Full text of "Entomology, with special reference to its biological and economic aspects"

ENTOMOLOGY

FOLSOM

DESCRIPTION OI^ FRONTISPIECE.
Protective Mimicry wiong Butterflies.

Fig. I. — Heliconins cucratc, one of the Heliconiinse, which are naturally immune from
the attacks of birds. From Brazil.

Fig. 2. — Perhybris pyrrha, female (Pierinae), which is edible by birds but probably
secures immunity by means of its resemblance to such species as No. i or No. 4.
Brazil.

Fig. 3. — Perhybris pyrrha, male, to show the colorational basis from which the
mimetic pattern of the female has been developed; under surface on right. Brazil.

Fig. 4. — Mechanitis lysimnia (Ithomiinae), naturally immune, but nevertheless
sharing a common color pattern with Heliconiinae (No. i). Brazil.

Fig. 5. — Papilio merope, male, having three forms of females (Nos. 7, 9 and 11),
which mimic, respectively, three species of Danainae (Nos. 6, 8 and 10). South
Africa.

Fig. 6. — Danais clirysippus, immune, mimicked by No. 7. South Africa.

Fig. 7. — Papilio merope, female, which mimics No. 6. South Africa.

Fig. 8. — Amauris niai.ius, " model " of No. 9. South Africa.

Fig. 9. — Papilio merope, female, " mimic " of No. 8. South Africa.

Fig. 10. — Amauris echeria, "model" of No. 11. South Africa.

Fig. 11.— Papilio merope, female, "mimic" of No. 10. South Africa.

The figures are about one half the natural size. Compiled, largely from Trimen
and Weismann.

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ENTOMOLOGY

WITH SPECIAL REFERENCE TO

ITS BIOLOGICAL AND ECONOMIC ASPECTS

JUSTLS W'ATSOX FOLSOM Sc.D. (Harvard)

INSTRUCTOR IN ENTOMOLOOY AT THE UNIVERSITY OF ILLINOIS

Ulitb Sfivc plates (One ColoreD)
anC» 300 ^TeitsJFiflures

PHILADELPHIA:
BLAKISTON'S SON & CO

IOI2 WALNUT STREET
1906

Press of

The New Era Printing Componv

Lahcasieb.Pi.

PREFACE

This book gives a comprehensi\-e and concise account of
insects. Though planned primarily for the student, it is in-
tended also for the general reader.

The book was written in an effort to meet the sfrowine
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 Laboratory of Natural History.

Permission to copy several illustrations from Government
publications was received from Dr. L. O. Howard, Chief of
the Bureau of Entomology ; 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 fig'ures are due also to
Dr. E. P. Felt, State Entomologist of New York; Dr. E. A.
Birge, Director of the W^isconsin Geological and Natural His-
tory Survey ; Prof. E. L. Mark and Prof. Roland Thaxter,
of Harvard University ; Prof. J. H. Comstock of Cornell Uni-
versitv: Prof. C. W. \A'oodworth of the Universitv of Cali-

VI PREFACE

fornia; Prof. G. ^Tacloskie of Princeton University; Prof. \V.
A. Locv of Northwestern University; Prof. J- G. Needham
of Lake Forest University; Dr. S. H. Scudder of Cambridge,
Alass. ; Dr. George Dimmock of Springfield, Mass.; Dr.
Howard Ayers of Cincinnati, Ohio; Dr. W. ]\I. Wheeler of
the American Mnseum of Xatnral History, Xew York City;
Dr. W. L. Tower of the University of Chicago; Dr. A. (j.
Mayer, Director of the ]\Iarine Biological Laboratory, Tortn-
gas, Fla. ; James H. Emerton of Boston, Mass. ; Dr. and Mrs.
G. W. Peckham of Milwaukee. Wis. ; Dr. Henry C. ]\IcCook
of Devon, Penn. ; Dr. A\'illiam Trelease, Director of the ]\Iis-
souri Botanical Garden ; Dr. Henry Skinner, as editor of " En-
tomological News " ; the editors of " The American Natural-
ist " ; and \\\ Saville-Kent, of Wallington, England.

Acknowledgments are further due to the Boston Society of
Natural History, the American Philosophical Society and the
.\cademy 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. Diimmler of Berlin, publisher of
Iv()lbe"s Einfiihrung; and Gustav Fischer (^f Jena, publisher of
Hertwig's Lehrbuch and Lang's Lehrbuch.

CONTENTS

Chapter Page

I. Classification i

II. Anatomy and Physiology 27

III. Development 146

lA'. Adaptations of Aquatic Insects 184

\". Color and Coloration 193

A'l. Adaptixe Coloration 216

A'll. Origin of Adaptations and of Species 237

\'III. Insects in Relation to Plants 252

IX. Insects in Relation to Other Animals 276

X. Interrelations of Insects 307

XL Insect Behavior 345

XII. Distribution 366

XIII. Insects in Relation to Man 393

Literature 409

Index 467

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 fonnd to have certain
fundamental characters in common. All are hilaterally sym-
metrical, are composed of a linear series of rings, or segments,
bearing paired, jointed appendages, and ha\-e 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 :

Diagram to express the fundamental structure of an arthropod, a, antenna: a!,
alimentary canal; b, brain; d, dorsal vessel; ex, exoskeleton ; /, limb; n, nerve chain;
s, suboesophageal ganglion. — After Schmeil.

above it extends the dorsal blood vessel and below lies the
ventral ladder-like series of segmental 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.
2 I

ENTOMOLOGY

Fi(

Furthermore, the sexes are ahnost invarial)ly separate and tlie
primary sexual organs consist of a single pair.

X() 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 arthropods have de-
scended fr(Mn annelid-like an-
cestors. 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-cralx tri-
lobites and a few other aber-
rant forms of uncertain posi-
tion, the members of the
series, or phylum. Arthropoda
fall into six distinct classes,
namelv, Crustacea., Arach-
nida, Alalacopoda. Diplopoda.
Chil( »p( )da an.d T n s e c t a .
These classes are character-
ized as fo'llows :

Crustacea. — A(|iiatic. as a
rule. Head and tliorax often united into a cephalothorax.
Numerous paired appendages, typically biramous (^ -shaped) ;
abdonunal limbs often present. Two ])airs of .antcnnce. Res-
piration branchial (by means of gills) or cutaneous (directly
through the skin). The exoskeleton contains carbonate and
])hospliate of lime in addition to chitin. Example, cray-
fish.

A scorpion, Biitlins. Natural size.

CLASSIFICATION 3

Arachnida. — Terrestrial. Usually two regions, cephalo-
thorax and abdomen; thongh various Acarina ha\-e but one
and Solpugida have all three — head, thorax and abdomen.
Cephalothorax unsegmented, bearing two pairs of oral append-

FlG. 3.

Pcripatns capciisis. Natural size. — After Moseley.

Fig. 4.

ages and four pairs of legs. Abdomen segmented or not,
limbless. Respiration tracheal, by means of book-leaf tra-
cheae, tubular tracheae, or both; stigmata almost always abdom-
inal, at most four pairs. Heart abdominal in position.
Example, Bitthus (Fig. 2).

Malacopoda. — Terrestrial.
Vermiform (worm-like), unseg-
mented 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 pres-
ent and these are arranged seg-
mentally in pairs. Two separate
longitudinal nerve cords, con-
nected by transverse commissures. Integument delicate. A
single genus. Peri pa f us (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 tw(^ pairs of short limbs, which are
inserted near the median ventral line. Eyes simple. antenUcC

A diplopod, Spiroboius marginatui
Natural size.

ENTOMOLOGY

Fir,. 5.

short, mouth parts consisting of a pair of man(hbles and a
compound plate, or gnathochilarinm. Genital openings sepa-
rate, anterior in position (on the second segment of the body).
Example, Spirobolus (V\g. 4).

Chilopoda. — Terrestrial. Two regions, head and body.
Body long and flattened, with numerous segments, each of

which bears a i)air of Irtng six-
or seven-jointed limbs, which are
not inserted near the median line.
Eyes simple and numerous (ag-
glomerate in Sciitii^cni ) , antennae
long. A pair of mandibles and
t\\(» pairs of maxillcT. A single
genital opening, on the preanal
segment. Example. Scolopciidra
(Fig. 5).

Insecta (Hexapoda) . — Pri-
marily terrestrial. Three distinct
regions — head, thorax and abdo-
men. Head with a pair of com-
jxuind eyes in most adults, one
pair of antenuce and three pairs
of mouth parts — mandiljles, max-
ilhe and labium — besides which
a hypopharynx, or tongue, is
present. Thorax with a pair of
legs on each of its three segments
cUid usuall)- a pair of wings on
each of the posterior two seg-
ments; though there mav be only
one p.air of wings (as in Diptera
and male C"occid;e); the ])ro-
thorax never bears wings. Ab-
domen typically with ten seg-
withoul legs, excei)ting in some
larva; (as those of I .cpidc.'ptera, Tenthredinida' and 1 'anor-

A centipede, Sci/lolH-iidra Iwros.
About two thirds the maximum
lengtli.

ments (seldom more) and

CLASSIFICATION 5

picte). Stigmata paired and seomentally arranged. A meta-
morphosis (direct or indirect) occnrs except in Thvsannra and
Collembola.

Relationships. — The interrelationships of the classes of
Arthropoda form an obscure and highly debatable sul)ject.

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 devel-
opment, but are inexplicable except in terms of community of
origin, as Carpenter has lately 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 Pcri/^atiis, are often spoken
of as bridging the gulf that separates Insecta, Chilopoda and
Diplopoda from Annelida. Pcripatiis indeed resembles the
choetopod annelids in its segmentally arranged nephridia,
dermo-muscular tube, coxal glands and soft integument, and
resembles the three other classes in its trachCcC, dorsal vessel,
lacunar circulation, mouth parts and salivary glands. These
resemblances, however, are by no means close, and Pcripatiis
does not form a direct link between the other tracheate arthro-
pods 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 de-
rived.

Though Diplopoda and Chilopoda ha\e long" been grouped
together under the name Myriopoda, they really have so little
in common, beyond the numerous limb-l)earing segments and
the characters that are possessed l)y all tracheate 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.

ENTOMOLOGY

Scolopciidrclhi, now placed either among Diplopoda or else
in a class 1)V itself, Syn.iphyla, presents a remarkable combina-

FiG. 6.

Fig.

Section of Scoli<j^cndrcl!a iiiiuiaciilata. b, brain; c, coxal gland; /, fore intestine;
h, liind intestine; iii. mid intestine; n , nerve cliain; o, opening of silk g"land; od,
oviduct; oz', ovary; s, silk gland; if, urinary tube. — After P.xckard.

tion of diplopodan and insectean characters. ScoIopcndrcUa
(l^ig. 6) and the thysannran Cam pod ca ha\-c the same kind
of head, with its long moniliform antennae, and agree in the
general structnre of the month parts;
the number of body segments is nearly
the same, the legs and claws are essen-
tially alike, and cerci and paired alxlom-
inal st}'lets are present in the two genera,
not to mention the c<^rrespon(lences of
internal organization. Indeed, it is
highly ■[)robable, as Packard maintained,
that the most primitive insects, Thys-
annra (and consequently all other in-
sects), originated from a form much like
Scolopcndrrlh!. A singular thysanuran.
Anajapyx ■I'csiculosus ( h'ig. /), has
lately been discovered by Sih'cstri, who
regards it as being in man_\- resiiects the
most ])rimiti\e insect known. coml)ining
as it does characters of S}'m])hyla, Diplo-
])oda and Cunipodca.
Idle following diagram ( l"ig. 8) expresses very crudely one
\'icw as to the annehd origin of the chief classes of Arthro-
poda.

// nnjapyx Z'csicitlosus.
Length, j nun. — .\fter

SlI-VESTRI.

CLASSIFICATION

The naturalness of the phyhim Arthropoda has been ques-
tioned by Kingsley and I^ackard. The latter author recently
divided Arthropoda into fi\'e independent phyla, holding that

CRUSTACEA

ARACHNIDA

DIPLOPODA

MALACOPODA
ANNELIDA

Diagram to indicate the origin of Arthropoda.

" there was no common ancestor of the Arthropoda as a
whole, and that the group is a polyphyletic one." This icono-
clastic view, however, by emphasizing unduly the structural
differences among arthropods, tends to conceal the many deep-
seated resemblances that exist between the classes of Arthro-
poda.

Carpenter, in a most sagacious summary of the whole sub-
ject of arthropod relationships, has recently brought together
no little evidence in favor of a revised form of the old Aliil-
lerian theory of crustacean origins. He traces all the classes
of Arthropoda back to common arthropodan ancestors with a
definite number of segments and distinctly crustacean in
character; then traces these primitive arthropods back to
forms like the nauplius larva of Crustacea, and these in turn

ENTOMOLOGY

to a hypothetical form hke the trochosphere larva of recent
polych?ete annelids.

Orders of Insects. — Linnc'eus arranged insects in seven
orders, namely. Coleoptera. Hemiptera, Lepidoptera. Xeurop-

Fig. 9.

Fig. 10.

Campodca. Length,
3 mm.

Lcpisina. Length,
10 mm.

tera, Hymenoptera, Diptera and Aptera. The wingless in-
sects termed .\ptera were soon found to helong to diverse
orders and the name has now hecome so ambiguous as to meet
with little approbatiorL

From the Linnrean group Hemiptera. the Orthoptera were
set a])art ; the old order Neuroptera. a heterogeneous and
unnatural grou]). has been split into several distinct orders,
and many other changes in the classification ha\e been neces-
sary.

Without entering any further into the history o\ the sub-
ject, it is suflicient to say that increasing discrimination on the

CLASSIFICATION

Fir

part of entomologists has been followed by a gradual increase
in the number of orders, until our present system has been
attained.

Ow^ng to the incomplete condition
of entomological knowledge, ho\Ae\er,
the best system as yet proposed is l)ut
tentative and more or less open to
objection. The most competent and
widely approved classifications 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 svn-
opsis of the orders of insects it is
necessary to use some terms, as iiicfa-
niorphosis and fhysamirifonii, in an-
ticipation of their subsequent defini-
tion.

I. Thysanura. — No metamorphosis.
Mouth parts mandiluilate, either free
(ectognathous) or enclosed in the
head ( entognathous). Wings inva-
riably absent. Thoracic segments simple and similar. Ab-
dominal segments ten,
with two to eig'ht pairs
of rudimentary limbs
and two or three anal
cerci. Eyes aggregate,
compound or absent.
Antenn.e multiarticulate.
Integument thin. Ex-
amples, Cauij^odca ( V\g.
9), Japyx, Maclulis,
Lcpisnia (Fig. 10). Some one hundred and seventy-fi\'e spe-
cies are known.

The snow flea, Acho-
yittes nk'icola. Length,
.; mm.

Fig. 12.

Sminthunis liortcnsis. Length, i.

ENTOMOLOGY

2. Collembola. — Xo metamDrphosis. Aloutli parts eiitog'-
nathous and t)-|)ically mandiliiilate. witli occasional secondary
suctorial modificati(Mis. A\'ing's in\'arial)ly al)sent. Thoracic
segments simple and similar or prothorax reduced. Body
cylindrical or globular; abdomen with six seg'ments. Ventral
tube and furcula usually present, rareh' rudimentary. Eyes
ocelliform or absent. Antennae of four segments in most
genera; five or six in a few genera. Integument delicate.
Examples, Achonifcs ■ (V\g. ii), Sniiiitlninis (Fig. 12).
Aliout se\'en hundred species have 1;)een descriljed.

Fig. 13.

Fig. 14.

Hcinimcrn.s tall^oiJcs.
Length, 11.5 mm. — After
Hansen.

Scliisfoccrca americana. Slightly reduced.

Under the term Aptcry^oia { Apterygogenea, Brauer;
Synaptera, Packard) the Thysanura and Colleml)ola. as primi-
tix'ely wingless insects, are conveniently distinguished from all
other insects, or Ft cry goto ( Pterygogenea, Brauer).

3. Orthoptera. — Metamorphosis direct. Mouth jiarts ULan-
dil;)ulate. Wings two pairs as a rule, though not infre(|uently
reduced or al)sent : front wings coriaceous (tegmina); hind

CLASSIFICATION I I

pair membranous, ample, closely reticulate, plicate along the
numerous radiating- principal' veins. Abdomen with ten or
ele\'en segments. Eight families : ForficulidcC, Hemimerida?
(Fig. 13), Blattidie, AlantidcC, Phasmidie (Fig. .240), Acri-
diida? (Fig. 14), Locustid?e, Gryllithe. 0\'er ten thousand
species are known.

Some authors prefer to separate Forficulidre from Orthop-
tera as a distinct order, for which Brauer and Packard pre-
serve the old term Dciinaptcra of Leach, while Comstock uses
Westwood's term Eiiplc.voptcra.

Hemimeridre consist at present of two African species
wdiose affinities appear to lie with Forficulida?, but deserve
further study.

4. Platyptera. — Aletamorphosis direct. ]\b)uth parts man-
dibulate. Wings, if present, two pairs, delicate, membranous,
efjual or hind pair smaller, and with the principal veins few
and simple. Integument usually thin. Nymphs thysanuri-
form. Two suborders.

Suborder Corrodentia. — Including three families, as fol-
lows :

Tcniiitichc. — Eyes facetted. Antennce 9-31 jointed.
Mouth parts prognathous or hypognathous.^ Prothorax
large. Wings elongate, alike, membranous, delicate, with
indefinite reticulation and with a characteristic basal suture.
Abdomen elongate, with ten segments and a pair of short,
two-jointed anal cerci. Integument tlelicate. Social in habit.
Example, Tcrnics (Fig. 2/^). Over one hundred species are
known.

Comstock places Termitid:e in an order by themselves,
I so pt era.

Embiidcc. — Eyes facetted. Antennae I5~3- jointed.
Mouth parts prognathous. Thorax elongate, prothorax re-
duced. Wings (sometimes absent) elongate, membranous,
delicate, with few and feebly developed longitudinal and cross
veins. Abdomen elongate, with ten or possibly eleven seg-

^ PrognatJious, directed forward; hypogiiathous, directed downward.

ENTOMOLOGY

Fin. IS.

Oligotoma )nicluic!i. I.t-ngth, 10.5 mm. — After
McLachl.^n.

ments, aiul a pair of stout Ijiarticnlate cerci. Integument deli-
cate. Not social in hal)it. Examples, Euibia, Oligotoma
(Fig'. 15). Some twenty species, all from warm climates.

These insects are most
nearly related to Termit-
\dx and Psocidre.

Psocichc. — Eyes facet-
ted. Antenna? I3~5<^
jointed. Mouth parts
h}'pognathous. Protho-
rax reduced. \A^ i n g s
present, rudimentary or
ahsent ; front pair the
larger; veins few and ir-
regular. Ahdomen with
nine or ten segments and
no cerci. Integument delicate. Example, Psocits (Fig. i6).
About two hundred species.

Comstock raises Psocida^ to the rank of an order, for which
he employs, in a new sense. Brauer's term Corrodcntia.

Suborder Mallophaga. — Wingless flattened insects, of para-
sitic hal)it. Head large. Eyes consisting of a few isolated

ocelli or else ahsent. An-

Fic. 16.
tenn?e t^-z^ jomted. Mouth

parts prognathous. Pro-
thorax distinct ; mesotho-
rax often and metathorax
usually transferred to the
abdominal region. Ab-
dominal segments eight to
ten in number; no cerci. Parasitic upon birds and a few mam-
mals. I^xample, Moiopon (Fig. 17). More than hfteen
hundred species ha\e been described.

Packard's order riaty fulcra originally included Perlid'c.
Brauer's order Corrodcntia consisted of Termitida-, Psocidre
and Mallophaga; Perlidre l)eing- set apart as an order {Plccop-

Psoctts vcnosus. Length, 5 mm.

CLASSIFICATION

Fig. 17.

fcra) and Embiidse being' transferred doubtfully to Orthop-
tera.

Enderlein's recent and thorough studies confirm the view
that Termitida?, Embiidas, Psocidie and JMallophaga constitute
a single order.

5. Plecoptera. — ^letamorphosis direct. Antenn;e long,
multiarticulate. Mouth parts niandibulate. Prothorax large.
Wings two pairs, memljranous, coarsely and complexly reticu-
late ; equal ov else hind wings larger
and with an ample plicate anal area.
Abdomen with ten segments and usu-
ally a pair of long multiarticulate cerci.
Nymphs thysanuriform, acjuatic ; adults
uni(|ue in having tracheal gills. Ex-
ample, Pfcroiiarcys (Fig. 18). A
single family, Perlidce, comprising two
hundred species.

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, rarely absent.
Abdomen slender, with ten segments
and three or two very long multi-
articulate cerci. Integument delicate. Nymphs thysanuri-
form, aquatic. Example, Hc.vagciiia (Fig. 19). Three hun-
dred species.

7. Odonata. — Metamorphosis direct. Antennre inconspicu-
ous, bristle-shaped. Mouth parts mandibulate. Prothorax
small. Wings four, elongate, sul)equal, similar, membranous,
minutely reticulate, with a costal joint, or nodus. Alxlomen
slender, with ten segments. Nymphs thysanuriform, a(juatic.
Example, Libcllula (Fig. 20). About two thousand species
have been described.

8. Thysanoptera (Physopoda). — ]^letamorphosis direct.

A chicken louse, Menol>on.
Length, 2 mm.

ENTOAIOLOGY
Fig. 1 8.

Ptcroiiarcys rcgalis. A, nymph (after Xewport) ;

Fig. ly.

imago. Slightlv reduced.

Uc.ragcnia -■ariabilis. A, nymph; B, imago. Natural size.

CLASSIFICATION

but including a subpupa stage. Mouth parts suctorial. Pro-
thorax long. Tarsus terminating in a bladder-like organ.

Fig. 20.

A B

Libcllula pulchella. A, last nymphal skin; B, imago. Slightly reduced.

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. ]\Iinute insects. Ex-
Fig. 21.

Eiitl\ri['S Iritici. Length, 1.2 mm.

ample, Eiitluips (Fig. 21). About one hundred and fifty
species have been described.

ENTOMOLOGY

g. Hemiptera. — Metamorphosis direct (excepting male
Coccida?). Antenn.T usually few-jointed. ]\Ionth parts suc-
torial. I'rothorax usually large. Wings usually ])resent,
except in the parasitic forms. Eighteen thousand species.
Three suhorders :

Suborder Heteroptera. — Wings four, folded flat: front
wings thickened basally. meml)ranous apical!}' (hemelytra),

Fig. 22.

Bcnacus griscus. Sliglitlv reduced.

overlapping oljliquely ; hind wings membranous. Head not
deflexed. Example, Bcnacus ( Eig. 22). About twelve thou-
sand species.

Suborder Homoptera. — ^Wings four, sloping roof-like, sim-
ilar and membranous or front pair somewhat coriaceous
throughout. Head deflexed. Example, Cicada (Eig. 206).
Six thousand si)ecies.

Suborder Parasita. — Wingless. Eyes simple (M" none..
"Jdior.acic segments inlimatel}' united; tarsus with a single
claw. Integument thin. Parasites upon mammals. Exam-
l)le, Pcdicithis (V\g. 23). Some fifty species are known.

10. Neuroptera. — Met.amorphosis indirect. .\ntenn;c con-

CLASSIFICATION

it ^^

.^i-

spicuoiis. Mouth parts mandibiilate. Fig. 23.

Prothorax large. Wings almost always -^ ' /a /

four, membranous, subequal or else hind 4 .^v ^/

pair smaller, complexly reticulate, not

plicate. Larvae thysanuriform or in

some cases eruciform, and aquatic or

terrestrial. Example, Clirysopa (Fig.

24). About six hundred species have

been named.

II. Mecoptera. — ^Metamorphosis indi-
rect. Mouth parts mandibulate, at the

end of a deflexed rostrum, or beak.

Prothorax small. Wings four, elongate,

membranous, naked, coarsely reticulate,

or else rudimentary or absent. Larvre

eruciform. caterpillar-like, with numerous prolegs, carnivo-
rous. Example, Bittacus (Fig. 25). A
single family, Panorpid^e, comprising but
few known species.

12. Trichoptera. — ^Metamorphosis in-
direct. Antenucne filiform. Mouth parts
of imago rudimentary or imperfectly
suctorial ; mandibles rudimentary or
absent. Prothorax small. Wings four,
veins moderate in number, cross veins

Head louse, Pediculus
capitis, female. Length,
2 mm.

Fk;. 24.

Chrysopa plorabunda.
Slightly reduced.

membranous, hairy
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. — ]\Ietamor-
phosis indirect. ]Mouth parts
suctorial, mandibles absent or
rudimentary (except in a few

Fig. 25.

Bittacus strigosus. Natural size.

15 ENTOMOLOGY

generalized species). Prothorax small. Wing's four, sim-
ilar, membranous, clothed with scales, veins moderate in num-
ber, cross veins few. LarvcC cruciform (caterpillars). i)hy-
tophag'ous (almost ne\'er carnix'orous ) . mandibulate. Some
fiftv thousand species have been described. Two suborders,
not sharplv separated from each other.

Suborder Heterocera. — AntenucC of \arious forms, but not
terminating in a distinct knob or club. Frenulum usually

Fig. 26.

i \

Molanna cincrca. A, larva; B, imago. X4 diameters. — After Felt.

present. Chiefly nocturnal in habit. Example. CaUosaiiiia
(Fig. 236).

Suborder Rhopalocera. — Antenna* simple, terminating in a
distinct club and \vithout conspicuous lateral processes. Fren-
ulum absent. Diurnal normally. Examples, Papilio (Fig.
27), Anosia (Fig. 243, x-i).

14. Coleoptera. — Metamorphosis indirect. Mouth parts
mandibulate. Prothorax large, as a rule. Wings four; front
])air horny (elytra), meeting in a straight line: hind pair mem-
branous, often folded. Larvre thysanuriform (jr cruciform.
Example, Hydropliilus (Fig. 28). About fifteen thousand
s])ecies.

CLASSIFICATION

15. Diptera. — Metamorpliosis indirect. Mouth parts typ-
ically suctorial, but modified for piercing, lapping', rasping, etc.
Prothorax small. One pair of wings ( mesothoracic), mem-
branous, transparent, ^\•it]^ few veins; wings rudimentary or
absent, however, in most of the parasitic species ; hind wings
represented by a pair of knoljl)ed threads, or l)alancers. Lar-
va" eruciform, with the head fre(|uently reduced to a mere
vestige with ur without a pair of mandibles, and usuallv with-

FiG. 27.

Papilio troilus. A, larva; B, larva sus]icii(.led for pupation; C, chrysalis
Natural size.

out true legs, though pseuclopods may be present. Example,
Tipitla (Fig. 29). iVbout forty thousand described species.

16. Siphonaptera (Aphaniptera). — Afetamorphosis indi-
rect. Head small. Eyes simple or a1)sent. IMouth parts
suctorial. Body laterally compressed. Thoracic segments
subequal. Wings absent or at most finite rudimentary. Lar-
Vce with a head, mandil)ulate, apodous. Parasitic insects.
Example, CtciioccpJialus ( l^'ig. 30). One hundred and fifty
species.

17. Hymenoptera. — Metamorphosis indirect. Mouth i)arts
at the same time mandibulate and suctorial. Prothorax usu-
ally small. Wings four, similar, membranous, transparent,

ENTOMOLOGY

with a few irregailar veins and cells : hind pair the smaller.
Females with an ovipositor, modified for sawing, boring or

Fig. 28.

Hydropi:ii:<s trid)iguiaris. Natural size.

stinging. Larvse eruciform. mandibulate. caterpillar-like,
with head and legs, or else maggot-like and apodoiis. Twenty-
five or thirty thousand species. Two suborders.

Fig. 29.

Tipiila. A, larva; B, cast pupal skin: C, imago. Slightly reduced.

Suborder Terebrantia (Phytophaga, Sessiliventres). —

Abdomen broadly attached to the thorax. Ovipositor modified

CLASSIFICATION

for boring, sawing or cutting. Larvae with complex mouth
parts and frequently abdominal legs. Phytophagous. Ex-
ample. Trcmc.v (Fig. 31).

Fig. 30.

Cat and dog flea, Ctenoccphalus canis. A, lana (after Kunckel d'Herculais) ;
B, adult. Length of adult, 2 mm.

Suborder Aculeata (Heterophaga, Petiolata). — Abdomen
petiolate or subpetiolate ; first abdominal segment transferred
to the thorax. Ovipositor
often modified to form a
sting. Larvie apodous. Ex-
ample, Af'is ( Fig. 2yy).

Interrelations of the
Orders. — The modern clas-
sification aims to express
relationships, and these are
most clearly to be ascer-
tained by a comparative
study of the facts of anat-
omy and development.

The most generalized, or
primitive, insects are the
T h y s a n u r a . Subtracting

their special, or adaptive, peculiarities, their remaining charac-
ters may properly be regarded as inheritances from some
vanished ancestral type of arthropod. This primordial type.

Trcmcx columba. A, imago; B, larva
(with parasitic Iar\a of Thalessa attached).
Natural size. — After Riley.

2 2 ENTOMOLOGY

then, probaljlv had three simple and equal thoracic segments
differing hut slightly fmm the ten alxlominal segments: three
pairs of legs and no wings; three pairs of exposed Ijiting
mouth parts; a pair of long many-jointed antenna and a pair
of cerci of the same descripti(^n ; a thin naked integument ; a
simple straight alimentary canal distinctl}- di\i(led into three
primary regions; a ganglion and a pair (.f spiracles for each
of the three th(iracic and the tirst eight al^dominal segments.
if not all the latter; no metam<3rphosis ; functional ahdominal
legs and active terrestrial habits.

The existing form that best meets these recjuirements is
Scolopendrella, which is not an insect, h(^wever. Iiut beh^ngs
among or near the diplopods. The most primitive of known
insects are Aiia/apy.v and Caiitpodca, through which other
insects trace their origin to the stock from which Symphyla
and Diplopoda arose.

Colleml)ola, though specialized in several important ways,
all have the same peculiar kind of entognathous mouth parts
as Campodca and Japx.v. for which reason and many others it
is belie\-ed that Colleml)ola are an offshoot from the thysanu-
ran stem. Collembola, howexer, are not nearly so primitive
as Thysanura, for the former have fewer abdominal segments
than the latter, exhibit much greater concentrati()n of the ner-
vous system, and are uniquely specialized in se\eral respects,
notably as regards the \-entral tulie and the furcula. or spring-
ing organ.

Returning to Thysanura — the genera Machilis and Lrpisiiui
show decided orthopteran affinities; thus their eyes are com-
pound and their mouth parts strongly orthopteran; indeed, the
likeness of Lcpisiini to a young- cockroach is striking", as is also
that of Jdpy.v to a }"oung forhculid.

In short, as Hyatt and Arms express it. " The generalized
form of Thysanura, and the manner in which it reappears in
the larvcC of other insects, is the natural key of the classiti-
^.ation."

Orthoptera probably arose dircctl\' from the original thvs-
anuriform stem.

CLASSIFICATION 23

Platyptera, as a whole, are most nearly related to Orthop-
tera on the one hand and to Plecoptera on the other. Termit-
idse have strong" orthopteran affinities and Embiidje have even
been placed in the order Orthoptera, though the latter family
is most nearly allied to Termitid^e and Psocidae. These two
are approached rather closely by Alallophaga and exhiljit, by
the way, some collembolan characters, as Enderlein has lately
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 re-
semblance 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, nev-
ertheless, by differences in the wings, mouth parts and other
organs. Ephemerida are almost unique among' insects in hav-
ing 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 from some mandibulate and winged form. The
conversion of mandibulate 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 meta-
morphosis or by a slight, or so-called " direct," or " incom-
plete," transformation. The following orders, on the con-
trary, are distinguished by an " indirect," or " complete,"

24 ENTOMOLOGY

metamorplKisis, which appears in Xeuroptera and attains its
maximum development in Diptera and Hymenoptera.

With Neuroptera the eruciform type of larva appears, as a
derivative of the earlier thysanuriform type. The larva of
Maiitispa. as Packard has shown, actually passes, during its
individual development, from the ])rimary, thysanuriform
stage to the secondary, eruciform condition.

Alecoptera form an isolated order, though their caterpillar-
like larvcC, with eleven or twelve pairs of legs, suggest affini-
ties with Lepidoptera and, more remotely, with the tenthred-
inid Hymenoptera.

Trichoptera, while much like Mecoptera in structure and
metamorphosis, are undoubtedly closely related to Lepidop-
tera ; in view of the extensive and deep-seated resemblances
between caddis flies and the most generalized moths (Microp-
terygidcC) there is little doubt that Trichoptera and Lepi-
doptera originated from the same stock.

The origin of the coherent group Coleoptera is by no means
clear, although thysanuriform larvcC 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 positicw of Coleop-
tera is largely arbitrary, and here the order is intruded between
Lepidoptera and Di])tera simply for want of a more satisfac-
tory place.

Lepidoptera. Trichoptera and ^lecoptera are probal)ly
branches from one stem. Lepidoi)tera. Diptera and Hymen-
optera are regarded by Packard as having had a common
origin from metabolic Xeuroptera.

Among Diptera. such larvcC as those of Culicidse are com-
paratively primitive, according to Packard, and larv?e of Mus-
cicke are secon<lary. or adaptive, forms.

Siphonaptera used to be regarded as Dijjtera and are prob-
ably an offshoot from the dipteran stem.

The most primiti\-e hymenopterous lar\Te are those of the

CLASSIFICATION

sawflies (Tentliredinidre ) , judging' from their reseml)lance to
mecopterons and lepidopterous larvje ; and the simple, maggot-
like form of the larvae of ants. bees, wasps and parasitic
Hymenoptera is dne to secondary modifications in correlation
with their sedentary mode of life.

In Diptera and Hymenoptera the phenomenon of metamor-
phosis 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 " high-
est " insects, when their remarkable psychological development
is taken into acconnt ; bnt 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 comparison can he made between them.

The following diagram (Fig. 7,2) is a graphic summary of
what has just been said in regard to the genealogy of the

Fk;. 3-

DIPTERA

HEMIPTERA

COLEOPTERA

THYSANURA

Genealogical diagram of the orders of insects.

orders of insects. The positions of Hemiptera and Coleoptera
are most open to criticism. The central group {T) is the

26 ENTOMOLOGY

hypothetical thvsanuroid source of ah insects. inclu(hng Thys-
anura themselves. Though Thysanura and CollenilDola show
no traces of wings, even in the embryo, it should be borne in
mind that all the other insects prol^ably 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 inde-
pendentlv in several different groups of insects.

CHAPTER II

ANATOMY AND PHYSIOLOGY

I. Skeleton

Number and Size of Insects. — The number of insect spe-
cies already known is aljont 300,000 and it is safe to estimate
the total nnml^er of existing- species as at least one million.

Among- the largest living species are the V^eneziielan beetle
Dyiiasfcs hcrciilcs, ^^•hich is 155 mm. long', and the \^eneznelan
grasshopper Acrid iitm lufrcillri, ^^■hich has a length of 166
mm. and an alar expanse of 240 mm. Among Lepidoptera,
Attacus atlas of Indo-China spreads 240 mm.; Attacus cccsar
of the Philippines, 255 mm. ; and the Brazilian noctuid Ercbits
agrippina, 280 mm. Some of the exotic woodd3oring larvre
attain a length of 150 mm.

The giants among insects have been found in the Carl)onif-
erous, from which Brongniart described a phasmid ( Tifaiio-
phasiiia) as being- one fourth of a meter long.

At the other extreme are beetles of the family Trichoptery-
gidae, some of which are only 0.25 mm. in length, as are also
certain hymenopterous egg-parasites of the families Chalcid-
id?e and Proctotrypid?e.

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
arthropods is their linear segmentation. The subject of the
orig-in of this segmentation 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 inher-
itance from annelid-like ancestors, the subject resolves itself

28 ENTOMOLOGY

into the question of the origin of the segmented from the un-
segmented " worms." Cope. Packard and others give the me-
chanical explanation which is here snmmarized. In a thin-
skinned, unsegmented worm, the llexures of the Ixxly initiated
hy the mnscnlar system 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 flex-
ure, i. e., the vallevs of the folds, and greatest at the jjlaces
of least flexure, i. e., the crests of the folds. This explana-
tion, which has been elaborated in some detail 1)y the Xeo-
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
primarv appendages have been brought together to co-operate
as mouth parts and sense organs, and the segiuents to which
thev belong have liecome compacted into a single mass — the
head — in which the original segmentation is difficult to trace.
The thickened cuticula (.f the head forms a skull, which
serves as a fulcrum for the mouth parts, furnishes a base of
attachment for muscles and protects the l)rain and other
organs.

\\'hile the jaws of most insects can only open and shut.
trans\erselv, their range of action is enlarged l)y movements
of the entire head, which are i)ermitted l)y the articulation
between the head and th<jrax.

As a rule, one segment o^'erlal)s the one next l)ehind; l)ut
the head, though not a single segment of course. ne\'er over-
laps the ])roth()rax in the typical manner, but is usually re-
ceix'ed into that segment. This condition, which may possil)ly
have been brought about simidy 1)_\' the l)ackward pull of the
muscles that mo\e the head, has certain meclianical advantages
over the alternative con(liti(.'n, in securing, most economicallv,
freedom of moNcment of the head and ])rotection for the artic-
ulation itself.

The size and strength of the skull are usually proportionate

ANATOMY AND PHYSIOLOGY

to the size and power of the month ])arts. In some insects
ahnost the entire snrface of the head is occnpied by the eyes,
as in Odonata (Fig-. 20, B) and Diptera (Fig. 39). In mus-
cid and many other (h])terons laryce, or " maggots," the head
is rechiced to the merest ruchment.

Though commonly more or less globose or oyate, the head
presents innnmeral)le forms ; it often bears nnarticulated out-
growths of yarious kinds, some of which are [)lainly adaptive,
while others are a])parently purposeless and often fantastic.

Sclerites and Regions of the Skull.— ^The dorsal part of
the skull (Fig.'33) consists almost entirely of the cpicnmiitm.

Fig. Zi-

Skull of a grasshopper, Mchmoplns ditJcrcntialis. a, antenna; c, clypeus; c, com-
pound eye; f, front; g, gena; /, labrum; ll>, labial palpus; m, mandible; nip, maxillary
palpus; o, ocelli; oc, occiput; pg. post-gena; ■;■, vertex.

which bears the compound eyes; it is usually a single piece,
or sdcritc, 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 sum-

ENTOMOLOGY

^f f^Sfiifil^^^^l^ %

iiiit of the head, is the region known as tlie I'crfcx; it
often bears ocelh. The clyl^ciis is easily recog-nized as l)eing
the sclerite to which the u])per hp, or labniiii. is hinged,
though the clypeus is not invarial)]y delimited as a distinct
sclerite. The cheeks of an insect are known as the gciuu,
and post-gciuc sometimes occur. On the under side of the
head is the giihi, \\hich hears the under li|), or lahiinn. That
part of the skull nearest the prctthorax is termed the occi-
j^iit ; usually it is not delimited from the epicranium, though
in some insects it is ccintinuous with the post-gence 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 meml:)rane

of the neck in Orthoptera
and some other insects con-
tains small ccri'ical sclcritcs,
dorsal, lateral or \'entral in
position ; these, in the opin-
ion of Comstock, ])ertain
to the last segment of the
head. Besides those de-
scribed, a few other cephalic
sclerites may occur, small
and inconspicuous, but ne\'-
ertheless of C()nsi(leral)le
morphok )gical importance.
Tentorium. — In the head is a chitinous supporting struc-
ture known as the fcntoriiini. This consists of a central plate
from which diverge two pairs of arms extending to the skull
(Fig. 34). ddie central plate lies lietween the l)rain and the
sul!(eso])hagcal ganglion and under the oesophagus, which
passes between the anterior pair of arms. The tentorium
braces the skull, affords muscular attachments and holds the
ce])lialic ganglia and the oesophagus in [ilace. It is not a true
internal skeleton, but arises from the same ectodermal layer

f;../.

.'^".^

Skull of a grasshopper, Dissostcira Caro-
lina. (1. occipital foramen; t. t, anterior
arms of tentorium.

ANATOMY AND PHYSIOLOGY

Fig. .1=;.

wliicli produces the external cuticnla : though authors are not
agreed as to the details of the development.

Eyes. — The eves are of two kinds — simple and com pound.
The latter, or eves proper, conspicuous on each side of the
head, are of common occurrence
except in the larvre of most holo-
metaholous insects, in some gene-
ralized forms (as Collemhola ) and
in parasitic insects. The compound
eyes (Fig. 40) are convex and often
hemispherical, though their outline
varies greatly ; thus it may l^e o\'al
(Orthoptera) or triangular {Xoto-
nccfa), while in the aquatic beetles
of the family Gyrinidre (Fig. t,-^)
each eye has a dorsal and a ventral
lobe, enabling the insect to see upward and downward at the
same time ; so also in Obcrca and other terrestrial beetles of the
same family. Superficialh-, a compound eye is divided into
minute areas, or facets, which though circular in the agglom-

Head of a gyrinid beetle, Dincu-
tits, to show divided eye.

Fig. 36.

Agglomerate eyes of a male
coccid, Leachia fuscipcnnis. —

After SiGNORET.

Fig. S7-

Facets of a compound
eye of Mclanojylus.
Highly magnified.

erate type of eye (Fig. 36) are commonly more or less hex-
agonal (Fig. 37), as the result of mutual pressure. These
facets are not necessarily equal in size, for in dragon Hies the
dorsal facets are frequently larger than the ventral. In diam-

ENTOMOLOGY

eter the facets range from .016 mm. ( Lyccriia) to .094 mm.
{Ccraiubx.v)- Their number is often enormons ; thus the
house flv (Miisca daiiicstica) has 4.000 to each eye, a butter-
fly iPapilio) 17,000, a l)eetle {Mor-
(Iclla) 25.000 and a sphingid moth
27,000; on the utlier hand, ants have
from 400 down, the worker ant of
Ecitoii ha\ing 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 (bursal in position. Lateral
ocelli (Fig. 38) occur in the larvcT of
most holometabolous insects and in
parasitic forms. Dorsal ocelli, sup-
plementary to the compound eyes,
occur on or near the vertex, and are
more commonly three in numl)er, ar-
ranged in a triangle, as in Odonata, Diptera (Fig. 39) and
Hymenoptera (Fig. 40) as well as many Orthoptera and He-
miptera. Few beetles have ocelli and almost no butterflies

Head of a catcrpiUar,
Sainia cccropia, to show
lateral ocelli.

Fig. 39.

' A

Ocelli and coini)ound eyes of a fly, Phormia rcgina. A, male; B, female.

(Lcrcma acciiis with its one ocellus being the only exception
known), though not a few moths ha\-e two ocelh.

As explained beyond, the com|)onnd eyes are adapted to per-
cei\e form and moxcmcnts and the ocelli to form images of

ANATOMY AND PHYSIOLOGY

objects at close range or simply to distinguish between light
and darkness.

Sexual Differences in Eyes. — In most Diptera (Fig. 39)
and in Hymenoptera (Fig. 40) and Ephemeridje as well, the
eyes of the male are larger and closer together (holoptic) than

riG. 40.

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

After CuEsiiiKE.

those of the female {dicJiopiic) . This difference is attributed
to the fact that the male is morg active than the female, espe-
cially in the matter of seeking out the opposite sex. Among
ants of the same species the different f(irms may differ greatly
in the number of lateral facets. Thus in Formica pralciisis,
according to Forel, the worker has about 600 facets in each
eye, the queen 800-900 and the male 1,200.

Blind Insects. — Many larvci?, 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 larvze, particularly such as are internal parasites
(Tachinidas, Ichneumonid?e), or such as feed within the tis-
sues of plants (many Buprestidse, Cerambycid?e and Curculi-
onidse). Subterranean or cavernicolous insects are either eye-
less or else their eyes are more or less degenerate, according
to the amount of light to which they have access. The state-
ment is made that blind insects never have functional wings.

Antennae. — The antennee, never more than a single pair
(though embryonic " second antennae " occur in Thysanura
4

ENTOMOLOGY

and Collembola), are situated near the compound eyes and
frequently between them. With rare exceptions the antennae
have always several and usually many segments. In form
these organs are exceedingly varied, though many of them
may be referred to the types represented in Figs. 41-43.

Fig. 41.

Various forms of antennae. A, filiform, Euschistus ; B, setaceous, Plathemis; C,
moniliform, Catogctiiis; D, geniculate, Bomhus; f, flagellum; p, pedicel; s, scape; E,
irregular, Phormia; a, arista; F, setaceous, Galcrita; G, clavate, Anosia; H, pectinate,
male Ptilodactyla; I, lamellate, Laclinostcrna ; J, capitate, Megalodacne; K, irregular,
D incut us.

Though homologous in all insects, the antennae are by no
means ecjuivalent in function. They are commonly tactile
(grasshoppers, etc.) or olfactory (beetles, moths) and occa-
sionally auditory (moscjuito), as described beyond, but may

ANATOMY AND PHYSIOLOGY

Antenna; of a moth, Samia cccropia. A,
male; B, female.

be adapted for other than sensory functions. Thus the anten-
nae of the aquatic beetle Hydropliiliis are used in connection
with respiration and those
of the male Mcloc to hold
the female.

Sexual Differences in An-
tennae. — In moths of the
family Saturniid?e (S. cccro-
pia, C. pronicthea, etc.) the
pectinate antenn?e of the male
are larger and more feathered
than those of the female,
and differ also in having more
segments (Fig. 42). Here
the antennre are chiefly olfac-
tory, 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 antenna? of the male mosquito (Fig. 43) are
highly developed organs of hearing, and are used to locate the
female; they have delicate fibrilhe of various lengths, some of
which are thrown into sympathetic ^•ibration by the note of
the female (p. 107).

Mcloc has just been mentioned. In Sminihurus iitalnr^rriiii
(Co]leml)(»la ) the antenn;e of the male are prox-ided with
hooks and otherwise adapted to grasp those of the female at
copulation.

Though systematists have recorded many instances of an-
tennal aiifigciiy, the interpretation of these sexual differences
has received very little attention; though a beginning in the
subject has been made by Schenk, whose results will be re-
ferred to in connection with the sense org'ans.

Mouth Parts.- — ^On account of their great range of diffe-

ENTOMOLOGY

rentiation, the mouth parts are of fundamental importance to
the systematist, particularly for the separation of insects into
orders. ]\lost of the orders fall into two groups according
as the mouth [larts are either hiting ( inaiidibiilafc) or sucking

Fig. 43.

Antennje of mosquito, Culcx pipiens. A, male; B, female.

(suctorial) . Collembola and Hymenoptera. however, com-
bine both functions ; Diptera, though suctorial, exhibit various
modifications for piercing, lapping or rasping; Thysanoptera
are partly mandilmlate but chiefly suctorial ; and adult Ephe-
merida and Trichoptera have but rudimentary mouth parts.

The mandibulate orders are Thysanura, Colleml^ola (pri-
marily). Orthoptera, Platyptera, Plecoptera. Ephemerida
(rudimentarily in adult), Odonata, Neuroptera, Mecoptera
and Coleoptera.

The mouth parts of an insect consist typically of labniiii,
mandibles, iiiaxillcc, labium and hypopharyux (Fig. 44),
though these organs differ greatly in different orders of in-
sects. The mandibulate, or primary t}pe. from which the
suctorial, or secondary type, has been derived, will be consid-
ered first.

Mandibulate Type. — The labniui. or upper lip, in biting

ANATOMY AND PHYSIOLOGY

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 mandibles in front and pulls food back
to these organs. On the roof of the pharynx, under the la-

FlG. 44.

Mouth parts of a cockroach, Ischnoftcra pennsylvaiiica. A, labrum; B, mandible;
C, hj'popharynx; D. maxilla: E, labium; c, cardo; g (of maxilla), galea; g (of labium),
glossa; /, lacinia; Ip, labial palpus; in, mentum; mp, maxillary palpus; p, paraglossa;
pf, palpifer; pg, palpiger; s, stipes; sm, submentum. B, D and E are in ventral
aspect.

brum and clypeus, is the cpipJiarynx : this consists of teeth,
tubercles or bristles, which serve in some insects merely to
hold food, though as a rule the epipharynx in mandil)ulate
insects bears end-organs of taste (Packard).

The iiumdiblcs, or jaws proper, move in a transverse plane,
being closed bv 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, A) it is compact, bluntly toothed, and often bears a molar,
or crushing, surface behind the incisi\e teeth. In carnivorous

ENTOMOLOGY

species (B) the man(lil)le is usually long, slender and sharply
toothed, without a mular surface. Often, as in soldier ants.

Fig. 45.

Variuus ioiuis of mandibles. A, Mclaiioplus : B, Cicindcla; C, Apis; D, Onthopliagus;
E, Chrysopa; F-I, soldier termites (after Hagen).

the mandibles 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 appa-
rently purposeless. The mandibles of
Oiifhophagiis (D) and many other dung-
beetles consist chiedy of a dexiljle lam-
ella, admirably adapted for its special
purpose. In Euphoria (Fig-. 261 ), which
feeds on pollen and the juices of fruits,
the mandiljles, 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 l)lood of plant lice is sucked
into the (esophagus. In termites (F-/)
the mandibles assume curious and often
inexplical)le forms.

Next in order are the iiia.vilhr, 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 of Harpaliis
caliginosus, ventral as-
pect, c, cardo; g, galea;
/, lacinia; p, paljius; pf,
palpi fer; s, stipes; sg,
subgalea.

ANATOMY AND PHYSIOLOGY

Fig. 47.

maxilla consists of three lo1)es, namely, palpus, galea and
lacinia, which are borne by a stipes, and hinged to the skull
by means of a cardo. The palpus, always lateral in position,
is usually four- or five-jointed and is tactile, olfactory or gus-
tatory 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 impor-
tance, often occur.

The labiiiin, or under lip. may properly be likened to a united
pair of maxilla, for both are formed on the same three-lobed
plan. This correspondence is evident
in the cockroach, among other gener-
alized insects. Thus, in this insect

(Fig. 44) :

Labium ^ Maxill.e

palpus = palpus

paraglossa = galea

glossa = lacinia

palpiger =^ palpifcr

vicntum = stipitcs

submcutmn with gula=^ caniiiics

In most mandibulate orders the
glossse unite to form a single median
organ, as in Harpalus (Fig. 47, g) .
The labium forms the floor of the

Labium of Harpalus caligi-
nosus, ventral aspect. g,
united glossse, termed the
glossa; m, mentum; p, palpus;

pharynx and assists in carrying food Ps, paipiger-, pr, paragiossa;

sm, submentum. The median

to the mandibles and maxilla?.

The use of the term " second

portion of the labium beyond
the mentum is termed the
ligula

maxillre " for the lal^ium of an in-
sect is open to objection, as it implies an ecjuivalence with
the second maxilla of Crustacea — which is by no means
established.

The tongue, or Jiypo pharynx, is a median fleshy organ (Fig.
44) which is usually united more or less with the base of the
labiunL In insects in general, the salivary glands open at the

ENTOMOLOGY

Fig. 48.

Hypopharynx of Hc-
niimerus talpoidcs. I,
lingua; s, superlingua. —
After Hansen.

base of the hypopharynx. In the most generahzed insects,
Thysanura and Collembola, the hypopharynx is a compound
organ, consisting of a median ventral lobe, or lingua, and two
dorso-lateral lobes, termed supcrlingiicc
by the author. Superlingure occur in a
few other mandibulate orders (Orthop-
tera. Fig. 48; Ephemerida, Fig. 49), but
have not yet been recognized in the more
specialized orders of insects.

Suctorial Types. — Owing to their
greater complexity, 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 Collembola (in
part), Thysanoptera (in part), Hemiptera, Trichoptera (im-
perfectly), Lepidoptera, Dip-
tera, Siphonaptera and Hy-
menoptera (which have
functional mandibles, how-
ever).

Hemiptera. — The beak,
or rostnuu, in Hemiptera
consists (Fig. 50) of a
conspicuous, one- to four-
jointed labium, which en-
sheathes hair-like mandil)les and maxilkT and is covered
above at its base by a short ]al)rum. d^he mandibles and max-
illae are sharply-pointed, piercing organs and the former fre-
quently bear retrorse barbs just behind the tip ; the two max-
illae lock together to form a sucking tul)e. Though primarily
a sheath, the labium l)ears at its extremity sensory hairs, which
are doubtless used to test the food. This general description
applies to all Hemiptera except the parasitic forms, which pre-

Hypopharynx of an ephemerid, Hct'ta-
gcnia. I, lingua; si, si, superlingua;. —
After V.w'SSiERE.

ANATOMY AND PHYSIOLOGY

sent special modifications. A pharyngeal pumping apparatus
is present, which is similar in its general plan to that of Lepi-
doptera and Diptera, as presently descriljed. though it differs
as regards the smaller details of construction.

Fk;, 50.

A D

Mouth parts of a hemipteron, Bcnactis grisetis. A, dorsal aspect; B, transverse sec-
tion; C, extremity of mandible; D, transverse section of mandibles and maxillse; c,
canal; /, labrum; li, labium; ?», mandible; mx, maxillre.

Lepidoptera, — In Lepidoptera. excepting Evince pliala, the
lahrum is reduced (Fig. 51) and the mandibles are either rudi-
mentary or absent (Rhopalocera). The two maxilL'c are rep-
resented by their galeae, which form a conspicuous proboscis ;
the grooved inner faces of the galeae (or lacini:e, according to
Kellogg) form the sucking tube, which opens into the (esoph-
agus. The labium is reduced, though the labial paljji (big.
52) are well developed. The so-called rudimentary mandi-
bles of Anosia and other forms have been shown l)y Kellogg
to be lateral projections of the la1)rum (Fig. 51) and he terms
them pilifers.

ENTOMOLOGY

Head of a sphingid moth, Plilc\
sc.vta. a, antenna; c, clypeus; c, eye; ,
m. mandible; p, pilifer; pr, proboscis.

•:thoiitius
labrum ;

The exceptional structure of the mouth parts in the g"ene-

rahzed genus Erioccphahi {Micropfcry.v) sheds much hght on

the morphologv of these
Fig. 51. . ' -

organs m other l^epidop-

tera, as Weaker and Kel-
ogg ha\e shown. In
this genus there are func-
tional mandihles ; the
maxilla presents palpus,
galea, lacinia, stipes and
cardo, though there is no
proboscis; the labium has
well de\-eloped submen-
tum, mentum and palpi ; a
hypopharynx is present.

The sucking apparatus,
as described Ijy LUu'gess,
is essentially like that of Diptera. Five muscles, originating
at the skull and inserted on the Fig. 52.

uall of a pharyngeal bulb, serve
to dilate the bulb that it may suck
in duids, Avhile numerous circular
muscles serve by contracting suc-
cessively to squeeze the contents
of the bulb l)ack into the stomach;
a hvpopharyngeal valve prevents
their return forward.

Diptera.- — In the female mos-
quito the mouth parts (Fig. 53)
are long and slender. As Dim-
mock has found, the lalirum and
epipharynx combine^ to form a
sucking tul)e ; the mandil)les and
maxill?e are delicate, linear, pierc-
ing organs, the latter lieing barl)ed
distally ; maxillary pali)i are pres-
^ Kulagin, however, describes them as remaining separate.

Head of a butterfly, Vanessa.
labial palpus; p, a, antennae; /,
proboscis.

ANATOMY AND PHYSIOLOGY

ent ; the hvpopharynx is linear also and ser\-es to conduct sa-
liva ; the labium forms a sheath, enclosing the other mouth
parts when they are not in use : a pair of sensory lobes, termed
labclla, occur at the extremity of the labium.

Fig. 5-

I li h

Mouth parts of female mosquito, Culcx pipicns. A, dorsal aspect; B, transverse
section; C, extremity of maxilla; D, extremity of labrum-eiiipharynx; a, antenna; e,
compound eye; h, hypopharynx; /, labrum-epipharynx; //, labium; m, mandible; mx,
maxilla; p, maxillary palpus. — B, after Dimmock.

The oesophagus is dilated to form a l)ull), or sucking organ,
from which muscles pass outward to the skull ; when these con-
tract, the bulb dilates and can suck in fluids, as blood or water,
which are forced back into the stomach by the elasticity of the
bulb itself, according to Dimmock ; the regurgitation of the
food is prevented by a valve.

The male moscjuito rarely if ever sucks blood and its mouth
parts diiTer from those of the female in that the mandibles are

ENTOMOLOGY

aljortecl and the maxilhc slightly developed, but with long
palpi, while the hypopharynx coalesces with the labium, and
there is n() oesophageal bulb.

Hymenoptera. — In the honey bee, which will sei"\'e as a
type, the labrum (Fig". 54) is simple; the mandibles are well
developed instruments for cutting and other purposes and the

Mouth parts of the honey bee, Apis incllifcra. a, base of antenna; hr, brain; c,
clypeus; h, hypopharynx; /, labrum: Ip, labial palpus; m. mentuni; ijhk mouth; m.v,
maxilla; sm, submentum. — After Cheshire.

remaining mouth parts form a highly complex suctorial appa-
ratus, as follows. The tongue is a long' flexi1)le organ, ter-
minating in a " spoon "' ( I-'ig-. 127) and clothed with hairs of
various kinds, fr)r gathering nectar or for sensory or mechan-
ical purposes. The maxilUe and labial palpi form a tube em-
bracing" the tongue, wdiile the epipharynx hts into the space
between the bases of the maxilhe to complete this tube.
Through this canal nectar is driven, by the expansion and con-
traction of the tube itself, according to Cheshire, except that
wdien only a small (|uantity of nectar is taken, this passes from
the spoon into a hue " central duct," or also into the " side
ducts," which are specially fitted to convey quantities of fluid
too small for the main tul)e. For a detailed account of the
highly complex and extjuisitely adapted mouth parts of the
honey bee, the reader is referred to Cheshire's admirable work
or to Packard's Text-Book.

Segmentation of the Head. — The determination of the

ANATOMY AND PHYSIOLOGY 45

number of segments entering into the composition of the insect
head has been a difficnh pro1)lem. 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 l:)asis, then, the antennae, mandibles,
maxill?e and labium may be taken to indicate so many seg-
ments; but in order to decide whether the eyes, labrum and
hypopharynx represent segments, other than purely anatom-
ical 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 appendages
are all alike (Fig. 194), i>r equivalent, though later they dif-
ferentiate into antenna?, mouth parts, legs, etc. IMoreover, the
nervous system exhibits a segmentation which corresponds to
that of the entire insect ; in other words, each pair of primitive
ganglia, constituting a iiciiroincrc, indicates a segment. Now
in front of the oesophagus three primiti\e segments appear, each
with its neuromere (Fig. 55) : first in position, an ocular seg-
ment, destined to bear the compound eyes; second, an aiitennal
segment; third, an {iifcrcalary ( /^rciiiaiidihiilar) segment,
which in the generalized orders Thysanura and Collembola
bears a transient pair of appendages that are probably homol-
ogous with the second antenn?e of Crustacea. In the adult,
the ganglia of these three segments ha\e united to form the
brain, and the original simplicity and distinctness have been
lost. The labrum, by the way, does not represent a pair of
appendages, but arises as a single median lobe, l^ehind the
CESOphagus, three embryonic segments are clearly distinguish-
able, each with its pair of appendages, namely, ///(///(///^//^//'.///a.r-
77/(7r3' and labial. Finally, the hypopharynx, or rather a part of
it, claims a i)lace in the series of segmental a])pcndages, as the
author has maintained ; for in Collembola its two dorsal con-
stituents, or supcrlingucc, develop essentially as do the other
paired appendages and, moreover, a superlingual neuromere
(I^^fe- 55) exists. The four primiti\e gangiia immediately

ENTOMOLOGY

behind the mouth eventually combine to form the suboesopha
geal ganglion.

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

Fig. 55.

Paramedian section of an embryo of tlie collembolan Anurida maritima, to show
the primitive ceplialic ganglia. /, ocular neuromere; 2, antennal; s, intercalary; 4,
mandibular; 5, superlingual; 6. maxillary; 7, labial; S, protlioracic; 9, mesothoracic;
a, antenna; /, labrum; li, labium; P^, l", P, thoracic legs; m, mandible; in.i; maxilla.
— After FoLsoM.

Thorax. — The thorax, or middle region, comprises the
three segments next l)ehind the head, which are termed, respec-
tively, pro-, iiicso- and iiictatJiora.v. In aculeate Hymenop-
tera, however, the thoracic mass includes also the first al)dom-
inal segment, then known as the propoiicinn , or iiicdnni scg-
nicnt. Each of the three thoracic segments l)ears a pair of

ANATOMY AND PHYSIOLOGY

Diagram of the principal scle-
rites of a thoracic segment, cm,
epimeron; es, episternum; p,
prjescutum; pr, parapteron ; ps,
postscutellum; s, scutum; si,
scutellum; st, sternum. — After

COMSTOCK.

legs in almost all adult insects, but only the meso- and meta-
thorax may bear wings.

The differentiation of the thorax as a distinct region is an
incidental result of the development of the organs of locomo-
tion, particularly the wings. Thus
in legless (apodoiis) larvae the
thoracic and abdominal segments
are alike; when legs are present, but
no wings, the thoracic segments are
somewhat enlarged ; and when
wings occur, the size of a wing-
bearing segment depends on the vol-
ume of the wing muscles, which in
turn is proportionate to the size of
the wings. When wings are absent
(as in Thysanura and Collembola)
or the two pairs ecjual in area (as
in Termitidae, Odonata, Trichoptera
and most Lepidoptera) the meso- and metathorax are equal. If
the fore wings exceed the hind ones (Ephemeridse, Hymenop-
tera) the mesothorax is proportionately larger than the meta-
thorax; as also in Diptera. where no hind wings occur. If
the fore wings are small ( Coleoptera ) or almost absent ( Sty-
lopid?e) 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 Orthop-
tera, Hemiptera and Coleoptera ; or, ( )n 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 notuui,
or tcrgitm; the ventral wall, the stcniiiiii ; and each lateral wall,
a plcuron; the restriction of these terms to particular segments
of the thorax being indicated by the prefixes pro-, nicso- or
mcta-. These parts are usually divided 1)y sutures into dis-

ENTOMOLOGY

Fig. 57.

tinct pieces, or sclerites, as represented diagrammatically in
Fig. 56. Thus the tergum of a wing-bearing segment is re-
garded as l3eing composed of four sclerites (fcrgitcs, Fig. 57),
namely and in order, prccscutum, sent 11 in, scntcUnni and post-
scntcllnni. The scutum and scutellum are commonly evident,

but the two other sclerites are
usually small and may be absent.
Each pleuron consists chiefly of
two sclerites (picnrifcs. Fig. 58),
separated from each other by a
m(/re or less oblicjue suture.
The anterior of these two, which
joins the sternum, is termed the
cpistcrnnin ; the other, the cpi-
incron. The f<jrmer is divided
into two sclerites in Odonata and
both are so divided in Neuroptera.
The sternum, though usually
a single plate, is in some in-
stances divided into halves, as
in the cockroach, or even into
five sclerites (Forficulidae).

To these should be added the
patagia of Lepidoptera — a pair
of erectile appendages of the
prothorax; and the paraptcra, or tcgnUc, of Lepidoptera and
Hymenoptera — a pair of small sclerites at the bases of the
front wings.

Each thoracic segment bears a pair of spiracles in the em-
bryo and in some adults as well {Campodca, 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 integument, brought about l)y the muscles
of the thorax. Thus the primitively wingless Thysanura and
Collembola have no hard thoracic sclerites, though certain

Dorsal aspect of the thorax of a
beetle, Hydrous piccus. J, pronotum:
2, mesoprsescutum; 3, mesoscutum; 4,
mesoscutellum; 5, mesopostscutellum;
6, metapr.-Escutum; 7, metascutum; S,
metascutellum; p. mctapostscutellum.
- — After Newport.

ANATOMY AND PHYSIOLOGY

creases about the bases of the legs may be regarded as incipi-
ent sutures, produced mechanically by the movements of the

Fig. 58.

'13

Ventral aspect of a carabid beetle, Galerita janns. i, prosternum; 2, proepisternum,
2, proepimeron; 4, coxal cavity; 5, inflexed side of pronotum; 6, mesosternum; 7, meso-
episternum; 8, mesoepimeron; p, metasternum; 10, antecoxal piece; 11, metaepisternum;
13, metaepimeron ; 13, inflexed side of elytron; a, sternum of an abdominal segment;
an, antenna; c, coxa; f, femur; Ip, labial palpus; md, mandible; mp, maxillary palpus;
t, trochanter; th, tibia; ts, tarsus.

legs. In soft nymphs and larv?e, the sclerites do not form until
the wings develop ; and in forms that have nearly or quite lost
their wings, as Pediculidse, Mallophaga, Siphonaptera and some
5

ENTOMOLOGY

Fig. 59.

parasitic Diptera, the sclerites of the thorax tend to disappear.
Fnrtliermore. tlie alisence of sclerites in the prothorax is prob-
ably 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 me-
chanical supports or as protections
for some of the internal organs.
The tentorium of the head has al-
ready been referred to. In the
thorax three kinds of chitinous in-
growths may be distinguished ac-
cording to their positions : ( i ) pJirag-
iiias, or dorsal projections; (2)
apodeiiies, lateral; (3) apophyses,
ventral. The phragmas (Fig. 59)
are commonly three large plates,
pertaining to the meso- and meta-
thorax, and serving for the origin
of indirect muscles of flight in
Lepidoptera, Diptera, Hymenoptera
and other strong-winged orders. The
apodemes are comparatively small in-
growths, occurring sometimes in all
three thoracic segments, though usu-
ally absent in the prothorax. The
apophyses occur in each thoracic seg-
ment as a pair of conspicuous proc-
esses, which either remain separate
or else unite more or less ; leaving, however, a passage for the
ventral nerve cord.

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, Pediculidce and Mal-
lophaga.

Transverse sections of the
thoracic segments of a beetle,
Goliathus, to show the endo-
skeletal processes. A, pro-
thorax; B, mesothorax ; C,
metathorax; a, a, apophyses;
orf, apodeme ; p, phragma. — ■
After KoLBE.

ANATOMY AND PHYSIOLOGY

Fig. 60.

Some ambiguity attends tlie use of these terms. Thus some
writers use the term apodemes for apophyses and otliers apply
the term apodeme to any of the three
kinds of ingrowths.

Legs. — In ahnost all adult insects and
in most larwe 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 seg-
ments (Fig. 60), in the following' order:
coxa, trochanter, femur, tibia, tarsus.
The coxa, or basal segment, often has a
posterior sclerite, the trocluintinc.^ The
trochanter is small, and in parasitic
Hymenoptera consists of two subseg-
ments. The femur is usually stout and
conspicuous, the tibia commonly slender.
The tarsus, rarely single-jointed, 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 larvcT ; between the claws in most
imagines is a pad, usually termed the
puk'illus. or cnipoiliuiii.

Adaptations of Legs. — The legs ex-
hibit a great variety of adaptive modifica-
tions. A walking or running insect, as a
carabid or cicindelid l)eetle (Fig. 62, A) presents an average
condition, as regards the legs. In leaping insects (g'rasshop-
pers, crickets, Haltica) the hind femora are enlarged {B) to
accommodate the powerful extensor muscles. In insects that
make little use of their legs, as Alay flies and TipulidcX, these
appendages are but weakly developed. The spinous legs of

^ But on account of the ambiguous use of this last term, the name vicron
(Fig. 61), proposed by Walton, is to be preferred.

Leg of a beetle, Calo-
sonia calidum. c, coxa;
cl, claws; f, femwr; s,
spur; f^-t'', tarsal seg-
ments; tb, tibia; tr,
trochanter.

ENTOMOLOGY

Fig. 6i.

Left hind leg of Bittacus. c, coxa
genuina; em, epimeron ; cs, cpisternum; /,
femur; m, meron; t, trochanter.

dragon flies form a basket for catching the prey on the wing.
Modifications of the front legs for the purpose of grasping
occur in manv insects, as the terrestrial families Mantida; (C)
and Reduviidci? and the aquatic families BelostomidcC and

Naucoridse (D). Swim-
ming species present special
adaptations of the legs (Fig.
2j8), as described in the
chapter on aquatic insects.
In digging insects, the fore
legs are expanded to form
shovel-like organs, notably
in the mole-cricket (Fig. 62,
E) , in which the fore tiV:)ia
has some resemblance to the
human hand, while the tarsus and tibia are remarkably adapted
for cutting roots, after the manner of shears. The Scara-
bseidce have fossorial leg's, the anterior tarsi of which are in
some genera reduced (F) or absent; they are rudimentary in
the female (G) of Pliaiurns carnifcx and absent in the male
(//), and absent in both sexes of DcltocJiiliini. Though
females of Plianccus lose their front tarsi by digging, the de-
generate 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 w by the two sexes
should differ in this respect. Many insects use the legs to
clean the antenna, head, mouth parts, wings or legs ; the honey
bee (with other bees, also ants, Carabidre, etc.) has a special
antenna-cleaner on the front legs (Fig". 263, D) , which is
described, with other interesting modifications of the legs, on
page 271.

Indeed, the legs serve many such minor purposes in addi-
tion to locomotion. They are generally used to hold the
female during coition, and in se\eral genera of Dytiscicke
{Dyfisciis, Cybistcr) the male (Fig. 62, /) has tarsal disks and
cupules, chiefly on the front tarsi, for this purpose. Among

ANATOMY AND PHYSIOLOGY

Fig. 6i

Adaptive modifications of the legs. A, Cicihdcla sexguttata; B, Ncmobius rittatus,
hind leg; C, Stagmomantis Carolina, left fore leg; D, Pelocoris femorata, right fore
leg; E, Gryllotalpa borealis, left fore leg; F, Canthon Icevis, right fore leg; G, Plianaus
carnifex, fore tibia and tarsus of female; H, P. carnifex, fore tibia of male; /, Dytis-
cus fasciventris, right fore leg of male; c, coxa; f, femur; s, spur; t, trochanter; tb,
tibia; ts, tarsus.

ENTOMOLOGY

Fig. 63.

other secondary sexual peculiarities of the legs may be men-
tioned the tibial brushes of the male Catocala concuuibciis,
regarded as scent organs, and the (jueer appendages of male

DolichopodidcT that dangle in the
air as these flies perform their
dances.

The pulvillus is commonly an
adhesive organ. In flies it has
glandular hairs that enable the in-
sects to walk on smooth surfaces
and to walk upside down; so also
in many beetles and notably in the
hone}' 1:)ee ( big. 63) ; in this insect
the pulvillus is released rapidly
from the surface to which it has
l)een 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
auditorv organs occur on the front til)i:e of Locustida?, Gryllidoe
and some ants. Finally, the legs may l3e used to produce sound,

Fic. 64.

Foot of honey bee, Apis mcl-
lifcra. c. c, claws: f, pulvillus:
fi-t^, tarsal segments. — After
Cheshire.

•^

Caterpillar of Plilcgcthontius sc.vta. Natural size.

ANATOMY AND PHYSIOLOGY

as in Stcnobothnis and snch other AcridiicLne as stridnlate by
rnbbing the femora against the tegmina.

Legs of Larvae. — Th(M-acic legs, terminating in a single
claw, are present in most larvae. Caterpillars have, in addi-
tion, fleshy abdominal legs (Fig. 64) ending in a circlet of
hooks. Most caterpillars have five 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 Geometrida; two (segments 6 and 10), while a few
caterpillars (Tisclicria, Liiiiacodcs) have none. Larva? of

Fig. 65;.

c?-..

Mechanics of an insect's leg. a, axis of coxa; c, coxa; cl, claw; c, extensor of
tibia; ec, extensor of claw; ct, 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) ; fi, tibia. — After Graber.

saw flies (Tenthredinida?) have seven or eight pairs of abdom-
inal legs and larva? of most Panorpidse, eight pairs. Not a
few coleopterous larva? (some Cerambycidcie, Phyfoiioiiuis)
also have abdominal legs, which are incompletely developed,
however, as compared with those of Lepidoptera.

The legless, or apodoiis, condition occurs frequently among
larvae and always in correlation with a sedentary mode of life;
as in the larvae of many Cerambycidce, nearly all Rhynchoph-
ora, a few Lepidoptera, all Diptera, and all ll^menoptera ex-
cept Tenthredinid.'e, Siricid;e, and other "J erebrantia.

ENTOMOLOGY

Fig. 66.

Among adult insects, female scale insects are exceptional in
lieing' 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 middle leg of the other move forward
almost simultaneously — though not quite, for the front leg
moves a little hefore the middle one,
which, in turn, precedes the hind leg.
During these movements the body is sup-
ported by the other three legs, as on a
tripod. The front leg, having been ex-
tended and its claws fixed, pulls the body
forward by means of the contraction of
the tibial flexors ; the hind leg, on the
contrary, pushes the body, by the short-
ening of the tibial extensors, against the
resistance afforded by the tibial spurs ; the
middle leg acts much like the hind one,
Ijut helps mainly to steady the body.
Different species show different peculiari-
ties 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 tiljia would
cause the tibial spur (s) to describe the
line jy' /,■ and the backward movement of
the leg due to the upper coxal rotator r
would cause the spur to follow the arc .s- j".
As the resultant of both these movements,
the path actually descril)ed by the tibial
spur is .9 2: then, as the leg moves forward, the curve is con-
tinued into a loop.

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

Muscles of left miil
leg of a cockroach, pos-
terior aspect. abc, ab-
ductor of coxa; adc,
adductor of coxa; cf,
extensor of femur; ct,
extensor of tibia; ff,
flexor of femur; ft,
flexor of tibia; fta,
flexor of tarsus; rt, re-
tractor of tarsus. — After
MiALL and Denny.

ANATOMY AND PHYSIOLOGY 57

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 to-
gether. 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 spurs are
driven, and the straightening of the leg" by means of the pow-
erful 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 movements 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
parjts, surpassing all the other organs as regards range of dif-
ferentiation, 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 insects are already
known.

Tvpically, there are two pairs of wings, attached respec-
tively 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 Coccidse, though in male Stylopida; it is the posterior
pair, the fore wings being rudimentary.

In bird lice, fleas and most other parasitic insects, the wings
have degenerated through disuse. In Thysanura and Collem-
bola 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 out-
growths; Tower, however, has recently shown that the wings
of Coleoptera, Orthoptera and Lepidoptera are pleural in ori-
gin, 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 [Kjsition.

58 ENTOMOLOGY

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 Orthoptera, they are
leathery, and are known as tc'^iiiiiia; in Coleoptera they are
usually horny, and are termed elytra : in Heteroptera, the hase
of the front wing is thickened and the apex remains mem-
branous, forming a hcniclylroii. Diptera have, in place of the
hind wings, a pair of cluljbed threads, known as balancers, or
haltcrcs, and male CoccidcC have on each side a bristle that
hooks into a pocket on the wing and serves to support the lat-
ter. In many muscid flies a doubly lobed memliranous 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 (Iianiiili) ; these are situ-
ated on the costal margin of the hind wing" and clutch a rod-
like fold of the fore wing. In very many m<:)ths. the two
wings are enabled to act as one by means of a frenulum, con-
sisting' of a spine or a bunch of bristles near the base of the
hind Aving, which, in some forms, engage a membranous loop
on the fore wnng.

Venation, or Neuration. — A wing is divided by its -z-cius,
or ncrvurcs, into spaces, or cells. The distribution of the
veins is of great systematic importance Init, 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 subject. For example, the term discal cell,
used in descriptions of Lepidoptera, Diptera. Trichoptera and
Psocid:e. has in no two of these groups l)een applied to the
same cell. The admirable work of Comstock and Needluun.
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 Acins, these authors ha\e arri\ed at a primi-
tive type of tracheation (Fig. 67) to which the more complex
types of tracheation and venation may be referred.

ANATOMY AND PHYSIOLOGY

In general, the following principal longitudinal veins may
be distinguished, in the following order: casta, sithcosta,
radius, media, cubitus and anal (Figs. 67-71).

3d A 2d A

IstA

Cu2

Hypothetical type of venation. A, anal vein: C, costa; Cii, cubitus; M, media; R,
radius; Sc, subcosta. — Figs. 67-71 after Comstock and Needh.\m.

The costa (C) strengthens the front margin of the wing
and is essentially unl:)ranched.

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

The radius (R), though sul)ject 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 Needham.

The cubitus (Cu) has two branches.

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

The Plecoptera, as a ^vhole, show the least departure from
the primitive type of venation ; which is \\ell preserxcd; also,
in the more generalized of the Trichoptera.

Starting from the primiti\e type, specialization has occurred
in two ways: by reduction and l)y addition. Reduction oc-
curs either l)y the afropliy of \eins or by the coalescence of
tw^o or more adjacent veins. Atrophy explains the lack of all
])ut one anal \'ein in Rliyf^lius (Fig. 68) and other Diptera,

ENTOMOLOGY

and the absence of the l)ase of the media in Aiiosia (Fig. 69)
and many other Lepidoptera ; in the pupa of Aiiosia, the media
may be found complete. Coalescence "takes place in two ways :
first, the point at which two veins separate occurs nearer and

/si A Cu^

Wing of a fly, Rhypliiis. Lettering as before.

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
marp'in of the wing until thev unite, and then the coalescence

2dA

Wing of a butterfly, Anosia. Lettering as before.

proceeds towards the base of the wing." (Comstock and Need-
hauL ) The former, or out-ward, kind of coalescence is com-
mon in most orders of insects; the latter, or ini^'ard, kind is
especially pre\alent in Diptera.

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

ANATOMY AND PHYSIOLOGY

Comstock and Needham have succeeded in homolog'izing
practically all the types of neuration, including such perplex-
ing 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

Fig. 70

Wings of a May fly. Lettering as before.

veins; there is no longer any excuse for the lamentable confu-
sion that has hitherto attended the study of venation.

Folding of Wing. — In some beetles (as Clirysobofhris) the
wings are no larger than the elytra and are not folded; in

A typical hymenopterous wing.

Lettering as before.

others, however, the wing-s exceed the el_\tra in size, and when
not in use are folded under the elytra in ways that are siniple
but efficient, as descril^ed by Kolbe and by Tower. To be
understood, the process of folding should be observed in the
hving insect. As described by Tower for the Colorado potato

ENTOMOLOGY

beetle, the folded wing- (Fig. 72, B) exhibits a costal joint
(a), a fold parallel to the transverse vein (&). and a complex
joint at (/. The wing- rotates upon the articnlar head (<///)
and when folded back beneath the wing-covers the inner
end of the cotyla (c) is brought into contact with a chitin-

FiG. 72.

Wing of Lcptinotarsa dcccmlincata. 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, posterior system of veins. — After Tower.

ons sclerite of the thorax, which stops the further movement
of the cotyla medi^uiward. and as the wing swinges farther back
the middle system of veins ( /// ) is pushed outward and ante-
riorly. 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 liga-
ments in the wing which could aid in the folding.

Mechanics of Flight. — The mechanism of insect iTght is
much less complex than one might anticipate. Indeed, owing
to the structure of the wing itself, simple up and down move-
ments are suflicient for the simplest kind of flight. During

ANATOMY AND PHYSIOLOGY 63

oscillation, the plane of the wing changes, as may be demon-
strated I)}' holding' a detached wing by its base and blowing at
right angles to its snrface : the membrane of the wing then yields
to the pressnre of the air while the rigid anterior margin does
not, to any great extent. Similarly, as the wing- moves down-
ward the membrane is inclined upward by the resistance of the
air. and as the wing moves upward the meml)rane bends down-
ward. Therefore, by becoming deflected, the wing encounters
a certain amount of resistance from
behind, which is sufticient to propel
the insect. The faster the wings
vibrate, the greater the deflection,
the greater the resistance from lie-
hind, and the faster the flight of the
insect.

The path traced in the air by Trajectory of the wing of an
... ... . ■ ,' insect.

a rapidly vibrating wmg may be

determined by fastening a bit of gold leaf t(^ 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 lumi-
nous elongate figure 8. During flight, the trajectory consists
of a continuous series of these figures, as in Fig. y^)-

Marey, the chief authority on animal locomotion, used
chronophotography, among other methods, in studying the
process of flight, and obtained at first twenty, and later one
hundred and ten. successive photographs 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. Ne\-ertheless. the
images could be interpreted without difficulty, in the light of
the results obtained l)y other methods. At length he obtained
sharp but isolated images of vibrating wings with an exposure
of only 1/25,000 of a second.

The frequency of wing vibration may be ascertained from
the note made by the wing- — if it vibrates rapidly enough to

ENTOMOLOGY

make one ; and, in any case, may be determined graphically by
means of a kymograph, which, in one of its forms consists of
a cylinder coyered with smoked paper and revolved 1)y clock-
work 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

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, Polistcs. The tuning fork in this instance had a vibration frequency of 97.6.

on the same paper by a tuning fork of known \'ibration period,
the frecjuency of wing 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 extreme 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 trajec-
tory may be obtained, as in Fig. 74, B. The wings of the two
sides move synchronously, as Marey found.

The smaller the wings are, the more rapidly they vibrate.
Thus a buttertiy (P. rapcc) makes 9 strokes per second, a
dragon fly 28, a sphingid moth yz, a bee 190 and a house
fly 330.

Wing Muscles. — The l)ase of a wing projects into the
thoracic cavity and serves for the insertion of the direct mus-
cles of flight. Regarding the wing as a lever (Fig. 75, A),

ANATOMY AND PHYSIOLOGY

^5.

with the fulcrum at p, it is easy to understand how the con-
traction of muscle c raises the wing" and that of muscle d low-
ers it. These muscles are shown diagrammatically in l^ig.
75, B. Besides these, there are certain muscles of flight which
act indirectly upon the wings, hy altering the form of the
thoracic wall. Thus

the muscle ic ( Fig-. 75, " ^^'

B) elevates the wing'
by pulling the tergum
toward the sternum ;
and the longitudinal
muscle /(/ depresses the
wing indirectly by
arching the tergum of
the thorax.

Though up and
down mo\ements are
all that are necessary
for the simplest kind
of insect flight, the
process becomes com-
plex in proportion to
the efticiency of the
flight. Thus in dragon
flies there are nine
muscles to each wing :
five depressors, three
elevators and one ad-
ductor.

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

Segments. — A t\-pical alxlominal segment bears a dorsal
6

A, diagram to illustrate the action of the wing
muscles of an insect. B, diagram of wing mus-
cles. (J, alimentary canal; en, muscle for con-
tracting the thorax, to depress the wings; d, de-
jiressor of wing; e, elevator of wing; ex, muscle
for expanding the thorax, to elevate the wings;
id, indirect depressor; ie, indirect elevator; /, leg
muscle; p, pivot, or fulcrum; s, sternum; t, ter-
gvun; ws,, wing. — After (iR.\BER.

Abdominal.

Tola

7
8

66 ENTOMOLOGY

plate, or fcri^iuii. and a ventral plate, or stcnnini. the two being
connected bv a pair of pleural iiicinbraiirs, which facilitate the
respiratory movements of the tergum and sternum. ]\Iost of
the abdominal segments have spiracles, one on each side, situ-
ated in or near the pleural membranes of the first seven or
eight segments. The total numljer of pairs of spiracles is as
follows :

Thoracic.

Caiiipodca, 3

Japyx, 4

Machilis. 2

Lcpisiua. 2

Blattidre. Acridiidie, 2

Odonata. 2

Heteroptera, 3

Lepidoptera, 2

Diptera, 2

In most embryo insects there are eleven pairs of spiracles
(three thoracic and eight abdominal) ; in adults. howe\-er. two
pairs are commonly suppressed — the prothoracic and the
eighth abdominal.

Number of Abdominal Segm.ents. — Though consisting
typically of ten segments — the numl)er e\ident in such general-
ized insects as Thysanura and Ephemerida — ele\"en occur in va-
rious adult Orthoptera, with traces of a twelfth, while Hey-
mons has detected twehe abdominal segments 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 al)domen in
relation to the thorax. Imt especially to modifications of the
extremity of the alxlomen. for sexual purposes.

Modifications. — In aculeate Hymenoptera the first segment
of the abdomen has been transferred to the thorax, where it
\s known as the pro pod cit III, or median segment: in other words,
what appears to be the first abdominal segment is actually the
second ; this, as in l)ees and \vasps. often forms a petiole, which
enables the sting to be applied in almost any direction. In Cy-
nipid.'c the tergum of segment two or three occupies most of the

ANATOMY AND PHYSIOLOGY

abdominal mass, the remaining segments being reduced and
inconspicuous. The terminal segments of the abdomen often
telescope into one another, as in p^^. _^^

many Coleoptera and Hymenop-
tera (Chrysidid?e), or undergo
other modifications of form and
position \\hich obscure the seg-
mentation. As to the nuiuber of
evident (not actual) abdominal
segments, Coleoptera show five or
six ventrally and seven or eight
dorsally; Lepidoptera, seven in
the female and eight in the male ;
Diptera, nine (male Tipulidje) or
only four or five ; and Hymenop-
tera, nine ( TenthredinidcT) or as
few as three (Chrysididcis). In
the lar\-a; of these insects, how-
e\-er, nine or ten abdominal seg-
ments are usually distinguishable,
though the tenth is frequently
modified, being in caterpillars
united with the ninth.

Appendages. — ^Rudimentary ab-
dominal limbs occur in Thysanura
(Macliilis, Fig. 76). Functional
abdominal legs do not occur in
adult insects, but in larwt the ab-
dominal pro-legs (often called " false legs," Fig, 64) are ho-
mologous with the thoracic legs and the other paired segmental
appendages, as the embr\-ology shows. The eml)ryo of CEcan-
tJuis, according to Ayers, has ten pairs of abdominal appen-
dages (Fig. 196), 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

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

OUDEMANS.

ENTOMOLOGY

Abdomen of female l)eetle, Crraiiiliyx, in
which the last three segments are used as an
ovipositor. — After Kolbe.

Orthoptera (to wliich order Qicautluis l)e]on^-s). In Collem-
bola, the enil)ry() has paired alxlominal hnil)S, and those of the
first alxlominal ses^'nient e\'entiial]y unite to form the i^ecuhar

■I'cntral fiibc ( Fig. 12)
of these insects, while
those of the fourth seg-
ment form the character-
istic leaping organ, or

flll'Cllhl.

Cerci. — In many of the
more generalized insects,
the alxlomen bears at its
extremity two or three
appendages termed ccrci. These occur in both sexes and are
frequently long and multiarticulate, as in Thysanura (Figs.
76,9, 10) and Fphemerida ( Figs. k^.B ; 84), though shorter in
cockroaches and reduced to a single sclerite in Acridiid;e (Fig.
87). The i)aired cerci, or ccrco/^oda of Packard, are usually
though not always associated with the tenth abdominal seg-
ment and are homologous with legs, as ,\yers has found in
CEcaiilhiis and Wdieeler in XipliiJiinii. As to their functi(in,
the cerci of Thysanura are tac-
tile, and those of the cockroach
olfactory, while the cerci of
male AcridiidcC often serve to
hold the female during' copu-
lation.

Extremity of Abdomen. —
Various modifications of the terminal segments of the abdo-
men occur for the purposes of defiTcation and especially repro-
duction. The anus, dorsal in ])osition, opens always through
the last segment and is often shielded aboxx ])\' a suraiuil j^latc
and on each side by a lateral j^lalc. The genital orifice is al-
ways ventral in ])osition and occurs commonl\- on the ninth
alxlominal segment, though there is some \ariation in this re-
spect. 'I he external, or accessory, organs of re])roduction are
termed the i:;ciiitalia.

Abdomen of a female midse. Cccido-
myia Icguiiiinicola, to show the pseudo-
ovipositor.

ANATOMY AND PHYSIOLOGY

Female Genitalia. — In Xenroptera, Coleoptera.Lepidoptera
and Diptera the \a,^'ina simply opens to the exterior or else
with the anus into a common chamher, or cloacd. Often, as
in Ccrambyx ( h'ig. yy) and Cccidouiyia (Fig-. 78) the attenu-

FiG. 79.

Ovipositor of Locusta. A, lateral aspect; B, ventral aspect; C, transverse section;
c, cerci; d, dorsal valve; i, inner valve; ■:■, ventral valve. The numbers refer to
abdominal segments. — After Kolbe and Dewitz.

ated distal segments of the alxlomen serve the purpose of an
ovipositor; thus in Cecidomyiid;e, the terminal segments, tele-
scoped into one another when not in use, form when extruded
a lash-like organ exceeding fre(|uently the remainder of the
hody in length.

A true ovipositor occurs in Tlixsanura, ( )rth(>ptera, Odo-
nata, Hemiptera. Hvmenoptera and some other orders of in-
sects. The ovipositor consists essentially of three pairs of
valves, or gojiapophxscs — a dorsal, a \entral and an inner
pair. The two inner \al\es form a channel through which
the eggs are conveyed. In Locustiche ( V\g. 79) the three

ENTOMOLOGY

valves of each side are held together
by tongues and gr()o\'es, which, how-
ever, permit sliding movements to take
place. Most anthorities have found
that the gonapophyses belong to the
segmental series of paired appendages
— are homodynamous with limbs — and

Cross section of the
ovipositor of Sircx. c,

channel; d, d, dorsal pertain commonlv to abdominal segments

valves; i, united inner . ' .

valves; i; v, ventral seven. eight and iiiiie.

valves. — After Taschen- The

IhG. Si.

o\-ipositor attains its greatest
complexity in Hymenoptera. in which
it becomes modified for
sawing, boring or sting-
ing. In Sircx (V\g. 80)
the inner valves are
united together ; in Aj^is
the dorsal valves are rep-

Sting and poison apparatus
of honey bee. ag, accessory
gland; p, palpus; pg, poison
gland (formic acid) ; r, reser-
voir; s. sting. — After Kraepe-

LIN.

Sting of honey bee. A, I, .', .?. positions
in three successive thrusts; i", sheath. B,
cross section; c, channel; ;', united inner
valves, forming the sheath; v, v, ventral
valves, or darts. — A, after Cheshire; B, after
Fencer.

resented by a pair of palpi, the
inner valves unite to form the
shcatli (Fig. 81, /?), and the ven-
tral two form the darts, each of
which has ten l)arl)ed teeth behind
its apex, which tend to prevent
the withdrawal of the sting from a
wonn<l. Idle action of the sting, as

ANATOMY AND PHYSIOLOGY

described by Cheshire, is rather complex. Briefly, the sheath
serves to open a wound and to guide the
darts ; these strike in ahernately, inter-
rupted at intervals by the deeper plung-
ing of the sheath (Fig. 81, A). The
poison of the honey bee is secreted b)'
two glands, one acid and the other alka-
line. 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
elYect ; and that in insects which simple-
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 gona-

pophyses correspond to those of the
female. The penis (Fig. 83) rep-
resents the two inner vah'es of the
ovipositor and is frecjuently enclosed
by one or two pairs of valves. In
Fphemerida the two inner valves
are partly or entirely separate from
each other, forming two intromit-
tent organs (Fig. 84).

In male Odonata, the ejaculatory
duct opens on the ninth abdominal
segment, l)ut the cojnilatory organ is
placed on the under side of the sec-
ond segment, to which the spermato-
zoa are transferred by the bending
of the abdomen. At copulation, the abdominal claspers of the

xtremity of abdomen
of a male beetle, Hy-
drophilns, ventral aspect.
g, genitalia; p, penis;
v'^, v^, pairs of valves
enclosing the penis; 6-g,
sterna of abdominal seg-
ments. — After KoLBE.

Fig. 84.

Extremity of abdomen of a
male May fly, Hexagenia varia-
bilis, ventral aspect. c, c, c,
cerci; cl, cl, claspers; i, i, in-
tromittent organs.

ENTOAIOLOGY

male grasp the neck of the female, and the latter 1)en<ls her
abdomen forward nntil the tip reaches the peculiar copnlatory
apparatus of the male.

Fig. 8s.

Genitalia of a moth, Saiiila cccropia. A, male; B, female; a, anus; c, c, claspers;
0, opening of common oviduct; p, penis; .?, uncus (the doubly hooked organ); v, vesti-
bule, into which the vagina opens. The numbers refer to abdominal segments.

The claspers of the male consist of a single pair, variously
formed. Thev are present in Ephemerida, Neuroptera, Tri-
choptera, Lepidoptera (Fig. 85), Diptera and some Hymen-
optera, though not in Coleoptera, and often afford good spe-
cific characters, as in Odonata. In butterflies of the genus

Fig. 86.

Terminal abdominal appendages of a dragon fly, Plathcinis tritnaculata. A, male;
B, female. i, inferior appendage; s, s, superior appendages (cerci). The numbers
refer to abdominal segments.

Thaitaos, the claspers are peculiar in l)eing strongly asym-
metrical. In Odonata (Fig. 86, A) and Orthoptera (Fig.
87, A) the cerci of the male often serve as claspers.

ANATOMY AND PHYSIOLOGY

In many insects tlie tergum of the last abdominal segment
forms a small suraiial plate (Fig. 87, B, sp) ; this sometimes

Fig. 87.

89 W ,,

9 10 n

Extremity of the abdomen of a grasshopper, Mclanol^his diffcrcntialis. A, male;
B, female. The terga and sterna are numbered, c, cerciis; d, dorsal valves of ovi-
positor; e, egg guide; p, podical plate; s, spiracle; sp, suranal plate; v, ventral valves
of ovipositor.

supplements the claspers of the male in their function, as in
Lepicloptera (Fig. 85, A, s).

2. Integument

Insects excel all other animals in respect to a(lapti\'e modi-
fications of the integument. Xo longer a simple limiting"
membrane, the integument has become hardened into an exter-
nal skeleton, evaginated to form manifold adaptive structures
such as hairs and scales, and imaginated. along with the un-
derh'ing cellular layer, to make glands of various kinds.

Chitin, — The skin, or ciificula,^ of an insect differs from
that of a worm, for example, in being thoroughly permeated
with a peculiar sulxstance known as chitin — the basis of the
arthropod skeleton. This is a substance of remarkable sta-
bility, for it is unaffected 1)y almost all ordinary acids and
alkalies, though it is soluble in sodic or potassic hyi)ochlorite
(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,

' The cuticiila of an insect should l)e (Hstinguislied from tlic cuticle of
a vertebrate, the former being a liardened llnid, while the latter consists
of cells themselves, in a dead and flattened condition.

ENTOMOLOGY

possibly a putrefaction, which accounts in a measure for the
rapid chsappearance of insect skeletons in the soil (Miall and
Denny). By boiling the skin of an insect in ])otassic hydrate
it is possible to dissolve away the cuticular framework, lea\--
ing' fairly pure chitin, without destroying the organized form
of the integument, though less than half the weight of the
integument is due to chitin. The formula of chitin is given
as CgHjsNO,. or CisH^jNOjo by Krukenberg, and Packard
adopts the formula Cj^HoeNoOjo ; though no two chemists
agree as to the exact [proportions of these elements, owing

probably to variations in the
substance itself in difTerent in-
sects or even in the same species
of insect. Iron, manganese
and certain pigments also enter
into the composition of the
integument.

Chitin is not peculiar to ar-
thropods, for it has been de-
tected in the setie and pharyn-
geal teeth of annelid worms,
the shell of Liiigiihi and the
pen of the cuttle fish (Kruken-
berg ) .

The chitinous integument (Fig. 88) of most insects con-
sists of two layers : ( i ) an outer layer, homogeneous, dense,
without lamellae or pore canals, and being the seat of the cutic-
ular colors; (2) an inner layer, "thickly pierced with pore
canals, and always in layers of different refractive indices and
different stainability." (Tower.) These two layers, respec-
tively primary and secondary cuticula, are radically different
in chemical and ])hysical properties. The chitinous cuticula
is secreted, as a fluid, from the hypodermis cells, luich layer
arises as a fluid secretion from the hypodermis cells, the pri-
mary cuticula being the first to form and harden.

The fluid that separates the old from the new cuticula at

Section through integument of a
beetle, Clirysobotliris. b, basement
membrane; c^ primary cuticula; c-,
secondary cuticula; /;, hypodermis cell;
n, nucleus. — After Tower.

ANATOMY AND PHYSIOLOGY

ecdysis is poured over the hypoderniis l)y certain large special
cells, which, according- to Tower, " are not true giands, but
the setigerons cells which, in earl}' life, are chiefly concerned
with the formation of the hairs upon the Ijody ; lout upon the

Fig. 89.

Modifications of the hairs of bees. A, B, Megachile; C, E, F, Collctcs;
D, Chclostoma. — After Saunders.

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 hypodcrmis cells ( Fig.
88). These cells, distinct in embryonic and often in early lar-
val life, subsecjuently become confluent by the disappearance 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 delicate, hyaline bascmciil inouhranc ; they
contain pigment granules, fat-drops, etc.

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

ENTOMOLOGY

Fk;. 00.

Hairs, Setse and Spines. — These occur universally, serv-
ing a great variety of purposes ; they
are not always sim]:)le in form, but are
often toothed, branched or otherwise
modified (Fig. 89). Hairs and bris-
tles are frequently tactile in function,
o\er the general integument or else
localh'; or olfactory, as on the antennie
of moths ; or occasionally auditory, as
on the antenn^'c of the male niosquito;
these and other sensory modifications
are described beyond. The hairy
clothing of some hiliernating cater-
pillars (as /,s-/(/ isdln^lhi) probably pro-
tects them from sudden changes of
temperature. Hairs and spines fre-
quently protect an insect from its ene-
mies, especiallv when these structures

Section of antenna of a
moth, Sattiriiia, to show
developing hairs, c, cutic-
ula; /, formative cell of
hair; Ii, hypodermis; t,
trachea. — After Semper.

Fig. 91.

are glandular and emit a
malodorous, nauseous or
irritant lluid. (dandular
hairs on the pulvilli of
many thes, 1)eetles, etc.,
enal)le these insects to walk
on slippery surfaces. The
twisted or branched hairs
of l)ees serve to gather
and hold pollen grains; in
short, these simple struc-
tures exhiljit a surprising-
variety of adaptive modifica-
tions, many of which will be
described in connection with
other sul)jects.

A hair arises from a
modified hyixxlermis cell (Fig. 90), the contents of which

Radial section tliruut;h the hase of a

hair of a caterjiillar, I'icris rap(C. c, cutic-

ula; /, formative cell; /;, hair; liy, hypo-
ilermis.

ANATOMY AND PHYSIOLOGY

Fig. 92

extend tliroiigh a pore canal into the interior of the hair (Fig.
91 ) ; sometimes, to Ije snre, as in glandular or sensory hairs,
the hair cell is multinucleate, re])-
resenting, therefore, as man)' cells
as there are nuclei. The wall of
a hair is continuous with the gen-
eral cuticula and at moulting each
hair is stripped off with the rest
of the cuticula, leaving in its place
a new hair, which has heen form-
ing inside the old one.

Scales. — Besides occurring
thr(.ughout the order Lepidoptera
and in numerous d^'ichoptcra.
scales are found in many Thys-
anura and Collemhola, several
families of Coleoptera (including
Dermestiche and CurculionidtC), a
few Diptera and a few Psocid;e.

Though diverse in form ( hdg.
92), scales are essentially Hattened

\"arious

sacs having at one end a short

tonus ot scales.
.-/, E, thysanuran, Macliilis; B,
beetle, Anthrcnus; C, butterfly,
Picris; D, moth, Liinacodcs.

pedicel for attachment to the in-
tegument. The scales usually l)ear markings, wliich are
more or less characteristic of the species ; these markings,
always minute, are in some species so exquisitely fine as
to test the highe.st powers of the microscope; the scales

of certain Collemhola ( Lcf^i-
docxrtits. etc.) ha\e long l^een
used, under the name of
" Todura " scales, to lest the

Fig. 93.

<3!Ct:3ca3jatfl0

Cross section of scale of Anusia.
After M.WER.

resolving power or objec-
tives, for which i)urpose they
are excelled only l)y some of the diatoms. Ihittertly scales
are marked with ])arallel longitudinal ridges ( I'ig. 92, C),
wdiich are confined alm.^st entirelv to the upper, or ex-

7«

ENTOMOLOGY

posed, surface of the scale (-Fig. 93) and mimljer from
33 or less (Aiiosia) to 1,400 (MorpJio) to each scale, the

stride beino- from .002 mm.
Fig. 94- " ,-,- ,

to .0007 mm. apart (Kel-
logg" ) ; Ijetween these longi-
tudinal ridges may be dis-
cerned delicate transverse
markings. Internally, scales
are hollow and often contain
pigments derived from the
bit )( 1(1.

On the wing of a butter-
dv the scales are arranged
in regular rows and overlap
one another, as in h^ig. 94;
in the more primitive moths
and in Trichoptera, how-
Arrangement of scales on the wing of a evcr, their clistributiou is

butterfly, Pahilio. ^ , . ,

rather n'regular.

A scale is the equivalent of a hair, for ( i) a complete series

of transitions 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, Spu-

FiG. 95.

Hairs and scales of a moth, Sainia cccropia.

ler, Mayer and others. Both hairs and scales arise as pro-
cesses from enlarged hypodermis cells, or forniahi'C cells ( I'ig.
96). The scale at first contains protoplasm, which gradually
withdraws, leaving short chitinous strands to hold the two
membranes of the scale together.

ANATOMY AND PHYSIOLOGY

Uses of Scales. — Anmno- Th^-saimra and Collenilxila. scales
occur nnl_\- on sucli species as li\-e in C()mparati\'elv dry sitna-
tions, from wliich it may 1)e inferred that tlie scales serve to
retard the evaporation of moisture through the delicate integu-
ment of these insects. This inference is supported l:)v the fact

Fig. 96.

Development of butterfly scales.
A, Vanessa; B, Anosia. b, base-
ment membrane; /, formative cell;
/;, hypodermis; s, scale. — After
Mayer.

Fig. 97.

Androconia of butter-
flies. A, Pieris ra[^cr; B,
Efcrcs comyntas.

that none of the scaleless Collem1)ola 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
Lepidoptera the scales are possibly of some value as a mechan-
ical protection; thev have no iniluence upon flight, as ■Mayer
has proved, and appear to be useful chietly as a Ijasis for the

ENTOMOLOGY

development of color and color patterns — which are not intre-
qnently adapti\-e.

Androconia. — The males of many buttertlies. and the males
only, have pecnliarlv shaped scales known as androconia (Fig-.
97) ; these are commi3nly confined to the npper snrfaces oi the
front wings, where thev are mingled with the ordinary scales
or else are disposed in special patches or under a fold of the

J'K,. oS.

costal margin of the wmg

SfClion across tarsus of
Hylobins, to show bulbous
hairs. — x\fter SiMMf;RMACHER.

a beetle,
glandular

( Thaiiaos). The characteris-
tic odo'rs of male butterflies
ha\-e long been attributed to
these androconia and M. \\.
Th()mas has ffjund that the
scales arise from glandular
cells, which doubtless secrete
a fluid that emanates from
the scale as an odorous va-
por, the evaporation of the
fluid being facilitated b}' the
spreading or l)ranching form
of the androconium. Similar
scales occur also on the wings r)f various moths and some
Trich( )ptera ( M ystacidcs ) .

Glands. — A great many glands of various form and func-
tion have l)een found in insects. Most of these, being formed
from the hypodermis, may logically l)e considered here, ex-
cepting some which are intimately concerned with digestion
or reproduction.

Glandular Hairs and Spines. — The presence of adhesive
hairs on the empodium of the foot of a fl_\' enal)les the insect
to wdlk on a smooth surface and to walk upside down; these
tcncni hairs emit a transparent sticky fluid through minute
pore canals in their apices. The tenent hairs of Hylobms
(Fig. 98) are each supplied with a flask-shaped unicellular
g-Jand, the glutinous secretion of which issues from the liull)ous

ANATOMY AND PHYSIOLOGY

Fig. 99.

Stinging hair of a caterpillar,
Gastropacha. c, cuticula; g,
gland cell; h, hair; hy, hypo-
dermis. — After Claus.

extremity of the hair. Bulbous tenent hairs occur also on the
tarsi of Collembola, Aphididae and other insects.

Nettling hairs or spines clothe the
caterpillars of certain Saturniidre
{Autoiiicris} , Liparid;e, 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
Lagoa crispata (Fig. 100) the irri-
tating fluid is secreted, as is usual,
by several large hypodermal cells
at the base of each spine. These
irritating hairs protect their pos-
sessors from almost all birds except
cuckoos.

Repellent Glands. — The various
offensive fluids emitted by insects

are also a highly effecti^'e means of defence against birds
and other insectivorous vertebrates as well as against preda-
ceous insects. The blood itself serves
as a repellent fluid in the oil-beetles
(Meloidc'e) and Coccinellidce, issuing as
a yellow fluid from a pore at the end
of the femur. The blood of MeloidcT
(one species of which is still used me-
dicinally under the name of " Spanish
Fly ") contains cantharidine. an ex-
tremely caustic substance, which is an
almost perfect protection against birds,
reptiles and predaceous insects. Coccinel-
lidie and Lampyridrc.are similarly exempt
from attack. Larvae of Ciinhcx when
disturbed squirt jets of a watery lluid
from glands opening above the spiracles. INIany Carabid^e
eject a pungent and often corrosive fluid from a pair of anal
7

Fig. 100.

Stinging spines of a
caterpillar, Lagoa cris
pata. — After P.\ckard.

82 ENTOMOLOGY

glands (Fig. 146) ; this fluid in BracJiinus, and occasionally
in Galerita jamis and a few other carabids, volatilizes explo-
sively upon contact with the air. AVhen one of these " l)om-
bardier-beetles " is molested it discharges a puff of vapor,
accompanied by a distinct report, reminding one of a minia-
ture cannon, and this performance may be repeated several
times in rapid succession; the vapor is acid and corrosive,
staining the human skin a rust-red color.
Individuals of a large South American
Brachiiiits when seized " immediately
began to play off their artillery, burning
and staining the flesh to such a degree
that onlv a few specimens could be cap-
tured with the naked hand, leaving a
mark which remained for a consideralile
time." (Westwood.)

As malodorous insects, Hemiptera are
Osnieterium of PatUio uotorious. tiiough uot a fcw hcmiptc-

polyxcncs. '.....

rous odors are ( apart from then" associa-
tions ) rather agreeable to the human olfactory sense. Com-
monly the odor is due to a fluid from a mesothoracic gland or
glands, opening between the hind coxae.

Eversible hypodermal glands of many khids are common in
larv?e of Coleoptera and Lepidoptera. The larvae of Mclasouia
lapponica. among other ChrysomelidcC, evert numerous paired
vesicles which emit a peculiar odor. The caterpillars of our
Papilio Ijutterflies, upon being irritated, evert from the pro-
thorax a yellow Y-shaped osiiicfcriuui (Fig. loi) which dif-
fuses a characteristic l>ut indescribable odor that is probably
repellent. The larva of Centra 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 coiiciiinhcns
disseminate an alluring odor fr()m scent tufts on the middle
legs. Female saturniid moths (as cccropia and proiiicthca)

ANATOMY AND PHYSIOLOGY 83

entice the males by means of a characteristic odor, emanating
from the extremity of the alxlomen. In lyccenid caterpillars,
an eversible sac on the dorsum of the seventh abdominal seg-
ment secretes a sweet tlnid, for the sake of which these larvse
are sought out l)y ants.

Wax Glands. — Wax is secreted by insects of several orders,
but especially Hymenoptera and Hemiptera. In the worker

Fig. 102.

Ventral aspect of worker honey bee, showing the four pairs of wax scales. — After

Cheshire.

honey hee the wax exudes from unicellular hypodermal glands
and appears on the under side of the abdomen as four pairs
of wax scales (Fig. 102). Plant lice of the genus ScJiiso-
ncnra owe their woolly appearance to dense white hlaments of
wax, which arise from glandular hypodermal cells. In scale
insects, waxen threads, emerging from cuticular pores. 1)ecome
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 Coccidai are simply
enlarged hypodermis cells.

Silk Glands. — Larvic 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, ichneu-
mons, wasps, bees, etc.), in Diptera (Cecidomyiidcc), Ncurop-

ENTOMOLOGY

tera (Chrysopidce, Mjn-meleonidje), and in various lar\\T
whose piipce are suspended from a silken support, as in the

coleopterous families Coc-
cinellidas and Chrysomel-
a "X ■ idae (in part) and the dip-

terous family Syrphida?,
as well as most diurnal

o -/-(® AV» \^ \^ II \ Lepidoptera.

Fig. 104.

Head of caterpillar of Saiuia cecropia. a,
antenna; c, clypeus; /, labriiin; //>, labial palpus;
tn, mandible; mp, maxillary palpi; o, ocelli; s,
spinneret.

The silk glands of caterpillars
are homologous with the true
salivary glands of other insects,
opening" as usual through the hy-
popharynx. which is modified ti)
form a spinning organ, or spin-
neret (Fig. 103). The silk glands
of Lepidoptera are a pair of long
tuhes, one on each side of the
body, but often much longer than
the body and consequently convo-
luted. Thus in the silk worm
{Bouihyx mori) they are from
four to five times as long as the
body and in Tclca polyphciiiiis,
seven times as long. In the silk
worm the convoluted glandular
portion of each tube (Fig. 104) opens into a dilatation, or silk
reservoir, which in turn empties into a slender duct, and the

^-^

Silk glands of the silk worm,
Boinbyx iimri. cd, common duct;
(/, one of the paired dticts; g, g,
Filippi's glands; gl, gland proper;
p, thread press; r, reservoir.

ANATOMY AND PHYSIOLOGY

Fig. 105.

two ducts join into a short common duct, which passes
through the tubular spinneret. Two divisions of the spinning
tube are distinguished: (i) 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 substance and the re-
mainder 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 glandular
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 (ectoder-
mal ) and the chitinous intima of each

gland is cast at each moult, along with

Sections of silk gland of
the silk worm. A, radial;
B, transverse, b, basement
membrane; i, intima; s,
glandular cell with branched
nucleus. — After Helm.

the general integument.

The silk glands of Trichoptera are essentially like those of

Lepidoptera, but the glands of Chrysopa, Myrnieleon, Coc-

cinellida;, ChrysomelidcC and Syri)hi(he, 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 surpris-
ingly large. A caterpillar, for exami)le, has about two
thousand.

ENTOMOLOGY

The muscles of the trunk are seg-mentally arranged — most
evidently so in the Ijody of a larva or the abdomen of an
imago, where the nuiscnlatnre is essential!)- the same in sev-
eral successive segments. In the thoracic segments of an ima-
go, however, the musculature is, at tirst sight, unlike that of

Fig. io6.

Fig. 107.

Fig. ioS.

abc

Muscles of cockroach; of ventral, dorsal and lateral walls, respectively. (7, alary
muscle; abc, abductor of coxa; adc, adductor of coxa; cf, extensor of femur; /;, head
muscles; Is, longitudinal sternal; It, longitudinal tergal; Ith, lateral thoracic; os,
oblique sternal; of, oblir4ue tergal; ts, tergo-sternal; ts'^, first tergo-sternal. — After
MiALL and Denny.

the abdomen, and in the head it is decidedlv different ; though
future studies will doubtless show that the thoracic and cepha-
lic kinds of musculature are only modifications of the simpler
abdominal type — modifications brought ab(3ut in relation to
the needs of the legs, wings, mouth parts, antennae and other
mo\'able structures.

The muscular system has been generally neglected by stu-
dents of insect anatomy; the only comprehensive studies upon
the subject being those of Straus-Diirckheim (i(S2(S) on the
beetle MclolontJia : Lyonet (1762), Newport (1834) and
Lubbock (1859) on caterpillars; and the more recent studies
of Lubbock and Janet on Hymenoptera.

ANATOMY AND PHYSIOLOGY

The more important muscles in the body of a cockroach are
represented in Figs. 106-108, from Miall and Denny. The
longitudinal stcrnals with the longitudinal tcrgals act to tele-
scope the abdominal segments: the oblique
stcrnals bend the alodomen laterally : the
tergo-stcrnals, or vertical expiratory mus-
cles, draw the tero-um and sternum to-

pic. 109.

Fig. iio.

gether. The muscles of the legs and the
wings have already been referred to.

Structure of Muscles. — The muscles
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 striated musde fiber of

.,.,., an insect.

membrane, or sarcolcninia, withni 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
j^l a striated appearance, owing
to alternate lig-ht and dark
bands (Fig\ 109), the for-
mer being singly refracting,
or isotropic, and the latter
doubly refracting, or aniso-
tropic.

The minute structure of
these fibers, being extremely

Minute struLlure of a striated nuisele clil^CUlt of interpretation,
fiber. A, longitudinal section; B, trans-
verse section in the region of /; C, trans- haS givCU riSC tO mucll dif-
verse section in the region of .. /. f^^.^^^^,^ ^f opilliou. The
longitudinal nbriUas; n, Krause s mem- J
brane; nl, nucleus; r, radial fibrilhe; 3, niOSt plaUSiblc VlCW is that
sarcolenima. — After Janet. . /--^ i i t

()t \-an uehuchlcii, Janet
and others, \\h() hold that both kinds of dark l)ands ( I'ig
no) consist of highly elastic threads of spongioplasin (aniso-
tropic) embedded in a matrix of clear, semi-fluid, nutritive

88 ENTOMOLOGY

hxaloplasni (isotropic). The spong-ioplasmic threads of tlie
long bands extend longitndinahy and those of the short bands
{" Krause's membrane") radiahy, in respect to the form of
the fiber. Moreover, the attenuated extremities of the longi-
tudinal fibrillae connect with the radial fibrillce, 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 fibrill^e.
When the stimulus ceases, the radial fibrillre, by their elas-
ticity, possibly pull the longitudinal ones back into place. The
last word has not been said, however, upon this perplexing
subject.

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

It is incorrect to say that the muscles of insects are stronger
than those of vertebrates, for, as a matter of fact, the contrac-
tile 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 1)(~ith sub-
stances. Furthermore, the external skeleton permits muscu-
lar attachments of the most advantageous kind as compared
with the internal skeleton, so that the muscles of insects sur-
pass 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

ANATOMY AND PHYSIOLOGY 89

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 i6. i 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. Always, as Plateau has shown, the
lighter of two insects is the stronger in respect to external
manifestations of muscular force — in the ratio of this muscu-
lar strength to its own weight.

To understand this, let us assume that a beetle continues to
grow (as never happens, of course). As its weight is increas-
ing 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 onlv as
the square of one dimension — its diameter. Therefore the
increase in strength lags behind that of weight more and
more; consequently more and more strength is required sim-
ply to move the insect itself, and less and less surplus strength
remains for carrying additional weight. Thus the larger in-
sect is apparently the weaker, though it is actuallv 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 Ixuly is no criterion of the muscular
power of an animal.

4. Nervous Sv.stem
The central nervous system extends along the median line
of the floor of the body as a series of ganglia connected by

ENTOMOLOGY

Fig. III.

sy--:::

///

Central nervous system
of a thysanuran, MacJiilis.
The thoracic and abdom-
inal ganglia are numbered
in succession, o, antennal

nerve cords. Typically, there is a gan-
giion ( doiil^le in origin) for each primary
segment, and the connecting cords, or
coniiiiissiircs, are paired; these conditions
are most nearly realized in embryos and
in the most generalized insects — Thysa-
nnra (Fig. iii). In all adult insects.
ho\yever. the originally separate ganglia
consolidate more or less (Fig. 112) and
the Commissures fre(|uently unite to
form single cords. Thus in Tabauus
{ y\g. I J 2. the three thoracic gan-
glia haye united into a single com-
pound ganglion and the aljdominal gan-
glia are C(»ncentrated in the anterior
])art of the aljdomen; in the grasshop-
per, the ner\'e cord, double in the tho-
rax, is single in the abdtniien. \'arious
(_)ther 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 sidnvsophui^cal gmiglioii
( disregarding a few anomalous cases
in which the latter is said to be
absent ) .

The l)rain. or siipraivsopJuigcal gcin-
glioii (Fig. 113), is formed by the union
of three primitive ganglia, or iiciironicrcs
(Fig. 55). namely, (i) the protoccrc-
bniiii, which gi\-es olT the pair of optic
nerves; (2) the dcutoccrcbnim, which

nerve; h, brain; c, compound eye; /, labial nerve; m,
mandibular nerve; inx, maxillary nerve; o, oesophagus;
ol, optic lobe; s, subcesophageal ganglion; sy, sympathetic
nerve. — After Oudemans.

ANATOMY AND PHYSIOLOGY

innervates the antennae; and (3) the tritoccrebnim, which in
Apteryg-Qta bears a pair of rudimentary appendages that are
regarded as traces of a second pair of antennae.

Fig. 112.

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

Fig. 113.

Nervous system of the head of a cockroach, a, aiitcnnal nerve; ag, anterior lateral
ganglion of sympathetic system; b, brain; d, salivary duct; f, frontal ganglion; //, hypo-
pharynx; /, labrum; li, labium; m. mandibular nerve; mx, maxillary neive; nl, nerve to
labrum; nli, nerve to labium; o, optic nerve; oc, cesophageal commissure; oc, oesophagus;
pg, posterior lateral ganglion of sympathetic system; r, recurrent nerve of sympa-
thetic system; s, subcesophageal ganglion. — After Hofkr.

The subcesophageal ganglion (I'ig'. 113) is always con-
nected with the brain by a pair of nerve cords {oesophageal

ENTOMOLOGY

coiiuiiissurcs) bet\\een which the ciesophagns passes. This
compound ganglion represents at most four neuromeres : ( i )
maihlibnlar. innervating the mandibles; (2) snpcrlingual,

found by the author in Collembola,
but not yet reported in the less gen-
eralized insects; (3) maxiUary, inner-
vating the maxillse; (4) labial, which
^^L il ^^ sends a pair of nerves to the labium.

^~- J .^"^■^^'^^ L<r, 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. — L y i n g
along the median dorsal line of the
oesophagus is a recurrent , or stoinato-
gastric, nerve (Fig-. 114), which
arises anteriorly in a frontal gan-
glion and terminates posteriorly in
a stomachic ganglion situated at
the anterior end of the mid intes-
tine. Connected with the recurrent
nerve are two pairs of lateral ganglia,
the anterior of which innervate the
dorsal vessel and the posterior, the
trache?e of the head. The ventral
nerve cord may include also a median
nerve thread (Fig. iii) wdiich gives
salivary glands; sf. stomachic ^ff paired trcUisversc uerves to the

ganglion. — After Kolbe.

muscles of the spiracles.
Structure of Ganglia and Nerves. — A ganglion consists
of (i) a dense cortex, composed of ganglion cells (Fig. 115),
each of which has a large rounded nucleus and gives off usu-
ally a single nerve fiber; and (2) a clear medullary portion

Sympathetic nervous system
of an insect, diagrammatically
represented. c7, antenna!
nerve; b, brain; f, frontal
ganglion; I, I, paired lateral
ganglia; m, nerves to upper
mouth parts; o, optic nerve;
Tj recurrent nerve; s, nerve to

ANATOMY AND PHYSIOLOGY

(Punkfsubslai!/^) derived from the processes of the cortical
gang'Hon cells and serving as the place of origin of nerve fibril-
l?e. There are. however, ganglion cells from which processes
may pass directly into nerve fibrillar.

A ner\e, in an insect, consists of an a.vis-cyli)idcr, composed
of fibrillcC. and an enveloping membrane, or iiciirilcnuiia. The
axis-cvlinder is the transmitting portion and the ganglia are

Fig. 115.

Transverse section of an abdominal ganglion of a caterpillar, a, axis-cylinder; g,
ganglion cells; n, neurilennna; p, Punktsubstanz.

the trophic centers, i. e., they regulate nutrition. A nerve is
always either sensory, transmitting impulses inward from a
sense org-an ; 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 antennre) and con\'erts the sensory stimuli that it
receives into motor stimuli, wdiich 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 a loose sense; it directs locomotor mo\'ements
of the legs and wing's. An insect deprived of its brain cannot
go to its food, though it is able to eat if food be placed in con-
tact with the end-organs of taste, as those of the pal^ii ; further-
more, it walks or flies in an erratic manner, indicating a lack
of co-ordination of muscular action.

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

94 ENTOMOLOGY

The thoracic gangha govern the appendages of their respec-
tive segments. These gangha and those of the abdomen are
to a great extent independent of brain control, each of these
gangha l)eing an individnal motor center for its particnlar
segment. Thus decapitated insects are still alile to Ijreathe,
walk or flv. and often retain for several days some power of
movement.

In regard to the sympathetic system, it has been shown ex-
perimentally that the frontal ganglion controls the swallowing
movements and exerts through the stomatogastric nerve a
regulative action upon digestion. The dorsal sympathetic sys-
tem controls the dorsal vessel and the salivary glands, while
the ventral sympathetic system is concerned with the spiracu-
lar 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
mr)st numerous and varied upon the head and its appendages,
particularly the antenn?e.

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

T. Sciisilliiiii ccrloconicum — a conical or peg-like projection
immersed in a pit (Figs. 116-117). In all probability
olfactory.

2. 6". basicouicuiii — a cone projecting above the general sur-
face (Fig. 118). Probably olfactory.

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

4. ^. chccticuin — a bristle-like sense organ (Fig. 120).
Tactile.

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

ANATOMY AND PHYSIOLOGY

6. .9. placodcnm — a membranous plate, its outer surface
continuous with the general integument (Fig. 123). l^\nic-

FiGs. 116-125.

Types of antennal sensilla, in longitudinal section (excepting I'igs. 119 and 120).
Fig. 116, sensillum cceloconicum; 117, coeloconicum; 118, basiconicum; 119, stylo-
conicum; 120, chseticum; 121, trichodeum; 122, trichodeum; 123, placodeum; 124,
ampullaceum; 125, ampullaceum; c, cuticula; h, hypodermis; n, nerve; s, sensory cell.
Figs. 116, 118, 121, 123, 124, honey bee, Apis mellifera; 117, 119, 122, moth, Fidonia
piniaria; 120, moth, Ino pruni; 125, wasp, Vcspa crabro. — After Schenk.

96 ENTOMOLOGY

tinn doubtful ; not auditory aud pro1jal)ly not olfactory, though
the functiou is doubtless a mechanical one ; Schenk suggests
that they are affected by air pressure, as when a hee or wasp
is moving' about in a confined space.

7. 6^. ampuUaccuin — a more or less flask-shaped cavity with
an axial rod (Figs. 124, 125). Probably auditory.

These types of sensilla will l)e 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 com-
monly distributed over the entire integument, though the an-
tenUcT, palpi and cerci are especially sensitive to tactile impres-
sions.

The end-organs of touch are bristles (sensilla chc'etica) or
hairs (sensilla trichodea ) , each arising from a special hypo-
dermis cell and having" connection with a nerve. Sensilla
chretica doubtless receive impressions from foreign bodies,
while sensilla trichodea, JDeing 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.

Not all the hairs of an insect are sensory, however, for many
of them have no ner\-e connections.

In blind cave insects the antennre are very long and are ex-
Cjuisitely sensitive to tactile impressions.

Taste. — The gustatory sense is uncjuestionably present in
insects, as is shown both by common olDservation and by pre-
cise experimentation. Will fed wasps with sugar and then
replaced it with powdered alum, which the wasps unsuspect-
ingly 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 oiYered ants honey mixed
with morphine or strychnine ; the ants began to feed but at
once rejected the mixture. In its range, however, the gusta-
tory sense of insects dift'ers often from that of man. Thus
Will found that Hymenoptera refused honey with which a

ANATOMY AND PHYSIOLOGY

very little glycerine had been mixed (though Muscidce did not
object to the glycerine) and Forel found that ants ate unsus-

FiG. 126.

Section through tongue of wasp, Vespa vulgaris, c, cuticula; g, gland cell; h,
hypodermis; n, nerve; ob, gustatory bristle; pli, protecting hair; sc, sensory cell; tb,
tactile bristle. — After Will.

Fig. 127.

pectingly 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 phosphorus
but not the glycerine.

Location of Gustatory Organs. — As
would be expected, the end-organs of
taste are situated near the mouth, com-
monly on the hypopharynx (Fig. 126),
epipharynx and maxillary palpi. On the
tongue of the honey bee the taste organs
appear externally as short set?e (Fig.
127) and on the maxilla; of a wasp as
pits, each with a cone, or peg. projecting
from its base (Figs. 128. 129). Similar

Apis mellifera. p. pro- ^,^g^g j^g ^^^^^y -^ j^.^^.g j^^^gj-, found bv

tecting bristles; s, ter- i i o

minai spoon; t, taste Packard Oil the cpipliaryux in most of the

setae. — After Will. i-i i , i r ■ ^

mandibulate orders ot insects.
Histology. — The end-organs of taste arise from special
hypodermis cells, as minute setre or, more commonly, pegs,
8

Tongue of honey bee,

ENTOMOLOGY

Fig. 128.

(c...

each seated in a pit, or cup, and connected with a nerve fiber
(Figs. 129, 130). In some cases, however, it is difficnh to

decide whether a given organ
is gustatory or olfactory, owing
to the similarity between these
two kinds of structures. In
aquatic insects, indeed, the
senses of taste and smell are not
differentiated, these forms ha\'-
ing 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 incon-
ceivably acute. Hosts of in-
sects depend chiefly on their
olfactory powers to find food,
for example many beetles, the
fiesh flies and the flower-visit-
ing 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 conclu-
sive experiments, Hauser and
others have shown that the
antenn?e are frecjuently olfac-
tory — though not to the ex-
clusion of tactile or auditory
functions, of course. Hauser
found that ants, wasps, vari-
ous flies, moths, beetles and
larvc-e, which react violently toward the vapor of turpen-

Under side of left maxilla of

wasp, Vespa vulgaris, p, palpus; pr,

protecting hairs; tc, taste cup; tli,
tactile hair. — After W'ill.

Longitudinal section of gustatory
end-organ {tc, of Fig. 128). c, cutic-
ula; h, hypodermis; sc, sensory cell;
tc, taste cup. — After Will.

ANATOMY AND PHYSIOLOGY

tine, acetic acid and other pungent fluids, no longer re-
spond to the same stimuli after their antenn<c have been
amputated or else covered with paraffine to exclude the
air. His experiments were conducted under conditions
such that the results could not he ascribed to the shock

Fig. 130.

Fig. 131.

Taste cup from maxilla Section of antenna] olfac-

of Boinbiis. sc, sensory tory organ of grasshopper,

cell; n, nerve. — After Will. Caloptenus. c, cuticula; m,

membrane; 11, nucleus of
sensory cell; «"', nerve; p,
pit with olfactory peg; pg,
pigment. — After H.\user.

of the operation or to effects upon the gustatory or res-
piratory systems; except for having lost the sense of smell,
the insects experimenterl upon behaved in a normal manner. It
should be said, however, that Carabus, Mclolontlia and Silpha
still reacted to some extent toward strong vapors even after the
extirpation of the antennrc ; while in Hemiptera the loss of the
antenUiT did not lessen the response to the odors used. These
facts indicate that the sense of smell is not always confined to
the antennse; indeed the maxillary palpi are frequently olfac-
tory, as in Silpha and Hydaticus; also the cerci, as in the cock-
roach and other Orthoptera. Experiments indicate that an

lOO

ENTOMOLOGY

insect perceives some odors by means of the antenna and

Fig. 132.

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

others l)y the palpi or other
organs. Hanser found that
the flies Sarcophaga and Cal-
liphora, after the amputation
of their antenuce, liecame
quite indifferent toward de-
cayed meat, to which they
had previously swarmed with
great persistence, though
their actions in all other re-
spects remained normal.
Males of many moths and a
few beetles are unal^le to find

Fig. 133.

the females (see beyond) when the for-
mer are deprived of the use of their
antennas.

End-Organs. — Structures which are
regarded as olfactory end-organs occur
commonly on the antenn?e, often on the
maxillary and labial palpi and sometimes
on the cerci. These end-organs are hy-
podermal in origin and consist, generally
speaking, of a multinucleate cell (Fig.
131 ) penetrated by a nerve and prolonged
into a chitinous bristle or peg, which is
more or less enclosed in a pit, as in Ta-
banus (Fig. 132). In many instances,
however, the end-organs take the form of
teeth or cones projecting from the gen-
eral surface of the antenna, as in ]\\<;pa
(Fig. 133 ). These cones are usually less
numerous than the pits; in ]\\^pa crabro,
for example, the teeth number 700 and "' ""'■''= '- ^d.— After

' Hauser.

the pits from 13,000 to 14.000 on each

antenna. The pits are even more numerous in some other

Longitudinal section
of antennal olfactory
organ of wasp, Vcspa.
c, olfactory cell; en, ol-
factory cone; ct, cutic-
ula; /;, hypodermis cells;

ANATOMY AND PHYSIOLOGY

lOI

e iJ 8 " *

insects ; thus there are as Fig. 134.

many as 17,000 on each an-
tenna of a blow fly (Hicks).
The male of Mcloloiitha "vul-
garis, which seeks out the
female by the sense of smell,
has according to Haiiser 39,-
000 pits on each antenna, and
the female only 35,000. Pits
presumably olfactory in func- "^
tion have been found l)y
Packard on the maxillary and y^_ Jjrzi - ~Z^S:Z ^B "
laljial palpi of Pcrla and on.

. Loneitudinal section of a portion of a

the CerCl Ot the C0Ckr(^ach caudaf appendage of a cricket, Gryllus

D ■,,.: hi ,,, ,/ . .,,, T-,'- .,, , \^. ,-,-, domcsticus. b, bladder-like hair; c, cutic-

' ula; II, hypodermis; n, nerve; ns, non-

Rath has deSCril:)ed four kinds sensory sttK; sc, sense cell; sh, sensory

. . hair.— After VOM R.\TH.

of sense ban's from the two

larger of the four caudal appen-
dages 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 Lepidop-
tera a large flask-shaped in\'agina-
tion (Fig. 135) into which pro-
ject numerous chitinous rods, each
a process of a sensor_\- cell, which
is supplied l)y a l)ranch of the prin-
cipal pal])al ner\e ; these peculiar
organs are inferred to be olfactory.
Idle chief reason for regard-
ing these various end-organs as
olfactory is that they ap])car
T„„„.„ ,■ , .. , , from their structure to be better

Longitudinal section of apex of

palpus of Pieris. c, cuticuia; /;, adapted to recei\-e that kind of

hypodermis; n, nerve; s, scales; . .

.-.-, sense cells.— After vom Rath. ^^ im])ressi<)n tliau any othcr. so

Fi(

I02 ENTOMOLOGY

far as we can jndg'e from our o\\n experience. Though it is
easy to demonstrate that the antennre, for example, are olfac-
tory, it frequently happens that the antenna; bear several dis-
tinct forms of sensory end-organs, so minute and intermingled
that their physiological differences can scarcely be ascertained
bv experiment but must be inferred from their peculiarities of
structure. Schenk, however, has arri\-ed at precise results
by comparing the antennal sensilla in the two sexes, selecting
species in which the antennre exhil:)it a pronounced sexual
dimorphism, in correlation with sexual differences of behavior.
Tn.k\ng Nofolof^hus (Orgyia) anfiqiia, in which the male seeks
out the female by means of antennal organs of smell, he finds
that the male has on each antenna about 600 sensilla coelo-
conica and the female only 75 ; similarly in the geometrid Fido-
nia, in which the ratio is 350 to 100. The sensilla styloconica,
also, of these two genera are regarded as olfactory organs.
These two kinds of end-organs are not only structurally adapted
for the reception of olfactory stimuli, Init 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 attract the opposite sex, often in consid-
erable numl)ers. Under favorable conditions, a freshly
emerged female of the proincthca 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 thev 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 con-
gregate on the ground at a spot where a female has been. If
one of these males is deprived of the use of his antennae, how-
ever, he flutters about in an aimless way and is no longer able
to find the female.

ANATOMY AND PHYSIOLOGY IO3

Among- beetles, males of PolyphyUa gather and scratch at
places where females are about to emerge from the ground.
Prionus also assembles, as Mrs. Dimmock observed in Massa-
chusetts. In this instance many males, with palpitating an-
tenna;, ran and flew to the female ; moreo\'er, a number of
females were attracted to the scene.

Sounds of Insects. — Before considering- the sense of hear-
ing, 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 reg-ularity 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 number of \ibrations may be
determined; thus A' means 440^ vibrations per second and
F', 352. The numbers thus ascertained may be ^•erified by
Marey's graphic method (Fig. 74) ; he found that the fly
referred to actually made 330 strokes per second against the
smoked surface of a revolving cylinder.

Flies, bees, dragon flies and some beetles make buzzing or
humming sounds by means of the spiracles, there being behind
each spiracle a membrane or chitinous projection which vi-
brates during respiration. This " voice " should be distin-
guished from the wing tone when both are present, as in bees
and flies. xV 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 E' if the insect is tired, while the spirac-
ular 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 ner-
vous system; in fact, it is possible and even probable that vari-
ous spiracular tones express difl^erent emotions, as is indicated
by the effects produced by the voice of the old queen bee upon
the young- cjueens and the males.

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

I04 ENTOMOLOGY

The well-known " shrilling- " of the male cicada is produced
1j_v the rapid vi1)ration of a pair of membranes, or drums, sit-
uated on the basal abdominal segment, and vil:)rated each by
means of a special muscle.

Frictional sounds are made by beetles in a great variety of
ways : by the rul:)bing of the pronotum against the mesonotum
(many Cerambycidre) ; or of abdominal ridges against elytra!
rasps (Elaplinis, Cychriis) ; or two dorsal abdominal rasps
against specialized portions of the wing folds (Passahis cor-
iiiitiis), 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 Passaliis coniutus both sexes stridulate.

A few moths (Sphingidre) and a few butterflies make
sounds; the South American butterfly Agcvoiiia fcronia 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; Mntilla,
however, makes a distinct scjueaking sound by means of a
stridulating organ similar to those of ants.

Stridulating- organs attain their best development in Orthop-
tera. in which group the ability to stridulate is often restricted
to the male, though not so often as is commonly supposed.
Among Acridiida?. StenohotJirus 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 Dissosfcira makes a crackling sound during
flight or while poising, by means of friction between the front
and hind wings, where the two overlap.

Locustidce and Gryllid^e stridulate by rubbing" the bases of
the tegmina against each other. Thus in the male Microcen-
triiin laurifoUuui the left tegmen, v.'hich 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.

ANATOMY AND PTI^'SIOLOGY

105

The tegmina are first spread a little: then, as tliey close gradn-
ally, 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 thev 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

Fig. 136.

Stridulating organs of Microccnfrnin laurifolium. A, dorsal aspect of Hie (st)
when the tegmina are closed; B, ventral aspect of left tegmen to show Hie; C, dorsal
aspect of right tegmen to show scraper (,?).

call and, moreover, is made by the opening of the tegmina.
These and other details of the courtship may readily be ob-
served in twilight and e\en under artificial light, as the latter,
if not too strong, does not disturl) the pair. Something sim-
ilar may be observed in the daytime in Orclieliuuim, Xiphidium
and the tree crickets, CEcauthus. The stridulating areas are
usually membranous and the rasping organs are modified veins.

I06 ENTOMOLOGY

Frequently the wing-covers bulge out to form a resonant cham-
ber 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, Orclicliiuuni -c'lilgarc, may be represented by a
prolonged cr . . . sound, followed by a staccato jip-jip-jip-
jip. ...

In Orthoptera, the frequency of stridulation increases with
the temperature ; and the correlation between the two is so
close that it is easy to compute the temperature from the num-
ber of calls per minute, by means of formulae. The formula
for a common cricket [probably a species of Grylhis], as given
by Professor Dolliear, is

/=5o+ - — .
4

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

A similar formula for the katydid (CyrfophyUus pcrspicil-

latiis). based upon observations made by R. Hay ward, would

A^- 19
r=6o + — -— .
3

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

Hearing. — There is no doubt that insects can hear. The
presence of sound-making organs is strong presumptive evi-
dence that the sense of hearing is present. Female grass-
hoppers 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, abdo-
men, 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

ANATOMY AND PHYSIOLOGY

107

proved by the well-kn* )\\n experiments of ]\Iayer. He fastened
a male C 11 lex 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
occurred in response to 512 vibrations per second, or the note
C", which is approximately the note upon which the female
hums. The male probably turns his head until the two an-
tennre are equally affected l)y the note of the female, \\hen, b}-

Fig. 137.

Inner aspect of right tympanal sense organ of a grasshopper, Caloptcnus italicus.
b, chitinous border; c, closing muscle of spiracle; g«. ganglion; m, tympanum; n,
ner\e; o, opening muscle of spiracle; p, p, processes resting against tympanum; s,
spiracle; im, tensor muscle of tympanum; v, vesicle. — After Graber.

going straight ahead, he is able to locate her with great
precision.

In the lack of experimental evidence, other organs are in-
ferred to be auditory on account of their structure. jVcridiid?e
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 trans-
mit sound-waves. The tympanum, or membrane, is tense,
and can vil)rate freely, as the air pressure against the two sur-

io8

ENTOMOLOGY

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), which serve jjroljaljly to transfer the vibra-
tions, 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
ner\-e terminations consist of
delicate bristle-like processes
which are probably affected by
the oscillations of the fluid con-
tained in the vesicle just re-
ferred to.

Other tympanal organs,
doubtless auditory, are found
on the fore tibiae of LocustidcC,
ants, termites and Perlida;, on
the femora of Pediculidx and
the tarsi of some Coleoptera.

Several tvpes of cliordofoiial
organs have been described, of
which those of the transparent
Caret lira larN'a may serve as an
example. These organs, situ-
ated on each side of abdominal
segments 4-10, inclusive, con-
sist each (Fig. 138) of a tense
cord, probal3ly capable of vil)ra-
tion, 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 ganglion, which receives a
ner\e from the principal ganglion of the segment.

Vision. — The external characters of the two kinds of eyes
— ocelli and compound eyes — have already been described.

Chordotonal sense organ of aquatic
drpterous larva, Corcthra plttinicornis.
cd, cord; eg, chordotonal ganglion; /,
fibers of an integumental nerve; g,
ganglion of ventral chain; /, ligament;
m, longitudinal muscles; n, chordotonal
nerve; r, rods (nerve terminations); t,
tactile sets. — After Graber.

ANATOMY AND PHYSIOLOGY

109

\Miile 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 (i) lens, (2)

vitreous body, ( 3 ) retina,

r \ jzi " , , u- I'iG. 139.

(4) nerve fibers, (5) pig-
mented Jiypodennis cells,
and (6) accessory cells, be-
tween the retinal cells and
the nerve fibers. The lens,
usually biconvex in form, is
a local thickening of the
general cuticula ; it is sup-
plemented in its function by
the vitreous body, consist-
ing of a layer of transpar-
ent hypodermis cells ; these
in many insects are elon-
gate, constituting a vitreous
layer of rather more im-
portance than the one rep-
resented 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. 140), according to Redi-
korzew and others, and in some instances (Calopteryx) a nerve
fiber enters the cell. Each retinula contains a longitudinal rod.
or rhabdoin, 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

Median ocellus of honey bee, Apis mel-
Ufcra, in sagittal section, h, hypodermis;
/, lens; n, nerve; p, iris pigment; r, retinal
cells; f, vitreous body. — After Redikorzew.

I lO

ENTOMOLOGY

Fig. 140.

somewhat the same plan as the human eye, its capacity for
forming' images must l)e extremely limited ; for since the form
of the lens is fixed and also the distance between the lens and
the retina, there is no power of accommo-
dation, 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 concerned ; furthermore, the small
number of retinal rods implies an image of
only the coarsest kind.

If the compound eyes of a grasshopper
are covered Avith an opaque varnish and
the insect is placed in a l)ox with only a
single opening, it readily finds its way out
bv 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 dis-
tinguish light from darkness — and they
are probablv more serviceable to the in-
sect in this wav than in forming images.
An oceiiar retinuia of Compound Eycs.— As regards deli-
the honey bee, composed cacv and iutricacy of structurc, the com-
pound eye of an insect is scarcely if at all
inferior to the eve of a vertebrate. In

of two retinal cells,
longitudinal section; B,
transverse section; n, n,
nerves; p, pigment; r,

rhabdom. — After redi- radial sectiou (Fig. 141), a compound eye

KORZEVV. • ,- • -1

appears as an aggregation ot similar
elongate elements, or ommatidia, each of wdiich ends exter-
nally in a facet. The following structures compose, or are
concerned with, each ommatidium : (i) cornea, (2) crystal-
line lens, or cone, (3) rhabdoni mul retinuia, (4) pigmoit (ins

ANATOMY AND PHYSIOLOGY

I I I

Fig. 141.

and retinal), (5) fenestrate iiieinbraiie, (6) fibers of the o/^tic
nerve, (7) traehear.

The cornea ( Fi"'. 142) is a biconvex transjiarent portion
of the external chitinons cuticula. Immediately beneath it are
the eone eells, which may contain a
clear fluid or else, as in most insects,
solid transparent cones. The rhab-
dom is a transparent chitinons rod
or a gTonp of rods (rhabdonieres)
situated in the long axis of the
ommatidium and surrounded by
greatly elongated cells, which
constitute the retinula. T w o
zones of pigment are present : an
outer zone, of iris pigment, in
which the pigment in the form of
fine black granules is contained
chiefly in short cells that surround
the retinula distally; and an inner
zone of retinal pigment, in which
the pigment cells are long and
slender, and enclose the retinula
proximally. All these parts are hypodermal in origin, as is also
the fenestrate 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 fi1)rous
optic tract of complex structure.

Physiology. — After much experimentation and discussion
upon the physiology of the compound eye — the subject of the
monumental works of Grenacher and Exner — Aluller's " mo-
saic " theory is still generally accepted, though it was proposed
early in the last century. 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.

Portion of compound eye of
fly, Calliphora vomitoria, radial
section, c, cornea; i, iris pig-
ment; n, nerve fibers; nc, nerve
cells; r, retinal pigment; t, tra-
chea. — After HiCKSON.

I 12

ENTOMOLOGY

Fig. 142.

Structure of an ommatid-
ium of Calliphora vomitoria.

A, radial section (chiefly) ;

B, transverse section through
middle region; C, transverse
section through basal region;
bm, basement membrane; c,
cornea; n, nucleus; nv, nerve
fibrillae; pc, psevidocone; pg^,
pg^, cells containing iris pig-
ment; pg^, cell containing ret-
inal pigment; r, one of the six

Each < jmmatidiiim is adapted to trans-
mit light along- its axis only ( Fig.
143). as ohlique rays are lost by ab-
sorption in the black pigment which
surronnds 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 inten-
sity and color of the light from one
particular portion of the field of
\'ision ; and when this is done hx hun-
dreds or thousands of contiguous om-
matidia, 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 posi-
tion that he finds in the object itself
■ — and this is essentially what the com-
pound eye does, so far as can be in-
ferred from its 'structure.

Exner, removing the cones with the
corneal cuticula ( in Lampyris ) , looked
through them from behind with the
aid of a microscope and found that the
images made by the separate iimma-
tidia were either very close together
or else overlapped one another, and
that in the latter case the details corre-
sponded ; 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

retinal cells which compose the retinula; Hi, rhab-
dom, composed of six rhabdomeres; t, trachea; tv,
tracheal vesicle. — After Hickson. '

ANATOMY AND PHYSIOLOGY

113

" superposition " image being correspondingly bright — an ad-
vantage, 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 impres-
sion, as Mollock says. If Miiller's
theory is true, an image may be formed
of an object at any reasonable distance,
no power of accommodation being ne-
cessary; 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 Lepi-
doptera, 68 cm. for Diptera and 58 cm.
for Hymenoptera.

It is generally agreed, however, that
the compound eyes are specially adapted
to perceive movements of objects. The
sensiti^'eness of insects to even slight
movements is a matter of common ob-
servation ; often, however, these insects 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 vertebrates. Furthermore, on the same principle,
the compound eyes are serviceal)lc for the perception of form
when the insect itself is moving rapidly.

The arrangement of the pigment depends ada]:)ti\ely upon
the quality of the light, as Stefanowska and Exner have
shown ; thus, when the light is too strong, the iris and retinal
9

Diagram of outer, trans-
parent portion of an omnia-
tidium to illustrate the
transmission of an axial ray
(/i) and the repeated reflec-
tion and absorption of an
oblique ray (B), which at
length emerges at C. p, iris
pigment.

114 ENTOMOLOGY

pigment cells elongate around the ommaticlinni and their pig-
ment granules absorh from the cone cells and rhabdom the
excess of light. If the light is weak, they shorten, and absorb
but a minimum amount of light.

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 plausi-
ble view, however, is probably incorrect, for these reasons
among others. In the ocellus, a single lens serves for all
the retinulcT, while in the compound eye there are as many
lenses as there are retinul?e. Moreover, ocelli do not pass
directly into compound eyes, but disappear, and the latter arise
independently of the former.

Probablv, as Grenacher holds, both the ocellus and the com-
pound eye are derived from a common and simpler type of
eye — are " sisters," so to speak, deri\ed from the same
parentage.

Perception of Light through the Integument. — In vari-
ous insects, as also in earthworms, blind chilopods and some
other animals, light affects the nervous system through the
general integument. Thus eyeless dipterous larv?e 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 350). The blind cave-beetles of the genus Anophthal-
jiiHS 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 col-
ors, though their color sense differs in range from our own.
Thus ants avoid violet lig"ht 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, which make no sensible impression upon us. Honey

ANATOMY AND PHYSIOLOGY

115

bees frequently select 1)Uie flowers; white l)iitterflies (Fieris)
prefer white flowers, and yellow butterflies (Colias) appear
to alight on yellow flowers in preference to white ones (Pack-
ard). 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

Fig. 144.

Alimentary tract of a collembolan, Orchcsclla. F, fore gut; H. hind gut; M, mid
gut; c, cardiac valve; cm, circular muscle; hii, longitudinal muscle; />, pharynx; py,
pyloric valve.

the brightl}' colored petals have l)een 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.

Problematical Sense Organs. — As all our ideas in regard
to the sensations of insects are necessarily inferences from our
own sensory experiences, they are inevitably inadequate.
While it is certain that insects have at least the senses of touch,
taste, smell, hearing- and sight, it is also certain that these
senses of theirs difl^er 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 man}- curious integumentary organs which from
their structure and ner\e connections are probably sensory
end-organs, though their functions are either doubtful or un-
known. Such an organ is the sensillum placodeum (p. 95),
the use of which is very doubtful, though the organ is pos-
sibly afl:'ected l)y air pressure. Insects are extremely sensitive

ii6

ENTOMOLOGY

to variations of wind, temperature, moisture and atmospheric
pressure, and very likely have special end-organs for the per-
ception 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, con-
tain sensory organs of some sort. They have been variously
regarded as olfactory ( Lee ) .auditory (Graber),and as organs
of ecjuilibration. When one or both halteres are removed,
the fly can no longer maintain its equililjrium in the air, and
Weinland holds that the direction of flight is affected by the
movements of these " Ijalancers."

6. Digestive System

The alimentary tract in its simplest form is to be seen in
Thysanura, Collem])ola and most larv;c, in which (Fig. 144)
it is a simple tube extending along the axis of the body and

Fig. 145.

Alimentary tract of a grasshopper, Melanoplus differentiaiis. c, colon; cr, crop;
g'c, gc, gastric cseca; i, ileum; m, mid intestine, or stomach; mt, Malpighian, or kid-
ney, tubes; o, asophagus; p, pharynx; r, rectum; s, salivary gland of left side.

consisting of three regions, namely, fore, mid and hind gut.
These regional distinctions are fundamental, as the embr}'-
ology shows, for the middle region is entodermal in origin
and the two others are ectodermal, as appears beyond.

There are many departures from this primiti\e condition,
and the most specialized insects exhibit the following modifi-
cations (Figs. 145, 146) of the three primary regions:

Fore intestine (stomodannn ) : mouth, pharynx, cesophagus,
crop, proventriculus (gizzard), cardiac vah-e.

ANATOMY AND PHYSIOLOGY

117

Mid intestine (niesenteron) : ventricukis (stomach).

Hind intestine ( proctodceuni) : pyloric valve, ileum, colon,

rectum, anus.

Stomodaeum, — The nioutJi, the anterior opening of the

food canal, is to be dis-

. 1 1 ,- ,, Fig. 146.

tmguished trom the

pharynx, a dilatation for
reception of food. In
the pharynx of mandib-
ulate insects the food is
acted upon by the saliva ;
in suctorial forms the
pharynx acts as a pump-
ing organ, in the manner
already described.

The Lvsophagns is com-
monly a simple tube of
small and uniform cali-
ber, varying greatly in
length according to the
kind of insect. Passing
between the commissures
that connect the brain
with the subcesophageal
ganglion ( Fig. 113), the
oesophagus leads grad-
ually or else abruptly
into the crop or gij:sard,
or when these are absent,
directly into the stomach.
In addition to its func-
tion of conducting food,
the oesophagus is some-
times glandular, as in the grasshopper, in which it is said
to secrete the " molasses "which these insects emit.

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
cjeca; i, ileiim; )}i, mid intestine; int, Mal-
pighian tubes; o, oesophagus; p, provcntricu-
lus; r, reservoir. — After Kolbe.

ii8

ENTOMOLOGY

Fig. 147.

The crop is conspicuous in most Orthoptera (Fig. 145) and
Coleoptera (Fig. 146) as a simple dilatation. In Neuroptera
(Fig. 147) its capacity is increased l^y
means of a lateral pocket — the food reser-
voir; this in Lepidoptera, Hymenoptera
and Diptera is a sac (Fig. 148. c) commu-
nicating with the oesophagus by means of
a shurt neck or a long tube, and serving as
a temporary receptacle for food. In her-
Ijivorous insects the crop contains glucose
formed from starch by the action of saliva
or the secretion of the crop itself; in car-
nivorous insects this secretion C(jn verts
all)uminoids into assimilable peptone-like
substances.

Next comes the enlargement known as
the proz'ciitriciiliis, or gij:::ard, which is
present in many insects, especially Orthop-
tera and Coleoptera (Fig. 146), and is
usually found in such mandi1)ulate insects
as feed upon hard sul^stances. The pro-
ventriculus is lined with chitinous teeth or
rids'es for strainins" the food, and has

Digestive system
Myrmcleon larva. <-,

caecum; cr, crop; m, mid ^ ^

intestine; mt, Malpighian poWCrful circuku" mUSclcS tO SCjUeCZe the
tubes; s, spinneret. — r i i i • i ^i i i 11

After meinert. ^'^'^^ h^-QK Hito the stomacli. as well as

longitudinal muscles for relaxing, or open-
ing, the gizzard. Some authors maintain that the proventricu-
lus not only serves as a strainer, 1)ut also helps to C()mminute
the food, like the gizzard of a Ijird.

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 stomoda?um into
the mesenteron, forming a circular lip which permits food to
pass backward, but closes upon pressure from l)ehind.

Mesenteron. — The veiitricnliis, otherwise known as the

ANATOMY AND PHYSIOLOGY

119

mid intestine, or stomach, is usually a simple tube of large
caliber, as compared with the oesophagus or intestine, and into

Fig. 148.

Alimentary tract of a moth, Sphinx, c, food reservoir; cl, colon; cj]i, cffcum; i, ileum;
m, mid intestine; mt, Alalpighian tubes; o, oesophagus; r, rectum; i, salivary gland. —
After Wagner.

Fig. 149.

the ventriculus may open glandular blind tubes, or gastric
cccca (Figs. 145. 146); these, though
numerous in some insects, are commonly
few in number and restricted to the ante-
rior region of the stomach. The gastric
cjeca of Orthoptera secrete a weak acid
which emulsifies fats, or one which passes
forward into the crop, there to act upon
a]l)uminoid substances. In the stomach
the food ma}' be acted upon by a fluid
secreted by specialized cells of the epithe-
lial wall. In various insects, certain cells
project periodically into tlie 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 phenomenon takes place in the larva
of PtycJioptera (van Gehuchten), also in
nymphs of Odonata (Xeedham), and is
probably of widespread occurrence among
insects. The chief function of the

Cardiac valve of young
muscid larva, o, oesoph-
agus; p, proventriculus;
'•, valve. In an older
larva the valve projects
into the mid intestine. —
After KovvALEVSKY.

I20

ENTOMOLOGY

..-S

-m

stomach, however, is absorption, which is effected by the
general epithehum. Physiologicahy, the su-called stomach of
an insect is quite iinhke the stomach of a ^•ertebrate. being more
hke an intestine.

Proctodaeum. — At the anterior end of the hind intestine
there is usually a pyloric valve, which prevents 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 CoUembola (Fig. 144), con-
sist of a backward-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, howe^•er, it presents two or
even three specialized regions, namely
and in order, ileum, colon and rectuui
(Fig. 145). The hind intestine varies
greatly in length and is frequently so
long' as to be thrown into convolutions
(Fig. 150). The ileum is short and
stout in grasshoppers (Fig. 145 ) ; long,
slender and convoluted in many carniv-
orous beetles ; and quite short in cater-
pillars and most other larva? ; its func-
tion is absorption. The colon, often
absent, is evident in Orthoptera and
Lepidoptera and may bear (Benacus,
Dytiscns, SilphidcT, Lepidoptera) a con-
spicuous Cc-ecal appendage (Figs. 148, 150) of doubtful func-
tion, though possibly a reservoir for .excretions. The colon
contains indigestible matter and the waste products of diges-
tion, including the excretions of the ]\Ialpighian tubes. The
rectum (Fig. 145) is thick-walled, strongly muscular and often
folded internally. Its office is to expel excrementitious matter,
consisting largely of the indigestible substances chitin, cellulose

Digestive system of Bclos-
toina. c, CKcum; i, ileum;
m, mid intestine; mt, Mal-
pighian tubes; r, salivary
reservoir; s, salivary gland.
— After LocY, from the
American Naturalist.

ANATOMY AND PHYSIOLOGY

121

and chlorophyll. The rectum terminates in the (7////.s\ which
opens through the last segment of the abdomen, always a1)ove
the genital aperture.

Histology. — The epithelial wall of the alimentary tract is
a single layer of cells (Fig. 151), which secretes the iiitima^
or lining layer, and the basement inembrane — a delicate, struc-
tureless enveloping layer.
The intima, which is contin-
uous with the external cutic-
ula, is chitinous in the fore
and hind gut (which are
ectodermal in origin), but
not in the mid gnt (entoder-
mal), and usually exhibits
extremely tine transverse
striae, which are due prob-
ably to minute pore canals.
Surrounding the basement
membrane is a series of cir-
eiilar muscles and outside
these is a layer of longifudi-
iial iiniscles. 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
longitudinal muscles, restricted almost entirely to the mid
intestine, act in opposition to the constricting muscles to en-
large 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 chitinized and variously
modified to form spines, teeth or ridges.

Salivary Glands. — In their simplest condition, the saliwary
glands are a pair of blind tubes (Fig. 152), one on each side
of the oesophagus and opening separately at the base of the
hypopharynx. Commonly, however, the glands open through

Wall of mid intestine of silk worm,
transverse section, b, basement membrane;
c, circular muscle; i, intima; /, longitudinal
muscle; n, n, nuclei of epithelial cells; s,
secretory cell.

I 22

ENTOMOLOGY

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 usuallv
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
CESophagus ; 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 hypo-
pharynx.

All these cephalic glands are evagina-
tions of the stomodceum (ectodermal in
origin) and consist of an epithelial layer
with the customary intima and basement
mem1)rane (Fig. 154). The nuclei are
large, as is usually the case in glandular
cells, and the cvtoplasm consists of a dense
framework (appearing- in sections as a
network) enclosing vacuoles of a clear
substance — the secretion ; the chitinous
Fig. 153.

A simple salivary
gland of Cacilius. c,
canal; (/, duct; g, g, gland-
ular cells. — .\fter Kolbe.

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

g, gland ; h.

ANATOMY AND PHYSIOLOGY

123

intima is penetrated by fine pore canals througli which the
secretion passes. In many insects, notably the cockroach, the
common duct is held distended by
spiral threads which gi\-e the duct
much the appearance of a tra-
chea.

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 Dytisciis. In the mosc[uito 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 facili-
tate 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 kidney, or Malpighian, tubes,
present in nearly all insects, are long, slender, blind tubes open-

Histology of salivary gland
of Cacilius, radial section. b,
basement membrane; c, canal;
g, glandular cell; i, intima; n,
nucleus. — After Kolbe.

Fig. 155.

ing into the intestine imme-
diately behind the stomach
as a rule (Figs. 145, 146),
^^^^^==s= l)ut always into the intestine.

One of the three-lobed salivary glands The HUmbcr of kiduCy tubcS is
of a mosquito. The middle lobe secretes i • rr • ^■ r-

the poison.— After Macloskie, from the vcry different 111 difl:erent in-

American Naturalist. ^^^^^. Colleml).)la have UOUC,

while Odonata ha\e fifty or more and AcridiidcC as manv as
one hundred and fifty; commonly, howexer, there are four or
six, as in Coleoptera, Lepidoptcra and many other orders.
Not more than six and frequently only four occur in the em-
bryo (Wheeler), though these few embryonic tubes may sub-
sequently branch into many.

124

ENTOMOLOGY

Fig. 156.

The ]\Ialpighian tubes (Fig. 156) are evaginations of the
proctodrcum and are consequently ectodermal. .V cross sec-
tion of a tube shows a ring" (^f 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 Ije branched, as in Lepidoptera.
A chitinous intima, traversed l)y pore-
canals, lines the tube, and a delicate base-
ment membrane is present, surrounded
by a peritoneal layer of connective tissue.
h\u"thermore, the urinary tubes are richly
supplied with trachccC. In function, the
?klalpighian tubes are analogous to the
vertebrate kidneys and contain a great
variety of substances, chief among
which are uric acid and its derivatives
( such as urate of sodium and of ammo-
nium), calcium oxalate and calcium car-
bonate.

Parts of the fat-body may also be
concerned in excretion ; thus the fat-
body in Collembola and Orthop- Yig. 157.
tera serves for the permanent stor-
age 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 filter Ci-oss section of Malpiglnan tube

eventually the dorsal vessel, which °f silkworm, Bowbyx mori b,

basement membrane; c, crystals; i,

reseml)les a heart merely in being intima; /, lumen; n, nucleus; p,

a propulsatory organ. p'^'"''""^^' ''''''■ ^'''''^ magnified.

Dorsal Vessel. — The dorsal vessel (Figs. 158, 162) is a

delicate tube extending: alono- the median dorsal line immedi-

Portion of Malpighian
tube of caterpillar, Samia
cccropia, surface view.

ANATOMY AND PHYSIOLOGY

12:

ately under the integument. A simple tulje in some larva?, it
consists in most adults chiefly of a series of chambers, each of

Fig. 158.

Dorsal vessel of beetle,
Lticaniis. a, aorta; al, alary
muscle; o, ostium. — After
Steaus-Durckheim.

Fig. i5g.

Diagram of a portion of the heart of a dragon
fly nymph, Epithcca. o, ostium; v, valve; the ar-
rows indicate the course of the blood. — After

KOLBE.

Fig. 160.

Diagrammatic cross section of pericardial
region of a grasshopper, Qidipoda. a, alary
muscle ; d, dorsal vessel ; s, suspensory mus-
cles; sp, septum. — .\fter Gr.^ber.

Fig. 161.

lilood corpuscles of a grasshopper, Stciiobotlinis. a f, corpuscles covered with fat-
globules; g, corpuscle after treatment witli glycerine, showing nucleus. — After GRAnER.

which has on each side a valvular opening, or ostiinii (Fig.
159) , which permits the ingress of blood but opposes its egress ;

126

ENTOMOLOGY

Fig. 162.

within tlie chambers occur other vah'iilar folds tliat allow the
blood to move forward only. With few exceptions ( Ephe-
meridas) 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 abdo-
men : 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 usuallv divides into
t\\'0 branches (Fig". 162),
each of which may again
branch. In the head the
blood leaves the aorta ab-
ruptly and enters the general
body cavity.

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

Structure of the Heart. — The dorsal vessel has a delicate
lining-mem1:)rane, or intima, and a thin enveloping meml)rane ;
between these, in the heart, is a layer of fine muscle fibers, cir-
cular or spiral in direction, which effect the contractions of the
organ.

Ventral Sinus. — In many if not most insects a pulsatory
septum (Fig. 177, i') extends across the floor of the body cav-

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

ANATOMY AND PHYSIOLOGY 12/

ity to form a siinis, in wliicli the l)lood flows backward. l)alliinc;"
the ventral ner\-e cord as it g'oes. This ventral sinus siipi)le-
ments the heart in a minor way. as do also the local pulsatory
sacs which have been disco\ere(l in the legs of aquatic Hemip-
tera and the head of Orthoptera.

Blood. — The blood, or liccniolyinpli. of an insect consists
chiefly of a watery fluid, or plasma, which contains corpuscles,
or leucocytes. Though usually colorless, the plasma is some-
times yellow (Coccinellid?e, Meloida?), often greenish in her-
bivorous insects from the presence of chlorophyll, and some-
times of other colors ; often the blood owes its hue to yellow
or red drops of fat on the surface of the blood corpuscles
(Fig. i6i).

Leucocytes. — The corpuscles, or leucocytes, are minute

nucleated cells, 6 to 30 fji in diameter, variable in form even

in the same species but commonly (Fig. 161) round, oval or

ovate in profile, though often disk-shaped, elongate or amce-

.boid in form.

Function of the Blood. — The blood of insects contains
many substances, including egg albumin, globulin, fibrin, iron,
potassium and sodium (]\Iayer), 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 cor-
puscles and has little or nothing to do with the aeration
of tissues, that function being relegated to the tracheal
system.

Circulation, — The course of the circulation is evident in
transparent aquatic nymphs or lar\-;e. In odonate or ephe-
merid nymphs, currents of blood may be seen (Fig. 162) flow-
ing through the spaces between muscles, trachere, ner\-es, etc.,
and bathing all the tissues ; separate outgoing and incoming
streams may be distinguished in the antennas 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, Ephe-

128 ENTOMOLOGY

merida, Coleoptera, Lepidoptera, etc., the currents trending
along- the tracheae ; this circulation ceases, however, with the
drying of the wings.

The chambers of the dorsal vessel expand and contract suc-
cessively from behind forward. At the expansion (diastole)
of a chamljer 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, afford-
ing- 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
acti\-ity of the insect and upon the temperature and the amount
of oxygen or carbonic acid gas in the surrounding atmosphere.
Oxygen accelerates the action of the heart and carbonic acid
g3.s retards it. A decrease of 8° or io° C. in the case of the
silkworm lowers the numl)er of lieats from 30 or 40 to 6 or
8 per minute. The more acti\e 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 ligiistri, according to
Newport, the mean numl:)er of pulsations in a moderately
active lar\'a before the first moult is about 82 or 83 per minute ;
before the second moult, 8g, sinking to 63 before the third
moult, to 45 befcjre 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
aljout 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 other organs and occupying a
large part of the body cavity. The distribution of the fat-
body is to a certain extent definite, however, for the fat-tissue

ANATOMY AND PHYSIOLOGY

129

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 masse?
of fat-body occur constantly on each side of the alimentary

Transverse section of the abdomen of a caterpillar, Pieris rapcr. b, blood corpus-
cles; c, euticula; d, dorsal vessel; f, fat-body; g, ganglion; h, hypodermis; /, leg; m,
muscle; mi, mid intestine, containing fragments of cabbage leaves; nit, Malpighian
tube; s, silk gland; sp, spiracle; tr, trachea.

tract and also at the sides of the dorsal yessel, 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 ^ipis and several in Musca), l)ut the celhilar
lo

ENTOMOLOGY

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,

Fig. 164.

leaving only a disorderly net-
work. The fat-cells sometimes
contain an albuminoid sub-
stance, and usually the fat-body
includes consideral)le cjuantities
of uric acid or its derivatives,

Fat-cells of a caterpillar, Pieris. A.
cells filled with drops of fat; B, cell
freed of fat-drops, showing nucleus.— freCjUeUtlv ill tllC form of COll-
After KoLBE.

spicu( »us concretions.
Functions. — The physiology of the fat-system is still ob-
scure. Probal)h- 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 lar\'a 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- ^^^'^- ^^5-

body indicates an excretory
function, particularly in Col-
lembola, which ha\e ikj Mal-
pighian tubes. The intimate
association between the ulti-
mate tracheal branches and
the fat-body has led some
authorities to ascribe a res-
piratory function to the lat-
ter. A close relation of
some sort exists also be-
tween the fat-system and
the blood-system ; fat-cells
are found free in the blood,

and the blood corpuscles originate in the thorax and abdo-
men from tissues that can scarcely be distinguished from

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

ANATOMY AND PHYSIOLOGY

I ^I

Fig. 1 66.

Qinocytes and accom-
panying trachcc, fi"om
abdomen of a silkworm.

fat-tissues. The corpuscles (leucocytes, or phagocytes) which
iu some insects absor!:) effete larval tissues during" meta-
morphosis have been by some authors regarded as wandering
fat-cells. Cells constituting the pericardial fat-body are at-
tached to the lateral muscles (alary muscles) of the dorsal
vessel, but almost nothing is known as
to their function. Associated with the
fat-body proper are the peculiar cells
known as cciwcytes. These occur in
most insects, in segmentally-arranged
clusters on each side of the abdomen,
and consist of exceptionally large cells,
more or less round or oval (Fig. i66),
each W'ith a large round, oval or elon-
gate nucleus. These peculiar cells are
usually separate from one another, but
are held in clusters by tracheal branches.
Their function is unknown. Finally, the

fat-body is the basis of the luminosity, or so-called phospho-
rescence, of insects.

Luminosity. — This phenomenon appears sporadically and
bv \arious means in protozoans, worms, insects, fishes and
other animals. Luminosity in insects, though sometimes
merely an incidental and pathological effect of bacteria, is usu-
ally produced 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 Py-
rophorus (ElateridcT), in which the pronotum bears a pair of
luminous spots, and the common fire-flies (Lampyrichc). In
Lampyrida?, the light is emitted from the ventral side of the
posterior abdominal segments. In our common Photiiiiis, the
seat of the light is a modified portion of the fat-body — a
photogenic plate, situated immediately under the integument
and supplied with a profusion of fine tracheal branches. The
cells of the photogenic plate, it is said, secrete a substance which

132

ENTOMOLOGY

undergoes rapid combustion in the rich supply of oxygen fur-
nished by the tracheae.

The ravs emitted by the common fire-t^ies are remarkable in
being' almost entirely light rays, with almost no thermal or

actinic ravs. Accordino- to
Fig. i(j7. ^, ' , , ' .

\ oung 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 illuminating pur-
poses ; while the light-giving
efhciency of the electric arc is
only ten per cent, and that of
sunlight only thirty-live per
cent. The light of the flre-
11}', howe\'er, may l^e rated at
one hundred per cent.; this
light, then, is perfect, and as
yet unapproached by artihcial
means.

As to the use of this lumi-
nosity, there is a general
opinion that the light exists
for the purpose of sexual
attraction — a belief held by
the author in regard to Plw-
timis, at least. Another view
is that the light is a warning

p, palpus; ., spiracle; st, spiracular, or ^j j ^^ UOCtumal birds, IxitS

stigmatal, branch; t, mam tracheal trunk; '-'

V, ventral branch; rs, visceral branch.— or Other iusecti VOrOUS ailiuials ;

After KoLBE. ... , , i r ^

this IS supported by the tact
that lampyrids are refused by birds in general, after ex-
perience ; young birds readily snap at a fire-fly for the first
time, but at once reject it and thereafter pay no attention to
these insects.

Tracheal system of an insect, a, an-
tenna; b, brain; /, leg; ii, nerve cord;

ANATOMY AND PHYSIOLOGY

I ^

9. Respiratory System
In insects, as contrasted with vertebrates, the air itself is
conveyed to the remotest tissues by means of an elal^orate sys-
tem of branching air-tnbes, or fracliccc, which receive air
through paired seg'mentally-arranged spiracles. Each spiracle
is commonly the mouth of a short tube which opens into a
main tracheal trunk (Fig. 167) extending along the side of

Diagrammatic cross section of the thorax of an insect, a, alimentary canal; d,
dorsal vessel; g, ganglion; 5, si)iracle; w, wing; /, dorsal tracheal branch; 2, visceral
branch; 5, ventral branch.

the body. From the two main trunks branches are sent which
divide and subdivide until they become extremelv delicate
tubes, which penetrate even between muscle fillers, between the
ommatidia of the compound eyes and possibly enter cells. In
most cases each main longitudinal trunk gives off in each seg-
ment (Fig. 168) three large branches: (i) an upper, or dor-
sal, branch, which goes to the dorsal muscles; (2) a middle,
or z'isccral, branch, which supi)lies 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 (dragon flies, Ijeetles, moths,
flies and bees) there occur tracheal |)ockets, or air-sacs, which

134

ENTOMOLOGY

Fig. I

were formerly and erroneously supposed to diminish the
weight of the insect, l)ut are now regarded as simply air-
reservoirs.

Types of Tracheation. — Two types of tracheal system are
distinguished for convenience: (i) The primary, open, or

holopiiciisfic type descrilied
above, in which the spiracles
are functional; (2) the sec-
ondary, closed, or apiiciistic
type, in which the spiracles
are either functionless or ab-
sent. This type is illustrated
in Collembola and such aquatic
nymphs and larvcC as breathe
either directly through the skin
or else by means of gills.
The two types, however, are
connected by all sorts of inter-
mediate stages.

Tracheal Gills, — In many
aquatic nymphs and larv.'c the
spiracles are suppressed (though they become functional in
the imago) and respiration is effected by means of gills; these
are cuticular outgrowths which usually,
thoug'h not invariably, contain tracheae,
and are commonly lateral or caudal in
position. Lateral tracJical gills are
highly developed in ephemerid nymphs
(Fig". 169). in which a pair occurs on
some or all of the first seven segments
of the abdomen ; a few genera, how-
ever, have cephalic or thoracic gills. Larvje of Trichoptera
ha\'e paired abdominal gills var}-ing greatly in form and posi-
tion, and Perlidne often have paired thoracic gills. Caudal
tracheal gills are conspicuous in nymphs of Agrionidie (Fig.
170) as three foliaceous appendages. A few coleopterous

Lateral gill from abdomen of a ;May
fly nymph, Hcxagenia 7'ariabilis. En-
larged.

Fig. 170.

Caudal
agrionid
larged.

gills of
nymph,

ANATOMY AND PHYSIOLOGY

135

larwne of aquatic habit, as Gyriiiiis and
Cnciiiidotiis, possess traclieal gills, as do
also caterpillars of the genus Paraponyx
(Fig. 171), 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 ex-
tensive respiratory surface; their integu-
ment is thin and the trachese spread
closely beneath it. These adaptations
are often supplemented by waving move-
ments 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
traclieal gills of odonate nymphs. In
these insects the lining of the rectum
forms numerous papilla; or lamellae, which

Fig. i/i.

Caterpillar of Para-
ponyx obscuralis, to show
tracheal gills. Length,
1 5 mm. — .\fter Hart.

Fig. 172.

Larva of Bittaco-
morpha clavipcs, show-
ing respiratory tube.
Natural size. — After
Hart.

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 respiration 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 Ptcronarcys
(Fig. 18), which hal)itually dips into
the water and rests in moist situations,
the gills probably supplement the spira-
cles. Further details on the respiration
of aquatic insects are given in Chapter
IV.

136

ENTOMOLOGY

Spiracles. — The paired external openings of the tracheae
occur on the sides of the thorax and al^domen, there being
never more than one pair to a segment. Though the thysa-
nuran Japyx has 11 pairs, no winged insect has more than 10;
ahhough there are in all 12 segments which may bear spiracles
- — the three thoracic and the first nine abdominal segments.
(Additional details are given on page 66.)

The spiracles, or stigmata, are usually provided with bris-
tles, 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. Larv?e that
live in water or mud may ha^•e spiracles at the end of a long

Fig. 173.

Apparatus for closing the spiracular trachea in a beetle, Litcaitus. A, trachea
opened; B, closed; b, bow; bd, band; c, external cuticula; /, lever; jit, muscle; s,
spiracle; t, trachea. — After Judeich and Nitsche.

tube, which can be thrust up into the pure air; this is true of
the dipterous larv?e of Eristalis, BittacoinorpJia (Fig. 172)
and Culcx (Fig. 229).

Closure of Spiracles. — As a rule, a spiracle is opened and
closed periodically by means of a valve, operated by a special
occlusor muscle. In dipterous larva; the closure is effected by
the contraction of a circular muscle, but Coleoptera and Lepi-
doptera, among other insects, have a somewhat complex appa-
ratus for closing the trachea immediately behind the spiracle.

ANATOMY AND PHYSIOLOGY

137

Fig. 174.

Thus, in the stag-heetle, a crescentic boic (Fig-. 173, b) extends
half around the tracliea, and the rest of the circnmference is
spanned l)y a liZ'cr (1) and a band ibd) ; these three chitinous
parts, articulated together, form a ring around the trachea.
Furthermore, a muscle (/// ) connects the lever and the hand.
As the muscle shortens, the lever
turning upon the end of the band as
a fulcrum, pulls the l)o\\- toward the
lever and band until the enclosed
trachea is pinched together. A\dien
the muscle relaxes, the trachea opens
by its own elasticity.

Structure of Tracheae. — The
trachea" originate in the eml)ryo as
simple in-pocketings of the outer
germ layer, or ectoderm, and from
these the countless tracheal branches
are derived by the same process
of invagination. The lining mem-
brane of a trachea is, then, con-
tinuous with the external cuticula,

and the cellular wall of a trachea is continuous with the
rest of the hypodermis. This wall consists of a la}-er of
polygonal cells (Fig. 174) fitting closely together as a pave-
ment cpitJicliiiiii. The chitinous lining, or iiifiiiia. is thick-
ened at regular intervals to form thread-like ridges, which
course around the inner circumference in essentially a spiral
manner, though the contiiuiity of the so-called spiral thread is
frecjuently interrupted. These elastic threads, or Uciiidia,
serve to keep the trachea open without affecting its llexibility.

The ultimate tracheal branches (Fig. 175) are extremely
delicate tubes, which do not end blindly, but anastomose with
one another, forming- a capillary network of contluent tubes.
Some authors have held that the finest tracheal filaments pene-
trate epithelial or other cells.

Respiration. — The external signs of respiration are the

Structure of a trachea, h,
tracheal hypodermis; i, intima;
i, tnsnidiuni.

ENTOMOLOGY

regular opening and closing movements of some of the spira-
cles and the rh_ythmic contraction and expansion of the abdo-
men. During contraction, the dorsal and ventral walls ap-

Tracheal capillary end-network from silk gland of Porthctria dispar. p, peritracheal
membrane; t, tracheal capillary. — After Wistinghausen.

proach each other (Fig. 176) and during expansion they
separate. The tergum moves more than the sternum in Cole-
optera and Heteroptera, and vice versa in Acridiidae, Odonata,
Diptera and aculeate Hymenoptera. The width of the abdo-
men usually changes but little during respiration, for the ter-
gal and sternal movements are taken up by the pleural iiiem-

FiG. 176.

Transverse sections of abdominal segments, to illustrate respiratory movements. A,

cockroach {Blatta); B, bee {Botnbus); s, sternum; f, tergum. The dotted lines

indicate positions of terga and sterna after expiration; the continuous lines, after
inspiration. — After Pl.\teau.

braiics which, as in the grasshopper, infold at contraction and
straighten out at expansion. Other respiratory movements
occur, but the}- are of minor importance.

ANATOMY AND PHYSIOLOGY

139

The rate of respiration increases or diminishes with the
activity of the insect and witli temperature and otlier condi-
tions. In six specimens of M chmopliis diffcrcntialis, held l)e-
tween the fingers, the thoracic spiracles opened and closed
respecti\-ely 34, 43, 45, 54, 60 and 61 times per minute. Four
individuals of M. fciniir-

riihruni under the same cir- ' ^^'

cumstances g'a\e 70, 78. 90
and 92.

At expansion inspiration
takes place, and at contrac-
tion expiration occurs. In
the grasshopper, the thoracic
spiracles open almost simul-
taneously with the expan-
sion of the ahdomen. Con-
traction is effected by special
vertical expirator}- muscles
(Fig. 177), but expansion
is due to the elasticity of
the abdominal wall, as a
rule ; this is the reverse
of \\hat occurs in mam-
mals, wdiere expiration is
passive and 'inspiration ac-
tive. Inspiratory muscles
are found, however, in Acridiida;, Trichoptera and Ilymen-
optera.

Though the respiratory movements 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 wav in which the air reaches the finest tracheal branches

Diagrammatic cross section of a1)domen
of a grasshopper, Acridium. d, dorsal
septum, or diaphragm; ex, expiratory mus-
cle; /, fat-body; g, ganglion; h, heart; in,
inspiratory muscle; v, ventral scptiun, be-
low whicli is the ventral sinus. The dorsal
and ventral septa rise and fall periodically.
— After Graber.

I40

ENTOMOLOGY

is not clearly ascertained, bnt it is thong'ht that air is forced
into these tubes by pressure from the abdominal muscles, while
its escape through the spiracles is being prevented by the com-
pression of the stigmatal trachea?.

The respiratory movements are entirely reflex and are inde-
pendent of the brain or subcesophageal ganglion, for they con-
tinue after decapitation 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.

lo. Reproductive System

The sexes are always separate in insects, hermaphroditism
occurring only as an abnormal condition. The sexual organs,
situated in the abdomen, consist essentially of a pair of ovaries

Fig. 178. Fig. 179.

Reproductive sj'stem of male beetle, Mclo
lontha. a, accessory gland; c, copulatory
organ; d, ejaculatory duct; s, seminal vesicle;
t, testis; v, vas deferens. — After Kolbe.

Reproductive system of male
Lepidoptera. a, accessory gland;
d, ejaculatory duct; t, united
testes; v, vas deferens. — After
Kolbe.

or testes and a pair of ducts {oviducts or seminal duets, respec-
tively). Primitively, the ducts open separately, as they still
do in Ephemeridc!?, but in nearly all other insects the two ducts
enter a common evacuating duct (I'agiiia or ejaculatory 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.

ANATOMY AND PHYSIOLOGY

141

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

Male. Female.

Testes = Oz'arics
Seminal ducts = Oi'iditcts
Ejaculatory duct = Vagina

Seminal z^esiele = Seminal I'eeeptaele
Accessory glands ^ .Iceessory glands
Penis and accessories =^ Oz'iposifor

Male Organs. — Each testis, thcjugh sometimes a single
blind tube, is usually a grou^) of tubes or sacs (Fig". 178),
testicular follicles, which open into a seminal duct (z'as defer-

FiG. I So.

Fig. iSi.

Spermatozoa. A, locustid
grasshopper; B, cockroach,
Blatta; C, beetle, Copris.
— After BiJTScuLi and Bal-

LOWITZ.

Reproductive system of queen
honey bee. o, accessory sac of
vagina; b, bulb of stinging ap-
paratus; c, colleterial, or cement,
gland; o, ovary; od, oviduct; p,
poison glands; pr, poison reser-
voir; r, reccptaculum seminis;
re, rectum; ?■, vagina. — After
Lkuckart.

ens). In most Lepidoptera the testes are secondarily united
into a single mass (Fig\ 179) as also in Acridiida-. The two
seminal ducts enter the common ejaculatory duct, which ter-

142

ENTOMOLOGY

minates in the intromittent organ, nr penis. Often each vas
deferens is dilated near its montli into a scniiiial c'csiclc, or
reservoir; or there may l)e only a single seminal vesicle, aris-
ing from the common duct. One or more pairs of glands
opening" into the vasa deferentia or the ductus cjaculatorius
secrete a fluid which mixes with the spermatozoa and often-
times unites them into packets, known as s/^cniiatopliorcs.

All these parts are sul)ser-
vient to the formation, pres-
ervation and emission of the
spcj'mai(>:::()(7. These minute
thread-like bodies (Fig. i8o)
arise in the testicular follicles
from a germinal epithelium,
and consist, as in vertel^rates,
of a liead. middle-piece and
a \'il)ratile, /(/// — without en-
tering into the finer struc-
ture.

Female Organs. — Each
ovary (Fig. i8i ) consists of
one or nmre tubes opening
into an oviduct. The two
oviducts enter a common
duct, the vagina, which
opens to the exterior, often
through an ovipositor. Fre-
quentlv the vagina is ex-
panded as a pouch, or bursa copulafri.v, though in Lepidoptera
the bursa and the vagina are distinct from each other and open
separately (Fig. 182). In most insects a dorsal evagination
of the vagina forms a seiniiud receptacle, or spcrmatlieca, from
which spermatozoa emerge to fertilize the eggs. The acces-
sory glands, either paired or single, provide a secretion for
attaching the eggs to foreign objects, cementing the eggs to-
gether, forming an egg-capsule, etc.

Reproductive system of female Lepi-
doptera. b, bursa copulatrix; /', terminal
filament; g, cement glands: o, o, ovaries;
od, oviduct; r, receptaculum seminis; v,
vagina; vs, vestibule, or entrance to
bursa. — After Kolbe.

ANATOMY AND PHYSIOLOGY

In each ovarian tnbe, or ovariole, are found ova in succes-
sive stages of growth, the largest and oldest ovum being near-
est the oviduct. In the jjrimitive t)'pe of egg-tube, as in Thys-
anura and Orthoptera (Fig. 183, A) every chamber contains
an ovum ; in m(;re specialized
types, every other chamber con-
tains a nutritive cell instead of a
germ cell, the nutriti\'e cells serv-
ing as food for the adjacent o\a
(B) \ or the nutritive cells, in-
stead of alternating with the ova,
ma}' be collected in a special
chamber, beyond the ovarian
chambers (C). An eg'g-tube is
usually prolonged distally as a
terminal fdament, (^r siispciisor,
the free end of which is attached
near the dorsal vessel.

Ovaries and testes arise from
indilTerent cells, or priiuitive
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 o\'um (Fig.
184). In the male, the primary
germ cells form cells termed
spcnnatogofiia ; each of these
forms a spcniuitocyft', and this
gives rise to four spcniiafocoa.

Hermaphroditism. — The phenomenon of hcniKif'hrodi-
fisiii, or the combination of male and female characters in the
same indi\idual, occurs only as an extremely rare abnormality
among insects. Spever estimated that in Lepidoptera only
one individual in thirty thousand is henuaphroditic. Bertkau
(1889) listed 335 hermaphroditic arthropods, of which 8 were

Types of ovarian tubes. .4, with-
out nutritive cells; B, with alternat-
ing nutritive and egg-cells; C, with
terminal nutritive chamber; c, ter-
minal chamber; e, egg-cell; ep, fol-
licle eiiithelium; f, terminal fila-
ment; .S-, strands connecting ova
with nutritive chamber; v, yolk, or
nutritive, cells. — From Lang's Lclir-
buch.

144

ENTOMOLOGY

Fig. 184.

crustaceans, 2 spiders, 2 Orthoptera, 8 Diptera, g Coleoptera,
51 Hvmenoptera 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
dimorphism is so prevalent in the
order that hermaphrodites are easily
recognized.

The most common kinrl of her-
maphroditism is that in which one
side is male and the other female, as in
Fig. 185. Bertkau found this right-
and-left hermaphroditism in 153 in-
dividuals. 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;
rarelv. 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 ^

Fig. 185.
phenomenon involves the

primary organs as well as
the secondary sexual char-
acters. \\ here dissections
have Ijeen made it has
been found usually that
hermaphroditism does ex-
tend to the reproductive
organs themselves. 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 abd(.»men and an
ovary on the left side.

Ovum of a butterflj', J'a-
nessa, in its follicle, e, fol-
licle epithelium; g, germinal
vesicle; n, branching nucleus
of nutritive cell; o, ovum. —
After WooDWORTH.

nermai>hrodite gypsy moth, Portlictria dis-
par; right side, male; left, female. Natural
size. — After T.\schenberg, from Hertwig's
Ldirbiicli.

ANATOMY AND PHYSIOLOGY 145

Parthenogenesis. — Reproduction without fertilization is a
normal phenomenon in not a few insects. This partheno-
genesis may easily lie 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 fertilized 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 Cynipida?. In some Cynipid?e, how-
ever, males are unknown ; such is the case also in some Ten-
thredinid?e. The statement has long been made that the un-
fertilized eggs of worker ants, bees and wasps produce invari-
ably males ; it has Ijeen found recently, however, that the par-
thenogenetic worker eggs of the ant Lasiiis niger may produce
normal workers (Reichenbach, Mrs. A. B. Comstock). ]\Iales
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 cj[ueen bee are fertilized. Parthenogenesis has been
recorded as occurring also in a few moths, some Coccidse and
many Thysanoptera.

Pasdogenesis. — In Miastor and some species of Cecido-
inyia, young are produced by the larva. This extraordinary
form of parthenog'enesis is termed pccdogenesis, and is limited

Fig. i{

Young psedogenetic larvK of Miastor in the body of the mother larva. Greatly en-
larged. — After Pagenstf.cher.

apparently to the family Cecidomyiicke. The paedogenetic
larvae of Miastor (Fig. i86) develop before the oviducts have
appeared and escape by the rupture of the mother. After
several successive generations of this kind the resulting larvae
pupate and form normal male and female flies. The pupa of
a species of Chirononins occasionally deposits unfertilized
eggs, which develop, however, in the same manner as the fer-
tilized eggs of the species.

CHAPTER III

DEVELOPMENT

I. Embryology
Ovum. — The ovum of an insect, as of any other animal,
is a single cell (Fig. 187), with a large nucleus { germinal
vesicle) , a large nucleolus, nutritive mat-
ter, or yolk {dento plasm) , contained in
the cytoplasm, and a cell wall {■ritelline
membrane) secreted by the ovum; the
eg"g-shell, or cJmrion, is secreted around
the o\-um 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 ft)ur cells; three of these,
however — the polar bodies — are minute
and rudimentary.

These phenomena of ovogenesis are
paralleled in the development of the sper-
matozoa, or spermafogoiesis; for the pri-
mary spermatocyte gives rise to two sec-
ondary spermatocytes, and these to four
spermatids, each of which forms a sper-
niato::odn.

By means of this nnituration process
the number of cJiromosomes in the egg-
nuclcus is reduced to half the number
normal for somatic cells (b()dy cells as
distinguished from germ cells). A sim-
ilar reduction occurs also during the de-
velopment of the si)ermatozoon, and when sperm-nucleus and

146

Sagittal section of egg
of fly, Musca, in process
of fertilization, c, cho-
rion; d, dorsal; iii, nii-
cropylc, with gelatinous
e.xudation ; p, male and
female ])ronuclei, before
union; pb, polar bodies;
pr, peripheral proto-
plasm; 1', ventral; vt,
vitelline membrane; y,
yolk. — After Hen king
and Blochmann.

DEVELOPMENT 147

egg-niiclciis 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 (lel)ate(l suljject.

Fertilization. — As the eggs pass through the vagina, they
are capable of being fertilized by spermatozoa, previously
stored in the seminal receptacle. Through the iiiicro/^ylc of
the chorion one or more spermatozoa enter and a sperm-
nucleus unites with the egg"-nucleus to form what is known as
the scgiiiciitatioji nucleus. Through this union of nuclear

Fig. 1 88.

-'g

Equatorial section of egg of a beetle, Clytra Icrvinsciila. h, blastoderm; g, germ
band; y, yolk granule; yc, yolk cell. — After Lec.mllon.

substances 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 importance.

Blastoderm. — In an arthropod ovum the yolk occupies a
central [)osition (ccnfrolccithal type), being' enclosed in a thin
layer of protoplasm. From the segmentation nucleus just
mentioned are deri\'ed many nuclei, some of \\hich migrate
outward with their attendant protoplasm to form with the
original peripheral protoplasm a continuous cellular layer, the
blastoderm (Fig. i88).

148

ENTOMOLOGY

Germ Band. — The lilastoderm, at first of uniform thick-
ness, becomes thicker in one region, by cell mnltiplication.
forming- the germ band [ primitive streak, etc.) ; this appears
in snrface view as an ox'al or elongate area, denser than the
remaining l)lastoderm, with which it is, of conrse, continnons.

Fig. 1S9.

Transverse section of germ band of Clytra at gastrulation.
laver. — After Lecah.lon.

^erm band; 1, inner

Gastrulation. — The germ band next infolds along the me-
dian line, appearing in cross section, as in Fig. i8<); the
two lips of the median groove close together over the inva-
ginated portion and form an outer layer, or ectoderm (Fig.
igo), while the invaginated portion spreads out as an inner

Fig. 190.

^-^.6'5v<SQ;:^Oi.o,CC)B

Transverse section of germ layers
and amnion folds of Clytra. a, am-
nion; c, ectoderm; i, inner layer
(meso-entoderm) ; s, serosa. — Original,
based on Lecaillon's figures.

'6&

Transverse section of germ layers and
embryonal membranes of Clytra. a, am-
nion; ac, amnion cavity; c, ectoderm; i,
inner layer (meso-entoderm) ; s, serosa.
— After Lec.^illon.

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 gastrula-
tion; it is an important stage in the development of all eggs,
and among insects several variations of the process occur.
Amnion and Serosa. — Meanwhile, the blastoderm has been

DEVELOPMENT

149

folding over the g'erm band from either side, as shown in Fig.
190. and at length the two folds meet and unite to form two
membranes (Fig. 191), namely, an inner one, or aiiinioii, and
an outer one, or serosa.

Fig. 192.

f 1

W.;-

■ mm

■4VA

■ft? ■■•'*.
M .si

■-iisiSs'

Germ band of a beetle, Mclasoina, in three successive stages. A, unsegmented;
B, with oral segments demarkated; C, with three oral, three thoracic and two ab-
dominal segments. — After Graber.

Segmentation and Appendages. — On the germ l)and,
which represents the ventral part of the future insect, the body
segments are marked off bv

,T^- " ^IG. 193.

transverse grooves (rigs.
192, 194) ; this segmentation
beginning usually at the an-
terior end of the germ band
and progressing backward.
Furthermore, an anterior in-
folding occurs (Fig. 193),
forming the sloiiiodcciiin,
from which the mouth,
pharynx, cesophagus and other parts of the fore gut are to
arise; a similar, but posterior inwiginatioii, or proctodcciDii

Diagrammatic sagittal section of
hymenopterous egg to show stomodaeal
(s) and proctodseal (p) invaginations
of the germ band (g). — After Graber.

ISO

ENTOMOLOGY

Fig. 194.

.S»3.-M..i:^:— -mx
.jal4iat::

---a'

(Fig. 193), is the beginning, or fundaiiiciit. of the hind gut.
At the anterior end of the germ band is a pair of large
proccpJialic lobes (Figs. 192, 194), which eventnahy bear the
lateral eves, and immediately behind these are the fundaments
of the antennre. The fundaments of the primary paired ap-
pendages are out-pocketings of the ecto-
dermal germ band, and at tirst antennae,
mouth parts and legs are all alike, except
in their relative positions. Behind the
antennre ( in Thysanura and Collembola
at least) appears a pair of rudimentary
appendages (Fig. 194, /) which are
thought to represent the second antenuce
of Crustacea ; instead of developing, they
disappear in the embryo or else persist in
the adult as mere rudiments. In front of
these transitory ijitcrcalary appendages is
the mouth-opening, above which the
labrum and clypeus are already indicated
l>v a single, median evagination. Behind
the mouth the mandibles, maxilke and
labium are represented by three pairs of
fundaments, and in Thysanura and Col-
lembola a fourth pair is present to form

appendages; i, intercalary the SUpCrliugUa; ( Fig. I 95, sl ) . ah'Cadv rC-
appendage: /, labrum; li. ^ , , - . 1" 1 '1

left labial appendage; lerred to. J\ cxt ui ordcr are tlie three
:;'; '"-edible; m.v, max- -.^ ^^f thoracic Icgs ( Fig. 1 94 ) aiid then,

lUa; p, proccphalic lobe; ^ & ^ & ^^ '

in many cases, paired abdominal appen-
dages (Figs. 194, 196), indicating an
ancestral myriopod-like condition ; some of these abdominal
limbs disappear in the embryo l)ut others develop into abdomi-
nal prolegs (Lepidoptera and Tcnthredinickc ) . external genital
organs (Orthoptera, Hymenoptera, etc.) or other structures.
The study of these embryonic fundaments sheds much light
upon the morphology of the appendages and the subject of
see'mentation.

'■■■;¥--

---a

■pr

\'entral aspect of germ
band of a collembolan,
Anurida maritima. a.
antenna; a'^-a^, abdominal

pr, ]iroctod.-eum
thoracic legs.

DEVELOPMENT

151

Two Types of Germ Bands. — The germ band described
above Ijelongs to the simple overgrown type, exemphfied in
Clytra, in which the germ l)an(l retains its original posi-
tion and the amnion and serosa arise l)}- a process of over-
growth (Figs. 190, 191), as distinguished from the invaginated
type, illustrated in Odonata, in which the germ band inva-
ginates into the egg", as in Fig. 197, until the ventral surface

Anterior aspect of embrj'onal mouth parts of a collembolan, Anurida maritima. a,
antenna; /, labrum; Ig, prothoracic leg; li, left fundament of labium; In, lingua; m,
mandible; mx, maxilla; p, maxillary palpus; si, superlingua. — After Folsom.

of the embryo becomes turned around and faces the dorsal side
of the eg'g. In this e\'ent. a subsequent process of revolution
occurs, by means of which the ventral surface of tlie eml^ryo
resumes its original position (Fig\ 198).

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. 199) until they finally close over to form the
dorsal wall of the insect. Besides this simple method, how-
ever, there are several other ways in which the dorsal closure
may be effected.

Nervous System. — Soon after gastrulation, the ventral ner-
vous system arises as a pair oi parallel cords from cells (Fig.

152

ENTOMOLOGY

-I'
— I'

— - [3

200, n) which have been (leri\ed l:)y chrect proHferation from
those of the germ band, and are tlierefore ectodermal in origin.
Tliis primitive double nerve cord Ijecomes constricted at inter-
vals into segments, or ncnroiiicrcs, which correspond to the
segments of the germ band. Each nenromere consists of a

pair of primitive ganglia, and these
are connected together by paired
nerve cords, which later may or
may not unite into single cords ;
, a moreover, some of the ganglia

finally unite to form compound
ganglia, such as the brain and the
.- mp suboesophageal ganglion. In front
^^ of the cesophagus (Fig. ^^) are

three neuromeres : (i) protoccrc-
bniiii, which is to bear the com-
pound eyes;' (2) dcutoccrcbnini , or
antennal neuromere ; (3) frifoccrc-
bnuii, which belongs to the seg-
ment which bears the rudimentary
intercalary appendages spoken of
above. Behind the oesophagus are,
at most, four neuromeres. namely
and in order, mandibular, siipcr-
liiigital (found only in Collembola
as yet), uiaxiUary and labial.
Then follow the three thoracic gan-
glia and ten (usually) abdominal
ganglia. The first three neuro-
meres always unite together to
form the brain, and the next four
(always three; 1)ut four in Col-
lembola and perhaps other insects), to form the suboeso-
phageal ganglion. Compound ganglia are frecjuently formed
also in the thorax and abdomen bv the union of primiti\"e
ganglia.

-'-a5

Embryo of Qlcaiithiis, ventral
aspect. a, antenna; ai-a^, ab-
dominal appendages; c, end of
abdomen; /, labrum; //, left
fundament of labium; /f, labial
palpus; l^-P, thoracic legs; m,
mandible; mp, maxillary palpus;
mx, maxilla; p, procephalic lobe;
pr, proctodseum. — After Ayers.

DEVELOPMENT

153

Tracheae. — The trachcc'e begin as paired im-aginations of
the ectoderm (Fig. 201, t) ; these simple pockets elongate and

Fig. 197.

Diagrammatic sagittal sections to illustrate invagination of germ band in Calop-
tcry.r. a, anterior pole; ac, amnion cavity: am, amnion; b, blastoderm; d, dorsal;
g, germ band; Ii, head end of germ band; jj, posterior pole; s, serosa; ■:■, ventral; y,
yolk. — After Brandt.

Fig. 1 98.

I I .
/ -

mx -
m -

Diagrammatic sagittal sections to illustrate revolution of Calopteryx embryo. a,
antenna; am, amnion; /, labium; /i-P, thoracic legs; m, mandible; mx, maxilla; s,
serosa. — After Brandt.

154

ENTOMOLOGY

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

Mesoderm. — From the inner layer which was derived
from the germ band by gastrulation (Figs. 189-191) are
formed the important germ layers known as mesoderm and eii-

FiG. 199.

Diagrammatic transverse sections to illustrate formation of dorsal wall in a beetle,
Leptinotarsa. a, amnion (breaking tip in C); g, germ band; s, serosa. — After
Wheeler, from the Journal of Morpliology.

todcnu. Most of the layer becomes mesoderm, and this splits
on either side into chambers, or ca:lom sacs (Fig. 200, 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

Fig. 200.

Tansverse section of germ layers of Clytra. c, ccelom sac; n,
neuroblasts (primitive nervous cells). — After Lecaillon.

may share in the formation of the definite body-cavity, though
the last arises independently, from spaces that form between
the }o]k and the mesodermal tissues. From the coelom 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
orisfin.

DEVELOPMENT

155

Entoderm. — At its anterior and posterior ends, the inner
layer just referred to gives rise to a mass of cells which are

Fig. 201.

--■yyiy

Fig. 202.

Transverse section of abdomen of Clytra embryo at an advanced stage of develop-
ment, a, appendage; c, epithelium of mid intestine; g, ganglion; m, Malpighian tube;
mi, muscular layer of mid intestine; ms, muscle elements; my, mesenchyme (source
■of fat-body); s, sexual organ; t, tracheal invagination. — After Lec.\illon.

destined to form the iiicsciitcroii, from which the mid intestine

develops. One mass is adjacent to the blind end of the stomo-

daeal invagination and the other to that of

the proctodccal in-folding. The two

masses become U-shaped (Fig. 202). and

the lateral arms of the two elongate and

join so that the entodermal masses become

connected by two lateral strands of cells ;

by overgrowth and nndergrowth from

these lateral strands a tube is formed

which is destined to l)ecome the stomach.

and by the disappearance (if the partitions

that separate the mesenteron from' the

stomoda^nm at one end and from the proc-

todtenm at the other end, the continnit^■

of the alimentary canal is established.

The fore and the hind gut, then, are

■ectodermal in origin, and the mid gut

entodermal.

Diagram of formation
of entoderm in Leptino-
tarsa. e, e, entodermal
masses; m, mesoderm. —
After Wheeler.

156

ENTOMOLOGY

2. EXTERXAL ]\IeTAMORPEIOSIS

Metamorphosis. — One of the most striking phenomena of
insect hfe is expressed 1:)y the term iiictaniorphosis, which
means conspicuons change of form after birth. The egg of
a Ijntterfly produces a larva: this eats and grows and at length
becomes a pupa; which, in turn, develops into an imago.
These stages are so dilTerent (Fig. 27) that without experi-

FiG. 203.

Cyllcnc pictiis. A, larva; B. pupa; C, imago, x 3.

ence one could not kno\\- that they pertained to the same
individual.

Holometabola. — The more specialized insects, namely,
Neuroptera, ]\Iecoptera, Trichii[)tera, Lepidoptera, Coleoptera
(Fig. 203). Diptera (Figs. 204, 29), Siph«^naptera (Fig. 30)
and Hymenoptera (Fig. 280), underg-o this indirect, or com-
plete,'^ metamorphosis, involving profound changes of form
and distinguished by an inacti\e pupal stage. These insects
are grouped together as Holometabola.

Larvae receive such popular names as " caterpillar " (Lepi-

^ These terms, though somewhat misleading in imphcation, are cur-
rently used.

DEVELOPMENT

157

doptera), "grub" (Coleoptera), and "maggot" (Diptera),
while tlie 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 having w^ngs and mature reproductive organs,
and the insect is active throughout life; hence the metamor-
phosis is termed direct, or iiicontplclc. This type of trans-

FlG. J04.

Plwrmia regina. A, larva; B, imiiarium; C, imago, x 5.

formation, without a true pupal period, is characteristic of
the more generalized of the metamorphic insects, namely,
Orthoptera, Platyptera, Plecoptera, Ephemerida (Fig. 19),
Odonata (Fig. 20), Thysanoptera and llemiptera (Fig. 205).
These orders constitute the group Hcicroiiictahola. Within
the limits of the group, however, various degrees of meta-
morphosis 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.

158

ENTOMOLOGY

206) ; while male Coccida? have what is essentially a complete
metamorphosis. In fact, the various kinds of metamorphosis

Fig. 20=;.

Six successive instars of the squash bug, Anasa tristis. x
Fir,. J06.

Cicada libiccn. A, invigo emerging from nymphal skin; B, the cast skin;
C, imago. Natural size.

grade into one another in such a way as to make their classifi-
cation to some extent ar1)itrarv and inadequate.

DEVELOPMENT

159

As there is no distinction between larva and pnpa in most
heterometabolous insects, it is customary to use the - term
nymph during" the interval between eg'g and imago.

Ametabola. — The most generalized insects, Thysanura and
Collembola, develop to sexual maturity without a metamor-
phosis ; the form at hatching' is retained essentially throughout
life, there are no traces of wings even in the embryo, and there
is no chang-e of habit. These two orders form the group
Ametabola. All other insects have a metamorphosis in the
broad sense of the term, and are therefore spoken of as Mefab-
ola. In this we follow Packard, rather than Brauer, who
uses a somewhat different set of terms to express the same
ideas.

Stadium and Instar, — During- the growth of every insect,
the skin is shed periodically, and with each moult, or ccdysis,
the appearance of the insect changes more or less. The inter-
vals between the moults are termed stages, or stadia. To
designate the insect at any particular stage, the term iiistar
has been proposed and is growing in favor ; thus the 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.
Commonly they are more or less spherical, oval, or elongate,
but there are innumerable special forms, some of which are

Fig. 207.

Eggs of various insects. A, butterfly, Polygonia interrogationis; B, house fly,
Musca domestica; C, chalcid, Bruchophagus funebris; D, butterfly, Papilio troilus; E,
midge, Cecidomyia trifolii; F, hemipteron, Triphleps insidiosKS ; G, hemipteron,
Podisus spinosus; H, fly, Drosophila ampclophila. Greatly magnified.

i6o

ENTOMOLOGY

quite fantastic,
in Fig". 207.

Something of the variety of form is shown
As regards size, most insect egg's can be
(hstingnished by the
naked eye ; many of
them tax the vision,
howexer. for example,
the elliptical eggs of
Ccciiloiiiyia Ici^iiiiiiin-
cola, which are l3ut
.300 mm. in length
and .075 mm. in
width : the o\a] eggs
of the cccropia moth,

Three eggs of the cabbage butterfly, Pieris
rapcc. Greatly magnified, l)ut all drawn to same
scale.

Fig. 209.

on the other hand, are as long as 3 mm.

The egg-shell, or cliorion, secreted
around the ovum by cells of the ovarian
follicle, may be smooth l:)ut 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 par-
ticular patterns displayed are probabh-
of no use, being incidentally produced
as impressions from the cells whicb
secrete the chorion. Variations of
form, size and pattern are frequent in
eggs of the same species, as appears in
Fig. 208.

Always the chorion is penetrated by
one or more openings, constituting the
iiiicrojiylr, for the entrance of sperma-
tozoa.

As a rule, the eggs when laid are accompanied 1)y a fluid of
some sort, which is secreted usually l)y a cement gland or
glands, opening into the \'agina. This lluid commoid}- serves

Clirysopa, laying eg
Slightly enlarged.

DEVELOPMENT l6l

to fasten the eg'gs to appropriate ol)jects, 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 Clirysopa (Fig.
209) ; may surround the egg's as a gelatinous envelope, as in
caddis flies, dragon tiies, etc. ; or may form a capsule enclosing
the eggs, as in the cockroach.

The number of eggs laid by one female differs greatly in
different species and varies considerably in different individ-
uals 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 cjueen honey bee may lay a million. Two
females of the beetle Prioniis laticolUs had, respectively, 332
and 597 eggs in the abdomen (Mann). A. A. Girault gives
the following numbers of eggs per female, from an examina-
tion of twenty egg-masses of each species :

Maximum.

Thyridopteryx ephcmcrccfor-mis 1076
CUsiocampa amcricana 466

Chioiiaspis fiirfura 84

Hatching. — Many lar\-:e, caterpillars for example, simply
eat their way out of the egg-shell. Some magg'ots rupture
the shell by contortions of the body. Some larva; have spe-
cial org-ans for opening the shell ; thus the grub of the Colo-
rado 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 hatch-
ing" varies greatly according to the species, but has received
very little attention.
» Larva, — Although larvae, generally speaking, diff'er from
one another much less than their imagines do. the}- are easily
referable to their orders and usually present specific dift'er-
ences. Larvae that display indi\idual adapti\e characters of
a positive kind (Lepidoptera, for example) are easy to place,
but larvce with negative adaptive characters ( niany Diptera
and Hymenoptera) are often hard to identify.
1 2

Minimum.

Average.

753

941

313

375-5

66.5

l62

ENTOMOLOGY

Thysanuriform Larvae. — Two types of larva? are recog-
nized by Brauer, Packard and other authorities: thysaiiiiri-
fonii and criiciforiii ; respectively generalized and specialized
in their organization. The former term is applied to many
larva? and nymphs (Fig. 210, C, D) on account of their resem-
blance to Thysanura, of which Cauipodea and Lcpisina are

Fig. 210.

Types of larvse. A, B. Thysanura; C, D, thysanuriform nymphs; E-I, eruciform
larvs. A, Campodea ; B, Lepisma; C, perlid nymph (Plecoptera) ; D, Libellula
(Odonata) ; E, Tcntliredopsis (Hymenoptera) ; F, Lachnostcnia (Coleoptera) ; G,
Melanotus (Coleoptera"); H, Bombus (Hymenoptera); /, Hypodcrma (Diptera).

types. The reseml^lance lies chiefly in the flattened form, hard
plates, long legs and antenna", caudal cerci. well-developed man-
dibulate 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 pron(3unced in nymphs
of Blattida?, Forflculid^e, PerlidcT, Ephemerid.e and Odonata,
but occur also in the larva? of some Neuroptera (Maniispa)
and Coleoptera (Carabid:e and Meloida?). These primitive
characters are gradually overpowered, in the course of larxal
evolution, Ijy secondary, or adaptive, features.

DEVELOPMENT

i6-

Eruciform Larvae. — The prevalent type of larva among
h()lometa])(;l()ns insects is the cruciform (Fig. 210, E-I), illus-
trated by a caterpillar or a mag'got. Here the body is cylin-
drical and often fleshy; the integument weak; the legs, anten-
nae, cerci, and mouth parts reduced, often to disappearance;
the habits sedentary and the sense org-ans correspondingly re-
duced. These characteristics are interpreted as l)eing results of
partial or entire disuse, the amount of reduction being propor-
tional to the degree of inactivity. Extreme reduction is seen
in the maggots of parasitic and such other Diptera as, secur-
ing 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 thy sanuri form 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

Fig. 211.

Mantisj>a. A, larva at hatcliing — thysaiiuriform ; B, same larva just before first
moult — now becoming cruciform. C, imago, the wings omitted; D, winged imago,
slightly enlarged. — A and B after Brauer; C and D after Emf.rton, from Packard's
Text-Book of Entomology, by permission of the Macmillan Co.

beginning of the eruciform type is found in Neuroptera, where
the campodeoid sialid larva assumes a quiescent pupal condi-
tion. The key to the origin of the complete metamorphosis.

164 ENTOMOLOGY

involving the eruciform condition, Packard finds in the nen-
ropterons genns Maiitispa (Fig. 211), the first hirva of which
is trnly campodea-form and active. Beginning a sedentary
hfe, however, in the egg-sac of a spider, it loses the use of its
legs and the antenna; l)ecome partly aborted, before the first
moult. In Packard's words, " (3wing to this change of hab-
its and surroundings from those of its active ancestors, it
changes its form, and the fully grown larva becomes cylin-
drical, with small slender legs, and, owing to the partial disuse
of its jaws, acquires a small, round head." Meloidre (Fig.
217) afl:'ord other excellent examples of the transition 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, Si-
phonaptera and Hymenoptera ) , they cease to appear, except
for a few embryonic traces — an illustrati(_)n of the principle of
" acceleration in development."

Growth. — The larval period is pre-eminenth' one of growth.
In Heterometal)ola, growth is continuous during the nymphal
stage, but in Holometabola this im[)ortant function becomes
relegated to the larval stage, and pupal development takes
place at the expense of a reser\'e supply of food accumulated
by the larva.

The rapidity of larval growth is remarkable. Trouvelot
found that the caterpillar of Tclca polyphciiius attains in 56
days 4,140 times its original weight (1/20 grain), and has
eaten an amount of food 86,000 times its primiti\e weight.
Other larv?e exceed e\'en these figures; thus tlie magg^ot of a
common flesh fly attains 200 times its original weight in 24
hours.

Ecdysis. — The exoskeleton, unfitted for accommodating
itself to the growth of the insect, is periodicallv shed, and
along with it go not onlv such integumentarv structiu'es as
hairs and scales, l)ut also the chitinous lining, or intima. of

DEVELOPMENT 1 65

the stomodreiim, proctoiLTum, trucheiie, integumentary g'lands,
etc. The process of mouUing, or ecdysis, in caterpillars is
briefly as follows. The old skin becomes detached from the
bodv by an intervening flnid 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 cxuvicc. 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 excretory importance
in the case of Collembola, which are exceptional among in-
sects in ha^■ing no Malpighian tubes.

Number of Moults. — The frequency of moulting differs
greatly in different orders of insects. Acridiidas have five
moults; Lepidoptera usually four or five, but often more, as
in Isia (Pyrrharctia) isabcUa, which moults as many as ten
times (Dyar) ; iMitsca doiiicsfica has three (Packard) ; the
honey bee probably six (Cheshire) ; and the seventeen-year
locust about twenty-five or thirty (Riley). Packard suggests
that cold and lack of food during hibernation in arctians (as
/. isabrlla) 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 sig-
nificance, as Weismann has attempted to show in the case of
sphingid larvae.

Adaptations of Larvae. — Larvae exhibit innumerable con-
formities 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-

1 66 ENTOMOLOGY

(le\'eloped sense organs, excellent powers of locomotion, spe-
cial protective and aggressive devices, etc. In insects as a
whole, the environment of the larva or nymph and that of the
adnlt are very different, as in the dragon fly or the l)ntterfly,
and the larvae are .modified in a thonsand ways for their own
immediate advantage, without any direct reference to the
needs of the imago.

The chief purpose, so to speak, of the larva is to feed and
grow, and the largest modifications of the larva depend upon
nutrition. Take as one extreme, the legless, headless, fleshy
and sluggish maggot, emhedded in an al)undance 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. i)rehension, 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 struc-
tures for obtaining' special food ; indirectly, as in respiratory
adaptations and protective structures, these latter being numer-
ous and varied.

Larvre that li\'e in concealment, as those that burrow in the
ground or in plants, have few if any special protective struc-
tures : active larv?e, as those of Carabida?, have an arm(3r-like
integument, but owe their protection from enemies chiefly to
their powers of locomotion and their aversion to light (iicga-
fk'c phofotropisiii) ; various aquatic nymphs ( Zaitha, Odonata )
are often coated with mud and therefore diflicult to distin-
guish so long as they do not mo\e ; caddis worms are con-
cealed in their cases, and caterpillars are often sheltered in a
leafy nest. There is no reason to suppose that insects conceal
themselves consciously, howe\er, and one is not warranted in
speaking of an instinct for conccahucnt in the case of insects —
since everything goes to show that the propensity to hide,
though ach'antageous indeed, is sim]il}' a retlex, inevital)le,

DEVELOPMENT 1 6/

negative reaction to light (negative pliototropism) or a positive
reaction to contact (positive tJiiginotvopisni).

Exposed, sedentary larvae, as those of many Lepidop-
tera and Coleoptera, often exhibit highly developed protective
adaptations. Caterpillars may be colored to match their sur-
roundings and may resemble twigs, bird-dung, etc. ; or larv?e
may possess a disagreeable taste or repellent fluids or spines,
these odious qualities being frequently associated with warn-
ing colors.

Larvae need protection also against ad^'erse climatal condi-
tions, especially low temperature and excessive moisture.
The thick hairy clothing of some hibernating caterpillars, as
Isia (Pyniiaretia) isabella, doubtless serves to mollify sudden
changes of temperature. Xaked 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. Exces-
sive moisture is fatal to immature insects in general — conspicu-
ously fatal to the chinch l^ug. 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 secondar}- adaptive modifications, larva?
may differ far more than their imagines. Thus Platygaster in
its extraordinary first lar\-al form (Fig. 218) is entirely unlike
the larvae of other parasitic Hymenoptera, reminding- one,
indeed, of the crustacean Cyclops rather than the larva of an
insect. As Lubbock has said, the characters of a larva depend
•(i) 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 holometal)©-
lous insects only. Most Lepidoptera and many Diptera have
an obtect pupa (Eig. 212), or one in which the appendages

1 68

ENTOMOLOGY

Fig. 21.

Obtect pupa of milk-
weed butterfly, Anosia
ple.vippus, natural size.

and body are compactly united : as distinguished from the free
pupa of Neuroptera, Trichoptera, Coleoptera and others, in
which the appendages are free (Fig. 203). This distinction,
however; cannot ahvays be drawn sharply. Diptera present
also the coarctote type of pupa (Fig.
204) , in which the pupa remains en-
closed in the old larval skin, or piipa-
riiini.

Pupal characters, though doubtless of
great adapti^■e and phylogenetic signifi-
cance, have received but little attention.
Lepidopterous pupce present many puz-
zling characters, for example, an eye-
like structure (Fig. 213) suggesting
an ancestral active condition, such as
still occurs among heterometabolous in-
sects.
Pupation of a Caterpillar. — The process of pupation in
a caterpillar has Ijeen carefully observed by Riley. The cater-
pillar of the milkweed butterfly (PI. i. A) spins a mass of
silk in which it entangles its suranal plate and anal prolegs
and then hangs downward, bending up
the anterior part of the body (B), wdiich
gradually becomes sw'Ollen. The skin
of the caterpillar splits dorsally, from
the head backward, and is worked back
toward the tail (C and D) by the con-
tortions of the larva.

The wav in which the pupa becomes at-
tached to its silken support is rather com-
plex. Briefly, wdiile the larval skin still

retains its hold on the support, the posterior end of the pupa
is witlidraw'n from the old integument and by the vigorous
wdiirling and twisting of the body the hooks of the terminal
cremasier of the pupa are entangled in the silken support. At
first the pupa is elongate (E) and soft, but in an hour or so

Fig. 213.

Head of chrysalis of
Papilio polyxcncs, to
show eye-like structure.
Eularged.

PLA'IK 1.

Successive sta.e. in U. .>,p.i,_f .^_ „,,^.,.,, ,,,,,.„„,^,.^ _.^„^^,^, ^^^.___^^^^^

DEVELOPMENT

169

Fig. 214.

it has contracted, hardened, and assumed its characteristic form
and coloration (F).

Pupal Respiration. — Except under special conditions, pupie
breathe by means of ordinary abdominal spiracles. Aquatic
pup^ie have special respiratory organs,
such as the tracheal filaments of Siiiin-
liiiiii (Fig. 230), and the respiratory
tubes of Culcx (Fig. 229).

Pupal Protection, — Inactive and
helpless, most pupa; are concealed in one
way or another from the observation of
enemies and are protected from mois-
ture, 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 {Lachiio-
stcnia, Osniodcniia, Pas'saliis, Lucanus,
etc.) make a chamber in earth or wood, the walls of the cell
being strengthened with a cementing fluid or more or less
silk, forming a rude cocoon. Silken cocoons are spun by
some Xeuroptera (Chrysopidse, Fig. 214), l)y Trichoptera
(whose cases are essentially cocoons), Lepidoptera, a few Co-
leoptera (as Curculionidx, Donacia) , some Diptera (as Cecido-
myiid?e), Siphonaptera, a'nd many Hymenoptera (for exam-
ple, TenthredinidcC, Ichneumonid?e, wasps, bees and some
ants).

The cocoon-making instinct is most highly developed in
Lepidoptera and the most elaborate cocoons are those of Satur-
niida?. The cocoon of Saiiiia cccropia is a tough, water-proof
structure and is double (Fig. 215), there being two air spaces
around the pupa; thus the pupa is protected against moisture
and sudden chang'es of temperature and from most birds as
well, though the downy woodi)ecker not infre(|uently punc-
tures the cocoon. 6". cccropia binds its cocoon hrmly to a

Cocoon of Chrysopa,
after emergence of
imago. Slightly en-
larged.

170 ENTOMOLOGY

twig'; Tropcca lima and Tcica polyl^licjinis spin among leaves,
and their cocoons (with some exceptions) fall to the ground:
CaUosaiiiia proiucfhca, 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
winter. The leaves surrounding' cocoons may render them
inconspicuous or may sevxe merely as a foundation for the
cocoon. While silk and often a water-proof gum or cement

Vic. 21^.

Cocoon of Sauiia cccropia, cut open to show the two silken layers and the enclosed

puim. Natural size.

form the basis of a cocoon, much foreign material, such as bits
of soil or wood, is often mixed in ; the cocoons of many com-
mon Arctiidas, as Diacrisin -c'lrgiiiicci and Isia isahclla. consist
principally of hairs, stripped from the body of the larva.

pjutterflies have discarded the cocoon, the last traces of
which occur in HesperiidcC. which draw together a few leaves
with a scantv supplv of silk to make a flimsy sulistitute for a
cocoon. Papilionid and pierid pupcT are supported by a silken
girdle (Fig. 27), and nymphalid chrysalides hang freely sus-
pended by the tail (Fig. 212).

Cocoon-Spinning. — The caterpillar of Tclca poIypJicmus
" feels with its head in all directions, to discover any leaves
to which to attach the iibres that are to give form to the co-
coon. If it finds the place suitable, it begins to wind a layer

DEVELOPMENT

171

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 zig--
zag lines of 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 dis-
tinguished 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 thick-
ness as the completion of the cocoon
advances, so that the last internal coat-
ing" is not half so thick and so strong
as the outside ones." (Trouvelot.)

Emergence of Pupa. — Subterranean
pup:e wriggle their way to the surface
of the ground, often by the aid of spines
(Fig. 216) that catch successi\^ely 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 pupce ; the extremity of the abdomen, also, bears
frequently one or more spinous projections, as in Tipulid?e,
Carabidae and Lepidoptera, to assist the escape of the pupa.

Subterranean pupa of
.'Inisota. Enlarged.

1/2 ■ ENTOMOLOGY

These structures are fouud also in pupa?, 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 accom-
plished in some cases 1)y the pupa, in others hv the imago.
Hemerobiida?, Trichoptera and the primitive lepidopteron
Ei'ioccl^liala use the pui)al mandibles to cut an openino" in the
cocoon ; while many lepidopterous pupa; have on the head a
beak for piercing the cocoon, or teeth for rending or cutting
the silk.

Eclosion. — During the last few hours before the emer-
g"ence of a butterfly tl:e colors of the imago de\'elop and may
be seen through the transparent skin of the chrysalis (PI.
2, A). No movement occurs, howe\'er, until several seconds
before emergence: then, after a few convulsi^•e m()\'ements of
the leg's 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 tlie back of the thorax, and the butterfly
emerges (C-E) with moist body, elongated abdomen and
miniature wings. Hanging to the emptv pupa case (F), or
to some other available support, the insect dries and its wings
gradually expand (G", // ) 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 iiiccojiiinii ) 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 (/).

T. polyphrimis 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 unit-
ing the fibres of the cocoon. This liquid is composed in great
part of bombycic acid. Wdien the insect has accomplished the
work of transformation which is going on under the pupa
skin, it manifests a great activitv, and soon the chrysalis cover-
ing bursts open longitudinallv upon the thorax; the head and
legs are soon disengaged, and the acid lluicl flows from its

PLATE II.

Successive stages in th

' """r:i;L;:r "Sri'r^'"^- '■'"" ""'"-■ '™

DEVELOPMENT 173

mouth, wetting" the inside of the cocoon. The process of ex-
ckision 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 attempt
to open the fibres, and seems to wait with patience this event.
Wdien the liquid has fully penetrated the cocoon, the pupa con-
tracts 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 repeated
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 transform. 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 mo\e-
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 unfolding the very short and small
pad-like wings. Every part of the insect on leaving the co-
coon, is perfect and with the form and size of maturity, 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 fecund a suitable place,
it remains quiet for a few minutes, and then the wings are seen
to grow very rapidly by the afilux of the fluids from the abdo-
men. In about twent^' minutes the winys attain their full

174 ENTOMOLOGY

size, but they are still like a piece of wet cloth, without con-
sistency and firmness, and as yet entirely unfit for fiight, l)ut
after one or two hours they become sufticiently stift", assuming
the beautiful form characteristic of the species." (Trouvelot.)
The expansion of the wing is due to blood-pressure brought
about chiefly by the alidominal muscles. In the freshly-
emerged insect, the two membranes of the wing are corru-
gated, and expansion consists in the flattening out of these
folds. The wing is a sac, which would tend to enlarge into
a 1)alloon-shaped bag, were it not for hypodermal fibers which
hold the wing-membranes closely together (Mayer). Saiiiia
cccropia also uses a dissolvent fluid; Tropara liiua, Philosamia
cxnthia and others cut and force an opening thrcuigh 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,
metamorphosis in\"olves more than three stages, owing to the
existence of supernumerary larval forms. This phenomenon
of hypcniicfaiiiorpJiasis (»ccurs notabl}' in the coleopterous
genera Mcloc, Epicautu, Sitaris, RhipipJionis and Stylops, in
male Coccidc^e and several parasitic Hymenoptera.

In Mcloc, as described l:)y Riley, the newly-hatched larva
i triiiiiguliii form) is active and campodea-form. It climbs
upon a flower and thence upon the body of a bee (Aiiflio-
pJiora), 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 lamelli-
corn larva ; it now appropriates the honey of the bee. AA'ith
plenty of rich food at hand the larva becomes sluggish, and
after another moult appears as a pseudo-pupa, with function-
less mouth parts and atrophied legs. From this pseudo-pupa
emerges a third larxal form, of the pure cruciform type, fat
and apodous like the bee-larvcC themselves. After these four
distinct stages the larva becomes a pupa and then a beetle.

Epicaiifa, another meloid, has a sinnlar history. The fri-
uuguliii (Fig. 21/, A) of E. I'ittata burrows into an egg-pod

DEVELOPMENT

of Jllclaih'pliis inffrrcntialis and eats the eggs of that grass-
hopper. After a monk the second larva (carabidoid form)
appears; this (B) is soft, with rechiced legs and nmntli parts
and less active than the triungulin. A second moult and the
scarabccidoid form of the second larva is assumed ; the legs

Fig. 217.

Stages in the hypermetamorjiliosis of Epicuuta. A. triungulin; B, carabidoid stage
of second larva; C, ultimate stage of second larva; D, coarctate larva; E, pupa; F,
imago. E is species cincrea; the others are vittata. All enlarged except F. — After
Riley, from Trans. St. Louis Acad. Science.

and mouth parts are now rudimentary and the body more
compact than before. A third and a fourth uKuilt occur with
little change in the form of the second larva, which is now in
its nlfiiiiate stage (C). After the fifth moult, however, the
coarctate lari'a, or psciido-piipa, appears; this {D) hibernates
and in spring sheds its skin and becomes the third larz'a, which
soon transforms to a true pupa (11). from which the beetle
(F) shortly emerges. Thus the pupal stage is preceded by
at least three distinct larval stages.

In the anomalous beetle Stylo j^s. the males are winged, but
the females are maggot-like and sedentary, li\ing in the l)odies
of bees and wasps. Packard found as many as three hundred

176

ENTOMOLOGY

trinngiilin larvtC issuing from a female Stylops in the body of
an Andrcna. The further Hfe history of Stylops is but im-
perfectly known ; probably the triung'ulin climbs upon a liee
or a wasp and enters its body, after the manner of the Euro-
pean Rlupiplionis paradoxus, whose lifediistory is much bet-
ter understood.

The most extraordinary metamorphoses have been found
among parasitic Hymenoptera, as in Platygastcr, a proctotry-
pid which infests the larva of Cecidomyia. The egg of Platy-
gastcr, according to Ganin, hatches into a larva of bizarre

Fig. 218.

Stages in the hypermetamorphosis of I'latygaste}'. A, first larva; B, second larva;
C, third larva; a, antenna; b, brain; /, fat-tissue; /(, hind intestine; m, mandible; mo,
mouth; ms, muscle; n, nerve cord; r, reproductive organ of one side; s, salivary
gland; t, trachea. — After Ganin.

form (Fig. 218, A), suggesting the crustacean Cyclops, rather
than an insect. This first larva has a blind food canal and no
nervous, circulatory or respiratory systems. After a uKiult
the outline is oval {B). and there are no appendages as yet,
though the nervous system is partially developed. Another
moult, and the thir<l larva appears (C), elliptical in contour,
externally segmented, with trache;c and a pair of mandibles.

DEVELOPMENT 1/7

From now on, the de^•elopment is essentially like that of other
parasitic Hymenoptera.

Equally anomalous are the changes undergone hy Poly-
iicuia, a proctotrypid parasite in the eggs of dragon flies, and
by the proctotrypid Tclcas, which affects the eggs of the tree
cricket (CEcaiitlius) . In all these cases the lar\je 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 metamorphosis." says Sharp, " appear to be the separation
in time of growth and development, and the limitation of the
reproducti\'e processes to a short period at the end of the indi-
vidual life."

The simplest insects, Thysanura, have no metamorphosis,
and show no traces of ever having had one. Hence it is in-
ferred that the first insects had none; in other words, the phe-
nomenon of metamorphosis originated later than insects them-
selves. Successive stages in the evolution of metamorphosis
are illustrated in the various orders of insects.

The distinctive mark of the simplest metamorphosis, as in
Orthoptera and Hemiptera, is the accjuisition 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 indi\-idual is practically the same.
Even when considerable difference exists between the nym-
phal and imaginal en\ironments, as in Ephemerida and
Odonata, the activity of the individual may still be continu-
ous, even if somewhat lessened as the period of transforma-
tion approaches.

With Neuroptera, the pupal stage appears. In these and
all other holometabolous insects the larva accumulates a sur-
plus of nutriment sufficient for the further development, which
becomes condensed into a single pupal stage, during which
external activity ceases temporarily.
13

178 ENTOMOLOGY

With the increasing' contrast between the organization of
the larva and that of the imag'o, the pupal stage gradually
becomes a necessity. ^Metamorphosis now means more than
the mere acquisition of wing-s, for the larva and the imago
have become adapted to widely different environments, chiefly
as regards food. The caterpillar has biting mouth parts for
eating leaves, while the adult has sucking organs for obtaining
licjuid nourishment ; the maggot, surrounded by food that may
be obtained 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 strikingly un-
like that of the larva ; so also in the case of the higher Hymen-
optera, where maternal or family care is responsible for the
helpless condition of the larva.

Thus it is evident that the change from larval to imaginal
adaptations is no longer congruous with continuous external
activity ; a cjuiescent period of reconstruction bec<:)mes in-
evitable.

As was said, the cruciform type of larva has 1)een 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 life-
time of the individual. Furthermore, the cruciform condi-
tion is plainly an adaptive one, brought about by an abundant
and easily obtainable supply of food. The lack of a thysa-
nuriform stage in the development of the most specialized
cruciform larv?e, as those of flies and bees, is regarded by
Hyatt and Arms as an illustration 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 subject, the appearance of temporary abdominal legs in
embryo bees is significant, as indicating an ancestral active

DEVELOPMENT

179

Fig. 219.

condition. In accounting" for the evolution of metamorpho-
sis, the theory of natural selection
finds one of its most important appli-
cations.

3. Internal Metamorphoses

In Heterometabola, the internal
post-embryonic changes are as di-
rect as the external changes of
form; in Holometalxda, on the con-
trary, not all the larval organs
pass directly into imaginal organs,
for certain larval tissues are de-
molished and their substance recon-
structed into imaginal tissues. When

Diagrammatic transverse

section of Corethra larva, to
sliow imaginal buds of wings
(w) and legs (/) ; h, hypoder-
mis; i, integument. — Modified
from Lang's Lchrbiich.

Fig. 220.

Diagrammatic transverse sections of muscid larvje, to show imaginal buds, h, lar-
val hypodermis; i, larval integument; ih, imaginal hypodermis; /, imaginal bud of
leg; w, imaginal bud of wing. — Modified from Lang's Lchrbiich.

i8o

ENTOMOLOGY

indirect, however, the internal metamrjrphosis is nevertheless
continuous and gradual, 'without the aliruptness that charac-
terizes the external transformation. In the larval stage ima-
ginal organs arise and grow ; in the pupal stage the purely
lar\al organs gradually disappear while the imaginal organs
are continuing their development.

Phagocytes. — The destruc-

ImG. 221. . .

tion of lar\-al tissues, or 7//,^-
toiysis,. is due often to the
amcel)oid blood corpuscles,
known as leucocytes or phago-
cytes, which attack some tis-
sues and absorb their n.iate-
rial, but later are themselves
\: »od for the de\-eloping imagi-
nal tissues. The construction
of tissues is termed Iiisto-
geiiesis.

In Coleoptera, however, the
degeneration of the larval mus-
cles is entirely chemical, there
1)eing" no evidence of phago-
cytosis, according to Dr. R. S.
Ih'eed. Berlese, indeed, goes
so far as to deny in general
the destructive action of leuco-
cytes on larval tissues.

Imaginal Buds.- — The wings
and legs of a tiy originate in
the larva in the form of cellu-
lar masses, or iiiiagiiial buds.
as Weismann disco\'ered. Thus
in the larva of CoretJira. there
are in each thoracic segment a pair of dorsal l)uds and a pair
of ventral buds (Fig. 219), each Inid being clearly an evagi-
nation of the hypodermis at the bottom of a previous invagi-

Imaginal buds of full growu larva
of Pieris, dorsal aspect, b, brain ;
m, mid intestine ; s^, prothoracic
spiracle; s*, first abdominal spiracle;
sg, silk gland; /, prothoracic bud:
II, bud of fore wing; ///, bud of
hind wing. — After Gonin.

DEVELOPMENT

iSl

nation. The six \'entral bnds form the leg's eventually; of
the dorsal buds, the middle and posterior pairs form, respec-
tively, the wings and the halteres, and the anterior pair form
the pupal respiratory processes. Each imaginal Ijud is situ-
ated in a pcripodal cavity, the wall of which (pcripodal iiiem-
braiic) is continuous with the general hypodermis ; as the legs
and wings develop, they emerge from their pcripodal sacs and
become free.

In Corctlira l)ut little histolysis occurs, most of the larval
structures passing directly into the corresponding- structures
of the adult. Core f lira, indeed, is in many respects interme-
diate between heterometabolous and holometabolous insects as
regards its internal changes.

Fig. 222.

Section through left hind wing in larva of Pieris rap(c, the section being a frontal
one of the caterpillar; the base of the wing is anterior in position, and the apex
posterior, c, cviticula; /i, hypodermis; t, traclica; w, developing wing. — After Mayer.

Muscidae. — In ]\Iuscid?e. as compared with Corctlira, the
imaginal buds are more deeply situated, the peripodal mem-
brane forming a stalk (Fig. 220), and the processes of his-
tolysis and histogenesis become extremely complicated. The
hypodermis, muscles, alimentary canal and tat-body are grad-
ually broken down and remodeled, and part of the respiratory
svstem is reorganized, though the dorsal vessel and the central
nervous system, uninterrupted in their functions, undergo
comparatively little alteration.

The imaginal hvpodermis of the thorax arises from thick-

I82

ENTOMOLOGY

enings of the peripodal memljrane \\hich spread over the lar-
val hypodermis, while the

Fig. 223.

latter is g-radually being
broken down Ijy the leuco-
cytes ; in the head and abdo-
men the process is essen-
tially the same as in the
thorax, the new hypodermis
arising from imaginal buds.

]\Iost of the larval mus-
cles, excepting the three
pairs of respiratory muscles,
undergo dissolution. The
imaginal muscles hd.\e l)een
traced back to mesodermal
cells such as are always as-
sociated with imaginal buds.

Hymenoptera and Lepi-
doptera. — The internal
transformation in Ilymen-
()ljtera, according to Bugn-
ion., is less profound than
in MuscidcC and more ex-
tensi\'e than in Coleoptera
and Lepidoptera. The in-
ternal metamorphosis in
Lepidoptera resemljles in
manv respects that of Corc-
tlira. In both these orders

Internal transformations of Sphinx ligiis- tllC d< »rsal paU' of prOtllO
tri. A, larva; B, pupa; C, moth; a, aorta:
an, antenna; b, brain; /. fore intestine:
/)', food reservoir: li, hind intestine; lit,
heart; in, mid intestine; mt, Malpighian
tubes; p, proboscis; s, subcesophageal gang-
lion; t, testis; tg, thoracic ganglia; 7', ven-
tral nerve cord. — After Newport.

racic Ijuds is a1>sent. In a
full-grown caterpillar the
fundaments of the imaginal
legs and wings (Fig. 221)
may be seen, the wings in a
frontal section of the larva appearing as in Fig. 222. Many

DEVELOPMENT 1 83

of the details of the internal metamorphosis in Lepidoptera
have been described by Newport and Gonin. Figure 223,
after Newport, shows some of the more evident internal dif-
ferences in the larva, pupa and imag'o of a lepidopterons insect.
Significance of Pupal Stage. — To repeat — among holo-
metabolous insects the function of nutrition becomes relegated
to the larval stag"e and that of reproduction to the imaginal
stage. Larva and imago become adapted to widely different
environments. So dissimilar are the two environments that
a gradual change from the one to the other is no longer pos-
sible : the revolutionary changes in structure necessitate a tem-
porary cessation of external activity.

CHAPTER IV

ADAPTATIONS OF AQUATIC INSECTS

Ease, versatility and perfection of adaptation are beauti-
fully exemplified in aquatic insects.

Systematic Position. — Aquatic insects do, not form a sepa-
rate group in the system of classification, but are distributed
among many orders, of which Plecoptera, Ephemerida, Odo-
nata and Trichoptera are pre-eminently 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 larv?e of acjuatic insects.

The change from the terrestrial to the aquatic habit has lieen
a gradual change of adaptation, not an abrupt one. Thus at
present there are some tipulid larvre 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 transitional
stages are to be found.

Food. — Insects have become adapted to utilize with re-
markable 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 Parapojivs (Fig. 171) feeds on submerged leaves, espe-
cially of ValUsncria, being in this respect unique among Lepi-
doptera. Hydrophilid beetles and many other aquatic insects
devour submerged vegetation. The larvre of the chr}'somelid
genus Donacia find both nourishment and air in the roots of
aquatic plants. Various Collembola subsist on floating alg?e,

184

ADAPTATIONS OF AQUATIC INSECTS

185

and larw'i? of mosquitoes and l)lack-ilies on microscopic ors^'an-
isms near the surface, while lar\';e of Chiroiioimis find food in
the sediment that accumulates at the hottom of a body of
water.

Predaceous species abound in the water. Nofoiiccta (Fig-.
224) approaches its prey from beneath, clasps it with the front

Fig. 224.

Fig.

Backswiminer, Notoiiccta insulata,
natural size.

Water-skater, Gcrris rciuigis, natural size.

Fig. 226.

pair of legs and pierces it. Ncpa and Ranatra likewise have
prehensile front legs along with powerful piercing organs.
Bclostoina and Bcnacus (Fig. 22) even
kill small fishes by their poisonous punc-
tures. Some other kinds, as the water-
skaters (Gerrid.e, Fig. 225), depend on
dead or disabled insects. The species of
Hydrophilus (Fig. 226) are to some ex-
tent carnivorous as larvae l)ut phytopha-
gous as imagines, while Dytiscidne are car-
nivorous throughout life. Aquatic insects
eat not only other insects, but also worms,
crustaceans, mollusks or any other a\ail-
able 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 Agrio
typus, which lays its eggs on the larvse of caddis flies.

Hydrophilus triangularis,
natural size.

1 86

ENTOMOLOGY

Locomotion. — Excellent adaptations for aquatic locomo-
tion are found in the common Hydro pJiilus iriangularis (Fig.
226). Its general form reminds one of a boat, and its long
legs resemble oars. The smoothly elliptical contour and the
polished surface serve to lessen friction. Owing to the form
of the body (Fig. --7^ --J) and the ])resence of a dorsal air-

Fic. 22y.

Transverse sections of {A) Hydroplilltts and (B) Notonccta. c, elytron; li, hemely-
tron; /, metathoracic leg.

chamljer under the elytra, the Ixick of the insect tends to re-
main uppermost, while in Xofoiiccfa ( Fig. 22'/, B) .on the other
hand, the conditions are reversed, and the insect swdms with
its back downward. The legs of Hydro/^hiliis, excepting the
first pair, are l)road and thin ( Fig. 22S, A ) and the tarsi are
fringed A\'ith long hairs, \\dien swimming, the " stroke " is
made by the fiat surface, aided bx' 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 gravity, are of most use in swim-
ming', though the second pair also are used for this purpose:
indeed, a terrestrial insect-, finding itself in the water, instinc-
tively relies upon the third pair of legs for locomotion. H\-
■ilrophilus uses its oar-like legs alternateh', in much the same
secjuence as land insects, but Cybistcr and other DytiscidcT,
which are even better adapted than Hydro/^/iiliis for aquatic
locomotion, move the hind legs simultaneouslv, and therefore
can swim in a straight line, without the wobbling and less
■econonfical movements that characterize Hydrophiliis.

ADAPTATIONS OF AQUATIC INSECTS

187

Larvoe of mosquitoes propel themselves by means of lash-
ing, or undnlatory. mo\-ements of the abdomen. A peculiar
mode of locomotion is found in dragon i\y nymphs, which
project themselves by forcibly ejecting a stream of water from
the anus.

On account of the large amount of air that thev carrv ajjout,
most aquatic imagines are lighter than the water in which they

Fig. 228.

Left hind legs of aquatic beetles. A, Hydropltiliis triaugiilaris; B, Cybistcr Ambrio-
lalus; c, co.xa; f, femur; .s", spur; /. tarsus; (;', tibia; tr, trochanter.

live, and therefore can rise witliout effort, but can descend only
by exertion, and can remain below only by clinging to chance
stationary objects. The mos(|uito larva (Fig. 229, A) is often
heavier than water, but the pupa (Fig. 229, B) is lighter, and
remains clinging to the surface film.

The tension of this surface iilm is sufficient to support the
weight of an insect up to a certain limit. pro\-ided the insect

i88

ENTOMOLOGY

Fig

has some means of keeping its body dry. This is accom-
phshed usnally by hairs, set together so thickly that water

cannot penetrate between tliem
As the legs and body of G err is
are rendered water-proof bv a vel-
vety clothing of hairs, the insect,
though hea^•ier than water, is able
to skate aljont on the surface.
Gyriiiiis, by means of a similar
adaptation, can circle a1)out on the
surface him, and minute collem-
bolans leap about on the surface as
readily as on land.

The modifications of the legs
for swimming have often impaired
their usefulness for walking, sO'
that many ac[uatic Coleoptera and
Hemiptera can move but awk-
wardly on land. When walking,
it is interesting to note, Cybistcr
and some other aquatic forms no
longer mo\-e their hind legs simul-
taneously as they do in swimming,
but use them alternately, like ter-
restrial species.

The adaptations for swimming
d(^ not necessarily affect the power
of flight. Dytisciis, HydropJiiliis,
Gyrinus, Nofoiiccta, Bcuaciis and
many other Coleoptera and Hemip-
tera lea\e the water at night and
fly around, often being found about
electric lights.

Respiration. — Aquatic insects have not only retained the
primitive, or open (liolopiiciisfic) , type of respiration, charac-

Larva (.-/) and pups
mosquito, Ciilcx pipicns.
ratorv tube; 1, tracheal

(B) of
r, res])!-

:ills.

ADAPTATIONS OF AQUATIC INSECTS 1 89

terized l^y the presence of spiracles, but have also developed
an adaptive, or closed (apiiciisfic) , type, for utilizing air that
is mixed with water.

Through minor modifications of structure and habit, many
holopneustic insects have become fitted for an aquatic life. In
these instances the insects have some means of carrying down
a supply of air from the surface of the water. Thus Noto-
necta bears on its body a silvery film of air entangled in closely
set hairs, which exclude the water. Gyriiuis descends with a
bubble of air at the end of the abdomen. Dytisciis and Hy-
dro pli Hits have each a capacious air-space between the elytra and
the abdomen, into which space the spiracles open. Nepa 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. 229, A, r) pro-
jecting from the penultimate abdominal segment ; the pupa,
however, bears a pair of respiratory tubes on the back of the
thorax (Fig. 229, 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. Similarly, in
the dipterous larva, BittacoinorpJia clavipcs (Fig. 172), the
posterior segments of the abclDUien are attenuated to form a
long respiratory tube. The larva of Donacia appears to have
no special adaptations for aquatic respiration except a pair of
spines near the end of the l)ody, 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 Agrioni(l;e, whose
skin at first is thin enough to allow a direct aeration of the
blood. This cutaneous respiration is possible during the early
life of many aquatic species.

190

ENTOMOLOGY

Fig. 230.

Branchial respiration, however, is the prevalent type amon_o:
aquatic nymphs and is perhaps the most important of their
adaptive characteristics. Thin-walled and extensive out-
growths of the integument, containing tracheal branches or,
rarely, only blood, enable these forms to obtain air from the
water. May fiy nymphs (Figs. 19, A ; 169). 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 commonl}- re-
stricted to the sides of the abd(jmen,
where they occur in pairs or in paired
clusters (Fig. 19, A). Caudal gills are
found in agrionid nymphs (Fig. 170).
The aquatic caterpillars of Paraponyx
(Fig. 171) are unique among Lepidop-
tera in having gills, which are filamentous
in this instance.

Caddis worms, enclosed in their cases,
maintain a current of water by means
of undulatory movements of the body, .
and the larva? and pupa? of most black flies
(Simuliidne, Fig. 230) secure a continuous
supply of fresh air simply by fastening
themselves to rocks in swiftly flowing streams.

Rectal respiration is highlv developed in odonate and ephe-
merid nvmphs. In these, the rectum is lined with thousands
of tracheal branches, \vhich 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
larvre have in addition spiracular respiration.

With the arrival of imaginal life, tracheal gills disappear,
except in PerlidcC, and even in these insects the gills are of
little if any use.

Marine Insects. — Except along the shore, the sea is almost

Simitliiim : A, larva; B,
pupa, showing respira-
tory filaments.

ADAPTATIONS OF AQUATIC INSECTS IQI

devoid of insect life, the exceptions being a few chironomid
larvre which have lieen dredged in deep water, and fifteen
species of Halobafcs ( belonging to the same family as our
familiar pond-skaters), which are fonnd on warm smooth seas,
where thev snbsist on floating animal remains.

Between tide-marks may be found various beetles and col-
lembolans, 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 sul)merged, for example the com-
mon Aiuirida maritiiiia.

Insect Drift, — Seaweed or other refuse cast upon the shcjre
harl)ors a great variety of insects, especially dipterous larvae,
staphvlinid scavengers and predaceous Caraliidre. On the
shores of inland ponds and lakes a similar assemblage of in-
sects 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 leew^ard 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 w^indrow, fifty or perhaps a hundred
miles long. Needham 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 crick-
ets (Ncmobius) , 20 per cent. AcridiidcC. and the remainder
mostly beetles (Carabid?e, Scarabcxida?, Chrysomelid;e, Coc-
cinellid;c, etc.), dragon flies, moths, butterflies {Aiiosia,
Picris, etc.) and various Hemiptera, Hymenoptera and Dip-
tera. A large proportion of the insects were aquatic forms,
such as Hydrophilus, Cybisfcr, Zaiflia, and a species of caddis
fly; these had doubtless been carried out by freshets, while the
butterflies and dragon flies had been Ijorne out In- 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 Coccinellidie, Trichoptera, Asilidce, Acridi-
idae and Gryllidae, nearly all the rest were dead or dying, in-

19- ENTOMOLOGY

chiding the (h-agon flies, flies, bumble bees and wasps. Fora-
ging Caraliid^e were o1>served in large numbers, also scaven-
gers of the families Staphylinidse, Silphidc'e and Dermestidae.

On the seashore and on the shores of the Great Lakes, the
salient features of insect life are essentially the same. Sim-
ilar 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 unobscured by the temporarv 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
primiti^'e, insects — -Thysanura — are without exception terres-
trial. Aquatic insects do not constitute a phylogenetlc unit,
but re^jresent various orders, which are for the most part un-
doul)tedly terrestrial, notwithstanding the fact that a few of
these orders (Plecoptera, Ephemerida, Odonata, Trichoptera)
are now wholly aquatic in habit. Adaptations for an acjuatic
existence ha^•e arisen independently and often, in the most
diverse orders of insects.

CHAPTER A'

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 ci)lors.

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
(chcmico-physical ) . which are produced in both ways at once.

Structural Colors. — The iridescence of a fly's wing and
that of a soap ljulj])le are produced in essentially the same way.
The wing, however, consists of two thin, transparent, slightly
separated lamelke, which diffract ^^■hite light into prismatic
rays, the color differences depending upon differences in the
distance l^etween the two membranes.

The brilliant iridescent hues of many butterfly scales are due
to the diffraction of light by fine, closely parallel stride (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 par-
ticular color produced depends in b()th cases upon the distance
between the strire. Though almost all ]ei)idopterous scales are
striated, it is only now and then that the stride are sufficiently
close together to give diffraction colors. In a Brazilian si)ecies
of Apatura the iridescent scales have 1050 stride to the milli-
meter, and in a species of Morpho, according to Kellogg, the
iridescent pigmented scales have 1,400 strise per millimeter, the
striae being only .0007 mm. apart ; while in some of the finest
Rowland gratings the)' are as far a])art as .0015 mm., tht:>ugh
numbering 1,700 per millimeter.

These interference colors of buttcrtly scales may be due, not
14 193

194 ENTOMOLOGY

only to surface marking's, but also to the lamination of the
scale and to the overlapping of two or more scales. In beetles
the metallic blues and greens, and iridescence in general, are
often produced by minute lines or pits that diffract the light.
Purely structural colors, however, are not so common as might
be supposed, according to Tower, who says, " The pits al()ne,
however, are powerless to produce any color; it is only when
they are combined with a highly reflecting and refractive sur-
face lamella and a pigmented layer below that the iridescent
color appears. The action of 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 com-
mon occurrence, but it is only when they are combined as
above that iridescent colors occur."

Silvery white eft'ects are usually caused by the total reflec-
tion of light from scales or other sacs that are filled with air;
the same silvery appearance is given also by air-filled tracheae
and by the air bubl:)les that many aquatic insects carr}" about
under water.

Violet, blue-green, coppery, silver and gold colors are, with
few exceptions, structural colors. (Mayer.)

Pigmental Colors. — These are either ciiticitlar or liypo-
dcniial. The predominant brown and black colors of insects
are made by pigment diffused 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 signifi-
cant that the cuticular pigments lie close to the surface of the
skin, i. e., where they are most exposed to atmospheric
influences. Tower finds, however, that cuticular colors " are
not due to drying, oxidation, secretion, or like processes," but
are due to " some katalytic agent or enzyme [formed l)y the
hypodermis] which, passing out through the pore canals,
comes in contact with the primary cuticula and there becomes
the active factor in the production of cuticula colors."

COLOR AND COLORATION I 95

The cuticular pigments are derived of course, from the
underlying- hypodermis cells, and these cells themselves, more-
over, 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 hypo-
dermal 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 Pieridas, Lyc?enida; and some
Geometridas.

Frequently a color pattern consists partly of cuticular and
partly of hypodermal colors, the hypodermal or sub-hypoder-
mal color forming " a groundwork upon which the pattern is
cut out Ijy the cuticular color." (Tower. ) Thus in Leptino-
tarsa dccciuJiiicata the pattern "is composed of a dark cutic-
ular pigment upon a yellow hypodermal background."

Combination Colors. — The splendid changeable hues of
Apatura, Eiipla\i 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 xiolet by reflected light, and to the un-
aided eye the color of the wing is either brown or violet, ac-
cording 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 belong all metallic, iri-
descent, 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 chlorophyll, which tinges the blood and shows through

196 ENTOMOLOGY

the transparent integument. Mayer has found that scales of
Lepidoptera contain only blood while the pigment is forming;
that the iirst 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 artiti-
cially from pupal blood. Pierid?e are peculiar in the nature
of their pigments, as Hopkins has shown. The wdiite pigment
of this family is uric acid and the reds and yellows of Picris,
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 Papilionid^e, Noctu-
idae, GeometridcC and Sphingidie are also said by some inves-
tigators 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^ constituent of chlorophyll, namely xantho-
phvll, frequently iiuparts 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. ]\Iost pig-
ments, however, are elaborated from the food by chemical
processes that are not well understood.

Many wdio have reared Lepidoptera extensively know that
the color of the imago is influenced by the character of the
larval food, other conditions being equal, and are able at will
to effect certain color changes simply Ijy feeding the larvae
from birth upon particular kinds of plants. In this country
we ha^•e few observations upon the sul^ject, but in Europe
the eft'ects of food upon coloration ha\'e been ascertained in
the case of many species of Lepidoptera. According to Greg-
son. Hyhcrnia dcfoUaria is richly colored wdien fed upon
birch, l)ut is dull colored and almost unmarked when fed on
elm. Pictet, by feeding larvre of ]\uicssa urticcc on the flow-
ers instead of the leaves of the nettle obtained the variety

COLOR AND COLORATION 197

known as urticoidcs. Food affects the color of the larva also,
as Poulton found in the case of caterpillars of Tryphcuna pro-
iiiiba, all from the same batch of egg'S. When fed with only
the white midribs of cabbage leaves, the larvre remained almost
white for a time, bnt afterward showed a moderate amount of
black pigment ; when fed with the yellow etiolated heart-leaves
or the dark green external leaves, however, the larvns all be-
came bright green or brown — the same pigment being derived
indifferently from etiolin (probably the same substance as
xanthophyll) or chlorophyll.

Though the pigments may differ in color or amount accord-
ing' to the kind of food, the color patterns vary without regard
to food. Thus CaUosainia proiucfhca, Lcptinofarsa dccem-
lineata (Colorado potato beetle). Coccinellidc-e (lady-bird
beetles) and a liost of other insects exhibit extensive individ-
ual variations in coloration under precisely the same food con-
ditions. Caterpillars of the same kind and age are often very
differently marked when feeding upon the same plant; for
example, Hcliothis aniiigcr (corn w^orm) and the sphingid
DcilephUa lincata. Furthermore, striking changes of colora-
tion accompany each moult in most caterpillars, but particu-
larly those of butterflies, and these changes may prove to have
an important phylogenetic significance. Individual differ-
ences of coloration apart from those due to the direct action
of food, light, temperature and other environmental condi-
tions are to be explained l)y 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
nuvitiuia is white at hatching, but soon becomes indigo l)lue,
unless shielded from sunlight, in which event it remains white
until exposed to the sunlight, when it assumes the blue color.
Subterranean or wood-boring larwe are commonly white or
yellow, but never highly colored, 'idie most notable instances,
however, are furnished by ca\-c insects. These, like other
cavernicolous animrds, are characteristically white or pale

198 ENTOMOLOGY

from the absence of pig'ment, if they hve in regions of con-
tinual darkness, l^nt have more or less pigmentation in propor-
tion respectively to the greater or less amount of sunlight to
which they have access.

Curiously enough, ligiit 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 essential for the sustension or
renew^al 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 Picris rapcv, raised
upon the same food plant (all other conditions being made as
nearly equal as possible) produced dark pupce if kept in dark-
ness for a few days just before pupation; yellow light arrested
the formation of the dark pigment and gave green pupas ; while
light colors in general gave light-colored pupse. This color re-
semblance 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 production.

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. Gastropacha qucrcifolia, 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

COLOR AND COLORATION 199

variegated coloration of lichens. Only the younger larVcT,
however, proved to be snsceptil^le to the colors of the environ-
ment; unlike those of AuipJiidasis hctularia, in which the older
larvas 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 sur-
rounding temperature during the pupal stage, when the pig-
ments are forming". Black or brown spots have been enlarged
artificially by subjecting chrysalides to cold ; hence it is probable
that the characteristically larg-e black spots on the under side
of the wing-s of the spring brood of our Cyaiiiris psciuiargioliis
are simply a direct effect of cold upon the wintering chrysal-
ides. Similarly the spring brood (variety niarcia) of Pliy-
ciodes tharos owes its distinctive coloration to cold, as Ed-
wards has proved experimentally. Lepidoptera have been the
subject of very many temperature experiments, 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 hig"h or low, seldom if ever
produces new pigments, but simply alters the amount and dis-
tribution of pigments that are present already.

Effects of Moisture. — Very little is known as to the effects
of moisture upon coloration. The dark colors of insular or
coastal insects as contrasted with inland forms, and the pre-
dominance of dull or suffused species in mountainous regions
of high humidity, have led c^bservers occasionally to ascribe
Tuclanisin and suffusion to humidity. In these cases, how-
ever, the possible influence of low temperature and other fac-
tors must be taken into consideration. The experiments of
Merrifield and of Standfuss showed no effect of moisture upon
lepidopterous pup?e.

200 ENTOMOLOGY

Pictet has recently found, however, that humidity acting
on the caterpillars of J\iucssa urficcr and J\ 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
wings, and the same results followed when the larv:e 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 remain so
until more is known about the eff'ects separately produced by
each of the several factors that go to make up \vhat 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 ex-
clusion 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 temperate regions. Carabidae, in fact, attain their
greatest brilliancy in the temperate zone, according to Wal-
lace, though butterflies certainly show a larger proportion of
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
■jiiay Ije due to the far greater number of species, which gives
a better opportunity for color sports to arise ; and not to any
direct influence of the climate. Furthermore, the number of

COLOR AND COLORATION 20I

broods which occur in a }-ear is much greater in the tropics
than in the temperate zones, so that the tropical species must
possess a corresponchngiy greater opportunity to vary.

Albinism and Melanism. — These interesting phenomena,
widespread among- the higher animals, are little understood,
l:)ut appear to be due chietly to tcmi)erature.

Albinism is exceptional whiteness or paleness of coloration,
and is due usually to lack or deficiency of pigment, but in
some instances (Pierid^e) to the presence of a white pigment.

The common yellow^ butterfly, C olios philodicc, and its rela-
tives, are frequently albinic. Indeed, as Scudder observes,
albinism among butterflies in America appears to 1)e confined
to a few Pieridre, antl to l)e restricted to the female sex ; it is
more common in subarctic and subalpine regions than in lower
latitudes and altitudes, and only in the former places does it
include all the females. At lo\\' altitudes, instead of appear-
ing early in the year as might l)e expected, the albinic forms
appear during" the warmer months.

In Europe there are many albinic species of butterflies, and
they are by no means confined to the family Pieridre.

Mclaiiisin is unusual blackness or darkness of coloration.
As to how it is produced little is known, though warmth is
probably the most potent influence, and some attrilwte it to
moisture, as was mentioned. Pictet obtained partial melan-
ism in Vanessa urticcc and ['. l^olycliJoros hx subjecting the
larvae to moisture.

In warm latitudes, some females of oin" Papilio glancus
are blackish brown with black markings, instead of being, as
usual, yellow with Ijlack markings. In the South, some males
of the spring- brood of Cyan iris psciulargiolus are partly or
wholly Ijrown instead of blue.

Seasonal Coloration. — When butterflies have more than
one 1)rood in a year, the broods usually dififer in aspect, some-
times so much that their si^ecific identity is revealed only
by rearing one brood from another. The same species may
exist under tw^o or more distinct forms during the same sea-

202

ENTOMOLOGY

son — in other words, may be seasonally dimorphic, triiiiorpJiic
or polyiiiorpJiic.

Thus Polygoiiia intcrrogatiouis has two forms, fabricii and
unibrosa, which differ not only in coloration, Init even in the
form of the wing's and the g'enitalia. In New England fabricii
hibernates and produces uiiibrosa, as a rule, while iinibrosa
usually yields fabricii.

The little blue butterfly, Cyaiiiris psciidargioliis (Fig. 231 ),
is polymorphic to a remarkable degree. In the high latitudes
of Canada, a single brood (Iiicia) occurs. About Boston, the
same spring brood appears, Ijut under two forms : an earlier
variety (lucia) , which is small, with large black markings

Fic. 231.

Cyaniris psciidargioliis ; A, form lucia; B, violacca; C, pseudargiolus proper.
Natural size.

beneath; and a later variety {violacca) , which is typically
larger, with smaller black spots, though it varies into the form
hicia. Finally, in summer, a third form {pseudargiolus
proper) appears, as the product of lucia or else the joint prod-
uct of lucia and violacca, and this is still larger, but the black
spots are now faint. In the warm South, the spring form is
violacca, but while some of the males are blue, others are
melanic, as just mentioned — a dimorphic condition which does
not occur in the North. Jlolacca then produces pseudargi-
olus, in which, however, all the males are blue.

Iphiclidcs ajax (Fig. 2^,2) is another polymorphic butterfly
whose life history is complex. The three principal varieties
of this species, known respecti\ely as inarccllus, fclanionidcs
and ajax, difl:er not only in coloration, but also in size and
form; inarccllus appears first, in spring; fclanionidcs appears

COLOR AND COLORATION

203

a little later (though before iiiurcclliis has disappeared) : and
aja.r is the summer form; as the season advances the varieties
become successively larger, with longer tails to the hind wings.

Fig. 232.

Ipliiclidcs ajiix, form tcliimi-niuics. on tliiwcr of button bush. Reduced.

Now Edwards submitted chrysalides of the summer form
ajax to cold and thereby obtained, in the same summer, butter-
flies \vith the form of aja.v but the markings of the spring

Fig. 233.

Phyciocles tharos; A, spring form, luarcia ; B. summer form, uiorphciis; under sur-
faces. Natural size.

form tclaiiioiiidcs. Some of the chrysalides, however, lasted
over until the next spring and then gave irlaiiioiiidrs.

204 ENTOMOLOGY

In Pliyciodcs fJiaros (Fig. 233) the spring' and summer
broods, termed respecti\'ely inarcia and morpJicus, were at first
regarded as distinct species. In inarcia the hind wings are
heavily and dififiisely marked beneath with strongly contrast-
ing colors, while in iiiorpJiciis thev are plain and but faintly
marked. Edwards placed upon ice eighteen chrysalides that
normally would have produced morpheas; but instead of this,
the fifteen imagines that emerged were all of the spring form
inarcia and Avere smaller than usual. Pupns derived from
eggs of niarcia gave, after artificial cooling, not niorpliciis,
but niarcia again. The evident conclusion is that the distinc-
tive coloration of the spring variety is brought about by low
temperature. In Labrador, only one brood occurs — inarcia;
in New York, the species is digoneutic (two-brooded) and in
West Virginia polygoncufic (several-brooded).

Extensive temperature experiments upon seasonal dimor-
phism in Lepidoptera have been conducted in Europe by some
of the most competent biologists. Weismann found that pup?e
of the summer form of Picris napi, 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 summer one
by the application of heat. Similar results have attended the
important and much-discussed experiments of Dorfmeister,
Weismann and others upon J'ancssa Icvana-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, responds
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 col-
ored in adaptation to its particular en\-ironment and that this
adaptation may have been brought about by natural selection —
though he does not succeed in this respect.

COLOR AND COLORATION 205

In several instances, local \arielies ha\e been artificially pro-
duced as results of temperature control. Thus Standfuss
produced in Germany, by the application of cold, individuals
of Vanessa nrticcc which were indistinguishable from the
northern variety Solaris; and from i)up;e of J\7iicssa cardiii.
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, ha\e accumulated a consideraljle mass of experimen-
tal evidence, the interpretation of which is in many respects
difficult, involving- as it does, not merely the direct effect of
temperature upon the organism, l)ut also deep questions of
heredity, including- reversion, indi\-idual variation, and the in-
heritance of accjuired characters.

The seasonal increase in size that is noticeable, as in C.
pseiidargiolus and /. aja.v, is doubtless an expression ^bf in-
creasing 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 cater-
pillars were so much stimulated by unusual \\armth that they
pupated before they were sufficiently fed, and gave, therefore,
undersized imagines. A moderate degree of warmth, how-
ever, undijubtedly hastens growth.

Sexual Coloration. — The sexes are often distinguished by
colorational as \\ell as structural differences. Colorational
antigeny (this word signifying secondary sexual dift'erences
of whatever sort) is most prevalent among butterflies, in
which it is the extreme phase of that differentiation of orna-
mentation for which Lepido])tera are unri\-aled.

The male of Picris protodkc (Fig. -34) has a few brown
spots on the front wings; the female is checkered with Ijrown
on both wings. In Colias pliilodicc (F"ig". 235) and C. ciirx-
tlicinc 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 g-enus Papilio the sexes

io6

ENTOMOLOGY

Fir;. 234.

Fin. 235.

Picris protoJicc ; male diii the left) and female (on the right). Natural size.

are often distinguished by colorational differences and in Hes-
periid?e the males often have an o1)hqne black dash across the
middle of each front wing. Callosainia pronicthca (Fig\
236), the gypsy moth and many other Lepidoptera exhibit
colorational antigeny. In not a few Sesiida; the sexes differ

greatly in coloration. Thus in the
male of the peach tree borer (San-
II i no idea c.vifiosa) all the wings are
colorless and transparent ; while in
the female the front wings are vio-
let and opac[ue and the fourth ab-
dominal segment is orange above.
The same sex may present two
types of colorati()n. as do males of
Cyaiii'ris pscudargioliis and females
of Pajvlio glaiiciis. already men-
tioned. Papiiio mcropc, of South
Africa, is remarkable in ha\'ing three
females (Frontispiece, Figs. 5. 7, 9,

Colias philodic

right fore

wing of male (above) and of jjA ^yhich are eutirclv (lift'ereiit in

female (below). Natural size.

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 col-
orational antigeny. The male of Caloptcryx inoculata is vel-

COLOR AND COLORATION

207

vety black; the female smoky, with a white ptcrostigmatal
spot. Among" Coleoptera. the male of HopUa frifasciata is
gTavish and the female reddish brown ; a few more examples
might be given, though sexual differences in coloration are

Fig. 236.

Callosamia proinctJica; A, male, clinging to cocoon; B, female. Reduced.

comparatively rare among beetles. Of Hymenoptera, some
of the TenthredinidcC exhibit colorational antigeny.

Among tropical butterflies there are not a few instances in
which the special coloration of the female is adaptive — har-
monizing with the surroundings or else imitating with remark-
able precision the coloration of another species which is known

208 ENTOMOLOGY

to 1)6 immune from the attacks of Ijirds — as described Ijeyond.
In this way, as W'ahace suggests, 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 selecti(jn.

In most insects, however, sexual differences in coloration
are apparently of no protective value and are usually so tri\'ial
and variable as prol^ably to be of no use for recognition ])ur-
poses. The usual statement that these dift'erences facilitate
sexual recognition is a pure assumpti(.'n, in the case of insects,
and one that is inadequate in si)ite of its plausibility, for (i)
it is extremely improl)al)le from our present knowledge of
insect \'ision that insects are aljle to percei\-e colors except in
the broadest way, namely, as masses; (2) the great majority
of insect species show no sexual differences in coloration ; ( 3 )
when colorati()nal antigeny is present it is probably unneces-
sary, to say the least, for sexual recognition. Thus, notwith-
standing the marked dissimilarit}' of coloration in the two
sexes of C. proincflica, the males, guided l)y an odor, seek out
their mates e\'en when the wings of the female have been am-
putated and male wings glued in their place, as Mayer fountl.

lience, when useless, colorational antigeny cannot have
been de\eloped by natural selection and may be due simph'
to the extended action of the same forces that have produced
variety of coloraticni in general.

Origin of Color Patterns. — Tower, who has written an
important work on the colors and color patterns of Coleop-
tera, finds that each of the Ijlack spots on the pronotum of the
Colorado potato beetle (Fig. 237) " is developed in connection
with a muscle, and marks the point of attachment of its fibers to
the cuticula." Thus the color pattern, in its origin, is not neces-
sarily useful. This point is so important that we quote Tow-
er'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

COLOR AND COLORATION 20CJ

one of the earlier sections of this i)ai)er 1 showed tliat tlie pig-
ment develops from before 1)ack\\ar(l 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 infrecjuent. 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 Ijetween the development of color, the hard-
ening of the cuticula. and the beginning of muscular acti\"ity;
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, segmentally developed.

" The relation which exists between cuticular color and the
stiffening of the cuticula is thus a physiological one, the cutic-
ula not being able to harden without 1)ecoming yellow or
brown. What bearing has this upon the origin of color pat-
terns? In the lower forms of tracheates, such as the Myria-
pods, colors appear as segmental repetitions of spots or pig-
mented areas which mark either important sclerites or muscle
attachments. On the abdomens of- insects, where segmenta-
tion is best observed, color appears as well-defined, segmen-
tally arranged spots, but on the thorax segmentation is ob-
scured 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 integimient of the ancestral tracheates as
necessary to the muscular activity of terrestri.al life. The
primitive colors were yellows, browns and blacks, correspond-
ing well with the surroundings in which the first terrestrial
insects are suppi.sed to have li\-ed. The color pattern was a
segmental one, showing' repetition of the same spots upon suc-
cessive segments, as upon the abdomen of Coleoptera.
'5

2IO ENTOMOLOGY

" So firmly have these characters become ingrained in the
tracheate series, and so important is this relation of the hard-
ening of the cnticnla to the mnsculatm'e and to the formation
of lx)dy sclerites, that even the most specialized forms show
this primitive system of coloration ; and, althong'h 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
coloration are, for the most part, obscure, it is possible, never-
theless, to point out certain paths along which coh^ration ap-
pears to have developed. These paths have been determined
by the comparison of color patterns in kindred groups of in-
sects and the study of colorational variations in adults of the
same species. The development of coloration in the individ-
ual, 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 stu-
dents 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 col-
ors prevail on the hind wings of most moths and on the less
exposed parts of the wings of highly colored butterflies. The
hind wing-s of moths are, as a rule, more primitively colored
than the front ones because, as Scudder says, " all difi^eren-
tiation in coloring has been greatly retarded by their almost
universal concealment by day beneath the overlapping front
wings." Exceptions to this statement are found in Geomet-
ridse and such other moths a^ rest 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 mar-
gin 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
condition to a distinct line or band of dark color parallel to
the margin. Or the marginal shade may, in a similar way,
break up into two or more transverse and parallel submarginal

COLOR AND COLORATION 211

lines, a very common style of ornamentation, especially in
moths. Or, again, starting with the suhmarginal 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 np 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 modi-
fications of simple trans\erse markings which adorn the wings
of Lepidoptera."

Briefly, one or more bands ma}' break up into spots or bars,
the breaks occurring either between the veins or, more com-
monly, at the veins ; and in the latter event, short l)ars 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-c<-)lored 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 symmetrical, both 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 longi-
tudinal nervures. ( b ) Spots tend to appear not in one inter-
space 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 np of l)ands. (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 vari-
able than the middle. (/) The position of spots situated near
the outer edges of the wing is largely contridled by the wing-
folds or creases."

These results ha\e been arrived at chiefly by the study of
the variations presented by color patterns.

Variation in Coloration. — It is safe to say that no two
insects are colored exactl}' alike. Some species, however, are

Fig. 237.

ii\l

* % ^« «

4'W

Colorational variations of the pronotum of the Colorado potato beetle, Lcptinotarsa

deccmlineata.

(212)

Fig. 23S.

/ ^

Elytral color patterns of species of Cicindela. iS illustrate reduction of dark area;
9-14, extension of dark area; 15, 16, formation of longitudinal vitta; //, iS, linear
extension of markings. I, C. vulgaris; 2, generosa; 3, generosa; 4, pamphila; 5, lim-
bata; 6, togata; 7, gratiosa ; 8, canosa; 9, fenuisignata; 10, marginipennis; 11, hentzii;
IS, sexguttata; 13, hemorrhagica; 14, splcndida; is, imperfecta; 16, Icmniscata;
17. gabbii; 18, saulcyi. — After Horn, from Entomological News. f^ v

214 ENTOMOLOGY

far more varial)le than others. Catocala ilia, f<_)r example,
occurs under more than fifty ^•arieties, each of which might
be given a (hstincti\'e name, were it not for the fact that these
varieties run into one another. One may examine hundreds
of potato beetles (L. dcccmluicata) without finding any two
that ha^'e precisely the same pattern on the pronotum. The
range of this variation in this species is partially indicated in
Fig. 237. and that of Cicindcia in Fig. 238.

Individuals of Cicindcia vary in pattern in a few definite
directions, and the patterns that characterize the various spe-
cies appear to be fixations of indi\'idual variations. In the
words of Dr. Horn : " ( i ) The type of marking is the same
in all our species. (2) Assuming a well-marked species (z'til-
garis. Fig. 238, j) as a central type, the markings of other
species vary from that type. ( (/ ) by a progressive spreading
of the white, {b) 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
invarial^le ( /. c, the individual variations are small in amount
as compared with those in other species). These fall into two
series: (a) those of the n(")rmal type, as vulgaris, Iiirticollis
and tcmiisigiiata ; (b) those in which some modification of the
type has become permanent, probably through isolation, as
iiiargiiiipciiiiis, togafa and Icimiiscafa. (4) Those species
which vary do so in one direction only." New types of pat-
tern, of specific value, appear to have arisen by the isolation
and perpetuation of individual variations.

Variations in g'eneral fall into two classes: coutiiiuoiis (in-
dividual z'ariatioiis) and discontinuous [sports). The former
are always present, are slight in extent and intergrade with
one another ; they are distributed symmetrically about a mean
condition. Tlie latter are occasional, of consideralile extent
and sharpl}' separated from the normal condition.

Replacements. — Examples of the replacement of one color
by another are familiar to all collectors. The red of J'ancssa
atalanta and CoccinellidcT may Ije replaced by yellow. These

COLOR AND COLORATION 21 5

two colors in many 1)ntterflies and l)eetles are dne to pigments
that are closely related to each other chemically. Thns in the
chrysomelid Melasoina lappoiiica 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 Ije prevented, however, by keep-
ing the beetle in the dark. After death, the red fades back
through 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
Paxilocapsus I i neat us are yellow before they become green, and
after death fade back to yellow. As the green pigment in most,
if not all. phytophagous insects is chlorophyll, these color
changes are probably similar to those that occur in leaves.
Leaves grown in darkness are}-ellow. from the presence of etio-
lin, and do not turn green until they are exposed to sunlight (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
\ery likely the same sul)stance as etiolin.

Ciciiidda scxguttata and Calosoiiui 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 liecome pink toward the
close of summer. No explanation has been offered for this
phenomenon, though it may be remarked that when grasshop-
pers 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 eff'ects of light, temperature or other
inoro-anic influences.

CHAPTER VI

ADAPTIVE COLORATION

Protective Resemblance. — Every naturalist knows of
many animals that tend to escape detection by reseml)ling' their
surroundings. This phenomenon of protect iz'c resemblance
is richly exemplified by insects, among" which one of the most
remarkable cases is furnished by the Kalliina butterthes, espe-
cially K. inachis of India and K. paralxleta of the Malay Archi-
pelago. The former species (Fig. 239) is conspicuous when

Fig. 239.

l^v .

■^

Kalluiui ini'L-liis; A, upper surface; B, with wings closed, showing resemblance to a

leaf. X i.

on the wing; its bright colors, however, are conhned to the
upper surfaces of the wings, and when these are folded to-
gether, as in repose, the insect resembles to perfection one of
the dead leaves among which it is accustomed to hide. The
form, size and color of the leaf are accurately reproduced, the
petiole being simulated by the tails of the wings. Two paral-
lel shades, one light and one dark, represent, respectively,

216

ADAPTIVE COLORATION

217

the illuminated and tlie shaded side of a mid-rih, and the side-
veins as well are imitated ; there are even small scattered 1)lack
spots resembling those made on the leaf bv a species of
fungus. Furthermore, the hutterf1\- habitually rests, not
among green leaves, where it would be conspicuous, but among

leaves W'ith wdiich it har-

, . Fig. 240.

momzes m coloration.

Notwithstanding a recent
discussion as to whether
it usually rests in pre-
cisely the same position
as a leaf, this insect cer-
tainly deceives experi-
enced entomologists and
presumably eludes birds
and other enemies by
means of its deceptive
coloration.

Some of the tropical
P h a s m i d se counterfeit
sticks, green leaves, or
dead leaves with minute
accuracy. Our common
phasmids, Diaplicroincra
fcniorata and vclici (Fig.
240), are well known as
" stick insects " ; indeed,
it is not necessary to go
Ijeyond the temperate zone
to lind plenty of examples
of protective resemblance, (icomctrid caterpillars imitate twigs,
holding the body stitfly from a branch and frequently reprodu-
cing the form and coloration of a twig with striking exactitude;
and the moths of the same t'amily are often colored like th.e
bark against which they spread their wings. I'Aen more per-
fectly do the Catocala moths resemble the bark upon which

Dial'licroincra iclici, on a twig. Natural size.

2l8

ENTOMOLOGY

they rest (Fig. 241), with their conspicuous and usually showy
hind wings concealed under the protectively colored front
wings. The caterpillars of Basilarchia arcJiippiis and Pa-
pilio fhoas, as well as other larvre and n(jt a few moths,
resemble closely the excrements of birds. Numerous grass-
Fin. 241.

Catocala lacrynwsa; A, upper surface; B, with wings closed, and resting on bark.

Reduced.

mating caterpillars are striped with green, as is also a sphingid
species (Ellcina harrisii) that li\es among pine needles. The
large green sphinx caterpillars perhaps owe their inconspicu-
ousness partly to their oblique lateral stripes, which cut a mass
of green into smaller areas. The caterpillar of Schisitra
ipoiiHVcc (Fig. 242), which is green with Ijrown patches, rests

ADAPTIVE COLORATION

219

for hours along" tlie eaten or torn edge of a bassworxl leaf, in
which position it bears an extremely decepti\'e resenililance to
the partially dead border of a leaf. The weexils that drop to
the p'round and remain immowable are often indistin^aiishable

Fig. 24-

Caterpillar of Scliicurci ipomacc clinging to a lurn leaf. Natural size.

to the collector on account of their likeness to l:)its of soil or
little pebbles. Everyone has noticed the extent to which some
of the grasshoppers resemble the soil in color; Triiucrotropis
maritinia is practically invisible ag'ainst the gray sand of the
seashore or other places to which it restricts itself; and Dis-
sosfcira Carolina, which varies greatly in color, rrmging from
ashy gray to yellowish or to reddish brown, is commonly found
on soil of its own color.

Adventitious Resemblance. — If, instead of hastily ascrib-
ing all cases apparenth- of protectixe resemblance to the action
of natural selecticMi, one inquires into the structural basis of
the resemblance in each instance, it is found that some cases
can be exi)lained, without the aid of natural selection, as being

2 20 ENTOMOLOGY

direct effects of food, light or other primary factors. Such cases,
tlien, are in a sense accidentah For example, manv inconspic-
uous 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
caterpillar is by no means exceptional in thinness or trans-
parency. Moreover, many leaf-mining caterpillars are green,
simply l^ecause 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 experi-
mented upon by Poulton, their 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 preser^'ed such in-
dividuals as were most responsive to the stimulus of the sur-
rounding 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 " protec-
tive resemblance " are very far-fetched. On the other hand,
when the resemblance is as specific and minutelv detailed as it
is in the Kalliuia butterflies — where, moreover, special instincts
are involved — the phenomenon 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 ha\-e been preserved
and accumulated until an extraordinary degree of adaptation
has been attained.

Value of Protective Resemblance. — The popular opinion
as to the efticiency of protective resemblances is undoubtedly
an exaggerated one, owing mainly to the false assumption that

ADAPTIVE COLORATION 221

the senses of the lower animals are co-extensive in rang-e
with onr own. As a matter of fact, hirds 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 s]iecies of
birds feed upon protectively colored grasshoppers, which they
destroy in immense numbers, and more than twenty species
prey upon the twig'-like geometrid larv?e ; while the wee\'ils
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 advantageous upon the whole, even if it is ineffectual in
thousands of instances. An adaptation may be successful
even if it does fall short of perfection; and it should be borne
in mind that the evolution of protective 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 protec-
tively colored species, there are many insects wdiich are so
vividly colored as to be extremely conspicuous amid their nat-
ural surroundings. Such are many Hemiptera (Lygcciis,
Murgantia), Coleoptera {Nccroplwnis, Lampyridie, Coccinel-
lid?e, Chrysomelid^e), Hymenoptera (Mutillid?e, Vespidse),
and numerous caterpillars and butterflies. Conspicuous col-
ors, being frequentl}' — though not always — associated with
cjualities that render their possessors unpalatable or offensive
to birds or other enemies, are advantageous if, by insuring
ready recognition, they exempt their owners trom attack.

Efficiency of Warning Colors. — Owing to much disagree-
ment as to the actual value ot '* warning" colors, several in-
vestigators ha\-e made many observations and experiments
upon the subject. Tests made by oft'ering various conspicu-
ous insects to l)irds, lizards, frogs, monkeys and other insec-
tivorous animals ha\-e given diverse results, according to cir-

222 ENTOMOLOGY

cumstances. Thus, one gaudy caterpillar is refused by a cer-
tain bird, at once, or else after being tasted, but another and
ecjually showy caterpillar 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 bv some
animals is accepted by others. Moreover, some of the experi-
ments with captive insecti\T)rous animals are open to objection
on the score of artificiality.

Nevertheless, from the data now accumulated, there emerge
some conclusions of definite value. Frank Finn, whose con-
clusions are cjuoted beyond, has found in India that the con-
spicuous colors of some butterflies (Danaina?. Acrcca violcc,
Delias ciuiiaris, Papilio aristoIocJiicc) are probably effective
as " warning " colors. ^Marshall found in South Africa that
mantids, which would devour most kinds of butterflies, includ-
ing warningly colored species, refused Acrcca, which appeared
to be not only distasteful but even unwholesome; Acrcca is
eaten, however, by the predaceous Asilidre, which feed indis-
criminately upon insects — for example, beetles, dragon flies and
even stinging Hymenoptera. The masterly studies of Mar-
shall and Poulton strongly support the general theory of warn-
ing 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 Mnrgantia Jiistrionica
and other large showy bugs are usually avoided by birds ; that
the showy, ill-fla\'ored Coccinellidje, and Chrysomelidas such
as the elm leaf beetle, Diabrofica, and Leptuiotarsa {Dory-
plwra), possess comparati\'e immunitv from birds; and that
]\Iacrodactyliis. ChaiiliogiialJius and Cyllciic are highly exempt
from attack. Such cases, he adds, are comparatively few
among insects, however, and in g'eneral, warning colors are
eft"ective against some enemies 1:)ut ineffective against others.

Generally speaking, hairs, stings and other protective de-
vices are accompanied Ijy conspicuous colors — though there

ADAPTIVE COLORATION 223

are many exceptions to this rule. Hiese warning" colors, liow-
ever, fail to accomplish their supijosed purpose in the follow-
ing instances, given by Judd. Taking- insects that are thought
to be protected by an otTensi\e odor or a disagreeable taste :
Heteroptera in general are eaten by all insectivorous birds, the
scjuash bug by hawks and the pentatomids by many birds;
among CarabidcC with their irritating- fluids, Harpalus caligi-
nosus and pcnnsylvaiiicus are food for the crow, catbird, robin
and six others; Carahus and Calosoma are relished by crows
and blackbirds; Silphid;c are taken by the crow, loggerhead
shrike and kingbird; and Lcpfiiiotarsa dccciiiliiicafa is eaten
l)y at least six kinds of birds : wood thrush, rose-breasted gros-
beak, cjuail, crow, cuckoo and catbird. Of hairy and spiny cat-
erpillars, ArctiidcT are eaten by the robin, bluebird, catbird,
cuckoo and others; the larvie of the gypsy moth are f(wd for
the blue-jay, robin, chickadee, Baltimore oriole and many
others [thirty-one birds, in Massachusetts] ; and the spiny
caterpillars of J\iiicssa aiitiopa are taken by cuckoos and ori-
oles. Of stinging- Hymenoptera,. bumble bees are eaten by the
bluebird, blue-jay and two flycatchers; the honey l)ee, by the
wood pewee, phoebe, olive-sided flycatcher and kingbird ;
Andrcna by many 1)irds, and ]\\<;pa and Polistes by the red-
bellied woodpecker, kingl^ird, and yellow-bellied flycatcher.

These facts by no means invalidate the general theory, but
they do show^ that " disagreeable " qualities and their associ-
ated color signals are of little or no avail against some enemies.
The weig'ht of evidence favors the theory of warning colora-
tion in a qualified form. While conspicuous 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 cokjration is explained l)y natural
selection ; in fact, we have no other theory to account for it.
The colors themselves, however, must have Ijeen present before
natural selection could begin to operate; their origin is a ques-
tion quite distinct from that of their subsequent preservation.

ENTOMOLOGY

Protective Mimicry. — This interesting and highly involved
phenomenon is a special form of protective resemlilance in
which one species imitates the appearance of another and

Fig. 243.

A, Auosia f^lcxippiis, the " mode! ";

silarchlii arcJiipl^iis, the " mimic.

Natural size.

better protected species, thereby sharing its immnnity from
destruction. Though it attains its highest development in the
tropics, mimicry is well illustrated in temperate regions. A
familiar example is furnished Ijy Basilarchia archippiis (Fig.
243, B ) , which departs widely from the prevailing dark colora-
tion of its genus to imitate the milkweed luittert^y, Auosia

ADAPTIVE COLORATION

22 i^

plc.vippiis. The latter species, or " model," appears to lie un-
molested l)y l)ir(ls, and the former species, or " mimic." is
thought to secure the same exemption from attack hy being-
mistaken for its unpalatable model. The common drone-tiy,
Eristalis tenax (Fig. 244, B) mimics a honey bee in form, size,

Fig. 244.

Protective mimicry. A, drone bee. Apis mellifcra; B, drone fly, Eristalis tcitax.

Natural size.

coloration and the manner in which it buzzes about flowers,
in company w^ith its model ; it does not deceive the kingbird
and the flicker, however. Some Asilid^e are remarkablv like
bumble bees in superficial appearance and certain Syrpliits flies
mimic wasps with more or less success. The beetle Casiwiiia
bears a remarkable resemblance to the ants with which it lives.
The classic cases are those of the Amazonian lieliconiidse
and Pieridae, in which mimicry was first detected by Bates.
The Heliconiidae (Frontispiece, Fig-, i) are abundant, vividly
colored and eminently free 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 dif-
ferent from Heliconiidte — imitate (Frontispiece, Fig. 2) the
protected Heliconiidse so successfully, in coh^-ation, form and
flight, that while other PieridcC are preyed upon by many foes,
the mimicking species tend to escape attack.

The family Heliconiid?e, referred to by Bates, C(Mn])rised
what are now known as the sul)families Ileliconiina-, Jtho-
miinre and DanaiucC ; similarly, Pierid-e and Papilionid;c are
16

2 26 ENTOMOLOGY

now often termed respectively Pierina; and PapilioniiicT.
Ithomiinre are mimicked also by Papilionina; and by moths of
the families CastniidcT and Pericopidje.

The discoveries of Bates in tropical South America were
paralleled and supported Ijy those of Wallace in India and the
Malay Archipelago (where Danainre are the chief "models"),
and of Trimen in South Africa (where AcrcTiucT and Danainre
serve as models). Trimen discovered a most remarkable case,
in which three species of Danainre are mimicked, each by a
distinct varietv of the female of Paj^ilio iiicropc (Frontispiece,
Figs. 5-1 1).

So much for that kind of mimicry — but how is the following
kind to be explained? The Ithomiinre of the Amazon valley
have the same form and coloration as the Heliconiinse (Frontis-
piece, Figs. I, 4), l)ut the Ithomiinre 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 sig'nals
instead of two. This is the essence of Aliiller's famous expla-
nation, 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 coun-
terfeiting the appearance of an inedible species; (2) that ob-
served by Bates and interpreted l)y jMiiller, in which both
species are inedible. These two kinds are known respectively
as Batesian and ]\Iullerian mimicry, though some writers prefer
to limit the term mimicry to the Batesian type.

Wallace's Rules. — The chief conditions under which mimi-
cry occurs have been stated by Wallace as follows :

'' I. 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 indi-
viduals.

" 4. That the imitators differ from the bulk of their allies.

" 5. That the imitation, however minute, is external and

ADAPTIVE COLORATION 2 2/

visible only, never extending to internal characters or to such
as do not affect the external appearance."

These rules relate chiehy to the Batesian form of mimicry
and need to be altered to apply to the jNIiillerian 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 Nymphalidae diverge from their relatives to mimic
the EuploeincT, 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 species may have arrived at a general resemblance to
another group without having as yet acc|uired a likeness to
any particular species of the group, the general likeness mean-
while being profitable.

The second condition named by Wallace is correct for
Batesian but not for INIiillerian mimicry.

The fulfilment uf 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 numliers. 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 e\ent, the consequent extra destruction of the
mimic would — at least theoretically — reduce its numbers back
to the point of protection.

In ^Miillerian mimicry, however, the inevital)le \ariation in
abundance of two or more converging and protected species is
far less disastrous ; though when two species, equally distaste-
ful, are involved, the rarer of the two has the advantage, as
Fritz Miiller has shown. His lucid explanation is essentially
as follows :

Suppose that the birds of a region have to destroy 1.200

228 ENTOMOLOGY

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 pro-
portion 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 I to 5, the relative advantage from their resemblance is as
25 to I.

If two or more distasteful species are equally numerous,
their resemblance to one another brings nearly equal advan-
tages. In cases of this kind — and many are known — it is
sometimes impossible to distinguish between model and mimic,
as all the participants seem to have converged toward a com-
mon protective appearance, through an interchange of features
— the " reciprocal mimicry " of Dr. Dixey.

From this explanation, the superior value of Miillerian as
compared with Batesian mimicry is evident.

The fourth condition — that the imitators differ from the
bulk of their allies — holds true to such a degree that even the
two sexes of the same species may differ extremely in colora-
tion, owing to the fact that the female has assumed the like-
ness of some other and protected species. The female of
Papilio luerope. indeed, occurs (as was just mentioned) under
three varieties, which mimic respectively three entirely dissim-
ilar species of Danainn?, and none of the females are any-
thing like their male in coloration (Frontispiece, Figs. 5-1 1).
The specific identity of these four South African varieties of
merope has been established by Trimen, Marshall and other
investigators.

The generally accepted explanation for these remarkable
but numerous cases in which the female alone is mimetic, is
that the female, burdened with eggs and consequently sluggish
in flight and much exposed to attack, is benefited by imitating

ADAPTIVE COLORATION 229

a species which is immune; while llie 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 external and
visible usually, and never extends to internal characters zvhich
do not affect the external appearance." For, as Poulton
points out, the alertness of a beetle which mimics a wasp,
implies appropriate changes in the nervous and muscular sys-
tems. In its intent, however, A\"allace'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 resemblance between caddis flies and moths is mimicry;
wdien 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 like-
ness expresses, then, not mimicry, but afiinity and parallel
development. The same objection applies to the assumed
cases of mimicry within the limits of a single family, as be-
tween two genera of Heliconiidce or between the chrysomelid
genera Lema and Diabrotica. The nearer two species are
related to each other, the more probable

P IG

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

..^. . . . .. A locustid, Mvrinc-

different orders that it cannot be attrib- cophana faiia.v, which
uted to affinity. Illustrations of this are '^^se-^b'es an am. Twice

•' natural length. From

the mimicry of the honey bee by the brunner von wat-

1 n ' 1 1 1 ' • ' • TENWYL.

drone ny, and the many other instances m

which stinging Hymenoptera are counterfeited by harmless
flies or beetles. A locustid of the Soudan resembles an ant
(Fig. 245), and the resemblance, by the way, is ol)tained in a
most remarkable manner. Upon the stout body of this or-
thopteron the abdomen of an ant is delineated in black, the rest

230 ENTOMOLOGY

of the body being' light in color and inconspicuous by contrast
with the black. Indeed the various means by which a super-
ficial resemJ^lance is brought about between remotely related
insects are often extraordinary.

Irrespective of affinity, insects of diverse orders may con-
verge in wholesale numbers toward a central protected form.
The most complete examples of this have recently 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 g^enus Lyais are imitated by nearly
forty species of other genera — a remarkable example of con-
verg'ence involving no less than eighteen families and five or-
ders, namely, Coleoptera, Hymenoptera, Hemiptera, Lepidop-
tera 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 Muller-
ian mimicry on an immense scale ; and if Miillerian mimicry
is profitable when only two species are concerned, what an
enormous l)enefit 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. Un-
til the last few years, however, there was altogether too little
positive evidence bearing upon the assumption itself, though
this was supported by such scattered observations as were
available. The oft-repeated assertion that this lack of evi-
dence 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 recjuisite amount of attention.

Erom his observations and experiments in India, Frank
Einn concludes :

" I. That there is a general appetite for butterflies among
insectivorous birds, even though they are rarely seen when
wild to attack them.

ADAPTIVE COLORATION 23 I

" 2. That many, probaljly most species, dislike, if not in-
tensely, at any rate in comparison with other bntterflies, the
warningly-colored Danain^e, Acrcca violce, Delias eiicharis, and
Papilio aristolochicc; of these the last being the most distaste-
ful, and the Danainre 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 theory 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 mam-
mal used). Professor Poulton's sug'gestion that animals may
be forced by hunger to eat unpalatable 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 ene-
mies, 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 investi-
gators have found that birds are to l)e counted as the principal
enemies of butterflies ; that the Danainje and Acr^einae, which
are noted as models, are particularly immune from destruc-
tion, while unprotected forms suffer; and that mimicking,
though palatable species, share the freedom of their models.
The same is true of beetles, of which Coccinellida?, Alala-
codermidje (notably Lycus), Cantharidx and many Chryso-
melidai 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

232 ENTOMOLOGY

place the theory of Batesian and Miillerian mimicry upon a
substantial foundation of observational and experimental
evidence.

In regard to the important question — do birds avoid un-
palatable insects instinctively or only as the result of experi-
ence — the evidence is all one way. Several investigators, in-
cluding Lloyd Morgan, have found that newly-hatched birds
have no instinctive aversions as regards food, but test every-
thing, 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 j\Kil-
lerian theory — upon a sound basis.

Though butterflies as a group are much subject to the at-
tacks of Ijirds in the tropics, there are very few recorded in-
stances of this for our temperate region. It may then be
asked, what advantage does the "viceroy " (Fig. 243, B) gain
by resembling the " monarch," in a region where all butter-
flies are exempt from destruction by birds? In reply, it may
be said that the premise of the argument is as yet little more
than an assumption, because so little attention has been given
to the relations between birds and butterflies in our own coun-
try. Or, admitting the premise, it may be said that the resem-
blance was advantageous once, if not now ; and that in any
event, the departure of arcliippus from its congeners toward
one of the Danaina; — 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 ex-
tends; and we find that mimicry is not of universal efl:'ective-
ness. Even the highly protected Heliconiina? and Danainai
are food for some predaceous insects. In this country, as
Judd has observed, the drone-fly (Eristalis fciia.v), which
mimics the honey bee, is eaten by the kingbird and the phoebe ;
the kingbird, indeed, eats the honey bee itself, but is said to

ADAPTIVE COLORATION 233

pick out the drones; chickens also discriminate l)et\veen drones
and workers, eating' the former and avoiding" the latter. Bum-
ble bees and wasps, imitated by many other insects, are them-
selves eaten by the kingbird, catljird and several other l)irds.
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 thcorv of mimicry but point out its limits.

Evolution of Mimicry. — Natural selection gives an adequate
explanation of the evolution of a mimetic pattern. Before
accepting this explanation, however, we must inquire : ( i )
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 demands that it
should be ? These pertinent questions have been answered by
Darwin, Wallace, Midler, Dixey and several other authorities.

The incipient mimic must have possessed, to begin with, col-
ors 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 heliconids.
More than this, however, Dixey has demonstrated — as appears
clearly from his colored figures — a complete and gradual tran-
sition from a typical non-mimetic pierid, Pieris locnsta, to the
mimetic pierid Mylothris pyrrha, the female of wdiich imitates
Heliconms nnrnata. 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 sur-
face of the males [compare Figs. 2 and 3 of Frontispiece] en-
able us to trace the history of the growth of the mimetic pat-
tern." Starting from Pieris locnsta, it is an easy step to
Mylothris lypera, thence to M. lorena, and from this to the
mimetic ^L pyrrJia. " Granted a beginning, however small,

234 ENTOMOLOGY

such as the l^asal red touches in the normal Pierines, an elabo-
rate 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 pat-
terns has — at least occasionally — been sufficiently suggestive
of the heliconid type to preserve the life of its possessor; espe-
ciallv 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 explana-
tion should 1)e tested as far as possi1)le by observations in the
field and Ijy experiments as well.

Adaptive Colors in General. — Several classes of adaptive
colors have been discriminated and defined by Poulton, whose
classification, necessarily somewhat arbitrary but nevertheless
very useful, is given below, in its abridged form.

I. APATETIC COLORS. — Colors resembling some part of the en-
vironment or the appearance of another species.

A. Cryptic Colors. — Protective and Aggressive Resemblances.

1. Procryptic colors. — Protective Resemblances. — Conceal-

ment as a protection against enemies. Example : Kal-
lima butterfly.

2. Aiiticryptic colors. — Aggressive Resemblances. — Conceal-

ment in order to facilitate attack. Example : Mantids
with leaf-like appendages.

B. PsEUDOSEMATic CoLORS. — False warning and signalling colors.

1. Pscndaposcmatic colors. — Protective Mimicry. Example:

Bee-like fly.

2. Pscudcpiscmatic colors. — Aggressive Mimicry and Allur-

ing Coloration. Examples: J^iliicclla, resembling bees
(Fig. 246); Flower-like mantid.
II. SEMATIC COLORS.— Warning and Signalling Colors.

1. Aposcinatic colors. — Warning Colors. Examples: Gaudy

colors of stinging insects.

2. Episcmatic colors. — Recognition IMarkings.

III. EPIGA^IIC COLORS.— Colors Displayed in Courtship.

Such of these classes as have not already been discussed
need brief reference.

ADAPTIVE COLORATION
Fig. 246.

235

Aggressive mimicry. On the left, a bee, Bombus iiiastyucaliis^
Volucclla bombylnns. Natural size.

in the right, a fly.

Aggressive Resemblances. — The resemblance of a car-
ni\'oroiis animal to its surroundings may not only be protec-
tive but may also 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 Volucclla, whose larvcT feed upon those of bumble bees
and wasps. The flies bear a close resemblance to the bees,
owing to which it is supposed that the former are able to enter
the nests of the latter and lav their eggs.

Alluring Coloration. — The best example of this phenom-
enon is aft'orded by an Indian mantid, Gongyhis gongyloidcs,
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 im-
portant among mammals and birds, as enabling indix'iduals of
the same species cjuickly to recognize and follow one another,
no special markings for this purpose are known to occur among
insects, not excepting the greg"arious migrant species, such as
Anosia plcvippus and the Rocky Mountain locust.

Epigamic Colors. — Among birds, frecjuently, the bright col-
ors of the male are displayed during courtship, and their evo-

236 ENTOMOLOGY

Intion has been attributed by Darwin and many of his follow-
ers to sexual selection — a highly debatable subject. Among
insects, however, no such phenomenon has been found ; when-
ever 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 re-
stricted to the preservation and accumulation of such advan-
tageous variations as may arise, from wdiatever causes. As
Poulton says, the vast body of facts, utterly meaningless 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

ORIGIN OF ADAPTATIONS AND OF SPECIES

I. Adaptations

Organic Evolution. — Organic evolution is essentially the
evolution of adaptive structures and functions. There remain
to be explained, however, non-adaptive structures and func-
tions, and no theory of evolution is adequate which does not
account for the useless as well as the useful characters.

Existing structures are due to the nature of the organism
and the nature of the environment ; in other words, are results
of the activity of protoplasm under the influence of environ-
mental forces. Variations arise which are useful or not and
either transmissible or not. E'seful transmissible variations
not only remain but tend to become more nearly perfect; while
useless variations tend to disappear.

The various theories of organic evolution difTer chiefly in
their answers to these questions: (i) What is the nature of
variations and how do they arise? Variations are classed as
either continuous or discontinuous; adaptive or unadaptive.
In asexual organisms, variations are brought about by the
direct influejice of temperature, light and otlier primary fac-
tors upon protoplasm; in sexual organisms, variations are due
to another cause as well, namely, the union of two kinds of
protoplasm. In any given case of variation, how much is due
immediately to protoplasm and how much to the environment?
(2) What kinds of \'ariations are transmissible? Discontinu-
ous variations (sports) are strongly transmissible as a rule,
while continuous (individual) variations are often non-trans-
missible; though it is often difficult to decide whether they are
transmissible or not. Each kind of variation has to be exam-
ined separately, on its own merits. DilTicidties arise from the

237

238 ENTOMOLOGY

fact that some variations which appear in successive genera-
tions are due not to inheritance hut to the chrect action of the
environment on each successive generation ; also to the fact
that some structural changes may have heen brought about by
selection of some sort, rather than l\v inheritance. Are the
results of use or disuse or mutilation inheritable? It has not
been proved as yet that these " acquired characters " are
transmissible. On the other hand, experiments show that
some organisms can become acclimatized to unusual degrees
of heat, density, etc., through inheritance, in cases where selec-
tion does not enter into the problem. Much of the confusion
attending the discussion of " the inheritance of acquired char-
acters " has l)een due to disag'reements as to what is meant by
the term "acquired characters." (3) What are the secondary
influences that have brought about the evolution of structures?
Of these influences, natural selection and isr)lation are by far
the most important; while in some instances extensive struc-
tural adaptations have arisen spontaneously, without a long
course of evolution.

Natural Selection. — The more intricate adaptations of
organism to environment, however, are for the most part inex-
plicable without the aid of Darwin's and Wallace's theory of
natural selection. After almost fifty years of searching criti-
cism and even violent opposition, this theory, though modified
in some respects, remains essentially as it was formulated, and
is at present the working hypothesis of most naturalists. This
doctrine is here outlined in its several factors.

Excessive Multiplication. — Any one species of animal or
plant, were its multiplication unchecked, would soon cover the
earth. The progeny of a single aphid in ten generations, as
calculated by Huxley, would " contain more ponderable sulv
stance than five hundred millions of stout men ; that is, more
than the wdiole population of China." The hop aphid (Phor-
odon lumiuli). studied by Riley, has thirteen generations a
3^ear, consisting entirely of females up to the last generation.
Assuming that each female produces 100 voung- and that the

ORIGIN OF ADAPTATIONS AND OF SPECIES 239

increase is unchecked, the number of individuals of the twelfth
generation, as the descendants of a single female of the first
generation, would be ten sextillions. These if placed in a
singie file, allowing lo aphids to an inch, would form a line so
long that light itself, traveling at the rate of 186,000 miles
per second, would require over 2,690 years to go from one
end of the line to the other.

As it is, many species become temporarily dominant under
favorable conditions ; for example, the Rocky Mountain locust,
chinch bug and gypsy moth. Even one of the least prolific
species would predominate in a surprisingly short time, were
it permitted to increase in its normal geometrical ratio. The
rate of sexual reproduction is highest in fishes and insects. An
insect averages one or two hundred eggs, while some forms,
as cjueen termites, lay them by thousands.

Struggle for Existence. — Although a single species is
potentially capable of covering the earth, there actually are at
least 1,000,000 species of insects, not to mention 250,000 spe-
cies of other animals and some 500,000 kinds of plants. This
means a tremendous prevention of reproduction among the
individuals of any one species — an intense " struggle for ex-
istence," as Darwin termed it. Among plants and the lower
animals, comparatively few individuals survive and reproduce ;
the majority die. The agents of destruction are manifold,
each species having its own army of enemies, organic and in-
organic. Thus insects are subject to unfavorable conditions
of temperature and moisture, to bacterial and fungous dis-
eases, vertebrate and invertebrate enemies, accidents, etc.
The aphids are at the same time among the most prolific and
the most defenceless of animals. These delicate insects suc-
cumb to very slight mechanical shocks and are killed by ex-
tremes of temperature that most other insects can endure.
They are often w^ashed off their food plants by rain. Their
rate of reproduction decreases if their food plant rccei\es in-
sufficient moisture. .Aphids form the chief food of coccinellid
larvae and beetles, are preyed upon by chrysopid and syr])hi(l

240 ENTOMOLOGY

larvcT, parasitized bv Braconidre and Chalcididre, carried off
by some of the digger-wasps (Mimesida?, Pemphrcdonidje) ,
and devoured by ants, carabids, other insects, spiders, and some
birds, as the chickadee. In damp weather, aphids are kihed
in countless numbers by a fungous disease. In short, the
aphid is threatened in every direction.

Elimination of the Unfit. — In the intense " struggle for
existence," as it is commonly, though misleadingly, called,
those comparatively few individuals that survive do so mani-
festly by virtue of certain advantages over their less fortunate
fellows. One egg can stand a little more cold than another;
one beetle drops to the ground when disturbed and thus
escapes an attacking bird, while its companions remain in place
and are destroyed ; some individuals escape by surpassing their
fellows in locomotor ability or by resembling the surface on
which they happen to rest.

Such fortunate individuals live to transmit their advantage-
ous peculiarities to their progeny, while the less favored indi-
viduals succumb. The progeny inherit the life-saving pecu-
liarities in dift'ering degrees, and the least favored of the
progeny are again weeded out. Thus by the continual elim-
ination of individuals that vary in unfavorable directions, the
individuals that remain become better and better adapted to
the surrounding conditions of life, through the preservation
and accumulation of advantageous variations. This preser-
vation and accumulation of advantageous variations through
the destruction of disadvantageous ones is the essence of nat-
ural selection, or the " survival of the fittest."

Favorable variations may have been so slight and infre-
quent as to have required geological ages for their accumula-
tion. On the other hand, adaptive variations are sometimes
so extensive from the beginning as to lead some writers to
doubt that these variations are preserved and improved by
natural selection.

Variation. — Natural selection cannot originate useful char-
acters, of course, but is limited to the preservation and accu-

ORIGIN OF ADAPTATIONS AND OF SPECIES 24 1

miilation of such advantageous variations as already exist.
Variation, then, is the basis of natural selection. Though the
question of the origin of variations is still unsettled, the fact
of their occurrence in a manner sufficient for the purposes of
natural selection is beyond dispute. Xo two individuals of a
species are ever exactly alike in structure or behavior, and
their differences furnish the material for the operation of
natural selection.

Two classes of variations are distinguished on the basis of
the amount of variation: (i) continuous (indiz'idual) varia-
tions, of small extent, intergrading with one another and with
the typical form; and (2) discontinuous variations (sports),
or considerable and isolated departures from the normal con-
dition. Furthermore, variations of either class are adaptive
or unadaptive, the latter kind being either harmful or simply
neutral.

Origin of Adaptive Variations. — Natural selection, as
was said, does not begin to- operate until useful variations are
already in existence; and the origin of these primary adaptive
variations is a c|uestion quite distinct from that of their sub-
sequent preservation and accumulation by natural selection.

That all adaptive variations are due to the response of pro-
toplasm to environmental influences (using the term " envi-
ronment " in its widest sense), it goes without saying. These
variations are, however, either direct or indirect. Direct
variations, appearing first in the soma, or body, of the organ-
ism, are termed somatogenic; indirect variations, apparently
spontaneous, and due immediately to the germ cells, arc termed
hlastogenic. Weismann places somatogenic variations, ac-
cording to their origin, into three categories: (i) injuries,
(2) functional variations, and (3) variations depending on
the so-called " influences of environment," these influences
being mainly climatic. These three kinds will receive brief
consideration.

Injuries. — There appears to be no good e\i(lcncc that in-
juries or mutilations can l)e transmitted. Xearly all the ex-
17

242 ENTOMOLOGY

periments upon the subject have given decidedly negative
resuhs. Thus Weismann found that the amputation of the
tails of hundreds of mice, down to the nineteenth generation,
had no influence on the tails of the descendants.

Mechanical injuries to the body of an organism are merely
casual, or accidental, effects of the environment and appear to
have no influence upon the germ cells. From the standpoint
of adaptation, injuries are only of minor importance.

Functional Variations. — \Adiile it is certain that the use
or disuse of organs affects their form in the individual, it
remains doubtful whether the effects of use and disuse are
transmissible. Weismann and his followers contend that they
are not. On the other hand, Neo-Lamarckians, as Cope,
Hyatt, H. F. Osborn, Packard and Eimer, have maintained
that they are. Weismann admits, however, that both use and
disuse may lead indirectly to variations, " the former wdien-
ever an increase as regards the character concerned is useful,
and the latter in all cases in which an organ is no longer of
any importance in the preservation of the species " ; and that
these variations may be acted upon by natural selection.
Thus, in a few words, the cjuestion stands.

Environmental Variations. — Under this head may be
classed such variations as are due directly to climate, nutrition
and other primary environmental inlluences. It is certain
that changes of temperature, light, and food, for example,
cause corresponding changes of form and function in the indi-
vidual organism ; though the inheritance of these changes
directly induced l)y the environment is the subject of much
debate.

Dallinger took flagellate infusorians that at first would die
at a temperature of 23° C, and by slowly raising the tempera-
ture through several years, broug"ht them safely to a tempera-
ture of 70'' C. There was some mortality, to be sure, in his
experiments, but other experimenters have obtained similar
results without the loss of a single individual, and therefore —
it is important to note — without the entrance of natural selec-

ORIGIN OF ADAPTATIONS AND OF SPECIES 243

tion. This progressive acclimatization of successive genera-
tions of an organism to heat is clearly due in large measure to
heredity. So also in the case of the entomostracan Artciuia,
whose specific form Schmankewitsch succeeded in changing,
by increasing the salinity of the water in which the animal
lived. Here, again, the adaptation was brought about with-
out the aid of selection.

Poulton's already-mentioned experiments on larva; and
pupae show that these may become protectively colored as the
direct effect of the surrounding light on the organism. Here,
of course, the possible influence of natural selection can scarcely
be excluded, though the fact remains that the color resem-
blances are initiated directly by the stimulus of light upon
protoplasm.

Protoplasm itself is to a certain extent adaptive, in that it
may become acclimatized to untoward conditions of heat, light
and other stimuli. From this point of view, Henslow's theory
of self-adaptation in plants deserves more consideration than
it has received, though Henslow did not adopt the theory of
natural selection.

Blastogenic Variations. — According to Weismann, only
congenital variations are inheritable, i. e.,only those that result
from modifications of the germ plasm. He holds that while
all variations are due ultimately to external influences, the
processes of reproduction (conjugation in unicellular, and
sexual reproduction in multicellular organisms) furnish fresh
combinations of individual \ariations for the operation of nat-
ural selection, and that this is the chief purpose of amphimixis,
or " the mingling of two individuals or of their germs."

Inheritance of Acquired Characters. — Weismann and his
followers, in opposition to the Neo-Lamarckians, hold that
somatogenic, or acquired, characters are not transmissible;
that every permanent (hereditary) variation proceeds from
the germ.

The subject of the inheritance of acquired characters has
aroused no end of discussion, much of which has been fruit-

244 ENTOMOLOGY

less, chiefly for two reasons. First, there is no httle disagree-
ment as to what is meant by the term " acquired characters."
An acquired character arises, not in the germ cells, but in the
soma, or body, and for the theoretical transmission of the
character the soma must affect the germ cells subsequently ;
though some maintain that a given external influence may
affect both soma and germ plasm at the same time. The defi-
nition of acquired characters excludes (i) sports; (2) changes
due to the renewed action of the environment upon successive
generations" of an organism; (3) changes which may have
been due to selection. Second, having defined the term, it is
often difficult if not impossible to say whether a given charac-
ter is acquired or not. Thus in an acclimatization experiment,
if heat, for example, affects first the soma and the latter affects
the germ cells subsequently, we have an example of the inheri-
tance of an acquired character. If, however, the heat aft'ects
soma and germ plasm simultaneously, the result is or is not
the inheritance of an acquired character, according as one de-
fines the term. Indeed, Weismann himself has found the
greatest difficulty in trying to explain the inheritance of " cli-
matic " variations in terms of his well-known hypothesis. In
fact, the distinction between acquired and non-acquired charac-
ters is to no little extent artificial and arbitrary ; and too strong
an insistence upon the distinction bars the way to the solution
of the more important question — What kinds of variations are
inheritable and what are not ?

To summarize: Of somatogenic, or acquired, characters,
(i) injuries or mutilations are unadaptive and probably unin-
heritable. (2) Functional variations are adaptive, but the
subject of their transmissibility is involved in doubt. As yet
there is no adequate experimental evidence upon the subject,
the discussion of which, therefore, is based chiefly on theoret-
ical grounds. There is a strong tendency, however, to believe
that results of use or disuse are to some extent transmissible
to the benefit of succeeding generations, and even Weismann,
the chief opponent of the Neo-Lamarckians, admits that the

ORIGIN OF ADAPTATIONS AND OF SPECIES 245

effects of use and disuse are important in organic evolution.
(3) Effects of climatal influences and of nutrition are fre-
quently adaptive and often transmissible, as experiments have
proved. There is. however, much difference of opinion as to
the precise way in which these effects are transmitted.

Incidental Adaptations. — Many leaf-eating caterpillars
and grasshoppers are green from the presence of chlorophyll
in their bodies; they owe their color directly to their food.
Now it may be admitted that this green color is often protec-
tive, without admitting that the color was acquired for that
purpose. In the case of green leaf-mining caterpillars, cer-
tainly, the color appears to be superfluous for protective pur-
poses. Even variegated protective coloration may be simply
a direct effect of the surrounding kinds of light, as Poulton
proved.

Again, take the various tropisnis, described in another
chapter. Often they are adaptive and often they are not; but
they occur inevitably, whether they result advantageously or
not. It is too much to say that a useful structure or function
appeared because of its usefulness. It first appeared, and then
proved to be either useful or not useful. If useful, a structure
may save the life of its possessor and possibly be transmitted to
the next generation; if harmful, it is self-eliminating.

2. Species

Modifications arise, and are either useful or not to their
possessors. For the systematist who aims merely to distin-
guish one species from another, this distinction matters but
little. To the biologist, however, the dift'erence is an essential
one, and he draws a line between specific peculiarities that are
adaptive and those that are not adaptive. The origin of
species and the origin of adaptations are by no means the
same thing.

Darwin's Origin of Species. — At the time Darwin's great
work was written, its immediate purpose was to demonstrate
a process of organic evolution : and this object was accom-

246 ENTOMOLOGY

plished in the most forcible way, namely, by shattering the
traditional belief in the immutability of species. Nowhere
does Darwin imply that nature is striving to produce " spe-
cies " for their own sake. A process of evolution was the
theme of Darwin and its key-note was adaptation.

Indeed, for the purposes of the present generation, Dar-
win's immortal work w^ould more properly be entitled — The
Evolution of Adaptations by Means of Natural Selection.
And to us, who now ridicule the old notion of the special
creation of species, the doctrine of natural selection appears in
a fresh light, with a new mission. For, in the words of
Romanes, the theory is " primarily, a theory of adaptations,
and only becomes secondarily a theory of species in those com-
paratively insignificant cases wdiere the adaptations happen to
be distinctive of the lowest order of taxonomic division."
The opposite view he compares " to that of an astronomer who
should define the nebular hypothesis as a theory of the origin
of Saturn's ring's. It is indeed a theory of the origin of
Saturn's rings ; but only because it is a theory of the origin of
the entire solar system, of which Saturn's rings form a part.
Similarly, the theory of natural selection is a theory of the
entire system of organic nature in respect of adaptations,
whether these happen to be distinctive of particular species
only, or are common to any number of species." It should he
remembered, of course, in using this comparison, that not all
specific characters are adaptive.

As reg"ards the origin of species, however, there are several
processes at work besides natural selection. Indeed, Darwin
himself knew this, for he expressly stated : " I am convinced
that natural selection has been the most important, but not the
exclusive, means of modification."

The Conception of " Species." — ^What is a " species " ?
The only practical criterion of species is isolation, or separate-
ness, of one kind or another. The majority of our " species "
are sharply separated from one another by structural dift'er-
ences ; the minoritv, however, blend into one another, and

ORIGIN OF ADAPTATIONS AND OF SPECIES 247

have so many characters in common that the separation into
species hecomes an arl)itrary matter, depending- upon the ^c^ood
Judgment of the systematist, who if wise, is neither a
'' lumper " nor a " sphtter." At present, the minutely dis-
criminating powers of an unfortunately large numljer of ento-
mological systematists are displayed in an extraordinary mul-
tiplication of generic and specific names, often to the sacrifice
of convenience and stability of nomenclature. This has been
carried to such an extent, however, that a reaction has already
set in, and there is now some promise of a rational termi-
nolog}^

Considering characters as of specific importance only, it
makes no immediate difference whether they are adaptive or
not. If adaptive, whatever their origin, they may have been
developed by natural selection; if not, they are incidental, and
mav be due to such iniluences as those next to be referred to.

Climate and Food. — Naturalists have recorded many in-
stances in which plants or animals when transferred to a new
climate ha^■e produced offspring markedly different from the
parent form. The term climate, however, has no precise
meaning for the naturalist, referring as it does collectively to
several distinct influences, chief among which are tempera-
ture, moisture, light and (indirectly) food conditions. Ex-
perimental evidence has already been adduced to show that
color changes in insects may be brought about as direct effects
of warmth, cold, light or food. Some of these color varia-
tions are possibly inheritable, and many of them, artificially
produced, would be regarded as distinctive of new species, if
found in a state of nature. In fact, the distinction between
varieties and species is often entirely arbitrary; varieties are
incipient species and it is often impossible to draw any sharp
line between the two.

Mutation Theory. — De \"ries' iiiufafioii theory, expounded
in 1901 as the result of nearly twenty years of experimenta-
tion, is at present an absorbing sul)ject of study and discussion
in the biological world, and will continue to be for many years,
until the full bearing of the theory is ascertained.

24S ENTOMOLOGY

De Vries has produced new species by experimental means
and without the aid of selection. ]\Ioreover. he has produced
them at once, showing that a species does not necessarily re-
quire hundreds of years to develop, by means of a long-con-
tinued process of selection.

It has long been customary to draw a distinction between
individual variations and sports. Darwin recognized the dis-
tinction and was one of the first to notice the extraordinary
persistence with which sports are transmitted, as compared
with the relative instability of individual variations. Not a
few dominant races of plants and animals are known to have
arisen from sports, and the belief has been gaining ground
with Bateson and others that species also have to some extent
arisen from sports, rather than from individual variations ;
though the rarity of sports as compared with individual varia-
tions is the strongest objection to this theory as a theory of
the origin of species in general.

De Vries, however, was the first to make extensive experi-
ments on sports, or mutations, as he calls them, and to formu-
late a definite theory of the subject from a considerable body
of evidence. He regards the cjualities of organisms as being
built up of definite but sharply separated units, or elements,
which combine in groups. The addition of a new unit means
a mutation, a sudden departure from the normal specific form:
in other words, a new species may arise from the parent form
without any evident gradation. The mutaljle condition exists
onlv at times, and some species are more mutaljle than others.
Acting upon this as a hypothesis, De Vries made a preliminary
study of a great number of plants in order to find one in its
period of mutation, and at length selected CEiiothcra Laniarck-
iana (probably a variety of our E. biennis, introduced into
Holland from America), because of its exceptionally vigorous
multiplication, dispersion and variation. By careful cultivation
and by means of artificial pollination, he succeeded in obtaining
seven or more new species. ]\b)St of these remained con-
stant from year to year in spite of intercrossing. Moreover,

ORIGIN OF ADAPTATIONS AND OF SPECIES 249

cross pollination was not necessary to the prodnction of new
species by mutation, and when employed did not accelerate the
results materially. As a botanist, De Vries confined his inves-
tigations to plants, but his g"eneral conclusions are perhaps
equally applicable to animals, and his experiments are doubt-
less being- repeated by zoologists.

Through his exhaustive experiments, De Vries has partly
attained a long-desired object, in that he has removed the ques-
tion of the origin of some species " from the purely theoretical
to the concrete.''

The mutation theory is not primarily a theory of the origin
of adaptive characters. It endeavors to account for the origin
of certain characters, which may or may not prove useful to
their possessors. Indeed, one great merit of De Vries' theory
is that it afTords an explanation for the existence of variations
which are not useful. Now Darwin does not pretend to
account for the origin of variations, but he shows how given
variations, if useful, may be preserved and accumulated.
Thus the theory of De Vries supplements that of Darwin and
does not antagonize it ; even though De Vries himself takes
much pains to contrast the two theories, and even asserts that
new species arise exclusively as mutations. Both theories,
indeed, are theories of the origin of species ; but according to
De A'ries, specific characters spring into existence, irrespective of
their usefulness; while according to Darwin, useful characters,
and these only, are premised , as the starting point of the evolu-
tion of certain kinds of species. Thus, as another has said,
natural selection begins where the mutation theory lea\-es off.

Isolation. — The theory of isolation as given by Gulick and
by Romanes is highly important as affording an explanation
of " the rise and continuance of specific characters which need
not necessarily be adapti^■e characters." By isolation is meant
" simply the prevention of intercrossing- between a separated
section of a species or kind and the rest of that species or
kind. ... So long as there is free intercrossing, heredity
cancels \-arial)ility, and makes in fa\<)r of fixity of type. Only

250 ENTOMOLOGY

when assisted by some form of discriminate isolation, which
determines the exckisive breeding of hke with hke, can hered-
ity make in favour of change of type, or lead to what we un-
derstand by organic e\'o]ution." (Romanes.)

" As soon as a portion of a species is separated from the
rest of that species, so that breeding" between the two portions
is no longer possible, the general average of characters in the
separated portion not being in all respects precisely the same
as it is in the other portion, the result of in-breeding among
all individuals of the separated portion will eventually be dif-
ferent from that which obtains in the other portion; so that,
after a number of generations, the separated portion may
become a distinct species from the etTect of isolation alone.
Even wdthout the aid of isolation, any original difference of
average characters may become, as it were, magnified in suc-
cessive generations, provided that the divergence is not harm-
ful to the individuals presenting it, and that it occurs in a
sufficient proportional number of indi\iduals not to l)e imme-
diately swamped by intercrossing." ( Romanes.)

Of the many modes of isolation, the most important are the
gcogmpJiical and the pJiysiological, both of which hav^ re-
ceived elalwrate treatment by Romanes.

The doctrine of geographical isolation offers a partial ex-
planation of the origin of the peculiar faun;e and ilorx of
remote islands. These island species, however peculiar,
doubtless came originally from the mainlands where their
nearest allies now occur; thus the endemic insects of the Gala-
pagos Islands are niost nearly related to species of western
South America.

The first individuals of Schistoccrca doubtless reached the
Galapagos Islands by means of the wind or on driftwood.
These individuals, separated from the main body of their spe-
cies, would interl)reed and might therebv give rise to a new
variety or species, if we may assume that the average of charac-
ters of the detached portion of the species differed from that
of the main body of individuals; in other words, that the iso-

ORIGIN OF ADAPTATIONS AND OF SPECIES 25 I

lated forms \-aried around a mean condition of their own, and
no longer around the mean of the species as a whole.

Besides this, the intiuences of new food and new climatal con-
ditions as means of modification must be taken into account.
Furthermore, though a new species might conceivably arise on
an island without the aid of natural selection, it is very likely
that selection has often played a part in the formation of such
a species, as in the apterous or subapterous forms that pre-
dominate on oceanic islands. While it is possible that the
earliest arrivals were already apterous, and arrived safely be-
cause on that account they clung to driftwood instead of flying
away, it is probable, on the other hand, that on wind-swept
islands the full-winged and more venturesome individuals
w^ould be carried out to sea and drowned, leaving the poorly
winged and less venturesome ones to remain and transmit
their own life-saving peculiarities; which would Ijecome inten-
sified by continual selection of the same kind. Romanes, in-
deed, regards natural selection itself as but one form of iso-
lation.

Physiological isolation, which though important will not be
discussed here, " arises in consequence of mutual infertility
between the members of any group of organisms and those of
all other similarly isolated groups occupying simultaneously
the same area." (Romanes.)

CHAPTER \'III

INSECTS IX RELATION TO PLANTS

Insects, in common with other animals, depend for food
primarily upon the plant world. Xo other animals, however,
sustain such intimate and complex relations to plants as in-
sects do. The more luxuriant and varied the tlora. the more
abundant and diversified is its accompanying; insect fauna.

Xot only ha\'e 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 ^■arious
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 un-
der contribution, the latter ha^"e not only vigorously sustained
the attack but have even pressed the enemy into their own ser-
vice, as it were.

Numerical Relations. — The numljer of insect species sup-
ported by one kind of plant is seldom small and often surpris-
ingly large. The poison ivy (Rhus toxicodendron) is almost
exempt from attack, though exen this plant is eaten by a leaf-
mining caterpillar, two pyralid larva? and the larva of a scolytid
beetle ( Schwarz, Dyar ) . Horse-chestnut and buckeye have per-
haps a dozen species at most : elm has eighty ; birches have over
one hundred, and so ha\'e luaples ; pines are known to harljor
I/O species and may yield as many more; while our oaks sus-
tain certainly 500 species of insects and probablv twice as many.
Turning to cultivated plants, the clover is affected, directlv or
indirectly, by about 200 species, including" predaceous insects,
parasites, and flower-visitors. Clover grows so vigorouslv that

INSECTS IN RELATION TO PLANTS 253

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 number some 400 species.

Not uncommonly, an insect is restricted to a single species of
plant. Thus the caterpillar of Hcodcs hypophlccas feeds only
on sorrel {Riiniex acctoscUa) , so far as is known. The chry-
somelid Chrysochus auratiis appears to be limited to Indian
hemp (Apocynuiii androsccinifoUiiuiy and to milkweed {As-
clepias) . In many instances, an insect feeds indifferently
upon several species of plants provided these have certain
attributes in common. Thus Argynnis cyhele, aphrodite and
atlantis eat the leaves of various species of violets, and the
Colorado potato beetle eats different species of Solanum.
Papilio thoas feeds upon orange, prickly ash and other Ruta-
cese. Anosia plexippus eats the various species of Asclepias
and also Apocymtm androscEmifoliimi; 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 botanically. The common cab-
bage butterfly {Pier is rapcv) though confined for the most part
to Cruciferae, such as cabbage, mustard, turnip, radish, horse-
radish, etc., often develops upon Tropceoliun, which belongs to
Geraniacere ; all its food plants, however, have a pungent odor,
which is probably the stimulus to oviposition.

Most phytophagous insects, however, 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 (Lygiis pratcnsis) feeds indiffer-
ently on all sorts of herbage, as does also the caterpillar of
Diacrisia virginica. ]\Iany of the insects of apple, pear,
quince, plum, peach, and other plants of the family Rosaceas
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 Mass-
achusetts, according to Forbush and Fernald, it fed in the field

254

ENTOMOLOGY

upon 78 species of plants, in captivity npon 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 unsuit-
able as food. The migratory
locust is notoriously omniv-
orous, and perhaps eats even
more kinds ui plants than the
g}'psy moth.

Galls. — yiost of the conspic-
uous plant outgrowths known
as " galls " are made by in-
sects, though many of the
smaller plant galls are made
by mites ( Acarina) and a few
plant excrescences are due to
nematode worms and to fungi.
Among insects, Cynipidre ( Hy-
menoptera) are pre-eminent
as gall-makers and next to
these, Cecidomyiidre (Diptera),
Aphididae and Psyllidae (Hemiptera) ; a few gall-insects occur

Ft,;. 248.

Holcaspis globulus. A, galls on oak,
natural size; B, the gall-maker, twice
natural length.

MH^^^

Calls of IJoUasfis iliin

among Tenthredinid;c ( Hymenoptera) and Trypeti(l;e (Dip-
tera), and one or two among Coleoptera and Lepidoptera.
Cynipi(ke affect the oaks (Figs. 247, 248) far more often

INSECTS IN RELATION TO PLANTS

255

-'4').

than any other plants, though not a few species select the wild
rose. Cecidomyiid galls occur on a great variety of plants, and
those of aphids on elm (Fig. 249), 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 usuall}^ characteristic, so
that it is often possible to classify
galls as species even before the
gall-maker is known.

Gall-Making. — The female cy-
nipid punctures the plant and lays
an egg in the wound ; the egg
hatches and the surrounding plant
tissue is stimulated to grow rapidly
and abnormally into a gall, which
serves as food for the larva; this
transforms within the gall and es-
capes 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 (le\-elo[)ment 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 l)egin to grow
until the egg has hatched, and then the gall grows along with
the larva ; exceptions to this are found in some Hymenoplera
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

j|H

wLfy

flH

^^^

'^^i.

Cockscomb gall of Colopha iitinicola,
on elm. Slightly reduced.

256 ENTOMOLOGY

and number. Why the gall should have a distinctive, or spe-
cific, form, it is not yet known. There is no evidence that the
form is of any adaptive importance, and the subject probably
admits of a purely mechanical explanation — a problem for the
future.

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 incjuilines are
attacked by parasitic Hymenoptera, making the interrelations
of these insects hard to determine. Many species of insects
feed upon, the substance of galls ; thus Sharp speaks of as
many as thirty different kinds of insects, belonging to nearly
all the orders, as having been reared from a single species of
gall.

Parthenogenesis and Alternation of Generations. — Par-
fhciiogciicsis has long been known to occur among Cynipidre.
It has repeatedly 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 gene-
rations, many other complications occur, making the study of
gall-insects an intricate and highly interesting subject.

Plant-Enemies of Insects. — Most of the floAvering plants
are comparatively 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 catch-
fly (Silcne z'irginica) , which entangles ants and small flies. A
few plants, however, actually feed upon insects themselves.
Thus the species of Drosera. as described in Darwin's classic
volume on insectivorous plants, ha\'e specialized leaves for the

INSECTS IN RELATION TO PLANTS

257

Fi(

250.

purpose of catching- insects. The stout hairs of these leaves
end each in a globular knol), which secretes a sticky fluid.
When a fly alights on one of these lea\'es 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 ^'alves, each of which bears three
trigger-like bristles, and when these are
touched by an insect the valves snap to-
gether and frequently imprison the insect,
which is eventually digested, as Ijefors.
In the common pitcher-plants, the pitcher,
fashioned from a leaf, is lined with down-
ward pointing bristles, which allow an
insect to enter but pre\'ent its escape.
The bottom of the pitcher contains water,
in which may be found the remains
of a great \'ariety of insects which
have drowned. There are even nectar
glands and conspicuous colors, presum-
ably to attract insects into these traps,
where their decomposition products are
more or less useful to the plant. In
Pinguknla the margin of a leaf rolls
over and envelops insects that ha\-e

been caught by the glandular hairs of the upper surface
of the leaf, a copious secretion digests the softer portions of
the insects, and the dissolved nitrogenous matter is absorbed
into the plant. L'triciilaria has little bladders which entrap
small aquatic insects. These plants are only partially dcpend-
18

Fructifying sprouts of
a fungus. Cordyceps rav7-
nclii, arising from the
body of a wliile grub,
Lacliiwstcrna. Slightly

reduced. — After Riley.

258

ENTOMOLOGY

ent on insect-food, li(»\\e\'er, for tliev all possess chlorophyll.

Bacteria cause epidemic diseases among- insects, as in the
flacherie of the silkworm; and fungi of a few gr(^ups are spe-
cially adapted to de\'elop in the bodies of living insects.

Those who rear insects know how- frequently caterpillars and
other larvcC are destroyed l)y fungi that g'ive the insects
a p()\\dered appearance. Idiese fungi, referred to the genus
Isaria, are in some cases known to be asexual stages of forms
of Cordyccps, which fonus ai)pear from the bodies of various
larva?, pup^e and imagines as long, conspicuous, fructifying
sprouts ( Fig. 250).

The chief fung'us parasites of insects belong to the large
familv Entomophth()racecC, represented l)y the common Euij^usa
iniiscic (Fig. 251) wdiich affects various flies. In autumn,

Fig. 251.

■:v5'-.^f{3p&

Empusa musccv, the common fly-funiAus. A. liousc fly {Musca 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 Thaxtf.r.

especially in warm moist weather, the common house fly may
often be seen in a dead or dying condition, sticking to a win-
dow-pane, its abdomen distended and presenting alternate black
and white bands, while around the flv at a little distance is a

INSECTS IN RELATION TO PLANTS 259

white powdery I'ing, or lialo. The \\ liite intersegmental bands
are made by threads of tlie fungus just named, and the white
halo by countless asexual spores known as coiiidia, which have
been forcibly discharged from the swollen threads that bore
them (Fig. 251) by pressure, resulting proljably from the ab-
sorption of moisture. These spores, ejected in all directions,
may infect another tly upon contact and produce a growth of
fungus threads, or JiypJuc, in its body. The fungus may be
propagated also by means of resting spores, as found by Thax-
ter, our authority u[)on the fungi of insects.

Einpusa aphidis is very common on plant lice and is an im-
portant check upon their multiplication. Aphids killed by this
fungus are found clinging to their food plant, with the body
swollen and discolored. Einpusa grylli attacks crickets, grass-
hoppers, caterpillars and other forms. Curiously enough,
grasshoppers affected by this fungus almost always crawl to
the top of some plant and die in this conspicuous position.

Sporotrichum, a genus of hyphomycetous fungi, afTects 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 insects may become in-
fected. Under favorable conditions, especially in moist sea-
sons, contagious fungus diseases constitute one of the most
important checks ui)on 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 neighl)oring states " was apparently due chiefly, if not
altogether, to parasitism by fungi." Artificial cultures of the
common SporotricJium globitJifrnim have been used exten-
sively as a means of spreading infection among chinch bugs
and grasshoppers, with, lio\\e\er, l)ut moderate success as yet.

Insects in Relation to Flowers. — Among the most marve-
lous phenomena known to the biologist are the innumerable
and complex adaptations by means of which flowers secure
cross pollination through the agency of insect \isitors.

26o

ENTOMOLOGY

Cross fertilization is actually a necessity for the continued
vigor and fertility of flowering plants, and while some of them
are adapted for cr()ss pollination by wind or water, the major-
ity of flowering plants exhiljit profound modifications of floral
structure for compelling insects (and a few other animals, as
birds or snails ) to carry pollen from one flower to another. In
general, the conspicuous colors of flowers are for the purpose

Fig. 252.

Bumble bee (Bombiix) entering fluwcr of l.)luu-liag {Iris i\'rsicolor) . Sliglitly

reduced.

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
indications to insects that edible nectar or pollen is at hand.
Such is the usual statement, and it is indeed proba1)le that

INSECTS IN RELATION TO PLANTS

261

Fig. 253.

insects actually do associate color and nectar, even though
thev will flv to bits of colored paper almost as readily as they
will to flowers of the same colors. It is not to be supposed,
however, that insects realize that they confer any benefit
upon the plant in the llowers of which they find 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 pollina- "''

tion l3y a few l^ees and flies.

Iris. — In the common blue-flag (Iris z'crsicolor.
Fig. 252), each of the three drooping sepals forms
the floor of an arched passageway leading to the nec-
tar. Over the entrance and pointing outward is a
movable lip (Fig. 253, /), the outer surface of which
is stigmatic. 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 Section to illustrate cross pollination

1 • 1 1 £ A.^ \ „ 1 ■ , ,j. of Iris, an, anther; /, stigmatic lip;

hairy back of the bee rubs against ^ ■ .,,

J * 11, nectary; s, sepal.

an overhanging" anther (c?//) and

becomes powdered with grains of pollen as the insect pushes
down towards the nectar. As the bee backs out of the pass-
ag'e it encounters the guardian lip again, but as this side of
the lip can not receive 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 i:)lant,
but as a matter of fact, they habitually fly away to another
plant; moreover, as Darwin found, foreign pollen is ])repotent
over pollen from the same flower. It may l)e added that bees

262

ENTOMOLOGY

and other pollenizing insects ordinarily visit in snccession sev-
eral tlowers of the same kind.

Orchids. — The (Orchids, with their fantastic forms, are really
elaborate traps to insnre cross pollination. In some orchids
(Habciiaria and others) the nectar, lying at the bottom of a
long" tube, is accessible onlv to the long-tong'ued Sphingid?s.
While probing for the nectar, a sphinx moth brings each eye
against a sticky disk to which a pollen mass is attached, and
fiies away carrving the mass on its eye. Then these poUuiia
bend down on their stalks in snch a way that when the moth
thrusts its head into the next tlower they are in the proper
position to encounter and adhere to the stigma. The orchid
Augrcccitin scsquij^cdalc, 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, — an
inference which proved to be C(^rrect.

Milkweed. — The various milkweeds are fascinating subjects
to the student of the interrelations of flowers and insects. The
flowers, like those of orchids, are remarkalilv formed with

Fig. 254.

Structure of milkweed flower (Asclcpias incarmita) with reference to cross pollina-
tion. A, a single flower; c, corolla: /;, hood; B. external aspect of fissure (/) leading
up to disk and also into stigmatic chamber; h, hood; C , poUinia; d, disk. Enlarged.

INSECTS IN RELATION TO PLANTS

iGt,

reference to cross pollination by insects. As a hone}' bee or
other insect crawls over the flowers (Fig. 254, A) to get the
nectar, its legs slip in between the peculiar nectariferous hoods
situated in front of each an f her. As a leg is drawn upward one
of its claws, hairs, or spines frequently catches in a A -shaped
fissure (/, Fig'. 254, B) and is guided along a slit to a notched
disk, or corpuscle (Fig. 254, C, d). This disk clings to the
leg of the insect, which carries ofi^ by means of the disk a pair
of pollen masses of polliiiia (Fig. 254. C). When first re-
moved from their enclosing pockets, or anthers, these thin
spatulate pollinia lie each pair in the same plane, but in a few
minutes the two pollinia twnst on their stalks and come face to
face in such a way that one of them can be easily introduced

into the stigmatic chamber of

Fig. 255.

a new flower visited by the in-
sect. Then the struggles of
the insect ordinarily break the
stem, or retiiiaciihim, of the
pollinium and free the insect.
Often, however, the insect loses
a leg or else is permanentlv
entrapped, particularly in the
case of such large-flowered
milkweeds as Asclcpias coniuti,
which often captures bees, flies
and moths of considerable size.
Pollination is accomplished by
a great variety of insects, chiefly Hymenoptera, Diptera, Lepi-
doptera and Coleoptera. These insects when collected about
milkweed flowers usually display the pollinia dangling from
their legs, as-in Fig. 255.

The details of pollination may be gathered by a close ob-
server 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 hoods of a flower; tirst to re-
move the pair of pollinia and then again to introduce one of
them into an empty stigmatic chamber.

A wasp, Spliex ichncumonea, with pol-
linia of milkweed attached to its legs.
Slightly enlarged.

264

ENTOMOLOGY

Fig.

Yucca. — An extraordinary example of the interdependence
of plants and insects was made known by Riley, whose
detailed account is here summarized. The yuccas of the
southern United States and ]\Iexico are among the few plants
that depend for pollination each upon a single species of insect.
The pollen of Yucca filaincntosa cannot be introduced into the
stigmatic tube of the flower without the help of a Httle white
tineid moth, Pronuha yuccasclla , the female of which pollen-
izes the flower and lays eggs among the ovules, that her larvae

may feed upon the
young seeds. While
the male has no un-
usual structural pecu-
liarities, the female is
adapted for her special
work by modifications
which are u n i q u e
a m o n g Lepidoptera,
namely, a pair of pre-
hensile and spinous
maxillary " tentacles "
(Fig. 256, A) and a
long protrusible ovi-
positor [B] which
combines in itself the
functions 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. 257) 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. 258) and lays a slender egg alongside seven or
eieht of the ovules. After lavino- one or more eggs she ascends

Proiiuba yuccasclla. A, maxillary tentacle
and palpus; B, ovipositor. — After Riley. Fig-
ures 256-258 are republished from the Third
Report of the Missouri Botanical Garden, by-
permission.

INSECTS IN RELATION TO PLANTS

265

the pistil and actually thrusts pollen into the stigmatic tube and
pushes it in firmly. The ovules develop p^^, 2-7

into seeds, some of wliich 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 ]'\tcca. 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 success-
ful as the normal method.

W'h}' does the insect do this? The lit-
tle nectar secreted at the base of the pistil
appears to be of no consequence, at pres-
ent, and the stigmatic fiuid is not necta-
rian ; indeed, the tongue of Pronuba, used
in clinging to the stamen, seems to have
lost partially or entirely its sucking power,
and the alimentarv canal is regarded as functionless. Ordina-

ProHuba yuccasella, fe-
male, gathering pollen
from anthers of Yucca.
Enlarged.

Fig. 2vS.

Pronuba moth ovipositing in flower of Yucca. Slightly reduced.

rily it is the flower which has become a(la])te(l to the insect,
which is enticed by means of pollen or nectar, but here is a

266

ENTOMOLOGY

flower which — though entonnjphilons 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 compensation in the
way of food, Ijut has e\-en l)ecome highly modified with refer-
ence to the needs of the plant, — its special modifications being-
unparalleled among insects with the exception of bees, and
being more puzzling than the more extensiye adaptations of
the bees when we take into consideration the impersonal nature
of the operations of Pronuha. Further inyestigation may
render these extraordinary interrelations more intelligible, or
less mysterious, than they are at present.

The boo"us Yucca moth

Fig. 259.

( Prodoxus qiiinqiicpinic-
iclki ) closely resembles
and associates with Pro- .
iiiiba l)ut oyiposits in the
flower stalks of Yucca
and has none of the spe-
cial adaptiye structures
found in Pronuha.

As regards floral adap-
tations, these examples
are sufficient for present
purposes; man.y others
haye l^een described by
the Ijotanist ; in fact, the
adaptations for cross pol-
lination by insects are as
yaried as the flowers them-
selyes.
Insect Pollenizers. — The great majority of entomophilous
flowers are pollenized by bees of yarious kinds; the apple,
pear, Ijlackljcrry, raspberry and many other rosaceous plants
depend chiefly upon the honey bee, while cloyer cannot set seed
without the aid of bumble bees or honey l)ees, assisted possibly

Phh-gcthontnis

\xta visiting He
Reduced.

:r of Pel 11 Ilia.

INSECTS IN RELATION TO PLANTS

267

l)v Ijutterflies. Lilies and orcliids fre(|uentl_v emplny l)ntterflies
and moths, as well as jjees. and the milkweed is adapted in a
remarkal)le manner for pollination hy 1)utterflies, 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

Fig. 260.

A butterfly, Politcs pcckius, stealing nectar from a flower of Iris versicolor.
Slightly reduced.

long--tonged sphinx moths (Fig. -259) ; the evening ])rimrosc,
like milkweed, is a favorite of noctuid moths. Umbelliferous
plants are pollenized chiefly by various Hies, but also by bees
and wasps. Pond lilies, golden rod and some other flowers
are pollenized largely 1))' beetles, though the flowers exhibit no
special modifications in relation to these particular insects. It

268

ENTOMOLOGY

Fig. 261.

is noteworthv that pollination is performed only by the more
highly org'anized 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 illegiti-
mately ; thus bumble bees puncture the nectaries of columbine,
snapdragon and trumpet creeper from the outside, and wasps
of the genus Ociviicnis cut through the corolla of Pcnfstcmon
Icrz'igatiis, making a hole opposite each nectary ; then there are
the many insects that devour the floral organs, and the insects
which are predaceous or parasitic upon the others. In the
Iris, according to Needham, two small Ijees (Clisodon fcniii-
iialis and Osiiiici disfiiicta) are the most important pollenizers,
and next to them a few syrphid flies, while bumble bees also

are of some impor-
tance. The beetle
Tricliiiis pigcr and sev-
eral small flies obtain
pollen without assist-
ing the plant, and
Pmnphiht, End a in us,
Chrysophaniis a n d
some other butterflies
succeed after many
trials in stealing the
nectar from the out-
side (Fig. 260). A
weevil (Moiioiiychus
z'lilpcculus) punctures
the nectary, and the
flowing nectar then at-
tracts a great variety of
insects. Grasshoppers
and caterpillars eat the
flowers, an ortalid fly destroys the buds, and several parasitic
or predaceous insects haunt the plant; in all, over sixty species
of insects are concerned in one way or another with the Ins.

^ B

A, riglit mandible; B, i-ight maxilla; C, hypo-
pharynx, of a pollen-eating beetle, Euphoria inda.
Enlarged. (The mandibles are remarkable in
being two-lobed.)

INSECTS IN RELATION TO PLANTS

269

Fig. 26.

Modifications of Insects with Reference to Flowers. —

^\'hile the manifold and exquisite adaptations of the flower for
cross polhnation have engaged universal attention, xerv Httle
has been recorded concerning the adaptations of insects in re-
lation to flowers. In fact, the adapta-
tion is largely one-sided ; flowers have
become adjusted to the structure of in-
sects as a matter of vital necessity — to
put it that way — -while insects have had
no such urgent need — so to speak — in
relation to floral structure. They hs-xe
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 adapta-
tions for gathering and using- pollen and
nectar.

Among mandibulate insects, l^eetles
and caterpillars that eat the floral en-
velopes show no special modifications
for this purpose; pollen-feeding beetles,
however, usually have the nnjuth parts

densely clothed with hairs, as in Euphoria (Fig. 261). In
suctorial insects, the mouth parts are frequently formed \\ith
reference to floral structure; this is the case in many but-
terflies and particularly in Sphingidte, 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 Aliiller, the mouth
parts of Syrphida^, Stratyomyii(l;e and Muscidse are specially
adapted for feeding on pollen. In Apid^e, the tongue as com-
pared with that of other Hymenoptera, is exceptionally long,
enal)ling the insect to reach deep into a flower, and is exqui-
sitely specialized ( 1' ig. 127) for lap])ing 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

Pollen-gathering hair
from a worker honey
bee, with a pollen grain
attached. Greatly mag-
nified.

2/0

ENTOMOLOGY

twisted or Ijranched ( Figs. 262, 89) to hold the pohen, do not
occur on other than pollen-gatliering species of insects. Cau-
dell found that out of 200 species of Hymenoptera only 23
species had branched hairs and that these species belonged
without exception t(3 the pollen-gathering group Anthophila,

Fig. 26,^.

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; b, brush; c,
coxa; CO, corbiculum; /, femur; pc, pollen combs; s. spur; sp, spines; ss, spines; t,
trochanter; ti, tibia; v, velum; w, wax pincers; 7-5, tarsal segments; i, metatarsus,
or planta.

no representative of which was found without such hairs.
Similar branched hairs occur als(T on the flower-frequenting
Bombyliidae and SyrphidcC.

The most extensi\'e modihcations in relation to flowers are
found in Prouuba, 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. 262),

INSECTS IN RELATION TO PLANTS 2/1

which entangle pollen grains. These are combed out of the
gathering hairs by means of special poUcn combs (Fig'. 263,

C, pc) on the inner surface (^f the proximal segment of the hind
tarsus, the middle legs also assisting in this operation. From
these combs, the pollen is transferred to the pollen baskets, or
corbiciila (Fig. 263, A, co), of the outer surface of each hind
ti1)ia; by crossing the legs, the pollen from one side is trans-
ferred to the corljiculum of the opposite side, the spines (ss) on
the posterior margin of the til)ia serving to scrape the pollen
from the combs. 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. 263, B, s) , this lever being' slipped in at the upper end
of the cor1)iculum and then pushed along the til)ia 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. This is true also of the i^'u.v-
piiiccrs of the hind legs (Fig. 263, A, C, -zc) at the til)io-tarsal
articulation ; these nippers are used by the worker to remove
the wax plates from the alxlomen.

For cleaning the antennae, a front leg' is passed over an
antenna, which slips into a semicircular scraper (Fig. 2()T,,

D, a) fashioned from the l^asal segment of the tarsus; when
the leg is bent at the til)io-tarsal articulation, an appendage, or
veluiii (v) , of the tibia falls into place to complete a circular
comb, through which the antenna is drawm. This comb is
itself cleaned by means of a brush of hairs ( /' ) 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. hyp(3phar_\nx and max-
ilLne (Fig. 54) are exquisitely constructed with reference to
gathering and sucking nectar ; the maxilhc 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

2/2

ENTOMOLOGY

worker, are used for cutting, scnqjing' 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
straining the honey from the accompanying pollen grains, as
described by Cheshire. The wax glands (Fig. 102) are re-
markable specializations in 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 develop-
ment.

Numerous special sensory adaptations also occur. In fact,
the whole organization of the honey bee has become pro-
foundly modified in relation to nectar and pollen. Many
other insects have the same food but none of them sustain such
intimate 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. In-
deed, it is often asserted that these plants have l)ecome modified

Fig. 264.

Acacid sl^Ji(croccj^liala, an ant-plant. /', one of the "Belt's bodies"; g, gland; s, !■,
hollow stipular thorns, perforated by ants. Reduced. — From Strasburger's Lchrbuch
dcr Botanik.

INSECTS IN RELATION TO PLANTS

273

with special reference to their use by ants, though this is a
gratuitous and improl^al^le assumption.

Belt found several species of Acacia in Nicaragua and the
Amazon valley which have large hollow stipular thorns, in-
habited by ants of the genus Fscudouiynna. The ants enter
by boring- a hole near the apex of a thorn ( Fig. 264, s). The
plant affords the ants food as well as shelter, for glands {g)

Fig. 265.

Fig. 266.

Portion of young stem of Cccropia adeiwl^us, Cccropia adenopus. Por-

showing internodal pits, a and b. Natural size. tion of a stem, split so as

Figures 265-267 are from Schimper's FiJanzen- to show internodal cham-
gcograpTite. bers and the intervening

septa perforated by ants.

at the bases of the petioles secrete a sugary fluid, while many
of the leaflets are tipped with small egg-shaped or ])ear-shaped
appendages (b) known as " Belt's bodies," which are rich in
all)umin, 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 the}' li\-e.
19

274

ENTOMOLOGY

The ant-trees (Cccropia adcuopiis) of Brazil and Central

America have often been referred to l)v travelers. When

one of these trees is handled roughly, hosts of ants rush out

^ , from small openinp's in the

Fig. 2b7. ^ .*

stems and pugnaciously at-
tack the disturber. Just
abo\'e the insertion of each
leaf is a small pit (Fig. 265,
(/, b) where the wall is so
thin as to form a mere dia-
phragm, through which an
ant (probably a fertilized
female) bores and reaches a
holl(~>w internode. To es-
tablish communication [be-
tween the internodal cham-
bers, the ants bore through
the intervening septa ( Fig.
266). They seldom leave
the Cccropia plant, unless
disturbed, and even keep
herds of aphids in their
abode. The base of each
petiole bears (Fig. 267) tender little egg-like bodies ("Mid-
ler's bodies") which the ants detach, store away and eat;
the presence of these bodies is a sure sign that the tree is un-
inhabited bv these ants, which, by the way, belong to the genus
Aj:tcca.

It is too much to assert that the ants protect the Cccropia
plant /// rcfiini for the food and shelter which they obtain.
All ants are hostile to all other species of ants, with few excep-
tions, and even to other colonies of their own species ; so that
their assaults upon leaf-cutting ants are by no means special
and adaptive in their nature, and any protection that a plant
derives thereby is merely incidental. Furthermore, hollow
stems, glandular petioles and pitted stems are of common oc-

Cccropia adenopus. Base of petiole showing
" Miiller's bodies." Slightly reduced.

INSECTS IN RELATION TO PLANTS

^73

currence when they bear no relation to the needs of ants.
These interrelations of ants and plants are too often misinter-
preted in popular and uncritical accounts of the subject.

The interesting habits of the leaf-cutting ants in relation to
the plants that thev attack are described in a subsequent chap-
ter, where will be found also an account of the harvesting ants.

Fig. 268.

Hydnopliytuin montanuin. Section of pscudu-lnilb, to show chambers inhabited by ants.
One fourth natural size. — After Forel.

The epiphytic plants Myniiccodia and Hyditophyliiiii, of
Java, form spongy bulb-like masses, the chambers of which
are usually tenanted by ants, which rush forth when disturlied.
These lumps (Fig. 268) are priniaril}- water-reser\-()irs, but
the ants utilize them by boring into them and from one cham-
ber into another. In plants of the genus Huuiboldtia the ants
can enter the hollow internodes through openings that already
exist.

CHAPTER IX

INSECTS IN RELATION TO OTHER ANIMALS

I. The General Subject

On the one hand, insects may cleri\'e their food from other
animals, either hving or dead; on the other hand, insects them-
selves are food for other animals, especially fishes and birds,
against which they protect themselves by \'arious 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, Ento-
mostraca, etc. ; this is especially the case with culicid and chi-
ronomid larv?e. Many aquatic Hemiptera and Coleoptera
prey upon planarians, nematodes, annelids, molluscs and
crustaceans; Bclosfoiiia sometimes pierces the bodies of tad-
poles and small fishes ; Dyfiscus also kills young fishes occa-
sionally and is distinctly carnivorous both as lar\-a and imago.
Among terrestrial insects, Carabidce 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.

Moscjuitoes aft'ect not only mammals but also, though
rarely, fishes and turtles. The gad flies ( Tabanid?e ) torment
horses and cattle by their jninctures ; and the black-flies, or
buffalo glials (Siimiliiint ) , persecute horses, mules, cattle,
fowls, and frequently become unenduraljle even to man. The
notorious tsetse fly (Glossiiia mcrsifaiis) of South Africa
spreads a deadly disease among horses, cattle and dogs, l:)y

276

INSECTS IN RELATION TO OTHER ANIMALS 2/7

inoculating them with a protozoan l^lood-parasite, to the etTects
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
wdiich Kellog'g 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 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 Ijird 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 suggested the interesting possibility
that such a species has persisted unchanged 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 mammals. These biting lice feed, not upon l)lood,
Init upon epidermal cells and portions of feathers or hairs.
They have flat tough bodies (Fig. 17), with no 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 Pediculid?e
(Hemiptera). These (Fig. 27^) 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, mon-
keys, seals, elephants, etc., and man is parasitized by three
species, namely, the head louse (Pcdiciiliis capitis), the body
louse {Pcdiculus vcstiiiicnii), and the crab louse (Phtliiriiis
pubis), though the first two are possil)ly the same species.

278 ENTOMOLOGY

An anomalous beetle, Plufypsylliis casforis, occurs through-
out North America and also in Europe as a parasite of the
beaver.

The tleas, allied to Diptera but constituting a distinct order
(Siphonaptera ) , are familiar parasites of chickens, cats, dogs
and human Ijeings. These insects (Fig. 30) are well adapted
by their laterally compressed bodies for slipping aljout among
hairs, and their saltatory powers and general elusiveness are
well known. Their wings are reduced to mere rudiments, their
eyes when jjresent are minute and simple and their mouth
parts are suctorial.

Among Diptera, there are a few external parasites, the l^est
known of which is the sheep tick { Mclopliui^us o-c'iiius) , though
several highly interesting but little-studied forms are parasitic
upon birds and bats.

The larvje of the hot tiies (CEstridie) are common internal
parasites of mammals. The sheep bot fly (CEsfnis Oc'is)
deposits her eggs or larwe on the nostrils of sheep: the
maggots develop in the frontal sinuses of the host, causing"
vertigo or even death, and ^^•hen full grown escape through
the nostrils and pupate in the S(_)il. The horse bot fly {Gas-
tropJiiliis cqiii) glues its eggs to the hairs of horses, especially
on the fore legs and shoulders, whence the larvie are licked oft'
and swallowed: once in the stctmach, the bots fasten them-
selves to its lining, by means of special hooks, and withstand
almost all eft'orts to dislodge them : though when the l^ots have
attained their growth they release their hold and pass with the
excrement to the soil. B(jts of the genus Hypodcnua form
tumors on cattle and other mammals, domesticated or wild.
The ox-warble [H. Uiicata, Fig. 210, /) reaches the oesophagus
of its host in the same manner as the horse l)ot, according to
Curtice, but then makes its \\ay into the sul)cutaneous tissue
and causes the well-known tumors on the back of the animal;
when full gr(3wn the l)ots scpiirm out of these tumors and drop
to the ground, lea\-ing permanent holes in the hide.

Parasitism in General. — I^arasitic insects evidentlv do not

INSECTS IN RELATION TO OTHER ANIMALS 2/9

constitute a phyloo-enetic unit, l)ut the ])arasitic habit has arisen
independently in many different orders. These insects do,
however, agree superficiahy, in certain respects, as the resuU
of what may be termed con\'erg-ence of adaptation. Thus a
dipterous larva, living as an internal parasite, in the presence
of an aljundant 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 l)ut is thin and delicate, the body is com-
pact and fleshy, and the digestive system is of a simplilied 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 com-
pound, are either simple or else absent. In some special cases,
howe\'er, as in a few dipterous parasites of birds and l:)ats, 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- chietiy 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 primitixe
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 adai)tation to a special envinmment,
however, sacrifices the general adaptability of the animal, —
makes it impossible for a parasite to adapt itself to new con-
ditions ; and while parasitism may be an immediate advantage
to a species, there are few parasites that have attained any
degree of dominance among animals. Ichneumonid;e, to l)e
sure, are remarkably dominant among insects, but here the
parasitic adaptations are limited for the most part to the larval
stage and the adults may be said to be as free for new adapta-
tions as are any other 1 lynieno])tera.

Scavenger and Carrion Insects. — Not a few families of

2SO ENTOMOLOGY

Diptera and Coleoptera derive their food from dead animal
matter. The aquatic famihes Dytiscidre and Gyrinida; are
largely scavengers. Among terrestrial forms, Silphidse feed
on dead animals of all kinds; the burying beetles (NccropJi-
onts). working in pairs, undermine and bury the bodies of
birds, frogs and other small animals, and lay their eggs in the
carcasses ; Histerid^e and Staphylinidre are carrion beetles, and
Dermestidre attack dried animal matter of almost every de-
scription, 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 Scarab.'cida; 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 // per cent, of its food
for the season, the remainder consisting of myriopods, spiders,
Crustacea, molluscs and worms, according 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 motionless insects but uses its extensile sticky tongue to lick
in moving insects or other prey, which it captures with sur-
prising speed and precision. In the cities one often sees many
toads under an arc-hght engaged in catching insects that fall
anywhere near them. Though its diet is varied and some-
what indiscriminate, the toad consumes such a large propor-
tion of noxious insects, such as May beetles and cutworms,
that it is unquestionably of service to man.

Moles are entirely insectivorous and destroy large numbers
of white grubs and caterpillars ; field mice and prairie squirrels
eat many insects, especially grasshoppers, and the skunk rev-
els in these insects, though it eats beetles frequently, as does

INSECTS IN RELATION TO OTIiER ANIMALS 28 1

also the raccoon, which is to some extent insectivorous.
Monkeys are onini\-orons l)nt devour nianv kinds of insects.

With these hasty references, we may pass at once to the
subject of the insect food of fishes and l)irds.

Insects in Relation to Fishes. — Insects constitute the
most important portion of the food of ackdt fresh water fishes,
furnishing forty per cent, of their foock according to Dr.
Forbes, from wdiose vahiable 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 Entomostraca, and yet do not bring them within
reach of fishes or Mollusca. Some of these fishes have pecu-
liar habits which render them especially dependent upon insect
life, the little minnow Phciiacobiiis, for example, which, ac-
cording to my studies, makes nearly all its food from insects
(ninety-eight per cent.) found under stones in running water.
Next are the pirate perch, ApJircdoderus (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 (Chcriio-
brytfiis) and the brook silversides (each fifty-four per cent.),
and the rock bass and the cyprinoid genus Notropis (each
fifty-two per cent.).

" Those which take few insects or none are mostly the mud-
feeders and the ichthyophagous species, Aniia (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 Inu'bot, the pike, the gar, the black liass. the wall-
eyed pike, and the great ri\cr catfish, and from that of the
hickory shad and the mud-eating minnows (the shiner, the fat-
head, etc.). It is to l)e 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. I'he mud-

282 ENTOMOLOGY

feeders, ho\ve\er, seem not to pass through this stage, but to
adopt the hmophag'ous habit as soon as they cease to depend
upon Entomostraca.

" Terrestrial insects, dropping int(_) the water accidentahy
or swept in Ijy rains, are e\-idently dihgently 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
{Sciiiotiliis, Pinicphalcs and Notropis).

" Among aquatic insects, minute slender dipterous larvae,
belonging mostly to Cliiroiioniiis, Corctlira and allied genera,
are of remarkable importance, making, in fact, nearly one
tenth of the food of all the tishes studied. They are most
abundant in PJicnacobius and Efhrosfoiiia, which g'enera have
become especially adapted to the search for these insect forms
in shallow rocky streams. Next I found them most generally
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 ri\er carp, and made nearly one fourth
that of fifty-one buft'alo fishes. Idiey a[)pear further in con-
siderable quantity in the food of a numl)er of the minnow
familv (Notropis. Pintcplialcs, etc.), which habitually fre-
Cjuent the swift waters of stony streams, but were curiously
deficient in the small collection of miller's thumbs (Cottid^e)
which hunt for food in similar situations. The sunfishes eal
but few of this important grouj), the a^'erage of the family
being only six per cent.

" Larvse of aquatic Ijeetles, 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 larva? of
Gyrinidce and Hydrophilid?e ; whereas the adult surface beetle?
themselves {Gyriiiiis, Diiiciitcs, etc.) — whose zigzag-darting
swarms no one can have failed to notice — were not once en-
countered in my studies.

INSECTS IN RELATION TO OTHER ANIMALS 283

" The almost equally well-known slender \\ater-skii)pers
{Hvgrotrcchiis) seem also completely protected by their habits
and activity from capture by fishes, only a single specimen oc-
curring- in the food of all my specimens. Indeed, the true
water bugs (Hemiptera) were generall}' rare, A\ith the excep-
tion of the small soft-bodied genus Corlsa. 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 Neuroptera [in the Ijroad 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 examined by me consisted of
aquatic larvae of this order, the greater part of them larvae of
day flies (Ephemeridcc), principally of the genus Hcxagcnia.
These neuropterous larvae were eaten especially by the miller's
thumb, the sheepshead, the \\hite 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 bro()k 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
buft'alo, five catfishes, the dog-fish, and the shovel fish, —
seventy species out of the eighty-se\en which I have studied.

" Among the abo\e, 1 found them the most important food
of the white l)ass, the toothed herring, the shovel fish (fifty-
one per cent.), and the croppies; while they made a fourth or
more of the alimentary contents of the sheepshead ( forty-six
per cent.), the darters, the pirate perch, the common sunfishes
(Lcpoiiiis and Cliccuobryftus) , the rock bass, the little pickerel,
and the common sucker ( thirty-six per cent. ).

" Ephemerid larvae were eaten by two hundred rmd thirteen
specimens of forty-eight species — not counting }-oung. The
larvae of Ihwagciiia, one of the commonest of the ' ri\er
flies,' was bv far the most important insect of this group, this
alone amounting to about half of all the Neuroptera eaten.
They made nearly nne half of the food of the shovel fish, more

284 ENTOMOLOGY

than one tenth that of the sunfishes, and the principal food re-
sonrces of half-grown sheepshead ; but were rarely taken Iw
the sucker family, and made only five per cent, of the food of
the catfish group.

" The various larvc'^ of the dragon tiies, on the other hand,
were much less frequently encountered. They seemed to l;)e
most abundant in the food of the grass pickerel (t\\enty-five
per cent.), and next to that, in the croppie, the pirate perch,
and the common perch (ten to thirteen per cent.).

"Case-worms ( PhryganeidcT ) were somewhat rarely
found, rising to fifteen per cent, in the rock bass and twelve
per cent, in the minnows of the Hybopsis gToup, l)ut otherwise
averaging from one to six per cent, in less than half of the
species."

Insects in Relation to Birds. — l^^rom an economic point
of view the relations between Ijirds 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 difiicult 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 F'orbes apply to particular years and
would undoubtedly vary more or less from year to year, they
are here for convenience regarded as representative of any
year and are spoken of in the present tense. Al)out 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,
larvse of Bibio cilbipciiiiis for the UKist part, and then caterpil-
lars and various beetles. When the small fruits appear, these
are largely eaten instead of insects ; thus in June, cherries and

INSECTS IN RELATION TO OTHER ANIMALS 285

raspberries form fifty-five per cent, and insects (ants, cater-
pillars, wire-worms and Carabidce ) fort}--two per cent, of the
food; and in Jnly, raspberries, blackl)erries 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 fortv-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 Ijerries and moonseed berries) se\'enty 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 Alichigan, wdio 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 injuri-
ous insects, and the comparatixely few cultivated 1)erries that
the bird appropriates are ordinarily but a meagre compensa-
tion for the valuable services rendered to man by this familiar
bird.

Catbird. — Not so much can be said for the catbird, howe\-er,
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 Alay, eighty-three per cent, of the food (»f ihe catloird
consists of insects, mostly beetles (Carabid?c. Rhynchophora,
etc.), crane-fiies, ants and caterpillars (Xoctuid;e) ; while dry
sumach berries are eaten to the extent of seven ])cr cent, h^or

286 ENTOMOLOGY

the first half of June, the record is much the same, with an in-
crease, however, in the numher 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 nf insects. This falls to eig'hteen per cent, in July,
when three quarters of the food consists of small fruits,
mostly blackberries, however. In Aug-ust. with the diminu-
tion of the smaller cultivated fruits, the ])ercentag-e of insects
rises to fortv-six per cent., nearly one half of which is made
up of ants and the rest of caterpillars, grasshoppers. Hemip-
tera. Coleoptera. etc. In September, with the appearance of
wild cherries, elderberries. Virginia 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 1)v Forbes, insects form forty-three per cent, of the
food of the catbird and fruits fifty-two per cent. As the in-
jurious insects killed are offset l)v the beneficial ones destroyed.
" the injury done in the fruit-garden Ijy these birds remains
without compensation unless we shall find it in the food of the
young." says Professor Forl^es. And this has l)een found, to
the credit of the catbird; for Weed learned that the food of
three nestlings consisted of insects, sixty-two per cent, of
which were cutworms and four per cent, grasshoppers; while
Judd found that fourteen nestlings ha<l eaten but four per
cent, of fruit, the diet Ijeing 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 everywhere as an enemy of noxious insects is well-de-

INSECTS IN RELATION TO OTHER ANIMALS 28/

served. From a study of one hundred and eight Ilhnois speci-
mens, Forbes finds that se\enty-eight per cent, of the food for
tlie year consists of insects, eight per cent, of Arachnida, one
per cent, of Juhda? and only thirteen per cent, of vegetable
matter, edible fruits forming merely one per cent, of the entire
food. The insects eaten are mostly caterpillars (chiedy cut-
worms), Orthoptera (grasshoppers and crickets) and Cole-
optera (Caraliidic and Scarab<T?id;r). Though some of the
insects are more or less loeneficial to man. such as Caral)i(lre
and TchneuuK^nida? (respectivel}' [jredaceous and parasitic),
the beneficial elements form onh- twenty-two per cent, of the
food for the vear. as against forty-nine per cent, of injurious
elements, the remaining twenty-nine per cent, consisting of
neutral elements. The food of the nestlings, according to
Judd, is essentially like that of the adults, being " lieetles,
caterpillars, grasshoppers, spiders and a few snails."

Other Insectivorous Birds. — Weed and Dearborn, from
wdiose excellent work the following notes are taken, find that
the common chickadee de\'ours immense numbers of canker-
worms, and that more than half its food during winter con-
sists of insects, largely in the form of eggs, including those of
the common tent caterpillar (C. aincricaiia) , the fall web-
worm ( //. cinica) and i)articular!y 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, and the total number destroyed
annually is inconceivably large. The house wren is almost
exclusively insectivorous, feeding upon caterpillars and other
larvtC, ants, grasshoppers, gnats, beetles, bugs, spiders, and
myriopods. The swallows, also, are highly insectivorous;
" most of their food is ca])tured on the wing, and consists of
small moths, two-winged fiies, especiall)- crane-thes, 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 kingi)ir(l "consists of insects, including such noxious
species as Alaydjeetles, clickd)eetles. wheat and fruit weevils.

288 ENTOMOLOGY

grasshoppers, and leaf hoppers." The honey bees eaten by
this bird are insignificant in nnml)er. AA^oodpeckers destroy
immense nnml)ers of wood-boring" laryse, bark-insects, ants,
caterpillars, etc. The cuckoos " are nnicjue in haying a taste
for insects that other birds reject. Most birds are ready to
deyour a smooth caterpillar that comes in their way, but they
leaye the hairy yarieties seyerely alone. The cuckoos, how-
eyer, make a specialty of deyouring such unpalatable crea-
tures ; eyen stink-bugs and the poisonous spiny laryae of the lo
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 cjuanti-
ties. " The nestling birds are fed chiefly with smooth cater-
pillars and grasshoppers, their stomachs probably being unaljle
to endure the hairy caterpillars. All in all, the cuckoos are of
the highest economic yalue. They do no harm and accom-
plish great good. If the orchardist could colonize his or-
chards with them, he would escape much loss." The Cjuail
feeds largely upon insects during the summer, frequently eat-
ing the Colorado potato beetle and the army worm ; the prairie
hen has similar food habits but liyes almost exclusixely 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 Liirds as do the locusts, or short-horned grasshop-
pers, of the family AcridiidcC. The enormous destructiye
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 bluebirds 67, 7 barn s\yallo\ys 139, 7
night hawks 348, 16 yellow-billed cuckoos 416, 8 flickers 252,
8 screech owls 219, and i humming bird 4; while crows and
l)lue-iays had eaten large numbers of the locusts; and grouse.

INSECTS IN RELATION TO OTHER ANIMALS 289

quail and prairie lien, ennrnidus numbers. Even shore birds,
such as g"eese, ducks, "-nils and ])elicans came to share in the
feast. Aug-hey estimated tliat the locusts eaten in one dav bv
the ]:)asserine l)irds of the eastern half of Nebraska were
sufficient to destroy in a single (la\- 174.397 tons of crops,
valued at $1,743.97.

WY^ed and Dearliorn state that, of Hemiptera, Jassid^e are verv
often found in the stomachs of birds, and that aphids and their
eg-gs form a large part of the food of many of the smaller birds,
such as the warblers, nuthatclies. kinglets and chickadees.
*' A large proportion of the caterjiillars of the Lcpidoj^tera are
eagerly de\'oured by birds, forming an important element of
the food of many species." The hairy caterpillars are eaten
Ijy cuckoos and blue-jays and the large saturniid cater])illars.
such as cccropia and polypJicinits,\)\ some of the hawks. Al-
most all kinds of Coleoptera are food for birds, but especially
the grubs of Scarabreidse, which are eagerly devoured Ijy
robins, blackljirds, crows and other 1)irds. Of the Diptera,
Cecidomyiidae and other gnats are eaten by swallows, swifts
and night hawks : while Tipulidae are often found in the stom-
achs of birds. Among" Hymenoi)tera, ants are eaten exten-
sively 1)y woodpeckers, catbirds and many other species, as are
also Ichneumonidc'e and other parasitic forms — these last b}"
the flycatchers in particular.

The Regulative Action of Birds upon Insect Oscilla-
tions. — The worst injuries by insects are done by s[)ecies that
tiuctuate excessively in number as the result of variations in
those manifold forces that act as checks upon the multiplica-
tion of the species.

In order to determine whether birds do anything to reduce
existing oscillations of injurious insects, l^rofessor lM)rl)es
made some admira1)le studies u])(in the food of birds which
were shot in an Illinois a])ple orchard which was being ravaged
by canker-worms. In this orchard. l)irds were present in
extraordinary number and \ariety, there being at least thirty-
five species, most of which were studied b}' bOrbes. Irom
20

290 ENTOMOLOGY

whose exhaustive tallies the fohowing food-percentages are
taken :

Birds

Examined.

Insects.

Canker-worms.

Rol)in,

21 %

Catlsird,

Brown Thrush,

Bhiebird.

Black-capped Chickadee.

100

House Wren,

Tennessee Warbler,

100

Summer Yellow Bird.

Black-throated Green Ws

irbler.

100

Maryland Yellow-throat,

100

Baltimore Oriole,

100

To quote Forl)es : " Tliree facts stand nut very clearlv as
resuhs of these investigations: i. Birds of the most ^'aried
character and lialiits, migrant and resident, of ah sizes, from
the tiny wren to the l)hie-jay, ])irds of the forest, garden and
meadow, those of arl)orea] and those of terrestrial 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 l;)irds congregated in this orchard should have consisted of
a sing-le 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
Ijalance of organic nature. And while looking for their in-
fluence over one insect outbreak wc stumbled upon at least two
others, less marked, perhaps incipient, but evident enough to
express themseh-es clearly in the changed food ratios of the
birds.

" 2. The comparisons made show plainly that the reflex efl:'ect
of this concentration on two or three unusually numerous in-
sects 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 commonly eaten. That is to
say, the abnormal pressure put upon the canker-worm and \'ine-

INSECTS IN RELATION TO OTHER ANIMALS 29 1

chafer was compensated by a g"eneral diminntion of tlie ratios
of all the other elements, and not by a ne,<^iect of one or two
alone. If the latter had been the case, the criticism mi,f;ht
easily have been made that the birds, in hel])ins4- to rednce 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 sitnation as many
caterpillars other than canker-worms as nsnal, sim])lv adding
their canker-worm ratios to those of other caterpillars, goes
to show that these insects are fa\()rites with a majority of
birds."

The Relations of Birds to Predaceous and Parasitic In-
sects. — The false assnmption is often made that a bird is
necessarily inimical to man's interest whenever it destroys a
parasitic or a predaceons insect. Weed and Dearborn attack
this assumption as follows:

" Suppose an ichneumon parasite is found in the stcomach of
a robin or other bird : it may belong to any one of the follow-
ing categories :

" I. The i)rimary parasite of an injurious insect.

" 2. The secondary parasite of an injurious insect.

" 3. The primary parasite of an insect feeding on a noxious
])lant.

" 4. The secondary ])arasite of an insect feeding on a nox-
ious plant.

" 5. ddie primary parasite of an insect feeding on a wild
plant of no economic \alue.

" 0. The secondary ])arasite of an insect feeding on a wild
plant of no economic \alue.

" 7. The primary ])arasite of a ])redaceous insect.

" 8. The primar}- parasite of a spider or a s])i(ler's egg.

" This list might easily be extended still farther, and the
assumption that the parasite Ijclongs to the first of these cate-
gories is unwarranted by the facts and does \iolence to the
]')rob<abilities of the case.

292 ENTOMOLOGY

" A correct idea of the economic role of the feathered triljes
ma\- l:)e (detained only hy a broader \-ie\v of nature's methods.
— a \'ie\v in which we must ever keep liefore 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 unstaljle ef|uilibrium commonly called ' the l:)alance
of nature.' "

This liroader y\e\v was first elaborated bv Professor Forbes,
in his masterly i)a])er, " On S< mie Interactions of Organisms,"
the su1)stance of which is gi\en l)elow.

" E\idently a species can not long maintain itself in num-
bers greater than can find sufficient foc^d. year after year. If
it is a phytophagous insect, f(M" example, it will soon dwindle
if it seriously lessens the numl)ers of the plants upon which it
feeds, either directly. l)y eating them up, or indirectly, by so
weakening" them that they labor under a marked disaih'antage
in the struggle with other plants for fonthold, air, light and
food. The interest ()f the insect is therefore identical with
the interest of the plant it feeds upon. Wdiatever injuriously
affects the latter, equally injures the former; and whate\"er
favors the latter, equally fa\-ors the former. This must,
therefore, be regarded as the extreme normal limit of the num-
bers of a phytophagous species. — a limit such that its depre-
dations shall do no es|)ecial harm to the i)lants upon which it
depends for food, l)ut shall remo\"e imh' the excess of foliage
or fruit, or else superfluous indix'iduals which must i)erish
otherwise, if not eaten, ()r. sur\'i\'ing, must injure their species
by o\'er-crowding. If the plant-feeder multiply beyond the
above limit, e\idently 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 C(»ntinuance.

" On the other hand, the reduction of the phytophagous in-
sect below the normal number, will e\"idently injure the food
plant by preventing a reduction of its excess of growth or
numbers, and will also set up an oscillation like the preceding,
except that the steps will he taken in reverse order.

INSECTS IN RELATION TO OTHER ANIMALS 293

" I next point out the fact that precisely tlie same reasoning-
applies to predaceons and parasitic insects. Their interests,
also are identical with the interests of the species thev i)ara-
sitize or prey npon. A diminntion of their food reacts to de-
crease their own nnm1)ers. Thev are thns \itallv interested
in confining their depredatic^ns to the excess of individnals
prodnced, or to redundant or otherwise unessential structures.
It is only hy a sort of unlucky accident that a destructi\-e spe-
cies really injures the species preyed upon.

"The discussion has thus far atYected 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 indifi^erently upon se\eral
plants or upon a \ariety of animals, or hoth. Let us take,
first, the case of a predaceons l)eetle feeding upon a variety of
other insects, — either in(hfferently, upon whatever species is
most numerous or most accessil:)le. or preferahly upon certain
species, resorting- to others only in case of an insufficiency of
its favorite food.

" It is at once e\'ident that, taking the group of its food-
insects as a unit, the same reasoning applies as if it were re-
stricted 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 surjjlus of
its food which would otherwise perish if not eaten — interested,
therefore, in estaljlishing a rate of reproduction for itself
which will not unduly lessen its food sup])ly. 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 l)y keeping each species at the highest num1)er
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 \-egetal)lc, or both. It also ap])lies to para-

294 ENTOMOLOGY

sitic plants. The ideal adjustment is one in which the repro-
ductive rate of each species should l)e so exactly adapted to its
food supply and to the \arious drains upon it that the species
preyed upon should normally produce an excess sufficient for
the species it supports. And this statement evidently applies
throughout the entire scale of l)eing. Among" all orders of
plants and animals, the ideal d)alance of Nature is one promo-
tive of the hig'hest good of all the species. In this ideal state,
towards which Nature seems continually striving-, every food-
producing species of plant or animal would grow and multiply
at a rate sufficient t(^ 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 fur-
nished. . . .

" Exact adjustment is douhtless never reached anywhere,
even for a single year. It is usually closely approached in
primitixe nature, l)ut the chances are practically inhnite against
its becoming really complete, and mal-adjustment in some de-
gree is therefore the general rule. All species must oscillate
more or less."

Professor Forbes then shows that oscillations are injuri(3us
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 sup-
ply, the species will e\-entually yield to its m<M'e prolific compet-
itors in the general struggle for existence. If, on the other
hand, its rate of multiplication is too high, the species will l)e
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 evidence of a fairly com-
plete adjustment ()f the rate of reproduction to the drains upon
the species." ... " We may be sure, therefore, that, as a
general rule, in the course of e\'olution, onlv those species
have been able to sur\-i\-e whose parasites, if any, were not
prolific enough sensibly to limit the numbers of their hosts for
anv leno-th of time.

INSECTS IN RELATION TO OTHER ANIMALS 295

" We notice incidentally that it is tlins made unlikely that an
injurious species can he exterminated, can even lie ])ermanently
lessened in numhers, by a parasite strictly dependent upon it, —
a conclusion which remarkably diminishes the economical role
of parasitism. The same line of argiunent 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, m(3St 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.

" Against the uprising of inordinate numbers of insects,
commonly harmless but capable of becoming temporarily in-
jurious, the most valuable and reliable protection is un-
doubtedly afforded by those predaceous birds and insects
which eat a mixed food, so that in the absence or diminution
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 over-
whelming attack against any threatening" foe. Especially
does the wonderful locomotive power of birds, enabling- them
to escape scarcity in one region which might otherwise deci-
mate them, by simply passing to another more favorable one,
without the loss of a life, fit them. abo\e all other animals and
agencies, to arrest disorder at the start, — to head oft' aspiring
and destructive rebellion before it has had time fairly to make

296 ENTOMOLOGY

head. But Ave should not therefrom derive the general, hut
false and mischievous notion, that the indefinite multiplication
of either hirds or predaceous insects is good. Too many of
either is nearly or quite as harmful as too few.

" There is a general consent that prime\-al nature, as in the
uninhahited forest or the untilled plain, presents a settled har-
monv of interaction among organic groups which is in strong
contrast with the many serious mal-adjustments of plants and
animals fcamd in countries occupied 1)y man.

" T(j man, as to nature at large, the question of adjustment
is of vast importance, since the eminently destructive species
are the widely oscillating ones. Those insects which are well
adjusted to their euAironments, organic and inorganic, are
either harmless or intlict hut moderate injury (our ordinary
crickets and grasshoppers are examples) ; while those that are
imperfectly adjusted, whose numl)ers are, therefore, subject
to wide fluctuations, like the Colorad*) grasshopper, the
chinch-l)ug and the army worm, are the enemies which we
have reason to dread. ]\Ian 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 rela-
tiA-ely stationary species into widely oscillating ones; second,
to destroy or render stationary all the oscillating species in-
jurious to him ; or, failing in this, to restrict their oscillations
within the narrowest limits possible.

" For exami)le, rememl)ering that every species oscillates to
some extent, and is held to relati\'elv coiistant numliers l)y the
joint action of several restraining forces, we see that the re-
moval or weakening of any check or barrier is sufiicient to
widen and intensify this dangerous oscillation; may even c<)n-
vert a perfectly harmless species into a frightful pest. Wit-
ness the maple bark louse, which is so rare in natural forests
as scarcely e\'er to be seen, limited there as it is by its feelole
locomotive power and the scattered situation of the trees it
infests. With the multiplication and concentration of its food
in towns, it has increased enormously, and, if it has not done

INSECTS IN RELATION TO OTHER ANIMALS 29/

the orfavest injury, it is l)ecanse tlie trees attacked l)y it are of
comparatively sli^iit ecom iniical value, and l)ecause it has
finahy reached new hniits whicli hem it in once more.

" We are therefore sure that the destruction of any species
of insecti^'orous l)ird or ])re(laceous insect, is a thins^" to he
done, if at ah, only after the fullest ac(|uaintance with the facts.
The natural presumptions are nearly all in their favor. It is
also certain that the species hest 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
l)^■ them, thev aiYord a very uncertain safeguard against the
rise of such oscillations. In fact, their undue increase would
be iinally as dangerous as their diminution.

" Notwithstanding the strong- presumption in fa\or of the
natural systeuL when we remember that the i)urposes of man
and what, for convenience' sake, we may call the purposes of
Nature do not fully harmonize, we find it incredible that, act-
ing intelligently, we should not be al)le to mo.dify existing" ar-
rangements 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 ha\e
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 conserwatism in deal-
ing with the system of things by which \\e are surrounded."

Efficiency of Protective Adaptations of Insects. — Inter-
esting fr<im a scientific point of \iew are the x'arious adaptations
by means of which insects are protected more or less from
their bird enemies. Colorational adaptations ha\ing been dis-
cussed in another chajiter, there remain for consideration —
(i) hairs. (2) stings, (3) odors. Haxors and irritants. Most
of what follows is from an admirable pajjcr by Dr. Judd,
whose data are based upon his examination of the stomach
contents of fifteen thousand birds.

298 ENTOMOLOGY

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 caterpihars." Judd observed
that Hyplianfria cujica infesting' a pear tree was not at all
molested, in spite of the fact that the tree was tenanted In'
three broods of birds at the time, namely, kingbirds, orchard
orioles and English si)arr()ws. The hairy arctiid caterpillars,
however, are eaten by a few birds : the robin, bluebird, catbird,
sparrow-ha\\k, cuckoos and shrikes; and the spiny larvre of
Vanessa aiitiopa by cuckoos and the Baltimore oriole; \\hile the
hairy caterpillars of the gypsy moth are known to be eaten in
Massachusetts by no less than thirty-one species of birds,
nr^talily cuckoos. Baltimore oriole, catbird, chickadee, blue-jay,
chipping sparrow, robin, vireos and the crow, these birds l)e-
ing of no little assistance in the suppression of this pest.
These are exceptional cases, howe\er, and in general the hairi-
ness of caterpillars appears to be a highly effective protection
against most birds.

Stings. — Some birds (chew ink, young ducks) are fatally
affected by eating honey bees. The l)lue-ja}'s, however, will
eat Bo nib lis and Xylocopa, and flycatchers and swallows feed
hal)itually upon stinging Hymenoptera, particularly ScoliidtC,
while a great many Ijirds eat Myrmicid;e, or stinging ants.
The formic acid of ants does not protect them from wholesale
destruction l)y birds; Judd found three thousand ants in the
stomach of a flicker. " Stingless ants pretend to sting but
many birds they do not deceive." The stinging caterpillar of
Aufonwris io is occasionally eaten by the yellow-billed cuckoo.
-Vside from these exceptions, however, the stings of insects are
an extremely efficient means of defence.

Odors, Flavors and Irritants. — The malodorous Heterop-
tera in general are food for most birds; Lygits, ReduviicL'e and
PentatomidcT are eaten by song sparrows, and EiiscJiisfiis by
blackbirds and crows. The odors of Heteroptera are by no
means uni\ersally protective.

Among Coleoptera, the showy, ill-scented or ill-flavored

INSECTS IN RELATION TO OTHER ANIMALS 299

Coccinelliclre are eaten by but very few l)ir(l.s — the llycatchers
and swallows — and are refused l)y caged IjJue-jays and song
sparrows even when these birds are hungry. Of Chrysomel-
idse, the Colorado potato l^eetle is refused 1)y the catbird, blue-
jay and song sparrow, and Diabrofica is not often eaten, ex-
cept by catbirds and thrushes. " The smaller C"arabid;e.
whether stinking or not, are eaten by practically all land birds."
Crows, blackbirds and jays eagerly swallow Calosoma scnifa-
tor, and the first two Ijirds are especially fond of Harpaliis
caligiiiosiis and H. f^ciiiisylz'aiilciis, and feed Galcrifa to their
young. " A score of smaller CarabicUe and Chrysomelidae,
metallic and conspicuously colored, are habitually eaten by
l)ir(ls that liave an abundance of other insect food to pick
from."

The stenches of Lampyrid;e appear to be more etTective
than those of Caral)idje. Tclcphonis is occasionally eaten, but
Pliofilms rarely if at all. Cluniliogiiafhus is not eaten by
many birds (though flycatchers and swallows select this in-
sect) and the genus is regarded unfavorably by caged catbirds
and blue-jays.

In regard to other insects, Judd finds that Epicaiifa, with its
irritant fluid, is immune from all but the kingbird; Cyllciie
seldom occurs in the stomachs of l)irds; May flies and caddis
flies, however, are terribly persecuted, but swiftly fl}ing Dip-
tera and Odonata are highly immune.

From such facts as these, Judd properly infers, " not cases
of protection and non-protection, but cases of greater and
lesser efticiency of protecti\e devices."

2. The Transmission of Dise.\ses 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 uni\ersal attention.

Malaria. — So far as is known, malaria is transmissible
only through the agenc_\' of mos(|uitoes.

;oo

ENTOMOLOGY

Life hisloiv of malaria parasite. PhisinodiiDii prccco.r. I, S]iorozoite, introduced by
mosquito into human blood; the sporozoite becomes a schizont. _', young schizont,
which enters a red blood corpuscle. ;?, young schizont in a red blood corpuscle. 4,
full-grown schizont, containing numerous granules of melanin. 5, nuclear division
preparatory to sporulation. 6. spores, or merozoites, derived from a single mother-
cell. 7, young macrogamete (female), derived from a merozoite and situated in a
red blood corpuscle, ya, young microgametoblast (.male), derived from a merozoite.

8, full-grown macrogamete. 8a, full-grown microgametoblast. In stages 8 and Sa the
parasite is taken into the stomach of a nu)si|uito: or else remains in the himian blood.

9, mature macrogamete, capable of fertilization; the round black extruded object may
probably be termed a " polar body." pii, mature microgametoblast, preparatory to

INSECTS IN RELATION TO OTHER ANIMALS 3OI

The malaria " germ," disctn-ered in 1880 l)y the h'rench
armv surgeon Laveran. may he found as a ])ale, auKeljoid
organism { PhisiiKnliuni . Fig. 269) in the red hlood c()r])us-
cles of persons atflicted with the disease, ddiis organism
{ schi.z\>ut, 2) grows at the expense of tlie ha'moglol)in of the
corpuscle i ^-3) and its growth is accompanied l)y an increasing
deposit of Ijlack granules { iiichntiii ) . which are doul)tless
excretory in their nature. At length, the amoehula divides
into many spores ( iiicroccitcs, 6), which hy the disintegration
of the corpuscle are set free in the plasma of the l)lood. Here
many if not most of the s])ores, and the pigment granules as
well, are attacked and aljsorhed hy leucoc\tes, or white blood
corpuscles, while some of the spores may inwade herdthy red
corpuscles and dexelop as before. The period of spornlation,
as Golgi found, is coincident with that of the " chill " experi-
enced by the patient; and quinine is most effective when ad-
ministered just 1)efore the sporulati(3n period. The destruc-
tion of red blood corpuscles explains the pallid, or mucimc,
condition which is characteristic of malarial patients. In
three or four days the numl)er of red corpuscles may be re-
duced from 5,000,000 per cubic millimeter — the normal num-
ber — to 3,000,000; and in three or four weeks of intermittent
fever, even to 1,000,000.

Three types of malaria are recognized: ( i ) the tertian, in
which the paroxysm recurs every two days; (2) the (juartan,
in which it happens every third day; and (3) the icstivo-
autumnal t3'pe (Fig. 269). These three kinds are by some

forming microgametes. gb, resting cell, bearing six flagellate microganietes (male).
10, fertilization of a macrogamete by a motile microgamete. The macrogamcte next
becomes an ookinete.' ii, ookinete, or wandering cell, which penetrates into the wall
of the stomach of the mosquito, ij, ookinete in the outer region of the wall of the
stomach, i. e., next to the body cavity, f,,^ young oocyst, derived from the ookinete.
14, oocyst, containing sporoblasts, which are to develop into sporo/.oites. 75. 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. //, transverse
section of salivary gland of an Anopheles mos(iuito, showing sporozoites of the malaria
parasite in the gland cells surrounding the central canal.

1-6 illustrate schisogony (asexual production of si>ores) ; 7-/(5, sporogouy (sexual
production of .spores).

After C^RASSi and Leuckart, by permission of Dr. Carl Chun.

302 ENTOMOLOGY

in\'estig'ators thought to Ije due to chfferent species of para-
sites; and when, as often happens, the malarial chill occurs
every day. this is attributed to two sets of tertian amcebulse,
sporulating on alternate days.

After several successive asexual generations, there are pro-
duced merozoites which develop — no longer into schizonts —
but into sexual forms, or gametes. These occur in red
blood corpuscles either as niacroganicfcs ( female, 7, S) or as
niicrogaiiicfoblasfs (male, /a, 8a). in which forms the parasite
is introduced into the stomach of a mosquito which has been
feeding upon the Ijlood of a malarial patient. The macro-
gamete now lea^"es its blood corpuscle and becomes spherical
( p ) , as does also the micrc )gametoblast ( ga ) ; but the latter puts
forth a definite number (si.v, in P. prcccox, gh) of flag'ella,
or iiiicrogamctcs, which separate off as motile male bodies,
capable of fertilizing the macrogametes. A microgamete
penetrates a macrogamete (/o) and the nucleus of the one
unites with that of the other. The fertilized macrogamete now
becomes a migrating cell, or ookiiicfc (//). which penetrates
almost through the wall of the stomach of the mosquito (/-')
and then becomes a resting cell, or cyst. This oocyst (/^?)
grows rapidly and its contents develop, by direct nuclear divis-
ion, into sporoblasts ( /-/, /_5 ) , which differentiate into spindle-
shaped spoi'o:::oitcs ( 16. I). The sporozoites are liljerated into
the body ca\'itv of the mosquito, carried in the blood to the sali-
vary glands (as well as elsewhere) and thence along the hypo-
pharynx 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 mala-
rial organisms was discovered by Manson and Ross and con-
iirmed by Koch, Sternlierg and others. It has been found
repeatedly that certain mosquitoes (AiiopJiclcs) after feeding
on the blood of a malarial patient can transmit the disease by
means of their " bites " to healthy persons. Thus, Anopheles
mosquitoes were fed on the Ijlood of malarial subjects in Rome
and then sent to London, where a son of Dr. Manson allowed

INSECTS IN RELATION TO OTHER ANIMALS 3O3

himself to be bitten by the insects. Though previously free
from the malarial org-anism, he contracted a well-marked
infection as the result of the inoculation.

Furthermore, it is higiily probable that malaria cannot be
transmitted to man except through the agency of the mos-
quito. This appears from the oft-cited experiment of Doc-
tors 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 h(^use carefully against moscjuitoes and to retire indoors
before the insects appeared in the evening. Simply by ex-
cluding Anopheles mosquitoes, with which the Campagna
swarmed, these investigators remained perfectly immune from
the malaria which was ravaging" the vicinity.

In a later experiment on the island of b^ormosa, one com-
pany of Japanese soldiers was [)rotected from mos(|uit()es and
suffered no malaria, while a second and unpr(jtected company
contracted the disease.

The evident pre\-enti\-e measures to be taken against ma-
laria are ( i ) the a\-oidance of mosquito l)ites, by means of
screens, and washes of eucalyptus oil, camphor, oil of penny-
royal, oil of tar, etc., applied to exposed parts of the body;
(2) the isolation of malarial patients from moscphtoes, in
order to prevent infection; (3) the destruction of mosquitoes
in their breeding places, especially by the use of kerosene and
by drainage. During una\'oi(lal)le exjiosure in malarious
regions, quinine should be taken in doses of six to ten grains
during the day at inter\'als of four or five days (Sternberg).

Culex and Anopheles. — The moS(|uitocs of Xorth America
number one hundred and twenty-fi\c known sijecies. Of these
only the genus Anopheles transmits malaria to man, though in
India, Ross found that Cnlex transmits a form of malaria to
sparrows. These two common genera are casilv distinguish-
able. In Culex the wings are clear; in Anoplieles thev are
spotted with brown. In Culex when resting, the axis of the

304 ENTOMOLOGY

body ff/rms a curx'ed line, the insect presenting a hnmp-l)acked
appearance: in Anopheles tlie axis forms a straight hne.
Ciilc.v has sliort maxillary palpi, while in Anopheles thev are
almost as long as the prol:)Oscis. The note of the female
Anopheles is several tones lower than that of Ciile.v, and only
the female is 1)loodthirsty, by the way. As regards eggs,
larvi'e and pupa-, the two genera differ greatly. The eggs of
Ciile.v are laid in a mass and those of Aiiopheh's singly; the
larvcC of Ciile.v hang from the surface film of a pool at an
angle of aliont forty-fi\-e degrees, while those of Anopheles
are almost parallel A\ith the surface of the water in which
they live.

The bite of an Ajiopheles 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 pro\'e that
malaria exists where there are no Anopheles mosquitoes,
b'inally, fe\'ers are sometimes diagnosed as malarial which are
n(jt so.

Possibly the malarial parasite can C(jm]:)!ete its cycle of
development in other animals than man. It is also possible
that originally the malarial organism was derived by mos-
quitoes from the stems or other parts of aquatic plants, and
that its effects (>n man are incidental phenomena.

Yellow Fever. — It has now been demonstrated that the
dreaded disease. }-ellow fe\'er, is transmitted from one human
being t(_) another by the l)ite of a mosquito { Stegoinyia fcis-
eicitci) and in no other \\a)' excepting, of course, l:)y the arti-
ficial injection of diseased blood, ddie discovery of the mode
of transmission of the disease was made in Cuba during igoo
and 1902 liy Dr. Reed and his corps of United States army sur-
geons. These investigators succeeded in transmitting the dis-
ease to healthy subjects l)v inoculation frcjm mosquitoes which
had previously fed on the blood of yellow fever patients. To
convey the disease, howe\-er, a period of ten to thirteen
days was necessarv between the original l)iting of a patient

INSECTS IN RE;.ATI0N TO OTHER ANIMALS 3O5

and the inoculation of a healthy sul)ject. The disease fol-
lowed the hite of an infected Sfci^ouiyla with remarkable
precision.

Furthermore, Dr. Reed and his associates found that yel-
low fe\'er could not be conveyed by means of the clothing,
bedding', etc., of fever patients, so long" as moscjuitoes were
excluded. In the absence of the mosquito the yellow fever
patient is harmless and in the absence of a patient the mos-
quito is harmless ( Sternl)erg-). The disease terminates in
cold weather with the disappearance of the mosquito.

rre\'entive measures based upon these recenth' accpiired
facts ha\e been wonderfully successful. The city of Havana,
in \\-hich yellow fe\-er had always pre\-ailed, has now been
freed of the disease.

The specific cause of yellow fever has as yet eluded detec-
tion in the human body. There has been discovered, how-
e\'er, in the stomach and salivary glands of mosquitoes in-
fected with }ellow fever, a protozoan parasite (order Coc-
cidiida), the sexual cycle of \\hich, ending in the development
of sporozoites, has been traced in the body of the Stcgomyia.
This coccidium may or may not prove to be concerned in the
transmission of the disease.

Other Diseases. — Typhoid fe\er is transmitted frequently
l)y the C(jmmon house il)', which may carry the bacillus from
the excreta of typhoid patients to food supplies in kitchens or
elsewhere. The spread of the disease in arm}- camps is due
chiefly to the house fly (Mitsca (loincsticd) , as was demon-
strated in 1898 l:)y a commission of the I'nited States army.

The dreaded disease tilariasis (elephantiasis) of Oriental
tropical regions is transmitted by mosquitoes of the genus
Ciilcx, as Dr. Manson disco\ered many years ago. The dis-
ease is due to a parasitic worm (l-ihiria), both sexes of which
lodge in the hniphatic vessels, ol)Struct the flow of the lymph
and thereby cause an abnormal enlargement of the parts in
which they occur. The embryos' of the parasite pass into the
blood and thence into the body of the mosquito; there they
21

306 ENTOMOLOGY

remain in the thoracic muscles for a time and become larv?s,
which at length pass through the proboscis of the moscjuito
into the skin of man. It is possiljle, though not proved, that
other mosquitoes than Ciilcx and indeed other kinds of insects
are involved in the transmission of iilariasis.

In Egypt, an eye disease is transmitted Ijv the house tlv.
There is some evidence that tlie buljonic plague is spread
through the agency of fleas. .Vnthrax of cattle is carried Ijy
gad flies (Tabanidre). A South African disease fatal to
horses, cattle and dogs, though not to man, is transmitted
from infected to healthy animals l)y the prol)oscis of a muscid
fly, Glossiua jiiorsifaiis, as has been mentioned. The specific
cause of this disease is a blood parasite similar to that of
malaria. Finally, the destructive Texas fever of cattle is
undoubtedly transmitted l)y the common cattle-tick, as was
discovered by Theobald Smith, though the tick is not, properly
speaking, an insect.

CHAPTER X

INTERRELATIONS OF INSECTS

Fig. 270.

Insects in general are adapted to ntilize all kinds of organic
matter as food, and they show all gradations of hahit from
herhivorous to carnivorous. The many forms that derive
their food from the hodies of other insects may con\-eniently
he classed as predaceous or parasitic.

Predaceous Insects. — Among Orthoptera, Alanticke 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 extensilile labium with
which to gather in the prey. The
adults catch with surpassing-
speed and precision a great va-
riety of flying insects, mosth'
small forms, but occasionally but-
terflies 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 instantly stripped and
devoured, these operations being-
facilitated l)y the excessive mobil-
ity of the head. The hemipter-
ous families Corixid?e, Notonect-
id;c (Fig. 224), Nepid?e, Belos-

tomid?e (Fig. 22), Xaucorid'c (h^ig. 62, D) . Re(luviid;e and
Phymatidre are predaceous, with raptorial front legs and sharp
beaks. Some of the Pentatomid.e (Fig. 270) are of con-
siderable economic \alue on account of their ])redaceous
habits. Most of the Xeuroptera feed upon other insects.

307

Nyiuiiii of I'odisiis sl^iiwsiis suck-
iiit; the blcKid fniin a clover cater-
pillar, Culias pliiluilicc. Natural
size.

30S ENTOMOLOGY

The Mynnclcoii lar\'a digs a fiuinel-sliaped pitfall, at the l)ot-
tom of which it l)uries itself to await the fall of some iinluck\"
ant. The Clirysof^a lar\-a impales an aphid on the points of
its mandil)les and sucks the blood through a groove along
each mandible (big. 45, E). the maxilla htting against this
groo\'e to form a closed cliannel. Several families of Coleop-
tera are almost entirely predaceous. Among aquatic beetles,
Dytiscidae are carnivorous both as larvae and imagines, Gvrin-
k\x subsist chietiy upon disal)led insects, l)ut occasionalh" eat
plant substances, and Hydro];)hilidae as larv;e catch and devour
other insects, though some of the l^eetles of this family {H.
triangularis, for example, l^'ig. 22C)) feed largely if not en-
tirely upon A'egetation. Of terrestrial Coleoptera, the tiger
beetles (Cicindeli(ke) are strictly predaceous upon other insects.
The Cicindcla larva lives in a burrow in the soil and lies in
wait for passing insects; a pair of hooks on the fifth segment
of the alidomen serves to pre\'ent the lar\'a from l)eing jerked
out of its burrow by the struggles of its captive. Idie large
famil)' CaraljidcC is chietly predaceous: these "running
beetles " l)oth as lar\-;e and adults easily overtake and capture
other terrestrial insects. The Carabiike, howe\"er. are by no
means exclusively carnivorous, for many of them feed to some
extent upon fungus sp(jres, pollen, ovules, root-tips and other
vegeta1)le matter, as Forbes has found ; Harpalns caligiiiosiis
eats the pollen of the ragweed in autumn: Galcrita jaiiiis eats
caterpillars and occasionall}- the seeds of grasses : Calosoiiia,
howe\'er, appears to be strictly carnix'orous. feeding" chiefly
upon caterpillars and being in this respect of considerable eco-
nomic importance. As a whole, Caraljidce prefer animal food,
as appears from the fact that when canker worms, for in-
stance, are unusually abundant thev form a correspondingly
large percentage (jf caral)id food, the increase being compen-
sated by a diminution in the amount of vegetable food taken
(Forl)es). Coccinellid larwe (excepting Epilacluia, \\hich
eats lea\'es) feed almost entirely u])( n plant lice and consti-
tute one of the most etTecti\'e checks upon their multiplication;

INTERRELATIONS OF INSECTS 3O9

the beetles eat aphides, but also fungus spores and pollen in
large quantities. Though Lepidnptera are pre-eminently phy-
tophagous, the larva of Fciiiscca farqitiiiius is unitpie in feeding
solely upon plant lice, particularly the woolly Sc/iLCoiiciira tcs-
scllata of the alder. Among Di])tera, AsilidcC, MidaidcT,
Thereyi(ke and Empididc-e are the chief predaceous families.
Asilid^e ferociously attack not only other flies, but also beetles,
bumble bees, butterflies and dragon flies ; as larvce they feed
largely upon the laryce of beetles. Many of the laryre of
SyrphidcC prey upon plant lice, and the larycie of / 'olitccUa feed
in Europe on the lar\';e of Immble l)ees and wasps. Of
Hymenoptera, the ants are to a great extent predaceous,
attacking all sorts of insects, but particularly softdjodied
kinds; while \"espidce 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 l)odies of birds and mammals, very
few occur as such on the bodies of other insects; one of the
few is Branla cccca, a wingless dipteron found on the body
of the honey bee.

A vast number of insects, however, undergo their larval
development as internal ])arasitcs of other insects, and most
of these parasites belong to the two most specialized orders,
Diptera and Hymenoptera.

The larva? of Bomb\liid;e feed upon the eggs of Orthop-
tera and upon lary;c of Lepidoptera and Hymenoptera.
Tachini(ke are the most important dipterous [)arasites of other
insects and lay their eggs most frequentl\- u])on caterpillars;
the larVfC bore into their victim, develop within its Ijody, and
at length emerge as winged insects. These parasites often
render an im])ortant serxice 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 primar)- dixisions of the order. They are immensely

3IO

ENTOMOLOGY

important frum an economic standpoint, particnlaiiy the Ich-
neumonid<e, of which more than ten thousand species are al-
ready known. Our most conspicuous ichneumonids are the
two species of llialcssa, T. atrata and T. liiinifor {V\g. 271),
with their long' ovipositors ( three inches long' in liiiiator, and

Fig. 271.

Oviposition of Tluilcssa luuator. Natural size. — After Riley.

four to four and three (|uarters inches in atrata). Thalcssa
bores into the trunks oi trees in order to reach the l)urrows of
another large hymenopteron, Trcmc.v coluiuba (Fig. 31 ), upon
wdiose larvcC the larx-a of Thalcssa feeds.

The enormous family Braconid;c, closely related to Tchneu-
monidcC, is illustrated 1)y the common ^4paiitclcs coiigrcgatiis,
which lays its eggs in the caterpillars of various Sphingid.T.
The parasitic lar\'cie feed upon the hlood and possiblv also the
fat-body of their host, and at length emerge and spin their co-
coons upon the exterior of the caterpillar ( Fig. 272) .sometimes
to tlie number of se\'eral hundred. Species of Apliitliiis trans-
form within the bodies of plant lice, one to each host, and the
imago cuts its way out throug'h a circular opening with a cor-
respondingly circular lid. Chalcidida-. of which some four
thousand species are kno\\n. are usually minute and ])arasitic;

INTERRELATIONS OF INSECTS

311

thoug'h some are phytophagous, for example. Isosoina Jiovdci,
which hves in the stems of grasses, especially wheat, rye and
barley. Chalcitls affect a great \'ariety of insects of one stage
or another, such as cateri)illars, pup;c. cockroach eggs, plant
lice and scale insects; while some of them dex'elop in cynipid
galls, either upon the larvcC of the gall-makers or upon the
larvss of in(|uilines. Giard in France reared more than three
thousand chalcids [Coj^idosoiua tniiicalcUum) from a single

Fig. 272.

A tomato worm, Flilcgcthuiil ins se.vta, bt-aring cocoons of the parasitic .-ipantclcs con-
grcgatus. Natural size.

caterpillar of Plusia. Proctotrypidic are remarkable as para-
sites. Most of them are minute; indeed this family and the
coleopterous family Trichopterygidcie contain the smallest
winged insects known — species but one third or one fourth
of a millimeter long. A large ])r()])ortion of the rroclotr\--
pid;e are parasitic in the eggs of other insects or of s])iders,
several sometimes developing in the same tgg; others affect
odonate nymphs and coleopterous or dii)ter(^us larv;e, while
several si)ecies have been reared from cccidomyiid and cynipid
galls, and many ])roctotrypi(ls are parasites of other parasitic
insects — in other words, .are Jiyj^crparasitcs.

312 ENTOMOLOGY

Hyperparasitism. — Not only are primary parasites fre-
quently attacked l)y other, or secondary, parasites, but tertiary
parasitism is known to occur in a few instances, and there is
some reason to beheve that even the quaternary type exists
among" insects, as in the following' case.

The caterpillar of Hcmcrocainpa (Orgyia) Iciicastigma
defoliates shade trees in the northeastern United States. An
en()rmous increase of this species in the city of Washington in
1895 was attended by a corresponding increase of parasitic
and predaceous species, and this unusual o^jportunity 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. Icucostigiiia numbered 2;^ spe-
cies — 17 Hymenoptera and 6 Diptera : of the hyperparasites
(all hvmenopterous ) 13 were secondary, 2 and pr()l)al)ly 5
were tertiary, and one of these ( Asccodcs albitarsis) may un-
der certain conditions prove to be a quaternary parasite. To
illustrate — The ichneumon Pimpla inquisitor, an important
primary parasite of lepidopterous lar\'ce, lays its eggs in cater-
pillars of H. Icucostigina : its larvae suck the blood of their
host and at length spin their coci^ons within the loose cocoon
of the Hcuicrocanipa. These cocoons have yielded a well-
known secondarv parasite, the chalcid Dibrachys bouchrajius.
Now an()ther chalcid, Asccodcs albitarsis, has been seen to issue
from a pupa of this Dibrachys, thus establishing tertiary para-
sitism. h\u'thermore, it is quite possible that DibracJiys itself
is a tertiary parasite, in which event the Asccodcs might be-
come a parasite of the quaternary order.

Economic Importance of Parasitism. — If a primary para-
site is l)enehcial, its own parasites are indirectly injurious, gen-
erally speaking: while those of the third and the fourth order
are respectively beneficial and injurious. The last two kinds
are so rare, howe^'er, as to he of no practical impcirtance from
an economic standpoint. The first two kinds are of immense
economic importance, particularly the primary parasites.
" Outbreaks of injurious irisects," says Howard, " are fre-

INTERRELATIONS OF INSECTS 313

(juently stopped as though l)y magic by the work of insect ene-
mies of tlie species. Hnlibard found, in iS.So. tliat a minute
parasite, Trichograinma prcfiosa, alone and unaided, almost
annihilated the fifth brood of the cotton worm in I^dorida, fully
ninety per cent, of the eggs of this prolific crop enemy Ijeing
infested by the parasite. \ot longer ago than 1895, in the
city of W^ashington, 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 in-
sects, to the complete relief oi the city the following year.
The Hessian fly, that destructive enemy to wheat crops in the
United States, is practically unconsidered by the wheat grow-
ers of certain states, for the reason that whene\"er its numbers
begin to be injuriously great its parasites increase to such a
degree as to prevent appreciable damage.

" The control of a plant-feeding insect by its insect enemies
in an extremely complicated matter, since, as we ha\'e already
hinted, the parasites of the parasites play an important part.
The undue multiplication of a \egetal)]e feeder is followed by
the undue multiplication of parasites, and their increase is fol-
lowed by the increase of hyperparasites. Following- the very
instance of the multiplication of the shade-tree caterpillar 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 prol)-
a1)ly did not exist, but even these ([uaternary 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 b}"
an abun<lant:e of i)rimar\- ])arasites, faxored b\' ;m abnndrmce
of secondary parasites (since these will destroy the primary-
parasites), hindered again by an abundance of tertiary jjara-
sites, and fax'ored again bv an abundance of (|naternarv para-
sites."

Entomologists hax'e made many attempts to import and

314 ENTOMOLOGY

propagate insect enemies of various introduced insect pests,
and some of their efforts have l^een crowned with success, as
was n()tal)ly the case when Noviits caniimilis, a ladv-bird
beetle, was taken from AustraHa to CaHfornia to destroy the
fluted scale.

Form of Parasitic Larvae. — The peculiar environment of
parasitic larva? is responsible for profound changes in their
organization. These larvie, in general, are apodous. the body
is com[)act and the head is more or less reduced, sometimes to
the merest rudiment. These characters, occurring also in such
dipterous larvcC as live in a mass of decaying' organic matter
and again in those hymenoi)terous larva? whose food is pro-
vided l)y the mother or by nurses, are to be attrilouted to the
presence of a plentiful supply of food, obtainable with little or
no exertion,, and indicate, not primitive simplicity of organiza-
tion, but a high degree of specialization, as we have said before.
The embryonic de\elopment of parasitic lar\;e is frequently
highly anomalous, as appears in the chapter on development.

Maternal Provision. — Excepting several families of Hy-
menoi)tera and the Termitiche, few insects make any special
provision for the welfare of the young beyond laying the eggs
in some appropriate situation. ]\Iany insects, as walking-
sticks (PhasmidcC) and Ma}- beetles ( Lachiiosfcnia ) simply
drop their eggs to the ground, lea\ing the young to shift for
themseh'es. Most insects, howe\-er, instincti^■e!y la_y their
eggs in situations where the larva is sure to lind its proi)er food
near at hand. Thus \arious flies and beetles deposit their eggs
on decaying animal matter, Ijutterflies 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 Ah\'r()phonis go so far as t() bury the body of a liird,
mouse or other animal in wdiich the eggs are to l)e laid ; and
in this instance the male assists the female in undermining and
afterward covering the 1)ody. A similar co-operation of the
two sexes occurs in the scaraba?id beetles known as " tumble-
bugs," a pair of which may often be seen rolling along labori-

INTERRELATIONS OF INSECTS 3 15

ously a ball oi (lun,^- which is to serve as larval food. The
female mole-cricket {Gryllolnlpa ) 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. Tenthredinichie simplv lav their eggs on
the proper food plants (;r else insert them into the tissues of
the plants. Sphecina make a nest, proxision it with food and
leaA-e the young to care for themsehes. Queen wasps and
bumble bees g'o a step further in feeding the first larvae and
carrying them to maturity, h'inally. in the honey bee the care
of the young is at once relegated by the cpieen to other individ-
uals of the colony, as is also the case among ants.

Some of the most elal)orate examples of purely maternal
provision are found among the digger wasps and the solitary
wasps; these instances are highly interesting, inxolving as they
do an intricate co-ordination of many retlex actions — as ap-
pears 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 ])ro\isioned with insects or spiders
wdiich have been stung in such a way as usuall}- to be para-
lyzed, with<»ut being actually killed. The various species of
Sphecina frecjuently select particular species of insects or
spiders as food for the young. Pepsis foruwsa (Pomi)ilida')
uses tarantulas for this purpose; Sphccius spcciosiis ( Bembe-
ciche ) stores her nest with a cicada; Xvssonid;c |)ick out cer-
tain species of Alembracida' : mud-daubers (Sphecid;e) use
spiders; and other families of Sphecina capture 1)ees, beetles,
plant lice or other insects, as the case may be. The solitary
wasps (Eumenid.'c) are similar to the digger wasps in h.abits.

Of the solitary bees, Mcgachilc is well known for its habit
of cutting pieces out of rose lea\es ; it uses oblong pieces to
form a thimble-shaped tube which, after being stored with ])ol-
len and nectar, is plugged with a circular piece of leat. d"he
larval cells are made either in tunnels excavated in wood by
the mother or else in cracks or other chance cavities.

ENTOMOLOGY

One of the carpenter Ijees, Ccrafiiia dupla, which l)uil(ls in
the hoUow stem of a plant a series of larval cells separated l)y
partitions, is said by Comstock to watch over her nest nntil
the young mature.

The transitifjn from the solitary to the social habit is indi-
cated in the life-histories of wasps and bumble bees, where a
solitary (|ueen founds the colony Ijut soon relegates to other
in(li\'i(luals all duties except that of egg-laying. The social
insects will now be considered.

Termites
Though popularlv known as " white ants." the termites are
Cjuite different from true ants, being indeed not \&v\ far re-
moved from the most primiti\'e insects. In \\q\\ of the ex-
treme contrast in structure and dex'elopment between termites
and ants, it is remarkable that the two groups should \ya\q
much the same kind <jf complex social organization.

Fig. 27^,.

N'ai'ious forms of Tcnncs liicifiigiis. A, adult worker; B. soldier; C. perfect winged
insect; D. perfect insect after shedding the wings; E. young complementary queen;
F, older complementary queen. Enlarged. — .\fter Grassi and S.\ndias.

Classes of Termites. — In general, four kinds of adults are
produced in a community of termites, namely — ■i^'orkcrs. sol-
diers, •K'iiiL^cd males and ■leijii^cJ fniialrs.

The workers (Fig. 2/T,, .^ ) , which are ordinarily the most
numerous, are of either sex, l)ut their reproducti\'e organs are
undex'eloped. A w'orker-ant or bee, however, is always a

INTERRELATIONS OF INSECTS

317

female. The termite workers, as the name impHes, do most
of the work; they make the nest, provide food, feed and care
for the young' and the ro)'al pair, and attend to many other
domestic duties.

The sokhers, hke the workers, are of either sex, with nnde-
\'eloijed sexual organs. With monstrous mandibles and head
(Fig. 2yT^, B), their chief dut)- ap])arentl}'
is to defend the colony, though they fre- "" "^"^'

quently fail to do so.

The winged males and females (Fig.
2"/^^, C) which are sexually mature,
s^^•arm from the nest and mate. After
the nuptial flight the pair burr(jw into
some cre\'ice and shed the wings, which
break off each along a peculiar transverse
suture, leaving four triangular stumps
(Fig. 2"/ 7^, D). The king and (|ueen
found a new colony and may live for
several years, sheltered in a special cham-
ber, the queen, meanwhile, becoming
enormously distended (Fig. 274) with
eggs and almost incapable of k^comotion.
The prolificacy of the queen is astonish-
ing; she can lay thousands of egg's,
sometimes at the rate of sixty per minute.
She is the nucleus of the colon}*, and
should she l)ecome inc;q)acitated. is replaced bv one or more
snhstiliitc (|ueens. which have been de\'elo])cd to meet the emer-
gency; similarly, a substitute king' is matured ui)on occasion.
These substitutes (Fig. 273. E) differ from the ]M'imary pair
in having nymphal wing-pads in place of the remains of func-
tional wings.

These six kinds are by no means all that may occur in a
single colony. Tcrincs lucifugus, according to Grassi. lias no
less than fifteen kinds of indi\iduals. counting n)"mphs in \-ari-
ous stages of development toward workers, soldiers, and pri-
mary or else complementary, or reserve, kings or cjueens.

Queen iif Tcnncs ohc-
siis. Natural size. — After

UACiEN.

3l8 ENTOMOLOGY

Origin of Castes. — Grassi maintains tliat 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 di-
\'ersities of caste, except the sexual ones, to the character and
amr>unt of the food.

Food. — The food of termites is of six kinds: (i) wood;
(2) matter emitted from the oesophagus or rectum, termed
respecti\'ely stomodreal and proctodreal food; (3) cast skins
and other exuxial stuff; (4) the bodies of their companions;
(5) saliva; (6) water. Of these the proctod?eal food is the
favorite. Xymphs receive at first only saliva; later thev get
stomodieal and proctodceal food until, finally, they are able to
eat wood — the staple food of a termite.

American Species. — Our common termite is Tcniics flavi-
pcs, which iiccurs throughout the United States, excavating-
its galleries in decaying logs, stumps or other dead wood. The
nuptial iiight 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 1jy 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 fe-
males are said to occur in the swarming season, a true queen
of T. flaz'ipcs is as yet unknown, the queen described by Hub-
bard being evidently, from her undeveloped wings, a substitu-
tion queen.

In the Western states, six species of termites are known, in-
cluding Tcniics lucifugiis, which has probably been introduced
from Europe. In this species the primar\- (|ueen is known to
exist. Regarding the Galifornian l\'nii<>psis inigiisficollis,
Dr. Heath says that if only one of the royal pair be destroyed
usually only one substitution form is developed, but when both
perish, from ten to forty substitutes appear, according to the
size of the colony; furthermore — a remarkable fact — these

INTERRELATIONS OF INSECTS

319

■rrJ

^^^ ''^^'i^

§:%<'.«?

-5*-^

iV' J'\ '^^i

suljstitution royalties may contain workers or even soldiers
capal)le of laying" eggs.

Architecture. — While many termites simpl}- hnrrow in dead
wood, other species construct more elaborate nests. A Jamai-
can species builds huge nests in the forks of trees, \\ith covered
passageways leading to the ground.

In parts of Africa and Australia, where they are free from

disturbance, termites erect huge mounds, frecjuently six to ten

and sometimes eighteen or twenty feet high, with galleries

extending as far 1)elow the

- Fir '"'■"

surface of the ground as '■ "'^

they do al>ove it. These im-
mense structures ( h^ig. 2y=^ )
consist chiefly of earth, ce-
mented by means of some
secretion int(T a stony clay,
with which also much excre-
mentitious matter is mixed :
they are pyramidal, colum-
nar, pinnacled or of \arious
other forms, according to
the species, and are perfor-
ated by thousands of pass-
ages and chambers, while
there are un<lerground gal-
leries extending awa\- from
the mound to a distance
of often several hundred
feet.

An extraordinary t_\-pc of mound is constructed l)v the
''compass," or "meridian," termites of Xorth Australia, for
their wedge-shaped mounds ( I'ig. 276), commonlv eiglit or
ten feet high, though sometimes as high as twent\- feet, are
directed north and south with surprising accuracv. JJv means
of this orientation the exposure to the heat of the sun is re-
duced to the nn'ninium, as occurs also in the case of manv Aus-

'IV-niiitc niiiund, Kinihcrley type, Australia.
— Aftor .Savii.le-Kent.

320

ENTOMOLOGY

Fig. 2/6.

tralian plants, the leax'es of which present their edges instead
of their faces to the sun.

More than one species of termite may inhal)it a single nest;
in one South African nest Haviland found five species of ter-
mites and three of ants. The
widely distributed genus Eiitcr-
nics is essentially a group of
inqiiiliitc, or guest, species,
d^ermite mounds afford shelter
to scor|)ions, snakes, lizards,
rats, and even l)irds, S()me of
which nest in them. The Aus-
tralian hushmen hollow out the
mounds to make temporary
ovens, and even eat the clay of
which they are composed, while
natives of India and Africa are
accustomed to eat the termites
themseh'es, the flavor of which
is said to he delicious.

Ravages. — In tropical re-
gions the amount of destruc-
tion done l3y termites is enor-
mous, and these formidable
pests are a constant source of
consternation and dread. The}-
emit a secretion that corrodes
metals and even glass, while
anything made of wo(_)d is sim-
ph' at their mercy. Always a\-oiding the light, they hollow
(;ut floors, rafters or furniture, lea\'ing onlv a thin outer shell,
and as a result of their insidious 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 l)e rebuilt on that account.

In the United States and Europe few species of termites

^Nlound of the " compass " termite
of North Australia. — After S.wille-
Kent.

INTERRELATIONS OF INSECTS

321

occur, and they do little injury as compared with the tropical
species; thoug'h our common Tcniics flavipcs 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 myrmecophilous species and ants. These
tcruiitopJiUous forms, howe\-er, 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 w^as highly prized by the old Greeks and Romans
(as appears from the writings 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 domesti-
cation, the honey bee, unlike most domesticated animals, is still
so little dependent upon man that it readily returns to a wild
life. Under many distinct races, which are due largely to
human intervention. Apis nicllifcra is widely distributed over
the earth.

Castes. — The species comprises three kinds of individuals :
qiiccii, drone and zuorker (Fig. 277). The workers are fe-

FiG. 277.

A B C

The honey bee, Afjis mcllifcra. A, queen; B, drone; C, worker. Natural size.

322

ENTOMOLOGY

males with an atrophied reproductix'e 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 man-
agement of the community. Though hibernating workers live
eight or nine months, the other workers live Init from five to
twelve weeks.

The term queen is, of course, a misnomer, for the govern-
ment of the hive is anything but monarchial. The chief duties
P ^„g 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 mat-
ing, 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.
'9Biftf^~f^. The Comb.— W^ax, of which the comb
'^i^ttiM^rr^ is built, is made from honey or sugar,
many pounds (twenty, according to
A, bases of comb cells; H\iber) of houcv 1)eing required to make

B, section of comb. Some- • • . o j.

what enlarged.— A f t e r one pouud of wax. The worlvcrs, gorged
with nectar, cling to one another in a
dense heated mass until the white films of wax appear under-
neath the abdomen (Fig. 102); these are transferred to the
mouth by means of the wax-pincers (Fig. 263, C) of the hind
legs and are masticated with a fluid, secreted by cephalic
glands, which alters the chemical composition of the wax and
makes it plastic.

The workers now contrilnite their wax to form a vertical,

INTERRELATIONS OF INSECTS

323

hanging septum, on the opposite sides of which they proceed
to bite out pits — the bottoms of the future cehs — using the
excavated wax in making the cell walls. The bottom of each
cell consists of three rhombic plates (Fig. 278, A), and the
cells of one side interdigitate with those of the other side (Fig.
278, B) in such a way that each rhomb serves for two cells
at once. Wax is such a precious substance that it is used
(instinctively, however) always with the greatest economy;
the cell walls are scraped to a thinness of 1/280 or even 1/400
of an inch, and nowhere is more wax used than is sufficient
for strength; one pound of wax makes from 35,000 to 50,000
worker cells. The cells, at first circular in cross section, be-
come 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 mathemat-
ical 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, des-
tined for drones or to hold
honey, are one cjuarter of
an inch across.

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, fw, horsechestinit
or other trees; though they will utilize instead such artificial
sul)stances as grease, pitch or varnish. As winter approaches,
the bees apply the propolis liberally, making their abode tight
and comfortable.

Comb of honey bee, showing the insect in
various stages. At the right are large queen
cells. — After Benton.

324

ENTOMOLOGY

Larval Development. — A\'hen the l^roocl cells are ready,
the queen, attended by workers, lays an egg in each cell and
has no further concern as to its fate. After three days the egg-
discloses a footless grub ( Figs. 279, 280 ) which depends at first
upon the milky food that bathes it and has been supplied 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 intestine of the larva do not communicate with each other,
the excretions 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 W'Orkers
having meanwhile covered the larval cell with a porous cap

Honey bee. /, feeding larva; p, pupa; s, spinning larva. — After Cheshire.

of wax and pollen (Fig. 280) 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-attentive nurses. Now, after accjuir-
ing the use of its faculties, 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 of days recjuired for development, as
appears in the following table, from Benton :

Egg. Larva. Pnpa. Total.

Queen, 3 5>^ 7 ^SYz

Worker, 3 5 13 21

Drone, 36 15 24

The cells in which queens develop (Fig. 279) are quite dif-
ferent from worker or drone cells, being much larger, more

INTERRELATIONS OF INSECTS 3^5

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 struc-
ture; 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 sen-
sory peculiarities ; there remain to be added, how' ever, some
other items of interest, chosen from the many.

A colony of bees in good condition at the opening of the
season contains 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, w^ith 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 spcrmatheca, opening into the egg-
passage. At the time the queen mates, there are in the hive
neither eggs nor young larvse from which to rear another
cjueen ; 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 \ery 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

326 ENTOMOLOGY

water. Bees snck or lap it up from such flowers as they can
reach with their flexil)le, sucking- tongTie, 0.25 to 0.28 inch
long. This nectar is taken into the Jioiicy 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 frequently far from agreeable. To make from this raw
product the healthful and delicious table luxury which honey
constitutes — " fit food for the gods " — is another of the func-
tions peculiar to the worker bee. The first step is the station-
ing of workers in lines near the hive entrances. These, l)y
incessant buzzing of their wings, drive currents of air into and
out of the hi\e and over the comb surfaces. If the hand be
held l)efore 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. Instead 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 propor-
tionate to the amount and thinness of the liquid. Frequently
the ripening honey is removed from one set of cells and placed
in others. This mav be to gain the use of certain combs for
the queen, or possibly it is merely incidental to the manipula-
tion the bees wish to give it. When, finally, the process has
been completed, it is found that the water content has usually
been reduced to 10 or 12 per cent., and that the disagreeable
odors and flavors, probably due to volatile oils, have also been
driven oft" in a great measure, if not wholly, by the heat of
the hi\'e, largely generated by the bees. Du'ring the manipu-
lation 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

INTERRELATIONS OF INSECTS 32/

to the brood and bees. The work of seaHng with waxen caps
then goes forward rapidly, the covering- being more or less
porons. Each kind of honey has its distinctive flavor and
aroma, derived, as already indicated, mainly from the particu-
lar blossoms by which it was secreted, but modified and soft-
ened by the manipulation given it in the hives. The last three
paragraphs are taken from Benton's useful manual.

The phenomenon of " swarming " results from the tremen-
dous reproductive capacity of the queen, though it is immedi-
ately an instance of posit iz'c phofofropisiii, 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,
however, and the departed queen is soon, if not already, re-
placed 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 of special form is constructed, and its occu-
pant, instead of being weaned, is fed almost entirelv 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 reproducti\e system
in proportion to the amount received. Drone larv?e get much
of it, though not so much as queens, while an occasional excess
of this " royal jelly " is believed to account for the abnormal
appearance of fertile workers.

Parthenogenesis, or reproduction without fertilization, is
known to occur in the bee, as well as in \arious other insects.
The always unfertilized eggs of workers [)roduce invariably
drones, as do also unfertilized eggs of the (jueen. Probably
the queen cannot control the sex of her eggs, as she has long
been supposed to do, for Dickel has recently found, among
other revolutionary facts, that all the eggs of the normal
mother bee are fertilized.

328 , entomology

Bumble Bees
Familiar as the biimljle l^ees are, their habits are but imper-
fectly known. The queen hibernates and in spring starts a
colony, utilizing" frequently for this purpose the deserted nest
of a field mouse or sometimes the burrow of a mole or gopher.
The queen lays her eggs in a small mass of pollen mixed with
nectar (Putnam). The larv?e 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 subsequently
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 different 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.

Social Wasps

The Social Wasps constitute the family Vespidce, of which
we have three genera, namely, J\-'spa, Polistcs and Polybia,
the last genus being represented by a single Californian species.

Vespa. — Some species of Vcspa, as J\ iiiaculafa, make a
nest which consists of several tiers of cells protected by an
envelope (Fig. 281), attaching" the nest frequently to a tree;
other species, as gcniianica and vulgaris, make a nest under-
ground. The paper of which the nests are composed is manu-
factured 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.

A solitary queen founds the colony in spring; she starts the
nest, lays eggs, feeds the young and bring"s forth the first
workers ; these then relieve her — continue the building" opera-
tions, collect food, nurse the young, in short, assume the bur-
den of the labor. In the latter part of summer, fertile males

INTERRELATIONS OF INSECTS

3-9

and females appear and pairing occurs. Though the statement
has often been made that only the }-oung queens survive the
winter, there is some reason to beheve that not only the queens
but also males and workers may hibernate successfully in the
nest.

The larvcC are fed at first. l)y regurgitation, upon the sugary
nectar of flowers and the juices of fruits, and later upon more

Fig. 281.

Nest of wasp, Vespa mnciilata. A, outer aspect; B. with envelope cut away to show
combs. Greatly reduced.

substantial food, such as the softer parts of caterpillars, flies,
bees, etc., reduced to a ])ulp by mastication; occasionally wasps
steal honey from bees.

The workers, as is usual among social ] lymenoptera. are
modified females, incapable of reproduction as a rule, though
the distinction between worker and queen is not nearly so sharp
among wasps as it is among bees. Worker eggs are said to
be parthenogenetic and to i)roduce onl_\' males. The males,
unlike those of the honey bee, are active laborers in the colony.
In the tropics there are wasps that form permanent colonies,
store honey and swarm, after the fashion of honey bees.

Polistes. — The preceding dcscri]jtion of J'cs/^a applies
equall)' well to our sexeral s])ecies of Polislcs, except that the

330 ENTOMOLOGY

nest of Polisfcs is a single comb hanging- by a pedicel and with-
out a protecting envelope. Miss Enteman, who has carefully
studied the habits of Polisfcs. finds that the larva spins a lin-
ing 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 Chi-
cago) 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 larg-e part of our knowdeclge of the habits of these remar-
kable insects has been obtained by the use of artificial formi-
caries, wdiich 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 ivorkers, 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 Formica fiisca, 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 S() often command at-
tention by their industry and pertinacity. In some species
certain of the workers are known as sohiiers; these may be
recognized by their larger heads and mandibles.

Polymorphism. — ^Ants and termites surpass all other in-
sects in respect to the number of forms under which a single

INTERRELATIONS OF INSECTS 331

species may occur. In some species of ants several types of
workers exist; these are distinguislied I)y structural peculiari-
ties of one kind or another, which possibly indicate special
functions, for the most part as yet unascertained. Further-
more, 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 crgatoid, 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 ferti-
lized, and the differences betw^een worker and queen and be-
tween workers themseh-es may be due to the quality and quan-
tity of the food that is supplied to the larvre by their nurses.
As in bees, the parthenogenetic eggs laid by abnormal workers
may produce males, as Forel, Lubbock and Miss Fielde have
found ; or they may produce normal workers, as Reichenbach
and Mrs. A. B. Comstock 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 helpless 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 i)upae
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 Ecifoii 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" cavi-
ties as nests; they make use of crevices in rocks and under
stones or l)ark, the holes made by l)ark-beetles, hollow stems
or roots, plant-galls, fruits, etc. The extraordinary " ant-
plants " have already received special consideration.

332 ENTOMOLOGY

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 gal-
leries and adding probably a secreted fluid which 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
subterranean galleries are often complex labyrinths ; frequentlv
there are long underground passages extending out in all direc-
tions, 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 egg"s, larvie or pupas.

Often a nest is excavated under a stone. As Forel ob-
serves, 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 pene-
trate the soil, while they go below as soon as the sun disap-
pears or when its heat becomes too strong. They select stones
that are neither too large nor too small to regulate the tem-
perature well, while other ants attain the same object by mak-
ing the nest under sheltering 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
cxscctoidcs, 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. cxscc-
toidcs is accustomed to form new colonies in connection with
the parent nest ; McCook found in the Alleghanies no less than
1, 600 nests, forming a single enormous community with hun-
dreds 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.

INTERRELATIONS OF INSECTS 333

As Forel says [translation] : " Tlie chief feature of ant
architecture, in contradistinction to that of the hees and the
wasps, is its irreg'ularity and want of uniformity — that is to
say, its adaptabihty, or the capacity of making all the sur-
roundings and incidents subserve the purpose of attaining 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 al)sorb the rays of the sun ; in a
forest it will live in warm, decayed trunks of trees ; in a rich
meadow it will li\'e in high, conical mounds of earth." Some
species construct peculiar pasteboard nests, as Lasiiis fuligiiio-
siis of Europe and tropical species of Crciiic7Sfogastcr; and
others spin silk to fasten leaves together, as Polyrhachis of
India and Qicophylla of tropical Asia and tropical Africa, the
silk l)eing probalily a salivary secretion, according to Forel.

Habits in General. — The habits of ants are an inexhaustible
and 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 recognize and spare members of their own colony,
even after manv months of separation and though the colony
may number half a million individuals. This recognition is
effected by means of an odor, distinctive of the colony and ap-
parently 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 statements apply
only to workers, howe\-er, for alien larvae and pui);e are fre-
quently captured and reared by ants, and Miss Fickle states

334 ENTOMOLOGY

that kings of one colony of Sfcnaiiinia 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 antenn?e 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
experiments that this phenomenon is purely mechanical and
involves no psychical Cjualities on the part of the ants. His
Dwn experiments, however, show that one ant can inform an-
other by means of an odor as to the whereabouts of food —
w'hich is certainly one form of communication.

Ants avoid sunlight as a rule but prefer rays of lower re-
frangibility to those of higher. Upon exposing ants to the
colors of the spectrum, as transmitted through glasses of dif-
ferent colors, Lubbock found that they congregated in greatest
numljers under the red glass and that the numbers diminished
regularly from the red to the violet end of the spectrum, there
being very few individuals under the violet glass.

Miss Fielde, experimenting with cjueens, \vorkers and young
of Stciiaimiia fidvuin piccuui in an artificial nest, covered half
the nest with orange glass and half with violet. " The ants re-
moved hastily from under the violet as often as an interchange
of the panes was made, once or twice a day, for about twenty
days. Thereafter they became indifferent to the violet rays."
" The plasticity of the ants is remarkably shown in their grad-
ually learning to stay where they were never disturbed by me,
imder rays from which their instincts at first withdrew them."

Ants are sensitive not only to the difTerent 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 Lubl^ock found. If, how-

INTERRELATIONS OF INSECTS 335

ever, 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 \'iolet ravs.

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 \'ersa. They show
no response to sounds of human contrivance, yet many of them
possess stridulating organs and organs that are doubtless audi-
tory; whence it may he inferred that ants can communicate
with one another l)y means of sounds. In rare instances the
stridulation of an ant can impress the human ear, as in a spe-
cies of At fa 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 reg'arded as purely instincti\-e and those that may indicate
some degree of intelligence. If any insects show signs of in-
telligence, the social Hymenoptera do so ; but in the study of
this recondite subject, false conclusions can be avoided only
by observation and experiment of the most critical kind.

Hunting Ants. — Some ants, as Formica fusca, live by the
chase, hunting their prey singly. The African " driver ants "
(Aiwiiniia arcciis), 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 \-er-
tebrates ; 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 liciton
(Fig. 283, B, C) ha\e similar habits and are likewise blind, or
else have but a single lens on each side of the head. These in-
sects hunt in armies of hundreds of thousands, to the terror of
every animate thin"' that thev come across. Thcv have no

336 • ENTOMOLOGY

permanent abode, but now and then appropriate some conveni-
ent hole for the purpose of raising- a new brood of marauders.

Slave-making Ants. — It is a fact that some ants make
sla\'es of other species. Foniiica saiigiiiiica, for example, will
attack a colon}' of Formica fiisca, kill its active members in
spite of their determined resistance, kidnap the larvse and pnpre
and carry them home, where the captives receive every care,
and at length, as imagines, serxe their masters as faithfully as
they would serve their own species. In the Alleghanies, ac-
cording to McCook, colonies of F. fiisca occur where there are
no " red ants " (F. saiiguinca) , but are hard to find wdiere the
ensla\-ing species occurs.

Although F. saiigiiiiica can exist very well without slaves,
Polycrgiis nifcscciis, of Europe, is notoriously dependent upon
their services, it being- doulitful whether it is capable of feed-
ing itself. This species is powerful as a warrior, but its man-
dibles are of little use, except to pierce the head of an adver-
sary. Strong\louotiis is still more helpless, while Ancrgatcs
(also of Europe) is said to depend absolutely upon its slaves.

Pi'lycrgiis lucid us occurs in the Alleghanies, where the col-
onies of this species, according to McCook, contain large num-
bers of the workers of Formica sclunifussi. The masters are
good fighters 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 workers
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 Myrmccocystus iiiciligcr, of

INTERRELATIONS OF INSECTS

337

Mexico, New Mexico and southern Colorado. In this species
some of the workers hang sluggishly from the roof of their
little dome-like chamber, several inches underground, and act
as permanent receptacles for the so-called honey, which is a
transparent sugary exudation from certain oak-galls ; it is gath-
ered at night by the foraging workers and regurgitated to the

Fig. 282.

Honey ants, Myniwcocystus mclligcr, clinging to the roof of their chamber. .Abont
natural size. — After McCf)0K.

mouths of the " honey-liearers," whose crops at length become
distended with honey to such an extent that the insects ( Fig.
282) 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.

Leaf-cutting Ants. — The most dangerous foes to vegeta-
tion in tropical America are the several species of Atta {Gico-
doiim. Fig. 283, A ). Living in enormous colonies and capable
of stripping a tree of its leaves in a few hours, these formida-
ble ants are the despair of the planter; where they arc a])un-
dant it becomes impossible to grow the orang-e, coffee, mango
and many other plants. These ants dig an extensive under-
ground nest, piling the excavated earth into a mound, some-
23

338

ENTOMOLOGY

times thirty or forty feet in diameter, and making paths in
various directions from the nest for access to the plants of the

Fig. 281

A, leaf-cutting ant, Atta ccphalotcs. B, wandering ant, Ecitoii drcpanopliontiii; C,
Eciton onmivorum. Natural size. — After Shipley.

vicinity ; Belt often found these ants at work half a mile from
their nest ; thev 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. 284) and carries it
home, or else drops it for another
worker to carr}' ; and two strings
of ants may be seen, one carry-
ing their leafy burdens toward the
nest, the other returning for more
plunder.

The use made of these leaves
has been the subject of much dis-
cussion. Belt found the true ex-
planation, but it remained ior
Moller to investigate the subject
so thoroughly as to leave no room
for doubt. The ants grow a fun-
gus upon these leaves and use it
A. B, cuts made in Cuphca as food. Tlic Ijits of Icavcs are

leaves in four or five minutes by l^i^gj^^jg^ Jj-ito a pulpy, SpOng^•
Atta discigera; natural size. C, j. j. y j. tj.

Atta discigera transporting severed maSS, UpOll wllicll tllC fuUg'US at

fragments of leaves; reduced. — , , ^r^, r ^ r

After Moller. length appears. The food for

INTERRELATIONS OF INSECTS

339

Fig. 28;.

the sake of whicli the ants carry on tlieir complex oper-
ations consists of the knohljeil ends of fnn^iis threads
(Fig. 285), and these l)0(hes, rich in hnich furni the most
important, if not the sole food of the leaf-cutting- ants. By
assiduously weeding out all foreign organisms the ants ob-
tain a pure culture of the fungus, and by pruning the fungus
they keep it in the vegeta-
tive condition and prevent
its fructification ; under
exceptional circumstances,
however, the fungus devel-
ops aerial organs of fructi-
fication of the agaricine
type, but this species (Ro-
cifcs gongylophora) has
never 1)een found outside
of ants' nests. The pecu-
liar clubbed threads were
produced by Moller in arti-
ficial cultures and are not
•spores, but products of cul-
tivation. Other ants are known to cultivate other kinds of
fungi for similar purposes.

]\IcCook has found a leaf-cutting ant (Atta fcrvciis) in
Texas, and mentions 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 fcrvciis 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 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 oljserver has gixen also a brief account of a leaf-
cutting ant that lives in New Jersey. This species (Atta scp-
tcntrioiialis) cuts the needle-like leaves of seedling pines into
little pieces, which are carried to the nest. Two columns of

Fungus clumps {Rozites gongylophora)
cultivated by ants of the genus Atta.
Greatly magnified. — After Moller.

340 ENTOMOLOGY

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
which are several small pulpy balls, consisting probably of
masticated leaves. Further studies upon our own leaf-cutting
ants, modeled after the admiral)le studies of Moller, are much
to be desired.

Harvesting Ants. — Lubbock observes that some ants col-
lect the seeds of violets and grasses and preserve them care-
fully for some purpose as yet unknown. From such a begin-
ning- as this may have arisen the extraordinary habits of the
agricultural, or harvesting, ants, of which some twenty species
are known from various parts of the world.

The Texas species Pogonouiyruicx barbatits, studied by
Lincecum and by ]\IcCook. clears away the herbage around its
nest (even plants several feet high and as thick as a man's
thumb) and le\-els the gTound, forming a disk often lo 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 eventually used as food. The ants pre-
fer the seeds of a grass, Aristida oligaiitlia, but the oft-repeated
statement that they sozu the seeds of this " ant-rice," guard it
and weed it, is denied by Wheeler.

Notwithstanding the elaborate studies of AlcCook upon this
subject, there still remain not a few essential cjuestions 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 niynnccopliiles. Most of
these are insects, of which Wasmann has catalogued 1,200
species, but not a few are spiders, mites, crustaceans, etc.

INTERRELATIONS OF INSECTS 341

Though the di\'erse relations l)et\\een myrmecophiles and ants
are bnt partially understood, these aliens may for convenience
be considered under fi\-e groups : capfiz'cs, guests, z'isifors, iii-
tntdcrs and parasites.

Captives. — Besides enslaving other species, as already men-
tioned, ants make use of aphids and some coccids for the sake
of their palatable products. The attendance of ants upon col-
onies of plant lice is a common 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, con-
trary 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 instances ants give much care
to their aphids, for example covering them with sheds of mud,
which are reached through covered passageways. ]\Iore than
this, however, some ants actually collect aphid eggs and pre-
serve them over winter as carefully as they do their own eg'gs.
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 eg-gs of the corn root louse (ApJiis maid irad ids) are col-
lected in autumn by ants (especially of the genus Lasiits) 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

342 ENTOMOLOGY

wing-ecl 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 Aphida? 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 Staphylinidre and
PselaphidcT. The rove-beetles make themselves useful by
devouring refuse organic matter, and these scavengers are un-
molested by the ants with which they live. A few myrme-

Lomcchusa struiiwsa being freed of mites by Dinarda dcntata. — After Wasmann.

cophilous beetles furnish their hosts wdth a much-coveted secre-
tion 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. LomccJuisa (Fig. 286) is one of
these favored guests, as it has abdominal tufts of hairs from
wdiich the ants secure a secreted fluid. Atcmclcs (Fig. 287)
is another ; it solicits and obtains food from the mouth of a
foraging ant as if it were an ant itself. In the Alleghanies,

INTERRELATIONS OF INSECTS

343

Atcinclcs cava occurs in the nests of Formica ntfa. and is much
prized by this ant on account of the fluid which tlie l)eetle
secretes from gianchilar hairs on the sides of the abdomen.
The beetle Clavigcr has at the base of each elytron a tuft
of hairs, which the ants lick persistently. This beetle is blind

Atcmclcs cmargiiiatiis being fed by an ant, Myrinica scabrinodis.^Aiter W^asmann.

and appears to be incapable of feeding itself ; for when de-
prived of ant-assistance it dies, even though surrounded by
food. These cases of symbiosis, or mutual benefit, are w-ell
authenticated.

Visitors. — Many myrmecophilous insects are not restricted
to ants' nests, but are free to enter or to leave. This is true of
such Staphylinidas as visit formicaries simply for shelter or to
feed upon detritus, and these visitors are treated with indif-
ference by the ants.

Intruders. — Xot so, however, with species that are inimical
to the interests of the ants, such as many species of Staphy-
linidae and Histerid.'c, which steal food from the ants, kill
them or devour their larv;e or pupre 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. Qiiediits brcvis and Mynncdonia, as Schwarz
observes, are soft-bodied forms which remain beside the walls
of the galleries or near the entrance of a nest and attack soli-
tary ants; while lictccriiis, which mixes with the ants, is pro-

344

ENTOMOLOGY

tecteil by its hard and smooth co\'ering-. under which the legs
and antenna? can be withdrawn. Such an enemy is an un-
avoidable evil from the standpoint of an ant.

Janet has described the amusing way in which an audacious
species of Lcpisiiiiiia steals food from the \ery mouths of ants.
As is w'ell known, ants are accustomed to feed one another
from mouth to uKJUth. When the foragers, filled 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 beg-
gar stand head to head, the former disgorges small drops of

Fig. 288.

Lcpisinina stealing food from a pair of ants. — After Janet.

food, which are seized by the latter. AMiile a pair of ants are
engaged in this performance (Fig. 288), and a drop of honey
is being passed, the Lcpisiiiiiia rushes in, grabs the drop and
hurries away. As mig'ht be expected, these interlopers are
constantly being chased by their victims from one corner of
the nest to another.

Parasites. — Nematode worms occu])y the pharyngeal glands
of ants ; larvas of Sfylo/^s inhal)it their bodies ; more than thirty
kinds of mites attach themselves to the heads or feet of ants;
while Chalcididas and Proctotrypidse parasitize ants' eggs.

CHAPTER XT

INSECT BEHAVIOR

The subject of insect behavior will be considered under three
heads: (i) Tropisms, (2) Instinct. (3) Intelligence.

I. Tropisms

Environmental influences, such as light, temperature or
moisture, may control the direction of locomotion of an organ-
ism 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 example, flies toward
a flame — is positively pJiototropic ; a cockroach, on the con-
trary, avoids the light — is ncgatiz'cly pJiototropic. A plant
turns toward the sun — in other w^ords, is positively Jiclio-
tropic.

An insect flies toward the light as inevitably and as mechan-
ically as a plant turns toward the sun ; indeed, the two phenom-
ena are fundamentally the same. Some students, however,
prefer to use the term taxis for bodily movements of motile
organisms, and the term tropisin for turning movements of
fixed organisms.

The study of tropic reactions, though comparatively new-,
has already illuminated the wdiole 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 investi-
gator, comparatively little having as yet been puljlished upon
the subject.

Chemotropism. — Positive and negative chciiiotropism, 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. Positi\e chemotropism enables many insects to find

345

34^ ENTOMOLOGY

tlieir food or their mates; and negative chemotropism enables
them to avoid injurious substances. This negative reaction
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 radiating diffusion from a piece
of meat, and follows a line of difi^usion to the center of diffu-
sion 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 sym-
metrically 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 posi-
tive chemotropism. Similarly also in the case of such butter-
flies 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 gen-
era //(7///i/;/,s- m'ld Hydroponts were positively hydrofropic ; 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 hydrotropism of Bcinhidiiiin,
ElapJirus, Oniophroii 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 eg'gs, larvae and pupae
to lower and moister galleries. In these instances, however,
we have to deal with tlicnnofropisiii as well as hydrotropism.

Thigmotropism. — Negative fhigiiiotropisiii, as displayed in

INSECT BEHAVIOR 34/

tlie withdrawal from contact, is a common phenomenon among
animals, from Protozoa to \^ertebrata, and is often condncive
to the safety of an organism; thongh 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
widespread among animals. Protozoa and Infusoria cling to
solid bodies and become aggregated about them. Cockroaches
squeeze themselves into crevices until their l)odies come into
close contact with surrounding surfaces. A moth, Pyropliila
(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 photo-
tropism, 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 which rested on
small blocks, and were raised just enough from the bottom to
allow an Auipliipvra 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 cor-
ner 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 current of water illustrate positive rheotropism.
When facing the current, the resistance of the water is sym-
metrically distributed on the body of the animal and is met
by symmetrical muscular action, in the most economical man-
ner. Many aquatic insects offer such examples of rheotropism,
either positive or negative.

Anemotropism. — \'arious flies orient the body with refer-

348 ENTOMOLOGY

ence to the direction of the wind Wheeler ol3ser\-ed swarms
of the male of Bibio albipciiiiis 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
Iciicosfoina ), 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 Syrphidre, he finds, either
males or females are positively aiiciiiofropic. The midges of
the genus Chiroiionius, which on summer davs dance in swarms
for hours over the same spot, orient themselves to every pass-
ing breeze. So also in the case of Empididse, which Wheeler
has observed swarming in one spot every dav for no less than
two weeks, possibly on account of " some odor emanating from
the soil and attracting and arresting the flies as they emerged
from their pupre."

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 phenom-
ena. As Wheeler says, " The poising flv 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 assumes the position in
which the pressure exerted on its surface is symmetrically dis-
tributed and can be overcome by a perfectly symmetrical action
of the musculature of the right and left halves of the body."

Geotropism. — Gravity frequently determines the orienta-
tion and direction of locomotion of an animal. .\ freshly
€merg-ed moth hangs with the abdomen downward and re-
mains in this position until the wings have expanded. Certain
dolichopodid flies found on the l)ark of trees " rest or w-alk
with the long axis of the body perpendicular to the earth and

INSECT BEHAVIOR

349

parallel with the long axis of the trunk of the tree and the
head pointing- upwards. When disturhed they fly off, hut
very soon alight nearer the earth and again walk upward."
(Wheeler.) Coccinellidce and cockroaches are also negatively
gcotropic. The latter insects, as Loeh has observed, tend to
leave a horizontal surface hut come to rest on a surface that
is vertical or as nearly so as possible.

Wheeler says. " Geotropic as well as anemotropic orienta-
tion is not altered for the sake of response to light. Even if
the insect be strongly heliotropic, as is the case in most Dip-
tera. it orients itself to the wind or to gravity no matter
whence the light may fall."

Phototropism. — It is a matter of common observation that
house flies, butterflies, bees and many other diurnal insects fly
toward the light ; and that cockroaches and bedbugs avoid the
light. These are familiar examples of pJiofofropisni. or the
" control of the direction of locomotion by light." The pho-

FiG. 289.

.-/, tracks made on paper by a larva of Liicilia casar moving out of a siiot of ink
miller the influence of light; a and b show respectively the first and second
directions of the light. B, tracks made in the dark. — After Pouchet.

350 ENTOMOLOGY

totropic response is either positive or negative according" as
the organism mo^•es, respectively, toward or away from the
source of hght. Maggots of LitcUia ccrsar and of many other
flies are negatively phototropic as a rule (Fig. 289, A), but in
the absence of light (other directive stimuli being excluded, of
course) wander about indifferently (Fig. 289, B).

Do the different rays of the spectrum differ in phototropic
power? This question has occurred to many investigators,
Avho have found that, in general, the rays of shorter wave
length, as violet or blue, are more effecti^'e than those of longer
wave length, as yellow or red ; the latter in fact acting like
darkness. Ants a^■()id \iolet rays as they wuuld avoid direct
sunlight, l)ut 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 formicaries an orange-red sheet of g"lass such as the
photographer uses for his dark room. Though ants avoid
violet rays, they prefer them to ultra-violet rays, as Lubbock
found ; though the latter rays produce no sensible effect on the
human organism.

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 ani-
mals to light are fundamentally the same.

Phototaxis and Photopathy. — A phototropic organism, if
bilaterally 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 organism 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 diff'erences
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 intensify of light and those of its direction. Thus by in-
geniously contri^'ed experiments, it has been found, apparently,

INSECT BEHAVIOR 35 ^

that Protista (Strasbiirg'er),Z)a/?/;/?7a (Davenport and Cannon)
and the caterpillars of Porthcsia (Loeb) 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 deter-
mined by the direction of the light rays, the term pJiototaxis
is by some authors (as Da\'enport) reserved. Usually, how-
ever, the direction of locomotion docs depend on differences
of intensity, without regard to the direction whence the lig-ht
comes. This " migration towards a region of greater or less
intensity of light " has been termed pliotopatJiy, and organisms
are said to be photophil or photophob, according as they move,
respectively, toward or away from a more intensely illumi-
nated area.

Verworn and others maintain that dift'erences of intensity
are sufficient to account for all phototropic phenomena.

Optimum Intensity, — It has been found that there is a
certain opiiiiium degree of light, differing according to the
organism, toward wdiich the organism will move, from either
a region of greater illumination or one of less. The organism
appears to be attuned to a " certain range of intensity." This
attunement is used by Davenport to explain apparent anoma-
lies 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 l)ecomes negatively phototropic. " Butter-
flies 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, pro-
duces a marked response in the moth." (Davenport.)

The circling of moths and other insects about a light is a
matter of common observation, ;ui explanation for which has
been given by Loel). Loeb says, " If a moth be struck by the
light on one side, those muscles which turn the head toward

352 ENTOMOLOGY

the light liecome 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 ravs 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 ravs 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 affected by the increasing heat as thev ap-
proach the flame ; the high temperature checks their progres-
sive movement and they walk or fly slowly about the flame."
As Loeb insists, the moth " does not fl}- into the flame out of
'curiosity,' neither is it 'attracted' by the light; it is only
oricufcd l)y 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 consecjuence of this orienta-
tion 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 photo-
tropism.

Loeb found that larvc-e of the moth Euprocfis clirysorrliTci,
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. This self-preservative " in-
stinct " is purely a response to light. The caterpillars are
positively phototropic, and as the horizontal components of the
surrounding light neutralize each other, only the lig"ht from
above is eft'ective as a stimulus to orientation. After feeding,
however, the larvce are no longer positively phototropic and

INSECT BEHAVIOR 353

crawl downward; in otlier words, they are positively photo-
tropic only so long- as they are unfed. Here the kind of pho-
totropism is dependent ni)on initrition.

Phototropism may he overruled hy chemotropism and influ-
enced 1)}- conditions of metabolism, as Parker found for the
butterdy faiicssa antiopa. In his words: J'aiicssa anfiopa, 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 ravs. ^^d^en, how-
ever, this surface is perpendicular to the sun's ravs 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 cer-
tain state of metabolism has been established.

V. anfiopa creeps and flies toward a source of light, that is,
it is positively phototropic in its locomotor responses. Posi-
ti\'e phototropism also occurs in intense sunlight, and is not
dependent u[)on any particular ])hase of metabolism.

Both negative and positive phototropism in this species are
independent of the " heat rays " of sunlight.

The position assumed in negative phototropism exposes the
color patterns of the wings to fullest illumination, and prob-
ably has to do with Ijringing the sexes together during the
breeding season.

To these may be added other im])ortant couclusions of
Parker's :

No light reactions are ol)taincd from the butterfly when
shadows are thrown upi>n any part of the body except the
head. W hen one e\e is i)ainte(l black the butterfly creeps or
flies in circles with the unalTected eye al\\a\s toward the cen-
ter. When both eyes are painted black all phototropic re-
sponses cease and the insect Ihes u])ward. lUitterflies with
normal eyes liljerated in a perfecll_\" dark room come to rest
24

354 ENTOMOLOGY

near the ceiling. This upward flight in Ijoth cases is due to
negative geotropism. not to phototropic activity.

/ '. aiitiopa does not (Hscriminate l)et\veen hghts of greater
or less intensity provided they are all of at least moderate
intensity and of approximately equal size. ['. antiopa does
discriminate between light deri\'ed from a large luminous area
and that from a small one, e\'en 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 posi-
tively 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.

['. antiopa retreats at night and emerges in the morning, not
so much because of light difi^erences, 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 Plionuia rcgiiia 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 ab(Xit aimlessly, but at length
burv 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 photo-
tropism, as Kellogg has observed.

Though adaptive in their results, these phototropic reac-
tions can scarcely be said to be performed on account of
their usefulness. They are performed anyway, and may re-
sult harmfully, as wdien they lead a moth into a flame or, to
take a more natural example, when they expose an insect to
its enemies.

INSECT BEHAVIOR 3 55

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 \-egetation, but with an increase in
warmth and light they move upwards along the stems and
leaves of the i)lauts. and, if the day be warm and sunny, escape
into the air."

Thermotropism. — Ants are strongly tlicniiotropic; they
carry their egg's, larwT and pup?e from a cooler to a warmer
place or vice versa, and thus secure optimum conditions of
temperature. Caterpillars and cockroaches 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 example, tonofropisin, 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 l)een experi-
mented upon by many skilled investigators, whose results fur-
nish a 1)road basis for the study of tlie subject in the higher
animals — a study which has scarcely begun. Even in the
simplest organisms, Ijehavior 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
experimentation; while in the higher animals, with their com-
plex organization, including specialized sense organs, the study
of behavior becomes intricate and cannot be carried on intelli-
gently without an extensive knowledge of the behavior of
unicellular organisms. The properties of protoplasm are the
key to the beha\'ior of organisms, though comparati\ely little
is known as yet in regard to these i)ro[)ertics. Furthermore.

3 5^ ENTOMOLOGY

the study of tropic reactions is complicated liy the fact that
they are (Uie not only to external stimuli, but also to little-
understood internal stimuli, arising from unknown conditions
of the alimentary canal, reproductive organs, etc.

A newly recognized property (»f protoplasm is that of adap-
tation, 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 possiljle and then flies into the air. If it happens to reach
the tip of a twig and finds aphids there, the l^eetle stops and
feeds upon them. This adaptive result is in a sense incidental
Yet, upon the whole., tropic reactions are wonderfully adaptive
in their results. Here natural selection is of- special value as
afl:'<:)rding an explanation of the phenomena.

As Loeb and Davenport have insisted, the mechanical reac-
tions to gravity, light, heat and other influences determine the
behavior of the organism.

2. Instinct

Insects are eminently instincti^•e ; though their automatic
behavior is often so remarkaljly successful as to appear ra-
tional, instead of purely instinctive.

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

INSECT BEHAVIOR 357

chain, each Hnk of which is a simple reflex act. In fact, no
sharp hne can be drawn between reflexi\e and instinctive
actions.

Basis of Instinct. — Reflex acts, the elements from which
instincti\'e actions are componnded, are the inevitable responses
of particnlar organs t(3 appropriate stimuli, and involve no
volition. The i)resence of an organ normally implies the
ability to use it. The newdy born butterfly needs no practice
preliminary to flight. The process of stinging is entirely
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 be-
havior among insects, as was said, often leads one to attril;)ute
intelligence to them, even when there is no evidence of its
existence. As an illustration, many plant-eating beetles, when
disturbed, habitually drop to the ground and may escape detec-
tion by remaining- immoval3le. We cannot, howe\-er, believe
that these insects " feig'n death " with any consciousness of
the l)ene(it thus to be derived. This act, widespread among
animals in general, is instinctive, or reflex, as W'hitman main-
tains, being-, at the same time, one of the simplest, most advan-
tageous 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 philciior butterfly hunts out
Aristolochia, which she cannot taste, in order to ser\e larva;,
of whose existence she can have no foreknowledge. Oviposi-
tion 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
necessary incentive to any reflex act. The first movements of
a larva within the egg-shell are doubtless due to a sensation,

358 ENTOMOLOGY

prol3a1)ly one of temperature. Simple contact with tlie eg'g-
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 dis-
tant period of pupation and the subsecjuent imaginal stage.
The ends of these reflex actions are proximate and not ulti-
mate, except from the standpoint of higher intelligence.

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 Peck-
hams have shown. All the operations 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 experi-
ence ; in other words, habits may have been forming and fix-
ing, so that the results of instinct become blended with those
of experience. Thus the first flight of a dragon fly is instinc-
tive and erratic, but later efforts, aided by experience, are well
under control.

When once shaped by experience, reflex or instinctive ac-
tions tend to become intense habits. Thus, certain caterpillars,
having eaten all the availa1)le leaves of a special kind, will
almost invariably die rather than adopt a new food plant,
whereas larvre 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

INSECT BEHAVIOR 3 59

consumes the remainder of the sheH — a reflex act, started by
a stimulus of contact against the jaws and continued until the
cessation of the stimulus, unless some stronger stimukis should
intervene. It has l)een said that the larva eats the remains of
the shell because they might betray its presence to its enemies.
\\ hether this is true or not, to assume conscious foresight of
such a result on the part of an inexperienced caterpillar is worse
than unnecessary.

A\'ith insects, as with other animals, many instincts are
transitory ; even when partially fixed by habit, they are replace-
able by stronger instincts. Thus the gregarious habit of lar-
vae is finally o\Trpowered b}' a propensity to wander, which
does not mature, however, until the approach of the transfor-
mation period. The reproductive instinct is another of those
impulses that do not ripen until a certain age in the indi\-idual.

Inflexibility of Instincts. — Broadly speaking, instincti\e
actions lack indi\'iduality — are performed in the same way by
every individual of the species. The solitary wasps of the
same species are remarkaljly 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 operations, more-
over, are performed in a sequence that is characteristic of the
species. Examples of this so-called inflexibility of instinct are
so omnipresent, indeed, that insect behavior as a whole is
admitted to be instinctive, or automatic,. Insects are capable
of an immense number of reflex imimlses, ready to act singly
or in intricate correlation, upon the re(|uisite stimuli from the
environment.

To normal conditions of the environment, the behavior of
an insect is accurately adjusted; in the face of abnormal cir-
cumstances, however, demanding the exercise of judgment,
most insects are helpless. The specialization to one kind of
food, though usualK' advantageous, is fatal if the sujjply be-
comes insufficient and the lar\a is unable to adcipt another
food. A species of Spluw habitually drags its grasshopper
victim by one antenna, k^abre cut off both antenn;e and then

36o

ENTOMOLOGY

found that the SpJic.r, after vain efforts to secure its customary
hold, abandoned the prey. Under such unaccustomed condi-
tions, insects often show a surprising stupidity, capable as they
are amid ordinary circumstances.

Flexibility of Instincts. — Notwithstanding- such examples,
the c<:)mmon assertion that instincts are absolutely " blind," or
inflexil)le, is incorrect. Instincti\e acts are not mechanically
invariable, though their variations are so inconspicuous as
frequentlv to escape casual observation. A precise observer
can detect indi\'i(lual variations in the performance of any
instincti\'e act — variations analogous to those of structure.

P^iG. 290.

Ammophila iirnaria using a stone to pound down the earth over her nest. Greatly
enlarged. — After Peckh.^m, from IJiill. Wisconsin Geol. and Nat. Hist. .Survey.

To take extreme examples, the Peckhams found that an
occasional queen of Polistes fusca would occupy a comb of the
pre\-ious year, instead of building a new one; and that an indi-
vidual of Pompilus iiiargi'iiatiis, 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 olxserved also that one
AiJiiiiophila, in order to pound down the earth over her nest,
actually used a stone, held between the mandibles (Fig. 290).

While most of the variations that one encounters are small

INSECT BEHAVIOR 3^1

and, in a sense, accidental, or purposeless, snch novel depart-
ures as those of the Polistcs or the Aniiiiophila would seem to
denote adaptability.

Even the despotic power of habit may be overborne by indi-
vidual adaptability. Among caterpillars that have exhausted
their customary food, there are often a few that will adopt a
new food plant and survive, lea\'ing- their more conservative
fellows to starve.

As Darwin himself held, the doctrine of natural selection is
applicable to instincts as well as structures. .Ml reflex acts are
to some extent variable. Disadvantageous reflexes or combi-
nations of reflexes eliminate themselves, wdiile advantageous
ones persist and accumulate.

Indeed, structures and instincts must frecjuently have
evolved hand in hand. The remarkable protective resemblance
of the Kail i ma butterfly 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 instinct 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 experience. This habit
theory, however, has little to support it, and assumes the in-
heritance of accjuired characters — which has not been proved.

The selection theory of Darwin. Weismann, Morgan and
others has much in its favor. It regards reflex acts as primi-
tive, as the raw material from which natural selection, as the
chief factor, has effected those coml)inations that arc termed
instincts.

Instincts and Tropisms. — We have already em])hasized
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 Iropisiii or a coml)ination of trol^isiiis. The
more important of these tropisms have been considered.
\\dienever possible it is better to discard the ambiguous term

362 ENTOMOLOGY

iiisfiiict in fa\'or of such more precise terms as pJwtotropisiii,
gcotropisiii , etc.; though the term instinct remains useful as
apphed to an action that is the resuhant of several tropic
responses.

The modern student of instincts aims to resolve them into
their component reflexes and to determine as precisely as pos-
sible the influence of each reflex component. Thanks to the
lalDors of a great number of skilled investigators, we are no
longer satisfied to class an action as " instinctive " 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 indicates some degree of intelligence.

Take, for example, the precision with wdiich bees or wasps
find their way Ijack to the nest. This is no longer to be
accounted for on the assumpti(^n of a luysterious " sense of
direction," for there is the best of evidence for believing that
it depends upon the recognition of surrounding objects.
When leaving the nest for the first time, these insects make
" locality studies," which are often elaborate. Referring" to
Splicx ichiiciiinoura, the Peckhams write: "At last, the nest
dug, she was readv to go out and seek for her store of pr(i-
vision and now came a most thorough and systematic study
of the surroundings. The nests that had been made and then
deserted had been left without any circling. Evidently she
was conscious of the dift'erence 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 gTound, and nr)w 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 diagram [Fig. 291, A]
gives a tracing" of her first study preparatory to departure.

INSECT BEHAVIOR

^6-

Very often after one thorougii stndy of the topog'raphv of lier
home has been made, a A\asp goes away a second time with
much less circhng or with none at ah. The second diagram
[Fig. 291, B] gives a fair ihnstration of one of these more
hasty departures. . . .

" If the examination of the o1)jects about the nest makes no
impression upon the wasp, or if it is not remembered, she ought
not to be inconvenienced nor tin-own off her track when weeds
and stones are remoNcd and the surface of the ground is
smoothed over; but this is just what happens. Aponis fasci-

FiG. 291.

Locality studies made by a wasp, Splicx icJiitatiiwnca. A, a thorough study; B,
a hasty study; n, nest. After Peckiiam, from Bull. Wisconsin Geol. and Nat. Hist.
Survey.

atiis entirely lost her way \vhen we broke oft' the leaf that
covered her nest, but found it without trouble, when the miss-
ing object was replaced. All the species of Ccrccris were ex-
tremely annoyed if we placed any new ol)ject near their nest-
ing-places. Our AuimopJula refused to make use of her bur-
row' after we had drawn some deep lines in the dust before it.
The same annoyance is exhibited when there is any change

364 ENTOMOLOGY

made near the spot upon wliich the prey of tlie wasp, whatever
it may l^e. is deposited temporarily."

If we take, as one criterion of intehigence, the power to
choose between alternatives, then insects are more intellig-ent
than is generally admitted. The control of locomotion, the
selection of prey, and the avoidance of enemies, as results of
experience, indicate powers of discrimination. The power of
intercommunication, conceded to exist among the social Hy-
menoptera, implies some degree of intellig'ence.

If instinct is Idind. or mechanical, with no adjustment of
means to ends, then a pronounced individuality of action must
signify sometliing more than instinct- — as in the case of the
Aiiuiiophila. In regard to a female Poiiipilus scclcstus, 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 t(_) the nest and began to make it larger. We have
several times seen wasps enlarg-e their holes when a trial had
demonstrated that the spider would not go in, but this seemed
a remarkably intelligent use of the comparati\'e faculty."

From the standpoint of pure instinct, indeed, much of the
behavior of the solitary wasps is inexplicable; while the actions
of the social Hymenoptera have led some of the most critical
students to ascrilje intelligence to these insects, ddie actixities
of the harvesting ants, the military or the slavediolding species,
are of such a nature that the possibility of education by experi-
ence 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 contrary, says: " Wasps do not imitate one another, hi-
stinct and individual experience account sufliciently for their
powers, and their apparent cooperation is due entirely to the
accident of their beino- born in the same nest." She finds that

INSECT BEHAVIOR 365

the worker Polistrs does not learn to feed the lar\';c l)y imi-
tating the qneen.

It is extremely difficnlt, ho\ve\-er, if not impossible, to draw
the line between instinct and intelligence; and in donbtfnl cases
there is a general tendency to exaggerate the importance of
intelligence rather than that of instinct. For example, the
well-known discrimination on the ])art of ants between mem-
bers of their own colony and those of cither colonies, even of
the same species, would seem to impl\' intelligent recognition.
This recognition, however, is due simply to a characteristic
odor, which is deri\ed from the mother of the community.
An ant after lieing washed recei\-es 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 that at least gleams of intelligence
appear in the most si)ecialized Hymenoptera.

Lack of Rationality. — However intelligent the social Hy-
menoptera may l:)e in their waw they show no signs of the
power of abstract reas()ning. Even ants, according to the
experiments of Lubbock, display profound stupidity in the
face of novel emergencies when they might extricate them-
selves by abstract reasoning of the simplest kind. The
thoughts of an ant or bee seem to be limited to simple associa-
tions of concrete things. Miss Enteman observed a Polistcs
worker which gnawed a piece out of the side of a dead larva
of its own kind and, turning, actually offered it as food to the
mouth of the same larva. In another instance, a larva was
attacked and killed, and then offered a piece of its own body.

Such examples as these emphasize the strength of the rellcx
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 memory, consciousness and
other attributes of intelligence will eventually be reduced to
this basis, improbable as it may now seem.

CHAPTER XTI

DISTRIBUTION

I. Geographical

Importance of Dispersion. — Dispersion enal)les species to
mitigate the intense competition and the rigid selection that
resuk from crowded nnml)ers; lience the tendency to disperse,
being self-preservative, has become nni\ersal. Some species
habitually emigrate in prodigious nuiubers : the African migra-
tory locust, the Rocky ^Mountain locust, and the milkweed but-
tertiy, which annually leaves the Northern states for the South
in immense swarms, in autumn, and in the following spring
straggles back t(3 the North. J\iiicssa cardui occasionally mi-
grates in immense numljers, as do also Picris, some dragon
flies and some beetles. nota1)lv Coccinellida?.

Wide Distribution of Insects. — Insects have l3een found in
almost e\-ery latitude and altitude explored by man. Butter-
flies and moscjuitoes occur beyond the polar circle, the former
in Lat. 83° N., the latter in Lat. 72^ N., and a species of
Eiiicsa closely allied to our common E. loiigipcs is recorded by
\\'hymper from an altitude of 16.500 ft. in Ecuador, where,
according- to the same tra\'eler. Orthoptera occur at 16,000
ft., Picris xaiifJiodicc ranges above 15,000 ft., and dragon flies,
Hymenoptera 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, Halobafcs
being found far at sea ; some kinds Vive 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 dis-
tribution, the most richly distributed are Coleoptera. Thys-

366

DISTRIBUTION 367

annra and Collembola. the last two feeding nsnallv upon
minute particles of org-anic matter in the soil and being remark-
ably tolerant of extremes of temperature. The four chief
families of 1:)utterflies occur the world oxqw as do several fam-
ilies of beetles. Of species that are essentially cosmopolitan
we may mention the collembolan Isotonia iiinctaria, and the
l)utterdies Wiucssa cardiii and .liiosia pUwippus. while among
beetles no less than one hundred species are cosmopolitan or
subcosmopolitan, including Tenehrio niolitor, Silz'aiins snri-
namensis, Dcrmcsfcs lardariits, Atfir^ciiiis piccus and Caknidra
uryzcr. The coccinellid genus Scyniiiits occurs in North
America. Europe, Hawaii, Galapagos Islands and New Zea-
land, and Anohium and Hydrobius are distributed as \Yidelv.
The huge noctuid, Erebus odora, occurring in Brazil on the
lowlands, and in Ecuador at an altitude of lo.ooo ft., finds its
way up into the United States and even into Canada. 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 ad\'antages for dispersal, chief
among which are the power of flight and the ability to be
carried l)y the wind. The migratory locust. Sc/iisloccrca
peregriiia, has been found on the wing- fi\-e hundred miles east
of South America. The home of the genus, according- to
Scudder, is Mexico and Central America, where 27^ species are
found; 20 occurring in South America, including the Gala-
pagos Islands. 11 in the United States and 6 in the West
Indies; and there is every reason to belieye that 5'. pcrcgriiia
— 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 ha\-e recorded mau^•
instances of insects being taken ali\e far at sea; Trimen men-
tions moths and longicorn beetles as occurring 230 miles west
of the African coast and SpJiiii.v cojiz'olz'ulus as flying aboard
ship 420 miles out. In these instances the insects ha\"e usually
been assisted or carried by strong winds, particularly the trade-

368 ENTOMOLOGY

winds, and oceanic islands have undoubtedly been colonized in
this way. On land, Webster has found that the direction in
which the Hessian fly spreads is determined larg-ely bv the
prevailing 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 prevailing winds than against them, the wind
carrying the larvre as if they were so manv particles of dust.
The pernicious bufl:"alo-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, larvre 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 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 dif-
fusion 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 im-
portant. Intentionally, he has spread such useful species as
the honey bee. the silkworm and certain useful parasites ; inci-
dentally 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 distril:)ution more or less successfully,
though a species may spread along one side of a range and
sooner or later pass through a l^reak or else around one end.
Mountain chains act as barriers, however, chiefly because they
present unendurable C(jnditions of climate and vegetation.

DISTRIBUTION 3^9

For the same reason deserts are liighly effecti\e l)arriers. In-
deed the most important checks upon distrilnition are those of
chmate, and of chmatal factors temperature is the most .power-
ful. Tropical species, as a rule, cannot sur\ive and reproduce
in reg'ions of frost ; most of the tropical species which have
entered the United States are restricted to its narrow tropical
belts (PI. 4). The stages of an insect are frequently so
accurately adjusted to particular climatal conditions that an
unfamiliar climate deranges the life cycle. Thus many South-
ern butterflies find their way every year to the Northern states,
only to perish without reproducing their kind. Insects, how-
ever, are more adaptable than most other animals in respect to
climate, and frequently follow their food plants into new cli-
mates, as in the case of the harlequin cabbage bug, which has
pushed north from the tropics to Missouri, southern Illinois
and Indiana.

Humidity ranks next to temperature in the importance of
its influence 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 bar-
rier 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 indi-
rectly by favoring the growth of fung'us diseases, to which
insects are much subject.

The absence of proper food is more effectixe than climate,
as a direct check upon the spread of an animal ; food itself being,
of course, dependent ultimately upon climatal factors and soil.
Many insects, being confined to a single food plant, cannot
exist long where this plant does not occur; 1)ul they will follow
the plant, as was just said, into new climates; thus Aiiosia
plexippus is following the milkweed over the world. The
25

370 ENTOMOLOGY

butterfly Eiiphydryas pliccton is remarkaJDly local in its occur-
rence, being limited to swamps where its chief food plant
(Chclonc glabra) grows; and Epidcmia epixaniJic is similarly
restricted to cranberry bogs, though its food-habits are as yet
unknown.

Former Highways of Distribution. — Many facts of dis-
tribution ^^•hich are inexplicable under the present conditions
of topog'raphy and climate become intelligible in the light of
geological history. The marked similarity Ijetween 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 pre-
vailed throughout what is now the .Vrctic region.

The extraordinary isolation of the butterfly Qiiicis sc-
rnidca on mountain summits in New Plampshire and Colo-
rado (particularly Mt. Washington, N. H., and Pike's Peak,
Col.) is explained by glacial geolog}^ The ancestors of this
species, it is thought, were dri\-en sc^uthward before an advan-
cing ice-sheet and then followed it back as it retreated north-
ward, adapted as they were to a rigorously cold climate.
Some of these ancestors presuma1)ly followed the melting ice
up the mountain sides, until they found themselves stranded
on the summits. Other individuals, undiverted from the low-
lands, followed the retreating glacier into the far north ; and
at present there occurs throughout Labrador a species of
CEiicis which differs but slightly from its lonely ally of the
mountain tops.

Glaciation undoul)tedly had a profound elTect upon the
fauna and flora of North America. " With the slow south-
ward 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 inhabitants or
with such limitations to the integ-ritv of the fauna as this inter-

DISTRIBUTION 371

ruption of local life may have caused." (Sciukler.) Probably
many species were exterminated and many others Ijecame
greatly modified, thongii little is known as to the relationship
of the present fauna to 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 favoraljle circumstances, is strikingly shown in the col-
onization of oceanic islands. Not a few insects, including
Vanessa carditi, have found their way to the isolated island
of St. Helena. In the Madeira Islands, according to Wollas-
ton, 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 Galapag'os Islands includes
twenty species of Orthoptera, which have been studied by
Scudder and by Snodgrass. Five of these are cosmopolitan
cockroaches, doubtless introduced commercially, and the re-
maining fifteen are all " distinctly South and Central American
in their affinities." Three of these fifteen are strong-winged
species wdiich doubtless arrived by flight from the neighboring
mainland; indeed, Scudder records a Sdiisfoccrca (S. cxsul)
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, noticeal)ly common on wind-sw'Cpt oceanic
islands, may have been carried thither on driftwood, though
it i? more likelv that the apterous condition arose on the
islands, where the better-winged and more venturesome indi-

1^2 ENTOMOLOGY

viduals may have lieen constantly swept out to sea and
drowned, lea\'ing" the more feeljle-winged and less venturesome
individuals Ijehind. to reproduce their own life-saving" pecu-
liarities.

The Coleoptera of the Hawaiian Islands, studied 1)y Dr.
Sharp, numher 428 species, representing" 38 families, and " are
mostly small or very minute insects," the few large forms being-
non-endemic, with little or no doul)t; 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 artifi-
cial means, such as with provisions, stores, building" timber,
ballast, or growing" plants ; many of these species are nearly
cosmopolitan. Second, species that have arri\ed in the islands,
and have become more or less completely naturalized ; they are
most of them known to Ije wood- or Ijark-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 Dytiscid^e, or water beetles,
may possibly have been introduced by violent winds. Third,
after making e\-ery allowance for introduction by these artifi-
cial 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 Cocciiiclla, Dcniicstcs,
Af^Iiodius, Biiprcstis, Ft in us and Ccranihyx. 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 l^een sufiiciently studied.
The endemic species number 214, or exactly half the total num-
ber of species, and are distributed among 9 families, as follows :

DISTRIBUTION

171

Families.

Species.

nera.

Endemic Genera.

Carabidse,

Staphylinidae,

NitidulidcTS,

ElateridiE,

Ptinidse (Anobiini),

Cioidae,

Agl3-cyderid£e,

Curculionidse

(Cossonini)

, 21

Cerambycidse,

Sharp writes : " I think it may lie looked on as certain that
these islands are the home of a larg-e number of peculiar spe-
cies 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 Ash-
mead, number 14 families, 69 genera and 128 species; only
eleven genera are endemic and most of the other genera are
represented in nearly all the known faunse of the earth. Ash-
mead concurs in the view that the Hawaiian fauna was origi-
nallv derived from the Australasian fauna — the view held by
all the specialists who have studied Hawaiian insects.

Geographical Varieties. — Darwin found that wide-ranging
species are as a rule highly variable. The cosmopolitan but-
terfly Vanessa cardiii presents striking variations in different
parts of the earth, largely on account of climatal differences,
as is indicated by the temperature experiments of se\-eral inves-
tigators. Standfuss exposed German pupa? of this insect to
cold, and obtained thereby a dark variety such as occurs in Lap-
land ; and by the influence of warmth, obtained a very pale form
such as occurs normally in the tropics only. Our Cyaniris
pscudai'giolus, which ranges from Alaska into Mexico and

374 ENTOMOLOGY

from the Pacific to the Atlantic, 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 dif-
ferent varieties of one and the same species, or even by differ-
ent 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 Tropidunis (a lizard) and
had onlv one species, with almost no exceptions. The same
phenomenon occurs in the two Galapagan species of Schisfo-
ccrcd — vS". iiiclaiioccra and 5. litcrosa. In nichnioccra. as
Scudder discovered, " Three or four distinct types are becom-
ing gradually dift'erentiated on the eight [now ten] islands
from which they are known." Snodgrass, who has recently
made important additions 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 distin-
guishing 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 pre-
sents 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 su1)jects are still needed. Isolation in
general we have considered briefly in Chapter VII.

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 faun?e overlap one another to
such an extent as to render their exact separation more or less
arbitrarv. Five realms, at least, are generallv recognized :

DISTRIBUTION 375

Holarctic, Neotropical, EtJiiopian. Oriental and Australian

(Pl-3)-

The Holarctie realm comprises the whole of Europe. North-
ern Africa as far south as the Sahara, Asia down to the Hima-
layas, and North America down to Mexico. Though the
fauUcT 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 Palccarclic, including
Europe and most of temperate Asia, heing limited roughly by
the Tropic of Cancer ; and the Nearetie, occupying almost the
entire continent of North America, including Greenland. The
northern portion of the Holarctic realm forms a circumpolar
l)elt with a remarka1:)le homogeneous fauna and flora ; there-
fore some authors distinguish an Arctic realm, limited by the
isotherm of 32", which marks very closely the tree-limit.

The boreal insects of Eurasia and North America are strik-
ingly alike. Dr. Hamilton has catalogued nearly six hundred
species of beetles as being holarctic in distribution; five hun-
dred of these are common to Europe, Asia and North x\merica,
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 hol-
arctic in origin, for example — Deniiestes lardariits and Tene-
brio III alitor. 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 represented 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 jMexico; Mexico
being for the most part a transition tract between the Neo-
tropical and the Nearetie. The richest butterfly fauna in the
world is found in tropical South America. To this region are
restricted, almost without exception, the Eupkeinrc and
Lemoniina? and over ninety-nine per cent, of the Libytheiuce;

376 ENTOMOLOGY

here the Hehconiiclce and Papihonicke attain their highest
development, as do also the Cerambycid?e, 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 Lciuurian. Ac-
cording to' Wallace, the Ethiopian realm has seventy-five pecu-
liar genera of Carabid?e and is marvelously rich in Cetoniid?e
and Lycrcnidce.

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. Danaid?e and
Papilionida? are abundant, while the genus Morpho is repre-
sented by some forty species; of C()le<3ptera, Buprestid?e are
important and Lucanid?e especially so.

The Australian realm embodies Australia, New^ Zealand, the
Eastern Malay Islands and Polynesia. Buprestidje are here
represented by forty-seven genera, of which twenty are pecu-
liar ; against this showing, the Oriental has forty-one genera
and the Neotropical thirty-nine (\A'allace). Strong afhnities
are said to exist between the .\ustralian and Neotropical insect
faunae.

Life Zones of North America. — Merriam, the chief au-
thority upon the subject, says : " The continent of North
America may be divided, according to the distribution of its
animals and plants, into three primary transcontinental regions
— Boreal, Austral and Tropical." ( PI. 4. )

The Boreal region covers the northern part of the continent
to about the northern boundary of the United States and con-
tinues southward along the hig'her portions of the mountain
ranges. This region is divided into three transcontinental
zones: (i) the Aretie-Alpine, l}'ing above the limits of tree
gro\\th, in latitude or altitude; (2) the Hucisonian, compris-
ing 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 regic^n. The butterfly Erynnis
inanitoha ( Eig. 292) is strictly boreal in distribution.

DISTRIBUTION

IT/

The Austral region " cox-ers the whole of the United States
and Mexico, except the Boreal mountains and the Tropical
lowlands." It comprises three transcontinental belts: (T) the
Transition zone, in which the Boreal and the .\nstral overlap ;
(2) the U [^pcr Austral; (3) the Lo-icrr Austral. The butter-

FiG. 292.

Fig. 293.

Distribution of Erynnis maiiitoba, a
butterfly restricted to subarctic and sub-
alpine regions. — After Scudder.

Distribution in the United States of
Eudamus protcns, primarily a tropical
butterfly. — After Scudder.

fly Eudamus protcus (Fig. 293) is restricted, generally speak-
ing, 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 distrilnition of
mammals. Ijirds and ])lants, and the three primary di\-isions
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 gi\'en beyond.

The insect fauna of the United States is upon the whole a
heterogeneous assemblage of species derived from se\eral
sources, and the foreign element of this fauna we shall con-
sider 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

37^ ENTOMOLOGY

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 barri-
ers. 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 accessions to our insect fauna have arrived chiefly from
Asia, Central and South x\merica, and Europe.

Webster, our foremost student of this subject, to Avhom the
author is indebted for most of his facts, names four paths along,
which insects ha\'e made their way into the United States:
( I ) A'ortJnvcst — Northern Asia into Alaska and thence south
and east: (2) Soitthzccst — Central America through Mexico;
(3) Soiifliccisf — 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 geol-
ogists assure us, Asia and North America were once con-
nected, at a time when a sul)tropical climate prevailed within
the Arctic Circle: in fact, the distribution is scarcely explic-
able 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.

CuccincUa quiiuptcnotata, occurring in Siberia and Alaska,
has spread to Hudson Bay, Greenland, Kansas, Utah, Califor-
nia and Mexico ; while C. sangninea, well known in Europe
and Asia, rang'es from Alaska to Patagonia ; and Megilla inac-
ulata from \^ancouver and Canada to Chile. About six hun-
dred species of beetles are holarctic in distribution, as was
mentioned. Some of them inhabit different climatal regions
in different parts of their range; thus McJasoma (Liiia) lop-
pojiica in the Old World " occurs only in the high north and
on high mountain ranges, whereas in North America it ex-
tends to the extreme southern portion of the country," being
widely diffused over the lowlands (Schwarz). Similarly,

DISTRIBUTION 379

Silpha lapponica is strictly arctic in Europe, but is distributed
n\er most of North America ; SilpJia opaca, on the contrary,
is common all over Europe, but is strictly arctic in North
America. Silplia afrafa, common throug'hout Euro]ie and
western Siberia, was introduced into North America, but failed
to establish itself.

Southwest. — \^ery many species have come to us from Cen-
tral America and even from South America. South America
appears to be the home of the genus Halisidofa, according to
Webster, who has traced several of our North American spe-
cies as offshoots of South American forms. A [any of our
species may be traced back to Yucatan. H. ciiicfipcs ranges
from South America to Texas and Florida; H. tcsscllaris has
spread northward from Central America and now occurs over
the middle and eastern United States, while a form closely like
tcsscllaris ranges from Argentina to Costa Rica ; H. carycu
follows fcsscUaris, and appears to have branched in Central
America, giving off H. agass{::ii. which extends northward
into California. Similarl}- in the case of the Colorado potato
beetle {Leptinotarsa dccciuUncata) and its relatives. Accord-
ing to Tower, the parent form. L. luidcccmlincata, seems to
have arisen in the northern part of South America, to ha\e
migrated northward and, in the diversified IMexican region, to
have split into several racial varieties. The parent form
grades into L. multiliiicata of the Mexican table lands, which
in turn, in the northern part of the Mexican plateau, passes
imperceptibly into L. dccciiiliiicata, which last species has
spread northward along the eastern slope of the western high-
lands, west of the arid region. In the lower part of the Mex-
ican region the parent form may be traced into L. Jiiiicta,
which has spread along the low humid (Tulf Coast, u\) the Miss-
issippi vallev to southern Illinois, and along the Culf C"oast
and up the Atlantic coast to ^Maryland, Delaware and New
Jersey. In general, the mountains of Central America and
jMexico and the plateau of ]\lexico have l)een barriers to the
northward spread of man_\- species, which have reached the

380 ENTOMOLOGY

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 ^^lississippi vaUev or along the
Atlantic coast, in the latter event traveling along the Pacific
coast to California and other Western states. Not a few spe-
cies, however, have made their way from the Mexican plateau
into Xew Mexico and Arizona ; this is true of many Sphin-
gidcT. The butterfly Aiiosia bcrcnicc ranges from South
America into Xew Mexico, Arizona and Colorado ; while many
of the Lil;)ythei(lcT have entered Arizona and neighboring states
from Mexico. The chrysomelid genus Diabrofica is almost
exclusively 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 1 1 extend into Guatemala, 8 into Mexico, and i
into the United States." We have 18 species of Diabrofica,
almost all of which can be traced back to Mexico, and several
of them- — as the common D. loiigiconiis — to Central America.
" The common Dyiiasics fifyiis 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." Ercbiis odora ranges from Ecuador and Brazil to
Colorado, Illinois, Ohio, New England 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 W'est
Indies, while some subtropical species ha\'e reached Florida
probably by following around the Gulf coast. The semi-
tropical insect fauna of southern and southwestern Florida,
including a1)out 300 specimens of Coleoptera, according to
Schwarz, is entirely of A\'est 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 Sphingicte. Ninety-five species of Hemiptera collected
in extreme southern Florida bv Schwarz and studied bv Uhler

DISTRIBUTION 38 1

are distinctly Central American and West Indian in their
affinities. Indeed Uliler is inclined to l)elieve that the principal
portion of the Hemiptera of the Lhiited States has Iieen derived
from the region of Central America and Mexico.

Eastern. — On the Atlantic coast are many Enropean species
of insects which ha\-e arri\-ed throngii the ag'encv of man.
Most of them have not as yet passed the Appalachian moun-
tain system, hnt some ha\-e worked their wav inland. Thus
the common cabhage luitterfly (Picris rupee), tirst noticed in
Quebec about i860, was found in the northern parts of Maine,
Xew Hampshire and Vermont five or six years later, was
established in those states by 1867, entered New York in 1868
and then Ohio. ApJnxliiis fossor followed much the same
course from New York into northeastern Ohio, as did also the
asparagus beetle (Crioccris asparagi), the clover leaf weevil
(Phytoiioiiiiis puiicfafiis) , the clover root borer (Hylastcs
obsciinis) and other species. In short, as Webster has j^ointed
out. New York ofTers 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. — Picris rapcr, the spread of which in
N^orth America has l)een thoroughly traced by Scudder,
reached northern New York in 1868 (as above), but appears
to ha^'e been independently introduced 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 ■asparagi, another native of Europe, became con-
spicuous in Long Island in 1856, spread southward to Mrginia
and westward to Ohio, ^vhere it was taken in 1886; it occurs
now in Illinois. This insect, as Lloward observes, flies read-
ily, and may be introduced commercially in the egg- or larval
stage on bunches of asparagus.

Cryptorliynchiis lapafhi, a beetle destructive to willows and

38 2 ENTOMOLOGY

poplars, and comnmn 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 be-
came noticeable in Ohio in 1901, and is steadily extending its
ravages, being- reported recently from Minnesota.

From Colorado the well-known potato beetle {Lcptinotarsa
dcccuiUncata) 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' (Lcptocoris trivit-
tatus) is similarly working eastward, having now reached
Indiana. The Rocky Mountain locust periodically migrates
eastward, l)ut meets a check in the moist valle}' of the Missis-
sippi, as has been said.

The chinch bug (Blissiis Icucoptcnts) , 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 : ( i ) Along the Atlantic
coast to Cape Breton; (2) along the Mississippi valley and
northward into Manitoba; (3) along the western coast of Cen-
tral 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. The harlecjuin cabbage bug {Murgan-
tia hisfrioiiica) has spread from Central America into Califor-
nia 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 Louisiana (1864) to Ohio, spreading through its
own efforts and not commercially to any great extent.

Every year some of the southern butterflies reach the North-
ern states, where they die without finding a food plant, or else
maintain a precarious existence. Thus Iphklidcs ajax occa-
sionally reaches Massachusetts as a visitor and a visitor only;
Lccvtias philciior, however, finds a liniited amount of food in

DISTRIBUTION 3^3

the cultivated Arisfolochia. P. ihoas. one of the pests of
the orange tree in the South, is highly prized as a raritv bv
New England collectors and is able to perpetuate itself in the
Middle States on the prickly ash {Xanthoxyliun) . The
strong-winged grasshopper, Scliistocerca auicricana, belonging
to a genus the center of whose dispersion is tropical America,
ranges freely over the interior of North America, sometimes
in great swarms, and its nymphs are al)le to survive in mode-
rate numbers in the southern parts of Illinois, Ohio and other
states of as high latitude, while the adults occasionallv reach
Ontario, Canada.

Alany species are now so widely distributed that their for-
mer paths of diffusion can no longer be ascertained. The
army worm ( HcHopJiila iiiiipuiicfa) , feeding on grasses, and
occurring all o\er the United States south of Lat. 44° 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 originated 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
palaiontological evidence, for determining centers of dispersal :

1. Location of greatest dift'erentiation 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 indi\iduals (Ridgway-
Allen).

5. Location of greatest producti\eness and its relative sta-
bility, in crops (Hyde).

6. Continuitv and convergence of lines of dispersal.

7. Location of least dependence upon a restricted habitat.

8. Continuity and directness of individual variations or
modifications radiating from the center of origin along the
highways of dispersal.

9. Direction indicated by biogeographical aflinities.

384 ENTOMOLOGY

10. Direction indicated l)y the annnal migration routes, in
birds (Palmen).

2. Geological

Means of Fossilization. — Almndant as insects are at pres-
ent, thev 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 sedimen-
tary rocks of marine origin is explained by the fact that almost
no insects inhal)it 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 per-
haps, in great measure, to the dissolution of chitin in the pres-
ence of moisture.

Most of the fossil insects that are known have been found
in vegetable accumulations such as coal, peat and lig^nite, or
else in ancient fresh-water basins, where the insects were prob-
ably 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 profu-
sion of fossil forms found in some of the ancient lake basins.

Insects in rich \ariety have been preserved in amber, the
fossilized resin of coniferous trees. This substance, as it
exuded, must have entangled and enveloped insect visitors just
as it does at present. Many of these amber insects are ex-
quisitely preserved, as if sealed in glass. Copal, a transparent,
amber-like resin from various tropical trees, particularly Legu-
minosa?, has also yielded many interesting insects.

Ill-adapted as insects are by organization and habit for the
commoner methods of fossilization, the number of fossil spe-
cies 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 extraordinary interest, as will he seen.

For Carboniferous species, Commentry in France is a noted
locality, through the admirable researches of Brongniart, who

DISTRCBUTION

3«5

Fig. 294.

described from there 97 species of 48 genera, representing 12
families or higher groups, 10 of which are regarded as extinct;
without inckuhng many hun(h"ed 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.

Alany fine fossils of the Jurassic period ha\-e been found in
the lithographic 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 Olig'ocene belong the am1)er insects, of
wdiich 900 species are known from Baltic amber alone, and to
the same epoch are ascribed the deposits of Florissant and
Wdiite Ri\er 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 aston-
ishing profusion. For M i o c e n e
forms, of which 1,550 European spe-
cies are known, the QEningen beds of
Bavaria are celebrated as having furnished 844 species, des-
cribed l)y 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, Protociincx, from the
Lower Silurian of Sweden. Next in age comes a wing,
Pahcoblattiiia (Fig. 294), of doul)tfnl i)Osition,^ from the
Middle Silurian of France. Following these are six speci-
mens of as many remarkable species from the Devonian shales

^ There is some evidence, it should be s;ud, that this species is not an
insect. Handhrsch denies also tliat Protociincx is an insect.
26

Palccohlattina douvillci, natural
size. — After P.ron'GN iart.

386

ENTOMOLOGY

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 satisfactorily with recent forms on account

Fig. 295.

Pldtcphcinera auiiqiia. natural size. — After Scudder.

of being highly synthetic in structure. Thus Platcphciiicra
aiifiqua (Fig. 295), though essentially a May fiy of gigantic
proportions (spreading pro1)a1)ly 135 mm.), has an odonate
type of reticulation; while Xcnoiiciira (Fig. 296) combines
characters which are now distributed among Ephemerid?e,
Sialidae, RhaphidiidcC, Coniopterygida?, and other families,
l:)esides being in many respects unicjue. These Devonian forms

I^^k;. 296.

Xcnonciira aiitiqnorum, five times natural size. — After Scudder.

attained huge dimensions as compared with their recent repre-
sentatives ; Gcrcphciiicra, for example, had an estimated ex-
panse of 175 millimeters.

Carboniferous. — The Carboniferous age, with its luxuriant
vegetation, is marked by the appearance of insects in great

DISTRIBUTION

387

Fig. 297.

number and variety, still restricted, however, to the more
g"eneralized orders. The dominance of cockroaches in the
Carboniferous is especially noteworthy, no less than 200 PahTO-
zoic species being known from Eu-
rope and North America. These
ancient roaches (Fig. 297) differed
from their modern descendants in
the similarity of the two pairs of
wings, which were alike in form,
size, transparency and general neu-
ration. with six principal ner\'ures
in each wing: while in recent cock-
roaches the front wings have l)e-
come tegmina, with certain of the
veins always Ijlended together,
thougli the hind wings have retained
their primitive characteristics with a
few modifications, such as the ex-
pansion of the anal area. Car-
boniferous cockroaches furthermore
exhibit ovipositors, straight, slender,
and half as long again as the abdo-
men — organs wdiich do not exist in
recent species.

Lithomantis (Fig. 298), 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 homologous \\\{\\ wings, represent
a third pair, either atrophied or undeveloped — a condition
wdiich is never found today, unless the patagia of Lepidoptera
represent wdngs, wdiich is unlikely.

From the rich deposits of Commentry, Brongniart has des-
cribed several forms of striking interest. Diciyoncura is a Car-
boniferous genus with neuropteroid wings and an orthopteroid
body, ha\-ing, in common with several contemporary genera,
strong isopteran affinities. Corydaloidcs scuddcri, a phasmid.

Etoblattina mazona, a Car-
boniferous cockroach from
Illinois. Twice natural size.
— After ScuDDER in Miall and
Denny.

388

ENTOMOLOGY

has an alar expanse of twenty-eight inches. The Carljonife-
rons prototypes of our Odonata were gigantic l)eside their
modern descendants, one of them (il/c^i^az/t^/z/^/ )ha\-ing a spread
of over two feet ; they were more g'enerahzed in structure than
recent Odonata, presenting a much simpler type of neuration
and less differentiation of the segments of the thorax. The
Carljoniferous ])recursors of our May tiies attained a high

Fig. 2C)8.

Lithoiiiaiitis carbonariiis, showing prothoracic appendages. Two thirds natural size. — •

After WooDW.\RD.

development in numl^er and variety ; in fact, the Ephemeridje,
like the Blattidie, 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 Eugercon
(Fig. 299) with hemipterous mouth parts associated with fili-
form antennae and orthopteroid wings. The earliest unc[ues-
tionable 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 familv. Through these Mesozoic

DISTRIBUTION

:)"■

species, the continuity l)et\veen Paheozoic and recent cock-
roaches is clearly estahlished — 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 molkiscan genus Planor-
bis. In the Triassic period occur the first fossils that can be

Fig. 299.

Eiigcrcon bocl'ingi. Three (|uartei's natural size. — After Dohrn.

referred indisputa1)ly to Coleoptera and Hymenoptera, the lat-
ter order being" represented tirst, as it happens, by some of
its most specialized meml)ers, namely ants.

Jurassic. — At length, in the Jurassic, all the large orders
except Lepidoptera (K'cur; Diptera appear for the first time,
and Odonata are represented by many well-preserved speci-
mens, while the Liassic Coleoptera studied by Heer number
over one hundred species. The Cretaceous has yielded but
few insects, as might l)e expected.

Tertiary. — In the rich Terti.ary deposits all orders of insects
occur. Baltic aml)er has yielded Collembola. some remarkable
Psocidas, many Diptera, and ants in abundance. Of 844 spe-

390

ENTOMOLOGY

cies taken from the noted Miocene beds of CEnin^^en, nearly
one half were Coleoptera, followed hy neuropteroid forms
(seventeen per cent.) and Hymenoptera (fonrteen 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 heen 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 calcified larval cases of
caddis flies.

At Florissant, as contrasted with CEningen bv 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 fam-
ilies are represented in great profusion. The material from
Florissant and neighboring localities includes a Lcpisma, fif-
teen species of Psocidae, over thirty species of Aphidida;, and
over one hundred species of Elaterid;e, while the Rhvnchoph-
ora number 193 species as against 150 species from the

Tertiar}' of Europe. Tipu-
lidc'e are abundant and ex-
quisitely preserved, while
Bibionids, as compared with
their present numbers, are
surprisingly common. Nu-
merous masses of eggs oc-
cur, undoubtedly sialid and
closely like those of Cory-
dalis. Sialid characters, in-
deed, appear in the oldest
fossils known, and are
strongly manifest through-
out the fossil series, though among recent insects Sialidie oc-
cupy only a subordinate place. Strange to say, few acjuatic
insects have been found in this ancient lake basin.

Fossil butterflies are among- the o-reatest rarities, onlv sev-

Prodryas l^crscphoiic, a fossil butterfly
from Colorado. Natural size. — • After
Scudder.

DISTRIBUTION 39I

enteen being known ; yet Florissant has contributed eight of
these, a few of which are marvelously weh preserved (Fig.
300), as appears from Scudder's figures. Two of the Floris-
sant specimens belong to Li1)ytheince, a group now scantily
represented, though widely distriljuted over the earth. The
group is structurally an archaic one, and its recent members
(forming only one eight-hundredth of the described species
of butterflies) 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,
ha\'e yielded fragments of the skeletons of beetles to the extent
of several hundred specimens, about one third of which
(chiefly elytra) were sufticiently complete or characteristic to
be identified by Dr. Scudder, wdio has fonnd in all 76 species
of beetles, representing 8 families, chiefly Carabida? and
Staphylinidce. 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 reseml)ling 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 re-
corded from the Pacific coast." (Scudder.) The writer, who
has studied these specimens, has been impressed most by their
likeness to modern species. It is indeed remarkal)le 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 synthetic indeed as compared with
their modern allies, .are at the same time highly organized, or

392 ENTOMOLOGY

far from primitive, and their ancestors have been obhterated.

The general plan of wing- structure, as Scudder finds, has
remained unaUered from the earhest times, though the De-
\-onian specimens exhibit many pecuHarities of venation, in
which respect some of them are more speciahzed than their
nearest Hving ahies, 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 tho-
racic segments were similar and unconsolidated, and the two
pairs of diaphanous wings were alike in every respect — in
groups that have since developed teg'mina and dissimilar tho-
racic segments. The Carboniferous precursors of our cock-
roaches, phasmids and May flies have been mentioned. Palae-
ozoic insects are grouped by Scudder into a single order,
PalcTodictyoptera, on account of their synthetic organization,
though other authors have tried to distril)ute 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 continuously traceable. In this era the large fam-
ilies became difl:'erentiated out.

Most of the Tertiary species are referable to recent genera,
peculiar families being highly exceptional, while all the Quater-
nary species belong to recent genera.

llemiptera appear in the Silurian; Neuroptera (in the old
sense) in the Devonian; Thysanura and Orthoptera, Carbonif-
erous; Coleoptera and Hymenoptera, Triassic; Diptera, Juras-
sic; and Lepidoptera not until the Tertiary.

CHAPTER XTTT

INSECTS IN RELATION TO MAN

A great many insects, eminently successful fi'dm their own
standpoint, so to speak, nevertheless interfere seriously with
the interests of man. On the other hanrl. 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
domestic animals, injure food, manufactured articles, etc., and
molest or harm man himself.

The cultivation of a plant in great quantity offers an un-
usual opportunity for the increase of its insect inhabitants.
The numljer of species affecting one kind of plant — to say
nothing of the numl)er 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, Kan-
sas 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 C()tton l)o]l wee\'il need
only be mentioned.

At times, an insect has been the source of a national calam-
ity, as was the case for forty years in France, when Phyllo.rera
threatened to exterminate the \ine. In Africa the migratory
locust is an unmitigated e\il.

Probably at least ten per cent, of every crop is lost through
the attacks of insects, though the loss is often so constant as

393

394 ENTOMOLOGY

to escape observation. Regarded as a direct tax of ten cents
upon tlie dollar, however, this loss becomes impressive. Web-
ster 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 l:)y Walsh and Riley to be $300,-
000,000 — 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 coun-
try cost in 1902 the sum of $235,000,000, and all higher insti-
tutions 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 whole
system of education for everybody's children.

" Furthermore, the yearly losses fr(jm insect ravages ag'gre-
gate nearly twice as much as it costs to maintain our army and
navy; more than twice the loss by fire; twice the capital in-
vested in manufacturing agricultural 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 annoyances, some inflict serious or even fatal injury,
as has been said. The gad flies persecute horses and cattle ;
the maggots of a hot fly grow in the frontal sinuses of sheep,
causing vertigo and often death ; another hot fly develops in
the stomach of the horse, enfeebling the animal. The worst
of the bot flies, howe\-er, is Hypodcrma liiicata, the ox-warble,
which not nnlv 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 food stuffs are attacked by insects, particularly

INSECTS IN RELATION TO MAN 395

cereals; clothing, especially of wool, fur or feathers; also fur-
niture 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 spe-
cies. Insects are useful as checks upon noxious insects and
plants, as pollenizers of tiowers, as scavengers, as sources of
human clothing, food, etc., and as food for birds and fishes.

Almost e\'ery insect is subject to the attacks of other insects,
predaceous 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 t(^o many illustrations of
the tremendous spread of an insect in the absence of its accus-
tomed natural enemies. One of these examples is that of the
gypsy moth, artificially introduced into Massachusetts from
Europe; another is the tinted scale, transported from Australia
to California. Some conception of the vast restricting influ-
ence of one species upon anc^ther may be gained from the fact
that the fluted scale has practically Ijeen exterminated in Cali-
fornia as the result of the importation from Australia of one
of its natural enemies, a lady-bird beetle known as A'oz'iiis car-
dlnalis. 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 ])arasites may develop in
the body of a single individual; thus o\er 3,000 specimens of
a hymenopterous parasite (Copidosoina trnncatcUuin) were
reared by Giard from a single Pliisia caterpillar.

Parasites themselves are frequently parasitized, this phe-
nomenon of hyperparasitism being of considerable economic
importance. A beneficial i)rimary parasite may Ije o\'erpow-
ered by a secondar\- i)arasitc, evidently to the indirect disad-
vantage of man, while the influence of a tertiary ])arasite would
be beneficial again. Xow parasites of the third order occur
and probablv of the fourth order, as appears from lloward's

39^ ENTOMOLOGY

studies, which we have ahxady summarized. ^Moreover, para-
sites of all degrees are attacked by predaceous iusects, l)irds,
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, in-
sects exercise a vast influence upon vegetation in general. A
conspicuous alteration in the vegetation has followed the inva-
sions of the Rocky Mountain locust, as Riley has said ; many
plants before unnoticed ha\-e grown in profusion 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
bevond 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 extermina-
tion. 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 thev do in incalculal)le quantit}' all kinds of dead and decay-
ing animal and vegetable matter. This function of insects is
most noticeable in the tropics, where the ants, in particular,
eradicate tons of decomposing matter that man lazily neglects.

The usefulness of the silk^vorms 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 ascril)ed
to many different insects. As human food, insects are of con-
siderable importance among semi-ci\'ilized races ; the migra-
tory locust is eaten in great quantities in Africa, and termites
in Africa and Australia, the latter insects being said to ha\'e
a delicious flavor ; in Mexico the eggs and adults of an aquatic
hemipteron, Cori.va, are highly relished by the natives.. As
food for fishes, game birds, song l)irds and poultry, insects are
of vast importance, it is needless to say.

INSECTS IN RELATION TO MAN 397

Introduction and Spread of Injurious Insects. — Many of
our worst insect pests were l)roiio-ht accidentally from Europe,
notably the Hessian fly, wheat midi^-e, codlini^- moth (prob-
ably), gypsy moth, cabl:)age Ijntterfly, cabbage aphis, clover
leaf beetle, clover root borer, asparagus beetle, imported cur-
rant worm and many cutworms ; though few American species
have ol)tained 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 (1890-
1899) and is not yet under control. The San Jose scale, a
native of North China according to Marlatt. was introduced
into the San Jose valley, California, about 1870, prol)aldv upon
the flowering- Chinese peach, l)ecame seriously destructive there
in 1873, '^'^'^s 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 (Anthonoinits grainlis)
crossed the Rio Grande river and appeared in Brownsville,
Texas, about 1892, since when it has spread over eastern Texas
and even into western Louisiana. Advancing as it does at
the rate of fifty miles a year, the insect would require but fif-
teen or eigiiteen years to cover the entire cotton belt. Idie
beetle hibernates and lays its eg'gs in the cotton bolls ; these
are injured both bv the larva feeding' within and by 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 annurd loss of $250,000,000. As it
is, the universal adoption of the cultural methods recommended
by the Bureau of Entomology promises to reduce the damage
to a point at which cotton can still l)e grown at a fair profit.

39^ ENTOMOLOGY

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 Sohniuin rosfrafiuit to the intro-
duced species, Solaiiiiiii fiibcrosinn, the potato. Alany of our
fruit tree insects feed upon wild, as well as cultivated, species
of Rosace-e ; the peach borer, a native of this country, probably
fed originally upon wild plum or wild cherry. Many of the
common scarabcTid larvce known as " white grubs " are native
t() 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 species, 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.

E\'en in the absence of cultivated plants their insect pests
continue to sustain themselves upon wild plants, as a rule; the
larva of the codling moth is very common in wild apples and
wild haws.

The Economic Entomologist. — To mitigate the tremen-
dous damage done by insects, the indi\'idual 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 uni-
versally appreciated by the intelligent.

Nearly every State now has one or more economic entomolo-
gists, responsible to the State or else to a State Experiment
Station, while the g'eneral Government attends to general ento-
mological needs in the most comprehensive and thorough
manner.

*' It is the special object of the economic entomologist,"
says Dr. Forljes, *' to investigate the conditions under which
these enormous losses of the food and labor of the country
occur, and to determine, tirst, whether any of them are in any
degree prexentable; second, if so, how they are to be prevented

INSECTS IN RELATION TO MAN 399

with the least possi1)le cost of labor and monev ; and, third, to
estimate as exactly as possible the expenses of snch prevention,
or to fnrnishi the data for snch an estimate, in order that each
may determine for himself what is for his interest in every
case arising".

" The snbject matter of this science is not insects alone, nor
plants alone, nor farming alone. One may be a most excellent
entomologist or botanist, or he may have the whole theory and
practice of agricnltnre at his tongne's end, and at his fingers'
ends as well, and yet be ^^"ithont knowledge or resonrces when
brought face to face with a new practical problem in economic
entomology. The snbject 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 in\'olves some knowledge of all of them.

"As far as the en.tomological part of the subject is con-
cerned, the chief recjuisites are a familiar accpiaintance with
the common injurious insects, and especially a thorough
knowledge of their life hist()ries, together with a 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 giAcn injurious species, we can-
not possil)ly tell when, where or how to strike it at its weakest
point.

" But besides this, we must also know the conditions favor-
able and unfavorable to it; the enemies which prey ui)on it,
whether l)ird or insect 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 s}-stem of things l)y which il is
affected. Without this we shall often be exposed to needless
alarm and expense, perhaps, in fighting by artificial remedies,
an insect already in process of rapid extinction by natural
causes; i)erhai)S gix'ing up in despair just at the time when the

* 400 ENTOMOLOGY

natural checks upon its career are about to lend their powerful
aid to its suppression. We may even, for lack of this knowl-
edge, 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, wdiich of our methods of cul-
ture stimulate their increase, and which, if any, may help to
keep it down. And we must also learn where strictly artifi-
cial measures can be used to advantage to destroy them.

" For the life histories of insects, close, accurate and con-
tinuous obser\'ation is of course necessary; and each species
studied must be followed nut only through its periods of de-
structive abundance, wdien it attracts general attention, but
through its times of scarcity as well, and season after season,
and year after year.

" The obser\'ations thus made must of course be collected,
collated and most cautiously generalized, wdth constant refer-
ence to the conditions under which they were made. No part
of the work requires more care than this.

" This work becomes still more difficult and intricate when
w'e 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 pre-
daceous insects are necessary, and a careful microscopic study
of their food, followed l\v summaries and tallies of the prin-
cipal results, a tedious and laborious undertaking, a specialty
in itself, requiring its special methods and its special knowl-
edge of the structures of insects and plants, since these must
be recognized in fragments, while the ordinary student sees
them (jnly 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 meteorology ; and if we undertake to master
the obscure subject of their diseases, especially those of epi-

INSECTS IN RELATION TO MAN 4° '

demic or contagious character, we shall find use for the highest
skill of the microscopist, and the best instruments of micro-
scopic 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 men-
tioned, 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 vary-
ing circumstances, until we are sure that all chances of mistake
or of accidental coincidence are removed. The whole subject
of artificial remedies for insect depredations, whether topical
applications or special modes of culture, must be gone o\er
critically in this way. So many of the so-called experiments
upon which current statements relating to the value of reme-
dies and pre\-entives are based, have been made by persons
unused to investigation, ignorant of the habits and the trans-
formations of the insects treated, without skill or training in
the estimation of evidence, and failing to understand the im-
portance of verification, that the whole subject is honeycombed
with blunders. Popular remedies for insect injuries have, in
fact, scarcely more value, as a rule, than popular remedies for
disease.

" Obser\'ation, record, generalization, experiment, verifica-
tion — these are the processes necessary for the mastery of this
subject, and they are the principal and ordinary processes of
all scientific research."

The official economic entomologist uses every means to
reach the public for whose benefit he works. Bulletins, circu-
lars 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 correspondence is carried
on with individual seekers for help, and personal influence is
27

402 ENTOMOLOGY

exerted in visits to infested localities and by addresses before
agricultural meetings. Special emergencies often tax e^'ery
resource of the official entomologist, especially if he is ham-
pered by inadequate legislative provision for his W()rk. 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 Mountain 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 properlv 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 writing's of Dr. Howard,
to which the reader is referred for additional details as well
as for a comprehensive review of the status of economic ento-
mology 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
Injurious to Vegetation," is still '' the vadc mcciiiii of the
working entomologist who resides in the northeastern section
of the country."

Dr. Alpheus S. Packard gave the state three short but use-
ful reports from 1871 to 1873.

As entomologist to the Hatch Experiment Station of the
Massachusetts Agricultural College, Prof. Charles H. Eernald
has issued important bulletins upon injurious insects, and has

INSECTS IX RELATION TO MAN 403

published in co]lal)Oi"ati(3n ^\■ith Edward H. Forbnsh a notal)lc
volume upon the g}'psy moth. For the suppression of this
pest, which threatened to exterminate vegetation over one hun-
dred square miles, the state of Massachusetts made annual
appropriations amounting in all to more than one million dol-
lars, and the operations, carried on by a committee of the State
Board of Agriculture, rank among the most extensive of their
kind.

New York. — Dr. Asa Fitch, appointed in 1854 by the New
York State Agricultural Society, under the authorization of
the legislature, was the first entomologist to be of^cially com-
missioned by any state. FTis fourteen reports (1855 to 1872)
embody the results of a large amount of painstaking investi-
gation.

In 1881, Dr. James A. Lintner became state entomologist
of New York. Highly competent for his chosen work, Lint-
ner made exevy effort to further the cause of economic ento-
mology, and his thirteen reports, accurate, thorough and ex-
tremely serviceable, rank among the best.

Lintner has had a most al)le successor in Dr. E. P. Felt, who
is continuing the work with exceptional vigor and the most
careful regard for the ent<^mological Avelfare of the state.
Felt has pul)lished at this writing eighteen Imlletins (including
seven annual reports), besides important papers on forest and
shade tree insects, and has directed the preparation by Need-
ham and his associates of three notable volumes on aquatic
insects.

The Cornell University Agricultund Experiment Station,
established in 1879, has issued man_\- \aluable publications
upon injurious insects, written by the master-hrmd n\ Pro-
fessor Comstock or else under his induence. ddie studies of
Comstock and Slingerland are always made in the most con-
scientious spirit and their bulletins — original, thorough and
practical — are models of what such works should be.

Illinois. — Air. IJenjamin D. \\'alsh, engaged in 1867 by the
Illinois State Horticultural Society. ])ul)lishcd in 1868. as act-

404 ENTOMOLOGY

ing State entomologist, a report in the interests of horticulture
— an accurate, sagacious and altogether excellent piece of ori-
ginal work. Like many other economic entomologists he was
a prolific writer for the agricultural press and his contribu-
tions, numliering' al)out four hundred, were in the highest
degree scientific and practical.

Walsh was succeeded l\v Dr. W^illiam LeBaron, who pub-
lished (1871 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
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. Thor-
oughly scientific, with a Inroad y\e\\ and a clear insig'ht into
the agricultural needs of the state, his authoritative and schol-
arly works upon economic entomology rank with those of the
highest \'alue. Of the twelve reports issued thus far by Dr.
Forbes, those dealing with the chinch bug, San Jose scale, corn
insects and sugar l)eet insects are especially noteworthy.

Missouri. — Appointed in 1868, Prof. Charles V. Riley pub-
lished (1869 to 1877) nine reports as state entomologist. To
quote Dr. Howard, " They are monuments to the state of Mis-
souri, and more especially to the man who wrote them. They
are original, practical and scientific. . . . They may be said to
have formed the l)asis for the new economic entomology of
the world." Riley's subsequent work will presentlv be spoken
of.

INSECTS IN RELATION TO MAN 405

State Experiment Stations. — The organization of State
Agricultural Experiment Stations in 1888, under the Hatch
Act, gave economic entomology an additional impetus. At
present, all the states and territories, except Indian Territory,
have an experiment station, and in a few instances two or even
three; while there are stations in Alaska, Hawaii and Porto
Rico. These stations, often in connection with state agricul-
tural colleg'es, maintain altogether over forty men who con-
cern 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 disseminat-
ing entomological information, and not a few of them are
based upon the investigations of their authors. Especially
noteworthy as regards originality, ^•olume and general useful-
ness are the publications of Slingerland in New York, Smith
in New^ Jersey, Webster in Ohio (formerly), 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 ser\-iceable information, pre-
sented in a popularly attractive manner.

While these workers have been conspicuously active in the
publication of their investigations, there are many other sta-
tion entomologists who devote themselves altogether to the
practical application of entomological knowledge, and whose
w^ork in this respect is highly important, even though its influ-
ence does not extend be}-(»nd the limits nf the state.

The U. S. Entomological Commission. — This commission
founded under a special Act of Congress in 1877 to investigate
the Rocky Mountain 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.

406 ENTOMOLOGY

The U. S. Department of Agriculture. — The first ento-
mological 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 laljor, out of all
proportion, however, to the practical value of his undertaking.

Glover was succeeded in 1878 by Riley, whose achievements
have aroused internati<jnal admiratir)n. He resigned in a year,
after writing a report, and was succeeded Ijy Prof. Comstock.
who held (jftice for two years, during which he wrote two
important volumes (published respectively 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, pub-
lished up to 1894, " 12 annual reports, 31 l)ulletins. 2 special
reports, 6 volumes of the periodical l)ulletin Insect Life, and
a large number of circulars of information." During his
vigorous and enterprising" adn"iinistration economic entomology
took an immense step in advance. The life hist()ries of injuri-
ous insects were studied with extreme care and many \'aluable
improvements in insecticides and insecticide machinery were
made. One of the notaljle 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
{Iccr\a purcJuisi), which tbreatened to put an end to the cul-
tivation of citrus trees in California. This disaster was
averted by the importation from Australia, in 1888, of a native
enen"iy of the scale, namel}", the lady-bird beetle Noi'ius
(Vcdalia) cardiiialis, which, in less than eighteen months after
its introduction into California, subjugated the noxious scale
insect. The L^nited States has since sent Xo-z'ius to South
Africa, Egypt and Portugal with similar beneficial results.

INSECTS IN RELATION TO MAN AO/

Based upon the foundation laid by Riley, the work of the
Division (now the Bureau) of Entomology has steadily pro-
gressed, under the leadership of Dr. Leland O. Howard. A\'ith
a comprehensive and hrm grasp of his suljject, alert to discover
and develop new possibilities, energetic and resourceful in
management. Dr. Howard has brought the go\ernment work
in applied entomology to its [)resent position of commanding
importance. Admirably organized, the Bureau now maintains
a corps of about fifty experts, and the total output of the Divi-
sion and the Bureau now amounts to nearly one hundred bul-
letins and more than half as many circulars.

The Department of Agriculture has recently succeeded in
starting a new and important industry in California — the cul-
ture of the Smyrna fig. The superior flavor of this variety
is due to the presence of ripe seeds, or, in other words, to
fertilization, and for this it is necessary for pollen of the wild
fig, or " caprifig." to l:>e transferred to the flowers of the
Smvrna fig. Normally this pollination, or " caprification,''
is dependent upon the services of a minute chalcid, Blastoph-
aga grossonim, which develops in the gall-like flowers of
the caprifig. The female insect, which in this exceptional in-
stance is winged while the mrde is not, emerges from the gall
covered with pollen, enters the y(~)ung' flowers of the Smyrna
fig to oviposit, and incidentally pollenizes them.

After many discouraging" attenii)ts, Blasfophaga, imported
from Algeria, has now been estal)lished in California, and the
new industry is de\Tloping ra])idl}'.

Canada. — The development of economic entomology in
Canada has been due largely to the efforts of Dr. James
Fletcher, of the IDominion Experimental I^'arms, Ottawa,
whose annual reports and other writings indicate al)ility of an
exceptional order. His work has l)cen furthered in excry way
by the " eminent director of the experimental farms system.
Dr. William Saunders, himself a pioneer in economic ento-
mology in Canada and the author of one of the most valuable
treatises up<")n the subject that has ever been ptfl)lishcd in
America."

408 ENTOMOLOGY

Outside of this, the work in Canada centers around the
Entomological Society of Ontario, whose excellent publica-
tions, sustained by the government, are of great scientific and
educational importance. In addition to its annual reports, this
society issues the Canadian Entomologist, one of the leading
serials of its kind, edited by its founder, the Rev. C. J. S.
Bethune, whose devoted ser\ices are appreciated by every
entomologist.

The Association of Official Economic Entomologists. —
Organized in 1889 by a few energetic workers, this association
has had a rapid and healthy growth and now numljers among
its members all the leading economic entomologists of America
and a large number of foreign workers. The annual meetings
of the association impart a vigorous stimulus to the individual
worker and tend to promote a well-balanced development of
the science of economic entomology.

Conclusion. — While working for the material welfare of
the agriculturist, the economic entomologist discovers phe-
nomena which are of the highest value to the purely scientific
mind. Indeed it is remarkaljle to notice the extent to which
the professedly practical entomologist is animated — not to say
dominated — l\v 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.

LITERATURE

The literature on entomological sulijects now numbers scarcely less than
100,000 titles. Tile works listed below have been selected chiefly on
account of their general usefulness and accessibility. Works incidentally
containing important bibliographies of their .special subjects 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.
Engelmann, W. Bibliotheca Historico-Naturalis. i vol. Leipzig, 1846.

Literature, 1700-1846.
Carus, J. v., and Engelmann, W. Bibliotheca Zoologica. 2 vols. Leipzig,

i86t. Literature, 1846-1860.
Taschenberg, 0. Bibliotheca Zoologica. 5 vols. Leipzig, 1887-1899.

Vols. 2 and 3, entomological literature, 1861-1880.
The Zoological Record. London. Annually since vol. for 1864.
Catalogue of Scientific Papers, Royal Society. London. Since 1868.
Zoologischer Anzeiger. Leipzig. Fortnightly since 187S. Bibliographica

Zoologica, annual volumes since 1896.
Concilium Bibliographicum. Zurich. Card catalogue of current zoological

literature since 1896.
Archiv fiir Naturgeschichte. Berlin. Annual summaries since 1835.
Journal of the Royal Microscopical Society. London. Summaries of the

most important works, beginning 1878.
Zoologischer Jahresbericht. Leipzig. Yearly summaries of literature

since 1879.
Zoologisches Centralblatt. Leipzig. Reviews of more important litera-
ture since 1895.
Psyche. Cambridge, Mass. Records of recent American literature. Also

earlier records, beginning 1874.
Entomological News. Philadelphia, 1890 to date. Records of current lit-
erature up to 1903.
Bibliography of the more important contributions to American Economic

Entomology. 8 parts. Pts. 1-5 by S. Henshaw ; pts. 6-8 by N.

Banks. 1318 pp. Washington, 1889-1905.
Catalogue of Scientific Serials, 1633-1876. S. II. Scudder. Cambridge,

Mass. Harvard University, 1879.
A Catalogue of Scientific and Technical Periodicals, 1665-1895. II. C.

Bolton. Washington, Snnthsonian Institution, 1897.

409

4IO ENTOMOLOGY

A List of Works on North American Entomology. N. Banks. Bull. U. S.
Dept. Agric, Div. Enl., no. 24 (11. s.), 95 pp. Washington, 1900.

GENERAL ENTOMOLOGY

Kirby, W., and Spence, W. 1822-26. An Litroduction to Entomology.

4 vols. 36 + 2413 pp., 30 pis. London.
Burmeister, H. 1832-55. Handbuch der Entomologie. 2 vols. 28+ 1746

pp., 16 taf. Trans, of Band i : 1836. W. E. Shnckard. A Man-
ual of Entomology. 124-654 pp.. 32 pis. London.
Westwood, J. 0. 1839-40. An Introduction to the Modern Classification

of Lisects. 2 vols. 23 -|- 620 pp.. 133 figs. London.
Graber, V. 1877-79. Die Insekten. 2 vols. 8 -f- 1008 pp., 404 figs.

Miinchen.
Miall, L. C, and Denny, A. 1886. The Structure and Life-History of the

Cockroach. 6 -j- 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, N. Y.
Kolbe, H. J. 1889-93. Einfuhrung in die Kenntnis der Insekten. 12 -|-

709 pp., 324 figs. Berlin. F. Dummler.*
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., 22;^ figs.

Boston. D. C. Heath & Co.*
Kirby, W. F. 1892. Elementary Text-Book of Entomology. Ed. 2. 8 +

2S1 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 Te.xt-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. 0. 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, Em-

bryogenie. iS + 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.

LITERATURE 4^^

PHYLOGENY AND CLASSIFICATION

Kirby, W., and Spence, W. 1822-26. An Inlroduclion to Entomology.

4 vols. 364- -413 pp.. 30 pis. London.
Burmeister, H. 1832. Handbuch der Entomologie. 2 vols. 284-1746

pp., 16 taf. Berlin. Translation of Band i : 1836. \V. E. Shnck-

ard. A Manual of Entomology. 124-654 pp., 32 pis. London.

Contains useful synopses of the older systems of classification.
Westwood, J. 0. 1839-40. An Introduction to the Modern Classification

of Insects. 2 vols. 234-620 pp.. 133 figs. London.
Miiller, F. 1864. Fiir Darwin. Leipzig. Trans. : 1869. W. S. Dallas.

Iv'icts and Figures in aid of Darwin. London.
Brauer, F. 1869. Betrachtungen iiber die Verwandlung der Insekten im

Sinne der Descendenz-Theoric. Varh. zool.-bot. Gesell. Wien, bd.

10, pp. 299-318; bd. 28 (1878). 1879, pp. 151-166.
Lubbock, J. 1873. On the Origin of Insects. Journ. Linn. Soc. ZooL,

vol. Ti, pp. 4-'-'-4^5-
Packard, A. S. 1873. Our Common Insects. 225 pp., 268 figs. Boston.

Estes & Lauriat.
Lubbock, J. 1874. On the Origin and JNIetamorphoses of Insects. 16 -j-

108 pp., 63 figs., 6 i)ls. London. Macmillan & Co.*
Mayer, P. 1876. LTeber Ontogenie vmd Phylogenie der Insekten. Jenais.

Zcits. 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. i83i. 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, pp. 698-704, fig. I.
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 rela-
tion to Other Orders of Insects. Third Rept. U. S. Ent. Comm.,

pp. 286-304.
Brauer, F. 1885. Systematisch-zoologische Studicn. Sitzh. Akad. Wiss.

Wien, bd. 91, pp. 237-413.*
Grassi, B. 1885. I progenitor! degli Insetti e dei ]\Iiriapodi. — Morfologia

delle Scolopendrelle. Atti. Accad. Torino, t. 21, pp. 48-50.
Haase, E. 1886. Die Vorfahren der Insccten. 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, j). 396.
Kingsley, J. S. 1888. The Classification of the Myriapoda. Amer. Nat.,

vol. 22, pp. 1118-1121.

412 ENTOMOLOGY

Haase, E. 1889. Die Abdominalanhange der Insekten mit Beritcksichti-

gung der ]\Iyriopoden. Morph, Jahrb., bd. 15, pp. 331-435, taf.

14. 15-
Fernald, H. T. 1890. The Rekitionships of Arthropods. Studies Biol.

Lai). 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. II, pp. 440-473. Trans, from Sitzb. Akad. Wiss. Wien,

math.-nat. CL, bd. loi, heft 2, pp. 237-274, taf. i.
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. 193-19S, 201-212.
Pocock, R. I. 1893. On some Points in the Morphology of the Arachnida

(s. s.) with Notes on the Classitication of the Group. Ann. Mag.

Nat. Hist., ser. 6, vol. 11, pp. 1-19, pis. i, 2.
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.

Nat., vol. 28, pp. 1 18-135, --20-235.*
Kenyon, F. C. 1895. The Morphology and Classification of the Pauro-

poda, with Note's on the Morphology of the Diplopoda. Tufts

Cdll. Studies, no. 4, pp. 77-146, pis. 1-3.
Schmidt, P. 1895. Beitriige zur Kenntnis der niederen IMyriapoden.

Zeits. wiss. Zool., bd. 59, pp. 436-510, taf. 26, 27.
Wagner, J. 1895. Contributions to the Phylogeny of the Arachnida:

Ann. Mag. Nat. Llist., ser. 6, vol. 15, pp. 285-315. Trans, from

Jenais. Zeits. Naturw., bd. 29, pp. 123-156.
Miall, L. C. 1895. The Transformations of Insects. Nature, vol. 53, pp.

152-158.
Sedgwick, A. 1895. Peripatus. Camb. Nat. 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. i2-(-ii30

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, i taf.

LITERATURE 4^3

Heymons, R. 1897. MittlKMlungeii iiber die Segmentierung und den
' Kdrperbau der Myriopoden. Sitzb. Akad. Wiss., P>erlin, bd. 40,

pp. 915-923. 2 figs.
Hansen, H. J., and Sorensen, W. 1897. Tbe Order Palpigradi Thor. and

its Relationsbip to the Arachnida. Ent. Tidsk., arg. 18, pp. 223-

240, pi. 4-
Hutton, F. W., and others. 1897. Are the Arthropoda a Natural Group?

Nat. Sc. vol. 10. pp. 97-117.
Lankester, E. R. 1897. Are the Arthropoda a Natural Group? Nat.

Sc, vol. ID, pp. 264-268.
Packard, A. S. 1898. A Text-Book of Entomology. 17 + 729 pp., 654

figs. New York and London. The Macmillan Co.*
Packard, A. S. 1899. Entomology for Beginners. Ed. 3. 16 + 367

pp., 273 figs. New York. Henry Holt & Co.*
Von Zittel, K. A. 1900, 1902. Text-Book of Palaeontology. 2 vols.

Trans. C. R. Eastman. London and New York. ALacmillan

& Co.*
Folsom, J. W. 1900. The Development of the Mouth Parts of Anurida

maritima Guer. Bull. Mus. Comp. ZooL, vol. 36, pp. 87-157, pis.

i-S.*
Hansen, H. J. 1902. On the Genera and Species of the Order Pauropoda.

Vidensk. Medd. Naturh. Foren. Kjobenhavn (1901), pp- 323-424.

pis. 1-6.
Carpenter, G. H. 1903. On the Relationships between the Classes of the

Arthropoda. Proc. R. Irish Acad., vol. 24, pp. 320-360, pi. 6.*
Enderlein, G. 1903. Ueber die INIorphologie, Gruppierung und systcmat-

ische Stellung der Corrodentien. Zool. Anz., bd. 26, pp. 423-

437, 4 figs.
Hansen, H. J. 1903. The Genera and Species of the Order Symphyla.

Quart. Journ. Alicr. Sc, vol. 47, pp. i-ioi, pis. 1-7.
Packard, A. S. 1903. Hints on the Classification of the Arthropoda; the

Group, a Polyphyletic One. Proc Amer. Phil. Soc, vol. 42, pp.

142-161.
Lankester, E. R. 1904. The Structure and Classification of the Arthro-
poda. Quart. Journ. Micr. Sc, vol. 47 (n. s.), pp. 523-582, pi.

42. (From Encyc. Britt., ed. 10.)
Carpenter, G. H. 1905. Notes on the Segmentation and Phylogeny of the

Arthropoda, with an Account of the Maxillae in Polyxenus lag-

urus. Quart. Journ. Micr. Sc, vol. 49, pt. 3, pp. 469-491, pi. 28.*

GENERAL ANATOMY

De Reaumur, R. A. F. 1734-42. Memoires pour scrvir a I'histoirc des

insectes. 7 vols. Paris.
Lyonet, P. 1762. Traite anatomiciue de la Chenille, qui ronge le Bois

de Saule. Ed. 2. 22 + 616 pp., 18 pis. La Haye.
Straus-Diirckheim, H. 1828. Considerations generales sur I'anatoniie

comparee des animaux articules, etc. 19 + 434 pp., 10 pis. Paris.

414 ENTOMOLOGY

Newport, G. 1839. Insecta. Todd's Cyclop?sdia Anat. Phys., vol. 2, pp.

853-994. figs. 3-'9-43<)-

Leydig, F. 1851. Anatomisches und Histologisches iiber die Larve von
Corethra plumicornis. Zeits. wis.s. Zool, bd. 3. pp. 435-451, taf.
16, figs. 1-4.

Leydig, F. 1855. Zum feineren Ban der Arthropoden. Midler's Archiv
Anat. Phys., pp. 376-480, taf. 3.

Leydig, F. 1857. Lehrbuch der Histologie des Menschen und der Thiere.
12 -H 551 pp., figs. Frankfurt.

Leydig, F. 1859. Zur Anatonne der Insecten. Midler's Archiv Anat.
Phys., pp. 33-89. 149-1S3, taf. 3.

Leydig, F. 1864. Vom Ban des tierischen Korpers. Tiibingen.

Huxley, T. H. 1877. -^ Manual of the Anatomy of Invertebrated Ani-
mals. London. J. and A. Churchill. 1878. New York. D.
Appleton & Co.

Packard, A. S., and Minot, C. S. 1878. Anatomy and Embryology [of
the locust]. First Rept. U. S. Ent. Comm., pp. 257-279, figs.
12-18. \\'ashington.

Lubbock, J. 1879. On the Anatomy of Ants. Trans. Linn. Soc. Zool,
ser. 2, vol. 2, pp. 141-154, pis.

Riley, C. V., Packard, A. S., and Thomas C. 1880, 1883. Second and
Third Repts. \J. S. Ent. Connn. Washington.

Minot, C. S. 1880. Histology of the Locust (Caloptenus) and the Cricket
(Anabrus). Second Rept. U. S. Ent. Connn., pp. 183-222, pis.
2-8. Washington.

Brooks, W. K. 1882. Handbook of Livertebrate Zoology, pp. 237-269,
figs. 129-141. Boston. S. E. Cassino.

Viallanes, H. 1882. Recherches sur I'histologie des insectes. Ann. Sc.
nat. Zool, ser. 6, t. 14, pp. 1-34S, pis. 1-18.

Leydig, F. 1883. LTntersuchungcn zur Anatomic und Histologie der
Thiere. 174 pp., 8 taf. Bonn.

Miall, L. C, and Denny, A. 1886. The Structure and Life-history of the
Cockroach. 6 -f- 224 pp., 125 figs. London, Lovell Reeve &
Co. ; Leeds, R. Jackson.

Schaeffer, C. 1889. Beitrage zur Histologie der Insekten. Zool. Jahrb.,
Morph. Abth., bd. 3. pp. 611-652, taf. 29, 30.

Lowne, B. T. 1890-92. The Anatomy, Physiology, Morphology and De-
velopment of the Blow-fly (Calliphora erythrocephala). A Study
in the Comparative Anatomy and Morphology of Insects. 8 4-
778 pp., 108 figs., 21 pis. London.*

Lang, A. 1891. Text-Book of Comparative Anatomy. Trans, by H. M.
and M. Bernard. Pt. i, pp. 438-508, figs. 301-356. London and
New York. ^Lacmillan & Co.*

Comstock, J. H., and Kellogg, V. L. 1899. ^ he Elements of Bisect Anat-
omy. Rev. ed. 134 pp., 11 figs. Ithaca, N. Y. Comstock Pub-
lishing Co.

LITERATURE 4^5

HEAD AND APPENDAGES

Schaum, H. 1863. Uber die Zusammensetzung des Kopfcs und die Zahl

der Abdominalsegmente hei den Insekten. Archiv Xaturg., jhg.

29, bd. I, pp. 247-260.
Basch, S. 1865. Skelett und Rluskehi des Kopfes von Termes. Zeits.

wiss. ZooL, bd. 15, pp. 55-75, i taf.
Breitenbach, W. 1877. Vorlaiifige Mitteilung uber einige neue Unter-

suchungen an Scbmetterlingsriisseln. Archiv mikr. Anat., bd. 14,

PP- 308-317. I taf.
Breitenbach, W. 1878. Untersuchungen an Sclunetterlingsrussehi. Ar-

cliiv mikr. Anat., bd. 15, pp. 8-29, i taf.
Breitenbach, W. 1879. Ucber SchmetterlingsriisseL Ent. Nacbr.. jlig. 5,

PP- -'37--243-
Burgess, E. 1880. Contributions to the. Anatomy of the Milk-weed But-
terfly (Danais archippus Fabr.). Anniv. Mem. Bost. Soc. Nat.

Hist., 16 pp., 2 pis.
Meinert, F. 1880. Sur la conformation de la tete et sur I'interpretation

des organes buccaux chez les Insectes, aiiisi que sur la systema-

tique de cet ordre. Ent. Tidsk., arg. i, pp. 147-150.
Dimmock, G. 1881. The Anatomy of the Mouth Parts and of the Suck-
ing Apparatus of some Diptera. 50 pp., 4 pis. Boston. A.

Williams & Co.*
Geise, 0. 1883. Die Mundtheile der Rhynchoten. Archiv Naturg., jhg.

49, bd. I, pp. 315-373. taf. 10.
Kraepelin, K. 1883. Zur Anatomic und Physiologic des Riissels von

Musca. Zeits. wiss. Zool, bd. 39, pp. 683-719, taf. 40, 41.
Briant, T. J. 1884. On the Anatomy and Functions of the Tongue of the

Honey Bee (worker). Journ. Linn. Soc. Zool., vol. 17, pp. 408-

417, pis. 18, 19.
Wedde, H. 1885. Beitrage zur Kenntniss des Rhynchotenriissels. Ar-
chiv Naturg., jhg. 51, bd. i, pp. 1 13-143, taf. 6, 7.
Walter, A. 1885. Beitrage zur Morphologic der Schmetterlinge. Jenais.

Zeits. Naturw., bd. 18, pp. 751-807, taf. 2ji. 24.
Walter, A. 1885. Zur Morphologic der Schmetterlingsmundthcile.

Jenais. Zeits. Naturw., bd. 19, pp. 19-27.
Breithaupt, P. F. i836. I'ebcr die Anatomic und die Functionen der

Bienenzunge. Archiv Naturg., jhg. 52, bd. I, pp. 47-112, taf. 4, 5.*
Blanc, L. 1891. La tete du Bombyx mori a I'etat larvaire, anatomic et

physiologic. Trav. Lab. fitud. Sole, 1889-1890, 180 pp., 95 figs.

Lyon.
Smith, J. B. 1892. The Mouth Parts of Copris Carolina; with Notes on

the Homologies of the Mandibles. Trans. Amer. Ent. Soc, vol.

19, pp. 83-87, pis. 2, 3.
Hansen, H. J. 1893. A Contribution to the ■Morphology of the Limbs

and Mouth Parts of Crustaceans and Insects. Ann. jNIag. Nat.

Hist, sen 6, vol. 12, pp. 417-434. Trans, from Zool. Anz., jhg.

16, pp. 193-198, 201-212.

4l6 ENTOMOLOGY

Kellogg, V. L. 1895. The Mouth Parts of the Lepidoptera. Amer. Nat.,

vol. 29, pp. 546-556, pi. 25, llgs. I, 2.
Smith, J. B. 1896. An Essay on the Development of the Mouth Parts

of certain Insects. Trans. Amer. Phil. Soc, vol. 19 (n. s.), pp.

175-198, pis. 1-3.
Folsom, J. W. 1899. The Anatomy and Physiology of the Mouth Parts

of the Collemholan, Orchesella cincta L. Bull. Mus. Comp. Z06I.,

vol. 35, pp. 7-39, pis. 1-4.*
Janet, C. 1899. Essai sur la constitution morphologique de la tete de

I'insecte. 74 pp., 7 pis. Paris. G. Carre et C. Naud.
Kellogg, V. L. 1899. The Mouth Parts of the Nematocerous Diptera.

Psyche, vol. 8, pp. 303-306, 3^7-330, 346-348. 355-359. 363-365,

figs. I-II.
Folsom, J. W. 1900. The Development of the Mouth Parts of Anurida

maritima Guer. Bull. Mus. Comp. Zool., vol. 36, pp. 87-157, pis.

1-8.*
Comstock, J. H., and Kochi, C. 1902. The Skeleton of the Head of In-
sects. Amer. Nat., vol. 36, pp. 13-45, figs- 1-29.*
Kellogg, V. L. 1902. The Development and Homologies of the Mouth

Parts of Insects. Amer. Nat., vol. 36, pp. 683-706, figs. 1-26.
Meek, W. J. 1903. On the Moutli Parts of the Hemiptera. Kansas

Univ. Sc. Bull., vol. 2 (12), pp. 257-277, pis. 7-1 1.*
Holmgren, N. 1904. Zur Morphologie des Insektenkopfes, Zeits. wiss.

Zool., bd. 76, pp. 439-477, taf. 27, 28.*
Kulagin, N. 1905. Der Kopfbau bei Culex und Anopheles. Zeits. wiss.

Zool., bd. 83, pp. 285-335, taf. 12-14.*

THORAX AND APPENDAGES; LOCOMOTION

Audouin, J. V. 1824. Rccherches anatomiques sur le thorax des animaux
articules et celui des insectes hexapodes en particulier. Ann. Sc.
nat. Zool, t. I. pp. 97-135, 416-432, figs.

MacLeay, W. S. 1830. Explanation of the comparative anatomy of the
thorax in winged insects, with a review of the present state of
the nomenclature of its parts. Zool. Journ., vol. 5, pp. 145-179,
2 pis.

Langer, K. i860. Ueber den Gelenkbau bei den Arthrozoen. Vierter
Beitrag zur \-ergleichenden Anatonne und ]\Iechanik der Gelenke.
Denks. Akad. Wiss. Wien., Phys. CL, l)(I. 18, pp. 99-140, 3 taf.

West, T. 1861. The Foot of the Fly; its Structure and Action; eluci-
dated l)y comparison with the feet of other Insects, etc. Trans.
Linn. Soc. Zool., vol. 23, pp. 393-421, pis. 41-43.

Plateau, F. 1871. Qu'est-ce que I'aile d'un Insecte? Stett. cut. Zeit.,
jfig- 3-'. PP- 33-4-2, pl. I.

Plateau, F. 1872. Rccherches experimentales sur la position du centre
de gravite chez les insectes. Archiv. Sc. phys. nat. Geneve, nouv.
per., t. 43, pp. 5-37.

LITERATURE 41/

Pettigrew, J. B. 1874. Animal Locomotion. 13 + 264 pp., 130 figs. New

York. D. Applet, m & Co.
Marey, E. J. 1874, 1879. Animal Meclianism. 16 + 283 PP-> n? figs.

New York. D. A])pleton & Co.
Hammond, A. 1881. On the Thorax of the Blow-fly (INIusca vomitoria).

Journ. Linn. Soc. Zool., vol. 15, pp. 9-31. pis. i, 2.
Von Lendenfeld, R. 1881. Der Flug der Libellen. Ein Beitrag zur Anat-
omic nnd Phy.siologie der Flugorgane der Insecten. Sitzb. Akad.

Wiss. Wien., bd. 83, pp. 289-376, taf. 1-7.
Brauer, F. 1882. Ueber das Segment mediaire Latreille's. Sitzb. Akad.

Wiss. Wien, bd. 85, pp. 218-244, taf. 1-3.
Dahl, F. 1884. Beitriige zur Kenntnis des Banes nnd der Funktionen der

Insektenbeine. Archiv Natnrg., jhg. 50. bd. i, pp. 146-193, taf.

11-13.
Dewitz, H. 1884. L^eber die Fortbewegung der Thiere an senkrechten

glatten Flachen vermittelst eines Sekretes. Pfliiger's Archiv ges.

Phys., bd. 33, pp. 440-481, taf. 7-9.
Oraber, V. 1884. Ueber die Mechanik des Insektenkorpers. L Mechanik

der Beine. Biol. Centralbl., bd. 4, pp. 560-570.
Amans, P. 1885. Comparaisons des organes du vol dans la serie animale.

Ann. So. nat. Zool., ser. 6, t. 19, pp. 1-222, pis. 1-8.
Redtenbacher, J. 1886. Vergleichende Studien iiber das Flitgelgeader der

Insecten. Ann. naturh. Hofm. Wien, bd. i, pp. 153-232, taf.

9-20.
Amans, P. C. 1888. Comparaisons des organes de la locomotion aqua-

tique. Ann. Sc. nat. Zool, ser. 7, t. 6, pp. 1-164, pis. 1-6.
Carlet, G. 1888. Snr le mode de locomotion des chenilles. Compt. rend.

Acad. Sc, t. 107, pp. 131-134.
Ockler, A. 1890. Das Krallenglied am Lisektenfuss. Archiv Natnrg.,

jhg. 56, bd. I, pp. 221-262, taf. 12, 13.
Demoor, J. 1891. Recherches snr la marche des Insectes et des Arach-

nides. Archiv. Biol., t. 10, pp. 567-608, pis. 18-20.
Hoffbauer, C. 1892. Beitriige zur Kenntnis der Insektenfliigel. Zeits.

wiss. Zool., !)d. 54, pp. 579-630, taf. 26, 27. 3 figs.*
Spuler, A. 1892. Zur Phylogenie und Ontogenie des Fliigelgeader der

Schmetterlinge. Zeits. wiss. Zool, bd. 53, pp. 597-646, taf. 25, 26.
Comstock, J. H. 1893. Evolution and Taxonomy. Wilder Quarter-
Century Book, pp. 37-114, pis. 1-3. Tthaca, N. Y.
Kellogg, V. L. 1895. The Affinities of the Lepidopterous Wing. Amer.

Xat., \iil. 29, pp. 709-717, figs. i-TO.
Marey, E. J. 1895. Movement. 15 + 323 pp., 204 figs. New York. D.

Appleton & Co.
Comstock, J. H., and Needham, J. G. 1898-99. The Wings of Insects.

Amcr. Nat., vols. 32, 33, pp. 43-48. 8i-8(j, 231-257. 335-340. 413-

424. 561-565, 769-777, 903-911, 117-T26, 573-582. 845-860, figs. 1-90.

Reprint, Ithaca, N. Y. Comstock Pub. Co.
Walton, L. B. 1900. The Basal Segments of the Ilexapod Leg. Amer.

Nat., vol. 34, pp. 267-274, figs. 1-6.

41 8 ENTOMOLOGY

Verhoeff, K. W. 1902. Beitriige zur vergleichenden Alorphologie des
Thorax der Insekten mit Beriicksichtigung der Chilopoden. Nova
Acta Leop. -Carol. Akad. Naturf., bd. 81, pp. 63-110, taf. 7-13.

Voss, F. 1904-05. Uber den Thorax von Grylhis domesticns. Zeits.
wiss. Zoo]., bd. 78, pp. 268-521, taf. 15, 16, 25 figs.

ABDOMEN AND APPENDAGES

Lacaze-Duthiers, H. 1849-53. Recherches sur rarmure genitale femelle

des insectes. Ann. Sc. nat Zool., ser. 3, t. 12-19, pis. Several

papers.
Fenger, W. H. 1863. Anatomie und Physiologie des Giftapparates bei

den Hymenopteren. Archiv Naturg., jhg. 29, bd. i, pp. 139-178,

I taf.
Schaum, H. 1863. Ueber die Zusammensetznng des Kopfes und die Zaht

der xA-bdominalsegmente bei den Insekten. Archiv Naturg., jhg.

29, bd. I, pp. 247-260.
Sollmann, A. 1863. Der Bienenstachel. Zeits. wiss. Zool, bd. 13, pp.

52S-540, I taf.
Packard, A. S. 1866. Observations on the Development and Position of

the Hynienoptera, with Notes on the Morphology of Insects.

Proc. Bost. Soc. Nat. Hist., vol. 10. pp. 279-295, figs. 1-4.
Goossens, T. 1868. Notes sur les pattes membraneuses des Chenilles.

Ann. Soc. ent. France, ser. 4, t. 8, pp. 745-748.
Packard, A. S. 1868. On the Structure of the Ovipositor and Homol-
ogous Parts in the ^Male Insect. Proc. Bost. Soc. Nat. Hist., vol.

II. PP- 393-399, figs. I-II.
Graber, V. 1870. Die Aehnlichkeit im Baue der iiusseren weiblichen

Geschlechtsorgane bei den Locustiden und Akridiern dargestellt

auf Grund ihrer Entwicklungsgeschichte. Sitzb. Akad. Wiss.

Wien, math.-naturw. CI., bd. 61, pp. 597-616, taf.
Scudder, S. H., and Burgess, E. 1870. On Asymmetry in the Appendages

of He.xapod Insects, especially as illustrated in the Lepidopterous

Genus Nisoniades. Proc. Bost. Soc. Nat. Hist., vol. 13, pp. 282-

306, I pi.
Krapelin, C. 1873. Untersuchungen iiber den Ban, Mechanismus und die

Entwicklungsgeschichte des Stachels der bienenartigen Thiere.

Zeits. wiss. Zool, bd. 23, pp. 289-330, taf. 15, 16.
Dewitz, H. 1875. Ueber Ban und Entwickelung des Stachels und der

Legescheide einiger Hymenopteren und der griinen Heuschrecke.

Zeits. wiss. Zool., bd. 25, pp. 174-200, taf. 12, 13.
White, F. B. 1876. On the Male Genital Armature in the Rhopalocera.

Trans. Linn. Soc. Zool.,' ser. i, vol. i, pp. 357-369, 3 pis.
Adler, H. 1877. Lege-Apparat und Eierlegen der Gallwespen. Deuts.

ent. Zeits., jhg. 21, pp. 305-33^, taf. 2.
Dewitz, H. 1877. Ueber Ban und Entwickelung des Stachels der Amei-

sen. Zeits. wiss. Zool., bd. 28, pp. 527-556, taf. 26.

LITERATURE 4 I 9

Davis, H. 1879. Notes on the Pygidia and Cerci of Insects. Jonrn. R.

Micr. Soc, vol. 2, pp. 252-255.
Kraatz, G. 1881. Ueber die Wichtigkeit der Untersnclinng des mann-

lichen Begattnngsgliedes der Kafer fur die Systematik und Artun-

tersclieidung. Dents, ent. Zeits., jlig. 25, pp. 1 13-126.
Dewitz, H. 1882. Ueber die Fiihrnng an den Korperhangcn der Insecten.

Berlin ent. Zeits., bd. 26, pp. 51-68, fig.
Gosse, P. H. 1882. On the Clasping Organs ancillary to Generation in

certain Groups of the Lepidoptera. Trans. Linn. Soc. Zool, ser.

2, vol. 2, pp. 265-345, 8 pis.
Von Hagens, D. 1882. Ueber die mannlichen Genitalien der Bienen-Gat-

tung Sphecodes. Dents, ent. Zeits., jhg. 26, pp. 209-228, taf. 6, 7-
Radoszkowski, 0. 1884. Revision des armures copulatrices des males du

genre Bombus. Bull. Soc. Nat. Moscou, t. 49, pp. 51-92, 4 pis.
Saunders, E. 1884. Further notes on the terminal segments of Aculeate

Hymenoptera. Trans. Ent. Soc. London, pp. 251-267.
Haase, E. 1885. Ueber se.xuelle Charactere bei Schmetterlingen. Zeits.

Ent. Breslau. n, f., bd. 9, pp. 15-19; bd. 10, pp. 36-44.
Radoszkowski, 0. 1885. Revision des armures copulatrices des males de

la famille des Mutillidse. Horre Soc. Ent. Ross., t. 19, pp. 3-49,

9 pis.
Von Ihering, H. 1886. Der Stachel der ^Meliponen. Ent. Nachr., jhg. 12,

pp. 177-188, taf. 8.
Goossens, T. 1887. Les pattes des Chenilles. Ann. Soc. ent. France, ser.

6, t. 7, pp. 385-404. pi. 7.
Graber, V. 1888. L^eber die Polypodie bei Insekten-Embryonen. JMorph.

Jahrb., bd. 13, pp. 586-615. taf. 25, 26.
Haase, E. 1889. Ueber Abdominalanhange bei Hexapoden. Sitzb. Gesell.

naturf. Freunde, pp. 19-29.
Haase, E. 1889. Die Abdominalanhiinge der Lisekten mit Beriicksichti-

gung der Myriopoden. Alorph. Jahrb., bd. 15, pp. 331-435, taf.

14. US-
Radoszkowski, 0. 1889. Revision des armures copulatrices des males de

la tribu des Chrysides. Horaa Soc. Ent. Ross., t. 23, pp. 3-40, pis.

1-6.
Beyer, 0. W. 1890. Der Giftapparat von Formica rufa, ein reduziertes

Organ. Jenais. Zeits. Naturw., bd. 25. pp. 26-112, taf. 3, 4.
Carlet, G. 1890. ]\Iemoire sur le venin et I'aiguillon de Tabcille. ;\nn.

Sc. nal. Zool., ser. 7, t. 9, pp. 1-17, pi. i.
Packard, A. S. 1890. Notes on some points in the external structure

and phylogeny of Lepidopterous larvae. Proc. Bost. Soc. Nat.

Hist.. \nl. 25, pp. 82-114, pis. T. 2.
Sharp, D. 1890. On the structure of the terminal segment in some male

Hemiptera. Trans. Ent. Soc. London, i)p. 399-427, pis. 12-14.
Wheeler, W. M. 1890. On the Appendages of the first abdominal Seg-
ment of embryo Insects. Trans. Wis. Acad. Sc, vol. 8, pp. 87-

140, pis. 1-3.*

420 ENTOMOLOGY

Escherich, K. 1892. Die biologische Bedeutung der Genitalanhange der

Insckten. Verh. zool.-bot. Ges. Wien, bd. 42, pp. 225-240, taf. 4.
Graber, V. 1892. Ueber die morphologiscbe Bedeutung der Abdominalan-

hiinge der Insekten-Embrvonen. Morph. Jabrb., bd. 17, pp. 467-

482.
Escherich, K. 1894. Anatomiscbe Studien iiber das mannbche Genital-
system der Coleopteren. Zeits. wiss. Zool., bd. 57, pp. 620-641,

taf. 26, 3 iigs.
Janet, C. 1894. Sur La jMorphologie du squelette des segments post-

thoraciques cbez 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 taxonomique. Ann. Soc. ent. France, t. 6^. pp. 74-Si, figs.

1-8.
Verhoeff, C. 1894. Vergleicbende Untersucbungen iiber die Abdominal-

segmente der weiblicben Hemiptera-Heteroptera und Homoptera.

Verh. nat. Ver. Bonn, jhg. 50, pp. 307-374.
Heymons, R. 1895. Die Segmentirung des Insectenkorpers. Anb. Abb.

Preuss. Akad. Wiss. Berlin, 39 pp.. i taf.
Heymons, R. 1895. Die Embryonalentwickelung von Dermapteren und

Orthopteren imter besonderer Beriicksicbtigung der Keimblatter-

bildung. 136 pp.. 12 taf., 33 figs. Jena.
Peytoureau, S. A. 1895. Contribution a I'etude de la morpbologie de

I'armure genitale des Insectes. 248 pp., 22 pis.. 43 figs. Paris.
Verhoeff, S. 1895. Beitriige zur vergleicbenden Morpbologie des Abdo-
mens der Coccinelliden. etc. Arcbiv Naturg., jbg. 61, bd. i, pp.

1-80, taf. 1-6.
Verhoeff, C. 1895. Vergleicbend-morphologiscbe Untersucbungen iiber

das Abdomen der Endomycbiden, Erotyliden und Languriiden

(ini alten Sinne) und iiber die 3iluskulatur des Copulationsap-

parates von Triplex. Arcbiv Naturg., jbg. 61. bd. i. pp. 213-287,

taf. 12. 13.
Verhoeff, C. 1895. Cerci und Styli der Tracheaten. Ent. Nacbr.. jbg.

21. pp. ib6-i6S.
Heymons, R. 1896. Grundziige der Entwickelung und des Korperbaues

von Odonaten und Epbemeriden. Anb. Abb, Akad. Wiss. Berlin.

66 pp., 2 taf.
Heymons, R. 1896. Zur Morpbologie des Alidominalanhiinge bei den

Insekten. Morpb. Jabrb., !)d. 24, pp. 178-204, taf. i.
Verhoeff, C. 1896. Zur jNbTrpbologie der Segmentanbange bei Insecten

und Myriopoden. Zool. Anz., bd. 19. pp. 378-383, 385-388.
Goddard, M. F. 1897. On tbe Second Abdominal Segment in a few Libel-

lulidas. Proc. Amer. Pbil. Soc, vol. 35, pp. 205-212, 2 pis.
Janet, C. 1897. Limitcs morpbologiques des anneaux post-cepbaliques et

Musculature des anneaux post-tboraciques cbez la ]Myrmica rubra.

Note 16. 35 pp., 10 figs. Lille.
Verhoeff, C. 1897. Bemerkungen iiber abdominale Korperanbange bei

Insecten und Myriopoden. Zool. Anz.. bd. 20, pp. 293-300.

LITERATURE 421

Janet, C. 1898. Aiguillon de la Myrmica rubra. Appareil dc fcrmeture
de la glande a venin. Note iS. 27 pp., 3 pis. Pari.s.

Zander, E. 1903. Beitrage zur ^^lorphologic der mannliclien Gcschlcchts-
anhange 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. Miiller's

.\rcliiv Anat. Phys., pp. 367-374. fig.
Leydig, F. 1855. Zinn feineren Ban der Arthropoden. iMiiller's Archiv

Anat. Phys.. pp. 376-480, taf. 3.
Semper, C. 1857. Beobachtungen iiber die Bildnng der Fliigel. Schuppen

und Haare bei den Lepidopteren. Zeits. wiss. Zool., bd. 8, pp.

326-339. taf. 15.
Sirodot, S. 1858. Recherches snr les secretions chez les Insectes. Ann.

Sc. nat. Zool., sen 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. n, 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.
Landois, H. 1871. Beitrage zur Enlwicklungsgeschichte der Schmetter-

lingsflugel 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 Ban, die Entwickelung und physiologische

Bedeutung der Rektaldriisen bei den Insekten. Abh. Senckenb.

naturf. Gesell., bd. 10, pp. 27-55, 4 taf. Separate, 1875, 31 pp., 4

taf. Frankfurt a. 'SI.
Miiller, F. 1877. Ueber PTaarpinsel, Filzflecke und ahnliche Gebilde auf

den Fliigeln mannlicher Schmetterlinge. Jenais Zeits. Naturw.,

bd. II, pp. 99-1 14.
Scudder, S. H. 1877. Antigeny or Sexual Dimorphism in Butterilies.

Prnc. Amer. Acad. Arts Sc. vol. 12. pp. 150-158.
Edwards, W. H. 1878. On the Larvje of Lye. pseudargiolus and atten-
dant -Ants. Can. Ent.. vol. 10, pp. 131-136, fig. 8.
Forel, A. 1878. Der Giftapparat und die Analdriisen der Amcisen.

Zeits. wiss. Zool.. bd. 30, su]ii).. pp. 28-68, taf. 3, 4.
Miiller, F. 1878. Die Duftschuppen der Schmetterlinge. Ent. Nachr.,

jhg. 4, pp. 29-32.
Saunders, E. 1878. Remarks on the Flairs of some of our British lly-

menoptcra. Trans. Ent. Soc. London, pp. 169-172, pi. 6.

42 2 ENTOMOLOGY

Schneider, R. 1878. Die Schuppen aus den verschiedenen Fliigel- und
Korperteileii der Lepidopteren. Zeits. gesammt. Naturw., bd. 51,

pp. 1-59-
Weismann, A. 1878. Ucber Duftschuppen. Zool. Anz., jhg. i, pp. 98, 99.
Goossens, T. 1881. Des chenilles urticantes. etc. Ann. Soc. ent. France.

t. I, 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. Verb. zool. -hot. Gesell. Wien, bd. 32,

PP- 459-474. 2 taf.
Dimmock, G. 1883. The Scales of Coleoptera. Ps3xhe, vol. 4, pp. i-ii,

2^-27, 4^-47- 63-71. figs. i-ii.
Osten-Sacken, C. R. 1884. An Essay on Comparative Chietotaxy. or the

Arrangement of characteristic Bristles of Diptera. Trans. Ent.

Soc. London, pp. 497-517.
Simmermacher, G. 1884. Untersuchungen fiber Haftapparate an Tarsal-

gliedern von Lisckten. Zeits. wiss. Zool., bd. 40, pp. 481-556, taf.

25-27, 2 figs.
Dahl, F. 1885. Die Fussdriisen der Lisekten. Archiv mikr. Anat., bd.

25, pp. 236-263, taf. 12, 13.
Witlaczil, E. 1885. Die Anatomic 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 Lisektenhaut. Archiv mikr. Anat.,

bd. 28, pp. 37-48, taf. 7.
Schaffer, C. 1889. Beitriige zur Histologic der Lisekten. Zool. Jahrb.,

AbtJT. Anat. Ont., bd. 3, pp. 611-652, taf. 29, 30.
Fernald, H. T. 1890. Rectal Glands in Coleoptera. Amer. Nat., vol. 24,

pp. 100, loi, pis. 4, 5.
Packard, A. S. 1890. Notes on some points in the external structure and

phylogeny of Icpidopterous larvae. Proc. Bost. Soc. Nat. Hist.,

vol. 25, pp. 82-114, pis. I, 2.
Borgert, H. 1891. Die Hautdriisen der Tracheaten. 81 pp., taf. Jena.
Thomas, M. B. 1893. The Androconia of Lepidoptcra. Amer. Nat., vol.

2y, pp. 101S-1021. pis. 22, 23.
Cuenot, L. 1894. Le rejet de sang comme moyen de defense chez quel-

ques Coleopteres. Compt. rend. Acad. Sc, t. 118, pp. 875-877.
Kellogg, V. L. 1894. The Taxonomic Value of the Scales of the Lepidop-
tcra. 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.

LITERATURE 423

Lutz, K. G. 1895. Das Bluten der Coccinelliden. Zool. Aiiz.. jhg. 18,

pp. -'44-255, I fig-.
Packard, A. S. 1895-96. The Eversible Repugnatorial Scent Glands of

Insects. Journ. N. Y. Ent. Soc, vol. 3, pp. 1 10-127, pi. 5; vol. 4,

pp. 26-32.*
Spuler, A. 1895. Beitrag zur Kenntniss des feineren Banes nnd der Phy-

logenie der Fliigelbedecknng der Schmetterlinge. Zool. Jahrb.,

Abth. Anat. Ont., 1x1. 8, pp. 520-543, taf. 36.
Mayer, A. G. 1896. The Development of the Wing Scales and their Pig-
ment in Bntterflies and Moths. Bnll. ^Ins. Comp. Zool., vol. 29.

pp. 209-236, pis. 1-7.*
Bordas, L. 1897. Description anatomiqne et etude histologique des

glandes a venin des Insectes hymenopteres. 53 pp., 2 pis. Paris.
Cuenot, L. 1897. Snr la saignee reflexe et les moyens de defense de

(|uelques 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 Formation of the Exuvial Fluid in Insects. Zool. Anz.,

bd. 2^, 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 (iber einige Elemente der

Haut bei den Insekten. Zeits. wiss. Zool., bd. 76, pp. 333-366,

taf. 21, 22, 2 figs.

MUSCULAR SYSTEM
Lyonet, P. 1762. Traite anatomiqne de la Chenille, qui rouge le Bois de

Saule. Ed. 2. 22 -f 616 pp., 18 pis. La Haye.
Straus-Diirckheim, H. 1828. Considerations generales sur I'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. 3^9-439-
Lubbock, J. 1859. On the Arrangement of the Cutaneous ^Muscles of the

Larva of Pygaera bucephala. Trans. Linn. Soc. Zool., vol. 22, pp.

163-191, 2 pis.
Basch, S. 1865. Skelett und ]\Iuskcln des Kopfes von Termes. Zeits.

wiss. Zool, bd. 15, pp. 55-75. I 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.,

b(i. 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. 121-142, pis. 189-192.
Lubbock, J. 1879. On the Anatomy of Ants. Trans. Linn. Soc. Zool.,

,ser. 2, vol. 2, pp. 1 41-154, 2 pis.

424 ENTOMOLOGY

Poletajeff, N. 1879. Du developpcment des muscles d'ailes chez les Odo-
nates. Hor^e Soc. Ent. Ross., t. 16, pp. 10-37, 5 pls.

Von Lendenfeld, R. 1881. Der Plug der Libellen. Ein Beitrag z.ur Anat-
omic und Physiologic der Plugorgane der Insecten. Sitzb. Akad.
Wiss. Wien, bd. 83. pp. 289-376, taf. 1-7.

Luks, C. 1883. Ueber die Brustmuskulatur der Insecten. Jenais. Zeits.
Natiirw., bd. 16, pp. 529-552, taf. 22. 23.

Dahl, F. 1884. Beitrage zur Kenntnis des Bancs nnd der Pnnktionen der
Inscktenbeine. Archiv Natnrg., jhg. 50, bd. i, pp. 146-193, taf.
11-13.

Van Gehuchten, A. 1886. fitudc sur la strncturc intime de la cellnlc mns-
cnlaire striec. La Cellule, t. 2, pp. 289-453, pls. 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.

Biitschli, 0., und Schewiakoff, W. 1891. L^ebcr den feineren Ban der
ciuergestreiftcn Muskeln von Arthropoden. Biol. Centralb., bd.
II, pp. 33-39, figs. 1-7.

Rollet, A. 1891. Ueber die Streifen N (Nebenschciben), das Sarko-
l)lasma und Contraktion der quergestreiften Muskelfasern. Ar-
chiv nnkr. Anat., bd. t,/. pp. 654-684, taf. 37.

Janet, C. 1895. Ltudes sur Ics Pourmis, les Guepes et les Abcillcs.
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 Pourmis, des Guepes et des Abeilles.
Compt. rend. Acad. Sc, t. 121, pp. 610-613, i fig.

NERVOUS SYSTEM

Newport, G. 1832, 1834. On the Nervous System of the Sphin.x 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 anatomiqucs et zoologiques sur le sys-
temc nerveux des animaux sans vertebres. Du systeme ncrveux
des insectes. Ann. Sc. nat. ZooL, ser. 3, t. 5, pp. 273-379, 8 pis.

Leydig, F. 1857. Lehrbuch der Histologic des Mcnschcn und der Thiere.
12 -|- 551 pp., figs. Prankfurt.

Leydig, F. 1864. Vom Bau des Tierischen Korpers. Tiibingcn.

Brandt, E. 1876. Recherches anatomiqucs et morphologiques sur le sys-
teme 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.

LITERATURE 425

Flogel, J. H. L. 1878. Ueber den einheitlichen Ban des Gehirns in den

verschiedenen Insecten-Ordnimgen. Zeits. wiss. Zool.. bd. 30,

Snppl.. pp. 556-592, taf. 23, 24.
Brandt, E. 1879. [Many articles on the nervons system.] Hone Soc.

Ent. Ross., bd. 14-15, taf.*
Newton, E. T. 1879. On the Brain of tlie Cockroach, Blatta orientalis.

Quart. Journ. Micr. Soc, n. s., vol. 19, pp. 340-356, pis. 15, 16.
Michels, H. 1880. Beschreibnng des Nervensystems von Oryctes nasicor-

nis ini Larven-, Pnppen- 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.

Comni., pp. 22^-242, pis. 9-15. fig. 9. Washington.*
Cattie, J. T. 1881. Beitnige zur Kenntnis der Chorda supra-spinalis der

Lepidoptera und des centralen, peripherischen und sympathischen

Nervensystems der Raupcn. 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. fitudes histologiques et organologiques snr les

centres nerveux et les organes des sens des animanx 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. Neue Beitrage zur Histologic des

Tierkorpers. 219 pp., 6 taf. Bonn.
Viallanes, H. 1887. Snr la morphologic comparee du cerveau des Insectcs

et des Crustaces. Compt. rend. Acad. Sc. t. 104, pp. 444-447.
Binet, A. 1894. Contribution a I'etu'dc du system nerveux sous-intestinal

des insectes. Journ. Anat. Phys., t. 30, pp. 449-580, pis. 12-15,

23 fis-^.

Pawlovi, M. I. 1895. On the Structure of the Blood-Vesscls and Sympa-
thetic Nervous 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 Arthro-
podcn. Anat. Anz., bd. 12, pp. 449-457, 7 figs.

Kenyon, F. C. 1896. The Brain of the Bee. Journ. Comp. Neurol, vol.
6. pp. 133-210, pis. 14-22.

Kenyon, F. C. 1896. The meaning and structure of the so-called " mu>h-
room bodies" of the hcxapod brain. Amer. Nat., vol. 30, pp. 643-
650, I 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.

SENSE ORGANS; SOUNDS

Miiller, J. 1826. Zur vergleichenden Physiologic des Gesichtsinncs der
Menschen imd der Tiere. 462 pp., 8 taf. Leipzig.

4^6 ENTOMOLOGY

Von Siebold, C. T. E. 1844. Ueber das Stimm- und Gehor-Organ der

(Jrthopteren. Arcliiv Naturg. jhg. 10, pp. 52-81, fig.
Gottsche, C. M. 1852. Beitrag zur Anatomie und Physiologic des Auges

(ler Krebse und Fliegen. Miiller's Archiv Anat. Phys., pp. 483-

492.
Claparede, E. 1859. Zur Morphologie der zusammengesetzten Augen bei

den Arthropoden. 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, I taf.
Landois, H. 1868. Das Gehororgan des Hirschkafers. Arcliiv mikr.

Anat., 1x1. 4, pp. 88-95.
Schultze, M. 1868. Untersuchungen iiber 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. 113-120, 5 figs.
Scudder, S. H. 1868. Notes on the Stridulation of Grasshoppers. Proc.

Bost. Soc. Nat. Hist., vol. 11, pp. 306-313.
Graber, V. 1872. Bemerkungen fiber die Gelir>r- und Stinimorgane der

Heuschrecken und Cicaden. Sitzb. Akad. Wiss. Wien, math.-

naturw. CI., bd. 66, pp. 205-213, 2 figs.
Paasch, A. 1873. Von den Simiesorganen der Insekten im Allgemeinen,

von Gelior- und Geruchsorganen im Besondern. Archiv Naturg..

jhg. 39, bd. I, pp. 248-275.
Forel, A. 1874. Les fourmis de la Suisse. Neue Denks. allg. Schweiz.

Gesell. Xaturw., bd. 26, 480 pp., 2 taf. Separate, 1874, 4 + 457

pp., 2 t;if. Geneve.
Mayer, A. M. 1874. Experiments on the supposed Auditory x\pparatus

of the Mosquito. Amer. Nat., vol. 8, pp. 577-592, fig. 92.
Ranke, J. 1875. Beitriige zu der Lehre von den Uebergangs-Sinnesor-

ganen. Das Gehororgan der Acridier und das Sehorgan der

Hirudineen. Zeits. wiss. Zool, bd. 25, pp. 143-164. taf. 10.
Schmidt, 0. 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 figs.
Forel, A. 1878. Beitrag zur Kenntniss der Sinnesempfindungen der In-
sekten. Alitth. Munch, ent. Vereins, jhg. 2, pp. 1-21.
Lowne, B. T. 1878. On the Modifications of the Simple and Compound

Eyes i)f Insects. Phil. Trans. Roy. Soc. London, vol. 169, pp.

S77-(:)02, pis. 5--54-
Graber, V. 1879. Ueber neue, otocystenartige Sinnesorgane der Insekten.

Archiv mikr. Anat.. bd. 16, pp. 35-37. 2 taf.

LITERATURE 42/

Grenadier, H. 1879. Untersuchungen iiber das Sehorgan der Arthro-

poden, insbesondere der Spinnen, Insekten und Crustaceen. 8 -|-

188 pp., II taf. Gottingen.
Hauser, G. 1880. Physiologische und histiologische Untersuchungen iiber

das Geruchsorgan der Insekten. Zeits. wiss. Zool, bd. 34, pp.

367-403, taf. 17-19.
Graber, V. 1882. Die chordotonalen Sinnesorgane imd das Gehor der

Insecten. Arcliiv mikr. Anat., bd. 20, pp. 506-640, taf. 30-35, 6

iigs. ; bd. 21, pp. 65-145. 4 figs.*
Lubbock, J. 1882. Ants, Bees and Wasps. 19 -f- 448 pp., 5 pis., 31 figs.

London. 1884, 1901, New York. D. Appleton & Co.
Graber, V. 1883. Fundamentalversuche fiber die Helligkeits- und Far-

benempfindlichkeit 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 Far-

bensinnes der Tiere. 8 -|- t,22 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 Vision 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., i 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 Arthro-

podes 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. 1-91.
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. i.
Graber, V. 1887. Neue Vcrsuche iiber die Funktion der Insektenfiihler.

Biol. Centralb., bd. 7, pp. 13-19.
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. iNIorph..

vol. I, pp. 67-92, pi. 3.
Will, F. 1887. A. Forel. Sur les Sensations des Insectes. Ent. Xachr.,

jhg. 13, pp. 227-233

428 ENTOMOLOGY

Patten, W. 1887, 1888. Studies on the Eyes of Arthropods. I. Develop-
ment of the Eyes of Vcspa, with Observations on the Ocelli of
some Insects. Journ. Morph., vol. i, pp. 193-226, i pi. II. Eyes
of Acilius. Journ. ]\Iorph., 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. 29-1-292 pp., 118
i'lgs. New York. D. Appleton & Co.

Vom Rath, 0. 1888. Uelicr die Ilatitsinnesorgane der Insekten. Zeits.
wiss. Zool., bd. 46, pp. 413-454, taf. 30, 31.

Ruland, F. 1888. Beitriige zur Kenntnis der antennalen Sinnesorgane der
Insekten. Zeits. wiss. Zool., bd. 46, pp. 602-628, taf. 'i'j.

Lowne, B. T. 1889. On the Structure of the Retina of the Blowfly ( Cal-
liphora erythrocephala). 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 ^landibulate Insects. Psyche, vol. 5, pp. 193-
199, 222-228.

Pankrath, 0. 1890. Das Auge der Raupen und Phryganidenlarven.
Zeits. wiss. Zool., bd. 49, pp. 690-708, taf. 34, 35.

Stefanowska, M. 1890. La disposition histologiciue du pigment dans les
yeux des Arthropodes sous I'influence de la lumiere directe et de
I'obscurite complete. Rec. zool. Suisse, t. 5, pp. 151-200, pis. 8, 9.

Watase, S. 1890. On the ^Morphology of the Compound Eyes of Arthro-
pods. Studies Biol. Lali. Johns Hopk. Univ., vol. 4, pp. 287-334,
pis. 29-35.

Weinland, E. 1890. Uel)er die Schwinger (Halteren) der Dipteren.
Zeits. wiss. Zool., bd. 51, pp. 55-166, taf. 7-1 1.

Exner, S. 1891. Die Physiologic der fazettierten Augen von Krebsen
und Insekten. tS -|- 206 pp., 8 taf., 22, figs. Leipzig und Wien.

Von Adelung, N. 1892. Beitriige zur Kenntnis des tibialen Gehorapparates
der Locustidcn. Zeits. wiss. Zool., bd. 54, pp. 316-349, taf. 14, 15.

Nagel, W. 1892. Die niederen Sinne der Insekten. 68 pp., 19 figs.
Tiiljingen.

Child, C. M. 1894. Ein bisher wenig beachtetes antennales Sinnesorgan
der Insekten, mit besonderer Berucksichtigung 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, 0. 1896. Zur Kenntnis der Ilautsinnesorgane und des sen-
siblen Nervensystems der Arthropoden. Zeits. wiss. Zool., bd. 61,
pp. 499-539, taf. 23, 24.

Redikorzew, W. 1900. Untersuchungen fiber den Ban der Ocellen der
Insekten. Zeits. wiss. Zool, bd. 68, pp. 581-624, taf. 39, 40, figs.

1-7-
Renter, E. 1896. L'eber die Palpen der Rhopaloceren, etc. Acta Soc. Sc.
Eenn., t. 22, pp. 16 + 578. 6 tab.

LITERATURE 429

Hesse, R. 1901. Untersucliungen iiber die Organc dcr Lichtcmpfindung
bei niederen Thicren. VII. Von den Arthropoden-Augen. Zcits.
wiss. ZooL, bd. 70, pp. 347-473, taf. 16-21, figs, i, 2.

Schenk, 0. 1903. Die antennalen Hautsinnesorganc einiger Lepidopteren
and Hymenopteren mit besonderer Beriicksiclitigung dcr sexuellen
Unterschiede. Zool. Jabrb., Abtli. Anat. Ont., bd. 17, pp. 573-618.
taf. 21, 22, 4 figs.*

DIGESTIVE SYSTEAI

Dufour, L. 1824-60. [I\Iany important papers.] Am. Sc. nat. Zool.
Basch, S. 1858. Untersucbungen iiber das cbylopoetiscbe nnd uropoetiscbe

System der Blatta orientabs. Sitzb. Ai<ad. Wiss. Wien, matb.-

natnrw. CL, bd. t,t,. pp. 234-260, 5 taf.
Sirodot, S. 1858. Recbercbcs sur les secretions cbez les Insectes. Ann.

Sc. nat. ZooL, ser. 4. t. 10, i)p. 141-189. 251-334, 12 pis.
Leydig, F. 1859. Zur Anatomic dcr Insectcn. Miiller's Arcbiv Anat.

Pbys., pp. 33-89, 149-183, 3 taf.
Fabre, J. L. 1862. fitude sur le role du tissu adipeu.x dans la secretion

urinaire chez les Insectes. Ann. Sc. nat. Zool., ser. 4, t. 19, pp.

351-382.
Plateau, F. 1874. Recbercbcs sur les pbenomenes de la digestion cbez

les Insectes. Mem. Acad. roy. Belgique, t. 41, 124 pp., 3 pis.
De Bellesme, J. 1876. Pbysiologie comparee. Recbercbcs experimentales

sur la digestion 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. Note additionelle an Memoire sur les pbenomenes de

la digestion cbez les Insectes. Bull. Acad. roy. Belgique, ser. 2,

t. 44, pp. 710-733-
Wilde, K. F. 1877. Untersucbungen iiber den Kaumagen dcr Ortbop-

leren. Arcbiv Naturg., jbg. 43, bd. i, pp. 135-172. 3 taf.
De Bellesme, J. 1878. Travaux originaux de Pbysiologie comparee. I.

Insectes. Digestion, Metamorpboses. 252 pp., 5 pis. Paris.
Schindler, E. 1878. Beitriige zur Kenntniss der JMalpigbi'schcn Gefiisse

der Insectcn. Zeits. wiss. Zool., bd. 30, pp. 587-660, taf. 38-40.
Krukenberg, C. F. W. 1880. Versucbe zur vergleichenden Physiologic

der Verdauung and vergleicbende physiologiscbe Beitriige zur

Kenntnis der Verdauungsvorgan.ge. Unters. pbys. Inst. Univ.

Heidelberg.
Frenzel, J. 1882. Ueber Ban und Thatigkeit des Verdauungskanals der

Larve des Tenebrio molitor mit Beriicksichtigung anderer Artbro-

pndcn. Berl. cut. Zcits., bd. 26, pp. 267-316. taf. 5.*
Leydig, F. 1883. Untersucbungen zur Anatomic und Histologic der

Tbiere. 174 pp., 8 taf. Bonn.

430 ENTOMOLOGY

Metschnikoff, E. 1883. Untersuchungen iiber die intrazellulare Verdaii-

ung bei wirbellosen Tieren. Arb. zool. Inst. Wien, bd. 5, pp. 141-

168. 2 taf.
Schiemenz, P. 1883. Ueber das Herkommen des Futtersaftes iind die

Speicheldriisen der Biene nebst einem Anbange iiber das Riech-

organ. Zeits. wiss. Zool., bd. 38, pp. 71-135, taf. 5-7.
Locy, W. A. 1884. Anatomy and Physiology of the family Nepidae.

Amer. Nat., vol. 18, pp. 250-255, 353-367, pis. 9-12.
Witlaczil, E. 1885. Zur Morphologie nnd Anatomie der Cocciden. Zeits.

wiss. Zool, bd. 43, pp. 149-174, taf. 5.
Frenzel, J. 1886. Einigcs fiber den Mitteldarm der Insekten, sowie fiber

Epithelregeneration. Archiv mikr. Aiiat., bd. 26, pp. 229-306, taf.

7-9-
Kniippel, A. 1886. Ueber Speicheldriisen von Insecten. Archiv Naturg.,

jhg. 52, bd. I, pp. 269-303, taf. 13, 14.
Cholodkovsky, N. 1887. Sur la morphologic de I'appareil nrinaire des

Lepidopteres. Archiv. Biol., t. 6, pp. 497-514, pi. 17.
Faussek, V. 1887. Beitrage znr Histologic des Darmkanals der Insekten.

Zeits. wiss. Zool., bd. 45, pp. 694-712, taf. 36.
Kowalevsky, A. 1887. Beitrage znr Kenntnis der nachembr\-onalen Ent-

wicklnng der Mnsciden. 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. 18S8. The Poison Apparatus of the Mosquito. Amer.

Nat., vol. 22, pp. 8S4-888, 2 figs.
Blanc, L. 1889. fitude sur la secretion de la soie et sur la structure du

brin et de la have 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 I'appareil digestif

de la larve de la Ptychoptera contaminata, I Part. £tude 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. L Lepidopteres; II. Trichopteres.

La Cellule, t. 6, pp. 115-182, pis. 1-3; t. 10, pp. 37-63, pi. 4.
Blanc, L. 1891. La tete du Bombyx niori a I'etat larvaire, anatomie et

physiologic. Trav. Lab. £tud. Soie, 1889-1890, 180 pp., 95 figs.

Lyon.
Wheeler, W. M. 1893. The primitive number of Malpighian vessels in

Insects. Psyche, vol. 6, pp. 457-460, 485-486, 497-498, 509-510,

539-541, 545-547. 561-564.

LITERATURE 43 I

Bordas, L. 1895. Apparcil glandulaire dcs Hxinenoptercs. (Glandes

salivaires, tube digestif, tubes de ]\Ialpighi ct glandes venimeuses.)

362 pp.. II pis. Paris.
Cuenot, L. 1895. fitudes physiolo.giques sur les Orthopteres. Arch.

r.iol.. 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. Rull., vol. I, pp. 103-113, figs. 1-10.

CIRCULATORY SYSTEM

Newport, G. 1839. Insecta. Todd's Cyclopaedia Anat. Phys., vol. 2, pp.

853-994. figs- 3-'9-4.r>
Newport, G. 1845. On the Structure and Development of the Blood.

Ann. Mag. Nat. Hist., vol. 15, pp. 281-284.
Verloren, M. C. 1847. [Memoire sur la circulation dans les insectes.]

?\Iem. 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 pls.
Leydig, F. 1851. Anatomisches und Histologisches iiber die Larve von

Corethra plumicornis. Zeits. wiss. Zool., bd. 3, pp. 435-451, taf.

16.
Scheiber, S. H. i860. Vcrgleichende Anatomic und Physiologic der

G-!striden-Larven. Sitzb. Akad. Wiss. Wien, math.-naturw. CI.,

bd. 41, pp. 409-496, 2 taf.
Landois, H. 1864. Beobachtungen iiber das Blut der Insektcn. Zeits.

wiss. Zool., bd. 14, pp, 55-70, 3 taf.
Graber, V. 1871. Ueber die Blutkorperchen der Insekten. Sitzb. Akad.

Wiss. Wien, math.-naturw. CL, 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. Journ. Micr. Sc, vol. 11 (n. s.), pp. 389-395,

I 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. CL, bd. 64 (1871), pp. 9-44.
Graber, V. 1876. Ueber den pulsierenden Bauchsinus der Insekten. Ar-
chiv mikr. Anat., bd. 12, pp. 575-582, i taf.
Dogiel, J. 1877. Anatomic und Physiologic des Herzens der Larve von

Corethra plumicornis. Mem. Acad. St. Petersbourg, ser. 7, t. 24,

Z7 pp., 2 pis. Separate, Leipzig. Voss,
Jaworovski, A. 1879. Ueber die Entwicklung des Riickengefasses und

speziell der Muskulatur bei Chironomus und einigen andcren In-
sekten. Sitzb. Akad. Wiss. Wien, math.-naturw. CI., bd. 80, pp.

238-258.

432 ENTOMOLOGY

Plateau, F. 1879. Communication preliminaire snr les mouvements et

I'innervation de Torgane central de la circulation chez les animanx

articnles. Bull. Acad. roy. Belgiqne, ser. 2. t. 46, pp. 203-212.
Zimmermann, 0. 1880. Ueber cine eigentluimliche Rildung des Riicken-

gefasses bei einigen Ephemeridenlarven. Zeits. wiss. Zool, bd. 34,

pp. 404-406, figs. 1-4.
Burgess, E. 1881. Note on the aorta in lepidopterous insects. Proc.

Bost. Soc. Nat. Hist., vol. 21, pp. 153-156. figs. 1-5.
Vayssiere, A. 1882. Rechcrches snr I'organisation des larves des Ephe-

merines. Ann. Sc. nat. Zool.. ser. 6. t. 13, pp. 1-137. pls. i-ii.
Viallanes, H. 1882. Rechcrches snr I'histologie des Insectes. et sur les

phenomenes histologiciues qui accompagnent le developpement

post-embryonnaire de ces aniniaux. Ann. Sc. nat. Zool., ser. 6. t.

14. pp. 1-34S. 4 pis. Bibl. ficole. bd. 26. 348 pp., 18 pis.
Creutzburg, N. 1885. Ueber den Kreislauf der Ephemerenlarven. Zool.

Anz.. jhg. 8, pp. 246-248.
Poletajewa, 0. 1886. Du c<enr des insectes. Zool. Anz.. jhg. 9, pp. 13-15.
Von Wielowiejski, H. R. 1886. Ueber das Blutgewebe der Insekten.

Zeits. wiss. Zool.. l>d. 43. pp. 512-536.
Dewitz, H. 1889. Eigenthatige Schwimmbewegnng der Blutkorperchen

der Gliederthiere. Zool. Anz.. jhg. 12. pp. 457-464. i fig.
Kowalevsky, A. i88g. Ein Beitrag zur Kenntins der Excretionsorgane.

Biol. Central!)., bd. 9, pp. 33-47, 65-7r), 127-128.
Schaffer, C. 1889. BeitrJige zur Histologic der Insekten. II. Ueber

Blutljildungsherde bei Insektcnlarven. Zool. Jahrb.. Abth. Anat.

Out., bd. 3. pp. 626-636. taf. 30.
Lankester, E. R. 1893. Note on the Cadom and Vascular System of

Mollusca and Arthropoda. Quart. Journ. ]\Iicr. Sc. vol. 34 (n.

s.), pp. 4-7-4.^-2.
Pawlowa, M. 1895. Ueber ampullenartige Blutcirculationsorgane im

Kopfe verschiedener Orthopteren. Zool. Anz.. jhg. 18. pp. 7-13,

I fig.

FAT BODY

Dufour, L. 1826. Rechcrches anatomiques sur les Carabiques et sur plu-

sienrs autres Insectes Coleopteres. Du tissu adipeux splanch-

nique. Ann. Sc. nat. Zool., t. 8, pp. 29-35.
Meyer, H. 1848. Ueber die Entwicklnng des Fettkorpers. der Tracheen

und der keimbereitenden Geschlechtstheile bei den Lepidopteren.

Zeits. wiss. Zool, bd. i. pp. 175-197, 4 taf.
Fabre, J. H. 1863. fitude sur le role du tissu adipeux dans la secretion

urinaire chez les Insectes. Ann. Sc. nat. Zool., ser. 4, t. 19, pp.

Landois, L. 1865. Ueber die Eunktion des Eettkorpers. Zeits. wiss.
Zool, bd. 15, pp. 371-372.

LITERATURE 433

Schultze, M. 1865. Zur Kenntniss der Leuchtorgane von Lampyris

splendidula. Archiv niikr. Anat., bd. i, pp. 124-137, taf. 5, 6.
Gadeau de Kerville, H. 1881, 1887. Les insectes phosphorescents. T. i,

55 pp.. 4 pis. ; t. 2, 135 pp. Rouen.*
Von Wielowiejski, H. R. 1882. Studien iiber Lampyriden. Zcits. wiss.

Zool., bd. T,7, pp. 354-428, taf. 23, 24.
Von Wielowiejski, H. 1883. Ueber den Fetlkorper von Coretbra plumi-

cornis und seine Entwicklung. Zool. Anz., jbg. 6, pp. 318-322.
Emery, C. 1884. Untersucbungen iiber Luciola italica L. Zeits. wiss.

Zool., bd. 40. pp. 338-355. taf. 19.
Emery, C. 1885. La luce della Luciola italica osservata con microscopic.

Bull. Soc. Ent. Ital., anno 17, pp. 351-355, tav. 5.
Dubois, R. 1886. Contribution a I'etude de la production de la lumiere

par les etres vivants. Les Elaterides lumineux. Bull. Soc. zool.

P^rance, ann. 11, pp. 1-275, pls. 1-9.
Heinemann, C. 1886. Zur Anatomie und Pbysiologie der Leucbtorgane

niexikaniscber Cucuyo's. Archiv mikr. Anat., bd. 2~, pp. 296-382.
Von Wielowiejski, H. R. 1886. Ueber das Blutgewebe der Insekten.

Zcits. wiss. Zool., bd. 43. pp. 512-536.
Schaffer, C. 1889. Beitrjige zur Histologie der Insekten. H. Ueber

Blutbildungsherde bei Lisektenlarven. Zool. Jahrb., Abth. Anat.

Out., bd. 3, pp. 626-636, taf. 30.
Von Wielowiejski, H. R. 1889. Beitrage zur Kenntnis der Leucbtorgane

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, 2i2)-^T,6, 253-258, pi. 7.
Cuenot, L. 1895. fitudes physiologiques sur les Orthopteres. Arch. Biol.,

t. 14, pp. 293-341, pis. 12, 13.
Schmidt, P. 1895. On the Luminosity of Midges (Chironomidas). Ann.

Mag. Nat. Hist., ser. 6, vol. 15, pp. 133-141. Trans, from Zool.

Jahrb., Abth. Syst., etc., bd. 8, pp. 58-66, 1894.

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 Si.isswasser-
schwammen lel)enden Larve. (Si.syra.) .A.rchiv Naturg., jhg. 9,
pp. 25^-327, figs.

Newport, G. 1844. On the existence of Branchi;e in the perfect State of
a Neuropterous Insect, Pteronarcys regalis Newm. and other spe-
cies of the same genus. Ann. Mag. Nat. Llist., vol. 13, pp. 21-25.
29

434 ENTOMOLOGY

Plainer, E. A. 1844. Alittheilungen iiber die Respirationsorgane und die
Haut der Seidenraupen. Midler's 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. "/(^Z-JT^- 1850. Trans.
Ann. Mag. Nat. Hist., ser. 2. vol. 6, pp. 112-118.

Newport, G. 1851. On the Formation and tlie Use of the Airsacs and
dihited Trachct'e in Insects. Trans. Linn. Soc. ZooL, vol. 20. pp.
4 1 9-4-33 •

Newport, G. 1851. On the Anatomy and Affinities of Pteronarcys regalis
Nevvm., etc. Trans. Linn. Soc. ZooL, vol. 20, pp. 425-453, i pi.

Dufour, L. 1852. fitudes anatomiqnes et physiologiqnes et observations
sur les larves des Libellnles. 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. ( Uelier 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 Alcchanism of Aquatic Respiration and on
the Structure of the Organs of Breathing in Invertebrate Ani-
mals. Trans. Ann. Mag. Nat. Hist., ser. 2. vols. 12-19, i/ pls.

Barlow, W. F. 1855. Observations of the Respiratory Movements of In-
sects. 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. Kon-
igsberg, jhg. i, pp. 99-138. taf. i.

Scheiber, S. H. 1862. Vergleichende Anatomic und Physiologic der
Qistriden-Larven. Respirationssystem. Sitzb. Akad. Wiss. Wien,
math.-naturw. CL, bd. 45. pp. 7-68. 3 taf.

Reinhard, H. 1865. Zur Entwicklungsgeschichte des Tracheensystems der
Hymenopteren mit besonderer Beziehung auf dessen morpholo-
gische Bedeutung. Berl. ent. Zeits., jhg. 9, pp. 187-218, taf. i, 2.

Landois, H., und Thelen, W. 1867. Der Tracheenverschluss bei den In-
sekten. Zeits. wiss. ZooL, bd. 17, pp. 187-214, i taf.

Oustalet, E. 1869. Note sur la respiration chez les nymphes des Libel-
lnles. Ann. Sc. nat. ZooL, ser. 5, t. 11, pp. 370-3S6, 3 pis.

Pouchet, G. 1872. Developpement du systeme tracheen de I'Anophele
( Corethra plumicornis). Archiv. ZooL exper., t. i, pp. 217-232,
I fig.

Gerstacker, A. 1874. L^eber das Vorkommen von Tracheenkiemen bei
ausgebildeten Insecten. Zeits. wiss. ZooL, bd. 24. pp. 204-252, i
taf.

Packard, A. S. 1874. On the Distribution and Primitive Number of
Spiracles in Insects. Amer. Nat., vol. 8. pp. 531-534.

LITERATURE 435

Palmen, J. A. 1877. Zur ^Morphologic des Trachecnsystems. io-|-i49
pp.. 2 taf. Helsingfors.

Sharp, D. 1877. Observations on the Respiratory Action of the Carnivo-
rous Water Beetles (Dyliscid?e). Journ. Linn. Soc. Zool., vol. 13,
pp. 161-183.

Haller, G. 1878. Kleinere Bruchstiicke zur vergleichenden Anatomic der
Arthropoden. I. Ueber das Atmungsorgan der Stechmiickcn-
larven. Archiv Naturg.. jhg. 44, bd. i, pp. gi-ioi, taf. 2.

Hagen, H. A. 1880. Beitrag zur Kcnntnis des Tracheensystems der Libel-
len-Larven. Zool. Anz., jhg. 3, pp. 157-161.

Hagen, H. A. 1880. Kicmenubcrreste bei einer Libelle ; glattc Muskel-
fasern bei Insecten. Zool. Anz., jhg. 3, pp. 304-305.

Poletajew, 0. 1880. Quelques mots sur les organes respiratoires des lar-
ves des Odonates. Horse Soc. Ent. Ross., t. 15, pp. 436-452, 2 pis.

Viallanes, H. 1880. Sur I'apparcil respiratoire ct circulatoirc de quelques
larvcs de Dipteres. Compt. rend. Acad. Sc, t. 90. pp. 1180-1182.

Krancher, 0. 1881. Der Bau der Stigmen bei den Insekten. Zcits. wiss.
Zool.. l)d. 35, pp. 505-574. taf. 28, 29.

Vayssiere, A. 1882. Recherches sur I'organisation des larves des Ephe-
merincs. Ann. Sc. nat. Zool., ser. 6, t. 13, pp. 1-137, pis. i-ii.

Macloskie, G. 1883. Pneumatic Functions of Insects. Psyche, vol. 3, pp.
375-378.

Macloskie, G. 1884. The Structure of the Trachese of Insects. Amer.
Nat., vol. 18. pp. 567-573. figs. 1-4-

Plateau, F. 1884. Recherches e.xperimentales sur les mouvements res-
piratoires des Inscctes. Alem. 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 Trachcje. 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 Cule.x nemorosus. Archiv Naturg.,
jhg. 53, bd. I, pp. 133-163, taf. 5. 6.

Schmidt-Schwedt, E. 1887. Ueber Athmung der Larvcn und Puppen
von Donacia crassipes. Berlin, ent. Zcits., bd. 31, pp. 325-334,
taf. 5b.

Vogler, C. 1887. Die Tracheenkiemen der Simulicn-Puppcn. Alitt.
schweiz. ent. Gesell., bd. 7, pp. 277-282.

Dewitz, H. 1888. Entnehmen die Larvcn der Donacicn vcrniittclst Stig-
men oder Athemrohren den Luftraumen der Pflanzen die sauer-
stoffhaltige Luft? Berl. ent. Zcits., bd. ^2, pp. 5-6, figs, i, 2.

Haase, E. 1889. Die Abdominalanhange der Insekten mit Bcriicksichti-
gung der Myriopoden. 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.
Zcits. wiss. Mikr., bd. 7, i)p. 332-342, taf. 2, figs. 1-3.

43^ . ENTOMOLOGY

Dewitz, H. 1890. Einige Beobachtungen, betreffend das gescblossene
Tracheensystem bei Insectenlarven. Zool. Anz., jhg. 13, pp. 500-
504, 525-531-

Von Wistinghausen, C. 1890. Ueber Tracheenendigungen in den Sericte-
rien dcr Raiipen. Zeits. wiss. Zool.. bd. 49, pp. 565-582. taf. 27.*

Miall, L. C. 1891. Some Difficulties in the Life of Aquatic Insects. Na-
ture, v(.il. 44, pp. 457-462.

Stokes, A. C. 1893. The Structure of Insect Tracheae, with Special Ref-
erence 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 -j-
395 PP- lit) figs. London and New York. jMacmillan & Co.

Sadones, J. 1895. L'appareil digestif et respiratoire larvaire des Odo-
nates. 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.

REPRODUCTIVE SYSTEM

Dufour, L. 1824-60. []\Iany 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 Crustacean. In-

secten. Gasteropoden und einiger andern wirbellosen Thiere.

IMiiller's Archiv Anat. Phys.. pp. 15-52. 2 taf.
Von Siebold, C. T. E. 1836. Fernerer Beobachtungen fiber die Spermato-
zoen der wirbellosen Thiere. Midler's Archiv Anat. Phys., p.

232. 1837, pp. 381-432, taf. I.
Doyere, L. 1837. Observations anatomiques sur les Organes de la genera-
tion 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 Naturg., jhg. 4. pp. 191-201.
Loew, H. 1841. Beitrag zur anatoniischen Kenntniss der inneren Ge-

schlechtstheile der zweifliigligen Insecten. Germar's Zeits. Ent.,

bd. 3. pp. 38f>-4o6, i taf.
Von Siebold, C. T. E. 1843. Ueber das Receptaculum seminis der Hy-

menopteren Weibchen. Germar's Zeits. Ent.. bd. 4. pp. 362-388,

I taf.
Stein, F. 1847. Vergleichende Anatomie und Physiologic der Insecten.

I. Monographic. Ueber die Geschlechts-Organe und den Bau des

Hinterleibes bei den weiblichen Kafern. 84-139 pp., 9 taf.

Berlin.

LITERATURE 437

Brauer, F. 1855. Beitriige ziir Kenntniss ties inneren Banes und der

Verwandlung der Neuroptercn. Verb, zool.-bot. Ver. Wien, bd.

5, pp. 700-726, 5 taf.
Kolliker, A. 1856. Pbysiologiscbe Studien iiber die Samenfliissigkeit.

Zeits. wiss. ZooL, bd. 7, pp. 201-272, i taf.
Huxley, T. H. 1858-59. On tbe Agamic Reprodnction and AbTrpliology

of Aphis. Trans. Linn. Soc. Zool., vol. 22, pp. 193-236. 5 i)ls.
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. LTeber die Verbindnng der Hoden mit dem Riickenge-

fass bei den Insekten. Zeits. wiss. ZooL, bd. 13, pp. 316-318, i

taf.
Claus, C. 1864. Beobachtungen iiber die Bildnng des Insekteneies. Zeits.

wiss. Zool., bd. 14, pp. 42-54, I taf.
Pagenstecher, H. A. 1864. Die ungeschlechtliche Vermehrung der Flie-

genlarven. Zeits. wiss. Zool., bd. 14, pp. 400-416, 2 taf.
Wagner, N. 1865. Ueber die viviparen Gallmiickenlarven. Zeits. wiss.

Zool., bd. 15. pp. 106-IT7.
Bessels, C. 1867. Stndien iiber die Entwicklnng der Sexnaldriisen 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. t,;!,. 88 pp., 5 taf.
Biitschli, 0. 1871. Nahere Mittheilungen iiber die Entwicklnng und den

Bau der Samenfiiden der Insecten. Zeits. wiss. Zool, bd. 21, pp.

526-534, taf. 40, 41.
Nusbaum, J. 1882. Zur Entwickelungsgeschichte der Ausfiihrungsgiinge

der Sexnaldriisen bei den Insecten. Zool. Anz., jlig. 5, pp. 637-

643-
Palmen, J. A. 1883. Zur vergleichenden Anatomic der Ausfuhrungsgange

der Sexualorgane bei den Insekten. Vorlaufige iMiltheilung.

INIorpb. Jahrb., bd. 9. pp. 169-176.
Will, L. 1883. Zur Bildung des Eies und des Blastoderms bei den vivi-
paren Aphiden. Arbeit, zool.-zoot. Inst. Univ. Wurzburg, bd. 6,

pp. 217-258, taf. 16.
Palmen, J. A. 1884. Lleber paarige Ausfuhrungsgange der Geschlechts-

organe bei Insecten. Ein morijhologische Untersuchung. 108 pp.,

5 taf. Helsingfors.
Gilson, G. 1885. fitude comparee de la spermatogenese chez Ics Arthro-

podes. La Cellule, t. i, pp. 7-188, pis. \-S/''
Schneider, A. 1885. Die luitwickhmg der Gcschlechtsorgane der Insecten.

Zool. Beitr. von A. Schneider, bd. i, pp. 257-300, 4 taf. Breslau.
Spichardt, C. 1886. Beitrag zur Entwickelung der mannlicbcn Genitalien

und ihrer Ausfiihrgange bei Lepidopteren. Verb, n.iturb. Ver

Bonn, jhg. 43, pp. 1-34, taf. i.
La Valette St. George. 1886, 1887. Spermatologische Beitnige. Arch.

mikr. Anat., bd. 2~. pp. 1-12, taf. i, 2; bd. 28, pp. 1-13, taf. 1-4;

bd. 30, pp. 4-'6-434. taf. 25.

438 ENTOMOLOGY

Von Wielowiejski, H. R. 1886. Zur ]\Iorphologie des Insectenovariums.
Zool. Anz., jhg. g, pp. 132-139.

Korschelt, E. 1887. Ueber einige interessante Vorgiinge bei der Bildung
der Insekteneier. Zeits. wiss. Zool., bd. 45, pp. 327-397, taf. 18, 19.

Nassonow, N. 1887. Tlie Morphology of Insects of Primitive Organiza-
tion. Studies Lab. Zool. Mus. Moscow, pp. 15-86, 2 pis., 68 figs.
( In Russian.)

Oudemans, J. T. 1888. Beitriige zur Kenntniss der Th\-sanura und Col-
lembola. Bijdr. Dierk., pp. 147-226, taf. 1-3. Amsterdam.

Bertkau, P. 1889. Beschreibung eines Zwitters von Gastropacha quercus,
nebst allgcmeinen Bemerkungen und einem Verzeichniss der
beschriebenen Arlhropodenzvvitter. Archiv Naturg., jhg. 55, bd. i,
pp. 75-116, figs. 1-3.*

Leydig, F. 1889. Beitrage zur Kenntniss des thierischen Eies im unbe-
fruchteten Zustande. Zool. Jahrb., Abth. Anat. Ont., bd. 3, pp.
287-432, taf. 11-17.

Lowne, B. T. 1889. On the Structure and Development of the Ovaries
and their Appendages in the Blowfly ( Calliphora erythrocephala).
Journ. Linn. Soc.Zool., vol. 20, pp. 418-442, pi. 28.*

Ballowitz, E. 1890. Untersuchungen iiber die Struktur der Spermato-
zoen, zugleich ein Beitrag zur Lehre vom feineren Bau der kon-
traktilen Elemente. Die Spermatozoen der Insekten. (I. Cole-
opteren.) Zeits. %\'iss. Zool, bd. 50, pp. 317-407, taf. 12-15.

Henking, H. 1890-92. Untersuchungen fiber die ersten Entwicklungsvor-
gange 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 Dar-
mes bei Chironomus. Zeits. wiss. Zool, bd. 50, pp. 408-427, taf.
16.

Heymons, R. 1891. Die Entwicklung der weiblichen Geschlechtsorgane
von Phyllodromia (Blatta) germanica L. Zeits. wiss. Zool., bd.
53, pp. 434-536. taf. 18-20.

Koschewnikoff, G. 1891. Zur Anatomic der manidichen Geschlechtsorgane
der Honigbiene. Zool. Anz., jhg. 14. pp. 393-396.

Ingenitzky, J. 1893. Zur Kcnntnis der Begattungsorgane der Libellu-
lidcn. Zool. Anz., jhg. 16, pp. 405-407, 2 figs.

Escherich, K. 1894. Anatomische Studien fiber das mannliche Genital-
system der Coleopteren. 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. LTniv. 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 ger-
manica. Archiv Naturg., jhg. 61, bd. i, pp. 159-198, taf. 10.

Peytoureau, A. 1895. Contributions a I'elude de la morphologic de Tar-
mure genitale des Insectes. 248 pp., 22 pis., 43 figs. Paris.

LITERATURE 439

Wilcox, E. V. 1895. Spermatogenesis of Caloptenus femur-rul)rum and
Cicada tibicen. Bull. Mus. Comp. Zool, vol. 27, pp. 1-32, pis.

Wilcox, E. V. 1896. I'urlluT Studies on the Spermatogenesis of Calop-
tenus femur-rul)rum. Bull. JMus. Comp. Zool., vol. 29, pp. 193-
202, pis. 1-3.

Fenard, A. 1897. Recherches sur les organes complementaires internes
de I'appareil genital des Orthopteres. Bull. sc. France Belgique,
t. 29, pp. 390-533. pis. 24-28.

Gross, J. 1903. Untersuchungen fiber die Histologie des Insectenovari-
ums. Zool. Jahrb., Abth. Anat. Ont., bd. 18, pp. 71-186, taf. 6-14.*

Griinberg, K. 1903. Untersuchungen fiber die Keim- und Nahrzellen in
den Hoden und Ovarien der Lepidoptera. Zeits. wiss. Zool., bd.
74, pp. 3-27-395. taf. 16-18.

Holmgren, N. 1903. Ueber vivipare Insecten. Zool. Jahrb., bd. 19, pp.
431-468, 10 figs.*

EMBRYOLOGY

Rathke, H. 1844. Ueber die Eier von Gryllotalpa und ihre Entwickelung.

Mfiller's Archiv Anat. Phys., bd. 2, pp. 27-37, figs. 1-5.
Meyer, G. H. 1848. Ueber Entwicklung des Fettkorpers, der Tracheen

und der keimbereitenden Geschlechtstheile bei den Lepidopteren.

Zeits. wiss. Zool., bd. i, pp. 175-197, 4 taf.
Leuckart, R. 1858. Die Fortptfanzung und Entwicklung der Pupiparen

nach Beobachtungen an Melophagus ovinus. Abh. naturf. Gesell.

Halle, bd. 4, pp. 145-226, 3 taf.
Weismann, A. 1863. Die Entwicklung der Dipteren im Ei, nach Beobacht-
ungen an Chironomus spec, Alusca 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. Beitriige zur Entwicklungsgeschichte der Libelluliden

und Hemipteren. Mem. Acad. St. Petersbourg, ser. 7, t. 13, pp.

1-33, 3 pis.
Melnikow, N. 1869. Beitriige zur Embryonalentwicklung der Insekten.

Archiv Naturg., jhg. 35, bd. i, pp. 136-189, 4 taf.
Biitschli, 0. 1870. Zur Entwicklungsgeschichte der Biene. Zeits. wiss.

Zool., bd. 20, pp. 519-564, taf. 24-27.
Kowalevsky, A. 1871. Embryologische Studien an W'urmern und Ar-

thropoden. Mem. Acad. St. Petersbourg, ser. 7, t. 16, pp. 1-70,

12 pis.
Dohrn, A. 1875. Notizen zur Kenntniss der Insectenentwicklung. Zeits.

wis>. Zool, bd. 26, pp. 1 12-138.
Hatschek, B. 1877. Beitriige zur Entwicklungsgeschichte der Lepidop-
teren. Jenais. Zeits. Naturw., 1x1. n, 38 pp., 3 taf., 2 tigs.

440 ENTOMOLOGY

Bobretzky, N. 1878. Ueber die Bildung des Blastoderms und der Keim-

lil;itter bei den Insecten. Zeits. wiss. ZooL, bd. 31, pp. 195-215,

tat, 14.
Korotneff, A. 1883. Entwicklung des Herzens bei Gryllotalpa. Zool.

Anz., jbg. 6, pp. 687-690. tigs. I, 2.
Packard, A. S. 1883. The Embryological Development of the Locust.

Third Rept. U. S. Ent. Comm., pp. 263-285. pis. 16-21, ligs. lo-ii.

Washington.
Will, L. 1883. Zur Bildung des Eies und des Blastoderms bei den vivi-

paren Aphiden. Arbeit, zool.-zoot. Inst. Univ. Wiirzburg, bd. 6,

pp. 217-258, taf. 16.
Ayers, H. 1884. On the Development of Qicanthus niveus and its Para-
site Teleas. Mem. Bost. Soc. Nat. Hist., vol. 3, pp. 225-2S1, pis.

18-25, figs. 1-41.*
Patten, W. 1884. The Development of Phryganids, with a Preliminary

Note on the Development of Blatta germanica. Quart. Journ.

Alicr. 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. i, pp. 257-300, 4

taf. Breslau.
Blochmann, F. 1887. Ueber die Richtungskorper bei Insecteneiern.

Morph. Jahrb., bd. 12. pp. 544-574. taf. 26, 2~ .
Biitschli, 0. 1888. Bemerkungen fiber die Entwicklungsgeschichte von

IMusca. }il(n-ph. 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. I. 2.
Graber, V. 1888. Ueber die Polypodic bei Insekten-Embryonen. Morph.

Jahrb.. bd. 13, pp. 586-615, taf. 25, 26.
Graber, V. 1888. Ueber die primiire Scgmentirung des Keimstreifs der

Insckten. Morph. Jahrb., bd. [4. 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. 2^-

26, 3 figs.
Will, L. 1888. Entwicklungsgcsch.ichte der viviparen Aphiden. Zool.

Jahrb., Abth. Anat. Ont., bd. 3. pp. 201-286. taf. 6-10.
Cholodkovsky, N. i88g. Studicn zur Entwicklungsgeschichte der Insek-

ten. Zeits. wiss. Zool.. bd. 48. pp. 89-100, taf. 8.
Graber, V. 1889. Ueber den Bau und die phylogenetische Bedeutung der

embryonalen Bauchanhange der Insekten. Biol. Centralb., jhg. g,

PP- 355-363-
Heider, K. 1889. Die Embryonalentwickhmg von Hydrophilus piceus L.

I. Theil. 98 pp., 13 taf., 9 figs. Jena.

LITERATURE 44.1

Leydig, F. 1889. Beitrage zur Kenntniss des thierisclien Eics ini iinlie-

fruchteten Znstaiule. Zool. JaliH)., Abtli. Anat. Ont., bd. 3, pp.

287-432, taf. 11-17.
Nusbaum, J. 1889. Zur r>age der Segmentierung des Keimstreifcnis iind

der Bauchanhiinge der Insektenembryonen. Biol. Centralb., jbg.

9, pp. 516-522, fig. I.
Voeltzkow, A. 1889. Entwickclung im Ei \-on JMusca vomitoria. Arbeit.

zool.-zoot. Inst. Univ. Wiirzburg, bd. 9, pp. 1-48, taf. 1-4.
Voeltzkow, A. 1889. Alelohjntlia vulgaris. Ein Beitrag zur Entwickclung

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 Dory-

phora decemlineata. Journ. Morph., vol. 3, pp. 291-386, pis. 15-

21, figs. 1-16.
Carriere, J. 1890. Die Entwicklung der Mauerbiene (Chalicodoma mur-

aria Eabr.) im Ei. Archiv mikr. Anat., bd. 35, pp. 141-165. taf.

8. 8a.
Henking, H. 1890-92. Untersuchungen fiber die ersten Entwicklungsvor-

gange in der Eiern der Insekten. Zeits. wiss. Zool., bd. 49, pp.

503-564, taf. 24-26; bd. 51, pp. 685-736, taf. 35-37". 'jd. 54, pp.

1-274, taf. 1-12, figs. 1-12.
Nusbaum, J. 1890. Zur Frage der Ruckenbildung bei den Insektenem-
bryonen. Biol. Centralb., jbg. 10, pp. 110-114.
Ritter, R. 1890. Die Entwicklung der Geschlechtsorgane und des Dar-

mes bei Chironomus. Zeits. wiss. Zool, bd. 50, pp. 408-427, taf.

16.
Wheeler, W. M. 1890. On the Appendages of the Eirst Abdominal Seg-
ment of Embryo Insects. Trans. Wis. Acad. Sc, vol. 8, pp. 87-

140, pis. 1-3.*
Cholodkowsky, N. 1891. Die Embryonalentwicklung von Phyllodromia

(Blatta germanica). ^lem. 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., jbg. 11, pp. 212-224.
Wheeler, W. M. 1891. Neuroblasts in the Arthropod Embryo. Journ.

Morph., vol. 4. pp. 337-343, I fig.
Graber, V. 1892. Ueber die morphologische Bedeutung der vcntralcn

.Vbdnminalanhj'inge der Insekten-Embryonen. Morph. Jahrb., bd.

17, pp. 467-482, figs. 1-6.
Korschelt, E., und Heider, K. 1892. Lehrbuch der verglcichcnden Ent-

wicklungsgeschichte der wirbellosen Thiere. Heft 2, pp. 761-890,

figs. Jena.* Trans. : 1899. M. Bernard and JM. E. Woodward.

Text-Book of the Embryology of Invertebrates. 12 + 441 pp., 198

figs. London, Swan Sonnenschein & Co., Ltd. ; New York, The

JMacmillan Co.*
Wheeler, W. M. 1893. .\ Contribution to Insect Embryology. Journ.

]\Iorph., vol. 8, pp. 1-160, pis. 1-6, figs. 1-7.

442 ENTOMOLOGY

Heymons, R. 1895. Die Embrj'onalentwickelung von Dermapteren und

Orthopteren unter besonderer Beriicksichtigung der Keimblatter-

iMldung. 84-136 pp., 12 taf., 33 figs. Jena.
Heymons, R. 1896. Grundziige der Entwickelung und des Korperbaues

von Odonaten und Ephemeriden. Anb. Abh. Akad. Wiss. Ber-
lin, 66 pp., 2 taf.
Heymons, R. 1897. Entwicklungsgeschiehtlicbe Untersucbungen an Le-

pisma saccbarina L. Zeits. wiss. ZooL, bd. 62. pp. 583-631, taf.

29, 30, 3 figs.
Kulagin, N. 1897. Beitriige zur Kenntnis der Entwicklungsgeschichte

von Platygaster. Zeits. wiss. ZooL. bd. 63, pp. 195-235, taf. 10, 11.
Claypole, A. M. 1898. Tlie Embr\-ology and Oogenesis of Anurida mari-

tima (Guer.). Journ. IMorpb., vol 14, pp. 219-300, pis. 20-25, 11

figs.
Uzel, H. 1898. Studien iiber die Entwicklung der apterygoten Insecten.

6 + 58 pp., 6 taf., 5 figs. Berlin.
Wilson, E. B. 1900. Tbe Cell in Development and Inheritance. 21 -|-

483 pp., 194 figs. New York and London. Tbe Macmillan Co.

POSTEMBRYONIC DEVELOPMENT. jMETAAIORPHOSIS
Fabre, J. L. 1856. Etude sur I'instinct et les metamorphoses des Sphe-

giens. Ann. So. nat. Zool., ser. 4, t. 6. pp. 137-189.
Fabre, J. L. 1857. Memoire sur rbypermetamorphose et les nioeurs des

Meloides. Ann. Sc. nat. ZooL, ser. 4, t. 7, pp. 299-365 ; i pi. ; 1858.

t. 9, pp. 265-276.
Mijller, F. 1864. Fur Darwin. Leipzig. Translation: Facts and Fig-
ures in aid of Darwin. London, 1869.
Weismann, A. 1864. Die nachembryonale Entwicklung der Musciden

nacb Beobacbtungen an Mnsca vomitoria und Sarcophaga car-

naria. 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. Tbe American Silk Worm. Amer. Nat., vol. i, pp.

30-38, 85-94, 145-149. 4 figs., pis. 5- 6.
Brauer, F. 1869. Betrachtungen iiber die Verwandlung der Insekten im

Sinne der Descendenz-Theorie. Verb, zool.-bot. Gesell. Wien, bd.

ig, pp. 299-318; bd. 28 (1878), 1879, pp. 151-166.
Ganin, M. 1869. Beitriige zur Kenntniss der Entwickelungsgescbichte

bei den Insecten. Zeits. wiss. ZooL, bd. 19, pp. 381-451, 3 taf.
Chapman, T. A. 1870. On tbe Parasitism of Rhipipborus paradoxus.

Ann. >.Iag. Nat. Hist., ser. 4, vol. 5, pp. 191-198.
Chapman, T. A. 1870. Some Facts towards a Life History of Rhipi-
pborus paradoxus. Ann. Mag. Nat. Hist., ser. 4, vol. 6, pp. 314-

326, pi. 16.
Landois, H. 1871. Beitriige zur Entwicklungsgeschichte der Schmetter-

lingsfliigel in der Raupe und Puppe. Zeits. wiss. ZooL. bd. 21, pp.

305-316, taf 23.

LITERATURE 443

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 4- 108 pp., 6 pis., 63 figs. London. Macmillan & Co.
Ganin, M. 1876. I^^Iaterials for a Knowledge of the Postemhryonal De-
velopment of Insects. Warsaw.] (In Russian.) Ahstracts :

Amer. Nat., vol. 11, 1877, pp. 423-430; Zeits. wiss. ZooL, hd. 28,

1877, pp. 386-389.
Riley, C. V. 1877. On the Larval Characters and Ilahits of the Blister-
beetles belonging to the Genera Macrobasis Lee. and Epicauta

Fabr. ; with Remarks on other Species of the Famih' Meloid^e.

Trans. St. Louis Acad. Sc. vol. 3, pp. 544-562, figs. 35-39, pi. 5-
Dewitz, H. 1878. BeitrJige znr Kenntniss der postembryonalen Glied-

massenbildung bci 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.
Dewitz, H. 1881. Ueber die Fliigelbildung bei Phryganiden und Lepi-

dopteren. Berl. ent. Zeits., bd. 25, pp. 53-60, taf. 3. 4.
Metschnikoff, E. 1883. Untersuchungen (iber die intracellnlare Verdau-

ung bei wirbellosen Thieren. Arb. zool. Inst. Wien, bd. 5, pp.

141-168, taf. 13, 14.
Viallanes, H. 1883. Recherches sur Thistologie des Insectes et sur les

phenomenes histologiqnes 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, 0. 1885. Metamorphose und Anatomic des mannlichen Aspidi-

otus neVii. Archiv Naturg.. jhg. 51, bd. i. pp. 169-200, taf. 9, 10.
Witlaczil, E. 1885. Zur Morphologic und Anatomic der Cocciden. Zeits.

wiss. Zool., bd. 43, pp. 149-174, taf. 5.
Kowalevsky, A. 1887. Beitrage zur Kenntniss der nachembryonalen Ent-
wicklung der Musciden. Zeits. wiss. Zool, bd. 45, pp. 542-594,

taf. 26-30.
Van Rees, J. 1888. Beitrage ztu- Kenntnis der inneren Metamorphose

von Musca vomitoria. Zool. Jahrh., .Mith. Anat. Ont., l)d. 3, pp.

1-134, taf. I, 2, 14 figs.
Hyatt, A., and Arms, J. M. 1890. Insccta. 23 + 300 pp., 13 pis., 223 figs.

Boston. D. C. Heath & Co.*
Bugnion, E. 1891. Recherches sur le developpement post-embryonnaire,

I'anatomie, et les mocurs de I'Encyrtus fuscicollis. Rec. zool.

Suisse, t. 5. pp. 435-534. pis. 20-25.

444 ENTOMOLOGY

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. 245-26,^. pis. 26, 27.
Korschelt, E., und Heider, K. 1892. Lehrbuch der vergleichenden Ent-

\vicl<lungsgeschichte der wirbellosen Thiere. Heft 2, pp. 761-890,

iigs. Jena.*
Miall, L. C, and Hammond, A. R. 1892. The Development of the Head

of Chironomns. Trans. Linn. Soc. Zool, ser. 2, vol. 5, pp. 265-

279, pis. 28-31.
Pratt, H. S. 1893. Beitrage znr Kenntnis der Pupiparen. Archiv Na-

tnrg., jhg. 59, bd. i, pp. 151-200, taf. 6.
Gonin, J. 1894. Recherches sur la metamorphose des Lepidopteres. De

la formation des appendices imaginau.x dans la chenille dn Pieris

brassicac. Bull. Soc. vaud. Sc. nat.. t. 30, pp. 1-52, 5 pis.
Miall, L. C. 1895. The Transformations of Lisects. Nature, 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 Entwickhmgsgeschichte

von Platygaster. Zeits. wiss. Zool.. bd. 63, pp. 195-235, taf. 10, 11.
Packard, A. S. 1897. Notes on the Transformations of Higher Hymen-

optcra. Jonrn. N. Y. Ent. Soc. vol. 4, pp. 155-166, hgs. 1-5; vol.

5. PP- //-S/. 109-120, figs. 6-13.
Pratt, H. S. 1897. Lnaginal Discs in Insects. Psyche, vol. 8. pp. 15-30,

T T figs.

Packard, A. S. 1898. A Text-Book of Entomology. 17 -f 7-^9 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.
Wahl, B. 1901. Ueber die Entwickhmg der hypodermalen Imaginalschei-

ben ini Thorax imd Abdomen der Larve von Eristalis Latr. Zeits.

wiss. Zool., bd. 70, pp. 171-191, taf. 9, figs. 1-4.
Perez, C. 1902. Contribution a I'etude des metamorphoses. Bull. sc.

France Belg., t. t,~, pp. 195-427, pis. 10-12, 32 figs.
Deegener, P. 1904. Die Entwickhmg des Darmcanals der Lisecten

wahrcnd der Aknamorphose. Zool. Jahrb., Abth. Anat. Ont., bd.

20, pp. 499-676, taf. 3,1-43-"
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.=^

LITERATURE 445

AQUATIC INSECTS

Dufour, L. 1849. Des divers modes de respiration aqiiatiqne 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. fitudes 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 friiberen 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 I^Iechanism of Aquatic Respiration and on
the Structure of the Organs of Breathing in Invertebrate Ani-
mals. Ann. Mag. Nat. Hist., ser. 2. vols. 12-19, ^7 pls.

Oustalet, E. 1869. Note sur la respiration chez les n\mphes des Libel-
lules. Ann. Sc. nat. Zool., ser. 5, t. 11, pp. 370-3S6, 3 pis.

Sharp, D. 1877. Observations on the Respiratory Action of the Carniv-
orous Water Beetles (Dytiscidse). Journ. Linn. Soc. Zool, vol.
13. pp. 161-183.

Poletajew, 0. 1880. Quelques mots sur les organes respiratoires des lar-
ves des Odonates. Horae Soc. Ent. Ross., t. 15, pp. 436-452, 2 pis.

Vayssiere, A. 1882. Recherches sur I'organisation des larves des Ephe-
merines. Ann. Sc. nat. Zool., ser. 6, t. 13, pp. 1-137, pis. i-ii.

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.
Voy. H. ^I. 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. 577-578-

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 aqua-
lique. Ann. Sc. nat. Zool., ser. 7, t. 6, pp. 1-164, pis. 1-6.

Dewitz, H. 1888. Entnehmen die Larven der Donacien vermittelst Stig-
men oder Athemrohren den Luftraumen der Pflanzen die sauer-
stofifhaltige Luft? Berl. ent. Zeits., bd. 32, pp. 5-6, 2 figs.

Garman, H, 1889. A Preliminary Report on the Animals of the Missis-
sippi 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 Difificulties in the Life of Aquatic Insects. Na-
ture, vol. 44. pp. 457-462.

Walker, J. J. 1893. On the Genus Halobates, Esch., and other Marine
Hemiptera. Ent. 'Slon. I\Iag., ser. 2, vol. 4 (29), pp. 227-232.

Carpenter, G. H. 1895. Pelagic Hemiptera. Nat. Sc, vol. 7, pp. 60-61.

44^ ENTOMOLOGY

Hart, C. A. 1895. On the Entomology of the IlHnois River and Adjacent
Waters. Bnll. 111. St. Lab. Nat. Hist., vol. 4, pp. 149-373, pis.

I-I5-
Miall, L. C. 1895, 1903. The Natural History of Aquatic Insects. ii-|-

395 PP-- 116 figs. London and New York. Macmillan & Co.*
Sadones, J. 1895. L'appareil digestif et respiratoire larvaire des Odo-

nates. 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, tigs. 1-3.
Comstock, J. H. 1897, 1901. Insect Life. 6 -|- 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. i, pp. 1-8, i fig.
Needham, J. G., and Betten, C. 1901. Aquatic Insects in the Adirondacks.

Bull. N. Y. St. ]\Ius., no. 47, pp. 383-612. 36 pis., 42 figs.
Needham, J. G., MacGillivray, A. D., Johannsen, 0. 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. LTeber die Einwirkung verschiedener, wahrend
den Entwicklungsperioden angewendeter Warmegrade auf die
Farbung und Zeichnung der. Schmetterlinge. ]\Iitth. naturw. Ver.
Steiermark, pp. 99-T08, i taf.

Landois, H. 1864. Beobachtungen fiber 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, i pi.

Weismann, A. 1875. Studien zur Descendenztheorie. I. LTeber den
Saison Dimorphisnius der Schmetterlinge. Leipzig. Trans. :
1880-81. R. ^Icldola. 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 Teniperatur bei der Erzeu-
gung der Schmetterlingsvarietaten. Mitth. naturw. Ver. Steier-
mark, jhg. 1879, pp. 3-8, I taf.

Scudder, S. H. 1881. Butterflies; their Structure, Changes and Life-
Histories, with Special Reference to American Eornis. 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, II figs.*

LITERATURE 447

Krukenberg, C. F. W. 1884. [Colors and Pigments of Insects. 1 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 hymenopterous larva. Trans. Ent.
Soc. London, pp. 27-60, pi. i.

Poulton, E. B. 1885. The Essential Nature of the Colouring of Phytopha-
gous Larva; and their Pupse, etc. Proc. Roy. Soc. London, vol.
38, pp. 269-315.

Poulton, E. B. 1885. Further Notes upon the Markings and Attitudes of
Lepidopterous Larvse. 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 Pupte and the Surfaces
which immediately surround them. Phil. Trans. Roy. Soc. Lon-
don, 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-AIark-
ings in certain Genera of the Nymphalidje. Trans. Ent. Soc. Lon-
don, pp. 89-129, pis. 1-3.

Merrifield, F. 1890. Systematic temperature experiments on some Lepi-
doptera 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., i pi., 66
figs. New York. D. Appleton & Co.

Seitz, A. 1890, 1893. Allgemeine Biologic 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 Lnsect Colors.
Entomologist, vol. 2^,, 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. i8gi. Conspicuous effects on the markings and colouring
of Lepidoptera caused by exposure of the pupas to different tem-
perature conditions. Trans. Ent. Soc. London, pp. 155-168, pi. 9.

Urech, F. 1891. Beobachtungen iiber die verschiedenen Schuppenfarben
und die zeitliche Succession ihres Auftretens (Farbenfelderung)
auf den Puppenfliigelchen von Vanessa urticae und lo. Zool.
Anz., jhg. 14, pp. 466-473.

Beddard, F. E. 1892. Animal Coloration. 8 -j- 288 pp., 4 pis., 36 figs.
London, Swan Sonncnschcin & Co. New York, Macmillan & Co.

Gould, L. J. 1892. Experiments in 1890 and 1891 on tlie colour-relation
between certain lepidopterous larvae ruid their surroundings, to-
gether with some other observations on lepidopterous larvae.
Trans. Ent. Soc. London, pp. 215-246, pi. 11.

Merrifield, F. 1892. The effects of artificial temperature on the colouring
of several species of Lepidoptera, with an accoinit of some experi-
ments on the efifects of light. Trans, luit. Soc. London, pp. 33-44.

448 ENTOMOLOGY

Poulton, E. B. 1892. Further experiments upon the colour-relation be-
tween certain lepidopterous larvae, pupae, cocoons and imagines
and their surroundings. Trans. Ent. Soc. London, pp. 293-487,
pis. 14, 15.

Urech, F. 1892. Beobachtungen uber die zeitliche Succession der Auf-
tretens der Farbenfelder auf den Puppenfliigelchen von Pieris
brassicas. Zool. Anz., jhg. 15, pp. 284-290, 293-299.

Urech, F. 1892. Ueber Eigenschaften der Schuppenpigmente einiger
Lcpidopteren-Species. Zool. Anz., jhg. 15, pp. 299-306.

Weismann, A. 1892, 1898. The Germ-Plasm. Trans, by W. N. Parker
and H. Ronnfeldt. See pp. 399-409, on climatic variation in
butterflies.

Dixey, F. A. 1893. On the phylogenetic significance of the variations
produced by difference 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 Lisektenschuppen.
Zeits. wiss. Zool, bd. S7- PP- 306-384.

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- Varia-
tion as bearing on Theories of Heredity. Trans. Ent. Soc. Lon-
don, pp. 439-446.

Hopkins, F. G. 1894. The Pigments of the Pieridae. Proc. Roy. Soc.
London, vol. ^J, pp. 5-6.

Kellogg, V. L. 1894. The Taxonomic Value of the Scales of the Lepidop-
tera. Kansas LTniv. Quart., vol. 3, pp. 45-89. 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 Phy-
logenie der Flugelbedeckung der Schmetterlinge. Zool. Jahrb.,
Abth. Anat. Out., 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.

LITERATURE 449

Mayer, A. G. 1896. The Development of the Wing Scales and their Pig-
ment 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 iiber 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. Beitriige zur e.Kpcrimentellen Lepidopterologie.
Illustr, Zeits. Ent., 1x1. 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.
i-io'. Also Bull. Mus. Comp. Zool., vol. 30, pp. 169-256, pis. i-io.

Von Linden, Grafin M. 1898. Untersuchungen fiber die Entwicklung der
Zeichnung des Schmetterlingsfliigels 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, Gral^n M. 1899. Untersuchungen iiber die Entwickelung der
Zeichnung der Schmetterlingsfliigels in der Puppe. Illustr. Zeits.
Ent., bd. 4, pp. 19-22.

Urech, F. 1899. Einige Bemerkungen zum zeitlichen Auftreten der
Schuppen-Pigmentstofife von Pieris brassicse. 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 I'ontogenese et la phylogenese
des especes, son origine et sa valeur systematique. Ann. So. nat.
Zool., ser. 8, t. 14, pp. 1-196, pis. 1-20.

Weismann, A. 1902. Vortriige iiber Descendenztheorie. 2 vols. 12 -j-
450 pp., 95 figs.; 6-I-462 pp., 3 pis., 36 figs. Jena. G. Fischer.
See p[). 65-102.

Von Linden, Grafin M. 1903. Jilorphologische und physiologisch-chemische
Untersuchungen fiber die Pigmente der Lepidopteren. i. Die
gelben und roten Farbstoffe der Vanessen. Archiv ges. Phys., bd.
98, pp. 1-89, I taf., 3 figs.

Poulton, E. B. 1903. Experiments in 1893, 1894 and 1896 upon the col-
our-relation between lepidopterous larvK 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.

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.

450 ENTOMOLOGY

Vernon, H. M. 1903. Variation in Animals and Plants. 9 + 415 PP-

New York. Henry Holt & Co.
Enteman, W. M. 1904. Coloration in Polistes. Pnbl. Carnegie Inst.

Washington, no. 19, 88 pp., 6 pis., 26 figs.*
Von Linden, Grafin M. 1905. Physiologische Untersuchimgen an Schmet-

terlingen. Zeits. wiss. Zool., bd. 82, pp. 411-444, taf. 25.*

ADAPTIVE COLORATION

Bates, H. W. 1862. Contributions to an Insect Fauna of the Amazon

Valley. Lepidoptera : Heliconidse. 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 Afri-
can 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.
Miiller, F. 1879. Ituna and Thyridia; a remarkable case of Mimicry in

Butterflies. Trans., R. Meldola, Proc. Ent. Soc. London, pp. 20-

29, figs. 1-4.
Blackiston, T., and Alexander, T. 1884. Protection by Mimicry — A

Problem in Mathematical 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 hymenopterous larva. Trans. Ent.

Soc. London, pp. 27-60, pi. i.
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, T,y figs. London and

New York. Macmillan & Co.
Poulton, E. B. 1890. The Colours of Animals. 13 + 360 pp., i pi., 66

figs. New York. D. Appleton & Co.
Beddard, F. E. 1892. Animal Coloration. 8 + 288 pp., 4 pis., 36 figs.

London, Swan Sonnenschein & Co. New York, Macmillan & Co.
Haase, E. 1893. Untersuchungen iiber die Mimicry auf Grundlage eines

natiirlichen Systems der Papilioniden. Bibl. Zool, Heft 8, Theil

I, 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.

LITERATURE 45 1

Piepers, M. C. i8g6. ^limetisme. Cong. Intern. Zool., 3 Sess., Leyden,
pp. 460-476.

Dixey, F. A. 1897. Mimetic Attraction. Trans. Ent. Soc. London, pp.
317-331. pl- 7-

Mayer, A. G. 1897. On the Color and Color-Patterns of Moths and
Butterflies. Proc. Best. Soc. Nat. Hist., vol. 27, pp. 243-330, pis.
i-io. Also Bull. Mus. Comp. Zool., vol. 30, pp. 169-256, pis. i-ic*

Trimen, R. 1897. ]\Iimicr\- in Insects. Proc. Ent. Soc. London, pp. 74-
97.*

Webster, F. M. 1897. Warning Colors. Protective Mimicry and Protec-
tive Coloration. 27th. Ann. Rcpt. Ent. Soc. Ontario (1896), pp.
80-86, figs. 80-82.

Newbigin, M. I. 1898. Colour in Nature. 12 4-3-14 PP- London. John
Murray.*

Poulton, E. B. 1898. Natural Selection the Cause of Mimetic Resem-
l)lance and Common Warning Colors. Journ. Linn. Soc. Zool.,
vol. 26, pp. 558-612, pis. 40-44, figs. 1-7.

Judd, S. D. 1899. The Efificiency of Some Protective Adaptations in
Securing Insects from Birds. Amer. Nat., vol. ,1,2, pp. 461-484.

Marshall, G. A. K., and Poulton, E. B. 1902. Five Years' Observations
and Experiments (1896-1901) on the Bionomics of South African
Insects, chiefly directed to the Investigation of Mimicry and
W^arning Colours. Trans. Ent. Soc. London, pp. 287-584, pis.
9-33-

Shelford, R. 1902. Observations on some ]\Iimetic Insects and Spiders
from Borneo and Singapore. Proc. Zool. Soc. London, 1902, vol.
2, pp. 230-284. pis. 19-23.

Weismann, A. 1902. Vortnige fiber Descendenztheorie. 2 vols. 12 -j-
456 pp., 95 figs. ; 6 "1- 462 pp., 3 pis., 36 figs. Jena. G. Eischer.
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 larvre 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. i(>-t8.

Packard, A. S. 1904. The Origin of the Markings of Organisms (Poecilo-
genesis) due to the Physical rather than to the Biological Envi-
ronment; with Criticisms of the Batcs-Miiller Hypothesis. Proc.
Amer. Phil. Soc, vol. 43, pp. 393-450.*

ORIGIN OF ADAPTATIONS AND OF SPECIES

Darwin, C. 1859, 1869. The Origin of Species by means of Natural
Selection. 11 -[-440 pp. London. New York. D. Appleton &
Co.

452 ENTOMOLOGY

Spencer, H. 1866-67. The Principles of Biology. 2 vols. 16 -j- 1041 pp.,

306 figs. New York. D. Appleton & Co.
Wallace, A. R. 1870. Contributions to the Theory of Natural Selection.

16 + 384 pp. London and New York. Alacmillan & Co.
Weismann, A. 1880-81. Studies in the Theory of Descent. Trans, by

R. jNIeldola. 554 pp., 8 pis. London.
Cope, E. D. 1887. The Origin of the Fittest. 194-467 pp., 18 pis., 81

figs. New York. D. Appleton & Co.
Henslow, G. 1888. The Origin of Floral Structures through Lisect and

other Agencies, ig -j- 349 pp., 88 figs. New York. D. Appleton

& Co.
Wallace, A. R. 1889. Darwinism. 16-)- 494 pp.. 37 figs. London and

New York. ^Nlacmillan & Co.
Eimer, G. H. T. 1890. Organic Evolution as the Result of the Liheritance

of Acquired Characters according to the Laws of Organic Growth.

Trans, by J. T. Cunningham. 28 -j- 435 pp. London and New

York. Macmillan & Co.
Weismann, A. 1891, 1892. Essays upon Heredity and Kindred Biological

Problems. . Ed. by E. B. Poulton, S. Schonland and A. E. Ship-
ley. Vol. I, 15 "1- 471 pp.; vol. 2, 8 + 226 pp. Ed. 2. Oxford.

Clarendon Press.
Romanes, G. J. 1892, 1897, 1901. Darwin and After Darwin. Vol. i,

The Darwinian Theory, 14 + 460 pp., 125 figs.; vol. 2, Heredity

and Utility, 10 + 344 pp., 4 figs. ; vol. 3, Isolation and Physiological

Selection, 8 +181 pp. Chicago. Open Court Pub. Co.
Weismann, A. 1892, 1898. The Germ-Plasm. A Theory of Heredity.

Trans, by W. N. Parker and H. Ronnfeldt. 22 + 477 pp., 24 figs.

New York. C. Scribner's Sons.
Romanes, G. J. 1893. -'^'i Examination of Weismannisni. 9 + 221 pp.

Chicago. Open Court Pub. Co.
Bateson, W. 1894. INIaterials 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. Macnnllan & Co.
Baldwin, J. M. 1895. Consciousness and Evolution. Science, vol. 2 (n.

s.), pp. 219-223.
Delage, Y. 1895. La structure du protoplasma et les theories sur I'here-

dite et les grands problemes de la biologic generale. 16 + 878 pp.

Paris. C. Reinwald et Cie.*
Baldwin, J. M. 1896. Physical and Social Heredity. Amer. Nat., vol. 30,

pp. 422-428.
Baldwin, J. M. 1896. A New Factor in Evolution. Amer. Nat., vol. 30.

pp. 441-451, 536-553-
Baldwin, J. M. 1896. Heredity and Instinct. Science, vol. 3 (n. s.). pp.

438-441, 558-561.
Cope, E. D. 1896. The Primary Factors of Organic Evolution. 16 |- 547

pp., 120 figs. Chicago. Open Court Pub. Co.
Morgan, C. Lloyd. 1896. On Modification and Variation. Science, vol. 4

(n. s.), pp. 73,V740.

LITERATURE 453

Morgan, C. Lloyd. 1896. TIaI)it and Inslinct. 351 pp. London and New

Y(irk. E. Arnold.
Osborn, H. F. 1896. Ontogenic and Pli\dogenic Variation. Science, vol.

4 (11. s.), pp. 786-789.
Bailey, L. H. 1896, 1897. The Snrvival of the Unlike. 515 pp. New

York and London. The Alacmillan Co.
Baldwin, J. M. 1897. Organic Selection. Science, vol. 5 (n. s.), pp.

634-636.
De Vries, H. 1901-3. Die Mntationstheorie. 14 + 752 pp., 12 pis., 159

figs. Leipzig. Veit & Co.*
Baldwin, J. M. 1902. Development and Evolution. 16 + 395 pp. New

York and London. The Macmillan Co.
Weismann, A. 1902. Vortrage iiber Descendenztheorie. Bd. i, 124-456

pp., 95 figs.; bd. 2, 6 + 462 pp., 36 figs., 3 taf. Jena. G. Fischer.
Morgan, T. H. 1903. Evolution and Adaptation. 13 + 470 pp., 5 figs.

New York and London. The Macmillan Co.
Vernon, H. M. 1903. Variation in Animals and Plants. 9 + 415 pp.

New York. Henry Holt & Co.
Kellogg, V. L., and Bell, R. G. 1904. Studies of Variation in Insects.

Proc. Wash. Acad. Sc, vol. 6. pp. 203-332, figs. 1-81.
Metcalf, M. M. 1904. An Outline of the Theory of- Organic Evolution.

22 + 204 pp., loi pis., 46 figs. New York and London. The

Macmillan Co.*
Weismann, A. 1904. The Evolution Theory. Trans, by J. A. Thomson

and ^[. R. Thomson. 2 vols. 16 + 821 pp., 131 figs. London. E.

Arnold.
De Vries, H. 1905. Species and Varieties : their Origin by ^Mutation.

Ed. by D. T. MacDougal. 18 + 847 pp. Chicago. Open Court

Pub. Co.
Gulick, J. T. 1905. Evolution, Racial and Habitudinal. 12 + 269 pp.

Carnegie Inst. Washington.
Reid, G. A. 1906. The Principles of Heredity. Ed. 2. 13 + 379 PP-

London. Chapman & Hall, Ltd.

INSECTS IN RELATION TO PLANTS

Darwin, C. 1877. The Effects of Cross and Self Fertilisation in the Vege-
table 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.

Miiller, H. 1883. The F'ertilisation of Flowers. 12 + 669 PP-. 186 figs.
London. ^lacmillan & Co.

Darwin, C. 1884. The Various Contrivances by wdiich Orchids are fer-
tilised by Insects. Ed. 2. 16 + 300 pp., 38 figs. New York. D.
Appletiin &: Co.

Darwin, C. 1884. Insectivorous Plants. 10 + 462 pp., 30 figs. New
York. D. Appleton & Co.

454 ENTOMOLOGY

Cheshire, F. R. 1886. Bees and Bee-keeping. 2 vols. Vol. i. 7 + 336
pp.. 71 figs., 8 pis.; vol. 2, 652 pp., 127 figs., I 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. i pi.

Thaxter, R. 1888. The Entomophthorese of the LTnited States. j\Iem.
Rost. Soc. Nat. Hist., vol. 4, pp. 133-201. pis, 14-21.

Robertson, C. 1889-99. Flowers and Insects. I-NIX. Bot. Gaz.. vols.
14-22, 25, 28.

Seitz, A. 1890, 1893, 1894. Allgemeine Biologic der Schmetterlinge.
Zool. Jahrb., Abth. Syst., etc., bd. 5, pp. 2S1-343; bd. 7, pp. 131-
186, 823-851.*

Eckstein, K. 1891. Pflanzengallen und Gallentiere 88 pp., 4 taf. Leip-
zig. 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 -f- 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. pls. 34-43-

Moller, A. 1893. Die Pilzgarten einiger siidamericanischer Ameisen.
Bot. Mitt, aus den Tropen, heft 6. 7-I-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 Biolo-
gical Study of Oak Galls and Gall Flies. 40 -|- 198 pp., 3 pis.
Oxford. Clarendon Press.*

Webster, F. M. 1894. Vegetal Parasitism among Insects. Journ. Colum-
bus ITort. Soc. pp. 1-19, pis. 3-5, figs. I, 2.

Heim, F. L. i8g8. 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. I'av. Sc. 1895. pp. 31-75-

Schimper, A. F. W. 1898. Pflanzen-Geographie auf physiologischer
Grundlage. 18 -f- 876 pp., 502 figs., 5 plates, 4 maps. Jena. G.
iMschcr. (See pp. 147-170.)* Trans: 1903. W. R. Fisher.
Plant-Geography upon a Physiological Basis. 304-839 pp., 502
figs., 4 maps. Oxford, Clarendon Press. (See pp. 126-156.)*

Benton, F. 1899. The Honey Bee : A Manual of Instruction in Apicul-
ture. Bull. U. S. Dept. Agric, Div. Ent.. no. i (n. s.). pp. 1-118,
pis. i-ii. figs. 1-76.*

Needham, J. G. 1900. The Fruiting of the Blue Flag (Iris versicolor L. ).
Amer. Nat., vol. 34. pp. 361-386. pi. I. figs. 1-4.

Gibson, W. H. 1901. Blossom Hosts and Insect Guests. 19 -|- 197 pp.,
figs. New York. Newson & Co.

LITERATURE 455

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.

Oliio Nat., vols. 2-4, pis. Same, Bull. Ohio St. Univ., ser. 6, no.

15; scr. 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 Natural History, Anatomy and

Physiology. Ed. 2. 12 + 220 pp., -/Ty figs. London. Ploulston &

Sons.*
Rossig, H. 1904. Von welchen Organen der Gallwespenlarven geht der

Reiz zur Bildung der Pflanzengalle aus? Zool. Jahrb., Abth.

Syst., etc., bd. 20, pp. 19-90, taf. ^-(i*

INSECTS IN RELATION TO OTHER ANIMALS

Aughey, S. 1878. Notes on the Nature of the Food of the Birds of

Nebraska. First Rept. \3. S. Ent. Comm., Appendix, 2, pp. 13-62.
Forbes, S. A. 1878. The Food of Illinois Fishes. Bull. 111. St. Lab. Nat.

Hist., vol. I, 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. Nat. Hist., vol. i, no. 3, pp. 3-17.
Forbes, S. A. 1880. The Food of Fishes. Bull. III. St. Lab. Nat. Hist.,

vol. I, no. 3, pp. 18-65.
Forbes, S. A. 1880. On the Food of Young Fishes. Bull. 111. St. Lab.

Nat. Hist., vol. i, no. 3, pp. 66-79.
Forbes, S. A. 1880. The Food of Birds. Bull. 111. St. Lab. Nat. Hist.,

vol. I, no. 3, pp. 80-148.
Forbes, S. A. 1883. The Regulative Action of Birds upon Insect Oscilla-
tions. Bull. 111. St. Lab. Nat. Hist., vol. i, no. 6, pp. 3-32.
Forbes, S. A. 1883. The Food of the Smaller Fresh-Water Fishes. Bull.

111. St. Lab. Nat. Hist., vol. i, no. 6. pp. 65-94.
Forbes, S. A. 1883. The First Food of the Common White-Fish. Bull.

III. St. Lab. Nat. Hist., vol. i, no. 6, pp. 95-109.
Dimmock, G. 1886. Belostomidse and some other Fish-destroying Bugs.

Ann. Rept. Fish Game Comm. Mass., pp. 67-74, i fig*
Forbes, S. A. 1888. Studies on the Food of Fresh-Water Fishes. Bull.

111. St. Lab. Nat. 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. Nat. 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-
Beal, F. E. L. 1897. Some Common Birds in their Relation to Agricul-
ture. Farmer's Bull. U. S. Dcpt. Agric, no. 54. pp. 1-40, figs.

1-22.

45^ ENTOMOLOGY

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 Et^ciency of Some Protective Adaptations in

Securing Insects from Birds. Amer. Nat., vol. 2:3- PP- 461-484.
Palmer, T. S. 1900. A Review of Economic Ornithology. Yearbook

U. S. Dcpt. 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, figs. 48-56.
Forbes, S. A. 1903. Studies of the Food of Birds, Insects and Fishes.

Second Ed. Bull. 111. St. Lab. Nat. Hist., vol. i, no. 3.
Weed, C. M., and Dearborn, N. 1903. Birds in their Relations to Man.

8 -(- 3S0 pp., figs. Philadelphia and London. J. B. Lippincott

Co.*

INSECTS IN RELATION TO DISEASES

Blandford, W. F. H. 1896. The Tsetse fly-disease. Nature, vol. 53, pp.
566-568, figs. I, 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
Nagana, 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. S. 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. i, 154 pp., 3 pis.

Ross, R. 1899. Life-History of the Parasites of Malaria. Nature, 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. 0. 1900. Notes on the Mosquitoes of the United States : giv-
ing some account of their structure and biology, with remarks on
remedies. Bull. V. S. Dept. Agric, Div. Ent., no. 25 (n. s.), 70
pp., 22 figs.

Howard, L. 0. 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. Nature, 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 Cn. s.), pp. 571-579. pis. 30. 31-

Grassi, B. 1901. Die Malaria-Studien eines Zoologen. 8 -}- 250 pp., 8
taf. Jena. G. Fischer.

LITERATURE 457

Howard, L. 0. igoi. Alosquitoes; how tliey live; liow they earry disease;
how they are classified : how they may be destroyed. 15 -f- 241
pp., 50 tigs., I pi. New York. McClure, Phillips & Co.

Sternberg, G. M. igoi. The Transmission of Yellow h'ever by Mos-
quitoes. Pop. Sc. ]Mon., vol. 59, pp. 225-241.

Howard, L. 0. 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.

Sternberg, G. M. 1903. Infection and Immunity; with special Reference
to the Prevention of Infectious Diseases. 5 -f- 293 pp., 12 figs.
New York and London. G. P. Putnam's Sons.

Blanchard, R. 1905. Les Moustiques. histoire naturelle et medicale.
^1Z PP-. 316 figs. Paris. De Rudeval.

INTERRELATIONS OF INSECTS

Van Beneden, P. J. 1876. Animal Parasites and Messmates. 28 4- 274

pp., 83 figs. New York. D. Appleton & Co.
McCook, H. C. 1877. IMound-making Ants of the Alleghenies, their

Architecture and Habits. Trans. Amer. Ent. Soc, vol. 6, pp. 253-

296, figs. 1-T3.
Fabre, J. H. 1879-1905. Souvenirs entomologiques. fitudes sur I'instinct

et les moeurs 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 Macmillan Co.
Forbes, S. A. 1880. Notes on Insectivorous Coleoptera. Pnill. 111. St.

Lab. Nat. Hist., vol. i, no. 3, pp. 153-160. 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. i. no. 3, pp. 149-152. Second Ed.,

1903.
McCook, H. C. 1881. Note on a new Northern Cutting Ant, Atta septen-

trionalis. Proc. Acad. Nat. Sc. Phila. 1880, pp. 359-363, i fig.
McCook, H. C. 1881. The Shining Slavemaker. Notes on the Architec-
ture and Habits of the American Slave-making Ant, Polyergus

lucidus. Proc. Acad. Nat. Sc. Phila. 1880, pp. 376-384, pi. 19.
Lubbock, J. 1882, 1901, 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 Carabidse and Coccinel-

lidcTe. Bull. 111. St. Lab. Nat. Hist, vol. i, no. 6, pp. 33-64.
Cheshire, F. R. 1886. Bees and Bee-keeping. 2 vols. Vol. i, "/ -\- 2)?>(>

pp., 8 pis.. 71 figs.; vol. 2, 652 pp., 127 figs., I pi. London. L.

Upcott Gill.

458 ENTOMOLOGY

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. Beitrjige zur Biologie der Hymenoptera. Zool. Jabrb.,

Abtli. Syst., etc., bd. 6, pp. 680-754, taf. 30, 31.
Wasmann, E. 1894. Kritisches Verzeicbnis der mymiekopbilen und ter-

mitophilen Artbropoden. 231 pp. Berlin. F. L. Dames.
Grassi, B., and Sandias, A. 1896-97. Tbe Constitution and Development

of tbe 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.. T^y pp., Paris.
Howard, L. 0. 1897. -^ Study in Insect Parasitism. Bull. U. S. Dept.

Agric, Div. Ent., tecb. scr. no. 5, pp. 1-57, figs. 1-24.
Peckham, G. W., and E. G. 1898. On tbe Instincts and Habits of tbe

Solitary Wasps. Bull. Wis. Geol. Nat. Hist. Surv., no. 2, sc. ser.

no. I. 4 + 245 pp., 14 pis.
Wasmann, E. 1898. Die Gaste der Ameisen und Termiten. Illustr.

Zeits. Ent., bd. 3, i taf.
Benton, F. 1899. The Honey Bee: A Manual of Instruction in Apicul-
ture. Bull. U. S. Dept. Agric, Div. Ent., no. i (n. s.), pp. 1-118,

pis. i-ii. figs. 1-76.*
Fielde, A. M. 1901. A Study of an Ant. Proc. Acad. Nat. Sc. Phila.,

vol. 53, pp. 4^5-449-
Fielde, A. M. 1901. Furtber Study of an Ant. Proc. Acad. Nat. Sc.

Pbila., vol. 53, pp. 5-'i-544-
Wheeler, W. M. 1901. Tbe 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 tbe Behavior of the Social

Wasps. Pop. Sc. Mon., vol. 61, pp. 339-351.
Fielde, A. M. 1902. Notes on an Ant. Proc. Acad. Nat. Sc. Pbila., vol.

54, pp. 599-625.
Dickel, F. 1903. Die Ursacben der gescblechtlicben Differenzirung im

Bienenstaat. Arcbiv ges. Phys., bd. 95, pp. 66-106, fig. i.
Fielde, A. M. 1903. Supplementary Notes on an Ant. Proc. Acad. Nat.

Sc. Pbila., vol. 55, pp. 491-495.
Heath, H. 1903. Tbe Habits of California Termites. Biol. Bull., vol. 4,

pp. 47-63. figs. 1-3-
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 figs.
Fielde, A. M., and Parker, G. H. 1904. Tbe Reactions of Ants to Material

Vibrations. Proc. Acad. Nat. Sc. Pbila., vol. 56, pp. 642-650.*

LITERATURE 459

Wheeler, W. M. 1904. A New T\'pe of Social Parasitism among Ants.
Bull. Amcr. ]\Ius. Nat. Hist., vol. 20, pp. 347-375.

INSECT BEHAVIOR

Pouchet, G. 1872. De I'influence de la lumiere sur les larves de dip-

tcres privees d'organes exterieurs de la vision. Rev. Mag. Zool.,

ser. 2, t. 23, pp. 110-117, etc., pis. 12-16.
Fabre, J. H. 1879-1905. Souvenirs entomologiques. fitudes sur I'instinci

et les moeurs des insectes. 9 Series. Paris. C. Delagrave.

Trans, of Ser. I: 1901. Fabre, J. H. Insect Life. 12 -(-3^0 pp.,

16 pis. London and New York. The Macmillan Co.
Lubbock, J. 1882, 1884. Ants, Bees and Wasps. 19 + 448 pp., 31 figs., 5

pis. New York. D. Appleton & Co.
Graber, V. 1884. Grundlinien zur Erforschung des Helligkeits- und Far-

bensinnes der Tiere. 8+322 pp. Prag und Leipzig.
Romanes, G. J. 1884. .\nimal Intelligence. 14 + 520 pp. New York.

D. Appleton & Co.
Lubbock, J. 1888. On the Senses, Instincts and Intelligence of Animals,

with Special Reference to Insects. 29 + 292 pp., 118 figs. New

York. D. Appleton & Co.
Plateau, F. 1889. Recherches e.xperimentales sur la Vision chez les Ar-

thropodes. Mem. cour. Acad. roy. Belgique, t. 43, pp. 1-91.
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 Uebereinstim-

numg mit dem Heliotropismus der Pflanzen. 118 pp. Wiirzburg.
Seitz, A. 1890. Allgemeine Biologic der Schmetterlinge. Zool. Jahrb.,

Abth. Syst., bd. 5, pp. 281-343.
Exner, S. 1891. Die Physiologic der facettirten Augen von Krebsen und

Insecten. 8 + 2c6 pp., 8 taf., 23 figs. Leipzig und Wicn.
Loeb, J. 1891. Ueber Geotropismus bei Thieren. Arch. ges. Pliys., bd.

49, PP- 175-189, figs.
Morgan, C. Lloyd. 1891. Animal Life and Intelligence. 13 + 512 pp., 40

figs. Boston. Ginn & Co.
James, W. 1893. The Principles of Psychology. 2 vols. 18+1393 pp.,

94 figs. New York. Henry Holt & Co.
Loeb, J. 1893. LVbcr kiinstliche Umwandlung positiv heliotropischer

Thiere in negativ heliotropische und umgckehrt. Arch. ges. Phys.,

bd. 54, pp. S1-107.
Baldwin, J. M. 1896. Llercdily and Instinct. Science, vol. 3 (n. s.), pp.

438-441, 558-561.
Morgan, C. Lloyd. 1896. Habit and Instinct. 351 pp. London and New

York. E. Arnold.
Davenport, C. B. 1897, 1899. Experimental Morphology. 2 Pts. 32 +

508 pp., 140 figs. New York and London. The Macmillan Co.

460 ENTOMOLOGY

Loeb, J. 1897. Zur Theorie der physiologischcn Licht- iind Schwerkraft-

wirkungen. Arch. ges. Phys., bd. 64, pp. 439-466.
Bethe, A. 1898. Diirfen wir den Ameisen und Bieneii psychische Quali-

tjiten zuschreiben? Archiv ges. Phys,, bd. 70. pp. 15-100. taf. i. 2.

5 figs.
Peckham, G. W., and E. G. 1898. On the Instincts and Habits of the

SoHtary Wasps. Bull. Wis. Geo!. Nat. Hist. .Surv., no. 2, sc.

ser. no. i. 4 + -45 PP-. 14 pis.
Verworn, M. 1899. General Physiology. An Outline of the Science of

Life. Trans, by F. S. Lee. 16 + 615 VT>-, 285 figs. London and

New York. ALacmillan & Co.
Wasmann, E. 1899. Die psychischen Fahigkeiten der Ameisen. Zoolog-

ica, heft 26, 6 -|- 132 pp., 3 taf. Stuttgart. E. Njigele.
Wheeler, W. M. 1899. Anemotropism and Other Tropisms in Insects.

Arch. Entw. Org., bd. 8, pp. 373-381.
Whitman, C. 0. 1899. Animal Behavior. Biol. Lect., Marine Biol. Lab.,

Wood's Holl, Mass., 1898, pp. 285-338. Boston. Ginn & Co.
Loeb, J. 1900. Comparative Physiology of the Brain and Comparative

Psychology. 309 pp., 39 figs. New York, G. P. Putnam's Sons.

London, J. Murray.*
Morgan, C. Lloyd. 1900. Animal Behaviour. 8 + 344 PP-. -6 figs. Lon-
don. E. Arnold.
Radl, E. 1901. L^eber den Phototropismus einiger Arthropoden. Biol.

Centralb.. bd. 21. pp. 75-86.
Radl, E. 1901. LTntersuchungen fiber die Lichtreaclioncn der Arthro-

prnk-n. Arch. ges. Phys., bd. 87, pp. 418-466.
Enteman, M. M. 1902. Some Observations on the Behavior of the Social

Wasps. Pop. Sc. Mon., vol. 61, pp. 339-351.
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. 159-181.
Kathariner, L. 1903. Versuche , fiber die Art der Orientierung bei der

Honigl)iene. Biol. Centralb., bd. 23, pp. 646-660, I 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. ^lark Anniv. Vol., pp. 453-469. pi. 33*
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.*
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.*

LITERATURE 46 1

Carpenter, F. W. 1905. The Reactions of the Pomace Fly (Drosophila
ampelophila Loew) to Light, Gravity, and Alechanical Stimula-
tion. Amer. Nat., vol. 39, pp. 157-171.*

Hartman, C. 1905. Observations on the Habits of some Solitary Wasps
of Texas. Bull. Univ. Texas, no. 65, sc. scr. 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. i, 2.

Wasmann, E. 1905. Comparative Studies in the Psychology of Ants and
of Higher Animals. 10 -|- 200 pp. St. Louis and Freiburg, B.
Herder; London and Edinburgh, Sands & Co.*

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 Mex-
ico. Smithson. Contrib., vol. 11, 6 -|- 58 pp., 2 pis., map.

Bates, H. W. 1864. The Naturalist on the River Amazons. 12 -J- 466
pp., figs. London. J. Murraj'.

Wallace, A. R. 1865. On the Phenomena of Variation and Geographical
Distribution as illustrated by the Papilionidae of the Malayan Re-
gion. Trans. Linn. Soc. ZooL, vol. 25, pp. 1-71, pis. 1-8.

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 Coleop-
terous h'aunse. Journ. Linn. Soc. ZooL, vol. 11, pp. 1-89.

Belt, T. 1874, 1888. The Naturalist in Nicaragua. 32-1-403 pp., figs.
London. J. Murray; E. Bumpus.

Wallace, A. R. 1876. The Geographical Distribution of Animals. 2 vols.
Vol. I, 21 + 503 pp., 13 pis., 5 maps; vol. 2, 8 -|- 607 pp., 7 pis., 2
ni;ii)s. New York. Harper & Bros.

Semper, K. 1881. Animal Life as affected by the Natural Conditions of
Existence. 164-472 pp., 106 figs., 2 maps. New York. D. Apple-
t(MT & Co.

Wallace, A. R. 1881. Island Life, or the Phenomena and Causes of Insu-
lar 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.,
\ol. 2, pp. 1-39.

Forbes, H. 0. 1885. A Naturalist's Wanderings in the Eastern Arclii-
pelago. 19 + 536 pp., figs., pis., maps. New York. Harper &
Bros.

462 ENTOMOLOGY

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 Fran-
cisco 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. Fnt. Soc. Wash., vol. i, pp. 182-194.
Seitz, A. 1890, 1893, 1894. Allgemeine Biologic der Schmetterlinge.

Zool. Jahrb., Abth. Syst., etc., bd. 5, pp. 281-343; bd. 7, pp. 131-

186, 823-851.*
Trouessart, E. L. 1890. La Geographie Zoologique. 114-338 pp., 63

figs., 2 maps. 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.

S9 + 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. Chapman & Hall.
Webster, F. M. 1892. Modern Geographical Distribution of Insects in

Indiana. Proc. Ind. Acad. Sc, pp. 81-88, map.
Merriam, C. H. 1893. The Geographic Distribution of Life in North

America, 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 Amer-
ica, Northern Asia and Europe, with Distribution and Bibliogra-
phy. Trans. Amer. Ent. Soc, vol. 21. pp. 345-416-1-19.
Merriam, C. H. 1894. Laws of Temperature Control of the Geographic

Distribution of Terrestrial Animals and Plants. Nat. Geogr.

]\Iag., vol. 6, pp. 229-238. 3 maps.
Scudder, S. H. 1894. The EiTect of Glaciation and of the Glacial Period

on the Present Fauna of North America. Amer. Journ. Sc, ser.

3, vnl. 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.
Whymper, E. 1894. Travels amongst the Great Andes of the Equator.

24 -|- 456 pp., 20 pis., 4 maps, 118 figs. New York. C. Scribner's

Sons. 1891. Suppl. Appendix. 22 -j- 147 pp., figs. London. J.

Murrav.

LITERATURE 463

Beddard, F. E. 1895. A Text-book of Zoogeography. 8+246 pp., 5
maps. Cambridge, Eng. University Press.

Howard, L. 0. 1895. Notes on the Geographical Distribution within the
United States of certain Insects injuring Cultivated Crops. Proc.
Ent. Soc. Wash., vol. 3, pp. 219-2J6.

Webster, F. M. 1895. Notes on the Distribution of some Injurious In-
sects. Proc. Ent. Soc. Wash., vol. 3, pp. 284-290.

Webster, F. M. 1896. The Probable Origin and Diffusion of Blissus
leucopterus and IMurgantia histrionica. Journ. Cine. Soc. Nat.
Hist., vol. 18, pp. 141-155, fig. I, pi. 5.

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 Ani-
mals. 12 -f- 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. Kept. Ohio St. Acad. Sc, pp. 32-46,
2 figs.

Merriam, C. H. i8g8. 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 -f- 552 pp., 4 maps, 86 figs. London and New York.
Macmillan & Co.

Tower, W. L. 1900. On the Origin and Distribution of Leptinotarsa
decem-lineata Say, and the Part that some of the Climatic Fac-
tors have played in its Dissemination. Proc. Amer. Ass. Adv.
Sc, vol. 49, pp. 225-227.

Adams, C. C. 1902. Postglacial Origin and Migrations of the Life of the
Northeastern Lhiited States. Journ. Geogr., vol. i, pp. 303-310,
352-357- map.

Adams, C. C. 1902. Southeastern United States as a Center of Geograph-
ical Distribution of Flora and Fauna. Biol. Bull., vol. 3, pp. 115-
131.*
Tutt, J. W. 1902. The Migration and Dispersal of Insects. 132 pp.
London. E. Stock.

Webster, F. M. 1902. The Trend of Insect Diffusion in North America.

32(1. Ann. Kept. Ent. Soc. Ontario (1901), pp. 63-67, maps 1-3.
Webster, F. M. 1902. Winds and Storms as Agents in the Diffusion of

Insects. .\mcr. Nat., vol. 36, pp. 795-801.
Webster, F. M. 1903. The Diffusion of Insects in Ndrth America.

Psyche, vol. 10, pp. 47-58. pi. 2.
Jacobi, A. 1904. Tiergeographie. 152 pp., 2 maps. Leipzig.

4^4 ENTOMOLOGY

GEOLOGICAL DISTRIBUTION

Herr, 0. 1847-53. Die Insectenfauna der Tertiargebilde von Qiningen
und von Radoboj in Croatien. 3 Th. 644 pp., 40 taf. Leipzig.
From Xeue Denks. schweiz. Gesell. Xaturw., bd. 8, 11, 13.

Scudder, S. H. 1880. The Devonian Insects of New Brunswick. Ann.
Mem. Bost. Soc. Nat. Hist., 41 pp., i pi.

Scudder, S. H. 1882. A Bibliography of Fossil Insects. Bibl. Contrib.
Libr. Harv. Laiiv., no. 13. 47 pp. Cambridge, ]\Iass.*

Scudder, S. H. 1885. The Earliest Winged Insects of America: a Re-
examination of the Devonian Insects of New Brunswick, etc. 8
pp., I pL, 2 figs. Cambridge, Mass.

Scudder, S. H. 1885. Systematische Uebersicht der fossilen Myriopoden,
Arachnoideen und Insekten. In K. A. Zittel : Handbuch der
Palseontologie, abth. i, bd. 2, pp. 721-831, figs. 894-1109. Trans.
1900. C. R. Eastman. Text-Book of Palaeontology, vol. i, pp.
682-691, figs. 1441-1476. London and New York. Macmillan &
Co.*

Scudder, S. H. 1886. The Cockroach of the Past. In L. C. Miall and
A. Denny. The Structure and Life-History of the Cockroach, pp.
205-220, figs. 1 19-125. London and Leeds.*

Scudder, S. H. 1886. Systematic Review of our Present Knowledge of
Fossil Insects. Bull. U. S. Geol. Surv., no. 31, 128 pp. Wash-
ington.

Scudder, S. H. 1889. The Fossil Butterflies of Florissant. Eighth Ann.
Rept. Dir. L'. 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. L\ S. Geol. Surv., no. 5g, 101 pp. Washington.*

Scudder, S. H. 1890. The Tertiary Insects of North America. LT. S.
Geol. Surv. Terr., vol. 13. 734 pp., 28 pis., i map, 3 figs. Wash-
ington.

Scudder, S. H. 1891. Index to the Known Fossil Insects of the World,
including ]Myriapods and Arachnids. Bull. L^ 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., mx 93, 35 pp., 3 pis. Washington.

Scudder, S. H. 1893. Insect Fauna of the Rhode Island Coal Field. Bull.
U. S. Geol. Surv.. no. loi, ly pp.. 2 pis. Washington.

Scudder, S. H. 1893. The American Tertiary Aphida?, 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. Monogr. U. S. Geol. Surv., vol. 21, 11 -j- 206 pp., 12 pis.
Washington.

LITERATURE 465

Brongniart, C. 1894. Recherches pour servir a I'histoire des insectes fos-
siles des temps primaires, etc. 2 vols. 537 pp., 2)7 P's. St.
fitienne.

Scudder, S. H. 1894. Tertiary TipulidEC, with Special Reference to those
of Florissant, Colorado. Proc. Anier. 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. Surv., 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., 11 pis. Washington.

Scudder, S. H. 1900. Canadian Fossil Insects. 4. Additions to the Cole-
opterous Fauna of the Interglacial Clays of the Toronto District,
etc. Contrib. Can. Pal, Geol. Surv. 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 im-
portant Contributions to American Economic Entomology. 8 pts.
1318 pp. Washington.*

Packard, A. S. 1889. Guide to the Study of Insects. Ed. 9. 12-1-715
pp., 668 figs., 15 pis. New York. Henry Holt & Co.

Howard, L. 0. 1894. A Brief Account of the Rise and Present Condition
of Official Economic Entomology. Insect Life, vol. 7, pp. 55-107.

Sempers, F. W. 1894. Injurious Insects and the Use of Insecticides.
10 -f- 216 pp., I 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. 0. 1899. The Economic Status of Insects as a Class. Sci-
ence, vol. 9 (n. s.), pp. 233-247.

Theobald, F. V. 1899. A Text-Book of Agricultural Zoology. 17 -L- 511
pp., 225 figs. Edinburgh and London. Wni. Blackwood & Sons.

Howard, L. 0. 1900. Progress in Economic Entomology in the United
States. Yearbook U. S. Dept. Agric, 1899, pp. 135-156, pi. 3.
31

466 ENTOMOLOGY

Sanderson, E. D. 1902. Insects Injurious to Staple Crops. 10 -j- 295
pp., 163 figs. New York. John Wiley & Sons.
Most of the hterature on the economic entomology of the United States
is contained in the following works : Reports U. S. Ent. Comni. ; Repts.
Govt. Entomologists; Bulletins U. S. Dept. Agric, Div. Ent.; Insect Life;
Reports and Bulletins by the several State Entomologists ; Bulletins of the
various Experiment Stations.

NDEX

An asterisk * denotes an illustration.

Abdomen, 65 ; appendages of, *67,
*i5o, *i52; extremity, 68; modifica-
tions, 66 ; segments, 65

Acacia, *272, 272

Accessory glands, *I40, *i4i. *I42

Achorntes, *g, 10

Acquired characters, 243

Acridiidse, *io, 11 ; moults of, 165;
spiracles, 66

Acridium , 27 ; respiratory muscles of,
*i39

Aculeata, 21

Adams, on dispersal, 383

Adaptations, of larvje, 165 : of legs, 51,
*53 ; of mandibles, t,7, *i^ '< origin
of, 237 ; protective. 297

Adaptive coloration, 216 : classifica-
tion, 234 : evolution, 236 ; variation,
241

Adelung. von, 428

Adler, 418, 454

Adventitious resemblance, 219

Ageronia, 104

Aggressive resemblance, 235

AsrrionidK, caudal gills of, *i34

Air-sacs, 133

Alary muscles, *i25

Albinism, 201

Alexander, 450

Alimentary tract (see Digestive Sys-
tem).

Alluring coloration, 235

Alternation of generations, 256

Amans, 417, 445

Amber insects, 385, 389

Ametabola, 159

Ammophila, *36o, 363

Amnion, *i48, 149, *i53

Amphidasis, 199

Amphimixis, 243

Amphipyra. 347

Ampullaceum, *95, 96

Anajapyx , *6, 22

Anal glands, 81, *ii7

Anasa, *is8

Androconia. *79, 80

Anemotropism, 347

Anergafes, 336

Angrcecuin, 262

Anisota, *i7i

Anisotropic, 87

Annelids, in relation to arthropods,
S, *7

Anomma, 335

Anopheles, 302, 303

Anophthahnus, 114

Aiwsia bercnice, 380 ; plexippus. an-
tenna of, *34 ; dispersal, 369 : eclo-
sion, 172; so-called mandibles, 41;
mimicked, *224, 232; pupa, *i68;
pupation, 168; scale, *77 : wing,
*6o

Antecoxal piece, *49

Antenn;e, forms of. ^34 : functions of,
34 : sexual differences in, *35

Antennal comb, *27o, 271 ; neuromere,
*46 : segment, 45 ; sensilla, 94, *g$

Anthonomns, 397

Anthrax, 306

Anthrcniis, *77

Antigeny, 35, 205

Ant-plants, *272

Ants, castes of, 330; color sense, 114;
facets, 32 ; general account, 330 ;
habits, 233 \ harvesting ants, 340 ;
honey ants, 336, *337 : hunting ants,
335 : larvt-E, 331 ; leaf-cutting, 337,
*338 : nests, 331 : slave-making, 336

Amirida, development of mouth parts,
*i5i : germ band, *i5o ; habits, 191 ;
pigment, 197

Anus, *72, 121

Aorta. *i2S, *i26

Apanteles, 310, *3ii

Apatetic colors, 234

Apatura, scales, 193 ; colors, 195

Aphaniptera, 19, *2i

Aphid ins, 310

Aphids, galls of, *255 : in relation to
ants, 341

Apis meUifera, antennal sensilla, *9S ;
cephalic glands, 122; comb, *322 ;
control of sex. 327 ; determination
of caste, 327 ; foot, *54 ; general
account, 321 : hair. *26o : larvae.
*324 ; legs, *27o : niandil)le, *38 ;
mimicry, 225 : modifications in rela-
tion to flowers, *27o, 271 ; moults,

467

468

INDEX

165 ; mouth parts, *44 : ocellus,
*i09, *iio; ovipositor, *7o ; repro-
ductive system, *i4i ; tongue, *97 ;
wax, *83, *322, *322

Apneustic, 134, 189

Apodemes, *so

Apodous larv?e, 47, 55

Apophyses, *5o

Aporus, 363

Appendages, development of, *i49

Apple, insects of, 253

Aptera, 8

Apterygota, 10

Aquatic insects, adaptations of, 184;
food, 184; locomotion, 186; origin,
192 : respiration, 188 ; systematic po-
sition, 184

Arachnida, *2, 3

Arctic realm, 375

Arista, *34

Aristida, 340

Arms, J. M., 410, 412, 443, 444

Army worm, 383

Artemia, 243

Arthropoda, characters of, *i ; classes,
2 : interrelationships, 5 ; naturalness
of phylum, 7 ; phylogeny, *7

Asclcpias, *262, *263

Asecodes, 312

Ashmead, on Hymenoptera of Hawaii,

37i
Assembling, 102
Atenicles, 342, *343
Atta, 335, 337, *338
Attaciis, 27

Auditory, hairs, 107 ; organs, 106, *io7
Audouin, 416
Aughey, on insectivorous birds, 288.

455
Austral region, 2,77
Australian realm, 376
Automeris, 81
Ayers, on abdominal appendages, 67,

440

Bailey, 453

Balancers, 58

Baldwin, 452, 453, 459

Ballowitz, 438

Banks, 409, 410, 465

Barlow, 434

Barriers, 368

Basch, 415, 423, 429

Basement membrane, *74, 75, *79, ^85,

*I2I

Basiconicum, 94, *95
Basidium, *258

Basilarchia. mimicry, *224, 222 ; pro-
tective resemblance, 218

Bates, on mimicry, 225 ; 450, 461, 462

Batesian mimicry, 226

Bateson, 448, 452

Beal, on food of robin, 285, 455

Beddard, 447, 450, 463

Bees, color sense of, 114; hairs, *7S

Beetles, sounds of, 104

Behavior of insects, 345

Bell, 453

Bellesme, de, 429

Belostoma, digestive system of, *i20 ;
predaceous, 185, 276

Belt, on leaf-cutting ants, 338, 461

Benaciis, *i6; caecum, 120; mouth
parts, *4i ; predaceous, 185

Beneden, van, 457

Beneficial insects, 395

Benton, on honey bee, 324, 325, 454,
4S8

Berlese, on phagocytosis, 180

Bernard, H. M., 412

Bernard, M., 441

Bertkau, on hermaphroditism, 143, 438

Bessels, 437

Bethe, on behavior of ants, 334, 460

Bethune, 408

Beyer, 419

Binet, 425

Birches, insects of, 252

Birds, insectivorous, 284, 287, 291 ;
regulating insect oscillations, 289

Bittacoinorpha, *i35, 189

Bittaciis, *i7, 52

Black-flies, 276

Blackiston, 450

Blanc, 415, 430

Blanchard, 424, 431, 457

Blandford, 456

Blastoderm, *i47

Blastogenic variations, 241, 243

Blastophaga, 407

Blatfa, muscles of, *86, 87 ; respira-
tion, *i38

Blattidse, 11 ; spiracles of, 66

Blind insects, 33

Blissiis leucopterus, distribution of,
382 ; losses through, 393 ; food of,
398

Blochmann, 440

Blood, corpuscles, 127; course of,
*i2S, *i26 ; function, 127

Bluebird, food of, 286

Boas, 444

Bobretzky, 440

Bolton, 409

Bonibus, antenna of, *34 ; general ac-
count, 328; larva, *i62 ; mimicry,
*235 ; respiration, *i38: taste cup,
*99

INDEX

469

Bombyx niori, Malpighian tubes of,

*i24 ; mid intestine, *i2i ; oenocytes,

*i3i ; silk glands, *84, *85
Bordas, 423. 431
Boreal region, 2>7^
Borgert, 422
Bot flies, 278
Brachinus, 82
Braconidas, 310

Brain, *go, *gi ; functions of, 93
Branchial respiration, 190
Brandt, A., 439
Brandt, E., 424, 425
Brauer, on classification, 9 ; types of

larvK, 162; 411, 417, 437, 442
Br aula, 309
Braun. 457

Breed, on phagocytosis, 180
Breitenbach, 415
Breithaupt, 415
Briant, 415
Brongniart, on Carboniferous insects,

384. 387, 465
Brooks, 414
Bruchophagits, *i59
Brues, 458

Brunner von Wattenwyl, 449
Bugnion, 182, 443
Bumble bees, general account, 328
Bureau of Entomology, 407
Burgess, 42, 415, 418, 432
Burmeister, 410, 411
Bursa copulatrix, *i42
Buthiis, *2, 3
Butler, 450

Biitschli, 424, 437. 439, 440
Butterflies, eclosion of, 172; fossil,

*390

Cabbage butterfly (see Pieris rupee)

Caeca, gastric, *ii6, *ii7, 119

CcBcilius, *i22, *i23

Csecum, *ii9, *i20

Cajal, 435

Caliiplwra, compound eyes of, *iit,

*II2

Callosamia, antennae, 35 ; assembling,

102; cocoon, 170; odor, 82; sexual

coloration, *207
Caloptemis, olfactory organ of, *99 ;

tympanal organ, *io7
Caloptcryx, development of, *i53 ;

sexual coloration, 206
Canipodca, 6, *8, 9, 22, 66, *i62
Candeze, 421

Canker worms, as food of birds, 289
Cannon, on phototaxis, 351
Canthon, *S3
Capitate, *34

Carabidae, anal glands of, 81, *ii7;

predaceous, 308
Carabidoid larva, *i75
Carabus, alimentary tract of, *iij
Carboniferous insects, 384, 386
Cardiac valve, *ii5, 116, 118, 119
Cardo, *38, 39
Carlet, 417, 419
Carpenter, F. W., 461
Carpenter, G. H., on relationships, 5,

7 :_ 410, 41.V 445, 463
Carriere, 427, 441
Carrion insects, 279
Carus, 409

Catbird, food of, 285
Caterpillar, 156; pupation of, 168
Catocala, scent tufts of, 54 ; protective

resemblance, *2i8
Catogenus. antenna of, 34
Cattie, 425
Caudal gills, 190

Cccidomyia, egg of, *iS9, 160; ovipos-
itor, *68, 69 ; pfedogenesis, 145
Cecidomyiidae, galls of, 255
Cecropia adenopus, *273, *274
Cecropia moth (see Samia)
Centrolecithal, *i47
Ccraiubyx. facets of, 2- '< ovipositor,

*68, 69
Ccratina, 316
Ccrceris, 363
Cerci, *8, *67, *7i, *73
Cercopoda, 68
Centra, 82

Cervical sclerites, 30
Chjetici:m, 94, *95
Chalcididae, 27, 310
Chapman. 442, 447
Chclosfonia, *75
Chemotropism, 345
Cheshire, on honey bee, *44, 71, 272,

3^3. 454. 457
Child, 4-28
Chilopoda, *4
Chinch bug, distribution of, 382 ; food

of, 398 : losses through, 393
Chionaspis, 161
Chironomiis, nervous system of, *9i ;

pupal eggs, 145 ; food, 185
Chitin, 72

Chlorophyll, as a pigment, 195, 215
Cholodkovsky, 412, 430, 440, 441
Chordotonal organs, *io8
Chorion, *i46, *i6o
Christy, 456
Chromosomes, 146
Chrysalis, 157
Chrysobothris, integument of, *74

470

INDEX

Chrysomelidiu, silk glands of, 85

Chrysopa, *i7: cocoon of, *i6g; lay-
ing eggs, *i6o; mandibles, *38 ;
predaceous, 308 ; silk glands, 85

Chun, 421

Cicada. metamorphosis of, *i58;
moults, 165; sound, 104

Cicindela, leg of, *S3 '• mandible, *38 :
predaceous, 308 ; variation in color-
ation, *2IS

Ciiiibcx, repellent glands, 81

Circular muscles, *i2i

Circulation, *i26, 127

Circulatory system, 124

Claparede, 426

Claspers, *7i, *72

Claus, 411, 421, 437

Clavate, *34

Claypole, 442

Climatal coloration, 200

Clisiocampa, number of eggs of, 161

Clisodon, 268

Cloaca, 69

Clover, insects of, 252 ; pollination of,
266

Clypeus, 30, *42

Clytra, embryology of, *i47. '^'148,
*iS4. *iSS

Cnemidotus, 135

Coarctate pupa, 168

Coccinella, distribution of, 378

Coccinellidje, predaceous, 308 ; silk-
glands, 8s

Cockroach, cephalic ganglia of, *gi :
fossil, *387, 388 ; mouth parts, *27 ',
muscles, *s6, *86 ; respiration, *i38 ;
salivary gland, *i22: spermatozoon,
*i4i

Cocoon, 169, *i7o

Coeloconicum, 94, ^95

Coelom sacs, *i54

Coleoptera, 18, *2o, 24

Colias, albinism of, 201 : color sense,
115; sexual coloration, 205, *2o6

Collembola, alimentary tract of, *ii5 ;
defined, 10; furcula, 68; primitive
condition, 22 ; ventral tube, 68

Collctcs. hairs of, *75

Colon, 120

Colopha, gall of, *2SS

Color, effects of food on, 196 ; sources
of, 193

Coloration, adaptive, 216, 234; cli-
matal, 200; development of, 210;
effects of moisture and temperature
on, 199 ; seasonal, 201 : sexual, 205 ;
variation in, 211 ; warning, 221

Color patterns, development of, 210;

origin, 208
Colors, combination, 195 ; pigmental,

194 ; structural, 193
Color sense, 114
Commissures, go, *9i
Complete metamorphosis, 156
Compound eyes, *3i; origin of, 114;

physiology, m ; structure, *iio,

III, *i 12
Comstock, A. B., on ants. 145, 331 :

410, 412
Comstock, J. H., on venation, 58 : 403,

406, 410, 412, 414, 416, 417, 435,

445, 446
Cone cells, 1 1 1, *i 12
Conidia, *258
Conidiophores, *258
Connold, 455
Cook, 455
Cooke, 454

Cope, on segmentation, 28 : 452
Copidosotna, 311
Copris, spermatozoon of, *i4i
Coquillett, 404
Corbiculum, *27o, 271
Cordyccps, *257 .
CorctJira, chordotonal organs of, *io8 ;

imaginal buds, *i79, 180
Corn insects, 253
Cornea, no, *iii, *ii2
Corrodentia, 11, 12
Corydaloidcs, 387
Costa, *59
Coste, 447

Cotton boll weevil, 397
Cotton worm, 393
Cowan, 455
Coxa, *49, *5i, *S3
Cremaster, 168
Cremastogaster, 333
Creutzburg, 432
Cricket, stridulation of, 106
Crioccris, 381
Crop. *i 17, *i 18
Crustacea, 2
Cryptorliyitclius. 381
Crystalline cone, iio, iii, *ii2
Ctenocephahts, 19, *2i
Cubitus, *59

Cuenot, 422, 423, 431, 433
Ciller, antennae of, *36 ; characteristics

of, 303 ; filariasis transmitted by,

305 : larva, *i88; mouth parts, *43 ;

respiration, *i88, 189
Cutaneous respiration, 189
Cuticula, 73, *74, *76
Cuticular colors, 194

INDEX

471

Cyaniris pscitdargiohis, coloration of,

199 ; geographical varieties, 373 ;

melanism, 201 ; polymorphism,* 202 ;

sexual coloration, 206
Cybistcr, leg of, *iS7 ; locomotion,

186, 188
Cychrus, stridulation of, 104
Cyllene, metamorphosis of, *i56
CynipidiE, abdomen of, 66 ; galls, *254 ;

parthenogenesis, 145, 256
Cyrtophyllus, stridulation of, 106

Dahl, 417, 422, 424

Dallinger, on acclimatization, 242

Darkness, as affecting pigmentation,
197

Darts. *7o

Darwin, on instinct, 361 ; natural se-
lection, 238 ; origin of species, 245 ;
451, 453, 461

Davenport, on phototaxis, 351 ; 459

Davis, 419

Dearborn, on insectivorous birds, 2S7,
289, 291, 456

Deegener, 444

Delage, 452

Demoor, 417

Denny, on chitin, 74 ; on muscles, 87 ;
410, 414, 424

Dermaptera, 1 1

Dermestidte, 280

Deutocerebrum, 90, 152

Deutoplasm, *i46

Development, 146

Devonian insects, 384, 385

Dewitz, 417, 418, 419, 432, 435, 436,
443, 445

Diabrotica, distribution of, 380

Diacrisia, cocoon of, 170

Diapheromera, *2iy

Diastole, 128

Dibrachys, 312

Dichoptic, *Z2>

Dickel, on control of sex, 327 ; on fer-
tilization, 145 ; 458

Dictyoneura, 387

Dietl, 424

Digestive system, ii6 ; of beetle, *ii7 ;
Belostoma, *i2o; Collemhola, *ii5;
grasshopper, *ii6; histology, *i2i ;
moth, *iig; Myrmeleon, *ii8

Digoneutic, 204

Dimmock, on assembling, 103; on
mouth parts of mosquito, 42, *43 ;
415, 422, 446, 455

Dimorphism, 202

Dinarda, 342

Dincutus, antenna of, *34 ; eyes of,

*3i
Diplopoda, *3
Diptera, 19, *20 ; eyes of, *Z2; hal-

teres, 116; mouth parts, 42, *43 ;

origin, 24; sounds, 103; spiracles,

66
Directing tube, 85
Direct metamorphosis, 157
Diseases, their transmission by in-
sects, 299
Dispersal, 366 ; centers of, 383 ; means

of, 367 ; in North America, 377
Dissosteira, protective resemblance of,

219; stridulation, 104
Distant, 462
Distribution, former highways of,

370 ; geographical, 366 ; geological,

384
Dixey, on evolution of mimicry, 233 ;

447, 448, 450, 451
Dogiel, 431
Dohrn, 439

Dolbear, on stridulation, 106
Dolichopodidae, 54
Donacia, 88, 184, 189
Dorfmeister, 446
Dorsal closure, 151, *i54
Dorsal vessel, 124, *i25
Doyere, 436

Drift, insect, 191

Drone, *32i, 322

Drosera, 256

Drosopbila, egg of, *iS9

Dubois, 433

Ductus ejaculatorius, *i40, 141, 142

Dufour, 421, 429, 432, 433, 434, 436,
445

Durham, 456

Dutrochet, 433, 436

Dyar, on moults, 165

Dynastes hercules, 27 ; tilyiis, distri-
bution of, 380

Dytiscus, caecum of, 120; leg of, *53 ;
predaceous, 276; respiration, 189

Ecdysis, 159, 164

Eciton, *338 ; eyes of, 32 ; habits. 276,

331, 335
Eckstein, 454
Eclosion, 172

Economic entomologist, 398
Ectoderm, *i48
Edwards, on 7. ajax, 203 ; on P. tharos,

204; 421
Egg-guide, *73
Egg-nucleus, *i46

4/2

INDEX

Eggs, form of, *i59; number, i6i ;
size, i6o

Eimer, 452, 459

Ejacnlatory duct, *i40, 141, 142

Elaplinis. stridulation of, 104

Elimination of unfit, 240

Elleiiia, protective resemblance of, 218

Elm, insects of, 252

Elwes, 462

Elytra, 58

Embia, 12

Embiidse, 11, *i2

Embryology, 146

Emery, 430, 433

Emcsa, 2i(^6

Enipis. nervous system of, *9i

Empodium, 51

Einpnsa, *2S8, 259

Enderlein, on Platyptera, 13, 23, 413

Endoskeleton, *50

Engelmann, 409

Enteman, on habits of Polistcs. 330,
365 ; 450, 458, 460

Entoderm, 148, 154, *i55

Entomophthoracese. *258

Environmental variations, 242

Ephemerida, 13, *i4; abdominal seg-
ments of, 66 ; eyes of, 33 ; origin, 23

Epicaiita, hypermetamorphosis of, 174,

*i7S

Epicranium, *29

Epigamic colors, 235

Epimeron, 48, *49

Epipharynx, 37

Episternum, 48, *49

Epitheca, dorsal vessel of. *i2S, *i26

Erehus agrippina, 27 ; odora. distribu-
tion of, 367, 380

Ergatoid, 331

Erioccphala, mouth parts of, 42

Eristalis. mimicry by, *225 ; respira-
tion, 189

Eruciform larvje, 24, *i62. 163, 178

Erynnis manitoba. distribution of, *377

Escherich, 420, 438

Ethiopian realm, 27^

Etiolin, 215

Etoblattina, ^387

Eudamus protciis, distribution of, 377

Eitgercon, 388, *389

Euphoria, mouth parts of, 38, *268,
269

Euplexoptera, 1 1

Euplcca, colors of, 195

Euproctis, 352

Euschistus , antenna of, *34

Eutermes, 320

Enthrips, *i5

Evcrcs. androconium of, *79

Excrements, 120

Exner, on compound eyes, in, 112,
428, 459

Expiration, 139

Exuvise, 165

Eyes, compound, *3i, no; kinds of,
*3i; simple, *32, ^109; sexual dif-
ferences in, *2>2i

Fabre, J. H., on Sphcx. 359 ; 432, 457,
459

Fabre, J. L., 429, 442

Facets, *3i

Fat-body, distribution of, 128, *i2g;
functions, 130 ; structure, *i30

Fat-cells, 129, *i30

Faun?e of islands, 371

Faunal realms, 374

Faussek, 430

Felt, E. P., 403

Female genitalia, *69

Femur, *49, *5i, *53

Fenard, 439

Fenestrate membrane, ni, *ii2

Fenger, 418

Feniseca, 309

Fernald, C. H., on gypsy moth, 253^
402

Fernald, H. T., 412, 422

Fertilization, 147

Fidoiiia, antennal sensilla, *95, 102

Fielde, on ants, 331, Zi3, 334, 3So.
458, 460

Filariasis, 305

Filiform, *34

Filippi's glands, *84

Finlay, 456

Finn, on mimicry, 230 ; warning col-
oration, 222, 450

Fire-flies, 131

Fischer, 449

Fishes, insectivorous, 281

Fitch, 403

Flagellum, *34

Fleas. 19, *2i, 278

Fletcher, 407

Flight, mechanics of. 62

Flogel, 425

Fluted scale, 395, 406

Follicles, 141, 143, *i44

Folsom, 413, 416

Food, its effects on color, 196

Food reservoir. 118, *n9

Forbes, H. O., 461

Forbes, S. A., on corn root louse,
341 ; on economic entomologist,
398 : food of Carabid:e. 308 ; insec-

INDEX

473

tivorous birds, 284 ; insectivorous

fishes, 281 ; insect oscillations, 289 ;

interactions of organisms, 292 ;

404; 454, 455, 456, 457
Forbush, on gypsy moth, 253, 403
Fore intestine, *ii5, *ii6
Forel, on ants, 331, .^32 ; on taste, 96 :

421, 426, 427, 460
Forficulidae, 11
Formative cells, *76, 78, *79
Formica exsectoides, mounds of, 332 ;

fusca, 330, 335, 336 ; pratensis, eyes

of, 33 ; sanguinea, 336
Fossil insects, localities for, 384
Fossilization, 384
Free pupa, 168
French, G. H., 404
Frenulum, 58
Frenzel, 429, 430
"Front, *29

Frontal ganglion, *9i, ^"92
Fimctional variations, 242
Fundament, 150
Fungi of insects, *257, *258
Furcula, 68

Gadeau de Kerville, 433

Gad flies, 276

Galapagos Ids., Orthoptera of, 371

Galea, *37, *38, 39

Galerita, anal glands of, 82 ; antenna,
*34 ; sternites, *49

Galls, *2S4

Ganglia, cephalic, ■■46, 90. *9i : func-
tions of, 93

Ganglion, structure of, 92, *93 ; sub-
cesophageal, *90, *9i ; supraoesopha-
geal, *9o, *9i

Ganglion cells, 92, *93

Ganin. on Plafygasfcr. *i76, 442; 443

Garman, 445

Gastric creca, *ii6, *ii7, 119

Gastropacha, larval coloration, 198 ;
stinging hair, *8i

Gastrophilus, 278

Gastrulation, *i48

Gehuchten, van. on digestion, 119;
424, 4.30

Geise, 415

Genre. 30

Geniculate, *34

Genitalia, 68 ; of female, *69 : grass-
hopper, *73 ; male. *~i ; moth, *y2

Geographical, distribution, 366 ; va-
rieties, 373

Geological distribution, 384

Geometridas, legs of larv.'c of, 55

Geotropism, 348

Gerephemera, 386

Germ band, *i47, *I48; types of, 151

Germ cells, 146

Germinal vesicle, 146

Gerris, *i85 ; locomotion of, 188

Gerstacker, 434

Gibson, 454

Gill, T., 461

Gillette, 405

Gills, *I34, *i35, *i90

Gilson, 430, 436, 437, 446

Girault, on numbers of eggs, 161

Gizzarrl, 118

Glaciation, its effects on distribution,

370
Glands, 80; accessory, *i4o, *i4i,

*i42 ; alluring, 82 ; repellent, 81 ;

salivary, 121, *i22; silk, 83, *84 ;

vi^ax, *83
Glandular hairs, *8o, *8i
Glossa, *37, *39
Glossina, 276, 306
Glover, 406
Goddard, 420
Golgi, on malaria, 301
Goliathus, endoskeleton of, *5o
Gonapophyses, *69
Gongylus, 235
Gonin, 444
Goossens, 419, 422
Goss, 465
Gosse. 419
Gottsche, 426
Gould, 447
Graber, on chordotonal organ, *io8;

halteres. 116: hearing, *io7; 410,

417, 418, 419, 420, 426, 427, 431,

44". 441- 45'T
Grasshopper, alimentary tract of, *ii6 ;

genitalia, *73 ; hearing, *io7
Grassi, on Teniics. 317, 318: 411, 456,

458
Gregson, on coloration, 196
Grenacher, on the compound eye, iii,

114, 427
Grobben, 412
Gross, 439
Growth, 164
Grub, 157
Grube, 433
Griinberg. 439
Gryllid.-e, 1 1
Gryllotolpa, leg of, *53 : maternal care,

.315
Grylliis, sense hairs, *ioi : stridula-

tion, 106
Gula, 30, 30

Gulick, on isolation, 249, 453
Gypsy moth fsee Porthctria).

474

INDEX

Gyrinidpe, eyes of. *3i
Gyrinus, locomotion of, iS8: respira-
tion, 189; tracheal gills, 135

Haase, 411, 412, 419, 435, 450

Hcemolymph, 127

Hagen, on Tcniics. 318 : 400, 434.

435, 445, 446

Hagens, von, 419

Hairs, development of, *76 : functions,
76 ; histology, *76 ; modifications,
*75, 76 ; pollen-gathering, *269 ; pro-
tective, 298 ; tenent. *8o

Halisidota, distribution of, 379

Haller, 435

Halohates, 191, 366

Halteres, 58, 116

Hamilton, on holarctic beetles, 375.
462

Hammond, 417, 444

Hamuli, 58

Hansen, 412, 413, 415

Harpalus, labium of, *39 ; maxilla, *38

Harris, 402, 465

Hart, 446

Hartman, 461

Hatching, 161

Hatschek, 439

Hauser, on smell, 98, 427

Haviland, on termites, 320

Hawaii, beetles of, ^72 : Hymenop-
tera, 373

Hayward, on stridulation, 106

Head, 28 ; segmentation of, 44, *46

Hearing, 106

Heart, *i25, *i26

Heath, on Tcruiopsis. 318: 458

Heer, on fossil insects, 385, 389, 464

Heider, 440, 441, 444

Heilprin, 463

Heim, 454

Heinemann, 433

Heliconiid.ie, mimicry, 225

Hcliopliila, 383

Helm, 429

Hemelytra, 58

Hemerocampa, parasites of, 312

Hemimeridje, 11

Hemimcrtis, *io ; hypopharynx of, *40

Hemiptera, defined. *i6: mouth parts,
40, *4i ; odors, 82 ; origin, 2^

Henking, 438, 440, 441

Henneguy, 410

Hensen, 426

Henshaw, 409, 465

Henslow, on self-adaptation, 243. 452

Hcptagciiia, hypopharynx. *40

Hermaphroditism, 143, *i44

Hesse, 429

Hessian fly. losses through, 393

Hetccrius, 343

Heterocera, defined, 18

Heterogeny, 145

Heterometabola, 157

Heterophaga, 21

Heteroptera, defined, *i6; spiracles of,
66

Hc.vagcnia, 13, *i4; male genitalia,
*/! ; tracheal gills, *i34

Hexapoda, defined, 4

Heymons, 412, 413, 420, 438, 442

Hicks, on olfactory pits, loi

HicKson, 427

Higgins, 446

Hilton, 423

Hind intestine, *ii7, *i20

Histogenesis, 180

Histolysis, 180

Hoffbauer, 417

Holarctic realm, 375

Holcaspis, galls of, ^254

Holmes, 461

Holmgren, 416, 425, 436, 439

Holometabola, 156

Holopneustic, 134, 188

Holoptic, *^T,

Homoptera, defined. 16

Honey, 326

Honey ants, 336, *T,i7

Honey bee (see Apis iiicllifcra)

Hopkins, A. D., 405

Hopkins, F. G., on pigments, 196,
447. 448

Hoplia, sexual coloration of, 207

Horn, on Cicindela, 214

House fly (see Musca)

Howard, on Crioceris, 381 ; economic
entomology, 402, 407 ; parasitism,
312: 410. 456, 457, 458, 463, 465

Hubliard, on parasitism, 313

Huber, on wax, 322

Hudson, 462

Humboldtia. 275

Hunter, 410

Hutton, 413

Huxley, on aphids. 238: 414. 437

Hyaloplasm, 88

Hyatt and Arms, quoted, 22 ; on accel-
eration of development, 178; 410,
412, 443. 444

Hybcniia, 196

Hydnophytnui , *2ys

Hydrophilns. 18, *20, *i85 : antennje,
35 ; leg, *i87 : locomotion, 186 ; male
genitalia, *7i ; respiration, 189

Hydrotropism, 346

INDEX

475

Hydrous, tergites of, *48

Hylastes, 381

Hylobius, glandular hairs of, *8o

Hymenoptera, defined, 19 ; cephalic
glands, 122; eyes of sexes, *23', i'l-
ternal metamorphosis, 182 ; mouth
parts, *44 ; ocelli, 32 ; origin, 24 ;
sounds, 103; wing, *6i

Hypermetamorphosis, 174

Hyperparasitism, 311, 312

Hypha", 259

Hyphantria, 298

Hypodcrma, larva of, *i62; lineata,
habits of, 278 ; losses through, 394

Hypodermal colors, 194

Hypoderniis, *74, 75, *-y6, *79

Hypognathous, 1 1

Hypopharynx, * 37 , 39, *43

Icerya, 406

Ichneumonidw, 310

Ihering, von, 419

Ileum, *i2o

Imaginal buds, *i79, *i8o

Imago, 156

Incomplete metamorphosis, 157

Indirect metamorphosis, *i56

Ingenitzky, 438

Inheritance of acquired characters, 243

Injuries, transmission of, 241

Injurious insects, 393 ; introduction

of, 397
Ino, antennal sensilla of, ^95
Inquilines, 256, 320
Insecta, defined, 4
Insectivorous birds, 284 ; fishes, 281 :

plants, 256 ; vertebrates, 280
Inspiration, 139
Instar, 159
Instinct, 356 ; apparent rationality of,

357 ; basis of, 357 ; flexibility, 360 ;

inflexibility, 359 ; modifications, 358 ;

origin, 361; stimuli, 357; and tro-

pisms, 361
Integument, y2i
Intelligence, 362
Interactions of organisms, 292
Intercalary, appendages, *i5o ; neuro-

mere, *46 ; segment, 45
Interglacial beetles, 391
Interrelations, of insects, 307 : of

orders, 21
Intima, *85, *i2i, *i37
Iphiclidcs ajax, polymorphism of, 202
Iridescence, 193
Iris pigment, *i09, *iii
Iris zersicolor, *26o, *26i
Irritants, 298

Isaria, 258

I schnoptera, mouth parts of, *37

Isia, cocoon of, 170; hairs, 76, 167;

moults, 165
Island fauna;, 371
Isolation, 249, 374
Isoptera, 11
Isosouia, 311
Isotropic, 87
Ithomiina;, mimicry, 225, 226

Jacobi, 463

James, \V., 459

Janet, on Lepismina, *344 ; muscles,
86, *87 ; 416, 420, 421, 424, 458

Japyx, 9, 22 ; spiracles of, 66

Jaworovski. 431

Jennings, 460

Judd, on food of bluebird, 287 ; mim-
icry, 2'i2 ; protective adaptations,
297 ; protective resemblance, 221 ;
warning coloration, 222; 451, 456

Jurassic insects, 385, 389

Kalliiua, protective resemblance of,
216

Kanthack, 456

Karsten, 421

Kathariner, 460

Katydid, stridulation of, 106

Kellogg, on Mallophaga, 277 ; mouth
parts, 42 ; phototropism, 354 : pili-
fers, *42 : scales, 78, 193 ; swarm-
ing, 327; 410, 414, 416, 417, 422.
448, 453, 460

Kenyon, 412, 425

Kidney tubes, 123, *i24

Kingsley, on Arthropoda, 7, 411, 412

Kirby, 410, 411

Kirkland, 456

Klemensiewicz, 422

Kluge, 438

Kniippel, 430

Koch, on malaria, 302

Kochi, 416

Koestler, 425

Kolbe, 410

Kolliker, 424, 437

Korotneff, 440

Korschelt, 438, 441, 444

Koschewnikofi^. 438

Kowalevsky, 430, 432, 439, 443

Kraatz. 419

Kraei)clin, 415, 418

Krancher, 435

Krause's membrane, *87, 88

Krukenberg, on chitin, 74 ; 429, 447

Kulagin, 42, 416, 442, 444

4/6

INDEX

Labella, *43

Labial, neiiromere, *46, 92, 152 ; seg-
ment. 45
Labium, 30. *2>7, *39. *43
Labrum, 30, 36, *37, *42
Lacaze-Duthiers, 418
Lachiiostenia. antenna of, *34 ; cocoon,

169 ; larva, *i62
Lacinia. *37. *38, 39
Lagoa. legs of, 55 ; stinging hairs, *8i
Lamarck, on instinct, 361
Lameere, 444
Lamellate. *34
Landois, 421, 426, 431, 432, 434, 437,

442. 446
Lang. 414
Langer, 416

Langley. on luminosity, 132
Lankester, 411, 413, 432
Larvs, 156: adaptations of, 165: legs.

55: nutrition, 166; parasitic, 314;

types, 162
Lasius, age of. 330 ; nest, 333 ; par-
thenogenesis, 145
Laveran, on malaria, 301
Leacliia. eyes of, *3i
Leaping, 57
Le Baron, 404
Le Conte, 461
Lee, on halteres, 116, 427
Legs, adaptations of. 51, *53 ; larval,

55 : mechanics. *55, 56 ; muscles,

*S6 ; segments, *5i
Lendenfeld, von, 417, 424
Lens, *io9

Lcpidocyrtus, scales of, ■/■/
Lepidoptera, defined, 17: internal

metamorphosis, *i82 ; moults, 165;

mouth parts, 41. ^42; origin, 24;

reproductive organs, *i40, ^142 ; silk

glands, *84 : spiracles, 66
Lepidotic acid, 196
Lcpisma, *8, 9, 22, *i62\ spiracles of,

66
Lcpisiitiua and ants. *344
Lcptinotarsa, color pattern of. 195,

208, *2i2: distribution, 379, 382;

dorsal wall, *i54: entoderm. *i55;

folding of wing, *62 : spread, 382,

398: variation in coloration, *2i2
Lcptocoris, 382
Lcrona, ocellus of, 2-
Leuckart. 439

Leucocytes. *i25, 127, 131. 180
Leydig, 414, 421, 424, 425. 429, 431,

4,37. 4.S8, 441
LibcUuIa, 13. *i5. *i62

Lice, biting, 12, *i3, 2-7; sucking, 16,
*I7, 277

Life zones, 376

Light, its effects on pigments, 197

Ligula. *39

Limacodcs. scale of. *77

Liiia (see Melasonia)

Linden, von, 449, 450

Lingua. *40

Linn3eus, on orders of insects, 8

Lintner, 403, 465

Lithotiiantis, 387, *388

Locality studies, 362, *363

Locustidae, 11; ovipositor, *69 ; sper-
matozoon. *i4i

Locy, 430

Loeb, on tropisms, 346, 347, 349, 351,
352, 356. 459. 460, 461

Loew, 436

Loiuechiisa, *342

Longitudinal muscles. *i2i

Losses through insects, 393

Low, on malaria, 303

Lowne, 414, 426, 427, 428. 438

Lubbock, on ants, 330, 331, 334, 336,
340, 341, 350 ; larval characters,
167; muscles, 86; vision, 113, 114:
411, 414, 423, 427, 428, 434, 437,
443. 453. 457. 459

Lucamis. cocoon of. 169 : dorsal ves-
sel. *i25 ; spiracles, *i36

Liiciha, 349, 350

Lugger, 405

Luks, 424

Luminosity, 131

Lutz, 423

Lycarna, facets of, 32

Lycffinid larvae, alluring gland of, 83

Lycus. mimicked. 230. 231

Lyonet, on muscles. 86, 413, 423

Machilis, 9, 22 ; abdominal appendages,

*67 : nervous system, *90 ; scales,

*77 ; spiracles, 66
MacLeay. 416
Macloskie, 430, 435, 445
Madeira Ids., beetles of, 371
Maggot. *i57
Malacopoda, defined, *3
Malaria, 299, *300
Male genitalia. *7i
Mallock. 428

Mallophaga, defined, 12, *i3; 2-77
Malpighian tubes, 123, *i24
Mandibles. *37 ; adaptations of, *38 ;

Ctilcx, *43 : Lepidoptera, *42
Mandibular, neuromere, *46, 92, 152;

segment, 45

INDEX

477

Mandibulate mouth parts, 36 ; orders,

36
Mann, on Prionus, 161
Manson, on filariasis, 305 ; malaria, 302
Mantidje, 1 1, 307
Mantispa, 24 ; metamorphosis of,

*i63, 164
Maples, insects of, 252
Mare)', on wing vibration. 63; 417
Marine insects, 190
Mark, 427
Marshall, on adaptive coloration, 230,

231, 451
Maternal provision, 314
Maturation, ^146
Maxillse, *37, *38 ; " second," 39
Maxillary, neuromere, *46, 92, 152:

segment, 45
Mayer, A. G., on color pattern, 211 :
Papilio, 200 ; scales, 78 ; 423, 449,
451
Mayer, A. M., on Citlcx, 107, 426
Mayer, P., 411, 426
May fly, male genitalia of, *-i ; wing.

*6i
McCook, on habits of ants. 2,^2, 336,

339, 340, 457
Meconium, 172

Mecoptera, defined, *i7; origin. 24
Media, *S9

Median segment, 46, 66
Meek, 416

Megachile, hairs of, */$
Megalodacnc, antenna of, *34
Meganciira, 388
MegiUa, 378
Meinert, 415
Melander, 458
Melanism, 201

Melanoplus, alimentary tract of, *ii6;
facets, *3i ; genitalia, *-;t, ; mandi-
ble, *38 ; respiration, 139 ; skull, *29
Melanotiis, larva of. *i62
Melasoma, color changes of, 215 : dis-
tribution, 378; germ band, *i49 ;
glands, 82
Meldola, 450
Melnikow, 439
Meloe, antenna of, 35 ; hypermetamor-

phosis, 174
Melolontha, male reproductive system,

*i40 ; olfactory pits, loi
Menopon, 12, *i3
Mentum, '^zy, * ig
Merkel, 423
Meron, 51, *S2

Merriam. on life zones, 376 ; 462. 463
Merrifield. 447. 448

Mesenchyme. *i55

Mesenteron, *ii5, *ii6, *ii7, *ii8,
155

Mesoderm, 148, *iS4

Meso-entoderm, *i48

Mesothorax, 46

Metabola, 159

Metamorphosis, defined, 156; external,
156: internal, 179; kinds, 22; sig-
nificance, 177; systematic value, 23

Metatarsus, *27o

Metathorax, 46

Metcalf, 453

Metschnikofi, 430, 439, 443

Meyer, G. H., 439

Meyer, H., 432

Miall, on chitin, 74 ; muscles, 87 ; 410,
412, 414, 424, 436, 444, 445, 446

Miastor, pedogenesis of, *I45

Michels, 425

Microccntrum, stridulation of, 104,
*io5

Micropteryx, mouth parts of. 42

Micropyle, 147, 160

Alid intestine, *ii7, *\\g

Milkweed, pollination of, *262

Mimicry, 224 ; evolution of, 233

Minot, 414, 422

Miocene insects, 385, 390

Moisture, its effects on coloration, 199

Molanna, 17, *i8

Moles, insectivorous, 280

Moller, on leaf-cutting ants, 338. 454

Mollock, on vision, 113

Moniez. 445

Moniliform, *34

Mononychns, 268

MordeUa, facets of. t,-

Morgan, C. Lloyd, on food of birds,
-23-2 : 452, 453, 459. 460

Morgan, T. H., 453, 460

Morplw, scales of, 78, 193

Moseley. 431

Mosquito, antennae of, 35, *36 ; hear-
ing, 107: locomotion of larvae, 187;
in relation to malaria, 299 ; mouth
parts, *43 ; respiration, *i88, 189

Moulting, 164

Moults, number of, 165

Mouth parts, dipterous, 42, *43 ;
hemipterous, 40, *4i ; hymenopte-
rous, *44 ; lepidopterous, 41. *42 :
mandibulate, 36, *37 ; orthopterous,
*37 ; suctorial, 40

Miiller, F., on mimicry, 227 ; wings,
S7 ; 4' I. 421, 44-2, 450

Miiller, H., 453

Miillerian mimicry. 226, 227

478

INDEX

Miiller, J., "mosaic" theory of, iii,

Mitrgaiitia. spread of, 382

Murray, 461

Miisca, egg of, *iS9 ; facets of, 32;

fungus of, *258 ; moults, 165 : ovum,

*i46 ; in relation to typhoid fever,

30s
Muscidse, cardiac \alve of, *iig: ima-

ginal buds of, *i7q, 181
Muscles, circular and longitudinal,

*i2i : of cockroach, *56. *86 : of leg,

*SS, *56 ; number, 85 : structure,

*87 ; of wing, 64, *6s
Muscular, power, 88; system, Fs
Mutation theory, 247 ; versus natural

selection, 249
Mjitilla, stridulation of, 104
Myriopoda. the term, 5
Mynnecocysfiis, *337
Myrmecodia. 275
Mynnecophana. mimicry by, *229
Myrmecophilism, 340
Mynnedonia, 343
Myniiclcon, digestive system of, *ii8;

predaceous, 308 ; silk glands, 85
Mynnica, *343
Mystacidcs, androconia of, 80

Nagel, 428

Nassonow, 438

Natural selection, 238

Nearctic realm, 375

Necrophonis, 280, 314

Needham, on digestion, 119; venation,

58: 417, 431, 446, 455
Neniobiiis, leg of, *53
Neotropical realm, 375
Nepa. respiration of, 189
Nerves, of head, *9i ; structure, *g3
Nervous system, 8g ; development of,

151, *iS4, *i55
Nervures, 58

Neuration, 58, *S9, *6o, *6i
Neurilemma, *93
Neuroblasts, *iS4
Neuromeres, defined, 45, 152; of head,

*46, 90
Neuroptera, defined, 16 ; metamor-
phosis of, 24, *i63
Newbigin, 449, 451
Newport, on metamorphosis, 183 ;

muscles, 86; 414. 423, 424, 431,

433. 434
Newton, 425

Notolophus, olfactory organs of, 102
Notoiiccta. *i8s ; locomotion of, *i86;

respiration, 189

Notum, 47

Nofius. 314. 395, 406
Nucleolus, 146
Number of insects, 27
Nusbaum, 437, 441
Nuttall, 456
Nymph, 159

Oaks, insects of, 252

Obcrca. eyes of, 31

Obtect pupa, 167, *i68

Occipital foramen, *3o

Occiput, 30

Ocelli, *i2; structure of, *io9 ; vision
by, 109

Ockler, 41 7

Ocular, neuromere, *46 ; segment, 45

Odonata, abdominal segments of, 66 ;
copulation of, 71: defined, 13;
ocelli, 2:2 ; origin, 2^ ; spiracles, 66

Odors, 82 ; efficiency of, 298

Odyncnis. 268

Qicanthus. abdominal appendages of,
67, *i52; embryo, *i52; stridula-
tion, 105

Qicodoiiia. 337

CEcophylla, 333

Gidipoda, dorsal vessel of, *i25

(Ends, distribution of, 370

CEnocytes, *i3i

Qisophageal commissures, *9i

CEsophagus, *ii7

CEstridc-e, 278

Olfactory organs, 98, *99, *ioo, *ioi

Oligocene insects, 385, 389

Oligotoiiia, *12

Ommatidium, no, *ii2

Onthophagus, mandiltle of, *38

Orchclimuin, stridulation of, 105, 106

Orders of insects, 8, 21, *25

Orgy in, olfactory organs of, 102 ; para-
sites of, 312

Oriental realm, 376

Origin of Arthropods, *7 ; of insects, 6

Orthoptera, abdominal segments of,
66: defined, *io; origin, 22; stridu-
lation, 104, *io5, 106

Osborn, 453

Osmeterium, *82

Osinia, 268

Osniodcnna, cocoon of, 169

Osten-Sacken, 422

Ostium, *i25

Oudemans, 438

Oustalet, 434, 445

Ovaries, 140, *i4i, *i42

Ovariole, *i43

Oviducts, 140, *I4I, *I42

INDEX

479

Ovipositor, *6g, *70, *73
Ovogenesis, 146

Ovum, of Miisca, *i46; l'a>icssa. *I44
Ox-warble, *i62, 278, 394

Paasch, 426

Packard, on Atiophthahims. 114: Ar-
thropoda, 7 ; classification, g ; Man-
tispa. 24, 164; olfactory pits, loi ;
origin of Coleoptera, 24 ; relation-
ships of orders, 23, 24 ; segmenta-
tion, 28 ; types of larvre, 162 ; wings,
57; 402, 405: 410, 41 T, 413, 414,
418, 419, 422. 423, 425, 428. J.34,
435, 440. 443. 444. 451. 462, 465

Pasdogenesis, 145

Pagenstecher, 437

Palajarctic realm, 375

Palcroblattina, *38s

Paljcodictyoptera, 392

Palmen, 435, 437

Palmer, 456

Palpifer, *37, *38, 39

Palpiger. *37. *3g

Palpus, *37. *38, *39, *42, *43, *44

Pankrath. 428

Panorpida;, *i7; legs of, 55

Papilio. colors of, 200 ; egg, *i59
facets. 32; head of pupa, *i68
melanism, 201 ; mimicry, 226, 228
osmeterium, *82 ; protective resem-
blance, 218 ; vicropc, mimicry liy,
226, 228 ; sexual coloration of, 206

Paraglossa, *3y, *3g

Paraponyx, *i35, 190

Paraptera. 48

Parasita, defined, 16, *i7

Parasitic insects, 277, 309, 314: in
relation to birds, 291

Parasitism, 278, 309 ; economic im-
portance of, 312

Parker, on phototropism, 353, 460

Parthenogenesis, 145, 256, 327, 331

Passahts, cocoon of, 169; stridulation,
104

Patagia, 48

Patten, 427, 428, 440

Pawlovi, 425

Pawlowa, 432

Peckham, on behavior, 360, 362, 364,
458, 460

Pectinate, *34

Pedicel. *34

Pediculidje, 277

Pcdicuhis, 16, *i7, 277

Pelocoris, leg of, *S3

Penis, *7i, *72, 142

Pepsi s, 315

Perez, C, 444

Perez, J., 420

Pericardial chamber, *i25, 126, *i39

Pevipatus, characters of, *3 ; syste-
matic position. 5

Periplanefa, olfactory pits of, loi

Peripodal. cavity, 181 : membrane.
i8i ; sac. 181

Perla, olfactory pits of. loi

Perlidfe, 12, 13, *i4; nymph, *i62;
tracheal gills, 135

Permian insects, 388

Petiolata, 21

Pettigrew, 417

Petunia, *266, 267

Peytoureau, 420, 438

Phagocytes, 131. 180

Phanccus, legs of, 52, *S3

Pharynx, 117

Phasmidas, 11, *2i7

Phlegethontiiis. head of moth. *42 ;
larva, *54 : moth. *266 : parasitized
larva, 311

Plioniiia, antenna of, *34 ; eyes, *22 ;
metamorphosis, *iS7; phototropism,
354

Phorodon, multiplication of, 238

Phosphorescence, 131

Photinus, luminosity of, 131, 132

Photogenic plate, 131

Photopathy, 350, 351

Photophil. 351

Photophob, 351

Phototaxis. 350. 351

Phototropism, *349

Phragmas, *so

Phthirius . 277

Phyeiodes, coloration of, 199, *203,
204

Phylloxera, 393, 397

Phylogeny. 5, *7. 21, *2S, 3Qi

Physopoda, 13, *is ; origin of, 23. *2$

Phytonomus. legs of, 55 ; spread of,
381

Phytophaga, 20, *2i

Pictet, on coloration. 196. 200

Piepers, 451

Pieris, color sense of, 115 : dispersion,
366; fat-cells, *i3o; imaginal buds,
*i8o; olfactory organs, *ioi ; scale,
*77 ; napi, temperature experiments
on, 204 ; protodice, sexual coloration
of, *2o6 ; rapcE, androconium of,
*79 : developing wing, *i8i ; distri-
bution, 381 ; eggs, *i6o ; food plants,
253 : hair, *76 ; larval tissues, *i29 ;
pupal coloration, 198 ; wing vibra-

48o

INDEX

tion, 64 : xanthodice, distribution of,

366
Pigmental colors, 194
Pigments, of eyes, *iio, *iii, *ii2,

*ii3; nature of, 195; of Pierids,

196
Pilifers, *42
Pimpla, 312
Pine, insects of, 252
Pinguicnla, 257
Placodeum, *95
Planta, *27o
Plants, insectivorous, 256 ; insects in

relation to, 252
Plasma, 127
Plasmodium, *300, 301
Plateau, on color sense, 115; muscti-

lar power, 88; respiration, 139;

416, 423, 427, 429, 432, 435, 459
Platephemera, *386
Platliemis, abdominal appendages of,

*72 ; antenna, *34
Platner, 434
Platygaster, hypermetamorphosis of,

167, *i76
Platypsyllus, 278
Platyptera, defined, 11, *i2 ; origin of,

23, *25
Plecoptera, defined, 13, *i4; nymph,

*i62; origin, 22, *2S
Pleistocene insects, 385, 391
Pleurites, 48, *49
Pleuron, 47
Plotnikow, 423
Pocock, 412
Podical plate, *73

Podisus, egg of, *iS9 ; predaceous, *307
Poccilocapsus, color changes of, 215
Pogonomyrmex , 340
Polar bodies, *i46
Poletajeff, N., 424
Poletajew, O., 435, 445
Poletajewa, 432
Polistcs, behavior of, 360, 365 ; habi's,

329 ; wing vibration, *64
Polites, on Iris, *267
Pollenizers, insect, 266
Pollination, 259, 266 : of Iris, *26o,

*26i ; milkweed, ^262 : orchids, 262 ;

Yucca, *264
Pollinia, *262
Polybia, 328
Polycrgus, 336
Polygoneutic, 204
Polygonia. dimorphism of, 202 ; egg,

*i59
Polymorphism, 202, 330
Polyncuia, 177

Polyphemus (see Tclca)

Polyphylla, assembling of, 103

Polyrliachis, 22,3

Pompilus. behavior of, 360, 364

Porthetria dispar, damage by, 397 ;
hermaphroditism, *i44; tracheae,
*i38

Post-genas, 30

Postscutellum, ^48

Potato beetle (see Lcptinotarsa)

Pouchet, 434, 459

Poulton, on adaptive coloration, 230,
231, 234: on colors of larvse and
])upK, 197, 198: 444, 447, 448, 449,
450, 451

Powell, 444

Pratt, 444

Predaceous insects, 276, *307 ; in rela-
tion to birds, 291

Premandibular, appendages, *i5o; seg-
ment, 45

Primitive insects, 21, 22

Primitive streak, 148

Primordial insect, 21

PrioiiHS. assembling of, 103 ; eggs, 161

Prolaoscis, *42

Procephalic lobes, *i49, *iSo, *i52

Proctodeum, 117, *i2o, *149

Proctotrypidje, 27, 311

Prodoxtis, 266

Prodryas, *390

Prognathous, 1 1

Promcthca (see Callosaiiiia)

Pronotum, *48

Pronuba, *264, *26s

Propodeum, 46, 66

Propolis, 222

Protective, adaptations, 297 ; mimicry,
*224, 223'. resemblance, *2i6, 220

Prothorax, 46

Protocerebrum, 90, 152

Protoplasm, adaptive, 243

Proventriculus, 118

Pseudocone, *ii2

Pseudomyrma, 272

Psocidae, *i2

Pteronarcys, 13, *i4: tracheal gills of,

135
Pterygota, 10

Ptilodactyla, antenna of, *34
Pulvillus, 51, *54
Punktsubstanz, ^93
Pupae, 156, 167; emergence of, 171;

protection, 169 ; respiration, 169
Pupal stage, significance of, 177, 183
Puparium, 168

Pupation of a caterpillar, 168
Putnam, on habits of Bombus, 328

INDEX

481

Pyloric valve, 120
Pyropliila, thigiiiotropism of, 347
Pyvophonis, luminosity of, 131
Pyrrliarctia (see Isia)

Quaternary insects, 391

Oiiedins. 343

Queen, honey bee, *32i, 322 : termite.

Radius, *S9

Radl, 460

Radoszkowski. 419

Ranafra, 185 ; respiration of, i8g

Ranke, 426

Raschke, 435

Rath, vorj, on sense hairs, *ioi, 428

Rathke, 434, 439

Rationality, apparent, 357 ; lack of,

36s
Realms, faunal, 374
Reaumur, de, 413
Receptaculum seminis, *i4i, *i42
Recognition markings, 235
Rectal respiration, 135, 190
Rectum, 120

Recurrent nerve, *9i, *92
Redikorzew, on ocelli, *io9, 428
Redtenbacher, 417
Reed, on yellow fever, 304
Rees. van, 443

Reichenbach, on ants, 145, 331
Reid, 453
Reinhard, 434
Relationships, of arthropods, 5, *7 ; of

orders, 21, *25
Repellent glands, 81
Replacements, 214
Reproductive system, 140
Respiration, 137, 169
Respiratory system, *i33
Retina, *iog

Retinula, 109, *iio, in, *ii2
Renter, 428

Rhabdom, 109, *iio, iii, *ii2
Rheotropism, 347
Rhipiphonts, 174, 176
Rhopalocera, 18
Rhyphns, *6o
Riley, on hypermetamorphoses, 174;

losses through insects, 393, 394 ;

multiplication of hop aphid, 238 ;

pollination of y^iicca, 264 ; pupation,

168: 404, 405, 406; 443, 454
Ritter, 438, 441
Robertson, 454
Robin, food of, 284

Rocky Mountain locust ; dispersion of,

366 ; as food of birds, 288
Rollet, 424
Romanes, on instinct, 361 ; isolation,

249, 250, 251 : 452, 459
Ross, on malaria, 302, 303, 456
Rossig, 455

Rostrum, 40
Rocitcs, *339
Ruland, 428

Sadones, 436, 446

Saliva of Dyfiscus, 123 : mosquito, 123

Salivary glands, 121, *i22, *i23

Sambon, on malaria, 303

Samia cecropia, antennae of, *3S ;
cocoon, *i7o ; egg, 160 ; food plants,
253 ; genitalia, *72 ; head of larva,
*84 ; Malpighian tubes, *i24; ocelli,
*2,2 ; odor, 82 ; scales, *78

Sanderson, 466

Sandias. 458

San Jose scale, 397

Sanninoidca, sexual coloration of, 206

Sarcolemma, *87

Sarcophaga, nervous system of, *9i

Saturnia, hairs of, *76

Saunders, E., 421

Saunders, W., 407, 465

Saville-Kent, 463

Scales, arrangement of, *78 ; develop-
ment, 78, *79 ; form, *-/y. 78 ; occur-
rence, yy ; uses, 79

Scape, *34

Scarabjeidoid larva, 175

Scavenger insects, 279

Schaffer, on scales, 78; 414, 422, 432,
433

Schaum, 415, 418

Scheiber, 431, 434

Schenk, on sensilla, 94, *95, 102, 429

Schewiakofif. 424

Schiemenz. 430

Schimper. 454

Schindler, 429

Schistocerca. distribution of, 367, 383 ;
of Galapagos Ids., 371 : isolation,

250, 374
Schizoneura. wax of, 83

Scliicura, protective resemblance of,

*2I9

Schmankewitsch, on Artcinia. 243
Schmidt, O., 426
Schmidt, P., 412, 433
Schmidt-Schwedt, 435
Schneider, A., 430, 437, 440
Schneider, R., 422
Schultze, 426, 433

482

INDEX

Schwarz, on distribution, 378, 380 ;
myrniecophilism, 343 ; 462

Schwedt, 445

Sclerite, 29

Scolopcndra. *4

Scolopcndrclla. *6, 22

Scudder, on albinism, 201 : coloration,
210; fossil insects, 385, 386, 390,
391, 392; glaciation, 370; mimicry,
22y ; Orthoptera of Galapagos Ids.,
371, 374- spread of P. rapir. 381 ;
stridulation, 106; 409, 41 8, 421,
422, 426, 446, 462, 464, 465

Scutellum, *48

Scutum, *48

Seasonal coloration, 201

Second maxillte, the term, 39

Sedgwick, 412

Segmentation, of arthropods, 27 : germ
band, *i49, *i5o, *i52: head, 44,
'^46

Segments of abdomen, 65. 66

Seitz, 447, 454, 458, 459. 462

Sematic colors, 234

Seminal, ducts, ^140, 141 ; receptacle,
*i4i, *i42; vesicle. *i40, 142

Semon, 463

Semper, C, on scales, 78, 421

Semper, K., 461

Sempers, 465

Sense organs, 94

Sensilla, 94, *95

Serosa, *i48, 149, *i53

Sessiliventres, 20, *2i

Setaceous, *34

Setae, modifications of, 76

Seventeen-year locust, number of
moults, 165

Sexual coloration, 205

Sharp, on Atta, 335 : Hawaiian beetles,
372; metamorphosis, 177; 410, 412.

419- 435, 445
Sheath, *7o
Shelford, 451
Siebold, von, 426, 436
Silk, 85

Silk glands, 83, *84, *85
Silkworm (see Bombyx mori)
Silpha, distribution of, 379
Silurian insects, *385
Silvestri, on Anajapy.v, *6
Simmermacher, 422
Simiiliiiin . 276; respiration. *i9o
Sinclair, 412
Siphonaptera, 19, *2i : origin of, 24.

*2S

Sircx. ovipositor of, *7o
Sirodot, 421, 429

Siiaris. 174

Size of insects, 27

Skin, 73

Skull, *29

Skunk, insectivorous, 280

Slingerland, on losses through insects,

394; 403. 405
Smell, 98: end-organs of, *99, *ioo,

*IOI

Siniutlntnis. *9, 10
Smith. J. B., 405, 415, 416, 465
Smith, T., on Texas fever, 306
Snodgrass, on Orthoptera of Galapa-
gos Ids.. 371. 374
Snow flea. *q

Soldier, ants. 330: termites, *3i6
Sollmann, 418
Somatic cells. 146
Somatogenic variations, 241
Sorensen, 413
Sounds, 103
Species, origin of, 245
Spence, 410, 41 1
Spencer, 452
Spermatheca. *i4i, *i42
Spermatogenesis, 146
Spermatophores, 142
Spermatozoa. *i4i, 142
Sperm-nucleus, *i46
Speyer, on hermaphroditiiEm, 143
Sphecina, 315
Sphccius. 315
Splic.v. *263 : behavior of, 359, 362,

*363

Sphingida;, as pollenizers, 262, *266

Sphinx, alimentary tract of, *iig : dis-
persal, 367 ; pulsations of heart,
128; transformation, *i82

Spichardt, 437

Spines, 76

Spinneret. *84

Spiracles, closure of, *i36: number,
66, 136

Spirobolus, *3, 4

Spongioplasm, 87

Sporotrichiiin, 259

Spuler, on scales, 78; 417, 423, 448

Spur, *53

Squama, 58

Squash bug, metamorphosis of, *i58

Stadium, i 59

Staguiomantis, leg of, *53

Standfuss, temperature experiments
of, 205, Z72, ; 448

Stefanowska. on pigment. 113, 428

Sfcgoiiiyiii, in relation to yellow fever.

304
Stein, 436

INDEX

483

Stenainiiui, 334

Stenobothnis. blood corpuscles of,

*I2S ; stridulation of, 104
Sternberg, on malaria, 302, 303 ; 456,

457
Sternum, *47, 48, *49, 66
Stigmata (see Spiracles)
Sting of honey bee, *70
Stinging hairs, *8i
Stings, efficiency of, 298
Stipes, *37, *38, 39
Stokes, 436
Stomach, *ii9
Stomachic ganglion, *92
Stomatogastric nerve, ^92
Stomodseum, *ii6, *ii7, *i49
Straton, 454
Straus-Diirckheim, on muscles, 86 ;

413. 423
Strength, muscular, 88
Stridulation, 104, *io5, 106
Stroiigylonotus. :^:^6
Structural colors, 193
Struggle for existence, 239
Styloconicum, 94, *9S
Stylops. hypermetamorphosis of. 175
Subcosta, *59
Subgalea, *38
Submentum, *37, *39
Subcesophageal ganglion, *9o, *9i, 93
Suctorial mouth parts, 40
Suffusion, 199
Superlinguje. *40, 150, *i5i
Superlingual, neuromere, *46, 92, 152;

segment, 45
Supraoesophageal ganglion, *9o. *9i,

93
Suranal plate, 68, */3
Surface film, 187
Suspensor, *i43
Suspensory muscles, *i25
Swarming, 327
Symbiosis, 343

Sympathetic system. *9o, *gi, *92, 94
Synaptera, 10

Syrphid^, silk glands of, 85
Systole, 128

Tabanidse, 276

Tabanus, nervous system, *9i ; olfac-
tory organ, *ioo

Tactile hairs, 76, *94, *9S, 96

TjEnidia, *i37

Tarsus, *49, *5i, *53

Taschenberg, 409

Taste, 96 ; end-organs of, *97, *98,
*99

Taxis, 345

Tegmina, 58

Tegulre, 48

Tclca polyphciiuis. cocoon of, 170;

eclosion, 172; larval growth, 164;

silk glands, 84; spinning, 170
Teleas, 177
Temperature, its effects on coloration,

199
Tenent hairs, *8o

TenthredinidK. 25 : larval legs of, 55
Tenthrcdopsis. larva of, *i62
Tentorium, *3o
Terebrantia, 20, *2i
Tergites, *48
Tergum, 47, 66
Tcrines fiavipcs. 318: liicifugiis. *3i6,

317. 318 ; obesus, *3i7
Termites, American species of, 318;

architecture, ^319, *32o : classes,

*3i6 ; '"compass," 319, ^320: food,

318: mandibles, *38 : origin of

castes. 318: queen, *3i7; rava.ges,

320
Termitidre. 11, 12
Termitophilism, 321
Ternwpsis. 318
Tertiary insects, 385, 389
Testes, *i40, 141
Texas fever, 306
Thalcssa, *3io
Thanaos. androconia of, 80 ; claspers,

7-
Thaxter. on Eiiipiisa. *258, 259, 454
Thelen, 434
Theobald, 465
Thermotropism, 355
Thigmotropism, 346
Thomas, C, 404, 405
Thomas, M. B., on androconia, 80, 422
Thorax, differentiation of, 47 ; parts,

46 ; sclerites, *47, *48
Thread-press, *84, 85
Thyridopteryx, number of eggs of, 161
Thysanoptera, 13. *i5; origin of, 23,

*2S

Thysanura, *8, 9 ; al)dominal seg-
ments, 66 : primitive, 21

Thysanuriform, 24, *i62, 178

Tibia, *49, *sr, +53

Tipiila. 19, *2o

Titanophasma, 27

Toad, insectivorous, 280

Tongue, 39

Touch, 96

Tower, on color patterns, 208 ; cuticu-
lar colors, 194: distribution of Lep-
tiuotarsa. 379; folding of wing, 61,
*62 ; integument, *74 ; ori.gin of

484

INDEX

wings. 57; structural colors, 194;

423, 449, 463
Toyama, 438
Tracheae, development of, 153, *i55 ;

distribution, *i32, *i33; structure,

*i37
Tracheal gills, *i34, *i35, 190
Tracheation, types of, 134
Trelease, 454
Tremex, *2i
Triassic insects, 388
Trichius, 268
Trichodeum, 94, *95
Triclwgraiiima, 313
Trichoptera, 17, *i8 ; origin of, 24,

*25 ; silk glands, 85
Trichopterygidse, size of, 27, 311
Trimen, on dispersal, 367 ; on P.

mcrope, 226, 228; 450, 451
Trinierotropis, protective resemlilance

of, 219
Trimorphism, 202
Triphleps, egg of, *i59
Tritocerebrum, 91, 152
Triungulin, 174, *i7S
Trochanter, *49, *5i, *S2, *53
Trochantine, 51
Tropcca liiiia, cocoon of, 170
Tropical region, 377
Tropisms, 345
Trouessart, 462
Trouvelot, on cocoon-spinning, 170;

eclosion, 172; larval growth, 164;

442
Tryphcvua, ig7
Tsetse fly, 276
Tutt, 463
Typhoid fever, 305

Uhler, on distribution, 380

Urech, 447, 448, 449

Uric acid, 124 ; as a pigment, 196

Utricularia, 257

Uzel, 442

Vagina, 140, *i4i, *i42

Valette St. George, la, 437

Vanessa, development of scales of,
*79 ; head of butterfly, ^42 ; autiopa,
298; phototropism, 353; atalanta.
color change, 214 : cardiii, disper-
sion, 366, 371 ; geographical varia-
tion, :i72 ; polycliloros, coloration,
200 ; melanism, 201 ; iirtic(r. colora-
tion, 196, 200 : melanism, 201 ; tem-
perature experiments, 205

Variation in coloration, 211, *2i2,

*2I3

Variations, blastogenic, 243 ; classes
of, 214, 241 ; congenital, 243 ; en-
vironmental, 242 ; functional, 242

Vas deferens, *i4o, 141

Vayssiere, 432, 435, 445

Vedalia (see Novins)

Veins, 58

Velum, *2 7o

Venation. 58, *59, *6o, *6i

Ventral sinus, 126, *i39

Ventral tube, *68

Ventriculus, *ii8

Verhoeff. 418, 420, 458

Verloren, 431

Vernon, 450, 453

Verson, 438

Vertex, 30

Verworn, on phototropism, 351 ; 460

Vcspa, nests of, 328, *329 ; olfactory
organ, *ioo ; sensillum, *95 ; taste
cups, *98 ; tongue, *g7

Vespidas, 328

Viallanes, 414. 425, 432, 435, 443

Vision. 108

Vitelline membrane, *i46

Vitreous body. *i09

Voeltzkow, 441

Vogler, 435

Volucella, mimicry by, ^235 : preda-
ceous, 309

Voss, 418

Vries, de, mutation theory of, 247, 453

Wagner, J., 412

^^^'lg^er, N,, 437

^^'ahl, 444

Walker. 445

Walking. 56

Wallace, on mimicry, 226 ; natural se-
lection, 238; 450, 452, 461, 462

Walsh, on losses through insects,
394 ; 403

Walter, on mouth parts, 42, 415

Walton, on meron, 51, 417

Warning coloration, 221

Wasmann, on myrmecophilism, 340 ;
458. 460, 461

Wasps, 328

Watase, 428

Wax. glands, 83 ; pincers, *270, 271

Webster, on dispersal, 368, 378, 381,
382 : losses through insects, 394 :
405 : 4SI, 454, 457, 462, 463

\\^edde, 415

Weed, on birds in relation to insects,
286. 287, 289, 291, 456

Weinland, 428

Weismann. on acquired characters.

INDEX

485

243 ; congenital variations, 243 ;
imaginal buds, 180; instinct, 361 ;
somatogenic variations, 241 ; tem-
perature experiments, 204 ; use and
disuse, 242 ; 422. 439, 442, 446, 448,
449, 4SI, 452, 453, 460

West, T., 416

Westwood, on Bvachinus, 82 : 410,
411

Wheeler, on harvesting ants, 340 :
Malpighian tubes, 123 ; tropisms,
345, 346, 348, 349, 355: 419, 430.
433. 441. 45S. 459. 460

White, F. B., 418, 445

White grubs, 398

Whitman, 460

Whymper, on distribution, 366, 462

Wielowiejski, von, 432, 433, 438. 443

Wilcox, 439, 455

Wilde, 429

Will, F., on taste, 96, 427

Will, L., 437, 440

Williams, 434, 445

Wilson, 442

Wings, 57 ; folding of, 61, *62 ; modifi-

cations, 58 ; muscles. *65 ; vibration,

63, 103
Wistinghausen, von. 436
Witlaczil, 422, 430, 440, 443
Wollaston, on beetles of Madeira Ids.,

371
Wood, T. W., 446
Wood-Mason, 411
Woodward, 441
Worker, ant, 330, 331 ; bee, *32i, 327,

328 ; termite, *3i6, 318 ; wasp, 329

Xanthophyll, as a pigment, 195. 215

Xenouciira. *386

Xiphidhint, stridulation of. 105

Yellow fever, 304

Yolk, *i46, *i47

Young, on luminosity, 132

Yucca, pollination of, *264, *265, 266

Zaitlia, 191
Zander, 421
Zimmermann, 432
Zittel. von, 413

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