South Africa. In some cases of mimicry, strange to say, the
precise model is unknown. Thus some Xymphalida? diverge from their
relatives to mimic the Euplceinae, though no particular model has been
found. In such instances, as Scudder suggests, the prototype may
exist without having been found; may have become extinct; or the

ADAPTIVE COLORATION

187

species may have arrived at a general resemblance to another group
without having as yet acquired a likeness to any particular species of
the group, the general likeness meanwhile being profitable.

The second condition named by Wallace is correct for Batesian but
not for Mullerian mimicry . .

The fulfilment of the third condition is requisite for the success of
Batesian mimicry. Bates noted that none of the pierid mimics were so
abundant as their heliconiid models. If they were, their protection
would be less; and should the mimic exceed its model in numbers, the
former would be more subject to attack than the latter. Sometimes,
indeed, as Miiller found, the mimic actually is more common than the
model; in which event, the consequent extra destruction of the mimic
would — at least theoretically — reduce its numbers back to the point of
protection.

In Mullerian mimicry, however, the inevitable variation in abundance
of two or more converging and protected species is far less disastrous;
though when two species, equally distasteful, are involved, the rarer of
the two has the advantage, as Fritz Miiller has shown. His lucid ex-
planation is essentially as follows:

Suppose that the birds of a region have to destroy 1,200 butterflies
of a distasteful species before it becomes recognized as such, and that
there exist in this region 2,000 individuals of species A and 10,000 of
species B; then, if they are different in appearance, each will lose 1,200
individuals, but if they are deceptively alike, this loss will be divided
among them in proportion to their numbers, and A will lose 200 and B
1,000. A accordingly saves 1,000, or 50 per cent, of the total number
of individuals of the species, and B saves only 200, or 2 per cent. Thus,
while the relative numbers of the two species are as 1 to 5, the relative
advantage from their resemblance is as 25 to 1.

If two or more distasteful species are equally numerous, their re-
semblance to one another brings nearly equal advantages. In cases of
this kind — and many are known — it is sometimes impossible to dis-
tinguish between model and mimic, as all the participants seem to have
converged toward a common protective appearance, through an inter-
change of features — the " reciprocal mimicry" of Dr. Dixey.

Marshall argues, however, against this diaposematism, maintaining
that in the case of two participants in Mullerian mimicry the evolution
of the mimetic pattern has been in one direction only — toward the more
abundant species — any variations in the opposite direction being dis-
advantageous.

ENTOMOLOGY

From this explanation, the superior value of MiillerifM) as compared
with Batesian mimicry is evident.

The fourth condition — that the imitators differ from the bulk of
their allies-r-holds true to such a degree that even the^wo sexes of the
same species may differ extremely in coloration, owing to the fact that
the female has assumed the likeness of some other and protected species.
The female of Papilio cenea, indeed, occurs (as was just mentioned)
under three varieties, which mimic respectively three entirely dissimilar
species of Danais, and none of the females are anything like their male
in coloration.

The generally accepted explanation for these remarkable but numer-
ous cases in which the female alone is mimetic, is that the female, bur-
dened with eggs and consequently sluggish in flight and much exposed
to attack, is benefited by imitating a species which is immune; while
the male has had no such incentive — so to speak —
to become mimetic. Of course, there has been no
conscious evolution of mimicry.

Wallace's fifth stipulation is important, but should
^ read this way: " The imitation, however minute, is but
Fig 246 — \ external and visible usually, and never extends to in-
locustid, Myrme- ternal characters which do not affect the external ap-

cophana f a Uai v, which * ,, _ _ . .

resembles an ant. pearance. For, as Poulton points out, the alertness
From SuntoTvon 0±" a beetle which mimics a wasp, implies appropriate
Wattenwyl. changes in the nervous and muscular systems. In

its intent, however, Wallace's rule holds good, and
by disregarding it some writers strain the theory of mimicry beyond
reasonable limits. Some have said, for example, that the resem-
blance between caddis flies and moths is mimicry; when the fact is
that this resemblance is not merely superficial but is deep-seated; the
entire organization of Trichoptera shows that they are closely related
to Lepidoptera. This likeness expresses, then, not mimicry, but affinity
and parallel development. The same objection applies to the assumed
cases of mimicry within the limits of a single family, as between two
genera of Heliconiidae or between the chrysomelid genera Lema and
Diabrotica. The more nearly two species are related to each other, the
more probable it becomes that their similarity is due — not to mimicry — but
to their common ancestry.

On the other hand, the resemblance frequently occurs between species
of such different orders that it cannot be attributed to affinity. Illus-
trations of this are the mimicry of the honey bee by the drone fly, and

ADAPTIVE COLORATION

189

the many other instances in which stinging Hymenoptera are counter-
feited by harmless flies or beetles. A locustid of the Soudan resembles
an ant (Fig. 246), and the resemblance, by the way. is obtained in a
most remarkable manner. Upon the stout body of this orthopteron
the abdomen of an ant is delineated in black, the rest of the body being
light in color and inconspicuous by contrast with the black. Indeed
the various means by which a superficial resemblance is brought about
between remotely related insects are often extraordinary.

Irrespective of affinity, insects of diverse orders may converge in
wholesale numbers toward a central protected form. The most com-
plete examples of this have been brought to light by Marshall and
Poulton, in their splendid work on the bionomics of South African
insects, in which is given, for instance, a colored plate showing how
closely six distasteful and dominant beetles of the genus Lycus are imi-
tated by almost forty species of other genera— a remarkable example of
convergence involving no less than eighteen families and five orders,
namely, Coleoptera. Hymenoptera, Hemiptera, Lepidoptera and Diptera.
Excepting a few unprotected, or Batesian, mimics (a fly and two or
three beetles), this association is one between species that are already
protected, by stings, bad tastes or other peculiarities. In other words,
here is Miillerian mimicry on an immense scale; and if Miillerian mim-
icry is profitable when only two species are concerned, what an enormous
benefit it must be to each of forty participants !

Strength of the Theory. — Evidently the theory of mimicry rests
upon the assumption that the mimics, by virtue of their mimicry, are
specially protected from insectivorous foes. Until the last few years,
however, there was altogether too little positive evidence bearing upon
the assumption itself, though this was supported by such scattered ob-
servations as were available. The oft-repeated assertion that this lack
of evidence was due simply to inattention to the subject, has been proved
to be true by the decisive results recently gained in the tropics by several
competent investigators who have been able to give the subject the
requisite amount of attention.

From his observations and experiments in India, Frank Finn con-
cludes:

"1. That there is a general appetite for butterflies among insec-
tivorous birds, even though they are rarely seen when wild to attack
them.

"2. That many, probably most, species dislike, if not intensely, at
any rate in comparison with other butterflies, the warningly-colored

ENTOMOLOGY

Danaina?, Acraza viola, Delias eucharis, and Papilio aristolochice; of
these the last being the most distasteful, and the Danainse the least so.

"3. That the mimics of these are at any rate relatively palatable,
and that the mimicry is commonly effectual under natural conditions.

"4. That each bird has separately to acquire its experience, and well
remembers what it has learned.

"That therefore on the whole, the theory7 of Wallace and Bates is
supported by the facts detailed in this and my former papers, so far as
they deal with birds (and with the one mammal used). Professor
Poulton's suggestion that animals may be forced by hunger to eat un-
palatable forms is also more than confirmed, as the unpalatable forms
were commonly eaten without the stimulus of actual hunger — generally,
also, I may add, without signs of dislike."

Though insects have many vertebrate and arthropod enemies, it is
probable that the evolution of mimetic resemblance, implying warning
coloration, has been brought about chiefly by insectivorous birds.

Neglecting papers of minor importance, we may pass at once to the
most important contribution upon this subject — the voluminous work
of Marshall and Poulton upon mimicry and warning colors in South
African insects. These investigators have found that birds are to be
counted as the principal enemies of butterflies; that the Danainse and
Acrseinse, which are noted as models, are particularly immune from de-
struction, while unprotected forms suffer; and that mimicking, though
palatable, species share the freedom of their models. The same is true
of beetles, of which Coccinellidae. Malacodeirnidae (notably Lycus),
Cantharidae and many Chrysomelidae serve as models for many other
Coleoptera, being "conspicuous and constantly refused by insect-
eaters." In short, the splendid work of Marshall and Poulton tends to
place the theory of Batesian and Mullerian mimicry upon a substantial
foundation of observational and experimental evidence.

In regard to the important question — do birds avoid unpalatable
insects instinctively or only as the result of experience — the evidence is
all one way. Several investigators, including Lloyd Morgan, have
found that newly-hatched birds have no instinctive aversions as regards
food, but test everything, and (except for some little parental guidance)
are obliged to learn for themselves what is good to eat and what is not.
This experimental evidence that the discrimination of food by birds
is due solely to experience, was evidently highly necessary to place the
theory of mimicry — especially the Mullerian theory — upon a sound
basis.

ADAPTIVE COLORATION

I9I

Though butterflies as a group are much subject to the attacks of
birds in the tropics, it has been asserted that butterflies in temperate
regions are as a whole almost exempt from the attacks of birds, and that
consequently the mimicry of the monarch (Fig. 244) by the viceroy is
of no advantage. In answer to this assertion Marshall has published a
long list of references showing that butterflies are attacked by birds
more commonly than has been generally supposed. At the same time
there is no proof that the viceroy profits at present by its mimetic pattern,
though it may have done so in the past. In any event, the departure of
ar chip pus from its congeners toward one of the Danainae — a famous
group of "models" in the tropics — is unintelligible except as an instance
of mimicry.

Granting that mimicry is upon the whole advantageous, it becomes
important to learn just how far the advantage extends; and we find that
mimicry is not of universal effectiveness. Even the highly protected
Heliconiinae and Danainae are food for some predaceous insects. In
this country, as Judd has observed, the drone-fly {Eristalis tenax), which
mimics the honey bee, is eaten by the kingbird and the phcebe; the
kingbird, indeed, eats the honey bee itself, but is said to pick out the
drones; chickens also discriminate between drones and workers, eating
the former and avoiding the latter. Bumble bees and wasps, imitated
by many other insects, are themselves eaten by the kingbird, catbird and
several other birds, though it is not known whether the stingless males
of these are singled out or not. Such facts as these do not discredit the
general theory of mimicry but point out its limits.

Evolution of Mimicry. — Natural selection gives an adequate ex-
planation of the evolution of a mimetic pattern. Before accepting this
explanation, however, we must inquire: (1) What were the first stages
in the development of a mimetic pattern? (2) What evidence is there
that every step in this development was vitally useful, as the theory de
mands that it should be? These pertinent questions have been answered
by Darwin, Wallace, Mtiller, Dixey and several other authorities.

The incipient mimic must have possessed, to begin with, colors or
patterns that were capable of mimetic development; evidently the raw
material must have been present. Now Miiller and Dixey in particular
have called attention to the fact that many pierids have at least touches
of the reds, yellows and other colors that are so conspicuous in the heli-
conids. More than this, however, Dixey has demonstrated — as appears
clearly from his colored figures — a complete and gradual transition from
a typical non-mimetic pierid, Pieris locusta, to the mimetic pierid

ENTOMOLOGY

Mylothris pyrrlia. the female of which imitates Heliconius numata. He
traces the transition chiefly through the males of several pierid species —
for the males, though for the most part white (the typical pierid color),
"show on the under surface, though in varying degrees, an approach
towards the Heliconiine pattern that is so completely imitated by their
mates. These partially developed features on the under surface of the
males enable us to trace the history of the growth of the mimetic pattern."
Starting from Pieris locusta, it is an easy step to Mylothris lypera, thence
to M. lorena, and from this to the mimetic M. pyrrha. ''Granted a
beginning, however small, such as the basal red touches in the normal
Pierines. an elaborate and practically perfect mimetic pattern may be
evolved therefrom by simple and easy stages."

Furthermore (in answer to the second question), it does not tax the
imagination to admit that any one of these color patterns has — at least
occasionally — been sufficiently suggestive of the heliconid type to pre-
serve the life of its possessor; especially when both bird and insect were
on the wing and perhaps some distance apart, when even a momentary
flash of red or yellow from a pierid might be enough to save it from
attack.

It is highly desirable, of course, that this plausible explanation should
be tested as far as possible by observations in the field and by experiments
as well.

Mimicry and Mendelism. — The weight of evidence is at present
vastly in favor of the theory of mimicry as against any other explanation
of the facts, even though the theory is sometimes stretched to impossible
limits by some of its enthusiastic adherents. The only opposing opinion
that has sufficient plausibility to demand much consideration as yet
is that of Punnett.

In India and Ceylon the butterfly Papilio polytes has in addition to
the normal female a second form of female which mimics P. aristolochice
and a third which imitates P. hector; polytes being palatable to birds
and its two models unpalatable.

This case, described by Wallace almost fifty years ago, is one of the
classic examples of mimicry. Punnett holds, however, that these re-
semblances are of no practical value and that natural selection has played
no part in the formation of these polymorphic forms and suggests that
Mendelism offers a better explanation of the phenomenon— a suggestion
that should be tested experimentally.

Adaptive Colors in General. — Several classes of adaptive colors
have been discriminated and defined by Poulton. whose classification.

ADAPTIVE COLORATION

193

necessarily somewhat arbitrary but nevertheless very useful, is given
below, in its abridged form.

I. APATETIC COLORS. — Colors resembling some part of the environment or
the appearance of another species.
A. Cryptic Colors. — Protective and Aggressive Resemblances.

1. Procryptic colors. — Protective Resemblances. — Concealment as a pro-

tection against enemies. Example: Kallima butterfly.

2. Anticryptic colors. — Aggressive Resemblances. — Concea'ment in order

to facilitate attack. Example: Mantids with leaf-like appendages.
B. Pseudosematic Colors. — False warning and signalling colors.

1. Pseudaposematic colors. — Protective Mimicry. Example: Bee-like fly.

2. Pseudcpisematic colors. — Aggressive Mimicry and Alluring Coloration.

Examples: Volucella, resembling bees (Fig. 247); Flower-like mantid,
II. SEMATIC COLORS.— Warning and Signalling Colors.

1. Aposcmatic colors. — Warning Colors. — Examples: Gaudy colors of

stinging insects.

2. Episematic colors. — Recognition Markings.

III. EPIGAMIC COLORS.— Colors Displayed in Courtship.

Such of these classes as have not already been discussed need brief
reference.

Aggressive Resemblances. — The resemblance of a carnivorous
animal to its surroundings may not only be protective but may also

Fig. 247. — Aggressive mimicry. On the left, a bee, Bombus mastrucatus; on the right, a fly,
Volucella bombylans. Natural size.

enable it to approach its prey undetected, as in the case of the polar bear
or the tiger. Among insects, however, the occurrence of aggressive
resemblance is rather doubtful, even in the case of the leaf-like mantids.

Aggressive Mimicry. — Under this head are placed those cases in
which one species mimics another to which it is hostile. The best known
instance is furnished by European flies of the genus Volucella, whose
larvae feed upon those of bumble bees and wasps. The flies bear a close

194

KNTOMOLOC.Y

resemblance to the bees, owing to which it is supposed that the former
are able to enter the nests of the latter and lay their eggs.

Alluring Coloration. The best example of this phenomenon is
afforded by an Indian mantid, Gongylus gongyloides. which resembles so
perfectly the brightly colored flowers among which it hides that insects
actually fly straight into its clutches.

Recognition Markings. — Though these are apparently important
among mammals and birds, as enabling individuals of the same species
quickly to recognize and follow one another, no special markings for
this purpose are known to occur among insects, not excepting the gregari-
ous migrant species, such as Anosia plexippus and the Rocky Mountain
locust.

Epigamic Colors. — Among birds, frequently, the bright colors of
the male are displayed during courtship, and their evolution has been
attributed by Darwin and many of his followers to sexual selection — a
highly debatable subject. Among insects, however, no such phenomenon
has been found; whenever the two sexes. differ in coloration the difference
does not appear to facilitate the recognition of even one sex by the other.

Evolution of Adaptive Coloration. — Natural selection is the only
theory of any consequence that explains the highly involved phenomena
of adaptive coloration. Against such vague and unsupported theories
as the action of food, climate, laws of growth or sexual selection, natural
selection alone accounts for the multitudinous and intricate correlations
of color, pattern, form, attitude, movement, place, time. etc.. that are
necessary to the development of a perfect case of protective resemblance
or mimicry. Natural selection cannot, of course, originate colors or any
other characters, its action being restricted to the preservation and
accumulation of such advantageous variations as may arise, from what-
ever causes. As Poulton says, the vast body of facts, utterly meaning-
less under any other theory, become at once intelligible as they fall har-
moniously into place under the principle of natural selection, to which,
indeed, they yield the finest kind of support.

CHAPTER VII

INSECTS IX RELATION TO PLANTS

Insects, in common with other animals, depend for food primarily
upon the plant world. No other animals, however, sustain such intimate
and complex relations to plants as insects do. The more luxuriant and
varied the flora, the more abundant and diversified is its accompanying
insect fauna.

Xot only have insects become profoundly modified for using all kinds
and all parts of plants for food and shelter, but plants themselves have
been modified to no small extent in relation to insects, as appears in their
protective devices against unwelcome insects, in the curious formations
known as "galls," the various insectivorous plants, and especially the
omnipresent and often intricate floral adaptations for cross-pollination
through the agency of insect visitors. Though insects have laid plants
under contribution, the latter have not only vigorously sustained the
attack but have even pressed the enemy into their own service, as it were.

Numerical Relations. — The number of insect species supported by
one kind of plant is seldom small and often surprisingly large. The
poison ivy (Rhus toxicodendron) is almost exempt from attack, though
even this plant is eaten by a leaf-mining caterpillar, two pyralid larvae
and the larva of a scolytid beetle (Schwarz, Dyar). Horse-chestnut
and buckeye have perhaps a dozen species at most; elm has eighty;
birches have over one hundred, and so have maples; pines are known to
harbor 170 species and may yield as many more; while our oaks sus-
tain certainly 500 species of insects and probably twice as many. Turn-
ing to cultivated plants, the clover is affected, directly or indirectly, by
about 200 species, including predaceous insects, parasites, and flower-
visitors. Clover grows so vigorously that it is able to withstand a great
deal of injury from insects. Corn is attacked by about 200 species, of
which 50 do notable injury and some 20 are pests. Apple insects num-
ber some 400 species.

Xot uncommonly, an insect is restricted to a single species of plant.
Thus the caterpillar of Heodes hypophleeas feeds only on sorrel (Rumex ace-
toselld), so far as is known. The chrysomelid Chrysochus auratus appears
to be limited to Indian hemp {'A pocynum andro see mi folium) and to milk-

195

iq6

KNTOMOLOGY

weed (Asclepias). In many instances an insect feeds indifferently upon
several species of plants provided these have certain attributes in com-
mon. Thus Argynnis cybdc. aphrodite and atlantis eat the leaves of
various species of violets, and the Colorado potato beetle eats different
species of Solanum. Papilla thoas feeds upon orange, prickly ash and
other Rutaceae. Anosia plcxippus eats the various species of Asclepias
and also Apocynum androscemijolium; while Chrysochus also is limited
to these two genera of plants, as was said. These plants agree in having
a milky juice; in fact the two genera are rather nearly related botanicallv.
The common cabbage butterfly (Pieris rapes) though confined for the
most part to Crucifera*. such as cabbage, mustard, turnip, radish, horse-

radish, etc.. often develops upon Tro-
ptEoliim, which belongs to Geraniaceae;
all its food plants, however, have a
pungent odor, which is probably the
stimulus to oviposition.

Most phytophagous insects, how-
ever, range over many food plants.
The cecropia caterpillar has more than
sixty of these, representing thirty-one
genera and eighteen orders of plants;
and the tarnished plant bug (Lygus
pratensis) feeds indifferently on all sorts
of herbage, as does also the caterpillar
of Diacrisia virginica. Many of the
insects of apple, pear, quince, plum,
peach, and other plants of the family
Rosaceae occur also on wild plants of
the same family; and the worst of our corn and wheat insects have
come from wild grasses. As regards number of food plants, the gypsy
moth "holds the record." for its caterpillar will eat almost any plant.
In Massachusetts, according to Forbush and Fernald, it fed in the field
upon 78 species of plants, in captivity upon 458 species (30 under stress
of hunger, the rest freely), and refused only 19 species, most of which
(such as larkspur and red pepper) had poisonous or pungent juices, or
were otherwise unsuitable as food. The migratory locust is notoriously
omnivorous, and perhaps eats even more kinds of plants than the gypsy
moth.

Galls. — Most of the conspicuous plant outgrowths known as " galls"
are made by insects, though many of the smaller plant galls are made

Fig. 248. — Holcaspis globulus. 4
galls on oak. natural size; B. the gall
maker, twice natural length.

INSECTS IN RELATION TO PLANTS

197

by mites (Acarina) and a few plant excrescences are due to nematode
worms and to fungi.

Among insects, Cynipidae (Hymenoptera) are pre-eminent as gall-

FiG. 249. — Galls of Holcaspis duricoria, on oak. Natural size.

makers and next to these, Cecidomyiidae (Diptera), Aphididae and
Psyllidae (Hemiptera)^ a few gall-insects occur among Tenthredinidae
(Hymenoptera) and Trypetidae (Diptera),
and one or two among Coleoptera and Lepi-
doptera.

Cynipidae affect the oaks (Figs. 248, 249)
far more often than any other plants, though
not a few species select the wild rose. Ceci-
domyiid galls occur on a great variety of
plants, and those of aphids on elm (Fig. 250),
poplar, and many other plants; while psyllid
galls are most frequent on hackberry. The
galls may occur anywhere on a plant, from
the roots to the flowers or seeds, though each
gall-maker always works on the same part of
its plant, — root, stem, bud, leaf, leaf-vein,
flower, seed, etc.

Galls present innumerable forms, but the
form and situation of a gall are usually char-
acteristic, so that it is often possible to classify
galls as species even before the gall-maker is
known.

Gall-Making. — The female simply lays the egg on the epidermis, or
else punctures the plant and deposits an egg in or near the cambium, or any
other tissue capable of growth; the egg hatches and the surrounding plant
tissue is stimulated to grow rapidly and abnormally into a gall, which

Fig. 250. — Cockscomb
of Colopha ulmicola, on
Slightly reduced.

gall
elm.

i g8

ENTOMOLOGY

serves as food for the larva; this transforms within the gall and escapes
as a winged insect. The physiology of gall-formation is far from being
understood. It has been found that the mechanical irritation from the
ovipositor is not the initial stimulus to the development of a gall; neither
is the fluid which is injected by the female during oviposition. this fluid
being probably a lubricant; if the egg is removed, the gall does not
appear. Ordinarily the gall does not begin to grow until the egg has
hatched, and then the gall grows along with the larva; exceptions to
this are found in some Tenthredinidae in which the egg itself increases
in volume, when the gall may grow with the egg. It appears that the
larva exudes some fluid which acts upon the protoplasm of certain plant
cells (the cambium and other cells capable of further growth and multi-
plication) in such a way as to stimulate their increase in size and number.
The following recent observations on this subject by A. Cosens are im-
portant. The cells of the plant that immediately surround the larva
are known as nutritive cells. In Cynipidae the larva gradually with-
draws the contents of these cells, by means of the mouth and not by
absorption, and the cells gradually collapse. The proportion of sugar
to starch decreases from the inside of the nutritive zone (nearest the
larva) to the outside. This is owing to an enzyme that changes starch
into sugar, the source of this enzyme being probably a pair of salivary
glands that open externally on each side just below the mouth of the
larva. The larva by accelerating the rate of change from starch to
sugar renders available to the plant more food than usual and therefore
stimulates the activity of the protoplasm toward greater cell-growth
and more rapid cell-reproduction. Thus the gall as well as the larva
draws food from the nutritive zone.

Why the gall should have a distinctive, or specific, form, it is not yet
known. There is no evidence that the form is of any adaptive impor-
tance, and the subject probably admits of a purely mechanical explana-
tion. One factor in determining the form of the gall is the direction in
which the stimulus is applied ; a spherical cynipid gall arising when the
influence is about equally distributed in all directions (Cosens).

Gall Insects. — The study of gall insects is in many respects difficult.
It is not at all certain that an insect which emerges from a gall is the
species that made it; for many species, even of Cynipidae. make no galls
themselves but lay their eggs in galls made by other species. Such
guest-insects are termed inquilines. Furthermore, both gall-makers
and inquilines are attacked by parasitic Hymenoptera. making the in-
terrelations of these insects hard to determine. Many species of insects

INSECTS IN RELATION TO PLANTS

199

feed upon the substance of galls ; thus Sharp speaks of as many as thirty
different kinds of insects, belong to almost all the orders, as having been
reared from a single species of gall.

Parthenogenesis and Alternation of Generations. — Partheno-
genesis has long been known to occur among Cynipidae. It has repeat-
edly been found that of thousands of insects emerging from galls of the
same kind, all were females. In one such instance the females were
induced by Adler to lay eggs on potted oaks, when it was found that the
resulting galls were quite unlike the original ones, and produced both
sexes of an insect which had up to that time been regarded as another
species. Besides parthenogenesis and this alternation of generations,
many other complications occur, making the study of gall-insects an
intricate and highly interesting subject.

Plant-Enemies of Insects. — Most of the flowering plants are com-
paratively helpless against the attacks of insects, though there are many
devices which prevent ''unwelcome" insects from entering flowers, for
instance the sticky calyx of the catchfly (Silene virginica), which
entangles ants and small flies. A few plants, however, actually feed upon
insects themselves. Thus the species of Drosera, as described in Dar-
win's classic volume on insectivorous plants, have specialized leaves for
the purpose of catching insects. The stout hairs of these leaves end
each in a globular knob, which secretes a sticky fluid. When a fly alights
on one of these leaves the hairs bend over and hold the insect; then a
fluid analogous to the gastric juice of the human stomach exudes, digests
the albuminoid substances of the insect and these are absorbed into the
tissues of the leaf; after which the tentacles unfold and are ready for the
next insect visitor. The Venus's flytrap is another well known example;
the trap, formed from the terminal portion of a leaf, consists of two
valves, each of which bears three trigger-like bristles, and when these are
touched by an insect the valves snap together and frequently imprison
the insect, which is eventually digested, as before. In the common
pitcher-plants, the pitcher, fashioned from a leaf, is lined with downward
pointing bristles, which allow an insect to enter but prevent its escape.
The bottom of the pitcher contains water, in which may be found the
remains of a great variety of insects which have drowned. There are
even nectar glands and conspicuous colors, presumably to attract in-
sects into these trapes, where their decomposition products are more or
less useful to the plant. In Pinguicula the margin of a leaf rolls over
and envelops insects that have been caught by the glandular hairs of the
upper surface of the leaf, a copious secretion digests the softer portions of

200

ENTOMOLOGY

the insects, and the dissolved nitrogenous matter is absorbed into the
plant. Utricularia has little bladders which entrap small aquatic in-
sects. These plants are only partially dependent on insect-food, how-
ever, for they all possess chlorophyll.

Bacteria cause epidemic diseases among insects, as in the flacherie of
the silkworm; and fungi of a few groups are specially
adapted to develop in the bodies of living insects.

Those who rear insects know how frequently cater-
pillars and other larvae are destroyed by fungi that
give the insects a powdered appearance. These fungi,
/ II referred to the genus Isaria, are in some cases known

to be asexual stages of forms of Cordyceps, which forms
appear from the bodies of various larvae, pupae and
imagines as long, conspicuous, fructifying sprouts (Fig.

251).

The chief fungus parasites of insects belong to
the large family Entomophthoraceae, represented by
the common Empusa muscce (Fig. 252) which affects
various flies. In autumn, especially in warm moist
weather, the common house fly may often be seen in a
dead or dying condition, sticking to a window-pane, its
abdomen distended and presenting alternate black and
white bands, while around the fly at a little distance
is a white powdery ring, or halo. The white interseg-
mental bands are made by threads of the fungus just
named, and the white halo by countless asexual spores
known as conidia, which have been forcibly discharged
from the swollen threads that bore them (Fig. 252) by
pressure, resulting probably from the absorption of
moisture. These spores, ejected in all directions, may
infect another fly upon contact and produce a growth
of fungus threads, or hyphce, in its body. The fungus
may be propagated also by means of resting spores,
as found by Thaxter, our authority upon the fungi of insects.

Empusa aphidis is very common on plant lice and is an important
check upon their multiplication. Aphids killed by this fungus are
found clinging to their food plant, with the body swollen and discolored.
Empusa grylli attacks crickets, grasshoppers, caterpillars and other
forms. Curiously enough, grasshoppers affected by this fungus almost
alwavs crawl to the top of some plant and die in this conspicuous position.

Fig. 251. — Fruc-
tifying sprouts of
a fungus. Cordyceps
ravenclii, arising
from the body of a
white grub, Lachno-
stcrna. Slightly
reduced. — After
Riley.

INSECTS IN RELATION TO PLANTS

20I

Sporotrichutn, a genus of hyphomycetous fungi, affects a great variety
of insects, spreading within the body of the host and at length emerging
to form on the body of the insect a dense white felt-like covering, this
consisting chiefly of myriads of spores, by means of which healthy in-
sects may become infected. Under favorable conditions, especially in
moist seasons, contagious fungus diseases constitute one of the most
important checks upon the increase of insects and are therefore of vast
economic importance. Thus the termination (in 1889) of a disastrous
outbreak of the chinch bug in Illinois and neighboring states "was ap-
parently due chiefly, if not altogether, to parasitism by fungi." Arti-

Fig. 252. — Empusa muscce, the common fly-fungus. A, house fly (Afusca domestica), sur-
rounded by fungus spores (conidia); B, group of conidiophores showing conidia in several
stages of development; C, basidium {b) bearing conidium (r) before discharge. B and C
after Thaxter.

facial cultures of the common S porotrichum globidij'erum have been used
extensively as a means of spreading infection among chinch bugs and
grasshoppers, with, however, but moderate success as yet.

Insects in Relation to Flowers. — Among the most marvelous
phenomena known to the biologist are the innumerable and complex
adaptations by means of which flowers secure cross pollination through
the agency of insect visitors. Cross fertilization is actually a necessity
for the continued vigor and fertility of flowering plants, and while some
of them are adapted for cross pollination by wind or water, the majority
of flowering plants exhibit profound modifications of floral structure for
compelling insects (and a few other animals, as birds or snails) to carry

202

KXTOMOLOCY

pollen from one flower to another. In general, the conspicuous colors
of flowers are for the purpose of attracting insects, as are also the odors
of flowers. Night-blooming flowers are often white or yellow and as. a
rule strongly scented. Colors and odors, however, are simply indica-
tions to insects that edible nectar or pollen is at hand. Such is the usual
statement, and it is indeed probable that insects actually do associate
color and nectar, even though they will fly to bits of colored paper almost
as readily as they will to flowers of the same colors. It is not to be sup-

Fig. 253. — Bumble bee (Bombus) entering flower of blue-flag (Iris versicolor). Slightly

reduced.

posed, however, that insects realize that they confer any benefit upon
the plant in the flowers of which the}" And food. At any rate, most
flowers are so constructed that certain insects cannot get the nectar or
pollen without carrying some pollen away, and cannot enter the next
flower of the same kind without leaving some of this pollen upon the
stigma of that flower. Take the iris, for example, which is admirably
adapted for pollination by a few bees and flies.

Iris. — In the common blue-flag {Iris versicolor. Fig. 253) each of the

INSECTS IX RELATION TO PLANTS

203

three drooping sepals forms the floor of an arched passageway leading
to the nectar. Over the entrance and pointing outward in a movable
lip (Fig. 254, /), the outer surface of which is stigma tic. An entering
bee hits and bends down the free edge of this lip, which scrapes pollen
from the back of the insect and then springs back into place. Within
the passage, the hairy back of the bee rubs against an overhanging anther
(an) and becomes powdered with grains of pollen as the insect pushes
down towards the nectar. As the bee backs out of the passage it en-
counters the guardian lip again, but as this side of the lip can not re-
ceive pollen, immediate close pollination
is prevented. Of course, it is possible for
bees to enter another part of the same
flower or another flower of the same plant,
but as a matter of fact, they habitually
fly away to another plant; moreover, as
Darwin found, foreign pollen is prepotent
over pollen from the same flower. It may
be added that bees and other pollenizing
insects ordinarily visit in succession several
flowers of the same kind.

Orchids. — The orchids, with their
fantastic forms, are really elaborate traps
to insure cross pollination. In some
orchids (Habenaria and others) the nec-
tar, lying at the bottom of a long tube,
is accessible only to the long-tongued
Sphingida\ While probing for the nectar,
a sphinx moth brings each eye against a
sticky disk to which a pollen mass is
attached, and flies away carrying the mass
on its eye. Then these pollinia bend down
on their stalks in such a way that when

the moth thrusts its head into the next flower they are in the proper
position to encounter and adhere to the stigma. The orchid Angr cecum
sesqui pedalc. of Madagascar, has a nectary tube more than eleven inches
long, from which Darwin inferred the existence of a sphinx moth with a
tongue equally long.

Milkweed. — The various milkweeds are fascinating subjects to the
student of the interrelations of flowers and insects. The flowers, like
those of orchids, are remarkably formed with reference to cross pollina-

Fig. 254. — Section to illustrate
cross pollination of Iris, an,
anther; /, stigmatic lip; n,
nectary; s, sepal.

204

ENTOMOLOGY

tion by insects. As a honey bee or other insect crawls over the flowers
(Fig. 255, A) to get the nectar, its legs slip in between the peculiar nec-
tariferous hoods situated in front of each anther. As a leg is drawn up-
ward one of its claws, hairs, or spines frequently catches in a V-shaped
fissure (f. Fig. 255, B) and is guided along a slit to a notched disk, or cor-
puscle (Fig. 255, C, d). This disk clings to the leg of the insect, which
carries off by means of the disk a pair of pollen masses, or pollinia (Fig.
255, C). When first removed from their enclosing pockets, or anthers,
these thin spatulate pollinia lie each pair in the same plane, but in a few
seconds the two pollinia twist on their stalks and come face to face in
such a wTay that one of them can be easily introduced into the stigmatic

Fig. 255. — Structure of milkweed flower {Asdepias incarnata) with reference to cross
pollination. A, a single flower; e, corolla; h, hood; B, external aspect of fissure (/) leading
up to disk and also into stigmatic chamber; //, hood; C, pollinia; d, disk. Enlarged.

chamber of a new flower visited by the insect. Then the struggles of the
insect ordinarily break the stem, or retinaculum , of the pollinium and
free the insect. Often, however, the insect loses a leg or else is per-
manently entrapped, particularly in the case of such large-flo\vered
milkweeds as Asdepias cornuti, which often captures bees, flies and
moths of considerable size. Pollination is accomplished by a great
variety of insects, chiefly Hymenoptera, Diptera, Lepidoptera and Cole-
optera. These insects when collected about milkweed flowers usually
display the pollinia dangling from their legs, as in Fig. 256.

The details of pollination may be gathered by a close observer from
observations in the field and may be demonstrated to perfection by using
a detached leg of an insect and dragging it upward between two of the

INSECTS IX RELATION TO PLANTS

Fig. 256. — A wasp, Sphcx ichncu-
monea, with pollinia of milkweed
attached to its legs. Slightly en-
larged.

hoods of a flower; first to remove the pair of pollinia and then again
to introduce one of them into an empty stigmatic chamber.

Yucca. — An extraordinary example of the interdependence of plants
and insects was made known by Riley,
whose detailed account is here summa-
rized. The yuccas of the southern United
States and Mexico are among the fewT
plants that depend for pollination each
upon a single species of insect. The
pollen of Yucca filamentosa cannot be
introduced into the stigmatic tube of
the flower without the help of a little
white tineid moth. Pronuba yuccasella,
the female of which pollenizes the flower
and lays eggs among the ovules, that
her larvae may feed upon the young
seeds. While the male has no unusual

structural peculiarities, the female is adapted for her special work by
modifications which are unique among Lepidoptera, namely, a pair of

prehensile and spinous maxillary
''tentacles" (Fig. 257, A) and a
long protrusible ovipositor (B)
which combines in itself the func-
tions of a lance and a saw.

The female begins to work
soon after dark, and will con-
tinue her operations even in the
light of a lantern. Clinging to a
stamen (Fig. 258) she scrapes off
pollen with her palpi and shapes
it into a pellet by using the front
legs. After gathering pollen from
several flowers she flies to another
flower, as a rule, thrusts her long
flexible ovipositor into the ovary
(Fig. 259) and lays a slender egg
alongside seven or eight of the
ovules. After laying one or more
eggs she ascends the pistil and actually thrusts pollen into the stigmatic
tube and pushes it in firmly. The ovules develop into seeds, some of

Fig. 257. — Pronuba yuccasella. A , maxillary
tentacle and palpus; B, ovipositor. — After
Riley. Figures 257-259 are republished from
the Third Report of the Missouri Botanical
Garden, by permission.

206

K.\T( ).M ()!.()( ;Y

which are consumed by the larvae, though plenty are left to perpetuate
the plant itself. Three species of Pronuba are known, each restricted to
particular species of Yucca. Riley says that Yucca never produces seed
where Pronuba does not occur or where she is excluded artificially, and
that artificial pollination is rarely so successful as the normal method.

Why does the insect do this ? The little nectar secreted at the base
of the pistil appears to be of no consequence, at present, and the stigmatic
fluid is not nectarian; indeed, the tongue of Pronuba, used in clinging to
the stamen, seems to have lost partially or entirely its sucking power,
and the alimentary canal is regarded as functionless. Ordinarily it is
the flower which has become adapted to the insect, which is enticed by

Fig. 258. — Pronuba yuccasclla, fe- Fig. 259. — Pronuba moth ovipositing in flower of
male, gathering pollen from anthers of Yucca. Slightly reduced.

Yucca. Enlarged.

means of pollen or nectar, but here is a flower which — though entomo-
philous in general structure — has apparently adapted itself in no way
to the single insect upon which it is dependent for the continuance of its
existence. More than this, the insect not only labors without compensa-
tion in the way of food, but has even become highly modified with refer-
ence to the needs of the plant, — its special modifications being unparal-
leled among insects with the exception of bees, and being more puzzling
than the more extensive adaptations of the bees when we take into con-
sideration the impersonal nature of the operations of Pronuba. Further
investigation may render these extraordinary interrelations more in-
telligible than they are at present.

INSECTS IX RELATION TO PLANTS

207

The bogus Yucca moth (Prodoxus quinquc punctella) closely resembles
and associates with Pronuba but oviposits in the flower stalks of Yucca
and has none of the special adaptive structures found in Pronuba.

As regards floral adaptations, these examples are sufficient for present
purposes; many others have been described by the botanist; in fact, the
adaptations for cross pollination by insects are as varied as the flowers
themselves.

Insect Pollenizers. — The great majority of entomophilous flowers
are pollenized by bees of various kinds; the apple, pear, blackberry,
raspberry and many other rosaceous plants depend chiefly upon the
honey bee, while clover cannot set seed without the aid of bumble bees
or honey bees, assisted possibly by
butterflies. Lilies and orchids fre-
quently employ butterflies and
moths, as well as bees, and the
milkweed is adapted in a remark-
able manner for pollination by
butterflies, moths and some wasps,
as was described. Honeysuckle,
lilac, azalea, tobacco, Petunia,
Datura and many other strongly
scented and conspicuous nocturnal
flowers attract for their own uses
the long-tonged sphinx moths (Fig.
260); the evening primrose, like
milkweed, is a favorite of noctuid
moths. Umbelliferous plants are
pollenized chiefly by various flies,

but also by bees and wasps. Pond lilies, golden rod and some other flowers
are pollenized largely by beetles, though the flowers exhibit no special
modifications in relation to these particular insects. It is noteworthy
that pollination is performed only by the more highly organized insects,
the bees heading the list.

Of all the insects that haunt the same flower, it frequently happens
that only a few are of any use to the flower itself; many come for pollen
only; many secure the nectar illegitimately; thus bumble bees puncture
the nectaries of columbine, snapdragon and trumpet creeper from the
outside, and wasps of the genus Odynerus cut through the corolla of
Pentestemon laroigatus, making a hole opposite each nectary; then there
are the many insects that devour the floral organs, and the insects which

Fig. 260.

Phlegethontius sexta visiting flower
of Petunia. Reduced.

208

KXTOM()l.< K i Y

are predaceous or [parasitic upon the others. In the Iris, according to
Xeedham, two small bees (Clisodon tvrminalis and Osmia distinda) are
the most important pollenizers, and next to them a few syrphid flies,
while bumble bees also are of some importance. The beetle Trickius
piger and several small flies obtain pollen without assisting the plant,
and Pamphila, Eudamus. Clirysophanus and some other butterflies
succeed after many trials in stealing the nectar from the outside (Fig. 261 ).
A weevil {Mononychus vulpecidus) punctures the nectary, and the flowing

Fig. 261. — A butterfly. P elites peckius, stealing nectar from a flower of Iris versicolor. Slightly

reduced.

nectar then attracts a great variety of insects. Grasshoppers and cater-
pillars eat the flowers, an ortalid fly destroys the buds, and several par-
asitic or predaceous insects haunt the plant; in all. over sixty species of
insects are concerned in one way or another with the Iris.

Modifications of Insects with Reference to Flowers.— While
the manifold and exquisite adaptations of the flower for cross pollination
have engaged universal attention, very little has been recorded concern-
ing the adaptations of insects in relation to flowers. In fact, the adapta-
tion is largely one-sided; flowers have become adjusted to the structure

INSECTS IN RELATION TO PLANTS 2O0,

of insects as a matter of vital necessity — to put it that way — while in-
sects have had no such urgent need — so to speak — in relation to floral
structure. They have been influenced by floral structure to some extent,
however, and in some cases to a very great extent, as appears from their
structural and physiological adaptations for gathering and using pollen
and nectar.

Among mandibulate insects, beetles and caterpillars that eat the
floral envelopes show no special modifications for this purpose; pollen-
feeding beetles, however, usually have the mouth parts densely clothed
with hairs, as in Euphoria (Fig. 262). In suctorial insects, the mouth

Fig. 262. — A, right mandible; J5, right maxilla; C, Fig. 263. — Pollen-gather-
hypopharynx, of a pollen-eating beetle, Euphoria inda. En- ing hair from a worker honey
larged. (The mandibles are remarkable in being two-lobed.) bee, with a pollen grain at-
tached. Greatly magnified.

parts are frequently formed with reference to floral structure; this is the
case in many butterflies and particularly in Sphingidae. in which the
length of the tongue bears a direct relation to the depth of the nectary
in the flowers that they visit. According to Muller, the mouth parts of
Syrphidae, Stratyomyiidae and Muscidae are specially adapted for feed-
ing on pollen. In Apidae, the tongue as compared with that of other
Hymenoptera, is exceptionally long, enabling the insect to reach deep
into a flower, and is exquisitely specialized (Fig. 127) for lapping up and
sucking in nectar.

Pollen-gathering flies and bees collect pollen in the hairs of the body
or the legs; these hairs, especially dense and often twisted or branched

!5

2 I O ENTOMOLOGY

(Figs. 263, 89) to hold the pollen, do not occur on other than pollen-
gathering species of insects. Caudell found that out of 200 species of
Hymenoptera only 23 species had branched hairs and that these species
belonged without exception to the pollen-gathering group Anthophila.
no representative of which was found without such hairs. Similar
branched hairs occur also on the flower-frequenting Bombyliidae and
Syrphida?.

The most extensive modifications in relation to flowers are found in

Fig. 264. — Adaptive modifications of the legs of the worker honey bee. A . outer aspect of
left hind leg; B, portion of left middle leg; C, inner aspect of tibio-tarsal region of left hind
leg; D, tibio-tarsal region of left fore leg; a, antenna comb; an, auricle; 6, brush; c, coxa;
co, corbiculum; /, femur; p, pecten; pc, pollen combs; s, spur; sp, spines; 55. spines; /,
trochanter; //.tibia; v, velum; w, so-called wax pincers; 1-5, tarsal segments; 1. metatarsus,
or planta.

Promiba, as already described, and above all in Apidae. especially the
honey bee.

Honey Bee. — The thorax and abdomen and the bases of the legs
are clothed with flexible branching hairs (Fig. 263), which entangle
pollen grains. These are combed out of the gathering hairs by means
of special pollen combs (Fig. 264. C, pc) on the inner surface of the planta
of the hind tarsus, the middle legs also assisting in this operation. From
these combs, the pollen is transferred to the pollen baskets, or corbicula
(Fig. 264, A, co), of the outer surface of each hind tibia, the pollen from

INSECTS EN RELATION TO PLANTS

211

one side being transferred to the corbiculum of the opposite side. This
is accomplished in the following manner: the left pecten combs out the
pollen from the right planta and a mass of pollen forms just above the
left pecten at the lower end of the corbiculum; this mass gradually
grows larger and is pushed up along the corbiculum by the upward
movement of the auricle: Further details are given by Casteel, whose
admirably precise and thorough studies on the manipulation of pollen
and wax by the honey bee have corrected certain prevalent errors and
added much to our knowledge of the subject. Arriving at the nest, the
hind legs are thrust into a cell and the mass of pollen on each corbiculum
is pried out by means of a spur situated at the apex of the middle tibia
(Fig. 264, B, s), this lever being slipped in at the upper end of the corbicu-
lum and then pushed along the tibia under the mass of pollen; the spur is
used also in cleaning the wings, which explains its presence on queen
and drone, as well as worker, but the pollen-gathering structures of the
hind legs are confined to the worker. The so-called wax-pincers of the
hind legs (Fig. 264, A, C, w) at the tibio-tarsal articulation, have nothing
to do with the transfer of wax scales from the abdomen to the mouth,
according to Casteel; a wax scale being removed from its pocket by
becoming impaled on stiff spines at the distal end of the inner face of the
planta.

For cleaning the antennae, a front leg is passed over an antenna,
which slips into a semicircular scraper (Fig. 264, D, a) fashioned from the
basal segment of the tarsus; when the leg is bent at the tibio-tarsal
articulation, an appendage, or velum (v) of the tibia falls into place to
complete a circular comb, through which the antenna is drawn. This
comb is itself cleaned by means of a brush of hairs (b) on the front margin
of the tibia. A series of erect spines (sp) along the anterior edge of the
metatarsus is used as an eye brush, to remove pollen grains or other
foreign bodies from the hairs of the compound eyes. The labium, hypo-
pharynx and maxillae (Fig. 54) are exquisitely constructed with reference
to gathering and sucking nectar; the maxillae are used also to smooth
the cell walls of the comb; the mandibles (Fig. 45, C), notched in queen
and drone but with a sharp entire edge in the worker, are used for cut-
ting, scraping and moulding wax, as well as for other purposes. The
entire digestive system of the honey bee is adapted in relation to nectar
and pollen as food; the proventriculus forms a reservoir for honey and.
is even provided at its mouth with a rather complex apparatus for strain-
ing the honey from the accompanying pollen grains, as described by
Cheshire. The wax glands (Fig. 102) are remarkable specializations in

212

i:.\T< >M()L< )G\

correlation with the food habits, as are also the various cephalic glands,
the chief functions of which are given as: (i) digestion, as the conversion
of cane sugar into grape sugar, and possibly starch into sugar; (2) the
chemical alteration of wax; (3) the production of special food substances,
which are highly important in larval development.

Numerous special sensory adaptations also occur. In fact, the
whole organization of the honey bee has become profoundly modified
in relation to nectar and pollen. Many other insects have the same food
but none of them sustain such intimiate relations to the flowers as do the
bees.

Ant-Plants. — There are several kinds of tropical plants which are
admirably suited to the ants that inhabit them. Indeed, it is often as-

Fig. 265. — Acacia sphcuroccphaia, an ant-piant. 6, one of the "'Beit's bodies"; g. giand;
5. s, hollow stipular thorns, perforated by ants. — Reduced. — From Strasburger's Lehrbuch
der Botanik.

serted that these plants have become modified with special reference to
their use by ants, though this is a gratuitous and improbable assumption.

Belt found several species of Acacia in Nicaragua and the Amazon
valley which have large hollow stipular thorns, inhabited by ants of the
genus Pseudomyrma. The ants enter by boring a hole near the apex of
a thorn (Fig. 265, s). The plant affords the ants food as well as shelter,
for glands (g) at the bases of the petioles secrete a sugary fluid, while
many of the leaflets are tipped with small egg-shaped or pear-shaped
appendages (b) known as ''Belt's bodies," wmich are rich in albumin,
fall off easily at a touch, and are eaten by the ants. These ants drive
away the leaf-cutting species, incidentally protecting the tree in which
they live.

The ant-trees (Cecropia adcnopus) of Brazil and Central America
have often been referred to by travelers. When one of these trees is

INSECTS IN RELATION TO PLANTS

213

handled roughly, hosts of ants rush out from small openings in the stems
and pugnaciously attack the disturber. Just above the insertion of
each leaf is a small pit (Fig. 266, a, b) where the wall is so thin as to form
a mere diaphragm, through which an ant (probably a fertilized female)
bores and reaches a hollow internode. To establish communication be-
tween the internodal chambers, the ants bore through the intervening
septa (Fig. 267). They seldom leave the Cecropia plant, unless disturbed,
and even keep herds of aphids in their abode. The base of each petiole

Fig. 266. — Portion of young stem of Cecropia adcnopus, Fig. 267. — Cecropia adenopus.

showing internodal pits, a and b. Natural size. Portion of a stem , split so as to show-

Figures 266-268 are from Schimper's Pjlanzcngeographie. internodal chambers and the inter-
vening septa perforated by ants.

bears (Fig. 268) tender little egg-like bodies ("Miiller's bodies") which
the ants detach, store away and eat; the presence of these bodies is a
sure sign that the tree is uninhabited by these ants, which, by the way,
belong to the genus Azteca.

It is too much to assert that the ants protect the Cecropia plant in
return for the food and shelter which they obtain. All ants are hostile
to all other species of ants, with few exceptions, and even to other col-
onies of their own species; so that their assaults upon leaf-cutting ants
are by no means special and adaptive in their nature, and any protec-

214

K \ TOM () Loca-

tion that a plant derives thereby is merely incidental. Furthermore,
hollow stems, glandular petioles and pitted stems are of common oc-
currence when they bear no relation to the needs of ants. These inter-
relations of ants and plants are too often misinterpreted in popular and
uncritical accounts of the subject.

The interesting habits of the leaf-cutting ants in relation to the
plants that they attack are described in a subsequent chapter, where
will be found also an account of the harvesting ants.

Fig. 268. — Cccropia adenopus. Base of Fig. 269. — Hydnophytum montanum. Sec-

petiole showing "Miiller's bodies." tion of pseudo-bulb, to show chambers inhabited
Slightly reduced. by ants. One-fourth natural size. — After Forel.

The epiphytic plants Myrmecodia and Hydnophytum. of Java, form
spongy bulb-like masses, the chambers of which are usually tenanted by
ants, which rush forth when disturbed. These lumps (Fig. 269) are
primarily water-reservoirs, but the ants utilize them by boring into them
and from one chamber into another. In plants of the genus Humboldtia
the ants can enter the hollow internodes through openings that already
exist.

CHAPTER VIII

INSECTS IN RELATION TO OTHER ANIMALS

On the one hand, insects may derive their food from other animals,
either living or dead; on the other hand, insects themselves are food for
other animals, especially fishes and birds, against which they protect
themselves by various means, more or less effective. These topics form
the principal subject of the present chapter.

Predaceous Insects. — Innumerable aquatic insects feed largely or
entirely upon microscopic Protozoa, Rotifera, Entomostraca, etc.; this
is especially the case with culicid and chironomid larvae. Many aquatic
Hemiptera and Coleoptera prey upon planarians. nematodes, annelids,
molluscs and crustaceans; Belostoma sometimes pierces the bodies of tad-
poles and small fishes; Dytiscus also kills young fishes occasionally and is
distinctly carnivorous both as larva and imago. Among terrestrial
insects, Carabidae are notably predaceous, preying not only upon other
insects but also upon molluscs, myriopods. mites and spiders. Ants do
not hesitate to attack all kinds of animals; in the tropics the wandering
ants (Eciton) attack lizards, rats and other vertebrates, and it is said that
even huge serpents, when in a torpid condition, are sometimes killed by
armies of these pugnacious insects.

Mosquitoes affect not only mammals but also, though rarely, fishes
and turtles. The gadflies (Tabanidae) torment horses and cattle by
their punctures; and the black-flies, or buffalo gnats (Simulium), per-
secute horses, mules, cattle, fowls, and frequently become unendurable
even to man. The notorious tsetse fly (Glossina morsitans) of South
Africa spreads a deadly disease among horses, cattle and dogs, by inocu-
lating them with a protozoan blood-parasite, to the effects of which,
fortunately, man is not susceptible.

Parasitic Insects. — Insects belonging to several diverse orders have
become peculiarly modified to exist as parasites either upon or within the
bodies of birds or mammals.

Almost all birds are infested by Mallophaga, or bird lice, of which
Kellogg has catalogued 264 species from 257 species of North American
birds. Sometimes a species of Mallophaga is restricted to a single
species of bird, though in the majority of cases this is not so. Several

215

2l6

K \ ! < IMMI.OOY

mallophagan species often infest a single bird; thus nine species occur
on the hen, and no less than twelve species, representing five genera, on
the American coot. These parasites spread by contact from male to
female, from old to young, and from one bird to another when the birds
are gregarious. When a single species of bird louse occurs on two or
more hosts, these are almost always closely allied, and Kellogg has sug-
gested the interesting possibility that such a species has persisted un-
changed from a host which was the common ancestor of the two or more
present hosts. Mallophaga are not altogether limited to birds, however,
for they may be found on cattle, horses, cats, dogs, and some other
mammals; Kellogg records eighteen species from fifteen species of mam-
mals. These biting lice feed, not upon blood, but upon epidermal cells
and portions of feathers or hairs. They have flat tough bodies (Fig. 17),
with rio traces of wings, and a large head with only simple eyes; the eggs
are glued to feathers or hairs.

Mammals only are infested by the sucking lice, or Pediculidae (Hemip-
tera). These (Fig. 23) have a large oval or rounded abdomen, no wings,
a small head, minute simple eyes or none, and claws that are adapted to
clutch hairs; the eggs are glued to hairs. Sucking lice affect horses,
cattle, sheep, dogs, monkeys, seals, elephants, etc., and man is para-
sitized by three species, namely, the head louse {Pediculus capitis), the
body louse (Pediculus vestimenti) , and the crab louse (Phthirius pubis),
though the first two are possibly the same species.

An anomalous beetle. Platypsyllus castor is, occurs throughout Xorth
America and also in Europe as a parasite of the beaver.

The fleas, allied to Diptera but constituting a distinct order (Siphon-
aptera), are familiar parasites of chickens, cats, dogs and human beings.
These insects (Fig. 30) are wrell adapted by their laterally compressed
bodies for slipping about among hairs, and their saltatory powers and
general elusiveness are well known. Their wings are reduced to mere
rudiments, their eyes when present are minute and simple and their
mouth parts are suctorial.

Among Diptera, there are a few external parasites, the best known
of which is the sheep tick (Melophagus ovinus), though several highly
interesting but little-studied forms are parasitic upon birds and bats.

The larvae of the bot-flies (CEstridae) are common internal parasites of
mammals. The sheep bot-fly (CEstrus ovis) deposits her eggs or larvae on
the nostrils of sheep; the maggots develop in the frontal sinuses of the
host, causing vertigo or even death, and when full grown escape through
the nostrils and pupate in the soil. The horse bot-fly (Gastrophilus equi)

INSECTS IN RELATION TO OTHER ANIMALS

217

glues its eggs to the hairs of horses, especially on the fore legs and shoul-
ders, whence the larvae are licked off and swallowed; once in the stomach,
the bots fasten themselves to its lining, by means of special hooks, and
withstand almost all efforts to dislodge them; though when the bots have
attained their growth they release their hold and pass with the excrement
to the soil. Bots of the genus Hypoderma form tumors on cattle and
other mammals, domesticated or wild. The ox-warble (H. lincata.
Fig. 2ii, /) reaches the oesophagus of its host in the same manner as the
horse bot, according to Curtice, but then makes its way into the sub-
cutaneous tissue and causes the well-known tumors on the back of the
animal; when full grown the bots squirm out of these tumors and drop
to the ground, leaving permanent holes in the hide.

Parasitism in General. — Parasitic insects evidently do not consti-
tute a phylogenetic unit, but the parasitic habit has arisen independently
in many different orders. These insects do, however, agree superficially,
in certain respects, as the result of what may be termed convergence of
adaptation. Thus a dipterous larva, living as an internal parasite, in
the presence of an abundant supply of food, has no legs, no eyes or anten-
nae, and the head is reduced to a mere rudiment, sufficient simply to
support a pair of feeble jaws; the skin, moreover, is no longer armor-like
but is thin and delicate, the body is compact and fleshy, and the digestive
system is of a simplified type. The same modifications are found in
hymenopterous larvae, under similar food-conditions, except that the
head usually undergoes less reduction. The various external parasites
lack wings, almost invariably, and the eyes, instead of being compound,
are either simple or else absent. In some special cases, however, as in a
few dipterous parasites of birds and bats, the wings are present, either
permanently or only temporarily, enabling the insects to reach their
hosts.

This so-called parasitic degeneration, widespread among animals in
general and consisting chiefly in the reduction or loss of locomotor and
sensory functions in correlation with an immediate and plentiful supply
of food, results in a simplicity of organization which is to be regarded —
not as a primitive condition — but as an expression of what is, in one
sense, a high degree of specialization to peculiar conditions of life. This
exquisite degree of adaptation to a special environment, however, sacri-
fices the general adaptability of the animal, — makes it impossible*for a
parasite to adapt itself to new conditions; and while parasitism may be
an immediate advantage to a species, there are few parasites that have
attained any degree of dominance among animals. Ichneumonidae, to

218

KNTOMOLOGY

be sure, are remarkably dominant among insects, but their parasitic
adaptations are limited for the most part to the larval stage and the
adults may be said to be as free for new adaptations as any other
Hymenoptera.

Scavenger and Carrion Insects. Not a few families of Diptera
and Coleoptera derive their food from dead animal matter. The aquatic
families Dytiscidae and Gyrinidae are largely scavengers. Among terres-
trial forms, Silphidae feed on dead animals of all kinds; the burying
beetles (Xecrophorus) , working in pairs, undermine and bury the bodies
of birds, frogs and other small animals, and lay their eggs in the carcasses;
Histeridae and Staphylinidae are carrion beetles, and Dermestidae attack
dried animal matter of almost every description, their depredations upon
furs, feathers, museum specimens, etc., being familiar to all. Ants are
famous as scavengers, destroying decaying organic matter in immense
quantities, particularly in the tropics. Many Scarabaeidae feed upon
excrementitious matter, for example the "tumble-bugs." which are
frequently seen in pairs, laboriously rolling along or burying a large ball
of dung, which is to serve as food for the larva.

Insects as Food for Vertebrates. — Lizards, frogs and toads are
insectivorous, especially toads. The American toad feeds chiefly upon
insects, which form 77 per cent, of its food for the season, the remainder
consisting of myriopods, spiders, Crustacea, molluscs and worms, accord-
ing to the observations of A. H. Kirkland. who states that Lepidoptera
form 28 per cent, of the total insect food, Coleoptera 27, Hymenoptera 19
and Orthoptera 3 per cent. The toad does not capture dead or motion-
less insects but uses its extensile sticky tongue to lick in moving insects
or other prey, which it captures with surprising speed and precision. In
the cities one often sees many toads under an arc-light engaged in catch-
ing insects that fall anywhere near them. Though its diet is varied and
somewhat indiscriminate, the toad consumes such a large proportion of
noxious insects, such as May beetles and cutworms, that it is unques-
tionably of service to man.

Moles are entirely insectivorous and destroy large numbers of white
grubs and caterpillars; held mice and prairie squirrels eat many insects,
especially grasshoppers, and the skunk revels in these insects, though it
eats beetles frequently, as does also the raccoon, which is to some extent
insectivorous. Monkeys are omnivorous but devour many kinds of
insects.

With these hasty references, we may pass at once to the subject of
the insect food of fishes and birds.

INSECTS IX RELATION TO OTHER ANIMALS

219

Insects in Relation to Fishes. — Insects constitute the most im-
portant portion of the food of adult fresh water fishes, furnishing forty
per cent, of their food, according to Dr. Forbes, from whose valuable
writings the following extracts are taken.

''The principal insectivorous fishes are the smaller species, whose
size and food structures, when adult, unfit them for the capture of Ento-
mostraca. and yet do not bring them within reach of fishes or Mollusca.
Some of these fishes have peculiar habits which render them especially
dependent upon insect life, the little minnow Phenacobius, for example,
which, according to my studies, makes nearly all its food from insects
(ninety-eight per cent.) found under stones in running water. Xext are
the pirate perch, Aphredoderus (ninety-one per cent.), then the darters
(eighty-seven per cent.), the croppies (seventy-three per cent.), half-
grown sheepshead (seventy-one per cent.), the shovel fish (fifty-nine per
cent.), the chub minnow (fifty-six per cent.), the black warrior sunfish
(Chcenobryttus) and the brook silversides (each fifty-four per cent.), and
the rock bass and the cyprinoid genus Xotropis (each fifty- two percent.).

" Those which take few insects or none are mostly the mud-feeders
and the ichthyophagous species, Anita (the dog-fish) being the only
exception noted to this general statement. Thus we find insects wholly
or nearly absent from the adult dietary of the burbot, the pike, the gar,
the black bass, the wall-eyed pike, and the great river catfish, and from
that of the hickory shad and the mud-eating minnows (the shiner, the
fathead, etc.). It is to be noted, however, that the larger fishes all go
through an insectivorous stage, whether their food when adult be almost
wholly other fishes, as with the gar and the pike, or molluscs, as with the
sheepshead. The mud-feeders, however, seem not to pass through this
stage, but to adopt the limophagous habit as soon as they cease to de-
pend upon Entomostraca.

" Terrestrial insects, dropping into the water accidentally or swept
in by rains, are evidently diligently sought and largely depended upon
by several species, such as the pirate perch, the brook minnow, the top
minnows or killifishes (cyprinodonts) the toothed herring and several
cyprinoids (Semotilns, Pimephales and Notropis).

" Among aquatic insects, minute slender dipterous larvae, belonging
mostly to Ckironomus, Corethra and allied genera are of remarkable
importance, making, in fact, nearly one tenth of the food of all the fishes
studied. They are most abundant in Phenacobius and Etheostonta,
which genera have become especially adapted to the search for these
insect forms in shallow rocky streams. Xext I found them most gener-

2 20

F.N TOMOLOCY

ally in the pirate perch, the brook silversides, and the stickleback, in
which they averaged forty-five per cent. They amounted to about one
third the food of fishes as large and important as the red horse and the
river carp, and made nearly one fourth that of fifty-one buffalo fishes.
They appear further in considerable quantity in the food of a number of
the minnow family (Xolropis, Pimephales. etc.), which habitually fre-
quent the swift wraters of stony streams, but were curiously deficient in
the small collection of miller's thumbs (Cottidae) which hunt for food in
similar situations. The sunfishes eat but few of this important group,
the average of the family being only six per cent.

"Larvae of aquatic beetles, notwithstanding the abundance of some
of the forms, occurred in only insignificant ratios, but were taken by fifty-
six specimens, belonging to nineteen of the species, — more frequently by
the sunfishes than by any other group. The kinds most commonly
captured were larvae of Gyrinidae and Hydrophilidae; whereas the adult
surface beetles themselves (Gyrinus, Dineutes. etc.) — whose zigzag-
darting swarms no one can have failed to notice — were not once en-
countered in my studies.

"The almost equally well-known slender water-skippers. (Hygro-
trechus) seem also completely protected by their habits and activity
from capture by fishes, only a single specimen occurring in the food of
all my specimens. Indeed, the true water bugs (Hemiptera) were gener-
ally rare, with the exception of the small soft-bodied genus Corisa.
which was taken by one hundred and ten specimens, belonging to twenty-
seven species. — most abundantly by the sunfishes and top minnows.

"From the order Xeuroptera [in the broad sense] fishes draw a larger
part of their food than from any other single group. In fact, nearly a
fifth of the entire amount of food consumed by all the adult fishes exam-
ined by me consisted of aquatic larvae of this order, the greater part of
them larvae of day flies (Ephemeridae), principally of the genus Hexa-
genia. These neuropterous larvae were eaten especially by the miller's
thumb, the sheepshead, the white and striped bass, the common perch,
thirteen species of the darters, both the black bass, seven of the sunfishes,
the rock bass and the croppies, the pirate perch, the brook silversides,
the sticklebacks, the mud minnow, the top minnows, the gizzard shad,
the toothed herring, twelve species each of the true minnow family and
of the suckers and buffalo, five catfishes, the dog-fish, and the shovel
fish, — seventy species out of the eighty-seven which I have studied.

"Among the above. I found them the most important food of the
white bass, the toothed herring, the shovel fish (fifty-one per cent.), and

INSECTS IX RELATION TO OTHER ANIMALS

221

the croppies; while they made a fourth or more of the alimentary con-
tents of the sheepshead (forty-six per cent.), the darters, the pirate perch,
the common sunfishes (Lepomis and Chanobryttus) , the rock bass, the
little pickerel, and the common sucker (thirty-six per cent.).

uEphemerid larvae were eaten by two hundred and thirteen specimens
of forty-eight species — not counting young. The larva of Hexagenia,
one of the commonest of the 'river flies,' was by far the most important
insect of this group, this alone amounting to about half of all the Xeurop-
tera eaten. It made nearly one half of the food of the shovel fish,
more than one tenth that of the sunfishes, and the principal food resource
of half-grown sheepshead; but was rarely taken by the sucker family,
and made only five per cent, of the food of the catfish group.

"The various larvae of the dragon flies, on the other hand, were much
less frequently encountered. They seemed to be most abundant in the
food of the grass pickerel (twenty-five per cent.) and next to that, in the
croppie, the pirate perch, and the common perch (ten to thirteen per
cent.).

"Case-worms (Phryganeidae) were somewhat rarely found, rising to
fifteen per cent, in the rock bass and twelve per cent, in the minnows of
the Hybopsis group, but otherwise averaging from one to six per cent,
in less than half of the species."

Insects in Relation to Birds. — From an economic point of view
the relations between birds and insects are extremely important, and from
a purely scientific standpoint they are no less important, involving as
they do biological interactions of remarkable complexity.

The prevalent popular opinion that birds in general are of inestimable
value as destroyers of noxious insects is a correct one, as Dr. Forbes
proved, from his precise and extensive studies upon the food of Illinois
birds, involving a laborious and difficult examination of the stomach
contents of many hundred specimens. All that follows is taken from
Forbes, when no other author's name is mentioned, and though the
percentages given by Forbes apply to particular years and would un-
doubtedly vary more or less from year to year, they are here for con-
venience regarded as representative of any year and are spoken of in the
present tense. About two thirds of the food of birds consists of insects.

Robin. — The food of the robin in Illinois, from February to May
inclusive, consists almost entirely of insects; at first, larvae of Bibio albi-
pennis for the most part, and then caterpillars and various beetles.
When the small fruits appear, these are largely eaten instead of insects;
thus in June, cherries and raspberries form fifty-five per cent, and insects

222

ENTOMOLOGY

(ants, caterpillars, wire-worms and Carabidae) forty-two per cent, of the
food; and in July, raspberries, blackberries and currants form seventy-
nine per cent, and insects (mostly caterpillars, beetles and crickets) but
twenty per cent, of the food. In August, insects rise to forty-three per
cent, and fruits drop to fifty-six per cent., and these are mostly cherries,
of which two thirds are wild kinds. In September, ants form fifteen per
cent, of the food, caterpillars five per cent, and fruits (mostly grapes-
mountain-ash berries and moonseed berries) seventy per cent. In
October, the food consists chiefly of wild grapes (fifty-three per cent.),
ants (thirty-five per cent.), and caterpillars (six per cent.).

For the year, judging from the stomach contents of one hundred and
fourteen birds, garden fruits form only twenty-nine per cent, of the food
of the robin, while insects constitute two thirds of the food. The results
are confirmed by those of Professor Beal in Michigan, who found that
more than forty-two per cent, of the food of the robin consists of insects
with some- other animal matter, the remainder being made up of various
small fruits, but notably the wild kinds.

Upon the whole, the robin deserves to be protected as an energetic
destroyer of cutworms, white grubs and other injurious insects, and the
comparatively few cultivated berries that the bird appropriates are
ordinarily but a meagre compensation for the valuable services rendered
to man by this familiar bird.

Catbird. — Xot so much can be said for the catbird, however, for,
though its food habits are similar to those of the robin, it arrives later and
departs earlier, with the result that it is less dependent than the robin
upon insects and that berries form a larger percentage of its total food.

In May. eighty-three per cent, of the food of the catbird consists of
insects, mostly beetles (Carabidae. Rhynchophora. etc.), crane-flies, ants
and caterpillars (Xoctuidae); while dry sumach berries are eaten to the
extent of seven per cent. For the first half of June, the record is much
the same, with an increase, however, in the number of May beetles eaten;
in the second half of the month the food consists chiefly of small fruits,
especially raspberries, cherries and currants; so that for the month as a
whole, only forty-nine per cent, of the food is made up of insects. This
falls to eighteen per cent, in July, when three quarters of the food con-
sists of small fruits, mostly blackberries, however. In August, with the
diminution of the smaller cultivated fruits, the percentage of insects
rises to forty-six per cent., nearly one half of which is made up of ants
and the rest of caterpillars, grasshoppers. Hemiptera. Coleoptera, etc.
In September, with the appearance of wild cherries, elderberries. Virginia

INSECTS IN RELATION TO OTHER ANIMALS

223

creeper berries and grapes, these are eaten to the extent of seventy-six
per cent., the insect element of the food falling to twenty-one per cent.,
of which almost half consists of ants, and the remainder of beetles and a
few caterpillars.

For the entire year, as appears from the study of seventy specimens
by Forbes, insects form forty-three per cent, of the food of the catbird
and fruits fifty- two per cent. As the injurious insects killed are offset
by the beneficial ones destroyed, "the injury done in the fruit-garden by
these birds remains without compensation unless we shall find it in the
food of the young," says Professor Forbes. And this has been found, to
the credit of the catbird; for Weed learned that the food of three nest-
lings consisted of insects, sixty-two per cent, of which were cutworms
and four per cent, grasshoppers; while Judd found that fourteen nest-
lings had eaten but four per cent, of fruit, the diet being chiefly ants,
beetles, caterpillars, spiders and grasshoppers. In fact, Weed believes
that, on the whole, the benefit received from the catbird is much greater
than the harm done, and that its destruction should never be permitted
except when necessary in order to save precious crops.

Bluebird. — The excellent reputation which the bluebird bears every-
where as an enemy of noxious insects is well deserved. From a study of
one hundred and eight Illinois specimens, Forbes finds that seventy-
eight per cent, of the food for the year consists of insects, eight per cent,
of Arachnida, one per cent, of Julidae and only thirteen per cent, of vege-
table matter, edible fruits forming merely one per cent, of the entire food.
The insects eaten are mostly caterpillars (chiefly cutworms), Orthoptera
(grasshoppers and crickets) and Coleoptera (Carabidae and Scarabaeidae) .
Though some of the insects are more or less beneficial to man, such as
Carabidae and Ichneumonidae (respectively predaceous and parasitic),
the beneficial elements form only twenty-two per cent, of the food for
the year, as against forty-nine per cent, of injurious elements, the remain-
ing twenty-nine per cent, consisting of neutral elements. The food of
the nestlings, according to Judd, is essentially like that of the adults,
being u beetles, caterpillars, grasshoppers, spiders and a few snails.' '

Other Insectivorous Birds. — Weed and Dearborn, from whose
excellent work the following notes are taken, find that the common
chickadee devours immense numbers of canker-worms, and that more
than half its food during winter consists of insects, largely in the form of
eggs, including those of the common tent caterpillar (C. americana),
the fall web-worm {H. cunea) and particularly plant lice, whose eggs, small
as they are, form more than one fifth of the entire food; more than four
hundred and fifty of them are sometimes eaten by a single bird in one day,

224

EXTOMOU )( ,V

and the total number destroyed annually is inconceivably large. The
house wren is almost exclusively insectivorous, feeding upon caterpillars
and other larvae, ants, grasshoppers, gnats, beetles, bugs, spiders, and
myriopods. The swallows, also, are highly insectivorous; "most of
their food is captured on the wing, and consists of small moths, two-
winged flies, especially crane-flies, beetles in great variety, flying bugs,
and occasionally small dragon-flies. The young are fed with insects."
Ninety per cent, of the food of the kingbird ''consists of insects, includ-
ing such noxious species as May-beetles, click-beetles, wheat and fruit
weevils, grasshoppers, and leaf hoppers." The honey bees eaten by this
bird are insignificant in number. Woodpeckers destroy immense num-
bers of wood-boring larva?, bark-insects, ants, caterpillars, etc. The
cuckoos "are unique in having a taste for insects that other birds reject.
Most birds are ready to devour a smooth caterpillar that comes in their
way. but they leave the hairy varieties severely alone. The cuckoos,
however, make a specialty of devouring such unpalatable creatures;
even stink-bugs and the poisonous spiny larva? of the Io moth are freely
taken." Caterpillars form fifty per cent, of the food for the year;
Orthoptera (grasshoppers, katydids, and tree crickets), thirty per cent.;
Coleoptera and Hemiptera, six per cent, each; and flies and ants are
taken in small quantities. "The nestling birds are fed chiefly with
smooth caterpillars and grasshoppers, their stomachs probably being
unable to endure the hairy caterpillars. All in all. the cuckoos are of
the highest economic value. They do no harm and accomplish great
good. If the orchardist could colonize his orchards with them, he would
escape much loss." The quail feeds largely upon insects during the
summer, frequently eating the Colorado potato beetle and the army
worm; the prairie hen has similar food habits but lives almost exclusively
on grasshoppers, when these are abundant.

The Insect Food of Birds. — "There are few groups of injurious
insects that enter so largely into the composition of the food of birds as
do the locusts, or short-horned grasshoppers, of the family Acridiidae.
The enormous destructive power of these insects is well known, but our
indebtedness to birds in checking their oscillations is less generally recog-
nized." Professor Aughey. who has made extensive studies upon the
relation of birds to the Rocky Mountain locust, found that upon one
occasion 6 robins had eaten 265 of these insects. 5 catbirds 152. 3 blue-
birds 67. 7 barn swallows 139. 7 night hawks 348. 16 yellow-billed cuckoos
416. 8 flickers 252. 8 screech owls 219. and 1 humming bird 4: while
crows and blue-jays had eaten large numbers of the locusts; and grouse,
quail and prairie hen. enormous numbers. Even shore birds, such as

INSECTS IX RELATION TO OTHER ANIMALS

225

geese, ducks, gulls and pelicans came to share in the feast. Aughey
estimated that the locusts eaten in one day by the passerine birds of the
eastern half of Nebraska were sufficient to destroy in a single day 174,397
tons of crops, valued at $1,743.97.

Weed and Dearborn state that, of Hemiptera, Jassidae are very often
found in the stomachs of birds, and that aphids and their eggs form a
large part of the food of many of the smaller birds, such as the warblers,
nuthatches, kinglets and chickadees. "A large proportion of the cater-
pillars of the Lepidoptera are eagerly devoured by birds, forming an
important element of the food of many species. The hairy caterpillars
are eaten by cuckoos and blue-jays and the large saturniid caterpillars,
such as cecropia and polyphemus] by some of the hawks. Almost all
kinds of Coleoptera are food for birds, but especially the grubs of Scara-
baeidae, which are eagerly devoured by robins, blackbirds, crows and
other birds. Of the Diptera, Cecidomyiidae and other gnats are eaten
by swallows, swifts and night hawks; while Tipulidae are often found in
the stomachs of birds. Among Hymenoptera, ants are eaten exten-
sively by woodpeckers, catbirds and many other species, as are also
Ichneumonidae and other parasitic forms — these last by the flycatchers
in particular.

The Regulative Action of Birds upon Insect Oscillations.—

The worst injuries by insects are done by species that fluctuate exces-
sively in number as the result of variations in those manifold forces that
act as checks upon the multiplication of the species.

In order to determine whether birds do anything to reduce existing
oscillations of injurious insects. Professor Forbes made some admirable
studies upon the food of birds which were shot in an Illinois apple or-
chard which was being ravaged by canker-worms. In this orchard,
birds were present in extraordinary number and variety, there being at
least thirty-five species, most of which were studied by Forbes, from
whose exhaustive tables the following food-percentages are taken :

Birds Examined.

Insects.

Canker-worms.

Robin,

9

93/o

21%

Catbird,

14

98

15

Brown Thrush,

4

94

12

Bluebird,

5

98

12

Black-capped Chickadee,

2

100

6l

House Wren, '

9i

46

Tennessee Warbler,

1

100

80

Summer Yellow Bird,

5

94

67

Black-throated Green Warbler, . .

1

100

70

Maryland Yellow-throat

2

100

37

Baltimore Oriole

3

100

40

16

226

ENTOMOLOGY

To quote Forbes: 1 1 Three facts stand out very clearly as results of
these investigations: i. Birds of the most varied character and habits,
migrant and resident, of all sizes, from the tiny wren to the blue-jay, birds
of the forest, garden and meadow, those of arboreal and those of terres-
trial habits, were certainly either attracted or detained here by the
bountiful supply of insect food, and were feeding freely upon the species
most abundant. That thirty-five per cent, of the food of all the birds
congregated in this orchard should have consisted of a single species of
insect, is a fact so extraordinary that its meaning can not be mistaken.
Whatever power the birds of this vicinity possessed as checks upon
destructive irruptions of insect life was being largely exerted here to
restore the broken balance of organic nature. And while looking for
their influence over one insect outbreak we stumbled upon at least two
others, less marked, perhaps incipient, but evident enough to express
themselves clearly in the changed food ratios of the birds.

" 2. The comparisons made show plainly that the reflex effect of this
concentration on two or three unusually numerous insects was so widely
distributed over the ordinary elements of their food that no especial
chance was given for the rise of new fluctuations among the species com-
monly eaten. That is to say, the abnormal pressure put upon the canker-
worm and vine-chafer was compensated by a general diminution of the
ratios of all the other elements, and not by a neglect of one or two alone.
If the latter had been the case, the criticism might easily have been made
that the birds, in helping to reduce one oscillation, were setting others on
foot.

"3. The fact that, with the exception of the indigo bird, the species
whose records in the orchard were compared with those made elsewhere
had eaten in the former situation as many caterpillars other than canker-
worms as usual, simply adding their canker-worm ratios to those of other
caterpillars, goes to show that these insects are favorites with a majority
of birds."'

The Relations of Birds to Predaceous and Parasitic Insects.

The false assumption is often made that a bird is necessarily inimical to
man's interest whenever it destroys a parasitic or a predaceous insect.
Weed and Dearborn attack this assumption as follows:

"Suppose an ichneumon parasite is found in the stomach of a robin
or other bird: it may belong to any one of the following categories:

"1. The primary parasite of an injurious insect.

"2. The secondary parasite of an injurious insect.

"3. The primary parasite of an insect feeding on a noxious plant.

INSECTS IN RELATION TO OTHER ANIMALS 227

"4. The secondary parasite of an insect feeding on a noxious plant.
"5, The primary parasite of an insect feeding on a wild plant of no
economic value.

"6. The secondary parasite of an insect feeding on a wild plant of no
economic value.

"7. The primary parasite of a predaceous insect.

"8. The primary parasite of a spider or a spider's egg.

"This list might easily be extended still farther, and the assumption
that the parasite belongs to the first of these categories is unwarranted
by the facts and does violence to the probabilities of the case.

"A correct idea of the economic role of the feathered tribes may be
obtained only by a broader view of nature's methods, — a view in which
we must ever keep before the mind's eye the fact that all the parts of
the organic world, from monad to man, are linked together in a thousand
ways, the net result being that unstable equiHbrium commonly called
'the balance of nature.'"

This broader view was first elaborated by Professor Forbes, in his
masterly paper, "On Some Interactions of Organisms," the substance of
which is given below.

"Evidently a species can not long maintain itself in numbers greater
than can find sufficient food, year after year. If it is a phytophagous
insect, for example, it will soon dwindle if it seriously lessens the numbers
of the plants upon which it feeds, either directly, by eating them up, or
indirectly, by so weakening them that they labor under a marked dis-
advantage in the struggle with other plants for foothold, air, light and
food. The interest of the insect is therefore identical with the interest of
the plant it feeds upon. Whatever injuriously affects the latter, equally
injures the former; and whatever favors the latter, equally favors the
former. This must, therefore, be regarded as the extreme normal limit
of the numbers of a phytophagous species, — a limit such that its depre-
dations shall do no especial harm to the plants upon which it depends for
food, but shall remove only the excess of foliage or fruit, or else super-
fluous individuals which must perish otherwise, if not eaten, or, surviv-
ing, must injure their species by over-crowding. If the plant-feeder
multiply beyond the above limit, evidently the diminution of its food
supply will soon react to diminish its own numbers; a counter reaction
will then take place in favor of the plant, and so on through an oscillation
of indefinite continuance.

"On the other hand, the reduction of the phytophagous insect below
the normal number will evidently injure the food plant by preventing a

228 ENTOMOLOGY

reduction of its excess of growth or numbers, and will also set up an
oscillation like the preceding, except that the steps will be taken in re-
verse order.

"I next point out the fact that precisely the same reasoning applies
to predaceous and parasitic insects. Their interests also are identical
with the interests of the species they parasitize or prey upon. A diminu-
tion of their food reacts to decrease their own numbers. They are thus
vitally interested in confining their depredations to the excess of indi-
viduals produced, or to redundant or otherwise unessential structures.
It is only by a sort of unlucky accident that a destructive species really
injures the species preyed upon.

"The discussion has thus far affected only such organisms as are
confined to a single species. It remains to see how it applies to such as
have several sources of support open to them, — such, for instance, as
feed indifferently upon several plants or upon a variety of animals, or
both. Let us take, first, the case of a predaceous beetle feeding upon a
variety of other insects, — either indifferently, upon whatever species is
most numerous or most accessible, or preferably upon certain species,
resorting to others only in case of an insufficiency of its favorite food.

"It is at once evident that, taking the group of its food-insects as a
unit, the same reasoning applies as if it were restricted to a single species
for food; that is. it is interested in the maintenance of these food-species
at the highest number consistent with the general conditions of the
environment, — interested to confine its own depredations to that sur-
plus of its food which would otherwise perish if not eaten — interested,
therefore, in establishing a rate of reproduction for itself which will not
unduly lessen its food supply. Its interest in the numbers of each species
of the group it eats will evidently be the same as its interest in the group
as a whole, since the group as a whole can be kept at the highest number
possible only by keeping each species at the highest number possible. . . .

"This argument holds for birds as well as for insects, for animals of
all kinds, in fact, whether their food be mixed or simple, animal or vege-
table, or both. It also applies to parasitic plants. The ideal adjust-
ment is one in which the reproductive rate of each species should be so
exactly adapted to its food supply and to the various drains upon it that
the species preyed upon should normally produce an excess sufficient for
the species it supports. And this statement evidently applies through-
out the entire scale of being. Among all orders of plants and animals,
the ideal balance of Nature is one promotive of the highest good of all
the species. In this ideal state, towards which Nature seems continually

INSECTS IX RELATION TO OTHER ANIMALS

229

striving, every food-producing species of plant or animal would grow and
multiply at a rate sufficient to furnish the required amount of food, and
every depredating species would reproduce at a rate no higher than just
sufficient to appropriate the food thus furnished. . . .

"Exact adjustment is doubtless never reached anywhere, even for a
single year. It is usually closely approached in primitive nature, but
the chances are practically infinite against its becoming really complete,
and mal-adjustment in some degree is therefore the general rule. All
species must oscillate more or less."

Professor Forbes then shows that oscillations are injurious to a species
and that the tendency of things is toward a healthy equilibrium. If the
rate of reproduction, as in a parasite for instance, is too small in relation
to the food supply, the species will eventually yield to its more proline
competitors in the general struggle for existence. If, on the other hand,
its rate of multiplication is too high, the species will be at a disadvantage
in the search for food, as compared with better adjusted species, and must
again suffer. "The fact of survival is therefore usually sufficient evi-
dence of a fairly complete adjustment of the rate of reproduction to the
drains upon the species." . . . "We may be sure, therefore, that, as a
general rule, in the course of evolution, only those species have been able
to survive whose parasites, if any, were not prolific enough sensibly to
limit the numbers of their hosts for any length of time.

"We notice incidentally that it is thus made unlikely that an injuri-
ous species can be exterminated, can even be permanently lessened in
numbers, by a parasite strictly dependent upon it, — a conclusion which
remarkably diminishes the economic role of parasitism. The same line
of argument will, of course, apply, with slight modifications, to any
animal, or even to any plant dependent upon any other animal or any
other plant for existence.

"It is a general truth, that those animals and plants are least likely
to oscillate widely which are preyed upon by the greatest number of
species, of the most varied habit. Then the occasional diminution of a
single enemy will not greatly affect them, as any consequent excess of
their own numbers will be largely cut down by their other enemies, and
especially as, in most cases, the backward oscillations of one set of ene-
mies will be neutralized by the forward oscillations of another set. But
by the operations of natural selection, most animals are compelled to
maintain a varied food habit, — so that if one element fails, others may be
available. Thus each species preyed upon is likely to have a number of
enemies, which will assist each other in keeping it properly in check.

23°

K X TOM ()L()( iV

" Against the uprising of inordinate numbers of insects, commonly
harmless but capable of becoming temporarily injurious, the most valu-
able and reliable protection is undoubtedly afforded by those predaceous
birds and insects which eat a mixed food, so that in the absence or diminu-
tion of any one element of their food, their own numbers are not seriously
affected. Resorting, then, to other food supplies, they are found ready,
on occasion, for immediate and overwhelming attack against any threat-
ening foe. Especially does the wonderful locomotive power of birds,
enabling them to escape scarcity in one region which might otherwise
decimate them, by simply passing to another more favorable one. with-
out the loss of a life, fit them, above all other animals and agencies, to
arrest disorder at the start, — to head off aspiring and destructive rebel-
lion before it has had time fairly to make head. But we should not
therefrom derive the general, but false and mischievous notion, that the
indefinite multiplication of either birds or predaceous insects is good.
Too many of either is nearly or quite as harmful as too few.

" There is a general consent that primeval nature, as in the unin-
habited forest or the untilled plain, presents a settled harmony of inter-
action among organic groups wrhich is in strong contrast with the many
serious mal-adjustments of plants and animals found in countries occu-
pied by man.

"To man, as to nature at large, the question of adjustment is of vast
importance, since the eminently destructive species are the widely oscil-
lating ones. Those insects which are well adjusted to their environ-
ments, organic and inorganic, are either harmless or inflict but moderate
injury (our ordinary crickets and grasshoppers are examples); while
those that are imperfectly adjusted, whose numbers are, therefore, sub-
ject to wide fluctuations, like the Colorado grasshopper, the chinch-bug
and the army worm, are the enemies which we have reason to dread.
Man should then especially address his efforts, first, to prevent any
unnecessary disturbance of the settled order of the life of his region
which will convert relatively stationary species into widely ocsillating
ones; second, to destroy or render stationary all the oscillating species
injurious to him; or, failing in this, to restrict their oscillations within the
narrowest limits possible.

"For example, remembering that every species oscillates to some
extent, and is held to relatively constant numbers by the joint action of
several restraining forces, we see that the removal or weakening of any
check or barrier is sufficient to widen and intensify this dangerous oscil-
lation; may even convert a perfectly harmless species into a frightful

INSECTS IX RELATION TO OTHER ANIMALS

pest. Witness the maple bark louse, which is so rare in natural forests
as scarcely ever to be seen, limited there as it is by its feeble locomotive
power and the scattered situation of the trees it infests. With the multi-
plication and concentration of its food in towns, it has increased enor-
mously, and, if it has not done the gravest injury, it is because the trees
attacked by it are of comparatively slight economic value, and because
it has finally reached new limits which hem it in once more.

" We are therefore sure that the destruction of any species of insectivo-
rous bird or predaceous insect is a thing to be done, if at all, only after
the fullest acquaintance with the facts. The natural presumptions are
nearly all in their favor. It is also certain that the species best worth
preserving are the mixed feeders and not those of narrowly restricted
dietary (parasites, for instance), — that while the destruction of the latter
would cause injurious oscillations in the species affected by them, they
afford a very uncertain safeguard against the rise of such oscillations.
In fact, their undue increase would be finally as dangerous as their
diminution.

" Notwithstanding the strong presumption in favor of the natural
system, when we remember that the purposes of man and what, for con-
venience' sake, we may call the purposes of Nature do not fully harmo-
nize, we find it incredible that, acting intelligently, we should not be able
to modify existing arrangements to our advantage, — especially since
much of the progress of the race is due to such modifications made in the
past. . . .

"But far the most important general conclusion we have reached is a
conviction of the general beneficence of nature, a profound respect for
the natural order, a belief that the part of wisdom is essentially that of
practical conservatism in dealing with the system of things by which we
are surrounded."

Efficiency of Protective Adaptations of Insects. — Interesting
from a scientific point of view are the various adaptations by means of
which insects are protected more or less from their bird enemies. Color-
ational adaptations having been discussed in another chapter, there
remain for consideration — (i) hairs, (2) stings, (3) odors, flavors and
irritants. Most of what follows is from an admirable paper by Dr. Judd,
whose data are based upon his examination of the stomach contents of
fifteen thousand birds.

Hairs. — "Excepting two species of cuckoos, no species of bird in the
eastern United States, so far as I am aware, makes a business of feeding
upon hairy caterpillars." Judd observed that Hyphantria cunea infest-

232

ENTOMOLOGY

ing a pear tree was not at all molested, in spite of the fact that the tree
was tenanted by three broods of birds at the time, namely, kingbirds,
orchard orioles and English sparrows. The hairy arctiid caterpillars,
however, are eaten by a few birds: the robin, bluebird, catbird, sparrow-
hawk, cuckoos and shrikes; and the spiny larvae of Vanessa antiopa by
cuckoos and the Baltimore oriole; while the hairy caterpillars of the gypsy
moth are known to be eaten in Massachusetts by no less than thirty-one
species of birds, notably cuckoos, Baltimore oriole, catbird, chickadee,
blue- jay, chipping sparrow, robin, vireos and the crow, these birds being
of no little assistance in the suppression of this pest. These are excep-
tional cases, however, and in general the hairiness of caterpillars appears
to be a highly effective protection against most birds.

Stings. — Some birds (chewink, young ducks) are fatally affected by
eating honey bees. The blue-jays, however, will eat Bombus and Xylo-
copa. and flycatchers and swallows feed habitually upon stinging Hymen-
optera, particularly Scoliidae, while a great many birds eat Myrmicidae,
or stinging ants. The formic acid of ants does not protect them from
wholesale destruction by birds; Judd found three thousand ants in the
stomach of a flicker. "Stingless ants pretend to sting but many birds
they do not deceive.'1 The stinging caterpillar of Automeris io is occa-
sionally eaten by the yellow-billed cuckoo. Aside from these exceptions,
however, the stings of insects are an extremely efficient means of defence.

Odors, Flavors and Irritants. — The malodorous Heteroptera in
general are food for most birds; Lygus, Reduviidae and Pentatomidae are
eaten by song sparrows, and Euschistus by blackbirds and crows. The
odors of Heteroptera are by no means universally protective.

Among Coleoptera, the showy, ill-scented or ill-flavored Coccinellidae
are eaten by but very few birds — the flycatchers and swallows — and are
refused by caged blue-jays and song sparrows even when these birds are
hungry. Of Chrysomelidae, the Colorado potato beetle is refused by the
catbird, blue-jay and song sparrow, and Diabrotica is not often eaten,
except by catbirds and thrushes. "The smaller Carabidae, whether
stinking or not, are eaten by practically all land birds." Crows, black-
birds and jays eagerly swallow Calosoma scrutator, and the first two birds
are especially fond of Har pains caliginosus and H. pennsyhanicus, and
feed Galerita to their young. "A score of smaller Carabidae and Chryso-
melidae, metallic and conspicuously colored, are habitually eaten by
birds that have an abundance of other insect food to pick from."

The stenches of Lampyridae appear to be more effective than those of
Carabidae. Telcphorus is occasionally eaten, but Photinus rarely if at

INSECTS IX RELATION TO OTHER ANIMALS

233

all. Chauliognathus is not eaten by many birds (though flycatchers and
swallows select this insect) and the genus is regarded unfavorably by
caged catbirds and blue- jays.

In regard to other insects, Judd finds that Epicauta, with its irritant
fluid, is immune from all but the kingbird; Cyllene seldom occurs in the
stomachs of birds; May flies%and caddis flies, however, are terribly perse-
cuted, but swiftly flying Diptera and Odonata are highly immune.

From such facts as these, Judd properly infers, i 'not cases of protec-
tion and non-protection, but cases of greater and lesser efficiency of
protective devices."

CHAPTER IX

TRANSMISSION' OF DISEASES BY INSECTS

It is now known that several kinds of insects are of vital importance
to man as agents in the transmission of certain diseases. This recently
demonstrated role of insects now commands universal attention.

Malaria

So far as is known, malaria is transmissible only through the agency
of mosquitoes.

The malaria "germ," discovered in 1880 by the French army surgeon
Laveran, may be found as a pale, amoeboid organism (Plasmodium,
Fig. 270) in the red blood corpuscles of persons afflicted with the disease.
This organism (schizont, 2) grows at the expense of the haemoglobin of
the corpuscle (3-5) and its growth is accompanied by an increasing
deposit of black granules (melanin), which are doubtless excretory in
their nature. At length, the amcebula divides into many spores (mero-
zoites. 6). which by the disintegration of the corpuscle are set free in the
plasma of the blood. Here many if not most of the spores, and the
pigment granules as well, are attacked and absorbed by leucocytes, or
white blood corpuscles, while some of the spores may invade healthy red
corpuscles and develop as before. The period of sporulation, as Golgi
found, is coincident with that of the "chill" experienced by the patient;
and quinine is most effective when administered just before the sporula-
tion period. The destruction of red blood corpuscles explains the pallid,
or ancemic, condition which is characteristic of malarial patients. In
three or four days the number of red corpuscles may be reduced from
5,000,000 per cubic millimeter — the normal number — to 3,000,000; and
in three or four weeks of intermittent fever, even to 1,000,000.

Threejypes of malaria are recognized: (1) the tertian, in which the
paroxysm recurs every two days; (2) the quartan, in which it happens
every third day; and (3) the aestivo-autumnal type (Fig. 270). These
three kinds are by some investigators thought to be due to different
species of parasites; and when, as often happens, the malarial chill occurs
every jiay, this is attributed to two sets of tertian amcebulae, sporulating
on alternate days.

234

Fig. 270. — Life history of malaria parasite, Plasmodium prcrcox. 1, sporozoite, introduced
by mosquito into human blood; the sporozoite becomes a schizont. 2, young schizont,
which enters a red blood corpuscle. 3, young schizont in a red blood corpuscle. 4, full-
grown schizont, containing numerous granules of melanin. 5, nuclear division preparatory
to sporulation. spores, or merozoites, derived from a single mother-cell. 7, young macro-
gamete (female), derived from a merozoite and situated in a red blood corpuscle, ya, young
microgametocyte (male) derived from a merozoite. 8, full-grown macrogamete. 8a, full-
grown microgametocyte. In stages 8 and 8a the parasite is taken into the stomach of a
mosquito; or else remains in the human blood, 9, mature macrogamete, capable of fertiliza-
tion; the round black extruded object may probably be termed a "polar body." gay mature
microgametocyte, preparatory to forming microgametes. gb, resting cell, bearing six flagellate
microgametes (male). 10, fertilization of a macrogamete by a motile microgamete. The
macrogamete next becomes an ookinete. 11, ookinete, or wandering cell, which penetrates
into the wall of the stomach of the mosquito. 12, ookinete in the outer region of the wall of
the stomach, i. e., next to the body cavity. 13, young oocyst, derived from the ookinete.
14, oocyst, containing sporoblasts, which are to develop into sporozoites. 15, older oocyst.
16, mature oocyst, containing sporozoites, which are liberated into the body cavity of the
mosquito and carried along in the blood of the insect. 77, transverse section of salivary gland
of an Anopheles mosquito, showing sporozoites of the malaria parasite in the gland cells
surrounding the central canal.

1-6 illustrate schizogony (asexual production of spores) ; j-i6,sporogony (sexual production
of spores).

After Grassi and Leuckart, by permission of Dr. Carl Chun.

235

236

KXT( )M ()!.()( ;Y

After several successive asexual generations, there are produced
merozoites which develop — no longer into schizonts — but into sexual
forms, or gametes. These occur in red blood corpuscles either as macro-
gametes (female, 7, 8) or as microgametocytes (male, 7a, 8a), in which
forms the parasite is introduced into the stomach of a mosquito which
has been feeding upon the blood of a malarial patient. The macro-
gamete now leaves its blood corpuscle and becomes spherical (p), as does
also the microgametocyte (ga)\ but the latter puts forth a definite
number (six, in P. prcccow gb) of flagella, or microgametes, which separate
off as motile male bodies, capable of fertilizing the macrogametes. A
microgamete penetrates a maciogamete (10) and the nucleus of the one
unites with that of the other. The fertilized macrogamete now becomes
a migrating cell, or ookinete (11), which penetrates almost through the
wall of the stomach of the mosquito (12) and then becomes a resting cell,
or cyst. This oocyst (13) grows rapidly and its contents develop, by
direct nuclear division, into sporoblasts (14, 15), which differentiate into
spindle-shaped sporozoites (16, 17). The sporozoites are liberated into
the body cavity of the mosquito, carried in the blood to the salivary
glands (as well as elsewhere) and thence along the hypopharynx into the
body of a human being, bird or other animal attacked by the insect.

The role of the mosquito as the intermediary host of malarial organ-
isms was discovered by Manson and Ross and confirmed by Koch, Stern-
berg and others. It has been found repeatedly that certain mosquitoes
{Anopheles) after feeding on the blood of a malarial patient can transmit
the disease by means of their ''bites'' to healthy persons. Thus, Anoph-
eles mosquitoes were fed on the blood of malarial subjects in Rome
and then sent to London, where a son of Dr. Manson allowed himself
to be bitten by the insects. Though previously free from the malarial
organism, he contracted a well-marked infection as the result of the
inoculation.

Furthermore, it is highly probable that malaria cannot be trans-
mitted to man except through the agency of the mosquito. This appears
from the oft-cited experiment of Doctors Sambon and Low on the Roman
Campagna, a place notorious for malaria. There the experimenters
lived during the malarial season of 1900, freely exposed to the emanations
of the marsh and taking no precautions except to screen their house
carefully against mosquitoes and to retire indoors before the insects
appeared in the evening. Simply by excluding Anopheles mosquitoes,
with which the Campagna swarmed, these investigators remained per-
fectly immune from the malaria which was ravaging the vicinity.

TRANSMISSION OF DISEASES BY INSECTS

237

In a later experiment on the island of Formosa, one company of
Japanese soldiers was protected from mosquitoes and suffered no malaria,
while a second and unprotected company contracted the disease.

The evident preventive measures to be taken against malaria are
(1) the avoidance of mosquito bites, by means of screens and washes of
eucalyptus oil, camphor, oil of pennyroyal, oil of tar, etc., applied to
exposed parts of the body; (2) the isolation of malarial patients from
mosquitoes, in order to prevent infection; (3) the destruction of mosqui-
toes in their breeding places, especially by the use of kerosene and by
drainage. During unavoidable exposure in malarious regions, quinine
should be taken in doses of six to ten grains during the day at intervals of
four or five days (Sternberg).

Culex and Anopheles. — The mosquitoes of North America number
one hundred and twenty-five known species. Of these only the genus
Anopheles transmits malaria to man, though in India, Ross found that
Culex transmits a form of malaria to sparrows. These two common
genera are easily distinguishable. In Culex the wings are clear; in
Anopheles they are spotted with brown. In Culex when resting, the axis
of the body forms a curved line, the insect presenting a hump-backed
appearance; in Anopheles the axis forms a straight line. Culex has short
maxillary palpi, while in Anopheles they are almost as long as the probos-
cis. The note of the female Anopheles is several tones lower than that of
Culex, and only the female is bloodthirsty, by the way. As regards eggs,
larvae and pupae, the two genera differ greatly. The eggs of Culex are
laid in a mass and those of Anopheles singly; the larvae of Culex hang
from the surface film of a pool at an angle of about forty-five degrees,
while those of Anopheles are almost parallel with the surface of the water
in which they live.

The bite of an Anopheles is not necessarily injurious, of course, unless
the insect has had recent access to a malarious person. Anopheles may
be present where there is no malaria. On the other hand, it has been
found impossible to prove that malaria exists where there are no Anoph-
eles mosquitoes. Finally, fevers are sometimes diagnosed as malarial
which are not so.

Possibly the malarial parasite can complete its cycle of development
in othei animals than man. It is also possible that originally the mala-
rial organism was derived by mosquitoes from the stems or other parts of
aquatic plants, and that its effects on man are incidental phenomena.

238

KXTOMOLOGY

Yellow Fever

From 1793 to 1900 there occurred in the United States not less than
half a million cases of yellow fever and one hundred thousand deaths
from the disease. New Orleans suffered the worst with more than forty-
one thousand deaths, followed by Philadelphia with ten thousand and
Memphis with almost eight thousand; while Charleston, New York City
and Norfolk, Virginia, lost together more than ten thousand lives.

The enormous financial loss from all the epidemics of yellow fever is
beyond exact computation; the epidemic of 1878 cost New Orleans more
than ten million dollars.

Yellow fever is now within human control; with no thanks to those
who at first violently opposed the theory, and later denied the fact, of
its transmission by mosquitoes.

Until 1 90 1 yellow fever was fought energetically, but fought in the
dark. An immense amount of energy was misdirected and millions of
dollars wasted in the fight. On the supposition that bacteria were the
cause of the disease, methods of quarantine, burning and fumigation were
employed that destroyed an enormous amount of property, including
valuable cargoes, and paralyzed the business and social activities of
great cities.

Official accounts of yellow fever published before 1900 often describe
the disease as due to some insidious poison borne by the air and intro-
duced into the human body probably through the respiratory system.
It was observed that the disease was often conveyed down the wind, that
it was not carried far from the nearest focus of infection, that infection
was less liable to occur in daylight than by night, and that cases arose on
shore when the only source of infection was a ship that had not yet
touched the land. These facts and many others which formerly involved
the disease in mystery, are now quite intelligible in the light of the mos-
quito- theory of transmission.

F inlay's Work. — The pioneer work leading toward the control of
yellow fever was done by Dr. Charles J. Finlay, of Havana, Cuba, who
not only advocated the mosquito-theory strongly for many years, but
also inoculated by means of mosquitoes ninety human subjects, some
of whom came down with what he believed to be a mild form of yellow
fever. His valuable work prepared the way for the brilliant investi-
gations of Major Reed and his associates.

United States Yellow Fever Commission. — Major Walter Reed
was president of the board of medical officers sent to Cuba in June, 1900,

TRANSMISSION OF DISEASES BY INSECTS

239

to study the acute infectious diseases of the island; his associates were
James Carroll, Jesse W. Lazear and A. Agramonte.

At that time Sanarelli's theory as to the bacillary causation of yellow
fever was in favor, though Reed and Carroll had already shown that the
bacillus of Sanarelli bore no special relation to the disease. After further
investigations on this subject in Cuba, with negative results, the commis-
sion " concluded to test the theory of. Finlay," in Dr. Reed's words.
For this purpose General Leonard Wood, the military governor of Cuba,
gave permission for experiments on human beings and granted a liberal
sum of money for the reward of volunteer subjects.

The commission succeeded in demonstrating how yellow fever is
transmitted; after that the methods of prevention to be employed were
evident.

The experiments, planned and directed by Major Reed, are models
of their kind. All possible sources of error were excluded; hence there
was no uncertainty in the interpretation of the results, the accuracy of
which has been confirmed by subsequent commissions and by many
independent investigators.

In the value of his services Major Walter Reed ranks among the
greatest benefactors of mankind. Before his death, which occurred in
1902, he received great honors for his brilliant achievements.

Experiments in Cuba. — For experimental purposes Major Reed
established a camp about four miles from Havana. To prevent the
introduction of the fever from the outside the inmates of the camp were
rigidly quarantined; non-immunes were confined to the camp or, if re-
leased, not allowed to return. In order that the study of yellow fever
might not be complicated by the presence of any other disease, a com-
plete record was kept of the health of every subject; furthermore, ample
time was allowed for any possible development of the disease within the
camp before the experiments were begun. In short, the precautions
taken were so thorough that yellow fever never appeared in the camp
except at the will of the experimenters.

Harmlessness of Fomites. — In a specially constructed building,
which was screened against mosquitoes and purposely ill- ventilated,
volunteers slept for twenty nights with bedding and clothing that had
been contaminated by yellow fever patients, and tried in every other way
to contract the disease, if possible, from the fomites, or belongings, of
fever subjects; yet the health of these volunteers remained unimpaired;
though they were not immunes, for some of them were subsequently
infected artificially by means of mosquitoes.

2-j.O

ENTOMOLOGY

Transmission by Transfusion. — It was found that the disease
could be conveyed to non-immunes by the subcutaneous injection of
blood taken from the veins of patients during the first three days of the
disease.

Experiments with Mosquitos. — These experiment were made at
a time of the year wThen there was the least chance of acquiring the dis-
ease naturally. The mosquitoes used were bred from the egg and kept
active by being maintained at a summer temperature. From time to
time some of them were taken away to a yellow fever hospital, fed on the
blood of patients and applied to non-immunes in the camp at varying
intervals from the time of feeding. The occupants of the camp were, of
course, protected carefully from accidental mosquito bites. When a
subject came down with yellow fever as the result of an experimental
inoculation he was at once removed from the camp to a yellow fever
hospital.

In a mosquito-proof building a single room was divided into two
compartments simply by means of a partition of wire netting. On one
side of the screen infected mosquitoes were liberated; and a brave non-
immune, who had been in quarantine for thirty- two days, entered the
compartment, allowed himself to be bitten several times, and contracted
the disease. In the opposite compartment, free from mosquitoes, non-
immunes slept with perfect safety; and the other room became harmless
as soon as the mosquitoes were removed.

In another experiment the subject acquired the disease by thrusting
his arm into a jar of infected mosquitoes. Eighteen non-immunes were
inoculated, ten of them successfully. It was demonstrated that yellow
fever is transmitted by the bite of a mosquito, and in no other way
except by the artificial injection of diseased blood. The mosquito can
obtain infected blood from a patient during only the first three days of
his disease; in other words, the patient is no longer a menace to other
persons after three days from the time when he comes down with yellow
fever, which is from three to six days after the bite.

After biting a patient the mosquito cannot convey the infection until
at least twelve days have elapsed; thereafter it can transmit the disease
for certainly six' weeks and possibly eight weeks.

Dr. James Carroll allowed himself to be bitten by an infected mos-
quito and consequently suffered a severe attack of yellow fever. He
recovered from this, but wras left with an affection of the heart from
which he died in 1907.

Dr. Lazear failed to acquire the disease artificially, early in the course

TRANSMISSION OF DISEASES BY INSECTS

24I

of the experiments; but a little later, while visiting yellow fever patients
in a hospital, was bitten by a mosquito which he deliberately allowed to
remain on his hand. Five days later he came down with yellow fever,
which caused his death. His life was a sacrifice for the benefit of the
human race.

Yellow Fever Mosquito. — The mosquito that transmits this fever
is Aedes calopus (Stegomyia fasciata) and no other species is as yet known
to be concerned in the disease. A. calopus is limited to warm regions;
at a temperature less than 68° F. the eggs do not hatch, and below 620 F.
the female does not bite (Reed). The dependence of the insect upon
warmth for .its development explains the cessation of the disease in New
Orleans in December, wTith a mean temperature of 55.30 F. and in cities
farther north when frost comes. In Cuba and Brazil the fever has
occurred every month in the year.

Causes of Yellow Fever. — The specific cause of yellow fever has as
yet eluded detection and is regarded by many investigators as being
ultra-microscopic. The U. S. Commission produced the disease by the
injection of blood serum that had been passed through a bacteria-proof
filter. Blood from a subject in whom the disease had been produced by
transfusion was capable of infecting a third person.

The weight of evidence indicates that the unknown cause of yellow
fever is an organism rather than a toxin.

Control of Yellow Fever. — The preventive measures based upon
the facts learned by the U. S. Army Commission were wonderfully suc-
cessful. In February, 1901, Major W. C. Gorgas began a campaign to
eradicate the disease in Havana. His efforts were directed against
mosquitoes. Every case of fever had to be reported promptly to the
authorities. Then the patient was isolated and all the rooms in the
building and in neighboring houses fumigated and the doors and windows
screened. Standing water in which mosquitoes might develop was
drained or treated with petroleum and water tanks and barrels were
screened.

In September. 1901, the last case of yellow fever arose in Havana,
where the disease had prevailed for 1 50 years, with an annual mortality
of 500 to 1600 or more. Cases are now and then brought into Havana
from Mexico, but are treated under screens in the regular hospitals with
impunity.

Yellow Fever in New Orleans. — In 1905 the last epidemic of yel-
low fever occurred in Xew Orleans. It might have been checked at its
inception had not the authorities adopted a policy of secrecy in regard
17

242

KXTOMOLOGY

to the presence of the disease. The city was freed from the fever before
frost came, by the same methods that had proved successful in Cuba;
but not without organized work of the most strenuous kind on the part
of the citizens, under the direction of the U. S. Public Health and Marine-
Hospital Service. At present the yellow fever mosquito is said to be a
rarity in Louisiana owing to the vigorous measures enforced in its sup-
pression throughout the state.

Fever in the Canal Zone. — The Panama Canal zone was formerly
one of the most unhealthful places on earth, chiefly on account of the
prevalence of malaria and yellow fever. When the United States ac-
quired the zone in 1904 it was realized that the first step toward building
the great canal was to protect the health of all those immediately con-
cerned in the undertaking, and the sanitation of the isthmus was placed
in charge of one eminently qualified for the work, Colonel W. C. Gorgas.

He adapted the methods he had used in Cuba to the conditions
existing on the isthmus, with the result that every year the death rate
decreased until in 1908 it became, among eight thousand white Americans
living there, 9.72 per thousand, "a rate no higher than for a similar popu-
lation in the healthiest localities in the United States, and much lower
than that for most parts of the country." The Sanitary Department
has succeeded in driving yellow fever from the isthmus and in checking
malaria and other diseases to such a degree that the canal zone is no
longer an unhealthful place.

Typhoid Fever

The specific cause of typhoid fever is Bacillus typhosus. In the
human body this bacillus occurs chiefly in the intestines; but also in the
urinary bladder and usually in the blood of infected persons.

The excreta of typhoid subjects contain the virulent bacilli; and some
persons, even after recovery, continue to be u chronic carriers" of the
disease for many years.

Transmission. — The typhoid bacillus is introduced into the human
system by eating or drinking. Most epidemics are due to infected
water and many to milk; occasionally the disease is acquired from raw
vegetables or from oysters contaminated with sewage. Often the bacillus
is conveyed to food by human hands and possibly it is sometimes carried
by dust, cockroaches or ants; but there is no doubt that the disease is
transmitted by certain flies, particularly the true house fly, Musca domes-
tica, which is by far the commonest fly found generally in houses, and
becomes a serious menace to health during epidemics of typhoid fever.

TRANSMISSION OF DISEASES BY INSECTS

243

The house fly is well adapted by its structure and habits to carry
bacteria. The adults often feed on substances contaminated with
typhoid or other bacteria and these infected substances cling readily
to the hairs of the insect, especially those of the feet, and to the pro-
boscis. The larvae develop chiefly in horse manure, but also in other
kinds of excreta, some of which may contain virulent typhoid bacilli.

Transmission by Flies. — During the Spanish- American war ty-
phoid fever occurred in every American regiment and raged in many of
the concentration camps, in consequence of which a special commission
was appointed to investigate the origin and spread of the disease in the
army. A report by one of the members of the commission, Doctor
Vaughan, presents the following conclusions:

"a. Flies swarmed over infected fecal matter in the pits and then
visited and fed upon the food prepared for the soldiers at the mess tents.
In some instances where lime had recently been sprinkled over the con-
tents of the pits, flies with their feet whitened with lime were seen walk-
ing over the food.

"b. Officers whose mess tents were protected by means of screens
suffered proportionally less from typhoid than did those whose tents
were not so protected.

uc. Typhoid fever gradually disappeared in the fall of 1898, with
the approach of cold weather, and the consequent disabling of the fly.

"It is possible for the fly to carry the typhoid bacillus in two ways.
In the first place, fecal matter containing the typhoid germ may adhere
to the fly and be mechanically transported. In the second place, it is
possible that the typhoid bacillus may be carried in the digestive organs
of the fly and may be deposited with its excrement."

Similar conclusions in regard to the agency of flies in the spread of
enteric fever among troops have been reached also by investigators in
Bermuda, South Africa and India.

Firth and Horrocks fed house flies on material contaminated with
Bacillus typhosus and then obtained cultures of the bacillus from objects
to which the flies had access. In another experiment they got cultures
from the heads, bodies, wings and legs of such flies. Other investigators
have obtained Bacillus typhosus from flies captured in rooms occupied
by typhoid cases.

Faichnie caught flies in a place where there was an outbreak of ty-
phoid fever, held them on a sterilized needle and passed them through a
flame until legs and wings were scorched; after which he obtained the

244

ENTOMOLOGY

typhoid bacillus from the mashed bodies of the flies, the bacilli having
been present in the alimentary tract, without doubt.

Faichnie also obtained cultures of Bacillus typhosus from the intes-
tines of flies which had developed from larvae fed on feces containing the
bacillus.

Jordan states that the bacilli survive the passage of the alimentary
canal of the fly.

Ficker recovered typhoid bacilli from flies twenty-three days after
they had been infected.

In fact, a great amount of evidence has accumulated proving that
flies transmit not only the bacilli of typhoid fever, but many other bac-
teria, and often in enormous numbers. For example. Esten and Mason
in their study of the sources of bacteria in milk, collected and examined
flies from stables, pig-pens, houses and other places, and found an average
of 1.222.570 bacteria per fly; the majority of these being objectionable
kinds of bacteria.

Musca domestica. — A single female of the common house fly lays
in all some six hundred eggs. In midsummer, in Washington. D. C.
the eggs hatch in about eight hours; the larval period is from four to
five days and the pupal period five days, making the cycle about ten
days in length. In cooler parts of the season the cycle requires more
time and in warm climates it may be as short as eight days. The number
of generations in Washington is probably not more than nine (Howard).

Control. — One of the best baits for flies in houses is formalin, which
is poisonous to flies but harmless to man. This is prepared by diluting
formaldehyde with five or six times as much water and exposing it in
shallow dishes, the addition of a little sugar or milk making the solution
more attractive to flies, which drink it and quickly die. Pyrethrum is
effective against flies, but only when it is pure and has been kept from
exposure to the air. Pyrethrum, the chief basis of all the common
insect powders, is applied by being puffed through a bellows or by being
burned. The powder may be moistened and shaped into cones which
when lighted at the top burn slowly and give off fumes that are suffocat-
ing to insects.

Dr. Howard estimates that more than ten million dollars are spent
every year in screening houses in the United States. Another enormous
sum is spent for fly papers and fly traps. The efficient way to deal with
the fly problem, however, is to prevent the insects from breeding. Ex-
crementitious substances should be enclosed in such a way as to prevent
the access of flies, or should be treated in a way to kill the larvae therein;

TRANSMISSION OF DISEASES BY INSECTS

245

one of the simplest methods of treating stable manure being to spread it
out to dry, since the maggots cannot develop without moisture.

For detailed information on everything of importance relating to the '
house fly, and particularly on the mitigation of the fly-nuisance by con-
certed action in communities, Dr. Howard's admirable book on the house
fly should be consulted.

Plague.

In the ancient history of Europe epidemics of plague occupy a large
place. In recent years this pestilence has thrived in China and India,
and following an outbreak in 1894 in Hong Kong, the plague reached
the western hemisphere for the first time, appearing in Brazil, Argentina
and other South American countries, in Mexico and San Francisco.

The cause of plague is Bacillus pestis, an organism abundant in the
secretions and excretions of plague-stricken animals.

Three varieties of the disease are distinguished as follows:

(1) the bubonic, in which the bacilli cause enlargements of lymphatic
glands;

(2) the septicemic, characterized by the presence of large numbers
of bacilli in the blood and highly virulent;

(3) the pneumonic, in which the respiratory organs are affected, the
sputum showing the bacilli in enormous numbers; this form, relatively
rare, is the most fatal.

Transmission. — Plague is primarily a disease of rats, an epidemic
of plague in these animals having often been observed to precede as
well as accompany an epidemic among human beings. The disease
affects also mice, cats, dogs, calves, sheep, pigs, ducks, geese and many
other animals.

Though rats and other of the lower animals may contract the septi-
cemic type of the disease from feeding on parts of animals killed by
plague or on cultures of Bacillus pestis, the disease is commonly trans-
mitted among rats neither by contact nor through the atmosphere, but
by means of fleas. Healthy rats in association with diseased rats do
not become infected as long as fleas are excluded; but a transfer of fleas
from the latter to the former starts the disease. By various experiments
the Indian Plague Commission demonstrated the important part played
by rat-fleas in the transmission of plague. Zirolia found that the bacilli
even multiply in the mid-intestine of the flea, retaining their virulence for
a week or more.

The weight of evidence, both observational and experimental, shows

246

ENTOMOLOGY

that plague is transmitted from rats to man by several species of fleas
and also by bedbugs. Verjbitski, whose experiments on this subject
were particularly precise and thorough, found that plague can be con-
veyed by the bites of these insects and that the opening made by the bite
affords entrance to plague bacilli when the bodies of the insects are
crushed or when the infected feces are introduced by the rubbing or
scratching of the wound.

The species of rat-flea most common in the orient is the cosmopolitan
" plague flea," Lczmopsylla cheopns.

In the United Sates the most common rat flea is Ceratophyllus fascia-
Ins. The common cat and dog flea, Ctenocephalus cams, affects rats as
does also the human flea, Culex irritans; and all these species are known
to bite man.

Plague in San Francisco. — Plague, long dreaded in American sea-
ports, finally entered San Francisco in 1900, killed 114 persons in the
next four years, became dormant and broke forth again, with violence,
in 1907. The city, just beginning to recover from the great fire of the
year before, was in a frightful sanitary condition and most of the popula-
tion, engaged in the work of reconstruction, paid little attention to the
deaths from plague and at first gave little aid toward the suppression
of the disease. As may be imagined, the campaign against the disease
undertaken by the U. S. Public Health and Marine-Hospital Service was
carried on in the face of great odds. It was, however, conducted most
efficiently and successfully under the command of Dr. Rupert Blue
(now Surgeon- General), who wisely attacked the disease by attacking
the rat population.

The labor involved in starving out the rats, trapping or poisoning
them, and making buildings rat-proof by the use of concrete or sheet
iron, was immense; but the undertaking was nevertheless carried to a
successful conclusion. More than one million rats were killed and the
disease was checked.

In California plague affects ground squirrels, which doubtless con-
tract the disease from the rats that use the runways of the squirrels in the
fields.

Trypanosomiases
Some, of the diseases known as trypanosomiases are among the dead-
liest that affect man and other vertebrates, and pathogenic trypanosomes
— the organisms causing these diseases — have received an immense
amount of study during the last fifteen years.

TRANSMISSION OF DISEASES BY INSECTS

247

Trypanosomas. — The organisms under consideration are flagellate
protozoans. A typical trypanosome, for example, T. leivisi (Fig. 271)
of the rat, is essentially an elongated cell, tapering at each end, serpen-
tine in form and with no definite cell- wall. A round or oval nucleus is
present, also a peculiar chromatin body situated often near the posterior
end of the cell and termed the blepharoplast. Along one side of the cell
is a delicate protoplasmic contractile membrane, the undulating mem-
brane, along the edge of which is a marginal cord, which arises by growth
from the blepharoplast and is continued beyond
the anterior end of the cell as a vibratile flagellum.

Asexual reproduction is by means of a longi-
tudinal division of the cell body, preceded by divi-
sion of the flagellum, blepharoplast and nucleus,
the nucleus dividing amitotically. In regard to the
existence of sexual stages, or gametes, the results
of investigators seem to be inconclusive as yet.

In a film of fresh blood under the. microscope,
any active trypanosomes in the field of view attract
attention as centers of commotion among the red
blood corpuscles, which are pushed aside by the
lashing, twisting and other movements of the try-
panosomes.

The nutrition is by means of osmosis. Try-
panosomes have not been seen to attack erythro-
cytes, but according to MacNeal and Novy haemo-
globin is useful if not indispensable to them.

All five classes of vertebrates serve as hosts for
trypanosomes, of which more than seventy species
have received names. Most of these species are
carried from one vertebrate host to another by
means as yet unknown, but about twenty per cent, are known or suspected
to be transmitted by an intermediate invertebrate host. Thus trvpano-
somes of frogs are conveyed by leeches; pigeons are infected by mosqui-
toes, rats by sucking lice and fleas, and many mammals through the
agency of blood-sucking flies of the genus Glossina, and probably also
by Stomoxys and certain Tabanidae.

Tsetse Flies.— The name tsetse fly, originally limited to Glossina
morsitans (Muscidae) is now used for any of the eight known species of
the genus. These flies are a little larger than the common house fly
{Musca domestica). Their wings, in the resting position, overlap exactly

Fig. 271. — Trypanoso-
ma lewisi. b, blepharo-
plast; /, flagellum; m,
marginal cord; n, nucleus;
u, undulating membrane.
Greatly magnified.

248

ENTOMOLOGY

(Fig. 272) instead of being separated at the tips. The proboscis projects
forward, and is stout, owing to the ensheathing palpi; the base of the
labium forms a prominent bulb. These are the moie conspicuous char-
acters that serve to distinguish tsetse flies from other blood-sucking flies
with which they might be confused.

The mode of reproduction as described by Brauer is similar to that
of the group of parasitic flies known as Pupipara. The fly produces a
full-grown larva, which at once creeps to some resting place and forms a
black puparium.

Tsetse flies frequent hot. humid regions, near bodies of water, and
are restricted to shaded situations, never occurring on the open plains.
Both sexes are bloodthirsty but bite only during the daytime as a rule;
though they may bite at night when the moonlight is bright. Travelers

take advantage of the habits of the fly to
journey by night; spending the day in an open
uninfested place.

Nagana. — The colonization of South Africa
has been greatly retarded by nagana, a disease
invariably fatal to the horse, donkey and dog,
and usually fatal to cattle, but not affecting
man. Livingstone and other explorers in re-
gions where nagana is prevalent record their
having been bitten by tsetse flies thousands
of times with no result other than a slight
irritation.

Fig. 272— Tsetse fly, Glossina „ , , , .

morsitans. X2^. Bruce was the first to prove the identity of

nagana and tsetse-fly disease and to demon-
strate the role of the fly in the transmission of the disease. His investi-
gations, begun in Zululand in 1894, are of fundamental importance and
have given an immense^stimulus to the study of trypanosomes.

After rinding that no bacteria were concerned in nagana, Bruce dis-
covered trypanosomes in the blood of cattle affected with the disease.
He inoculated their blood into healthy horses and dogs and in a few days
the blood of these animals was teeming with trypanosomes. Then he
took healthy animals from the mountain on which he had located down
into the "fly country"; there they contracted the tsetse-fly disease and
showed in their blood trypanosomes indistinguishable from those of
nagana.

Horses taken into the fly country but not allowed to eat or drink
there, took the disease ^furthermore, supplies of grass and water brought

TRANSMISSION OF DISEASES BY INSECTS

249

from the fly country and fed to healthy horses failed to convey the
disease.

Then the influence of the fly was tested. Tsetse flies caught in the
lowland, carried to the mountain and placed at once on healthy animals
gave rise to the disease; but the flies never retained the power of infecting
a healthy animal for more than forty-eight hours after feeding upon a
sick animal. Thus wild flies, kept without food for three days and then
fed on a healthy dog. never gave rise to the disease. The fly alone trans-
mitted the disease; and this by means of trypanosomes adhering to the
proboscis either inside or out. Bruce found these organisms in the diges-
tive tract also, but with no change in their form.

He discovered further that buffaloes, antelopes and many other wild
animals carried the parasite in their blood, and was
able by injecting this blood to transmit the disease
to healthy domesticated animals. The parasites
were never numerous in the blood of their wild hosts,
however, and the latter seemed to be unaffected by
their presence. The 44 big game" of Africa serves,
generally speaking, as a reservoir for supplies of
trypanosomes.

The species of parasite that Bruce studied is
named Trypanosoma brucci (Fig. 273). The flies
concerned are Glossina morsitans, G. pallidipes and
G. fusca, particularly the first two, the distribution
of which coincides with that of nagana.

Xo certain remedies for the disease are yet
known. Human serum injected into infected ani-
mals causes the trypanosomes to disappear, at least soma brucei. Greatly
temporarily; but this fact is of more scientific in- magm e '
terest than practical importance. The precaution of traveling by night
is often adopted. Creolin and some other substances rubbed on animals
serve to repel the flies, and the smoke of encampments drives them away.
The protection of horses by means of screens is of course effective.

Human Trypanosomiasis. — Sleeping sickness is most prevalent in
the Congo basin, whence it has spread rapidly in equatorial Africa, where
it kills about fifty thousand natives every year. The reported cases of
recovery are so extremely rare that the mortality is placed at one hundred
per cent.

In the first stage of the disease, marked by the appearance of trypano-
somes in the blood, negroes show no symptoms as a rule, though whites

KXTOMOLOdY

are subject to fever. The symptoms may appear as early as four weeks
after infection or as late as seven years.

In the second stage trypanosomes appear in the cerebro-spinal fluid
and in large numbers in the lymphatic glands, those of the neck, axillae
and groins becoming enlarged. There is tremor of the tongue and
hands, drowsiness, emaciation and mental degeneration. The drowsi-
ness passes into periods of lethargy which become gradually stronger
until the patient becomes comatose and dies. Some victims do not
sleep excessively, but are lethargic, and "profoundly indifferent to all
going on around them."

There is some disagreement among authors as to the precise effects of
trypanosomes on human tissues and organs, but the evidence indicates
at least that trypanosomes produce a toxin which sets up irritations of
the lymphatic glands in general and those of the brain in particular.
Many of the symptoms of trypanosomiasis are traceable primarily to
inflammation of the lymphatics of the nervous system.

The specific cause of sleeping sickness is T. gambiense, discovered in
1 90 1 by Forde and named by Dutton. Two eminent English investi-
gators of sleeping sickness, Dutton and Tullock, sacrificed their lives to
the disease they were studying.

As the result of the labors of many investigators, human trypano-
somiasis is now well understood. Bruce and Xabarro demonstrated by
means of inoculation experiments with monkeys that T. gambiense is
transmitted chiefly, if not solely, by a tsetse fly, Glossina palpalis.
They and Greig showed that the distribution of the disease in Uganda
coincided with that of the fly. In some regions where the fly is present
the disease is unknown; which means simply that cases of the disease
have not yet been introduced.

Notwithstanding the great activity in the study of this disease no
good remedy for it has been found. Wise travelers in tropical Africa
take every precaution against being bitten by tsetse flies. Much effort
is being exerted to check the spread of the disease among the natives in
some of the infected regions; chiefly by removing patients from the fly
region, by screening dwellings or by building them away from the damp
and marshy areas where the flies breed.

Filariasis

The first disease found to be transmitted by an insect was filariasis,
the subject of important investigations by Manson, Bancroft and others.
This disease of tropical and subtropical regions is caused by a thread-

TRANSMISSION OF DISEASES BY INSECTS

worm, or nematode, known as Filaria bancrofti, which occurs in the
blood of man and of several of the lower animals as a slender larva
(microfilaria) about one-quarter of a millimeter in length. At night these
larvae swarm in the peripheral circulation, from which they are taken
into the alimentary canal of a blood-sucking mosquito (chiefly Culex
fatigans). In the mid-intestine of the mosquito the larva escapes from
its sheath and penetrates into muscular tissue, where it grows and devel-
ops for two or three weeks, after which it goes to some other part of the
mosquito's body, often to the base of the proboscis, whence the larvae
are carried into the blood of some vertebrate host, there to develop to
sexual maturity.

The larvae are often common in human blood without seeming to
injure the host in any way, but the adults (three or four inches long and
often found in groups) and ova that have escaped from the parent female
sometimes obstruct the lymphatic canals and cause enormous swellings
of feet, legs, arms or other parts of the human body; this condition being
known as elephantiasis.

Other Diseases

Cholera is undoubtedly transmitted by flies. As long ago as 1899
Dr. Nuttall wrote: "The body of evidence as to the role of flies in the
diffusion of cholera is, I believe, absolutely convincing."

Dysentery is probably carried by flies, as Dr. Orton and others have
inferred from their experiments.

Spillman and Haushalter, as well as several others, examined flies
that had fed on tubercular sputum and found in the intestinal contents
and in the dejections of these flies the bacilli of tuberculosis.

Dr. F. T. Lord summarizes his important investigations on this
subject as follows :

"1. Flies may ingest tubercular sputum and excrete tubercle bacilli,
the virulence of which may last for at Jeast fifteen days.

"2. The danger of human infection from the tubercular fly-specks is
by the ingestion of the specks on food. Spontaneous liberation of tuber-
cle bacilli from fly-specks is unlikely. If mechanically disturbed, infec-
tion of the surrounding air may occur."

If it is true that tuberculosis can be transmitted by means of food, as
recent experiments with some of the lower animals seem to indicate, the
house fly is evidently a factor that must be reckoned with in the fight
against this disease.

There is conclusive evidence that Egyptian ophthalmia is transmitted

*

ENTOMOU K1Y

by flies and it is highly probable that certain other infections of the eye
are conveyed by the same means. Other diseases that are probably
carried by flies are anthrax, yaws and tropical sore.

Dr. H. Graham has shown that the tropical disease known as dengue
is transmitted by the common mosquito, Culex faiigans. Dr. W. S.
Patton has proved that the deadly kala-azar is conveyed by a bedbug,
Cimex rotundatus, in India.

In 1912 Professor M. J. Rosenau and Dr. C. T. Brues announced that
they had succeeded in transmitting infantile paralysis (poliomyelitis)
to monkeys by means of the stable fly, Stomoxys calcitrans, and their
results were confirmed by Dr. J. F. Anderson. Whether this is the usual
means of transmission among human beings it remains to be determined.

Dr. Sambon's hypothesis that pellagra is transmitted by black-
flies (Simtdium) has aroused considerable interest, but as yet no definite
relation between the fly and the disease has been proved to exist.

CHAPTER X

INTERRELATIONS OF INSECTS

Insects in general are adapted to utilize all kinds of organic matter
as food, and they show all gradations of habit from herbivorous to carniv-
orous. The many forms that derive their food from the bodies of other
insects may conveniently be classed as predaceous or parasitic.

Predaceous Insects. — Among Orthoptera, Mantidae are notably
predatory, their front legs (Fig. 62, C) being well fitted for grasping and
killing other insects. The predaceous odonate nymphs have a peculiar
hinged extensible labium with which to
gather in the prey. The adults catch with
surpassing speed and precision a great vari-
ety of flying insects, mostly small forms,
but occasionally butterflies of considerable
size. The eyes of a dragon fly are remark-
ably large; the legs form a spiny basket,
probably to catch the prey, which is in-
stantly stripped and devoured, these opera-
tions being facilitated by the excessive
mobility of the head. The hemipterous
families Corixidae, Xotonectidae (Fig. 225),
Xepidae, Belostomidae (Fig. 22), Naucoridae
(Fig. 62, D), Reduviidae and Phymatidae are
predaceous, with raptorial front legs and
sharp beaks. Some of the Pentatomidae

(Fig. 274) are of considerable economic value on account of their predace-
ous habits. Most of the Neuroptera feed upon other insects. The Myrnte-
leon larva digs a funnel-shaped pitfall, at the bottom of which it buries
itself to await the fall of some unlucky ant. The Chrysopa larva impales
an aphid on the points of its mandibles and sucks the blood through a
groove along each mandible (Fig. 45, £), the maxilla fitting against this
groove to form a closed channel. Several families of Coleoptera are almost
entirely predaceous. Among aquatic beetles, Dytiscidae are carnivorous

253

Fig. 274. — Nymph of Podisus
maculivcntris sucking the blood
from a clover caterpillar, Colias
philodice. Natural size.

254

KXTOMOLOGY

both as larvae and imagines, Gyrinidae subsist chiefly upon disabled insects,
but occasionally eat plant substances, and Hydrophilidae as larvae catch
and devour other insects, though some of the beetles of this family (H. tri-
angularis, for example. Fig. 227) feed largely if not entirely upon vegetation.
Of terrestrial Coleoptera, the tiger beetles (Cicindelidae) are strictly pre-
daceous upon other insects. The Cicindela larva lives in a burrow in the
soil and lies in wait for passing insects; a pair of hooks on the fifth seg-
ment of the abdomen serves to prevent the larva from being jerked out
of its burrow by the struggles of its captive. The large family Carabidae
is chiefly predaceous; these ''running beetles'' both as larvae and adults
easily overtake and capture other terrestrial insects. The Carabidae,
however, are by no means exclusively carnivorous, for many of them feed
to some extent upon fungus spores, pollen, ovules, root-tips and other
vegetable matter, as Forbes has found; Harpalus caliginosus eats the
pollen of the ragweed in autumn; Galerita janus eats caterpillars and
occasionally the seeds of grasses; Calosoma. however, appears to be
strictly carnivorous, feeding chiefly upon caterpillars and being in this *
respect of considerable economic importance. As a whole. Carabidae
prefer animal food, as appears from the fact that when canker worms,
for instance, are unusually abundant they form a correspondingly large
percentage of carabid food, the increase being compensated by a dim-
inution in the amount of vegetable food taken (Forbes). Coccinellid
larvae (excepting Epilachna. which eats leaves) feed almost entirely upon
plant lice and constitute one of the most effective checks upon their
multiplication; the beetles eat aphides, but also fungus spores and pollen
in large quantities. Though Lepidoptera are pre-eminently phytoph-
agous, the larva of Fcniseca tarquinius is unique in feeding solely upon
plant lice, particularly the woolly Schizoneura tcsscllata of the alder.
Among Diptera, Asilidae. Midaidae, Therevidae and Empididae are the
chief predaceous families. Asilidae ferociously attack not only other
flies, but also beetles, bumble bees, butterflies and dragon flies; as larvae
they feed largely upon the larvae of beetles. Many of the larvae of
Syrphidae prey upon plant lice, and the larvae of Yolucella feed in Europe
on the larvae of bumble bees and wasps. Of Hymenoptera, the ants are
to a great extent predaceous. attacking all sorts of insects, but partic-
ularly soft-bodied kinds; while Vespidae feed largely upon other insects,
though like the ants, they are fond of the nectar of flowers and the juices
of fruits.

Parasitic Insects. — Though very many insects occur as external
parasites on the bodies of birds and mammals, very few occur as such on

INTERRELATIONS OF INSECTS

255

the bodies of other insects; one of the few is Br aula cceca, a wingless
dipteron found on the body of the honey bee.

A vast number of insects, however, undergo their larval develop-
ment as internal parasites of other insects, and most of these parasites
belong to the two most specialized orders, Diptera and Hymenoptera.

The larvae of Bombyliidae feed upon the eggs of Orthoptera and upon
larvae of Lepidoptera and Hymenoptera. Tachinidse are the most im-
portant dipterous parasites of other insects and lay their eggs most
frequently upon caterpillars; the larvae bore into their victim, develop
within its body, and at length emerge as winged insects. These parasites
often render an important
service to man in checking
the increase of noxious
Lepidoptera.

The great majority of
insect parasites — many
thousand species — belong
to the order Hymenoptera,
constituting one of the
primary divisions of the
order. They are immense-
ly important from an eco-
nomic standpoint, partic-
ularly the Ichneumonidae,
of which more than ten
thousand species are

already known. Our most conspicuous ichneumonids are the two species
of Thalessa, T. atrata and T. lunator (Fig. 275), with their long ovipositors
(three inches long in lunator, and four to four and three-quarters inches
in atrata). Thalessa bores into the trunks of trees in order to reach the
burrows of another large hymenopteron, Tremex columba (Fig. 31), upon
whose larvae the larva of Thalessa feeds.

The enormous family Braconidae, closely related to Ichneumonidae,
is illustrated by the common Apanteles congregatus, which lays its eggs
in the caterpillars of various Sphingidae. The parasitic larvae feed upon
the blood and possibly also the fat-body of their host, and at length
emerge and spin their cocoons upon the exterior of the caterpillar (Fig.
276), sometimes to the number of several hundred. Species of Aphidius
transform within the bodies of plant lice, one to each host, and the imago
cuts its way out through a circular opening with a correspondingly

Fig. 275. — Oviposition of Thalessa lunator.

— After Riley.

Natural size.

256

ENTOMOLOGY

circular lid. Chalcididae, of which some four thousand species are known,
are usually minute and parasitic; though some are phytophagous, for
example, Isosoma hordei, which lives in the stems of grasses, especially
wheat, rye and barley. Chalcids affect a great variety of insects of one
stage or another, such as caterpillars, pupae, cockroach eggs, plant lice
and scale insects; while some of them develop in cynipid galls, either
upon the larvae of the gall-makers or upon the larvae of inquilines. Giard
in France reared more than three thousand chalcids (Copidosoma trun-
catellum) from a single caterpillar of Plusia. Proctotrypidae are re-
markable as parasites. Most of them are minute; indeed, this family and
the coleopterous family Trichopterygidae contain the smallest winged

Fig. 276. — A tomato worm, Phlegethontius sexta, bearing cocoons of the parasitic Apanteles

congregatus. Natural size.

insects known — species but one-third or one-fourth of a millimeter long.
A large proportion of the Proctotrypidae are parasitic in the eggs of other
insects or of spiders, several sometimes developing in the same egg;
others affect odonate nymphs and coleopterous or dipterous larvae,
while several species have been reared from cecidomyiid and cynipid
galls, and many proctotrypids are parasites of other parasitic insects —
in other words, are hyper parasites.

Hyperparasitism. — Xot only are primary parasites frequently
attacked by other, or secondary, parasites, but tertiary parasitism is
known to occur in a few instances, and there is some reason to believe
that even the quaternary type exists among insects, as in the following
case.

INTERRELATIONS OF INSECTS

257

The caterpillar of Hemerocampa {Orgyia) leucostigma defoliates shade
trees in the northeastern United States. An enormous increase of this
species in the city of Washington in 1895 was attended by a correspond-
ing increase of parasitic and predaceous species, and this unusual oppor-
tunity for the study of parasitism was made the most of by Dr. Howard,
from whose admirable paper these facts are taken.

The primary parasites of H. leucostigma numbered 23 species — 17
Hymenoptera and 6 Diptera ; of the hyperparasites (all hymenopterous)
13 were secondary, 2 and probably 5 were tertiary, and one of these
(Asecodes albitarsis) may under certain conditions prove to be a quater-
nary parasite. To illustrate — The ichneumon Pimpla inquisitor, an
important primary parasite of lepidopterous larvae, lays its eggs in cater-
pillars of H. leucostigma; its larvae suck the blood of their host and at
length spin their cocoons within the loose cocoon of the Hemerocampa.
These cocoons have yielded a well-known secondary parasite, the chalcid
Dibrachys boucheanus. Now another chalcid, Asecodes albitarsis, has
been seen to issue from a pupa of this Dibrachys, thus establishing tertiary
parasitism. Furthermore, it is quite possible that Dibrachys itself is a
tertiary parasite, in which event the Asecodes might become a parasite
of the quaternary order.

Economic Importance of Parasitism. — If a primary parasite is
beneficial, its own parasites are indirectly injurious, generally speaking;
while those of the third and the fourth order are respectively beneficial
and injurious. The last two kinds are so rare, however, as to be of no
practical importance from an economic standpoint. The first two kinds
are of immense economic importance, particularly the primary parasites.
" Outbreaks of injurious insects," says Howard, "are frequently stopped
as though by magic by the work of insect enemies of the species. Hub-
bard found, in 1880, that a minute parasite, Trichogramma pretiosa, alone
and unaided, almost annihilated the fifth brood of the cotton worm in
Florida, fully ninety per cent, of the eggs of this prolific crop enemy
being infested by the parasite. Not longer ago than 1895, in the city of
Washington, more than ninety-seven per cent, of the caterpillars of one
of our most important shade-tree pests [Orgyia, as just mentioned] were
destroyed by parasitic insects, to the complete relief of the city the
following year. The Hessian fly, that destructive enemy to wheat crops
in the United States, is practically unconsidered by the wheat growers
of certain states, for the reason that whenever its numbers begin to be
injuriously great its parasites increase to such a degree as to prevent
appreciable damage.
18

25»

ENTOMOLOGY

"The control of a plant-feeding insect by its insect enemies is an ex-
tremely complicated matter, since, as we have already hinted, the parasites
of the parasites play an important part. The undue multiplication of
a vegetable feeder is followed by the undue multiplication of parasites,
and their increase is followed by the increase of hyperparasites. Fol-
lowing the very instance of the multiplication of the shade-tree cater-
pillar just mentioned, the writer [Howard] was able to determine this
parasitic chain during the next season down to quaternary parasitism.
Beyond this point, true internal parasitism probably did not exist, but
even these quaternary parasites were subject to bacterial or fungus
disease and to the attacks of predatory insects.

"The prime cause of the abundance or scarcity of a leaf-feeding
species is, therefore, obscure, since it is hindered by an abundance of
primary parasites, favored by an abundance of secondary parasites
(since these will destroy the primary parasites), hindered again by an
abundance of tertiary parasites, and favored again by an abundance of
quaternary parasites. "

Entomologists have made many attempts to import and propagate
insect enemies of various introduced insect pests, and some of their
efforts have been crowned with success, as was notably the case when
Novius cardinalis, a lady-bird beetle, was taken from Australia to Cali-
fornia to destroy the fluted scale.

Form of Parasitic Larvae. — The peculiar environment of parasitic
larvae is responsible for profound changes in their organization. These
larvae, in general, are apodous, the body is compact and the head is more
or less reduced, sometimes to the merest rudiment. These characters,
occurring also in such dipterous larvae as live in a mass of decaying or-
ganic matter and again in those hymenopterous larvae whose food is pro-
vided by the mother or by nurses, are to be attributed to the presence
of a plentiful supply of food, obtainable with little or no exertion, and
indicate, not primitive simplicity of organization, but a high degree of
specialization, as we have said before. The embryonic development of
parasitic larvae is frequently highly anomalous, as appears in the chapter
on development.

Maternal Provision. — Excepting several families of Hymenoptera
and the Termitidae, few insects make any special provision for the wel-
fare of the young beyond laying the eggs in some appropriate situation.
Many insects, as walking-sticks (Phasmidae) and some butterflies (Argyn-
nis) simply drop their eggs to the ground, leaving the young to shift for
themselves. Most insects, however, instinctively lay their eggs in

INTERRELATIONS OF INSECTS

259

situations where the larva is sure to find its proper food near at hand.
Thus various flies and beetles deposit their eggs on decaying animal
matter, butterflies and moths are more or less restricted to particular
species of plants, and parasitic Hymenoptera to certain species of insects.
The beetles of the genus Xecrophorus go so far as to bury the body of a
bird, mouse or other animal in which the eggs are to be laid; and in this
instance the male assists the female in undermining and afterward cover-
ing the body. A similar co-operation of the two sexes occurs in the
scarabaeid beetles known as " tumblebugs, " a pair of which may often
be seen rolling along laboriously a ball of dung which is to serve as larval
food. The female mole-cricket (Gryllotalpa) is said to care for her eggs
and even to feed the young at first.

Hymenoptera display all degrees of complexity in regard to maternal
provision. Tenthredinidae simply lay their eggs on the proper food
plants or else insert them into the tissues of the plants. Sphecina make
a nest, provision it with food and leave the young to care for themselves.
Queen wasps and bumble bees go a step further in feeding the first larva;
and carrying them to maturity. Finally, in the honey bee the care of
the young is at once relegated by the queen to other individuals of the
colony, as is also the case among ants.

Some of the most elaborate examples of purely maternal provision
are found among the digger wasps and the solitary wasps; these instances
are highly interesting, involving as they do an intricate co-ordination
of many reflex actions — as appears in the discussion of insect behavior.

Among the Sphecina, or digger wasps, the female makes a nest by
burrowing into the ground, by mining into such pithy plants as elder or
sumach, or else by plastering bits of mud together. The nest is provi-
sioned with insects or spiders which have been stung in such a way as
usually to be paralyzed, without being actually killed. The various
species of Sphecina frequently select particular species of insects or
spiders as food for the young. Pepsis Jormosa (Pompilidae) uses taran-
tulas for this purpose; Sphecius speciosus (Bembecidae) stores her nest
with a cicada; Xyssonidae pick out certain species of Membracidae;
mud-daubers (Sphecidae) use spiders; and other families of Sphecina
capture bees, beetles, plant lice or other insects, as the case may be. The
solitary wasps (Eumenidae) are similar to the digger wasps in habits.

Of the solitary bees, Megachile is well known for its habit of cutting
pieces out of rose leaves; it uses oblong pieces to form a thimble-shaped
tube which, after being stored with pollen and nectar, is plugged with a
circular piece of leaf. The larval cells are made either in tunnels ex-

2()Q

I NK )M( )!.< )GY

cavated in wood by the mother or else in cracks or other ehance
cavities.

One of the carpenter bees, Ceratina dupla, which builds in the hollow-
stem of a plant a series of larval cells separated by partitions, is said by
Comstock to watch over her nest until the young mature.

The transition from the solitary to the social habit is indicated in the
life-histories of wasps and bumble bees, where a solitary queen founds
the colony but soon relegates to other individuals all duties except that
of egg-laying. The social insects will now be considered.

Termites

Though popularly known as ''white ants," the termites are quite
different from true ants, being indeed not very far removed from the
most primitive insects. In view of the extreme contrast in structure
and development between termites and ants, it is remarkable that the
two groups should have much the same kind of complex social organiza-
tion.

Classes of Termites. — In general, four kinds of adults are produced

winged insect; D, perfect insect after shedding the wings; E, young complementary queen;
F, older complementary queen. Enlarged.— After Grassi and Sandias.

in a community of termites, namely — workers, soldiers, winged males
and winged females.

The workers (Fig. 277 , .4) , which are ordinarily the most numerous, are
of either sex, but their reproductive organs are undeveloped. A worker-
ant or bee, however, is always a female. The termite workers, as the
name implies, do most of the work; they make the nest, provide food,
feed and care for the young and the royal pair, and attend to many other
domestic duties.

The soldiers, like the workers, are of either sex, with undeveloped

INTERRELATIONS OF INSECTS

26l

sexual organs. With monstrous mandibles and head (Fig. 277, B),
their chief duty apparently is to defend the colony, though they fre-
quently fail to do so.

The winged males and females (Fig. 277, C) which are sexually ma-
ture, swarm from the nest and mate. After the nuptial flight the pair
burrow into some crevice and shed the wings, which break off each along
a peculiar transverse suture, leaving four triangular stumps (Fig. 277, D).
The king and queen found a new colony and may live for several years,
sheltered in a special chamber, the queen, meanwhile, becoming enor-
mously distended (Fig. 278) with eggs and almost incapable of locomotion.
The prolificacy of the queen is astonishing; she can
lay thousands of eggs, sometimes at the rate of sixty
per minute. She is the nucleus of the colony, and
should she become incapacitated, is replaced by one
or more substitute queens, which have been developed
to meet the emergency; similarly, a substitute king is
matured upon occasion. These substitutes (Fig. 277, E)
differ from the primary pair in having nymphal wing-
pads in place of the remains of functional wings.

These six kinds are by no means all that may occur
in a single colony. Tcrmes lucifugus, according to
Grassi, has no less than fifteen kinds of individuals,
counting nymphs in various stages of development
toward workers, soldiers, and primary or else comple-
mentary, or reserve, kings or queens.

Origin of Castes. — Grassi maintains that all the
forms are alike at birth except as regards sex, and that
the differences between worker and soldier, which are
independent of sex, depend probably upon nutrition.
Grassi attributes all the diversities of caste, except
the sexual ones, to the character and amount of the food.

Food. — The food of termites is of six kinds: (1) wood; (2) matter
emitted from the oesophagus or rectum, termed respectively stomodaeal
and proctodaeal food; (3) cast skins and other exuvial stuff; (4) the bodies
of their companions; (5) saliva; (6) water. Of these the proctodaeal
food is the favorite. Nymphs receive at first only saliva; later they get
stomodaeal and proctodaeal food until, finally . they are able to eat wood
— the staple food of a termite.

American Species.— Our common termite is Termes flavipes. which
occurs throughout the United States, excavating its galleries in decaying

Fig. 278.— Queen
of Tcrmes obesus.
Natural size. — After
Hagen.

262 ENTOMOLOGY

logs, stumps or other dead wood. The nuptial flight of this species
takes place in spring, when the two sexes swarm in numbers that are
sometimes enormous. One swarm, as recorded by Hagen, appeared as
a dense cloud, and was being followed and attacked by no less than
fifteen species of birds, among which were robins, bluebirds and sparrows;
some of the robins were so gorged to the mouth with termites that their
beaks stood open. Though plenty of winged females are said to occur
in the swarming season, the true queen of T. flavipes is extremely rare,
the queen usually found being evidently, from her undeveloped wings, a
substitute queen.

In the Western states, six species of termites are known, including

Termes lucifugus, which has probably
been introduced from Europe. In this
species the primary queen is known
to exist. Regarding the Californian
Termopsis angusticollis. Dr. Heath
says that if only one of the royal pair
be destroyed usually only one sub-
stitution form is developed, but when
both perish, from ten to forty substi-
tutes appear, according to the size of
the colony; furthermore — a remark-
able fact — these substitution royalties
may contain workers or even soldiers
capable of laying eggs.

Architecture. — While many ter-
mites simply burrow in dead wood,
other species construct more elaborate
nests. A Jamaican species builds huge
nests in the forks of trees, with covered
passageways leading to the ground.
In parts of Africa and Australia, where they are free from disturb-
ance, termites erect huge mounds, frequently six to ten and sometimes
eighteen or twenty feet high, with galleries extending as far below the
surface of the ground as they do above it. These immense structures
(Fig. 279) consist chiefly of earth, cemented by means of some secretion
into a stonyxlay, with which also much excrementitious matter is mixed;
they are pyramidal, columnar, pinnacled or of various other forms, ac-
cording to the species, and are perforated by thousands of passages and

INTERRELATIONS OF INSECTS

263

chambers, while there are underground galleries extending away from
the mound to a distance of often several hundred feet.

An extraordinary type of mound is constructed by the "compass,"
or ''meridian," termites of North Australia, for their wedge-shaped
mounds (Fig. 280), commonly eight or ten feet high, though sometimes
as high as twenty feet, are directed north and south with surprising
accuracy. By means of this orientation the exposure to the heat of the
sun is reduced to the minimum, as occurs
also in the case of many Australian plants,
the leaves of which present their edges in-
stead of their faces to the sun.

More than one species of termite may
inhabit a single nest; in one South African
nest Haviland found five species of ter-
mites and three of ants. The widely dis-
tributed genus Eutermes is essentially a
group of inquiline, or guest, species. Ter-
mite mounds afford shelter to scorpions,
snakes, lizards, rats, and even birds, some
of which nest in them. The Australian
bushmen hollow out the mounds to make
temporary ovens, and even eat the clay of
which they are composed, while hill-
tribes of India are accustomed to eat
the termites themselves, the flavor of
which is said to be delicious.

Ravages. — In tropical regions the
amount of destruction done by termites
is enormous, and these formidable pests
are a constant source of consternation
and dread. They emit a secretion that
corrodes metals and even glass, while anything made of wood is simply at
their mercy. Always avoiding the light, they hollow out floors, rafters
or furniture, leaving only a thin outer shell, and as a result of their in-
sidious work a chair or a table may unexpectedly crumble at a touch.
Jamestown, the capital of St. Helena, was largely destroyed by termites
(1870) and had to be rebuilt on that account.

In the United States and Europe few species of termites occur, and
they do little injury as compared with the tropical species; though our

264

ENTOMOLOGY

common Tcrmcs Jlavipes occasionally damages woodwork, books, plants,
etc., in an extensive way, particularly in the Southern states.

Termitophilism. Associating with termites are found various
other arthropods, mostly insects. Their relations to the termites are,
so far as is known, similar to those described beyond between myrme-
cophilous species and ants. These tcrmitophilous forms, however, have
received as yet but little attention.

Honey Bee

For more than three thousand years the honey bee has been almost
unique among insects as an object of human care and study. It was
highly prized by the old Greeks and Romans (as appears from the writ-
ings of Aristotle, 330 B. C, and Cato, about 200 B. C.) and actually
worshiped as a symbol of royalty by the ancient Egyptians, through
whose papyri and scarabs the honey bee may be traced back to the time
of Rameses I., or 1400 B. C.

Though its habits have been somewhat modified by domestication,
the honey bee, unlike most domesticated animals, is still so little de-

a b c

Fig. 2S1. — The honey bee. Apis meUifcra. A. queen; B, drone; C. worker. Xatural size.

pendent upon man that it readily returns to a wild life. Under many
distinct races, which are due largely to human intervention. Apis mel-
lijera is widely distributed over the earth.

Castes. — The species comprises three kinds of individuals: queen,
drone and worker (Fig. 281). The workers are females with an atrophied
reproductive system. They constitute the vast majority in any colony
and are the only kind that is commonly seen out of doors. Upon the
industrious workers falls the burden of the labor; they build the comb,
nurse the young, gather food, clean and repair the nest, guard it from
intruders, control larval development, expel the drones — briefly, the
workers alone are responsible for the general management of the com-

INTERRELATIONS OF INSECTS

265

munity. Though hibernating workers live eight or nine months, the
other workers live but from live to twelve weeks.

The term queen is. of course, a misnomer, for the government of
the hive is anything but monarchical. The chief duties of the queen,
or mother, are simply to lay eggs and to lead away a swarm. She is able
to deposit as many as 4.000 eggs in twenty-four hours. After a single
mating, the spermatozoa retain their vitality in the spermatheca of the
queen for three or four years — the lifetime of a queen. The males, or
drones, apart from their occasional sexual usefulness, are of little or no
service, and their very name has become an expression for laziness.

The Comb. — Wax, of which the comb is built, is made from honev or
sugar, many pounds (twenty, according to Huber)
of honey being required to make one pound of
wax. The workers, gorged with nectar, cling to
one another in a dense heated mass until the white
films of wax appear underneath the abdomen (Fig.
102); these are transferred to the mouth,
as described on page 211, and are masti-
cated with a fluid, secreted by cephalic
glands, which alters the chemical composition of
the wax and makes it plastic.

The workers now contribute their wax to form
a vertical, hanging septum, on the opposite sides of
which they proceed to bite out pits — the bottoms
of the future cells — using the excavated wax in
making the cell walls. The bottom of each cell
consists of three rhombic plates (Fig. 282, A ), and
.the cells of one side interdigitate with those of the
other side (Fig. 282, B) in such a way that each rhomb serves for two
cells at once. Wax is such a precious substance that it is used (in-
stinctively, however) always with the greatest economy; the cell walls
' are scraped to a thinness of o4tt or t^o of an inch, and nowhere is
more wax used than is sufficient for strength: one pound of wax makes
from 35,000 to 50. coo worker cells. The cells, at first circular in cross
section, become hexagonal from the mutual interference of workers on
opposite sides of the same wall; the form, however, is by no means a
regular hexagon in the mathematical sense, for it is difficult to find a
cell with errors of less than 3 or 4 degrees in its angles (Cheshire).
Worker cells are one fifth of an inch in diameter, while the larger cells,
destined for drones or to hold honey, are one quarter of an inch across.

Fig. 282. — A, Bases
of comb cells; B, section
of comb. Somewhat en-
larged.— After Cheshire.

266

ENTOMOLOGY

To strengthen the edges of cells or to fill crevices, the workers use
propolis, the sticky exudation from the buds or leaf axils of poplar, fir,
horse-chestnut or other trees; though they will utilize instead such arti-
ficial substances as grease, pitch or
varnish. As winter approaches, the
bees apply the propolis liberally,
making their abode tight and com-
fortable.

Larval Development. — When

the brood cells are ready, the queen,
attended by workers, lays an egg in
each cell and has no further con-
cern as to its fate. After three
days the egg discloses a footless
grub (Figs. 283, 284) which de-
pends at first upon the milky food
that bathes it and has been sup-
plied from the mouths of the worker
nurses. Later the larva is weaned
by its nurses to pollen, honey and
water. As the stomach and the in-
testine of the larva do not com-
municate with each other, the ex-
cretions of the larva cannot contaminate the surrounding nutriment,
and they are retained until the final moult. Five days after hatching,
the larva spins its cocoon, the workers having meanwhile covered the
larval cells with a porous
cap of wax and pollen (Fig.
284) and on the twenty-
first day after the egg was
laid the winged bee cuts
its way out. assisted in this
operation by the ever-at-
tentive nurses. Xow. after
acquiring the use of its fac-
ulties, the newly emerged

bee itself assumes the duties of a nurse, but as soon as its cephalic nurs-
ing glands are exhausted it becomes a forager. This account applies to
the worker; the three kinds of individuals differ in respect to the number

Fig. 283. — Comb of honey bee, show-
ing the insect in various stages. At the
right are large queen cells. — After Bex-
tox.

Fig. 284. — Honey bee. /, feeding larva; p. pupa;
s. spinning larva. — After Cheshire.

INTERRELATIONS OF INSECTS

267

of days required for development, as appears in the following table, from
Benton:

Egg.

Larva.

Pupa.

Total.

Queen,

3

7

Worker,

3

5

13

21

Drone,

3

6

*5

24

The cells in which queens develop (Fig. 283) are quite different from
worker or drone cells, being much larger, more or less irregular in form,
and vertical instead of horizontal; they are attached usually to the lower
edge of a comb or else to one of the side edges.

Other Facts. — The entire organization of the honey bee has been
profoundly modified with reference to floral structure; the life of the
bee is wrapped up in that of the flower. The more important structural
adaptations of bees in relation to flowers have been described, as well as
many of their sensory peculiarities; there remain to be added, however,
some other items of interest, chosen from the many.

A colony of bees in good condition at the opening of the season con-
tains a laying queen and some 30.000 to 40.000 worker bees, or six to
eight quarts by measurement. Besides this there should be four, five,
or even more combs fairly stocked with developing brood, with a good
supply of honey about it. Drones may also be present, even to the
number of several hundred.

Ordinarily the queen mates but once, flying from the hive to meet the
drone high in the air, when five to nine days old generally. Seminal
fluid sufficient to impregnate the greater number of eggs she will deposit
during the next two or three years (sometimes even four or five years)
is stored at the time of mating in a sac — the spermatheca, opening into
the egg-passage. At the time the queen mates there are in the hive
neither eggs nor young larvae from which to rear another queen; hence,
should she be lost, no more fertilized eggs would be deposited, and the
old workers gradually dying off without being replaced by young ones,
the colony would become extinct in the course of a few months at most,
or meet a speedier fate through intruders, such as wax-moth larvae,
robber bees, wasps, etc., which its weakness would prevent its repelling
longer; or cold is very likely to finish such a decimated colony, especially
as the bees, because queenless, are uneasy and do not cluster compactly.

The liquid secreted in the nectaries of flowers is usually quite thin,
containing, when just gathered, a large percentage of water. Bees suck
or lap it up from such flowers as they can reach with their flexible, suck-
ing tongue, 0.25 to 0.28 inch long. This nectar is taken into the honey

268

KXTOMOLOCY

sac, located in the abdomen, for transportation to the hive. Besides
being thin, the nectar has at first a raw, rank taste, generally the flavor
and odor peculiar to the plant from which gathered, and these are fre-
quently far from agreeable. To make from this raw product the health-
ful and delicious table luxury which honey constitutes — "fit food for the
gods1'- — is another of the functions peculiar to the worker bee. The
first step is the stationing of workers in lines near the hive entrances.
These, by incessant buzzing of their wings, drive currents of air into and
out of the hive and over the comb surfaces. If the hand be held before
the entrance at such a time a strong current of warm air may be felt
coming out. The loud buzzing heard at night during the summer time
is due to the wings of workers engaged chiefly in ripening nectar. In-
stead of being at rest, as many suppose, the busy workers are caring for
the last-gathered lot of nectar and making room for further accessions.
This may go on far into the night, or even all night, to a greater or less
extent, the loudness and activity being proportionate to the amount and
thinness of the liquid. Frequently the ripening honey is removed from
one set of cells and placed in others. This may be to gain the use of
certain combs for the queen, or possibly it is merely incidental to the
manipulation the bees wish to give it. When, finally, the process has
been completed, it is found that the water content has usually been re-
duced to 10 or 12 per cent., and that the disagreeable odors and flavors,
probably due to volatile oils, have also been driven off in a great measure,
if not wholly, by the heat of the hive, largely generated by the bees.
During the manipulation an antiseptic (formic acid), secreted by glands
in the head of the bee, and possibly other glandular secretions as well
have been added. The finished product is stored in waxen cells above
and around the brood nest and the main cluster of bees, as far from the
entrance as it can be and still be near to the brood and bees. The work
of sealing with waxen caps then goes forward rapidly, the covering being
more or less porous. Each kind of honey has its distinctive flavor and
aroma, derived, as already indicated, mainly from the particular blossoms
by which it was secreted, but modified and softened by the manipulation
given it in the hives. The last three paragraphs are taken from Ben-
ton's useful manual.

The phenomenon of "swarming'' results from the tremendous re-
productive capacity of the queen, though it is immediately an instance
of positive phototropisnu as Kellogg has shown. Accompanied by most of
the workers, the old queen abandons the hive to establish a new colony.
The workers that remain behind have provided against this contingency,

INTERRELATIONS OF INSECTS

269

however, and the departed queen is soon, if not already, replaced by a
new one.

Determination of Caste. — The difference between queen and
worker depends solely upon nutrition, both forms being derived from
precisely the same kind of egg. To produce a queen, a large cell ot
special form is constructed, and its occupant, instead of being weaned, is
fed almost entirely upon the highly nutritious secretion which worker
grubs receive only at first and in limited quantity. This nitrogenous
food, the product of cephalic glands, develops the reproductive system
in proportion to the amount received. Drone larvae get much of it
though not so much as queens, while an occasional excess of this "royal
jelKT ,? is believed to account for the abnormal appearance of fertile
wrorkers.

Parthenogenesis, or reproduction without fertilization, is known to
occur in the bee, as well as in various other insects. The always un-
fertilized eggs of workers produce invariably drones, as do also unfertil-
ized eggs of the queen, but it does not follow that males never come from
fertilized eggs, as Dzierzon believed. Dickel and others hold that all
the eggs laid by a fertilized queen have been fertilized. Dickel stated
that the sex is determined by the nutrition of the larva, but it seems
more probable that the sex is determined before the egg is laid.

Bumble Bees

Familiar as the bumble bees are, their habits have been little studied
in this country. The queen hibernates and in spring starts a colony, utiliz-
ing frequently for this purpose the deserted nest of a field mouse or some-
times the burrow of a mole or gopher. The queen lays her eggs in a
small mass of pollen mixed with nectar (Putnam). The larvae eat out
cavities in the mass of food and when full grown spin silken cocoons,
from which the imago cuts its way out; the empty cocoon being sub-
sequently used as a receptacle for honey. At first only workers are
produced and they at once relieve the queen of the duties of collecting
nectar and pollen, caring for the young, etc. The workers are of dif-
ferent sizes, the smaller ones being nurses or builders and the larger ones
foragers — the kind commonly seen out of doors. In the latter part of
summer both males and females are produced, but when severe frost
arrives, the old queen, the workers and the males succumb, leaving only
the young queens to survive the winter.

270

KXTO MOM UN-

SOCIAL Wasps

The Social Wasps constitute the family Vespidae, of which we have
three genera, namely. Yes pa, Polistes and Polybia, the last genus being
represented by a single Californian species.

Vespa. — Some species of Vespa, as V. maculata, make a nest which
consists of several tiers of cells protected by an envelope (Fig. 285), at-
taching the nest frequently to a tree; other species, as germanica and
vulgaris, make a nest underground. The paper of which the nests are
composed is manufactured from weather-worn shreds of wood, which are
torn off by the mandibles and then masticated with a secreted fluid
which cements the paper and makes it waterproof.

Fig. 285. — Xest of wasp, Vespa maculata. A. outer aspect; B. with envelope cut away to

show combs. Greatly reduced.

A solitary queen founds the colony in spring; she starts the nest,
lays eggs, feeds the young and brings forth the first workers; these then
relieve her — continue the building operations, collect food, nurse the
young, in short, assume the burden of the labor. In the latter part of
summer, fertile males and females appear and pairing occurs. Though
the statement has often been made that only the young queens survive
the winter, there is some reason to believe that not only the queens but
also males and workers may hibernate successfully in the nest.

The larvae are fed at first, by regurgitation, upon the sugary nectar of
flowers and the juices of fruits, and later upon more substantial food,
such as the softer parts of caterpillars, flies, bees, etc., reduced to a pulp
by mastication; occasionally wasps steal honey from bees.

INTERRELATIONS OF INSECTS

271

The workers, as is usual among social Hymenoptera, are modified
females, incapable of reproduction as a rule, though the distinction be-
tween worker and queen is not nearly so sharp among wasps as it is
among bees. Worker eggs are said to be parthenogenetic and to pro-
duce only males. The males, unlike those of the honey bee, are active
laborers in the colony. In the tropics there are wasps that form per-
manent colonies, store honey and swarm, after the fashion of honey bees.

Polistes. — The preceding description of Vespa applies equally well
to our several species of Polistes, except that the nest of Polistes is a
single comb hanging by a pedicel and without a protecting envelope.
Miss Enteman, who has carefully studied the habits of Polistes, finds
that the larva spins a lining as well as a cap for its cell, by means of a
fluid from the mouth, and that the adults emerge after a pupal period of
three weeks, males and females appearing (in the vicinity of Chicago)
in the latter part of August and early in September.

Ants

The habits of ants have engaged the serious attention of some of the
most sagacious students of the phenomena of life. Any species of ant
presents innumerable problems to the thoughtful investigator and no
less than two thousand species of ants are already known.

A large part of our knowledge of the habits of these remarkable in-
sects has been obtained by the use of artificial formicaries, which are
easily constructed and have yielded important results in the hands of
Lubbock, Forel, Janet, Wasmann, Fielde, Wheeler and other well-known
students of ants.

Castes. — In a colony of ants three kinds of individuals are produced
as a rule : males, females and workers, the last being sexually imperfect
females.

The males and females swarm into the air for a nuptial flight, after
which the males die, but the females shed their wings and enter upon a
new and prolific existence, which may last for many years; a queen of
Lasius niger was kept alive by Lubbock for nine years, and one of For-
mica fusca, fifteen years, and then its death was due to an accident.

The workers live from one to seven years, according to the same
authority. They constitute the vast majority in any colony and are the
familiar forms that so often command attention by their industry and
pertinacity. In some species certain of the workers are known as soldiers;
these may be recognized by their larger heads and mandibles.

Polymorphism.- — Ants and termites surpass all other insects in

272

ENTOMOLOGY

respect to the number of forms under which a single species may occur.
In some species of ants several types of workers exist; these are distin-
guished by structural peculiarities of one kind or another, which possibly
indicate special functions, for the most part as yet unascertained. Fur-
thermore, the sexual individuals are not necessarily winged; some or all
of them may be wingless, especially the females. These wingless males
and females are termed ergatoid, on account of their resemblance to
workers.

As to how these various forms are produced, very little is known.
Probably, as among bees, workers and queens are produced from the same
kind of eggs, which have been fertilized, and the differences between
worker and queen and between workers themselves may be due to the
quality and quantity of the food that is supplied to the larvae by their
nurses. As in bees, the parthenogenetic eggs laid by abnormal wrorkers
may produce males, as Forel, Lubbock and Miss Fielde have found; or
they may produce normal workers, as Reichenbach and Airs. A. B. Corn-
stock have found to be the case in Lasius niger. Wheeler points out
the possibility of the inheritance of worker characters through the male
offspring of workers.

Larvae. — The numerous eggs laid by one or more queens are taken
in charge by the young workers, through whose assiduous care the help-
less larvae are carried to maturity. The nurses feed the larvae from their
own mouths, clean the larvae, and carry them from one place to another
in order to secure the optimum conditions of temperature, moisture, etc.
When a nest is broken open, the workers seize the larvae and pupae and
hurry into some dark place. The pupa is either naked or else enclosed
in a cocoon, spun by the larva.

Nests. — The species of the tropical genus Eciton do not make nests
but occupy temporarily any suitable retreat which they may happen to
find in the course of their wanderings. Ants in general know how to
utilize all sorts of existing cavities as nests; they make use of crevices
in rocks and under stones or bark, the holes made by bark-beetles, hollow
stems or roots, plant-galls, fruits, etc. The extraordinary "ant-plants"
have already received special consideration.

Very many ants excavate their nests in the ground ; after a rain these
ants are especially industrious in the improvement of the nest, pressing
the wet earth into the walls of the galleries and adding probably a se-
creted fluid wdiich acts as a cement; stones and sticks are often worked
into the walls of a nest and the mounds of ants are frequently fashioned
about blades of grass or* growing herbage of whatever kind. The sub-

INTERRELATIONS OF INSECTS

273

terranean galleries are often complex labyrinths; frequently there are
long underground passages extending out in all directions, sometimes,
to aphid-infested roots of plants or, as in the case of the leaf-cutting
ants of the tropics, to trees which are destined to be attacked; special
chambers are set apart for the storage of food and others for eggs, larvae
or pupae.

Often a nest is excavated under a stone. As Forel observes, the stone
warms speedily under the rays of the sun, and in damp or cool weather
the ants are always in the highest story of the nest as soon as the sun's
warmth begins to penetrate the soil, while they go below as soon as the
sun disappears or when its heat becomes too strong. They select stones
that are neither too large nor too small to regulate the temperature well,
while other ants attain the same object by making the nest under shelter-
ing herbage or by making a mound with a hard cemented roof.

The well-known ant-hills may consist simply of excavated particles
of soil or else, as in the huge mounds of Formica exsectoides , may contain
labyrinthine passages in addition to those underground. The mounds
of this species are elaborate structures which may last a man's lifetime
at least. F. exsectoides is accustomed to form new colonies in connec-
tion with the parent nest ; McCook found in the Alleghanies no less than
1,600 nests, forming a single enormous community with hundreds of
millions of inhabitants, hostile to all other colonies of ants, even those
of the same species. This ant covers its mound with twigs, dead leaves,
grass and all sorts of foreign material, and is said to close the exits of the
nest with bits of wood at night and in rainy weather, removing them in
the morning or when the weather becomes favorable.

As Forel says [translation]: "The chief feature of ant architecture,
in contradistinction to that of the bees and the wasps, is its irregularity
and want of uniformity— that is to say, adaptability, or the capacity of
making all the surroundings and incidents subserve the purpose of at-
taining the greatest possible economy of space and time and the greatest
possible comfort. For instance, the same species will live in the Alps
under stones which absorb the rays of the sun; in a forest it will live in
warm, decayed trunks of trees; in a rich meadow it will live in high,
conical mounds of earth." Some species construct peculiar pasteboard
nests, as Lasius Juliginosus of Europe and tropical species of Cremasto-
gaster; and others spin silk to fasten leaves together, as Polyrliachis of
India and (Ecophylla of tropical Asia and tropical Africa, the silk being
probably a salivary secretion, according to Forel.

Habits in General. — The habits of ants are an inexhaustible and
19

274

K XTOM OUK iY

ever-fascinating subject of study to the naturalist, and well repay the
most critical observation. While each species has its characteristic
habits, ants in general have many customs in common.

Thus ants of one colony exhibit, as a rule, a pronounced hostility
toward ants of any other colony, even one of the same species, but recog-
nize and spare members of their own colony, even after many months
of separation and though the colony may number half a million indi-
viduals. This recognition is effected by means of an odor, distinctive
of the colony and apparently inheritable. When an ant is washed and
then restored to its fellows, it is treated at first as an intruder and may
even be killed. The same is true when the ant has been smeared with
juices from the bodies of alien ants. According to Miss Fielde. workers
of colony A , smeared with the juices from crushed ants of colony B and
then placed in colony B are received amicably, but at once set about
to destroy their hosts, like " wolves in sheep's clothing." These state-
ments apply only to workers, however, for alien larvae and pupae are
frequently captured and reared by ants, and Miss Fielde states that
kings of one colony of Stenamma when introduced into another colony
are even cordially received.

Some of the most careful students of the habits of ants agree that
these insects can communicate with one another. An ant discovers a
supply of food, returns toward the nest, meets a fellow worker, the two
stroke antennae and then both start back to the food; before long other
members of the colony swarm to the prize. It has been thought that
the odor of the food or some other odor, left by the first ant, serves as a
trail for the other ants to follow. Bethe, indeed, infers from his experi-
ments that this phenomenon is purely mechanical and involves no
psychical qualities on the part of the ants. His own experiments, how-
ever, show that one ant can inform another by means of an odor as to
the whereabouts of food — which is certainly one form of communication.

Ants avoid sunlight as a rule but prefer rays of lower refrangibility
to those of higher. Upon exposing ants to the colors of the spectrum,
as transmitted through glasses of different colors, Lubbock found that
they congregated in greatest numbers under the red glass and that the
numbers diminished regularly from the red to the violet end of the spec-
trum, there being very few individuals under the violet glass.

Miss Fielde, experimenting with queens, workers and young of Ste-
namma fulvum piceum in an artificial nest, covered half the nest with
orange glass and half with* violet. "The ants removed hastily from
under the violet as often as an interchange of the panes was made, once

INTERRELATIONS OF INSECTS

275

or twice a day, for about twenty days. Thereafter they became in-
different to the violet rays." "The plasticity of the ants is remarkably
shown in their gradually learning to stay where they were never disturbed
by me, under rays from wThich their instincts at first withdrew them."

Ants are sensitive not only to the different colors of the spectrum
but also to the ultra-violet rays, which produce no appreciable effect
on the human retina (though they induce chemical changes) . If obliged
to choose between the two, ants prefer violet to ultra-violet rays, as
Lubbock found. If, however, the ultra-violet rays are intercepted, by
means of a screen of sulphate of quinine or bisulphide of carbon, the ants
then collect under the screen in preference to under the violet rays.

From lack of experience we can form no adequate idea as to the range
of sensation in ants or other insects. Ants can taste substances that we
cannot, and vice versa. They show no response to sounds of human
.contrivance, yet many of them possess stridulating organs and organs
that are doubtless auditory; whence it may be inferred that ants can
communicate with one another by means of sounds. In rare instances
the stridulation of an ant can impress the human ear, as in a species of
A tta mentioned by Sharp.

Experiments show that ants, as well as bees and wasps, find their
way back to the nest, not by a mysterious "sense of direction," but by
remembering the details of the surroundings, and in the case of ants, by
means of an odor left along the trail.

In studying the habits of ants, the greatest care must be exercised in
order to discriminate between actions that may be regarded as purely
instinctive and those that may indicate some degree of intelligence. If
any insects show signs of intelligence, the social Hymenoptera do; but
in the study of this recondite subject, false conclusions can be avoided
only by observation and experimentation of the most critical kind.

Hunting Ants. — Some ants, as Formica fusca, live by the chase,
hunting their prey singly. The African "driver ants" (Anotnma arcens),
although blind, hunt in immense droves, consuming all the animal refuse
in their way, devouring all the insects they meet, and not hesitating to
attack all kinds of vertebrates; these ants ransack houses from time to
time and clear them of all vermin, though they themselves are a great
nuisance to the householder. The Brazilian species of Eciton (Fig. 287,
B, C) have similar habits and are likewise blind, or else have but a single
lens on each side of the head. These insects hunt in armies of hundreds
of thousands, to the terror of every animate thing that they come across.

276

ENTOMOLOGY

They have no permanent abode, but now and then appropriate some
convenient hole for the purpose of raising a new brood of marauders.

Slave-making Ants. It is a fact that some ants make slaves of
other species. Formica sanguined, for example, will attack a colony of
Formica j'usca, kill its active members in spite of their determined re-
sistance, kidnap the larvae and pupa4 and carry them home, where the
captives receive every care, and at length, as imagines, serve their masters
as faithfully as they would serve their own species. In the Alleghanies,
according to McCook, colonies of F. fusca occur where there are no ''red
ants" (F. sanguinea), but are hard to rind where the enslaving species
occurs.

Although F. sanguinea can exist very well without slaves, Polyergus
rujescens, of Europe, is notoriously dependent upon their services, it
being doubtful whether it is capable of feeding itself. This species is
powerful as a warrior, but its mandibles are of little use, except to pierce
the head of an adversary. Strongylonotus is still more helpless, while
Aner gates (also of Europe) is said to depend absolutely upon its slaves.

Polyergus lucidus occurs in the Alleghanies, where the colonies of this
species, according to McCook, contain large numbers of the workers of
Formica schaufussi. The masters are good lighters but do no other work,
and have not been seen to feed themselves, though they may often be
seen feeding from the mouths of their slaves.

Honey Ants. — Among ants in general, the workers that stay in the
nest receive food from the mouths of the foragers — a custom which has
led to the extraordinary conditions found in the ''honey ants," in which
certain of the wrorkers sacrifice their own activity in order to act as living
reservoirs of food for the benefit of the other members of the colony.
This remarkable habit has arisen independently, in different genera of
ants, in North America, Australia and South Africa, as Lubbock observes.

The honey ant whose habits are best known, through the studies of
McCook and others, is M yrmecocystus melliger, of Mexico. Xew Mexico
and southern Colorado. In this species some of the workers hang slug-
gishly from the roof of their little dome-like chamber, several inches under-
ground, and act as permanent receptacles for the so-called honey, which
is a transparent sugary exudation from certain oak-galls; it is gathered
at night by the foraging workers and regurgitated to the mouths of the
"honey-bearers," whose crops at length become distended with honey
to such an extent that the insects (Fig. 286) look like so many little
translucent grapes or good-sized currants. This stored food is in all
probability drawn upon by the other ants when necessary.

INTERRELATIONS OF INSECTS

277

Leaf-cutting Ants. — The most dangerous foes to vegetation in
tropical America are the several species of Atta (CEcodoma. Fig. 287, A).
Living in enormous colonies and capable of stripping a tree of its leaves
in a few hours, these formidable ants are the despair of the planter;

Fig. 286. — Honey ants, Myrmecocystus nielli gcr. clinging to the roof of their chamber. About

natural size. — After McCook.

where they are abundant it becomes impossible to grow the orange, coffee,
mango and many other plants. These ants dig an extensive under-
ground nest, piling the excavated earth into a mound, sometimes thirty
or forty feet in diameter, and making paths in various directions from

Fig. 287. — A, leaf-cutting ant, Atta cephalotes. B, wandering ant. Eciton drcpanophorum;
C, Eciton omnivorum. Natural size. — After Shipley.

the nest for access to the plants of the vicinity; Belt often found these
ants at work half a mile from their nest; they attack flowers, fruits and
seeds, but chiefly leaves. Each ant, by laboring four or five minutes,
bites out a more or less circular fragment of a leaf (Fig. 288) and carries
it home, or else drops it for another worker to carry; and two strings of

278

K\T< IMUI.OdY

ants may be seen, one carrying their leafy burdens toward the nest, the

other returning for more plunder.

The use made of these leaves has been
the subject of much discussion. Belt found
the true explanation, but it remained for
Moller to investigate the subject so thorough-
ly as to leave no room for doubt. The ants
grow a fungus upon these leaves and use it
as food. The bits of leaves are kneaded into
a pulpy, spongy mass, upon which the fungus
at length appears. The food for the sake of
which the ants carry on their complex opera-
tions consists of the knobbed ends of fungus
tS^35l I Vtfyi threads (Fig. 289), and these bodies, rich in

fluid, form the most important, if not the
sole food of the leaf-cutting ants. By assidu-
ously weeding out all foreign organisms the
ants obtain a pure culture of the fungus, and
by pruning the fungus they keep it in the
vegetative condition and prevent its fructi-
fication; under exceptional circumstances,
however, the fungus develops aerial organs
of fructification of the agaricine type, but
this species (Rozites gongylophora) has never been found outside of ants'
nests. The peculiar clubbed threads
were produced by Moller in artificial
cultures and are not spores, but prod-
ucts of cultivation. Other ants are
known to cultivate other kinds of fungi
for similar purposes.

McCook has found a leaf-cutting
ant (Atta fervens) in Texas, and men-
tions that it cuts circular pieces out
of leaves of chiefly the live-oak. these
being dropped to the ground and taken
to the nest by another set of workers.
He records an underground tunnel of
Atta fervens which extended 448 feet
from the nest and then opened into a

path 185 feet in length; the tunnel was 18 inches below the surface on an

Fig. 28S. — A, B. cuts made
in Cuphca leaves in four or five
minutes by Atta discigera;
natural size. C. Atta dis-
cigera transporting* severed
fragments of leaves; reduced. —
After Moller.

Fig. 289. — Fungus clumps (Rozites
gongylophora) cultivated by ants of the
genus Atta. Greatly magnified. — After
Moller.

INTERRELATIONS OF INSECTS

average, though occasionally as deep as 6 feet, and the entire route led
with remarkable precision to a tree which was being defoliated.

The same observer has given also a brief account of a leaf-cutting ant
that lives in New Jersey. This species (Atta septentrionalis) cuts the
needle-like leaves of seedling pines into little pieces, which are carried
to the nest. Two columns of workers may be seen, one composed of
individuals returning to the nest, each with a piece of a pine needle, the
other of outgoing workers. The nest is a simple structure, extending
some seven inches underground and ending in a chamber in wrhich are
several small pulpy balls, consisting probably of masticated leaves.
Further studies upon our own leaf -cutting ants, modeled after the ad-
mirable studies of Moller, are much to be desired.

Harvesting Ants. — Lubbock observes that some ants collect the
seeds of violets and grasses and preserve them carefully for some purpose
as yet unknowm. From such a beginning as this may have arisen the
extraordinary habits of the agricultural, or harvesting, ants, of wdiich
some twenty species are known from various parts of the world.

The Texas species Pogonomyrmex barbatus, studied by Lincecum
and by McCook, clears away the herbage around its nest (even plants
several feet high and as thick as a man's- thumb) and levels the ground,
forming a disk often 10 or 12 and sometimes 15 to 20 feet in diameter,
from which radiating paths are made, from 60 to 300 feet in length. The
ants go back and forth along these roads, carrying to the nest seeds which
they have collected from the ground or else have cut from plants; these
seeds are stored in " granaries'' several feet underground and are even-
tually used as food. The ants prefer the seeds of a grass, Aristida oligantha,
but the oft-repeated statement that they saw the seeds of this "ant-rice,"
guard it and weed it, is denied by Wheeler.

Notwithstanding the elaborate studies of McCook upon this subject,
there still remain not a few essential questions to be answered.

Myrmecophilism. — To add to the complexity of ant-life, the nests
of ants, when at all extensive, are frequented by a great variety of other
arthropods, which on account of their association with ants are termed
myrmecophiles. Most of these are insects, of which Wasmann has
catalogued 1,200 species, but not a few are spiders, mites, crustaceans,
etc. Though the diverse relations between myrmecophiles and ants
are but partially understood, these aliens may for convenience be con-
sidered under five groups: captives, guests, visitors, intruders and parasites.

Captives. — Besides enslaving other species, as already mentioned,
ants make use of aphids and some coccids for the sake of their palatable

280

1 . XI' iMOUKiY

products. The attendance of ants upon colonies of plant lice is a com-
mon occurrence and one that repays careful observation. With the
aid of a hand-lens, one may see the ants hastening about among the plant
lice and patting them nervously with the antennae until at length some
aphid responds by emitting from the end of the abdomen a glistening
drop of watery fluid, which the ant snatches. This fluid, contrary to
prevalent accounts, is not furnished by the so-called honey-tubes of the
aphid, but comes from the alimentary canal; the " honey-tubes " are
glandular indeed, but are probably repellent in function. In some in-
stances ants give much care to their aphids, for example covering them
with sheds of mud, which are reached through covered passageways.
More than this, however, some ants actually collect aphid eggs and pre-
serve them over winter as carefully as they do their own eggs. In one
such instance Lubbock found that the aphids upon hatching, after six
months, were brought out by the ants and placed upon young shoots of
the English daisy, their proper food plant. In our own country, as
Forbes has discovered, the eggs of the corn root louse (Aphis maidir ad-
dicts) are collected in autumn by ants (especially of the genus Lasius) and
stored in the underground nests. In winter the eggs are taken to the
deepest parts of the nest, and on bright spring days they are brought up
and even scattered about temporarily in the sunshine; while if a nest is
opened, the ants carry off the aphid eggs as they would their own. In
spring the ants tunnel to the roots of pigeon grass and smartweed, seize
the aphids and carry them to these roots, and later to the roots of Indian
corn. Throughout the year the ants exercise supervision over these
aphids; occasionally, as Forbes says, an ant seizes a winged louse in the
field and carries it down out of sight, and in one such instance it appeared
that the wings had been gnawed away near the body, as if to prevent the
escape of the louse. Similar relations exist also between ants and some
species of scale insects.

Guests. — Though Aphididae and Coccidae are able almost always to
live without the help of ants, there are some insects which have never
been found outside the nests of ants. Most of these insect guests are
beetles, notably Staphylinidae and Pselaphidae. The rove-beetles make
themselves useful by devouring refuse organic matter, and these scav-
engers are unmolested by the ants with which they live. A few myrme-
cophilous beetles furnish their hosts with a much-coveted secretion and
receive every attention from the ants, which clean these valuable beetles
and even feed them mouth to mouth, as the ants feed one another.
Lomechusa (Fig. 290) is one of these favored guests, as it has abdominal

INTERRELATIONS OF INSECTS

28l

tufts of hairs from which the ants secure a secreted fluid. Atemeles
(Fig. 291) is another; it solicits and obtains food from the mouth of a
foraging ant as if it were an ant itself. In the Alleghanies. Atemeles
cava occurs in the nests
of Formica rufa, and is
much prized by this ant
on account of the fluid
which the beetle secretes
from glandular hairs on
the sides of the abdomen.

The beetle Claviger
has at the base of each
elytron a tuft of hairs,
which the ants lick per-
sistently. This beetle is
blind and appears to be
incapable of feeding it-
self; for when deprived
of ant-assistance it dies,
even though surrounded

by food. These cases of symbiosis, or mutual benefit, are well authen-
ticated.

Visitors. — Many myrmecophilous insects are not restricted to ants'
nests, but are free to enter or to leave. This is true of such Staphylinidae

Fig. 290. — Lotnechusa strumosa being freed of mites by
Dinarda dcntata. — After WASMANK.

Fig. 291. — Atemeles cmarginatus being fed by an ant, Myrmica seabrinodis. — After WasmaNN.

as visit formicaries simply for shelter or to feed upon detritus, and these
visitors are treated with indifference by the ants.

Intruders. — Xot so. fiowever. with species that are inimical to the
interests of the ants, such as many species of Staphylinidae and His-

282

K X TOM () LOGY

teridae, which steal food from the ants, kill them or devour their larvae
or pupa1 at every opportunity. The ants are hostile to these marauders,
though the latter often escape through their agility or else rely upon their
armor for protection. Qucdius brews and Myrmedonia, as Schwarz ob-
serves, are soft-bodied forms which remain beside the walls of the gal-
leries or near the entrance of a nest and attack solitary ants; while
HekcriuSj which mixes with the ants, is protected by its hard and smooth
covering, under which the legs and antennae can be withdrawn. Such
an enemy is an unavoidable evil from the standpoint of an ant.

Janet has described the amusing way in which an audacious species
of Atelura steals food from the very mouths of ants. As is well known,
ants are accustomed to feed one another from mouth to mouth. When

Fig. 292. — Atelura formicaria stealing food from a pair of ants. — After Janet.

the foragers, rilled with honey or other food, return to the nest, they are
solicited for food by those that have remained at home; as a forager and
a beggar stand head to head, the former disgorges small drops of food,
which are seized by the latter. While a pair of ants are engaged in this
performance (Fig. 292), and a drop of honey is being passed, the Atelura
rushes in, grabs the drop and hurries away. As might be expected,
these interlopers are constantly being chased by their victims from one
corner of the nest to another.

Parasites. — Nematode worms occupy the pharyngeal glands of ants;
larvae of Stylo ps inhabit- their bodies; more than thirty kinds of mites
attach themselves to the heads or feet of ants; while Chalcididae and
Proctotrypidae parasitize ants' eggs.

CHAPTER XI

INSECT BEHAVIOR

The subject of insect behavior will be considered under three heads:
(i) Tropisms, (2) Instinct, (3) Intelligence.

1. Tropisms

Environmental influences, such as light, temperature or moisture,
may control the direction of locomotion of an organism by determining
the orientation of its body. The reaction of the organism under these
circumstances is known as a tropic, or tactic, reaction. A moth, for ex-
ample, flies toward a flame — is positively phototropic; a cockroach, on
the contrary, avoids the light — is negatively phototropic. A plant turns
toward the sun — in other words, is positively heliotropic.

An insect flies toward the light as inevitably and as mechanically as
a plant turns toward the sun; indeed, the two phenomena are funda-
mentally the same. Some students, however, prefer to use the term
taxis for bodily movements of motile organisms, and the term tropism
for turning movements of fixed organisms.

The study of tropic reactions, though comparatively new, has al-
ready illuminated the whole subject of the behavior of organisms and
placed it on a rational basis. The complex tropisms of insects offer a
fresh and large field to the investigator, comparatively little having as
yet been published upon the subject.

Chemotropism. — Positive and negative chemotropism. as Wheeler
observes, "are among the most potent factors in the lives of insects."
Insects are affected positively or negatively by such substances as can
affect their end-organs of smell or taste. Positive chemotropism en-
ables many insects to find their food or their mates; and negative chemo-
tropism enables them to avoid injurious substances. This negative re-
action on the part of other organisms is made use of also by such insects
as emit repellent odors.

A maggot orients its body with reference to a source of food and then
moves toward the food just as mechanically as a moth flies to a flame.
The maggot, as Loeb maintains, is influenced chemically by the radiat-
ing diffusion from a piece of meat, and follows a line of diffusion to the

283

284

KM < >M< )!.<)( , Y

center of diffusion in much the same way that a moth follows a ray of
light to its source. In both cases a stimulus affects muscular tissue;
the animal orients its body until the muscular tension is symmetrically
distributed, and then locomotion brings the animal to the source of the
stimulus, whether it be food or light or something else.

The remarkable "instinctive " action of the fly in laying her eggs on.
meat is due, according to Loeb, simply to the fact that both the fly and
the maggot have the same kind of positive chemotropism. Similarly
also in the case of such butterflies or other insects as lay their eggs on a
special kind of plant. It is certain that " neither experience nor volition
plays any part in these processes."

Hydrotropism. — Wheeler observed that beetles of the genera Hali-
plus and Hydroporus were positively hydrotropic; that when released on
the shore from a bunch of water plants, they scrambled toward the lake,
twenty feet away. Collectors take advantage of the negative hydro-
tropism of Bembidium. Elaphrns, Omophron and other shore-dwelling
beetles by splashing the water upon the dry bank, when the beetles leave
their places of concealment and are easily caught.

It is well known that after a rain ants carry their young out into the
sunshine, though when the upper parts of the nest become too dry, the
ants transfer their eggs, larvae and pupae to lower and moister galleries.
In these instances, however, we have to deal with thermotropism as well
as hydrotropism.

Thigmotropism. — Negative thigmotropism, as displayed in the with-
drawal from contact, is a common phenomenon among animals, from
Protozoa to Vertebrata. and is often conducive to the safety of an or-
ganism; though the negative response occurs none the less, whether it
is to prove useful or not, and occurs as automatically as the collapse of a
sensitive plant at a touch.

Positive thigmotropism is less common, though nevertheless wide-
spread among animals. Protozoa and Infusoria cling to solid bodies and
become aggregated about them. Cockroaches squeeze themselves into
crevices until their bodies come into close contact with surrounding sur-
faces. A moth, Pyrophila (Amphipyra) pyramidoides, is accustomed to
squeeze into crevices under loose bark or elsewhere, though this habit,
though doubtless protective, is not performed for the purpose of self-
concealment. That this is not a case of negative phototropism, it was
proved by Loeb, who wrote: ''I placed some of these animals in a box,
one-half of which was covered with a non-transparent body, the other
half with glass. I covered the bottom of the box with small glass plates

INSECT BEHAVIOR

285

which rested on small blocks, and were raised just enough from the
bottom to allow an Amphipyra to get under them. Then the Amphipyra
collected under the little glass plates, where their bodies were in contact
with solid bodies on every side, not in the dark corner where they would
have been concealed from their enemies. They even did this when in so
doing they were exposed to direct sunlight. This reaction also occurred
when the whole box was dark. It was then impossible for anything but
the stereotropic [thigmotropic] stimuli to produce the reaction."

Rheotropism. — Fishes swimming or heading directly against a cur-
rent of water illustrate positive rheotropism. When facing the current,
the resistance of the water is symmetrically distributed on the body of
the animal and is met by symmetrical muscular action, in the most eco-
nomical manner. Many aquatic insects offer such examples of rheo-
tropism, either positive or negative.

Anemotropism. — Various flies orient the body with reference to the
direction of the wind. Wheeler observed swarms of the male of Bibio
albipennis poising in the air, with all the flies headed directly toward the
gentle wind that was blowing. If the wind shifted, the insects at once
changed their position so as again to face to windward; a strong wind,
however, blew them to the ground. The males of an anthomyiid (Ophyra
leucostoma) , according to the same naturalist, hover in swarms in the
shade for hours at a time; if the breeze subsides they lose their definite
orientation, but if it is renewed they face the wind with military precision.
In Syrphidae, he finds, either males or females are positively anemotropic.
The midges of the genus Chironomus, which on summer days dance in
swarms for hours over the same spot, orient themselves to every passing
breeze. So also in the case of Empididae. which Wheeler has observed
swarming in one spot every day for no less than two weeks, possibly on
account of ilsome odor emanating from the soil and attracting and arrest-
ing the flies as they emerged from their pupae.''

The Rocky Mountain locusts "move with the wind and when the air-
current is feeble are headed away from its source"; when the wind is
strong, however, they turn their heads toward it.

Anemotropism and rheotropism are closely allied phenomena. As
Wheeler says, <kThe poising fly orients itself to the wind in the same way
as the swimming fish heads upstream," adjusting itself to a gaseous
instead of a liquid current. "In both cases the organism naturally as-
sumes the position in which the pressure exerted on its surface is sym-
metrically distributed and can be overcome by a perfectly symmetrical
action of the musculature of the right and left halves of the body."

286

ENTOMOLOGY

Geotropism. Gravity frequently determines the orientation and
direction of locomotion of an animal. A freshly emerged moth hangs
with the abdomen downward and remains in this position until the wings
have expanded. Certain dolichopodid flies found on the bark of trees
"rest or walk with the long axis of the body perpendicular to the earth
and parallel with the long axis of the trunk of the tree and the head
pointing upwards. When disturbed they fly off, but very soon alight
nearer the earth and again walk upward." (Wheeler.) Coccinellidae
and cockroaches are also negatively geotropic. The latter insects, as

Loeb has observed, tend to
leave a horizontal surface
but come to rest on a sur-
face that is vertical or as
nearly so as possible.

Wlieeler says, "Geotro-
pic as well as anemotropic
orientation is not altered
for the sake of response to
light. Even if the insect
be strongly heliotropic, as
is the case in most Diptera,
it orients itself to the wind
or to gravity no matter
whence the light may fall."

Phototropism. — It is a
matter of common observa-
tion that house flies, butter-
flies, bees and many other
diurnal insects fly toward
the light; and that cock-
roaches and bedbugs avoid
the light. These are familiar examples of phototropism. or the "control
of the direction of locomotion by light." The phototropic response is
either positive or negative according as the organism moves, respectively,
toward or away from the source of light. Maggots of Lucilia ccesar and
of many other flies are negatively phototropic as a rule (Fig. 293, A)>
but in the absence of light (other directive stimuli being excluded, of
course) wander about indifferently (Fig. 293, B).

Do the different rays of the spectrum differ in phototropic power?
This question has occurred to many investigators, who have found that,

Fig. 293. — A. tracks made on paper by a larva of
Lucilia ccrsar moving out of a spot of ink under the in-
fluence of light; a and b show respectively the first and
second directions of the light. B, tracks made in the
dark. — After PouCHET.

INSECT BEHAVIOR

287

in general, the rays of shorter wave length, as violet or blue, are more
effective than those of longer wave length, as yellow or red; the latter in
fact acting like 'darkness. Ants avoid violet rays as they would avoid
direct sunlight, but carry on their operations under yellowish red light
as they would in darkness. Miss Fielde has made use of this fact in
studying the habits of ants, by using as a cover for her artificial formi-
caries an orange-red sheet of glass such as the photographer uses for his
dark room. Though ants avoid violet rays, they prefer them to ultra-
violet rays, as Lubbock found.

These responses to light are inevitable on the part of the organism,
whether they are beneficial or harmful, and it is now becoming recognized
that the reactions of both plants and animals to light are fundamentally
the same.

Phototaxis and Photopathy. — A phototropic organism, if bilater-
ally symmetrical, orients itself with the head directly toward or else
directly away from the source of light and moves toward or away from
the light, as the case may be. In either event the long axis of the or-
ganism becomes parallel with the rays of light. Now a ray of light is
ever diminishing in intensity from its source, and it would seem that
differences of intensity along the paths of light rays determine the orien-
tation and consequent direction of locomotion of the organism. Some
investigators, however, distinguish between the effects of intensity of
light and those of its direction. Thus by ingeniously contrived experi-
ments, it has been found, apparently, that Protista (Strasburger), Daph-
nia (Davenport and Cannon) and the caterpillars of Porthesia (Xoeb)
move toward a source of light even while, in so doing, they are passing
into regions of less intensity of illumination. For this migration as de-
termined by the direction of the light rays, the term phototaxis is by some
authors (as Davenport) reserved. Usually, however, the direction of
locomotion does depend on differences of intensity, without regard to the
direction whence the light comes. This " migration towards a region of
greater or less intensity of light" has been termed photopathy, and or-
ganisms are said to be photophil or photo phob, according as they move,
respectively, toward or away from a more intensely illuminated area.

Verworn and others maintain that differences of intensity are suf-
ficient to account for all phototropic phenomena.

\ Optimum Intensity.— It has been found that there is a certain
optimum degree of light, differing according to the organism, toward
which the organism will move, from either a region of greater illumina-
tion or one of less. The organism appears to be attuned to a " certain

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range of intensity.** This attunement is used by Davenport to explain
apparent anomalies between the response to light of a butterfly and
that of a moth. Butterflies are positively phototropic to sunlight and
most moths are negatively so. Why, then, do moths fly toward a lamp
or an electric light? The answer is given that the moth is positively
phototropic up to a certain intensity of light, at which it becomes nega-
tively phototropic. ''Butterflies are attuned to a high intensity of
light, moths to a low intensity; so that bright sunlight, which calls
forth the one, causes the other to retreat. On the other hand, a light
like that of a candle, so weak as not to stimulate a butterfly, produces a
marked response in the moth." (Davenport.)

The circling of moths and other insects about a light is a matter of
common observation, an explanation for which has been given by Loeb.
Loeb says, "If a moth be struck by the light on one side, those muscles
which turn the head toward the light become more active than those of
the opposite side, and correspondingly the head of the animal is turned
toward the source of light. As soon as the head of the animal has this
orientation and the median-plane (or plane of symmetry) comes into the
direction of the rays of light, the symmetrical points of the surface of the
body are struck by the rays of light at the same angle. The intensity of
light is the same on both sides, and there is no reason why the animal
should turn to the right or left, away from the direction of the rays of
light. Thus it is led to the source of the light. Animals that move
rapidly (like the moth) get into the flame before the heat of the flame has
time to check them in their flight. Animals that move slowly are af-
fected by the increasing heat as they approach the flame; the high tem-
perature checks their progressive movement and they walk or fly slowly
about the flame." As Loeb insists, the moth u does not fly into the flame
out of 'curiosity,' neither is it 'attracted1 by the light; it is only oriented
by it and in such a manner that its median-plane is brought into the
direction of the rays and its head directed toward the source of light.
In consequence of this orientation its progressive movements must lead
it to the source of light."

Factors Influencing Phototropism. — The response of an organism
to light is influenced by previous exposure to light, by temperature,
moisture, nutrition and other factors, all of which have to be taken into
account in experiments on phototropism.

Loeb found that larvae of the moth Eu prod is chrysorrhoea, driven by
the warm sunshine out of the nest in which they have hibernated, crawl
upward to the tips of branches and feed upon the buds and new leaves.

INSECT BEHAVIOR

289

This self -preservative " instinct" is purely a response to light. The cater-
pillars are positively phototropic, and as the horizontal components of
the surrounding light neutralize each other, only the light from above is
effective as a stimulus to orientation. After feeding, however, the
larvae are no longer positively phototropic and crawl downward; in
other words, they are positively phototropic only so long as they are
unfed. Here the kind of phototropism is dependent upon nutrition.

Phototropism may be overruled by chemotropism and influenced by
conditions of metabolism, as Parker found for the butterfly Vanessa
antiopa. In his words: Vanessa antiopa, in bright sunlight, comes to
rest with the head away from the source of light, that is, it is negatively
phototropic, when the surface on which it settles is not perpendicular or
very nearly perpendicular to the direction of the sun's rays. When,
however, this surface is perpendicular to the sun's rays the insect settles
without reference to the direction of the rays. When feeding or near
food [such as running sap] the butterflies do not respond phototropically.

This negative phototropism is seen only in intense sunlight and after
the butterfly has been on the wing, i. e., after a certain state of metab-
olism has been established.

V. antiopa creeps and flies toward a source of light, that is, it is posi-
tively phototropic in its locomotor responses. Positive phototropism
also occurs in intense sunlight, and is not dependent upon any particular
phase of metabolism.

Both negative and positive phototropism in this species are independ-
ent of the "heat rays" of sunlight.

The position assumed in negative phototropism exposes the color
patterns of the wings to fullest illumination, and probably has to do
with bringing the sexes together during the breeding season.

To these may be added other important conclusions of Parker's:

No light reactions are obtained from the butterfly when shadows are
thrown upon any part of the body except the head. When one eye is
painted black the butterfly creeps or flies in circles with the unaffected
eye always toward the center. When both eyes are painted black all
phototropic responses cease and the insect flies upward. Butterflies
with normal eyes liberated in a perfectly dark room come to rest near
the ceiling. This upward flight in both cases is due to negative geotrop-
ism, not to phototropic activity.

V. antiopa does not discriminate between lights of greater or less
intensity provided they are all of at least moderate intensity and of
approximately equal size. V. antiopa does discriminate between light
20

290

ENTOMOLOGY

derived from a large luminous area and that from a small one, even when
the light from these two sources is of equal intensity as it falls on the
animal. These butterflies usually fly toward the larger areas of light.
This species remains in flight near the ground because it reacts positively
to large patches of bright sunlight rather than to small ones, even though
the latter, as in the case of the sun, may be much more intense.

V. antiopa retreats at night and emerges in the morning, not so much
because of light differences, as because of temperature changes. On
warm days it will, however, become quiet or active, without retreating,
depending upon a sudden decrease or increase of light.

The maggots of the muscid Phormia rcgina are. as the author has
observed, negatively phototropic until full grown, when they become
positively phototropic for an hour or less, leave the decaying matter in
which they have developed and wriggle along the ground toward the
sun; or if the sunlight is diffused by clouds, wander about aimlessly, but
at length bury themselves in the ground to pupate. Here the positive
phototropism just before pupation is adaptive, as it is in the case of
sexually mature ants, which make a nuptial flight into the sunlight when
they have acquired wings. The swarming of the honey bee is likewise a
case of periodic positive phototropism, as Kellogg has observed.

Though adaptive in their results, these phototropic reactions can
scarcely be said to be performed on account of their usefulness. They are
performed anyway, and may result harmfully, as when they lead a moth
into a flame or, to take a more natural example, when they expose an
insect to its enemies.

Phototropism and thermotropism, either together or singly, as Wheeler
suggests, may explain the up and down migration of insects in vegetation.
''On cold, cloudy days few insects are taken because they lurk quietly
near the surface of the soil and about the roots of the vegetation, but
with an increase in warmth and light they move upwards along the
stems and leaves of the plants, and, if the day be warm and sunny, es-
cape into the air."

Thermotropism. — Ants are strongly ther inotropic; they carry their
eggs, larvae and pupae from a cooler to a warmer place or vice versa, and
thus secure optimum conditions of temperature. Caterpillars and cock-
roaches migrate to regions of optimum temperature.

In thermotropism it appears that the direction of heat rays has little
or no effect as compared with differences of intensity.

Tropisms in General. — Other kinds of tropisms are known, for

INSECT BEHAVIOR

291

example, tonotropism, or the control of the direction of locomotion by
density, and electrotropism; not to mention any more.

All these phenomena are responses of protoplasm to definite stimuli
and are almost as inevitable as the response of a needle to a magnet.

The tropisms of the lower organisms have been experimented upon
by many skilled investigators, whose results furnish a broad basis for the
study of the subject in the higher animals — a study which has scarcely
begun. Even in the simplest organisms, behavior is the resultant effect
of several or many stimuli acting at once, and the precise effect of each
stimulus can be ascertained only by the most guarded kind of experi-
mentation; while in the higher animals, with their complex organiza-
tion, including specialized sense organs, the study of behavior becomes
intricate and cannot be carried on intelligently without an extensive
knowledge of the behavior of unicellular organisms. The properties of
protoplasm are the key to the behavior of organisms, though compara-
tively little is known as yet in regard to these properties. Furthermore,
the study of tropic reactions is complicated by the fact that they are due
not only to external stimuli, but also to little-understood internal stim-
uli, arising from unknown conditions of the alimentary canal, reproduc-
tive organs, etc.

A newly recognized property of protoplasm is that of adaptation, as
manifested in the acclimatization of protoplasm to untoward conditions
of temperature, light, contact and other stimuli; and this adaptation to
unusual conditions may take place without the aid of natural selection.

A tropic reaction occurs, whether it is to prove useful to the organism
or not. Thus a lady-bird beetle walks upward, on a branch, on a fence,
on one's finger. It walks upward as far as possible and then flies into the
air. If it happens to reach the tip of a twig and finds aphids there, the
beetle stops and feeds upon them. This adaptive result is in a sense
incidental. Yet, upon the whole, tropic reactions are wonderfully adapt-
ive in their, results. Here natural selection is of special value as afford-
ing an explanation of the phenomena.

As Loeb and Davenport have insisted, the mechanical reactions to
gravity, light, heat and other influences determine the behavior of the
organism.

2. Instinct

Insects are eminently instinctive; though their automatic behavior
is often so remarkably successful as to appear rational, instead of purely
instinctive.

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ENTOMOLOGY

Instinct, as distinguished from reason, attains adaptive ends without
prevision and without experience. For example, a butterfly selects a
particular species of plant upon which to lay her eggs. Caterpillars of
the same species construct the same kind of nest, though so isolated from
one another as to exclude the possibility of imitation. Every caterpillar
that pupates accomplishes the intricate process after the manner of its
kind, without the aid of experience.

Instinctive actions belong to the reflex type — they consist of co-
ordinated reflex acts. A complex instinctive action is a chain, each link
of which is a simple reflex act. In fact, no sharp line can be drawn be-
tween reflexive and instinctive actions.

Basis of Instinct.— Reflex acts, the elements from which instinctive
actions are compounded, are the inevitable responses of particular organs
to appropriate stimuli, and involve no volition. The presence of an
organ normally implies the ability to use it. The newly born butterfly
needs no practice preliminary to flight. The process of stinging is en-
tirely reflex; a decapitated wasp retains the power to sting, directing its
weapon toward any part of the body that is irritated; and a freshly
emerged wasp, without any practice, performs the stinging movements
with greatest precision.

As Whitman observes, the roots of instincts are to be sought in the
constitutional activities of protoplasm.

Apparent Rationality. — The ostensible rationality of behavior
among insects, as was said, often leads one to attribute intelligence to
them, even when there is no evidence of its existence. An an illustration,
many plant-eating beetles, when disturbed, habitually drop to the ground
and may escape detection by remaining immovable. We cannot, how-
ever, believe that these insects ''feign death" with any consciousness of
the benefit thus to be derived. This act. widespread among animals in
general, is instinctive, or reflex, as Whitman maintains, being, at the
same time, one of the simplest, most advantageous and deeply seated of
all instinctive performances.

Take the many cases in which an insect lays her eggs upon only one
species of plant. The philenor butterfly hunts out Aristolochia, which
she cannot taste, in order to serve larvas, of whose existence she can have
no foreknowledge. Oviposition is here an instinctive act, not performed
until it is evoked by some sort of stimulus — perhaps an olfactory one —
from a particular kind of plant.

Stimuli. — Some determinate sensory stimulus, indeed, is the neces-
sary incentive to any reflex act. The first movements of a larva within

INSECT BEHAVIOR

293

the egg-shell are doubtless due to a sensation, probably one of temperature.
Simple contact with the egg-shell is probably sufficient to stimulate the
jaws to work, and the caterpillar eats its way out; yet it cannot foresee
that its biting is to result in its liberation. Nor, later on, when vora-
ciously devouring leaves, can the caterpillar be supposed to know that
it is storing up a reserve supply of food for the distant period of pupation
and the subsequent imaginal stage. The ends of these reflex actions are
proximate and not ultimate, except from the standpoint of higher in-
telligence.

Just as simple reflexes link together to form an instinctive action, so
may instincts themselves combine. The complex behavior of a solitary
wasp is a chain of instincts, as the Peckhams have shown. All the opera-
tions of making the nest, stinging the prey, carrying it to the nest, etc.,
are performed as a rule in a definite, predicable sequence, and even a
slight interference with the normal sequence disconcerts the insect.
Just as the performance of one reflex act may serve as the stimulus for
the next reflex in order, so the completion of one instinctive action may
be in part the stimulus for the next one.

Modification of Instincts. — An action can be regarded as purely
instinctive in its initial performance only, because every subsequent
performance may have been modified by experience; in other words,
habits may have been forming and fixing, so that the results of instinct
become blended with those of experience. Thus the first flight of a
dragon fly is instinctive and erratic, but later efforts, aided by experience,
are well under control.

When once shaped by experience, reflex or instinctive actions tend
to become intense habits. Thus, certain caterpillars, having eaten all
the available leaves of a special kind, will almost invariably die rather
than adopt a new food plant, whereas larvae of the same species will eat
a strange plant if it is offered to them at birth. An act is strengthened
in each repetition by the influence of habit, to the increasing exclusion
of other possible modes of action. Many a caterpillar, having eaten its
way out of the egg-shell, does not stop eating, but consumes the remain-
der of the shell — a reflex act, started by a stimulus of contact against the
jaws and continued until the cessation of the stimulus, unless some
stronger stimulus should intervene. It has been said that the larva eats
the remains of the shell because they might betray its presence to its
enemies. Whether this is true or not, to assume conscious foresight of
such a result on the part of an inexperienced caterpillar is worse than
unnecessary.

ENTOMOLOGY

With insects, as with other animals, many instincts are transitory;
even when partially fixed by habit, they are replaceable by stronger in-
stincts. Thus the gregarious habit of larvae is finally overpowered by
a propensity to wander, which does not mature, however, until the
approach of the transformation period. The reproductive instinct is
another of those impulses that do not ripen until a certain age in the
individual.

Inflexibility of Instincts. — Broadly speaking, instinctive actions
lack individuality — are performed in the same way by even* individual
of the species. The solitary wasps of the same species are remarkably
consistent in architecture, in the selection of a special kind of prey, in the
way they sting it. carry it to the nest and dispose of it: all these opera-
tions, moreover, are performed in a sequence that is characteristic of the
species. Examples of this so-called inflexibility of instinct are so omni-
present, indeed, that insect behavior as a whole is admitted to be in-
stinctive, or automatic. Insects are capable of an immense number of
reflex impulses, ready to act singly or in intricate correlation, upon the
requisite stimuli from the environment.

To normal conditions of the environment, the behavior of an insect
is accurately adjusted: in the face of abnormal circumstances, however,
demanding the exercise of judgment, most insects are helpless. The
specialization to one kind of food, though usually advantageous, is fatal
if the supply becomes ^sufficient and the larva is unable to adopt an-
other food. A species of Sphrx habitually drags its grasshopper Wctim
by one antenna. Fabre cut off both antennae and then found that the
Spkex. after vain efforts to secure its customary hold, abandoned the
prey. Under such unaccustomed conditions, insects often show a sur-
prising stupidity, capable as they are amid ordinary circumstances.

Flexibility of Instincts. — Notwithstanding such examples, the
common assertion that instincts are absolutely *" blind." or inflexible, is
incorrect. Instinctive acts are not mechanically invariable, though
their variations are so inconspicuous as frequently to escape casual ob-
servation. A precise observer can detect individual variations in the
performance of any instinctive act — variations analogous to those of
structure.

To take extreme examples, the Peckhams found that an occasional
queen of Polistes fused would occupy a comb of the previous year, instead
of building a new one; and that an individual of Pompilus marginatum.
instead of hiding her captured spider in a hole or under a lump of earth
as usual, hung it up in the fork of a purslane plant. They observed also

INSECT BEHAVIOR

295

that one Ammophila, in order to pound down the earth over her nest,
actually used a stone, held between the mandibles (Fig. 294).

While most of the variations that one encounters are small and, in
a sense, accidental, or purposeless, such novel departures as those of the
Polistes or the Ammophila would seem to denote adaptability.

Even the despotic power of habit may be overborne by individual
adaptability. Among caterpillars that have exhausted their customary
food, there are often a few that will adopt a new food plant and survive,
leaving their more conservative fellows to starve.

As Darwin himself held, the doctrine of natural selection is applicable
to instincts as well as structures. All reflex acts are to some extent vari-

Fig. 294. — Ammophila urnaria using a stone to pound clown the earth over her nest.
Greatly enlarged— After PECKHAM, from Bull. Wisconsin Geol. and Nat. Hist. Survey.

able. Disadvantageous reflexes or combinations of reflexes eliminate
themselves, while advantageous ones persist and accumulate.

Indeed, structures and instincts must frequently have evolved hand
in hand. The remarkable protective resemblance of the Kallima butter-
fly would be useless, did not the insect instinctively rest among dead
leaves of the appropriate kind.

Origin of Instinct. — There are two leading theories as to the origin
of instinct. Lamarck, Romanes and their followers have regarded in-
stinct as inherited habit; have supposed that instincts have originated
by the relegation to the reflex type of actions that at first were rational,
and that instincts represent the accumulated results of ancestral experi-
ence. This habit theory, however, has little to support it, and assumes
the inheritance of acquired characters — which has not been proved.

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ENTOMOLOGY

The selection theory of Darwin. Weismann, Morgan and others has
much in its favor. It regards reflex acts as primitive, as the raw material
from which natural selection, as the chief factor, has effected those com-
binations that are termed instincts.

Instincts and Tropisms.— We have already emphasized the fact
that an instinct is a reflex act or a combination of reflex acts. The same
fact may now be stated in these words: an instinct is a tropism or a
combination of tropisms. The more important of these tropisms have
been considered. Whenever possible it is better to discard the ambigu-
ous term instinct in favor of such more precise terms as phototropism.
geotropism. etc.; though the term instinct remains useful as applied to an
action that is the resultant of several tropic responses.

The modern student of instincts aims to resolve them into their
component reflexes and to determine as precisely as possible the influence
of each reflex component. Thanks to the labors of a great number of
skilled investigators, we are no longer satisfied to class an action as "in-
stinctive" and then dismiss it from thought ; for now we are in a position
to analyze the action, and may hope to explain it eventually in terms of
the physical and chemical properties of protoplasm.

3. Intelligence

Though manifestly dominant, pure instinct fails to account for all
insect behavior. The ability of an insect to profit by experience indi-
cates some degree of intelligence.

Take, for example, the precision with which bees or wasps find their
way back to the nest. This is no longer to be accounted for on the as-
sumption of a mysterious "sense of direction." for there is the best of
evidence for believing that it depends upon the recognition of surround-
ing objects. When leaving the nest for the first time, these insects make
"locality studies." which are often elaborate. Referring to Sphex
ichneumonea, the Peckhams write: "At last, the nest dug, she was ready
to go out and seek for her store of provision and now came a most thor-
ough and systematic study of the surroundings. The nests that had
been made and then deserted had been left without any circling. Evi-
dently she was conscious of the difference and meant, now. to take all
necessary precautions against losing her way. She flew in and out
among the plants first in narrow circles near the surface of the ground,
and now in wider and wider ones as she rose higher in the air. until at
last she took a straight line and disappeared in the distance. The dia-
gram [Fig. 295. .4] gives a tracing of her first study preparatory to de-

INSECT BEHAVIOR

297

parture. Very often after one thorough study of the topography of her
home has been made, a wasp goes away a second time with much less
circling or with none at all. The second diagram [Fig. 295, B] gives a
fair illustration of one of these more hasty departures. . . .

"If the examination of the objects about the nest makes no impression
upon the wasp, or if it is not remembered, she ought not to be incon-
venienced nor thrown off her track when weeds and stones are removed
and the surface of the ground is smoothed over; but this is just what
happens. Aporus jasciatus entirely lost her way when we broke off the
leaf that covered her nest, but found it without trouble when the missing
object was replaced. All the species of Cerceris were extremely annoyed

Fig. 295. — Locality studies made by a wasp, Sphcx ichneumonea. A, a thorough study; B, a
hasty study; nest. — After Peckham, from Bull. Wisconsin Geol. and Xat. Hist. Survey.

if we placed any new object near their nesting-places. Our Ammophila
refused to make use of her burrow after we had drawn some deep lines
in the dust before it. The same annoyance is exhibited when there is
any change made near the spot upon which the prey of the wasp,- what-
ever it may be, is deposited temporarily."

If we take, as one criterion of intelligence, the power to choose be-
tween alternatives, then insects are more intelligent than is generally
admitted. The control of locomotion, the selection of prey, and the
avoidance of enemies, as results of experience, indicate powers of dis-
crimination. The power of intercommunication, conceded to exist
among social Hymenoptera, implies some degree of intelligence.

298

ENTOMOLOGY

If instinct is blind, or mechanical, with no adjustment of means to
ends, then a pronounced individuality of action must signify something
more than instinct — as in the case of the Ammophila. In regard to a
female Pompilus scelestus. which had dragged a large spider nearly to her
nest, the Peckhams observe: " Presently she went to look at her nest
and seemed to be struck with a thought that had already occurred to us —
that it was decidedly too small to hold the spider. Back she went for
another survey of her bulky victim, measured it with her eye, without
touching it, drew her conclusions, and at once returned to the nest and
began to make it larger. We have several times seen wasps enlarge their
holes when a trial had demonstrated that the spider would not go in.
but this seemed a remarkably intelligent use of the comparative faculty."

From the standpoint of pure instinct, indeed, much of the behavior
of the solitary wasps is inexplicable; while the actions of the social Hy-
menoptera have led some of the most critical students to ascribe intelli-
gence to these insects. The activities of the harvesting ants, the mili-
tary or the slave-holding species, are of such a nature that the possibility
of education by experience and instruction is strong, to say the least.
In fact. Forel has maintained that a young ant is actually trained to its
domestic duties by its older companions. Miss Enteman. on the con-
trary, says : " Wasps do not imitate one another. Instinct and individual
experience account sufficiently for their powers, and their apparent co-
operation is due entirely to the accident of their being born in the same
nest." She finds that the worker Polistes does not learn to feed the
larvae by imitating the queen.

It is extremely difficult, however, if not impossible, to draw the line
between instinct and intelligence; and in doubtful cases there is a gen-
eral tendency to exaggerate the importance of intelligence rather than
that of instinct. For example, the well-known discrimination on the part
of ants between members of their own colony and those of other colonies,
even of the same species, would seem to imply intelligent recognition.
This recognition, however, is due simply to a characteristic odor, which
is derived from the mother of the community. An ant after being washed
receives hostile treatment from others of its own colony; while an alien
ant after being smeared with the juices of hostile ants is treated by the
latter as a friend.

Each instance of apparent intelligence must be examined impartially
on its own merits. At present it may be said that, while most of the
behavior of insects is purely instinctive, there is some reason to believe

INSECT BEHAVIOR

299

that at least gleams of intelligence appear in the most specialized Hy-
menoptera.

Lack of Rationality. — However intelligent the social Hymenoptera
may be in their way, they show no signs of the power of abstract reason-
ing. Even ants, according to the experiments of Lubbock, display
profound stupidity in the face of novel emergencies when they might
extricate themselves by abstract reasoning of the simplest kind. The
thoughts of an ant or bee seem to be limited to simple associations of
concrete things. Miss Enteman observed a Polistes worker which
gnawed a piece out of the side of a dead larva of its own kind and, turn-
ing, actually offered it as food to the mouth of the same larva. In an-
other instance a larva wTas attacked and killed, and then offered a piece
of its own body.

Such examples as these emphasize the strength of the reflex factor in
the behavior of insects. Indeed, the basis of all behavior is being sought
in the reactions of protoplasm to external stimuli. Possibly even mem-
ory, consciousness and other attributes of intelligence will eventually be
reduced to this basis, improbable as it may now seem.

CHAPTER XII

DISTRIBl [TON

I. Geographical

Importance of Dispersion. — Dispersion enables species to miti-
gate the intense competition and the rigid selection that result from
crowded numbers; hence the tendency to disperse, being self-preserva-
tive, has become universal. Some species habitually emigrate in pro-
digious numbers: the African migratory locust, the Rocky Mountain
locust, and the milkweed butterfly, which annually leaves the Northern
states for the South an immense swarms, in autumn, and in the following
spring straggles back to the North. Vanessa cardni occasionally mi-
grates in immense numbers, as do also Pieris, some dragon flies and some
beetles, notably Coccinellidas.

Wide Distribution of Insects. — Insects have been found in almost
every latitude and altitude explored by man. Butterflies and mos-
quitoes occur beyond the polar circle, the former in Lat. 830 N., the latter
in Lat. 720 N., and a species of Emesa closely allied to our common E.
longipes is recorded by Whymper from an altitude of 16,500 ft. in Ecua-
dor, where, according to the same traveler, Orthoptera occur at 16,000
ft., Pieris xanthodice ranges above 15,000 ft., and dragon flies, Hymen-
optera and scorpions reach a height of 12,000 ft., while twenty-nine
species of Lepidoptera range upward of 7,300 ft. A very few species of
insects inhabit salt water, Halobates being found far at sea; some kinds
live in arid regions and a few even in hot springs, while caves furnish
many peculiar species. In short, insects are the most widely distributed
of all animals, excepting Protozoa and possibly Mollusca.

While all the large orders of insects are world-wide in distribution, the
most richly distributed are Coleoptera, Thysanura and Collembola, the
last two feeding usually upon minute particles of organic matter in the
soil and being remarkably tolerant of extremes of temperature. The
four chief families of butterflies occur the world over, as do several fam-
ilies of beetles. Of species that are essentially cosmopolitan we may
mention the collembolan Isotoma fimetaria, and the butterflies Vanessa
cardui and Anosia plexippus, while among beetles no less than one hun-
dred species are cosmopolitan or subcosmopolitan, including Tenebrio

300

DISTRIBUTION

30I

molitor, Silvanus surinamensis , Dermestes lardarius, Attagenus piceus and
Calandra oryzce. The coccinellid genus Scymnus occurs in North Amer-
ica, Europe. Hawaii, Galapagos Islands and New Zealand, and Anobium
and Hydrobius are distributed as widely. The huge noctuid, Erebus
odora, occurring in Brazil on the lowlands, and in Ecuador at an altitude
of 10,000 ft., finds its way up into the United States and even into Can-
ada. The chinch bug and many other Central American forms also
spread far northward, as described beyond.

Means of Dispersal. — This exceptional range of insects is due to
their exceptional natural advantages for dispersal, chief among which
are the power of flight and the ability to be carried by the wind. The
migratory locust, Schistocerca peregrina. has been found on the wing five
hundred miles east of South America. The home of the genus, according
to Scudder, is Mexico and Central America, where 23 species are found;
20 occurring in South America, including the Galapagos Islands, 11 in
the United States and 6 in the West Indies; and there is every reason to
believe that 5. peregrina — the biblical locust and the only representative
of its genus in Africa — crossed over from South America, where it is
found indeed at present. Darwin and others have recorded many in-
stances of insects being taken alive far at sea; Trimen mentions moths
and longicorn beetles as occurring 230 miles west of the African coast and
Sphinx convolvulus as flying aboard ship 420 miles out. In these in-
stances the insects have usually been assisted or carried by strong winds,
particularly the trade-winds, and oceanic islands have undoubtedly
been colonized in this way. On land, Webster has found that the direc-
tion in which the Hessian fly spreads is determined largely by the pre-
vailing winds at the time when these delicate insects are on the wing,
and that the San Jose scale insect spreads far more rapidly with the pre-
vailing winds than against them, the wind carrying the larvae as if they
were so many particles of dust. The pernicious buffalo-gnat of the
South emerges from the waters of the bayous and may be carried on a
strong wind to appear suddenly in enormous numbers twenty miles
distant from its breeding place. Mosquitoes are distributed locally by
light breezes, but cling to the herbage during strong winds.

Ocean currents may carry eggs, larvae or adults on vegetable drift to
new places thousands of miles away. Thus the Gulf Stream annually
transports thousands of tropical insects to the shores of Great Britain,
where they do not survive, however,

Fresh-water streams convey incalculable numbers of insects in all
stages; and insects as a whole are very tenacious of life, being able to

ENTOMOLOGY

withstand prolonged immersion in water, and even freezing, in many
instances, while they can live for a long time without food.

The universal process of soil-denudation must aid the diffusion of
insects, slowly but constantly.

Birds and mammals disseminate various insects in one way or another,
while the agency of man is, of course, highly important. Intentionally,
he has spread such useful species as the honey bee, the silkworm and
certain useful parasites; incidentally he has distributed the San Jose
scale, Colorado potato beetle, gypsy moth and many other pests.

Barriers. — The most important of the mechanical barriers which
limit the spread of terrestrial species is evidently the sea. Mountain
ranges retard distribution more or less successfully, though a species may
spread along one side of a range and sooner or later pass through a break
or else around one end. Mountain chains act as barriers, however,
chiefly because they present unendurable conditions of climate and
vegetation. For the same reason deserts are highly effective barriers.
Indeed the most important checks upon distribution are those of climate,
and of climatal factors temperature is the most powerful. Tropical
species, as a rule, cannot survive and reproduce in regions of frost; most
of the tropical species which have entered the United States are restricted
to its narrow tropical belts (Plate IV) . The stages of an insect are fre-
quently so accurately adjusted to particular climatal conditions that an
unfamiliar climate deranges the life cycle. Thus many Southern butter-
flies find their way every year to the Northern states, only to perish
without reproducing their kind. Insects, however, are more adaptable
than most other animals in respect to climate, and frequently follow
their food plants into new climates, as in the case of the harlequin cab-
bage bug, which has pushed north from the tropics to Missouri, southern
Illinois and Indiana.

Humidity ranks next to temperature in the importance of its in-
fluence upon the distribution of organisms, but in the case of animals acts
for the most part indirectly, by its effects upon vegetation. Thus the
effectiveness of an arid region as a barrier is due chiefly to the lack of
vegetation in consequence of the lack of moisture. Excessive moisture,
on the other hand, may act as a barrier. The Rocky Mountain locust,
migrating eastward in immense swarms, succumbs in the moist valley
of the Mississippi; the chinch bug is never seriously injurious in wet
years. Moisture checks the development of these and other insects in
ways as yet unascertained; possibly it acts indirectly by favoring the
growth of fungus diseases, to which insects are much subject.

DISTRIBUTION

The absence of proper food is more effective than climate, as a direct
check upon the spread of an animal; food itself being, of course, de-
pendent ultimately upon climatal factors and soil. Many insects, being
confined to a single food plant, cannot exist long where this plant does
not occur; but they will follow the plant, as was just said, into new cli-
mates; thus Anosia plexippns is following the milkweed over the world.
The butterfly Euphydryas phaeton is remarkably local in its occurrence,
being limited to swamps where its chief food plant (C ketone glabra) grows;
and Epidemia epixanthe is similarly restricted to cranberry bogs, though
its food-habits are as yet unknown.

Former Highways of Distribution. — Many facts of distribution
which are inexplicable under the present conditions of topography and
climate become intelligible in the light of geological history. The marked
similarity between the fauna of Europe and that of North America means
community of origin; and though the Arctic zone now interposes as a
barrier, there was once an opportunity for free dispersion when, in the
early Pleistocene or late Pliocene, a land connection existed between
Asia and North America and a warm climate prevailed throughout what
is now the Arctic region.

The extraordinary isolation of the butterfly (Eneis scmidea on moun-
tain summits in New Hampshire and Colorado (particularly Mt. Wash-
ington, N. H., and Pikes Peak, Col.) is explained by glacial geology.
The ancestors of this species, it is thought, were driven southward be-
fore an advancing ice-sheet and then followed it back as it retreated
northward, adapted as they were to a rigorously cold climate. Some
of these ancestors presumably followed the melting ice up the mountain
sides, until they found themselves stranded on the summits. Other
individuals, undiverted from the lowlands, followed the retreating glacier
into the far north; and at present there occurs throughout Labrador a
species of (Ends which differs but slightly from its lonely ally of the
mountain tops.

Glaciation undoubtedly had a profound effect upon the fauna and
flora of North America. "With the slow southward advance of the ice,
animals were crowded southward; with its recession they advanced
again northward to reoccupy the desolated region, until now it has long
been repopulated, either with the direct descendants of its former in-
habitants or with such limitations to the integrity of the fauna as this
interruption of local life may have caused.'' (Scudder.) Probably
many species were exterminated and many others became greatly modi-
tied, though little is known as to the relationship of the present fauna to

304

ENTOMOLOGY

the preglacial fauna. ''The glacial cold still lingers over the northern
part of this continent and our present animals are only a remnant of
the rich fauna that existed in former ages, when the magnolia and the
sassafras thrived in Greenland.''

Island Faunae. — The ability of insects to surmount barriers, under
favorable circumstances, is strikingly shown in the colonization of oceanic
islands. Not a few insects, including Vanessa cardui, have found their
way to the isolated island of St. Helena. In the Madeira Islands, ac-
cording to Wollaston, there are 580 species of Coleoptera, of which 314
are known to occur in Europe, while all the rest are closely allied to
European forms. Subtracting 120 species as having been introduced
probably or possibly through the agency of man. there remain 194 that
have been introduced by "natural" means. The rest, 266 species, are
endemic, though akin to European species.

The scanty insect fauna of the Galapagos Isands includes twenty
species of Orthoptera. which have been studied by Scudder and by Snod-
grass. Five of these are cosmopolitan cockroaches, doubtless introduced
commercially, and the remaining fifteen are all "distinctly South and
Central American in their affinities." Three of these fifteen are strong-
winged species which doubtless arrived by flight from the neighboring
mainland; indeed, Scudder records a Schistocerca (S. exsul) as having
been taken at sea two hundred miles off the west coast of South America,
or nearly half way to the Galapagos Islands. Thirteen of the fifteen
are endemic, and five are apterous or subapterous, while a sixth has an
apterous female. Apterous insects, noticeably common on wind-swept
oceanic islands, may have been carried thither on driftwood, though it
is more likely that the apterous condition arose on the islands, where the
better-winged and more venturesome individuals may have been con-
stantly swept out to sea and drowned, leaving the more feeble-winged
and less venturesome individuals behind, to reproduce their own life-
saving peculiarities.

The Coleoptera of the Hawaiian Islands, studied by Dr. Sharp, num-
ber 428 species, representing 38 families, and ''are mostly small or very
minute insects," the few large forms being non-endemic, with little or
no doubt; 352 species are at present known only from this archipelago.
Dr. Sharp distinguishes three elements in the fauna: "First, species that
have been introduced, in all probability comparatively recently, by arti-
ficial means, such as with provisions, stores, building timber, ballast, or
growing plants; many of these species are nearly cosmopolitan. Second,
species that have arrived in the islands, and have become more or less

DISTRIBUTION 305

completely naturalized; they are most of them known to be wood- or
bark-beetles, but some that are not so may have come with the earth
adhering to the roots of floating trees; a few, such as the Dytiscidae. or
water beetles, may possibly have been introduced by violent winds.
Third, after making every allowance for introduction by these artificial
and natural methods, there still remains a large portion standing out
in striking contrast with the others, which we are justified in considering
strictly endemic or autochthonous." Among the introduced genera are
Coccinella, Dermestes, Aphodius. Buprestis, Ptinus and Cerambyx. The
immigrant longicorns appear to have been derived "from the nearest
lands in various directions'' — the Philippine Islands, tropical America
and the Polynesian Islands — and the same conclusion will probably be
found to hold for the other immigrants, when their general distribution
shall have been sufficiently studied. The endemic species number 214,
or exactly half the total number of species, and are distributed among 9
families, as follows:

Families. Species. Genera. Endemic Genera.

Carabidae 51 7 7

Staphylinidae 19 3 1

Nitidulidae 38 2 1

Elateridae 711

Ptinidae (Anobiini) 19 3 3

Cioidae 19 1 o

Aglycyderidae 30 1 1

Curculionidae (Cossonini) 21 3 3

Cerambycidae 10 1 1

Sharp writes: "I think it may be looked on as certain that these
islands are the home of a large number of peculiar species not at present
existing elsewhere, and if so it follows that either they must have existed
formerly elsewhere and migrated to the islands, and since have become
extinct in their original homes, or that they must have been produced
within the islands. This last seems the simpler and more probable sup-
position, and it appears highly probable that there has been a large
amount of endemic evolution within the limits of these isolated islands."

The parasitic Hymenoptera of Hawaii, according to Ashmead, num-
ber 14 families, 69 genera and 128 species; only eleven genera are en-
demic and most of the other genera are represented in nearly all the known
faunae of the earth. Ashmead concurs in the view that the Hawaiian
fauna was originally derived from the Australasian fauna — the view
held by all the specialists who have studied Hawaiian insects.
21

306

ENTOMOLOGY

Geographical Varieties. — Darwin found that wide-ranging species
are as a rule highly variable. The cosmopolitan butterfly Vanessa
cardui presents striking variations in different parts of the earth, largely
on account of climatal differences, as is indicated by the temperature
experiments of several investigators. Standfuss exposed German pupae
of this insect to cold, and obtained thereby a dark variety such as occurs
in Lapland; and by the influence of warmth, obtained a very pale form
such as occurs normally in the tropics only. Our Cyaniris psendargiolus,
which ranges from Alaska into Mexico and from the Pacific to the At-
lantic, exhibits many geographical varieties, some of which are clearly
due to temperature, as experiments have shown.

Geographical isolation is often followed by changes in the specific
characters of an organism, as witness the endemic species and varieties
of oceanic islands. Even in the same archipelago, the different islands
may be characterized by different varieties of one and the same species,
or even by different but closely allied species of the same genus. Thus
Darwin and Alexander Agassiz found that in the Galapagos Islands each
island had its own species of Tropiduriis (a lizard) and had only one
species, with almost no exceptions. The same phenomenon occurs in
the two Galapagan species of Schistocerca — S. melanocera and S. liter osa.
In melanocera, as Scudder discovered, ''Three or four distinct types are
becoming gradually differentiated on the eight [now ten] islands from
which they are knowTi." Snodgrass, who has made important addi-
tions to Scudder's account, says, in regard to the two species. ''The
specimens from the different islands show striking, though, in most cases,
slight differences distinguishing the individuals of each island as a race,
from those inhabiting any other island. There are two exceptions.
Abingdon and Bindloe have the same form, and Albemarle supports at
least two races. " Each of these two species presents no less than five
racial types, to which distinctive names have been applied. Though
the relationships and evolution of these races have been ably discussed
by Snodgrass, definite conclusions upon these subjects are still needed.

Faunal Realms. — The general distribution of life is such that
naturalists divide the earth into several realms, each of which has its
characteristic fauna and flora. As to the precise boundaries of these
faunal realms, zoologists do not all agree, owing chiefly to the fact that
faunae overlap one another to such an extent as to render their exact
separation more or less arbitrary. Five realms, at least, are generally
recognized: Holarctic, Neotropical, Ethiopian. Oriental and Australian
(Plate III).

Plate III.

DISTRIBUTION

309

The Holarctic realm comprises the whole of Europe, Northern
Africa as far south as the Sahara, Asia down to the Himalayas, and North
America down to Mexico. Though the faunae of all these areas are
fundamentally alike (as Merriam and other authorities maintain), it is
often convenient to divide the Holarctic into two parts : the Palcearctic,
including Europe and most of temperate Asia, being limited roughly by
the Tropic of Cancer; and the Nearctic, occupying almost the entire
continent of North America, including Greenland. The northern portion
of the Holarctic realm forms a circumpolar belt with a remarkably homo-
geneous fauna and flora; therefore some authors distinguish an Arctic
realm, limited by the isotherm of 320, which marks very closely the tree-
limit.

The boreal insects of Eurasia and North America are strikingly
alike. Dr. Hamilton has catalogued almost six hundred species of
beetles as being holarctic in distribution; live hundred of these are com-
mon to Europe, Asia and North America, and the remainder are known
to occur in North America and also in Europe or Asia; one hundred are
cosmopolitan or sub-cosmopolitan, to be sure, but fifty of these are
probably holarctic in origin, for example — Dermestes lardarius and Tene-
brio molitor. Of butterflies, out of some two hundred and fifty species
that are found in the United States east of the Rocky Mountains, scarcely
more than a dozen occur also in the old world. North of the United
States, however, as Scudder finds, no less than thirteen genera are repre-
sented in the old world by the same or by allied species.

The Neotropical realm embraces South America, Central America,
the West Indies and the coasts of Mexico; Mexico being for the most
part a transition tract between the Neotropical and the Nearctic. The
richest butterfly fauna in the world is found in tropical South America.
To this region are restricted, almost without exception, the Euplceinae
and Lemoniinae and over ninety-nine per cent, of the Libytheinae; here
the Heliconiidae and Papilionidae attain their highest development, as
do also the Cerambycidae, or longicorn beetles.

The Ethiopian realm consists of Africa south of the Sahara, Southern
Arabia and Madagascar; though some prefer to regard Madagascar as
a distinct realm, the Lemurian. According to Wallace, the Ethiopian
realm has seventy-five peculiar genera of Carabidae and is marvelously
rich in Cetoniidae and Lycaenidae.

The Oriental realm includes India, Ceylon, Tropical China, and the
Western Malay Islands. In the richness of its insect fauna, this realm
vies with the Neotropical. Danaidae and Papilionidae are abundant,

ENTOMOLOGY

while the genus Morpho is represented by some forty species; of Cole-
optera, Buprestidae are important and Lucanidae especially so.

The Australian realm embodies Australia, New Zealand, the Eastern
Malay Islands and Polynesia. Buprestidae are here represented by
forty-seven genera, of which twenty are peculiar; against this showing,
the Oriental has forty-one genera and the Neotropical thirty-nine (Wal-
lace). Strong affinities are said to exist between the Australian and
Neotropical insect faunae.

Life Zones of North America.— Merriam, the chief authority
upon the subject, says: "The continent of North America may be di-
vided, according to the distribution of its animals and plants, into
three primary transcontinental regions — Boreal, Austral and Tropical.11
(Plate IV.)

Fig. 296. — Distribution of Erynnis mani- Fig. 297. — Distribution in the United

toba, a butterfly restricted to subarctic and States of Eudamus proteus, primarily a trop-
subalpine regions. — After Scudder. ical butterfly. — After Scudder.

The Boreal region covers the northern part of the continent to about
the northern boundary of the United States and continues southward
along the higher portions of the mountain ranges. This region is divided
into three transcontinental zones: (1) the Arctic- Alpine, lying above the
limits of tree growth, in latitude or altitude; (2) the Hudsonian, com-
prising the northern part of the great transcontinental coniferous forest
and the upper timbered slopes of the highest mountains of the United
States and Mexico; (3) the Canadian, covering the remainder of the
Boreal region. The butterfly Erynnis manitoba (Fig. 296) is strictly
boreal in distribution.

The Austral region " covers the whole of the United States and
Mexico, except the Boreal mountains and the Tropical lowlands. '' It
comprises three transcontinental belts: (1) the Transition zone, in
which the Boreal and the Austral overlap; (2) the Upper Austral; (3)
the Lower Austral. The butterfly Eudamus proteus (Fig. 297) is re-

Plate IV.

DISTRIBUTION

313

stricted, generally speaking, to the Tropical region and the warmer and
more humid portions of the Austral.

The Tropical region covers the southern extremity of Florida and
of Lower California, most of Central America and a narrow strip along
the two coasts of Mexico, the western strip extending up into California
and Arizona.

These divisions are based primarily upon the distribution of mam-
mals, birds and plants, and the three primary divisions serve almost
equally well for insects also. In regard to the zones, however, not so
much can be said — for insects are to a high degree independent of minor
differences of climate. Many instances of this are given beyond.

The insect fauna of the United States is upon the whole a hetero-
geneous assemblage of species derived from several sources, and the
foreign element of this fauna we shall consider at some length.

Paths of Diffusion in North America. — It may be laid down as a
general rule that every species tends to spread in all directions and does
so spread until its further progress is prevented, in one way or another.
The paths along which a species spreads are determined, then, by the
absence of barriers. The diffusion of insects in our own country has
received much attention from entomologists, especially in the case of
such insects as are important from an economic standpoint. The ac-
cessions to our insect fauna have arrived chiefly from Asia, Central and
South America, and Europe.

Webster, our foremost student of this subject, to whom the author
is indebted for most of his facts, names four paths along which insects
have made their way into the United States: (1) Northwest — Northern
Asia into Alaska and thence south and east; (2) Southwest — Central
America through Mexico; (3) Southeast — West Indies into Florida; (4)
Eastern — from Europe, commercially.

Northwest. — The northern parts of Europe, Asia and North America
have in common very many identical or closely allied species, whose
distribution is accounted for if, as geologists assure us, Asia and North
America were once connected, at a time when a subtropical climate
prevailed within the Arctic Circle; in fact, the distribution is scarcely
explicable upon any other theory. Curiously enough, the trend of
diffusion seems to have been from Asia into North America and rarely
the reverse, so far as can be inferred.

Coccinella quinquenotata, occurring in Siberia and Alaska, has spread
to Hudson Bay, Greenland, Kansas, Utah, California and Mexico; while
C. sanguined, well known in Europe and Asia, ranges from Alaska to

314

ENTOMOLOGY

Patagonia; and Megilla metadata from Vancouver and Canada to Chile.
About six hundred species of beetles are holarctic in distribution, as was
mentioned. Some of them inhabit different climatal regions in dif-
ferent parts of their range; thus Melasoma {Lino) lapponica in the Old
World " occurs only in the high north and on high mountain ranges,
whereas in North America it extends to the extreme southern portion
of the country," being widely diffused over the lowlands (Schwartz).
Similarly. Silpha lapponica is strictly arctic in Europe, but is distributed
over most of North America; Silpha opaca, on the contrary, is common
all over Europe, but is strictly arctic in North America. Silpha atrata,
common throughout Europe and western Siberia, was introduced into
North America, but failed to establish itself.

Southwest. — Very many species have come to us from Central
America and even from South America. South America appears to be
the home of the genus Halisidota, according to Webster, who has traced
several of our North American species as offshoots of South American
forms. Many of our species may be traced back to Yucatan. H. cinc-
tipes ranges from South America to Texas and Florida; H. tessellaris
has spread northward from Central America and now occurs over the
middle and eastern United States, while a form closely like tessellaris
ranges from Argentina to Costa Rica; H. caryce follows tessellaris, and
appears to have branched in Central America, giving off H. agassizii,
which extends northward into California. Similarly in the case of the
Colorado potato beetle (Leptinotarsa decemlineata) and its relatives.
According to Tower, the parent form, L. undecemlineata , seems to have
arisen in the northern part of South America, to have migrated north-
ward and, in the diversified Mexican region, to have split into several
racial varieties. The parent form grades into L. multilineata of the
Mexican table Jands, which in turn, in the northern part of the Mexican
plateau, passes imperceptibly into L. decemlineata, wThich last species has
spread northward along the eastern slope of the western highlands, wrest
of the arid region. In the lower part of the Mexican region the parent
form may be traced into L.juncta, which has spread along the low humid
Gulf Coast, up the Mississippi valley to southern Illinois, and along the
Gulf Coast and up the Atlantic coast to Maryland, Delaware and New
Jersey. In general, the mountains of Central America and Mexico and
the plateau of Mexico have been barriers to the northward spread of
many species, which have reached the United States by passing to the
east or to the west of these barriers, in the former case skirting the Gulf
of Mexico and spreading northward along the Mississippi valley or along

DISTRIBUTION

315

the Atlantic coast, in the latter event traveling along the Pacific coast
to California and other Western states. Xot a few species, however,
have made their way from the Mexican plateau into Xew Mexico and
Arizona; this is true of many Sphingidae. The butterfly Anosia berenice
ranges from South America into New Mexico, Arizona and Colorado;
while many of the Libytheidae have entered Arizona and neighboring
states from Mexico. The chrysomelid genus Diabrotica is almost ex-
clusively confined to the western hemisphere and its home is clearly in
South America, where no less than 367 species are found. About 100
species occur in Venezuela and Colombia, ''of which 11 extend into
Guatemala, 8 into Mexico, and 1 into the United States." We have 18
species of Diabrotica, almost all of which can be traced back to Mexico,
and several of them — as the common D. longicornis — to Central America.
"The common Dynastes tityus occurs from Brazil through Central
America and Mexico, and in the United States from Texas to Illinois
and east to southern New York and New England." Erebus odor a
ranges from Ecuador and Brazil to Colorado, Illinois, Ohio, New Eng-
land and into Canada, though it is not known to breed in North America,
being in fact a rare visitor in our northern states.

Southeast. — Many South American species have made their way
into southern and western Florida by way of the WTest Indies, while
some subtropical species have reached Florida probably by following
around the Gulf coast. The semitropical insect fauna of southern and
southwestern Florida, including about 300 specimens of Coleoptera,
according to Schwarz, is entirely of West Indian and Central American
origin, the species having been introduced with their food plants, chiefly
by the Gulf Stream, but also by flight, as in the case of Sphingidae.
Ninety-five species of Hemiptera collected in extreme southern Florida
by Schwarz and studied by Uhler are distinctly Central American and
West Indian in their affinities. Indeed Uhler is inclined to believe that
the principal portion of the Hemiptera of the United States has been
derived from the region of Central America and Mexico.

Eastern. — On the Atlantic coast are many European species of
insects which have arrived through the agency of man. Most of them
have not as yet passed the Appalachian mountain system, but some have
worked their way inland. Thus the common cabbage butterfly (Pieris
rapce), first noticed in Quebec about i860, was found in the northern
parts of Maine, New Hampshire and Vermont five or six years later, was
established in those states by 1867, entered New York in 1868 and then
Ohio. Aphodius fossor followed much the same course from Xew York

3i6

ENTOMOLOGY

into northeastern Ohio, as did also the asparagus beetle (Crioceris as-
paragi), the clover leaf weevil (Phytonomiis punctatus), the clover root
borer (Hylastes obscurus) and other species. In short, as Webster has
pointed out, New York offers a natural gateway through which species
introduced from Europe spread westward, passing either to the north
or to the south of Lake Erie.

Inland Distribution. — Pieris rapce, the spread of which in North
America has been thoroughly traced by Scudder, reached northern New
York in 1868 (as above), but appears to have been independently intro-
duced into New Jersey in 1868, whence it reached eastern New York
again in 1870; it was seen in northeastern Ohio in 1873, Chicago 1875,
Iowa 1878, Minnesota 1880, Colorado 1886, and has extended as far
south as northern Florida, but is apparently unable to make its way
down into the peninsula.

Crioceris as para gi, another native of Europe, became conspicuous
in Long Island in 1856, spread southward to Virginia and westward to
Ohio, where it was taken in 1886; it occurs now in Illinois. This insect,
as Howard observes, flies readily, and may be introduced commercially
in the egg or larval stage on bunches of asparagus.

Cryptorhynchus lapathi, a beetle destructive to willows and poplars,
and common in Europe, Siberia and Japan, was found in New Jersey in
1882 and in New York in 1896, though known for many years previously
in Massachusetts. It became noticeable in Ohio in 1901, and is steadily
extending its ravages, being reported recently from [Minnesota.

From Colorado the well-known potato beetle (Leptinotarsa decem-
Uneata) has worked eastward since 1840, reaching the Atlantic coast
within twenty years, and has even made its way several times into Great
Britain, only to be stamped out with commendable energy. The box-
elder bug (Leptocoris trivittatus) is similarly working eastward, having
now reached Indiana. The Rocky Mountain locust periodically mi-
grates eastward, but meets a check in the moist valley of the Mississippi,
as has been said.

The chinch bug (Blissns lencopterus), the distribution of which has
been traced by Webster, has spread from Central America and Mexico
northward along the Gulf coast into the United States, following three
paths: (1) Along the Atlantic coast to Cape Breton; (2) along the Mis-
sissippi valley and northward into Manitoba; (3) along the western
coast of Central America and Mexico into California and other Western
states. Everywhere this insect has found wild grasses upon which to
feed, but has readily forsaken these for cultivated grasses upon occasion.

DISTRIBUTION

317

The harlequin cabbage bug (Murgantia histrionica) has spread from
Central America into California and Nevada, and has steadily progressed
in the Mississippi basin as far north as Illinois, Indiana and Ohio, though
it appears to be unable to maintain itself in the northern parts of these
states. This insect required about twenty-five years to pass from Loui-
siana (1864) to Ohio, spreading through its own efforts and not commer-
cially to any great extent.

Every year some of the southern butterflies reach the Northern states,
where they die without finding a food plant, or else maintain a precarious
existence. Thus Iphiclides ajax occasionally reaches Massachusetts
as a visitor and a visitor only; Lcertias philenor, however, rinds a limited
amount of food in the cultivated Aristolochia. P. thoas. one of the pests
of the orange tree in the South, is highly prized as a rarity by New Eng-
land collectors and is able to perpetuate itself in the Middle States on the
prickly ash (Xanthoxylum). The strong-winged grasshopper, Schisto-
cerca americana, belonging to a genus the center of whose dispersion is
tropical America, ranges freely over the interior of North America, some-
times in great swarms, and its nymphs are able to survive in moderate
numbers in the southern parts of Illinois, Ohio and other states of as
high latitude, while the adults occasionally reach Ontario, Canada.

Many species are now so widely distributed that their former paths
of diffusion can no longer be ascertained. The army worm (Heliophila
unipuncta), feeding on grasses, and occurring all over the United States
south of Lat. 440 N., is found also in Central America, throughout South
America, and in Europe, Africa, Japan. China, India, etc.; in short, it
occurs in all except the coldest parts of the earth, and where it origi-
nated no one knows.

Determination of Centers of Dispersal. — In accounting for the
present distribution of life, naturalists employ several kinds of evidence.
Adams recognizes ten criteria, aside from palaeontological evidence, for
determining centers of dispersal:

1. Location of greatest differentiation of a type.

2. Location of dominance or great abundance of individuals.

3. Location of synthetic or closely related forms (Allen).

4. Location of maximum size of individuals (Ridgway- Allen).

5. Location of greatest productiveness and its relative stability, in
crops (Hyde) .

6. Continuity and convergence of lines of dispersal.

7. Location of least dependence upon a restricted habitat.

8. Continuity and directness of individual variations or modifica-

3i8

ENTOMOLOGY

tions radiating from the center of origin along the highways of dispersal.
9. Direction indicated by biogeographical affinities.
10. Direction indicated by the annual migration routes, in birds
(Palmen).

2. Geological

Means of Fossilization. — Abundant as insects are at present, they
are comparatively rare as fossils, the fossil species forming but one per-
cent, of the total number of described species of insects. The absence
of insect remains in sedimentary rocks of marine origin is explained by
the fact that almost no insects inhabit salt water; and terrestrial forms
in general are ill-adapted for fossilization. The hosts of insects that die
each year leave remarkably few traces in the soil, owing perhaps, in great
measure, to the dissolution of chitin in the presence of moisture.

Most of the fossil insects that are known have been found in vege-
table accumulations such as coal, peat and lignite, or else in ancient
fresh-water basins, where the insects were probably drowned and rapidly
imbedded. At present, enormous numbers of insects are sometimes
cast upon the shores of our great lakes — a phenomenon which helps to
explain the profusion of fossil forms in some of the ancient lake basins.

Insects in rich variety have been preserved in amber, the fossilized
resin of coniferous trees. This substance, as it exuded, must have en-
tangled and enveloped insect visitors just as it does at present. Many
of these amber insects are exquisitely preserved, as if sealed in glass.
Copal, a transparent, amber-like resin from various tropical trees, par-
ticularly Leguminosae, has also yielded many interesting insects.

Ill-adapted as insects are by organization and habit for the com-
moner methods of fossilization, the number of fossil species already
described is no less than three thousand.

Localities for Fossil Insects. — The Devonian of New Brunswick
has furnished a few forms, found near St. John, in a small ledge that
outcrops between tide-marks; these forms, though few, are of extraor-
dinary interest, as will be seen.

For Carboniferous species, Commentry in France is a noted locality,
through the admirable researches of Brongniart, who described from
there 97 species of 48 genera, representing 12 families or higher groups,
10 of which are regarded as extinct; without including many hundred
specimens of cockroaches which he found but did not study. In this
country many species have been found in the coal fields of Illinois,
Nova Scotia, Rhode Island, Pennsylvania and Ohio.

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319

Many fine fossils of the Jurassic period have been found in the litho-
graphic limestones of Bavaria; 143 species from the Lias — four fifths of
them beetles — were studied by Heer.

The Tertiary period has furnished the majority of fossil specimens.
To the Oligocene belong the amber insects, of which 900 species are known
from Baltic amber alone, and to the same epoch are ascribed the deposits
of Florissant and White River in Colorado and of Green River, Wyoming.
These localities — the richest in the world — have
been made famous by the monumental works
of Scudder. At Florissant there is an extinct
lake, in the bed of which, entombed in shales
derived from volcanic sand and ash, the re-
mains of insects are found in astonishing pro-
fusion. For Miocene forms, of which 1,550

' Fig. 298. — Palceoblat-
tina douvittei, natural size.
— After Brongniart.

European species are known, the (Eningen beds of Bavaria are celebrated
as having furnished 844 species, described by the illustrious Heer.

Pleistocene species are supplied by the peats of France and Europe,
the lignites of Bavaria, and the interglacial clays of Switzerland and
Ontario, Canada.

Silurian and Devonian. — The oldest fossil insect known consists
of a single hemipterous wing, Protocimcx. from the Lower Silurian of

Sweden. Next in age comes
a wing, PalceoblaUina (Fig.
298), of doubtful position,1
from the Middle Silurian of
France. Following these are
six specimens of as many re-
markable species from the
Devonian shales of New
Brunswick. The specimens,
to be sure, are nothing but
broken wings, yet these few fragments, interpreted by Dr. Scudder, are rich
in meaning. All are neuropteroid, but they cannot be classified satisfac-
torily with recent forms on account of being highly synthetic in structure.
Thus Platephemera antiqua (Fig. 299), though essentially a May fly of
gigantic proportions (spreading probably 135 mm.), has an odonate type
of reticulation; while Xenoneura (Fig. 300) combines characters which
are now distributed among Ephemeridae, Sialidae, Rhaphidiidae, Con-
iopterygidae, and other families, besides being in many respects unique.

1 There is some evidence, it should be said, that this species is not an insect. Handlirsch
denies also that Protocimcx is an insect.

Fig. 299. — Platephemera antiqua, natural size.
Scudder.

After

320

ENTOMOLOGY

These Devonian forms attained huge dimensions as compared with their
recent representatives; Ger ephemera, for example, had an estimated ex-
panse of 175 millimeters.

Carboniferous. The Carboniferous age, with its luxuriant vegeta-
tion, is marked by the appearance of insects in great number and variety,

Fig. 300. — Xenoneura anti quorum, five times natural size. — After Scudder.

still restricted, however, to the more generalized orders. The domi-
nance of cockroaches in the Carboniferous is especially noteworthy, no
less than 200 Palaeozoic species being known from Europe and North

Fig. 301. — Etoblatthia ma- Fig. 302. — Lithomantis carbonarius, showing protho-

zona, a Carboniferous cock- racic appendages. Two thirds natural size. — After Wood-

roach from Illinois. Twice ward.
natural size. — After Scudder
in Miall and Denny.

America. These ancient roaches (Fig. 301) differed from their modern
descendants in the similarity of the two pairs of wings, which were alike
in form, size, transparency and general neuration, with six principal
nervures in each wing; while in recent cockroaches the front wings have

DISTRIBUTION

321

become tegmina, with certain of the veins always blended together,
though the hind wings have retained their primitive characteristics with
a few modifications, such as the expansion of the anal area. Carbon-
iferous cockroaches furthermore exhibit ovipositors, straight, slender,
and half as long again as the abdomen — organs which do not exist in
recent species.

Lithomantis (Fig. 302), a remarkable form from Scotland, possessed
in addition to its four large neuropteroid wings, a pair of prothoracic
wing-like appendages which, provided they may be regarded as homolo-
gous with wings, represent a third pair, either atrophied or undeveloped —
a condition which is never
found today, unless the
patagia of Lepidoptera rep-
resent wings, which is un-
likely.

From the rich deposits
of Commentry, Brongniart
has described several forms
of striking interest. Dictyo-
neura is a Carboniferous
genus with neuropteroid
wings and an orthopteroid
body, having, in common
with several contemporary
genera, strong isopteran
affinities. Corydaloides
scudderi. a phasmid. has
an alar expanse of twenty-
eight inches. The Carbo-
niferous prototypes of our

Odonata were gigantic beside their modern descendants, one of them
(Meganeura) having a spread of over two feet; they were more generalized
in structure than recent Odonata, presenting a much simpler type of neura-
tion and less differentiation of the segments of the thorax. The Carbonif-
erous precursors of our May flies attained a high development in number
and variety; in fact, the Ephemeridae, like the Blattidae. achieved their
maximum development ages ago, when they attained an importance
strongly contrasting with their present meager representation.

The Permian has supplied a remarkable genus Eugereon (Fig. 303)
with hemipterous mouth parts associated with filiform antennae and

Fig. 303. — Eugereon bockingi. Three quarters natural
size. — After Dohr.v

322

I.N To Mo !.()(. V

orthopteroid wings. The earliest unquestionable traces of insects with
an indirect metamorphosis are found in the Permian of Bohemia, in
the shape of caddis-worm cases.

Triassic— Triassic cockroaches present interesting stages in the
evolution of their family. Through these Mesozoic species the con-
tinuity between Palaeozoic and recent cockroaches is clearly established —
which can be said of no other insects; and in fact of no other animals,
the only comparable cases being those of the horse and the molluscan
genus Planorbis. In the Triassic period occur the first fossils that can
be referred indisputably to Coleoptera and Hymenoptera, the latter order
being represented first, as it happens, by some of its most specialized
members, namely ants.

Jurassic. — At length, in the Jurassic, all the large orders except Lep-
idoptera occur; Diptera appear for the first time, and Odonata are rep-
resented by many well-preserved specimens, while the Liassic Coleoptera
studied by Heer number over one hundred species. The Cretaceous
has yielded but few insects, as might be expected.

Tertiary. — In the rich Tertiary deposits all orders of insects occur.
Baltic amber has yielded Collembola, some remarkable Psocidae, many
Diptera, and ants in abundance. Of 844 species taken from the noted
Miocene beds of (Eningen, nearly one half were Coleoptera, followed by
neuropteroid forms (seventeen per cent.) and Hymenoptera (fourteen
per cent.); ants were twice as numerous in species as they are at present
in Europe. Almost half the known species of fossil insects have been
described from the Miocene of Europe. To the Miocene belongs the
indusial limestone of Auvergne, France, where extensive beds — in some
places two or three meters deep — consist for the most part of the cal-
cified larval cases of caddis flies.

At Florissant, as contrasted with CEningen by Scudder, Hymenoptera
constitute 40 per cent, of the specimens, owing chiefly to the predominance
of ants; Diptera follow with 30 per cent, and then Coleoptera with 13
per cent. Modern families are represented in great profusion. The
material from Florissant and neighboring localities includes a Lepisma.
fifteen species of Psocidae, over thirty species of Aphididae, and over one
hundred species of Elateridae, while the Rhynchophora number 193
species as against 150 species from the Tertiary of Europe. Tipulidae
are abundant and exquisitely preserved, while Bibionidae, as compared
with their present numbers, are surprisingly common. Numerous masses
of eggs occur, undoubtedly sialid and closely like those of Corydalis.
Sialid characters, indeed, appear in the oldest fossils known, and are

DISTRIBUTION '

323

strongly manifest throughout the fossil series, though among recent
insects Sialidae occupy only a subordinate place. Strange to say, few
aquatic insects have been found in this ancient lake basin.

Fossil butterflies are among the greatest rarities, only seventeen
being known; yet Florissant has contributed eight of these, a few of
which are marvelously wrell preserved (Fig. 304), as appears from Scud-
der s figures. Two of the Florissant specimens belong to Libytheinae,
a group now scantily represented, though widely distributed over the
earth. The group is structurally an archaic one, and its recent members
(forming only one eight-hundredth of the described species of butter-
flies) are doubtless relicts.

Taken as a whole, the insect facies of Tertiary times was apparently
much the same as at present. The Florissant fauna and flora indicate,
however, a former climate in Colorado
as warm as the present climate of
Georgia.

Quaternary. — The interglacial
clays of Toronto, Ontario, have yielded
fragments of the skeletons of beetles to
the extent of several hundred speci-
mens, about one third of which (chiefly
elytra) wrere sufliciently complete or
characteristic to be identified by Dr.
Scudder, who has found in all 76 species
of beetles, representing 8 families,
chiefly Carabidae and Staphylinidae.

All these interglacial beetles are referable to recent genera, but none of
them to recent species, though the differences between the interglacial
species and their recent allies are very slight. As a whole, these species
" indicate a climate closely resembling that of Ontario to-day, or perhaps
a slightly colder one. . . . One cannot fail, also, to notice that a
large number of the allies of the interglacial forms are recorded from the
Pacific coast." (Scudder.) The writer, wrho has studied these speci-
mens, has been impressed most by their likeness to modern species. It
is indeed remarkable that so little specific differentiation has occurred in
these beetles since the interglacial epoch — certainly ten thousand and
possibly two or three hundred thousand years ago.

General Conclusions. — Unfortunately, the earliest fossils with
which we are acquainted shed much less light upon the subject of insect
phylogeny than one might expect. The few Devonian forms, though

Fig. 304. — Prodryas persephone, a
fossil butterfly from Colorado. Natural
size. — After Scudder.

3 24

ENTOMOLOGY

synthetic indeed as compared with their modern allies, are at the same
time highly organized, or far from primitive, and their ancestors have
been obliterated.

The general plan of wing structure, as Scudder finds, has remained
unaltered from the earliest times, though the Devonian specimens ex-
hibit many peculiarities of venation, in which respect some of them are
more specialized than their nearest living allies, while none of them have
much special relation to Carboniferous forms.

Carboniferous insects are more nearly related to recent forms than are
the Devonian species, but present a number of significant generalized
features. Generally speaking, the thoracic segments were similar and
unconsolidated, and the two pairs of diaphanous wings were alike in
every respect — in groups that have since developed tegmina and dis-
similiar thoracic segments. The Carboniferous precursors of our cock-
roaches, phasmids and May flies have been mentioned. Palaeozoic in-
sects are grouped by Scudder into a single order. Palaeodictyoptera, on
account of their synthetic organization, though other authors have tried
to distribute them among the modern orders. This disagreement will
continue until, with increasing knowledge, our classification becomes less
arbitrary and more natural.

Mesozoic insects are interesting chiefly as evolutionary links, notably
so in the case of cockroaches — the only insects whose ancestry is con-
tinuously traceable. In this era the large families became differentiated
out.

Most of the Tertiary species are referable to recent genera, peculiar
families being highly exceptional, while all the Quaternary species belong
to recent genera.

Hemiptera appear in the Silurian; Xeuroptera (in the old sense) in
the Devonian; Thysanura and Orthoptera. Carboniferous; Coleoptera
and Hymenoptera, Triassic; Diptera, Jurassic; and Lepidoptera not
until the Tertiary.

CHAPTER XIII

INSECTS IN RELATION TO MAN

A great many insects, eminently successful from their own standpoint,
so to speak, nevertheless interfere seriously with the interests of man.
On the other hand, many insects are directly or indirectly so useful to
man that their services form no small compensation for the damage done
by other species.

Injurious Insects. — Insects destroy cultivated plants, infest do-
mestic animals, injure food, manufactured articles, etc., and molest or
harm man himself.

The cultivation of a plant in great quantity offers an unusual oppor-
tunity for the increase of its insect inhabitants. The number of species
affecting one kind of plant — to say nothing of the number of individuals —
is often great. Thus about 200 species attack Indian corn, 50 of them
doing notable injury; 200 affect clover, directly or indirectly; and 400
the apple; while the oaks harbor probably 1,000 species.

The average annual loss through the cotton worm, i860 to 1874, was
$15,000,000, according to Packard; the loss from the Rocky Mountain
locust, in 1874, in Iowa, Missouri, Kansas and Nebraska, $40,000,000
(Thomas); and the total loss from this pest, 1874 to 1877, $200,000,000.
The loss through the chinch bug, in 1864, was $73,000,000 in Illinois
alone, as estimated by Riley. The ravages of the Hessian fly, fluted
scale, San Jose scale, gypsy moth and cotton boll weevil need only be
mentioned.

At times, an insect has been the source of a national calamity, as was
the case for forty years in France, when Phylloxera threatened to ex-
terminate the vine. In Africa the migratory locust is an unmitigated
evil.

Probably at least ten per cent, of every crop is lost through the at-
tacks of insects, though the loss is often so constant as to escape obser-
vation. Regarded as a direct tax of ten cents upon the dollar, however,
this loss becomes impressive. Webster says: "It costs the American
farmer more to feed his insect foes than it does to educate his children.' '
The average annual damage done by insects to crops in the United States
was conservatively estimated by Walsh and Riley to be $300,000,000 —

325

326

ENTOMOLOGY

or about $50 for each farm. "A recent estimate by experts put the
yearly loss from forest insect depredations at not less than $100,000,000.
The common schools of the country cost in 1902 the sum of $235,000,000,
and all higher institutions of learning cost less than $50,000,000, making
the total cost of education in the United States considerably less than
the farmers lost from insect ravages. Thus it would be within the
statistical truth to make a still more startling statement than Webster's,
and say that it costs American farmers more to feed their insect foes
than it does to maintain the wrhole system of education for everybody's
children.

" Furthermore, the yearly losses from insect ravages aggregate nearly
twice as much as it costs to maintain our army and navy; more than
twice the loss by fire; twice the capital invested in manufacturing agri-
cultural implements; and nearly three times the estimated value of the
products of all the fruit orchards, vineyards, and small fruit farms in the
country." (Slingerland.)

Though most of the parasites of domestic animals are merely annoy-
ances, some inflict serious or even fatal injury, as has been said. The
gad flies persecute horses and cattle; the maggots of a bot fly grow in
the frontal sinuses of sheep, causing vertigo and often death; another
bot fly develops in the stomach of the horse, enfeebling the animal.
The worst of the bot flies, however, is Hypoderma lineata, the ox-warble,
which not only impairs the beef but damages the hide by its perforations;
the loss from this insect for one period of six months (Chicago, 1889) was
conservatively estimated as $3,336,565, of which $667,513 represented
the injury to hides.

All sorts of foodstuffs are attacked by insects, particularly cereals;
clothing, especially of wool, fur or feathers; also furniture and hundreds
of other useful articles.

As carriers of disease germs, insects are of vital importance to man,
as we have shown.

Beneficial Insects. — The vast benefits derived from insects are too
often overlooked, for the reason that they are often so unobvious as
compared with the injuries done by other species. Insects are useful
as checks upon noxious insects and plants, as pollenizers of flowers, as
scavengers, as sources of human clothing, food, etc., and as food for
birds and fishes.

Almost every insect is subject to the attacks of other insects, pre-
daceous or parasitic — to say nothing of its many other enemies — and but
for this a single species of insect might soon overrun the earth. There
are only too many illustrations of the tremendous spread of an insect

INSECTS IX RELATION TO MAX

327

in the absence of its accustomed natural enemies. One of these examples
is that of the gypsy moth, artificially introduced into Massachusetts
from Europe; another is the fluted scale, transported from Australia to
California. Some conception of the vast restricting influence of one
species upon another may be gained from the fact that the fluted scale
has practically been exterminated in California as the result of the im-
portation from Australia of one of its natural enemies, a lady-bird beetle
known as Xovius cardinalis. The plant lice, though of unparalleled
fecundity, are ordinarily held in check by a host of enemies, as was
described.

An astonishingly large number of parasites may develop in the body
of a single individual; thus over 3,000 specimens of a hymenopterous
parasite {Copidosoma truncatellum) were reared by Giard from a single
Plusia caterpillar.

Parasites themselves are frequently parasitized, this phenomenon of
hyperparasitism being of considerable economic importance. A bene-
ficial primary parasite may be overpowered by a secondary parasite,
evidently to the indirect disadvantage of man, while the influence of a
tertiary parasite would be beneficial again. Now parasites of the third
order occur and probably of the fourth order, as appears from Howard's
studies, which we have already summarized. Moreover, parasites of all
degrees are attacked by predaceous insects, birds, bacteria, fungi, etc.
The control of one insect by another becomes, then, a subject of extreme
intricacy.

Insects render an important, though commonly unnoticed, service
to man in checking the growth of weeds. Indeed, insects exercise a vast
influence upon vegetation in general. A conspicuous alteration in the
vegetation has followed the invasions of the Rocky Mountain locust,
as Riley has said; many plants before unnoticed have grown in profu-
sion and many common kinds have attained an unusual luxuriance.

As agents in the cross pollination of flowers, insects are eminently
important. Darwin and his followers have proved beyond question
that as a rule cross pollination is indispensable to the continued vitality
of flowering plants; that repeated close pollination impairs their vigor
to the point of extermination. Without the visits of bees and other
insects our fruit trees would yield little or nothing, and the fruit grower
owes these helpers a debt which is too often overlooked.

As scavengers, insects are of inestimable benefit, consuming as they
do in incalculable quantity all kinds of dead and decaying animal and
vegetable matter. This function of insects is most noticeable in the

328

ENTOMOLOGY

tropics, where the ants, in particular, eradicate tons of decomposing
matter that man lazily neglects.

The usefulness of the silkworms and the honey bee need only be
mentioned, and after these, the cochineal insect and the lac insects.
The "Spanish fly" — a meloid beetle — is still used medicinally, and in
China medicinal properties are ascribed to many different insects. As
human food, insects are of considerable importance among semi-civilized
races; the migratory locust is eaten in great quantities in Africa, and
termites in Africa and Australia, the latter insects being said to have a
delicious flavor; in Mexico the eggs and adults of an aquatic hemipteron,
Corixa, are highly relished by some of the natives. As food for fishes,
game birds, song birds and poultry, insects are of vast importance, it is
needless to say.

Introduction and Spread of Injurious Insects. — Many of our
worst insect pests were brought accidentally from Europe, notably the
Hessian fly, wheat midge, codling moth (probably), gypsy moth, cabbage
butterfly, cabbage aphis, clover leaf beetle, clover root borer, asparagus
beetle, imported currant worm and many cutworms; though few Ameri-
can species have obtained a foothold in Europe, one of the few being the
dreaded Phylloxera, which appeared in France in 1863.

The gypsy moth, liberated in Massachusetts in 1868, cost the state
over one million dollars in appropriations (1 890-1 899) and is not yet
under full control. The San Jose scale insect, a native of North China
according to Marlatt, was introduced into the San Jose valley, California,
about 1870, probably upon the flowering Chinese peach, became seriously
destructive there in 1873, was carried across the continent to New Jersey
in 1886 or 1887 on plum stock, and thence distributed directly to several
other states, upon nursery stock. At present the San Jose scale is a
permanent menace to horticulture throughout the United States and is
being checked or subdued only by the vigorous and continuous work of
official entomologists, acting under special legislation. This pernicious
insect occurs also in Japan, Hawaii, Australia and Chile, in these places
probably as a recent introduction.

The Mexican cotton boll weevil (Anthonomus grandis) crossed the Rio
Grande river and appeared in Brownsville, Texas, about 1892, since
when it has spread over eastern Texas and into Louisiana, Mississippi,
Alabama and Arkansas. Advancing as it does at the rate of fifty miles a
year, the insect would require but fifteen or eighteen years to cover
the entire cotton belt. The beetle hibernates and lays its eggs in the
cotton bolls; these are injured both by the larva feeding within and by

INSECTS IN RELATION TO MAN

329

the beetles, whose feeding-punctures destroy the bolls and cause them to
drop. If unchecked, this pest would destroy fully one half the cotton
crop, entailing an annual loss of $250,000,000. As it is, the universal
adoption of the cultural methods recommended by the Bureau of Ento-
mology promises to reduce the damage to a point at which cotton can
still be grown at a fair profit.

An insect often passes readily from a wild plant to a nearly related
cultivated species. Thus the Colorado potato beetle passed from the wild
species Solanum rostratum to the introduced species, Solanum tuberosum,
the potato. Many of our fruit-tree insects feed upon wild, as well as
cultivated, species of Rosaceae; the peach borer, a native of this country,
probably fed originally upon wild plum or wild cherry. Many of the
common scarabaeid larva? known as " white grubs" are native to prairie
sod, and attack the roots of various cultivated grasses, including corn,
and those of strawberry, potato and other plants. The chinch bug fed
originally upon native grasses, but is equally at home on cultivated spe-
cies, particularly millet, Hungarian grass, rice, wheat, barley, rye and
corn. In fact, the worst corn insects, such as the chinch bug, wire worms,
white grubs and cutworms, are species derived from wild grasses.

Even in the absence of cultivated plants their insect pests continue
to sustain themselves upon wild plants, as a rule; the larva of the cod-
ling moth, for example, is very common in wild apples and wild haws.

The Economic Entomologist. — To mitigate the tremendous dam-
age done by insects, the individual cultivator is almost helpless without
expert advice, and the immense agricultural interests of this country have
necessitated the development of the economic entomologist, the value of
whose services is universally appreciated by the intelligent.

Almost every State now has one or more economic entomologists,
responsible to the State or else to a State Experiment Station, while the
general Government attends to general entomological needs in the most
comprehensive and thorough manner.

"It is the special object of the economic entomologist," says Dr.
Forbes, "to investigate the conditions under which these enormous losses
of the food and labor of the country occur, and to determine, first,
whether any of them are in any degree preventable; second, if so, how
they are to be prevented with the least possible cost of labor and money;
and, third, to estimate as exactly as possible the expenses of such pre-
vention, or to furnish the data for such an estimate, in order that each
may determine for himself what is for his interest in every case arising.

"The subject matter of this science is not insects alone, nor plants
alone, nor farming alone. One may be a most excellent entomologist

33°

ENTOMOLOGY

or botanist, or he may have the whole theory and practice of agriculture
at his tongue's end, and at his fingers' ends as well, and yet be without
knowledge or resources when brought face to face with a new practical
problem in economic entomology. The subject is essentially that of
the relations of these things to each other; of insect to plant and of plant
to insect, and of both these to the purposes and operations of the farm,
and it involves some knowledge of all of them.

"As far as the entomological part of the subject is concerned, the
chief requisites are a familiar acquaintance with the common injurious
insects, and especially a thorough knowledge of their life histories, to-
gether with practical familiarity with methods of entomological study
and research. The life histories of insects lie at the foundation of the
whole subject of economic entomology; and constitute, in fact, the
principal part of the science; for until these are clearly and completely
made out for any given injurious species, we cannot possibly tell when,
where or how to strike it at its weakest point.

"But besides this, we must also know the conditions favorable and
unfavorable to it; the enemies which prey upon it, whether bird or in-
sect or plant parasite; the diseases to which it is subject, and the effects
of the various changes of weather and season. We should make, in fact,
a thorough study of it in relation to the whole system of things by which
it is affected. Without this we shall often be exposed to needless alarm
and expense, perhaps, in righting by artificial remedies, an insect already
in process of rapid extinction by natural causes; perhaps giving up in
despair just at the time when the natural checks upon its career are
about to lend their powerful aid to its suppression. We may even, for
lack of this knowledge, destroy our best friends under the supposition
that they are the authors of the mischief which they are really exerting
themselves to prevent. In addition to this knowledge of the relations
of our farm pests to what we may call the natural conditions of their life,
we must know how our own artificial farming operations affect them,
which of our methods of culture stimulate their increase, and which, if
any, may help to keep it down. And we must also learn where strictly
artificial measures can be used to advantage to destroy them.

"For the life histories of insects, close, accurate and continuous ob-
servation is of course necessary; and each species studied must be fol-
lowed not only through its periods of destructive abundance, when it
attracts general attention, but through its times of scarcity as well, and
season after season, and year after year.

"The observations thus made must of course be collected, collated

INSECTS IX RELATION TO MAN

331

and most cautiously generalized, with constant reference to the con-
ditions under which they were made. Xo part of the work requires
more care than this.

"This work becomes still more difficult and intricate when we pass
from the simple life histories of insects to a study of the natural checks
upon their increase. Here hundreds and even thousands of dissections
of insectivorous birds and predaceous insects are necessary, and a care-
ful microscopic study of their food, followed by summaries and tables
of the principal results, a tedious and laborious undertaking, a specialty
in itself, requiring its special methods and its special knowledge of the
structures of insects and plants, since these must be recognized in frag-
ments, while the ordinary student sees them only entire.

"If we would understand the relations of season and weather to the
abundance of injurious insects, we are led up to the science of meteor-
ology; and if we undertake to master the obscure subject of their diseases,
especially those of epidemic or contagious character, we shall find use
for the highest skill of the microscopist, and the best instruments of
microscopic research.

"All these investigations are preliminary to the practical part of our
subject! What shall the farmer do to protect his crops? To answer
this question, besides the studies just mentioned, much careful experiment
is necessary. All practical methods of fighting the injurious insects
must be tried — first on a small scale, and under conditions which the
experimenter can control completely, and then on the larger scale of
actual practice; and these experiments must be repeated under varying
circumstances, until we are sure that all chances of mistake or of acci-
dental coincidence are removed. The whole subject of artificial remedies
for insect depredations, whether topical applications or special modes of
culture, must be gone over critically in this way. So many of the so-
called experiments upon'which current statements relating to the value
of remedies and preventives are based, have been made by persons
unused to investigation, ignorant of the habits and the transformations
of the insects treated, without skill or training in the estimation of evi-
dence, and failing to understand the importance of verification, that the
whole subject is honeycombed witfi blunders. Popular remedies for
insect injuries have, in fact, scarcely more value, as a rule, than popular
remedies for disease.

"Observation, record, generalization, experiment, verification — ■
these are the processes necessary for the mastery of this subject, and
they are the principal and ordinary processes of all scientific research."

332

ENTOMOLOGY

The official economic entomologist uses every means to reach the
public for whose benefit he works. Bulletins, circulars and reports,
embodying most serviceable information, are distributed freely where
they will do the most good, and timely advice is disseminated through
newspapers and agricultural journals. An immense amount of corre-
spondence is carried on with individual seekers for help, and personal
influence is exerted in visits to infested localities and by addresses before
agricultural meetings. Special emergencies often tax every resource
of the official entomologist, especially if he is hampered by inadequate
legislative provision for his work. Too often the public, disregarding
the prophetic voice of the expert, refuses to "close the door until the
horse is stolen."

Aside from these emergencies, such as outbreaks of the Rocky Moun-
tain locust, chinch bug, Hessian fly, San Jose scale and others, the State
or Experiment Station entomologist has his hands full in any State of
agricultural importance; in fact, can scarcely discharge his duties prop-
erly without the aid of a corps of competent assistants.

This chapter would be incomplete without some mention of the
progress of economic entomology in this country, especially since America
is pre-eminently the home of the science. The history of the science is
largely the history of the State and Government entomologists, for the
following account of whose work we are indebted chiefly to the writings
of Dr. Howard, to which the reader is referred for additional details as
well as for a comprehensive review of the status of economic entomology
in foreign countries.

Massachusetts. — Dr. Thaddeus W. Harris, though preceded as a
writer upon economic entomology by William D. Peck, was our pioneer
official entomologist — official simply in the sense that his classic volume
was prepared and published at the expense of the state of Massachusetts,
first (1841) as a "Report" and later as a "Treatise." The splendid
Flint edition (1862), entitled "A Treatise on Some of the Insects In-
jurious to Vegetation," is still "the vade mecum of the working ento-
mologist who resides in the northeastern section of the country."

Dr. Alpheus S. Packard gave the state three short but useful reports
from 1871 to 1873.

As entomologist to the Hatch Experiment Station of the Massachu-
setts Agricultural College, Prof. Charles H. Fernald has issued important
bulletins upon injurious insects, and has published in collaboration with
Edward H. Forbush a notable volume upon the gypsy moth. For the
suppression of this pest, which threatened to exterminate vegetation

INSECTS IN RELATION TO MAN

333

over one hundred square miles, the state of Massachusetts made annual
appropriations amounting in all to more than one million dollars, and the
operations, carried on by a committee of the State Board of Agriculture,
rank among the most extensive of their kind. At present the Bureau
of Entomology is making successful efforts toward the eradication of
this pest.

New York. — Dr. Asa Fitch, appointed in 1854 by the Xew York State
Agricultural Society, under the authorization of the legislature, was the
first entomologist to be officially commissioned by any state. His
fourteen reports (1855 to 1872) embody the results of a large amount of
painstaking investigation.

In 1881 Dr. James A. Lintner became state entomologist of New
York. Highly competent for his chosen work, Lintner made every
effort to further the cause of economic entomology, and his thirteen
reports, accurate, thorough and extremely serviceable, rank among the
best. Lintner has had a most able successor in Dr. E. P. Felt, who is
continuing the work with exceptional vigor and the most careful regard
for the entomological welfare of the state. Felt has published at this
writing thirty bulletins (including fourteen annual reports), besides im-
portant papers on forest and shade-tree insects, and has directed the
preparation by Xeedham and his associates of three notable volumes on
aquatic insects.

The Cornell University Agricultural Experiment Station, established
in 1879, has issued many valuable publications upon injurious insects,
written by the master-hand of Professor Comstock or else under his
influence. The studies of Comstock and Slingerland were always made
in the most conscientious spirit and their bulletins — original, thorough
and practical — are models of what such works should be.

Illinois. — Mr. Benjamin D. Walsh, engaged in 1867 by the Illinois
State Horticultural Society, published in 1868, as acting state entomolo-
gist, a report in the interests of horticulture — an accurate, sagacious
and altogether excellent piece of original work. Like many other eco-
nomic entomologists he was a prolific writer for the agricultural press and
his contributions, numbering about four hundred, were in the highest
degree scientific and practical.

Walsh was succeeded by Dr. William LeBaron, who published (187 1
to 1874) four able reports of great practical value. In the words of Dr.
Howard, "He records in his first report the first successful experiment
in the transportation of parasites of an injurious species from one locality
to another, and in his second report recommended the use of Paris green

334

KNTOMOLOdY

against the canker worm on apple trees, the legitimate outcome from
which has been the extensive use of the same substance against the
codling moth, which may safely be called one of the great discoveries
in economic entomology of late years."

Following LeBaron as state entomologist, Rev. Cyrus Thomas and
his assistants, G. H. French and D. W. Coquillett, produced a creditable
series of six reports (1875 to 1880) as part of a projected manual of the
economic entomology of Illinois.

Since 1882 Prof. Stephen A. Forbes has fulfilled the duties of state
entomologist in the most efficient manner. Thoroughly scientific, with
a broad view and a clear insight into the agricultural needs of the state,
his authoritative and scholarly works upon economic entomology rank
with those of the highest value. Of the sixteen reports issued thus far
by Dr. Forbes, those dealing with the chinch bug, San Jose scale, corn
insects and sugar-beet insects are especially noteworthy.

Missouri. — Appointed in 1868, Prof. Charles V. Riley published
(1869 to 1877) nine reports as state entomologist. To quote Dr. How-
ard, "They are monuments to the state of Missouri, and more especially
to the man who wrote them. They are original, practical and scientific.
. . . They may be said to have formed the basis for the new economic
entomology of the world." Riley's subsequent work will presently be
spoken of.

State Experiment Stations. — The organization of State Agri-
cultural Experiment Stations in 1888, under the Hatch Act, gave eco-
nomic entomology an additional impetus. At present at least one ex-
periment station is in operation in every state and territory; there being
stations in Alaska, Hawaii, Porto Rico and Guam. These stations,
often in connection with state agricultural colleges, maintain altogether
over fifty men who concern themselves more or less with entomology,
and have issued a great number of bulletins upon injurious insects.
These publications are extremely valuable as a means of disseminating
entomological information, and not a few of them are based upon the
investigations of their authors. Especially noteworthy as regards
originality, volume and general usefulness are the publications of Slinger-
land in Xew York, Smith in New Jersey, Webster in Ohio (formerly),
Garman in Kentucky, Hopkins in West Virginia, Gillette and Osborn
in Iowa and Gillette in Colorado. The reports that Lugger issued in
Minnesota, though compiled for the most part, contain much serviceable
information, presented in a popularly attractive manner.

While these workers have been conspicuously active in the publica-

INSECTS IX RELATION TO MAN

335

tion of their investigations, there are many other station entomologists
who devote themselves altogether to the practical application of en-
tomological knowledge, and whose work in this respect is highly impor-
tant, even though its influence does not extend beyond the limits of the
state.

The U. S. Entomological Commission. — This commission, founded
under a special Act of Congress in 1877 to investigate the Rocky Moun-
tain locust, consisted of Dr. C. V. Riley, Dr. A. S. Packard and Rev.
Cyrus Thomas, remained in existence until 1881, and published five
reports and seven bulletins, all of lasting value. The first two reports
form a most elaborate monograph of the Rocky Mountain locust; the
third report includes important work upon the army worm and the
canker worm; the fourth, written by Riley, is an admirable volume on
'the cotton worm and boll worm; and the fifth, by Packard, is a useful
treatise on forest and shade-tree insects.

The U. S. Department of Agriculture. — The first entomological
expert appointed under the general government was Townend Glover,
in 1854. He issued a large number of reports (1863-1877), which "are
storehouses of interesting and important facts which are too little used
by the working entomologists of to-day," as Howard says. Glover
prepared, moreover, a most elaborate series of illustrations of North
American insects, at an enormous expense of labor, out of all proportion,
however, to the practical value of his undertaking.

Glover was succeeded in 1878 by Riley, whose achievements have
aroused international admiration. He resigned in a year, after writing
a report, and was succeeded by Prof. Comstock, who held office for two
years, during which he wrote two important volumes (published re-
spectively in 1880 and 1881) dealing especially with cotton, orange and
scale insects. His work on scale insects laid the foundation for all our
subsequent investigation of the subject.

Riley, assuming the office of government entomologist, published up
to 1894, "12 annual reports, 31 bulletins, 2 special reports, 6 volumes of
the periodical bulletin Insect Life, and a large number of circulars of
information." During his vigorous and enterprising administration
economic entomology took an immense step in advance. The life
histories of injurious insects were studied with extreme care and many
valuable improvements in insecticides and insecticide machinery were
made. One of the notable successes of Dr. Riley and his co-workers,
which has attracted an exceptional amount of public attention, was the
practical extermination of the fluted scale {I eery a purchasi), which

336

ENTOMOLOGY

threatened to put an end to the cultivation of citrus trees in California.
This disaster was averted by the importation from Australia, in 1888, of
a native enemy of the scale, namely, the lady-bird beetle Novius (Vedalia)
cardinalis, which, in less than eighteen months after its introduction into
California, subjugated the noxious scale insect. The United States has
since sent Novius to South Africa, Egypt and Portugal with similar bene-
ficial results.

Based upon the foundation laid by Riley, the work of the Division
(now the Bureau) of Entomology has steadily progressed, under the
leadership of Dr. Leland 0. Howard. With a comprehensive and firm
grasp of his subject, alert to discover and develop new possibilities, ener-
getic and resourceful in management. Dr. Howard has brought the
government work in applied entomology to its present position of com-
manding importance. Admirably organized, the Bureau now requires
the services of more than six hundred people, and the total output of
the Division and the Bureau at this writing amounts to one hundred
and forty-eight bulletins and one hundred and seventy-one circulars.

The Department of Agriculture succeeded in starting a new and im-
portant industry in California— the culture of the Smyrna fig. The su-
perior flavor of this variety is due to the presence of ripe seeds, in other
words, to fertilization, and for this it is necessary for pollen of the wild
fig, or "caprifig," to be transferred to the flowers of the Smyrna fig.
Normally this pollination, or "caprification, ,? is dependent upon the ser-
vices of a minute chalcid, Blastophaga grossorum. which develops in the
gall-like flowers of the caprifig. The female insect, which in this excep-
tional instance is winged while the male is not, emerges from the gall
covered with pollen, enters the young flowers of the Smyrna fig to ovi-
posit, and incidentally pollenizes them.

After many discouraging attempts, Blastophaga, imported from
Algeria, has now been established in California, and. the new industry
is developing rapidly.

Canada. — The development of economic entomology in Canada
was due largely to the efforts of the late Dr. James Fletcher, of the Do-
minion Experimental Farms, Ottawa, whose annual reports and other
writings were of exceptional value. His work was furthered in every
way by the "eminent director of the experimental farms system. Dr.
William Saunders, himself a pioneer in economic entomology in Canada
and the author of one of the most valuable treatises upon the subject
that has ever been published in America. " Dr. Fletcher was succeeded

INSECTS IX RELATION TO MAN

337

by Dr. C. Gordon Hewitt, who is ably maintaining the standard of work
set by his predecessor.

Outside of this, the work in Canada centers around the Entomo-
logical Society of Ontario, whose excellent publications, sustained by the
government, are of great scientific and educational importance. In
addition to its annual reports, this society issues the Canadian Ento-
mologist, one of the leading serials of its kind, edited by its founder, the
Rev. C. J. S. Bethune, whose devoted services are appreciated by every
entomologist.

The Association of Official Economic Entomologists. — Organ-
ized in 1889 by a few energetic workers, this association has had a rapid
and healthy growth and now numbers among its members all the leading
economic entomologists of America and a large number of foreign work-
ers. The annual meetings of the association impart a vigorous stimulus
to the individual worker and tend to promote a well-balanced develop-
ment of the science of economic entomology.

Conclusion. — While working for the material welfare of the agri-
culturist, the economic entomologist discovers phenomena which are of
the highest value to the purely scientific mind. Indeed it is remarkable
to notice the extent to which the professedly practical entomologist is
animated — not to say dominated — by the same spirit which has led
many of the most profound thinkers that the world has ever produced
to devote their lives to the study of life itself.

23

LITERATURE

The literature on entomological subjects now numbers no less than 120,000 titles. The
works listed below have been selected chiefly on account of their general usefulness and
accessibility. Works incidentally containing important bibliographies of their special sub-
jects are designated each by an asterisk — *.

BIBLIOGRAPHICAL WORKS
Hagen, H. A. Bibliotheca Entomologica. 2 vols. Leipzig, 1862-1863. Covers the

entire literature of entomology up to 1862.
Englemann, W. Bibliotheca Historico-Naturalis. 1 vol. Leipzig, 1846. Literature,

1 700-1846.

Carus, J. V., and Englemann, W. Bibliotheca Zoologica. 2 vols. Leipzig, 186 1. Litera-
ture, 1 846-1 860.

Taschenberg, O. Bibliotheca Zoologica. 5 vols. Leipzig, 1887-1899. Vols. 2 and 3,

entomological literature, 1 861-1880.
The Zoological Record. London. Annually since vol. for 1864.
Catalogue of Scientific Papers, Royal Society. London. Since 1868.
Zoologischer Anzeiger. Leipzig. Fortnightly since 1878. Bibliographica Zoologica,

annual volumes since 1896.
Concilium Bibliographicum. Zurich. Card catalogue of current zoological literature

since 1896.

Archiv fur Naturgeschichte. Berlin. Annual summaries since 1835.

Journal of the Royal Microscopical Society. London. Summaries of the most impor-
tant works, beginning 1878.

Zoologischer Jahresbericht. Leipzig. Yearly summaries of literature since 1879.

Zoologisches Centralblatt. Leipzig. Reviews of more important literature since 1895.

Psyche. Cambridge, Mass. Records of recent American literature. Also earlier records,
beginning 1874.

Entomological News. Philadelphia, 1890 to date. Records of current literature.
Bibliography of the more important contributions to American Economic Entomology.

8 parts. Pts. 1-5 by S. Henshaw; pts. 6-8 by N. Banks. 13 18 pp. Washington,

1889-1905.

Catalogue of Scientific Serials, 1633-1876. S. H. Scudder. Cambridge, Mass. Harvard
University, 1879.

A Catalogue of Scientific and Technical Periodicals, 1665-1895. H. C. Bolton. Wash-
ington, Smithsonian Institution, 1897.

A List of Works on North American Entomology. X. Banks. Bull. U. S. Dept. Agric,
Div. Ent., no. 24 (n. s.), 95 pp. Washington, 1900.

GENERAL ENTOMOLOGY
Kirby, W., and Spence, W. 1822-26. An Introduction to Entomology. 4 vols. 36 -f-
2413 pp., 30 pis. London.

339

340

V. X TO M O LOG V

Burmeister, H. 1832-55. Handhuch der Entomologie. 2 vols. 28 + 1746 pp., 16 taf.

Trans, of Band 1 : 1836. \V. K. Shuckard. A Manual of Entomology. 12 + 654
pp., 32 pis. London.

Westwood, J. O. 1839 40. An Introduction to the Modern Classification of Insects.

2 vols. 23 + 620 pp., 133 figs. London.
Graber, V. 1877-79. Die Insekten. 2 vols. 8 + 1008 pp., 404 figs. Munchen.
Miall, L. C, and Denny, A. 1886. The Structure and Life-History of the Cockroach.

6 + 224 pp., 125 figs. London, Lovell Reeve & Co.; Leeds. R. Jackson.
Comstock, J. H. 1888. An Introduction to Entomology. 4 + 234 pp., 201 figs. Ithaca.

X. Y.

Kolbe,H. J. 1889-93. Einfiihrung in die Kenntnis der Insekten. 12 + 709 pp., 324 figs.
Berlin. F. Diimmler.*

Packard, A. S. 1889. Guide to the Study of Insects. Ed. 9. 12 + 715 pp., 668 figs.,

15 pis. New York. Henry Holt & Co.
Hyatt, A., and Arms, J. M. 1890. Insecta. 23 + 300 pp., 13 pis., 223 figs. Boston.

D. C. Heath & Co.*

Kirby, W. F. 1892. Elementary Text-Book of Entomology. Ed. 2. 8 + 281 pp., 87 pis.

London. Swan Sonnenschein & Co.
Comstock, J. H. and A. B. 1895. A Manual for the Study of Insects. 7 + 701 pp.,

797 figs., 6 pis. Ithaca, N. Y. Comstock Pub. Co.
Sharp, D. 1895, 1901. Insects. Cambr. Nat. Hist., vols. 5, 6. 12 + 1130 pp., 618 figs.

London and New York. Macmillan & Co.*
Comstock, J. H. 1897, 1901. Insect Life. 6 + 349 pp., 18 pis., 296 figs. New York.

D. Appleton & Co.

Packard, A. S. 1898. A Text-Book of Entomology. 17 + 729 pp., 654 figs. New York

and London. The Macmillan Co.*
Carpenter, G. H. 1899. Insects; their Structure and Life. 11 + 404 pp., 184 figs.

London. J. M. Dent & Co.*
Packard, A. S. 1899. Entomology for Beginners. Ed. 3. 16 + 367 pp., 273 figs. New

York. Henry Holt & Co.*
Howard, L. O. 1901. The Insect Book. 27 + 429 pp., 48 pis., 264 figs. New York.

Doubleday, Page & Co.
Hunter, S. J. 1902. Elementary Studies in Insect Life. 18 + 344 pp., 234 figs. Topeka.

Crane & Co.

Henneguy, L. F. 1904. Les Insectes. Morphologic Reproduction, Embryogenie. 18 +

804 pp., 622 figs., 4 pis. Paris. Masson et Cie.*
Kellogg, V. L. 1905. American Insects. 7 + 674 pp., 13 pis., 812 figs. New York.

Henry Holt & Co.

Berlese, A. 1909-13. Gli Insetti. Vol. 1, 1004 pp., 1292 figs., 10 pis. Vol. 2, 176 pp.,

182 figs, to date. Milan.
Sanderson, E. D., and Jackson, C. F. Elementary Entomology. 5 + 372 pp., 496 figs.

Boston and New York. Ginn & Co.

Kirby, W., and Spence, W. 1822-26. An Introduction^ Entomology. 4 vols. 36 +
2413 pp., 30 pis. London.

Burmeister, H. 1832. Handbuch der Entomologie. 2 vols. 28 + 1746 pp., 16 taf.

Berlin. Translation of Band 1 : 1836. \V. E. Shuckard. A Manual of Entomol-
ogy. 12 + 654 pp., 32 pis. London. Contains useful synopses of the older sys-
tems of classification.

PHYLOGENY AND CLASSIFICATION

LITERATURE

341

Westwood, J. O. 1839-40. An Introduction to the Modern Classification of Insects.

2 vols. 23 + 620 pp., 133 figs. London.
Miiller, F. 1864. Fur Darwin. Leipzig. Trans.: 1869. W. S. Dallas. Facts and

Figures in aid of Darwin. London.
Brauer, F. 1869. Betrachtungen iiber die Verwandlung der Insekten im Sinne der Des-

cendenz-Theorie. Verh. zool.-bot. Gesell. Wien, bd. 19, pp. 299-318; bd. 28 (1878),

1879, pp. 151-166.

Lubbock, J. 1873. On the Origin of Insects. Journ. Linn. Soc. Zool., vol. 11, pp. 422-425^
Packard, A. S. 1873. Our Common Insects. 225 pp., 268 figs. Boston. Estes &
Lauriat.

Lubbock, J. 1874. On the Origin and Metamorphoses of Insects. 16 + 108 pp., 63 figs.,

6 pis. London. Macmillan & Co.*
Mayer, P. 1876. Ueber Ontogenie und Phylogenie der Insekten. Jenais. Zeits. Naturw.,

bd. 10, pp. 125-221, taf. 6-6c.
Wood-Mason, J. 1879. Morphological Notes bearing on the Origin of Insects. Trans.

Ent. Soc. London, pp. 145-167, figs. 1-9.
Haase, E. 1881. Beitrag zur Phylogenie und Ontogenie der Chilopoden. Zeits. Ent.

Breslau, bd. 8, heft 2, pp. 93-115.
Lankester, E. R. 1881. Limulus an Arachnid. Quart. Journ. Micr. Sc., vol. 21 (n. s.),

pp. 504-548, 609-649, pis. 28, 29, figs. 1-20.
Packard, A. S. 1881. Scolopendrella and its Position in Nature. Amer. Nat., vol. 15,

15, pp. 698-704, fig. 1.

Kingsley, J. S. 1883. Is the Group Arthropoda a valid one? Amer. Nat., vol. 17, pp.
1034-1037.

Packard, A. S. 1883. The Systematic Position of the Orthoptera in relation to Other
Orders of Insects. Third Kept. U. S. Ent. Comm., pp. 286-304.

Brauer, F. 1885. Systematisch-zoologische Studien. Sitzb. Akad. Wiss., Wien, bd. 91,
pp. 237-413.*

Grassi, B. 1885. I progenitori degli Insetti e dei Miriapodi. — Morfologia delle Scolo-

pendrelle. Atti. Accad. Torino, t. 21, pp. 48-50.
Haase, E. 1886. Die Yorfahren der Insecten. Sitzb. Abh. Isis. Dresden, pp. 85-91.
Claus, C. 1887. On the Relations of the Groups of Arthropoda. Ann. Mag. Nat. Hist.

ser. 5, vol. 19, p. 396.

Kingsley, J. S. 1888. The Classification of the Myriapoda. Amer. Nat., vol. 22, pp.
1118-1121.

Haase, E. 1889. Die Abdominalanhange der Insekten mit Beriicksichtigung der Myrio-

poden. Morph. Jahrb., bd. 15, pp. 331-435, taf. 14, 15.
Fernald, H. T. 1890. The Relationships of Arthropods. Studies Biol. Lab. Johns

Hopk. Univ., vol. 4, pp. 431-513, pis. 48-50.
Hyatt, A., and Arms, J. M. 1890. Insecta. 23 + 300 pp., 13 pis., 223 figs. Boston.

D. C. Heath & Co.*

Cholodkowsky, N. 1892. On the Morphology and Phylogeny of Insects. Ann. Mag.

Nat. Hist., ser. 6, vol. 10, pp. 429-451.
Grobben, C. 1893. A Contribution to the Knowledge of the Genealogy and Classification

of the Crustacea. Ann. Mag. Nat. Hist., ser. 6, vol. 11, pp. 440-473. Trans, from

Sitzb. Akad. Wiss. Wien, math.-nat. CI., bd. 101, heft 2, pp. 237-274, taf. 1.
Hansen, H. J. 1893. A Contribution to the Morphology of the Limbs and Mouth-parts

of Crustaceans and Insects. Ann. Mag. Nat. Hist., ser. 6, vol. 12, pp. 417-434.

Trans, from Zool. Anz., jhg. 16, pp. 193-198, 201-212.
Pocock, R. I. 1893. On some Points in the Morphology of the Arachnida (s. s.) with

Notes on the Classification of the Group. Ann. Mag. Nat. Hist., ser. 6, vol. n,

pp. 1-19, pis. 1, 2.

/

342

ENTOMOLOGY

Pocock, R. I. 1893. On the Classification of the Tracheate Arthropoda. Zool. Anz , jhg.
16, pp. 271-275.

Bernard, H. M. 1894. The Systematic Position of the Trilobites. Quart. Journ. Geol.

Soc. London, vol. 50, pp. 411-434, figs. 1-17.
Kingsley, J. S. 1894. The Classification of the Arthropoda. Amer. Xat., vol. 28, pp.

1 18-135, 220-235.*

Kenyon, F. C. 1895. The Morphology and Classification of the Pauropoda, with Notes on '

the Morphology of the Diplopoda. Tufts Coll. Studies, no. 4, pp. 77-146, pis. 1-3.
Schmidt, P. 1895. Beitrage zur Kenntnis der niederen Myriapoden. Zeits. wiss. Zool.,

bd. 59- 436-510, taf. 26, 27.
Wagner, J. 1895. Contributions to the Phylogeny of the Arachnida. Ann. Mag. Nat.

Hist., ser. 6, vol. 15, pp. 285-315. Trans, from Jenais. Zeits. Xatunv., bd. 29,

pp. 123-156.

Miall, L. C. 1895. The Transformations of Insects. Nature, vol. 53, pp. 152-158.

Sedgwick, A. 1895. Peripatus. Camb. Xat. Hist., vol. 5, pp. 1-26, figs. 1-14.

Sinclair, F. G. 1895. Myriapoda. Camb. Nat. Hist., vol. 5, pp. 27-80, figs. 15-46.

Sharp, D. 1895, 1901. Insects. Camb. Nat. Hist., vols. 5, 6. 12 + 1130 pp., 618 figs.
London and New York. Macmillan & Co.*

Comstock, J. H. and A. B. 1895. A Manual for the Study of Insects. 7 + 701 pp., 797
figs., 6 pis. Ithaca, N. Y. Comstock Pub. Co.

Heymons, R. 1896. Zur Morphologie der Abdominalanhange bei den Insecten. Morph.
Jahrb., bd. 24, pp. 178-204, 1 taf.

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HEAD AXD APPENDAGES
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Breitenbach, W. 1877. Yorlaufige Mitteilung uber einige neue Untersuchungen an

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Breitenbach, W. 1879. Ueber Schmetterlingsriissel. Ent. Xachr., jhg. 5, pp. 237-243.
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Dimmock, G. 1881. The Anatomy of the Mouth Parts and of the Sucking Apparatus of
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Geise, O. 1883. Die Mundtheile der Rhynchoten. Archiv Xaturg., jhg. 49, bd. 1, pp.
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Kraepelin, K. 1883. Zur Anatomie und Physiologie des Riissels von Musca. Zeits. wiss.

Zool., bd. 39 pp., 683-719, taf. 40, 41.
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Wedde, H. 1885. Beitrage zur Kenntniss des Rhynchotenrussels. Archiv Xaturg. jhg.

51, bd. 1, pp. 113-143, taf. 6, 7.
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Breithaupt, P. F. 1886. Ueber die Anatomie und die Functionen der Bienenzunge.

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Kellogg, V. L. 1895. The Mouth Parts of the Lepidoptera. Amer. Xat., vol. 29, pp.

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Demoll, R. 1909. Die Mundteile der Vespen, etc., Zeits. wiss. Zool., bd. 92, pp. 187-209,
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Dietrich, W. 1909. Die Facettenaugen der Dipteren. Zeits. wiss. Zool., bd. 92, pp.

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THORAX AND APPENDAGES; LOCOMOTION
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Brauer, F. 1882. Ueber das Segment mediaire Latreille's. Sitzb. Akad. Wiss. Wein,

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Crampton, G. C. 1909. A Contribution to the Comparative Morphology of the Thoracic
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Haase, E. 1889. Die Abdominalanhange der Insekten mit Berucksichtigung der Myri-

opoden. Morph. Jahrb., bd. 15, pp. 331-435, taf. 14, 15.
Radoszkowski, O. 1889. Revision des armures copulatrices des males de la tribu des

Chrysides. Horae Soc. Ent. Ross., t. 23, pp. 3-40, pis. 1-6.
Beyer, O. W. 1890. Der Giftapparat von Formica rufa, ein reduziertes Organ. Jenais.

Zeits. Xaturw., bd. 25, pp. 26-112, taf. 3, 4.
Carlet, G. 1890. Memoire sur le venin et Taiguillon de Fabeille. Ann. Sc. nat. Zool., ser.

7, t. 9, pp. 1-17, pi. 1.
Packard, A. S. 1890. Notes on some points in the external structure and phylogeny of

Lepidopterous larvae. Proc. Bost. Soc. Nat. Hist., vol. 25, pp. 82-114, pis. 1, 2.
Sharp, D. 1890. On the structure of the terminal segment in some male Hemiptera.

Trans. Ent. Soc. London, pp. 399-427, pis. 12-14.
Wheeler, W. M. 1890. On the Appendages of the first abdominal Segment of embryo

Insects. Trans. Wis. Acad. Sc., vol. 8, pp. 87-140, pis. 1-3.*
Escherich, K. 1892. Die biologische Bedeutung der Genitalanhange der Insekten.

Verh. zool.-bot. Ges. Wien, bd. 42, pp. 225-240, taf. 4.
Graber, V. 1892. Ueber die morphologische Bedeutung der Abdominalanhange der

Insekten-Embryonen. Morph. Jahrb., bd. 17, pp. 467-482.
Escherich, K. 1894. Anatomische Studien iiber das mannliche Genital-system der Cole-

opteren. Zeits. wiss. Zool., bd. 57, pp. 620-641, taf. 26, 3 figs.
Janet, C. 1894. Sur la Morphologie du squelette des segments post-thoraciques chez les

Myrmicides. Note 5. Mem. Soc. acad. Oise, t. 15, pp. 591-611, figs. 1-5.
Perez, J. 1894. De Torgane copulateur male des Hymenopteres et de sa valeur taxo-

nomique. Ann. Soc. ent. France, t. 63, pp. 74-81, figs. 1-8.

LITERATURE

349

Verhoeff, C. 1894. Yergleichende Untersuchungen iiber die Abdominalsegmente der
weiblichen Hemiptera-Heteroptera und Homoptera. Verh. nat. Ver. Bonn, jhg.
50, pp. 307-374.

Heymons, R. 1895. Die Segmentirung des Insectenkdrpers. Anh. Abh. Preuss. Akad.

Wiss. Berlin, 39 pp., 1 taf.
Heymons, R. 1895. Die Embryonalentwickelung von Dermapteren und Orthopteren

unter besonderer Berticksichtigung der Keimblatterbildung. 136 pp., 12 taf., 33

figs. Jena.

Peytoureau, S. A. 1895. Contribution a l'etude de la morphologie de l'armure genitale

des Insectes. 248 pp., 22 pis., 43 figs. Paris.
Verhoeff, S. 1895. Beitrage zur vergleichenden Morphologie des Abdomens der Coccinel-

liden, etc. Archiv Xaturg., jhg. 61, bd. 1, pp. 1-80, taf. 1-6.
Verhoeff, C. 1895. Vergleichend-morphologische Untersuchungen iiber das Abdomen

der Endomychiden, Erotyliden und Languriiden (im alten Sinne) und iiber die

Muskulatur des Copulationsapparates von Triplex. Archiv Xaturg., jhg. 61, bd.

1, pp. 213-287, taf. 12, 13.
Verhoeff, C. 1895. Cerci und Styli der Tracheaten. Ent. Xachr., jhg. 21, pp. 166-168.
Heymons, R. 1896. Grundziige der Entwickelung und des Korperbaues von Odonaten

und I^phemeriden. Anh. Abh. Akad. Wiss. Berlin, pp. 66, 2 taf.
Heymons, R. 1896. Zur Morphologie des Abdominalanhange bei den Insekten. Morph.

Jahrb., bd. 24, pp. 178-204, taf. 1.
Verhoeff, C. 1896. Zur Morphologie der Segmentanhange bei Insecten und Myriopoden.

Zool. Anz., bd. 19, pp. 378-383, 385-388.
Goddard, M. F. 1897. On the Second Abdominal Segment in a few Libellulidae. Proc.

Amer. Phil. Soc, vol. 35, pp. 205-212, 2 pis.
Janet, C. 1897. Limites morphologiques des anneaux post-cephaliques et Musculature

des anneaux post-thoraciques chez la Myrmica rubra. Xote 16. 35 pp., 10 figs.

Lille.

Verhoeff, C. 1897. Bemerkungen iiber abdominale Kbrperanhange bei Insecten und

Myriopoden. Zool. Anz., bd. 20, pp. 293-300.
Janet, C. 1898. Aiguillon de la Myrmica rubra. Appareil de fermeture de la glande a

venin. Xote 18. 27 pp., 3 pis. Paris.
Zander, E. 1903. Beitrage zur Morphologie der mannlichen Geschlechtsanhange der

Lepidopteren. Zeits. wiss. Zool., bd. 74, pp. 557-615, taf. 29, figs. 1-15.*

INTEGUMENT

Dufour, L. 1824-26. Recherches anatomiques sur les Carabiques et sur plusieurs autres
Coleopteres. Ann. Sc. nat. Zool., t. 2-8, pis. Several papers.

Karsten, H. 1848. Harnorgane des Brachinus complanatus. Muller's Archiv Anat.
Phys., pp. 367-374, fig.

Leydig, F. 1855. Zum feineren Bau der Arthropoden. Muller's Archiv Anat. Phys.,
PP- 376-480, taf. 3.

Semper, C. 1857. Beobachtungen iiber die Bildung der Fliigel, Schuppen und Haare bei

den Lepidopteren. Zeits. wiss. Zool., bd. 8, pp. 326-339, taf. 15.
Sirodot, S. 1858. Recherches sur les secretions chez les Insectes. Ann. Sc. nat. Zool.,

ser. 4, t. 10, pp. 141-189, 251-334, 12 pis.
Claus, C. 1861. Ueber die Seitendriisen der Larve von Chrysomela populi. Zeits. wiss.

Zool., bd. 11, pp. 309-314, taf. 25.
Landois, H. 1864. Beobachtungen iiber das Blut der Insecten. Zeits. wiss. Zool., bd.

14, pp. 55-70, taf. 7-9.

35°

ENTOMOLOGY

Landois, H. 1871. Beitrage zur Entwicklungsgeschichte der Schmetterlingsfliigel in der

Raupe und Puppe. Zeits. wiss. Zool., bd. 21, pp. 305-316, taf. 23.
Candeze, E. 1874. Les moyens d'attaque et de defense chez les Insectes. Bull. Acad.

roy. Belgique, ser. 2, t. 38, pp. 787-816.
Chun, C. 1876. Ueber den Bau, die Entwickelung und physiologische Bedeutung der

Rektaldrusen bei den Insekten. Abh. Senckenb. naturf. Gesell., bd. 10, pp. 27-55,

4 taf. Separate, 1875, 31 pp., 4 taf. Frankfurt a. M.
MuTler, F. 1877. Ueber Haarpinsel, Filzflecke und ahnliche Gebilde auf den Flugeln

mannlicher Schmetterlinge. Jenais Zeits. Naturw., bd. 11, pp. 99-114.
Scudder, S. H. 1877. Antigeny or Sexual Dimorphism in Butterflies. Proc. Amer. Acad.

Arts Sc., vol. 12, pp. 150-158.
Edwards, W. H. 1878. On the Larvae of Lyc. pseudargiolus and attendant Ants. Can.

Ent., vol. 10, pp. 131-136, fig. 8.
Forel, A. 1878. Der Giftapparat und die Analdriisen der Ameisen. Zeits. wiss. Zool.,

bd. 30, supp., pp. 28-68, taf. 3, 4.
MuTler, F. 1878. Die Duftschuppen der Schmetterlinge. Ent. Xachr., jhg. 4, pp. 29-32.
Saunders, E. 1878. Remarks on the Hairs of some of our British Hymenoptera. Trans.

Ent. Soc. London, pp. 169-172, pi. 6.
Schneider, R. 1878. Die Schuppen aus den verschiedenen Fliigel- und Korperteilen der

Lepidopteren. Zeits. gesammt. Naturw., bd. 51, pp. 1-59.
Weismann, A. 1878. Ueber Duftschuppen. Zool. Anz., jhg. 1, pp. 98, 99.
Goossens, T. 1881. Des chenilles urticantes, etc. Ann. Soc. ent. France, t. r, pp. 231-

236.

Scudder, S. H. 1881. Butterflies; Their Structure, Changes and Life-Histories, with
Special Reference to American Forms. 9 + 322 pp., 201 figs. New York. Henry
Holt & Co.

Dimmock, G. 1882. On some Glands which open externally on Insects. Psyche, vol. 3,
PP- 387-401.*

Klemensiewicz, S. 1882. Zur naheren Kenntniss der Hautdriisen bei den Raupen und
bei Malachius. Verh. zool.-bot. Gesell. Wien, bd. 32, pp. 459-474, 2 taf.

Dimmock, G. 1883. The Scales of Coleoptera. Psyche, vol. 4, pp. 1-11, 23-27, 43-47,
63-71, figs. 1-11.

Osten-Sacken, C. R. 1884. An Essay on Comparative Chaetotaxy, or the Arrangement
of characteristic Bristles of Diptera. Trans. Ent. Soc. London, pp. 497-517.

Sirnmermacher, G. 1884. Untersuchungen liber Haftapparate an Tarsalgliedern von
Insekten. Zeits. wiss. Zool., bd. 40, pp. 481-556, taf. 25-27, 2 figs.

Dahl, F. 1885. Die Fussdrusen der Insekten. Archiv mikr. Anat., bd. 25, pp. 236-263,
taf. 12, 13.

Witlaczil, E. 1885. Die Anatomie der Psylliden. Zeits. wiss. Zool., bd. 42, pp. 569-638,
taf. 20-22.

Goossens, T. 1886. Des chenilles vesicantes. Ann. Soc. ent. France, ser. 6, t. 6, pp.

461-464.*

Minot, C. S. 1886. Zur Kenntniss der Insektenhaut. Archiv mikr. Anat., bd. 28, pp.

37-48, taf. 7.

Schaffer, C. 1889. Beitrage zur Histologic der Insekten. Zool. Jahrb., Abth. Anat. Ont.,

bd. 3, pp. 611-652, taf. 29, 30.
Fernald, H. T. 1890. Rectal Glands in Coleoptera. Amer. Nat., vol. 24, pp. 100, 101,

pis. 4, 5.

Packard, A. S. 1890. Notes on some points in the external structure and phylogeny of

lepidopterous larvae. Proc. Bost. Soc. Nat. Hist., vol. 25, pp. 82-114, pis. 1, 2.
Borgert, H. 1891. Die Hautdriisen der Tracheaten. 81 pp., taf. Jena.

LITERATURE

351

Thomas, M. B. 1893. The Androconia of Lepidoptera. Amer. Nat., vol. 27, pp. 1018-
1021, pis. 22, 23.

Cuenot, L. 1894. Le rejet de sang comme moyen de defense chez quelques Coleopteres.

Compt. rend. Acad. Sc., t. 118, pp. 875-877. '
Kellogg, V. L. 1894. The Taxonomic Value of the Scales of the Lepidoptera. Kansas

Univ. Quart., vol. 3, pp. 45-89, pis. 9, 10, figs. 1-17.
Packard, A. S. 1894. A Study of the Transformations and Anatomy of Lagoa crispata,

a Bombycine Moth. Proc. Amer. Phil. Soc, vol. 32, pp. 275-292, pis. 1-7.
Lutz, K. G. 1895. Das Bluten der Coccinelliden. Zool. Anz., jhg. 18, pp. 244-255, 1 fig.
Packard, A. S. 1895-96. The Eversible Repugnatorial Scent Glands of Insects. Journ.

X. Y. Ent. Soc, vol. 3, pp. 110-127, pi. 5; vol. 4, pp. 26-32.*
Spuler, A. 1895. Beitrag zur Kenntniss des feineren Baues und der Phylogenie der

Flugelbedeckung der Schmetterlinge. Zool. Jahrb., Abth. Anat. Ont., bd. 8, pp.

52o-543, taf. 36.

Mayer, A. G. 1896. The Development of the Wing Scales and their Pigment in Butterflies
and Moths. Bull. Mus. Comp. Zool., vol. 29, pp. 209-236, pis. 1-7.*

Bordas, L. 1897. Description anatomique et etude histologique des glandes a venin des
Insectes hymenopteres. 53 pp., 2 pis. Paris.

Cuenot, L. 1897. Sur la saignee reflexe et les moyens de defense de quelques Insectes.
Arch. Zool. exp., ser. 3, t. 4, pp. 655-680, 4 figs.

Hilton, W. A. 1902. The Body Sense Hairs of Lepidopterous Larvae. Amer. Nat., vol.

36, pp. 561-578, figs. 1-23.*
* Tower, W. L. 1902. Observations on the Structure of the Exuvial Glands and the For-
mation of the Exuvial Fluid in Insects. Zool. Anz., bd. 25, pp. 466-472, figs. 1-8.

Tower, W. L. 1903. The Development of the Colors and Color Patterns of Coleoptera,
with Observations upon the Development of Color in Other Orders of Insects. Univ.
Chicago, Decenn. Publ., vol. 10, 140 pp., 3 pis.

Plotnikow, W. 1904. Uber die Hautung und iiber einige Elemente der Haut bei den
Insekten. Zeits. wiss. Zool., bd. 76, pp. 333-366, taf. 21, 22, 2 figs.

Kapzov, S. 191 1. Untersuchungen iiber den feineren Bau der Cuticula bei Insekten.
Zeits. wiss. Zool., bd. 98, pp. 297-337, taf. 14-16, 3 figs.*

MUSCULAR SYSTEM
Lyonet, P. 1762. Traite anatomique de la Chenille qui ronge le Bois de Saule. Ed. 2.

22 -f- 616 pp., 18 pis. La Haye.
Straus-Durckheim, H. 1828. Considerations generates sur l'anatomie comparee des

animaux articules, etc. 434 pp., 10 pis. Paris.
Newport, G. 1839. Insecta. Todd's Cyclopaedia Anat. Phys., vol. 2, pp. 853-994, figs.

329-439.

Lubbock, J. 1859. On the Arrangement of the Cutaneous Muscles of the Larva of Py-
gaera bucephala. Trans. Linn. Soc. Zool., vol. 22, pp. 163-191, 2 pis.

Basch, S. 1865. Skelett und Muskeln des Kopfes von Termes. Zeits. wiss. Zool. bd. 15,
PP- 55-75, 1 taf.

Plateau, F. 1865, 1866. Sur la force musculaire des insectes. Bull. Acad. roy. Belgique,

ser. 2, t. 20, pp. 732-757; t. 22, pp. 283-308.
Merkel, F. 1872, 1873. Der quergestreifte Muskel. Archiv mikr. Anat., bd. 8, pp.

244-268, 2 taf.; bd. 9, pp. 293-307.
Lubbock, J. 1877. On some Points in the Anatomy of Ants. Month. Micr. Journ., vol.

18, pp. 121-1^2, pis. 189-192.
Lubbock, J. 1879. On the Anatomy of Ants. Trans. Linn. Soc. Zool., ser. 2, vol. 2, pp.

141-154, 2 pis.

352

i:\TOMO LOGY

Poletajeff, N. 1879. Du developpement des muscles d'ailes chez les Odonates. Hora
Soc. Ent. Ross., t. 16, pp. 10-37, 5 pis.

Von Lendenfeld, R. 1881. Der Plug der Libellen. Kin Beitrag zur Anatomie und Phy-
siologic der Flugorgane der Insccten. Sitzb. Akad. Wiss. Wien, bd.83, pp. 289-376,
taf. 1-7.

Luks, C. 1882. Ueber die Brustmuskulatur der Insekten. Jenais. Zeits. Naturw. bd.

16, pp. 529-552, taf. 22, 23.
Dahl, F. 1884. Beitrage zur Kenntnis des Baues und der Funktionen der Insektenbeine.

Archiv Xaturg., jhg. 50, bd. 1, pp. 146-193, taf. n-13.
Van Gehuchten, A. 1886. fitude sur la structure intime de la cellule musculaire striee.

La Cellule, t. 2, pp. 289-453, pis. 1-6.
Miall, L. C, and Denny, A. 1886. The Structure and Life-history of the Cockroach.

London and Leeds.* (See pp. 71-84.)
Kolliker, A. 1888. Zur Kenntnis der quergestreiften Muskelfasern. Zeits. wiss. Zool.,

bd. 47, pp. 689-710, taf. 44, 45.
Butschli, O., und Schewiakoff, W. 1891. Ueber deii feineren Bau der quergestreiften

Muskeln von Arthropoden. Biol. Centralb., bd. 11, pp. 33-39 figs. 1-7.
Rollet, A. 1891. Ueber die Streifen N. (Nebenscheiben); das Sarkoplasma und Contrak-

tion der quergestreiften Muskelfasern. Archiv mikr. Anat., bd. 37, pp. 654-684,

taf. 37.

Janet, C. 1895. Etudes sur les Fourmis les Guepes et les Abeilles. Note 12. Structure
des Membranes articulaires des Tendons et des Muscles (Myrmica, Camponotus,
Vespa, Apis). 26 pp., 11 figs. Limoges.

Janet, C. 1895. Sur les Muscles des Fourmis, des Guepes et des Abeilles. Compt. rend.
Acad. Sc., t. 121, pp. 610-613, 1 fig.

NERVOUS SYSTEM

Newport, G. 1832, 1834. On the Nervous System of the Sphinx Ligustri Linn., and on the

changes which it undergoes during a part of the Metamorphoses of the Insect.

Phil. Trans. Roy. Soc. London, vol. 122, pp. 383-398, 2 pis.* Part II. Phil.

Trans. Roy. Soc. London, vol. 124, pp. 389-423, 5 pis.
Blanchard, E. 1846. Recherches anatomiques et zoologiques sur le systeme nerveux des

animaux sans vertebres. Du systeme nerveux des insectes. Ann. Sc. nat. Zool.,

ser. 3, t. 5, pp. 273-379, 8 pis.
Leydig, F. 1857. Lehrbuch der Histologic des Menschen und der Thiere. 12 + 551 pp.,

figs. Frankfurt.

Leydig, F. 1864. Vom Bau des Tierischen Korpers. Tubingen.

Brandt, E. 1876. Recherches anatomiques et morphologiques sur le systeme nerveux des

Insectes Hymenopteres. Compt. rend. Acad. Sc., t. 83, pp. 613-616.
Dietl, M. J. 1876. Die Organisation des Arthropodengehirns. Zeits. wiss. Zool. bd. 27,

pp. 488-517, taf. 36-38.
Flogel, J. H. L. 1878. Ueber den einheitlichen Bau des GehirnS in den verschiedenen

Insecten-Ordnungen. Zeits. wiss. Zool., bd. 30, Suppl., pp. 556-592, taf. 23, 24.
Brandt, E. 1879. [Many articles on the nervous system.] Florae Soc. Ent. Ross., bd.

14-15, taf.*

Newton, E. T. 1879. On the Brain of the Cockroach, Blatta orientalis. Quart. Journ.

Micr. Soc, n. s., vol. 19, pp. 340-356, pis. 15, 16.
Michels, H. 1880. Beschreibung des Nervensystems von Oryctes nasicornis im Larven-,

Puppen- und Kaferzustande. Zeits. wiss. Zool., bd. 34, pp. 641-702, taf. 33-36.
Packard, A. S. 1880. The Brain of the Locust. Second Rept. U. S. Ent. Comm., pp.

223-242, pis. 9-15, fig. 9. Washington.*

LITERATURE

353

Cattie, J. T. 1881. Beitrage zur Kenntnis der Chorda supra-spinalis der Lepidoptera und

des cerrtralen, peripherischen und sympathischen Nervensystems der Raupen.

Zeits. wiss. Zool., bd. 35, pp. 304-320, taf. 16.
Koestler, M. 1883. Ueber das Eingeweidenervensystem von Periplaneta orientalis.

Zeits. wiss. Zool., bd. 39, pp. 572-595. taf. 34.
Viallanes, H. 1884-87. Etudes histologiques et organologiques sur les centres nerveux et

les organes des sens des animaux articules. Mem. 1-5. Ann. Sc. nat. Zool., ser. 6,

t. 17-19; ser. 7, t. 2, 4; 22 pis.
Leydig, F. 1885. Zelle und Gewebe. Xeue Beitrage zur Histologic des Tierkorpers.

219 pp., 6 taf. Bonn.

Viallanes, H. 1887. Sur la morphologie comparee du cerveau des Insectes et des Crustaces.

Compt. rend. Acad. Sc., t. 104, pp. 444-447.
Binet, A. 1894. Contribution a Tetude du system nerveux sous-intestinal des insectes.

Journ. Anat. Phys., t. 30. pp. 449-580, pis. 12-15, 23 nSs-
Pawlovi, M. I. 1895. On the Structure of the Blood- Vessels and Sympathetic Xervous

System of Insects, particularly Orthoptera. Works Lab. Zool. Cab. Imp. Univ.

Warsaw, pp. 96 + 22, tab. 1-6. In Russian.
Holmgren, E. 1896. Zur Kenntnis des Hauptnervensystems der Arthropoden. Anat.

Anz., bd. 12, pp. 449-457, 7 figs.
Kenyon, F. C. 1896. The Brain of the Bee. Journ. Comp. Xeurol.. vol. 6, pp. 133-210,

pis. 14-22.

Kenyon, F. C. 1896. The meaning and structure of the so-called ''mushroom bodies"
of the hexapod brain. Amer. Nat., vol. 30, pp. 643-650, 1 fig.

Kenyon, F. C. 1897. The optic lobes of the bee's brain in the light of recent neurological
methods. Amer. Nat., vol. 31, pp. 369-376, pi. 9.

SEXSE ORGAXS; SOUXDS

Miiller, J. 1826. Zur vergleichenden Physiologie des Gesichtsinnes der Menschen und der
Tiere. 462 pp., 8 taf. Leipzig.

Von Siebold, C. T. E. 1844. Ueber das Stimm- und Gehor-Organ der Orthopteren.
Archiv Xaturg. jhg. 10, pp. 52-81, fig.

Gottsche, CM. 1852. Beitrag zur Anatomic und Physiologie des Auges der Krebse und
Fliegen. Muller's Archiv Anat. Phys.. pp. 483-492.

Claparede, E. 1859. Zur Morphologie der zusammengesetzten Augen bei den Arthro-
poden. Zeits. wiss. Zool., bd. 10, pp. 191-214. 3 taf.

Hensen, V. 1866. Ueber das Gehororgan von Locusta. Zeits. wiss. Zool., bd. 16, pp.
190-207, 1 taf.

Landois, H. 1868. Das Gehororgan des Hirschkafers. Archiv mikr. Anat., bd. 4,
pp. 88-95.

Schultze, M. 1868. Untersuchungen liber die zusammengesetzten Augen der Krebse und

Insekten. 8 + 32 pp., 12 taf. Bonn.
Scudder, S. H. 1868. The Songs of the Grasshoppers. Amer. Nat., vol. 2, pp. 1 13-120,

5 rigs.

Scudder, S. H. 1868. Xotes on the Stridulation of Grasshoppers. Proc. Bost. Soc.

Xat. Hist., vol. 11, pp. 306-313.
Graber, V. 1872. Bemerkungen iiber die Gehor- und Stimmorgane der Heuschrecken und

Cicaden. Sitzb. Akad. Wiss. Wien, math.- naturw. CI., bd. 66, pp. 205-213, 2 figs.
Paasch, A. 1873. Yon den Sinnesorganen der Insekten im Allgemeinen von Gehor- und

Geruchsorganen im Besondern. Archiv Xaturg., jhg. 39, bd. 1, pp. 248-275.
Forel, A. 1874. Les fourmis de la Suisse. Xeue Denks. allg. Schweiz. Gesell. Naturw.,

bd. 26, 480 pp., 2 taf. Separate, 1874, 4 -f- 457 pp., 2 taf. Geneve.

24

354

ENTOMOLOGY

Mayer, A. M. 1874. Experiments on the supposed Auditory Apparatus of the Mosquito.

Amer. Nat., vol. 8, pp. 577-592, fig. 92.
Ranke, J. 1875. Beitrage zu der Lehre von den Uebergangs-Sinnesorganen. Das Gehor-

organ der Acridier und das Sehorgan der Hirudineen. Zeits. wiss. Zool., bid. 25,

pp. 143-164, taf. 10.

Schmidt, O. 1875. Die Gehororgane der Heuschrecken. Archiv mikr. Anat., bd. 11,

pp. 195-215, taf. 10-12.
Graber, V. 1876. Die tympanalen Sinnesapparate der Orthopteren. Denks. Akad.

Wiss. Wien, bd. 36, pp. 1-140, 10 taf.
Graber, V. 1876. Die abdominalen Tympanalorgane der Cicaden und Gryllodeen.

Denks. Akad. Wiss. Wien, bd. 36, pp. 273-296, 2 taf.
Mayer, P. 1877. Der Tonapparat der Cikaden. Zeits. wiss. Zool., bd. 28, pp. 79-92,

3 ngs-

Forel, A. 1878. Beitrag zur Kenntniss der Sinnesempfindungen der Insekten. Mitth.

Munch, ent. Vereins, jhg. 2, pp. 1-2 1.
Lowne, B. T. 1878. On the Modifications of the Simple and Compound Eyes of Insects.

Phil. Trans. Roy. Soc. London, vol. 169, pp. 577-602, pis. 52-54.
Graber, V. 1879. Ueber neue otocystenartige Sinnesorgane der Insekten. Archiv mikr.

Anat., bd. 16, pp. 35-37, 2 taf.
Grenadier, H. 1879. Untersuchungen iiber das Sehorgan der Arthropoden, insbesondere

der Spinnen. Insekten und Crustaceen. 8 + 188 pp., n taf. Gottingen.
Hauser, G. 1880. Physiologische und histiologische Untersuchungen iiber das Geruchs-

organ der Insekten. Zeits. wiss. Zool., bd. 34, pp. 367-403, taf. 17-19.
Graber, V. 1882. Die chordotonalen Sinnesorgane und das Gehor der Insecten. Archiv

mikr. Anat., bd. 20, pp. 506-640, taf. 30-35, 6 figs.; bd. 21, pp. 65-145, 4 figs.*
Lubbock, J. 1882. Ants. Bees and Wasps. 19 + 448 pp., 5 pis., 31 figs. London.

1884, 1901, Xew York. D. Appleton & Co.
Graber, V. 1883. Fundamentalversuche iiber die Helligkeits- und Farbenempfindlichkeit

augenloser und geblendeter Tiere. Sitzb. Akad. Wiss. Wien, bd. 87, pp. 201-236.
Carriere, J. 1884. On the Eyes of some Invertebrata. Quart. Journ. Micr. Sc., vol. 24

(n. s.), pp. 673-681, pi. 45.
Graber, V. 1884. Grundlinien zur Erforschung des Helligkeits und Farbensinnes der

Tiere. 8 + 322 pp. Prag und Leipzig.
Lee, A. B. 1884. Bemerkungen iiber den feineren Bau der Chordotonal-Organe. Archiv

mikr. Anat., bd. 23, pp. 133-140, taf. 7b.
Lowne, B. T. 1884. On the Compound Yision and the Morphology of the Eye in Insects.

Trans. Linn. Soc. Zool., vol. 2, pp. 389-420, pis. 40-43.
Carriere, J. 1885. Die Sehorgane der Thiere, vergleichend anatomisch dargestellt. 6 +

205 pp., 1 taf., 147 figs. Miinchen und Leipzig. R. Oldenbourg.
Hickson, S. J. 1885. The Eye and Optic Tract of Insects. Quart. Journ. Micr. Sc., vol.

25, pp. 215-251, pis. 15-17.
Plateau, F. 1885. Experiences sur le role des palpes chez les Arthropodes maxilles. Palpes

des Insectes broyeurs. Bull. Soc. zool. France, t. 10, pp. 67-90.
Plateau, F. 1885-88. Recherches experimentales sur la vision chez les Insectes. Bull.

Acad. roy. Belgique, ser. 3, t. 10, 14, 15, 16. Mem. Acad. roy. Belgique, t. 43, pp.

1-9 1.

Will, F. 1885. Das Geschmacksorgan der Insekten. Zeits. wiss. Zool., bd. 42, pp. 674-
707, taf. 27.

Forel, A. 1886-87. Experiences et remarques critiques sur les sensations des Insectes.

Rec. zool. Suisse, t. 4, pp. 1-50, 145-240, pi. 1.
Graber, V. 1887. Xeue Yersuche iiber die Funktion der Insektenfiihler. Biol. Centralb.,

bd. 7, pp. 13-19.

LITERATURE

355

Mark, E. L. 1887. Simple Eyes in Arthropods. Bull. Mus. Comp. Zool., vol. 13, pp. 49-
105, pis. 1-5.

Patten, W. 1887. Eyes of Molluscs and Arthropods. Journ. Morph., vol. 1, pp. 67-92,
pl-3-

Will, F. 1887. A. Forel. Sur les Sensations des Insectes. Ent. Xachr., jhg. 13, pp. 127-
233-

Patten, W. 1887, 1888. Studies on the Eyes of Arthropods. I. Development of the
Eyes of Vespa, with Observations on the Ocelli of some Insects. Journ. Morph.,
vol. i, pp. 193-226, 1 pi. II. Eyes of Acilius. Journ. Morph., vol. 2, pp. 97-190,
pis. 7-13.

Lubbock, J. 1888, 1902. On the Senses, Instincts and Intelligence of Animals, with
Special Reference to Insects. 29 + 292 pp., 118 figs. New York. D. Appleton &
Co.

Vom Rath, O. 1888. Ueber die Hautsinnesorgane der Insekten. Zeits. wiss. Zool., bd.

46, pp. 413-454, taf. 30, 31.
Ruland, F. 1888. Beitrage zur Kenntnis der antennalen Sinnesorgane der Insekten.

Zeits. wiss. Zool., bd. 46, pp. 602-628, taf. 37.
Lowne, B. T. 1889. On the Structure of the Retina of the Blowfly (Calliphora erythro-

cephala). Journ. Linn. Soc. Zool., vol. 20, pp. 406-417, pi. 27.
Packard, A. S. 1889. Notes on the Epipharynx, and the Epipharyngeal Organs of Taste

in Mandibulate Insects. Psyche, vol. 5, pp. 193-199, 222-228.
Pankrath, O. 1890. Das Auge der Raupen und Phryganidenlarven. Zeits. wiss. Zool.,

bd. 49, pp. 690-708, taf. 34, 35.
Stefanowska, M. 1890. La disposition histologique du pigment dans les yeux des Arthro-

podes sous l'influence de la lumiere directe et de l'obscurite complete. Rec. zool.

suisse, t. 5, pp. 151-200, pis. 8, 9.
Watase, S. 1890. On the Morphology of the Compound Eyes of Arthropods. Studies

Biol. Lab. Johns Hopk. Univ., vol. 4, pp. 287-334, pis. 29-35.
Weinland, E. 1890. Ueber die Schwinger (Halteren) der Dipteren. Zeits. wiss. Zool.,

bd. 51, pp. 55-166, taf. 7-1 1.
Exner, S. 1891. Die Physiologie der fazettierten Augen von Krebsen und Insekten.

8 + 206 pp., 8 taf., 23 figs. Leipzig und Wien.
Von Adelung, N. 1892. Beitrage zur Kenntnis des tibialen Gehorapparates der Locustiden.

Zeits. wiss. Zool., bd. 54, pp. 316-349, taf. 14, 15.
Nagel, W. 1892. Die niederen Sinne der Insekten. 68 pp., 19 figs. Tubingen.
Child, C. M. 1894. Ein bisher wenig beachtetes antennales Sinnesorgan der Insekten,

mit besonderer Beriicksichtigung der Culiciden und Chironomiden. Zeits. wiss.

Zool., bd. 58, pp. 475-528, taf. 30, 31.
Mallock, A. 1894. Insect Sight and the Defining Power of Composite Eyes. Proc. Roy.

Soc. London, vol. 55, pp. 85-90, figs. 1-3.
Vom Rath, O. 1896. Zur Kenntnis der Hautsinnesorgane und des sensiblen Nerven-

systems der Arthropoden. Zeits. wiss. Zool., bd. 61, pp. 499-539, taf. 23, 24.
Redikorzew, W. 1900. Untersuchungen iiber den Bau der Ocellen der Insekten. Zeits.

wiss. Zool., bd. 68, pp. 581-624, taf. 39, 40, figs. 1-7.
Reuter, E. 1896. Ueber die Palpen der Rhopaloceren, etc. Acta Soc. Sc. Fenn., t. 22,

pp. 16 4- 578, 6 tab.

Hesse, R. 1901. Untersuchungen iiber die Organe der Lichtempfindung bei niederen

Thieren. VII. Von den Arthropoden- Augen. Zeits. wiss. Zool., bd. 70, pp. 347-

473, taf. 16-21, figs. 1, 2.
Schenk, O. 1903. Die antennalen Hautsinnesorgane einiger Lepidopteren und Hymen-

opteren mit besonderer Beriicksichtigung der sexuellen Unterschiede. Zool. Jahrb.,

Abth. Anat. Ont., bd. 17, pp. 573-618, taf. 21, 22, 4 figs.*

356 ENTOMOLOGY

Shull, A. F. 1907. The Stridulation of the Snowy Tree-cricket ((Ecanthus niveus). Can.

Ent., vol. 39, pp. 213-225. figs. 14, 15.*
Link, E. 1909. Ueber die Stirnaugen der Xeuropteren und Lepidopteren. Zool. Jahrb.,

Abt. Anat. Ont., bd. 27, pp. 213-242, taf. 15-17. 5 rigs.*
Link, E. 1909. Ueber die Stirnaugen der hemimetabolen Insecten. Zool. Jahrb., Abt.

Anat. Ont.. bd. 27, pp. 281-376, taf. 21-24, 14 figs.*
Lovell, J. H. 1910, 1912. The Color Sense of the Honey Bee. Amer. Xat., vol. 44, pp.

673-692; vol. 46, pp. 83-107.
Turner, C. H. 1910. Experiments on Color-vision of the Honey-bee. Biol. Bull., vol. 19,

pp. 257-279, 3 figs.

Allard, H. A. 1911. Studying the Stridulations of Orthoptera. Proc. Ent. Soc. Wash.,
vol. 13, pp. 141-148.

Schon, A. 191 1 . Bau und Entwicklung des tibialen Chordotonalorgans bei der Honigbiene
und bei Ameisen. Zool. Jahrb., Abg. Anat. Ont., bd. 31, pp. 439-472, taf. 17-19,
9 ngs-*

Demoll, R., and Scheuring, L. 1912. Die Bedeutung der Ocellen der Insecten. Zool.

Jahrb., Abt. Allg. Zool. Phys., bd. 31, pp. 519-628, 23 figs.*
Gunther, K. 1912. Die Sehorgane der Larve und Imago von Dytiscus marginalis. Zeits.

\viss. Zool., bd. 100, pp. 60-115. 36 figs.*
Caesar, C. J. 1913. Die Stirnaugen der Ameisen. Zool. Jahrb.. Abt. Anat. Ont., bd. 35,

pp. 161-240, taf. 7-10, 29 figs.*

DIGESTIVE SYSTEM
Dufour, L. 1824-60. [Many important papers.] Ann. Sc. nat. Zool.
Basch, S. 1858. Untersuchungen iiber das chylopoetische und uropoetische System der

Blatta orientalis. Sitzb. Akad. Wiss. Wien, math.-naturw. CI., bd. 33, pp. 234-260,

5 taf.

Sirodot, S. 1858. Recherches sur les secretions chez les Insectes. Ann. Sc. nat. Zool.,

ser. 4. t. 10, pp. 141-189. 251-334. 12 pis.
Leydig, F. 1859. Zur Anatomie der Insecten. Miiller's Archiv Anat. Phys., pp. 33-89,

149-183. 3 taf.

Fabre, J. L. 1862. Etude sur le role du tissu adipeux dans la secretion urinaire chez les
Insectes. Ann. Sc. nat. Zool., ser. 4. t. 19. pp. 351-382.

Plateau, F. 1874. Recherches sur les phenomenes de la digestion chez les Insectes. Mem.
Acad. roy. Belgique. t. 41. 124 pp.. 3 pis.

De^Bellesme, J. 1876. Physiologie comparee. Recherches experimentales sur la diges-
tion des insectes et en particulier de la blatte. 7 + 96 pp.. 3 pis. Paris.

Helm/F. E. 1876. Ueber die Spinndriisen der Lepidopteren. Zeits. wiss. Zool., bd. 26,
pp. 434-469, taf. 27, 28.

Plateau, F. 1877. Xote additionelle au Memoire sur les phenomenes de la digestion chez
les Insectes. Bull. Acad. roy. Belgique, ser. 2. t. 44. pp. 710-733.

Wilde, K. F. 1877. L'ntersuchungen iiber den Kaumagen der Orthopteren. Archiv
Xaturg., jhg. 43, bd. 1. pp. 135-172. 3 taf.

De Bellesme, J. 1878. Travaux originaux de Physiologie comparee. I. Insectes. Diges-
tion, Metamorphoses. 252 pp., 5 pis. Paris.

Schindler, E. 1878. Beitrage zur Kenntniss der Malpighi'schen Gefasse der Insecten.
Zeits. wiss. Zool., bd. 30, pp. 587-660. taf. 38-40.

Krukenberg, C. F. W. 1880. Ycrsuche zur vergleichenden Physiologie der Yerdauung
und vergleichende physiologische Beitrage zur Kenntnis der Yerdauungsvorgange.
Unters. phys. Inst. Univ. Heidelberg.

LITERATURE

357

Frenzel, J. 1882. Ueber Bau und Thatigkeit des Yerdauungskanals der Larve des Tene-
brio molitor mit Beriicksichtigung anderer Arthropoden. Berl. ent. Zeits., bd. 26,
pp. 267-316, taf. 5.*

Leydig, F. 1883. Untersuchungen zur Anatomie und Histologic der Thiere. 174 pp.,
8 taf. Bonn.

Metschnikoff , E. 1883. Untersuchungen iiber die intrazellulare Yerdauung bei wirbel-
losen Tieren. Arb. zool. Inst. Wien, bd. 5, pp. 141-168, 2 taf.

Schiemenz, P. 1883. Ueber das Herkommen des Futtersaftes und die Speicheldriisen
der Biene nebst einen Anhange iiber das Reichorgan. Zeits. wiss. Zool., bd. 38,
PP- 7i-i35, taf. 5-7.

Locy, W. A. 1884. Anatomy and Physiology of the family Xepidae. Amer. Xat., vol. 18,

pp. 250-255, 353-307, Pis- 9-12.
Witlaczil, E. 1885. Zur Morphologie und Anatomie der Cocciden. Zeits. wiss. Zool.,

bd. 43? PP- 149-174, taf. 5.
Frenzel, J. 1886. Einiges iiber den Mitteldarm der Insekten, sowie iiber Epithelregenera-

tion. Archiv mikr. Anat., bd. 26, pp. 229-306, taf. 7-9.
Kniippel, A. 1886. Ueber Speicheldriisen von Insecten. Archiv Xaturg., jhg. 52, bd. 1,

pp. 269-303, taf. 13, 14.
Cholodkovsky, N. 1887. Sur la morphologie de l'appareil urinaire des Lepidopteres.

Archiv. Biol., t. 6, pp. 497-514, pi. 17.
Faussek, V. 1887. Beitrage zur Histologic des Darmkanals der Insekten. Zeits. wiss.

Zool., bd. 45, pp. 694-712, taf. 36.
Kowalevsky, A. 1887. Beitrage zur Kenntnis der nachembryonalen Entwicklung der

Musciden. Zeits. wiss. Zool., bd. 45, pp. 542-594, taf. 26-30.
Schneider, A. 1887. Ueber den Darmcanal der Arthropoden. Zool. Beitr. von A.

Schneider, bd. 2, pp. 82-96, taf. 8-10.
Emery, C. 1888. Ueber den sogenannten Kaumagen einiger Ameisen. Zeits. wiss. Zool.,

bd. 46, pp. 378-412, taf. 27-29.
Macloskie, G. 1888. The Poison Apparatus of the Mosquito. Amer. Xat., vol. 22,

pp. 884-888, 2 figs.

Blanc, L. 1889. Etude sur la secretion de la soie et sur la structure du brin et de la bave

dans le Bombyx mori. 56 pp., 4 pis. Lyon.
Kowalevsky, A. 1889. Ein Beitrag zur Kenntnis der Exkretionsorgane. Biol. Centralb.,

bd. 9, pp. 33-47, 65-76, 127-128.
Van Gehuchten, A. 1890. Recherches histologiques sur l'appareil digestif de la larve de

la Ptychoptera contaminata. I Part. Etude du revetement epithelial et recherches

sur la secretion. La Cellule, t. 6, pp. 183-291, pis. 1-6.
Gilson, G. 1890, 1893. Recherches sur les cellules secretantes. La soie et les appareils

sericigenes. I. Lepidopteres; II. Trichopteres. La Cellule, t. 6, pp. 1 15-182, pis.

1-3; t. 10, pp. 37-63, pl- 4-
Blanc, L. 1891. La tete du Bombyx mori a. l'etat larvaire, anatomie et physiologic Trav.

Lab. Etud. Soie, 1889-1890, 180 pp., 95 figs. Lyon.
Wheeler, W. M. 1893. The primitive number of Malpighian vessels in Insects. Psyche,

vol. 6, pp. 457-46o, 485-486, 497-498, 509-510, 539-541, 545-547, 561-564-
Bordas, L. 1895. Appareil glandulaire des Hymenopteres. (Glandes salivaires, tube

digestif, tubes de Malpighi et glandes venimeuses.) 362 pp., n pis. Paris.
Cuenot, L. 1895. Etudes physiologiques sur les Orthopteres. Arch. Biol., t. 14, pp.

293-341, pis. 12, 13.

Bordas, L. 1897. L'appareil digestif des Orthopteres. Ann. Sc. nat. Zool., ser. 8, t. 5, pp.
1-208, pis. 1-12.

Needham, J. G. 1897. The digestive epithelium of dragon fly nymphs. Zool. Bull., vol.
1, pp. 103-113, figs. 1-10.

358

KNTOMOLOGY

CIRCULATORY SYSTEM

Newport, G. 1839. Insecta. Todd's Cyclopaedia Anat. Phys., vol. 2, pp. 853-994, figs.
329-439.

Newport, G. 1845. On the Structure and Development of the Blood. Ann. Mag. Xat.

Hist., vol. 15, pp. 281-284.
Verloren, M. C. 1847. [Memoire sur la circulation dans les insectes.] Mem. Acad. roy.

Belgique, t. 19, 93 pp., 7 pis.
Blanchard, E. 1848. De la circulation dans les insectes. Ann. Sc. nat. Zool., ser. 3, t. 9,

PP- 359-398, 5 pis.

Leydig, F. 1851. Anatomisches und Histologisches liber die Larve von Corethra plumi-

cornis. Zeits. wiss. Zool., bd. 3, pp. 435-451, taf. 16.
Scheiber, S. H. i860. Yergleichende Anatomie und Physiologie der QEstriden-Larven.

Sitzb. Akad. Wiss. Wien, math.-naturw. CI., bd. 41, pp. 409-496, 2 taf.
Landois, H. 1864. Beobachtungen liber das Blut der Insekten. Zeits. wiss. Zool., bd.

14, PP- 55-7o, 3 taf.

Graber, V. 1871. Ueber die Blutkorperchen der Insekten. Sitzb. Akad. Wiss. Wien,

math.-naturw. CI., bd. 64, pp. 9-44.
Moseley, H. N. 1871. On the circulation in the wings of Blatta orientalis and other

insects, and on a new method of injecting the vessels of insects. Quart. Jo urn.

Micr. Sc., vol. 11 (n. s.), pp. 389-395.. 1 pi-
Graber, V. 1873. Ueber den propulsatorischen Apparat der Insekten. Archiv mikr.

Anat., bd. 9, pp. 129-196, 3 taf.
Graber, V. 1873. Ueber die Blutkorperchen der Insekten. Sitzb. Akad. Wiss. Wien,

math,-naturw. CI., bd. 64 (1871), pp. 9-44.
Graber, V. 1876. Ueber den pulsierenden Bauchsinus der Insekten. Archiv mikr. Anat.,

bd. 12, pp. 575-582. 1 taf.
Dogiel, J. 1877. Anatomie und Physiologie des Herzens der Larve von Corethra plumi-

cornis. Mem. Acad. St. Petersburg, ser. 7, t. 24, 37 pp., 2 pis. Separate, Leipzig.

Yoss.

Jaworovski, A. 1879. Ueber die Entwicklung des Riickengefasses und speziell der Musku-

latur bei Chironomus und einigen anderen Insekten. Sitzb. Akad. Wiss. Wien,

math.-naturw. CI., bd. 80, pp. 238-258.
Plateau, F. 1879. Communication preliminaire sur les mouvements et Tinnervation de

Torgane central de la circulation chez les animaux articules. Bull. Acad. roy. Bel-
gique, ser. 2, t. 46, pp. 203-212.
Zimmermann, O. 1880. Ueber eine eigenthlimliche Bildung des Riickengefasses bei

einigen Ephemeridenlarven. Zeits. wiss. Zool., bd. 34, pp. 404-406, figs. 1-4.
Burgess, E. 1881. Note on the aorta m lepidopterous insects. Proc. Bost. Soc. Nat.

Hist., vol. 21, pp. 153-156, figs. 1-5.
Vayssiere, A. 1882. Recherches sur l'organisation des larves des Ephemerines. Ann. Sc.

nat. Zool., ser. 6, t. 13, pp. 1-137, pis. 1-11.
Viallanes, H. 1882. Recherches sur Thistologie des Insectes, et sur les phenomenes histo-

logiques qui accompagnent le developpement post-embryonnaire de ces animaux.

Ann. Sc. nat. Zool., ser, 6, t. 14, pp. 1-348, 4 pis. Bibl. Ecole, bd. 26, 348 pp.,

18 pis.

Creutzburg, N. 1885. Ueber den Kreislauf der Ephemerenlarven. Zool. Anz., jhg. 8,
pp. 246-248.

Poletajewa, O. 1886. Du coeur des insectes. Zool. Anz., jhg. 9. pp. 13-15.
Von Wielowiejski, H. R. 1886. Ueber das Blutgewebe der Insekten. Zeits. wiss. Zool.,
bd. 43, pp. 512-536.

LITERATURE

359

Dewitz, H. 1889. Eigenthatige Schwimmbewegung der Blutkorperchen der Glieder-

thiere. Zool. Anz.,«jhg. 12, pp. 457-464, 1 fig.
Kowalevsky, A. 1889. Ein Beitrag zur Kenntnis der Excretionsorgane. Biol. Centralb.,

bd. 9, pp. 33-47, 65-76, 127-128.
S chaffer, C. 1889. Beitrage zur Histologic der Insekten. II. Ueber Blutbildungsherde

bei Insektenlarven. Zool. Jahrb., Abth. Anat. Ont., bd. 3, pp. 626-636, taf. 30.
Lankester, E. R. 1893. Note on the Coelom and Vascular System of Mollusca and

Arthropoda. Quart. Journ. Micr. Sc., vol. 34 (n. s.), pp. 427-432.
Pawlowa, M. 1895. Ueber ampullenartige Blutcirculationsorgane im Kopfe verschiedener

Orthopteren. Zool. Anz., jhg. 18, pp. 7-13, 1 fig.

FAT BODY

Dufour, L. 1826. Recherches anatomiques sur les Carabiques et sur plusieurs autres
Insectes Coleopteres. Du tissu adipeux splanchnique. Ann. Sc. nat. Zool., t. 8,
pp. 29-35.

Meyer, H. 1848. Ueber die Entwicklung des Fettkorpers, der Tracheen und der keim-
bereitenden Geschlechtstheile bei den Lepidopteren. Zeits. wiss. Zool, bd. 1, pp.
175-197, 4 taf.

Fabre, J. H. 1863. Etude sur le role du tissu adipeux dans la secretion urinaire chez les

Insectes. Ann. Sc. nat. Zool., ser. 4, t. 19, pp. 351-382.
Landois, L. 1865. Ueber die Funktion des Fettkorpers. Zeits. wiss. -Zool., bd. 15, pp.

371-372.

Schultze,M. 1865. Zur Kenntniss der Leuchtorgane von Lampyris splendidula. Archiv.

mikr. Anat., bd. 1, pp. 124-137, taf. 5, 6.
Gadeau de Kerville, H. 1881, 1887. Les insectes phosphorescents. T. 1, 55 pp., 4 pis.;

t. 2, 135 pp. Rouen.*

Von Wielowiejski, H. R. 1882. Studien iiber Lampyriden. Zeits. wiss. Zool, bd. 37,

PP- 354-428, taf. 23, 24.
Von Wielowiejski, H. 1883. Ueber den Fettkorper von Corethra plumicornis und seine

Entwicklung. Zool. Anz., jhg. 6, pp. 318-322.
Emery, C. 1884. LTntersuchungen iiber Luciola italica L. Zeits. wiss. Zool., bd. 40, pp.

338-355, taf. 19.

Emery, C. 1885. La mce della Luciola italica osservata con microscopio. Bull. Soc. Ent.

Ital., anno 17, pp. 351-355, tav. 5.
Dubois, R. 1886. Contribution a l'etude de la production de la lumiere par les etres

vivants. Les Elaterides lumineux. Bull. Soc. zool. France, ann. 11, pp. 1-275, pis-

1-9.

Heinemann, C. 1886. Zur Anatomie und Physiologie der Leuchtorgane mexikanischer

Cucuyo's. Archiv mikr. Anat., bd. 27, pp. 296-382.
Von Wielowiejski, H. R. 1886. Ueber das Blutgewebe der Insekten. Zeits. wiss. Zool.,

bd. 43, pp. 512-536.

Schaffer, C. 1889. Beitrage zur Histologie der Insekten. H. Ueber Blutbildungsherde

bei Insektenlarven. Zool. Jahrb., Abth. Anat. Ont., bd. 3, pp. 626-636, taf. 30.
Von Wielowiejski, H. R. 1889. Beitrage zur Kenntnis der Leuchtorgane der Insecten.

Zool. Anz., jhg. 12, pp. 594-600.
Wheeler, W. M. 1892. Concerning the "blood tissue" of the Insecta. Psyche, vol. 6,

pp. 216-220, 233-236, 253-258, pi. 7.
Cuenot, L. 1895. Etudes physiologiques sur les Orthopteres. Arch. Biol., t. 14, pp.

293-341, pis. 12, 13.

ENTOMOLOGY

Schmidt, P. 1895. On the Luminosity of Midges I Chironomida.-). Ann. Mag. Xat. Hist.,
ser. 6, vol. 15, pp. 133-141. Trans, from Zool. Jahrb?, Abth. Syst., etc., bd. 8, pp.
58-66, 1894.

Townsend, A. B. 1904. The Histology of the Light Organs of Photinus marginellus.

Amer. Xat., vol. 38, pp. 1 27-151 , figs. 1-11.*
Lund, E. J. 191 1. On the Structure, Physiology and Use of Photogenic Organs. Journ.

Exp. Zool., vol. 11, pp. 415-461, pis. 1-3; figs. 1, 2.*
McDermott, F. A. 1911. Some Further Observations on the Light Emission of American

Lampyridae. Can. Ent., vol. 43, pp. 399-406.
Coblentz, W. W. 1912. A Physical Study of the Firefly. Publ. Xo. 164, Carnegie Inst.,

Wash., 47 pp., 14 figs., 1 pi.*
Glaser, R. W. 1912. A Contribution to Our Knowledge of the Function of the (Enocytes

of Insects. Biol. Bull., vol. 23, pp. 213-224.*
McDermott, F. A. 1912. Recent Advances in Our Knowledge of the Production of Light

in Living Organisms. Rept. Smithson. Inst. 191 1, pp. 345-362.*

RESPIRATORY SYSTEM
Dufour, L. 1825-60. [Many papers on respiratory system.] Ann. Sc. nat. Zool.
Dutrochet, R. J. H. 1833. Du mecanisme de la respiration des Insectes. Ann. Sc. nat.

Zool. t. 28, pp. 31-44. 1838. Mem. Acad. Sc. Paris, t. 14, pp. 81-93.
Newport, G. 1836. On the Respiration of Insects. Phil. Trans. Roy. Soc. London, vol.

126, pp. 529-566.

Grube, A. E. 1844. Beschreibung einer auffallenden an Siisswasserschwammen lebenden

Larve. (Sisyra.) Archiv Xaturg., jhg. 9, pp. 331-337, figs.
Newport, G. 1844. On the existence of Branchiae in the perfect State of a Xeuropterous

Insect, Pteronarcys regalis Xewm. and other species of the same genus. Ann. Mag.

Xat. Hist., vol. 13, pp. 21-25.
Platner, E. A. 1844. Mittheilungen iiber die Respirationsorgane und die Haut der Seiden-

raupen. Miillers Archiv Anat. Phys., pp. 38-49, figs.
Dufour, L. 1849. Des divers modes de respiration aquatique dans les insectes. Compt.

rend. Acad. Sc., t. 29, pp. 763-770. 1850. Trans. Ann. Mag. Xat. Hist., ser. 2,

vol. 6, pp. 1 1 2-1 18.

Newport, G. 1851. On the Formation and the Use of the Airsacs and dilated Tracheae in

Insects. Trans. Linn. Soc. Zool., vol. 20, pp. 419-423.
Newport, G. 1851. On the Anatomy and Affinities of Pteronarcys regalis Xewm., etc.

Trans. Linn. Soc. Zool., vol. 20. pp. 425-453, 1 pi.
Dufour, L. 1852. Etudes anatomiques et physiologiques et observations sur les larves des

Libellules. Ann. Sc. nat. Zool.. ser. 3, t. 17, pp. 65-110, 3 pis.
Hagen, H. A. 1853. Leon Dufour iiber die Larven der Libellen mit Beriicksichtigung der

friiheren Arbeiten. (Ueber Respiration der Insecten.) Stett. ent. Zeit., bd. 14,

pp. 98-106, 237-238, 260-270, 311-325. 334-346.
Williams, T. 1853-57. On the Mechanism of Aquatic Respiration and on the Structure of

the Organs of Breathing in Invertebrate Animals. Trans. Ann. Mag. Xat. Hist.,

ser. 2, vols. 12-19, 1~ P^s-
Barlow, W. F. 1855. Observations of the Respiratory Movements of Insects. Phil.

Trans. Roy. Soc. London, vol. 145, pp. 139-148.
Lubbock, J. i860. On the Distribution of the Tracheae in Insects. Trans. Linn. Soc.

Zool., vol. 23, pp. 23-50, pi. 4.
Rathke, H. 1861. Anatomisch-physiologische Untersuchungen iiber den Athmungsprocess

der Insecten. Schrift, phys.-oek. Gesell. Konigsberg, jhg. 1, pp. 99-138, taf. 1.

LITERATURE

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Scheiber, S. H. 1862. Vergleichende Anatomie imd Physiologie der (Estriden-Larven.

Respirationssystem. Sitzb. Akad. Wiss. Wien, math.-naturw. CI., bd. 45, pp. 7-68,
3- taf.

Reinhard, H. 1865. Zur Entwicklungsgeschichte des Tracheensystems der Hymen-

opteren mit besonderer Beziehung auf dessen morphologische Bedeutimg. Berl.

ent. Zeits., jhg. 9, pp. 187-218, taf. 1, 2.
Landois, H., und Thelen, W. 1867. Der Tracheenverschluss bei den Insekten. Zeits.

wiss. Zool., bd. 17, pp. 187-214, 1 taf.
Oustalet, E. 1869. Note sur la respiration chez les nymphes des Libellules. Ann. Sc. nat.

Zool., ser. 5, t. 11, pp. 370-386, 3 pis.
Pouchet, G. 1872. Developpement du systeme tracheen de l'Anophele (Corethra plumi-

cornis). Archiv. Zool. exper., t. 1, pp. 217-232, 1 fig.
Gerstacker, A. 1874. Ueber das Yorkommen von Tracheenkiemen bei ausgebildeten

Insecten. Zeits. wiss. Zool., bd. 24, pp. 204-252, 1 taf.
Packard, A. S. 1874. On the Distribution and Primitive Number of Spiracles in Insects.

Amer. Nat., vol. 8. pp. 531-534-
Palmen, J. A. 1877. Zur Morphologie des Tracheensystems. 10 + 149 pp., 2 taf.

Helsingfors.

Sharp, D. 1877. Observations on the Respiratory Action of the Carnivorous Water
Beetles (Dytiscidae). Journ. Linn. Soc. Zool., vol. 13, pp. 161-183.

Haller, G. 1878. Kleinere Bruchstiicke zur vergleichenden Anatomie der Arthropoden.

I. Ueber das Atmungsorgan der Stechmuckenlarven. Archiv Naturg., jhg. 44, bd.
1, pp. 91-101, taf. 2.

Hagen, H. A. 1880. Beitrag zur Kenntnis des Tracheensystems der Libellen-Larven.

Zool. Anz., jhg. 3, pp. 157-161.
Hagen, H. A. 1880. Kiementiberreste bei einer Libelle; glatte Muskelfasern bei Insecten.

Zool. Anz., jhg. 3, pp. 304-305.
Poletajew, O. 1880. Quelques mots sur les organes respiratoires des larves des Odonates.

Horae Soc. Ent. Ross., t. 15, pp. 436-452, 2 pis.
Viallanes, H. 1880. Sur l'appareil respiratoire et circulatoire de quelques larves de

Dipteres. Compt. rend. Acad. Sc., t. 90, pp. 1180-1182.
Krancher, O. 1881. Der Bau der Stigmen bei den Insekten. Zeits. wiss. Zool., bd. 35,

PP- 505-574, taf. 28, 29.
Vayssiere, A. 1882. Recherches sur Torganisation des larves des Ephemerines. Ann. Sc.

nat. Zool., ser. 6, t. 13, pp. 1-137, pis. 1-11.
Macloskie, G. 1883. Pneumatic Functions of Insects. Psyche, vol. 3, pp. 375-378.
Macloskie, G. 1884. The Structure of the Tracheae of Insects. Amer. Nat., vol. 18, pp.

507-573, figs. 1-4.

Plateau, F. 1884. Recherches experimentales sur les mouvements respiratoires des
Insectes. Mem. Acad. roy. Belgique, t. 45, 219 pp., 7 pis., 56 figs.

Packard, A. S. 1886. On the Nature and Origin of the so-called "Spiral Thread" of
Tracheae. Amer. Nat., vol. 20, pp. 438-442, figs. 1-3.

Comstock, J. H. 1887. Note on Respiration of Aquatic Bugs. Amer. Nat., vol. 21, pp
577-578.

Raschke, E. W. 1887. Die Larve von Culex nemorosus. Archiv Naturg., jhg. 53, bd. 1,
pp. 133-163. taf. 5. 6.

Schmidt-Schwedt, E. 1887. Ueber Athmung der Larven und Puppen von Donacia

crassipes. Berlin, ent. Zeits., bd. 31, pp. 325-334, taf. 5b.
Vogler, C. 1887. Die Tracheenkiemen der Simulien-Puppen. Mitt, schweiz. ent.

Gesell., bd. 7, pp. 277-282.

362

i:\T( >.Moi.( k;y

Dewitz, H. 1888. Knlnehmen die Larven der Donacien vermittelst Stigmen oder Athem-

rohren den Luftraumen der Pflanzen die sauerstoffhaltige Luft? Berl. ent. Zeits.,

bd. 32, pp. 5-6, figs, i, 2.
Haase, E. 1889. Die Abdominalanhange der Insekten mit Beriicksichtigung der Myri-

opoden. Morph. Jahrb., bd. 15, pp. 331-435, taf. 14, 15.
Cajal, S. R. 1890. Coloration par la methode de Golgi des terminaisons des trachees et

des nerfs dans les muscles des ailes des insectes. Zeits. wiss. Mikr., bd. 7, pp. 3*32-

342, taf. 2, figs. 1-3.

Dewitz, H. 1890. Einige Beobachtungen, betreffend das geschlossene Tracheensystem
bei Insectenlarven. Zool. Anz., jhg. 13, pp. 500-504, 525-531.

Von Wistinghausen, C. 1890. Ueber Tracheenendigungen in den Sericterien der Raupen.
Zeits. wiss. Zool., bd. 49, pp. 565-582, taf. 27.*

Miall, L. C. 1891. Some Difficulties in the Life of Aquatic Insects. Xature, vol. 44, pp.
457-462.

Stokes, A. C. 1893. The Structure of Insect Tracheae, with Special Reference to those of

Zaitha fluminea. Science, vol. 21, pp. 44-46, figs. 1-7.
Miall, L. C. 1895, 1903. The Natural History of Aquatic Insects. 11 +395 pp., 116 figs.

London and New York. Macmillan & Co.
Sadones, J. 1895. L'appareil digestif et respiratoire larvaire des Odonates. La Cellule,

t. 11, pp. 271-325, pis. 1-3.
Gilson, G., and Sadones, J. 1896. The Larval Gills of the Odonata. Journ. Linn. Soc.

Zool., vol. 25, pp. 413-418, figs. 1-3.
Holmgren, E. 1896. Ueber das respiratorische Epithel der Tracheen bei Raupen. Festsk.

Lilljeborg, Upsala, pp. 79-96, taf. 5, 6.
Mammen, H. 1912. Ueber die Morphologie der Heteropteren und Homopterenstigmen.

Zool. Jahrb., Abt. Anat. Ont., bd. 34, pp. 1 21-178, taf. 7-9, 22 figs.*

REPRODUCTIVE SYSTEM
Dufour, L. 1824-60. [Many papers on reproductive system.] Ann. Sc. nat. Zool.
Dutrochet, R. J. H. 1833. Observations sur les organes de la generation chez les Pucerons.

Ann. Sc. nat. Zool., t. 30, pp. 204-209.
Von Siebold, C. T. E. 1836. Ueber die Spermatozoen der Crustaceen, Insecten, Gaster-

opoden und einiger andern wirbellosen Thiere. Miiller's Archiv Anat. Phys., pp.

15-52, 2 taf.

Von Siebold, C. T. E. 1836. Fernerer Beobachtungen liber die Spermatozoen der wirbel-
losen Thiere. Miiller's Archiv Anat. Phys., p. 232. 1837, pp. 381-432, taf. r.

Doyere, L. 1837. Observations anatomiques sur les Organes de la generation chez la
Cigale femelle. Ann. Sc. nat. Zool., t. 7, pp. 200-206, figs.

Von Siebold, C. T. E. 1838. Ueber die weiblichen Geschlechtsorgane der Tachinen.
Archiv Xaturg., jhg. 4, pp. 191-201.

Loew, H. 1841. Beitrag zur anatomischen Kenntniss der inneren Geschlechtstheile der
zweiniigligen Insecten. Germar's Zeits. Ent., bd. 3, pp. 386-406, 1 taf.

Von Siebold, C. T. E. 1843. Ueber das Receptaculum seminis der Hymenopteren Weib-
chen. Germar's Zeits. Ent., bd. 4, pp. 362-388, 1 taf.

Stein, F. 1847. Yergleichende Anatomie und Physiologie der Insecten. I. Monographic
Ueber die Geschlechts-Organe und den Bau des Hinterleibes bei den weiblichen
Kafern. 8 + 139 pp., 9 taf. Berlin.

Brauer, F. 1855. Beitrage zur Kenntniss des inneren Baues und der Yerwandlung der
Xeuropteren. Yerh. zool.-bot. Yer. Wien, bd. 5, pp. 700-726, 5 taf.

Kolliker, A. 1856. Physiologische Studien liber die Samenflussigkeit. Zeits. wiss. Zool.
bd. 7, pp. 201-272, 1 taf.

LITERATURE

363

Huxley, T. H. 1858-59. On the Agamic Reproduction and Morphology of Aphis. Trans.

Linn. Soc. Zool., vol. 22, pp. 193-236, 5 pis.
Lubbock, J. 1859. On the Ova and Pseudova of Insects. Phil. Trans. Roy. Soc. London,

vol. 149, pp. 341-369, pis. 16-18.
Landois, H. 1863. Ueber die Verbindung der Hoden mit dem Ruckengefass bei den

Insekten. Zeits. wiss. Zool., bd. 13, pp. 316-318, 1 taf.
Claus, C. 1864. Beobachtungen iiber die Bildung des Insekteneies. Zeits. wiss. Zool.,

bd. 14, pp. 42-54, 1 taf.
Pagenstecher, H. A. 1864. Die ungeschlechtliche Yermehrung der Fliegenlarven. Zeits.

wiss. Zool., bd.^14, pp. 400-416, 2 taf.
Wagner, N. 1865. Ueber die viviparen Gallmiickenlarven. Zeits. wiss. Zool., bd. 15, pp.

106-117.

Bessels, C. 1867. Studien iiber die Entwicklung der Sexualdriisen bei den Lepidopteren.
Zeits. wiss. Zool., bd. 17, pp. 545-564, 3 taf.

Leydig, F. 1867. Der Eierstock und die Samentasche der Insekten. Nova Acta Acad.
Leop.-Carol., bd. 33, 88 pp., 5 taf.

Butschli, O. 1871. Xahere Mittheilungen iiber die Entwicklung und den Bau der Samen-
faden der Insecten. Zeits. wiss Zool., bd. 21, pp. 526-534, taf. 40, 41.

Nusbaum, J. 1882. Zur Entwickelungsgeschichte der Ausfuhrungsgange der Sexual-
driisen bei den Insecten. Zool. Anz., jhg. 5, pp. 637-643.

Palmen, J. A. 1883. Zur vergleichenden Anatomie der Ausfuhrungsgange der Sexual-
organe bei den Insekten. Vorlaufige Mittheilung. Morph. Jahrb., bd. 9, pp. 169-
176.

Will, L. 1883. Zur Bildung des Eies und des Blastoderms bei den viviparen Aphiden.

Arbeit, zool.-zoot. Inst. Univ. Wurzburg. bd. 6, pp. 217-258, taf. 16.
Palmen, J. A. 1884. Ueber paarige Ausfuhrungsgange der Geschlechtsorgane bei Insecten.

Ein morphologische Untersuchung. 108 pp., 5 taf. Helsingfors.
Gilson, G. 1885. Etude comparee de la spermatogenese chez les Arthropodes. La Cellule,

t. 1, pp. 7-188, pis. 1-8.*
Schneider, A. 1885. Die Entwicklung der Geschlechtsorgane der Insecten. Zool. Beitr.

von A. Schneider, bd. 1, pp. 257-300, 4 taf. Breslau.
Spichardt, C. 1886. Beitrag zur Entwickelung der mannlichen Genitalien und ihrer

Ausfuhrgange bei Lepidopteren. Verh. naturh. Ver Bonn, jhg. 43, pp. 1-34, taf. 1.
La Valette St. George. 1886, 1887. Spermatologische Beitrage. Arch. mikr. Anat.,

bd. 27, pp. 1-12, taf. 1, 2; bd. 28, pp. 1-13, taf. 1-4; bd. 30, pp. 426-434, taf. 25
Von Wielowiejski, H. R. 1886. Zur Morphologie des Insectenovariums. Zool. Anz., jhg.

9, pp. 132-139.

Korschelt, E. 1887. Ueber einige interessante Vorgange bei der Bildung der Insekteneier.
Zeits. wiss. Zool., bd. 45, pp. 327-397, taf. 18, 19.

Nassonow, N. 1887. The Morphology of Insects of Primitive Organization. Studies Lab.
Zool. Mus. Moscow, pp. 15-86, 2 pis., 68 figs. (In Russian.)

Oudemans, J. T. 1888. Beitrage zur Kenntniss der Thysanura und Collembola. Bijdr.
Dierk., pp. 147-226, taf. 1-3. Amsterdam.

Bertkau, P. 1889. Beschreibung eines Zwitters von Gastropacha quercus, nebst allge-
meinen Bemerkungen und einem Verzeichniss der beschriebenen Arthropoden-
zwitter. Archiv Naturg., jhg. 55, bd. 1, pp. 75-116, figs. 1-3.*

Leydig, F. 1889. Beitrage zur Kenntniss des thierischen Eies im unbefruchteten Zu-
stande. Zool. Jahrb., Abth. Anat. Ont., bd. 3, pp. 287-432, taf. n-17.

Lowne, B. T. 1889. On the Structure and Development of the Ovaries and their Append-
ages in the Blowfly (Calliphora erythrocephala). Journ. Linn. Soc. Zool., vol. 20,
pp. 418-442, pi. 28.*

364

ENTOMOLOGY

Ballowitz, E. 1890. I'nursuchungen iiber die Struktur der Spermatozocn, zugleich ein
Beitrag zur Lchre vom fcincren Ban der kontraktilen Elcmente. Die Spermatozocn
der Insekten. (I. Coleopteren.) Zeits. wiss. Zool., bd. 50, pp. 317-407, taf. 12-15.

Henking, H. 1890-92. Untersuchungen iiber die ersten Entwicklungsvorgange in der
Eiern der Insekten. Zeits. wiss. Zool., bd. 49, pp. 503-564, taf. 24-26; bd. 51, pp.
685-736, taf. 35-37; bd. 54, pp. 1-274, taf. 1-12, figs. 1-12.

Ritter, R. 1890. Die Entwicklung der Geschlechtsorgane und des Darmes bei Chironomus.
Zeits. wiss. Zool., bd. 50, pp. 408-427, taf. 16.

Heymons, R. 1891. Die Entwicklung der weiblichen Geschlechtsorgane von Phyllo-
dromia (Blatta) germanica L. Zeits. wiss. Zool., bd. 53, pp. 434-536, taf. 18-20.

Koschewnikoff, G. 1891. Zur Anatomie der mannlichen Geschlechtsorgane der Honig-
biene. Zool. Anz., jhg. 14, pp. 393-396.

Ingenitzky, J. 1893. Zur Kenntnis der Begattungsorgane der Libelluliden. Zool. Anz.,
jhg. 16, pp. 405-407, 2 figs.

Escherich, K. 1894. Anatomische Studien iiber das mannliche Genital-system der Cole-
opteren. Zeits. wiss. Zool., bd. 57, pp. 620-641, taf. 26, figs. 1-3.

Toyama, K. 1894. On the Spermatogenesis of the Silk Worm. Bull. Coll. Agr. Univ.
Tokyo, vol. 2. pp. 125-157, pis. 3, 4.

Verson, E. 1894. Zur Spermatogenesis bei der Seidenraupe. Zeits. wiss. Zool., bd. 58,
PP- 303-313- taf. 17.

Kluge, M. H. E. 1895. Das mannliche Geschlechtsorgan von Vespa germanica. Archiv

Naturg., jhg. 6i, bd. 1, pp. 159-198, taf. 10.
Peytoureau, A. 1895. Contributions a Tetude de la morphologie de 1'armure genitale des

Insectes. 248 pp., 22 pis., 43 figs. Paris.
Wilcox, E. V. 1895. Spermatogenesis of Caloptenus femur-rubrum and Cicada tibicen.

Bull. Mus. Comp. Zool., vol. 27, pp. 1-32. pis. 1-5.*
Wilcox, E. V. 1896. Further Studies on the Spermatogenesis of Caloptenus femur-rubrum.

Bull. Mus. Comp. Zool., vol. 29, pp. 193-202, pis. 1-3.
Fenard, A. 1897. Recherches sur les organes complementaires internes de Tappareil

genital des Orthopteres. Bull. sc. France Belgique. t. 29. pp. 390-533, pis. 24-28.
Gross, J. 1903. Untersuchungen iiber die Histologic des Insectenovariums. Zool. Jahrb.,

Abth. Anat. Ont.; bd. 18, pp. 71-186. taf. 6-14.*
Griinberg, K. 1903. Untersuchungen iiber die Keim- und Xahrzellen in den Hoden und

Ovarien der Lepidoptera. Zeits. wiss. Zool., bd. 74, pp. 327-395, taf. 16-18.
Holmgren, N. 1903. Ueber vivipare Insecten. Zool. Jahrb., bd. 19, pp. 431-468,

10 figs*.

Doten, S. B. 191 1. Concerning the Relation of Food to Reproductive Activity and
Longevity in Certain Hymenopterous Parasites. Tech. Bull. 78, Agr. Exp. Sta.,
Univ. Nevada, 30 pp., 10 pis.

Felt, E. P. 1911. Miastor americana Felt, an Account of Pedogenesis. Twenty-sixth
Rept. St. Ent. X. Y., pp. 82-104, figs. 7-9.*

EMBRYOLOGY

Rathke, H. 1844. Ueber die Eier von Gryllotalpa und ihre Entwickelung. Miiller's

Archiv Anat. Phys., bd. 2, pp. 27-37, figs. 1-5.
Meyer, G. H. 1848. Ueber Entwicklung des Fettkorpers, der Tracheen und der keim-

bereitenden Geschlechtstheile bei den Lepidopteren. Zeits. wiss. Zool., bd. r, pp.

175-197, 4 taf.

Leuckart, R. 1858. Die Fortpflanzung und Entwicklung der Pupiparen nach Beobach-
tungen an Melophagus ovinus. Abh. naturf. Gesell. Halle, bd. 4, pp. 145-226, 3 taf.

LITERATURE

365

Weismann, A. 1863. Die Entwicklung der Dipteren im Ei, nach Beobachtungen an
Chironomus spec, Musca vomitoria und Pulex canis. Zeits. wiss. Zool.. bd. 13, pp.
107-220, 7 taf. Separate. 1864, 263 pp.. 14 taf.

Metschnikoff, E. 1866. Embryologische Studien an Insecten. Zeits. wiss. Zool., bd. 16,
pp. 389-500. 10 taf.

Brandt, A. 1869. Beitrage zur Entwicklungsgeschichte der Libelluliden und Hemipteren.

Mem. Acad. St. Petersbourg, ser. 7. t. 13, pp. 1-33, 3 pis.
Melnikow, N. 1869. Beitrage zur Embryonalentwicklung der Insekten. Archiv Xaturg.,

jhg. 35. bd. r, pp. 136-189. 4 taf.
Biitschli, O. 1870. Zur Entwicklungsgeschichte der Biene. Zeits. wiss. Zool.. bd. 20,

PP- 519-564. taf. 24-27.
Kowalevsky, A. 1871. Embryologische Studien an Wurmern und Arthropoden. Mem.

Acad. St. Petersbourg. ser. 7, t. 16, pp. 1-70. 12 pis.
Dohrn, A. 1875. Xotizen zur Kenntniss der Insectenentwicklung. Zeits. wiss. Zool., bd.

26, pp. 112-138.

Hatschek, B. 1877. Beitrage zur Entwicklungsgeschichte der Lepidopteren. Jenais.

Zeits. Naturw., bd. n, 38 pp., 3 taf., 2 figs.
Bobretzky, N. 1878. Ueber die Bildung des Blastoderms und der Keimblatter bei den

Insecten. Zeits. wiss. Zool., bd. 31, pp. 195-215, taf. 14.
Korotneff, A. 1883. Entwicklung des Herzens bei Gryllotalpa. Zool. Anz., jhg. 6, pp.

687-690, figs. 1,2.

Packard, A. S. 1883. The Embryological Development of the Locust. Third Rept.

U. S. Ent. Comm., pp. 263-285, pis. 16-21, figs. 10-n. Washington.
Will, L. 1883. Zur Bildung des Eies und des Blastoderms bei den viviparen Aphiden.

Arbeit, zool.-zoot. Inst. Univ. YViirzburg, bd. 6, pp. 217-258, taf. 16.
Ayers,H. 1884. On the Development of (Ecanthus niveus and its Parasite Teleas. Mem.

Bost. Soc. Xat. Hist., vol. 3, pp. 225-281, pis. 18-25, figs. 1-41.*
Patten, W. 1884. The Development of Phryganids. with a Preliminary Xote on the

Development of Blatta germanica. Quart. Journ. Micr. Sc., vol. 24 (n. s.), pp.

549-602, pis. 36a, b, c.

Witlaczil, E. 1884. Entwicklungsgeschichte der Aphiden. Zeits. wiss. Zool., bd. 40, pp.
559-696, taf. 28-34.*

Korotneff, A. 1885. Die Embryologie der Gryllotalpa. Zeits. wiss. Zool., bd. 41, pp.
570-604, taf. 29-31.

Schneider, A. 1885. Ueber die Entwicklung der Geschlechtsorgane der Insecten. Zool.

Beitr. von. A. Schneider, bd. 1, pp. 257-300, 4 taf. Breslau.
Blochmann, F. 1887. Ueber die Richtungskdrper bei Insecteneiern. Morph. Jahrb.,

bd. 12, pp. 544-574.. taf. 26, 27.
Biitschli, O. 1888. Bemerkungen iiber die Entwicklungsgeschichte von Musca. Morph.

Jahrb., bd. 14, pp. 170-174, 3 figs.
Cholodkovsky, N. 1888. Ueber die Bildung des Entoderms bei Blatta germanica. Zool.

Anz., jhg. 11. pp. 163-166, figs. 1, 2.
Graber, V. 1888. Ueber die Polypodie bei Insekten-Embryonen. Morph. Jahrb., bd. 13,

pp. 586-615, taf. 25, 26.
Graber, V. 1888. Ueber die primare Segmentirung des Keimstreifs der Insekten. Morph.

Jahrb., bd. 14, pp. 345-368, taf. 14, 15, 4 figs.
Henking, H. 1888. Die ersten Entwicklungsvorgange im Fliegenei und freie Kernbildung.

Zeits. wiss. Zool., bd. 46, pp. 289-336, taf. 23-26, 3 figs.
Will, L. 1888. Entwicklungsgeschichte der viviparen Aphiden. Zool. Jahrb., Abth. Anat.

Ont., bd. 3, pp. 201-286, taf. 6-10.
Cholodkovsky, N. 1889. Studien zur Entwicklungsgeschichte der Insekten. Zeits

wiss. Zool., bd. 48, pp. 89-100, taf. 8.

366

ENTOMOLOGY

Graber, V. 1889. Ueber den Bau und die phylogenetische Bedeutung der embryonalen
Bauchanhange der Insekten. Biol. Centralb., jhg. 9, pp. 355-363.

Heider, K. 1889. Die Embryonalentwicklung von Hydrophilus piceus L. I. Theil. 99
pp., 13 taf., 9 figs. Jena.

Leydig, F. 1889. Beitrage zur Kenntniss des thierischen Eies im unbefruchteten Zustande.
Zool. Jahrb., Abth. Anat. Ont., bd. 3, pp. 287-432, taf. 11-17.

Nusbaum, J. 1889. ^ur Frage der Segmentierung des Keimstreifens und der Bauchan-
hange der Insektenembryonen. Biol. Centralb., jhg. 9, pp. 516-522, fig. 1.

Voeltzkow, A. 1889. Entwickelung im Ei von Musca vomitoria. Arbeit, zool.-zoot.
Inst. Univ. Wiirzburg, bd. 9, pp. 1-48, taf. 1-4.

Voeltzkow, A. 1889. Melolontha vulgaris. Ein Beitrag zur Entwickelung im Ei bei
Insekten. Arbeit, zool.-zoot. Inst. Univ. Wiirzburg, bd. 9, pp. 49-64, taf. 5.

Wheeler, W. M. 1889. The Embryology of Blatta germanica and Doryphora decem-
lineata. Journ. Morph., vol. 3, pp. 291-386, pis. 15-21, figs. 1-16.

Carriere, J. 1890. Die Entwicklung der Mauerbiene (Chalicodoma muraria Fabr.) im
Ei. Archiv mikr. Anat., bd. 35, pp. 141-165, taf. 8, 8a.

Henking, H. 1890-92. Untersuchungen iiber die ersten Entwicklungsvorgange in der
Eiern der Insekten. Zeits. wiss. Zool., bd. 49, pp. 503-564, taf. 24-26; bd. 51, pp.
685-736, taf. 35-37; bd. 54, pp. 1-274, taf. 1-12, figs. 1-12.

Nusbaum, J. 1890. Zur Frage der Riickenbildung bei den Insektenembryonen. Biol.
Centralb., jhg. 10, pp. 110-114.

Ritter, R. 1890. Die Entwicklung der Geschlechtsorgane und des Darmes bei Chironomus.
Zeits. wiss. Zool., bd. 50, pp. 408-427, taf. 16.

Wheeler, W. M. 1890. On the Appendages of the First Abdominal Segment of Embryo
Insects. Trans. Wis. Acad. Sc., vol. 8, pp. 87-140, pis. 1-3.*

Cholodkowsky, N. 1891. Die Embryonalentwicklung von Phyllodromia (Blatta ger-
manica). Mem. Acad. St. Petersbourg, ser. 7, t. 38, 4+120 pp., 6 pis., 6 figs.

Graber, V. 1891. Ueber die embryonale Anlage des Blut- und Fettgewebes der Insekten.
* Biol. Centralb., jhg. n, pp. 212-224.

Wheeler, W. M. 1891. Neuroblasts in the Arthropod Embryo. Journ. Morph., vol. 4,
PP- 337-343> 1

Graber, V. 1892. Ueber die morphologische Bedeutung der ventralen Abdominalanhange

der Insekten-Embryonen. Morph. Jahrb., bd. 17, pp. 467-482, figs. 1-6.
Korschelt, E., und Heider, K. 1892. Lehrbuch der vergleichenden Entwicklungsge-

schichte der wirbellosen Thiere. Heft 2, pp. 761-890, figs. Jena.* Trans.: 1899.

M. Bernard and M. F. Woodward. Text-Book of the Embryology of Invertebrates.

12 + 441 pp., 198 figs. London, Swan Sonnenschein & Co., Ltd.; New York, The

Macmillan Co.*

Wheeler, W. M. 1893. A Contribution to Insect Embryology. Journ. Morph., vol. -8,

pp. 1-160, pis. 1-6, figs. 1-7.
Heymons, R. 1895. Die Embryonalentwickelung von Dermapteren und Orthopteren

unter besonderer Beriicksichtigung der Keimblatterbildung. 8 + 136 pp., 12 taf.,

33 figs. Jena.

Heymons, R. 1896. Grundzuge der Entwickelung und des Korperbaues von Odonaten

und Ephemeriden. Anh. Abh. Akad. Wiss. Berlin, 66 pp., 2 taf.
Heymons, R. 1897. Entwicklungsgeschichtliche Untersuchungen an Lepisma saccharina

L. Zeits. wiss. Zool., bd. 62, pp. 583-631, taf. 29, 30, 3 figs.
Kulagin, N. 1897. Beitrage zur Kenntnis der Entwicklungsgeschichte von Platygaster.

Zeits. wiss. Zool., bd. 63, pp. 195-235, taf. 10, n.
Claypole, A. M. 1898. The Embryology and Oogenesis of Anurida maritima (Guer.).

Journ. Morph., vol. 14, pp. 219-300, pis. 20-25, 11 figs.

LITERATURE

367

Uzel, H. 1898. Studien iiber die Entwicklung der apterygoten Insecten. 6 + 58 pp.,
6 taf., 5 figs. Berlin.

Wilson, E. B. 1900. The Cell in Development and Inheritance. 21 + 483 pp., 194 figs.

New York and London. The Macmillan Co.
Marchal, P. 1904. La Polyembryonie Specifique. Arch. Zool. exp. gen., ser. 4, t. 2, pp.

257-335, pis. 9-I3-*

Heymons, R. 1912. Ueber den Genitalapparat und die Entwicklung von Hemimerus
talpoides Walk. Zool. Jahrb., Supplement 15, bd. 2, pp. 141-184, pis. 7-1 1, 3 figs.

Korschelt, E. 1912. Zur Embryonalentwicklung des Dytiscus marginalis L. Zool.
Jahrb., Supplement 15, bd. 2, pp. 499-532, 24 figs.*

POSTEMBRYOXIC DEVELOPMENT. METAMORPHOSIS
Fabre, J. L. 1856. Etude sur l'instinct et les metamorphoses des Sphegiens. Ann. Sc.

nat. Zool., ser. 4, t. 6, pp. 137-189.
Fabre, J. L. 1857. Memoire sur l'hypermetamorphose et les mceurs des Meloides. Ann.

Sc. nat. Zool., ser. 4, t. 7, pp. 299-365; 1 pi.; 1858, t. 9, pp. 265-276.
Miiller, F. 1864. Fur Darwin. Leipzig. Translation: Facts and Figures in aid of

Darwin, London, 1869.

Weismann, A. 1864. Die nachembryonale Entwicklung der Musciden nach Beobach-
tungen an Musca vomitoria und Sarcophaga carnaria. Zeits. wiss. Zool., bd. 14,
pp. 187-336.

Weismann, A. 1866. Die Metamorphose von Corethra plumicornis. Zeits. wiss. Zool.,

bd. 16, pp. 45-127, 5 taf.
Trouvelot, L. 1867. The American Silk Worm. Amer. Xat., vol. 1, pp. 30-38, 85-94,

145-149, 4 figs., pis. 5, 6.
Brauer, F. 1869. Betrachtungen iiber die Yerwandlung der Insekten im Sinne der Des-

cendenz-Theorie. Yerh. zool.-bot. Gesell. Wien, bd. 19, pp. 299-318; bd. 28 (1878),

1879, pp. 151-166.

Ganin, M. 1869. Beitrage zur Kenntniss der Entwickelungsgeschichte bei den Insecten.

Zeits. wiss. Zool., bd. 19, pp. 381-451, 3 taf.
Chapman, T. A. 1870. On the Parasitism of Rhipiphorus paradoxus. Ann. Mag. Xat.

Hist., ser. 4, vol. 5, pp. 191-198.
Chapman, T. A. 1870. Some Facts towards a Life History of Rhipiphorus paradoxus.

Ann. Mag. Xat. Hist., ser. 4, vol. 6, pp. 314-326, pi. 16.
Landois, H. 1871. Beitrage zur Entwicklungsgeschichte der Schmetterlingsfliigel in der

Raupe und Puppe. Zeits. wiss. Zool., bd. 21, pp. 305-316, taf. 23.
Packard, A. S. 1873. Our Common Insects. 225 pp., 268 figs. Boston. Estes and

Lauriat.

Lubbock, J. 1874, 1883. On the Origin and Metamorphoses of Insects. 16 + 108 pp.,

6 pis., 63 figs. London. Macmillan & Co.
Ganin, M. 1876. [Materials for a Knowledge of the Postembryonal Development of

Insects. Warsaw.] (In Russian.) Abstracts: Amer. Xat., vol. 11, 1877, pp.

423-430; Zeits. wiss. Zool., bd. 28, 1877, pp. 386-389.
Riley, C. V. 1877. On the Larval Characters and Habits of the Blister-beetles belonging

to the Genera Macrobasis Lec. and Epicauta Fabr. ; with Remarks on other Species

of the Family Meloidae. Trans. St. Louis Acad. Sc., vol. 3, pp. 544-562, figs. 35-39

Pi. 5-

Dewitz, H. 1878. Beitrage zur Kenntniss der postembryonalen Gliedmassenbildung bei
den Insecten. Zeits. wiss. Zool., bd. 30, suppl., pp. 78-105, taf. 5.

Packard, A. S. 1878. Metamorphoses [of Locusts]. First Rept. U. S. Ent. Comm., pp.
279-284, pis. 1-3, figs. 19, 20.

368

ENTOMOLOGY

Dewitz, H. 1881. Ueber die Flugdbildung bei Phryganiden und Lepidopteren. Berl.

ent. Zeits., bd. 25, pp. 53-60, taf. 3, 4.
Metschnikoff , E. 1883. Untersuchungen iiber die intracellular Yerdauung bei wirbel-

losen Thieren. Arb. zool. Inst. Wien, bd. 5, pp. 141-168, taf. 13, 14.
Viallanes, H. 1883. Recherches sur l'histologie des Insectes et sur les phenomenes histo-

logiques qui accompagnent le developpement post-embryonnaire de ces animaux.

Ann. Sc. nat. Zool., ser. 6, t. 14, 348 pp., 18 pis.
Von Wielowiejsky, H. R. 1883. Ueber den Fettkorper von Corethra plumicornis und

seine Entwicklung. Zool. Anz., jhg. 6, pp. 318-322.
Kowalevsky, A. 1885. Beitrage zur nachembryonalen Entwicklung der Musciden. Zool.

Anz., jhg. 8, pp. 98-103, 123-128, 153-157-
Schmidt, O. 1885. Metamorphose und Anatomie des mannlichen Aspidiotus nerii.

Archiv Xaturg., jhg. 51, bd. 1, pp. 169-200, taf. 9, 10.
Witlaczil, E. 1884. Zur Morphologie und Anatomie der Cocciden. Zeits. wiss. Zool.,

bd. 43, pp. 149-174.. taf. 5.
Kowalevsky, A. 1887. Beitrage zur Kenntniss der nachembryonalen Entwicklung der

Musciden. Zeits. wiss. Zool., bd. 45, pp. 542-594, taf. 26-30.
Van Rees, J. 1888. Beitrage zur Kenntnis der inneren Metamorphose von Musca vomi-

toria. Zool. Jahrb., Abth. Anat. Ont., bd. 3, pp. 1-134, taf. 1, 2, 14 figs.
Hyatt, A., and Arms, J. M. 1890. Insecta. 23 + 300 pp., 13 pis., 223 figs. Boston.

D. C. Heath & Co.*

Bugnion, E. 1891. Recherches sur le developpement post-embryonnaire, l'anatomie, et les
moeurs de l'Encyrtus fuscicollis. Rec. zool. Suisse, t. 5, pp. 435-534, pis.
20-25.

Poulton, E. B. 1891. The External Morphology of the Lepidopterous Pupa: its Relation

to that of the other Stages and to the Origin and History of Metamorphosis. Trans.

Linn. Soc. Zool., ser. 2, vol. 5, pp. 245-263, pis. 26, 27.
Korschelt, E., und Heider, K. 1892. Lehrbuch der vergleichenden Entwicklungsge-

schichte der wirbellosen Thiere. Heft 2, pp. 761-890, figs. Jena.*
Miall, L. C, and Hammond, A. R. 1892. The Development of the Head of Chironomus.

Trans. Linn. Soc. Zool., ser. 2, vol. 5, pp. 265-279, pis. 28-31.
Pratt, H. S. 1893. Beitrage zur Kenntnis der Pupiparen. Archiv Xaturg., jhg. 59, bd.

1, pp. 151-200, taf. 6.

Gonin, J. 1894. Recherches sur la metamorphose des Lepidopteres. De la formation des
appendices imaginaux dans la chenille du Pieris brassicae. Bull. Soc. vaud. Sc. nat.,
t. 30, pp. 1-52. 5 pis.

Miall, L. C. 1895. The Transformations of Insects. Xature. vol. 53. pp. 152-158.
Hyatt, A., and Arms, J. M. 1896. The Meaning of Metamorphosis. Nat. Sc., vol. 8,
pp. 395-403-

Kulagin, N. 1897. Beitrage zur Kenntnis der Entwicklungsgeschichte von Platygaster.

Zeits. wiss. Zool., bd. 63, pp. 195-235, taf. 10. 11.
Packard, A. S. 1897. Xotes on the Transformations of Higher Hymenoptera. Journ.

N. Y. Ent. Soc, vol. 4, pp. 155-166, figs. 1-5; vol. 5, pp. 77-87, 109-120, figs. 6-13.
Pratt, H. S. 1897. Imaginal Discs in Insects. Psyche, vol. 8, pp. 15-30, n figs.
Packard, A. S. 1898. A Text-Book of Entomology. 17 + 729 pp., 654 figs. New York

and London. The Macmillan Co.*
Boas, J. E. V. 1899. Einige Bemerkungen iiber die Metamorphose der Insecten. Zool.

Jahrb., Abth. Syst., bd. 12, pp. 385-402, taf. 20. figs. 1-3.
Lameere, A. 1899. La raison d'etre des metamorphoses chez les Insectes. Ann. Soc. ent.

Belg., t. 43, pp. 619-636.
Perez, C. 1899. Sur la metamorphose des insectes. Bull. Soc. ent. France, pp. 398-402.

LITERATURE

369

Wahl, B. 1901. Ueber die Entwicklung der hypodermalen Imaginalscheiben im Thorax
und Abdomen der Larve von Eristalis Latr. Zeits. wiss. Zool., bd. 70, pp. 171-191,
taf. 9, figs. 1-4.

Perez, C. 1902. Contribution a l'etude des metamorphoses. Bull. sc. France Belg., t.
37, pp. 195-427, pis. 10-12, 32 figs.

Deegener, P. 1904. Die Entwicklung des Darmcanals der Insecten wahrend der Meta-
morphose. Zool. Jahrb., Abth. Anat. Ont., bd. 20, pp. 499-676, taf. 33-43-*

Powell, P. B. 1904-05. The Development of Wings of Certain Beetles, and some Studies
of the Origin of the Wings of Insects. Journ. N. Y. Ent. Soc, vol. 12, pp. 237-243,
pis. 11-17; vol. 13, pp. 5-22.*

Perez, C. 1910. Recherches histologiques sur la metamorphose des Muscides. .-Arch.
Zool. exp. gen., ser. 5, t. 4, pp. 1-270, pis. 1-16, 162 figs.

AQUATIC INSECTS

Dufour, L. 1849. Des divers modes de respiration aquatique dans les insectes. Compt.

rend. Acad. Sc., t. 29, pp. 763-770. Ann. Mag. Nat. Hist., ser. 2, vol. 6, 1850, pp.
112-118.

Dufour, L. 1852. Etudes anatomiques et physiologiques et observations sur les larves des

Libellules. Ann. Sc. nat. Zool., ser. 3, t. 17, pp. 65-110, 3 pis.
Hagen, H. A. 1853. Leon Dufour iiber die Larven der Libellen mit Beriicksichtigung der

friiheren Arbeiten. (Ueber Respiration der Insecten.) Stett. ent. Zeit., bd. 14,

pp. 98-106, 237-238, 260-270, 311-325, 334-346.
Williams, T. 1853-57. Cm the Mechanism of Aquatic Respiration and on the Structure

of the Organs of Breathing in Invertebrate Animals. Ann. Mag. Nat. Hist., ser.

2, vols. 12-19, 17 pis.

Oustalet, E. 1869. Note sur la respiration chez les nymphes des Libellules. Ann. Sc.

nat. Zool., ser. 5, t. 11, pp. 370-386, 3 pis.
Sharp, D. 1877. Observations on the Respiratory Action of the Carnivorous Water Beetles

(Dytiscidae). Journ. Linn. Soc. Zool., vol. 13, pp. 161-183.
Poletajew, O. 1880. Quelques mots sur les organes respiratoires des larves des Odonates.

Horae Soc. Ent. Ross., t. 15, pp. 436-452, 2 pis.
Vayssiere, A. 1882. Recherches sur l'organisation des larves des Ephemerines. Ann.

Sc. nat. Zool., ser. 6, t. 13, pp. 1-137, pis. 1-11.
Macloskie, G. 1883. Pneumatic Functions of Insects. Psyche, vol. 3, pp. 375-378.
White, F. B. 1883. Report on the Pelagic Hemiptera. Rept. Sc. Res. Vqy. H. M. S.

Challenger, 1873-1876, Zoology, vol. 7, 82 pp., 3 pis.
Comstock, J. H. 1887. Note on Respiration of Aquatic Bugs. Amer. Nat., vol. 21, pp.

577-5/8.

Schwedt, E. 1887. Ueber Athmung der Larven und Puppen von Donacia crassipes.

Berl. ent. Zeits., bd. 31, pp. 325~334, taf. 5b.
Amans, P. C. 1888. Comparaisons des organes de la locomotion aquatique. Ann. Sc.

nat. Zool., ser. 7, t. 6, pp. 1-164, pis. 1-6.
Dewitz, H. 1888. Entnehmen die Larven der Donacien vermittelst Stigmen oder Athem-

rohren den Luftraumen der Pflanzen die sauerstoffhaltige Luft? Berl. ent. Zeits.,

bd. 32, pp. 5-6, 2 figs.

Garman, H. 1889. A Preliminary Report on the Animals of the Mississippi Bottoms near

Quincy, Illinois, in August, 1888. Bull. 111. St. Lab. Nat. Hist., vol. 3, pp. 123-184.
Moniez, R. 1890. Acariens et Insectes marins des cotes du Boulonnais. Rev. biol. nord

France, t. 2, pp. 321, etc.
Miall, L. C. 1891. Some Difficulties in the Life of Aquatic Insects. Nature, vol. 44, pp-

457-462.

25

37°

KXTOMOLOGY

Walker, J. J. 1893. On the Genus Halobates, Esch., and other Marine Hemiptera. Ent.

Mon. Mag., ser. 2, vol. 4 (29), pp. 227-232.
Carpenter, G. H. 1895. Pelagic Hemiptera. Nat. Sc., vol. 7, pp. 60-61.
Hart, C. A. 1895. On the Entomology of the Illinois River and Adjacent Waters. Bull.

111. St. Lab. Nat. Hist., vol. 4, pp. 149-273, pis. 1-15.
Miall, L. C. 1895, 1903. The Natural History of Aquatic Insects, n + 395 pp., 116 figs.

London and New York. Macmillan & Co.*
Sadones, J. 1895. L'appareil digestif et respiratoire larvaire des Odonates. La Cellule,

t. ir, pp. 271-325, pis. 1-3.
Gilson, G., and Sadones, J. 1896. The Larval Gills of the Odonata. Journ. Linn. Soc.

ZooLj vol. 25, pp. 413-418, figs. 1-3.
Comstock, J. H. 1897, 1901. Insect Life. 6 4- 349 pp., 18 pis., 296 figs. New York.

D. Appleton & Co.*

Needham, J. G. 1900. Insect Drift on the Shore of Lake Michigan. Occas. Mem.

Chicago Ent. Soc, vol. r, pp. 1-8, 1 fig.
Needham, J. G., and Betten, C. 1901. Aquatic Insects in the Adirondacks. Bull.

N. Y. St. Mus., no. 47, pp. 383-612, 36 pis., 42 figs.
Needham, J. G., MacGillivray, A. D., Johannsen, O. A., and Davis, K. C. 1903.

Aquatic Insects in New York State. Bull. N. Y. St. Mus., No. 68, 321 pp., 52 pis.,

26 figs.*

COLOR AND COLORATION
Dorfmeister, G. 1864. L/eber die Einwirkurig verschiedener. wahrend den Entwicklungs-

perioden angewendeter Warmegrade auf die Farbung und Zeichnung der Schmetter-

linge. Mitth. naturw. Yer. Steiermark, pp. 99-108, 1 taf.
Landois, H. 1864. Beobachtungen iiber das Blut der Insecten. Zeits. wiss. Zool., bd.

14, pp. 55-70, taf. 7-9.

Wood, T. W. 1867. Remarks on the Coloration of Chrysalides. Trans. Ent. Soc. London,

ser. 3, vol. 5, Proc, pp. 99-101.
Higgins, H. H. 1868. On the Colour-Patterns of Butterflies. Quart. Journ. Sc., vol. 5,

pp. 323-329, 1 pi.

Weismann, A. 1875. Studien zur Descendenztheorie. I. L'eber den Saison Dimor-

phismus der Schmetterlinge. Leipzig. Trans.: 1880-81. R. Meldola. Studies

in the Theory of Descent. 554 pp., 8 pis. London.
Scudder, S. H. 1877. Antigeny, or Sexual Dimorphism in Butterflies. Proc. Amer.

Acad. Arts Sc., vol. 12, pp. 150-158.
Dorfmeister, G. 1880. Ueber den Einfluss der Temperatur bei der Erzeugung der Schmet-

terlingsvarietaten. Mitth. natunv. Ver. Steiermark, jhg. 1879, PP- 3-8, 1 taf.
Scudder, S. H. 1881 . Butterflies; their Structure, Changes and Life-Histories, with Special

Reference to American Forms. 9 + 322 pp., 201 figs. New York. Henry Holt

& Co.

Hagen, H. A. 1882. On the Color and the Pattern of Insects. Proc. Amer. Acad. Arts

Sc., vol. 17, pp. 234-267.
Dimmock, G. 1883. The Scales of Coleoptera. Psyche, vol. 4, pp. 3-1 1, 23-27, 43-47,
63-71, 11 ngs.*

Krukenberg, C. F. W. 1884. [Color and Pigments of Insects.] Ent. Nachr., jhg. 10,

pp. 291-296.

Poulton, E. B. 1884. Notes upon, or suggested by the Colours, Markings and Protective
Attitudes of certain Lepidopterous Larvae and Pupae, and of a phytophagous hymen-
opterous larva. Trans. Ent. Soc. London, pp. 27-60, pi. 1.

Poulton, E. B. 1885. The Essential Nature of the Colouring of Phytophagous Larvae and
their Pupae, etc. Proc. Roy. Soc. London, vol. 38, pp. 269-315.

LITERATURE

371

Poulton, E. B. 1885. Further Notes upon the Markings and Attitudes of Lepidopterous

Larvae. Trans. Ent. Soc. London, pp. 281-329, pi. 7.
Poulton, E. B. 1887. An Enquiry into the Cause and Extent of a Special Colour-Relation

between Certain Exposed Pupae and the Surfaces which immediately surround them.

Phil. Trans. Roy. Soc. London, vol. 178, pp. 311-441, pi. 26.
Chapman, T. A. 1888. On Melanism in Lepidoptera. Ent. Mon. Mag., vol. 25, p. 40.
Dixey, F. A. 1890. On the Phylogenetic Significance of the Wing-Markings in certain

Genera of the Xymphalidae. Trans. Ent. Soc. London, pp. 89-129, pis. 1-3.
Merrifield, F. 1890. Systematic temperature experiments on some Lepidoptera in all

their stages. Trans. Ent. Soc. London, pp. 131-159, pis. 4, 5.
Poulton, E. B. 1890. The Colours of Animals. 13 + 360 pp., 1 pi., 66 figs. New York.

D. Appelton & Co.

Seitz, A. 1890, 1893. Allgemeine Biologie der Schmetterlinge. Zool. Jahrb., Abth. Syst.,

etc., bd. 5, pp. 281-343; bd. 7, pp. 131-186 *
Coste, F. H. P. 1890-91. Contributions to the Chemistry of Insect Colors. Entomol-
ogist, vol. 23, pp. 128-132, etc.; vol. 24, pp. 9-15, etc.
Hopkins, F. G. 1891. Pigment in Yellow Butterflies. Nature, vol. 45, pp. 197-198.
Merrifield, F. 1891. Conspicuous effects on the markings and colouring of Lepidoptera

caused by exposure of the pupae to different temperature conditions. Trans. Ent.

Soc. London, pp. 155-168, pi. 9.
Urech, F. 1891. Beobachtungen liber die verschiedenen Schuppenfarben und die zeitliche

Succession ihres Auftretens (Farbenfelderung) auf den Puppenfliigelchen von Vanessa

urticae und Io. Zool. Anz., jhg. 14, pp. 466-473.
Beddard, F. E. 1892. Animal Coloration. 8 + 288 pp., 4 pis., 36 figs. London, Swan,

Sonnenschein & Co. New York, Macmillan & Co.
Gould, L. J. 1892. Experiments in 1890 and 1891 on the colour-relation between certain

lepidopterous larvae and their surroundings, together with some other observations

on lepidopterous larvae. Trans. Ent. Soc. London, pp. 215-246, pi. n.
Merrifield, F. 1892. The effects of artificial temperature on the colouring of several species

of Lepidoptera, with an account of some experiments on the effects of light. Trans.

Ent. Soc. London, pp. 33-44.
Poulton, E. B. 1892. Further experiments upon the colour-relation between certain

lepidopterous larvae, pupae, cocoons and imagines and their surroundings. Trans.

Ent. Soc. London, pp. 293-487, pis. 14, 15.
Urech, F. 1892. Beobachtungen liber die zeitliche Succession der Auftretens der Farben-

felder auf den Puppenfliigelchen von Pieris brassicae. Zool. Anz., jhg. 15, pp.

284-290, 293-299.

Urech, F. 1892. Ueber Eigenschaften der Schuppenpigmente einiger Lepidopteren-

Species. Zool. Anz., jhg. 15, pp. 299-306.
Weismann, A. 1892, 1898. The Germ-Plasm. Trans, by \V. N. Parker and H. R6nn-

feldt. See pp. 399-409, on climatic variation in butterflies.
Dixey, F. A. 1893. On the phylogenetic significance of the variations produced by differ-
ence of temperature in Vanessa atalanta. Trans. Ent. Soc. London, pp. 69-73.
Merrifield, F. 1893. The effects of temperature in the pupal stage on the colouring of

Pieris napi, Vanessa atalanta, Chrysophanus phlceas, and Ephyra punctaria. Trans.

Ent. Soc. London, pp. 55-67, pi. 4.
Poulton, E. B. 1893. The Experimental Proof that the Colours of certain Lepidopterous

Larvae are largely due to modified plant Pigments derived from Food. Proc. Roy.

Soc. London, vol. 54, pp. 417-430, pis. 3, 4.
Urech, F. 1893. Beitrage zur Kenntniss der Farbe von Insektenschuppen. Zeits. wiss.

Zool., bd. 57, pp. 306-384.

372

ENTOMOLOGY

Bateson, W. 1894. Materials for the Study of Variation treated with especial Regard to

Discontinuity in the Origin of Species. 16 + 598 pp., 209 figs. London and New

York. Macmillan & Co.
Dixey, F. A. 1894. Mr. Merrifield's Experiments in Temperature-Variation as hearing on

Theories of Heredity. Trans. Ent. Soc. London, pp. 439-446.
Hopkins, F. G. 1894. The Pigments of the Pierida?. Proc. Roy. Soc. London, vol. 57. pp.

5-6-

Kellogg, V. L. 1894. The Taxonomic Value of the Scales of the Lepidoptera. Kansas

Univ. Quart., vol. 3, pp. 55-89, pis. 9, 10, figs. 1-17.
Merrifield, F. 1894. Temperature Experiments in 1893 on several species of Vanessa

and other Lepidoptera. Trans. Ent. Soc. London, pp. 425-438, pi. 9.
Hopkins, F. G. 1895. The Pigments of the Pieridae: A Contribution to the Study of

Excretory Substances which function in Ornament. Phil. Trans. Roy. Soc. London,

vol. 186, pp. 661-682.

Spuler, A. 1895. Beitrag zur Kenntniss des feineren Baues und der Phylogenie der Flugel-
bedeckung der Schmetterlinge. Zool. Jahrb., Abth. Anat. Ont., bd. 8, pp. 520-543,
taf. 36.

Standfuss, M. 1895. On the Causes of Variation and Aberration in the Imago Stage of

Butterflies, with Suggestions on the Establishment of New Species. Trans, by

F. A. Dixey. Entomologist, vol. 28, pp. 69-76, 102-114, 142-150.
Mayer, A. G. 1896. The Development of the Wing Scales and their Pigment in Butterflies

and Moths. Bull. Mus. Comp. Zool., vol. 29, pp. 209-236, pis. 1-7.
Weismann, A. 1896. New Experiments on the Seasonal Dimorphism of Lepidoptera.

Trans, by W. E. Nicholson. The Entomologist, vol. 29, pp. 29-39, etc-
Brunner von Wattenwyl, C. 1897. Betrachtungen liber die Farbenpracht der Insekten.

16 pp., 9 taf. Leipzig. Trans, by E. J. Bles: Observations on the Coloration of

Insects. 16 pp., 9 pis. Leipsic.
Fischer, E. 1897-99. Beitrage zur experimentellen Lepidopterologie. Illustr. Zeits.

Ent., bd. 2-4. 12 taf.

Mayer, A. G. 1897. On the Color and Color-Patterns of Moths and Butterflies. Proc.

Bost. Soc. Nat. Hist.,, vol. 27, pp. 243-330. pis. 1-10. Also Bull. Mus. Comp. Zool.,
vol. 30, pp. 169-256, pis. 1-10.

Von Linden, Grafin, M. 1898. Untersuchungen uber die Entwicklung der Zeichnung des
Schmetterlingsflugels in der Puppe. Zeits. wiss. Zool., bd. 65, pp. 1-49, taf. 1-3.

Newbigin, M. I. 1898. Colour in Nature. 12 + 344 pp. London. John Murray.*

Von Linden, Grafin, M. 1899. Untersuchungen uber die Entwickelung der Zeichnung
der Schmetterlingsflugels in der Puppe. Illustr. Zeits. Ent., bd. 4, pp. 19-22.

Urech, F. 1899. Einige Bemerkungen zum zeitlichen Auftreten der Schuppen-Pigment-
stoffe von Pieris brassicae. Illustr. Zeits. Ent.. bd. 4. pp. 51-53.

Von Linden, la Comtesse M. 1902. Le dessin des ailes des Lepidopteres. Recherches
sur son evolution dans l'ontogenese et la phylogenese des especes, son origine et sa
valeur systematique. Ann. Sc. nat. Zool., ser. 8. t. 14, pp. 1-196, pis. 1-20.

Weismann, A. 1902. Vortrage uber Descendenztheorie. 2 vols. 12 + 456 pp., 95 figs.;
6 + 462 pp., 3 pis., 36 figs. Jena. G. Fischer. See pp. 65-102.

Von Linden, Grafin M. 1903. Morphologische und physiologisch-chemische Untersuch-
ungen liber die Pigmente der Lepidopteren. 1. Die gelben und roten Farbstoffe der
Vanessen. Archiv ges. Phys., bd. 98, pp. 1-89. 1 taf., 3 figs.

Poulton, E. B. 1903. Experiments in 1893. 1894 and 1896 upon the colour-relation between
lepidopterous larvae and their surroundings, and especially the effect of lichen-
covered bark upon Odontopera bidentata, Gastropacha quercifolia, etc. Trans.
Ent. Soc. London, pp. 311-374, pis. 16-18.

LITERATURE

373

Tower, W. L. 1903. The Development of the Colors and Color Patterns of Coleoptera,
with Observations upon the Development of Color in other Orders of Insects. Univ.
Chicago Decenn. Publ., vol. 10, pp. 1-40, pis. 1-3.

Vernon, H. M. 1903. Variation in Animals and Plants. 9 + 415 pp. New York. Henry
Holt & Co.

Enteman, W. M. 1904. Coloration in Polistes. Publ. Carnegie Inst. Washington, no. 19
88 pp., 6 pis., 26 figs.*

Von Linden, Grafin M. 1905. Physiologische Untersuchungen an Schmetterlingen.

Zeits. wiss. Zool., bd. 82, pp. 41 1-444, taf. 25.*
Friese, H., and v. Wagner, F. 1910. Zoologischen Studien an Hummeln. Zool. Jahrb.,

Abt. Syst. Geogr. Biol., bd. 29, pp. 1-104, taf. 1-7, 20 figs.*
Johnson, R. H. 1910. Determinate Evolution in the Color Pattern of the Lady Beetles.

Publ. Xo. 122, Carnegie Inst. Wash., 104 pp., 92 figs.
Gerould, J. H. 191 1. The Inheritance of Polymorphism and Sex in Colias philodice.

Amer. Nat., vol. 45, pp. 257-283, figs. 1-5.*
Gortner, R. A. 191 1. Studies on Melanin. Amer. Nat., vol. 45, pp. 743-755.*
Von Voss, H. 191 1 . Die Entwicklung der Raupenzeichnung bei einigen Sphingiden. Zool.

Jahrb., Abt. Syst. Geogr. Biol., bd. 30, pp. 573-642, taf. 16-19, 6 figs.*
Friese, H., and v. Wagner, F. 1912. Zoologische Studien an Hummeln. Zool. Jahrb.,

Supplement 15, bd. 1, pp. 155-210, taf. 5-9, 20 figs.

ADAPTIVE COLORATION
Bates, H. W. 1862. Contributions to an Insect Fauna of the Amazon Valley. Lepidop-

tera: Heliconidae. Trans. Linn. Soc. Zool., vol. 23, pp. 495-566, pis. 55, 56.
Wallace, A. R. 1867. [Theory of Warning Coloration.] Trans. Ent. Soc. London, ser. 3,

vol. 5, Proc, pp. 80-81.
Butler, A. G. 1869. Remarks upon certain Caterpillars., etc., which are unpalatable to

their enemies. Trans. Ent. Soc. London, pp. 27-29.
Trimen, R. 1869. On some remarkable Mimetic Analogies among African Butterflies.

Trans. Linn. Soc. Zool., vol. 26, pp. 497-522, pis. 42, 43.
Meldola, R. 1873. On a certain Class of Cases of Variable Protective Colouring in Insects.

Proc. Zool. Soc. London, pp. 153-162.
MuTler, F. 1879. Ituna and Thyridia; a remarkable case of Mimicry in Butterflies.

Trans., R. Meldola, Proc. Ent. Soc. London, pp. 20-29, figs- I_4-
Blackiston, T., and Alexander, T. 1884. Protection by Mimicry — A Problem in Mathe-
matical Zoology. Nature, vol. 29, pp. 405-406.
Poulton, E. B. 1884. Notes upon or suggested by the Colours, Markings and Protective

Attitudes of certain Lepidopterous Larvae and Pupae, and of a phytophagous hymen-

opterous larva. Trans. Ent. Soc. London, pp. 27-60, pi. 1.
Poulton, E. B. 1885. Further notes upon the markings and attitudes of lepidopterous

larvae. Trans. Ent. Soc. London, pp. 281-329, pi. 7.
Poulton, E. B. 1887. The Experimental Proof of the Protective Value of Colour and

Markings in Insects in reference to their Vertebrate Enemies. Proc. Zool. Soc.

London, pp. 191-274.

Wallace, A. R. 1889. Darwinism. 16 + 494 pp., 37 figs. London and New York. Mac-
millan & Co.

Poulton, E. B. 1890. The Colours of Animals. 13 + 360 pp., 1 pi., 66 figs. New York.
D. Appelton & Co.

Beddard, F. E. 1892. Animal Coloration. 8 + 288 pp., 4 pis., 36 figs. London, Swan,
Sonnenschein & Co. New York, Macmillan & Co.

374 ENTOMOLOGY

Haase, E. 1893. Untcrsuchungcn iiber die Mimicry auf Grundlage eines nattirlichen
Systems der Papilioniden. Bibl. Zool., Heft 8, Theil 1, 120 pp., 6 taf.; Theil 2, 161
pp., 8 taf. Trans. Theil 2, C. M. Child, Stuttgart, 1896, 154 pp., 8 pis.

Finn, F. 1895-97. Contributions to the Theory of Warning Colours and Mimicry. Journ.
Asiat. Soc. Bengal, vols. 64-67.

Dixey, F. A. 1896. On the Relation of Mimetic Patterns to the Original Form. Trans.
Ent. Soc. London, pp. 65-79, pis- 3~5-

Piepers, M. C. 1896. Mimetisme. Cong. Intern. Zool., 3 Sess>, Leyden, pp. 460-476.

Dixey, F. A. 1897. Mimetic Attraction. Trans. Ent. Soc. London, pp. 317-331, pi. 7.

Mayer, A. G. 1897. On the Color and Color-Patterns of Moths and Butterflies. Proc.

Bost. Soc. Nat. Hist., vol. 27, pp. 243-330, pis. 1-10. Also Bull. Mus. Comp. Zool.,
vol. 30, pp. 169-256, pis. 1-10.*

Trimen, R. 1897. Mimicry in Insects. Proc. Ent. Soc. London, pp. 74-97.*

Webster, F. M. 1897. Warning Colors, Protective Mimicry and Protective Coloration.
27th Ann. Rept. Ent. Soc. Ontario (1896), pp. 80-86, figs. 80-82.

Newbigin, M. I. 1898. Colour in Nature. 12 + 344 pp. London. John Murray.*

Poulton, E. B. 1898. Natural Selection the Cause of Mimetic Resemblance and Common
Warning Colors. Journ. Linn. Soc. Zool., vol. 26, pp. 558-612, pis. 40-44, figs. 1-7.

Judd, S. D. 1899. The Efficiency of Some Protective Adaptations in Securing Insects
from Birds. Amer. Nat., vol. 33, pp. 461-484.

Marshall, G. A. K., and Poulton, E. B. 1902. Five Years' Observations and Experi-
ments ( 1 896-1 901) on the Bionomics of South African Insects, chiefly directed to
the Investigation of Mimicry and Warning Colours. Trans. Ent. Soc. London,
pp. 287-584, pis. 9-23.

Shelf ord, R. 1902. Observations on some Mimetic Insects and Spiders from Borneo and
Singapore. Proc. Zool. Soc. London, 1902, vol. 2, pp. 230-284, pis. 19-23.

Weismann, A. 1902. Vortrage iiber Descendenztheorie. 2 vols. 12 + 456 pp., 95 figs.;
6 + 462 pp., 3 pis., 36 figs. Jena. G. Fischer. See pp. 103-133.

Piepers, M. C. 1903. Mimikry, Selektion und Darwinismus. 452 pp. Leiden. E. J.
Brill.

Poulton, E. B. 1903. Experiments in 1893, 1894 and 1896 upon the colour-relation between
lepidopterous larvae and their surroundings, and especially the effect of lichen-
covered bark upon Odontopera bidentata, Gastropacha quercifolia, etc. Trans.
Ent. Soc. London, pp. 311-374, pis. 16-18.

Packard, A. S. 1904. The Origin of the Markings of Organisms (Pcecilogenesis) due to the
Physical rather than to the Biological Environment; with Criticisms of the Bates-
Miiller Hypothesis. Proc. Amer. Phil. Soc, vol. 43, pp. 393-450.*

Marshall, G. A. K. 1908. On Diaposematism, with Reference to Some Limitations of the
Miillerian Hypothesis of Mimicry. Trans. Ent. Soc. London, pp. 93-142.

Zugmayer, E. 1908. Ueber Mimikry und verwandte Erscheinungen. Zeits. wiss. Zool.,
bd. 90, pp. 313-326.

Eltringham, H. 1909. An Account of Some Experiments on the Edibility of Certain

Lepidopterous Larvae. Trans. Ent. Soc. London, pp. 471-478.
Marshall, G. A. K. 1909. Birds as a Factor in the Production of Mimetic Resemblances

among Butterflies. Trans. Ent. Soc. London, pp. 329-383.
Moulton, J. C. 1909. On Some of the Principal Mimetic (Miillerian) Combinations of

Tropical American Butterflies. Trans. Ent. Soc. London, 1908, pp. 585-606,

pis. 30-34-

Poulton, E. B. 1909. Mimetic North American Species of the Genus Limenitis. Trans.

Ent. Soc. London, 1908, pp. 447-488, pi. 25.
Eltringham, H. 1910. African Mimetic Butterflies. 4 + 136 pp., 10 pis. Oxford.

LITERATURE

375

Punnett, R. C. 1910. "Mimicry" in Ceylon Butterflies, with a Suggestion as to the
Nature of Polymorphism. Spolia Zeylanica, vol. 7, pp. 1-24, pis. 1, 2.

Bridges, E. 191 1. Experiments in 1909 and 1910 upon the Colour Relation between
Lepidopterous Larvae and Pupae and their Surroundings. Trans. Ent. Soc. London,
pp. 136-147.

McAtee, W. L. 1912. The Experimental Method of Testing the Efficiency of Warning
and Cryptic Coloration in Protecting Animals from their Enemies. Proc. Acad.
Nat. Sc. Phila., vol. 64, pp. 281-364.*

INSECTS IN RELATION TO PLANTS

Darwin, C. 1877. The Effects of Cross and Self Fertilisation in the Vegetable Kingdom.
8 + 482 pp. New York. D. Appleton & Co.

Lubbock, J. 1882. On British Wild Flowers considered in Relation to Insects. Ed. 4.
16 + 186 pp., 130 figs. London. Macmillan & Co.

Muller, H. 1883. The Fertilisation of Flowers. 12 + 669 pp., 186 figs. London. Mac-
millan & Co.

Darwin, C. 1884. The Various Contrivances by which Orchids are fertilised by Insects.
Ed. 2. 16 + 300 pp., 38 figs. New York. D. Appelton & Co.

Darwin, C. 1884. Insectivorous Plants. 10 + 462 pp., 30 figs. New York. D. Apple-
ton & Co.

Cheshire, F. R. 1886. Bees and Bee-keeping. 2 vols. Vol. 1,7 + 336 pp., 71 figs.,

8 pis.; vol. 2, 652 pp., 127 figs., 1 pi. London. L. Upcott Gill.
Forbes, S. A. 1886. Studies on the Contagious Diseases of Insects. Bull. 111. St. Lab.

Nat. Hist., vol. 2, pp. 257-321, 1 pi.
Thaxter, R. 1888. The Entomophthoreae of the United States. Mem. Bost. Soc. Nat.

Hist., vol. 4, pp. 133-201, pis. 14-21.
Robertson, C. 1889-99. Flowers and Insects. I-XIX. Bot. Gaz., vols. 14-22, 25, 28.
Seitz, A. 1890, 1893, 1894. Allgemeine Biologie der Schmetterlinge. Zool. Jahrb.. Abth.

Syst., etc., bd. 5, pp. 281-243; bd. 7, pp. 131-186, 823-851.*
Eckstein, K. 1891. Pflanzengallen und Gallentiere. 88 pp., 4 taf. Leipzig. R. Freese.
Robertson, C. 1891-96. Flowers and Insects. Trans. Acad. Sc., St. Louis, vols. 5-7.
Cooke, M. C. 1892. Vegetable Wasps and Plant Worms. 5 + 364 pp., 4 pis., 51 figs.

London.

Riley, C. V. 1892. Some Interrelations of Plants and Insects. Proc. Biol. Soc. Wash.,

vol. 7, pp. 81-104, figs. 1-15.
Riley, C. V. 1892. The Yucca Moth and Yucca Pollination. Third Ann.. Rept. Mo. Bot.

Garden, pp. 99-158, pis. 34~43-
Moller, A. 1893. Die Pilzgarten einiger siidamericanischer Ameisen. Bot. Mitt, aus den

Tropen, heft 6. 7 + 127 pp., 7 taf., 4 figs. Jena. G. Fischer.
Trelease,W. 1893. Further Studies of Yuccas and their Pollination. Fourth Ann. Rept.

Mo. Bot. Garden, pp. 181-226, pis. 1-23.
Adler, H., and Straton, C. R. 1894. Alternating Generations. A Biological Study of

Oak Galls and Gall Flies. 40 + 198 pp., 3 pis. Oxford. Clarendon Press.*
Webster, F. M. 1894. Vegetal Parasitism among Insects. Journ. Columbus Hort. Soc,

pp. 1-19, pis. 3-5, figs. 1, 2.
Heim, F. L. 1898. The Biologic Relations between Plants and Ants. Ann. Rept. Smiths.
, Inst. 1896, pp. 411-455, pis. 17-22. Trans, from Compt. rend. 24me Sess. Ass.

fr. l'av. Sc. 1895, pp. 31-75-
Schimper, A. F. W. 1898. Pflanzen-Geographie auf physiologischer Grundlage. 18 +

876 pp., 502 figs., 5 plates, 4 maps. Jena. G. Fischer. (See pp. 147-170.)*

Trans: 1903. W. R. Fischer. Plant- Geography upon a Physiological Basis.

30 + 839 pp., 502 figs., 4 maps. Oxford, Clarendon Press. (See pp. 126-156.)*

376

ENTOMOLOGY

Benton, F. 1899. The Honey Bee: A Manual of Instruction in Apiculture. Bull. U. S.

Dept. Agric, Div. Ent., no. 1 (n. s.j, pp. 1-118, pis. 1-11, figs. 1-76.*
Needham, J. G. 1900. The Fruiting of the Blue Flag (Iris versicolor L.j. Anur. Xat.,

vol. 34, pp. 361-386, pi. 1, figs. 1-4.
Gibson, W. H. 1901. Blossom Hosts and Insect Guests. 19 + 197 pp., figs. New York.

Xewson & Co.

Connold, E. T. 1902. British Vegetable Galls. 12 + 312 pp., 130 pis., 10 figs. New

York. E. P. Dutton & Co.
Cook,M.T. 1902-04. Galls and Insects Producing Them. Pts. I-IX. Ohio Xat., vols.

2-4, pis. Same, Bull. Ohio St. Univ., ser. 6, no. 15; ser. 7, no. 20; ser. 8, no. 13.
Needham, J. G. 1903. Button-Bush Insects. Psyche, vol. 10, pp. 22-31.
Cowan, T. W. 1904. The Honey Bee: its Xatural History, Anatomy and Physiology.

Ed. 2. 12 + 220 pp., 73 figs. London. Houlston & Sons.*
Rbssig, H. 1904. Yon welchen Organen der Galhvespenlarven geht der Reiz zur Bildung

der Pflanzengalle aus? ZddI. Jahrb., Abth. Syst., etc., bi. 20, pp. 19-90, taf. 3-6.*
Casteel, D. B. 1912. The Manipulation of the Wax Scales of the Honey Bee. Circ. 161,

U. S. Dept. Agr., Bur. Ent. 13 pp., 7 figs.
Casteel, D. B. 1912. The Behavior of the Honey Bee in Pollen Collecting. Bull. 121,

U. S. Dept. Agr., Bur. Ent. 36 pp., 9 figs.*
Cosens, A. 1912. A Contribution to the Morphology and Biology of Insect Galls. Trans.

Canadian Inst., vol. 9, pp. 297-387, 13 pis., 9 figs.

IXSECTS IX RELATIOX TO OTHER AXIMALS
Aughey, S. 1878. Xotes on the Xature of the Food of the Birds of Xebraska. First

Rept. U. S. Ent. Comm., Appendix, 2, pp. 13-62.
Forbes, S. A. 1878. The Food of Illinois Fishes. Bull. 111. St. Lab. Xat. Hist., vol. 1, no.

2, pp. 71-89.

Forbes, S. A. 1880. The Food of Birds. Trans. 111. St. Hort. Soc, vol. 13 (1879), PP.
120-172.

Forbes, S. A. 1880. On Some Interactions of Organisms. Bull. 111. St. Lab. X'at. Hist.,
vol. 1, no. 3. pp. 3-17.

Forbes, S. A. 1880. The Food of Fishes. Bull. 111. St. Lab. Xat. Hist., vol. 1, no. 3, pp.

18-65.

Forbes, S. A. 1880. On the Food of Y/oung Fishes. Bull. 111. St. Lab. Nat. Hist., vol. 1,
no. 3, pp. 66-79.

Forbes, S. A. 1880. The Food of Birds. Bull. 111. St. Lab. Xat. Hist., vol. 1, no. 3, pp.
80-148.

Forbes, S. A. 1883. The Regulative Action of Birds upon Insect Oscillations. Bull.

111. St. Lab. Xat. Hist., vol. 1, no. 6, pp. 3-32.
Forbes, S. A. 1883. The Food of the Smaller Fresh-Water Fishes. Bull. 111. St. Lab.

Xat. Hist., vol. 1, no. 6, pp. 65-94.
Forbes, S. A. 1883. The First Food of the Common White-Fish. Bull. 111. St. Lab. Xat.

Hist., vol. 1, no. 6, pp. 95-109.
Dimmock, G. 1886. Belostomidae and some other Fish-destroying Bugs. Ann. Rept.

Fish Game Comm. Mass., pp. 67-74, 1 fig.*
Forbes, S. A. 1888. Studies on the Food of Fresh-Water Fishes. Bull. 111. St. Lab. Xat.

Hist., vol. 2, pp. 433-473-
Forbes, S. A. 1888. On the Food Relations of Fresh-Water Fishes: a Summary and

Discussion. Bull. 111. St. Lab. Xat. Hist., vol. 2, pp. 475-538.
Wilcox, E. V. 1892. The Food of the Robin. Bull. Ohio Agr. Exp. Sta., no. 43, pp. 115-

131-

LITERATURE

377

Beal, F. E. L. 1897. Some Common Birds in their Relations to Agriculture. Farmer's

Bull. U. S. Dept. Agric, no. 54. pp. 1-40, figs. 1-22.
Kirkland, A. H. 1897. The Habits, Food and Economic Value of the American Toad.

Bull. Hatch Exp. Sta. Mass. Agr. Coll., no. 46. pp. 3-30, pi. 2.
Judd, S. D. 1899. The Efficiency of Some Protective Adaptations in Securing Insects

from Birds. Amer. Xat.. vol. 33. pp. 461-484.
Palmer, T. S. 1900. A Review of Economic Ornithology. Yearbook U. S. Dept. Agric.

1899, pp. 259-292.

Judd, S. D. 1901. The Food of Nestling Birds. Yearbook U. S. Dept. Agric. 1900, pp.

411-436, pis. 49-53, ngs. 48-56.
Forbes, S. A. 1903. Studies of the Food of Birds, Insects and Fishes. Second Ed. Bull.

111. St. Lab. Xat. Hist., vol. 1, no. 3.
Weed, C. M., and Dearborn, N. 1903. Birds in their Relations to Man. 8 + 380 pp.,

figs. Philadelphia and London. J. B. Lippincott Co.*

INSECTS IX RELATIOX TO DISEASES
Blandford, W. F. H. 1896. The Tsetse fly-disease. Xature, vol. 53, pp. 566-568, figs.
1, 2.

Sternberg, G. M. 1897. The Malarial Parasite and other Pathogenic Protozoa. Pop.

Sc. Mon., vol. 50, pp. 628-641, figs. 1-3.
Kanthack, A. A., Durham, H. E., and Blandford, W. F.H. 1898. On Xagana, or Tsetse

fly disease. Proc. Roy. Soc. Lond., vol. 64, pp. 100-118.
Finlay, C. J. 1899. Mosquitoes considered as Transmitters of Yellow Fever and Malaria.

Psyche, vol. 8, pp. 379-384.
Nuttall, G. H. F. 1899. On the role of Insects. Arachnids and Myriapods, as carriers in

the spread of Bacterial and Parasitic Diseases of Man and Animals. A Critical and

Historical Study. Johns Hopk. Hosp. Rept., vol. 8, no. 1, 154 pp., 3 pis.
Ross, R. 1899. Life-History of the Parasites of Malaria. Xature, vol. 60, pp. 322-324.
Christy, C. 1900. Mosquitos and Malaria: a summary of knowledge on the subject up

to date; with an account of the natural history of mosquitos. 9 + 80 pp., 5 pis.

London.

Howard, L. O. 1900. Xotes on the Mosquitoes of the United States: giving some account

of their structure and biology, with remarks on remedies. Bull. U. S. Dept. Agric,

Div. Ent., no. 25 (n. s.), 70 pp., 22 figs.
Howard, L. O. 1900. A contribution to the study of the insect fauna of human excrement

(with especial reference to the spread of typhoid fever by flies). Proc. Wash. Acad.

Sc., vol. 2, pp. 541-604, pis. 30, 31, figs. 17-38.
Ross, R. 1900. Malaria and Mosquitoes. Xature, vol. 61, pp. 522-527.
Ross, R., and Fielding-Ould, R. 1900. Diagrams illustrating the Life-history of the

Parasites of Malaria. Quart. Journ. Micr. Sc., vol. 43 (n. s.), pp. 571-579, pis. 30, 31.
Grassi, B. 1901. Die Malaria-Studien eines Zoologen. 8 + 250 pp., 8 taf. Jena. G.

Fischer.

Howard, L. O. 1901. Mosquitoes; how they live; how they carry disease; how they are

classified; how they may be destroyed. 15 + 241 pp., 50 figs., 1 pi. Xew York.

McClure, Phillips & Co.
Sternberg, G. M. 1901. The Transmission of Yellow Fever by Mosquitoes. Pop. Sc.

Mon., vol. 59, pp. 225-241.
Howard, L. O. 1902. Insects as Carriers and Spreaders of Disease. Year-book U. S.

Dept. Agric. 1901, pp. 177-192, figs. 5-20.
Braun, M. 1903. Die thierischen Parasiten des Menschen. Rev. Ed. 12 + 360 pp.,

272 figs. Wiirzburg.

378

KN TO MO LOGY

Sternberg, G. M. 1903. Infection and Immunity; with special Reference to the Preven-
tion of Infectious Diseases. 5 + 293 pp., 12 figs. New York and London. G. P.
Putnam's Sons.

Blanchard, R. 1905. Les Moustiques, histoire naturelle et medicale. 673 pp., 316 figs.
Paris. De Rudeval.

Austen, E. E. 1903. A Monograph of the Tsetse Flies. 9 + 319 pp., 9 pis. London.
British Museum.

Braun, M. 1906. The Animal Parasites of Man. Trans. Sambon and Theobald. 19 +

453 PP-> 294 ngs- New Y'ork. Wm. Wood & Co.
Bruce, D. 1907. Trypanosomiasis. In Osier's Modern Medicine, vol. 1, pp, 460-487,

figs. 31-34, pi. 4. Phila. and New York. Lea Bros. & Co.
Calvert, W. J. 1907. Plague. In Osier's Modern Medicine, vol. 2, pp. 760-780. Phila.

and New Y'ork. Lea Bros. & Co.
Carroll, J. 1907. Yellow Fever. In Osier's Modern Medicine, vol. 2, pp. 736-759.

Phila. and New York. Lea Bros. & Co.
Craig, C. F. 1907. The Malarial Fevers. In Osier's Modern Medicine, vol. 1, pp., 392-

448, figs. 26-30, pis. 1-3. Phila. and New Y^ork. Lea Bros. & Co.
Griinberg,K. 1907. Die blutsaugenden Dipteren. 6 +188 pp. Jena. G.Fischer.
Jackson, T. W. 1907. Tropical Medicine. 8 + 536 pp., 106 figs. Phila. P. Blakiston's

Son & Co.

Laveran, A., and Mesnil, F. 1907. Trypanosomes and Trypanosomiases. Trans. D.

Nabarro. 19 + 538 pp., 81 figs., 1 pi. London. Bailliere, Tindall & Co.*
Mitchell, E. G. 1907. Mosquito Life. 22 + 281 pp., 54 figs. New Y^ork and London.

G. P. Putnam's Sons.

Stephens, J. W. W., and Christophers, S. R. 1908. The Practical Study of Malaria and
Other Blood Parasites, Ed. 3. 18 + 414 pp., 128 figs. London. Williams and
Norgate.

Boyce, R. W. 1909. Mosquito or Man? The Conquest of the Tropical World. 16 +

267 pp., 44 figs. London. John Murray.
Calkins, G. N. 1909. Protozoology. 9 + 349 PP-, 125 figs., 4 pis. New York and

Phila., Lea & Febiger.*

Thimm, C. A. 1909. Bibliography of Trypanosomiasis. 228 pp. London. Sleeping
Sickness Bureau.

Braun, M., and Luhe, M. 1910. A Handbook of Practical Parasitology. Tr. L. Forster.

8 + 208 pp., 100 figs. London. John Bale, Sons & Danielsson.
Doane, R. W. 1910. Insects and Disease. 14 + 227 pp., 112 figs., 1 pi. New York.
Henry Holt & Co.*

Austen, E. E. 191 1. A Handbook of the Tsetse-flies (Genus Glossina) 10 + no pp.,

10 pis. London. British Museum.
Doane, R. W. 191 1, 1912. An Annotated List of the Literature on Insects and Disease. «

Journ. Econ. Ent., vol. 4, pp. 386-398; vol. 5, pp. 268-285.
Howard, L. O. 191 1. The House Fly; Disease Carrier. 19 + 312 pp., 40 figs., 1 pi.

New Y'ork. F. A. Stokes Co.*
Manson, P. 191 1. Tropical Diseases. Ed. 4. 20 + 876 pp., 241 figs., 7 pis. London

and New York. Cassell & Co.
Reed, W., Carroll, J., Gorgas, W. C, and Others. 1911. Yellow Fever; a Compilation

of Various Publications. Doc. No. 822, U. S. Senate, 61st Congress. 250 pp., 7 figs.,

5 pis. Washington. Govt. Printing Office.
Brues, C. T. 1913. The Relation of the Stable Fly (Stomoxys calcitrans) to the Trans-
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INTERRELATIONS OF INSECTS
Van Beneden, P. J. 1876. Animal Parasites and Messmates. 28 + 274 pp., 83 figs.

New York. D. Appleton & Co.
McCook, H. C. 1877. Mound-making Ants of the Alleghenies, their Architecture and

Habits. Trans. Amer. Ent. Soc, vol. 6, pp. 253-296, figs. 1-13.
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des insectes. 9 Series. Paris. C. Delagrave. Trans, of Ser. I: 1901. Fabre,

J. H. Insect Life. 1 2 + 320 pp., 16 pis. London and New York. The Macmillan

Co.

Forbes, S. A. 1880. Notes on Insectivorous Coleoptera. Bull. 111. St. Lab. Nat. Hist.,

vol. 1, no. 3, pp. 153-169. Second Ed., 1903.
McCook, H. C. 1880. The Natural History of the Agricultural Ant of Texas. 310 pp.,

24 pis. Philadelphia. J. B. Lippincott & Co.
Webster, F. M. 1880. Notes upon the Food of Predaceous Beetles. Bull. 111. St. Lab.

Nat. Hist., vol. 1, no. 3, pp. 149-152. Second Ed., 1903.
McCook, H. C. 1881. Note on a new Northern Cutting Ant, Atta septentrionalis. Proc.

Acad. Nat. Sc. Phila. 1880, pp. 359-363, 1 fig.
McCook, H. C. 1881. The. Shining Slavemaker. Notes on the Architecture and Habits

of the American Slave-making Ant., Polyergus lucidus. Proc. Acad. Nat. Sc. Phila.

1880, pp. 376-384, pi. 19.
Lubbock, J. 1882, 1902, 1904. Ants, Bees and Wasps. 19 + 448 pp., 31 figs., 5 pis.

New York. D. Appleton & Co.
McCook, H. C. 1882. The Honey Ants of the Garden of the Gods, and the Occident Ants

of the American Plains. 188 pp., 13 pis. Philadelphia. J. B. Lippincott & Co.
Forbes, S. A. 1883. The Food Relations of the Carabidae and Coccinellidae. Bull. 111.

St. Lab. Nat. Hist., vol. 1, no. 6, pp. 33-64.
Cheshire, F. R. 1886. Bees and Bee-keeping. 2 vols. Vol. 1, 7 + 336 pp., 8 pis., 71

figs.; vol. 2, 652 pp., 127 figs., 1 pi. London. L. Upcott Gill.
Seitz, A. 1890, 1893, 1894. Allgemeine Biologie der Schmetterlinge. Zool. Jahrb., Abth.

Syst., etc., bd. 5, pp. 281-343; bd. 7, pp. 131-186, 823-851.*
Verhoeff, C. 1892. Beitrage zur Biologie der Hymenoptera. Zool. Jahrb., Abth. Syst.,

etc., bd. 6, pp. 680-754, taf. 30, 31.
Wasmann, E. 1984. Kritisches Yerzeichnis der myrmekophilen und termitophilen Arthro-

poden. 231 pp. Berlin. F. L. Dames.
Grassi, B., and Sandias, A. 1896-97. The Constitution and Development of the Society

of Termites, etc. Trans, by W. F. H. Blandford. Quart. Journ. Micr. Sc., vol. 39.

pp. 245-322, pis. 16-20; vol. 40, pp. 1-75.
Janet, C. 1896. Les Fourmis. Bull. Soc. zool. France, vol. 21, pp. 60-93. Sep., 37 pp.,

Paris.

Howard, L. O. 1897. A Study in Insect Parasitism. Bull. U. S. Dept. Agric, Div. Ent.,

tech. ser. no. 5, pp. 1-57. figs. 1-24.
Peckham, G. W., and E. G. 1898. On the Instincts and Habits of the Solitary Wasps.

Bull. Wis. Geol. Nat. Hist. Surv., no. 2, sc. ser. no. 1,4+ 245 pp., 14 pis.
Wasmann, E. 1898. Die Gaste der Ameisen und Termiten. Illustr. Zeits. Ent., bd. 3,

-1 taf.

Benton, F. 1899. The Honey Bee: A Manual of Instruction in Apiculture. Bull. U. S.

Dept. Agric, Div. Ent., no. 1 (n. s.), pp. 1-118, pis. 1-11, figs. 1-76.*
Fielde, A. M. 1901. A Study of an Ant. Proc. Acad. Nat. Sc. Phila., vol. 53, pp. 425-

449.

Fielde, A. M. 1901. Further Study of an Ant. Proc. Acad. Nat. Sc. Phila., vol. 53, pp.
521-544-

38o

ENTOMOLOGY

Wheeler, W. M. 1901. The Compound and Mixed Nests of American Ants. Amer. Nat.,

vol. 35, pp. 431, 513, 701. 791, figs. 1-20.
Enteman, M. M. 1902. Some Observations on the Behavior of the Social Wasps. Pop.

Sc. Mon., vol. 61, pp. 339-351-
Fielde, A. M. 1902. Notes on an Ant. Proc. Acad. Xat. Sc. Phila., vol. 54, pp. 599-625.
Dickel, F. 1903. Die Ursachen der geschlechtlichen DirTerenzirung im Bienenstaat.

Archiv. ges. Phys., bd. 95, pp. 66-106, fig. 1.
Fielde, A. M. 1903. Supplementary Notes on an Ant. Proc. Acad. Nat. Sc. Phila., vol.

55, PP- 491-495-

Heath, H. 1903. The Habits of California Termites. Biol. Bull., vol. 4, pp. 47-63, figs.
i-3-

Janet, C. 1903. Observations sur les guepes. 85 pp., 30 figs. Paris. C. Naud.
Melander, A. L., and Brues, C. T. 1903. Guests and Parasites of the Burrowing Bee

Halictus. Biol. Bull., vol. 5, pp. 1-27, figs. 1-7.
Fielde, A. M. 1904. Power of Recognition among Ants. Biol. Bull., vol. 7, pp. 227-250,

4 ngs.

Fielde, A. M., and Parker, G. H. 1904. The Reactions of Ants to Material Vibrations.

Proc. Acad. Nat. Sc. Phila., vol. 56, pp. 642-650.*
Wheeler, W. M. 1904. A New Type of Social Parasitism among Ants. Bull. Amer.

Mus. Nat. Hist., vol. 20, pp. 347-375.
Emery, C. 1904. Zur Kenntniss des Polymorphismus der Ameisen. Zool. Jahrb., Sup-
plement, bd. 7, pp. 587-610, 6 figs.
Forel, A. 1904. Ueber Polymorphismus und Variation bei den Ameisen. Zool. Jahrb.,

Supplement, bd. 7, pp. 571-586.
Holmgren, N. 1906. Studien iiber sudamerikanische Termiten. Zool. Jahrb., Abt.

Anat. Ont., bd. 23, pp. 521-676, 81 figs.*
Wheeler, W. M. 1906. The Habits of the Tent-building Ant (Cremastogaster lineolata

Say). Bull. Amer. Mus. Nat. Hist., vol. 22, pp. 1-18, pis. 1-6.
Wheeler, W. M. 1906. On the Founding of Colonies by Queen Ants, etc. Bull. Amer.

Mus. Nat. Hist., vol. 22, pp. 33-105, pis. 8-14.
Wheeler, W. M. 1907. The Polymorphism of Ants, with an Account of Some Singular

Abnormalities due to Parasitism. Bull. Amer. Mus. Nat. Hist., vol. 23, pp. 1-93,

pis. 1-6.

Wheeler, W. M. 1907. The Fungus-growing Ants of North America. Bull. Amer. Mus.

Nat. Hist., vol. 23, pp. 669-807, pis. 49-53, 31 figs.*
Pricer, J. L. 1908. The Life History of the Carpenter Ant. Biol. Bull., vol. 14, pp. 177-

218, figs. 1-7.*

Donisthorpe, J. K. 1910. Some Experiments with Ants' Nests. Trans. Ent. Soc.
London, pp. 142-150.

Wheeler, W. M. 1910. Ants; their Structure, Development and Behavior, xxv + 663

pp., 286 figs., 1 pi. New York. Columbia Univ. Press.*
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INSECT BEHAVIOR
Pouchet, G. 1872. De l'mfluence de la lumiere sur les larves de dipteres privees d'organes

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des insectes. 9 Series. Paris. C. Delagrave. Trans, of Ser. I: 1901. Fabre,

J. H. Insect Life. 12 + 320 pp., 16 pis. London and New York. The Mac-

millan Co.

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York. D. Appleton & Co.
Graber, V. 1884. Grundlinien zur Erforschung des Helligkeits- und Farbensinnes der

Tiere. 8 + 322 pp. Prag und Leipzig.
Romanes, G. J. 1884. Animal Intelligence. 14 + 520 pp. New York. D. Appleton

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Lubbock, J. 1888. On the Senses, Instincts and Intelligence of Animals, with Special
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Plateau, F. 1889. Recherches experimentales sur la Yision chez les Arthropodes. Mem.
cour. Acad. roy. Belgique, t. 43, pp. 1-9 1.

Eimer, G. H. T. 1890. Organic Evolution as the Result of the Inheritance of Acquired
Characters according to the Laws of Organic Growth. 28 + 435 pp. Trans, by
J. T. Cunningham. London and New York. Macmillan & Co.

Loeb, J. 1890. Der Heliotropismus der Thiere und seine Uebereinstimmung mit dem
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Seitz, A. 1890. Allgemeine Biologie der Schmetterlinge. Zool. Jahrb., Abth. Syst., bd.
5, pp. 281-343-

Exner, S. 1891. Die Physiologie der facettirten Augen von Krebsen und Insecten. 8 +

206 pp., 8 taf., 23 figs. Leipzig und Wien.
Loeb, J. 1891. Leber Geotropismus bei Thieren. Arch. ges. Phys., bd. 49, pp. 175-189,

figs-

Morgan, C. Lloyd. 1891. Animal Life and Intelligence. 13 + 512 pp., 40 figs. Boston.
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James, W. 1893. The Principles of Psychology. 2 vols. 18 + 1393 pp., 94 figs. Xew

York. Henry Holt & Co.
Loeb, J. 1893. Leber kiinstliche Umwandlung positiv heliotropischer Thiere in negativ

heliotropische und umgekehrt. Arch. ges. Phys., bd. 54. pp. 81-107.
Baldwin, J. M. 1896. Heredity and Instinct. Science, vol. 3 (n. s.), pp. 438-441, 558—

561.

Morgan, C. Lloyd. 1896. Habit and Instinct. 351 pp. London and Xew York. E.
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Davenport, C. B. 1897, 1899. Experimental Morphology. 2 Pts. 32 + 508 pp., 140

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Loeb, J. 1897. Zur Theorie der physiologischen Licht- und Schwerkraftwirkungen.

Arch, ges Phys., bd. 64, pp. 439-466.
Bethe, A. 1898. Diirfen wir den Ameisen und Bienen psychische Qualitaten zuschreiben?

Archiv ges. Phys., bd. 70. pp. 1 5-1 10. taf. 1, 2, 5 figs.
Peckham, G. W., and E. G. 1898. On the Instincts and Habits of the Solitary Wasps.

Bull. Wis. Geol. Xat. Hist. Surw, no. 2, sc. ser. no. 1. 4 + 245 pp., 14 pis.
Verworn, M. 1899. General Physiology. An Outline of the Science of Life. Trans.

by F. S. Lee. 16 + 615 pp., 285 figs. London and Xew York. Macmillan & Co.
Wasmann, E. 1899. Die psychischen Fahigkeiten der Ameisen. Zoologica, heft 26,

6 + 132 pp., 3 taf. Stuttgart. E. Xagele.
Wheeler, W.M. 1899. Anemotropism and Other Tropisms in Insects. Arch. Entw. Org.,

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Whitman, C. O. 1899. Animal Behavior. Biol. Lect., Marine Biol. Lab., Woods Hole,

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Loeb, J. 1900. Comparative Physiology of the Brain and Comparative Psychology. 309

pp., 39 figs. Xew York, G. P. Putnam's Sons. London, J. Murray.*
Morgan, C. Lloyd. 1900. Animal Behaviour. 8 + 344 pp., 26 figs. London. E.

Arnold.

3«2

entomology

Radl, E. 1901. Ueber den Phototropismus ciniger Arthropoden. Biol. Centralb., bd. 21,

pp. 75-86.

Radl, E. 1901. Untcrsuchungen iiber die Lichtreactionen der Arthropoden. Arch. ges.

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Enteman, M. M. 1902. Some Observations on the Behavior of the Social Wasps. Pop.

Sc. Mon., vol. 61, pp. 339-35I-
Weismann, A. 1902. Yortrage iiber Descendenztheorie. 2 vols. 12 + 456 pp., 95 figs.;

6 -f- 462 pp., 3 pis., 36 figs. Jena. G. Fischer. See pp. 159-181.
Kathariner, L. 1903. Versuche iiber die Art der Orientierung bei der Honigbiene. Biol.

Centralb., bd. 23, pp. 646-660, 1 fig.
Kellogg, V. L. 1903. Some Insect Reflexes. Science, vol. 18 (n. s.), pp. 693-696.
Morgan, T. H. 1903. Evolution and Adaptation. 13 + 470 pp., 5 figs. New York and

London. The Macmillan Co.
Parker, G. H. 1903. The Phototropism of the Mourning-cloak Butterfly, Vanessa antiopa

Linn. Mark Anniv. Vol., pp. 453-469, pi. 33.*
Fielde, A. M., and Parker, G. H. 1904. The Relations of Ants to Material Vibrations.

Proc. Acad. Nat. Sc. Phila., vol. 56, pp. 642-650.*
Forel, A. 1904. The Psychical Faculties of Ants and some other Insects. Ann. Rept.

Smiths. Inst. 1903, pp. 587-599. Trans, from Proc. Fifth Intern. Zool. Congr.

Berlin, 1901, pp. 141-169.
Jennings, H. S. 1904. Contributions to the Study of the Behavior of Lower Organisms.

256 pp., 81 figs. Carnegie Inst. Washington.*
Carpenter, F. W. 1905. The Reactions of the Pomace Fly (Drosophila ampelophila Loew)

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Hartman, C. 1905. Observations on the Habits of some Solitary Wasps of Texas. Bull.

Univ. Texas, no. 65, sc. ser. no. 7, pp. 1-73, 4 pis.
Holmes, S. J. • 1905. The Reactions of Ranatra to Light. Journ. Comp. Neur. Psych.,

vol. 15, pp. 305-349, figs- 1-6.
Loeb, J. 1905. Studies in General Physiology. 2 vols. 24 + 782 pp., 162 figs. Univ.

Chicago Decenn. Publ., ser. 2, vol. 15, pts. 1, 2.
Wasmann, E. 1905. Comparative Studies in the Psychology of Ants and of Higher Ani-
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Holmes, S. J. 1906. Death-feigning in Ranatra. Journ. Comp. Xeur. Psych., vol. 16,
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Barrows, W. M. 1907. The Reactions of the Pomace Fly, Drosophila ampelophila Loew,
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Herms, W. B. The Photic Reactions of Sarcophagid Flies, etc. Journ. Exp. Zool., vol. 10,
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GEOGRAPHICAL DISTRIBUTION
Darwin, C. 1859, 1869. On the Origin of Species by means of Natural Selection. Pp.

11 + 440. New York. D. Appleton & Co. See pp. 302-357.
LeConte, J. L. 1859. The Coleoptera of Kansas and Eastern New Mexico. Smithson.

Contrib., vol. 11. 6 + 58 pp., 2 pis., map.
Bates, H.W. 1864. The Naturalist on the River Amazons. 12 -f 466 pp., figs. London.

J. Murray.

Wallace, A. R. 1865. On the Phenomena of Variation and Geographical Distribution as
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383

Wallace, A. R. 1869. The Malay Archipelago. 12 + 638 pp., 51 figs., 10 maps. New

York. Harper & Bros.
Murray, A. 1873. On the Geographical Relations of the Chief Coleopterous Faunae.

Journ. Linn. Soc. Zool., vol. 11, pp. 1-89.
Belt, T. 1874, 1888. The Naturalist in Nicaragua. 32 + 403 pp., figs. London. J.

Murray; E. Bumpus.

Wallace, A. R. 1876. The Geographical Distribution of Animals. 2 vols. Vol. 1,21 +
503 pp., 13 pis., 5 maps; vol. 2, 8 + 607 pp., 7 pis., 2 maps. New York. Harper &
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Semper, K. 1881. Animal Life as affected by the Natural Conditions of Existence. 16 +

472 pp., 106 figs., 2 maps. New York. D. Appleton & Co.
Wallace, A. R. 1881. Island Life, or the Phenomena and Causes of Insular Faunas and

Floras, etc. 16 + 522 pp., 26 maps and figs. New York. Harper & Bros.
Gill, T. 1884. The Principles of Zoogeography. Proc. Biol. Soc. Wash., vol. 2, pp. 1-39.
Forbes, H. O. 1885. A Naturalist's Wanderings in the Eastern Archipelago. 19 +536

pp., figs., pis., maps. New York. Harper & Bros.
Schwarz, E. A. 1888. The Insect Fauna of Semitropical Florida, with Special Regard to

the Coleoptera. Ent. Amer., vol. 4, pp. 165-175.
Merriam, C. H. 1890. Results of a Biological Survey of the San Francisco Mountain

Region and Desert of the Little Colorado, Arizona. U. S. Dept. Agric, Div. Ornith.

Mamm., N. A. Fauna, no. 3, 6 + 136 pp., 13 pis., 5 maps, 2 figs.
Schwarz, E. A. 1890. On the Coleoptera common to North America and other Countries.

Proc. Ent. Soc. Wash., vol. 1, pp. 182-194.
Seitz, A. 1890, 1893, 1894. Allgemeine Biologie der Schmetterlinge. Zool. Jahrb., Abth.

Syst., etc., bd. 5, pp. 281-343; bd. 7, pp. 131-186, 823-851.*
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Paris.

Wallace, A. R. 1890. A Narrative of Travels on the Amazon and Rio Negro, etc. Ed. 3.

14 + 363 pp., 16 pis. London, New York and Melbourne. Ward, Lock & Co.
Packard, A. S. 1891. The Labrador Coast. 513 pp., figs. New York. N. D. C. Hodges.
Bates, H. W. 1892. The Naturalist on the River Amazons. Reprint. 89 + 395 pp.,

figs. London. J. Murray.
Distant, W. L. 1892. A Naturalist in the Transvaal. 16 + 277 pp., pis., figs. London.

R. H. Porter.

Hudson, W. H. 1892. The Naturalist in La Plata. 8 + 388 pp., figs. London. Chap-
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Webster, F. M. 1892. Modern Geographical Distribution of Insects in Indiana. Proc.

Ind. Acad. Sc., pp. 8 1-88 , map.
Merriam, C. H. 1893. The Geographic Distribution of Life in North American, with

special Reference to the Mammalia. Smithson. Rept. 1891, pp. 365-415. From

Proc. Biol. Soc. Wash., vol. 7, pp. 1-64.
Elwes, H. J. 1894. The Geographical Distribution of Butterflies. Trans. Ent. Soc.

London. Proc, pp. 52-84.
Hamilton, J. 1894. Catalogue of the Coleoptera common to North America, Northern

Asia and Europe, with Distribution and Bibliography. Trans. Amer. Ent. Soc,

vol. 21, pp. 345-416 + 19-
Merriam, C. H. 1894. Laws of Temperature Control of the Geographic Distribution of

Terrestrial Animals and Plants. Nat. Geogr. Mag., vol. 6, pp. 229-238, 3 maps.
Scudder, S. H. 1894. The Effect of Glaciation and of the Glacial Period on the Present

Fauna of North America. Amer. Journ. Sc., ser. 3, vol. 48, pp. 179-187.
Webster, F. M. 1894. Some Insect Immigrants in Ohio. Bull. Ohio Agr. Exp. Sta.,

ser. 2, vol. 6, no. 51 (1893), pp. 1 18-129, figs. 17, 18.

3^4

ENTOMOLOGY

Whymper, E. 1894. Travels amongst the Great Andes of the Equator. 24 -f 456 pp.,

20 pis.. 4 maps, 1 18 figs. New York. C. Scribner's Sons. 1891. Suppl. Appendix.

22 -f- 147 pp.. figs. London. J. Murray.
Beddard, F. E. 1895. A Text-book of Zoogeography. 8 + 246 pp., 5 maps. Cambridge,

Eng. University Press.
Howard, L. O. 1895. Notes on the Geographical Distribution within the United States

of certain Insects injuring Cultivated Crops. Proc. Ent. Soc. Wash., vol. 3, pp.

219-226.

Webster, F. M. 1895. Notes on the Distribution of some Injurious Insects. Proc. Ent.

Soc. Wash., vol. 3, pp. 284-290.
Webster, F. M. 1896. The Probable Origin and Diffusion of Blissus leucopterus and

Murgantia histrionica. Journ. Cine. Soc. Nat. Hist., vol. 18, pp. 141-155. fig. 1, pi.

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Carpenter, G. H. 1897. The Geographical Distribution of Dragon-flies. Proc. Roy.

Dublin Soc. vol. 8. pp. 439-468, pi. 17.
Heilprin, A. 1897. The Geographical and Geological Distribution of Animals. 12 + 435

pp., map. New York. D. Appleton & Co.
Saville-Kent, W. 1897. The Naturalist in Australia. 15 + 302 pp.. 50 pis.. 104 figs.

London. Chapman & Hall.
Webster, F. M. 1897. Biological Effects of Civilization on the Insect Fauna of Ohio.

Fifth Ann. Rept. Ohio St. Acad. Sc., pp. 32-46, 2 figs.
Merriam, C.H. 1898. Life Zones and Crop Zones of the United States. Bull. U. S. Dept.

Agric, Div. Biol. Surv.. no. 10, pp. 1-79. map.
Webster, F. M. 1898. The Chinch Bug. Bull. U. S. Dept. Agric, Div. Ent., no. 15

(n. s.), 82 pp., 19 figs. (See pp. 66-82.)
Semon, R. 1899, In the Australian Bush and on the Coast of the Coral Sea, etc 15 +

552 pp., 4 maps, 86 figs. London and Xew Y'ork. Macmillan & Co.
Tower, W. L. 1900. On the Origin and Distribution of Leptinotarsa decem-lineata Say,

and the Part that some of the Climatic Factors have played in its Dissemination.

Proc Amer. Ass. Adv. Sc., vol. 49, pp. 22^-22-.
Adams, C. C. 1902. Postglacial Origin and Migrations of the Life of the Northeastern

United States. Journ. Geogr., vol. 1, pp. 303-310. 352-357. map.
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Ent. Soc. Ontario (1901), pp. 63-67, maps 1-3.
Webster, F. M. 1902. Winds and Storms as Agents in the Diffusion of Insects. Amer.

Nat., vol. 36. pp. 795-801.
Webster, F. M. 1903. The Diffusion of Insects in North America. Psyche, vol. 10. pp.

47-58. pi. 2.

Jacobi, A. 1904. Tiergeographie. 152 pp.. 2 maps. Leipzig.

Morse, A. P. 1904. Researches on North American Acridiida?. Publ. Xo. 18, Carnegie

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551-618, 19 figs.

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GEOLOGICAL DISTRIBUTION'

Herr, O. 1847-53. Die Insectenfauna der Tertiargebilde von (Eningen und von Radoboj
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Scudder, S. H. 1885. The Earliest Winged Insects of America: a Re-examination of the
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Scudder, S. H. 1885. Systematische Uebersicht der fossilen Myriopoden, Arachnoideen
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Scudder, S. H. 1886. The Cockroach of the Past. In L. C. Miall and A. Denny. The
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Scudder, S. H. 1886. Systematic Review of our Present Knowledge of Fossil Insects.

Bull. U. S. GeoL Surv., no. 31, 128 pp. Washington.
Scudder, S. H. 1889. The Fossil Butterflies of Florissant. Eighth Ann. Rept. Dir. U. S.

Geol. Surv., pp. 433-474, pi. 53. Washington.
Scudder, S. H. 1890. The Work of a Decade upon Fossil Insects. Psyche, vol. 5, pp.

287-295.

Scudder, S. H. 1890. A Classed and Annotated Bibliography of Fossil Insects. Bull.

U. S. Geol. Surv., no. 69, 101 pp. Washington.*
Scudder, S. H. 1890. The Tertiary Insects of North America. U. S. Geol. Surv. Terr.,

vol. 13, 734 pp., 28 pis., 1 map, 3 figs. Washington.
Scudder, S. H. 1891. Index to the Known Fossil Insects of the World, including Myria-

pods and Arachnids. Bull. U. S. Geol. Surv., no. 71, 744 pp. Washington.*
Scudder, S. H. 1892. Some Insects of Special Interest from Florissant, Colorado, and

other Points in the Territories of Colorado and Utah. Bull. U. S. Geol. Surv., no.

93, 35 PP-, 3 pis. Washington.
Scudder, S. H. 1893. Insect Fauna of the Rhode Island Coal Field. Bull. U. S. Geol.

Sun.-., no. 101, 27 pp., 2 pis. Washington.
Scudder, S. H. 1893. The American Tertiary Aphidae, with a List of the Known Species

and Tables for their Determination. Thirteenth Ann. Rept. U. S. Geol. Surv., pt.

2, pp. 341-372, pis. 102-106. Washington.
Scudder, S. H. 1893. Tertiary Rhynchophorous Coleoptera of the United States. Mon-

ogr. U. S. Geol. Surv., vol. 21, 11 -f 206 pp., 12 pis. Washington.
Brongniart, C. 1894. Recherches pour servir a l'histoire des insectes fossiles des temps

primaires, etc. 2 vols. 537 pp., 37 pis. St. Etienne.
Scudder, S. H. 1894. Tertiary Tipulidae, with Special Reference to those of Florissant,

Colorado. Proc. Amer. Phil. Soc, vol. 32, 83 pp., 9 pis.
Scudder, S. H. 1896. Revision of the American Fossil Cockroaches, with Descriptions of

New Forms. Bull. U. S. Geol. Sun-., no. 124, 176 pp., 12 pis. Washington.
Goss, H. 1900. The Geological Antiquity of Insects. Ed. 2. 4 + 52 pp. London.

Gurney & Jackson.*

Scudder, S. H. 1900. Adephagous and Clavicorn Coleoptera from the Tertiary Deposits
at Florissant, Colorado, etc. Monogr. U. S. Geol. Surv., vol. 40, 148 pp., n pis.
Washington.
26

386

ENTOMOLOGY

Scudder, S. H. 1900. Canadian Fossil Insects. 4. Additions to the Coleopterous Fauna
of the Interglacial Clays of the Toronto District, etc. Contrib. Can. Pal., Geol.
Sun*. Can., vol. 2, pp. 67-92, pis. 6-15. Ottawa.

INSECTS IN RELATION TO MAN
Harris, T. W. 1862. A Treatise on Some of the Insects Injurious to Vegetation. Third

Ed. 11 + 640 pp., 278 figs., 8 pis. Boston.
Lintner, J. A. 1882. Importance of Entomological Study, etc. First Ann. Rept. Inj.

Ins., pp. 1-80, figs. 1-12.
Saunders, W. 1883. Insects Injurious to Fruits. 436 pp., 440 figs. Philadelphia. J. B.

Lippincott & Co.

Henshaw, S., and Banks, N. 1889-1901. Bibliography of the more important Contribu-
tions to American Economic Entomology. 8 pts. 13 18 pp. Washington.*

Packard, A. S. 1889. Guide to the Study of Insects. Ed. 9. 12 + 715 pp., 668 figs.,
1 5 pis. New York. Henry Holt & Co.

Howard, L. O. 1894. A Brief Account of the Rise and Present Condition of Official Eco-
nomic Entomology. Insect Life, vol. 7, pp. 55-107.

Sempers, F. W. 1894. Injurious Insects and the Use of Insecticides. 10 + 216 pp., 1 pi.,
184 figs. Philadelphia. W. A. Burpee & Co.

Smith, J. B. 1896. Economic Entomology for the Farmer and Fruit-Grower, etc. Pp.
12 + 11-481, 483 figs. Philadelphia. J. B. Lippincott Co.

Howard, L. O. 1899. The Economic Status of Insects as a Class. Science, vol. 9 (n. s.),
pp. 233-247.

Theobald, F. V. 1899. A Text-Book of Agricultural Zoology. 17 + 51 1 PP-> 225 figs.

Edinburgh and London. Wm. Blackwood & Sons.
Howard, L. O. 1900. Progress in Economic Entomology in the United States. Yearbook

U. S. Dept. Agric, 1899, pp.' 135-156, pi. 3.
Sanderson, E. D. 1902. Insects Injurious to Staple Crops. 10 + 295 pp., 163 figs. New

Y/ork. John Wiley & Sons.
O'Kane, W. C. 1912. Injurious Insects; How to Recognize and Control Them. 11 -r

414 pp., 606 figs. Xew Y'ork. Macmillan Co.
Sanderson, E. D. 1912. Insect Pests of Farm, Garden and Orchard, 12 -f 684 pp., 513

figs. Xew Y'ork. John Wiley & Sons.
Most of the literature on the economic entomology of the United States is contained in the
following works: Reports L\ S. Ent. Comm.; Repts. Govt. Entomologists; Bulletins U. S.
Dept. Agric, Bur. Ent.; Insect Life; Reports and Bulletins by the several State Entomolo-
gists; Bulletins of the various Experiment Stations; Journal of Economic Entomology.

INDEX

An asterisk * denotes an illustration.

Abdomen, 51; appendages of, *53, *I2I,
*i22; extremity, 54; modifications, 52;
segments, 52

Acacia, *2iz

Accessory glands, *H3, *H4
Acerentomon, 5
Achorutes, *8

Acridiidae, *8; moults of, 133; spiracles, 52
.Acridium, 21; respiratory muscles of, *ii2
Aculeata, 17

Adams, on dispersal, 317, 384

Adaptations, of larvae, 133; of legs, 40, *42;

of mandibles, 29, *3o; protective, 231
Adaptive coloration, 178; classification, 193;

evolution, 194
Adelung, von, 355
Adler, 347, 375

Adventitious resemblance, 180
A'edes, 241
Ageronia, 83

Aggressive resemblance, 193
Agrionidae, caudal gills of, *io9
Air-sacs, 107
Alary muscles, *ioo
Albinism, 165
Alexander, 373

Alimentary tract (see Digestive System)
Allard, 356

Alluring coloration, 194
Alternation of generations, 199
Amans, 346, 369
Amber insects, 319, 322
Ametabola, 127
Ammophila, *2Q$, 297
Amnion, 120, *i24
Amphidasis, 163
Amphipyra, 284
Ampullaceum, *75
Anajapyx, *$, 17
Anal glands, 65, *94
Anasa, *n-j
Androconia, *6$
Anemotropism, 285
Aner gates, 276
Angr cecum, 203
Anisota, *i^o
Anisotropic, 69

Annelids, in relation to arthropods, 4, *6
Anomma, 275
Anopheles, 236, 237
Anophthalmia, 91

Anosia berenice, 315; plexippus, antenna of,
*26; dispersal, 303; eclosion, 140; so-called
mandibles, 33; mimicked, *i84, 191; pupa,
*I35; pupation, 135; scale, *6i; wing, *47

Antecoxal piece, *3p

Antennae, forms of, *26; functions of, 27;

sexual differences in, *2 7
Antennal comb, *2io, 211; neuromere, *t)6;

segment, 36; sensilla, 75,
Anthonomus, 328
Anthrax, 252
Anthrenus, *6i
Antigeny, 28, 169
Ant-plants, *2i2

Ants, castes of, 271; color sense, 91; facets,
25; general account, 27^1; habits, 273;
harvesting ants, 279; honey ants, 276,
*277; hunting ants, 275; larvae, 272; leaf-
cutting, *277; nests, 272; slavemaking, 276

Anurida, development of mouth parts, *i2i;
germ band, *i2i; habits, 157; pigment, 162

Anus, *57, 96

Aorta, *ioo, *ioi

Apanteles, 255, *2$6

Apatetic colors, 193

Apatura, scales, 159; colors, 161

Aphaniptera, 15, *i7

Aphid ins, 255

Aphids, galls of, *i97; in relation to ants, 280

Apis mellifera, antennal sensilla, *76; cepha-
lic glands, 97; comb, *265; control of sex,
269; determination of caste, 269; foot, *43;
general account, 264; hair, *209; larvae,
*266; legs, *2io; mandible, *3o; mimicry,
*i85; modifications in relation to flowers,
*2io; moults, 133; mouth parts, *35;
ocellus, *87; ovipositor, *56; reproductive
system, *ii5; tongue, *77; wax, *65, *26$

Apneustic, 107, 155

Apodemes, *4o

Apodous larvae, 37, 43

Apophyses, *4o

.4 porus, 297

Appendages, development of, *i20
Apple, insects of, 195
Aptera, 6
Apterygota, 8

Aquatic insects, adaptations of, 152; food,
152; locomotion, 153; origin, 158; respira-
tion, 155; systematic position, 152

Arachnida, *2

Arctic realm, 309

Arista, *26

Aristida, 279

Arms, J. M., 340, 368

Army worm, 317

Arthropoda, characters of, *i; classes, 2;
interrelationships, 4; naturalness of phy-
lum, 6; phylogeny, *6

387

388

INDEX

Asclepias, 203, *204, *205
Asecodes, 257

Ashmead, on Hymenoptera of Hawaii, 305

Assembling, 81

Atelura, *282

Atcmeles, *28i

Atta, 275, *277

At lac us, 21

Auditory hairs, 85; organs, 85, *86
Audouin, 345

Aughey, on insectivorous birds, 224, 376

Auricle, *2io, 211

Austen, 378

Austral region, 310

Australian realm, 310

Automeris, 64

Avers, on abdominal appendages, 53; 365

Balancers, 46
Baldwin, 381
Ballowitz, 364
Banks, 339, 386 .
Barlow, 360
Barriers, 302
Barrows, 382
Basch, 344, 351, 356

Basement membrane, *59, *63, *68, *g6
Basiconicum, 75, *j6
Basidium, *2oi

Basilarchia, mimicry, *i84, 191; protective

resemblance, 180
Bates, on mimicry, 185; 373, 382, 383
Batesian mimicry, 186
Bateson, 372

Beal, on food of robin, 222, 377
Beddard, 371, 373, 384
Bees, color sense of, 91; hairs, *6o
Beetles, sounds of, 82
Behavior of insects, 283
Bellesme, de, 356

Belostoma, digestive system of, *g6; pre-

daceous, 153, 215
Belt, on leaf -cutting ants, 277; 383
Benacus, *i3; caecum, 96; mouth parts, *32;

predaceous, 153
Beneden, van, 379
Beneficial insects, 326
Benton, on honey bee, 267; 376
Berlese, on phagocytosis, 149; 340, 343
Bernard, H. M., 342
Bernard, M., 366

Bertkau, on hermaphroditism, 115; 363
Bessels, 363

Bethe, on behavior of ants, 274; 381
Bethune, 337
Beyer, 348
Binet, 353

Birches, insects of, 195

Birds, insectivorous, 221, 223, 226; regulat-
ing insect oscillations, 225
Bittacomorpha, *no, 156
Bittacus, *i3, *4i
Black-flies, 215
Blackiston, 373
Blanc, 344, 357

Blanchard, 352, 358, 378
Blandford, 377
Blastoderm, *i 19
Blaslophaga, 336

Blalta, muscles of, *68; respiration, *ni
Blattidae, 8; spiracles of, 52
Blind insects, 27

Blissus leucopterus, distribution of, 316;

losses through, 325; food of, 329
Blochmann, 365

Blood, corpuscles, *ioi; course of, *ioo, *ioi;

function, 101
Bluebird, food of, 223
Boas, 368
Bobretzky, 365
Bolton, 339

Bombus, antenna of, *26; general account,
269; larva, *i3i; mimicry, *i93; respira-
tion, *in; taste cup, *79

Bombyx mori, Malpighian tubes of, *99;
mid intestine, *gb; cenocytes, *io5; silk
glands, *67, *68

Bordas, 351, 357

Boreal region, 310

Borgert, 350

Borner, 343

Bot flies, 216

Boyce, 378

Brachinus, 65

Braconidae, 255

Brain, *72, *73; functions of, 73
Branchial respiration, 156
Brandt, A., 365
Brandt, E., 352

Brauer, on classification, 7; types of larvae,

130; 34i, 346, 362, 367
Braula, 255
Braun, 377, 378
Breed, on phagocytosis, 149
Breitenbach, 344
Breithaupt, 344
Briant, 344
Bridges, 374

Brongniart, on Carboniferous insects, 318,

321; 385
Brooks, 343

Bruce, 248, 249, 250; 378

Bruchophagus, *i28

Brues, 378, 380

Brunner von Wattenwyl, 372

Bugnion, 151, 368

Bumble bees, general account, 269

Bureau of Entomology, 336

Burgess, 33; 344, 347, 358

Burmeister, 340

Bursa copula trix, *ii5

Buthus, *2

Butler, 373

Biitschli, 352, 363, 365

Butterflies, eclosion of, 140, *i4i; fossil, *3 23

Cabbage butterfly (see Pieris rapes)
Caeca, gastric, *93, *94, 95
Ccecilius, *gj, *gS
Caecum, *95, *g6

INDEX 389

Cajal, 362
Calkins, 378

Calliphora, compound eyes of, *88, *8o.

Callosamia, antennae, 27; assembling, 81
cocoon, 136; odor ,66 ; sexual coloration, * 1 70

Caloptenus, olfactory organ of, *yg; tym-
panal organ, *86

Calopteryx, development of, *i23; sexual
coloration, 170

Calvert, 378

Campodea, 5, *y, 17, 52, "131
Candeze, 350

Canker worms, as food of birds, 225
Cannon, on phototaxis, 287
Canthon, *42
Capitate, *26

Carabidae, anal glands of, 65, *94; predace-

ous, 254
Carabidoid larva, *i45
Carabus, alimentary tract of, *94
Carboniferous insects, 318, 320
Cardiac valve, *92, 93, 94, *95
Cardo, *30
Carlet, 346, 348
Carpenter, F. W., 382

Carpenter, G. H., on relationships, 4, 6;
340, 342, 370, 384

Carriere, 354, 366

Carrion insects, 218

Carroll, 239, 240; 378

Cams, 339

Casteel, 211; 376

Catbird, food of, 222

Caterpillar, 126; pupation of, 135, *i37

Catocala, scent tufts of, 41; protective re-
semblance, *i79

Catogenns, antenna of, *26

Cattie, 353

Caudal gills, 156

Cecidomyia, egg of, *i28, 129; ovipositor,

*54; pedogenesis, 117
Cecidomyiidae, galls of, 197
C ectopia adcnopus, *2i3, 214
Cecropia moth (see Samia)
Centrolecithal, *ii9

Cerambyx, facets of, 25; ovipositor, *54

Ceralina, 260

Cerceris, 297

Cerci, *y. *$3, *57

Cercopoda, 53

Centra, 66

Cervical sclerites, 23

Chaeticum, 75, *76

Chalcididae, 21, 256

Chapman, 367, 371

Chelo stoma, *6o

Chemotropism, 283

Cheshire, on honey bee, *35, 55, 211, 265,

375, 379
Child, 355
Chilopoda, 3, *4

Chinch bug, distribution of, 316; food of,

329; losses through, 325
Chionaspis, 130

Chironomus, nervous system of, *73; pupal

eggs, 117; food, 152
Chitin, 57

Chlorophyll, as a pigment, 161, 177
Cholera, 251

Cholodkovsky, 341, 357, 365, 366
Chordotonal organs, *86
Chorion, *n8, *i29
Christy, 377
Chromosomes, 118
Chrysalis, 126

Chrysobothris, integument of, *5g
Chrysomelidae, silk glands of, 68
Chrysopa, cocoon of, *i36; laying eggs,

*i29; mandibles, *3o; predaceous, 253;

silk glands, 68
Chun, 350

Cicada, metamorphosis of, *i28; moults,
133; sound, 82

Cicindela, leg of, *42; mandible, *3o; pre-
daceous, 254; variation in coloration, *i76

Cimbex, repellent glands, 65

Circular muscles, *96

Circulation, *ioi, 102

Circulatory system, 99

Claparede, 353

Claspers, *57, *58

Claus, 341, 349, 363

Clavate, *26

Claypole, 366

Climatal coloration, 164

Clisiocampa, number of eggs of, 130

Clisodon, 208

Cloaca, 54

Clover, insects of, 195; pollination of, 207
Clypeus, 22, *33

Clytra, embryology of, *ng, *i20, *i24, *i25

Cnemidotus, 108

Coarctate pupa, 135

Coblentz, 106; 360

Coccinella, distribution of, 313

Coccinellidae, predaceous, 254; silk glands, 68

Cockroach, cephalic ganglia of, *73; fossil,
*320, 322; mouth parts, *29; muscles, *45,
*68; respiration, *m; salivary gland,
*98; spermatozoon, *ii4

Cocoon, 136, *i39

Coeloconicum, 75, *76

Ccelom sacs, *i24

Coleoptera, 15, *i6, 19

Colias, albinism of, 165; color sense, 91;
sexual coloration, *i69

Collembola, alimentary tract of, *92; de-
fined, 7; furcula, 53; primitive condition,
18; ventral tube, 53

Colleles, hairs of, *6o

Colon, 96

Colopha, gall of, *i97

Color, effects of food on, 161; sources of, 159
Coloration, adaptive, 178, 192; climatal,
164; development of, 172; effects of mois-
ture and temperature on, 164; seasonal,
166; sexual, 169; variation in, 173; warn-
ing, 182

39°

INDEX

Color patterns, development of, 172; origin,
171

Colors, combination, 161; pigmental, 160;
structural, 159

Color sense, 91

Commissures, 71, *js

Complete metamorphosis, 126

Compound eyes, *24; origin of, 91; physi-
ology, 89; structure, *88, *89

Comstock, A. B., on ants, 117, 272; 340, 342

Comstock, J. H., on venation, 46; 333, 335,
340, 342, 344, 345, 340, 361, 30Q> 3?o

Cone cells, 88, *89

Conidia, *2oi

Conidiophores, *2oi

Connold, 376

Cook, 376

Cooke, 375

Cope, on segmentation, 21
Copidosoma, 256
Copris, spermatozoon of, *ii4
Coquillett, 334
Corbiculum, *2io
Cordyceps, *2oo

Corethra, chordo tonal organs of, *86; im-

aginal buds, *i48, 149
Corn insects, 195
Cornea, *88, *89
Corrodentia, 8, 10
Corydaloides, 321
Cosens, 198; 376
Costa, *46
Coste, 371

Cotton boll weevil, 328
Cotton worm, 325
Cowan, 376
Coxa, *39, *4i, *42
Craig, 378
Crampton, 347
Crawley, 380
Cremaster, 136
Cremastogaster, 273
Creutzburg, 358
Cricket, stridulation of, 84
Crioceris, 316
Crop, 93, *94
Crustacea, 2
Cryptorhynchus, 316
Crystalline cone, 88, *89
Ctenocephalns, 16, *i7
Cubitus, *46
Cuenot, 351, 357, 359

Culex, antennae of, *28; characteristics of,
237; nlariasis transmitted by, 251; larva,
*i55; mouth parts, *34; respiration, *i55,

Cutaneous respiration, 156
Cuticula, 57, *59, *6o
Cuticular colors, 160

Cyaniris psendargiolus, coloration of, 163;
geographical varieties, 306; melanism, 166;
polymorphism, *i66; sexual coloration,
169

Cybister, leg of, *i54", locomotion, 154, 155

Cychrus, stridulation of, 82

Cyllene, metamorphosis of, *i26

Cynipicke, abdomen of, 52; galls, *iq6,

*i97; parthenogenesis, 117, 199
Cyrtophyllus, stridulation of, 84

Dahl, 346, 350, 352

Darkness, as affecting pigmentation, 162
Darts, *s6

Darwin, on instinct, 296; 375, 382
Davenport, on phototaxis, 287, 288; 381
Davis, 348

Dearborn, on insectivorous birds, 223, 225,

226; 377
Deegener, 369
Demoll, 345, 356
Demoor, 346

Denny, on chitin, 58; on muscles, 69; 340,

343, 352
Dermaptera, 8
Dermestidae, 218
Deutocerebrum, 71, 124
Deutoplasm, *n8
Development, 118
Devonian insects, 318, 319
Dewitz, 346, 347, 348, 359, 362, 367, 369
Diabrotica, distribution of, 315
Diacrisia, cocoon of, 139
Diapheromera, 179
Diastole, 102
Dibrachys, 257
Dichoptic, *25

Dickel, on control of sex, 269; on fertiliza-
tion, 117; 380
Dictyoneura, 321
Dietl, 352
Dietrich, 345

Digestive system, 92; of beetle. *94; Belo-
stoma, *g6; Collembola, *92; grasshopper,
*93; histology, *96, 97; moth. *gs; Myr-
meleon, *g^

Digoneutic, 168

Dimmock, on assembling", 82; on mouth
parts of mosquito, 33, *34; 344, 350, 370,
376

Dimorphism, 166
Dinarda, *28i

Dineutus, antenna of, *26; eyes of, *24
Diplopoda, *3

Diptera, 15, *i6; eyes of, *2$; halteres. 92;

mouth parts, 33, *34; origin, 19; sounds,

82; spiracles, 52
Directing tube. 67
Direct metamorphosis, 126
Diseases, their transmission by insects, 234
Dispersal, 300; centers of, 317; means of, 301;

In North America, 313
Dissosteira, protective resemblance of, 180;

stridulation, 83
Distant, 383

Distribution, former highways of, 303; geo-
graphical, 300; geological, 318

Dixey, on evolution of mimicry, 191; 371,
372, 374

INDEX

391

Doane, 378
Dogiel, 358
Dohrn, 365

Dolbear, on stridulation, 84
Dolichopodidae, 41
Donacia, 70, 152, 156
Donisthorpe, 380
Dorfmeister, 370
Dorsal closure, 122, *i24
Dorsal vessel, 99, *ioo
Doten, 364
Doyere, 362
Drift, insect, 157
Drone, *264*
Drosera, 199
Drosophila, egg of, *i28
Dubois, 359

Ductus ejaculatorius, *H3, 114
Dufoui, 349, 356, 359, 360, 362, 369
Durham, 377
Diirken, 346
Dutrochet, 360, 362
Dyar, on moults, 133

Dynastes hercules, 21; tityus, distribution of,
3i5

Dytiscus, caecum of, 96; leg of, *42; predace-

ous, 215; respiration, 156
Dzierzon, 269

Ecdysis, 128, 132

Eciton, *277; eyes of, 25; habits, 215, 272,

275 .
Eckstein, 375
Eclosion, 140

Economic entomologist, 329
Ectoderm, 119, *i2o

Edwards, on I. ajax, 167; on P. tharos, 167;

Egg-guide, *58
Egg-nucleus, *n8

Eggs, form of, *i28; number, 130; size, 129
Eimer, 381

Ejaculatory duct, *ii3, 114

Elaphrus, stridulation of, 82

Ellema, protective resemblance of, 180

Elm, insects of, 195

Eltringham, 374

Elwes, 383

Elytra, 45

Embia, 10

Embiidae, *g, 10

Embryology, 118

Emery, 357, 359, 380

Emesa, 300

Empis, nervous system of, *73
Empodium, 40
Empusa, *2oi

Enderlein, on Platyptera, 10, 18; 342
Endoskeleton, 38, *40
Engelmann, 339

Enteman, on habits of Polistes, 271, 299;

373, 380, 382
Entoderm, 119, 124, *i2$
Entomophthoraceae, 200, *20i

Ephemerida, *n; abdominal segments of, 52;

eyes of, 25; origin, 18
Epicauta, hypermetamorphosis of. 144, *i4S
Epicranium, 22
Epigamic colors, 194
Epimeron, 38, *39
Epipharynx, 29
Episternum, 38, *39
Epitheca, dorsal vessel of, *ioo, *ioi
Erebus agrippina, 21; odora, distribution of,

3oi> 315
Ergatoid, 272

Eriocephala, mouth parts of, 33

Eristalis, mimicry by, *i85; respiration, 156

Eruciform larvae, 19, *i3i, 147

Erynnis manitoba, distribution of, *3io

Escherich, 348, 364

Ethiopian realm, 309

Etiolin, 177

Etoblattina, *320

Eudamus proteus, distribution of, *3io
Eugereon, *$2i

Euphoria, mouth parts of, 30, *209

Euplexoptera, 8

Euploea, colors of, 161

Euproctis, 288

Euschistus, antenna of, *26

Eutermes, 263

Euthrips, *i2

Everes, androconium of, *6$
Excrements, 96

Exner, on compound eyes, 89; 355. 381
Expiration, 112
Exuviae, 133

Eyes, compound, *24, 88; kinds of, *24;
simple, *24, *25; sexual differences in, *2$

Fabre, J. H., on Sphex, 294; 359, 379, 380
Fabre, J. L., 356, 367
Facets, *24

Fat-body > distribution of, 102, *io3; func-
tions, 104; structure, 103, *io4
Fat-cells, 103, *io4
Faunae of islands, 304
Faunal realms, 306
Faussek, 357
Felt, E. P., 333; 364
Female genitalia *54, *55
Femur, *39, 40, *4i
Fenard, 364

Fenestrate membrane, 88, *89
Fenger, 347
Feniseca, 254

Fernald, C. H., on gypsy moth, 196, 332
Fernald, H. T., 341, 350
Fertilization, 118

Fidonia, antennal sensilla, *76, 81

Fielde, on ants, 272, 274, 287; 379, 380, 382

Filariasis, 250

Filiform, *26

Filippi's glands, *67

Finlay, 238; 377

Finn, on mimicry, 189; warning coloration,
182, 374

392

INDEX

Fire-flies, 105, 106
Fischer. 372

Fishes, insectivorous, 219

Fitch, 333

Flagellum, *26

Fleas, 15, *i7, 216

Fletcher, 336

Flight, mechanics of, 49

Flogel, 352

Fluted scale, 327, 335

Follicles, 113, *n6

Folsom, 342, 345

Food, its effects on color, 161

P'ood reservoir, 93, *95

Forbes, H. O., 383

Forbes, S. A., on corn root louse, 280; on
economic entomologist, 329; food of
Carabidae, 254; insectivorous birds. 221;
insectivorous fishes, 219; insect oscilla-
tions, 225; interactions of organisms, 227;
3345 375, 376, 377, 379

Forbush, on gypsy moth, 196, 332

Fore intestine, *92, *93

Forel, on ants, 272, 273; on taste, 77; 350,
353, 354, 380, 382

Forficulidae, 8

Formative cells, *6o, 62, *6s

Formica exsedoides, mounds of, 273; fusca,

271, 275, 276; pratensis, eyes of, 26;

sanguined, 276
Fossil insects, localities for, 318
Fossilization, 318
Free pupa, 135
French, G. H., 334
Frenulum, 46
Frenzel, 357
Friese, 373
Front, *22, *23
Frontal ganglion, *73, *74
Fundament, 120
Fungi of insects; *2oo, *2oi
Furcula, 53

Gadeau de Kerville, 359
Gad flies, 215

Galapagos Ids., Orthoptera of, 304
Galea, *29, *3o

Galerita, anal glands of, 65; antenna, *26;

sternites, *39
Galls, *i96, *i97

Ganglia, cephalic, *$6, 71, *73; functions of,
73 .

Ganglion, structure of, 72, *74; subcesopha-
geal, *72, *73; supracesophageal, *j2, *73

Ganglion cells, 72, *74

Ganin, on Platygaster, *i46; 367

Garman, 369

Gastric caeca, *93, *94, 95

Gastropacha, larval coloration, 163; stinging
hair, *64

Gastrophilus, 216

Gastrulation, *ii9

Gehuchten, van, on digestion, 95; 352, 357
Geise, 344

Genae, 22
Geniculate, *26

Genitalia, 54; of female, *55; grasshopper,

*58; male, 55; moth, *57
Geographical, distribution, 300; varieties, 306
Geological distribution, 318
Geometridae, legs of larvae of, 43
Geotropism, 286
Gercphcmera, 320
Germ band, *ii9; types of, 122
Germ cells, 118
Germinal vesicle, 118
Gerould, 165; 373
Gcrris, *i53; locomotion of, 155
Gerstacker, 361
Gibson, 376
Gill, T., 383
Gillette, 334
Gills, *io8, *io9, *i57
Gilson, 357, 362, 363, 370
Girault, on numbers of eggs, 130
Gizzard, 93, *94

Glaciation, its effects on distribution 303

Glands, 63; accessory, *ii3, *ii5; allur-
ing, 66; repellent, 64; salivary, *97, *98;
silk, 63, *67; wax, *66

Glandular hairs, *64, *65

Glaser, 105; 360

Glossa, *29, *3i

Glossina, 247, *248

Glover, 335

Goddard, 349

Golgi, on malaria, 234

Goliathus, endoskeleton of, *40

Gonapophyses, 54, *55

Gongylus, 194

Gonin, 368

Goossens, 348, 350

Gorgas, 241, 242; 378

Gortner, 160; 373

Goss, 385

Gosse, 348

Gottsche, 353

Gould, 371

Graber, on chordotonal organ, *86; halteres,
92; hearing, *86; 340, 346, 347, 348, 353,
354, 358, 365, 366, 381

Grasshopper, alimentary tract of, *93;
genitalia, *58; hearing, *86

Grassi, on Termes, 261; 341, 377, 379

Gregson, on coloration, 162

Grenacher on the compound eye; 89, 91;

354
Grobben, 341
Gross, 364
Growth, 132
Grub, 126
Grube, 360
Grunberg, 364, 378
Gryllidce, 8

Gryllotalpa, leg of, *42; maternal care, 259
Gryllus, sense hairs, *8i; stridulation, 83
Gula, 23, 31

Gypsy moth (see Porthetria) .

INDEX

393

Gyrinidae, eyes of, *24

Gyrinus, locomotion of, 155; respiration, 156;
tracheal gills, 108

Haase, 341, 348, 362, 374
Haemolymph, 101

Hagen, on Termes, 262; 339, 360, 361, 369,
37o

Hagens, von, 348

Hairs, development of, *6o; functions, 59;

histology, *6o; modifications, 59, *6o;

pollen-gathering, *209; protective, 231;

tenent, *64
Halisidota, distribution of, 314
Haller, 361
Halobates, 157, 300
Halteres, 46, 92

Hamilton, on holarctic beetles, 309; 383

Hammond, 346, 368

Hamuli, 46

Hansen, 341, 342, 344

Harpalus, labium of, *3i; maxilla, *30

Harris, 332; 386

Hart, 370

Hartman, 382

Hatching, 130

Hatschek, 365

Hauser, on smell, 78; 354

Haviland, on termites, 263

Hawaii, beetles of, 304; Hymenoptera, 305

Hay ward, on stridulation, 84

Head, 22; segmentation of, 35, *$6

Hearing, 85

Heart, *ioo, *ioi

Heath, on Termopsis, 262; *38o

Heer, on fossil insects, 319, 322; 385

Heider, 366, 368

Heilprin, 384

Heim, 375

Heinemann, 359

Heliconiidae, mimicry, 185

Heliophila, 317

Helm, 356

Hemelytra, 45

Hemerocampa, parasites of, 257
Hemimeridae, 8

Hemimerus, *g; hypopharynx of, *3i
Hemiptera, defined, 12, *i3; mouth parts,

*32; odors, 65; origin, 18
Henking, 364, 365, 366
Henneguy, 340
Hensen, 353
Henshaw, 339, 386
Heptagenia, hypopharynx, *32
Hermaphroditism, 115, *ii7
Herms, 382
Hesse, 355

Hessian fly, losses through, 325
Hettzrius, 282
Heterocera, defined, 14
Heterogeny, 116
Heterometabola, 126
Heterophaga, 17

Heteroptera, defined, spiracles of, 52
Hewitt, 337; 344

Hexagenia, *n, 12; male genitalia, *57;

tracheal gills, *io8
Hexapoda, defined, 3
Heymons, 342, 349, 364, 366, 367
Hicks, on olfactory pits, 80
Hickson, 354
Higgins, 370
Hilton, 351

Hind intestine, *93, *gd

Histogenesis, 149

Histolysis, 148

Hoffbauer, 346

Holarctic realm, 309

H okas pis, galls of, *i97

Holmes, 382

Holmgren, 345, 353, 362, 364, 380
Holometabola, 126
Holopneustic, 107, 155
Holoptic, *2$
Homoptera, defined, 13
Honey, 268
Honey ants, 276, *277
Honey bee (see Apis mellifera)
Hopkins, A. D., 334

Hopkins, F. G., on pigments, 161, 371, 372
Hoplia, sexual coloration of, 170
Horn, on Cicindela, 174
House fly (see Musca)

Howard, on Crioceris, 316; economic ento-
mology, 332, 336; parasitism, 257; 340,
377, 379, 384, 386

Hubbard, on parasitism, 257

Huber, on wax, 265

Hudson, 383

Humboldtia, 214

Hunter, 340

Hutton, 342

Huxley, 343, 363

Hyaloplasm, 70

Hyatt and Arms, quoted, 18; on accelera-
tion of development, 147; 340, 341, 368
Hybemia, 162
II yd no phylum, *2i4

Hydrophilus, 15, *i6, *i53; antennae, 27;

leg, *i54", locomotion, 153; male genitalia,

*57; respiration, 156
Hydrotropism, 284
Hydrous, tergites of, *38
Hylastes, 316

Hylobius, glandular hairs of, *64

Hymenoptera, defined, 16; cephalic glands,
97; eyes of sexes, *26; internal meta-
morphosis, 151; mouth parts, *35; ocelli,
25; origin, 19; sounds, 82; wing, *48

Hypermetamorphosis, 144

Hyperparasitism, 256

Hyphae, 200

Hyphantria, 231

Hypoderma, larva of, *i3i; lineata, habits of,

217; losses through, 326
Hypodermal colors, 160
Hypodermis, *59, *6o, *6$

394

INDEX

Hypognathous, 9
Hypopharynx, *2Q, 31, *3a

I eery a, 335
Ichneumonidae, *255
Ihering, von, 348
Ileum, *96

Imaginal buds, *I48, *i49
Imago, 126

Incomplete metamorphosis, 126
Indirect metamorphosis, 126
Ingenitzky, 364

Injurious insects, 325; introduction of, 328
Ino, antennal sensilla of, *j6
Inquilines, 198, 263
Insecta, defined, 3

Insectivorous birds, 221; fishes, 219; plants,

199; vertebrates, 218
Inspiration, 112
Instar, 128

Instinct, 291; apparent rationality of, 292;

basis of , 292; flexibility, 294; inflexibility,

294; modifications, 293; origin, 295;

stimuli, 292; and tropisms, 296
Integument, 56
Intelligence, 296
Interactions of organisms, 227
Intercalary, appendages, *i2i; neuromere,

*36; segment, 36
Interglacial beetles, 323
Interrelations, of insects, 253; of orders, 17
Intima, *67, 68, *g6, *in
Iphiclides ajax, polymorphism of, 166
Iridescence, 159
Iris pigment, *87, *88
Iris versicolor, *202, *203
Irritants, 232
Isaria, 200

Ischnoptera. mouth parts of, *29
Isia, cocoon of, 139; hairs, 60, 134; moults,
133

Island faunae, 304
Isolation, 306
Isoptera, 9
Isosoma, 256
Isotropic, 69

Ithomiinae, mimicry, 185, 186

Jackson, C. F., 340
Jackson, T. W., 378
Jacobi, 384
James, W., 381

Janet, on Atelura, *282; muscles, *6g\ 345,

348, 349, 352, 379, 380
Japyx, 7, 18; spiracles of, 52
Jaworovski, 358
Jennings, 382
Johnson, 373

Judd, on food of bluebird, 223; mimicry, 191;
protective adaptations, 231; protective
resemblance, 181; warning coloration, 183;
374, 377

Jurassic insects, 319, 322

Kallima, protective resemblance of, *i78

Kanthack, 377

Kapzov, 351

Karsten, 349

Kathariner, 382

Katydid, stridulation of, 84

Kellogg, on Mallophaga, 215; mouth parts,

33; phototropism, 290; pilifers, *33;

scales, 61, 159; swarming, 268; 340, 344,

345, 346, 35i, 372, 382
Kenyon, 342, 353
Kidney tubes, 98, *99
Kingsley, on Arthropoda, 6; 341, 342
Kirby, 339, 340
Kirkland, 377
Klemensiewicz, 350
Kluge, 364
Knuppel, 357
Koch, on malaria, 236
Kochi, 345
Koestler, 353
Kolbe, 340
Kolliker, 352, 362
Korotneff , 365

Korschelt, 363, 366, 367, 368
Koschewnikoff, 364
Kowalevsky, 357, 359, 365, 368
Kraatz, 348
Kraepelin, 344, 347
Krancher, 361

Krause's membrane, *6g, 70
Krukenberg, on chitin, 58; 356, 370
Kulagin, 33; 345, 366, 368

Labella, *34

Labial, neuromere, *$6, 72, 124; segment, 36
Labium, 23, *29, *3i, *34
Labrum, 22, 28, *29, *33
Lacaze-Duthiers, 347

Lachnostema, antenna of, *26; cocoon, 136;

larva,
Lacinia, *29, *30, 31
Lagoa, legs of, 43; stinging hairs, *65
Lamarck, on instinct, 295
Lameere, 368
Lamellate, *26

Landois, 349, 350, 358, 359, 361, 363, 367, 370
Lang, 344
Langer, 345

Langley, on luminosity, 106

Lankester, 341, 342, 359

Larvae, 126; adaptations of, 133; legs, 42;

nutrition, 134; parasitic, 258; types, 130,

*i3i

Lasins, age of, 271; nest, 273; partheno-
genesis, 117
Laveran, on malaria, 234; 378
Leachia, eyes of, *24
Leaping, 44
Le Baron, 333
Le Conte, 382
Lee, on halteres, 92; 354

INDEX

395

Legs, adaptations of, 40, *42; larval, 42;
mechanics, *44; muscles, *45; segments,
*4i

Lendenfeld, von, 346, 352
Lens, *87

Lepidocyrtus , scales of, 61

Lepidoptera, denned, 14; internal metamor-
phosis, *iSo; moults, 133; mouth parts,
*33; origin, 19; reproductive organs, *i 13,
*ii5; silk glands, *6 7; spiracles, 52

Lepidotic acid, 161

Lepisma, *7, 18, *i3i; spiracles of, 52
Leptinotarsa, color pattern of, 161, I7i,*i75;
distribution, 314, 316; dorsal wall, *i24;
entoderm, *i25; folding of wing, *49J
spread, 316, 329; variation in coloration,

*i75
Leplocoris, 316
Lerema, ocellus of, 25
Leuckart, 364
Leucocytes, *ioi, 104, 148
Leydig, 343, 349, 352, 353, 356, 358, 363,

366

Libellula, *i2, *i3i

Lice, biting, *io, 215; sucking, *I3, 216
Life zones, 310

Light, its effects on pigments, 162
Zigula, *3i

Limacodes, scale of, *6i
Lina (see Melasoma)
Linden, von, 372, 373
Lingua, *3i
Link, 356

Linnaeus, on orders of insects, 6

Lintner, 333, 386

Lithomantis, *32o, 321

Locality studies, 296, *297

Locustidae, 8; ovipositor, *55; spermatozoon,

*ii4
Locy, 357

Loeb, on tropisms, 283, 284, 286, 287, 288,

291; 381, 382
Loew, 362
Lomechusa, *28i
Longitudinal muscles, *97
Losses through insects, 325
Low, on malaria, 236
Lowne, 344, 354, 355, 363
Lubbock, on ants, 271, 272, 274, 276, 279,

280, 287; larval characters, 135; muscles,

69; vision, 90, 91; 341, 343, 351, 354, 355,

360, 363, 367, 375, 379, 381
Lucanus, cocoon of, 136; dorsal vessel, *ioo;

spiracles, *no
Lucilia, *286
Lugger, 334
Luks, 352
Luminosity, 105
Lund, 360
Lutz, 351

Lyccena, facets of, 25
Lycaenid larvae, alluring gland of, 66
Lycus, mimicked, 189, 190
Lyonet, on muscles, 69; 343, 351

Machilis, 7, 18; abdominal appendages, *53;
nervous system, *7 2; scales, *6i; spiracles,
52

MacLeay, 345
Macloskie, 357, 361, 369
Madeira Ids., beetles of, 304
Maggot, *i2 7
Malacopoda, denned, 2, *3
Malaria, 234, *235
Male genitalia, 55, *57, *$8
Mallock, 355

Mallophaga, denned, *io; 215
Malpighian tubes, 98, *99
Mammen, 362

Mandibles, *29; adaptations of, *3o; Cidex,
*34; Lepidoptera, *33

Mandibular, neuromere, *36, 72, 124; seg-
ment, 36

Mandibulate mouth parts, 29; orders, 28
Mann, on Prionus, 130
Manomera, 179

Manson, on filariasis, 250; malaria, 236; 378
Mantidae, 8, 253

Mantispa, 19; metamorphosis of, *i3i, 132

Maples, insects of, 195

Marchal, 125; 367

Marey, on wing vibration, 49; 346

Marine insects, 157

Mark, 355

Marshall, on adaptive coloration, 189, 190;
374

Maternal provision, 258
Maturation, *n8
Maxillae, *29, 30; "second," 31
Maxillary, neuromere, *36, 72, 124; segment,
36

Mayer, A. G., on color pattern, 173; Papiho,

165; scales, 62; 351, 372, 374
Mayer, A. M., on Culex, 85; 354
Mayer, P., 341, 354

May fly, male genitalia of, *57; wing, *48
McAtee, 374

McCook, on habits of ants, 273, 276, 278,

279; 379
McDermott, 106; 360
Meconium, 140

Mecoptera, defined, 14; origin, 19
Media, *46, 47
Median segment, 37, 52
Meek, 345

Megachile, hairs of, *6o
Megalodacne, antenna of, *26
Meganeura, 321
Megilla, 314
Meinert, 344
Melander, 380
Melanism, 165

Melanoplus, alimentary tract of, *93; facets,
*24; genitalia, *58; mandible, *3o; res-
piration, 112; skull, *23

Melanotics, larva of, *i3i

Melasoma, color changes of, 174; distribu-
tion, 314; germ band, *i2o; glands, 65

Meldola, 373

396

INDEX

Metnikow, 365

Meloe, antenna of, 27; hypermetamorphosis,
144

Mclolontha, male reproductive system, *i 13 ;

olfactory pits, 80
Mendelism. 192
Meuopon, *io
Mentum, *2Q,
Merkel, 351
Meron, 40, *4i

Merriam, on life zones, 310; 383, 384

Merrifield, 371, 372

Mesenchyme, *i25

Mesenteron, *g2, *93, *04, *95, 125

Mesoderm, 119, *i24

Meso-entoderm, *i20

Mesothorax, 37

Metabola, 128

Metamorphosis, denned, 126; external, 126;

internal, 148; kinds, 19; significance, 146;

systematic value, 19
Metatarsus, *2io
Metathorax, 37
Metschnikoff, 357, 365, 368
Meyer, G. H., 364
Meyer, H., 359

Miall, on chitin, 58; muscles, 69; 340, 342,

362, 368, 369, 370
Miastor, paedogenesis of, *ii7
Michels, 352

Microcentrum, stridulation of, 83, *84
Micropteryx, mouth parts of, 33
Micropyle, 118, 129
Mid intestine, *93, *94, *95
Milkweed, pollination of, 203, *204
Mimicry, 184; evolution of, 191
Minot. 343, 350
'Miocene insects, 319, 322
Mitchell, 378

Moisture, its effects on coloration, 164

Molanna, *i4

Moles, insectivorous, 218

Moller, on leaf-cutting ants, 278, 375

Mollock, on vision, 90

Moniez, 369

Moniliform, *26

MononyckuSj 208

Mordella, facets of, 25

Morgan, C. Lloyd, on food of birds, 190; 381
Morgan, T. H., 382
Morpho, scales of, 61, 159
Morse, 384
Moseley, 358

Mosquito, antennae of, 27, *28; hearing, 85;
locomotion of larva?, 154; in relation to
malaria, 234; mouth parts, *34; respira-
tion, *i55, 156

Moulting, 132

Moulton, 374

Moults, number of, 133

Mouth parts, dipterous, 33, *34; hemip-
terous, *32; hymenopterous, *35; lepi-
dopterous, *33; mandibulate, *2g; orthop-
terous, *29; suctorial, 31

Miiller, V.. on mimicry, 187; wings, 45;

34i, 35o, 373
Miiller, H., 375
Mtillerian mimicry, 186, 187
Miiller, J., "mosaic" theory of, 89; 353
'Murgantia, spread of, 317
Murray, 383

Musca, egg of, *i28; facets of, 25; fungus of,
*2oi; moults, 133; ovum, *n8; in rela-
tion to typhoid fever, 242, 244

Muscidse, cardiac valve of, *95; imaginal
buds of, *i48, 149

Muscles, circular and longitudinal, *g6; of
cockroach, *45, *68; of leg, *44; number,
68; structure, *6g; of wing. *5i

Muscular, power, 70; system, 68

Mutilla, stridulation of, 83

Myrientomata, 5

Myriopoda, the term, 4

Myrmecocystus, *2J7

Myrmecodia, 214

Myrmecophana, mimicry by, *i88
Myrmecophilism, 279
Myrmedonia, 282

Myrmeleon, digestive system of, *94; pre-

daceous, 253; silk glands, 68
Mynnica, *28i

Mystacides, androconia of, 63

Xagana, 248
Xagel, 355
Xassonow, 363
Xearctic realm, 309
Xecrophorus, 218, 259

Xeedham, on digestion, 95; venation, 46;

346, 357, 370, 376
Xemobius, leg of, *42
Xeotropical realm, 309
Xepa, respiration of, 156
Nerves, of head, 72, ^73; structure. *73
Xervous system, 71; development of, 122,

*I24, *I25

Xervures, 46
Xeuration, *46, *47, *48
X'euroblasts, *i24

Xeuromeres, defined, 36, 122; of head, *36,
71

Xeuroptera, defined, 13; metamorphosis of,

19, *I3*
X'ewbigin, 372

Xe^port, on metamorphosis, 151; muscles,

69; 343, 35i, 352, 35§; 360
Xewton, 352

Xotolophus, olfactory organs of, 80
Xotonecta, *iS3', locomotion of, *i54; res-
piration, 156
Xotum, 37
Novius, 258, 327, 336
Xucleolus, 118
Xumber of insects. 21
Xusbaum, 363, 366
Xuttall, 377
Xymph, 127

INDEX

397

Oaks, insects of, 195
Oberea, eyes of, 24
Obtect pupa, *i^5
Occipital foramen, 23, *i\
Occiput, 23

Ocelli, *25; structure of, *8y; vision by, 87
Ockler, 346

Ocular, neuromere, *36; segment, 36

Odonata, abdominal segments of, 52; copula-
tion of , 56; denned, 12; ocelli, 25; origin,
18; spiracles, 52

Odors, 65; efficiency of, 232

Odynerus, 207

(Ecantkus, abdominal appendages of, 53,

*i22; embryo, *i22; stridulation, 83
(Ecodoma, 277
(Ecophylla, 273

(Edipoda, dorsal vessel of, *ioo
(Eneis, distribution of, 303
(Enocytes, 104, *io5
(Esophageal commissures, *73
(Esophagus, *93
(Estridae, 216
O'Kane, 386

Olfactory organs, 78, *7Q, *8o, *8i
Oligocene insects, 319, 322
Oligotoma, *9
Ommatidium, 88, *89
Onthophagus, mandible of, *30
Orchelimum, stridulation of, 83
Orders of insects, 6, 17, *2o
Orgyia, olfactory organs of, 80; parasites of,
?57

Oriental realm, 309

Origin of Arthropods, *6; of insects, *5
Orthoptera, abdominal segments of, 52; de-
fined, 8; origin, 18; stridulation, 83, *84
Osmeterium, *65
Osmia, 208

Osmoderma, cocoon of, 136
Osten-Satken, 350
Ostium, *ioo
Oudemans, 363
Oustalet, 361, 369
Ovaries, 113, *ii4, *ii5
Ovariole, *n6
Oviducts, 113, *ii5
Ovipositor, *54, *$$, *s8
Ovogenesis, 118

Ovum, of Musca, *n8; Vanessa, *n6
Ox-warble, *i3i, 217, 326

Paasch, 353

Packard, on Anophthalmus, 91; Arthropoda,
6; classification, 7; Mantis pa, 19, 132;
olfactory pits, 80; origin of Coleoptera, 19;
relationships of orders, 18, 19; segmenta-
tion, 21; types of larvae, 130; wings, 45;
332, 335; 340, 34i, 342, 343, 347, 348, 350,
35i, 352, 355, 361, 365, 367, 368, 374, 383,
386

Paedogenesis, 117
Pagenstecher, 363

Palasarctic realm, 309
Palceoblattina, *2>*9
Palaeodictyoptera, 324
Palmen, 361, 363
Palmer, 377
Palpifer, *29, *3o, 31
Palpiger, *29, *3i

Palpus, *29, *3o, *3i, *33, *34, *35

Pankrath, 355

Panorpidae, 14; legs of, 43

Papilio, colors of, 165; egg, *i28"; facets, 25;
head of pupa, *i35; melanism, 165; mimi-
cry, 185, 188; osmeterium, *65; protective
resemblance, 180; merope, mimicry by,
186, 188; sexual coloration of, 169

Paraglossa, *29, *3i

Paralysis, infantile, 252

Paraponyx, *iog, 156

Paraptera, 38

Parasita, defined, *i3

Parasitic insects, 215, 254, 258; in relation

to birds, 226
Parasitism, 217, 254; economic importance

of, 257

Parker, on phototropism, 289; 382
Parthenogenesis, 116, 199, 269, 272
Passalus, cocoon of, 136; stridulation, 83
Patagia, 38
Patten, 355, 365
Pawlovi, 353
Pawlowa, 359

Peckham, on behavior, 294, 296, 298, 379, 381

Pecten, *2io, 211

Pectinate, *26

Pedicel, *26

Pediculidae, 216

Pcdiculus, *i3, 216

Pellagra, 252

Pelocoris, leg of, *42

Penis, 55, *57, 114

Pepsi's, 259

Perez, C, 369

Perez, J., 348, 369

Pericardial chamber, *ioo, *ii2

Peri pat us, characters of, *3, 4; systemic

position, 4 *
Periplaneta, olfactory pits of, 80
Peripodal, cavity, 149; membrane, 149; sac,

149

Perla, olfactory pits of, 80

Perlidae, 10, *n; nymph, tracheal

gills, 109
Permian insects, 321
Petiolata, 17
Pettigrew, 345
Petunia, *2oy
Peytoureau, 349, 364
Pflugstaedt, 347
Phagocytes, 104, 148
Phanaus, legs of, 41, *\2
Pharynx, 93
Phasmidae, 8, *i79

Phlegcthontius, head of moth, *^y, larva, *43;
moth, *207; parasitized larva, *2$6

398

INDEX

Phormia, antenna of, *26; eyes, *2$; meta-
morphosis, *i2;; phototropism, 290
Phosphorescence, 105
Photinus, luminosity of, *io5, 106
Photogeny, 105
Photopathy, 287
Photophil, 287
Photophob, 287
Phototaxis, 287
Phototropism, *286
Photuris, 106
Phragmas, *40
Phtliirius, 216

Phyciodes, coloration of, 164, *i6j
Phylloxera, 325, 328
Phytogeny, 4, % 17, *2o, 323
Physopoda, *i2, 18; origin of, *2o
Phytonomus, legs of, 43; spread of, 316
Phytophaga, 16, *ij
Pictet, on coloration, 162, 164
Piepers, 374

Picris, color sense of, 91; dispersion, 300;
fat-cells, *io4; imaginal buds, *i49; ol-
factory organs, *8i; scale, *6i; napi,
temperature experiments on, 168; proto-
dice, sexual coloration of, *i69; rapa,
androconium of, *6y, developing wing,
*i5o; distribution, 316; eggs, *i29; food
plants, 196; hair, *6o; larval tissues, *io3;
pupal coloration, 163; wing vibration, 51;
xanthodice, distribution of, 300

Pigmental colors, 160

Pigments of eyes, *87, *88, *89, *9o; nature

of, 161; of Pieridae, 161
Pilifers, *33
Pimpla, 257
Pine, insects of, 195
Pinguicula, 199
Placodeum, *76
Plague, 245
Planta, *2io

Plants, insectivorous, 199; insects in relation

to, 195
Plasma, 101
Plasmodium, *235

Platedu, on color sense, 91; muscular power,
70; respiration, 112; 345, 351, 354, 356,
358, 361, 381

Plaiephemera, *$ig

Plathcmis, abdominal appendages of, *$S;

antenna, *4i
Platner, 360

Platxgaster, hvpermetamorphosis of, 135,

*i46
Platypsyllus, 216

Platyptera, denned, 8; origin of, 18, *2o
Plecoptera, denned, 10, *n; nymph, *i3i;

origin, 18, *2o
Pleistocene insects, 319, 323
Pleurites, 38, *39
Pleuron, 37
Plotnikow, 351
Pocock, 341
Podical plate, *$8

Podisus, egg of, *i28; predaceous, *253
Pcecilocapsus, color changes of, 177
Pogonomyrmex, 279
Polar bodies, *n8
Poletajeff, X., 352
Poletajew, O., 361, 369
Poletajewa, 358
Poliomyelitis, 252

Polistes, behavior of, 294, 299; habits, 271;

wing vibration, *5o
Polites, on Iris, *2o8
Pollenizers, insect, 207

Pollination, 201, 207; of Iris, *203; milk-
weed, *204; orchids, 203; Yucca, *2o$,

*206

Pollinia, *204
Polybia, 270
Polyembryony, 125
Polyergus, 276
Polygoneutic, 168

Polygonia, dimorphism of, 166; egg, *i28
Polymorphism, 166, 271
Polynema, 146
Polyphemus (see Telea)
Polyphylla, assembling of, 82
Polyrhachis, 273

Pompilus, behavior of, 294, 298
Porthctria dispar, damage by, 328; herma-
phroditism, *ii7; tracheae, *in
Post-genas, 22
Postscutellum, *38
Potato beetle (see Leptinotarsa)
Pouchet, 361, 380

Poulton, on adaptive coloration, 189, 190,
192; on colors of larvae and pupae, 162,

163; 368,370,371,372,373,374
Powell, 369
Pratt, 368

Predaceous insects, 215, *253; in relation to
birds, 226

Premandibular, appendages, *i2i; segment,

36

Pricer, 380

Primitive insects, 17, 18

Primitive streak, 119

Primordial insect, 17

Prionus, assembling of, 82; eggs, 130

Proboscis, *33

Procephalic lobes, *i20, *i2i, *i2 2
Proctodaeum, 93, 95, 120
Proctotrypidae, 21, 256
Prodoxus, 207
Prodryas, *$23
Prognathous, 9
Promcihea (see Callosamia)
Pronotum, *38
Pronuba, *205, *2o6
Propodeum, 37, 52
Propolis, 266
Protapteron, 5

Protective, adaptations, 231; mimicry, *i84,

191; resemblance, *i78, 181
Prothorax, 37
Protocerebrum, 71, 124

INDEX

399

Protura, 5

Proventriculus, 93, *94, *95
Pseudocone, *89
Pseudomyrma, 212
Psocicise, *io

Pteronarcys, 10, *n; tracheal gills of, 109
Pterygota, 8

Ptilodactyla, antenna of, *26
Pulvillus, 40, *43
Punktsubstanz, 72
Punnett, 192

Pupae, 126, 135; 374; emergence of, 140;

protection, 136; respiration, 136
Pupal stage, significance of, 147, 151
Puparium, 135

Pupation of a caterpillar, 135, *i37
Putnam, on habits of Bombus, 269
Pyloric valve, 95
Pyrophila, thigmotropism of, 284
Pyrophorus, luminosity of, 105
Pyrrharctia (see Isia)

Quaternary insects, 323
Quedius, 282

Queen, honey bee, *264, 265; termite, *26i

Radius, *46

Radl, 382

Radoszkowski, 348

Ranatra, 152; respiration of, 156

Ranke, 354

Raschke, 361

Rath, von, on sense hairs, *8i, 355
Rathke, 360, 364

Rationality, apparent, 292; lack of, 299
Realms, faunal, 306
Reaumur, de, 343

Receptaculum seminis, 113, 114, *n$
Recognition markings, 194
Rectal respiration, 109, 157
Rectum, 96

Recurrent nerve, 72, *73< *74
Redikorzew, on ocelli, *87; 355
Redtenbacher, 346
Reed, on yellow fever, 238, 239; 378
Rees, van, 368

Reichenbach, on ants, 117, 272
Reinhard, 361

Relationships, of arthropods, 4, *6; of orders,

17, *20

Repellent glands, 64
Replacements, 174
Reproductive system, 113
Respiration, in, 136
Respiratory system, *io7
Retina, *87
Retinula, *87, 88, *&g
Reuter, 355
Rhabdom, *87, *89
Rheotropism, 285
Rhipiphorus, 144, 145
Rhopalocera, 15

Rhyphus, *47

Riley, on hypermetamorp hoses, 144; losses
through insects, 325; pollination of Yucca,
205; pupation, 135; 334, 335; 367, 375

Rimsky-Korsakow, 5; 343

Ritter, 364, 366

Robertson, 375

Robin, food of, 221

Rocky Mountain locust; dispersion of, 300;

as food of birds, 224
Rollet, 352

Romanes, on instinct, 295; 381
Ross, on malaria, 236; 377
Rossig, 376
Rostrum, 40
Rosites, *339
Ruland, 355

Sadones, 362, 370

Saliva of Dytiscus, 98; mosquito, 98

Salivary glands, *97, *98

Sambon, on malaria, 236

Samia cecropia, antennae of, *2 7; cocoon,
*i39; egg, 129; food plants, 196; genitalia,
*57; head of larva, *66; Malpighian,
tubes, *99; ocelli, *25; odor, 66; scales,

*62

Sanderson, 340, 386

Sandias, 379

San Jose scale, 328

Sanminoidea, sexual coloration of, 169
Sarcolemma, *69

Sarcophaga, nervous system of, *73
Saturnia, hairs of, *6o
Saunders, E., 350
Saunders, W., 336; 386
Saville-Kent, 384

Scales, arrangement of, *62; development,
62, *63; form, *6i, *62; occurrence, 61,
uses, 62

Scape, *26

Scarabaeidoid larva, 144

Scavenger insects, 218

Schaffer, on scales, 62; 344, 350, 359

Schaum, 344, 347

Scheiber, 358, 361

Schenk, on senilla, 75, *76, 80; 355

Schepotieff, 5 ; 343

Schewiakoff, 352

Schiemenz, 357

Schimper, 375

Schindler, 356

Schistocerca, distribution of, 301, 317; of

Galapagos Ids., 304; isolation, 306
Schizoneura, wax of, 66
Schizura, protective resemblance of, *i8o
Schmidt, O., 354
Schmidt, P., 342, 360
Schmidt-Schwedt, 361
Schneider, A., 357, 363, 365
Schneider, R., 350
Schon, 356
Schultze, 353, 359

400

INDEX

Schwarz, on distribution, 314, 315; myr-

mecophilism, 282
Schwedt, 369
Sclerite, 22
Scolopendra, *4
Scolopcndrclla, *$, 17

Scudder, on albinism, 165; coloration. 172;
fossil insects, 319, 322, 323, 324; glacia-
tion, 303; mimicry, 186; Orthoptera of
Galapagos Ids., 304, 306; spread of P.
rapcB, 316; stridulation, 83; 339, 347, 350,

353, 370, 383, 385
Scutellum,
Scutum, *38
Seasonal coloration, 166
Second maxillae, the term, 31
Sedgwick, 342, 343

Segmentation, of arthropods, 21; germ band,

*i2o, *i2i, *i22; head, 35,
Segments of abdomen, 52
Seitz, 371, 375, 379, 381, 383
Semafic colors, 193

Seminal, ducts, *H3, 114; receptacle, 113,

*ii5; vesicle, *ii3, 114
Semon, 384

Semper, C, on scales, 62; 349
Semper, K., 383
Sempers, 386
Sense organs, 75
Sensilla, 75, *76
Serosa, *i2o, *i23
Sessiliventres, 16, *iy
Setaceous, *26
Seta;, modifications of, 59
Seventeen-year locust, number of moults,
133

Sexual coloration, 169

Sharp, on Atta, 275; Hawaiian beetles, 304;
metamorphosis, 146; 340, 342, 348, 361,

309
Sheath, *56
Shelford, R., 374
Shelford, V. E., 384
Shull, 85; 356
Siebold, von, 353, 362
Silk, 67

Silk glands, 66, *67
Silkworm (see Bombyx mori)
Silpha, distribution of, 314
Silurian insects, 319
Silvestri, on Anajapyx, *5; 343
Simmermacher, 350
Simnlium, 215; respiration, 157
Sinclair, 342,

Siphonaptera, 15, origin of, 19, *2o
Sirex, ovipositor of, *55
Sirodot, 349, 356
Sitaris, 144
Size of insects, 21
Skin, 57
Skull, 22, *23
Skunk, insectivorous, 218
Slingerland, on losses through insects, 326,
333, 334

Smell, 78; end-organs of, *79, *8o, *8i
Sminthitrus, *8

Smith, J. B., 334; 344, 345, 386

Snodgrass, on Orthoptera of Galapagos Ids.,

304, 306; 347
Snow flea, *8

Soldier, ants, 271, termites, *26o

Sollmann, 347

Somatic cells, 118

Sorensen, 342

Sounds, 82

Spence, 339, 340

Spermatheca, 114, *ii5

Spermatogenesis, 118

Spermatophores, 114

Spermatozoa, *ii4

Sperm-nucleus, 118

Speyer, on hermaphroditism, 115

Sphecina, 259

Sphecius, 259

Sphex, *205; behavior of, 294, 296, *297
Sphingidae, as pollenizers, 203, *207
Sphinx, alimentary tract of, *95; dispersal,
301; pulsations of heart, 102; transforma-
tion, *i5o
Spichardt, 363
Spines, 59
Spinneret, *66

Spiracles, closure of, 109, *no; number,

52, 109
Spirobolus, *3
Spongioplasm, 70
Sporotrichum, 201

Spuler, on scales, 62; 346, 351, 372
Spur, *42
Squama, 46

Squash bug, metamorphosis of, *i2 7

Stadium, 128

Stagmomantis, leg of, *42

Standfuss, temperature experiments of, 168,

306; 372
Stefanowska, on pigment, 90; 355
Stegomyia, in relation to yellow fever, 241
Stein, 362
Stellwaag, 347
Stenamma, 274

Stenobothrus, blood corpuscles of, *ioi;

stridulation of, 83
Sternberg, on malaria, 236, 237; 377, 378
Sternum, *37, *39, 52
Stigmata (see Spiracles)
Sting of honey bee, 54, *56
Stinging hairs, *64
Stings, efficiency of , 232
Stipes, *29, *3o, 31
Stokes, 362
Stomach, *95

Stomachic ganglion, 72, *74
Stomatogastric nerve, 72, *74
Stomodaeum, *93, *94, *i2i
Straton, 375

Straus-Diirckheim, on muscles, 69; 343, 351
Strength, muscular, 70
Stephens, 378

INDEX

4OI

Stridulation, 83, *84
Strongylonotus, 276
Structural colors, 159
Styloconicum, 75, *'j6
Stylops, hypermetamorphosis of, 145
Subcosta, *46
Subgalea, *30
Submentum, *2g, *3i
Subcesophageal ganglion, 71, *72, 73
Suctorial mouth parts, 31
Suffusion, 164
Superlinguae, *3i, *32, *i2i
Superlingual, neuromere, *$6, 72, 124; seg-
ment, 36

Supracesophageal ganglion, 7 1, 72, 73

Suranal plate, 54, *58

Surface film, 155

Suspensor, *n6

Suspensory muscles, *ioo

Swarming, 268

Symbiosis, 281

Sympathetic system, *72, *73, *74
Synaptera, 8

Syrphidae, silk glands of, 68
Systole, 102

Tabanidae, 215

Tabanus, nervous system, *73; olfactory

organ, *8o
Tactile hairs, 59, 75, *76
Taenidia, *in
Tarsus, *39, 40, *4i, *42
Taschenberg, 339

Taste, 76; end-organs of, *78, *79
Taxis, 283
Tegmina, 45
Tegulae, 38

Telea Polyphemus, cocoon of, 136; eclosion,
143; larval growth, 132; silk glands, 67;
spinning, 139

Teleas, 146

Temperature, its effects on coloration, 163
Tenent hairs, *64

Tenthredinidae, 20; larval legs of, 43
Tenthredopsis, larva of,
Tentorium, *24
Terebrantia, 16, *iy
Tergites, 37, *38
Tergum, 37, 52

Termes flavipes, 261; lucifugus, *26o, 261,
262; obesus, *26i

Termites, American species of, 261; archi-
tecture, *262, *263; classes, *26o; "com-
pass," *263; food, 261; mandibles, *3o;
origin of castes, 261; queen, *26i; ravages,
263

Termitidae, 9
Termitophilism, 264
Termopsis, 262
Tertiary insects, 319. 322
Testes, *ii3
Thalessa, *2$$

Thanaos, androconia of, 63; claspers, 56

Thaxter, on Empasa, 200, *20i; 375

Thelen, 361

Theobald, 386

Thermotropism, 290

Thigmotropism, 284

Thimm, 378

Thomas, C, 334, 335

Thomas, M. B., on androconia, 63; 351

Thorax, differentiation of, 37; parts, 37;

sclerites, *37, *38
Thread-press, *6y

Thyridopteryx, number of eggs of, 130
Thysanoptera, *i2, 18; origin of, *2o
Thysanura, *7; abdominal segments, 52;

primitive, 17
Thysanuriform, 19, 130, *i3i, 147
Tibia, 40, *4i, *42
Tipula, 15, *i6
Titanophasma, 21
Toad, insectivorous, 218
Tongue, 31
Touch, 75

Tower, on color patterns, 171; cuticular
colors, 160; distribution of Leptinotarsa,
314; folding of wing, 48, *49; integument,
*59; origin of wings, 45; structural colors,

159; 35i, 373> 384
Townsend, 105; 360
Toyama, 364

Tracheae, development of, 124, *i25; dis-
tribution, *io7, *io8; structure, no, *m
Tracheal gills, *io8, *io9, 156
Tracheation, types of, 107
Trelease, 375
Tremex, *i7
Triassic insects, 322
Trichius, 208
Trichodeum, 75, *y6
Trichogramma, 257

Trichoptera, *i4; origin of, 19, *2o; silk

glands, 68
Trichopterygidae, size of, 21, 256
Trimen, on dispersal, 301; on P. merope,

186. 188; 373, 374 ,
Trunerotropis, protective resemblance of , 180
Trimorphism, 166
Triphleps, egg of, *i28
Tritocerebrum, 72, 124
Triungulin, 144, *i45
Trochanter, 40, *4i, *42
Trochantine, 40
Tropcea lima, cocoon of, 136
Tropical region, 313
Tropisms, 283
Trouessart, 383

Trouvelot, on cocoon-spinning, 139; eclosion,

143; larval growth, 132; 367
Trypanosomes, *247; *249
Trypanosomiases, 246, 248, 249
Tryphozna, 162
Tsetse fly, 247, *248
Tuberculosis, 251
Turner, 91; 356

27

INDEX

Tutt, 384

Typhoid fever, 242

Uhler, on distribution, 315
Urech, 371, 372

Uric acid, 99; as a pigment, 161
Utricularia, 200
Uzel, 367

Vagina, 113, 114, *i 15

Yalette St. George, la, 363

Vanessa, development of scales of, *by, head

of butterfly, *33; antiopa, 232; photo-

tropism, 289; atalanta, color change, 174;

cardui, dispersion, 300, 304; geographical

variation, 306; polychloros, coloration, 164;

melanism, 165; urticai, coloration, 162, 164;

melanism, 165; temperature experiments,

168

Variation in coloration, 173, *i 75, *i76

Variations, 174

Yas deferens. *ii3, 114

Vayssiere, 358, 361, 369

Vcdalia (see Xovius)

Veins, 46

Velum, *2io

Venation, *46

Ventral sinus, 101, *ii2

Ventral tube, 53

Ventri cuius, 95

Verhoefif, 346, 349, 379

Yerloren, 358

Vernon, 373

Verson, 364

Vertex, 22

Yenvorn, on phototropism, 287; 381

Vespa, nests of, *27o; olfactory organ, *8o;

sensillum, *j6; taste cups, *78; tongue,

*77

\ espidae, 270

Viallanes, 343, 353, 358, 361, 368
Vision, 86

Vitelline membrane, *n8
Vitreous body, *87
Yoeltzkow, 366
Vogler, 361

Volucella, mimicry by, *i93; predaceous, 254
Voss, F., 347
Voss, H. v., 373

Walter, on mouth parts, 33; 344

Walton, on meron, 40; 346

Warning coloration, 182

Wasmann, on mvrmecophilism, 279; 779,

381, 382
Wasps, 270
Watase, 355

Wax, glands, 66; pincers, *2io, 211
Webster, on dispersal, 301, 313, 316; losses
through insects, 325; 334; 374, 375, 379,

383, 384
Wedde, 344

Weed, on birds in relation to insects, 223, 225,

226; 377
Weinland, 355

Weismann, imaginal buds, 149; instinct, 296;

temperature experiments, 168; 350, 365.

367, 37o, 37i, 372, 374, 382
Wesche, 345
West, T., 345

\\ estwood, on Brachinus, 65; 340, 341

Wheeler, on harvesting ants, 279; Mal-
pighian tubes, 99; tropisms, 283, 284, 285,
286, 290; 348, 357, 359, 366, 380, 381

White, F. B., 347, 369

White grubs, 329

Whitman, 381

Whymper, on distribution, 300; 384
Wielowiejski, von, 358, 359, 363, 368
Wilcox, 364, 376
Wilde, 356

Will, F., on taste, 77; 354, 355
Will. L., 363, 365
Williams, 360, 369
Wilson, 367

Wings, 45; folding of, 48, *49; modifications,

45; muscles, *5i; vibration, 49, *50, 82
Wistinghausen, von, 362
Witlaczil, 350, 357, 365, 368
Wollaston, on beetles of Madeira Ids., 304
Wood, T. W., 370
Wood-Mason, 341
Woodward, 366
Woodworth, 346

Worker, ant, 271; bee, *264, 269, 270; ter-
mite, *26o, 261; wasp, 271

Xanthophyll, as a pigment, 160, 177

Xenoneura, *32o

Xiphidium, stridulation of, 83

Yellow fever, 238

Yolk, *n8, *ii9

Y^oung, on luminosity, 106

Yucca, pollination of, *205, *2o6

Wagner, F. v., 373
Wagner, J., 342
Wagner, N., 363
Wahl, 369
Walker, 370
Walking, 43

Wallace, on mimicry, 186; 373, 383
Walsh, on losses through insects, 325, 333

Zaitha, 158
Zander, 349
Zimmermann, 358
Zittel, von, 342
Zugmayer, 374

AMY 9, 3 1955

MAI 12