oman | |S oem |= one |= omni | |
2 commen | | =- 2 memes | | = 2 moments || =
amma | | 2 emma | | 2 sae | |
eas || SS memes | | a o meee | |
oct |
SMITHSONIAN
SCIENTIFIC SERIES
Editor-in-chief
CHARLES GREELEY ABBOT, D.Sc.
Secretary of the
Smithsonian Institution
Published by
SMITHSONIAN INSTITUTION SERIES, Inc.
NEW YORK
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INSECTS
THEIR WAYS AND MEANS
OF LIVING,
By
Ropert Evans Snopcrass
United States Bureau of Entomology
VOLUME FIVE
OF THE
SMITHSONIAN SCIENTIFIC SERIES
1930
CopyRIGHT 1930, BY
SMITHSONIAN INSTITUTION SERIES, Inc.
{Printed in the United States of America]
All rights reserved
Copyright Under the Articles of the Copyright Convention
of the Pan-American Republics and the
United States, August 11, 1910
CONTENTS
PREFACE
THE GRASSHOPPER ;
THE GRASSHOPPER’S COUSINS :
RoacHES AND OTHER ANCIENT INSECTS
Ways ano Means oF LivinG
TERMITES
Piant Lice
THE PeErtopicaL CicaDA
Insect MetTaMoRPHOSIS .
. THe CATERPILLAR AND THE Motu
MosquiToEs AND FLIEs .
INDEX
Sens
FOR ROS SI TaHEe PO
eee. os
SIARE SOP AOS SI ANE po
PELUS TRATIONS
LIST OF PLATES
The Carolina Locust
Miscellaneous insects
The Green Apple Aphis
The Rosy Apple Aphis
The Apple-grain Aphis . . .
Nymph of the Periodical Cicada .
Newly emerged Cicada
Cicada laying eggs .
Egg nests and eggs of the Periodical Cicada
Two species of large moths.
The Cecropia Moth and the Polyphemus Moth
The Ribbed-cocoon Maker
The Peach-borer Moth . .
The Red-humped Caterpillar .
The Tent Caterpillar
LIST OF TEXT FIGURES
Young grasshoppers. .
End structures of a grasshopper’ s body .
Grasshopper laying eggs ;
Egg-pods of a grasshopper
Eggs of a grasshopper - :
Young grasshopper ememinet from the cee
Eggs of a katydid .
A young grasshopper :
The growth stages of a grasshopper :
A parasitic fly 5 is :
Blister beetles
A triungulin larva of a blister beetle
Second-stage larva of a blister beetle
Examples of Arthropoda
A “singing” grasshopper
Another “‘singing” grasshopper
The feet of Orthoptera
Sound-making organs of a meadow grasshopper
. Frontispiece
28
154
160
170
184
192
198
212
228
230
252
254
260
262
19.
20. Auditory organ of a katydid .
21. A bush katydid . :
22. The oblong-winged katydid
23. The angular-winged katydid .
24. The true katydid
25. The katydid in various attitudes :
26. Sound-making organs of the eos
27. Aconehead katydid
28. The robust katydid eer
29. The common meadow katydid
jo. The handsome meadow katydid .
31. The slender meadow katydid .
32. The Coulee cricket . ;
33- Wings of a tree cricket
Mig Ainge Gs - . -
35. The striped ground cricket
36. The common black cricket
37- The snowy tree cricket i
38. Antennal marks of the tree crickets :
39. The narrow-winged tree cricket .
40. A broad-winged tree cricket
41. Back glands of a tree cricket .
42. The jumping bush cricket
43. The common walking-stick insect
44. A gigantic walking-stick insect
45. A leaf insect Seas?
46. The praying mantis
47. A shield-bearing mantis
48. Egg case of a mantis
49. Common household roaches
so. Eggcasesofroaches . .
51. Young of the Croton bug .
52. The house centipede
53. Wings of acockroach .
54. A Paleozoic forest .
55. Fossil roaches
56. Early fossil insects .
57. Machilis .
58. Dragonflies . . .
59. A young dragonfly .
60. A mayfly
61. A young mayfly
62. The relation of the germ cells and body cells
63. External structure of an insect 2
64. Leg of a young grasshopper
Sound-making organs and ears of a conehead katydid
. Legs of a honeybee
Head and mouth parts of a grasshopper
Internal organs of a grasshopper .
Alimentary canal of a grasshopper
Heart of an insect .
Respiratory system of a caterpillar
The brain of a grasshopper
Nervous system of a grasshopper
Reproductive organs of an insect
Ovipositor of a race
Termites
Termite work in a piece of wood .
Worker and soldier castes and young of a termite
Heads of termite soldiers .
Winged caste of a termite . :
Short-winged reproductive caste of a termite
A wingless termite queen .
Termite king and queen
Wing of an ordinary termite .
Wings of a Mastotermes :
Section of an underground termite nest .
Four types of termite nests
Large termite nest .
Group of aphids feeding
How an aphis feeds 2
Section of the beak of an aphis
Aphis eggs
Aphis eggs just before hatching
Young aphis emerging from the egg .
Young aphids on apple buds . ie
Young of three species of apple aphids .
Apple leaves infested by green ne itis ;
The green apple aphis . ;
The rosy apple aphis on apple
The rosy apple aphis on plantain
Male and female of the rosy apple aphis
Some common aphids of the garden .
A ladybird beetle :
The aphis-lion ;
The golden-eye, Chry sopa :
Larva of a syrphus fly oe on aphids
Adult syrphus flies .
A parasitized aphis_—.
An aphis parasite, Aphidius
A female Aphidius i inserting an egg ina living aphis
Parasitized aphids on parasite cocoons
A parasitized lady-beetle larva
A common cicada su Nye
106
108
109
112
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120
2)
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126
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138
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145
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169
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173
174
176
176
177
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178
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179
181
183
149.
1So.
154.
155.
156.
ST
159.
Young nymph of the periodical cicada
Older nymph of the periodical cicada
Underground cells of the periodical cicada .
Fore leg of a cicada nymph
Cicada turrets :
Transformation of the cicada -
Two forms of the periodical cicada
Male of the periodical cicada .
The head and beak of a cicada
The sucking organ of a cicada
Section of a cicada’s body
Sound-making organs of a cicada
Egg and newly-hatched nymph of the cicada
Young cicada nymph :
Moths of the fall webworm :
The celery ca etl and py :
The Luna moth :
Life of a cutworm
A maybeetle and its grub
Life stages of a lady-beetle
Life stages of a wasp
A dragonfly nymph
Various habitats of plant- feeding caterpillars
External structure of a caterpillar
Adult and larval forms of beetles
Diagram of insect metamorphosis
Springtails :
A bristletail, Thermobia
The relation of a pupa to other insect t forms
Muscle attachment on the body wall
Young tent caterpillars
Eggs and newly-hatched tent caterpillars
First tent of young tent caterpillars .
Young tent caterpillars on a sheet of silk
Mature tent caterpillars feeding .
Mature tent caterpillars a:
Twigs denuded by tent caterpillars .
A tent caterpillar jumping from a tree
Cocoon of a tent caterpillar
Head of a tent caterpillar .
Jaws of a tent caterpillar .
Internal organs of a caterpillar
The spinning organs of a caterpillar .
The alimentary canal of a tent caterpillar
Crystals formed in the Malpighian tubules .
The fat-body of a caterpillar . :
Transformation of the tent caterpillar
186
187
188
190
192
196
200
200
202
204
206
Beit)
220
224
DOF
229
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DAN
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263
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278
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282
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287
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294
160.
161.
162.
163.
164.
165.
166.
167.
168.
169.
170.
17.
172
IRs
174.
alse
176.
177.
178.
179.
180.
181.
132.
183.
184.
185.
186.
Contents of the pupal blood
Moths of the tent caterpillar .
Head of a tent caterpillar moth
Head of a peach borer moth
Transformation of the alimentary canal
Reproductive organs of a female moth
Young tent caterpillars in the egg
A robber fly . :
Wings of insects
The black horsefly .
Mouth parts of a horsefly .
Structure of a fly maggot .
Rat-tailed maggots
Larva and pupa of a horsefly .
Life stages of a mosquito .
Structure of a mosquito larva
Mouth parts of a mosquito
A male mosquito
Mosquito larvae
Mosquito pupae :
The female malaria mosquito :
Feeding positions of mosquito la1vae
Life stages of the house fly
Head and mouth parts of the koma: Hy :
Head of the stable fly .
A tsetse fly .
Head and nonce parts ate thet tsetse Ay
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INSECTS
THEIR WAYS AND MEANS
OF LIVING
PREFACE
In the early days of zoology there were naturalists who
spent much time out of doors observing the ways of the
birds, the insects, and the other creatures of the fields and
woods. These men were not steeped in technical learning.
Nature was a source of inspiration and a delight to them;
her manifestations were to be taken for granted and not
questioned too closely. A mind able to accept appear-
ances for truth can express itself in the words of everyday
language—for language was invented long ago when
people did not bother themselves much with facts—-and
some of those early writers, inspired direct from nature,
have left us a delightful literature based on their observa-
tions and reflections on the things of nature. The public
has liked to read the works of these men because they tell
of interesting things in an interesting way and in words
that can be understood.
At the same time there was another class of nature
students who did not care particularly what an animal did,
but who wanted to know how it was made. The devotees
of this cult looked at things through microscopes; they
dissected all kinds of creatures in order to learn their con-
struction and their structural relationships. But they
found many things on the inside of animals that had never
been named, so for these things they invented names; and
when their books were printed the public could not read
them because of the strange words they contained. More-
over, since nature does not usually embellish her hidden
works, the anatomists could not enhance their writings
with descriptive metaphors in the way the outdoor
naturalists could. Consequently, the students of struc-
ture have never come into favor with the reading public,
and their works are denounced as dry and tedious.
[i]
PREFACE
Then there arose still another group of inquiring minds.
Members of this school could not see anything worth while
in knowing merely either what an animal did or how it was
made. They devoted their efforts to discovering the
secrets of its workings. They invented instruments for
measuring the power of its muscles, for testing the nature
of the force that resides in its nerves; they made analyses
of its food and its tissues; they devised all kinds of experi-
ments for revealing the causes of its behavior. The work-
ers in this branch, the physiologists, had to have a con-
siderable grounding in physics and chemistry; conse-
quently they came to write more or less in the languages
of those sciences and to express themselves in chemical and
mathematical formulae. Their writings are hard for the
public to understand. Their statements, moreover, are
often at odds with preconceived ‘ideas, since precon-
ceived ideas are conceived in ignorance, and the public at
large does not take to this sort of thing—it cherishes above
all its inherited opinions.
Therefore the old-time naturalist is still venerated, as
he deserves to be, and those who call themselves “nature
lovers” still like to decry the laboratory worker as an evil
being who would take the beauty from nature and destroy
the soul of man. A modern writer of the old school may
sell his wares, but when something goes wrong with his
stomach or his nerves, or when his plants or his animals
are attacked by disease, it is the knowledge of the labora-
tory scientist that comes to his aid.
The reason that the specific truths of nature must be
found out in laboratories is that there are too many things
mixed together in the fields. The laboratory naturalist
endeavors to untangle the confusion of elements in the
outdoor environment and to isolate the different factors
that affect the life and behavior of an animal, in order
that he may be sure with just what he is dealing in his ef-
forts to determine the value of each one separately. By
creating a set of artificial environments in each of which
[ii]
PREFACE
only one natural factor is allowed to be operative at the
same time, he is in a position to observe correctly, after
repeated experiments, just what effects proceed from this
cause and what from that.
Nature study, in the superficial sense, may be enter-
taining. We of the present age, however, must learn to
take a deeper insight into the lives of the other living
things about us. Insects, for example, are not curiosities;
they are creatures in common with ourselves bound by
the laws of the physical universe, which laws decree that
everything alive must live by observing the same ele-
mental principles that make life possible. It is only in
the ways and means by which we comply with the condi-
tions laid down by physical nature that we differ.
Many sincere people find it difficult to believe in evolu-
tion. Their difficulty arises largely from the fact that
they look to the differences in structure between the
diverse types of living things and do not see the unity in
function that underlies all physical forms of life. Conse-
quently they do not understand that evolution means the
progressive structural divergence of the various life forms
from one another, resulting from the different ways that
each has adopted and perfected for accomplishing the
same ends. Man and the insects represent the extremi-
ties of two most divergent lines of animal evolution, and
by reason of the very disparity in structure between us the
bond of unity in function becomes all the more apparent.
A study of insects, therefore, will help us the better to
understand ourselves in so far as it helps us to grasp the
fundamental principles of life.
Some writers seem to think that the sole purpose of
writing is that it shall be read. Just as reasonable would
it be to claim that the only purpose of food is that
it shall be eaten. In the following chapters the reader
is offered an entomological menu in which the consider-
ation of nutrient value and the requirements of a balanced
meal have been given first attention. As a concession to
[ ii ]
PREFACE
palatability, however, as much as possible of the dis-
tasteful matter of technical terminology has been ex-
tracted, and an attempt has been made to avoid the pure
scientific style of literary cuisine, which forbids the use of
all those ingredients whose object is that of inflation but
which, if properly admixed, will greatly aid in the process
of digestion.
Much of the material in several chapters is taken from
articles already printed in the Annual Reports of the’
Smithsonian Institution. The original drawings of most
of the color plates and line cuts are the property of the
United States Bureau of Entomology, though some of
them are here published for the first time.
RBS:
[iv |
INSECTS
THEIR WAYS AND MEANS OF LIVING
CHAPTER
hab GRASSHOPPER
SOMETIME in spring, earlier or later according to the lati-
tude or the season, the fields, the lawns, the gardens, sud-
denly are teeming with young grasshoppers. Comical little
fellows are they, with big heads, no wings, and strong hind
legs (Fig. 1). They feed on the fresh herbage and hop
lightly here and there, as if their existence in no way in-
volved the mystery of life nor raised any questions as to
why they are here, how they came to be here, and whence
they came. Of these questions, the last is the only one
to which at present we can give a definite answer.
If we should search the ground closely at this season,
it might be possible to see that the infant and apparently
motherless grasshoppers are delivered into the visible
world from the earth itself. With this information, a
nature student of ancient times would have been satisfied
—grasshoppers, he would then announce, are bred spon-
taneously from matter in the earth; the public would
believe him, and thereafter would countenance no con-
trary opinion. There came a time in history, however,
when some naturalist succeeded in overthrowing this idea
and established in its place the dictum that every life comes
from an egg. This being still our creed, we must look for
the grasshopper’s egg.
ad
INSECTS
The entomologist who plans to investigate the lives of
grasshoppers finds it easier to begin his studies the year
before; instead of sifting the earth to find the eggs from
which the young insects are hatched in the spring, he ob-
serves the mature insects in the fall and secures a supply of
eggs freshly laid by the females, either in the field or in
cages properly equipped for them. In the laboratory then
Fic. 1. Young grasshoppers
he can closely watch the hatching and observe with ac-
curacy the details of the emergence. So, let us reverse the
calendar and take note of what the mature grasshoppers of
last season’s crop are doing in August and September.
First, however, it is necessary to know just what insect
is a grasshopper, or what insect we designate by the name;
for, unfortunately, names do not always signify the same
thing in different countries, nor is the same name always
applied to the same thing in different parts of the same
country. It happens to be thus with the term “grass-
hopper.” In most other countries they call grasshoppers
“locusts,” or rather, the truth is that we in the United
States call locusts “grasshoppers,” for we must, of course,
concede priority to Old World usage. When you read of
a “plague of locusts,” therefore, you must understand
“grasshoppers.” But a swarm of “‘seventeen-year locusts”
means quite another insect, neither locust nor grasshopper
—correctly, a cicada. All this mix-up of names and many
other misfits in our popular natural history parlance we
[2]
THE GRASSHOPPER
can blame probably on the early settlers of our States, who
bestowed upon the creatures encountered in the New
World the names of animals familiar at home; but, having
no zoologists along for their guidance, they made many
errors of identification. Scientists have sought to estab-
lish a better state of nomenclatural affairs by creating a
set of international names for all living things, but since
their names are in Latin,
or Latinized Greek, they
are seldom practicable
for everyday purposes.
Knowing now that a
grasshopper is a locust,
it only needs to be
said that a true locust
is any grasshopperlike
insect with short horns,
or antennae (see Fron-
tispiece). A similar in-
sect with long slender
antennae is either a
katydid (Figs. 23, 24),
or a member of the
cricket family (Fig. 39).
If you will collect and
Fic. 2. The end of the body of a male and
examine a few specimens a female grasshopper
of locusts, which we will The body, or abdomen, of a male (A) is
2 bluntly rounded; that of the female (B)
proceed to call grass- bears two pairs of thick prongs, which
hoppers, you may ob- constitute the egg-laying organ, or ovi-
positor (Oup)
serve that some have
the rear end of the body smoothly rounded and that others
have the body ending in four horny prongs. The second
kind are females (Fig. 2 B); the others (A) are males and
may be disregarded for the present. It is one of the pro-
visions of nature that whatever any creature is compelled
by its instinct to do, for the doing of that thing it is pro-
vided with appropriate tools. Its tools, however, unless
[3]
INSECGES
it is a human animal, are always parts of its body, or of its
jaws or its legs. The set of prongs at the end of the body
of the female grasshopper constitutes a digging tool, an
instrument by means of which the insect makes a hole in
the ground wherein she deposits her eggs. Entomologists
call the organ an ovipositor, or egg-placer. Figure 2 B
Fic. 3. A female grasshopper in the position of depositing a pod of eggs in a
hole in the ground dug with her ovipositor. (Drawn from a photograph in
U.S. Bur. Ent.)
shows the general form of a grasshopper’s ovipositor; the
prongs are short and thick, the points of the upper pair are
curved upward, those of the lower bent downward.
When the female grasshopper is ready to deposit a
batch of eggs, she selects a suitable spot, which is almost
any place in an open sunny field where her ovipositor can
penetrate the soil, and there she inserts the tip of her
organ with the prongs tightly closed. When the latter
are well within the ground, they are probably spread
apart so as to compress the earth outward, for the drilling
4]
THE GRASSHOPPER
process brings no detritus to the surface, and gradually
the end of the insect’s body sinks deeper and deeper, until
a considerable length of it is buried in the ground (Fig. 3).
Now all is ready for the discharge of the eggs. The exit
duct from the tubes of the ovary, which are filled with
eggs already ripe, opens just below and between the bases
of the lower prongs of the ovipositor, so that, when the
upper and lower prongs are separated, the eggs escape
from the passage between them. While the eggs are
being placed in the bottom of the well, a frothy gluelike
substance from the body of
the insect is discharged
over them. This sub-
stance hardens about the
eggs as it dries, but not in
a solid mass, for its frothy
nature leaves it full of
cavities, like a sponge, and
affords the eggs, and the
young grasshoppers when
they hatch, an abundance
of space for air. To the
outside of the covering
substance, while it 1s fresh
and sticky, particles of Fr Fes pods‘of = euasshopper, show
earth adhere and make a "the egas within. (Much enlarged)
finely granular coating
over the mass, which, when hardened, looks like a small
pod or capsule that has been molded into the shape of the
cavity containing it (Fig. 4). The number of eggs within
each pod varies greatly, some pods coritaining only half
a dozen eggs, and others as many as one hundred and
fifty. Each female also deposits several batches of eggs,
each lot in a separate burrow and pod, before her egg
supply is exhausted. Some species arrange the eggs
regularly in the pods, while others cram them in hap-
hazard.
[5]
INSECTS
The egg of a grasshopper is elongate-oval in shape
(Fig. 5), those of ordinary-sized grasshoppers being about
three-sixteenths of an inch in length, or a little longer.
The ends of the
eggs are rounded
or bbhamn tly
pointed, and the
lower extremity
(the egg being
generally placed
on end) appears
to have a small
cap over it. One
side of the egg is
always more
curved than the
opposite side,
Fic. 5. Eggs of a grasshopper; one split at the upper ven i il
end, showing the young grasshopper about to emerge which may be al-
most straight.
The surface is smooth and lustrous to the naked eye, but
under the microscope it 1s seen to be marked off by slightly
raised lines into many small polygonal areas.
Within each egg is the germ that is to produce a new
grasshopper. This germ, the living matter of the egg, is
but a minute fraction of the entire egg contents, for the
bulk of the latter consists of a nutrient substance, called
yolk, the purpose of which is to nourish the embryo as it
develops. The tiny germ contains in some form, that even
the strongest microscope will not reveal, the properties
which will determine every detail of structure in the future
grasshopper, except such as may be caused by external cir-
cumstances. It would be highly interesting to follow the
course of the development of the embryo insect within the
egg, and most of the important facts about it are known;
but the story would be entirely too long to be given here,
though a few things about the grasshopper’s development
should be noted.
[6]
THE GRASSHOPPER
The egg germ begins its development as soon as the eggs
are laid in the fall. In temperate or northern latitudes,
however, low temperatures soon intervene, and develop-
ment is thereby checked until the return of warmth in the
spring—or until some entomologist takes the eggs into an
artificially heated laboratory. The eggs of some species of
grasshoppers, if brought indoors before the advent of
freezing weather and kept in a warm place, will proceed
with their development, and young grasshoppers will
emerge from them in about six weeks. On the other hand,
the eggs of certain species, when thus treated, will not
hatch at all; the embryos within them reach a certain
stage of development and there they stop, and most of
them never will resume their growth unless they are sub-
jected to a freezing temperature! But, after a thorough
chilling, the young grasshoppers will come out, even in
January, if the eggs are then transferred to a warm place.
To refuse to complete its development until frozen and
then warmed seems like a preposterous bit of inconsistency
on the part of an insect embryo; but the embryos of many
kinds of insects besides the grasshopper have this same
habit from which they will not depart, and so we must con-
clude that it is not a whim but a useful physiological prop-
erty with which they are endowed. The special deity of
nature delegated to look after living creatures knows well
that Boreas sometimes oversleeps and that an egg laid in
the fall, if it depended entirely on warmth for its develop-
ment, might hatch that same season if mild weather should
continue. And then, what chance would the poor fledgling
have when a delayed winter comes upon it? None at all,
of course, and the whole scheme for perpetuation of the
species would be upset. But, if it is so arranged.that
development within the egg can reach completion only
after the chilling effect of freezing weather, the emergence
of the young insect will be deferred until the return of
warmth in the spring, and thus the species will have a
guarantee that its members will not be cut down by unsea-
lira
INSECTS
sonable hatching. There are, however, species not thus in-
sured, and these do suffer losses from fall hatching every
time winter makes a late arrival. Eggs laid in the spring
are designed to hatch the same season, and the eggs of
species that live in warm climates never require freezing
for their development.
The tough shell of the grasshopper’s
egg is composed of two distinct coats, an
outer, thicker, opaque one of a pale
brown color, and an inner one which is
thin and transparent. Just before hatch-
ing, the outer coat splits open in an ir-
regular break over the upper end of the
egg, and usually half or two-thirds of the
way down the flat side. This outer coat
can easily be removed artificially, and
the inner coat then appears as a glisten-
ing capsule, through the semitransparent
walls of which the little grasshopper in-
side can be seen, its members all tightly
folded beneath its body. When the
hatching takes place normally, however,
both layers of the eggshell are split, and
ae eee the young grasshopper emerges by slowly
its eggshell making its way out of the cleft (Fig. 6).
Newly-hatched grasshoppers that have
come out of eggs which some meddlesome investigator has
removed from their pods for observation very soon proceed
to shed an outer skin from their bodies. This skin, which is
already loosened at the time of hatching, appears now as a
rather tightly fitting garment that cramps the soft legs and
feet of the delicate creature within it. The latter, however,
after a few forward heaves of the body, accompanied by
expansions of two swellings on the back of the neck (Fig.
6), succeeds in splitting the skin over the neck and the
back of the head, and the pellicle then rapidly shrinks and
slides down over the body. The insect, thus first exposed,
[8]
THE GRASSHOPPER
liberates itself from the shriveled remnant of its hatching
skin, and becomes a free new creature in the world. Being
a grasshopper, it proceeds to jump, and with its first ef-
forts clears a distance of four or five inches, something like
fifteen or twenty times the length of its own body.
When the young locusts hatch under normal undisturbed
conditions, however, we must picture them as coming out
of the eggs into the cavernous spaces of the egg pod, and
all buried in the earth. They are by no means yet free
creatures, and they can gain their liberty only by burrow-
ing upward until they come out at the surface of the
ground. Of course, they are not very far beneath the sur-
face, and most of the way will be through the easily pene-
trated walls of the cells of the egg covering. But above the
latter is a thin layer of soil which may be hard-packed
after the winter’s rains, and breaking through this layer
can not ordinarily be an easy task. Not many entomolo-
gists have closely watched the newly-hatched grasshopper
emerge from the earth, but Fabre has studied them under
artificial conditions, covered with soil in a glass tube. He
tells of the arduous efforts the tiny creatures make, press-
ing their delicate bodies upward through the earth by
means of their straightened hind legs, while the vesicles on
the back of the neck alternately contract and expand to
widen the passage above. All this, Fabre says, is done
before the hatching skin 1s shed, and it is only after the
surface is reached and the insect has attained the freedom
of the upper world that the inclosing membrane is cast off
and the limbs are unencumbered.
The things that insects do and the ways in which they do
them are always interesting as mere facts, but how much
wiser might we be if we could discover why they do them!
Consider the young locust buried in the earth, for example,
scarcely yet more than an embryo. How does it know
that it is not destined to live here in this dark cavity in
which it first finds itself? What force activates the mech-
anism that propels it through the earth? And finally,
Lg]
INSECTS
what tells the creature that liberty is to be found above,
and not horizontally or downward? Many people believe
that these questions are not to be answered by human
knowledge, but the scientist has faith in the ultimate solu-
tion of all problems, at least in terms of the elemental
forces that control the activities of the universe.
We know that all the activities of animals depend upon
the nervous system, within which a form of energy resides
that is delicately responsive to external influences. Any
kind of energy harnessed to a physical mechanism will
produce results depending on the con-
struction of the mechanism. So the ef-
fects of the nerve force within a living
animal are determined by the physical
structure of the animal. An instinctive
action, then, is the expression of nerve
energy working in a particular kind of
machine. It would involve a digression
too long to explain here the modern con-
ception of the nature of instinct; it is
SX sufficient to say that something in the
surroundings encountered by the newly-
PA
aes hatched grasshopper, or some substance
generated within it, sets its nerve energy
into action, that the nerve energy work-
ing on a definite mechanism produces the
motions of the insect, and that the
Fic. 7. Eggs of a
species of katydid at-
tached to a twig; the
young insect in suc-
cessive stages of emerg-
ing from an egg; and
the newly-hatched
young
mechanism is of such a nature that it
works against the pull of gravity. Hence
the creature, if normal and healthy in all
respects, and if the obstacles are not too
great, arrives at the surface of the ground
as inevitably as a submerged cork comes
to the surface of the water. Some
readers will object that an idea like this destroys the
romance of life, but whoever wants romance must go to
the fiction writers; and even romance is not good fiction
[10]
THE GRASSHOPPER
unless it represents an effort to portray some truth.
Insects hatched from eggs laid in the open may begin life
under conditions a little easier than those imposed upon
the young grasshopper. Here, for example (Fig. 7), are
some eggs of insects belonging to the katydid family.
They look like flat oval seeds stuck in overlapping rows,
some on a twig, others along the edge of a leaf. When
about to hatch, each egg splits halfway down one edge and
crosswise on the exposed flat surface, allowing a flap to
open on this side, which gives an easy exit to the young
insect about toemerge. The latter is inclosed in a delicate
transparent sheath, within which its long legs and an-
tennae are closely doubled up beneath the body; but when
the egg breaks open, the sheath splits also, and as the
young insect emerges it sheds the skin and leaves it within
the shell. The new creature has nothing to do now but to
stretch its long legs, upon which it walks away, and, if
given suitable food, it will soon be contentedly feeding.
Let us now take closer notice of the little grasshoppers
(Fig. 8) that have just come into the great world from the
dark subterranean chambers of their egg-pods. Such an
inordinately large head surely, you would say, must over-
balance the short tapering body, though supported on
three pairs of legs. But, whatever the proportions, nature’s
works never have the appearance of being out of drawing;
because of some law of recompense, they never give you
the uneasy feeling of an error in construction. In spite of
its enormous head, the grasshopper infant is an agile crea-
ture. Its six legs are all attached to the part of the body
immediately behind the head, which is known as the
thorax (Fig. 63, Th), and the rest of the body, called the
abdomen (Ab), projects free without support. An insect,
according to its name, is a creature divided into parts, for
“insect” means “‘in-cut.’’ A fly or a wasp, therefore, comes
closer to being the ideal insect; but, while not literally in-
sected between the thorax and abdomen, the grasshopper,
like the fly and the wasp and all other insects, consists of a
Parl
INSECTS
head, a thorax bearing the legs, and a terminal abdomen
(Fig. 63). On the head is located a pair of long, slender
antennae (Ant) and a pair of large eyes (E). Winged in-
sects have usually two pairs of wings attached to the back
of the thorax (W2, W3).
The outside of the insect’s body, instead of presenting a
continuous surface like that of most animals, shows many
encircling rings where the hard integument appears to be
infolded, as it really is, dividing each body region except
the head into a series of short overlapping sections. These
body sections are called
segments, and all insects
and their relatives, in-
cluding the centipedes,
the shrimps, lobsters, and
= crabs, and the scorpions
and spiders, are seg-
mented animals. The in-
sect’s thorax consists of
three segments, the first
of which carries the first
pair of legs, the second
the middle pair of legs, and the third the hind pair of legs.
The abdomen usually consists of ten or eleven segments,
but generally has no appendages, except a pair of small
peglike organs at the end known as the cerci, and, in the
adult female, the prongs of the ovipositor (Fig. 2 B), which
belong to the eighth and ninth segments.
The head, besides carrying the antennae (Fig. 63, 41),
has three pairs of appendages grouped about the mouth,
which serve as feeding organs and are known collectively
as the mouth parts. The presence of four pairs of append-
ages on the head raises the question, then, as to why the
head is not segmented like the thorax and the abdomen.
At an early stage of embryonic growth the head 7s seg-
mented, and each pair of its appendages is borne by a
single segment, but the head segments are later condensed
[12]
Fic. 8. A young grasshopper, or nymph,
in the second stage after hatching
THE GRASSHOPPER
into the solid capsule of the cranium. Thus we see that
the entire body of an insect is composed of a series of seg-
ments which have become grouped into the three body
regions. Note that the insect does not have a
“nose” or any breathing apertures on its head.
It has, however, many nostrils, called spiracles
(Fig. 70, Sp), distributed along each side of
the thorax and the abdomen. Its breathing ~
system is quite different from ours, but will wag
be described in another chapter treating of
the internal organization (page 114).
Most young insects grow rapidly be-
cause they must compress their entire
lives within the limits of a
single season. Generally a few
weeks suffice for them to reach
maturity, or at least the ma-
ture growth of the form in
which they leave the egg, for,
as we shall see, many in-
sects complicate their lives
by having several different
stages, in each of which
they present quite a dif-
ferent form. The grass-
hopper, however, is an in-
sect that grows by
a direct course from
its form at hatch-
ing to that of the
adult, and at all
stages it Is recog-
nizable as a grass-
hopper (Fig. 9). A
young moth, on Fic. 9. The metamorphosis of a grasshopper,
Melanoplus atlanus, showing its six stages of develop-
the other hand, ment from the newly-hatched nymph to the fully-
hatching In the winged adult. (Twice natural size)
Pea
INSEGES
form of a caterpillar, has no resemblance to its parent, and
the same is true of a young fly, which is a maggot, and of
the grublike young of a bee. The changes of form that
insects undergo during their growth are known as meta-
morphosis. There are different degrees of such trans-
formation; the grasshopper and its relatives have a simple
metamorphosis.
An insect differs from a vertebrate animal in that its
muscles are attached to its skin. Most species of insects
have the skin hardened by the formation of a strong out-
side cuticula to give a firm support to the muscles and to
resist their pull. This function of the cuticula, however,
imposes a condition of permanency on it after it is once
formed. As a consequence the growing insect is con-
fronted with the alternatives, after reaching a certain
size, of being cramped to death within its own skin, or of
discarding the old covering and getting a new and larger
one. It has adopted the course of expediency, and peri-
odically mo/ts. Thus it comes about that the life of an
insect progresses by stages separated by the molts, or the
shedding of the cuticula.
The grasshopper makes six molts between the time of
hatching and its attainment of the final adult form, a
period of about six weeks, and goes through six post-
embryonic stages (Fig. 9). The first molt is the shedding
of the embryonic skin, which, we have seen, takes place
normally as soon as the young insect emerges from the
earth. The grasshopper now lives uneventfully for about
a week, feeding by preference on young clover leaves, but
taking almost any green thing at hand. During this time
its abdomen lengthens by the extension of the membranes
between its segments, but the hard parts of the body do
not change either in size or in shape. At the end of seven
or eight days, the insect ceases its activities and remains
quiet for a while until the cuticula opens in a lengthwise
split over the back of the thorax and on the top of the
head. ‘The dead skin is then cast off, or rather, the grass-
[14]
THE GRASSHOPPER
hopper emerges from it, carefully pulling its legs and an-
tennae from their containing sheaths. The whole process
consumes only a few minutes. The emerged grasshopper
is now entering its third stage after hatching, but the shed-
ding of the hatching skin is usually not counted in the
series of molts, and the first subsequent molt, then, we will
say, ushers it into its second stage of aboveground life.
In this state the insect is different in some respects from
what it was in the first stage: it is not only larger, but the
body is longer in proportion to the size of the head, as are
also the antennae, and particularly the hind legs. Again
the insect becomes active and pursues its routine life for
another week; then it undergoes a second molting, ac-
companied by changes in form and proportions that make
it a little more like a mature grasshopper. After shedding
its cuticula on three succeeding occasions, it appears in the
adult form, which it will retain throughout the remainder
of its life.
The grasshopper developed its legs, its antennae, and
most of its other organs while it was in the egg. It was
hatched, however, without wings, and yet, as everyone
knows, most full-grown grasshoppers have two pairs of
wings (Fig. 63, W2, W;), one pair attached to the back of
the middle segment of the thorax, the other to the third
segment. It has acquired its wings, therefore, during its
growth from youth to maturity, and by examining the
insect in its different stages (Fig. 9), we may learn some-
thing of how the wings are developed. In the first stage,
evidence of the coming wings is scarcely apparent, but in
the second, the lower hind angles of the plates covering the
back of the second and third thoracic segments are a little
enlarged and project very slightly as a pair of lobes. In
the third stage, the lobes have increased in size and may
now be suspected of being rudiments of the wings, which,
indeed, they are. At the next molt, when the insect
enters its fourth stage, the little wing pads are turned
upward and laid over the back, which disposition not only
Nera |
INSECTS
reverses the natural position of the wings, but brings the
hind pair outside the front pair. At the next molt, the
wings retain their reversed positions, but they are once
more increased in size, though they still remain far short
of the dimensions of the wings of an adult grasshopper.
At the time of the last molt, the grasshopper takes a
position with its head downward on some stem or twig,
which it grasps securely with the claws of its feet. Then,
when its cuticula splits, it crawls downward out of the
skin. Once free, however, it reverses its position, and the
wisdom of this act is seen on observing the rapidly expand-
ing and lengthening wings, which can now hang down-
ward and spread out freely without danger of crumpling.
In a quarter of an hour the wings have enlarged from small,
insignificant pads to long, thin, membranous fans eat
reach to the tip of the body. This rapid growth 1s ex-
plained by the fact that the wings are hollow sacs; their
visible increase in size is a mere distention of their wrinkled
walls, for they were fully formed beneath the old cuticula
and lay there before the molt as little crumpled wads,
which, when released by the removal of the cases that
cramped them, rapidly spread out to their full dimensions.
Their thin, soft walls then come together, dry, and harden,
and the limp, flabby bags are converted into organs of
flight.
It isimportant to understand the process of molting as
it takes place in the grasshopper, because the processes of
metamorphosis, such as those which accomplish the trans-
formation of a caterpillar into a butterfly, differ only in
degree from those that accompany the shedding of the
skin between any two stages of the grasshopper’s life. The
principal growth of the insect 1s made during those resting
periods preceding the molts. It is then that the various
parts enlarge and make whatever alterations in shape they
are to have. The old cuticula is already loosened and the
changes go on beneath it, while at the same time a new
cuticula is generated over the remodeled surfaces. The
[ 16 |
THE GRASSHOPPER
increased size of the antennae, legs, and wings causes them
to be compressed in the narrow space between the new and
the old cuticula, and, when the latter is cast off, the
crumpled appendages expand to their full size. The ob-
server then gets the 1 impression that he is witnessing a sud-
den transformation. The impression, however, is a false
one; what is really going on is comparable with the display
of new dresses and coats that the merchant puts into his
show windows at the proper season for their use, which he
has just unpacked from their cases but which were pro-
duced in the factories long before.
The adult grasshoppers lead prosaic lives, but, like a
great many good people, they fill the places allotted to
them in the world, and see to it that there will be other
occupants of their own kind for these same places when
they themselves are forced to vacate. If they seldom fly
high, it is because it 1s not the nature of locusts to do so;
and if, in the East, one does sometimes soar above his
fellows, he accomplishes nothing, unless he happens to
land on the upper regions of a Manhattan skyscraper,
when he may attain the glory of a newspaper mention of
his exploit—most likely, though, with his name spelled
wrong.
On the other hand, like all common folk born to ob-
scurity and enduring impotency as individuals, the grass-
hopper in masses of his kind becomes a formidable creature.
Plagues of locusts are of historic renown in countries south
of the Mediterranean, and even in our own country hordes
of grasshoppers known as the Rocky Mountain locust did
such damage at one time in the States of the Middle West
that the government sent out a commission of entomolo-
gists to investigate them. This was in the years following
the Civil War, when, for some reason, the locusts that
normally inhabited the Northwest, east of the Rocky
Mountains, became dissatisfied with their usual breeding
grounds and migrated in great swarms into the States of
the Mississippi valley, where they brought destruction to
[nz]
INSECTS
all kinds of crops wherever they chanced to alight. In
the new localities they would lay their eggs, and the young
of the next season, after acquiring their wings, would
migrate back toward the- ‘region whence the parent swarm
had come the year before.
The entomologists of the investigating commission in
the year 1877 tell us that on a favorable day the migrating
locusts “rise early in the forenoon, from eight to ten
o'clock, and settle down to eat from four to five in the
afternoon. The rate at which they travel is variously
estimated from three to fifteen or twenty miles an hour,
determined by the velocity of the wind. Thus, insects
which began to fly in Montana by the middle of July may
not reach Missouri until August or early September, a
period of about six weeks elapsing before they reach their
destined breeding grounds.” The appearance of a swarm
in the air was described as being like that of “‘a vast body
of fleecy clouds,’ ” or a “cloud of snowflakes,” the mass of
flying insects “often having a depth that reaches from
comparatively near the ground to a height that baffles
the keenest eye to distinguish the insects in the upper
stratum.” It was estimated that the locusts could fly
at an elevation of two and a half miles from the general
surface of the ground, or 15,000 feet above sea level. The
descending swarm falls upon the country “like a plague
or a blight,” said one of the entomologists of the com-
mission, Dr. C. V. Riley, who has left us the following
graphic picture of the circumstances:
The farmer plows and plants. He cultivates in hope, watching his
growing grain in graceful, wave-like motion wafted to and fro by the
warm summer winds. The green begins to golden; the harvest is at
hand. Joy lightens his labor as the fruit of past toil is about to be
realized. The day breaks with a smiling sun that sends his ripening
rays through laden orchards and: promising fields. Kine and stock
of every sort are sleek with plenty, and all the earth seems glad. The
day grows. Suddenly the sun’s‘face is darkened, and clouds obscure
the sky. The joy of the morn gives way to ominous fear. The day
closes, and ravenous locust-swarms have fallen upon the land. The
[18]
THE GRASSHOPPER
morrow comes, and, ah! what a change it brings! The fertile land of
promise and plenty has become a desolate waste, and old Sol, even at
his brightest, shines sadly through an atmosphere alive with myriads
of glittering insects.
Even today the farmers of the Middle Western States
are often hard put to it to harvest crops, especially alfalfa
and grasses, from fields that are teeming with hungry
grasshoppers. By two means, principally, they seek relief
from the devouring hordes. One method 1s that of driv-
ing across the fields a device known as a “‘hopperdozer,’
which collects the insects bodily and destroys them. The
dozer consists essentially of a long shallow pan, twelve or
fifteen feet in length, set on low runners and provided with
a high back made either of metal or of cloth stretched over
a wooden frame. The pan contains water with a thin
film of kerosene over it. As the dozer is driven over the
field, great numbers of the grasshoppers that fly up before it
either land directly in the pan or fall into it after striking
the back, and the kerosene film on the water does the rest,
for kerosene even in very small quantity is fatal to the
insects. In this manner, many bushels of dead locusts
are taken often from each acre of an alfalfa field; but still
great numbers of them escape, and the dozer naturally
can not be used on rough or uneven ground, in pastures,
or in fields with standing crops. A more generally effec-
tive method of killing the pests is that of poisoning them.
A mixture 1s prepared of bran, arsenic, cheap molasses, and
water, sufficiently moist to adhere in small lumps, with
usually some substance added which is supposed to make
the “mash” more attractive to the insects. The deadly
bait is then finely broadcast over the infested fields.
While such methods of destruction are effective, they
bear the crude and commonplace stamp of human ways.
See how the thing is done when insect contends against
insect. A fly, not an ordinary fly, but one known to
entomologists as Sarcophaga kellyi (Fig. 10), being
named after Dr. KF. O. G. Kelly, who has given us a
[19 |
INSECTS
description of its habits, frequents the fields in Kansas
where grasshoppers are abundant. Individuals of this
fly, according to Doctor Kelly’s account, are often seen
to dart after grass-
hoppers on the
wing and _ strike
against them.
The stricken in-
sect at once drops
to the ground.
Examination re-
veals no physical
injury to the vic-
tim, but on a close
inspection there
Fic. 10. A fly whose larvae are parasitic on grass- may be found ad-
hoppers, Sarcophaga kellyi. (Much enlarged) hering to the un-
der surface of a
wing several tiny, soft, white bodies. Poison pills?
Pellets of infection? Nothing so ordinary. The things
are alive, they creep along the folds of the wing toward
its base—they are, in short, young flies born at the instant
the body of the mother fly struck the wing of the grass-
hopper. But a young fly would never be recognized as the
offspring of its parent; it is a wormlike creature, or maggot,
having neither wings nor legs and capable of moving only
by extending and contracting its soft, flexible body ae
182 D).
In form, the young Sarcophaga kellyi does not differ par-
ticularly from the maggots of other kinds of flies, but the
Sarcophaga flies in general differ from most other insects
in that their eggs are hatched within the bodies of the
females, and these flies, therefore, give birth to young
maggots instead of laying eggs. The female of Sarcophaga
kellyi, then, when she launches her attack on the flying
grasshopper, is munitioned with a load of young maggots
ready to be discharged and stuck by the moisture of their
[ 20 |
THE GRASSHOPPER
bodies to the object of contact. The young parasites thus
palmed off by their mother on the grasshopper, who has no
idea what has happened to him, make their way to the base
of the wing of their unwitting host, where they find a ten-
der membranous area which they penetrate and thereby
enter the body of the victim. Here they feed upon the
liquids or tissues of the now helpless insect and grow to
maturity in from ten to thirty days. Meanwhile, how-
ever, the grasshopper has died; and when the parasites are
full grown, they leave the dead body and bury themselves
in the earth to a depth of from two to six inches. Here
they undergo the transformation that will give them the
form of their parents, and when they attain this stage they
issue from the earth as adult winged flies. Thus, one
insect 1s destroyed that another may live.
Is the Sarcophaga kellyi a creature of uncanny shrewd-
ness, an ingenious 1 inventor of a novel way for avoiding the
work of caring for her offspring? Certainly her method
is an improvement on that of leaving one’s newborn prog-
eny on a stranger’s doorstep, for the victim of the fly must
accept the responsibility thrust upon him whether he will
or not. But Doctor Kelly tells us that the flies do not
know grasshoppers from other flying insects, such as
moths and butterflies, in which their maggots do not find
congenial hosts and never reach maturity. Furthermore,
he says, the ardent fly mothers will go after pieces oF
crumpled paper thrown into the wind and will discharge
their maggots upon them, towhich the helpless infants cling
without hope of survival. Such performances, and many
similar ones that could be recounted of other insects, show
that instinct is indeed blind and depends, not upon fore-
sight, but on some mechanical action of the nervous sys-
tem, which gives the desired result in the majority of cases
but which is not guarded against unusual conditions or
emergencies.
When we consider the many perfected instincts among
insects, we are often shocked to find apparent cases of
Lan |
INSECTS
flagrant neglect on the part of nature for her creatures,
where it would seem a remedy for their ills would be easy
to supply.
In human society of modern times the criminal ‘element
has come to look no different from the law-abiding class of
citizens. Formerly, if we may judge from pictures and
stage representations, thieves and thugs were tough-look-
ing individuals that could not be mistaken on sight, but
Fic. 11. Two blister beetles whose larvae feed on grasshopper
eggs. (Twice natural size)
A, Epicauta marginata. B, Epicauta vittata
today our bandits are spruce young fellows that pass with-
out suspicion in the crowd. And thus it is with the in-
sects, all unsuspectingly one may be rubbing elbows with
another that overnight will despoil his home, or that has
already committed some act of violence against his neigh-
bor. Here, for example e, in the same field with the grass-
hoppers, is an innocent-looking beetle, about three-
quarters of an inch in length, black and striped with yellow
(Fig. 11 B). His entomological name is Epicauta vittata,
which, of course, means nothing to a locust. He is now
a vegetarian, but in his younger days he ravished the nest
of a grasshopper and devoured the eggs, and his progeny
will do the same again. Epicauta and others of his family
Pee)
THE GRASSHOPPER
are known as “blister beetles’? because they have a sub-
stance in their blood, called cantharidin, famous for its
blistering properties and formerly much used in medicine.
The female blister beetles of several species lay their eggs
in the ground in regions frequented by grasshoppers, where
the young on hatching can find the egg-pods of the latter.
The little beetles (Fig. 12) hatch in a form quite different
from that of their parents and are known as /riungulins
because of two spines beside the single claw on each of
their feet, which gives the foot a three-clawed appearance.
Though the young scapegrace of a beetle is a housebreaker
and a thief, his story, like that of too many criminals,
unfortunately, makes interesting read-
ing, and the following account is taken, ¥
with a few omissions, from the history ;
of Epicauta vittata as given by Dr.
CoV Riley:
Ss
oe
From July till the middle of October the
eggs are being laid in the ground in loose, irreg-
ular masses of about 130 on an average—the
female excavating a hole for the purpose, and
afterwards covering up the mass by scratching
with her feet. She lays at several different =I
intervals, producing in the aggregate probably
from four to five hundred ova. She prefers for R
purposes of oviposition the very same warm
sunny locations chosen by the locusts, and
doubtless instinctively places her eggs near
those of these last, as I have on several occa- Fic. 12. The _ first-
sions found them in close proximity. In the — stage Jarva, or “triun-
course of about 10 days—more or less, accord- ae ote, coped
3 ; : ister beetle (fig. 11
ing to the temperature of the ground—the g). Enlarged 12 times
first larva or triungulin hatches. These little (From Riley)
triungulins (Fig. 12), at first feeble and per-
fectly white, soon assume their natural light-brown color and commence
to move about. At night, or during cold or wet weather, all those
of a batch huddle together with little motion, but when warmed by
the sun they become very active, running with their long legs over the
ground, and prying with their large heads and strong jaws into every
crease and crevice in the soil, into which, in due time, they burrow
[231]
\
INSECTS
and hide. As becomes a carnivorous creature whose prey must be
industriously sought, they display great powers of endurance, and
will survive for a fortnight without food in a moderate temperature.
Yet in the search for locust eggs many are, without doubt, doomed
to perish, and only the more fortunate succeed in finding appropriate
diet.
Reaching a locust egg-pod, our triungulin, by chance, or instinct,
or both combined, commences to burrow through the mucous neck,
or covering, and makes its first repast thereon. If it has been long
in search, and its jaws are well hardened, it makes quick work through
this porous and cellular matter, and at once gnaws away at an egg,
first devouring a portion of the shell, and then, in the course of two
or three days, sucking up the contents. Should two or more triun-
gulins enter the same egg-pod, a deadly conflict sooner or later ensues
until one alone remains the victorious possessor.
The surviving triungulin then attacks a second egg and
more or less completely exhausts its contents, when, after
about eight days from the time of its hatching, it ceases
from its feeding and enters a period of
rest. Soon the skin splits along the
back, and the creature issues in the
second stage of its existence. Very
curiously, it 1s now quite different in
appearance, being white and soft-bodied
and having much shorter legs than
before (Fig. 13). After feeding again on
the eggs for about a week, the creature
molts a second time and appears in a
still different form. Then once more,
and yet a fourth time, it sheds its skin
and changes its form. Just before the
Fic. 13. The second. fourth molt, however, it quits the eggs
stage larva of the and burrows a short distance into the
Pee ye soil, where it composes itself for a
period of retirement, and here undergoes
another molt, in which the skin is not cast of. Thus the
half-grown insect passes the winter, and in spring molts a
sixth time and becomes active again, but not for long—its
larval life is now about to close, and with another molt
| 24 ]
THE GRASSHOPPER
it changes to a pupa, the stage in which it is to be trans-
formed back into the form of its beetle parents. The final
change is accomplished in less than a week, and the
creature then emerges from the soil, now a fully-formed
striped blister beetle.
The grasshoppers’ eggs furnish food for many other
insects besides the young blister beetles. There are species
of flies and of small wasplike insects whose larvae feed in
the egg-pods in much the same manner as do the triungu-
lins, and there are still other species of general feeders
that devour the locust eggs as a part of their miscellaneous
diet. Notwithstanding all this destruction of the germs
of their future progeny, however, the grasshoppers still
thrive in abundance, for grasshoppers, like most other
insects, put their trust in the admonition that there is
safety innumbers. So many eggs are produced and stored
away in the ground each season that the whole force of
their enemies combined can not destroy them all, and
enough are sure to come through intact to render certain
the continuance of the species. Thus we see that nature
has various ways of accomplishing her ends—she might
have given the grasshopper eggs better protection in the
pods, but, being usually careless of individuals, she chose
to guarantee perpetuance with fertility.
[25]
CHAPTERS
THE GRASSHOPPER’S COUSINS
Nature’s tendency is to produce groups rather than in-
dividuals. Any animal you can think of resembles in
some way another animal or a number of other animals.
An insect resembles on the one hand a shrimp or a crab,
and on the other a centipede or a spider. Resemblances
among animals are either superficial or fundamental. For
example, a whale or a porpoise resembles a fish and lives
the life of a fish, but has the skeleton and other organs of
land-inhabiting mammals. Therefore, notwithstanding
their form and aquatic habits, whales and porpoises are
classed as mammals and not as fishes.
When resemblances between animals are of a funda-
mental nature, we believe that they represent actual blood
relationships carried down from some far-distant common
ancestor; but the determination of relationships between
animals is not always an easy matter, because it is often
dificult to know what are fundamental characters and
what are superficial ones. It is a part of the work of
zoologists, however, to investigate closely the structure of
all animals and to establish their true relationships. The
ideas of relationship which the zoologist deduces from his
studies of the structure of animals are expressed in his
classification of them. The primary divisions of the
Animal Kingdom, which is generally likened to a tree, are
called branches, or pAy/a (singular, phy/um).
The insects, the centipedes, the spiders, and the shrimps,
crayfish, lobsters, crabs, and other such creatures belong to
the phylum Arthropoda. The name of this phylum means
[ 26 ]
fHE GRASSHOPPER’S. COUSINS
“jointed-legs”’; but, since many other animals have jointed
legs, the name is not distinctive, except in that the legs of
the arthropods are particularly jointed, each being com-
posed of a series of pieces that bend upon each other in
different directions. A name, however, as everybody
knows, does not have to mean anything, for Mr. Smith
lic. 14. Examples of four common classes of the Arthropoda
A,a crab (Crustacea). B,a spider (Arachnida). C, a centipede (Chilopoda).
D, a fly (Insecta, or Hexapoda)
may be a carpenter, and Mr. Carpenter a smith. A phylum
is divided into classes, a class into orders, an order into
families, a family into genera (singular, genus), and a genus
is composed of species (the singular of which is also species).
Species are hard to define, but they are what we ordinarily
regard as the individual kinds of animals. Species are
given double names, first the genus name, and second a
specific name. For example, species of a common grass-
hopper genus named Me/anoplus are distinguished as
Melanoplus atlanus, Melanoplus femur-rubrum, Melanoplus
differentialis, etc.
[ 27 ]
INSECTS
The insects belong to the class of the Arthropoda known
as the Insecta, or Hexapoda. The word “insect,” as we
have seen, means “‘in-cut,” while ‘“‘hexapod” means “‘six-
legged” —either term, then, doing very well for insects.
The centipedes (Fig. 14 C) are the Myriapoda, or many-
footed arthropods; the crabs (A), shrimps, lobsters, and
others of their kind are the Crustacea, so called because
most of them have hard shells; the spiders (B) are the
Arachnida, named after that ancient Greek maiden so
boastful of her spinning that Minerva turned her into a
spider; but some arachnids, such as the scorpion, do not
make webs.
The principal groups of insects are the orders. The
grasshopper and its relatives constitute an order; the
beetles are an order; the moths and butterflies are another
order; the flies another; the wasps, bees, and ants still
another. The grasshopper’ s order 1 is called the Orthoptera,
the word meaning “‘straight- wings,’ * but, again, not sig-
nificant in all cases, though serving very well as a name.
The order is a group of related families, and, in the Or-
thoptera, the grasshoppers, or locusts, make one family,
the katydids another, the crickets a third; and all these 1n-
sects, together with some others less familiar, may be said
to be the grasshopper’s cousins.
The orthopteran families are notable in many ways,
some for the great size attained by their members, some
for their remarkable forms, and some for musical talent.
While this chapter will be devoted principally to the
cousins of the grasshopper, a few things of interest may
still be said about the grasshopper himself, in addition to
what was given in the preceding chapter.
THe GRASSHOPPER FAMILY
The family of the grasshoppers, or locusts, is the
Acrididae. All the members are much alike in form and
habits, though some have long wings and some short wings,
and some reach the enormous size of nearly six inches in
[ 28 ]
READE, t
A group of insects representing five common entomological Orders.
Figure 2 is a damselfly, a kind of dragonfly, from New Guinea, Order
Odonata; 4 is a grasshopper, and 6 a winged walking-stick of Japan,
representing two families of Orthoptera; 1 and 8 are sucking bugs,
Order Hemiptera, which includes also the aphids and the cicadas;
3 is a wasp from Paraguay, and 7 a solitary bee from Chile, Order
Hymenoptera; 5 is a two-winged fly of the Order Diptera, from Japan.
To entomologists these insects are known as follows: 1, Paryphes
laetus; 2, unidentified; 3, Pepsis completa; 4, Heliastus benjamini; 5,
Pantophthalmus vittatus; 6, Micadina phluctanotdes; 7, Caupolicana
fulvicollis; 8, Margasus afzeli
THE GRASSHOPPER’S COUSINS
length. The front wings are long and narrow (Fig. 63,
W.), somewhat stiff, and of a leathery texture. They are
laid over the thinner hind wings as a protection to the
latter when the wings are folded over the back, and for
this reason they are called the tegmina (singular, fegmen).
The hind wings, when spread (V3), are seen to be large
fans, each with many ribs, or veins, springing from the
base. These wings are gliders rather than organs of flight.
For most grasshoppers leap into the air by means of
their strong hind legs and then sail off on the outspread
wings as far as a weak fluttering of the latter will
carry them. One of our common species, however, the
Carolina locust (Frontispiece), is a strong flyer, and when
Fic. 15. A grasshopper, CAloealtis conspersa, that makes a sound by scraping
its hind thighs over sharp-edged veins of its wings
A, the male grasshopper, showing the sound-making veins of the wing (4). B,
inner surface of right hind leg, showing row of teeth (a) on the femur. C,
several teeth of the femur (enlarged)
flushed flits away on an undulating course over the
weeds and bushes and sometimes over the tops of small
trees, but always swerving this way and that as if unde-
cided where to alight. The great flights of the migratory
locusts, described in the last chapter, are said to have been
accomplished more by the winds than by the insects’
strength of wing.
The locusts are distinguished by the possession of large
[ 2g ]
INSECTS
organs on the sides of the body that appear to be designed
for purposes of hearing. No insect, of course, has “ears”
on its head; the grasshopper’s supposed hearing organs are
located on the base of the abdomen, one on each side
(Fig. 63, Tm). Each consists of an oval depression of the
body wall with a thin eardrumlike membrane, or tympa-
num, stretched over it. Air sacs lie against the inner face
of the membrane, furnishing the equilibrium of air pressure
necessary for free vibration in response to sound waves,
and a complicated sensory apparatus is attached to its
inner wall. Even with such large ears, however, attempts
at making the grasshopper hear are never very successful;
but its tympanal organs have the same structure as those
of insects noted for their singing, which presumably,
therefore, can hear their own sound productions.
Not many of the grasshoppers are muscial. They are
mostly sedate creatures that conceal their sentiments, if
they have any. They are awake in the daytime and they
sleep at night—commendable traits, but habits that seldom
beget much in the way of artistic attainment. Yet a few
of the grasshoppers make sounds that are perhaps music
in their own ears. One such is an unpretentious little
brown species (Fig. 15) about seven-eighths of an inch in
length, marked by a large black spot on each side of the
saddlelike shield that covers his back between the head and
the wings. He has no other name than his scientific one of
Chloealtis conspersa, for he is not widely known, since his
music is of a very feeble sort. According to Scudder, his
only notes resemble ¢sikk-tstkk-tsikk, repeated ten or twelve
times in about three seconds in the sun, but at a slightly
lower rate in the shade. Chloealtis is a fiddler and plays
two instruments at once. The fiddles are his front wings,
and the bows his hind legs. On the inner surface of each
hind thigh, or femur, there is a row of minute teeth (Fig.
i5 B, a), shown more magnified at C. When the thighs
are rubbed over the edges of the wings, their teeth scrape
on a sharp-edged vein indicated by 4. This produces the
eter
fHE-GRASSHOPPER’S ‘COUSINS
tsikk-sound just mentioned. Such notes contain little
music to us, but Scudder says he has seen three males sing-
ing to one female at the same time. This female. however,
SS)
Se
ND ay & jesse
pS
Vib 5 a) \
Cate a M
amet
eee NS ary
CLs “22 D>
STE Tee
se se WEL so ‘\
Cs Arp mani®5<5 5-76 Seo' y
Cea NT OO /
Fic. 16. A grasshopper, Mecostethus gracilis, that makes a sound
by scraping sharp ridges on the inner surfaces of its hind thighs
over toothed veins of the wings
A, the male grasshopper. B, left front wing; the rasping vein is
the one marked J. C, a part of the rasping vein and its branches
more enlarged, showing rows of teeth
was busy laying her eggs in a near-by stump, and there is
no evidence given to show that even she appreciated the
efforts of her serenaders.
Several other little grasshoppers fiddle after the manner
of Chloealtis; but another, Mecostethus gracilis by name
(Fig. 16), instead of having the rasping points on the legs,
has on each fore wing one vein (B, /) and its branches pro-
vided with many small teeth, shown enlarged at C, upon
which it scrapes a sharp ridge situated on the inner sur-
face of the hind thigh.
In another group of grasshoppers there are certain
species that make a noise as they fly, a crackling sound
[31]
INSECTS
apparently produced in some way by the wings themselves.
One of these, common through the Northern States, is
known as the cracker locust, Circotettix verruculatus, on
account of the loud snapping notes it emits. Several
other members of the same genus are also cracklers, the
noisiest being a western species called C. carlingianus.
Scudder says he has had his attention drawn to this grass-
hopper “‘by its obstreperous crackle more than a quarter of
a mile away. In the arid parts of the West it has a
great fondness for rocky hillsides and the hot vicinity of
abrupt cliffs in the full exposure to the sun, where its
clattering rattle re-echoes from the walls.”
THe Katypip FamiLy
While the grasshoppers give examples of the more
primitive attempts of insects at musical production and
may be compared in this respect to the more primitive of
human races, the katydids show the highest development
of the art attained by insects. But, just as the accom-
plishments of one member of a human family may give
prestige to all his relations and descendants, so the talent
of one noted member of the katydid family has given
notoriety to all his congeners, and his justly deserved
name has come to be applied by the undiscriminating
public to a whole tribe of singers of lesser or very mediocre
talent whose only claim to the name of katydid is that of
family relationship. In Europe the katydids are called
simply the longhorn grasshoppers. In entomology the
family is now the Tettigoniidae, though it had long been
known as'the Locustidae.
The katydids in general are most easily distinguished
from the locusts, or shorthorn grasshoppers, by the great
length of their antennae, those delicate, sensitive, tapering
threads projecting from the forehead. But the two fami-
lies differ also in the number of joints in their feet, the
grasshoppers having three (Fig. 17 A) and the katydids
four (B). The grasshoppers place the entire foot on the
[32]
THE GRASSHOPPER’S COUSINS
ground, while the katydids ordinarily walk on the three
basal segments only, carrying the long terminal joint
elevated. The basal segments have pads on their under
sides that adhere to any smooth surface such as that of a
leaf, but the terminal joint bears a pair of claws used
when it is necessary to grasp the edge of a support. The
katydids are mostly creatures of the night and, though
usually plain green in color, many of them have elegant
forms. Their attitudes and general
comportment suggest much more re-
finement and a higher breeding than
that of the heavy-bodied locusts.
Though some members of the katydid A
family live in the fields and are very
grasshopperlike or even cricketlike
in form and manners, the character-
istic species are seclusive inhabitants
of shrubbery or trees. These are the
true aristocrats of the Orthoptera.
An insect musician differs in many
respects from a human musician,
3 : c : Fic. 17. Distinctive char-
aside from that of being an insect in- acters in the feet of the
Seddsoraeiumane being. Uhesect ‘hee familics of singing
5 a ‘ Orthoptera
artists are all instrumentalists; but 4 hind foot of a a
since the poets and other ignorant hopper. B, hind foot of a
people always speak of the “singing” “*t¥4i@-_ ©, hind foot of
of the crickets and katydids, it will be
easier to use the language of the public than to correct it,
especially since we have nothing better to offer than the
word stridu/ating, a \.atin derivative meaning “‘to creak.”
But words do not matter if we explain what we mean by
them. It must be understood, therefore, that though we
speak of the “‘songs’’ of insects, insects do not have true
voices in the sense that “voice” is the production of sound
by the breath playing on vocal cords. All the musical
instruments of insects, it is true, are parts of their bodies;
but they are to be likened to fiddles or drums, since, for the
se
INSECTS
production of sound, they depend upon rasping and vibrat-
ing surfaces. The rasping surfaces are usually, as in the
instruments of the grasshoppers (Figs. 15, 16), parts of
the legs and the wings. The sound may be intensified, as
in the bedy of a stringed instrument, by special resonating
Fic. 18. The front wings, or tegmina, of a
meadow grasshopper, Orchelimum laticauda,
illustrating the sound-making organs typical
of the katydid family
A, left front wing and basal part of right wing
of male, showing the four main veins: subcosta
(Sc), radius (R), media (M), and cubitus (Cuz);
also the enlarged basal vibrating area, or
tympanum (7m), of each wing, the thick file
vein (fc) on the left, and the scraper (s) on
the right
B, lower surface of base of left wing of male,
showing the file (f) on under side of the file
vein (A, fv)
C, right front wing of female, which has no
sound-making organs, showing simple normal
venation
[ 34]
areas, sometimes on
the wings, sometimes
on the body. The
cicadas, a group of
musical insects to be
described in a special
chapter, have large
drumheads in the wall
of the body with
which they produce
their shrill music.
They do not beat
these drums, but
cause them to vibrate
by muscles in the
body. The musical
members of the insect
families are in nearly
all cases the males,
and it 1s usually sup-
posed that they give
their concerts for the
purpose of engaging
the females, but that
this is so in all cases
wecan not be certain.
The musical instru-
ments of the katydids
are quite different
from those of the
grasshoppers, _ being
situated on the over-
a
THE GRASSHOPPER’S COUSINS
lapping bases of the front wings, or tegmina. On this
account the front wings of the males are always different
from those of the females, the latter retaining the usual or
primitive structure. The right wing of a female in one of
the more grasshopperlike species, Orchelimum Jaticauda
(Fig. 30), is shown at C of Figure 18. The wing is trav-
ersed by four principal veins springing from the base.
The one nearest the inner
edge is called the cubitus
(Cu) and the space be-
tween it and this margin
of the wing is filled with
a network of small veins
having no particular ar-
rangement. In the wings
of the male, however,
shown at A of the same
figure, this inner basal
field is much enlarged
and consists of a thin,
crisp membrane (7m),
braced by a number of
veins branching from the
cubitus (Cu). One of
these (fv), running cross-
wise through the mem-
brane, is very thick on
the left wing, and when
the wing is turned over
(B) it is seen to have a
close series of small cross-
ridges on its under sur-
face which convert it into
Fic. 19. Wings, sound-making organs,
and the “ears” of a conehead grasshopper,
Neoconocephalus ensiger, a member of the
katydid family
A, B, right and left wings, showing the
scraper (s) on the right, and the file vein
(fe) on the left. C, under surface of the
file vein, showing the file (f). D, front
leg, showing slits (e) on the tibia opening
into pockets containing the hearing
organs (fig. 20 A)
a veritable file (f). On the right wing this same vein is
much more slender and its file is very weak, but on the
basal angle of this wing there is a stiff ridge (s) not de-
veloped on the other. The katydids always fold the
[35]
&
INSECTS
wings with the /eft overlapping the right, and in this position
the file of the former lies above the ridge (s) of the latter.
If now the wings are moved sidewise, the f/e grating on the
ridge or scraper causes a rasping sound, and this is the way
the katydid makes the notes of its music. _The tone and
volume of the sound, however, are probably in large part
produced by the vibration of the thin basal membranes of
the wings, which are called the tympana (Tm).
The instruments of different players differ somewhat in
the details of their structure. There are variations in the
form and size of the file and the scraper on the wings of dif-
ferent species, and differences in the veins supporting the
tympanal areas, as shown in the drawings of these parts
from a conehead (Fig. 27) given at A, B, and C, of Figure
ig. In the true katydid, the greatest singer of the family,
the file, the scraper, the tympana, and the wings them-
selves (Fig. 26) are all very highly developed to form an
instrument of great efficiency. But, in general, the instru-
ments of different species do not Bice: nearly so much as
do the notes produced from them by their owners. An
endless number of tunes may be played upon the same
fiddle. With the insects each musician knows only one
tune, or a few simple variations of it, and this he has in-
herited from his ancestors along with a knowledge of how
to play it on his inherited instrument. The stridulating
organs are not functionally developed until maturity, and
then the insect forthwith plays his native air. He never
disturbs the neighbors with doleful notes while learning.
Very curiously, none of the katydids nor any member of
their family ha; the earlike organs on the sides of the body
possessed by the locusts. What are commonly supposed
to be their organs of hearing are located in their front legs,
as are the similar organs of the crickets. Two vertical
slits on the upper parts of the shins, or /1d/ae (Fig. 19 D, e),
open each into a small pocket (Fig. 20 A, E) with a tym-
panumlike membrane (Tm) stretched across its inner wall.
Between the membranes are air cavities (Tra) and a com-
[ 36 |
THE GRASSHOPPER’S COUSINS
plicated sensory receptive apparatus (B) connected by a
nerve through the basal part of the leg with the central
nervous system.
There are several groups of katydids, classed as sub-
‘
‘aie
i
98)
Fic.20. The probable auditory organ of the front leg of Decticus,
a member of the katydid family. (Simplified from Schwabe)
A, cross-section of the leg through the auditory organ, showing
the ear slits (e, e) leading into the large ear cavities (EZ, E) with
the tympana (7m, Tm) on their inner faces. Between the
tympana are two tracheae (Tra, Tra) dividing the leg cavity into
an upper and a lower channel (BC, BC). The sensory apparatus
forms a crest on the outer surface of the inner trachea, each ele-
ment consisting of a cap cell (CC/), an enveloping cell (EC/) con-
taining a sense rod (Sco), and a sense cell (SC/). Ct, the thick
cuticula forming the hard wall of the leg
B, surface view of the sensory organ, showing the elements
graded in size from above downward. The sense cells (SC/) are
attached to the nerve (Nv) along the inner side of the leg
families. A subfamily name ends in inae to distinguish it
from a family name, which, after the Latin fashion, termi-
nates in idae.
THE ROUND-HEADED KATYDIDS
The members of this first group of the katydid family
are characterized by having large wings and a smooth
ise)
INSECTS
round forehead. They compose the subfamily Phanerop-
terinae, which includes species that attain the acme of
grace, elegance, and refinement to be found in the entire
orthopteran order. Nearly all the round-headed katydids
are musical to some degree, but their productions are not
Vi,
Fic. 21. A bush katydid, Scuddéria furcata
Upper figure, a male; lower, a female in the act of cleaning a
hind foot
of a high’ order. On the other hand, though their notes
are in a high key, they are usually not loud and not of the
kind that keep you awake at night.
Among this group are the bush katydids, the species of
which are of medium size with slenderer wings than the
others, and are comprised in the genus usually known as
Scudderia but also called Phaneroptera. They have ac-
quired the name of bush katydids because they are usually
found on low shrubbery, particularly along the edges of
moist meadows, though they inhabit other places, too, and
their notes are often heard at night about the house. Our
[ 38]
THE. GRASSHOPPER’S COUSINS
commonest species, and one that occurs over most of the
United States, is the fork-tailed bush katydid (Scudderia
furcata). Figure 21 shows a male and a female, the female
in the act of cleaning the pads on one of her hind feet. The
katydids are all very particular about keeping their feet
clean, for it is quite essential to have their adhesive pads
always in perfect working order; but they are so con-
tinually stopping whatever they may be doing to lick one
foot or another, like a dog scratching fleas, that it looks
more like an ingrown habit with them than a necessary act
of cleanliness. The fork-tailed katydid is an unpreten-
tious singer and has only one note, a high-pitched zeep re-
iterated several times in succession. But it does not re-
peat the series continuously, as most other singers do, and
its music is likely to be lost to human ears in the general
din from the jazzing bands of crickets. Yet occasionally
its soft zeep, zeep, zeep may be heard from a near-by bush
or from the lower branches of a tree.
The notes of other species have been described as zkk,
zikk, zikk, or zeet, zeet, zeet, and some observers have re-
corded two notes for the same species. Thus Scudder says
that the day notes and the night notes of Scudderia curvi-
cauda differ considerably, the day note being represented
by ézrwi, the night note, which is only half as long as the
other, by ¢chw. (With a little practice the reader should
be able to give a good imitation of this katydid.) Scudder
furthermore says that they change from the day note to
the night note when a cloud passes over the sun as they are
singing by day.
The genus 4mé/ycorypha includes a group of species hav-
ing wider wings than those of the bush katydids. Most of
them are indifferent singers; but one, the oblong-winged
katydid (4. oblongifolia), found over all the eastern half of
the United States and southern Canada, is noted for its
large size and dignified manners. A male (Fig. 22), kept
by the writer one summer in a cage, never once lost his
decorum by the humiliation of confinement. He lived ap-
[39 |
INSECTS
parently a natural and contented life, feeding on grape
leaves and on ripe grapes, obtaining the pulp of the latter
by gnawing holes through the skin. He was always sedate,
always composed, his motions always slow and deliberate.
In walking he carefully lifted each foot and brought the leg
forward with a steady movement to the new position,
where the foot was carefully set down again. Only in the
act of jumping did he ever make a quick movement of any
sort. But his preparations for the leap were as calm and
unhurried as his other acts: pointing the head upward,
dipping the abdomen slowly downward, the two long hind
legs bending up in a sharp inverted V on each side of the
body, he would lead one to think he was deliberately pre-
paring to sit down on a tack; but, all at once, a catch
seems to be released somewhere as he suddenly springs
upward into the leaves overhead at which he had taken
such long and careful aim.
For a long time the aristocratic prisoner uttered no
sound, but at last one evening he repeated three times a
[ 40 |
THE GRASSHOPPER’S COUSINS
squeaking note resembling shriek with the s much aspi-
rated and with a prolonged vibration on the ze. The next
evening he played again, making at first a weak swish,
swish, swish, with the s very sibilant and the 7 very vibra-
tory. But after giving this as a prelude he began a sh Ill
shrie-e-e-e-k, shrie-e-e-e-k, repeated six times, a loud
sound described by Blatchley as a “creaking squawk—like
the noise made by drawing a fine-toothed comb over a
taut string.”
The best-known members of the round-headed katydids,
and perhaps of the whole family, are the angular-winged
katydids (Fig. 23). These are large, maple-leaf green in-
sects, much flattened from side to side, with the leaflike
wings folded high over the back and abruptly bent on their
upper margins, giving the creatures the humpbacked ap-
pearance from which they get their name of angular-
winged katydids. The sloping surface of the back in front
of the hump makes a large flat triangle, plain in the female,
but in the male corrugated and roughened by the veins of
the musical apparatus.
There are two species of the angular-winged katydids in
the United States, both belonging to the genus Microcen-
trum, one distinguished as the larger angular-winged katy-
did, M. rhombifolium, and the other as the smaller angu-
lar-winged katydid, M. retinerve. The females of the
larger species (Fig. 23), which is the more common one,
reach a length of 236 melee measured to the tips of the
wings. They lay flat, oval eggs, stuck in rows overlapping
like scales along the surface of some twig or on the edge
of a leaf.
The angular-winged katydids are attracted to lights and
may frequently be found on warm summer nights in the
shrubbery about the house, or even on the porch and the
screen doors. Members of the larger species usually make
their presence known by their soft but high-pitched notes
resembling /zeet uttered in short series, the first notes re-
peated rapidly, the others successively more slowly as the
[41]
INSEGKS
tone becomes also less sharp and piercing. The song
may be written /zeet-/zeet-tzeet-tzeet-tzek-tzek-tzek-tzuk-tzuk,
though the high key and shrill tones of the notes must be
Fic. 23. The larger angular-winged katydid, Microcentrum rhombifolium
Upper figure, a male; lower, a female
imagined. Riley describes the song as a series of raspings
“‘as of a stiff quill drawn across a coarse file,” and Allard
[ 42 ]
HE GRASSHOPPER’S COUSINS
says the notes “‘are sharp, snapping crepitations and sound
like the slow snapping of the teeth of a stiff comb as some
object is slowly drawn across it.’’ He represents them
thus: fek-ek-ek-ek-ek-ek-ek-ek-ek-ek-ek-tzip. But, however
the song of Microcentrum is to be translated into English,
it contains no suggestion of the notes of his famous cousin,
the true katydid. Yet most people confuse the two species,
or rather, hearing the one and seeing the other, they draw
the obvious but erroneous conclusion that the one seen
makes the sounds that are heard.
The smaller angular-winged katydid, Microcentrum reti-
nerve, 1s not so frequently seen as the other, but it has simi-
lar habits, and may be heard in the vines or shrubbery
about the house at night. Its song is a sharp zeet, eet, zeet,
the three syllables spaced as in ka-ty-did, and it is probable
that many people mistake these notes for those of the true
katydid.
The angular-winged katydids are very gentle and un-
suspicious creatures, allowing themselves to be picked up
without any attempt at escaping. But they are good
flyers, and when launched into the air sail about like minia-
ture airplanes, with their large wings spread out straight
on each side. When at rest they have a comical habit of
leaning over sidewise as 1f their flat forms were top-heavy.
LHE, TRUE KATYDID
We now come to that artist who bears by right the name
f ““katydid,” the insect (Fig. 24) known to science as
Pterophylla camellifolia and to the American public as the
greatest of insect singers. Whether the katydid is really a
musician or not, of course, depends upon the critic, but of
his fame there can be no question, for his name is a house-
hold term as familiar as that of any of our own great
artists, notwithstanding that there is no phonographic
record ine his music. To be sure, the cicada has more of a
world-wide reputation than the katydid, for he has repre-
sentatives in many lands, but he has not put his song into
[ 43 ]
INSECTS
words the public can understand. And if simplicity be the
test of true art, the song of the katydid stands the test, for
nothing could be simpler than merely katy-did, or its easy
variations, such as katy, katy- she-did, and katy-didn’t.
Yet though the music of the katydid is known by ear or
by reputation to almost every native American, few of us
Fic. 24. The true katydid, Pterophylla camellifolia, a male
are acquainted with the musician himself. This is because
he almost invariably chooses the tops of the tallest trees for
his stage and seldom descends from it. His lofty platform,
moreover, is also his studio, his home, and his world, and
the reporter who would have a personal interview must be
efficient in tree climbing. Occasionally, though, it happens
that a singer may be located in a smaller tree where access
to him is easier or from which he may be dislodged by
shaking. A specimen, secured in this way on August 12
lived till October 18 and furnished material for the follow:
ing notes:
The physical characters of the captive and some of his
attitudes are shown in Figures 24 and 25. His length is
134 inches from the forehead to the tips of the folded
wits: the front legs are longer and thicker than in most
other members of the family, while the hind legs are un-
usually short. The antennae, though, are extremely long,
slender, and very delicate filaments, 2'’/16 inches in length.
1 44 |
THE GRASSHOPPER’S COUSINS
z
Ren
Fic. 25. The katydid in various attitudes
A, usual position of a male while singing. B, attitude while running rapidly on
a smooth surface. C, preparing to leap from a vertical surface. D, a male,
seen from above, showing the stridulating area at the base of the wings. E, a
female, showing the broad, flat, curved ovipositor
[45 |
INSECWS
Between the bases of the antennae on the forehead there
is a small conical projection, a physical character which
separates the true katydid from the round-headed katy-
dids and assigns him to the subfamily called the Pseudo-
phyllinae, which includes, besides our species, many others
that live mostly in the tropics. The rear margins of the
wings are evenly rounded and their sides strongly bulged
outward as if to cover a very plump body, but the space
between them is mostly empty and probably forms a
resonance chamber to give tone and volume to the sound
produced by the stridulating parts. What might be the
katydid’s waistcoat, the part of the body exposed beneath
the wings, has a row of prominent buttonlike swellings
along the middle which rhythmically heave and sink with
each respiratory movement. All the katydids are deep
abdominal breathers.
The color of the katydid is plain green, with a conspicu-
ous dark-brown triangle on the back covering the stridulat-
ing area of the wings. The tips of the mouth parts are
yellowish. The eyes are of a pale transparent green, but
each has a dark center which, like the pupil in a painting, 1s
always fixed upon you from oiheneaee angle you retreat.
The movements of the captive individual are slow,
though in the open he can run rather rapidly, and when he
is in a hurry he often takes the rather absurd attitude
shown at B of Figure 25, with the head down and the
wings and body elevated. He never flies, and was never
seen to spread his wings, but when making short leaps the
wings are slightly fluttered. In preparing for a leap, if
only one of a few inches or a foot, he makes very careful
preparations, scrutinizing the proposed landing place long
and closely, though perhaps he sees better in the dark and
acts then with more agility. If the leap is to be made
from a horizontal surface, he slowly crouches with the legs
drawn together, assuming an attitude more familiar in a
cat; but, if the jump ts to be from a vertical support, he
raises himself on his long front legs as at C of Figure 25,
[ 46 J
THE GRASSHOPPER’S COUSINS
suggesting a camel browsing on the leaves of a tree. He
sparingly eats leaves of oak and maple supplied to him in
his cage, but appears to prefer fresh fruit and grapes, and
relishes bread soaked in water. He drinks rather less than
most orthopterons.
When the katydids are singing at night in the woods they
appear to be most wary of disturbance, and often the voice
of a person approaching or a crackle underfoot is sufficient
to quiet a singer far overhead. The male in the cage never
utters a note until he has been in darkness and quiet for a
considerable time. But when he seems to be assured of
solitude he starts his music, a sound of tremendous volume
in a room, the tones incredibly harsh and rasping at close
range, lacking entirely that melody they acquire with space
and distance. It is only by extreme caution that the per-
former may be approached while singing, and even then
the brief flash of a light is usually enough to silence those
stentorian notes. Yet occasionally a glimpse may be had
of the musician as he plays, most frequently standing head
downward, the body braced rather stiffly on the legs, the
front wings only slightly elevated, the tips of the hind
wings projecting a little from between them, the abdomen
depressed and breathing strongly, the long antennal
threads waving about in all directions. Each syllable ap-
pears to be produced by a separate series of vibrations
made by a rapid shufling of the wings, the middle one be-
ing more hurried and the last more conclusively stressed,
thus producing the sound so suggestive of ka-ty-did’, ka-ty-
did’, which is repeated regularly about sixty times a minute
on warm nights. Usually at the start, and often for some
time, only two notes are uttered, ka-ty, as if the player has
difficulty i in falling at once into the full swing of ka-ty-did.
The structure of the wings and the details of the stridu-
lating parts are shown in Figure 26. The wings (A, B) fold
vertically against the sides of the body, but their inner
basal parts form wide, stiff, horizontal, triangular flaps that
overlap, the left on top of the right. A thick, sunken,
[ 47 ]
INSECTS
crosswise vein (fv) at the base of the left tympanum (7m) is
the file vein. It is shown from below at C where the
broad, heavy file (f) is seen with its row of extremely
coarse rasping ridges. The same vein on the right wing
(B) is much smaller and has no file, but the inner basal
angle of the tympanum is produced into a large lobe bear-
ing a strong scraper (5) on its
margin.
The quality of the katy-
did’s song seems to differ
somewhat in different parts
of the country. In the vicin-
ity of Washington, the in-
sects certainly say ka-ty-did
as plainly as any insect could.
Of course, the sound is more
literally to be represented as
ka ki-kak’, accented on the
last syllable. When only two
syllables are pronounced they
are always the first two.
Sometimes an individual in a
band utters four syllables,
“katy-she-did” or ka ki-ka-
kak’, and again a whole band
Frc. 26. Wings and the sound-mak- 1S heard singing in four notes
ing organs of the male katydid with only an occasional
A font wing sowing heart” Singer giving three. Itis said
thick file vein (fo). B, base of right that in certain parts of the
fore wing with res seraper om South the katydid is called
vein. GC, under surface of file veinof a “‘ cackle - jack,” a name
ch be es > fat, Which, it must be admitted,
is a very literal translation of
the notes, but one lacking in sentiment and unbefitting an
artist of such repute. In New England, the katydids
heard by the writer in Connecticut and in the western
part of Massachusetts uttered only two syllables much
[ 48 ]
THE GRASSHOPPER’S COUSINS
more commonly than three, and the sounds were extremely
harsh and rasping, being a loud sgud-wik’, squa-wak',
squa-wak’, the second syllable a little longer than the first.
This is not the case with those that sey ka-ty. When there
were three syllables the series was squa-wa- wak’. Tf all
New England katydids sing thus, it is not surprising that
some New England writers have failed to see how the
insects ever got the name of “‘katydid.” Scudder says
“their notes have a shocking lack of melody”; he rep-
resents the sound by xr, and records that ‘the song is
usually of only two syllables. “That is,” he says, “ they
rasp their fore wings twice rather chan thrice; these
two notes are of equal (and extraordinary) emphasis, the
latter about one-quarter longer than the former; or if three
notes are given, the first and second are alike and a little
shorter than the last.”
When we listen to insects singing, the question always
arises of why they sing, and we might as well admit that
we do not know what motive impels them. It is prob-
ably an instinct with males to use their stridulating organs,
but in many cases the tones emitted are clearly modified by
the physical or emotional state of the player. The music
seems in some way to be connected with the mating of the
sexes, and the usual idea is that the sounds are attractive
to the females. With many of the crickets, however, the
real attraction that the male has for the female is a liquid
exuded on his back, the song apparently being a mere ad-
vertisement of his wares. In any case the ecstacies of love
and passion ascribed to male insects in connection with
their music are probably more fanciful than real. The
subject is an enchanted field wherein the scientist has
most often weakened and wandered from the narrow
path of observed facts, and where he has indulged in a free-
dom of imagination permissible to a poet or to a newspaper
reporter who wishes to enliven his chronicle of some event
in the daily news, but which does not contribute anything
substantial to our knowledge of the truth.
[49 ]
INSECTS
THE CONEHEADS
This group of the katydid family contains slender,
grasshopperlike insects that have the forehead produced
into a_ large
} ; cone and the
face strongly
receding, but
which also pos-
sess long, slen-
der antennae
that distinguish
them from the
true or short-
horn grasshop-
pers. They con-
stitute the sub-
family Copi-
phorinae.
One of the
commonest and
Fic. 27. A conehead grasshopper, or katydid, Neocono- most widel y
cephalus retusus
Upper figure, a male; lower, a female, with extremely long distributed of
ovipositor the larger cone-
heads is the
species known as Neoconocephalus ensiger, or the ““sword-
bearing conehead.” It is the female, however, that carries
the sword; and it is not a sword either, but merely the
immensely long egg-laying instrument properly called the
ovipositor. The female conehead shown at B of Figure 27,
has a similar organ, though she belongs to a species called
retusus. The two species are very similar in all respects
except for slight differences in the shape of the cone on the
head. They look like slim, sharp-headed grasshoppers,
11% to 134 inches in length, usually bright green in color,
though sometimes brown.
| 50]
THE GRASSHOPPER’S COUSINS
The song of evsiger sounds like the noise of a miniature
sewing machine, consisting merely of a long series of one
note, fick, tick, tick, tick, etc., repeated indefinitely.
Scudder says evsiger begins with a note like drw, then
pauses an instant and immediately
emits a rapid succession of sounds
like chwi at the rate of about five
per second and continues them an
unlimited time. McNeil repre-
sents the notes as zip, zip, zip;
Davis expresses them as 7k, ik, ik;
and Allard hears them as ¢s7p, ¢sip,
tsip. The song of retusus (Fig. 27)
is quite different. It consists of a
long shrill whir which Rehn and
Hebard describe as a continuous
zeeeeeeeeee. The sound is not loud
but is in a very high key and rises
in pitch as the player gains speed
in his wing movements, till to some
human ears it becomes almost in-
audible, though to others it is a
plain and distinct screech.
A large conehead and one with
a much stronger instrument is the
robust conehead, Neoconocephalus
robustus (Fig. 28). He is one of
the loudest singers of North
American Orthoptera, his song
being an intense, continuous buzz, Fic. 28. The robust cone-
somewhat resembling that of a eae Detar Gah
cicada. A caged specimen singing fore wings separated and
somewhat elevated, the head
in a room makes a deafening noise. Ae era!
The principal buzzing sound is ac-
companied by a lower, droning hum, the origin of which
is not clear, but which is probably some secondary vibra-
tion of the wings. The player always sits head downward
Se]
INSECTS
while performing, and the breathing motions of the abdo-
men are very deep and rapid. The robust conehead is an
inhabitant of dry, sandy places along the Atlantic coast
from Massachusetts to Virginia and, according to Blatch-
ley, of similar places near the shores of Lake Michigan in
Indiana. The writer made its acquaintance in Con-
necticut on the sandy flats of the Quinnipiac Valley, north
of New Haven, where its shrill song may be heard on
summer nights from long distances.
THE MEADOW GRASSHOPPERS
These are trim, slim little grasshopperlike insects, active
by day, that live in moist meadows where the vegetation 1s
always fresh and juicy. They constitute the subfamily
Conocephalinae of the katydid family, having conical
Fic. 29. The common meadow grasshopper, Orchelimum vulgare, a member of
the katydid family
heads like the last group, but being mostly of smaller size.
There are numerous species of the meadow grasshoppers,
but most of them in the eastern part of the United States
belong to two genera known as Orchelimum and Conoceph-
alus. The most abundant and most widely distributed
member of the first is the common meadow grasshopper,
Orchelimum vulgare. A male is shown in Figure 29. He
is a little over an inch in length, with head rather large
for his size and with big eyes of a bright orange color. The
ground color of his body is greenish, but the top of the
head and the thoracic shield is occupied by a long tri-
angular dark-brown patch, while the stridulating area of
[52a]
HE GRASSHOPPER’S COUSINS
Fic. 30. The hand-
some meadow grass-
hopper, Orchelimum
laticauda
Upper figure, a male;
lower, a female
lable repeated many times. These two
elements, the z7p and zee, are charac-
teristic of the songs of all the Orcheli-
mums, some giving more stress to the
first and others to the second, and
the wings is marked by a brown
spot at each corner. These little
grasshoppers readily sing in con-
finement, both in the day and at
night. Their music is very unpre-
tentious and might easily be lost
out of doors, consisting mostly of a
soft, rustling buzz that lasts two or
three seconds. Often the buzz is
preceded or followed by a series of
clicks made by a slower movement
of the wings. Frequently the
player opens the wings for the
start of the song with a single click,
then proceeds with the buzz, and
finally closes with a few slow
movements that produce the con-
cluding series of clicks. But very
commonly he gives only the buzz
without prelude
or staccato end-
ing.
Another com-
mon member of
the genus is the
agile meadow
grasshopper, Or-
chelimum agile.
Its music is said
to be a long zp,
1p, ZIP, Zee-e-e-€,
with the z7p syl-
Fic. 31. The slender
meadow grasshopper,
Conocephalus fasciatus,
one of the smallest
members of the katy-
did family
[53]
INSECTS
sometimes either one or the other 1s omitted. A very
pretty species of the genus is the handsome meadow
grasshopper, Orchelimum laticauda (or pulchellum) shown
in Figure 30, When at rest, both males and females
usually sit close to a stem or leaf with the middle of the
body in contact with the support and the long hind legs
stretched out behind. Davis says the song of this species
iS a 2p, 2p, Zap ez, 2, Guiie distinguishable from that of
O. vulgare.
Still smaller meadow grasshoppers belong to the genus
Conocephalus, more commonly called Xiphidium. One of
the most abundant species, the slender meadow grass-
hopper, C. fasciatus, is shown in Figure 31. It is less than
an inch in length, the body green, the back of the thorax
dark brown, the wings reddish-brown, and the back of the
abdomen marked with a broad Ceoean stripe. Allard says
the song of this little meadow grasshopper may be ex-
pressed as lip, tip, tip, tseeeeeeeeeeeeee, but that the entire
song is so faint as almost to escape the hearing. Piers
describes it as ple-e-e-e-e-e, (zit, (zit, fzit, tzit. Like the song
of Orchelimum vulgare it apparently may either begin or
end with staccato notes.
THE SHIELD BEARERS
Another large group of the katydid family is the sub-
family Decticinae, mostly cricketlike insects that live on
the ground, but which have wings so short (Fig. 32) that
they are poor musicians. They are called “‘shield bearers”
because the large back plate of the first body segment is
more or less prolonged like a shield over the back. Most of
the species live in the western parts of the United States,
where the individuals sometimes become so abundant as
to form large and very destructive bands. One such
species 1s the Mormon cricket, 4xabrus simplex, and an-
other is the Coulee cricket, Peranabrus scabricollis (Fig. 32),
of the dry central region of the State of Washington. The
females of these species are commonly wingless, but the
[54 |
THE GRASSHOPPER’S COUSINS
males have short stubs of front wings that retain the
stridulating organs and enable them to sing with a brisk
chirp.
Still another large subfamily of the Tettigoniidae is the
Fic. 32. The Coulee cricket, Peranabrus scabricollis, male and female, an
example of a cricketlike member of the katydid family
Rhadophorinae, including the insects known as “camel
crickets.”’ But these are all wingless, and therefore silent.
Tue Cricket Famity
The chirp of the cricket is probably the most familiar
note of all orthopteran music. But the only cricket com-
monly known to the public is the black fteld cricket, the
lively chirper of our yards and gardens. His European
cousin, the house cricket, is famous as the “cricket on the
hearth” on account of his fondness for fireside warmth
which so stimulates him that he must express his animation
in song. This house cricket has been known as Gryllus
since the time of the ancient Greeks and Romans, and his
name has been made the basis for the name of his family,
the Gryllidae, for there are numerous other crickets, some
that live in trees, some in shrubbery, some on the ground,
and others in the earth.
The crickets have long slender antennae like those of the
katydids, and also stridulating organs on the bases of the
wings, and ears in their front legs. But they differ from the
katydids in having only three joints in their feet (Fig.
17 C). The cricket’s foot in this respect resembles the foot
[55]
INSEGES
of the grasshopper (A), but usually differs from that of the
grasshopper in having the basal joint smooth or hairy all
around or with only one pad on the under surface. In most
crickets, also, the second joint of the foot is very small.
ys see EL
LILA SLR RE
weet eee ee eee
Doon = =
Fic. 33. The wings of a tree cricket
A, right front wing of an immature female, showing normal arrangement of
veins: Sc, subcosta; R, radius; M, media; Cu, first branch of cubitus; Cue,
second branch of cubitus; 74, first anal. (From Comstock and Needham)
B, front wing of an adult female of the narrow-winged tree cricket
C, front wing of an immature male, showing widening of inner half to form
vibrating area, or tympanum, and modification of veins in this area. (From
Comstock and Needham)
D, right front wing of adult male of the narrow-winged tree cricket; the second
branch of cubitus (Cuz) becomes the curved file vein (fv); s, the scraper
Some crickets have large wings, some small wings, some no
wings at all. The females are provided with long oviposi-
tors for placing their eggs in twigs of trees or in the ground
(Figs. 35, 36).
The musical or stridulating organs of the crickets are
similar to those of the katydids, being formed from the
veins of the basal parts of the front wings. But in the
crickets the organs are equally developed on each wing, and
it looks as if these insects could play with either wing up-
permost. Yet most of them consistently keep the right
[ 56 |
Por
THE GRASSHOPPER’S COUSINS
wing on top and use the file of this wing and the scraper
of the left, just the reverse of the custom among the
katydids.
The front wings of male crickets are usually very broad
and have the outer edges turned down in a wide flap that
folds over the sides of the body when the wings are closed.
The wings of the females are simpler and usually smaller.
The differences between the front wings in the male and
the female of one of the tree crickets (Fig. 37) is shown
at B and D of Figure 33. The inner half of the wing (or
the rear half when the wing is extended) is very large in the
male (D) and has only a few veins, which brace or stiffen
the wide membranous vibratory area or tympanum. The
inner basal part, or ana/ area, of the male wing is also
larger than in the female and contains a prominent vein
(Cuz) which makes a sharp curve toward the edge of the
wing. This vein has the stridulating file on its under sur-
face. The veins in the wing of an
adult female (B) are comparatively
simple, and those of a young female (A)
are more so. But the complicated
venation of the male wing has been de-
veloped from the simple type of the
female, which is that common to in-
sects in general. The wing of a young
male (C) is not so different from that
of a young female (A) but that the cor-
responding veins can be identified, as
shown by the lettering. Taking next
the wing of the adult male (D), it is an
easy matter to determine which veins
3 Fic. 34. A mole cricket,
have been distorted to produce the Neocurtilla hexadactyla
stridulating apparatus. When the tree
crickets sing they elevate the wings above the back like
two broad fans (Figs. 37, 40) and move them sidewise so
that the file of the right rubs over the scraper of the
left.
[57]
INSECUS
THE MOLE CRICKETS
The mole crickets (Fig. 34) are solemn creatures of the
earth. They live like true moles in burrows underground,
usually in wet fields or along streams. Their forefeet are
broad and turned outward for digging like the front feet of
moles. But the mole crickets differ from real moles in
having wings, and sometimes they leave their burrows at
night and fly about, being occasionally attracted to lights.
Their front wings are short and lie flat on the back over
the base of the abdomen, but the long hind wings are
folded lengthwise over the back and project beyond the tip
of the body.
Notwithstanding the gloomy nature of their habitat, the
male mole crickets sing. Their music, however, 1s a sleone
and monotonous, being always a series of loud, deep-toned
chirps, like churp, churp, churp, repeated very regularly
about a hundred times a minute and continued indefinitely
if the singer is not disturbed. Since the notes are most
frequently heard coming from a marshy field or from the
edge of a stream, they might be supposed to be those of a
small frog. It is difficult to capture a mole cricket in the
act of singing, for he is most likely standing at an opening
in his burrow into which he retreats before he is discovered.
THE FIELD CRICKETS
This group of crickets includes Gry//us as its typical
member, but entomologists give first place to a smaller
brown cricket called Nemobius. There are numerous spe-
cies of this genus, but a widely distributed one is N. vitta-
tus, the striped ground cricket. This is a little cricket,
about three-eighths of an inch in length, brownish in color,
with three darker stripes on the abdomen, common in
fields and dooryards (Fig. 35). In the fall the females lay
their eggs in the ground with their slender ovipositors
(D, E) and the eggs (F) hatch the following summer.
The song of the male Nemobius is a continuous twitter-
[58]
THE GRASSHOPPER’S COUSINS
Fic. 35. The striped ground cricket, Nemobius vittatus
A, B, females, distinguished by the long ovipositor. C,a male. D, a female
in the act of thrusting her ovipositor into the ground. E, a female, with oviposi-
tor full length in the ground, and extruding an egg from its tip. F, an eggin
the ground
ing trill so faint that you must listen attentively to hear it.
In singing the male raises his wings at an angle of about
45°. The stridulating vein is set with such fine ridges that
[59]
INSECTS
they would seem incapable of producing even those whis-
pering | Nemobius notes. Most of the muscial instruments
of insects can be made to produce a swish, a creak, or a
grating noise of some sort when handled with our clumsy
fingers or with a pair of forceps, but only the skill of the
living insect can bring from them the tones and the volume
of sound they are capable of producing.
Our best-known cricket is Gryllus, the black cricket
(Fig. 36), so common everywhere in fields and yards and
occasionally entering houses. The true house cricket of
Europe, Gry//us domesticus, has become naturalized in this
country and occurs in small numbers through the Eastern
States. But our common native species is Gry//us assimiits.
Entomologists distinguish several varieties, though they
are inclined to regard them all as belonging to the one
species.
Mature individuals of Gryllus are particularly abundant
in the fall; in southern New England they appear every
year at this season by the millions, swarming everywhere,
hopping across the country roads in such numbers that it is
impossible to ride or walk without crushing them. Most
of the females lay their eggs in September and October, de-
positing them singly in the ground (Fig. 36 D, E) in the
same way that Nemobius does. These eggs hatch about
the first of June the following year. But at this same time
another group of individuals reaches maturity, a group
that hatched in midsummer of the preceding year and
passed the winter in an immature condition. The males of
these begin singing at Washington during the last part of
May, in Connecticut the first of June, and may be heard
until the end of June. Then there is seldom any sound of
Gryllus until the middle of August, when the males of the
spring group begin to mature. From now on their notes
become more and more common and by early fall they are
to be heard almost continuously day and night until frost.
The notes of Gryllus are always vivacious, usually cheer-
ful, sometimes angry in tone. gk hey are merely chirps, and
[ 60 |
THE GRASSHOPPER’S COUSINS
may be known from all others by a broken or vibratory
sound. There is little music in them, but the player has
enough conceit to make up for this lack. Two vigorous
Fic. 36. The common black cricket, Gryllus assimilis
A, a male with wings raised in the attitude of singing. B, a female with long
“ ovipositor. C, young crickets recently hatched (enlarged about 24 times).
D, a female inserting her ovipositor in the ground. E, a female with ovipositor
buried full length in the ground
[61]
INSECTS
males that were kept in a cage together with several
females gave each other little peace. Whenever one began
to play his fiddle the other started up, to the plain disgust
of the first one, and either was always greatly annoyed and
provoked to anger if any of the females happened to run
into him while he was playing. If one male was fiddling
alone and the other approached him, the first dashed at
the intruder with jaws open, increasing the speed of his
strokes at the same time till the notes became almost a
shrill whistle. The other male usually retaliated by play-
ing, too, In an apparent attempt to outfiddle the first. The
chirps from both sides now came quicker and quicker, their
pitch mounting higher and higher, till each player reached
his limit. Then both would stop and begin over again.
Neither male ever inflicted any actual damage on his rival,
and in spite of their savage threats neither was ever seen
really to grasp any part of the other with his jaws. Either
would dash madly at a female that happened to disturb
him while fiddling, but neither was ever seen to threaten a
female with open jaws.
The weather has much influence on the spirits of the
males; their chirps are always loudest and their rivalry
keenest when it is bright and warm. Setting their cage in
the sun on cold days always started the two males at once
to singing. Out of doors, though the crickets sing in all
weather and at all hours, variations of their notes in tone
and strength according to the temperature are very notice-
able. This is not owing to any effect of humidity on their
instruments, for the two belligerent males kept in the house
never had the temper on cold and gloomy days that char-
acterized their actions and their song on days that were
warm and bright. This, in connection with the fact that
their music is usually aimed at each other in a spirit clearly
suggestive of vindictiveness and anger, is all good evidence
that Gryllus sings to express himse/f and not to “charm the
females.” In fact, it is often hard to feel certain whether
he is singing or swearing. If we could understand the
| 62 |
WME GRASSHOPPER’S COUSINS
words, we might be shocked at the awful Janguage he is
hurling at his rival. However, swearing is only a form of
emotional expression, and singing is another. Gryllus,
like an opera singer, simply expresses a// his emotions in
music, and, whether we can understand the words or not,
we page cad the sentiment.
At last one of the two caged rivals died; whether from
natural causes or by foul means was never ascertained.
He was alive early on the day of his demise but apparently
weak, though still intact. In the middle of the afternoon,
however, he lay on his back, his hind legs stretched out
straight and stiff; only a few movements of the front legs
showed that life was not yet quite extinct. One antenna
was lacking and the upper lip and adjoining parts of the
face were gone, evidently chewed off. But this is not neces-
sarily evidence that death had followed violence, for, in
cricketdom, violence more commonly follows death; that
is, cannibalism is substituted for interment. A few days
before, a dead female in the cage had been devoured
quickly, all but the skull. After the death of this male,
the remaining one no longer fiddled so often, nor with the
same sharp challenging tone as before. Yet this could not
be attributed to sadness; he had despised his rival and had
clearly desired to be rid of him; his change was due rather
to the lack of any special stimulus for expression.
Ln SRE CRICKETS
The unceasing ringing that always rises on summer eve-
nings as soon as the shadows begin to darken, that shrill
melody of sound that seems to come from nothing but
from everywhere out of doors, is mostly the chorus of the
tree crickets, the blend of notes from innumerable harpists
playing unseen in the darkness. This sound must be the
most familiar of all insect sounds, but the musicians them-
selves are but little known to the general public. And
when one of them happens to come to the window or into
the house and plays in solo, the sound is so surprisingly
[ 63 |
INSECTS
loud that the player is not suspected of being one of that
band whose mingled notes are heard outside softened by
distance and muffled by screens of foliage.
Out of doors the music of an individual cricket is so
elusive that even when you think you have located the ex-
Fic. 37. The snowy tree cricket, Oecanthus niveus
The upper figures, males, the one on the right with fore wings
raised vertically in attitude of singing; below, a female, with
narrow wings folded close against the body
act bush or vine from which it comes the notes seem to
shift and dodge. Surely, you think, the player must be
under that leaf; but when you approach your ear to it, the
sound as certainly comes from another over yonder; but
here you are equally convinced that it comes from still
[ 64 |
Tak GRASSHOPPER’S:; COUSINS
another place farther off. Finally, though, it strikes the
ear with such intensity that there can be no mistaking the
source of its origin, and, right there in plain sight on a leaf
sits a little, delicate, slim-legged, pale-green insect with
hazy, transparent sails outspread above its back. But
can such an insignificant creature be making such a deafen-
ing sound! It has required very cautious tactics to ap-
proach thus close without stopping the music, and it needs
but a touch on stem or leaf to make it cease. But now
those gauzy sails that before were a blurred vignette have
acquired a definite outline, and a little more disturbance
may cause them to be lowered and spread flat on the
creature’s back. The music will not begin anew until you
have passed a period of silent waiting. Then, suddenly,
the lacy films go up, once more their arehees blur, and
that intense scream again pierces your ear. In short, you
are witnessing a private performance of the broad- winged
tree cricket, Oecanthus latipennis.
But if you pay attention to the notes of other singers,
you will observe that there is a variety of airs in the medley
going on. Many notes are long trills like the one just
identified, lasting indefinitely; but others are softer purr-
ing sounds, about two seconds in length, while still others
are short beats repeated regularly a hundred or more times
every minute. The last are the notes of the snowy tree
cricket, Oecanthus niveus, so-called on account of his pale-
ness. He is really green in color, but a green of such a
very pale shade that he looks almost white in the dark. The
male (Fig. 37) is a little longer than half an inch, his wings
are wide and flat, overlapping when folded on the back,
with the edges turned down against the sides of the body.
The female is heavier-bodied than the male, but her wings
are narrow, and when folded are furled along the back.
She has a long ovipositor for inserting her eggs into the
bark of trees.
The males of the snowy cricket reach maturity and begin
to sing about the middle of July. The singer raises his
[65 ]
INSECTS
wings vertically above the back and vibrates them sidewise
so rapidly that they are momentarily blurred with each
note. The sound is that freat, treat, treat, treat already de-
scribed, repeated regularly, rhythmically, and monoto-
nously all through the night. At the first of the season
there may be about 125 beats every minute, but later, on
hot nights, the strokes become more rapid and mount to
160 a minute. In the fall again the rate decreases on cool
evenings to perhaps a hundred. And finally, at the end of
the season, when the players are benumbed with cold, the
Fic. 38. Distinguishing marks on the basal segments of the
antennae of common species of tree crickets
A, B, narrow-winged tree cricket, Oecanthus angustipennis. .C»
snowy tree cricket, miveus. D, four-spotted tree cricket, migri@
cornis quadripunctatus. E, black-horned tree cricket, nigricornis:
F, broad-winged tree cricket, /atipennis
notes become hoarse bleats repeated slowly and irregularly
as if produced with pain and difficulty.
The several species of tree crickets belonging to the
genus Oecanthus are similar in appearance, though the
males differ somewhat in the width of the wings and some
species are more or less diffused with a brownish color.
But on their antennae most species bear distinctive marks
(Fig. 38) by which they may be easily identified. The
snowy cricket, for example, has a single oval spot of black
on the under side of each of the two basal antennal joints
(Fig. 38 C). Another, the narrow-winged tree cricket, has
[ 66 |
THE GRASSHOPPER’S COUSINS
a spot on the second joint and a black J on the first (A, B).
A third, the four-spotted cricket (D), has a dash and dot
side by side on each joint. A fourth, the black-horned or
striped tree cricket (E), has two spots on each joint more
or less run together, or sometimes has the whole base of
the antenna blackish, while the color may also spread over
the fore parts of the body and, on some individuals, form
Fic. 39. Male and female of the narrow-winged tree cricket, Oecanthus angusti-
pennis
The female is feeding on a liquid exuded from the back of the male, while the
latter holds his fore wings in the attitude of singing. (Enlarged about 3 times)
stripes along the back. Ai fifth species, the broad-winged
(F), has no marks on the antennae, which are uniformly
brownish.
The narrow-winged tree cricket (Oecanthus angusti-
pennis) is almost everywhere associated with the snowy,
but its notes are very easily distinguished. They consist
of slower, purring sounds, usually prolonged about two
seconds, and separated by intervals of the same length, but
as fall approaches they become slower and longer. Always
they are sad in tone and sound far off.
The three other common tree crickets, the black-horned
or striped cricket, Oecanthus nigricornis, the four-spotted,
[ 67 |
INSECYs
O. nigricornis quadripunctatus,
and the broad-winged, O. /ati-
pennis, are all trillers; that 1s,
their music consists oF a long,
shrill whir kept up indefinitely.
Of these the broad-winged cricket
makes the loudest sound and the
one predominant near Washing-
ton. The black-horned is the
common triller farther north, and
is particularly a daylight singer.
In Connecticut his shrill note
rings everywhere along the road-
sides, on warm bright afternoons
Fic. 40. A male of the broad- ~— of September and October, as the
winged tree cricket, Oecanthus : Z
latipennis, with wings elevated Player sits on leaf or twig fully
in Position of singing, seen from exposed to the sun. At this
above and behind, showing
the basin (B) on his back into | season also, both the snowy and
which the liquid is exuded that the narrow-winged sing by day
attracts the female i
but usually later in the after-
noon and generally from more concealed places.
We should naturally like to know why these little
creatures are such _ persistent
singers and of what use their
music is to them. Do the males
really sing to charm and attract
the females as is usually pre-
sumed? We do not know; but
sometimes when a male is sing-
ing, a female approaches him
from behind, noses about on his
back, and soon finds there a deep
basinlike cavity situated just
behind the bases of the elevated te en eee ci
wings. This basin contains a broad-winged tree cricket,
clear liquid which dhe (Sree with its basin (B) that receives
secretion from the glands (G/)
proceeds to lap up very eagerly, inside the body
[ 68 ]
THE GRASSHOPPER’S COUSINS
as the male remains quiet with wings upraised though he
has ceased to play (Fig. 39). We must suspect, then, that
in this case the female has been attracted to the male
rather by his confectionery offering than by his music.
The purpose of the latter, therefore, would appear to be to
advertise to the female the whereabouts of the male, who
she knows has sweets to offer; or if the liquid is sour or
bitter it is all the same—the female likes it and comes
after it. If, now, this luring of the female sometimes ends
in marriage, we may see here the real reason for the male’s
possessing his music-making organs and his instinct to
play them so continuously.
A male cricket with his front wings raised, seen from
above and behind as he might look to a female, is shown in
Figure 40. The basin (B) on his back is a deep cavity on
the dorsal plate of the third thoracic segment. A pair of
large branching glands (Fig. 41, G/) within the body open
just inside the rear lip of the basin, and these glands fur-
nish the liquid that the female obtains.
There is another kind of tree cricket belonging to an-
other genus, Neoxadia, called the two-spotted tree cricket,
N. bipunctata, on account of two pairs of dark spots on the
wings of the female. This cricket 1s larger than any of the
species of Oecanthus and 1s of a pinkish brown color. It is
widely distributed over the eastern half of the United
States, but is comparatively rare and seldom met with.
Allard says its notes are low, deep, mellow trills con-
tinued for a few seconds and separated by short intervals,
as are the notes of the narrow-winged Oecanthus, but that
their tone more resembles that of the broad-winged.
THE BUSH CRICKETS
The bush crickets differ from the other crickets in having
the middle joint in the foot larger and shaped more like the
third joint in the foot of a katydid (Fig. 17 B). Among the
bush crickets there is one notable singer common in the
neighborhood of Washington. This is the jumping bush
[69]
INSECTS
cricket, Orocharis saltator (Fig. 42), who comes on the stage
late in the season, about the middle of August, or shortly
after. His notes are loud, clear, piping chirps with a rising
inflection toward the end, suggestive of the notes of a
small tree toad, and they at once strike the listener as
something new and
different in the insect
program. The play-
ers, however, are at
first very hard to lo-
cate, for they do not
perform continuously
—one note seems to
come from here, a
second from over
there, and a third
from a different an-
gle, so that it is al-
most impossible to
place any one of
them. But vafter ya
Fic. 42. The jumping bush cricket, Orocharts week or so the crick-
saltator ets become more nu-
Upper figure, a male; lower, a female merous and each
player more persistent till soon their notes are the predomi-
nant sounds in the nightly concerts, standing out loud and
clear against the whole tree-cricket chorus. As Riley says,
this chirp “is so distinctive that when once studied it is
never lost amid the louder racket of the katydids and
other night choristers.”
After the first of September it is not hard to locate one of
the performers, and when discovered with a flashlight, he is
found to be a medium-sized, brown, short-legged cricket,
built somewhat on the Style of Gr -yllius but smaller (Fig.
42). The male, however, while singing raises his wings
straight up, after the manner of the tree crickets, and he
too, carries a basin of liquid on his back much sought after
[70 ]
THE GRASSHOPPER’S COUSINS
by the female. In fact the liquid is so attractive to her
that, at least in a cage, she is sometimes so persistent in her
efforts to obtain it that the male is clearly annoyed and
tries to avoid her. One male was observed to say very
distinctly by his actions, as he repeatedly tried to escape
the nibbling of a female, presumably his wife since she was
taken with him when captured, “I do wish you would quit
pestering me and let me sing!” Here is another piece of
evidence suggesting that the male cricket sings to express
his own emotions, whatever they may be, and not pri-
marily to attract the female. But if, as in the case of the
tree crickets, his music
tells the female where
she may find her favorite
confection, and this in
turn leads to matrimony,
when the male is in the
proper mood, it suggests
a practical use and a rea-
son for the stridulating
apparatus and the song
of the male insect.
WALKING-STICKS AND
Lear INSEcTs
Talent often seems to
run in families, or in re-
lated families, but it does
not necessarily express it-
self in the same way. If
the katydids and crickets
Aron Fic. 43. The common walking-stick in-
are noted musicians, sect, Diapheromera femorata, of the eastern
some of their relatives part of the United States. (Length 2%
)
inches)
belonging to the family
Phasmidae, are incomparable mimics. Their mimicry,
however, is not a conscious imitation, but is one bred in
their bodily forms through a long line of ancestors.
[71]
INSECTS
If sometime in the woods you should chance to see a
short, slender piece of twig suddenly come to life and
slowly walk away on six slim legs, the marvel would not be
a miracle, but a walking-stick in-
sect (Fig. 43). These insects are
fairly common in the eastern parts
t | )) of the United States, but on ac-
p as count of their resemblance to
twigs, and their habit of remaining
perfectly quiet for a long time
with the body pressed close to a
branch of a tree, they are more
frequently overlooked than seen.
Sometimes, however, they occur
locally in great numbers. It is
supposed that the stick insects so
closely resemble twigs for the pur-
pose of protection from their
enemies, but it has not been shown
just what enemies they avoid by
their elusive shape. The stick in-
sects are more common in the
South and in tropical countries,
where some attain a remarkable
length, one species from Africa,
for example, being eleven inches
long when full-grown. In New
Guinea there lives a species that
looks more like a small club than
Fic. 44. A gigantic spiny é jf
walking-stick insect, Eury- ae stick, It being = large, heavy-
canthus horrida, from New bodied, spiny creature, nearly
Guinea. (Length 5%
eS SIX Tene in length and an
inch in width through the thick-
est part of its body (Fig. 44).
Other members of the phasmid family have specialized
on imitating leaves. These insects have wings in the
adult stage, and, of course, the wings make it easier for
[72]
THE GRASSHOPPER’S COUSINS
them to take the form of leaves. One famous species that
lives in the East Indies looks so much like two leaves stuck
together that it is truly marvelous that an insect could be
so fashioned (Fig. 45). The
whole body is flat, and about
three inches long, the bases of
the legs are broad and irregu-
larly notched, the abdomen is
spread out almost as thin as a
real leaf, and the leaflike wings
are held close above it. Finally,
the color, which is leaf-green
or brown, gives the last touch
necessary for complete dissim-
ulation.
THe Manrtips
It is often observed that
genius may be perverted, or
put to evil purposes. Here isa
family of insects, the Man-
Fic. 45. A tropical Jeaf insect,
i Pulchriphyllium pulchrifolium, a
tidae, related to the grass- member of the walking-stick fam-
ily. (Length 3 inches)
hoppers, katydids, and crick-
ets, the members of which are clever enough, but are
deceitful and malicious.
The praying mantis, Stagmomantis carolina (Fig. 46),
though he may go by the aliases of ‘“‘rear-horse’”’ and
“soothsayer,” gets his more common name from the
prayerful attitude he commonly assumes when at rest.
The long, necklike prothorax, supporting the small head,
is elevated and the front legs are meekly folded. But if
you examine closely one of these folded legs, you will see
that the second and third parts are armed with suspicious-
looking spikes, which are concealed when the two parts
are closed upon each other. In truth, the mantis is an
arch hypocrite, and his devotional attitude and meek
looks betoken no humility of spirit. The spiny arms,
eel
INSECES:
so innocently folded upon the breast, are direful weapons
held ready to strike as soon as some unsuspecting insect
happens within their reach. Let a small grasshopper
come near the posing saint: immediately a sly tilt of the
head belies the suppliant manner, the crafty eyes leer
upon the approaching insect, losing no detail of his
movements. Then, suddenly, without warning, the pray-
ing mantis becomes a demon in action. With a nice cal-
culation of distance, a swift movement, a snatch of the
Fic. 46. The praying mantis, Stagmomantis carolina, and remains of its
last meal. (Length 21% inches)
terrible clasps, the unlucky grasshopper is a doomed
captive, as securely held as if a steel trap had closed upon
his body. As the hapless creature kicks and wrestles, the
jaws of the captor sink into the back of his head, evidently
in search of the brain; and hardly do his weakening strug-
gles cease before the victim is devoured. Legs, wings,
and other fragments unsuitable to the taste of an epicure
are thrown aside, when once more the mantis sinks into
repose, piously folds his arms, and meekly awaits the
[74 ]
THE GRASSHOPPER’S COUSINS
chance arrival of the next
course in his ever unfinished
banquet of living fare.
Some exotic species of
mantids have the sides of
the prothorax extended to
form a wide shield (Fig. 47),
beneath which the forelegs
are folded and completely
hidden. Itis not clear what
advantage they derive from
this device, but it seems to
be one more expression of
deceit.
Of course, as we _ shall
take occasion to observe
later, goodness and _bad-
ness are largely matters of
relativity.
Fic. 47. A mantis from Ecuador with
a shieldlike extension of its back.
(Length 334 inches)
The mantis is an evil creature from the
standpoint of a grasshopper, but he
would be regarded as a benefactor by
those who have a grudge against grass-
hoppers or against other insects that the
mantis destroys. Hence, we must reckon
the mantis as at least a bonsioel: insect
relative to human welfare. A _ large
species of mantis, introduced a few years
ago into the eastern States from China,
is now regarded as a valuable agricul.
tural asset because of the number of
harmful insects it destroys.
The mantids lay their eggs in large
cases stuck to the twigs of trees (Fig. 48).
Fic. 48. Eggcaseofa The substance of which the case is made
mantis attached to a i¢ similar to that with which the locusts
twig, Stagmomantis
carolina inclose their eggs, and is exuded from the
[75]
INSECTS
body of the female mantis when the eggs are laid. The
young mantids are active little creatures, without wings
but with long legs, and it is the fate of those unprotected
green bugs, the aphids, or plant lice, that infest the leaves
of almost all kinds of plants, to become the principal
victims of their youthful appetites.
CHAPTER Th
ROACHES SAND OLE ANCIENT INSECTS
WE used to speak quite confidently of time as something
definite, measurable by the clock, and of a year or a cen-
tury as specific quantities of duration. In this present age
of relativity, however, we do not feel so certain about these
things. Geologists calculate in years the probable age of
the earth, and the length of time that has elapsed since
certain events took place upon it, but their figures mean
only that the earth has gone around the sun approximately
so many times during the interval. * In biology it signifies
nothing that one animal has been on the earth for a million
years, and another for a hundred million, for the unit of
evolution is not a year, but a generation. If one animal,
such as most insects, has from one to many generations
every year, and another, such as man, has only four or five
in a century, it is evident that the first, by evolutionary
reckoning, will be vastly older than the second, even
though the two have made the same number of trips with
the earth around the sun. An insect that antedates man
by several hundred million years, therefore, is ancient
indeed.
The roach scarcely needs an introduction, being quite
well known to all classes of society in every inhabited part
of the world. That he has long been established in human
communities is shown by the fact that the various nations
have bestowed different names upon him. His common
English name of “cockroach” is said to come from the
Spanish, cucaracha. The Germans call him, rather dis-
respectfully, AKichenschabe, which signifies “‘kitchen
[77]
INSECTS
louse.” The ancient Romans called him Blatta, and on
this his scientific family name of Blattidae is based. A
small species of Europe, named by the entomologists
Fic. 49. The four species of common household roaches
A, the German roach, or Croton bug, Blattella germanica (Jength % inch). B,
the American cockroach, Periplaneta americana (length 13% inches). C, the
Australian cockroach, Periplaneta australasiae (length 134 inches). D, the
wingless female of the Oriental roach, Blatta orientalis (length 11% inches). E,
the winged male of the Oriental roach (length 1 inch)
[78]
ROACHES AND OTHER ANCIENT INSECTS
Blattella germanica, which is now our most common
American roach, received the nickname of ‘“‘Croton bug”’
in New York, because somehow he seemed to spread with
the introduction of the Croton Valley water system, and
this appelation has stuck to him in many parts of the
country.
The Croton bug, or German roach (Fig. 49 A), is the
smallest of the “domestic” varieties of roaches. It is
that rather slender, pale-brown species, about five-eighths
of an inch in length, with the two dark spots on the front
shield of its body. This roach is the principal pest of the
kitchen in the eastern part of the United States, and prob-
OA
TUS ir OR Ee
bs MOO eE Lier Ate Ley
Fic. 50. Egg cases of five species of roaches. (Twice natural size)
A, egg case of the Australian roach (fig. 49 C). _B, that of the American
roach (fig. 49 B); the other three are made by out-of-door species
ably the best support of the trade in roach powders. Sev-
eral other larger species are fortunately less numerous,
but still familiar enough. Among these are one called
the American roach (Fig. 49 B), a second known as the
Australian roach (C), and a third as the Oriental roach
(D, E). These four species of cockroaches are all great
travelers and recognize no ties of nationality. They are
equally at home on land and at sea, and, as uninvited
[79]
INSEC IES
passengers on ships, they have spread to all countries
where ships have gone.
Besides the household roaches, there are great numbers
of species that live out of doors, especially in warm and
tropical regions. Most of these are plain brown of various
shades, or blackish, but some are green, and a few are
spotted, banded, or striped. Different species vary much
in size, some of the largest reaching a length of four inches,
measured to the tips of the folded wings, while the smallest
are no longer than three thirty-seconds of an inch in
length. They nearly all have the familiar flattened form,
with the head bent down beneath the front part of the
body, and the long, slender antennae projecting forward.
Most species have wings which they keep closely folded
over the back. In the Oriental roach, the wings of the
female are very short (Fig. 49 D), a character which gives
them such a different appearance from the males (E) that
the two sexes were formerly supposed to be different species.
The roach, of course, was not designed to be a household
insect, and it lived out of doors for ages before man con-
structed dwellings, but it happens that its instincts and its
form of body particularly adapt it to a life in houses. Its
keen sense, its agility, its nocturnal habits, its omnivorous
appetite, and its flattened shape are all qualities very
fitting for success as a domestic pest.
Many kinds of roaches give birth to living young; but
most of our common species lay eggs, which they inclose in
hard-shelled capsules. The material of the capsule is a
tough but flexible substance resembling horn, and 1s pro-
duced as a secretion by a special gland in the body of the
female opening into the egg duct. The capsule is formed
in the egg duct, and the eggs are discharged into it while
the case is held in the orifice of the duct. When the re-
ceptacle is full its open edge is closed, and the eggs are thus
tightly sealed within it. The sealed border is finely
notched, and transverse impressions on the surface of the
capsule indicate the position of the eggs within it.
[ 80 ]
ROACHES AND OTHER ANCIENT INSECTS
The Croton bug, or German roach (Fig. 49 A), makes a
small flat tabloid egg case, which the female usually carries
about with her for some time projecting from the end of
her body, and sometimes the eggs hatch while she is still
carrying the case. The American and Australian roaches
(Fig. 49 B, C) make egg cases much resembling miniature
pocketbooks or tobacco pouches, about three-eighths or
half an inch in length, with a serrated clasp along the upper
edge (Fig. 50 A, B). The cases of some of the smaller
species of roaches are only one-sixteenth of an inch long
Fic. 51. Young of the German roach, or Croton bug (fig. 49 A), in various
stages just before and after hatching
A, the young roach in the egg just before hatching. B, the young roach just
after hatching, shedding its embryonic covering membrane. C, young roach
after shedding the embryonic covering. D, the same individual half an hour old
(C), while larger species may make a case three-quarters
of an inch in length (E).
The embryo roaches mature within the eggs, and when
they are ready to hatch they emerge inside the egg case.
By some means, the roughened edge of the case where it
was last closed is opened to allow the imprisoned insects
to escape. Small masses of the tiny creatures now bulge
out, and finally the whole wriggling contents of the cap-
sule is projecting from the slit. First one or two indi-
viduals free themselves, then several together fall out,
then more of them, until soon the case containing the
empty eggshells is deserted.
[81]
INSECTS
When the young roaches first liberate themselves from
the capsule, they are helpless creatures, for each is con-
tained in a close-fitting membrane that binds its folded
legs and antennae tightly to the body and keeps the head
pressed down against the breast (Fig. 51 A). The inclos-
ing sheath, however, a film so delicate as to be almost
invisible, is soon burst by the struggling of the little roach
anxious to be free—it splits and rapidly slides down over
the body (B), from which it is at last pushed off. The
shrunken, discarded remnant of the skin is now such an
insignificant flake that it scarce seems possible it so re-
cently could have enveloped the body of the insect.
The newly liberated young roach dashes off on its slim
legs with an activity quite surprising 1n a creature that has
never had the use of its legs before. It is so slender of
figure (Fig. 51 C) that it does not look like a roach, and it is
pale and colorless except for a mass of bright green material
in its abdomen. But, almost at once, it begins to change;
the back plates of the thorax flatten out, the body shortens
by the overlapping of its segments, the abdomen takes on
a broad, pear-shaped outline, the head is retracted be-
neath the prothoracic shield, and by the end of half an
hour the little insect is unmistakably a young cockroach
(D):
The roaches have a potent enemy in the house centipede,
that creature of so many legs (Fig. 52) that it looks like
an animated blur as it occasionally darts across the living-
room floor or disappears in the shades of the basement
before you are sure whether you have seen something or
not, but which is often trapped in the bathtub, where its
appearance is likely to drive the housewife into hysteria.
Unless you are fond of roaches, however, the house centi-
pede should be protected and encouraged. The writer
once placed one of these centipedes in a covered glass dish
containing a female Croton bug and a capsule of her eggs
which were hatching. No sooner were the young roaches
running about than the centipede began a feast which
[ 82 J
"2
ROACHES AND OTHER ANCIENT INSECTS
ended only when the last of the brood had been devoured.
The mother roach was not at the time molested, but next
morning she lay dead on her back, her head severed and
dragged some distance from the
body, which was sucked dry of /
its Juices—mute evidence of the js
tragedy that had befallen some- /
time in the night, probably when
the pangs of returning hunger
stirred the centipede to renewed
activity. The house centipede
does not confine itself to a diet of
live roaches, for it will eat almost
any kind of food, but it is never
a pest of the household larder. PBN
Most species of roaches have igs:s
two pairs of well-developed }
wings, which they ordinarily keep
folded over the back, for in their
usual pursuits the domestic spe-
cies do not often fly, except oc-
casionally when hard pressed to
avoid capture. The front wings
are longer and thicker than the “
hind wings, and are laid over the \
latter, which are thin and folded
fanwise when not inuse. In these Fic. 52. The common house
characters the roaches resemble ee eee
the grasshoppers and katydids, young roaches
and their family, the Blattidae, is
usually placed with these insects in the order Orthoptera.
The wings of insects are interesting objects to study.
When spread out flat, as are those of the roach shown in
Figure 53, they are seen to consist of a thin membranous
tissue strengthened by many branching ribs, or veins,
extending outward from the base. The wings seit insects
are constructed on the same general plan and have the
[83 ]
INSECTS
same primary veins; but, since the great specialty of in-
sects is flight, in their evolution they have concentrated
on the wings, and the different groups have tried out
different styles of venation, with the result that now
each is distinguished by some particular pattern in the
arrangement of the veins and their branches. The
entomologist can thus not only distinguish by their wing
structure the various orders of insects, as the Orthoptera,
the dragonflies, the moths, the bees, and the flies, but in
Fic. 53. Wings of a cockroach, Periplaneta, showing the vein
pattern characteristic of the roach family
many cases he can identify families and even genera.
Particularly are the wings of value to the student of fossil
insects, for the bodies are so poorly preserved in most
cases that without the wings the paleontologist could
have made little headway in the study of insects of the
past. As it 1s, however, much is known of insects of
former times, and a study of their fossil remains has con-
tributed a great deal to our knowledge of this most
versatile and widespread group of animals.
[ 84]
ROACHES AND OTHER ANCIENT INSECTS
The paleontological history of life on the earth shows
us that the land has been inhabited successively by
different forms of animals and plants. A particular group
of creatures appears upon the scene, first in comparative
insignificance; then it increases in Alene. in diversity
of forms, and usually in the size of individuals, and may
become the dominant form of life; then again it falls
back to insignificance as its individuals decrease in size,
its species in numbers, until perhaps its type becomes
extinct. Meanwhile another group, representing another
type of structure, comes into prominence, flourishes, and
declines. It is a mistake, however, to get the impression
that all forms of life have had this succession of up and
down in their history, for there are many animals that
have existed with little change for immense periods of
time.
The history of insects gives us a good example of per-
manence. The insects must have begun to be insects
somewhere in those remote periods of time before the
earliest known records of animals were preserved in the
rocks. They must have been present during the age when
the water swarmed with sharks and great armored fishes;
they certainly flourished during the era when our coal
beds were being deposited; they saw the rise of the huge
amphibians and the great reptilian beasts, the Dinosaurus,
the /chthyosaurus, the Plestosaurus, the Mosasaurus, ane
all the rest of that monster tribe whose names are now
familiar household words and whose bones are to be seen
in all our museums. The insects were branching out
into new forms during the time when birds had teeth and
were being evolved from their reptile ancestors, and when
the flowering plants were beginning to decorate the land-
scape; they were present from the beginning of the age
of mammals to its culmination in the great fur-bearing
creatures but recently extinct; they attended the advent
of man and have followed man’s whole evolution to the
present time; they are with us yet—a vigorous race that
[85]
INSECTS
shows no sign of weakening or of decrease in numbers.
Of all the land animals, the insects are the true blue-blood
aristocrats by length of pedigree.
The first remains of insects known are found in the
upper beds of the rocks laid down in the geological period
of the earth’s history known as the Carboniferous. Dur-
Fic. 54. A group of common Carboniferous plants reaching the size and pro-
portions of large trees. (From Chamberlin and Salisbury, drawn by Mildred
Marvin from restorations of fossil specimens.) Courtesy of Henry Holt & Co.
Of the two large trees in the foreground, the one on the left is a Sigt//aria, that
on the right a Lepidodendron; of the two large central trees in the background
the left is a Cordaites, the right a tree fern; the tall stalks in the outermost circle
are Calamites, plants related to our horsetail ferns
ing Carboniferous times much of the land along the
shores of inland seas or lakes was marshy and supported
great forests from which our coal deposits have been
formed. But the Carboniferous landscape would have
had a strange and curious look to us, accustomed as we
| 86 |
ROACHES AND OTHER ANCIENT INSECTS
are to an abundance of hard-wood, leafy trees and shrubs,
and a multitude of flowering plants. None of these
forms of vegetation had yet appeared.
Much of the undergrowth of the Carboniferous swamps
was composed of fernlike plants, many of which were,
indeed, true ferns, and perhaps the ancestors of our
modern brackens. Some of these ancient ferns grew to
a great size, and rose above the rest in treelike forms, at-
taining a height of sixty feet and more, to branch out
in a feathery crown of huge spreading fronds. Another
group of plants characteristic of the Carboniferous flora
comprised the seed ferns, so named because, while closely
resembling ferns in general appearance, they differed
from true ferns in that they bore seeds instead of spores.
The seed ferns were mostly small plants with delicate,
ornate leaves, and they have left no descendants to modern
times.
Along with the numerous ferns and seed ferns in the
Carboniferous swamps, there were gigantic club mosses,
or lycopods, which, ascending to a height sometimes of
much more than a hundred feet, were the conspicuous big
trees in the forests of their day (Fig. 54). These lycopods
had long, cylindrical trunks covered with small scales
arranged in regular spiral rows. Some had thick branch-
ing limbs starting from the upper part of the trunk and
closely beset with stiff, sharp-pointed leaves; others
bore at the top of the trunk a great cluster of long slender
leaves, giving them somewhat the aspect of a gigantic
variety of our present-day yucca, or Spanish bayonet.
The bases of the larger trees expanded to a diameter of
three or four feet, and were supported on huge spreading
underground branches from which issued the roots—a
device, perhaps, that gave them an ample foundation in
the soft mud of the swamps in which they grew.
The Carboniferous lycopods furnished most of our coal,
and then, in later times, their places were taken by other
types of vegetation. But their race is not yet extinct,
[ 87 ]
INSECTS
for we have numerous representatives of them with us
today in those lowly evergreen plants known as club
mosses, whose spreading, much-branched limbs, usually
trailing on the ground, are covered by rows of short,
stiff leaves. The most familiar of the club mosses, though
not a typical species, is the “ground pine.” This humble
little shrub, so much sought for Christmas decoration,
still in some places carpets our woods with its soft, broad,
frondlike stems. In the fall when its rich dark green
SO pleasingly contrasts with the somber tones of the
season’s dying foliage, it seems to be an expression of
the vitality that has preserved the lycopod race through
the millions of years which have elapsed since the days of
its great ancestors. The “‘resurrection plant,” often sold
to housekeepers under false or exaggerated claims of a
marvelous capacity for rejuvenation, is also a descendant
of the proud lycopods of ancient times.
In our present woodlands, along the banks of streams
or in other moist places, there grows also another plant
that has been preserved to us from the Carboniferous
forests—the common “‘horsetail fern,” or Eguisetum, that
green, rough-ribbed stalk with the whorls of slender
branches growing from its joints. Our equisetums are
modest plants, seldom attaining a height of more than a
few feet, though in South American countries some species
may reach aa aleieude of thirty feet; but in Carboniferous
times their ancestors grew to the stature of trees (Fig. 54)
and measured their robust stalks with the trunks of the
lycopods and giant ferns.
Aside from the numerous representatives of these sev-
eral groups of plants, all more or less allied to the ferns,
the Carboniferous forests contained another group of
treelike plants, called Cordaites, from which the cycads
of later times and our present-day maidenhair tree, or
ginko, are probably descended. Then, too, there were a
few representatives of a type that gave origin to our
modern conifers.
[ 88 |
ROACHES AND OTHER ANCIENT INSECTS
It is probable that a visitor to those days of long ago
might give us a more complete account of the vegetation
that grew in the Carboniferous swamps than can be known
from the records of the rocks, but the paleobotanist has
a wealth of material now at hand sufficient to give us
at least a pretty reliable picture of the setting in which
the earliest of known insects lived and died.
And now, what were the insects like that inhabited
the forests af those early times? Were they, too, strangely
fashioned creatures, fit denizens of a far-off fairyland?
No, nothing of the sort, at least not in appearance or
structure, though “‘fit”’ ey probably were, from a physi-
cal standpoint, for insects are fitted to live almost any-
where. In short, the Carboniferous insects were prin-
cipally roaches! Yes, those woods and swamps of millions
of years ago were alive with roaches little different from
our own familiar household pests, or from the numerous
species that have not forsaken their native habitats for
life in the cities.
Whoever looks to the geological records for evidence
of the evolution of insects is sorely disappointed, for
even in the venation of the wings those early roaches
(Fig. 55) were almost identical with our present species
(Big.263). As typical examples of the Carboniferous
roaches, the species shown in Figure 55 serve well, and
anyone can see, even though the specimens lack antennae
and legs, that the creatures were just common roaches.
Hence, we can easily picture these ancient roaches scut-
tling up the tall trunks of the scaly lycopods, and shuffling
in and out among the bases of the close-set leaf stems
of the tree ferns, and we should expect to find an abundant
infestation of them in the vegetational refuse matted on
the ground. Insects of those days must have been com-
paratively free from enemies, for birds did not yet exist,
and all that host of parasitic insects that attack other
insects were not evolved until more recent times.
Though by far the greater number of the Carboniferous
[ 89 ]
INSECES
insects known are roaches, or insects closely related to
roaches, there were many other forms besides. Some of
these are of particular interest to entomologists because,
in some ways, they are more simple in structure than are
Fic. 55. Fossil cockroaches from Upper Carboniferous rocks
A, Asemoblatta mazona, found in Illinois, length of wing one inch.
(From Handlirsch after Scudder.) B, Phyloblatta carbonaria,
found in Germany. (From Handlirsch)
any of the modern insects, and in this respect they ap-
parently stand closer to the hypothetical primitive insects
than do any others that we know. And yet, the charac-
ters by which these oldest known insects, called the
Paleodictyoptera, ditter from modern forms are so slight
that they would scarcely be noticed by anyone except
an entomologist; to the casual observer, the Paleodic-
tyoptera would be just insects. Their chief distinguish-
ing marks are in the pattern of the wing venation, which
is more symmetrical than in other winged insects, and,
therefore, probably closer to that of the primitive ances-
tors of all the winged insects. These ancient insects
probably did not fold the wings over the back, as do most
present-day insects, showing thus another primitive
[ go ]
ROACHES AND OTHER ANCIENT INSECTS
character, though not a distinctive one, since modern
dragonflies (Fig. 58) and mayflies (Fig. 60) likewise
keep the wings extended when at rest.
The question of how insects ‘acquired wings 1s always
one of special interest, since, while we know perfectly
well that the wing of a bird or of a bat is merely a modi-
fied fore limb, the nature of the primitive organ from
which the insect wing has been evolved is still a mystery.
The Paleodictyoptera, however, may throw light upon
the subject, for some of them had small flat lobes on the
lateral edges of the back plate of the prothorax, which in
fossil specimens look like undeveloped wings (Fig. 56).
The presence of these prothoracic lobes, occurring as they
do in some of the oldest known insects, has suggested the
Fic. 56. Examples of the earliest known fossil insects, called the Paleodic-
tyoptera, having small lobes (a) projecting like wings from the prothorax
A, Stenodictya lobata (from Brongniart). B, Eudbleptus danielsi (drawn from
specimen in U. S. Nat. Mus.): Ti, T2, Ts, back plates of three thoracic segments
idea that the true wings were evolved from similar flaps
of the mesothorax and metathorax. If so, we must pic-
ture the immediate ancestors of the winged insects as
creatures provided with a row of three flaps on each side
of the body projecting stifly outward from the edges of
the thoracic segments. Of course, the creatures could
not actually fly with wings of this sort, but probably
[91]
INSEGES
they could glide through the air from the branches of one
tree to another as well as can a modern flying squirrel by
means of the folds of skin stretched along the sides of its
body between the fore and the hind legs. If such lobes
then became flexible at their bases, 1t required only a
slight adjustment of the muscles already present in the
body to give them motion in an up-and-down direction;
and the wings of modern insects, in most cases, are still
moved by a very simple mechanism which has involved
the acquisition of few extra muscles.
It appears, however, that three pairs of fully-developed
wings would be too many for mechanical efficiency. In
the later evolution of insects, therefore, the prothoracic
lobes were never developed beyond the glider stage, and
in all modern insects this first pair of lobes has been lost.
Furthermore, it was subsequently found that swift flight
is best attained with a single pair of wings; and nearly
all the more perfected insects of the present time have
the hind pair of wings reduced in size and locked to the
front pair to insure unity of action. The flies have
carried this evolution toward a two-winged condition so
far that they have practically achieved the goal, for with
them the hind wings are so greatly reduced that they
no longer have the form or function of organs of flight, and
these insects, named the Diptera, or two- winged insects,
fly with one highly specialized and efficient pair of wings
(Fig. 167).
The Paleodictyoptera became extinct by the end of the
Carboniferous period, and their disappearance gives
added support to the idea that they were the last sur-
vivors of an earlier type of insect. But they were by
no means the primitive ancestors of insects, for, in the
possession of wings alone, they show that they must have
undergone a long evolution while wings were in the course
of development; but of this stage in the history of insects
we know nothing. The rocks, so far as has yet been
revealed, contain no records of insect life below the upper
[92]
ROACHES AND OTHER ANCIENT INSECTS
beds of the Carboniferous deposits, when insects were
already fully winged. This fact shows how cautious
we must be in making negative statements concerning
the extinct inhabitants of the earth, for we know that
insects must have lived long before we have evidence of
their existence. The absence of insect fossils earlier than
the Carboniferous is hard to explain, because for millions
of years the remains of other animals and plants had
Fic. 57. Machilis, a modern representative of ancient insects before the
development of wings. (Length of body %» inch)
been preserved, and have since been found in compara-
tive abundance. As a consequence, we have no concrete
knowledge of insects before they became winged creatures
evolved almost to their modern form.
At the present time there are wingless insects. Some
of them show clearly that they are recent descendants
from winged forms. Others suggest by their structure
that their ancestors never had wings. Such as these,
therefore, may have come down to us by a long line ee
descent from the primitive wingless ancestors of all the
insects. The common “fish moth,” known to entomolo-
gists as Lepisma, and its near relation, Machi/is (Fig. 57),
are familiar examples of the truly wingless insects of the
present time, and if their remote ancestors were as fragile
and as easily crushed as they, we may see a reason why
they never left their i impressions in the rocks.
Along with the Carboniferous roaches and the Paleo-
dictyoptera, there lived a few other kinds of insects,
many of which are representative of certain modern
[93]
INSECTS
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[94 |
ROACHES AND OTHER ANCIENT INSECTS
groups. Among the latter were dragonflies, and some of
these must have been of gigantic size, for insects, because
they attained a wing expanse of fully two feet, while the
largest of modern dragonflies do not measure more than
eight inches across the expanded wings. But the length
of wing of the extinct giant dragonflies does not necessarily
mean that the bulk of the body was much greater than
that of the largest insects living today. In general, the
insects of the past were of ordinary size, the majority of
them probably matching with insects of the present time.
The modern dragonflies (Fig. 58) are noted for their
rapid flight and for the ability to make instantaneous
changes in the direction of their course while flying.
These qualities enable them to catch other insects on the
wing, which constitute their food. Their wings are pro-
vided with sets of special muscles, such as other insects
do not possess, showing that the dragonflies are descended
along a line of their own from their Carboniferous pro-
genitors. They still retain a character of their ancestors
in that they are unable to fold the wings flat over the back
in the manner that most other insects fold their wings
when they are not using them. The larger dragonflies
hold the wings straight out from the sides of the body
when at rest (Fig. 58); but a group of slender dragonflies,
known as the damselflies (Plate 1, Fig. 2), bring the wings
together over the back in a vertical plane.
The dragonflies are usually found most abundantly in
the neighborhood of open bodies of water. Over the
unobstructed surface of the water the larger species find
a convenient hunting ground; but a more important
reason for their association with water is that they lay
their eggs either in the water or in the stems of plants
growing in or beside it. The young dragonflies (Fig. 59)
are aquatic and must have an easy access to water. They
are homely, often positively ugly, creatures, having none
of the elegance of their parents. They feed on other
living creatures which their swimming powers enable
[95]
INSECUS
them to pursue, and which they capture by means of
grasping hooks on the end of their extraordinarily long
underlip (Fig. 134 A), which can be shot out in front of
the head (B). The great swampy lakes of Paleozoic times
must have furnished an ideal habitat for dragonflies, and
it is probable that the most ancient
dragonflies known had a structure
and habits not very different from
those of modern species.
Another very common insect of
the present time, which appears
ltkewise to be a direct descendant
of Paleozoic ancestors, 1s the may-
fly (Fig. 60). The young mayflies
(Fig. 61) also live in the water, and
are provided with gills for aquatic-
breathing, having the form of flaps
or filaments situated in a row along
each side of the body. The adults
(Fig. 60) are very delicate insects
with four gauzy wings, and a pair
of long threadlike tails projecting
Fis. gg. Ayounp dragons icOM) Cheereat end Gietite DodyaneG
fly, an aquatic creature the time of their transformation
that leaves the water only 5 5
when ready to transform they often issue in great swarms
into the adult (fig. 58) from the water, and they are par-
ticularly attracted to strong lights.
For this reason large numbers of them come to the cities
at night, and in the morning they may be seen sitting
about on walls and windows, where they find themselves
in a situation totally strange to their native habits and
instincts. The mayflies do not fold their wings horizon-
tally, but when at rest bring them together vertically
over the back (Fig. 60). In this respect they, too, appear
to preserve a character of their Paleozoic ancestors;
though it must be observed that the highly evolved
modern butterflies close their wings in the same fashion.
[ 96 |
BROACHES AND OTHER ANCIENT INSECTS
The roaches, the dragonflies, and the mayflies attest
the great antiquity of insects, for since these forms ex-
isted practically as they are today i in Paleozoic times, the
primitive ancestors of all the insects, of which we have
no remains in the geological records, must have lived in
times vastly more remote. However, though we may
search in vain the paleontological records for evidence
of the origin and early development of insects, the sub-
sequent evolution of the higher forms of modern insects
is clearly shown by the species preserved in eras later
Fic. 60. A mayfly, representative of another order of primitive
winged insects having numerous relations in Paleozoic times.
(Twice natural size)
than the Carboniferous. Such insects as the beetles,
the moths, the butterflies, the wasps, the bees, and the
flies are entirely absent in the older rocks, but make their
appearance at later periods or in comparatively recent
times, thus confirming the idea derived from a study of
their structure that they have been evolved from an-
cestors more closely resembling the paleodictyopteran
types of the Carboniferous beds.
The long line of descent of the roach, with almost no
change of form or structure, furnishes material for a
special lesson in evolution. If evolution has been a
[97]
INSECTS
matter of survival of the fittest, the roach, judged by
survival, must be a most fit insect. Its fitness, however,
is of a general nature; it is one that adapts the roach to
live successfully in many kinds of conditions and circum-
stances. Most other forms of mod-
ern insects have been evolved
through an adaptation to more
special kinds of habitats and to
particular ways of living or of feed-
ing. Such insects we say are
specialized, while those exemplified
in the roach are said to be general-
ized. Survival, therefore, may de-
pend either on generalization or on
specialization. Generalized forms
of animals have a better chance of
surviving through a series of chang-
ing conditions than has an animal
which is specifically adapted to one
kind of life, though the latter may
have an advantage as long as con-
ditions are favorable to it.
The roaches, therefore, have sur-
vived to present times, and will
Fic. 61. A young mayfly, :
5 Tae nbeee sk probably live as long as the earth is
ture. (One-half larger habitable, because, when driven
than natural size) :
from one environment, they make
themselves at home in another; but we have all seen how
the specialized mosquito disappears when its breeding
places are destroyed. From this consideration we can
draw some consolation for the human race, if we do not
mind likening ourselves to roaches; for, as the roach,
man is a versatile animal, capable of adapting himself to
all conditions of living, and of thriving in extremes.
[98]
CHAPTER IV
WAYS AND MEANS OF LIVING
In our human society each individual must obtain the
things necessary for existence; the manner by which he
acquires them, whether by one trade or another, by this
means or by that, does not physically matter so long as he
provides himself and his family with food, clothing, and
shelter. Exactly so it is with all forms of life. The
physical demands of living matter make certain things
necessary for the maintenance of life in that matter, but
nature has no law specifying that any necessity shall be
acquired in a certain manner. Life itself is a circum-
scribed thing, but it has complete freedom of choice in
the ways and means of living.
It is useless to attempt to make a definition of what
living matter 1s, or of how it differs from non-living matter,
for all definitions have failed to distinguish animate from
non-animate substance. But we all know that living things
are distinguishable from ordinary non-living things by the
fact that they make some kind of response to changes in
the contact between themselves and their environment.
The “environment,” of course, must be broadly inter-
preted. Biologically, it includes all things and forces that
in any way touch upon living matter. Not only has every
plant and animal as a whole its environment, but every
part of it has an environment. The cells of an animal’s
stomach, for example, have their environment in the blood
and lymph on one side, the contents of the stomach on the
other; in the energy of the nerves distributed to them; and
in the effects of heat and cold that penetrate them.
[99]
INSECTS
The environmental conditions of the life of cells in a
complex animal are too complicated for an elemental
study; the elements of life and its basic necessities are bet-
ter understood in a simple organism, or in a one-celled
animal; but for purposes of description, it is most con-
venient to speak of the properties of mere protoplasm.
All the vital needs of the most highly organized animal are
present in any part of the protoplasmic substance of which
it is composed.
Protoplasm is a chemical substance, or group of sub-
stances, the structure of which is very complex but 1s main-
tained so long as there 1s no disturbance in the environ-
Fic. 62. Diagram showing the relation of the germ cells (GC/s) and the body
cells (BC/s) in successive generations
A fertilized germ cell of generation A forms the germ cells and body cells of B,
a fertilized germ cell of B forms the germ cells and body cells of C, and so on.
The offspring C of B derives nothing from the body cells of the parent B, but
both offspring C and parent B have a common origin in a germ cell of A
ment. Let some least thing happen, however, such as a
change in the temperature, in the strength of the light, in
the weight of pressure, or in the chemical composition of
the surrounding medium, and the protoplasmic molecules,
in the presence of oxygen, are likely to have the balance of
their constituent particles upset, whereupon they partly
decompose by the union of their less stable elements with
oxygen to form simpler and more permanent compounds.
The decomposition of the protoplasmic substances, like all
processes of decomposition, liberates a certain amount of
energy that had been stored in the making of the molecule,
and this energy may manifest itself in various ways. If it
[| 100 }
WAYS AND MEANS OF LIVING
takes the form of a change of shape in the protoplasmic
mass, Or movement, we say the mass exhibits signs of life.
The state of being alive, however, is more truly shown if
the act can be repeated, for the essential property of living
matter is its power of reverting to its former chemical
composition, and its ability thus gained of again reacting
to another change in the environment. In restoring its
lost elements, it must get these elements anew from the
environment, for 1t can not take them back from the sub-
stances that have been lost.
Here, expressed in its lowest terms, is the riddle of the
physical basis of life and of the incentive to evolution in
the forms of life. Not that these mysteries are any more
easily understood for being thus analyzed, but they are
more nearly comprehended. Being alive is maintaining the
power of repeating an action; it involves sensitivity to
stimuli, the constant presence of free oxygen, elimination
of waste, and a supply of substances from which carbon,
hydrogen, nitrogen, and oxygen, or other necessary ele-
ments, are readily available for replacement purposes.
Evolution results from the continual effort of living matter
to perform its life processes in a more efficient manner, and
the different groups of living things are the result of the
different methods that life has tried and found advan-
tageous for accomplishing its ends. Living organisms are
machines that have become more and more complex in
structure, but always for doing the same things.
If animals may be compared with machines in their
physical mechanism, they are like them, too, in the fact
that they wear out and are at last beyond repair. But
here the simile ends, for when your car will no longer run,
you must go to the dealer and order a new one. Nature
provides continuous service by a much better scheme, for
each organism is responsible for its own successor. This
phase of life, the replacement of individuals, opens another
subject involving ways and means, and it, likewise, can be
understood best in its simpler manifestations.
[ ror |
INSECTS
The facts of reproduction in animals are not well ex-
pressed by our name for them. Instead of “reproduc-
tion,” it would be truer to say ‘‘repeated production,” for
individuals do not literally reproduce themselves. Genera-
tions are serially related, not each to the preceding; they
follow one another as do the buds along the twig of a tree,
Fic. 63. The external structure of an insect
The body of a grasshopper dissected showing the head (H), the thorax (TA),
and the abdomen (44). The head carries the eyes (Z), the antennae (4nt), and
the mouth parts, which include the labrum (Zm), the mandibles (Md), the
maxillae (Mx), and the labium (Ld). The thorax consists of three segments
(7, 2, 3), the first separate and carrying the first legs (Zi), the other two com-
bined and carrying the wings (42, 4#’s), and the second and third legs (Zz, Ls).
The abdomen consists of a series of segments; that of the grasshopper has a
large tympanal organ (7m), probably an ear, on each side of its base. The end
of the abdomen carries the external organs of reproduction and egg-laying
and buds on the same twig are identical or nearly so, not
because one produces the next, but because all are the
result of the same generative forces in the twig. If the
spaces of the twig between the buds were shortened until
[ 102 |
WAYS AND MEANS OF LIVING
one bud became contiguous with the one before, or became
enveloped by it, a relation would be established between
the two buds similar to that which exists between succes-
sive generations of life forms. The so-called parent gen-
eration, in other words,
contains the germs of the
succeeding generation,
but it does not produce
them. Each generation
is simply the custodian
of the germ cells entrust-
ed to it, and the “‘off-
spring” resembles the
parent, wot because it is
a chip off the parental
block, but because both
parent and offspring are
developed from the same
line of germ cells.
Parents create the
conditions under which
the germ cells will de-
velop; they nourish and
protect them during the
period of their develop-
ment; and, when each
generation has_ served
the purpose of its ex-
istence, it sooner or
later dies. But the in-
Fic. 64. The leg of a young grasshopper,
showing the typical segmentation of an
insect’s leg
The leg is supported on a pleural plate
(Pl) in the lateral wall of its segment.
The basal segment of the free part of the
leg is the coxa (Cx), then comes a small
trochanter (Jr), next a long femur (F)
separated by the knee bend from the
tibia (7), and lastly the foot, consisting
of a sub-segmented tarsus (Tar), and a
pair of terminal claws (C/) with an ad-
hesive lobe between them
dividuals produced from its germ cells do the same
for another set of germ cells produced simultaneously
with themselves, and so on as long as the species
persists.
To express the facts of succession in each specific form of
animal, then, we should analyze each generation into germ
cells and an accompanying mass of protective cells which
[ 103 ]
INSECTS
forms a body, or soma, the so-called parent. Both the
body, or somatic, cells and the germ cells are formed from a
single primary cell, which, of course, is usually produced
by the union of two incomplete germ cells, a spermatozoon
and an egg. The primary germ cell divides, the daughter
cells divide, the cells of this division again divide, and the
division continues indefinitely until a mass of cells 1s pro-
duced. At a very early stage of division, however, two
groups of cells are set apart, one representing the germ
cells, the other the somatic cells. The former refrain from
further development at this time; the latter proceed to
build up the body of the parent. The relation of the
somatic cells to the germ cells may be represented diagram-
matically as in Figure 62, except that the usual dual par-
entage and the union of germ cells is not expressed. The
sexual form of reproduction is not necessary with all lower
animals, nor with all generations of plants; in some insects
the eggs can develop without fertilization.
The fully-developed mass of somatic cells, whose real
function is that of a servant to the germ cells, has assumed
such an importance, as public servants are prone to do,
that we ordinarily think of it, the body, the active sentient
animal, as the essential thing. This attitude on our part
is natural, for we, ourselves, are highly organized masses
of somatic cells. From a cosmic standpoint, however, no
creature is important. Species of animals and plants exist
because they have found ways and means of living that
have allowed them to survive, but the physical universe
cares nothing about them—the sunshine is not made for
them, the winds are not tempered to suit their conven-
ence. Life must accept what it finds and make the best
of it, and the question of how best to further its own wel-
fare is the problem that confronts every species.
The sciences of anatomy and physiology are a study of
the methods by which the soma, or body, has contrived to
meet the requirements imposed upon it by the unchanging
laws of the physical universe. The methods adopted are as
[ 104 ]
WAYS AND MEANS OF LIVING
numerous as the species of plants and animals that have
existed since life began. A treatise on entomology, there-
fore, is an account of the ways and means of living that
insects have adopted and perfected in their somatic organ-
ization. Before discussing insects in particular, however,
we must understand a little more fully the principal con-
ditions of living that na-
ture places on all forms of
life.
As we have seen, life is
a series of chemical re-
actions in a_ particular
kind of matter that can
carry on these reactions.
A “reaction” is an action;
and every act of living
matter involves a break-
ing down of some of the
substances in the proto-
plasm, the discharging of
the waste materials, and
the acquisition of new
materials to replace those
lost. The reaction is in-
herent in the physical or Fic. 65. Legs i Senay se showing
. . a special modi cations
chemical properties of A, outer surface of a hind leg, with a
protoplasmic compounds pollen basket on the tibia (74) loaded
ea d h with pollen. B, a fore leg, showing the
an epends upon the antenna cleaner (a) between the tibia and
substances with which the tarsus, and the long, hairy basal
segment of the tarsus (7 Tar), which is
the protoplasm 1s Sur- used as a brush for cleaning the body
rounded. It is the func-
tion of the creature’s mechanism to see that the con-
ditions surrounding its living cells are right for the con-
tinuance of the cell reactions. Each cell must be
provided with the means of eliminating waste material
and of restoring its lost material, since it can not utilize
that which it has discarded.
[ 105 |
INSECTS
With the conditions of living granted, however, proto-
plasm is still only potentially alive, for there is yet required
a stimulus to set it into activity. The stimulus for life
activities comes from changes in the physical forms of
energy that surround or infringe upon the potentially
living substance; for, “‘live’”’ matter, like all other matter,
is subject to the law of inertia, which decrees that it must
remain at rest until motion is imparted to it by other
Fic. 66. The head and mouth parts of a grasshopper
A, facial view of the head, showing the positions of the antennae (4nf), the
large compound eyes (Z), the simple eyes, or ocelli (OQ), the broad front lip,
or labrum (Lm) suspended from the cranium by the clypeus (C/p), and the
bases of the mandibles (Ad, Md) closed behind the labrum
B, the mouth parts separated from the head in relative positions, seen from
in front: HpAy, hypopharynx, or tongue, attached to base of labium; Lé, labium;
Lm, labrum; Md, mandibles; Mx, maxillae
motion. A very small degree of stimulating energy, how-
ever, may result in the release of a great quantity of
stored energy
The food of all living matter must contain carbon,
hydrogen, nitrogen, and oxygen. The mechanism of
plants enables them to take these elements from com-
pounds dissolved in the water of the soil. Animals must
get them from other living things, or from the products of
{ 106 |
WAYS AND MEANS OF LIVING
living things. Therefore, animals principally have de-
veloped the power of movement; they have acquired grasp-
ing organs of some sort, a mouth, and an alimentary canal
for holding the food when once obtained.
In the insects, the locomotory function is subserved by
the legs and by the wings. Since all these organs, the three
pairs of legs and the two pairs of wings, are carried by the
thorax (Fig. 63, TA), this region of the body is distinctly
the locomotor center of the insect. The legs (Fig. 64) are
adapted, by modifications of structure in different species,
for walking, running, leaping, digging, climbing, swim-
ming, and for many varieties of each of these ways of pro-
gression, fitting each species for its particular mode of
living and of obtaining its food. The wings of insects are
important accessions to their locomotory equipment,
since they greatly increase their means of getting about,
and thereby extend their range of feeding. The legs, fur-
thermore, are often modified in special ways to perform
some function accessory to feeding. The honeybee, as is
well known, has pollen-collecting brushes on its front legs
(Fig. 65 B), and pollen-carrying baskets on its hind legs
(A). The mantis, which captures other insects and eats
them alive, has its front legs made over into those efficient
organs for grasping its prey and for holding the struggling
victim which have already been described (Fig. 46).
The principal organs by which insects obtain and ma-
nipulate their food consist of a set of appendages situated on
the head in the neighborhood of the mouth, which, in their
essential structure, are of the nature of the legs, for insects
have no jaws comparable with those of vertebrate animals.
The mouth appendages, or mouth parts as they are called,
are very different in form in the various groups of insects
that have different feeding habits, but in all cases they
consist of the same fundamental pieces. Most important
is a pair of jawlike appendages, known as the mandibles
(Fig. 66 B, Ma), placed at the sides of the mouth (A, Ma),
where they swing sidewise and close upon each other
[ 107 ]
INSECTS
below the mouth. Behind the mandibles is a pair of
maxillae (B, Mx) of more complicated form, fitted rather
for holding the food than for crushing it. Following the
maxillae is a large under lip, or /abium (L4), having the
SoeGng VNC Int
Fic. 67. Lengthwise section of a grasshopper, showing the general location
of the principal internal organs, except the respiratory tracheal system and
the organs of reproduction
An, anus; Ant, antenna; Br, brain; Cr, crop; Ht, heart; Int, intestine; Mai,
Malpighian tubules; Mrs, mouth; Oe, aesophagus; SeeGng, suboesophageal
ganglion; Vent, stomach (ventriculus); “NC, ventral nerve cord; W, wings
structure of two maxillae united by their inner margins.
A broad flap hangs downward before the mouth to form
an upper lip, or /abrum (Lm). Between the mouth ap-
pendages and attached to the front of the labium there is a
large median lobe of the lower head wall behind the mouth,
known as the Aypopharynx (Hphy).
Insects feed, some on solid foods, others on liquids, and
their mouth parts are modified accordingly. So it comes
about that, according to their feeding habits, insects may
be separated i into two groups, which, like the fox and the
stork, could not feed either at the table of the other. Those
insects, such as the grasshoppers, the crickets, the beetles,
and the caterpillars, that bite off pieces of food tissue and
chew them, have the mandibles and the other mouth
parts of the type described above. Insects that partake
only of liquids, as do the plant lice, the cicadas, the moths,
the butterflies, the mosquitoes and other flies, have the
[ 108 |
WAYS AND MEANS OF LIVING
mouth parts fitted for sucking, or for piercing and sucking.
Some of the sucking types of mouth parts will be described
in other chapters (Figs. 121, 163, 183), but it will be seen
that all are merely adaptations of form based on the ordi-
nary biting type of mouth appendages. The fossil records
of the history of insects show that the sucking insects are
the more recent products of evolution, since all the earlier
kinds of insects, the cockroaches and their kin, have
typical biting mouth parts.
The principal thing to observe concerning the organs of
feeding, in a study of the physiological aspect of anatomy,
is that they serve in all cases to pass the natural food
materials from the outside of the animal into the alimen-
tary canal, and to give them whatever crushing or masti-
cation is necessary. It is within the alimentary canal,
therefore, that the next steps toward the final nutrition
of the animal take place.
The alimentary canal of most insects is a simple tube
(Fig. 68), extending either straight through the body, or
Cx GC Vent AInt MInt Rect
\ / us | /
\ / / / | /
San ss i i
Sa —. —
: ? : SSS es Ne
Meh, = : ; =
Hphy Lb
Fic. 68. The alimentary canal of a grasshopper
Alnt, anterior intestine; 47, anus; Cr, crop; GC, gastric caeca, pouches of the
stomach; Hphy, hypopharynx (tongue); Lé, base of labium; Ma/, Malpighian
tubules; A¢7nt, mid-intestine; 44¢4, mouth; Oc, oesophagus; Rec/, hind intestine
(rectum); S/G/, salivary glands opening by their united ducts at base of hypo-
pharynx; Vent, ventriculus (stomach)
making only a few turns or loops in its course. It con-
sists of three principal parts, of which the middle part is
the true stomach, or ventriculus (Vent) as it is called by
insect anatomists. The first part of the tube includes a
[ 109 |
INSECTS
pharynx immediately behind the mouth, followed by a
narrower, tubular oesophagus (Oe), after which comes a sac-
like enlargement, or crop (Cr), in which the food is tem-
porarily stored, and finally an antechamber to the stomach,
named the proventriculus. The third part of the alimen-
tary canal, connecting the stomach with the anal opening,
is the intestine, usually composed of a narrow anterior
part, anda wage posterior part, or rectum (Rect). Muscle
layers surrounding the entire alimentary tube cause the
food to be swallowed and to be passed along from one
section to the next toward the rear exit.
With the taking of the food into the alimentary canal,
the matter of nutrition is by no means accomplished, for
the animal is still confronted with the problem of getting
the nutrient materials into the inside of its body, where
alone they can be used. The alimentary tube has no
openings anywhere along its course into the body cavity.
Whatever food substances the tissues of the animal receive,
therefore, must be taken through the walls of the tube in
which they are inclosed, ahd this transposition 1s accom-
plished by dissolving them in a liquid. Most of the nutri-
ent materials in the raw food matter, however, are not
soluble in ordinary liquids; they must be changed chem-
ically into a form that will dissolve. The process of get-
ting the nutrient parts of the raw foodstuff into solution
constitutes digestion.
The digestive liquids in insects are furnished mostly
by the stomach walls or the walls of tubular glands that
open into the stomach, but the secretion of a pair of large
glands, called the salivary glands (Fig. 68, S/G/), which
open between the mouth parts, perhaps has in some
cases a digestive action on the food as it 1s taken into the
mouth.
Digestion is a purely chemical process, but it must be
a rapid one. Consequently the digestive juices contain
not only substances that will transform the food materials
into soluble compounds, but other substances that will
[110]
WAYS AND MEANS OF LIVING
speed up these reactions, for otherwise the animal would
starve on a full stomach by reason of the slowness of its
gastric service. The quickening substances of the diges-
tive fluids are called enzymes, and each kind of enzyme
acts on only one class of food material. An animal’s prac-
tical digestive powers, therefore, depend entirely upon
the specific enzymes its digestive liquids contain. Lacking
this or that enzyme it can not digest the things that depend
upon it, and usually its instincts are correlated with its
enzymes so that it does not fill its stomach with food it can
not digest. A few analyses of the digestive liquids of in-
sects have been made, enough to show that their digestive
processes depend upon the presence of the same enzymes as
those of other animals, including man.
The grosser digestive substances, in cooperation with
the enzymes, soon change all the parts of the food ma-
terials in the stomach that the animal needs for its suste-
nance into soluble compounds which are dissolved in the
liquid part of the digestive secretions. Thus is produced
a rich, nutrient juice within the alimentary canal which
can be absorbed through the walls of the stomach and intes-
tine and can so enter the closed cavity of the body. The
next problem is that of distribution, for still the food ma-
terials must reach the individual cells of the tissues that
compose the animal.
The insect’s way of feeding, of digesting its food, and of
absorbing it is not essentially different from that of the
higher animals, including ourselves, for alimentation 1s a
very old and fundamental function of all animals. Its
means of distributing the digested food within its body,
however, is quite different from that of vertebrates. The
absorbed pabulum, instead of being received into a set of
lymphatic vessels and from these sent into blood-filled
tubes to be pumped to all parts of the organism, goes
directly from the alimentary walls into the general body
cavity, which is filled with a liquid that bathes the inner
surfaces of all the body tissues. This body liquid 1s called
brri
INSECTS
the “blood” of the insect, but it is a colorless or slightly
yellow-tinted lymph. It is kept in motion, however, by a
vy V
Fic. 69. Diagram of the
typical structure of an insect’s
heart and supporting dia-
phragm, with the course of the
circulating blood marked by
arrows
Ao, aorta, or anterior tubular
part of the heart without
lateral openings; Dph, mem-
branous diaphragm; Ht, ante-
rior three chambers of the
heart, which usually extends
to the posterior end of the
body; Mc/, muscles of dia-
phragm, the fibers spreading
from the body wall to the
heart; Ost, ostium, or oneof the
lateral openings into the heart
chambers
pulsating vessel, or heart, lying
in the dorsal part of the body;
and by this means the food, now
dissolved in the body liquid, 1s
carried into the spaces between
the various organs, where the
cells of the latter can have access
to it.
The heart of the insect 1s a
slender tube suspended along the
midline of the back close to the
dorsal wall of the body (Fig. 67,
Ht). It has intake apertures
along its sides (Fig. 69, Ost), and
its anterior end opens into the
body cavity. It pulsates - for-
ward, by means of muscle fibers
in its walls, thereby sucking the
blood in through the lateral
openings and discharging it by
way of the front exit. An im-
perfect circulation of the blood
is thus established through the
spaces between the organs of the
body cavity, sufficient for the
purposes of so small an animal as
an insect.
The final act of nutrition comes
now when the blood, charged
with the nutrient materials ab-
sorbed from the digested food
in the alimentary canal, brings
these materials into contact with
the inner tissues. The tissue
cells, by the inherent power of
| 112 ]
WAYS AND MEANS OF LIVING
all living matter (which depends on the laws of osmosis
and on chemical affinity), take for themselves whatever
they need from the menu offered by the blood, and with
this matter they build up their own substance. It is
evident, therefore, that the blood must contain a sufh-
cient quantity and variety of dietary elements to satisfy
all possible cell appetites; that the stomach’s walls and
their associated glands must furnish the enzymes appro-
priate for making the necessary elements available from
the raw food matter in the stomach; and, finally, that it
must be a part of the instincts of each animal species to
consume such native foodstuffs of its environment as will
supply every variety of nourishing elements that the cells
demand.
As we have seen, the demand for food comes from the
loss of materials that are decomposed in the tissues during
cell activity. Better stated, perhaps, the chemical break-
down within the cell is the cause of the cell activity, or is
the cell activity itself. The way in which the activity is
expressed does not matter; whether by the contraction of a
muscle cell, the secretion of a gland cell, the generation of
nerve energy by a nerve cell, or just the minimum activity
that maintains life, the result is the same always—the loss
of certain Substances: But, as with most chemical reduc-
tion processes, the protoplasmic activity depends upon the
presence of available oxygen; for the decomposition of the
unstable substances of the protoplasm is the result of the
affinity of some of their elements for oxygen. Conse-
quently, when the stimulus for action comes over a nerve
from a nerve center, a sudden reorganization takes place
between these protoplasmic elements and the oxygen
atoms which results in the formation of water, carbon
dioxide, and various stable nitrogenous compounds.
The substances discarded as a result of the cell activi-
ties are waste products, and must be eliminated from the
organism for their presence would clog the further activity
of the cells or would be poisonous to them. The animal,
[ 113 ]
INSECGES
therefore, must have, in addition to its mechanisms for
bringing food and oxygen to the cells, a means for the re-
moval of wastes.
The supplying of oxygen and the removing of carbon
dioxide and some of the excess water are accomplished by
respiration. Respiration is primarily the exchange of gases
between the cells of the body and the outside air. If an
animal is sufficiently small and soft-skinned, the gas ex-
change can be made directly by diffusion through the skin.
Larger animals, however, must have a device for conveying
air into the body where the tissues will have closer access
to it. It will be evident, then, that there is not neces-
sarily only one way of accomplishing the purposes of
respiration.
Vertebrate animals inhale air into a sac or pair of sacs,
called the lungs, through the very thin walls of which the
oxygen and carbon dioxide can go into and out of the
blood respectively. The blood contains a special oxygen
carrier in the red matter, hemoglobin, of its red corpuscles,
by means of which the oxygen taken in from the air is
transported to the tissues. The carbon dioxide is carried
from the tissues partly by the hemoglobin, and partly
dissolved in the blood liquid.
Insects have no lungs, nor have they hemoglobin in their
blood, which, as we have seen, is merely the liquid that fills
the spaces of the body cavity between the organs. Insects
have adopted and perfected a method of getting air dis-
tributed through their bodies quite different from that of
the vertebrates. They have a system of air tubes, called
tracheae (Fig. 70), opening from the exterior by small
breathing pores, or spiracles (Sp), along the sides of the
body, and branching minutely within the body to all parts
of the tissues. By this means the air is conveyed directly
to the parts where respiration takes place. There are
usually in insects ten pairs of spiracles, two on the sides of
the thorax, and eight on the abdomen. The spiracles
communicate with a pair of large tracheal trunks lying
[114]
WAYS AND MEANS OF LIVING
along the sides of the body (Fig. 70), and from these
trunks are given off branches into each body segment and
into the head, which go to the alimentary canal, the heart,
the nervous system, the muscles, and to all the other
organs, where they break up into finer branches that
terminate in minute end tubes going
practically to every cell of the body.
Many insects breathe by regular
movements of expansion and contrac-
tion of the under surface of the abdo-
men, but experimenters have not yet
agreed as to whether the air goes in
and out of the same spiracles or
whether it enters one set and is ex-
pelled through another. It is probable
that the fresh air goes into the smaller
tracheal branches principally by gas
diffusion, for some insects make no
perceptible respiratory movements.
The actual exchange of oxygen from
the air and carbon dioxide from the
tissues takes place through the thin
walls of the minute end tubes of the
tracheae. Since these tubes lie in im-
mediate contact with the cell surfaces
the gases do not have to go far in
order to reach their destinations, and
the insect has little need of an oxygen
carrier in its blood—its whole body,
practically, is a lung. And yet some
investigations have made it appear
likely that the insect blood does con-
tain an oxygen carrier that functions
in a manner similar to that of the
hemoglobin of vertebrate blood,
though the importance of oxygen
transportation in insect physiology has
hans: |
Nt a fi
Fic. 70. Respiratory
system of a caterpillar,
The external breathing
apertures, or spiracles
(Sp, Sp), along the
sides of the body open
into. lateral tracheal
trunks (a, a), which
are connected crosswise
by transverse tubes
(4, 6) and give off mi-
nutely branching tra-
cheae into all parts of
the head (H) and body
INSECTS
not been determined. In any case, the tracheal method
of respiration must be a very efficient one; for, consider-
ing the activity of insects, especially the rate at which the
wing muscles act during flight, the consumption of oxygen
must at times be pretty high.
The activity of insects depends very much, as every one
knows, upon the temperature. We have all observed how
the house flies disappear upon the first cold snap in the fall
and then surprise us by showing up again when the weather
turns warm, Just after we have taken down the screens.
All insects depend largely upon external warmth for the
heat necessary to maintain cellular activity. While their
movements produce heat, they have no means of con-
serving this heat in their bodies, as have “warm-blooded”
animals. That insects radiate heat, however, is very
evident from the high temperature that bees can maintain
in their hives during winter by motion of the wings. All
insects exhale much water vapor from their spiracles, an-
other evidence of the production of heat in their bodies.
The solid matter thrown off from the cells in activity is
discharged into the blood. These waste materials, which
are mostly compounds of nitrogen in the form of salts,
must then be removed from the blood, for their accumula-
tion in the body would be injurious to the tissues. In
vertebrate animals, the nitrogenous wastes are eliminated
by the kidneys. Insects have a set of tubes, comparable
with the kidneys in function, which open into the intestine
at the junction of the latter with the stomach (Fig. 68,
Ma/), and which are named, after their discoverer, the
Malpighian tubules. These tubes extend through the prin-
cipal spaces of the body cavity, where they are looped
and tangled like threads about the other organs and are
continually bathed in the blood. The cells of the tube
walls pick out the nitrogenous wastes from the blood and
discharge them into the intestine, whence they are passed
to the exterior with the undigested food refuse.
We thus see that the inside of an insect is not an unor-
[ 176°]
WAYS AND MEANS OF LIVING
ganized mass of pulp, as believed by those people whose
education in such matters comes principally from under-
foot. The physical unity of all forms of life makes it neces-
sary that every creature must perform the same vital
functions. The insects have, in many respects, adopted
their own ways of accomplishing these functions, but, as
already pointed out, the means of doing a thing does not
count with nature so long as the end results are attained.
The essential conditions are the supply of necessities and
the removal of wastes.
The body of a complex animal may be likened to a great
factory, in which the individual workers are represented by
the cells, and groups of workers by the organs. That the
factory may accomplish its purpose, the activities of each
worker must be coordinated with those of all the other
workers by orders from a directing office. Just so, the ac-
tivities of the cells and organs of the animal must be con-
trolled and coordinated; and the directing office of the
animal organization is the central nervous system. The
work of almost every cell in the body is ordered and con-
trolled by a ‘“‘nerve impulse” sent to it over a nerve fiber
from a nerve center.
The inner structure of the nervous tissues and the work-
ing mechanism of the nerve centers are essentially alike in
all animals, but the form and arrangement of the nerve
tissue masses and the distribution of the nerve fibers may
differ much according to the plan of the general body or-
ganization. The insects, instead of following the verte-
brate plan of having the central nerve cord along the back
inclosed in a bony sheath, have found it just as well for
their purposes to have the principal nerve cord lying free in
the lower part of the body (Fig. 67, “NC). In the head
there is a brain (Figs. 67, 72, Br) situated above the
oesophagus (Fig. 67, Oe), but it is connected by a pair of
cords with another nerve mass below the pharynx in the
lower part of the head (SoeGng). From this nerve mass
another pair of nerve cords goes to a third nerve mass
Faia
INSECIS
LmNv_
MxNv_
Fic. 71. The nervous system of the head of a grass-
hopper, as seen by removal of the facial wall
AntN2, antennal nerve; 7Br, 2Br, 7Br, the three parts
of the brain; CoeCon, circumoesophageal connectives;
3Com, suboesophageal commissure of the third lobes
of the brain; FrGvg, frontal ganglion; FrCon, frontal
ganglion connective with the brain; LéNo, labial
nerve; LmNb, labral nerve; MdNv, mandibular nerve;
MxNo, maxillary nerve; O, simple eye; OpZ, optic
lobe connected with the brain; RN», recurrent nerve;
SoeGng, suboesophageal ganglion
lying against the
lower wall of the
first body seg-
ment (Fig. 72,
Gng 1), which is
likewise connect-
ed with a fourth
mass in the sec-
ondsegment,and
so on. The cen-
tral nervous sys-
tem of the insect
thus consists of
a series of small
nerve masses
united by double
nerve cords. The
nerve masses are
known as gan-
glia (Gng), and
the uniting cords
are called the
connectives (Fig.
71, Con). Typi-
cally there is a
ganglion for each
of the first
eleven body seg-
ments, besides
the brain and
the lower gan-
glion of the head.
The brain of an insect (Fig. 71) has a highly complex
internal structure, but it is a less important controlling
center than is the brain of a vertebrate animal. The other
ganglia have much independence of function, each giving
the stimuli for movements of its own segment.
[ 118 ]
For this
WAYS AND MEANS OF LIVING
reason, the head of an insect may be cut off and the rest
of the creature may still be able to walk and to do various
other things until it dies of starvation. Similarly, with
some species, the abdomen may be severed and the insect
will still eat, though the food runs out of the cut end of the
alimentary canal. The detached abdomen may lay eggs,
if properly stimulated. Though the insect thus appears to
be largely a creature of automatic regulations, acts are not
initiated without the brain, and full coordination of the
functions is possible only when the entire nervous system
is intact.
The active elements of the nerve centers are nerve cells;
the nerve fibers are merely conducting threads extended
from the cells. If the nerve force that stimulates the other
kinds of cells into activity comes from nerve cells, the
question then arises as to whence comes the primary
stimulus that activates the nerve cells. We must discard
the old idea that nerve cells act automatically; being mat-
ter, they are subject to the laws of matter—they are inert
until compelled to act. The stimulus of the nerve cells
comes from something outside of them, either from the
environmental forces of the external world or from sub-
stances formed by other cells within the body.
Nothing is known definitely of the internal stimuli of
insects, but there can be no doubt that substances are
formed by the physiological activities of the insect tissues,
similar to the hormones, or secretions of the ductless glands
of other animals, that control action in other organs either
directly or through the nervous system. Thus, some in-
ternal condition must prompt the insect to feed when its
stomach is empty, and the entrance of food into its pharynx
must stimulate the alimentary glands to prepare the diges-
tive juices. Probably a secretion from the reproductive
organs of the female, when the eggs are ripe in the ovaries,
gives the stimulus for mating, and later sets into motion
the reflexes that govern the laying of the eggs. The cater-
pillar spins its cocoon at the proper time for doing so; the
[ 119]
INSECES
TR
+[I+ hy t,/.
“iia
Fic. 72. The general nervous system of a grass-
hopper, as seen from above
Ant, antenna; Ao, aorta; Br, brain; Cer, cercus; E,
compound eye; Gng/, ganglion of prothorax;
Gng2, ganglion of mesothorax; Gug3+J+J/+II1,
compound ganglion of metathorax, comprising
the ganglia belonging to the metathorax and the
first three abdominal segments; GugJ V—GngVIII,
ganglia of the fourth to eighth abdominal seg-
ments; O, ocelli; Proc, proctodeum, or posterior
part of alimentary canal; Sa, suranal plate;
SegII—X, second to tenth segments of abdomen;
SoeGng, suboesophageal ganglion; Stom, stomo-
deum, or anterior part of alimentary canal
[ 120 |
stimulus, most like-
ly, comes from the
products of physio-
logical changes be-
ginning to take place
in the body that will
soon result in the
transformation of
the caterpillar into
a chrysalis, a stage
when the insect
needs the protection
of a cocoon. These
activities of insects
we call instincts, but
the term is simply a
cover for our ignor-
ance of the processes
that cause them.
External stimuli
are things of the
outer environment
that affect the living
organism. They in-
clude matter, elec-
tromagnetic energy,
and gravity; but the
known stimuli do
not comprise all the
activities of matter
or of the “ether.”
The common stimuli
are: pressure of
solids, liquids, and
gases; humidity;
chemical qualities
(odors and tastes);
WAYS AND MEANS OF LIVING
sound, heat, light, and gravity. Most of these things stim-
ulate the nerve centers indirectly through nerves connected
with the skin or with specialized parts of the skin called
sense organs. An animal can respond, therefore, only to
those stimuli, or to the degrees of a particular stimulus, to
which it is sensitive. If, for example, an animal has no re-
ceptive apparatus for sound waves, it will not be affected
by sound; if it is not sensitized to certain wave lengths of
light, the corresponding colors will not stimulate it. There
are few kinds of natural activities in the environment that
animals do not perceive; but even our own perceptive
powers fall far short of registering all the degrees of any
activity that are known to exist and which the physicist
can measure.
Insects respond to most of the kinds of stimuli that we
perceive by our senses; but if we say that they see, hear,
smell, taste, or touch we make the implication that insects
have consciousness. It is most likely that their reactions
to external stimuli are for the most part performed un-
consciously, and that their behavior under the effect of a
stimulus is an automatic action entirely comparable to
our reflex actions. Behavioristic acts that result from
reflexes the biologist calls sropisms. Coordinated groups
of tropisms constitute an instinct, though, as we have
seen, an instinct may depend also on internal stimuli. It
can not be said that consciousness does not play a small
part in determining the activities of some insects, es-
pecially of those species in which memory, 7.¢., stored
impressions, appears to give a power of choice beaween
different conditions presented. The subject of insect
psychology, however, is too intricate to be discussed
here.
The phases of life thus far described, the complexity
of physical organization, the response to stimuli, the
phenomena of consciousness from their lowest to their
highest manifestations, all pertain to the soma. Yet,
somehow, the plan of the edifice is carried along in the
INSECTS
germ cells, and by them the whole somatic structure is
rebuilt with but little change of detail from generation to
generation. This phase of life activity is still a mystery
to us, for no attempted explanation seems adequate to
account for the organizing power resident in the germ
cells that accomplishes the familiar facts of repeated
Fic. 73. Diagrams of the internal organs of reproduction in insects
A, the female organs, comprising a pair of ovaries (Ov), each composed of a
group of egg tubules (ov), a pair of oviducts (DOv), and a median outlet tube, or
vagina (Vg), with usually a pair of colleterial glands (C/G/) discharging into
the vagina, and a sperm receptacle, or spermatheca (Spm), opening from the
upper surface of the latter
B, the male organs, comprising a pair of testes (Tes) composed of spermatic
tubules, a pair of sperm ducts, or vasa deferentia (/D), a pair of sperm vesicles
(VS), and an outlet tube, or ductus ejaculatorius (DE), with usually a pair of
mucous glands (MG/) discharging into the ducts of the sperm vesicles
development which we call reproduction. When we can
explain the repetition of buds along the twig, we may
have a key to the secret of the germ cells—and possibly
to that of organic evolution.
The organs that house the germ cells in the mature
insect consist of a pair of ovaries in the female (Fig. 73 A,
Ov) in which the eggs mature, and of a pair of testes in the
[1299,]
WAYS AND MEANS OF LIVING
male (B, Tes) in which the spermatozoa reach their com-
plete growth. Appropriate ducts connect the ovaries or
the testes with the exterior near the rear end of the body.
The female usually has a sac connected with the egg duct
(A, Spm) in which the sperm, received at mating, are
stored until the eggs are ready to be laid, when they are
Fic. 74. The ovipositor of a long-horned grasshopper, a member of the katydid
family, showing the typical structure of the egg-laying organ of female insects
A, the ovipositor (Ovp) in natural condition, projecting from near the posterior
end of the body
B, the parts of the ovipositor separated, showing the six component pieces,
two arising from the eighth abdominal segment {/JJ/), and four from the ninth
(1X). An, anus; Cer, cerci; JX, ninth abdominal segment; Oup, ovipositor; /gO,
vaginal opening; /JJ/, eighth abdominal segment; X, tenth abdominal segment
extruded upon the latter and bring about fertilization.
The egg cells ordinarily are all alike, but the spermatozoa
are of two kinds; and according to the kind of sperm re-
ceived by any particular egg, the future individual will be
male or female.
[ 123 ]
INSECTS
The germ cells accompanying each new soma undergo a
series of transformations within the parent body before
they themselves are capable of accomplishing their pur-
pose. They multiply enormously. With some animals,
only a few of them ever produce new members of the race;
but with insects, whose motto is “‘safety in numbers,”
each species produces every season a great abundance of
new individuals, to the end that the many forces arrayed
against them may not bring about their extermination.
The world seems full of forces opposed to organized life.
But the truth is, all organization is an opposition to
established forces. The reason that the forms of life now
existing have held their places in nature is that they have
found and perfected ways and means of opposing, for a
time, the forces that tend to the dissipation of energy.
Life is a revolt against inertia. Those species that have
died out are extinct, either because they came to the end
of their resources, or because they became so inflexibly
adapted to a certain kind-of life that they were unable to
meet the emergency of a change in the conditions that
made this life possible. Efficiency in the ordinary means
of living, rather than specialization for a particular way of
living, appears to be the best guarantee of continued
existence.
[124 ]
CHAPTER 'V
TERMITES
Ir was the custom, not long ago, to teach the inexperienced
that the will can achieve whatever ambition may desire.
“Believe that you can, and you can, 1f only you work hard
enough”’; this was the subject of many a maxim very en-
couraging, no doubt, to the young adventurer, but just as
likely to lead to a bench in Union Square as to a Fifth
Avenue studio or a seat in the Stock Exchange.
Now it is the fashion to give us mental tests and voca-
tional suggestions, and we are admonished that it 1s no
use trying to be one thing if nature has made us for some-
thing else. This is sound advice; the only trouble is the
difficulty of being able to detect at an early age the char-
acters that are to distinguish a plumber from a doctor, a
cook from an actress, or a financier from an entomologist.
Of course, there really are differences between all classes
of people from the time they are born, and a fine thing
it would be if we could know in our youth just what each
one of us is designed to become. In the present chap-
ter we are to learn that certain insects appear to have
achieved this very thing.
The termites are social insects; consequently in study-
ing them, we shall be confronted with questions of con-
duct. Therefore, it will be well at the outset to look
somewhat into the subject of morality; not, be assured,
to learn any of its irksome precepts, but to discover its
biological significance.
Right and wrong, some people think, are general ab-
stractions that exist in the very nature of things. They
P25]
INSECTS
are, on the contrary, specific attributes that are condi-
tioned by circumstances. An act that is right is one in
accord with the nature of the creature performing it; that
which is wrong is a contrary act. Hence, what is right for
one species of animal may be wrong for another, and the
reverse.
The conduct of adult human individuals, according to
human standards of right and wrong, we call morals; the
similar conduct of other animals is a part of what biolo-
gists call behavior. But we unconsciously recognize some-
thing in common between morals and behavior when we
speak of the acts of a child, which we call his behavior
rather than his morals.
Behavior, in other
words, we regard as in-
volving less of personal
responsibility than mo-
rality. Hence we say
Fic. 75: Avcommen that janineals! andclil=
species of termite of dren behave, but that
eastern North America :
inhabiting dead wood, @dult human beings con-
Reticulitermes flavipes. sciously do right or
a aris! frm Wrong. Yet, the two
modes of action accom-
plish similar results: if the child behaves
properly, his actions are right; if the
adult has a properly developed moral
sense, he too does the right thing, or at
least he refrains from doing the wrong
thing unless misguided by circumstances
or by his reasoning.
Animals other than the human, it
appears, generally do what is right from their standpoint;
but their actions, we say, are instinctive. Some will insist
that the terms “right”? and “wrong” can have no appli-
cation to them. Substitute then, if you please, the
expression “appropriate or non-appropriate to the ani-
[ 126 ]
TERMITES
mal’s way of living.” And still, our morality will analyze
into the same two elements; our acts are right or wrong
according as they are appropriate or non-appropriate to
our way of living.
The difference between human actions and those of
other animals is not essentially in the acts themselves, but
in the methods by which they are brought about. Animals
are controlled by instincts, mostly; man is controlled by a
conscious feeling that he should do this or that—‘‘con-
science,” we call it—and his specific actions are the result
of his reasoning or teaching as to what is right and what 1s
wrong, excepting, of course, the acts of perverted indi-
viduals who lack either a functional conscience or a well-
adjusted power of reason, or of individuals in whom the
instincts of an earlier way of living are still strong. The
general truth is clear, however, that in behavior, as in
physiology, there is not just one way of arriving ata
common result, and that nature may employ quite dif-
ferent means for determining and activating conduct in
her creatures.
Since right and wrong, then, are not abstract prop-
erties, but are terms expressing fitness or non-fitness,
judged according to circumstances, or an animal’s way of
living, it is evident that the quality of actions will differ
much according to how a species lives. Particularly
will there be a difference in the necessary behavior of
species that live as individuals and of those that live as
groups of individuals. In other words, that which may
be right for an individualistic species may be wrong for
a communal species; for, with the latter, the group re-
places the individual, and relations are now established
within the group, or pertaining to the group as a whole,
that before applied to the individual, while relations that
formerly existed between individuals become now rela-
tions between groups.
The majority of animals live as individuals, each
wandering here and there, wherever its fancy leads or
[ 127 ]
INSEGIS
wherever the food supply attracts it, recognizing no ties
or responsibilities to others of its species and contending
with its fellows, often in deadly combat, for whatever
advantage it can gain. A few animals are communistic
\9
q
SS me IRE
_
JAN ME pared,
1
Titi
AT EV TE 8
S == :
DAD OD SSIES SSS SAP SSL
Fic. 76. Termite work in a piece of
wood. Tunnels following the grain are
made by species of Reticulitermes, the com-
mon underground termites of the eastern
United States
ee es
or social in their mode
of life; notably so are
man and certain insects.
The best-known exam-
ples of social insects are
the ants and some of the
_bees and wasps. The
termites, however, con-
stitute another group of
social insects of no less
interest than the ants
and bees, but whose hab-
its have not been so long
observed.
More familiarly to
some people, termites are
known as “white ants.”
But since they are not
ants, nor always white
or even pale in color, we
should discard this mis-
leading and unjustifiable
appellation and learn to
know the termites by the
name under which they
are universally known to
entomologists.
If you split open an
old board that has been
lying almost anywhere
on the ground for some
time, or if, when out in
the woods, you cut into
TERMITES
a dead stump or a log, you are more than likely to find
it tunneled all through with small tubular galleries running
with the grain of the wood, but everywhere connected
crosswise by small openings or short passages. Within
the exposed galleries there will be seen numerous small,
pale, wingless insects running here and there in an effort
to conceal themselves. These insects are termites.
They are the miners or the descendants of miners that
have excavated the tunnels in which they live. Not all
of the galleries in the nest are open runways, many of
them being packed solidly with small pellets of refuse.
If the termites confined themselves to useless wood,
they would be known only as interesting insects; but
since they often extend their operations into fence posts,
telegraph poles, the woodwork of houses, and even into
furniture, they have placed themselves among the de-
structive insects and have acquired an important place
in the pages of economic entomology. Stored papers,
books, cloth, and leather are not exempt from their at-
tack. In the United States it not infrequently happens
that the flooring or other wooden parts of buildings must
be replaced, owing to the unsuspected work of termites;
and piled lumber ts especially liable to invasion by these
insidious insects. But in tropical countries the termites
are far more numerous than in temperate regions, and
are vastly more destructive than they are with us. Their
seclusive habits make the termites a particularly vexa-
tious pest, because they have usually accomplished an
irreparable amount of damage before their presence is
known or suspected. The economic entomologist study-
ing termites gives most of his attention, therefore, to
devising methods of preventing the access of the insects
to all wooden structures that they might destroy.
The work of termites and the ways and means that
have been contrived to prevent their ravages have been
described in many agricultural publications, and the
reader whose tastes are purely practical is referred to
[ 129 ]
INSECTS
the latter for information. Here we will look more closely
into the lives of the termites themselves to see what
lessons we may learn from these creatures that have
adopted something of our own way of living.
When a termite nest is broken open, it does not appear
that there is much of an organization among the insects
Fic. 77. Reticulitermes flavipes (much enlarged)
A, a mature worker. B, a mature soldier. C, a young termite.
D, an immature winged form
hurrying to take refuge in the recesses of the galleries,
but neither when a bomb strikes one of our own dwellings
is there probably much evidence of order within. The
most casual observation of the termites, however, will
[ 130 ]
TERMITES
show something of interest concerning them. In the
first place, it is to be seen that not all the members of the
colony are alike. Some, usually the greater number, are
small, ordinary, soft-bodied, wingless insects with rounded
heads and inconspicuous jaws (Figs.75 D,77 A). Others,
less numerous, have bodies like the first, and are also
wingless, but their heads are relatively of enormous size
and support a pair of large, strong Jaws projecting out
in front (Figs. 75 C, 77 B). The individuals of the latter
kind are known as so/diers, and the name is not entirely
fanciful, since fighting is not necessarily the everyday
occupation of one in military service. The others, the
small-headed individuals, are called workers, and they
earn their title literally, for, even with their small jaws,
they do most of the work of excavating the tunnels, and
they perform whatever other labors are to be done within
the nest.
Both the workers and the soldiers are males and females,
but so far as reproductive powers go, they may be called
“neuters,”’ since their reproductive organs never mature
and they take no part in the replenishment of the colony.
In most species of termites the workers and the soldiers
are blind, having no eyes or but rudiments of eyes. In
a few of the more primitive termite genera, workers are
absent, and in the higher genera they may be of two
types of structure. The large jaws of the soldiers (Fig.
78 A) are weapons of defense in some species, and the
soldiers are said to present themselves at any break in the
walls of the nest ready to defend the colony against in-
vasion. In some species, the soldiers have a long tubular
horn projecting forward from the face (Fig. 78 B), through
which opens the duct of a gland that emits a sticky,
semiliquid substance. This glue is discharged upon an
attacking enemy, who is generally an ant, and so thor-
oughly gums him up that he is rendered helpless—a
means of combat yet to be adopted in human warfare.
The facial gland is developed to such efficiency as a
[131]
INSECTS
weapon in many species of one termite family that the
soldiers of these species have no need of jaws, and their
mandibles have become rudimentary. In all cases, the
military specialization of the soldiers has rendered them
incapable of feeding themselves, and they must depend
on the workers for food.
In addition to the soldiers and the workers, there
would probably be seen within the termite nest, at cer-
Frc. 78. Two forms of defensive organs of termite soldiers
A, head of soldier of Termopsis, showing the highly developed mandibles (Ma),
and the great muscles within the head (admd) that close them. BB, a soldier of
Nasutitermes (from Banks and Snyder); the head has small jaws but is provided
with a long snoutlike horn through which is ejected a gummy liquid used for
defense
tain seasons of the year, many individuals (Fig. 77 D)
that have small wing rudiments on their thoracic seg-
ments. As the season advances, the wing pads of these
individuals increase in length, until at last they become
long, gauzy, fully-developed wings extending much beyond
the tip of the body (Figs. 75 A, B, 79). The color of the
body also becomes darker, and finally blackish when the
insects are mature. Then, on some particular day, the
egal
TERMITES
whole winged brood issues from the nest in a great swarm.
Since insects are normally winged creatures, it is evident
that these flying termites represent the perfect forms of
the termite colony 1 ly mature
males and females.
The several forms of individuals in the termite com-
munity are known as castes.
An intensive search through the galleries of a termite
nest might reveal, besides workers, soldiers, and the
members of the winged brood in various stages of devel-
opment, a few individuals of still different kinds. These
have heads like the winged forms, but rather larger bodies;
some have short wing rudiments (Fig. 80), others have
none; and finally there are two individuals, a male and
a female, bearing wing stubs from which, evidently,
fully-formed wings have been broken off. ae male of
this last pair is just an ordinary-looking, though dark-
bodied termite
(Fig. 82 A); but
the female is dis-
tinguished from
all the other mem-
bers of the colony
by the great size
of her abdomen
(B).
Through the in-
vestigations of
entomologists it is
known that the Fic. 79. Adult winged caste of Reticulitermes tibialis,
wings shown on one side of the body only. (From
short-winged -and Banks and Snyder)
wingless individu-
als of this group comprise both males and females that
are potentially capable of reproduction, but that in
general all the eggs of the colony are actually produced
by the large-bodied female, whose consort is the male
that has lost his wings. In other words, this fertile
[ 133 ]
INSECTS
female corresponds with the “queen” in a hive of bees;
but, unlike the queen bee, the queen termite allows the
“king” termite to live with her throughout her life in the
community.
It appears, then, that the termite community 1s a com-
plex society of castes, for we must now add to the worker
and soldier castes the two castes of potentially repro-
ductive individuals, and the “royal” or actual producing
caste, consisting of the king and the queen. We are thus
introduced to a social state quite different from anything
known in our own civilization, for, though we may have
castes, the distinctions between them are largely matters
of polite concession by the less aspiring members of the
community. We theoretically claim that we are al] born
equal. Though we know that this is but a gratifying
illusion, our inequalities at least do not go by recognized
caste. A termite, however, is literally born into his
place in society and eventually has his caste insignia in-
delibly stamped in the structure of his body. This state
of affairs upsets all our ideas and doctrines of the funda-
mental naturalness and rightness of democracy; and, if
it 1s true that nature not only recognizes castes but
creates them, we must look more closely into the affairs
of the termite society to see how such things may come
about.
Let us go back to the swarm of winged males and
females that have issued from the nest. The birds are
already feeding upon them, for the termites’ powers of
flight are at best feeble and uncertain. The winds have
scattered them, and in a short time the fluttering horde
will be dispersed and probably most of its members will
be destroyed one way or another. The object of the
swarming, however, is the distribution of the insects, and,
if a few survive, that is all that will be necessary for the
continuance of the race. When the fluttering insects
alight they no longer have need of their wings, and by
brushing against objects, or by twisting the body until
[ 134 |
TERMITES
the tip of the abdomen comes against the wing bases,
the encumbering organs are broken off. It may be
observed that there is a suture across the base of each
wing just to make the breaking easy.
The now wingless termites, being young males and
females Just come to maturity, naturally pair off; but
Fic. 80. The second form, or short-winged reproductive caste,
of Reticulitermes tibialis. (From Banks and Snyder)
A, male. B, female
not for a companionate marriage, which, it must be
confessed, is the popular form of matrimony with most
insects. The termites take the vows of lifetime fidelity,
or “‘till death do us part,” for with the female termite
intensive domesticity and maternity are the ruling pas-
sions. To find a home site and there found a colony 1s
her consuming ambition, and, whether the male likes
it or not, he must accept her conditions. The female,
therefore, searches out a hole or a crevice in a dead tree
or a decayed stump, or crawls under a piece of wood
lying on the ground, and the male follows. If the site
[ 135 ]
INSECTS
proves suitable, the female begins digging into the wood
or into the ground beneath it, using her jaws as exca-
vating tools, perhaps helped a little by the male, and
soon a shaft is sunk at the end of which a cavity is hol-
lowed out of sufficient size to accommodate the pair and
to serve the purposes of a nest where true matrimony
may begin.
Naturally it would be a very difficult matter to follow
the whole course of events in the building of a termite
community from one of these newly married pairs, for
the termites live in absolute seclusion and any disturbance
of their nests breaks up the routine of their lives and
frustrates the efforts of the investigator. Many phases,
however, of the life and habits of our common eastern
United States termites, particularly of species belonging
to the genus Reticulitermes, have been discovered and
recorded in numerous papers by Dr. T. E. Snyder of the
U. S. Bureau of Entomology, and, thanks to Doctor
Snyder’s work, we are able to give the following account
of the life of these termites and the history of the de-
velopment of a fairly complex community from the
progeny of a single pair of insects.
The young married couple live amicably together in
conjugal relations within their narrow cell. The male,
perhaps, was forced to eject a would-be rival or two, but
eventually the mouth of the tunnel is permanently sealed,
and from now on the lives of this pair will be completely
shut in from the outside world. In due time, a month
or six weeks after the mating, the female lays her first
eggs, six or a dozen of them, deposited in a mass on the
floor of the chamber. About ten days thereafter the
eggs hatch, and the new home becomes enlivened with a
brood of little termites.
The young termites, though active and able to run
about, are not capable of feeding themselves, and the
parents are now confronted_with the task of keeping a
dozen growing appetites appeased. The feeding formula
[ 136 ]
TERMITES
of the termite nursery calls for predigested wood pulp;
but fortunately this does not have to be supplied from
outside—the walls of the house furnish an abundance of
raw material and the digesting 1s done in the stomachs
of the parents. The pulp needs then only to be regurgi-
tated and handed to the infants. This feature in the
termite economy has a double convenience, for not only
are the young inexpensively fed, but the gathering of
the food automatically enlarges the home to accommodate
the increasing need for space of the growing family.
That insects should gnaw tunnels through dead wood
is not surprising; but that they should be able to subsist
on sawdust is a truly remarkable thing and a dietetic
feat that few other animals could perform. Dry wood
consists mostly of a substance called cellulose, which,
while it is related to the starches and sugars, is a carbo-
hydrate that is entirely indigestible to ordinary animals,
though eaten in abundance as a part of all vegetable
food. The termites, however, are unusually gifted, not
with a special digestive enzyme, but with minute, one-
celled, cellulose-digesting protozoan parasites that live
in their alimentary canals. It is through the agency of
their intestinal inhabitants, then, that the termites are
able to live on a diet of dead wood. The young termites
receive some of the organisms with the food given them
by their parents and are soon able to be wood eaters
themselves. Not all termites, however, are known to
possess these intestinal protozoa, and, as we shall see,
many of them feed on other things than wood.
The termite brood thrives upon its wood-pulp diet,
and by December following the spring in which the young
were hatched, the members of the new generation begin
to attain maturity after having progressed through a
series of moltings, as does any other growing insect. But
observe, the individuals of this generation, instead of
developing into replicas of their parents, have taken on
the form of workers and soldiers! However, one should
gz
INSEGIS
never express surprise when dealing with insects; and for
the present we must accept the strange development
of the young termites as a matter of fact, and pass on.
During the middle of winter things remain thus in the
new family colony. The members of termite species
that live in the ground, or that pass from wood into the
ground, probably have tunneled deep into the earth for
protection from the cold. But in
February, the mother termite, now
the queen of the brood, responds
again to the urge of maternity with
some more eggs, probably with a
greater number this time than on
the first occasion. A month later,
or during March, the termitary is
once more enlivened with young
termites. The king and the queen
are now, however, relieved of the
routine of nursery duties by the
workers of the first brood. The
latter take over the feeding and
care of their new brothers and
sisters, and also do all the excava-
tion work involved in the enlarging
of the home.
In the spring the termites as-
cend to the surface of the ground
beneath a board or log, or at the
Fic. 81. A queen of the
third form, or wingless re- base of a stump, and reoccupy
productive caste, of Reti- their former habitation. As the
culitermes flavipes. (From a A ‘
Banksand Snyden galleries are extended, the family
moves along, slowly migrating thus
to uneaten parts of the wood and leaving the old tunnels
behind them mostly packed with excreted wood-pulp and
earth.
When June comes again, the young family may consist
of several dozen individuals; but all, except the king and
[ 138]
TERMITES
queen, are soldiers and workers, the latter much out-
numbering the former. During the second year, the queen
lays a still greater number of eggs and probably produces
them at more frequent intervals. With the increase in
the activity of her ovaries, her abdomen enlarges and she
takes on a matronly appearance, attaining a length fully
twice that of her virgin figure and a girth in proportion.
The king, however, remains faithful to his spouse; and
he, too, may fatten up a little, sufficiently to give him
some distinction amongst his multiplying subjects. The
termite king 1s truly a king, in the modern way, for he has
renounced all authority and responsibility and leads a
care-free life, observing only the decorums of polite
society and adhering to the traditions of a gentleman;
but he also achieves the highest distinction of democracy,
for he is literally the father of his country.
Another year rolls by, bringing more eggs, more workers,
more soldiers. And now, perhaps, other forms appear
in the maturing broods. These are marked at a certain
stage of their development by the possession of short
wing stubs or pads on the back of the normally wing-
bearing segments. With succeeding molts the wing pads
become larger and larger, until they finally develop, in
most of these individuals, into long wings like those of
the king and the queen when they first flew out from the
parent colony. At last, then, the new family is to have
its first swarm; and when the fully-winged members are
all ready for the event and the proper kind of day arrives,
the workers open a few exits from the galleries, and the
winged ones are off. We already know their history,
for they will only do what their parents did before them
and what their ancestors have done for millions of gener-
ations. Let us go back to the galleries.
A few of the individuals that developed winged pads
are fated to disappointment, for their wings never grow to
a functional size and they are thereby prevented from
joining the swarm. Their reproductive organs and their
[ 139 ]
INSECTS
instincts, however, attain maturity, and these short-
winged individuals, therefore, become males and females
capable of procreation. They differ from the fully-winged
sexual forms in a few respects other than the length of the
wings, and they constitute a true caste of the termite
community, that of the short-winged males and females
(Fig. 80). The members of this caste mature along
with the others, and, Doctor Snyder tells us, many of
them, regardless of their handicap, actually leave the nest
at the time the long-winged caste is swarming; as if in
them, too, the instinct for flight is felt, though the organs
for accomplishing it are unable to play their part. Just
what becomes of these unfortunates is a mystery, for
Doctor Snyder says that after the swarming none of them
is to be found in the nest. It may be that some of them
pair and found new colonies after the manner of the
winged forms, but the facts concerning their history are
not known. It is at least true that colonies are some-
times found which have no true royal pair, but in which
the propagating individuals are members of this short-
winged reproductive caste.
Finally, there are also found in the termite colonies
certain wingless individuals that otherwise resemble the
winged forms, and which, as the latter, are functionally
capable of reproduction when mature. These individuals
constitute a third reproductive caste—the wingless males
and females. Little is known of the members of this
caste, but it is surmised that they may leave the nests
by subterranean passages and found new colonies of their
own.
Just how long the primary queen of a colony can keep
on laying eggs is not known, but in the course of years
she normally comes to the end of her resources, and before
that time she may be injured or killed through some ac-
cident. Her death in any case, however, does not mean
the end of the colony, for the king may provide for the
continuance of his race, and at the same time console
[ 140 ]
TERMITES
himself in his bereavement, by the adoption of a whole
harem of young short-winged females. But if he too
should be lost, then the workers give the succession to
one or more pairs of the second- or third-caste repro-
ductive forms, to whom they grant the royal prerogatives.
The progeny of any of the fertile castes will include the
caste of the parents and all castes below them. In other
words, only winged forms can produce the whole series of
castes; short-winged parents can not produce long-winged
offspring: and wingless parents can not produce winged
Fic. 82. The usual king (A) and queen (B), or winged repro-
ductive caste after having lost the wings (fig. 79), of Reticuli-
termes flavipes. (From Banks and Snyder)
offspring of any form; but both short-winged and wing-
less parents can produce soldiers and workers. It ap-
pears, therefore, that each imperfect fertile insect lacks
something in its constitution that is necessary for the pro-
duction of a complete termite individual.
The production of constitutionally different castes
from the eggs of a single pair of parents would be a
[141]
INSECTS
highly disconcerting event if it happened anywhere else
than in a termite colony, where it is the regular thing.
But the fact of its being regular with termites makes it
none the less disconcerting to entomologists, for it seems
to defy the very laws of heredity.
There can be no doubt of the utility of a caste system
where the members of each caste know their places and
their duties, and where nobody ever thinks of starting
a social revolution. But we should like to know how
such a system was ever established, and how individuals
of a family are not only born different but are made to
admit it and to act accordingly.
These are abstruse questions, and entomologists are
divided in opinion as to the proper answers. Some have
maintained that the termite castes are not distinguished
when the various individuals are young, but are pro-
duced Jater by differences in the feeding—in other words,
it is claimed the castes are made to order by the termites
themselves. One particular objection to this view is that
no one has succeeded in finding out what the miraculous
pabulum may be, and no one has been able to bring about
a structural change in any termite by controlling its diet.
On the other hand, it has been shown that in some species
there are actual differences in the young at the time of
hatching, and such observations establish the fact that
insects from eggs laid by one female can, at least, give
rise to offspring of two or more forms, beoce those of
sex, and that potential differences are fecsninee in the
eggs. It is most probable that in these forms no struc-
tural differences could be discovered at an early embryonic
period, and hence it may be that, where differences are
not perceptible at the time of hatching, the period of
differentiation has only been delayed to a later stage of
growth. It is possible that a solution to the problem of
the termite castes will be found when a study of the eggs
themselves has been made.
We may conclude, therefore, that the structural differ-
[ 142]
TERMITES
ences between the termite castes are probably innate,
and that they arise from differences in the constitutional
elements of the germ cells that direct the subsequent
development of the embryos in the eggs and of the young
after hatching
Still, however, there remain questions as to the nature
of the force that controls termite behavior. Why do the
termites remain together in a community instead of
scattering, each to live its own life as do most other in-
sects? Why do the workers accept their lot and perform
all the menial duties assigned to them? Why do the sol-
diers expose themselves to danger as defenders of the
nests? Structure can account for the things it is im-
possible for an animal to do, but it can not explain positive
behavior where seemingly the animal makes a choice
between many lines of possible action open to it.
In the community of the cells that make up the body
of an animal, as we learned in Chapter IV, organization
and control are brought about either through the nerves,
which transmit an activating or inhibiting force to each
cell from a central controlling station, or through chemical
substances thrown into the blood. In the insect com-
munity, however, there is nothing corresponding to
either of these regulating influences; nor 1s there a law-
making individual or group of individuals as in human
societies, nor a police force to execute the orders if any
were issued. It would seem that there must be some
inscrutable power that maintains law and order in the
termite galleries. Are we, then, to admit that there is a
“spirit of the nest,” an “dame collective,” as Maeterlinck
would have us believe—some pervading force that unites
the individuals and guides the destinies of the colony
as a whole? No, scientists can not accept any such idea
as that, because it assumes that nature’s resources are
no greater than those of man’s imagination. Nature 1s
always natural, and her ways and means of accomplish-
ing anything, when once discovered, never invoke things
[ 143 ]
INSECTS
that the human mind can not grasp, except in their
ultimate analysis into first principles. Those who have
faith in the consistency of nature endeavor to push a
little farther into the great unknown knowable.
There are a few things known about the termites that
help to explain some of the apparent mysteries concerning
them. For example, the members of a colony are for-
ever licking or nibbling at one another; the workers ap-
pear to be always cleaning the queen, and they are as-
siduous in stroking the young. These labial attentions,
or lip affections, moreover, are not unrewarded, for it
appears that each member of the colony exudes some
substance through its skin that is highly agreeable to
the other members. Furthermore, the termites all feed
one another with food material ejected from the alimen-
tary canal, sometimes from one end, sometimes from the
other. Each individual, therefore, is a triple source of
nourishment to his fellows—he has to offer exudates
from the skin, crop food from the mouth, and intestinal
food from the anus—and this mutual exchange of food
appears to form the basis for much of the attachment
that exists among the members of the colony. It accounts
for the maternal affections, the care of the queen and the
young by the workers, the brotherly love between the
workers and the soldiers. The golden rule of the termite
colony is ‘feed others as you would be fed by them.”
The termites, therefore, are social creatures because,
for physical reasons, no individual could live and be
happy away from his fellows. The same might be said
of us, though, of course, we like to believe that our social
instincts have not a purely physical basis. Be that as
it may, we must recognize that any kind of social tie
is but one of various possible means by which the benefits
of community life are insured to the members of the
community.
The custom of food exchange in the termite colonies
can not be held to account by any means for all the things
[144]
TERMITES
that termites do. Where other explanations fail, we have
always to fall back on “instinct.” A true instinct is a
response bred in the nervous system; and the behavior
of termites, as of all other insects, is largely brought
Fic. 83. A fore wing of a termite, Kalotermes approximatus,
showing the humeral suture (4s) where the wing breaks off when
it is discarded
about by automatic reflexes that come into action when
external and internal conditions are right for their pro-
duction. The physical qualities of the nervous system
that make certain reactions automatic and inevitable
are inherited; they are transmitted from parent to off-
spring, and bring about all those features of the animal’s
behavior that are repeated from generation to genera-
tion and which are not to be attributed to the individual’s
response to environmental changes.
The termites have an ancient lineage, for though no
traces of their family have been found in the earlier
records, there can be no doubt that the ancestors of the
termites were closely related to those of the roaches; and
the roach family, as we have seen in Chapter III, may be
reckoned among the very oldest of winged insects. In
human society it means a great deal to belong to an “old
family,” at least to the members of that family; but in
biology generally it is the newer forms, the upstarts of
more recent times, that attain the highest degree of
organization; and most of the social insects—the ants,
the bees, and the wasps—belong to families of compara-
tively recent origin. It is refreshing, therefore, to find
[145 ]
INSECTS
the belief in aristocracy vindicated by the ancient and
honorable line of descent represented by the roaches and
flowering in the termites.
One particular piece of evidence of the roach ancestry
of the termites is furnished by the wings. With most
termites the wings (Fig. 83) are not well developed, and
Fic. 84. Wings of Mastotermes, the hind wing with a basal
expansion similar to that of the hind wing of a roach (fig. 53),
suggesting a relationship between termites and roaches
their muscles are partly degenerate. In some forms, how-
ever, the wings (Fig. 84) are distinctly of the roach type
of structure (Fig. 53), and-these forms are undoubtedly
more closely representative of the ancestral termites than
are the species with the usual termite wing structure.
Our termites and those of other temperate regions con-
stitute the mere fringes of termite civilization. The ter-
mites are particularly insects of warm climates, and it is
in the tropics that they find their most congenial environ-
ment and attain the full expression of their possibilities.
In the tropics the characteristic termites are not those
that inhabit dead wood, but species that construct definite
and permanent nests, some placed beneath the ground,
[ 146 ]
TERMITES
others reared above the surface, and still others built
against the trunks or branches of trees. Different species
employ different building materials in the construction
of their nests. Some use particles of earth, sand grains,
or clay; others use earth mixed with saliva; still others
make use of the partly digested wood pulp ejected from
their bodies; and some use mixed materials. Certain
kinds of tropical termites, moreover, have foraging habits.
fe
Ke eZ eS Eo Yd Zag
ace BLU, YZ = LG ty, (
Ea = m\
mh?
or By re gh Dy i Sha
Viz
=
>
Fic. 85. Vertical section of an underground nest of an African termite, Termes
badius. (From Hegh, after Fuller)
The large central chamber is the principal “fungus garden”; in the wall at the
left is the royal chamber (rc); tunnels lead from the main part of the nest to
smaller chambers containing fungus, and to the small mounds at the surface
Great armies of workers of these species leave the nests,
even in broad daylight, and march in wide columns
guarded by the soldiers to the foraging grounds, where
they gather bits of leaves, dead stems, or lichens, and
return laden with provender for home consumption.
The underground nests (Fig. 85) consist chiefly of a
[ 147 ]
INSECTS
cavity in the earth, perhaps two by three feet in diameter
and a foot beneath the surface, walled with a thick cement
lining; but from this chamber there may extend tunnels
upward to the surface, or horizontally to other smaller
chambers located at a distance from the central one.
The termites that live in these nests subsist principally
upon home-grown food, and it is in the great vaulted
central chamber that they raise the staple article of their
diet. The cavity is filled almost entirely with a porous,
spongy mass of living fungus. The fungi as we ordinarily
see them are the toadstools and mushrooms, but these
fungus forms are merely the fruiting bodies sent up from
a part of the plant concealed beneath the ground or in
the dead wood; and this hidden part has the form of a
network of fine, branching threads, called a mycelium.
The mycelium lives on decaying wood, and it is the
mycelial part of the fungus that the termites cultivate.
They feed on small spore-bearing stalks that sprout from
the threads of the mycelium. The substratum of the
termite fungus beds is generally made of pellets of partly
digested wood pulp.
The nests that termites erect above the ground include
the most remarkable architectural structures produced
by insects. They are found in South America, Australia,
and particularly in Africa. In size they vary from mere
turrets a few inches high to great edifices six, twelve,
or even twenty feet in altitude. Some are simple mounds
(Fig. 86 A), or mere hillocks; others have the form of
towers, obelisks, and pyramids (B); still others look
like fantastic cathedrals with buttressed walls and taper-
ing spires (Fig. 87); while lastly, the strangest of all re-
semble huge toadstools with thick cylindrical stalks and
broad-brimmed caps (Fig. 86 C). Many of the termites
that build mound nests are also fungus-growing species,
and one chamber or several chambers in the nest are
given over to the fungus culture.
Termite nests built in trees are usually outlying retreats
[ 148 ]
TERMITES
of colonies that live in the ground, for such nests (Fig.
86 D) are connected with an underground nest by covered
runways extending down the trunk of the tree.
The queens of nearly all the termites that live in perma-
nent nests attain an enormous size by the growth of the
abdomen, the body becoming thus so huge that the royal
Za
me : ee A Zale
vu Lay y bn S hang” ye er LAG
phic we
—— AY
Fic. 86. Four common types of above-ground nests made by tropical termites
A, type of small mound nest, varying from a few inches to several feet in height.
B, type of a large tower or steeple nest, reaching a height of g or 10 feet. C,
a mushroom-shaped nest, made by certain African termites, from 3 to 16 inches
high. D, a tree nest, showing the covered runway going down to the ground
female 1s rendered completely helpless, and must be
attended in all her wants by the workers. With such
species the queen is housed in a special royal chamber
which she never leaves. Her body becomes practically a
great bag in which the eggs are produced, and so great
is the fertility of one of these queens that the ripened eggs
continually issue from her body. It has been estimated
that in one such species the queen lays four thousand
eggs a day, and that in another species her daily output
may be thirty thousand. Ten million eggs a year is pos-
[ 149 ]
INSECTS
a
Ne
Win,
inyeteer j
wer ae
Fic. 87. Type of pinnacled nest made by species of African termites, some-
times reaching a height of twenty feet or more
[150]
TERMITES
sibly a world record in ovulation. The royal chamber is
usually placed near the fungus gardens, and as fast as
the eggs are delivered by the queen the attendant workers
carry them off to the garden and distribute them over
the fungus beds, where the young on hatching can feed
and grow without further attention.
From a study of the termites we may draw a few lessons
for ourselves. In the first place, we see that the social
form of life is only one of the ways of living; but that,
wherever it is adopted, it involves an interdependence of
individuals upon one another. The social or community
way of living 1 is best promoted by a division of labor among
groups of individuals, allowing each to specialize and there-
by to attain proficiency in his particular kind of work.
The means by which the termites have achieved the bene-
fits of social life are not the same as those adopted by
the ants or social bees, and they have little in common
with the principles of our own social organization. All of
which goes to show that in the social world, as in the
physical world, the end alone justifies the means, so far as
nature is concerned. Justice to the individual is a human
concept; we strive to equalize the benefits and hardships
of the social form of life, and in so far as we achieve this
aim our civilization differs from that of the insects.
[151]
CHAPTERS VE
PLANT Lice
“Pant lice! Ugh,” you say, “who wants to read about
those nasty things! All I want to know is how to get rid
of them.” Yes, but the very fact that those soft green
bugs that cover your roses, your nasturtiums, your cab-
bages, and your fruit trees at certain seasons reappear
so persistently, after you think you have exterminated
them, shows that they possess some hidden source of
power; and the secrets of a resourceful enemy are at least
worth knowing—besides, they may be interesting.
Really, however, insects are not our enemies; they are
only living their appointed lives, and it just happens that
we want to eat some of the same plants that they and their
ancestors have always fed on. Our trouble with the in-
sects is Just that same old economic conflict that has bred
the majority of wars; and, in the case between us and the
insects, it is we who are the aggressors and the enemies of
the insects. We are the newcomers on the earth, but we
fume around because we find it already occupied by a host
of other creatures, and we ask what right have they to be
here to interfere with us! Insects existed millions of
years before we attained the human form and aspirations,
and they have a perfectly legitimate right to everything
they feed on. Of course, it must be admitted, they do not
respect the rights of private property; and therein lies
their hard luck, and ours.
The plant lice are well known to anyone who has a
garden, a greenhouse, an orchard, or a field of grain.
Some call them “green bugs’’; entomologists usually call
( 152]
PLANT RICE
them aphids. A single plant louse is an apAis, or an aphid;
more than one are usually called aphides, or aphids.
The distinguishing feature of the plant lice, or aphids,
as we shall by preference call them, is their manner of feed-
ing. All the insects described in the preceding chapters
eat in the usual fashion of biting off pieces of their food,
chewing them, and swallowing the masticated bits. The
Fic. 88. Group of green apple aphids feeding along a rib on
under surface of an apple leaf
aphids are sucking insects; they feed on the juices of the
plants they inhabit. Instead of jaws, they have a piercing
and sucking beak (Fig. 89), consisting of an outer sheath
inclosing four slender, sharp-pointed bristles which can be
thrust deep into the tissues of a leaf or stem (Fig. 89 B).
Between the bristles of the innermost pair (Fig. go, Mx)
are two canals. Through one canal, the lower one (4), a
liquid secretion from glands of the head 1s injected into the
plant, perhaps breaking down its tissues; through the
other (a) the plant sap and probably some of the proto-
plasmic contents of the plant cells are drawn up into the
mouth. A sucking apparatus like that of the aphids is
possessed by all insects related to the aphids, comprising
the order Hemiptera, and will be more fully described
[153]
INSEGIS
in the next chapter, which treats of the cicada, a large
cousin of the aphids.
When we observe, now, that different insects feed in
two quite different ways, some by means of the biting
type of mouth parts, and others by means of the sucking
type, it becomes evident that we must know which kind
of insect we are dealing with in the case of pests we may be
trying to control. A biting and chewing insect can be
killed by the mere expedient of putting poison on the out-
side of its food, if it does not become aware of the poison
and desist from eating it; but this method would not
work with the piercing and sucking insects, which extract
their food from beneath the surface of the plants on
which they feed. Sucking insects are, therefore, to be
destroyed by means
of sprays or dusts
that will kill them by
contact with their
bodies. Aphids are
usually attacked with
Irritant sprays, and in
general it is not a
difficult matter to rid
infested plants of
them, though in most
cases the spraying
must be repeated
through the season.
When any species
of aphis becomes well
established ona plant,
Fic. 89. The way an aphis feeds on the :
icceabaipiene the infested leaves
A, an aphis with its beak thrust into a rib of a (Fi 4 88) may be al-
leaf. B. ion th h the midrib of
eaf. B, section through the midrib of a young
apple leaf, showing the mouth bristles from the most aS crowded as an
beak of an aphis penetrating between the cells East Side street on a
of the leaf tissue to the vascular bundles,
while the sheath of the beak is retracted by hot summer after-
folding back beneath the head noon. But there 1s
[154]
PLATE 2
The green apple aphis (4phis pomi)
A, adult sexual female; B, adult male; C, young female; D, female lay-
ing an egg; E, eggs, which turn from green to black after they are laid.
(Enlarged about 20 times)
PEANT EICE
no bustle, no commotion, for each insect has its sucking
bristles buried in the leaf, and its pump is busy keeping
the stomach supplied with liquid food. The aphis crowds
are mere herds, not communities or social groups as in
the case of the termites, ants, or bees.
Wherever there are aphids there are ants, and in con-
trast to the aphids, the ants are always rushing about all
over the place as if they were looking for something and
each wanted to be the first to find it. Suddenly one spies
a droplet of some clear liquid lying on the leaf and gob-
bles it up, swallowing it so quickly that the spherule
seems to vanish by magic, and then the ant is off again
in the same excited manner. The explanation of the
presence and the actions of the ants among the aphids
is this: the sap of the plants furnishes an unbalanced diet,
the sugar content being far too great in proportion to the
protein. Consequently the aphids eject from their bodies
drops of sweet liquid, and it is this liquid, called “honey
dew,” that the ants search out so eagerly. Some of the
ants induce the aphids to give up the honey dew by strok-
ing the bodies of the latter. The glistening coat often
seen on the leaves of city shade trees and the shiny liquid
that bespatters the sidewalks beneath is honey dew dis-
charged from innumerable aphids infesting the under sur-
faces of the leaves.
In studying the termites, we learned that it is possible
for a single pair of insects to produce regularly several
kinds of offspring differing in other ways than those of
sex. In the aphids, a somewhat similar thing occurs in
that each species may be represented by a number of
forms; but with the aphids these different forms con-
stitute successive generations. If events took place in
a human family as they do in an aphid family, children
born of normal parents would grow up to be quite different
from either their father or their mother; the children of
these children would again be different from their parents
and also from their grandparents, and when mature they
[155]
INSECTS
perhaps would migrate to some other part of the country;
here they would have children of their own, and the new
fourth generation would be unlike any of the three pre-
ceding; this generation would then produce another,
again different; and the latter would return to the home
town of their grandparents
Lm Mx and great-grandparents, and
\ / here bring forth children that
Ja would grow up in the like-
< ness of their great-great-
BY Niet great-grandparents! “This
seems like a fantastic tale of
fiction, too preposterous to
if be taken seriously, but it 1s a
commonplace fact among the
5 aphids, and the actual gen-
ealogy may be even more
if ;
ils; complicated than that above
outlined. Moreover, the
Fic. go. Cross-section through story is not Ver complete,
the base of the beak of an aphis.
Giron Davidson) for it must be added that all
ithe omtarshendh alt dhe thealk fe dhe the generations of the aphids,
labium (Zé), covered basally by except one in each series, are
the labrum (Zm). The four in-
closed bristles are the mandibles composed entirely of fonmales
(Md) and the maxillae (Mx), the capable in themselves of re-
latter containing between them a : cA Aa
food canal (a) and a salivary canal production. In warm cli-
(2). Only the inner walls of the mates, it appears, the female
labrum and Jabium are shown in
the section succession may be uninter-
rupted.
How insects do upset our generalizations and our peace
of mind! We have heard of feminist reformers who would
abolish men. With patient scorn we have listened to their
predictions of a millenium where males will be unknown
and unneeded—and here the insects show us not only that
the thing 1s possible but that it is practicable, at least for
a certain length of time, and that the time can be in-
definitely extended under favorable conditions.
[156]
PEANT EICE
Since special cases are always more convincing than
general statements, let us follow the seasonal history of
some particular aphids, taking as examples the species
that commonly infest the apple.
Let the time be a day in the early part of March.
Probably a raw, gusty wind is blowing from the north-
west, and only the silver maples with their dark purplish
clusters of frowzy flowers already open give any sug-
gestion of the approach of spring. Find an old apple
tree somewhere that has not been sprayed, the kind of
tree an entomologist always likes to have around, since
it is sure to be full of insects. Look closely at the ends
of some of the twigs and
you will probably find a
number of little shiny
black things stuck close
to the bark, especially
about the bases of the
buds, or tucked under the
projecting edges of scars
and tiny crevices (Fig.
gi). Each little speck is
oval and about one thirty-
sixth of an inch in length.
To the touch the ob-
jects are firm, but elastic,
and if you puncture one a
pulpy liquid issues from
it; or so it appears, at
least, to the naked eye— Lee
: : Fic. gt. Aphis eggs on apple twigs in
a microscope would show March; an enlarged ceg below
that in this liquid there is
organization. In short, the tiny capsule contains a young
aphid, because it is an aphid egg. The egg was de-
posited on the twig last fall by a female aphis, and its
living contents have remained alive since then, though
fully exposed to the inclemencies of winter.
[157]
INSECGES
Immediately after being laid in the fall, the germ
nucleus of the aphis egg begins development, and soon
forms a band of tissue lying lengthwise on the under sur-
face of the yolk. Then this scarcely-formed embryo
undergoes a curious process of revolution in the egg,
turning on a crosswise axis head foremost into the yolk
and finally stretching out within the latter with the back
down and the head toward the original rear end of the
egg. Thus it remains through the winter. In March
it again becomes active, reverses itself to its first posi-
tion, and now completes its development.
The date of hatching of the apple aphis eggs depends
much upon the weather and will vary, therefore, ac-
cording to the season, the elevation, and the latitude; but
in latitudes from that of Washington north, it is some
time in April, usually from the first to the third week of
the month. The éggs of most insects resemble seeds in
their capacity for lying inert un-
til proper conditions of warmth
and moisture bring forth the
creature biding its time within.
The eggs of one of the apple
aphids, however, are killed by
premature warm weather, or if
artificially warmed too long be-
fore the normal time of hatching.
In general, the final development
of the aphis embryos keeps pace
with the development of the
apple buds, since both are con-
trolled by the same weather con-
ditions, and this coordination
usually insures the young aphids
octe eee against starvation; but the eggs
apple aphis with outer cover- commonly hatch a little in ad-
ings split before hatching; vance of the opening of the buds,
below, an egg removed from
its covering and a subsequent spell of cold
[ 158]
PEANT LICE
weather may give the young lice a long wait for their
first meal.
The approaching time of hatching is signaled in most
RES ody ras
Fic. 93. Hatching of the green apple aphis, Aphis pomi
A, the egg. B, an egg with the outer coat split. C, the same egg with the
inner shell split at one end. D-—F, three successive stages in the emergence of
the young insect. GJ, shedding the hatching membrane. K, the empty
eggshell. L, the young aphid
[159]
INSECTS
cases by the splitting of an outer sheath of the egg (Fig.
g2), exposing the glistening, black, true shell of the egg
within. Then, from one to several days later, the shell
itself shows a cleft within the rupture of the outer coat,
extending along half the length of the exposed egg sur-
face and down around the forward end (Fig. 93 C).
From this split emerges the soft head of the young aphis
(D), bearing a hard, toothed crest, evidently the instru-
ment by which the leathery shell was broken open, and
for this reason known as the “egg burster.” Once ex-
posed, the head continues to swell out farther and far-
ther as if the creature had been compressed within the
egg. Soon the shoulders appear, and now the young
aphis begins squirming, bending, inflating its fore parts
and contracting its rear parts, until it works its body
mostly out of the egg (KF, F) and stands finally upright
on the tip of its abdomen which is still held in the cleft
of the shell (G).
The young aphis at this stage, however, like the young
roach, is still inclosed in a thin, tight-fitting, membranous
bag having no pouches for the legs or other members,
which are all cramped within it. The closely swathed head
swells and contracts, especially the facial part, and sud-
denly the top of the bag splits close to the right side of
the egg burster (Fig. 93 H). The cleft pulls down over
the head, enlarges to a circle, slides along over the shoul-
ders, and then slips down the body. As the tightly stretched
membrane rapidly contracts, the appendages are freed
and spring out from the body (I). The shrunken pellicle
is reduced at last to a small goblet supporting the aphid
upright on its stalk, still held by the tip of the abdomen
and the hind feet (1). To liberate itself entirely the
insect must make a few more exertions (J), when, finally,
it pulls its legs and body from the grip of the drying
skin, and is at last a free young aphid (L).
The emergence from the egg and from the hatching
membrane is a critical period in the life of an aphid. The
[| 160 }
PLATE 3
The rosy apple aphis (4nuraphis roseus)
A, apple leaves and young fruit distorted by the aphids; B, under surface
of an infested leaf; C, immature wingless aphid (greatly enlarged); D,
immature winged aphis
PEANTE LICE
process may be completed in a few minutes, or it may
take as long as half an hour, but if the feeble creature
should be unable to free itself at last from the drying and
contracting tissue, it remains a captive struggling in the
grip of its embryonic vestment until it expires. The
young aphid successfully delivered takes a few uncertain,
staggering steps on its weak and colorless legs, and then
complacently rests awhile; but after about twenty min-
Fic. 94. Young aphids on apple buds in spring
utes or half an hour it is able to walk in proper insect
fashion, and it proceeds upward on its twig, a course
sure eventually to lead it to a bud.
While the aphid eggs are hatching, or shortly there-
after, the apple buds are opening and unfolding their
delicate, pale-green leaves, and from everywhere now
the young aphids come swarming upon them, till the tips
are often blackened by their numbers (Fig. 94). The
hungry horde plunges into the hearts of the buds, and
soon the new leaves are punctured with tiny beaks that
rob them of their food; and the young foliage, upon which
[ 161 ]
INSECTS
the tree depends for a proper start of its spring growth, is
stunted and yellowed. Now is the time for the orchardist
to spray if he has not already done so.
The entomologist, however, takes note that all the
young aphids on the apple trees are not alike; perhaps
there are three kinds of them in the orchard (Fig. 95);
differing slightly, but enough to show that each belongs
to a separate species. When the first buds infested are
Fic. 95. Three species of young aphids found on apples in the spring
A, the apple-grain aphis, Rhopalostphum pruntfoltae. B, the green apple aphis,
Aphis pomi. C, the rosy apple aphis, Anuraphis roseus
exhausted, the insects migrate to others, and later they
spread to the larger leaves, the blossoms, and the young
fruit. The aphids all grow rapidly, and in the course
of two or three weeks they reach maturity.
The full-grown insects of this first generation, those
produced from the winter eggs, are entirely wingless, and
they are all females. But this state of affairs in no wise
hinders the multiplication of the species, for these re-
markable females are able of themselves to produce off-
spring (a faculty known as parthenogenesis), and further-
more, they do not lay eggs, but give birth to active young.
Since they are destined to give rise to a long line of sum-
mer generations, they are known as the stem mothers.
One of the three aphid species of the apple buds is
known as the green apple aphis (Fig. 95 B). During the
[ 162 J
PEAN Tt LICE
early part of the season the individuals of this species
are found particularly on the under surfaces of the apple
leaves. They cause the infested leaves to curl and to
become distorted in a characteristic manner (Fig. 96).
The stem mothers (Fig. 97 A, B) begin giving birth to
young (C) about twenty-four hours after reaching ma-
turity, and any one of the mothers, during the course of
her life of from ten to thirty days, may produce an aver-
age family of fifty or more daughters, for all her offspring
are females, too. When
these daughters grow up,
however, none of them is
exactly like their mother.
They all have one more
segment in each antenna;
most of them are wing-
less (D), but many of
them have wings—some,
mere padlike stumps, but
others well developed or-
gans capable of flight
(Fig. 97 E).
Both the wingless and
the winged individuals of
this second generation are
also parthenogenetic, and
they give birth to a third
generation like them-
selves, including wing-
less, half-winged, and
fully-winged forms, but
with a reater ropor- Fic. 96. Leaves of apple infested and
2 8 BiOP distorted by the green apple aphis on
tion of the last. From under surfaces
now on there follows a
large number of such generations continuing through the
season. The winged forms fly from one tree to another,
or to a distant orchard, and found new colonies. In
[ 163 |
INSECTS
summer, the green apple aphis is found principally on
young shoots of the apple twigs, and on water sprouts
growing in the orchard.
During the early part of the summer, the rate of pro-
duction rapidly increases in the aphid colonies, and in-
dividuals of the summer generations sometimes give
birth to young a week after they themselves were born.
In the fall, however, the period of growth again 1s length-
ened, and the families drop off in size; until the last females
of the season produce each a scant half dozen young,
though they may live to a much greater age than do the
summer individuals.
The young summer aphids born as active insects are
inclosed at birth in a tight-fitting, seamless, sleeveless,
and legless tunic, as are those hatched from the winter
eggs. Thus swathed, each emerges, rear end first, from
the body of the mother, but is finally held fast by the
face when it is nearly free. In this position, the em-
bryonic bag splits over the head and contracts over the
body of the young aphid to the tip of the abdomen,
where it remains as a cap of shriveled membrane aie
it finally drops off or is pushed away by the feet. The
infant, now vigorously kicking, is still held in the ma-
ternal grasp, and eventually liberates itself only after
some rather violent struggling; but soon after it is free
it walks away to find a feeding place among its com-
panions on the leaf. The mother is but little concerned
with the birth of her child, and she usually continues
to feed during its delivery, though she may be somewhat
annoyed by its kicking. The average summer female
gives birth to two or three young aphids every day.
The succession of forms in the families 1s one of the
most interesting phases of aphid life. Investigations
have shown that the winged individuals are produced
principally by wingless forms, and experiments have
demonstrated that the occurrence of the winged forms
is correlated with changes in the temperature, the food
[ 164 |
PLANT LICE
supply, and the duration of light. At a temperature
around sixty-five degrees few winged individuals ever
appear, but they are produced at temperatures either
below or above this point. Likewise it has been found
that when the food supply gives out through the drying
Fic. 97. The green apple aphis, 4phis pomi. A, B, adult stem mothers.
C, a newly-born young of the summer forms. D, a wingless summer
form. E, a winged summer form
of the leaves or by the crowding of the aphids on them,
winged forms appear, thus making possible a migration
to fresh feeding grounds. Then, too, certain chemical
substances, particularly salts of magnesium, added to
the water or wet sand in which are growing cuttings
of plants infested with aphids, will cause an increase of
winged forms in the insects subsequently born. This
does not happen if the plants are rooted, but it shows
that a change in the food can have an effect on wing
production.
| 165 |
INSECYS
Finally, it has recently been shown experimentally by
Dr. A. Franklin Shull that winged and wingless condi-
tions in the potato aphis may be produced artificially by
a variation in the relative amount of alternating light
and darkness the aphids receive during each twenty-four
hours. Shortening the illumination period to twelve
hours or less results in a marked increase in the number of
winged forms born of wingless parents. Continuous
darkness, however, produces few winged offspring. Maxi-
mum results perhaps are obtained with eight hours of
light. The effect of decreased light appears from Doctor
Shull’s experiments to be directly operative on the young
from thirty-four to sixteen hours before birth, and it is
not to be attributed to any physiological effect on the
plant on which the insects are feeding.
It is evident, therefore, that various unfavorable local
conditions may give rise to winged individuals in a colony
of wingless aphids, thus enabling representatives of the
colony to migrate in the chance of finding a more suit-
able place for the continuance of their line. The regular
production of spring and fall migrants is brought about
possibly by the shorter periods of daylight in the earlier
and later parts of the season.
The final chapter of the aphid story opens in the fall
and, like all last chapters done according to the rules,
it contains the sequel to the plot and brings everything
out right in the end.
All through the spring and summer the aphid colonies
have consisted exclusively of virgin females, winged and
wingless, that give birth to virgin females in ever-in-
creasing numbers. A prosperous, self-supporting femi-
nist dominion appears to be established. When summer’s
warmth, however, gives way to the chills of autumn,
when the food supply begins to fail, the birth rate slack-
ens and falls off steadily, until extermination seems to
threaten. By the end of September conditions have
reached a desperate state. October arrives, and the
| 166 |
PLANT LICE
surviving virgins give birth in forlorn hope to a brood
that must be destined for the end. But now, it appears,
another of those miraculous events that occur so fre-
quently in the lives of insects has happened here, for the
members of this new brood are seen at once to be quite
different creatures from their parents. When they grow
up, it develops that they constitute a sexual generation,
composed of females and males! (Plate 2 A, B.)
Feminism is dethroned. The race is cared The mar-
riage instinct now is dominant, and if marital relations
in this new generation are pretty loose, the time 1s Octo-
ber, and there is much to be accomplished before winter
comes.
The sexual females differ from their virgin mothers
and grandmothers in being of darker green color and in
having a broadly pear-shaped body, widest near the end
(Plate 2A). The males (B) are much smaller than the
females, their color is yellowish brown or brownish green,
and they have long spiderlike legs on which they actively
run about. Neither the males nor the females of the green
apple aphis have wings. Soon the females begin to pro-
duce, not active young, but eggs (D). The eggs are de-
posited most anywhere along the apple twigs, in crevices
where the bark is rough, and about the bases of the buds.
The newly-laid eggs are yellowish or greenish (D), but
they soon turn to green, then to dark green, and finally
become deep black (E). There are not many of them,
for each female lays only from one to a dozen; but it
is these eggs that are to remain on the trees through the
winter to produce the stem mothers of next spring, who
will start another cycle of aphid life repeating the his-
tory of that just closed.
The production of sexual forms in the fall in temperate
climates seems to have some immediate connection with
the lowered temperature, for in the tropics, it is said,
the aphid succession continues indefinitely through par-
thenogenetic females, and in most tropical species sexual
[ 167 |
INSECTS
males and females are unknown. In the warmer regions
of the West Coast of the United States, species that regu-
larly produce males and females every fall in the East
continue without a reversion to the sexual forms.
Of the other two species of apple aphids that infest
the buds in the spring, one is
known as the rosy apple aphis
(Fig. 95 C). The name comes
from the fact that the early
summer individuals of this
species have a waxy pink tint
more or less spread over the
ground color of green (Plate 3),
though many of the adult
stem mothers (Fig. 98 B) are
of a deep purplish color. The
early generations of the rosy
aphis infest the leaves (Fig.
98 A, Plate 3 A) and the young
fruit (Fig. 98/C,, Place 3) Ale
causing the former to curl up
in tightly rolled spirals, and the
latter to become dwarfed and
distorted in form.
The stem mothers of the
rosy aphis give birth partheno-
genetically to a second gen-
eration of females which are
Fic. 98. The rosy apple ‘ 5 :
aphis, Anuraphis roseus, on mostly wingless like their moth-
sae ers; but in the next generation
A, a cluster of infested and . erent ki E
Hr eroceeiilenvee acetate many individuals have wings.
stem mother. C, young apples Several more generations now
dwarfed and distorted by the 2 pi
Esige heen ae rapidly follow, all females; in
fact, as with the green aphis,
no males are produced till ]ate in the season. The winged
forms, however, appear in increasing numbers, and by
the first of July almost all the individuals born have wings.
[ 168 ]
BEANE LICE
Heretofore, the species has remained on the apple trees,
but now the winged ones are possessed with a desire for a
change, a complete change both of scenery and of diet.
They leave the apples, and when next discovered they are
found to have established themselves in summer colonies
on those common weeds known as plantains, and mostly
on the narrow-leaved variety, the rib-grass, or English
plantain (Fig. gg).
As soon as the mi-
grants land upon the
plantains they give birth
to offspring quite unlike
themselves or any of the
preceding generations.
These individuals are of a
yellowish-green color and
nearly all of them are
wingless (Fig. gg). So
well do they disguise
their species that ento-
mologists were a_ long
time in discovering their
identity. Generations of
wingless yellow females
now follow upon the
plantain. But a weed is
no fit place for the stor-
age of winter eggs, so,
with the advent of fall,
winged forms again ap-
pear in abundance, and Fic. 99. The rosy apple aphis on nar-
: row-leaved plantain in summer; above, a
these migrate back to the wingless summer form (enlarged)
apples. The fall mi
grants, however, are of two varieties: one is simply a
winged female like the earlier migrants that came to the
plantain from the apple, but the other is a winged male
(Fig. 100 A). Both forms go back to the apple trees, and
[ 169 ]
INSECTS
there the females give birth to a generation of wingless
sexual females (B), which, when mature, mate with the
males and produce the winter eggs.
The third of the aphid species that infest the spring
buds of the apple is known as the app/le-grain aphis, so
called because, being a migratory species like the rosy
Fic. 100. The winged male (A) and the wingless sexual female (B) of the
rosy apple aphis
aphis, it spends the summer upon the leaves of grains
and grasses. The eggs of the apple-grain aphis are usually
the first to hatch in the spring, and the young aphids of
this species (Fig. 95 A) are distinguished by their very
dark green color, which gives them a blackish appear-
ance when massed upon the buds. Later they spread
to the older leaves and to the petals of the apple blossoms,
but on the whole their damage to the apple trees is less
than that of either of the other two species. The summer
history of the apple-grain aphids is similar to that of the
rosy aphis, excepting that they make their summer home
on grains and grasses instead of on plantains. In the
fall, the winged female migrants (Plate 4) come back to
the apple and there give birth to wingless sexual females,
which are later sought out by the winged males.
It would be impossible here even to enumerate the
[ 170 ]
(Gelecjalers
3 215 2 Py dy3 ul paonpoad WIIOJ pesurm Site p
posse q) Weepnl ajddv 94} (onl uIvIs ey WOOLY SOJRIGIU qt ui II a) [3 I I I
(avyofiunsd wnydisojodoyy) siyde uress-ajdde ay J,
¥ ULV 1d
PEANT LICE
Fic. 101. Some common aphids of the garden
A, winged form of the potato aphis, I/linoia solanifolii, one of the largest of
the garden aphids. B, winged form of the peach aphis, Myzus persicae,
which infests peach trees and various garden plants. C, wingless form of
the peach aphis. D, wingless form of the melon aphis, 4phis gossypit. E,
winged form of the melon aphis
Paya
INSECTS
many species of aphids that infest our common field and
garden plants (Fig. 101) and cultivated shrubs and trees,
to say nothing of those that inhabit the weeds, the wild
shrubbery, and the forest trees. Almost every natural
group of plants has its particular kind of aphid, and many
of them are migratory species like the rosy and grain
aphis of the apple. There are root-inhabiting species as
well as those that live on the leaves and stems. The
Phylloxera, that pest of vineyards in California and
France, is a root aphid. Those cottony masses that
often appear on the apple twigs in late summer mark
the presence of the woolly aphis, the individuals of which
exude a fleecy covering of white waxy threads from their
backs. The woolly aphis is more common on the roots
of apple trees, being especially a pest of nursery stock, but
it migrates to both the twigs and the roots of the apple
from the elm, which is the home of its winter eggs.
An underground aphid of particular interest is one that
lives on the roots of corn. We have seen that all aphids
are much sought after by ants because of the honey dew
they excrete, a substance greatly relished and prized by
the ants. It is said that some ants protect groups of
aphids on twigs by building earthen sheds over them; but
the corn-root aphis owes its very existence to the ants.
A species of ant that makes its nests in cornfields runs
tunnels from the underground chambers of the nests to
the bases of nearby cornstalks. In the fall the ants gather
the winter eggs of the aphids from the corn roots and take
them into their nests where they are protected from
freezing during the winter. Then in the spring the ants
bring the eggs up from the storage cellars and place
them on the roots of various early weeds. Here the
stem mothers hatch and give rise to several spring gen-
erations; but, as the new corn begins to sprout, the ants
transfer many of the aphids to the corn roots, where
they live and multiply during the summer and, in the fall,
give birth to the sexual males and females, which produce
[eenae
PEANT LICE
the winter eggs. The eggs are again collected by the ants
and carried to safety for the winter into the depths of their
underground abodes. All this the ants do for the aphids
in exchange for the honey dew they receive from them.
The ants have so domesticated these corn-root aphids
that the aphids would perish without their care. The
farmer, therefore, who would rid his cornfield of the aphid
pest, proceeds with extermination measures against the
ants.
The crowded aphid colonies exposed on stems and
leaves naturally form the happy hunting grounds for a
Fic. 102. A common ladybird beetle, Coccinella navemnotata, that
feeds on aphids. (Enlarged 5 times)
A, the larva. B, the adult beetle
host of predacious insects. Here are thousands of soft-
bodied creatures, all herded together, and each tethered
to one spot by the bristles of its beak thrust deep into the
tissues of the plant—a pot-hunter’s paradise, truly.
Consequently, the placid lives of the aphids have many
interruptions, and vast numbers of the succulent creatures
serve only as half-way stages in the food cycle of some
other insect. The aphids have small powers of active
[173]
INSECTS
defense. A pair of slender tubes, the cornicles, projecting
from the rear end of the body, eject a sticky liquid which
the aphids are said to smear on the faces of attacking
insects; but the ruse at best probably does not give much
protection. Parthenogenesis and large families are the
principal policies by which the aphids insure their race
against extinction.
The presence of “evil” in the world has always been a
thorn for those who would preserve their faith in the idea
of beneficence in nature. The irritation, however, is not
We)
yy
ib
MR
Si,
SK ———
(eee
SSS
Fic. 103. The aphis-lion, feeding on an aphis held in its jaws
in the flesh but in a distorted growth of the mind, and
consequently may be alleviated by a change of mental
attitude. The thorn itself, however, is real and can not
be explained away. Beneficence is not a part of the
scheme by which plants and animals have attained
through evolution their present conditions and relations.
On the other hand, there are not good species and bad
species; for every creature, including ourselves, is a thorn
to some other, since each attacks a weaker that may
contribute to its existence. There are many insects that
destroy the aphids, but these are “enemies” of the aphids
only in the sense that we are enemies of chickens and of
cabbages, or of any other thing we kill for food or other
purposes.
[174]
PEANT ICE
Recognizing, then, that evil, like everything else, is a
matter of relativity and depends upon whose standpoint
it is from which we take our view, it becomes only a par-
donable bias in a writer if he views the subject from the
standpoint of the heroes of his story. With this under-
standing we may note a few of the “‘enemies’’ of the
aphids.
Everybody knows the “‘ladybirds,” those little oval,
hard-shelled beetles, usually of a dark red color with
black spots on their rounded backs (Fig. 102 B). The
female ladybirds, or better, lady-beetles, lay their orange-
colored eggs in small groups stuck usually to the under
surfaces of leaves (Fig. 132 B) and in the neighborhood
of aphids. When the eggs hatch, they give forth, not
ornate insects resembling lady-beetles, but blackish little
beasts with thick bodies and six short legs. The young
creatures at once seek out the aphids, for aphids are
their natural food, and begin ruthlessly feeding upon
them. As the young lady-beetles mature, they grow
even uglier in form, some of them becoming conspicu-
ously spiny, but their bodies are variegated with areas of
brilliant color—red, blue, and yellow—the pattern differ-
ing according to the species. A common one is shown at
A of Figure 102. When one of these miniature monsters
becomes full-grown, it ceases its depredations on the
aphid flocks, enters a period of quietude, and fixes the
rear end of its body to a leaf by exuding a glue from the
extremity of its abdomen. Then it sheds its skin, which
shrinks down over the body and forms a spiny mat ad-
hering to the leaf and supporting the former occupant
by only the tip of the body (Fig. 132 E). With the
shedding of the skin, the insect has changed from a /arva
to a pupa, and after a short time it will transform into a
perfect lady-beetle like its father or mother.
Another little villian, a remarkably good imitation of a
small dragon (Fig. 103), with long, curved, sicklelike
jaws extending forward from the head, and a vicious tem-
[175]
INSEGES
/ perament to match,
is also a common
frequenter of the
aphid colonies and
levies a toll on the
lives of the meek
and helpless insects.
This marauders
well named the
aphis-lion. He is the larva of a gentle,
harmless creature with large pale-green
lacy wings and brilliant golden eyes
(Fig. 104A). The parent females
show a remarkable prescience of the
nature of their offspring, for they sup-
port their eggs on the tips of long
threadlike
stalks, usu-
Fic. 104.. The golden-
eye, Chrysopa, the par-
ent of the aphis-lion, ally attached
and its eggs
A, the adult insect. B, to the under
a group of eggs sup- surfaces of
ported on long thread-
like stalks on the under leaves (B ).
surface of a leaf The device
seems to be a
scheme for preventing the first
of the greedy brood that will
hatch from devouring its own
brothers and sisters still in their
eggs.
Wherever the aphids are
crowded there is almost sure
to be seen crawling among
them soft grayish or green
wormlike creatures, mostly less
than a quarter of an inch in
length. The body is legless and
Fic. 105. A larva of a syrphus
tapers to the forward end, fly feeding on aphids
[ 176 ]
PEANT- LICE
which has no distinct head but from which is protruded
and retracted a pair of strong, dark hooks. Watch one
of these things as it creeps upon an unsuspecting aphid;
with a quick movement of the outstretched forward end
of the body it makes a swing at the fated insect, grabs
it with the extended hooks, swings it aloft kicking and
struggling, and relentlessly sucks the juices from its
body (Fig. 105). Then with a toss it flings the shrunken
skin aside, and repeats the attack on another aphid. This
heartless blood-sucker is a maggot, the larva of a fly
(Fig. 106) belonging to a family called the Syrphidae.
The adult flies of this family are entirely harmless, though
Fic. 106. Two common species of syrphus flies whose larvae feed on aphids.
(Enlarged about 314 times)
A, Allograpta obliqua. B, Syrphus americana
some of them look like bees, but the females of those
species whose maggots feed on aphids know the habits
of their offspring and place their eggs on the leaves where
aphids are feeding. One of them may be seen hovering
near a well-infested leaf. Suddenly she darts toward
the leaf and then as quickly is off again; but in the moment
of passing, an egg has been stuck to the surface right
in the midst of the feeding insects. Here it hatches
where the young maggot will find its prey close at hand.
In addition to these predacious creatures that openly
and honestly attack their victims and eat them alive,
the aphids have other enemies with more insidious methods
of procedure. If you look over the aphid-infested leaves
[177]
INSEGES
Fic. 107. A dead potato
aphis that has contained a
parasite, which when adult
escaped through the door cut
in the back of the aphis
home. The guest that so
ravishes its protector 1s
the grub of a small wasp-
like insect (Fig. 108) with
a long, sharp ovipositor
by means of which it
thrusts an egg into the
body of a living aphid
Fic. 108. <Aphidius, a com-
mon small wasplike parasite of
aphids
on almost any plant, you will
most likely note here and there
a much swollen aphid of a brown-
ish color. Closer examination
reveals that such individuals are
dead, and many of them have a
large round hole in the back,
perhaps with a lid standing up
from one edge like a trap door
(Fig. 107). These aphids have
not died natural deaths; each
has been made the involuntary
host of another insect that con-
verted its body into a temporary
Fic. 109. A female 4phidius inserting an
egg into the body of a living aphis, where
the egg hatches; the larva grows to ma-
turity by feeding in the tissues of the
aphis. (From Webster)
(Fig. 109). Here the egg hatches
and the young grub feeds on
the juices of the aphid until it
is itself full-grown, by which
time the aphid is exhausted and
dead. Then the grub slits open
the lower wall of the hollow
corpse and spins a web between
the lips of the opening and
against the surface of the leaf
below, which attaches the aphid
shell to the support. Thus se-
cured, the grub proceeds to give
[ 178]
PEAN PF GIckE
its gruesome chamber a lining of silk web; which done, it
lies down to rest and soon changes to a pupa. After a
short time it again transforms, this time into the adult
of its species, and the latter cuts with its Jaws the hole in
the back of the aphid and emerges.
In other cases, the dead aphid does not rest flat on
the leaf but is elevated on a small mound (Fig. 110 A).
Such victims have been inhabited by the grub of a re-
lated species, which, when full-grown, spins a flat cocoon
beneath the dead body of its host, and in this inclosure
undergoes its transformation. The adult insect then
cuts a door in the side of the cocoon (B), through which
it makes its exit.
Insects that usurp the bodies of other insects for their
own purposes are called parasites. Parasites are the
Fic. 110. Aphids parasitized by a parasite that makes a cocoon beneath
the body of the aphis, where it changes to a pupa and, when adult,
emerges through a door cut in the side of the cocoon
worst enemies that insects have to contend against; but
really they do not contend against them in most cases,
except in the way characteristic of insects, which is to
insure themselves against extermination by the number
of their offspring. The aphid colonies are often, how-
ever, greatly depleted during a season favorable to the
predacious and parasitic insects that attack them; but no
species is ever annihilated by its enemies, for this would
mean starvation to the next year’s brood of the latter.
The laws of compensation usually maintain a balance
[179 ]
INSECTS
in nature between the procreative and the destructive
forces.
The insect parasites and predators of other insects in
general comprise a class of insects that are most beneficial
to us by reason of their large-scale destruction of species
injurious to our crops. But, unfortunately, parasites as
a class do not respect our classification of other creatures
into harmful and useful species. Even as some predator
is stalking its prey, another insect is likely to be shadowing
it, awaiting the chance to inject into its body the egg
which will mean finally death to the destroyer. Immature
insects are often found in a sluggish or half-alive condi-
tion, and an internal examination of their bodies usually
reveals that they are occupied by one or more parasitic
larvae. A larva of any of the lady- beetles, for example,
is frequently seen attached to a leaf for pupation (Fig. Tanne
which, instead of transforming to a pupa, remains inert
and soon becomes a lifeless form, though still adhering
to the leaf and bent in the attitude that the pupa would
assume. In a short time there issues through the dried
skin a parasite, giving evidence of the fate that has be-
fallen the unfortunate larva; even if the usurper 1s not
seen, the exit hole in the larval skin bears witness to his
former occupancy and escape.
And the parasites themselves, do they lead unmolested
lives? Are they the final arbiters of life and death in the
insect world? If you are fortunate sometime while study-
ing aphids out-of-doors, you may see a tiny black mite,
no bigger than the smallest gnat, hovering about an in-
fested plant or darting uncertainly from one leaf to
another, with the air of searching for something but not
knowing j just where to look. You would probably suspect
the intruder of being a parasite seeking a chance to place
an egg in the body of an aphid; but here she hovers over
a group of fat lice without selecting a victim, then per-
haps alights and runs about on the leaf nervously and
intensely eager, still finding nothing to her choice. Her
[ 180 ]
PRANT LICK
senses must be dull, indeed, if it is aphids that she wants.
Do not lose sight of her, however, for her attitude has
changed; now she certainly has her eye upon something
that holds her attention, but the object is nothing other
than one of those swollen parasitized aphids. Yet she
excitedly runs up to it, feels it, grasps it, mounts upon
it, examines it all over. Evidently she is satisfied. She
dismounts, turns about, backs her abdomen against the
inflated mummy; now
out comes the swordlike
ovipositor, and with a
thrust it is sunken into
the already parasitized
aphid. Two minutes
later her business 1s
ended, the ovipositor 1s
withdrawn, once more
sheathed, and the insect
is off and away.
This tiny creature is a
hyperparasite, which is to
say, a parasite of a para-
site. In the act just wit- =
nessed she, too, has thrust Pig pl Emer of dy
an egp in to the aphid, The larva of the beetle has attached itself
but the erub that will to a leaf preparatory to pupation, but has
bag Sates ill not changed to a pupa because of the
hatch from it will devour parasites within it. Above, one of the
the parasitic occupant parasites, which escaped from the beetle
4 - larva through a hole it cut in the skin of
that is already in pos- the latter
session of the aphid’s
skin. There are also parasites of hyperparasites, but the
series does not go on “ad infinitum’ as in the old rhyme,
for the limitation of size must intervene.
[ 181 ]
CHAPTER Vil
THE PERIODICAL CICADA
Ir is to be observed, in most of our human affairs, that
we give greatest acclaim to the spectacular, and, further-
more, that when once a hero has delivered the great thrill,
all his acts of everyday life acquire headline values. Thus
a biographer may run on at great length about the petty
details in the life of some great person, knowing well that
the public, under the spell of hero worship, will read with
avidity of things that would make but the dullest plati-
tudes if told of any undistinguished mortal. Therefore,
in the following history of our famous insect, universally
known as the “‘seventeen-year locust,” the writer does not
hesitate to insert matter that would be dry and tedious
if given in connection with a commonplace creature.
Most unfortunate it 1s, now, that we are compelled to
divest our hero of his long-worn epithet of “‘seventeen-year
locust,’ and to present him in the disguise of his true
patronymic, which is cicada (pronounced s7-ka’'-da). In
a scientific book, however, we must have full respect for
the proprieties of nomenclature; and since, as already
explained in Chapter I, the name “locust” belongs to
the grasshopper, we can not continue to designate a cicada
by this term, for so doing would but propagate confusion.
Moreover, even the praenomen of “‘seventeen-year”’ 1s
misleading, for some of the members of the species have
thirteen-year lives. Entomologists, therefore, have re-
christened the ‘‘seventeen-year locust’ the periodical
cicada.
The cicada family, the Cicadidae, includes many species -
[ 182 |
DHE PERIODICAL CICADA
of cicadas in both the New World and the Old, and some
of them are more familiar, at least by sound, than our
periodical cicada, because not only are the males noto-
riously musical, but they are to be heard every year (Fig.
112). The cicadas of southern Europe were highly es-
teemed by the ancient Greeks and Romans for their song,
and they were often kept in cages to furnish entertainment
Fic. 112. One of the common annual cicadas whose loud song is
heard every year through the later part of the summer
with their music. The Greeks called the cicada fettix,
and Aesop, who always found the weak spot in every-
body’s character, wrote a fable about the tettix and the
ant, in which the tettix, or cicada, after having sung all
summer, asked a bite of food from the ant when the chill
winds of coming winter found him unprovisioned. But
the practical ant heartlessly replied, “Well, now you can
dance.”” This is an unjust piece of satire because the
moral is drawn to the disparagement of the cicada.
Human musicians have learned their lesson, however, and
sign their contracts with the box-office management in
advance.
[ 183]
INSECTS
In the United States there are numerous species of
“annual’’ cicadas, so called because they appear every
year, but their life histories are not actually known in
most cases. These species are called “locusts,” “‘harvest
flies,” and ‘‘dog-day cicadas” (Fig. 112). They are the
insects that sit in the trees during the latter half of sum-
mer and make those long shrill sounds that seem to be
the natural accompaniment of hot weather. Some give
a rising and falling inflection to their song, which re-
sembles zwing, zwing, zwing, zwing, (repeated in a long
series); others make a vibratory rattling sound; and still
others utter just a continuous whistling buzz.
During the interval between the times of the appear-
ance of the adult cicadas, the insects live underground.
The periodical cicada comprises two races, one of which
lives in its subterranean abodes for most of seventeen
years, the other for most of thirteen years. Both races
inhabit the eastern part of the United States, but the
longer-lived race is northern, and the other southern,
though their territories overlap. Most of our familiar in-
sects complete their life cycle in a single year, and many
of them produce two or more generations every season.
For this reason we marvel at the long life of the periodical
cicada. Yet there are other common insects that normally
require two or three years to reach maturity, and certain
beetles have been known to live for twenty years or more
in an immature stage, though under conditions adverse
for transforming to the adult.
Throughout the period of their underground life the
cicadas have a form quite different from that which they
take on when they leave the earth to spend a brief period
in the trees. The form of the young periodical cicada
at the time it is ready to emerge from the ground is shown
in Plate 5. It will be seen that it suggests one of those
familiar shells so often found clinging to the trunk of a
tree or the side of a post. These shells, in fact, are the
empty skins of young cicadas that have discarded their
[ 184 ]
PLATE 5
The mature nymph of the periodical
cicada in the form in which it leaves the
ground to transform to the winged adult
after a subterranean life of nearly
seventeen years
THE PERIODICAL CICADA
earthly form for that of a winged insect of the upper world
and sunshine, though the skins ordinarily seen are those of
the annual species.
The cicada undergoes a striking transformation from
the young to the adult, but 1t does so directly and not by
means of an intervening stage, or pupa. The young of
an insect that transforms directly is termed a nymph by
most American entomologists. The last nymphal stage
is sometimes called a “‘pupa,’”’ but it 1s not properly so
designated.
The life of the periodical cicada stirs our imagination
as that of no other insect does. For years we do not see
the creatures, and then a springtime comes when countless
thousands of them issue from the earth, undergo their
transformation, and swarm into the trees. Now, for
several weeks, the very air seems swayed with the mo-
notonous rhythm of their song, while the business of ma-
ting and egg-laying goes rapidly on; and soon the twigs of
trees and shrubs are everywhere scarred with slits and
punctures where the eggs have been inserted. In a few
weeks the noisy multitude is gone, but for the rest of the
season the trees bear witness to the busy throng that so
briefly inhabited them by a spotting of their foliage with
masses of brown and dying leaves where the punctured
stems have broken in the wind. The young cicadas that
hatch from the eggs later in the summer silently drop to
the earth and hastily bury themselves beneath the sur-
face. Here they live in solitude, seldom observed by
creatures of the upper world, through the long period of
their adolescent years, only to enjoy at the end a few
brief weeks of life in the open air in the fellowship of
their kind.
THe Nympus
Of the underground life of the periodical cicada we
still know very little. The fullest account of the history
of this species is that given by Dr. C. L. Marlatt in his
[ 185 ]
INSECTS
Bulletin, The Periodical Cicada, published by the United
States Sonese of Entomology in 1g07. Doctor Marlatt
describes six immature stages of the periodical cicada
between the egg and the adult.
The young cicada that first enters the ground is a
minute, soft-bodied, pale-skinned creature about a twelfth
of an inch in length (Fig. 126). The body ts cylindrical
and is supported on two pairs of legs, the front legs being
the digging organs; the somewhat elongate head bears a
pair of small dark eyes and two slender, jointed antennae.
At no stage has the cicada jaws like those of the grass-
hopper; it is a sucking insect, related to the aphids, and
is provided with a beak arising from the under surface
of the head, but when not in use the beak is turned back-
ward peneen the bases of the front legs. Throughout
the period of its underground life, the cicada subsists
on the sap of roots.
During more than a year the young cicada retains ap-
proximately the form it has at hatching, though the body
changes somewhat in shape, principally by an increase
in the size of the abdomen (Fig. 113). According to
Doctor Marlatt, a nymph of the seventeen-year race first
sheds its skin, or molts, some-
time during the first two or
three months of the second
year of its life.
In its second stage it be-
comes a little larger and 1s
marked by a change in the
structure of the front legs,
Fic. 113. Nymph of the periodi- the terminal foot part of
cal cicada in the first stage, about each being reduced to a
18 months old, enlarged 15 times.
(From Marlatt) mere spur and the fourth
section being developed into
a strong, sharp-pointed pick which forms a more efficient
organ for digging. The second stage lasts nearly two
years; then the creature molts again and enters its third
| 186 |
THE PERIODICAL CICADA
stage, which is about a year in length. In the fourth
stage, which lasts perhaps three or four years, the nymph
(Fig. 114) shows distinct wing pads on the two wing-
bearing segments of the
thorax. In the fifth stage
the insect, sometimes now
called a “‘pupa,” takes on
the form it has when it
finally emerges from the
earth; its front feet are
restored and its wing
pads are well developed,
but it has entirely lost its
small nymphal eyes. Fic. 114. Nymph of the periodical
ace more, Betanemite cicada in the fourth stage, about 12 years
old, enlarged 234 times. (From Marlatt)
long underground sen-
tence is up, the nymph molts, and enters the sixth and
last stage of its subterranean life. When mature (Plate 5)
it is about an inch and a quarter in length, thick-bodied,
and brown in color; it appears to have a pair of bright-red
eyes on the head, but these are the eyes of the adult
inside showing through the nymphal skin.
According to the investigations of Doctor Marlatt, the
nymphs of the periodical cicada do not ordinarily burrow
into the earth below two feet, and most of them are to be
found at depths varying from eight to eighteen inches.
However, there are reports of their having been discovered
ten feet beneath the surface, and they have been known
to emerge from the floors of cellars at the time of trans-
formation to the adult stage. There is no evidence that
the insects, even when present in great numbers in the
earth, do any appreciable damage to the vegetation on
the roots of which they feed.
Some time before the mature nymphs emerge from the
ground, probably in April of the last year of their lives,
the insects come up from their subterranean burrows and
construct a chamber of varying depth just below the
[ 187 ]
INSECES
SU
Fic. 115. Outlines of plaster casts of underground resting chambers of the
mature nymph of the periodical cicada (about one-half natural size)
[ 188 |
TRE PERTODICAL CICADA
surface. A good idea of the size and shape of these cham-
bers may be obtained by filling the opened holes with a
mixture of plaster of Paris in water, letting the plaster
harden, and then digging up the casts. Figure 115 shows
casts of anumber of chambers made in this way. Some, it
is seen, are mere cups about an inch in depth, but most of
them are long and narrow, descending several inches into
the ground, the longest being six inches or more in depth.
The width is usually about five-eighths of an inch. All
the chambers have a distinct enlargement at the bottom,
and most of them are slightly widened at the top. The
upper wall of each is separated from the surface by a
layer of undisturbed soil about half an inch in thick-
ness, which is not broken until the insect is ready to
emerge.
The shafts are seldom straight, their courses being
more or less tortuous and inclined to the surface, as the
miner had to avoid roots and stones obstructing the
vertical path. The interior contains no débris of any
kind, and the walls are smooth and compact. Below
each chamber there is always evidence of a narrower
burrow going irregularly downward into the earth, but
this tunnel is filled to the chamber floor with black granu-
lar earth. The burrows examined by the writer near
Washington in 191g were dug through compact red clay,
and the lower tunnels here made a distinct black path
through the red of the surrounding clay, where some
could be followed for a considerable distance. The black
color of the earth filling the tunnels was possibly due to
an admixture of fecal matter.
The chambers, as we have noted, are closed at the top
until the cicada is ready toemerge. The largest chambers
are many times the bulk of the nymph in volume, and it
becomes, then, a question as to what the insect does with
the material it removed in making a hole of such size. It
seems improbable that it could have been carried down
into the lower tunnel, for this would be filled with its own
[ 189 ]
INSECTS
débris. The insects themselves will give an answer to
the question if several of them are placed in glass tubes
and covered with earth; but, to understand the cicada’s
technique, we must first study the mechanism of its
digging tools, the front legs.
The front leg of a mature cicada nymph (Fig. 116 A) is
composed of the same
parts as any other of its
legs. The third segment
from the base, which is
the femur (F), is large
and swollen, and has a
pair of strong spines and
a comb of smaller ones
projecting from its lower
edge. The next segment
is the sibia (Tb). It is
curved and terminates
in a strong recurved
Fic, 116. The digging organ, or front
leg, of the mature cicada nymph point (B). Finally, at-
A, right leg, inner surface (4 times natural tached to the inner sur-
size). B, the tarsus (Tar) bent inward at face of the tibia, well up
right angles to the tibia (7%), the posi- - ye :
tion in which it is used as a rake from its terminal point,
Cx, basal joint or coxa; Tr, trochanter; EB; is the slender farsus
femur; Td, tibia; Tar, tarsus, with two
see dese (Tar). The tarsus can
be extended beyond the
tibial point when the insect is walking or climbing, but
can also be turned inward at a right angle to the latter,
as shown at B, or bent back against the inner surface of
the tibia.
Let us now return to the insects in the earth-filled
tubes, where they are industriously at work. It will be
seen that they are using the curved, sharp-pointed tibiae
as picks with which to loosen the earth, the tarsi being
turned back and out of the way. The two legs, working
alternately, soon accumulate a small mass of loosened
material in front of the insect’s body. Now there is a
Th
[ 190 }
TaEP PERIODICAL CICADA
cessation of digging and the tarsi are turned forward at
right angles to the tibiae to serve as rakes (Fig. 116 B).
The mass of earth pellets is scraped in toward the body,
and—here comes the important part, the cicada’s special
technique—the little pile of rakings is grasped by one
front leg between the tibia and the femur (Fig. 116 A,
Tb and F), the former closing up against the spiny margin
of the latter, the leg strikes forcibly outward, and the
mass of loosened earth is pushed back into the surrounding
earth. The process is repeated, first with one leg, then
with the other. The miner looks like a pugilist training
on a punching bag. Now and then the worker stops and
rubs his legs over the protruding front of the head to
clean them on the rows of bristles which cover each side
of the face. Then he proceeds again, clawing, raking,
gathering up the loosened particles, thrusting them back
into the wall of the growing chamber. His back 1s firmly
pressed against the opposite side of the cavity, the middle
legs are bent forward until their knees are almost against
the bases of the front legs, their tibiae lying along the wing
pads. The hind legs keep a normal position, though
held close against the sides of the body.
From what we know of the cicada’s spring habits
underground, we can infer that the nymphs construct
their chambers on their arrival near the surface during
April, and that, when the chambers are completed, the
insects wait within for the signal to emerge and trans-
form into the adult. Then they break through the thin
caps at the surface and come out. It would be difficult
to explain how they know when they are so near the top
of the ground, and why some construct ample chambers
several inches deep while others make mere cells scarcely
larger than their bodies. Do they burrow upward till the
pressure tells them that the surface is only a quarter of
an inch or so away, and then widen the débris-filled
tunnel downward? Evidently not, because the chamber
walls are made of clean, compacted clay in which there
[igi]
INSECTS
is no admixture of the blackened contents of the burrows.
It is unlikely, too, that they base their judgments on a
sense of temperature, because their acts are not regulated
by the nature of the season, which, if early or late, would
fool them in their calculations.
Early in the spring, before the proper emergence season,
cicada nymphs are often found beneath logs and stones.
This is to be expected, for, to the ascending insect, some-
thing impenetrable has blocked the way, and there is
nothing to tell it that it has already reached the level of
the surface.
A more curious thing, often observed in some localities,
is that the insects some-
times continue _ their
chambers up above the
surface of the ground
within closed turrets of
mud from two to several
inches in height (Fig.
117). At certain places
these cicada “huts” have
been reported as occur-
ring in great numbers;
and it has been supposed
that they may be built
wherever there is some-
thing about the nature of
Fe, De, tes eae eet alte a eae
cicada as continuations from their under- do not like, the earth
the tubular cavity within, (Brom pheee, b€tNg perhaps too damp,
graph by Marlatt) for they are frequently
found where the ground
is unusually wet. On the other hand, the turrets have
been observed in dry situations as well, and towers and
holes flush with the surface frequently occur intermingled.
The writer has had no opportunity of studying the cicada
turrets, but a most interesting description of them is given
[ 192 ]
PLATE 6
The cicada just after emergence from the nymphal
skin. (inlarged two-thirds)
TBE PERIODICAL CICADA
by Dr. J. A. Lintner in his Twelfth Report on the Insects of
New York, published in 1897. Dr. Lintner says the
turrets are constructed by the nymphs with soft pellets
of clay or mud brought up from below and firmly pressed
into place, and he records an observation on a nymph
caught at work with a pellet of mud in its claws. We
may infer, then, that the cicada’s style of work as a
mason is only a aed iceiean of its working methods as a
miner, but it appears that no one has yet actually watched
the construction of one of the turrets. At emergence
time the towers are opened at the top and the insects come
forth as they would from an ordinary chamber beneath the
level of the ground.
THe TRANSFORMATION
The period of emergence for most of the cicadas of the
northern, or seventeen-year, race is the latter part of
May. The time of their appearance over large areas is
much more nearly uniform than with most other insects,
which show a wide variation according to temperature as
determined by the season, the elevation, and the latitude.
Nevertheless, observations in different localities show
that the cicada, too, is influenced by these conditions.
In the South, members of the thirteen- year race may
emerge even a month earlier, the first individuals of the
‘southernmost broods appearing in the latter part of
April.
By some feeling of impending change the mature
nymph, waiting in its chamber, knows when the time of
transformation is at hand. Somehow nature regulates
the event so that it will happen in the evening, but, once
the hour has come, no time is to be lost. The nymph
must break out of its cell, find a suitable molting site
and one in accord with the traditions of its race, and there
fix itself by a firm grip of the tarsal claws. At the be-
ginning of the principal emergence period Jarge numbers
of the insects come out of their chambers as early as
[ 193 ]
INSECTS
five o'clock in the afternoon; but after the rush of the
first few days not many appear before dusk.
It is difficult to catch a nymph in the very act of making
its exit from the ground, and apparently no observations
have been recorded on the manner of its leaving. Do the
insects leisurely open their doors some time in advance
of their actual need and wait below till the proper hour,
or do they break through the thin caps of earth and emerge
at once? Digging up many open chambers revealed a
living nymph in only one. Another issued from one of
several dozen holes filled with liquid plaster for obtaining
casts. Add to this the fact that great numbers of fresh
holes are to be seen every morning during the emergence
season, and the evidence would appear to indicate that
the insects open their doors in the evening and come out
at once. Only one chamber was found in the daytime
partly opened.
If the insects are elusive and wary of being spied
upon as they make their début into the upper world, a
witness of their subsequent behavior does not embarrass
them at all. However, events are imminent; there is
no time to waste. The crawling insects head for any
upright object within their range of vision—a tree is the
ideal goal if it can be attained, and since the creatures
were born in trees there is likely to be one near by. Yet
it frequently happens that trees in which many were
hatched have been since cut down, in which case the
returning pilgrims must make a longer journey perhaps
than anticipated. But the transformation can not be
delayed; if a tree is not accessible, a bush or a weed, a
post, a telegraph pole, or a blade of grass will do. On
the trees some get only so far as the trunk, others attain
the branches, but the mob gets out, upon the leaves.
Though thousands emerge almost simultaneously, they
have not all been timed alike. Some have but a few
minutes to spare, others can travel about for an hour or
so before anything happens.
[ 194 |
.
THE, PERTODICAL CICADA
The external phase of transformation, more strictly
the shedding of the last nymphal skin, has been many
times observed. It is nothing more than what all insects
do. But the cicada is notorious because it does the thing
in such a spectacular way, almost courting publicity
where most insects are shy and retiring. As a conse-
quence the cicada is famous; the others are known only
to prying entomologists.
Let us suppose now that our crawling nymph has
reached a place that suits it, say on the trunk of a tree,
or better still on a piece of branch provided for it and
taken into a lighted room where its doings can be more
clearly observed. Though the insects choose the evening
for emergence, they are not bashful at all about changing
their clothes in the glare of artificial light. The progress
of this performance 1s illustrated by Figure 118. The
first drawing shows the nymph still creeping upward;
but in the next (2) it has come to rest and is cleaning
its ffont feet and claws on the brushes of its face, just
as did those confined to the glass tubes to give a demon-
stration of their digging methods. The front feet done,
the hind ones are next attended to. First one and then
the other is slowly flexed and then straightened back-
ward (3) while the foot scrapes over the side of the ab-
domen. Several times these acts are repeated calmly
and deliberately, for it is an important thing that the
claws be well freed from any particles of dry earth that
might impair their grip on the support. At last the
toilet 1s completed, though the middle feet are always
neglected, and the insect feels about on the twig, grasp-
ing now here, now there, till its claws take a firm hold
on the bark. At the same time it sways the body gently
from side to side as if trying to settle comfortably for the
next act.
Thirty-five minutes may be consumed in the above
preliminaries and there is next a ten-minute interval of
quietude before the real show begins. Then suddenly
[195 ]
INSECTS
Fic. 118. Transformation of the periodical cicada from the mature
nymph to the adult
| 196 |
TEPER RIODICAL CICADA
the insect humps its back (4), the skin splits along the
midline of the thorax (5), the rupture extending forward
over the top of the head and rearward into the first seg-
ment of the abdomen. A creamy white back, stamped
with two large jet-black spots, now bulges out (6, 7);
next comes a head with two brilliant red eyes (8); this is
followed by the front part of a body (g) which bends
backward and pulls out legs and bases of wings. Soon
one leg is free (70), then four legs (77), while four long,
glistening white threads pull out of the rod of the issuing
creature but remain attached to the empty shell. These
are the linings of the thoracic air tubes being shed with
the nymphal skin. Now the body hangs back down,
when all the legs come free (72), and now it sags peril-
ously (737) as the wings begin to expand and visibly
lengthen.
Here another rest intervenes; perhaps twenty-five min-
utes may elapse, while the soft new creature, like an in-
verted gargoyle supported only by the rear end of its
body, hangs motionless far out from the split in the back
of the shell. Now we understand why the nymph took
such pains to get a firm anchorage, for, should the dead
claws give way at this critical stage, the resulting fall
most probably would prove fatal.
The next act begins abruptly. The gargoyle moves
again, bends its body upward (4), grasps the head and
shoulders of the slough (75), and pulls the rear parts
of its body free from the gaping skin (76). The body
straightens and hangs downward (77). At last we be-
hold the free imago, not yet mature but rapidly assum-
ing the characters of an adult cicada. The new creature
hangs for a while from the discarded shell-like skin,
clinging by the front and middle legs, sometimes by the
first alone; the hind ones spread out sideways or bend
against the body, rarely grasping the skin. The wings
continue to unfold and lengthen, finally hang flat, fully
formed, but soft and white (78). Here the creature
[ 197 ]
INSECYs
usually becomes restless, leaves the empty skin (7g), and
takes up a new position several inches away (20).
At this stage the cicada is strangely beautiful. Its
creamy-yellow paleness, intensified by the great black
patches just behind the head and relieved by the pearly
flesh tint of the mesothoracic shield, its shining red eyes,
and the milky, semitransparent wings with deep chrome
on their bases make a unique impression on the mind.
There is a look of unreality about the thing, which out of
doors (Plate 6) becomes a ghostlike vision against the
night. But, even as we watch, the color changes; the
unearthly paleness is suffused with bluish gray, which
deepens to blackish gray; the wings flutter, fold against
the back, and the spell is broken—an insect sits in the
place of the vanished specter.
The rest is commonplace. The colors deepen, the grays
become blackish and then black, and after a few hours the
creature has all the characters of a fully matured cicada.
Early the next morning it is fluttering about, restless to
be off with its mates to the woods.
The time consumed by the entire performance, from
the splitting of the skin (Fig. 118, 5) to the folding of the
wings above the back (27), varies with different indi-
viduals, observed at the same time and under the same
conditions, from forty-five minutes to one hour and
twelve minutes. Most of the insects have issued from
the nymphal skins before eleven o’clock at night, but oc-
casionally a straggler may be seen in the last act as late
as nine o'clock the following morning—probably a be-
lated arrival who overslept the night before.
Thus, to the eye, the burrowing and crawling creature
of the earth becomes transfigured to a creature of the air;
yet the visible change 1s mostly but the final escape of
the mature insect from the skin of its preceding stage.
Aside from a few last adjustments and the expansion of the
wings, the real change has been in progress within the
nymphal skin perhaps for years. We do not truly witness
[ 198 ]
(sown om} pasivpuq) *simj o[ddv uv yo aovyins sapun ayy ojut s0z1s0dta0 JOY YIM soda Suljsasur apeuray VY
(w12apuasdas vpvrtaisvyy) epesio [eoipotsed ayy,
L AaLV Id
THEE RIODICAL CICADA
the transformation; we see only the throwing off of the
shell that concealed it, as the circus performer strips off
the costume of the clown and appears already dressed
in that of the accomplished acrobat.
Tue AbDULTS
The adult cicada bears the stamp of individuality. In
form he does not closely resemble any of our everyday
insects, and he has a personality all his own; he impresses
us as a “distinguished foreigner in our midst.” The body
of the periodical cicada is thick-set (Fig. 119), the face is
bulging, the forehead is wide, with the eyes set out promi-
nently on each side; from the under side of the head the
short, strong beak projects downward and backward be-
tween the bases of the front legs. The colors are dis-
tinctive but not striking. The back is plain black (Plate
7); the eyes are bright red; the wings are shiny transparent
amber with strongly marked orange-red veins; the legs
and beak are reddish, and there are bands of the same
color on the rings of the abdomen. Each front wing is
branded near the tip with a conspicuous dark-brown W.
With both the seventeen-year race and the thirteen-
year race of the periodical cicada there is associated a
small cicada, which, however, differs so little except in
size from the others (Fig. 119) that entomologists gener-
ally regard it as a mere variety of the larger form, the
latter always including by far the greater number of
individuals in any brood.
The male cicada has a pair of large drumheads beneath
the bases of the wings on the front end of the abdomen
(Fig. 120, Tm). These are the instruments by which
he produces his music, and we will give them more atten-
tion presently. The female cicada has no drums nor other
sound-making organs; she is voiceless, and must keep
silence no matter how much her noisy mate may disturb
her peace. The chief distinction of the female is her
ovipositor, a long, swordlike instrument used for inserting
[ 199 J
INSECTS
the eggs into the twigs of trees and bushes. Ordinarily the
ovipositor is kept in a sheath beneath the rear half of the
abdomen, but when in use it can be turned downward
and forward by a hinge at its base (Plate 7). The oviposi-
tor consists of two
lateral blades, and a
guide-rail above. The
blades excavate a cav-
ity in the wood in-
to which the eggs
are passed through
the space between the
blades.
It was formerly sup-
posed that the period-
ical cicada takes no
food during the brief
time of its adult life,
but we know from the
observations of Mr. W. T. Davis, Dr. A. L. Quaintance,
and others and from a study of the stomach contents made
by the writer that the insects do feed abundantly by
sucking the sap from the trees on which they live. The
cicada, being a
near relative of
the aphids, has
also, as we have
already noted, a
piercing and suck-
ing beak by which
it punctures the
plant tissues and
draws the sap up
to its mouth. Un-
like the other
sucking insects
Fic. 119. Males of the large and small form
of the periodical cicada (natural size)
Fic. 120. A male of the periodical cicada with the
ire wings spread, showing the ribbed sound-producing
that infest plan ese organs, or tympana (7m), on the base of the abdomen
[ 200 }
THE PERIODICAL CICADA
however, the cicadas cause no visible damage to the trees
by their feeding. Perhaps this is because their attack
lasts such a short time and comes at a season when the
trees are at their fullest vigor.
The details of the head structure of the cicada and
the exposed part of the beak are shown in Figure 121,
which gives in side view the head of a fully matured
adult, detached from the body by the torn neck mem-
brane (NMé), with the beak (Bk) extending downward
and backward below. The large eyes (E) project from
the sides of the upper part of the head. The face is
covered by a large protruding, striated plate (C/p). The
cheek regions are formed by a long plate (Ge) on each side
below the eyes; and between each cheek plate and the
striated facial plate is partly concealed a narrower plate
(Md). The cicada has no jaws. Its true mouth is shut
in between the large flap (4C/p), below the striated facial
plate, and the base of the beak.
If the outer parts of the head about the mouth can be
separated, there will be seen within them some other very
important parts ordinarily hidden from view. In a
specimen that has been killed in the act of emerging from
the nymphal skin, when it is still soft, the outer parts are
easily separated, exposing the structures shown at B of
the same figure.
It is now to be seen (Fig. 121 B) that the beak con-
sists of a long troughlike appendage (L4) suspended from
beneath the back part of the head, having a deep groove
on its front surface in which are normally ensheathed
two pairs of slender bristles (dB, MxB), of which only
the two of the left side are shown in the figure. In front
of the bases of the bristles there is exposed a large tongue-
like organ which is the hypopharynx (Hphjy). Between
this tongue and the flap hanging from the front of the
face is the wide-open mouth (M/A), the roof of which (e)
bulges downward and almost fills the mouth cavity.
The way in which the cicada obtains its liquid food de-
[ 201 |
INSECTS
pends upon the finer structure and the mechanism of
the parts before us.
Each one of the second pair of bristles has a furrow
along the entire length of its inner surface, and the two
Fic. 121. The structure of the head and sucking beak of the adult cicada
A, the head in side view with the beak (Bk) in natural position
B, the head of an immature adult: the mouth (M/A) opened, exposing the roof
(e) of the sucking pump (see fig. 122), and the tonguelike hypopharynx (Hphy);
the parts of the beak separated, showing that it is composed of the labium
(Zé), inclosing normally two pairs of long slender bristles (M/dB, MxB, only
one of each pair shown)
a, bridge between base of mandibular plate (Md) and hypopharynx (Hphy);
Aclp, anteclypeus; 4nt, antenna; Bk, beak; C/p, clypeus; e, roof of mouth cavity,
or sucking pump; Ge, gena (cheek plate); Hphy, hypopharynx; Lé, labium; Lm,
labrum; Md, base of mandible; MdB, mandibular bristle; Mth, mouth; Mx,
maxilla; MxB, maxillary bristle; NMé, neck membrane; O, ocelli
bristles, small as they are, are fastened together by inter-
locking ridges and grooves, so that their apposed fur-
rows are converted into a single tubular channel. In
the natural position, these second bristles lie in the
sheath of the beak (Fig. 121 A) between the somewhat
larger first bristles. Their bases separate at the tip’of
| 202 }
THE PERIODICAL CICADA
the tongue (HpAy) to pass to either side of the latter
organ, but the channel between them here becomes con-
tinuous with a groove on the middle of the forward sur-
face of the tongue. When the mouth-opening is closed,
as it always is in the fully matured insect, the tongue
groove is converted into a tube which leads upward from
the channel between the second bristles into the inner
cavity of the mouth. It is through this minute passage
that the cicada obtains its liquid food; but obviously
there must be a pumping apparatus to furnish the sucking
force.
The sucking mechanism is the mouth cavity and its
muscles. The mouth cavity, as seen in a section of the
head (Fig. 122, Pmp), is a long, oval, thick-walled capsule
having its roof, or anterior wall (e), ordinarily bent inward
so far as almost to fill the cavity. Upon the midline
of the roof is inserted a great mass of muscle fibers
(PmpMcls) that have their other attachment on the
striated plate of the face (C/p). The contraction of these
muscles lifts the roof, and the vacuum thus created in
the cavity of the mouth sucks up the liquid food. Then
the muscles relax, and the elastic roof again collapses,
but the lower end comes down first and forces the liquid
upward through the rear exit of the mouth cavity into
the pharynx, a small muscular-walled sac (Phy) lying
in the back of the head. From the pharynx, the food
is driven into the tubular gullet, or oesophagus (OZ),
and so on into the stomach.
The bases of both pairs of bristles are retracted into
pouches of the lower head wall behind the tongue, and
upon each bristle base are inserted sets of protractor
and retractor muscle fibers. By means of these muscles,
the bristles can be thrust out from the tip of the beak or
withdrawn, and the bristles of the stronger first pair
are probably the chief organs with which the insect
punctures the tissues of the plant on which it feeds. As
the bristles enter the wood, the sheath of the beak can
[ 203 ]
[INSECES
be retracted into the flexible membrane of the neck at
its base.
One other structure of interest in the cicada’s head
should be observed.
This is a force pump connected
with the duct (Fig. 122, Sa/D) of the large salivary glands
(G/, G/) and used probably for injecting into the wound
of the plant a secretion which perhaps softens the tissues
of the latter as the bristles are inserted.
Median section of the head and beak of
an adult cicada
Fic. 122.
The sucking pump (Pmp) is the mouth cavity, the
collapsed roof of which (¢) can be lifted like a piston
by the large ‘muscles (PmpMcls) arising on the
clypeus (C/p). The liquid food ascends through a
channel between the maxillary bristles (MB), is
drawn into the mouth opening (Mk), and pumped
back into the pharynx (Phy), from which it goes into
the oesophagus (OZ). Ai salivary pump (Sa/Pmp)
opens at the tip of the hypopharynx (Hphy), dis-
charging the secretion of the large glands (G/, G/)
into the beak
[ 204 }
Possibly the
saliva has also a
digestive action
on the food liquid.
hes Ysaliwamy
pump (Sa/Pmp)
lies behind the
mouth, and its
duct opens on the
extreme tip of the
tongue, where the
Saliva team. bie
driven into the
channel of the
second bristles.
Most sucking in-
sects have two
parallel channels
between these
bristles (Fig. go),
one for taking
food, the other
for ejecting saliva,
and the cicada
probably has two
also, though in-
vestigators differ
as to whether
there are two or
only one.
THE PERTODICAL, CICADA
The head of the cicada is thus seen to be a wonderful
mechanism for enabling the insect to feed on plant sap.
The piercing beak and the sucking apparatus, however,
are characters distinguishing the members of a whole
order of insects, the Hemiptera, or Rhynchota. This
order includes, besides the cicadas, such familiar insects
as the plant lice, the scale insects, the squash bugs,
the giant water bugs, the water striders, and the bed
bugs. To the sucking insects properly belongs the name
“bug,” which is not a synonym of “‘insect.
It 1s believed, of course, that the parts of the sucking
beak of a hemipteran insect correspond with the mouth
parts of a biting insect, described in Chapter IV (Fig.
66), but it has been a difficult matter to determine the
identities of the parts in the two cases. Probably the
anterior narrow plate on the side of the cicada’s head
(Fig. 121, Md) is a rudiment of the base of the true jaw,
or mandible. The first bristles (MdB) are outgrowths
of the mandibular plates, which have become detached
from them and made independently movable by special
sets of muscles. The second bristles (xB) are out-
growths of the maxillae, which are otherwise reduced
to small lobes (Mx) depending from the cheek plates
(Ge). The sheath of the beak (4) 1s the labium. We
have here, therefore, a most instructive lesson on the
manner in which organs may be made over in form, by
the processes of evolution, adapting them to new and
often highly special uses.
The abdomen of the cicada is thick, and strongly
arched above. Its external appearance of plumpness
suggests that it would furnish a Juicy meal for a bird,
and birds do destroy large numbers of the insects. Yet
when the interior of a cicada 1s examined (Fig. 123), it is
found that almost the entire abdomen is occupied by a
great air chamber! The soft viscera are packed into
narrow spaces about the air chamber, the stomach (Stom)
being crowded forward into the rear part of the thorax.
[ 205 ]
INSECTS
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| 206 |
THE PERIODICAL CICADA
The air chamber is a large, thin-walled sac of the tracheal
respiratory system, and receives its air supply directly
through the spiracles of the first abdominal segment.
From the sac are given off tracheal tubes to the muscles
of the thorax and to the walls of the stomach.
Many insects have tracheal air sacs of smaller size,
and the purpose of the sacs in general appears to be that
of holding reserve supplies of air for respiratory pur-
poses. The great size of the air sac in the cicada’s abdo-
men, however, suggests that it has some special function,
and it is natural to suppose that it acts as a resonating
chamber in connection with the sound-producing drums.
Yet the sac is as well developed in the female as in the
male. Possibly, therefore, it serves too for giving buoy-
ancy to the insects, for it can readily be seen that if the
space occupied by the sac were filled with blood or other
tissues, as it is in most other insects, the weight of the
cicada would be greatly increased; or, on the other
hand, if the body were contracted to such a size as to
accommodate only its scanty viscera, it would lose
buoyancy through lack of sufficient extent of surface—
a paper bag crumpled up drops immediately when re-
leased, but the same bag inflated almost floats in the air.
THE SounD-PropucING ORGANS AND THE SONG
The cicadas produce their music by instruments quite
different from those of any of the singing Orthoptera
—the grasshoppers, katydids, and crickets, described
in Chapter II. On the body of the male cicada, just
back of the base of each hind wing, as we have already
observed, in the position of the “ear” of the grasshopper
(Fig. 63, Tm), there is an oval membrane like the head
of a drum set into a solid frame of the body wall (Fig.
120, Tm). Each drumhead, or tympanum, is a mem-
brane closely ribbed with stiff vertical thickenings, the
number of ribs varying in different species of cicadas
and perhaps accounting in part for the different qualities
[ 207 ]
INSECTS
of sound produced. In the periodical cicada, the drum-
heads are exposed and are easily seen when the wings
are lifted; in our other common cicadas each drum is
concealed by a flap of the body wall.
The sound made by an ordinary drum is produced by
the vibration of the drumhead that is struck by the
player, but the tone and volume of the sound are given
by the air space within the drum and by the sympathetic
vibration of the opposite head. The air within the
drum, then, must be in communication with the air
outside the drum, else it would impede the vibration of
the drumheads.
All these conditions imposed upon a drum are met by
the cicada. The abdomen of the insect, as we have seen,
is largely occupied by a great air chamber (Fig. 123),
and the air within the chamber communicates with the
outside air through the spiracles of the first abdominal
segment (/Sp). In addition to the two drumheads whose
activity produces the sound, there are two other thin,
taut membranous areas set into oval frames tn the lower
side walls of the front part of the abdomen (not seen
in the figures). These ventral drumheads have such
smooth and glistening surfaces that they are often desig-
nated the “mirrors.” The wall of the air sac is applied
closely to their inner surfaces, but both membranes are
so thin that it 1s possible to see through them right into
the hollow of the cicada’s body. The ventral drum-
heads are not exposed externally, however, for they are
covered by two large, flat lobes projecting back beneath
them from the under part of the thorax.
The cicada does not beat its drums or play upon them
with any external part of its body. When a male is
“singing,” the exposed drumheads are seen to be in very
rapid vibration, as if endowed with the power of auto-
matic movement. An inspection of the interior of the
body of a dead specimen, however, shows that con-
nected with the inner face of each drumhead is a thick
{| 208 |
THE PERIODICAL CICADA
muscle which arises below from a special support on the
ventral wall of the second abdominal segment (Figs.
129) 194 nicl). It is by the contraction of ‘these
muscles that the drum membranes are set in motion.
IT Tis is
Fic. 124. The abdomen and sound-making organs of the male periodical
cicada
A, the abdomen cut open from above, exposing the air chamber (4irSc), and
showing the great tympanal muscles (TmMc/) inserted on the tympana (Tm).
The arrows indicate the position of the first spiracles opening into the air chamber
(see fig. 123, 7Sp)
B, inner view of right half of first and second abdominal segments, showing the
ribbed tympanum (7m), and the muscles that vibrate it (TmMc/)
AirSc, air chamber; DMcl, dorsal muscles; JS, JJS, IIIS, sternal plates of first
three abdominal segments; /Sp, first abdominal spiracle; JT, IIT, IIIT, tergal
plates of first three abdominal segments; Ne, tergal plate of third thoracic seg-
ment; Tm, tympanum; TmMci, tympanal muscle; 3, base of hind wing; YMcl,
ventral muscles
But a muscle pulls in only one direction; the drum muscles
produce directly the inward stroke of the drumhead
membranes; the return stroke results from the outward
convexity and the elasticity of the heads themselves
and the stiff ribs in their walls.
When a cicada starts its music, it lifts the abdomen a
little, thus opening the space between its ventral drum-
| 209 |
INSECTS
heads and the protecting flaps beneath, and the sound
comes out in perceptibly increased volume. There can
be little doubt that the air chamber of the body andthe
ventral membranes are important accessories in the
sound-producing apparatus. Living cicadas are often
found with half or more of the abdomen broken off, leav-
ing the air sac open to the exterior. Such individuals
may vibrate the drumheads, but the sound produced is
weak and entirely lacks the quality of that made by the
perfect insect.
Wherever the periodical cicada appears in great num-
bers, the daily choruses of the males leave an impression
long remembered in the neighborhood; and, curiously,
the sound appears to become increasingly louder in
retrospect, until, after the lapse of years, each hearer is
convinced it was a deafening clamor that almost deprived
him of his senses. Fortunately the cicadas are day-
time performers and are seldom heard at night. The
song of the periodical species has no resemblance to the
shrill, undulating screech of the annual cicadas so com-
mon every summer in August and September. All the
notes of the more common large form of the seventeen-
year race are characterized by a durr sound, and at
least four different utterances may be distinguished; the
quality of three of the notes probably depends on the
age of the individual insect, the fourth is an expression
of fright or anger.
The simplest notes to be heard are soft purring sounds,
generally made by solitary insects sitting low in the
bushes, probably individuals that have but recently
emerged from the ground. The next is a longer and
louder note, characterized by a rougher burr, lasting about
five seconds, and always given a falling inflection at the
close. This sound is the one popularly known as the
“Pharaoh” song, because of a fancied resemblance to
the name if the first syllable 1s sufficiently prolonged and
the second allowed to drop off abruptly at the end. It
[ 210 ]
THE PERIODICAL CICADA
is repeated at intervals of from two to five seconds, and
is given always as a solo by individuals sitting in the
bushes or on lower branches of the trees. Males singing
the Pharaoh song, therefore, are easily observed in the
act of performing. With the beginning of each note, the
singer lifts his abdomen to a rigid, horizontal position,
thus opening the cavity beneath the lower drumheads
and letting out the full volume of the sound. Toward the
end of the note, the abdomen drops again to the usual
somewhat sagging position, appearing thus to give the
abrupt falling inflection at the close.
The grand choruses, by which the periodical cicada is
chiefly known and remembered, are given by the fully
matured males of the swarm, always high in the trees
where the singers may seldom be closely observed while
performing. The individual notes are prolonged bur-r-r-r-
like sounds, repeated all day and day after day, but all
single voices are blended and lost in the continuous hum
of the multitude.
The fourth note of the larger form of the cicada is
uttered by males when they appear to be surprised or
frightened. On such occasions, as the insect darts
away, he makes a loud, rough kourid: and the same note
is often uttered when a male is picked up or otherwise
handled.
The notes of the small form of the seventeen-year race
of the cicada have an entirely different character from
those of his larger relative. The regular song of the little
males much more resembles that of the annual summer
cicadas, though it is not so long and is less continuous
in tone. It opens with a few short chirps; then follows
a series of strong, shrill sounds like zwing, zwing, zwing,
and so on, closing again with a number of chirps. The
whole song lasts about fifteen seconds. Several of these
males kept in cages for observation sang this song re-
peatedly and no other. It is common out of doors, but
always heard in solo, never in chorus. When handled
arieie ||
INSECTS
or otherwise disturbed, the small males utter a succession
of sharp chirps very suggestive of the notes of some
miniature wren angrily scolding at an intruder. Never
does the small form of the cicada utter notes having the
burr tone of those of the larger species, and the vocal
differences of the two varieties are strikingly evident
when several males of both kinds are caged together.
When disturbed, each produces his own sound, one the
burr, the other the chirp; and there is never any sugges-
tion of similarity or of gradation between them.
Ecc Layinc
The cicadas lay their eggs in the twigs of trees and
shrubs and frequently in the stalks of deciduous plants.
They show no particular choice of species except that
conifers are usually avoided.
The eggs are not stuck into the wood at random, but
are carefully placed in skillfully constructed nests whieh
the female excavates in the twigs with the blades of her
ovipositor (Plate 8). These nests are perhaps always
on the under surfaces of the twigs, unless the latter are
vertical, and usually there are rows of from half a dozen
to twenty or more of them together.
Figg laying begins in the early part of June, and by
the tenth of June it is at its height. The female cicadas
can easily be watched at work, taking flight only from
actual interference. They usually select twigs of last
year’s growth, but a use older ones or green ones of
the same season. In the majority of cases the female
works outward on the twig; but if this is a rule, it is a
very loosely observed one, for many work in the opposite
direction.
Each nest is double; that is, it consists of two chambers
having a common exit, but separated by a thin vertical
partition of wood (Plate 8, D, F). The eggs are placed
on end in the chambers in two rows, with their head ends
Lanret]
Egg punctures and the eggs of the periodical cicada
A, B, C, twigs of dogwood, oak, and apple containing rows of cicada
egg nests. D, cross-section of a twig through an egg nest, showing the
two chambers, each containing a double row of eggs. E, vertical
lengthwise section through two egg nests, showing the rows of slanting
eggs and the frayed lip of the nest opening. F, horizontal section
showing each chamber filled with a double row of eggs. G, several eggs
(much enlarged)
THE PERIODICAL CICADA
downward and slanted toward the door. Generally there
are six or seven eggs in each row (£), making twenty-four
to twenty-eight eggs in the whole nest, but frequently
there are more than this. The wood fibers at the en-
trance are much frayed by the action of the ovipositor
and make a fan-shaped platform in front of the door
(A, B, C). Here the young shed their hatching garments
on emerging from the nest. The series of cuts in the bark
eventually run together into a continuous slit, the edges
of which shrink back so that the row of nests comes to have
the appearance of being made in a long groove. This
mutilation kills many twigs, especially those of oaks and
hickories, the former soon showing the attacks of the
insects by the dying leaves. The landscape of oak-
covered regions thus becomes spotted all over with red-
brown patches which often almost cover individual trees
from top to bottom. Other trees are not so much in-
jured directly, but the weakened twigs often break in the
wind and then hang down and die.
An ovipositing female (Plate 7) finishes each egg nest
in about twenty-five minutes; that 1s, she digs it out and
fills it with eggs in this length of time, for each chamber
is filled as it is excavated. A female about to oviposit
alights on a twig, moves around to the under surface,
and selects a place that suits her. Then, elevating the
abdomen, she turns her ovipositor forward out of its
sheath and directs its tip perpendicularly against the bark.
As the point enters it goes backward, and when in at full
length the shaft slants at an angle of about forty-five
degrees.
In a number of cases females were frightened away at
different stages of their work, and an examination of the
unfinished nests showed that each chamber is filled with
eggs as soon as it is excavated; that is, the insect com-
pletes one chamber first and fills it with eggs, then digs
out the other chamber which in turn receives its quota of
eggs, and the whole job is done. The female now moves
[ 213 |
INSECTS
forward a few steps and begins work on another nest,
which is completed in the same fashion. Some series
consist of only three or four nests, while others contain
as many as twenty and a few even more, but perhaps
eight to twelve are the usual numbers. When the female
has finished what she deems sufficient on one twig, she
flies away and is said to make further layings elsewhere,
till she has disposed of her 400 to 600 eggs, but the writer
made no observations covering this point. Probably
the cicada feels it safer not to intrust all her eggs to one
tree, on the principle of not putting all your money in the
same bank.
DEATH OF THE ADULTS
The din of music in the trees continues with monot-
onous regularity into the second week of June, by which
time the mating season is over. Soon thereafter the per-
formers lose their vitality; large numbers of them drop
to the earth where many perish from an internal fungus
disease that eats off the terminal rings of the body;
others are mutilated and destroyed by birds, and the
rest perhaps just die a natural death. Beneath the trees,
where a great swarm has but recently given such abundant
evidence of life, the ground 1s now strewn with the dead
or dying. A large percentage of the living are in various
stages of disfigurement—wings are torn off, abdomens are
broken open or gone entirely, mere fragments crawl about,
still alive if the head and thorax are intact. In the males
often the great muscle columns of the drums are exposed
and visibly quivering, and many of the insects, game to
the end, even in their dilapidated condition still utter
purring remnants of their song.
From now on till the latter part of July, the only evi-
dence of the late swarm of noisy visitors will be the scarred
twigs on the trees and bushes that have received the eggs
and the red-brown patches of dying leaves that every-
where disfigure the oaks and hickories.
[ 214]
THE PERIODICAL CICADA
THE Broops
The two races of the periodical cicada, the seventeen-
year and the thirteen-year, together occupy most of the
eastern part of the United States, except the northern
part of New England, the southeastern corner of Georgia,
and the peninsula of Florida. The western limits extend
into the eastern part of Nebraska, Kansas, Oklahoma,
and Texas. In general, the seventeen-year race is north-
ern, and the thirteen-year race is southern, but, though
the geographic line between the two races is remarkably
distinct, there is considerable overlapping.
While the two cicada races are distinguished from each
other by the length of their life cycle, the members of each
race do not all appear in the adult stage in any one year.
Both the seventeen-year race and the thirteen-year race
are broken up into groups of individuals that emerge in
different years, and these groups are known as “broods.”’
Each brood has its definite year of emergence, and in
general a pretty well-defined territory. The territories of
the different broods, however, overlap, or the range of a
small brood may be included in that of a larger one.
Hence, in any particular locality, there is not always an
interval of thirteen or seventeen years between the ap-
pearance of the insects; and it may happen that members
of a thirteen-year brood and of a seventeen-year brood
will emerge in the same year at the same place.
The emergence years of the principal cicada broods
have now been recorded for a long time, and the oldest
record of a swarm is that of the appearance of the “‘locusts”’
in New England two hundred and ninety-five years ago.
A full account of the broods of both races of the periodical
cicada, their distribution, and the dates of their emergence,
is given in Dr. C. L. Marlatt’s Bulletin, already cited, and
the following abstract is taken from this source:
Wherever a well-defined cicada brood appears in a
certain year, it is generally observed that a few individuals
[ang]
INSECES
come out the year before or the year after. This fact has
suggested the idea that the various broods established at
the present time had their origin from individuals of a
primary brood that, as we might say, got their dates
mixed, and came out a year too soon or a year too late,
the multiplying descendants of these individuals thus
founding a new brood dated a year in advance or a year
behind the emergence time of the parent stock. In this
way, it is conceivable, the seventeen-year race might come
to appear on each of seventeen consecutive years, and the
thirteen-year race on each of thirteen consecutive years.
Individuals emerging on the eighteenth or fourteenth year,
according to the race, would be reckoned as a part of the
first brood of its race.
The facts known concerning the emergence of the
cicadas seem to confirm the above theory, for members of
the seventeen-year race appear somewhere every year
within the limits of their range, and the emergence of
members of the thirteen-year race has been recorded for at
least eleven out of the possible thirteen years. All the
individuals of a brood are not, of course, descendants of a
single group of ancestors, nor do they necessarily occur
together in a restricted area—they are simply individuals
that coincide in the year of their emergence. However, at
least thirteen of the broods of the seventeen-year race are
well defined groups, for the most part with definitely circum-
scribed territories, though overlapping in many cases. The
broods of the thirteen-year race are not so well developed.
The broods are conveniently designated by Roman
numerals. According to the system of brood numbering
proposed by Doctor Marlatt, and now generally adopted,
the brood of the seventeen-year race that appeared last in
1927 is Brood I. This is not a large brood, but it has
representatives in Pennsylvania, Maryland, District of
Columbia, Virginia, West Virginia, North Carolina,
Kentucky, Indiana, Illinois, and eastern Kansas. Brood
IJ, 1928, lives in the Middle Atlantic States, with a few
periont
TE PERIODICAL CICADA
scattering colonies farther west. Brood III, 1929, is
mostly confined to Iowa, Illinois, and Missouri. The
largest of the broods is X, covering almost the entire range
of the seventeen-year race. This brood made its last
appearance in Ig1g, and is due next, therefore, in 1936.
The series of broods as numbered thus follows the suc-
cessive years to Brood XVII, the last brood of the seven-
teen-year race, which will return next in 1943.
The small and uncertain broods of the seventeen-year
mace are VIN MII, XV, XVI, and XVII. The cicadas
that emerge in aye years corresponding with these num-
bers represent incipient broods, being probably the
descendants of a few individuals that sometime became
separated from the larger broods of the years preceding
or following. One of the smallest of the seventeen- year
broods is XJ, but since its colonies occur in Massachu-
setts, Commestiont, and Rhode Island, it is likely that it
was more numerous in individuals in former times than
at present. The brood with the oldest recorded history
is XIV. This is a large brood extending over much of
the range of the seventeen-year race, with colonies in
eastern Massachusetts on Cape Cod nad near Plymouth,
the emergence of which was observed by the early settlers
probably in 1634.
The broods of the thirteen-year race are numbered
from XVIII to XXX, Brood XVIII being that which
appeared last in Igig. But there are only two important
broods of this southern race, XIX, which emerged in
1920, and XXII, which emerged in 1924. In most of the
other years the shorter- lived race is represented by only
a few individuals that emerge here and there over its
range; and none at all are known to appear during the
years corresponding with the numbers XXV and XXVIII.
Tue Hatcuinc oF THE Eccs
Five weeks have elapsed since the departure of the
cicada swarms. It is nearly six weeks since egg laying
[207]
INSECTS
was at its height, and the eggs are now due to hatch almost
any time. When studying the cicadas of Brood X near
Washington in 1g1g, the writer found the first evidence
of hatching on the twenty-fourth of July. Perhaps the
normal time of hatching had been delayed somewhat by
heavy rains that fell almost continuously during the ten
days previous, for many eggs examined during this time
were found to be dead and turning brown, though the
percentage of these was small. The twenty-fifth was hot
and bright all day. The trees were inspected in the
afternoon. Their twigs had been bare the day before.
Now, at the entrance holes of the egg nests were little
heaps of shriveled skins, thousands in all, and each so
light that the merest breath of air sufficed to blow it off;
so, if according to this evidence thousands of nymphs had
hatched and gone, the evidence of as many more must
have been carried away by the winds. An examination
of many egg nests themselves showed that over half con-
tained nothing but empty shells. Whole series were thus
deserted, and usually all or nearly all, of the eggs in any
one series of nests would be either hatched or unhatched.
But often the eggs of one or more nests would be un-
hatched or mostly so in a series containing otherwise only
empty shells. Delay appeared to go by nests rather than
by individual eggs.
As a very general rule the eggs nearest the door of an
egg chamber are the ones that hatch first, the others
following in succession, though not in absolute order.
But unhatched eggs, if present, are always found at the
bottom of the nest, with the usual exception of one or two
farther forward. Only occasionally an empty shell occurs
in the middle of an unhatched row. If the actual hatching
of the eggs is observed in an opened nest, several nymphs
are usually seen coming out at the same time, and in
nearly all cases they are in neighboring eggs, though not
always contiguous ones. So this rule of hatching, like
most rules, is general but not binding.
[ 218 ]
THE PERIODICAL +CICADA
The procedure of the female in placing the eggs leaves
no doubt that the first-laid ones are those at the bottom of
the cell, showing that the order of laying has no relation to
the order of hatching, except that it is mostly the reverse.
It seems hardly reasonable to suppose that the eggs nearest
the door are affected by greater heat or by a fresher sup-
ply of air, so it is suggested that the order of hatching
may be due simply to the successive release of pressure
along the tightly packed rows, giving the compressed
embryos a chance to squirm and kick enough to split the
inclosing shells. When hatching once commences it pro-
ceeds very rapidly through the whole nest, showing that
the eggs are all at the bursting point when the rupture of
the first takes place.
In each lateral compartment of an egg nest the eggs
(Plate 8, E, F) stand in two rows with their lower or
head ends slanted toward the door. (It must be re-
membered that the punctures are made on the lower sides
of the twigs, so that the eggs are inverted in their natural
position in the nests.) On hatching, each egg splits ver-
tically over the head and about one-third of the length
along the back, but for only a short distance on the
ventral side. As soon as this rupture occurs, the head
of the young cicada bulges out; and then, by a bending
of the body back and forth, the creature slowly works its
way out of the shell, which, when empty, remains behind
in its original place. The nymphs nearest the door have
an easy exit, but those from the depths of the cell find
themselves still in a confined space between the project-
ing ends of the empty shells ahead of them and the chamber
wall, a passage almost as narrow as the egg itself, through
which the delicate creatures must squirm to freedom.
A newly-hatched or a newly-born aphid, as we have
seen in Chapter VI, is done up in a tight-fitting garment
with neither sleeves nor legs, but nature has been more
considerate in the case of the young cicada. It, too,
comes out of the egg clothed in a skin-tight jacket, but
[ 219 ]
INSEGTS
iY
2. Newly-hatched nymph
Shedding
the embryonic \,
7. Free nymph
WE Snodgrass’
Fic. 125. The egg, the newly-hatched nymph shedding the embryonic
skin, and the free nymph of the periodical cicada
| 220) }
THE PERTODICAL CICADA
this garment is not a mere bag; it is provided with special
pouches for the appendages or a part of them (Fig. 125, 2).
The incased antennae and the labrum project backward
as three small points lying against the breast. The
front legs are free to the bases of the femora, though so
tightly held in their narrow sleeves that their joints have
no independent motion. The middle and hind legs are
also incased in long, slim sheaths, but they always adhere
close to the sides of the body. Thus the cicada nymph
newly-hatched much resembles a tiny fish provided only
with two sets of ventral fins, but when it gets into action
its motions are comparable with the clumsy flopping of a
seal stranded on the beach and trying to get back into
the water (3).
The infant cicada knows it is not destined to spend its
life in the narrow cavern of its birth, or at least 1t has no
desire to do so. With its head pointed toward the exit,
it begins at once contortionistic bendings of the body,
which slowly drive it forward. By throwing the head
and thorax back, the antennal tips and the front legs are
made to project so that their points may take hold on
any irregularity injche path, Thenva contractile wave
running forward through the abdomen brings up the rear
parts of the body as the front parts are again bent back,
and the ‘ ‘flippers”’ grasp a new point of support. As
these motions are repeated over and over again, the tiny,
awkward thing painfully but surely moves forward, per-
haps helped in its progress by the inclined tips oF the
flexible eggshells pressing against it, on the same prin-
ciple that a head of barley automatically crawls up the
inside of your sleeve.
Once out of the door no time is lost in discarding the
encumbering garment, but it is never shed in the nest
under normal conditions. If, however, the nest is cut
open and the hatching nymph finds itself in a free, open
space, the embryonic sheath is cast off immediately, often
while the posterior end of the insect’s body 1s still in the
| oar |
INSECTS
egg, so that the skin may be left sticking in the open end
of the shell. If the young cicada did not have to gain its
liberty through that narrow corridor, it might be born
in a smooth bag as are its relations, the aphids.
Watching at the door of an undisturbed nest during a
hatching day, we soon may see a tiny pointed head come
poking out of the narrow hole. The threshold is soon
crossed, but no more; this traveling in a bag is not a
pleasure trip. A few contortions are always necessary
to rupture the skin, and sometimes several minutes are
consumed in violent twistings and bendings before it
splits. When it does break, a vertical rent is formed
over the top of the head, which latter bulges out until
the cleft becomes a circle that enlarges as the entire head
pushes through, followed rapidly by the body (Fig. 125, 4).
The appendages come out of their sheaths like fingers out
of a glove, turning the pouches outside in. The antennae
are free first; they pop out and hang stiffly downward.
Then the front legs are released and hang stiff and rigid
but quivering with a violent trembling. In a second or
so this has passed, the joints double up and assume the
characteristic attitude, while they violently claw the air.
Then the other legs and the abdomen come out and the
embryo is a free young cicada (7). All this usually
happens in Jess than a minute, and the new creature is
already off without so much as a backward glance at
the clothes it has just removed or at the home of its in-
cubation period. Sentiment has no place in the insect
mind.
As the nymphs emerge from the nest, one after an-
other, and shed their skins, the glistening white mem-
branes accumulate in. a loose pile before the entrance,
where they remain until wafted off on the breeze. Each
discarded sheath has a goblet form (Fig. 125, 5, 6), the
upper stiff part remaining open like a bowl, the lower
part shriveling to a twisted stalk. The antennal and
labral pouches project from the skin as distinct append-
[ 222]
THE VPERIODICAL, CICADA
ages, but those of the legs are usually inverted during
the shedding and disappear from the outside of the slough,
though the holes where they were pulled in can be found
before the membrane becomes too dry.
The nymph (Figs. 125, 7; 126) usually runs about at
first in the groove of the twig containing its egg nest and
then goes out on the smooth bark. Here any current
of air is likely to carry it off immediately, but many
wander about for some time, usually going toward the
tips of the twigs, some even getting clear out on the leaves.
But only a few nymphs are ever to be found on twigs
where piles of embryonic skins show that hundreds have
recently hatched; so it is evident that the great majority
either fall off or are blown away very shortly after emerg-
ing. Many undoubtedly fall before the shedding of the
egg membrane, for the inclosed creature has no possible
way of holding on, and even the free nymph has but feeble
clinging powers. Those observed on twigs kept indoors
often fell helplessly from the smooth bark while appar-
ently making real efforts to retain their grasp. Their
weak claws could get no grip on the hard surface. In-
stead, then, of deliberately launching themselves into
space in response to some mysterious call from below,
the young cicadas simply fall from their birthplace by
mere inability to hold on. But the same end is gained—
they reach the ground, which is all that matters. Nature
is ever careless of the means, so long as the object is at-
tained. Some acts of unreasoning creatures are assured
by bestowing an instinct, others are forced by with-
holding the means of acting otherwise.
The cicada nymphs are at first attracted by the light.
Those allowed to hatch on a table in a room will leave
the twigs and head straight for the windows ten feet
away. This instinct under natural conditions serves to
entice the young insects toward the outer parts of the
tree, where they have the best chance of a clear drop
to earth; but even so, adverse breezes, irregularity of the
| 223)
INSEGHS
trees, underbrush, and weeds can not but make their
downward journey one of many a bump and slide from
leaf to leaf before the earth receives them.
The creatures are too small to be followed with the eye
as they drop, and so their actual course and their be-
havior when the ground 1s reached are not recorded. But
several hatched indoors were placed on loose earth packed
Fic. 126. The young cicada nymph ready to enter the ground (greatly enlarged)
flat in a small dish. These at once proceeded to get be-
low the surface. They did not dig in, but stmply entered
the first crevice that they met 1n running about. If the
first happened to terminate abruptly, the nymph came
out again and tried another. In a few minutes all had
found satisfactory retreats and remained below. The
eagerness with w hich the insects ae ed into any opening
that presents itself indicates that the call to enter the
earth is instinctive and imperative once their feet have
touched the ground. Note, then, how within a few
minutes their instincts shift to opposites: on hatching,
their first effort is to extricate themselves from the narrow
confines of the egg nest, and it seems unlikely that enough
light can penetrate the depths of this chamber to guide
them to the exit; but once out and divested of their en-
cumbering embryonic clothes, the insects are irresistibly
drawn in the direction of the strongest light, even though
this takes them upward—just the opposite of their
[224 |
THE PERIODICAL CICADA
destined course. When this instinct has served its purpose
and has taken the creatures to the port of freest passage
to the earth, all their love of light is lost or swallowed up
in the call to enter some dark crevice narrower even than
the one so recently left by such physical exertion.
When the young cicadas have entered the earth we
practically have to say good-bye to them until their
return. Yet this recurring event is ever full of interest
to us, for, much as the cicadas have been studied, it seems
fhat there is still plenty to be learned from them each
time they make their visit to our part of the world.
[225 |
CHAPTER Vill
INSECT METAMORPHOSIS
THE fascination of mythology and the charm of fairy
tales lie in the power of the characters to change their
form or to be changed by others. Zeus would court the
lovely Semele, but knowing well she could not endure the
radiance of a god, he takes the form of a mortal. Omit
the metamorphosis, and what becomes of the myth?
And who would remember the story of Cinderella if the
fairy godmother were left out? The flirtation between
the heroine and the prince, the triumph of beauty, the
chagrin of the haughty sisters—these are but ingredients
in the pot of common fiction. But the transformation
of rats into prancing horses, of lizards into coachman
and lackeys, of rags into fine raiment—this imparts the
thrill that endures a lifetime!
It is not surprising, then, that the insects, by reason
of the never-ending marvel of their transformations, hold
first place in every course of nature study in our modern
schools, or that nature writers of all times have found a
principal source of inspiration in the “‘wonders of insect
life.” Nor, finally, should it be made a matter of scorn
if the insects have attached themselves to our emotions,
knowing how ardently the natural human mind craves a
sign of the supernatural. The butterfly, spirit of the
lowly caterpillar, has thus been exalted as a symbol of
human resurrection, and its image, carved on graveyard
gates, still offers hope to those unfortunates interred
behind the walls.
Metamorphosis is a magic word, in spite of its formidable
[ 226 |
INSECT METAMORPHOSIS
appearance; but rendered into English it means simply
“change of form.” Not every change of form, however, ts
a metamorphosis. The change of a kitten into a cat, of
a child into a grown-up, of a small fish into a large fish
are not examples of metamorphosis, at least not of what
is called metamorphosis. There must be something spec-
tacular or unexpected about the change, as in the trans-
formation of the tadpole into a frog, the change of the
wormlike caterpillar into a moth, or of a maggot into a
Fic. 127. Moths of the fall webworm
fly. This arbitrary limiting of the use of a word that
might, from its derivation, have a much more general
meaning, is a common practice in science, and for this
reason every scientific term must be defined. Meta-
morphosis, then, as it is used in biology, signifies not
merely a change of form, but a particular kind or degree
of change; the kind of change, we might say, that would
appear to lie outside the direct line of development from
the egg to the adult.
At once it becomes evident that, by reason of the very
definition we have adopted, our subject is going to be-
come complicated; for how are we to decide if an observed
change during the growth of an animal is in line or out of
line with direct development? There, indeed, lies a seri-
ous difficulty, and we can only leave it to the biologist to
decide in any particularly doubtful case. But there are
plenty of cases concerning which there is no doubt. A
[227 ]
INSECTS
caterpillar, for example, certainly is not a form headed
toward a butterfly in its growth, and yet we know it is a
young butterfly because it hatches out of the butterfly’s
egg. And, as the caterpillar grows from a small cater-
pillar to a large caterpillar, it becomes no more like a
butterfly than it was at first. It is only after it has
reached maturity as a caterpillar that it undergoes a
process of transformation by which it attains at last the
form of the insect that produced it.
The question now arises as to whether the butterfly is a
form superadded to the caterpillar, or the caterpillar a
form that has deviated from the developmental line of
its ancestors. This question is easily answered: the but-
terfly represents the true adult form of its species, for it
has the essential structure of all other insects, and it alone
matures the sexual organs and acquires the power of re-
production. The caterpillar is an aberrant form that
somehow has been interpolated between the egg and the
adult of its kind. The real metamorphosis in the life of
the butterfly, therefore, is not the change of the cater-
pillar into the adult, but the change of the butterfly
embryo in the egg into a caterpillar. Yet the term is
usually applied to the reverse process by which the
caterpillar is turned back into the normal form of its
species.
The caterpillar and the butterfly (Fig. 128) furnish the
classical example of insect metamorphosis. Many other
insects, however, undergo the same kind of transforma-
tion. All the moths as well as the butterflies are cater-
pillars when they are young: the famous giant moths
(Plate 10), including the Cecropia, the Promethea, and the
beautiful Luna (Fig. 129), as every nature student knows,
come from huge fat caterpillars; the humble cutworms
(Fig. 130), when their work of destruction is completed,
change into those familiar brown or gray furry moths of
moderate size (A) often found hidden away in the day-
time and attracted to lights at night. In the spring, the
[ 228 |
PLATE 9
Two species of large moths, natural size, showing the beautiful markings
and colors with which even night-flying insects may be adorned.
Upper figure, Heliconisa arpi Schaus, from Brazil; lower, Dirphia
carminata Schaus, from Mexico. (From J. M. Aldrich)
INSECT METAMORPHOSIS
Fic. 128. The cellery caterpillar, and the butterfly into which it transforms
[INSE CIs
May beetles, or “June bugs” appear (Fig. 131 A); they are
the parents of the common white grubs (B) which every
gardener will recognize. The common ladybird beetles
(Fig. 132 A) are the adults of the ugly larvae (D) that feed
so voraciously on aphids. In the comb of the beehive or
Fic. 129. The Luna moth
of the wasps’ nest, there are many cells that contain small,
legless, wormlike creatures; these are the young bees or
wasps, but you would never know it from their structure,
for they have scarcely anything in common with ei
parents (Fig. 133 A, B). The young mosquito (Fig. 174
D) we all know, from seeing it often pictured and de-
scribed’ and from observing that mosquitoes abound
wherever these wigglers are allowed to live. The young
PLATE 10
Two species of giant moths
Upper figure, the Cecropia moth, female; lower, the Polyphemus moth,
male. (From A. H. Clark)
INSECT METAMORPHOSIS
fly is a maggot (Fig. 182 D). The maggots of the house
fly inhabit manure piles; those of the blow fly live in dead
animals where they feed on the decaying flesh.
We might go on and fill a whole chapter, or a whole book
for that matter, with descriptions of the forms that insects
go through in their metamorphoses, but since other writers
have demonstrated that this can be done and without ex-
ae
Fic. 130. The life of a cutworm
A, the parent moth. B, eggs laid by the moth on a blade of grass. C, a cut-
worm at its characteristic night work, eating off a young garden plant at the
root. D, other cutworms climbing the stalk of plants to feed on the leaves.
E, the cutworm hidden within the earth during the day
hausting the subject, we shall rather turn our attention
here to what may be regarded as the deeper and more ab-
struse phases of insect metamorphosis. Where the facts
themselves are highly interesting, the explanation of them
must be still more so. Explanations, however, are always
more difficult to present than the facts that are to be ex-
[ 231 ]
INSECTS
plained, and if a writer often does not succeed so well with
the reader in this undertaking, the reader should remember
that his own difficulties of reading are perhaps no greater
than the difficulties of the writer in writing. With a little
extra effort on both sides, then, we may be able to arrive
at a mutual understanding.
In the first place, let us see in what particular manner
the young and the adults of insects differ from each other.
The adult, of course, is the fully matured form, and it
alone has the organs of reproduction functionally devel-
oped; but this is true of all animals. The caterpillar and
the moth, the grub and the beetle, the maggot and the fly,
however, differ widely in many other respects, and are so
diverse in appearance and in general structure that their
identities can be known only by observing their transfor-
mations. On the other hand, the young grasshopper
(Fig. 8), the young roach (Fig. 51), or the young aphis
(Fig. 97) is so much like its parents that its family rela-
tionships are apparent on sight. Still, in the case of all
winged insects, there is one persistent difference between
the young and the adult, and this is with respect to the
development of the wings. The wings are always imper-
fect or lacking in the young. The inability to fly puts a
limitation on the activities of the immature insect and
compels it to seek its living by more ordinary modes of
progression. It may inhabit the land or the water; 1t may
live on the surface; it may burrow into the earth or into
the stems or wood of plants—in short, it may live in a
thousand different places, wherever legs or squirming
movements will take it, but it can not invade the air,
except as it may be carried by the wind.
As a first principle in the study of metamorphosis, then,
we must recognize the fact that on/y the adult insect is
capable of flight.
Let us now turn back to the grasshopper (Chapter I);
it furnishes a good example of an insect in which the adults
differ but little from the young, except in the matter of
[ 232 ]
INSECT METAMORPHOSIS
the wings and the organs of reproduction. As might be
expected, therefore, the young grasshoppers and the
adults live in the same places and eat the same kinds of
food in the same way. This likewise is true of the roaches,
the katydids, the crickets, the aphids, and other related
Fic. 131. A May beetle and its grub
A, the adult beetle which feeds on the leaves of shrubs and trees.
B, the larva, a white grub, which lives in the ground and feeds
on roots
insects. The adults here take no advantage over the
young in matters of everyday life by reason of their
wings.
In many other insects, however, the adults have
adopted new ways of living and particularly of feeding,
made possible and advantageous to them because of their
power of flight. Then, in adaptation to their new habits,
they have acquired a special form of the body, of the
mouth parts, or of the alimentary canal. But all such
modifications, if thrust upon the young, would only be an
impediment to them, because the young are not capable of
flight. Take the dragonflies as an example. The adult
dragonfly (Fig. 58) feeds on small insects which it catches
in the air, and it can do so because it has a powerful flying
mechanism. The young dragonfly (Figs. 59, 134), how-
ever, could not follow the feeding habits of its parents; if it
had to inherit the parental form of body and mouth parts
eke
INSECTS
it would be greatly handicapped for living its own life, and
this would be quite as detrimental to the adult, which
must be developed from the young. Therefore, nature
has devised a scheme for separating the young from the
adult, by which the latter is allowed to take full advan-
tage of its wings without imposing a hardship or a dis-
ability on its flightless offspring. The device sets aside
the ordinary workings of heredity and makes it possible
for a structural modification to be developed in the adult
and to be suppressed in the young until the time of change
from the last immature stage to that of the adult.
Thus we may state as a second principle of metamor-
phosis that an adult insect may develop structural characters
adaptive to habits that depend on the power of flight, which
are suppressed in the young, where they would be detrimental
by reason of the lack of wings.
When parents, now, assert their independence, what
can we expect of the offspring? Certainly only a similar
declaration of rights. A young insect, once freed from
any obligation to follow in the anatomical footsteps of its
progenitors, so long as it finally reverts to the form of the
latter, soon adopts habits of its own; and then acquires
a form, physical characters, and instincts adapted to such
habits. Thus, the young dragonfly (Fig. 134) has de-
parted from the path of its ancestors; it has adopted a life
in the water, where it feeds upon living creatures which it
pursues by its perfection in the art of swimming and cap-
tures by a special grasping organ developed from the
under lip (B). Life in the water, too, entails an adaptation
for aquatic respiration. All the special acquisitions in
the structure of the young insect, however, must be dis-
carded at the time of its change to the adult.
A third principle, then, which follows somewhat as a
corollary from the second, shows us that ‘he young of
insects may adopt habits advantageous to themselves, and
take on adaptive structures that have no regard to the form of
the adult and that are discarded at the final transformation.
[ 234 ]
INSECT METAMORPHOSIS
The degree of departure of the young from the parental
form varies much in different insects. In the cicada, for
example, the nymph is not essentially different in structure
from the adult except in the matter of the wings, the
organs of reproduction and egg laying, and the musical
Fic. 132. The life history of a ladybeetle, Adalia bipunctata
A, the adult beetle. B, group of eggs on under surface of a leaf. C, a young
larval beetle covered with white wax. D, the full-grown larva. E, the pupa
attached to a leaf by the discarded larval skin
instrument. But the habitats of the two forms are widely
separated, and it is unquestionable that, in the case of the
cicada, it is the nymph that has made the innovation in
adopting an underground life, for with most of the rela-
tives of the cicada the young live practically the same life
as the adults.
Animals live for business, not for pleasure; and all their
instincts and their useful structures are developed for
practical purposes. Therefore, where the young and the
adult of any species differ in form or structure, we may be
sure that each is modified for some particular purpose of
its own. The two principal functions of any animal are
the obtaining of food for its own sustenance, and the
[ 235 |
INSECTS
production of offspring. The adult insect is necessarily
the reproductive stage, but in most cases it must support
itself as well: the immature insect has no other direct
object in life than that of feeding and of preparing itself
for its transformation into the adult. The feeding func-
tion, however, as we have seen in Chapter IV, involves
Fic. 133. Wasps, or yellow jackets
A, an adult male of Vespula maculata.
B, C, D, larva, pupa, and adult worker of
Vespula maculifrons. The worker is a non-
reproductive female and uses her oviposi-
tor as a sting
most of the activities and structures of the animal, in-
cluding its adaptation to its environment, its modes of
locomotion, its devices for avoiding enemies, its means of
obtaining food. Hence, in studying any young insect, we
must understand that we are dealing almost exclusively
with characters that are adaptive to the feeding function.
When we observe the life of any caterpillar we soon
realize that its principal business is that of eating. The
caterpillar is one creature, at least, that may openly pro-
claim it lives to eat. Whatever else it does, except acts
[ 236 ]
INSECT METAMORPHOSIS
connected with its transformation, is subservient to the
function of procuring food. Most species feed on plants
and live in the open (Fig. 135 A); but some tunnel into the
leaves (B), into the fruit (D), or into the stem or wood
(C). Other species feed on seeds, stored grain, and cereal
preparations. The caterpillars of the clothes moths,
however, feed on animal wool, and a few other caterpillars
are Carnivorous.
The whole structure of the caterpillar (Fig. 136) be-
tokens its gluttonous habits. Its short legs (L, 4bL) keep
it in close contact with the food material; its Jong, thick,
wormlike body accommodates an ample food storage sal
gives space for a large stomach for digestive purposes; its
hard-walled head supports a pair of strong jaws (Md), and
since the caterpillar has small use for eyes or antennae,
these organs are but little developed. The muscle system
of the caterpillar presents a wonderful exhibition of com-
plexity in anatomical structure, and gives the soft body of
the insect the power of turning and twisting in every con-
ceivable manner. In contrast to the caterpillar, the moth
or the butterfly feeds but little, and its food consists of
liquids, mostly the nectar of flowers, which is rich 1
sugars and high in energy-giving properties but contains
little or none of the tissue-building proteins.
When we examine the young of other insects that
differ markedly from the parent form, we discover the
same thing about them, namely, the general adaptation of
their body form and of their habits to the function of eat-
ing. Not all, however, differ as widely from the parent
as does the caterpillar from the moth. The young of
some beetles, for example (Fig. 137), more closely re-
semble the adults except for the lack of wings. Most of
the adult beetles, too, are voracious feeders, and are per-
haps not outdone in food consumption by the young. But
here another advantage of the double life is demon-
strated, for usually the grub and the adult beetle have
different modes of life and live in quite different kinds of
[eg7
INSECTS
places. Each individual of the species, therefore, occupies
at different times two distinct environments during its
life and derives advantages from each. It is true that
with some beetles, the young and the adults live together.
Fic. 134. The nymph of a dragonfly
A, the entire insect, showing the long underlip, or labium (LA),
closed against the under surface of the head. B, the head and
first segment of the thorax of the nymph, with the labium ready
for action, showing the strong grasping hooks with which the
insect captures living prey
Such cases, however, are only examples of the general rule
that all things in nature show gradations; but this condi-
tion, instead of upsetting our generalizations, furnishes
the key to evolution, by which so many riddles may be
solved.
The grub of the bee or the wasp (Fig. 133 B) gives an
excellent example of the extreme specialization in form
that the young of an insect may take on. The creature
spends its whole life in a cell of the comb or the nest where
[ 238 ]
INSECT METAMORPHOSIS
it is provided with food by the parents. Some of the
wasps store paralyzed insects in the cells of the nest for
the young to feed on; the bees give their young a diet of
honey and pollen, with an admixture of a secretion from a
pair of glands in their own bodies. The grubs have noth-
ing to do but to eat; they have no legs, eyes, or antennae;
each is a mere body with a mouth and a stomach. The
adult bees consume much honey, which, like its con-
stituent, nectar, is an energy-forming food; but they also
eat a considerable quantity of protein-containing pollen.
Yet it is a great advantage to the bees in their social life
to have their young in the form of helpless grubs that
must stay in their cells until full-grown, when, by a quick
transformation, they can take on the adult form and be-
come at once responsible members of the community. Any
parents distracted by the incorrigibilities of their offspring
in the adolescent stage can appreciate this.
The young mosquito (Fig. 174 D, E) lives in the water,
where it obtains its food, which consists of minute par-
ticles of organic matter. Some species feed at the surface,
others under the surface or at the bottom of the water.
The young mosquito is legless and its only means of pro-
gression through the water is by a wiggling movement
of the soft cylindrical body. It spends much of its time,
however, just beneath the surface, from which it hangs
suspended by a tube that projects from near the rear end
of the body. The tip of the tube just barely emerges
above the water surface, where a circlet of small flaps
spread out flat from its margin serves to keep the creature
afloat. But the tube is primarily a respiratory device, for
the two principal trunks of the tracheal system open at its
end and thus allow the insect to breathe while its body is
submerged.
The adult mosquito (Fig. 174 A), as everybody knows, is
a winged insect, the females of which feed on the blood of
animals and must go after their victims by use of their
wings. It is clear, therefore, that it would be quite im-
[ 239 ]
INSECTS
possible for a young mosquito, deprived of the power of
flight, to live the life of its parents and to feed after the
manner of its mother. Hence, the young mosquito has
adopted its own way of living and of feeding, and this has
allowed the adult mosquitoes to perfect their specialties
without inflicting a hereditary handicap on their offspring.
Thus again we see the great advantage which the
species as a whole derives from the double life of its
individuals.
The fly will only give another example of the same
thing. The specialized form of the young fly, the maggot
(Fig. 171), which is adapted to the requirements of quite
a different kind of life from that of the adult fly, relieves
the latter from all responsibility to its offspring. As a
consequence, the adult fly has been able to adapt its
structure, during the course of evolution, to a way of
living best suited to its own purposes, unhampered as it
would be if its characters were to be inherited by the
young, to whom they would become a great impediment,
and probably a fatal handicap.
A fourth principle of metamorphosis, then, we may say,
is that the species as a whole has acquired an advantage by
a double mode of existence, which allows it to take advantage
of two environments during its lifetime, one suited to the
functions of the young, the other to the functions of the
adult.
We noted, in passing, that the young insect is free to
live its own life and to develop structures suited to its own
purposes under one proviso, which is that it must even-
tually revert to the form of the adult of its species. At
the period of transformation, the particular characters of
the young must be discarded, and those of the adult must
be developed.
Insects such as the grasshoppers, the katydids, the
roaches, the dragonflies, the aphids, and the cicadas ap-
pear in the adult form when the young sheds its skin for
the last time. The change that has produced the adult,
[ 240 ]
INSECT METAMORPHOSIS
however, began at an earlier period, and the apparently
new creature was partially or almost entirely formed
within the old skin before the latter was finally shed.
Fic. 135. Various habitats of plant-feeding caterpillars
A, a caterpillar feeding in the open on a leaf. B, leaf miners in an apple leaf,
the trumpet miner at a, the serpentine miner at 4. C, the corn borer feeding
within a corn stalk. D, the apple worm, or larva of the codling moth, feeding
at the core of an apple
After the molt, only a few last alterations in structure and
some final adjustments are made while the wings and legs
of the creature that had been confined in the closely fitting
skin expand to their full length. The structural changes
accomplished after the molt, however, vary with different
[241 ]
INSECTS
species of insects, and with some they involve a consider-
able degree of actual growth and change in the form of
certain parts. The true transformation process, then, is
really a period of rapid reconstructive growth preceding
and following the molt, in which the shedding of the skin
is a mere incident like the raising of the curtain for a new
act in a play. During the intermission the actors have
changed their costumes, the old scenery has been re-
moved, and the new has been set in place. Thus it is
Fic. 136. External structure of a caterpillar
Ab, abdomen; 46L, abdominal legs; H, head; Li, Z2, La, the thoracic legs; Md,
.jaws; Sp, breathing apertures; Tf, thoracic segments
with the insect at the time of its transformation—the
special accouterments of the young have been removed,
and those of the adult have been put on.
The life of the insect, however, would not make a good
theatrical production; it is too much of the nature of two
plays given by the same set of actors. The young insect
is dressed for a performance of its own in a stage setting
appropriate to its act; the adult gives another play and is
costumed accordingly. The actor is the same in each
case only in the continuity of his individuality. His
rehabilitation between the two acts will differ in degree
according to the disparity between the parts he plays,
that is, according to how far each impersonation is re-
moved from his natural self.
It is evident, therefore, that the transformation changes
of an insect will differ in degree, or quantity, according to
[ 242 J
INSECT METAMORPHOSIS
the sum of the departure of the young and the departure of
the adult from what would have been the normal line of devel-
opment if neither had become structurally adapted to a special
kind of life.
We may express this idea graphically by a diagram
(Fig. 138), in which the line xm represents what might
have been the straight course of evolution if neither the
adult (7) nor the young (Z) had departed along special
lines of their own. But, when the adult and the young
have diverged from some point (a) in their past history,
the line L/, which is the sum of 7m to L and of nm to J,
represents the change which the young is bound to make
in reverting to the adult form. The young must, there-
fore, prepare itself for this event in proportion as the
distance L/ is short or long.
Where the structural disparity between the young and
the adult is not great, or is mostly in the external form
of the body, the young insect changes directly into the
adult, as we have seen in the case of the grasshopper
(Fig. g) and the cicada (Fig. 118). But with many in-
sects, either because of the degree of difference that has
arisen between the young and the adult, or for some
other reason, the processes of transformation are not ac-
complished so quickly and require a longer period for their
completion. In such cases, the creature that issues at
the last shedding of the skin by the young insect is in a
very unfinished state, and must yet undergo a great
amount of reconstruction before it will attain the form
and structure of the fully adult insect. This happens in
all the groups of the more highly evolved insects, including
the beetles; the moths and butterflies; the mosquitoes and
flies; the wasps, bees, ants; and others. The newly
transformed insect must remain in a helpless condition
without the use of its legs and wings for a period of time
varying in length with different species, until the adult
organs, particularly the muscles, are completely formed.
In the meantime, however, the soft cuticular layer of
[ 243 ]
INSECTS
the skin of the newly emerged insect has hardened,
thus preventing a further growth or change in the cellular
layer of the body wall beneath it. Reorganization can
proceed within the body, but the outer form is fixed and
Fic. 137. Adult and larval form of beetles (Order Coleoptera)
A, aground beetle, Pferosticus. B, the same beetle with the right wings spread.
C, the larva of Prerosticus. D, an adult beetle, Silpha surinamensis, with the
left wings elevated. E, the larva of the same species, showing the similarity
in structure to the adult (D) except for the Jack of wings and the shortness of
the legs
| 244 ]
INSECT METAMORPHOSIS
must remain at the stage it had reached when the cuticula
hardened. Only by a subsequent separation of this
cuticula, allowing another period of growth in the cells of
the body wall, can the form and the external organs of
the adult be perfected. With another molt, therefore,
the fully formed insect is at last set free, and it now re-
quires only a short time for the expansion of the legs and
wings to their normal size and shape and for the hardening
of the final cuticular layer which will preserve the contours
of the adult.
It thus comes about that the members of a large group
of insects have acquired an extra stage in their life cycle,
namely, a final reconstructive stage beginning some time
before the last molt of the young and completed with a final
added molt which liberates the fully formed adult. The
insect in this stage is called a pupa. The entire pupal
stage is divided by the last molting of the young into a
propupal period, still occupying the loosened cuticula of
the insect in its last adolescent stage, and a true pupal
period, which is that between the shedding of this last
skin of the young and the final molt which discloses the
matured insect.
All insects that undergo a metamorphosis may be
divided, therefore, into two classes according as the trans-
Someden from the young into the adult is direct or is
completed in an intervening pupal stage. Insects of the
first class are said to have incomplete metamorphosis; those
of the second class, complete metamorphosis. The ex-
pressions are convenient, but misleading if taken literally,
for, as we shall see, there are many degrees of “complete”
metamorphosis.
The young of any insect that has a pupal stage In its
life cycle is called a /arva, and the young of an insect
that does not have a pupal stage is termed a nymph, ac-
cording to the modern custom of American entomologists.
But the term “larva” was formerly applied to the im-
mature stage of all insects, a usage which should have
[245 |
INSECTS
been preserved; and many European entomologists use
the word “nymph” for the stage we call a pupa.
A larva is distinguished from a nymph by the lack of
wing rudiments visible externally, and by the absence of
the compound eyes. Many larvae are blind, but some
of them have a group of simple eyes on each side of the
head substituting for the compound eyes. Nymphs in
general have the compound eyes of the adult insect, and,
m
a
17
Fic. 138. Diagram of
metamorphosis
If during the course of
their evolution, the
adult (J) and the larva
(Z)have independently
diverged from astraight
line of development
(mm), the larva must
finally attain the adult
stage by a transforma-
tion (metamorphosis),
the degree of which is
represented by the
length of the line Z to Z
as seen in the young grasshopper
(Fig. 9), the young dragonfly (Fig. 59),
and the young cicada (Fig. 114), the
nymphal wings are small pads that
grow from the thoracic segments after
the first or second molt. The larva,
however, is not actually wingless any
more than is the nymph; its wings are
simply developed internally instead
of externally. When the groups of
cells that are destined to form the
wings begin to multiply, the wing
rudiments push inward instead of
outward, and become small sacs in-
vaginated into the cavity of the body,
in which position they remain through
all the active life of the larva. Then,
at the time of the transformation, the
wing sacs are everted, and appear on
the outside of the pupa when the last
larval skin is cast off.
It is difficult to discover any neces-
sary correlation between the exter-
nally wingless condition of the larva
and the existence of a pupal stage in
the life of the insect; but the two for
some reason go together. Perhaps it
is only a coincidence. To have use-
less organs removed from the surface
[ 246 |
INSECT METAMORPHOSIS
is undoubtedly an advantage to a larva, especially to
such species as live in narrow spaces, or that burrow into
the ground or into the stems and twigs of plants; but
it probably just happened that the pupal stage was first
developed in an insect that had ingrowing wings.
The typical larvae are the caterpillars, the grubs, and
the maggots, young insects with little or no resemblance
to their parents. The larvae of
some of the beetles (Fig. 137) and
of some members of the order
Neuroptera, however, are much
like the adults of their species,
except for the lack of external
wings and the compound eyes;
and even among the typical
larvae some species have more of
the adult characters than others.
The caterpillar (Fig. 136) or the
grub of the May-beetle (Fig. 131
B), for example, both being pro-
vided with legs, have a much
greater resemblance to an adult
insect than has the wormlike leg-
less grub of the wasp (Fig. 133 B)
or the maggot of the fly (Fig. 5,
- 139. Springtails, mem-
182 D). Hence, WE SEE, the de- bers of the Order Collembola,
Cc <6 : a 4 insects perhaps directly de-
Preeoithadsiohmation may Vaby ccaded. from the unknown
much even among insects that wingless ancestors of winged
have a_ so-called ‘‘complete’’ aes
metamorphosis.
There are a few insects that have no metamorphosis at
all. These are wingless insects belonging to the groups
known as Collembola and Thysanura (Figs. 57, 139, 149)
and are probably direct descendants from the primitive
wingless ancestors of the winged insects. These insects
during their growth shed the skin at intervals, but they
do not undergo a change of form; they illustrate the
| 247 ]
INSECES
normal procedure of growth by direct development from
the embryo to the adult.
It must appear that the nymph, or young of an insect
with incomplete metamorphosis, is merely an aberrant
development of the normal form of the young as it
occurs in an insect without metamorphosis. This is
evident from the fact that the nymph has external wings,
fully developed compound eyes, and in general the same
details of structure in the legs and other parts of the body
as has the adult. Most larvae, on the other hand, have
few or none of the structural details
of the adult that might be expected to
occur in a normal postembryonic ado-
lescent form; but they do have many
characters that appear to belong to a
primitive stage of evolution and that
we might expect to find in an em-
bryonic stage of development. The
caterpillar, for example, has legs on
the abdomen (Fig. 136, d4éL), an
embryonic feature possessed by none
of the higher insects in the adult
stage; it has only one claw on its
thoracic legs, a character of crusta-
ceans and myriapods, but not of adult
winged insects or of nymphs. Like-
, wise, there are certain features of the
Fic. 140. A_ bristle- 0 :
tail, Thermobia,amem- internal structure of the caterpillar
ber of the order Thy- that are more primitive than in any
sanura, another primi- .
ive grouper windleas. adult Insect on my mpieand the same
insects. (Twice natu- evidence of primitive or embryonic
ral size) 4 5
characters might be cited of other
larvae. On the other hand, the structural details of some
larvae are very much like those of the adults, and such
larvae differ from the adults of their species principally
in the lack of the compound eyes and of external wings.
Now, if all the insects with complete metamorphosis
[ 248 ]
/
INSECT METAMORPHOSIS
have been derived from a common ancestor, as seems
almost certain, then the original larvae must have been
all alike, and they must have had approximately the
structure of those larvae of the present time that depart
least from the structure of the adult. Therefore it is
evident that many larvae of the present time have some-
how acquired certain embryonic characters. We may
suppose, therefore, either that such larvae have had a
retrogressive evolution into the embryonic stage by
hatching at successively earlier ages, or that certain
embryonic characters representing ancestral characters
but ordinarily quickly passed over in the embryonic
development, have been retained and carried on into the
larval stage. The latter view seems the more probable
when we consider that no larva has a purely embryonic
structure, and that those larvae which have embryonic
features in their anatomy present an incongruous mixture
of embryonic and adult characters.
We may, therefore, finally conclude that the larva of
insects with complete metamorphosis represents the nymphal
stage of insects with incomplete metamorphosis; and that
the structure of the larva has resulted from a suppression of
the peculiarly adult characters, from an invagination of the
wings, a loss of the compound eyes, the retention of certain
embryonic characters, and a special development of the body
form and the organs suited to the particular mode of life of
the larva. By allowing for variations in all these elements
that contribute to the larval make-up, except the two
constants—the invagination of the wings and the loss of
the compound eyes—we may account for all the variety
in form and structure that the larva presents.
While, in general, the larva remains the same in struc-
ture from the time it is hatched until it transforms to the
pupa, there are nearly always minor changes observable
that are characteristic of its individual stages. In
Chapter I we encountered the case of the little blister
beetle that goes through several very different forms dur-
[ 249 ]
INSECGHS
ing its development (Figs. 12, 13), and other examples of
a metamorphosis during the larval life might be given
from the other groups of insects. A larval metamorphosis
of this kind is known as Aypermetamorphosis, and it shows
that the larva may be structurally diversified during its
growth to adapt it to several different environments or
ways of obtaining its food.
The reader was given fair warning that the subject of
insect metamorphosis would become difficult to follow,
and even now, with its realization, the writer can not
assure him that the above analysis is by any means com-
plete or final. Much more might be said for which there
is no space here, and it is not likely that all entomologists
will accept all that has been said without a discussion,
and possibly some dissension. However, we have not
yet reached the end, for we have so far been dealing only
with the phase of metamorphosis that has produced the
nymph or the larva, and have only briefly touched upon
the reverse process which reconverts the creature into the
adult.
The pupa unquestionably has the aspect of an imma-
ture adult. It has lost all the characteristic features of
the larva, and its organs are those of the adult in the
making. It has external wing pads, legs, antennae, com-
pound eyes. Its mouth parts are usually in a stage of
development intermediate between those of the larva and
those of the adult. Most of the pupal organs are useless,
since they are neither those of the larva nor entirely those
of the adult, and are not adapted to any special use the
pupa might make of them, except in a very few cases.
The pupa is, therefore, a helpless creature, unable to
eat, or to make any movement except by motions of the
body. It is usually said to be a “resting” stage, but its
rest is an enforced immobility, and some species attest
their impatience by an almost continuous squirming,
twisting, or wriggling of the movable parts of the body.
It is evident that it must be an advantage to the pupa
| 250 }
INSECT METAMORPHOSIS
to have some kind of protection, either from the weather,
or from predacious creatures that might destroy it. While
most pupae are protected in one way or another, there are
some that remain in exposed situations with no kind of
shelter or concealment. The mosquito pupa is one of
these, for it lives in the water along with the larva and
floats just beneath the surface (Fig. 174 F), breathing
by a pair of trumpetlike tubes that project above the
surface from the anterior part of the body. The mos-
quito pupa is a very active creature, and can propel itself
through the water, usually downward, with almost as
much agility as can the larva, and by this means probably
avoids its enemies. The pupa of the common lady-beetle
gives another example of an unprotected pupa (Fig.
132 E). The larvae of these insects transform on the
leaves where they have been feeding, and the pupae re-
main here attached to the leaf, unable to move except by
bending the body up and down. The pupae of some of
the butterflies also hang naked from the stems or leaves
of plants.
The pupae of many different kinds of insects are to be
found in the ground, beneath stones, under the bark of
trees, or in tunnels of the leaves, twigs, or wood of plants
where the larvae have spent their lives. Some of these,
especially beetle pupae, are naked, soft-bodied creatures,
depending on their concealment for protection. The
pupae of moths and butterflies, however, are character-
istically smooth, hard-shelled objects with the outlines
of the legs and wings apparently sculptured on the sur-
face (Plate 14 F). Pupae of this kind are called chrysa-
lides (singular, chrysalis). Their dense covering is formed
of a gluelike substance, exuded from the skin, that dries
and forms a hard coating over the entire outer surface,
binding the antennae, legs, and wings close to the body.
In addition, the pupae of many moths are inclosed in a
silk cocoon spun by the caterpillar. The caterpillars,
as we shall learn in the next chapter, are provided with
[251 ]
INSECTS
a pair of silk-producing glands which open through a hol-
low spine on the lower lip beneath the mouth (Fig. 155).
The silk is used by the caterpillars during the feeding
part of their lives in various ways, but it serves particu-
larly for the construction of the cocoon. The most
highly perfected instinct of the caterpillar is that which
impels it to build the cocoon, often an intricately woven
structure, just before the time of its transformation to
the pupa. The caterpillar spins the cocoon around itself,
then sheds its skin, which is thrust into the rear end of
the cocoon as a crumpled wad. Plate 11 shows the cater-
pillar of a small moth that infests apple trees constructing
its cocoon, finally inclosing itself within the latter, and
there transforming to the pupa.
The larvae of the wasps and bees likewise inclose them-
selves within cocoons formed inside the cells of the comb
in which they have been reared. The cocoon is made of
threads, but the material is soft, and the freshly spun
strands run together into a sheet that dries as a parch-
mentlike lining of the cell. The larvae of many of the
wasplike parasitic insects that feed within the bodies of
other living insects leave their hosts when ready for trans-
formation, and spin cocoons either near the deserted host
or on its body.
The maggots, or larvae, of the flies have adopted an-
other method of acquiring protection during the pupal
stage. Instead of shedding the loosened cuticula previ-
ous to the transformation, the maggot transforms within
the skin, and the latter then shrinks and hardens until it
becomes a tough oval capsule inclosing the larva (Fig.
182 E). The capsule 1s called a puparium. It appears,
however, that the larva within the puparium undergoes an-
other molt before it actually becomes a pupa, for, when the
pupa is formed, it is found to be surrounded by a delicate
membranous sheath inside the hard wall of the puparium,
and when the adult fly issues it leaves this sheath and a
thin pupal skin behind in the puparial shell.
[ 252]
PLATE 11
was Sno dgras¢
The ribbed-cocoon maker (Bucculatrix pomifoliella), a small caterpillar
that inhabits apple leaves
At A the caterpillar is spinning a mat of silk on the surface of a twig.
B shows the silk thread issuing from the spinneret (a) on the under
lip of the caterpillar. At C the caterpillar is erecting a line of silk
palisades around the site of the cocoon. D and E show the cocoon in
the course of construction, built on the silk mat. F is a diagram of
the cocoon on under surface of the support, containing the pupa (g)
and the shed skin of the caterpillar (4). G shows the interior of the
cocoon, its double walls (c, d), and partitions (f) at the front end.
H is the finished cocoon surrounded by the palisades
ae jLtas ~ a . ee
INSECT METAMORPHOSIS
The pupa has so many of the characters of the mature
insect that we might say it is self-evident that it is a part
of the adult stage, except that to say anything is “‘self-
evident” is almost an unpardonable remark in scientific
writing. However, it is clear to the eye that the pupa,
in casting off the skin of the larva, has entirely discarded
the larval form, except in certain insects that have a
larval form in rie adult stage. The pupa may retain a
few unimportant larval characters, but all its principal
organs are those of an adult insect in a halfway stage of
development. In studying the cicada, it, was observed
that the adult issues from the skin of the nymph in a very
immature condition. A careful dissection of a specimen
at this time would show that the creature is still imperfect
in many ways besides those which appear externally. By
very rapid growth during the course of an hour, however,
the adult form and organs are perfected. We have also
noted that with insects of incomplete metamorphosis the
adult 1s mostly formed within the nymphal skin some
time before the latter is cast of. The same thing is true
of a pupa. For several days before the caterpillar is
ready to molt the last time, 1t remains almost motionless
and its body contracts to perhaps less than half of the
original length. The caterpillar is now said to be in a
“prepupal” stage, but examination of a specimen will
reveal that it has already transformed, for inside its skin
is a soft pupa in a preliminary stage of development
(Fig. 141 B).
This first stage of the pupa of a moth or butterfly (Fig.
141 B) is entirely comparable with the immature adult
of the cicada formed inside the skin of the last stage of
the nymph (Fig. 141 A). The entire pupal period,
therefore, corresponds with the formative stage of the
cicada, which begins within the nymphal skin and is com-
pleted about an hour after the emergence. The only
external difference between the two cases is that the pupa
sheds its skin, making a final added molt before it becomes
[ 253]
INSECTS
a perfect insect, while the immature adult cicada goes
over into the fully mature form quickly and without a
molt.
We may conclude, therefore, that the pupa of insects
with complete metamorphosis corresponds with the immature
stage of the adult in insects with incomplete metamorphosis.
This idea concerning the nature of the insect pupa has
been well expressed and
more fully substantiated
by E. Poyarkoff, and it
appears to have more in
its favor than the older
view that the pupa cor-
responds with the last
nymphal stage in insects
with incomplete meta-
morphosis. | According
to Poyarkoff’s theory,
the pupa has no phylo-
genetic significance, that
is, it does not represent
any free-living stage in
the evolution or ances-
tral history of insects;
it 1s simply a prolonged
resting period following
the shedding of the last
larval skin, which termi-
nates with an added
molt when the adult is
fully formed.
It frequently happens
Fic. 141. Showing the resemblance of
the pupa of an insect with complete
metamorphosis to the immature adult that a pupa has some
form of an insect with incomplete meta-
aorehoats of the adult characters
A, immature adult cicada, taken from the better developed than
last nymphal skin. B, immature pupa . 5 c
of a moth, taken from the last larval has the adult itself, The
skin. C, the mature pupa of a wasp pupae of insects that
[254]
PLATE 12
The peach-borer moth (Aegeria exitiosa)
Upper figure, the adult male moth (about twice natural size);
lower figure, the cocoon made by the caterpillar from bits of
wood, with the empty shell of the pupa projecting from the
opened end
INSECT METAMORPHOSIS
have rudimentary or shortened wings in the adult stage
often have wings larger than those of the adult, indicat-
ing that the wings have been reduced in the adult since
the time when the pupa was first established. Here,
therefore, we see a case of metamorphosis between the
pupa and the adult. Adult moths and butterflies have no
mandibles or have mere rudiments of them (Fig. 163),
but the jaws are often quite visible in the pupae (Fig.
1$9 H, Md), and the pupa of one moth has long, toothed
mandibles which it uses to liberate itself from the cocoon
before transforming to the adult.
The structural changes that accompany the transfor-
mation of the larva into an adult insect are by no means
confined to the outside of the body. Much internal re-
organization goes on which involves changes in the tissues
themselves. The larva may have built up a highly eff-
cient alimentary canal well adapted for handling its own
particular kind of food, but perhaps the adult has adopted
an entirely different diet. The alimentary canal, there-
fore, must be completely remodeled during the pupal
stage. The nervous system and the tracheal system are
often different in the larval and the adult stages, but the
change in these organs is usually in the nature of a greater
elaboration for the purposes of the adult, though the
larva may have developed special features that are dis-
carded.
It is in the muscles usually that the most radical re-
constructive processes of the transformation from larva to
adult take place. The muscles of adult insects are at-
tached to the outer cuticular layer of the body wall, which
in hard-bodied insects constitutes the “skeleton,” and the
mechanical differences between the larva and the adult
lie in the relation between the muscles and the cuticula.
With the change in the external parts between the two
active stages of the insect, therefore, the larval muscles
are likely to become entirely unsuited to the purposes of
the adult. The special larval muscles, then, must be
[255 ]
INSECTS
cleared away, and a new muscle system must be built up
suitable to the adult mechanism. Most of the other.
organs are transformed by a gradual replacement of cells in
their tissues, with the result that each organ itself remains
intact during the whole period of its alteration—the
insect is never without a complete alimentary canal, its
body wall always maintains a continuous surface. This
condition, however, is not entirely true of the muscles,
for with some insects undergoing a high degree of meta-
morphosis in external structure, the muscular system may
sutter a complete disorganization, the fibers of the larval
system being 1 in a state of dissolution while those of the
adult are in the process of development.
The muscles of adult insects, as we have just said, are
attached to the outer
Tfbl Epet layer of the body wall
‘ 4 (Fig. 142). This layer
is composed partly of
a substance called
chitin formed by the
cellular layer of the
body wall beneath it,
‘and constitutes the
“Mel cuticular skin that 1s
shed when the insect
‘molts. The newly-
formed cuticula 1s soft
Fic. 142. Diagram of the attachment of a and takes the con-
muscle to the body wall of an adult insect by e <
means of the terminal fibrillae (7/4) tour of the cellular
BM, basement membrane; Enct, endocuticula; lay er product ng it.
Epct, epicuticula, Epd, epidermis; Exct, The muscles of the
exocuticula; Mc/, muscle; Tfe/, terminal |: iF
fibrillae of the muscle anchored in the cuticula Pa that go over
into the adult stage
and the new muscles of the adult must become fastened
to the new cuticula, and this is possible only when the
cuticula is in the soft formative stage. It has been
pointed out by Poyarkotf that, for this reason, whenever
[ 256 |
tan Ih) My
LMT
MINIM
INSECT METAMORPHOSIS
new muscles are formed in an insect a new cuticula must
also be produced in order that the muscle fibers may
become attached to the skeleton. New muscles com-
pleted at the time of a molt may be anchored into the new
cuticula formed at this time; but if the completion of the
muscle tissue is delayed, the new fibers can become func-
tional only by attaching themselves at the following molt.
Conversely, if the new muscles are not perfected at the
time of the last normal molt, the insect must have an
extra molt later in order to give the muscles a functional
connection with the body wall.
Thus Poyarkoff would explain the origin of the pupal
stage in the life cycle of the insect. His theory has much
to commend it, for, as Poyarkoff shows in an analysis of
the various processes accompanying metamorphosis, none
of the changes in any of the organs other than the muscles
would seem to necessitate the production of a new cutic-
ula and thus involve an added molt. If insects with
incomplete metamorphosis add new muscles for the
adult stage, such muscles must be ready-formed at the
time of the last nymphal molt; but it is probable that
there are few such cases in this class of insects.
Adopting Poyarkoft’s theory, then, as the most plausi-
ble explanation of why a pupal stage has become separated
by a molt from the fully-matured adult stage, we may
say that the reason for the pupa is probably to be found in
the delayed growth of the adult muscles and in the conse-
quent need of a new cuticula for their attachment.
With a pupal stage once established, however, the pupa
has undergone an evolution of its own, as has the larva
and the adult, though to a smaller degree than either
of these two active stages. The pupa is characteristically
different in each of the orders of insects, and many of its
features are clearly adaptations to its own mode of life.
It is one thing to know the facts and to see the mean-
ing of metamorphosis; it is quite another to understand
how it has come about that an animal undergoes a meta-
[ 257 ]
INSEGHES
morphic transformation, and yet another to discover how
the change is accomplished in the individual. Meta-
morphosis can be only a special modification of general
developmental growth, and growth toward maturity by
the individual goes over the same field that the species
traversed in its evolution. Yet, the individual in its
development may depart widely from the path of its
ancestors. It may make many a detour to the right or
the left; it may speed up at one place and loiter along at
another; and, since the individual is rather an army of
cells than a single thing, certain groups of its cells may
forge ahead or go off on a bypath, while others lag behind
or stop for a rest. Only one condition is mandatory, and
this is that the whole army shall finally arrive at the same
point at the same time. In each species, the deviations
from the ancestral path, traveled for many generations,
have become themselves fixed and definite trails followed
by all individuals of the species. The development of
the individual, therefore, may thus come to be very
different from is evolutionary history of its species; and
the life history of an insect with complete metamorphosis
is but an extreme example of the complex course that
may result when a species leaves the path of direct de-
velopment to wander in the fields along the way.
The larva and the adult insect have become in many
cases so divergent in structure, as a result of their separate
departures from the snes path, that the embryo has
become almost a double creature, comprising one set of
cells that develop directly into the organs of the embryo
and another set held in reserve to build up the adult
organs at the end of the larval life. The characters of
the adult are, of course, impressed upon the germ cells
and must be carried over to the next generation through
the embryo, but they can not be developed at the same
time that the larval organs are functional. Conse-
quently, the cells, that are to form the special tissues
of the adult remain through the larval period as small
[258 ]
INSECT METAMORPHOSIS
groups or islands of cells in the larval tissues. These
dormant cell groups are known as imaginal discs, or his-
toblasts. (Imaginal is from imago, an image, referring
to the adult; Azstob/ast means a tissue bud.)
When analyzed closely, the apparent “double’’ struc-
ture of the embryo will be found to be only the result
of an exaggeration of the usual processes of growth, ac-
companied by an acceleration in certain tissues and a
retardation in others. In general, wherever an adult
organ is represented by an organ in the larva, even though
the latter is greatly reduced, the cells that are to give this
organ its adult form do not begin to develop until the
larval growth is completed. But if an organ 1s lacking
in the larval stage, the regenerative cells may start to
develop at an earlier period—even in the embryo mya
few cases. Hence, the remodeling of a larval organ in the
pupal stage is only a completion of that organ’s normal de-
velopment, and the production of a “new organ is only
the deferred development of one that has been suppressed
during the larval period.
The special organs or forms of organs that the larva
has built up for its own purposes necessarily become
useless when the larval life has been completed. Such
organs, therefore, must be destroyed if they can not be
directly made over into corresponding adult organs.
Their tissues consequently undergo a process of dissolu-
tion, called Aisto/ysis. It can not be explained at the pres-
ent time what causes histolysis, or why it begins at a
certain time and in particular tissues, but histolysis is
only one of the physiological processes that depend
probably on the action of enzymes. In some insects a
part of the degenerating tissues of the larva 1s devoured
during the pupal stage by ameboid cells of the blood,
known as phagocytes. It was once supposed that the
phagocytes are the active agents of the destruction of the
larval tissues, but this now seems improbable, since histol-
ysis takes place whether phagocytes are present or absent.
[ 259]
INSECES
While the larval tissues are undergoing dissolution,
the adult tissues are being built up from those groups of
dormant cells, the histoblasts, that have retained their
vitality. Whatever it is that produces histolysis in the
defunct larval tissues, it has no effect on the regenerative
tissues, which now begin a period of active development,
or Aistogenesis (i.e., tissue building), which results in the
completion of the adult organs. In most of the organs
the two processes, histolysis and histogenesis, are com-
plemental to each other, the new tissues spreading as the
old are dissolved, so that there is never a lack of con-
tinuity in the parts undergoing reconstruction. It 1s only
in the muscles, as we have already observed, that the
old tissues are destroyed before the new ones are formed.
Because of the high physiological activity (metabolism)
going on within the pupa, the blood of the insect at this
stage becomes filled with a great quantity of matter re-
sulting from the dissolution of the larval tissues. During
the pupal period, the insect takes no food nor does it
discharge any waste materials—the substance of the
growing tissues is derived from the débris of those degen-
erating. But the transformation is not all direct. The
insect is provided with an organ for converting some of
the products of histolysis into proteid compounds that
can be utilized by the tissues in histogenesis. This organ
is the fat-body (see Chapter IV and Figure 158). During
the larval life the cells of the fat body store up large
quantities of fat, and in some insects glycogen, both of
which energy-forming substances are discharged into the
blood at the beginning of the pupal period. And now
the fat cells become also active agents in the conversion
of histolytic products into proteid bodies, probably by
enzymes given off from their nuclei. These proteid
bodies are finally also discharged into the blood, where
they are absorbed as nutriment by the tissues of the
newly-formed organs. At the close of the pupal period,
the fat-body itself is often almost entirely consumed or
[ 260 ]
PEATE) 13
The red-humped caterpillar (Schizura concinna)
A, the moth in position of repose (natural size). B, moth with wings
spread. C, under surface of apple leaf, showing eggs at a, and young
caterpillars feeding at 4. D, a caterpillar in next to last stage of growth.
E, full-grown caterpillars (one-half larger than natural size). F, two
cocoons on ground among grass and dead leaves, one cut open showing
caterpillar within before transforming to pupa
INSECT METAMORPHOSIS
is reduced to a few scattered cells, which build up the fat-
body of the adult.
The internal adult organs undergo a continuous develop-
ment throughout the pupal period and are practically
complete when the latter terminates with the molt to the
adult. But the external parts, after quickly attaining a
halfway stage of development at the beginning of the
pupal metamorphosis are checked in their growth by the
hardening of the cuticular covering of the body wall, and
in their half-formed shape they must remain to the end
of the pupal period. It is only by a subsequent growth
of the cellular layer of the body wall beneath the loosened
cuticula of the pupa that the external adult parts are
finally perfected in structure; and it is only when the
pupal cuticula is then cast off and the organs cramped
within it are given freedom to expand that the adult
insect at last appears in its fully mature form.
[ 261 |
CHAPPER LS
THE CATERPILEAR AND HE View
Ter tre or A GAtERPrneaR
Ir is one of those bleak days of early spring that so often
follow a period of warmth and sunshine, when living things
seem led to believe the fine weather has come to stay.
Out in the woods a band of little caterpillars is clinging
to the surface of something that appears to be an oval
swelling near the end of a twig on a wild cherry tree
(Fig. 143). The tiny creatures, scarce a tenth of an inch
in length, sit motionless, benumbed by the cold, many
with bodies bent into half circles as if too nearly frozen
to straighten out. Probably, however, they are all un-
conscious and suffering nothing. Yet, if they were Ca-
pable of it, they would be wondering what fate brought
them into such a forbidding world.
But fate in this case was disguised most likely in the
warmth of yesterday, which induced the caterpillars to
leave the eggs in which they had safely passed the winter.
The empty ‘eggshells are inside the spindle- shaped thing
that looks so like a swelling of the twig, for in fact this is
merely a protective covering over a mass of eggs glued
fast to the bark. The surface of the covering is perfor-
ated by many little holes from which the caterpillars
emerged, and is swathed in a network of fine silk threads
which the caterpillars spun over it to give themselves a
surer footing and one they might cling to unconsciously
in the event of adverse weather, such as that which makes
them helpless now. When nature designs any creature
[ 262 ]
PLATE 14
The tent caterpillar (Malacosoma americana)
A, an egg mass on an apple twig (about natural size). B, young
caterpillar feeding on an opening leaf bud. C, branches of an apple
tree with a tent in a fork, from which trails of silk lead outward to
the twigs where the caterpillars are feeding on the leaves. D, a full-
grown caterpillar (three-fourths natural size). E, cocoon. F, pupa,
taken from a cocoon. G, male moth. H, female moth laying eggs
THE CATERPILLAR AND THE MOTH
to live under trying circumstances she grants it some
safeguard against destruction.
The web-spinning habit is one which, as we shall see,
these caterpillars will develop to a much greater extent
later in their lives, for our little acquaintances are young
tent caterpillars. They are found most often among
woodland trees, on the chokecherry and the wild black
cherry. But they commonly infest apple trees in the
orchards, and for this reason their species has been named
the apple-tree tent caterpillar, to distinguish it from
related forms,that do not com-
monly inhabit cultivated fruit
trees. The scientific name is
Malacosoma americana.
The egg masses of the tent
caterpillar moths are not hard to
find at this season. They are
generally placed near the tips of
the twigs, which they appear to
surround, and being of the same
brownish color as the bark, they
look like swollen parts of the
twigs themselves (Plate 14 A,
Fig. 144 A). Most of them are
five-eighths to seven-eighths of Re Waste cameniee
an inch in length and almost half pillars on the egg mass from
of this in width, but they vary in SE eaten i arse
thickness with the diameter of
the twig. A closer inspection shows that the mass really
clasps the twig, or incloses it like a thick jacket lapped
clear around. In form the masses are usually sym-
metrical, tapering at each end, but some are of irregular
shapes, and those that have been placed at a forking or
against a bud have one end enlarged.
The greater part of an egg mass consists of the cover-
ing material, which is a brittle, filmy substance like dry
mucilage. Some of it is often broken away, and some-
[ 263 ]
)
<—
mac
INSECTS
times the tops of the eggs are entirely bare. The eggs
are placed in a single layer next the bark (Fig. 144 B),
and there are usually 300 or 400 of them. They look like
little, pale-gray porcelain jars packed closely together
and glued to the twig by their rounded and somewhat
compressed lower ends. The tops are flat or a little
convex. Each egg is the twenty-fourth of an inch in
height, about two-thirds of this in width, and has a
capacity of one caterpillar. The covering is usually half
again as deep as the height of the eggs, but varies in thick-
ness in different specimens. The outer surface is smooth
and polished, but the interior is full of irregular, many-
sided air spaces, separated from one another by thin
partitions (B).
Wherever the covering of an egg mass has been broken
away, the bases of the partition walls leave brown lines
that look like cords strapped and tied into an irregular
net over the eggs (B), as if for double security against
Insurrection on the part of the inmates. But neither
shells nor fastenings will offer effective resistance to the
little caterpillars when they are taken with the urge for
freedom. Each is provided with efficient cutting in-
struments in the form of sharp-toothed jaws that will
enable it to open a round hole through the roof of its cell
(Fig. 144 C). The superstructure is then easily pene-
trated, and the emerging caterpillar finds itself on the
surface of its former prison, along with several hundred
brothers and sisters when all are out.
All this time the members of that unfortunate brood
we noted first have been clinging benumbed and motion-
less to the silk network on the covering of their deserted
eggs. The cold continues, the clouds are threatening,
and during the afternoon the hapless creatures are
drenched by hard and chilling rains. Through the night
following they are tossed in a northwest gale, while the
temperature drops below freezing. The next day the
wind continues, and frost comes again at night. For three
[ 264 |
THE CATERPILLAR AND THE MOTH
days the caterpillars endure the hostility of the elements,
without food, without shelter. But already the buds on
the cherry tree are sending out long green points, and
when the temperature moderates on the fourth day and
Fic. 144. Eggs and newly-hatched larvae of the
tent caterpillar
A, egg masses on twigs, about natural size. B,
eggs exposed beneath the covering. C, several
eggs (more enlarged) three with holes in the tops
from which the young caterpillars have emerged.
D, newly-hatched caterpillars (enlarged about
nine times)
the sun shines again for a brief
period, the revived outcasts are
able to find a few fresh tips on
which to nibble. In another day
the young leaves are unfolding, of- S
fering an abundance of tender for- Wi lNy),)
age, and the season of adversity
for these infant caterpillars is over.
This family of tent caterpillars was
hatched near Washington on the
25th of March.
The newly-hatched caterpillars
(Fig. 144 D) are about one-tenth
of an inch in length. The body is
widest through the first segment
[ 265 ]
INSECTS
and tapers somewhat toward the other end. The general
color is blackish, but there is a pale gray collar on the
first segment back of the head and a grayish line along
the sides of the body. Most of the segments have pale
rear margins above, which are often bright yellow or
orange on the fourth to the seventh segments. There is
usually a darker line along the middle of the back. The
body is covered with long gray hairs, those on the sides
spreading outward, those on the back curving forward.
After a few days of feeding the caterpillars increase to
nearly twice their length at hatching.
When the weather continues fair after the time of
hatching, the caterpillars begin their lives with happier
days, and their early history is different from that of
those unfortunates described above. Three other broods,
which were found hatching on March 22, before the period
of bad weather had begun, were brought indoors and
reared under more favorable circumstances. These
caterpillars spent but little time on the egg masses and
wasted only a few strands of silk upon them. They were
soon off on exploring expeditions, small processions going
outward on the twigs leading from the eggs or their
vicinity, while some individuals dropped at the ends of
threads to see what might be below. Most, however, at
first went upward, as if they knew the opening leaf buds
should lie in that direction. If this course, though, hap-
pened to lead them up a barren spur, a squirming, furry
mob would collect on the summit, apparently bewildered
by the trick their instinct had played upon them. On
the other hand, many followed those that first dropped
down on threads, these in turn adding other strands till
soon a silken stairway was constructed on which indi-
viduals or masses of little woolly bodies dangled and
twisted, as if either enjoying the sport or too fearful to
go farther.
For several days the young caterpillars led this happy,
irresponsible life, exploring twigs, feeding wherever an
[ 266 |
THE CATERPILLAR AND THE MOTH
open leaf bud was encountered, dangling in loose webs,
but spinning threads everywhere. Yet, in each brood,
the individuals kept within reach of one another, and the
trails of silk leading back to the main branch always
insured the possibility of a family reunion whenever this
should be desired.
One morning, the 27th, one family had gathered in its
scattered members and these had already spun a little
tentlike web in the a
crotch between the NY Sy\
main stem of the sup- \ YAW
porting twig and two
small branches (Fig.
145). Some members
\
a
Dy
L))
Zz -
\ BINS
j ix
were crawling on the ES
surface of the tent, \V
others were resting N
SS
AV
within, still others were
traveling back and
forth on the silk trails
leading outward on the
branches, and the rest
were massed about
the buds devouring the
young leaves. The es-
tablishment of the tent
marks the beginning of
a change in the cater-
pillars’ lives; it entails
responsibilities that de- "5, (ep mai, by young se
mand a fixed course of
daily living. In the lives of the tent caterpillars this
point is what the beginning of school days is to us—the
end of irresponsible freedom, and the beginning of sub-
jection to conventional routine.
Every tent caterpillar family that survives infancy
eventually reaches the point where it begins the con-
[ 267 ]
INSECES
struction of a tent, but the early days are not always spent
alike, even under similar circumstances, nor is the tent
always begun in the same manner.
In the State of Connecticut, where the season for both
plants and insects is much later than in the latitude of
Washington, three broods of tent caterpillars were ob-
served hatching on April 8 of the same year. These
caterpillars also met with dull and chilly weather that
kept them huddled on their egg coverings for several
days. After four days the temperature moderated suffi-
ciently to allow the caterpillars to move about a little on
the twigs, but none was seen feeding till the 14th—six
days after the hatching.
Yet they had increased
in size to about one-
eighth of an inch in
length.
Wherever these cater-
pillars camped in their
wanderings over the small
apple trees they inhabit-
ed, they spun a carpet
of silk to rest upon, and
there the whole family
collected in such a
crowded mass that it
looked like a round, furry
mat (Fig. 146). The car-
pets afforded the cater-
Fic. 146. Young tent caterpillars matted pillars a much safer bed
on a flat sheet of web spun in the crotch than the bare wet bark
between two branches. (About natural E a was
Size) of the tree, for if the
sleepers should become
stupefied by cold the claws of their feet would mechanically
hold them fast to the silk during the period of their help-
lessness. The test came on the 16th and the night fol-
lowing, when the campers were soaked by hard, cold rains
{ 268 |
hE CATERPILEAR AND THE MOTH
till they became so inert they seemed reduced to lifeless
masses of soggy wool. On the afternoon of the 17th the
temperature moderated, the sun came out a few times,
the wetness evaporated from the trees, and most of the
caterpillars revived sufficiently to move about a little and
dry their fur. Though a few had been washed off the
carpets by the violence of the storm and had perished
on the ground, and in one camp about twenty dead were
left behind on the web, the majority had survived.
For several days after this, during better weather, the
caterpillars of these families continued their free exist-
ence, feeding at large on the opening buds, but returning
during resting periods to the webs, or constructing new
ones at more convenient places. Often each family split
into several bands, each with its own retreat, yet all re-
mained in communication by means of the silk trails the
members left wherever they went.
The camping sites were either against the surface of a
branch or in the hollow of a crotch. Though the carpet-
like webs stretched over these places were spun appar-
ently only to give secure footing, those at the crotches
often roofed over a space well protected beneath, and fre-
quently many of the caterpillars crawled into these spaces
to avail themselves of their shelter. Yet for twelve days
none of the broods constructed webs designed for cover-
ings. Then, on the morning of the 20th, one family was
found to have spun several sheets of silk above the carpet
on which its members had rested for a week, and all were
now inside their first tent. These caterpillars were near-
ing the end of their first stage, and two days later the
first molted skins were found in the tent, fourteen days
after the date of hatching.
In Stage II the caterpillars have a new color pattern
and one which begins to suggest that characteristic of the
species in its more mature stages (Fig. 148). On the upper
part of the sides the dark color is broken into a series of
quadrate spots each spot partially split lengthwise by a
[ 269 |
INSECTS
light streak, and the whole series on each side is bordered
above and below by distinct pale lines, the upper line
often yellowish. Below the lower line there is a dark
band, and below this another pale line just above the
bases of the legs. The back of the first body segment
has a brown transverse shield, and the last three segments
are continuously brown, without spots or lines.
From now on the tents increase rapidly in size by suc-
cessive additions of web spun over the tops and sides,
each new sheet covering a flat space between itself and the
last. The old roofs thus become successively the floors
of the new stories. The latter, of course, lap over on the
sides, and many continue clear around and beneath the
original structure; but since the tent was started in a
crotch, the principal growth is upward with a continual
expansion at the top. During the building period a
symmetrical tent is really a beautiful object (Plate 14 C).
Half hidden among the leaves, its silvery whiteness pleas-
ingly contrasts with the green of the foliage; its smooth
silk walls glisten where the sun falls upon them and reflect
warm grays and purples from their shadows.
The caterpillars have adopted now a community form
of living; all feed together, all rest and digest at the same
time, all work at the same time, and their days are divided
into definite periods for each of their several duties.
There is, however, no visible system of government or
regulation, but with caterpillars acts are probably func-
tions; that is, the urge probably comes from some physio-
logical process going on within them, which may be in-
fluenced somewhat by the weather.
The activities of the day begin with breakfast. Early
in the morning the family assembles on the tent roof, and
about six-thirty, proceeds outward in one or several
orderly columns on the branches. The leaves on the
terminal twigs furnish the material for the meal. After
two hours or more of feeding, appetites are appeased, and
[ 270 ]
THE CATERPILLAR AND THE MOTH
the caterpillars go back to the surface of the tent, usually
by eight-thirty or nine o'clock. Here they do a little spin-
ning on its walls, but no strenuous work is attempted at
—
—
SSS
>=
%
PANY
a
hy NOEL,
TERR
Uy N,
‘ Tie
Fic. 147. Mature tent caterpillars feeding at night
this time, and generally within half an hour the entire
family is reassembled inside the tent. Most frequently
the crowd collects first in the shady side of the outermost
story, but as the morning advances the caterpillars seek
[271]
INSECTS
the cooler inner chambers, where they remain hidden
from view.
In the early part of the afternoon a light lunch is taken.
The usual hour is one o’clock, but there is no set time.
Occasionally the participants appear shortly after eleven,
sometimes at noon, and again not until two or enree
o’clock, and rarely as late as four. As they assemble
on the roof of the tent they spin and weave again until
all are ready to proceed to the feeding grounds. This
meal lasts about an hour. When the caterpillars return
to the tent they do a little more spinning before they
retire for the afternoon siesta. Luncheon is not always
fully attended and is more popular with caterpillars in
the younger stages, being dispensed with entirely, as we
shall see, in the last stage.
Dinner, in the evening, is the principal meal of the
day, and again there is much variation in the time of
service. Daily observations made on five Connecticut
colonies from the 8th to the 26th of May gave six- thirty
p-m. as the earliest record for the start of the evening
feeding, and nine o’clock as the latest; but the dinner
hour is preceded by a great activity of the prospective
diners assembled on the outsides of the tents. Though
the energy of the tent caterpillars is never excessive, it
appears to reach its highest expression at this time. The
tent roofs are covered with restless throngs, most of the
individuals busily occupied with the weaving of new web,
working apparently in desperate haste as if a certain task
had been set for them to finish before they should be
allowed to eat. Possibly, though, the stimulus comes
merely from a congestion of the silk reservoirs in their
bodies, and the spinning of the thread affords relief.
The tent caterpillar does not weave its web in regular
loops of thread laid on by a methodical swinging of the
head from side to side, which is the method of most
caterpillars. It bends the entire body to one side, at-
[ 272]
THE, CATERPILLAR AND THE MOTH
taches the thread as far back as it can reach, then runs
forward a few paces and repeats the movement, sometimes
on the same side, sometimes on the other. The direction
in which the dread is carried, however, is a haphazard
one, depending on the obstruction the spinner meets from
Geek working in the same manner. Among the crowd of
weavers there are always a few individuals that are not
working, though they are just as active as the others.
These are
run ni ng
back and
forth over
the surface
ot, the tent,
like boarders
impatiently
awaiting the
sound of the
dinner bell.
Piet hia pis
they are in-
dividuals that have finished their
work by exhausting their supply
of silk.
At last the signal for dinner
is sounded. It is heard by the
caterpillars, though it is not
audible to an outsider. <A
few respond at first and start
off on one of the branches
leading from the tent. Others
follow, and presently a column
is marching outward, usually
keeping to the well-marked
paths of silk till the dis-
tant branches are reached.
; 2 Fic. 148. Mature tent cater-
Here the line breaks up into pillars. (Natural size)
[273 ]
INSECTS
several sections which spread out over the foliage. The
tent is soon deserted. For one, two, or three hours
the repast continues, the diners often returning home
late at night. Observations indicate that this is the
regular habit of the tent caterpillar in its earlier stages,
and perhaps up to the sixth or last stage of its life. In
at least nine instances the writer noted entire colonies
back in the tent for the night at hours ranging from
nine to eleven p.m.; but sometimes a part of the crowd
was still feeding when last observed.
In describing the life of a community of insects it is
seldom possible to make general statements that will
apply to all the individuals. The best that a writer can
do is to say what he sees most of the insects do, for, as in
other communities, there are always those eccentric mem-
bers who will not conform with the customs of the major-
ity. Occasionally a solitary tent caterpillar may be seen
feeding between regular mealtimes. Often one works
alone on the tent, spinning and weaving long after its
companions have quit and gone below for the midday
rest. Such a one appears to be afflicted with an over-
developed sense of responsibility. Then, too, there is
nearly always one among the group in the tent who can
not get to sleep. He flops this way and that, striking his
companions on either side and keeping them awake also.
These are annoyed, but they do not retaliate; they seem
to realize that their restless comrade has but a common
caterpillar affliction and must be endured.
Many of these little traits make the caterpillars seem
almost human. But, of course, this is just a popular
form of expression; in fact, it expresses an idea too popular
—we take an over amount of satisfaction in referring to
our faults as particularly human characteristics. What
we really should say is not how much tent caterpillars
are like us in their shortcomings, but how much we are
still like tent caterpillars. We both revert more or less
in our instincts to times before we lived in communities,
[ 274]
WHE CATERPILLAR AND THE MOTH
to times when our ancestors lived as individuals irre-
sponsible one to another.
The tent caterpillars ordinarily shed their skins six
times during their lives. At each molt the skin splits
along the middle of the back on the first three body seg-
ments and around the back of the head. It is then
pushed off over the rear end of the body, usually in one
piece, though most other caterpillars cast off the head
covering separate from the skin of the body in all molts
but the last. The moltings take place in the tent, except
the molt of the caterpillar to the pupa, and each molt
renders the caterpillars inactive for the greater part of
two days. When most of them shed their skins at the
same time there results an abrupt cessation of activity in
the colony. By the time the caterpillars reach maturity
the discarded skins in a tent outnumber the caterpillars
five to one.
The first stage of the caterpillars, as already described
(Fig. 144 D), suggests nothing of the color pattern of the
later stages, but in Stage II the spots and stripes of the
mature caterpillars begin to be formed. In succeeding
stages the characters become more and more like those of
the sixth or last stage (Plate 14 D, Fig. 148), when the
colors are most intensified and their pattern best defined.
Particularly striking now are the velvety black head with
the gray collar behind; the black shield of the first seg-
ment split with a medium zone of brown; the white stripe
down the middle of the back; the large black lateral
blotches, each inclosing a spot of silvery bluish white; the
distinctly bluish color between and below the blotches;
and the hump on the eleventh segment, where the median
white line is almost obliterated by the crowding of the
black from the sides. Yet the creatures wearing all this
lavishness of decoration make no ostentatious show, for the
colors are all nicely subdued beneath the long reddish-
brown hairs that clothe the body. In the last stage, the
average full-grown caterpillar is about two inches long,
[275]
INSECTS
but some reach a length of two and a half inches when
fully stretched out.
In Connecticut, the tent caterpillars begin to go into
their sixth and last stage about the middle of May. They
now change their habits in many ways, disregarding the
conventionalities and refusing the responsibilities that
bound them in their earlier stages. They do little if any
spinning on the tent, not even keeping it in decent repair.
They stay out all night to feed (Fig. 147), unless adverse
weather interferes, thus merging dinner into breakfast in
one long nocturnal repast. This is attested by observa-
tions made through most of several nights, when the
caterpillars of four colonies which went out at the usual
time in the evenings were found feeding till at least four
o’clock the following mornings, but were always back in
the tents at seven-thirty a.m. When the caterpillars begin
these all-night banquets, they dispense with the mid-
day lunch, their crops being so crammed with food by
morning that the entire day is required for its digestion.
Some writers have described the tent caterpillars as
nocturnal feeders, and some have said they feed three
times a day. Both statements, it appears, are correct,
but the observers have not noted that the two habits
pertain to different periods of the caterpillars’ history.
At any time during the caterpillars’ lives adverse
weather conditions may upset their daily routine. For two
weeks during May, days and nights had been fair and
generally warm, but on the 17th the temperature did not
get above 65° F., and in the afternoon threatening clouds
covered the sky. In the evening light rains fell, but the
caterpillars of the five colonies under observation came out
as usual for dinner and were still feeding when last ob-
served at nine p.m. Rains continued through the night,
however, and the temperature stood almost stationary
between 50° and 55°.
The next morning three of the small trees containing the
colonies were festooned with water-soaked caterpillars, all
[ 276 ]
THE CATERPILLAR AND THE MOTH
hanging motionless from leaves, petioles, and twigs, be-
numbed with exposure and incapable of action—more
miserable-looking insects could not be imagined. No in-
stinct of protection, apparently, had prevailed over their
appetites; till at last, overcome by wet and cold, they
were saved only by some impulse that led them to grasp
the support so firmly with the abdominal feet that they
hung there mechanically when senses and power of move-
ment were gone. Some clung by the hindmost pair of feet
only, others grasped the support with all the abdominal
feet. One colony and most of another were safely housed
in their tents. These had evidently retreated before
helplessness overtook them.
By eight o*clock in the morning many of the suspended
caterpillars were sufficiently revived to resume activity.
Some fed a little, others crawled feebly toward the tents.
By 9:45 most were on their way home, and at 10:46 all
were under shelter.
Gentle rains fell during most of the day, but the tem-
perature gradually rose to a maximum of 65°. Only a few
caterpillars from the youngest colony came out to feed at
noon. In the evening there was a hard, drenching rain,
after which several caterpillars from two of the tents ap-
peared for dinner. The next morning, the 1gth, the tem-
perature dropped to 49°, light rains continued, and not a
caterpillar from any colony ventured out for breakfast. It
looked as if they had learned their lesson; but it is more
probable they were simply too cold and stiff to leave the
tents. In the afternoon the sky cleared, the temperature
rose, and the colonies resumed their normal life.
The tent caterpillars’ mode of feeding is to devour the
leaves clear down to the midribs (Figs. 148, 149), and in
this fashion they denude whole branches of the trees they
inhabit. Since the caterpillars have big appetites, it some-
times happens that a large colony in a small tree or several
colonies in the same tree may strip the tree bare before
they reach maturity. The writer never saw a colony
[277 |
INSECTS
reduced to this extremity by its own feeding, but produced
similar conditions for one in a small apple tree by removing
all the leaves. This was on May 1g, and the caterpillars
were mostly in their fifth stage. At seven o’clock in the
Fic. 149. Twigs of choke cherry and of apple de-
nuded by tent caterpillars
evening the cater-
pillars in this col-
ony came out as
usual, and, after
doing the cus-
tomary spinning
on ‘hte temcs
started off to get
their dinner, sus-
pecting nothing
till they came to
the cut-off ends
of the branches.
Then they were
clearly bewildered
--they returned
and tried the
course over again;
they tried another
branch, ally “the
other branches;
but all ended
alike in bare
stumps. Yet there
were the accus-
tomed trails, and
their instincts
clearly said that
silk paths led to
food. So all night
the caterpillars hunted for the missing leaves; they went
over and over the same courses, but none ventured below
the upper part of the trunk. By 3:45 in the morning
[ 278 |
THE CATERPILLAR AND THE MOTH
many had given up and had gone back to the tent, but the
rest continued the hopeless search. At seven-thirty a few
bold explorers had discovered some remnants of water
sprouts at the base of the tree and fed there till ten o’clock.
At eleven all were back in the tent.
At two o’clock in the afternoon the crowd was out again
and a mass meeting was being held at the base of the tree.
But nobody seemed to have any idea of what to do, and no
leader rose to the occasion. A few cautious scouts were
making investigations over the ground to the extent of a
foot or a little more from the base of the trunk, but, though
there were small apple trees on three sides five feet away,
only one small caterpillar ventured off toward one of
these. He, however, missed the mark by twelve inches
and continued onward; but probably chance eventually
rewarded him. At three p.m. the meeting broke up,
and the members went home. They were not seen again
that evening or the next morning.
During this day, the 21st, and the next, an occasional
caterpillar came out of the tent but soon returned, and it
was not till the evening of the 22nd that a large number
appeared. These once more explored the naked branches
and traveled up and down the new paths on the trunk, but
none was observed to leave the tree. On the 23rd and
24th no caterpillars were seen. On the 25th the tent was
opened and only two small individuals were found within
it. Each of these was weak and flabby, its alimentary
canal completely empty. But what had become of the
rest? Probably they had wandered off unobserved one
by one. Certainly there had been no organized migra-
tion. Solitary caterpillars were subsequently found on a
dozen or more small apple trees in the immediate vicinity.
It is likely that most of these had molted and had gone
into the last stage, since their time was ripe, but this was
not determined.
After the caterpillars go over into their last stage, the
tents are neglected and rapidly fall into a state of dilapida-
[ 279 ]
INSECTS
tion. Birds often poke holes in them with their bills and
rip off sheets of silk which they carry away for nest-build-
ing purposes. The caterpillars do not even repair these
damages. The rooms of the tent become filled with ac-
cumulations of frass, molted skins, and the shriveled
bodies of dead caterpillars. The walls are discolored by
rains which beat into the openings and soak through the
refuse. Thus, what were shapely objects of glistening silk
are transmuted into formless masses of dirty rags.
But the caterpillars, now in their finest dress, are ob-
livious of their sordid surroundings and sleep all day
amidst these disgusting and apparently insanitary condi-
tions. However, the life in the tents will soon be over;
so it appears the caterpillars simply think, “What’s the
use?” But of course caterpillars do not think; they arrive
at results by instinct, in this case by the lack of an instinct,
for they have no impulse to keep the tents clean or in
repair when doing so
would be energy wasted.
Nature demands a prac-
tical reason for most
things.
eS Zi a = _o xP 5
OE The tent life continues
LMU, about a week after the
<y- last molt, and then the
family begins to break
up, the members leaving
singly or in bands, but al-
Fic. 150. A tent caterpillar in the last Ways as individuals with-
stage of its growth, leaving the tree con- out further concern for
taining its nest by jumping from the end :
of a twig to the ground one another. Judging
from their previous me-
thodical habits, one would suppose that the caterpillars
starting off on their journeys would simply go down the
trunks of the trees and walk away. But no; once in their
life they must have a dramatic moment. A caterpillar
comes rushing out of a tent as if suddenly awakened from
[ 280 |
THE CATERPILLAR AND THE MOTH
some terrible dream or as if pursued by a demon, hurries
outward along a branch, goes to the end of a spur or the
tip of a leaf, and without slackening continues into space
till the end of the support tickles his stomach, when sud-
denly he gives a flip into the air, turns a somersault, and
lands on the ground (Fig. 150).
The first performance of this sort was observed on
May 15 in the Connecticut colonies. On the afternoon
of the 1gth, twenty or more caterpillars from two neigh-
boring colonies were seen leaving the trees in the same
fashion within half an hour. Most of the members of one
of these colonies had their last molt on May 12 and 13.
During the next few days other caterpillars were ob-
served jumping from four trees containing colonies under
observation. All of these went off individually at various
times, but most of them early in the afternoon. Many
caterpillars simply drop of when they reach the end of
the branch, without the acrobatic touch, but only three
were seen to go down the trunk of a tree in commonplace
style.
The population of the tents gradually decreases during
several days following the time when the first caterpillar
departs. One of the two tents from which the general
exodus was noted on May 1g was opened on the 21st and
was found to contain only one remaining caterpillar. On
the evening of the 22nd a solitary individual was out feed-
ing from the other tent. The two younger colonies main-
tained their numbers until the 22nd, after which they
diminished till, within a few days, their tents also were
deserted. The members of all these colonies hatched
from, the eggs on April 8, g, and 10, so seven weeks is the
greatest length of time that any of them spent on the trees
of their birth. The caterpillar that left the tent on the
1§th came from a colony that began to hatch on April to,
giving an observed minimum of thirty-six days.
After the mature caterpillars leave the tents, they
wander at large and feed wherever they find suitable
[ 281 | ,
INSECTS
provender, enjoying for a while a new life free from the
domestic routine that has bound them since the days of
their infancy. But even their liberty has an ulterior pur-
pose: the time is now approaching when their lives as
caterpillars must end and the creatures must go through
the mysteries of transformation, which, if successfully
accomplished, will convert them into winged moths. It
would clearly be most unwise for the caterpillars of a
colony to undergo the period of their metamorphosis
huddled in the remains of the tent, where some untoward
event might bring destruction to them all. Nature has,
therefore, implanted in the tent caterpillar a migratory
urge, which now becomes active and leads the members of
a family to scatter far and
wide. About a week is
allowed for the dispersal,
and then, as each wan-
derer feels within the
first warnings of ap-
proaching dissolution, it
selects a suitable place
for inclosing itself in a
cocoon,
It is difficult to find many cocoons in the neighborhood
where large numbers of caterpillars have dispersed, but
such as may be recovered will be found among blades of
grass, under ledges of fences, or in sheds and barns where
they are not disturbed. The cocoon is a slender oval or
almost spindle-shaped object, the larger ones being about
an inch long and half an inch in width at the middle
(Plate 14 E, Fig. 151). The structure is spun of white silk
thread, but its walls are stiffened and colored by a yellow-
ish substance infiltrated like starch through the meshes
of the fabric.
In building the cocoon the caterpillar first spins a loose
network of threads at the place selected, and then, using
this for a support, weaves about itself the walls of the final
[ 282 ]
Fic. 151. The cocoon of a tent cater-
pillar. (Natural size)
THE GATERPIELAR AND THE MOTH
structure. On account of its large size, as compared with
the size of the cocoon, the caterpillar is forced to double
on itself to fit its self-imposed cell. Most of its hairs, how-
ever, are brushed off and become interlaced with the
threads to form a part of the cocoon fabric. When the
spinning is finished, the caterpillar ejects a yellowish,
pasty liquid from its intestine, which it smears all over the
inner surface of the case; but the substance spreads
through the meshes of the silk, where it quickly dries and
gives the starchy stiffness to the walls of the finished
cocoon. It readily crumbles into a yellow powder, which
becomes dusted over the caterpillar within and floats off in
a small yellow cloud whenever a cocoon is pulled loose
from its attachments.
The cocoon is the last resting place of the caterpillar. If
the insect lives, it will come out of its prison as a moth,
leaving the garments of the worm behind. It may, koe
ever, be attacked by parasites that will shortly bring about
its destruction. But even if it goes through the period of
change successfully it must remain in the cocoon about
three weeks. In the meantime it will be of interest to learn
something of the structure of a caterpillar, the better to
understand some of the details of the process of its trans-
formation.
THE STRUCTURE AND PHYSIOLOGY OF THE CATERPILLAR
A caterpillar is a young moth that has carried the idea
of the independence of youth to an extreme degree, but
which, instead of rising superior to its parents, has de-
generated into the form of a worm. An excellent theme
this would furnish to those who at present are bewailing
what they believe to be a shocking tendency toward an
excess of independence on the part of the young of the
human species; but the moral aspect of the lesson some-
what loses its force when we learn that this freedom of the
caterpillar from parental restraint gives advantages to
both young and adults and therefore results in good to
[ 283 ]
INSEGIES
the species as a whole. Independence entails responsibil-
ities. A creature that leaves the beaten paths of its an-
cestors must learn to take care of itself in a new way. And
Fic. 152. The head of a tent caterpillar
A, facial view. B, under surface. C, side view. mt, antenna; Clp, clypeus;
For, opening of back of head into body; HpAy, hypopharynx; Zé, labium; Lm,
labrum; Md, mandible; Mx, maxilla; O, eyes; Spt, spinneret
this the caterpillar has learned to do preeminently well,
as 1t has come up the long road of evolution, till now it
possesses both instincts and physical organs that make it
Fic. 153.
The mandibles, or
biting jaws, of the tent cater-
pillar detached from the head
A, front view of right mandi-
ble. B, under side of the left
mandible. a@ and p, the an-
terior socket and posterior
knob by which the jaw is
hinged to the head; EMcl,
RM¢cl, abductor and adductor
muscles that move the jaw in
a transverse plane
one of the dominant forms of in-
sect life.
The external organs of princi-
pal interest in the caterpillar are
those of the head (Fig. 152).
These include the eyes, the an-
tennae, the mouth, the jaws, and
the silk-spinning instrument. A
facial view of a caterpillar’s head
shows two large, hemispherical
lateral areas separated by a medi-
an suture above and a triangular
plate (C/p) below. The walls of
the lateral hemispheres give at-
tachment to the muscles that
move the jaws, and their size is
no index of the brain-power of
[ 284 ]
THE CATERPILLAR AND THE MOTH
the caterpillar, since the insect’s brain occupies but a small
part of the interior of the head (Fig. 154, Br). From the
lower edge of the triangular facial plate (Fig. 152, C/p) is
suspended the broad, notched front lip, or labrum (Lm)
that hangs as a protective flap over the bases of the jaws.
At the sides of the labrum are the very small antennae
(Ant) of the caterpillar. On the lower part of each lateral
hemisphere of the head are six small simple eyes, or
ocelli (OQ), five in an upper group, and one near the base of
the antenna. With all its eyes, however, the caterpillar
Cr Vent Ht Mal Int
Fic. 154. Diagrammatic lengthwise section of a caterpillar, showing the
principal internal organs, except the tracheal system
An, anus; Br, brain; Cr, crop; H¢, heart; Int, intestine; Ma/, Malpighian tubule
(two others are cut off near their bases); Msh, mouth; Oe, oesophagus; PAy,
pharynx; Rect, rectum; S&G/, silk gland; SoeGng, suboesophageal ganglion; Vent,
stomach, or ventriculus; / NC, ventral nerve cord
appears to be very nearsighted and gives little evidence of
being able to distinguish more than the presence or ab-
sence of an object before it, or the difference between light
and darkness. Those tent caterpillars that were starving
on the denuded tree failed to perceive other food trees in
full leaf only a few feet away.
The general external form and structure of the tent
caterpillar is shown at A of Figure 159. The body is soft
and cylindrical. The head is a small, hard-walled capsule
attached to the body by a short flexible neck. Back of
the head and neck comes first a body region consisting
of three segments that bear each a pair of small, jointed
legs (LZ); and then comes a long region composed of ten
segments supported on five pairs of short, unjointed legs
[ 285 ]
INSECTS
(AL), the first four pairs being on the third, fourth, fifth
and sixth segments, and the last on the tenth segment.
The region of the three segments in the caterpillar bear-
ing the jointed legs corresponds with the thorax of an
adult insect (Fig. 63, TA), and that following corresponds
with the abdomen (44). The thorax of the adult insect
constitutes the locomotor center of the body, but the
wormlike caterpillar has no special locomotor region, and
hence its body is not separated into thorax and abdomen.
The thoracic legs of the caterpillar terminate each in a
single claw, but the foot of each of the abdominal legs
has a broad sole provided with a series or circlet of claws
and with a central vacuum cup. The abdominal legs
of the caterpillar, therefore, are important organs of pro-
gression, and are the chief organs of grasping or of cling-
ing to hard or flat surfaces.
The jaws of the caterpillar consist of a pair of large,
strong mandibles (Fig. 152, Md) concealed, when closed,
behind the labrum. Each jaw is hinged to the lower
edge of the cranium at the side of the mouth by two ball-
and-socket hinges in such a manner that, when in action,
it swings outward and inward on a lengthwise axis. The
cutting edges are provided with a number of strong teeth
(Fig. 153), the points of which come together or slide
past each other when the jaws are closed.
The large complex organ that projects behind or below
the mouth like a thick under lip (Fig. 152 C) is a com-
bination of three parts that are separate in other insects.
These are the second pair of soft Jaw appendages, called
maxillae (B, C, Mx), and the true under lip, or /abium
(Lé). The most important part of this composite struc-
ture in the caterpillar, however, is a hollow spine (A,
B, C, Spt) pointed downward and backward from the
end of the labium. This is the spinneret. From it issues
the silk thread with which the Pail weaves its tent
and its cocoon.
[ 286 ]
THE CATERPILLAR AND THE MOTH
The fresh silk is a liquid formed in two long, tubular
glands extending far back from the head into the body of
the caterpillar (Fig. 154, SkG/). The middle part of each
tube is enlarged to serve as a reservoir where the silk
liquid may accumulate (Fig. 155 A, Res); the anterior
narrowed part constitutes the duct (Det), and the ducts
Fic. 155. The silk glands and spinning organs of the tent caterpillar
A, the silk-forming organs, consisting of a pair of tubular glands (G/, G/), each
enlarging into a reservoir (Res), and opening through a long duct (Det) into
the silk press (Pr), with a pair of accessory glands (glands of Filippi, G/F) opening
into the ducts
B, side view of the hypopharynx (Hp/y) with terminal parts of right maxilla
(Mx) and labium (Ld) attached, showing the silk press (Pr), its muscles, and
the ducts (Dect) opening into it, and the spinneret (Spr) through which the silk is
discharged from the press
C, upper view of the silk press (Pr), showing the four sets of muscles (Mc/s)
inserted on its walls and on the rod-like raphe (RpA) in its roof
D, side view of the silk press, spinneret, raphe, and muscles
E, cross-section of the silk press, showing its cavity, or lumen (Zum), which is
expanded by the contraction of the muscles
[ 287 ]
INSECTS
from the two glands unite in a median thick-walled sac
known as the si/k press (Pr), which opens to the exterior
through the spinneret. Two small accessory glands, which
look like bunches of grapes and which are sometimes
called the glands of Filippi (Fig. 155 A, B, C, G/F), open
into the silk ducts near their front ends.
The relation of the silk ducts and the silk press to the
spinneret is seen in the side view of the terminal parts of
the labium and the left maxilla, given at B of Figure 155.
The silk press (Pr) is apparently an organ for regulating
the flow of the liquid silk material into the spinneret. It
has been supposed, too, that it
gives form and thickness to the
thread, but the liquid material has
still to pass through the rigid tube
of the spinneret.
The cut end of the press, given at
E of Figure 155, shows the crescent
form of the cavity (Lum) in cross-
section, and the thickening in its
roof (RpA), called the raphe. Mus-
cles (Mc/s) inserted on the raphe
and on the sides of the press serve
to enlarge the cavity of the press
by lifting the infolded roof. The
four sets of these muscles in the
tent caterpillar are shown at C.
The dilation of the press sucks the
liquid silk into the cavity through
the ducts from the reservoirs, and
Fic. 156. The alimentary when the muscles relax, the elastic
canal of the tent cater- :
pillar roof springs back and exerts a
A, before feeding. B, after pressure on the silk material, which
feeding. Cr, crop; Int, in- ~
testing; Mai, Malpighian ‘forces the latter through thesvabe
tubules; OZ, cesophaguss of the spinberet. Lhe continuous
Rect, rectum; Vent, ventri-
culus passageway from the ducts through
[| 288 }
tHE, CATERPILLAR AND THE MOTH
the press and into the spinneret is seen from the side
at D.
The silk liquid is gummy and adheres tightly to what-
ever it touches, while at the same time it hardens rapidly
and becomes a tough, inelastic thread as it 1s drawn out
of the spinneret when the caterpillar swings its head away
from the point of attachment.
The mouth of the caterpillar lies between the jaws and
the lips. It opens into a short gullet, or oesophagus, which,
with the pharynx, constitutes the first part of the alimen-
tary canal (Fig. 154, Phy, Oc). The rest of the canal is a
wide tube occupying most of the space within the cater-
pillar’s body and is divided into the crop (Cr), the stomach,
or ventriculus (Vent), and the intestine (Int). The crop is
a sac for receiving the food and varies in size according
to the amount of food it contains (Fig. 156 A, B, Cr).
The stomach (Vent) is the largest part of the canal. Its
walls are loose and wrinkled when it is empty, or smooth
and tense when it is full. The in-
testine (/7¢) consists of three divi-
sions, a short part just back of the
Bech: a larger middle part, anda
saclike end part called the rectum
(Rect). Six long tubes (Ma/) are
wrapped in many coils about the in-
testine and run forward and back in
long loops over the rear half of the
stomach. The three on each side Fic. 157. _ Crystals
unite into a short basal tube, which oe te, Me penian
opens into the first part of the intes- caterpillar, which are
tine. The terminal parts of the tubes —“I*"ted. into. the walls
are coiled inside the muscular coat
of the rectum. These tubes are the Ma/pighian tubules.
When a tent caterpillar goes out to feed, the fore part
of its body is soft and flabby; when it returns to the tent
the same part is tight and firm. This is because the tent
caterpillar carries its dinner home in its crop, digests it
[ 289 ]
INSECTS
slowly while in the tent, and then goes out for more when
the crop is empty. It is quite easy to tell by feeling one
of these caterpillars whether it is hungry or not. The
empty, contracted crop is a smal] bag contained in the
first three segments of the body (Fig. 156 A, Cr); but the
full crop stretches out to a long cylinder like a sausage,
filling the first six segments of the body (B, Cr), its rear
end sunken into the stomach, and its front end pressed
against the back of the head.
The fresh food in the crop consists of a soft, pulpy mass
of leaf fragments. As this is passed into hie stomach,
the crop contracts and the stomach expands, and te
caterpillar’s center of gravity 1s shifted backward with the
food burden. As the stomach becomes empty there ac-
cumulates in it a dark-brown liquid, and it becomes in-
flated with bubbles of gas. When the caterpillar goes to
its meals both crop and stomach are sometimes empty,
but usually the stomach still contains some food besides
an abundance of the brown liquid and numerous gas
bubbles. The refuse that accumulates in the middle sec-
tion of the intestine is subjected to pressure by the mus-
cles of the intestinal wall, and is here molded into a pellet
which retains the imprint of the constrictions and pouches
of this part of the intestine and looks like a small mulberry
when passed on into the rectum and finally extruded from
the body.
The alimentary canal is a tube made of a single layer
of cells extending through the body; but its outer surface,
that toward the body cavity, is covered by a muscle layer
of lengthwise and crosswise fibers, which cause the move-
ment of the food through the canal. The gullet and crop
and the intestine are lined internally with a thin cuticula
continuous with that covering the surface of the body,
and these linings are shed with the body cuticula every
time the caterpillar molts.
The Malpighian tubules (Figs. 154, 156 A, Ma/), being
the kidneys of insects, are excretory organs that remove
[ 2g0 }
THE CATERPILLAR AND THE MOTH
from the blood the waste products containing nitrogen,
and discharge them into the intestine along with the waste
parts of the food from the stomach. Ordinarily the Mal-
pighian tubules are of a whitish color, but just before the
tent caterpillar is ready to spin its cocoon they become
congested with a bright yellow substance. Under the
microscope this is seen to consist of masses of square,
oblong, and rod-shaped crystals (Fig. 157). At this time
the caterpillar has ceased to feed and the alimentary canal
contains no food or food refuse. The intestine, however,
Fic. 158. A piece of the fat-body of the fall webworm
a, a, globules of fatty oil in the cells; Nu, Nu, nuclei of the cells
becomes filled with the yellow mass from the Malpighian
tubules; and this 1s the material with which the tent
caterpillar plasters the walls of its cocoon, giving them
their yellowish color and stiffened texture. The yellow
powder of the cocoon, therefore, consists of the crystals
from the Malpighian tubules.
We now come to the question of why the caterpillar eats
so much. It is almost equivalent to asking, ““Why is a
caterpillar?” The caterpillar is the principal feeding
stage ih the insect’s life; eating is its business, its reason
for being a caterpillar. It eats not only to build up its
own organs, many of which are to be broken down to
furnish building material for those of the moth, but it
eats also to store up within its body certain materials in
excess of its own needs, which likewise will contribute to
the growth of the moth.
[ 291 |
UNSECYS
The most abundant of the food reserves stored by the
caterpillar is fat. With insects, however, fat does not
accumulate among the muscles and beneath the skin. In-
sects do not become “‘fat” in external appearance. Their
fatty products are held in a special organ called the fat-
body.
The fat tissue of a caterpillar consists of many small,
flat, irregular masses of fat-containing cells scattered all
through the body cavity, some of the masses adhering in
chains and sheets forming a loose open network about the
alimentary canal, others being distributed against the
muscle layers and between the muscles and the body wall.
The cells composing the tissue vary much in size and
shape, but they are always closely adherent, and in fresh
material it is often difficult to distinguish the cell bound-
aries. Specimens prepared and stained for microscopic
examination, however, show distinctly the cellular struc-
ture (Fig. 158). Each cell contains a darkly-stained
nucleus (Nw), but the nuclei are seen only where they lie
in the plane of the section. The protoplasmic area about
the nucleus in each cell appears to be occupied mostly
with hollow cavities of various sizes (2), but in life each
cavity contains a small globule of fatty oil. The proto-
plasmic material between the oil globules contains also
glycogen, or animal starch, as can be shown by staining
with iodine. Both fat and glycogen are energy-forming
compounds, and their presence in the fat cells of the
caterpillar shows that the fat-body serves as a storage
organ for these materials during the larval life. The stored
fat and glycogen will be consumed during the period of
metamorphosis, when the insect is deprived of the power
of feeding and receives no further nourishment from the
alimentary canal. The transformation processes will then
depend upon the food materials that the caterpillar has
stored in its own body; and the success of the pupal meta-
morphosis will depend in large measure on the quantity
of these food reserves. A starved caterpillar, therefore,
[ 292 ]
THE CATERPILLAR AND THE MOTH
is likely to be unable to accomplish its transformation, or
it will produce a dwarfed or an imperfect adult.
How THE CaTERPILLAR Becomes A Moru
A short time before the caterpillar is ready to spin its
cocoon, it ceases feeding. Its body, as we have just
learned) contains now an abundance of energy-giving sub-
stances stored in the cells of its fat tissue. When the work
of constructing the cocoon is started, the alimentary canal
is devoid of food material, the crop is contracted to a
narrow cylinder, and the stomach is shrunken and flabby.
The stomach, however, contains a mass of soft, orange-
brown substance which, when examined under the micro-
scope, is found to consist, not of plant tissue, but of animal
cells; it is, in fact, the cellular lining of the caterpillar’s
stomach which has already been cast off into the cavity
of the stomach. The latter is now provided with a new
cell wall. The shedding of the old stomach wall marks the
first stage in the dismantling of the caterpillar; it is the
beginning of the pupal metamorphosis which will convert
the caterpillar into the moth. The new stomach wall will
first digest and absorb the débris of the old, in order to
conserve its proteid materials for the constructive work
of the pupa, and it will then itself become transformed
into the stomach of the moth.
After the caterpillar has shut itself into the cocoon, its
life as a caterpillar is almost ended. Its external appear-
ance is already much altered by the contraction of the
body and the loss of the hairy covering, and during the
next three or four days a further characteristic change of
form takes place. As the body continues to shorten, the
first three segments become crowded together; but the
abdomen swells out, while the abdominal legs are re-
tracted until they all but disappear. The creature 1s now
(Fig. 159 B) only half the length of the active caterpillar
(A), and it would scarcely be recognized as the same in-
dividual that so recently spun itself into the cocoon.
[ 293 ]
INSECTS
During the progress of change in the external form, the
caterpillar gradually loses the power of movement. The
resultant inactive period in an insect’s life, immediately
preceding the visible change to the pupa, is called the
srk =
‘)
:
J
Fic. 159. Transformation of the tent caterpillar into the moth
[ 294 ]
thE CATERPILLAR AND THE MOTH
prepupal stage of the larva. The insect in the prepupal
stage has suffered no change in external structure, it still
wears the larval skin, and its visible difference from the
active larva is a mere alteration in form. Internally, how-
ever, important reconstructive processes are now taking
place.
The internal activities of reconstruction, which bring
about the pupal metamorphosis of the larva to the adult,
begin at the head end of the insect and progress poste-
riorly. They are preceded by a loosening and subsequent
detachment of the larval cuticula from the cellular layer
of the skin, or epidermis, beneath it. The latter, known
also as the ‘hypodermis, freed now from restraint, enters a
period of rapid growth. On the head, the head walls are
remodeled and take on a new form, and new antennae and
new mouth parts are produced. The new structures have
no regard for the forms of the old, though each is pro-
duced from a part of the corresponding larval organ. The
new antennae, for example, are formed from the larval
antennae, but the antennae of the moth are to be much
larger than those of the caterpillar. Only the tip, there-
fore, of each new organ can be formed within the cuticular
sheath of the old; the base pushes inward, and the elon-
gating shaft folds against the face of the newly forming
head. The same thing is true of the maxillae and labium,
but in the case of the mandibles the procedure is simpler,
for the Jaws are to be reduced in the moth. The epi-
dermal core of each mandible, therefore, simply shrinks
within the cuticular sheath oe the eval organ, leaving
the cavity of the latter almost empty.
As the separation of the cuticula from the epidermis
progresses over the region of the thorax and a free space
is created between the two layers, the wing buds, which
heretofore have been turned inside the caterpillar’s body,
now evert and come to be external appendages of the pupal
body though still covered by the cuticula of the larva
(Fig. 159 C, W2, W;). The legs of the moth pupa are
[ 295 ]
INSEGES
formed in the same way as are the antennae and the mouth
parts, that is, they are developed from the epidermis of
the corresponding larval legs; but, by reason of their inl=
creased size, they are forced to bend upward against the
sides of the body of the pupa, and, when fully formed,
each is found to have only its terminal part within the
cuticular sheath of the leg of the caterpillar.
From the thorax, the loosening of the cuticula spreads
backward over the abdomen, until at last the entire insect
lies free within the cuticular skin of the caterpillar. The
so-called prepupal period of the caterpillar, therefore, 1s
scarcely to be regarded as a truly larval stage of the in-
sect. It is still clothed in the larval cuticula, and retains
externally all the structural characters of the larva; but
the creature itself is in a first growth period of the pupal
stage, and may appropriately be designated a propupa.
When the cuticula is separated from the epidermis all
over the body, it may be cut open and taken off without
injury to the wearer. The latter, now a propupa (Fig.
159 C), is then discovered to be a thing entirely different
in appearance from the caterpillar. It has a small head
bent downward, a thoracic region of three segments, and
a large abdomen. The head bears the mouth parts and a
pair of large antennae (4mf); the thorax carries the wings
(W2, Ws) and the legs (LZ), which latter are much longer
than those of the caterpillar, but, being folded beneath
the wings, only their ends are visible in side view. The
abdomen consists of ten segments and has lost all ves-
tiges of the abdominal legs of the caterpillar (A, 4Z).
Many important changes have taken place in the form
and structure of the head and in the appendages about
the mouth during the change from the caterpillar to the
propupa, as may be seen by comparing Figure 1§9 H, with
Figure 152. Most of the lateral areas of the caterpillar’s
head (Fig. 152), including the region of the six small eyes
on each side, have been converted into the two huge eye
areas of the pupa (Fig. 159 H, £), which cover the develop-
[ 296 }
THE CATERPILLAR AND THE MOTH
ing compound eyes of the adult. The antennae (47/1), as
already noted, have increased greatly in size, and they
show evidence of their future multiple segmentation.
The upper lip, or labrum (Lm), on the other hand, is much
smaller in the propupa than in the caterpillar, and the
great biting jaws of the caterpillar are reduced to mere
rudiments in the propupa (Md), while the spinneret (Fig.
152, Spt) is gone entirely. ihe labium and the two
spol are longer and more distinct from each other in
the propupa (Fig. 159 H, £4, Mx) than in the caterpillar,
and their parts are scnerin more simplified. The
labium bears two prominent palpi (L4P/p).
The remodeling in the external form of the insect pro-
ceeds from particular groups of cells in the epidermis,
cells that have remained inactive since the time of the
embryo, and which, as a consequence, retain an unused
vitality. These groups of regenerative epidermal cells,
which are the histoblasts, or imaginal discs, of the body
wall, have not been particularly studied in the caterpillar;
but in certain other insects they have been found to occur
in each segment, ty pically a pair of them on each side of
the back, and a pair on each side of the ventral surface.
At the beginning of metamorphosis, as the larval cuticula
separates from the epidermis, the cells of the discs multiply
and spread from their several centers, and the areas newly
formed by them take on the contour and structure of the
pupa instead of that of the larva. The old cells of the
larval epidermis, which have reached the limits of their
growing powers and are now in a state of senescence, give
way before the advancing ranks of invading cells; their
tissues go into dissolution and are absorbed into the body.
The new epidermal areas finally meet and unite, and to-
gether constitute the body wall of the pupa.
While the new epidermis is giving external form to the
pupa beneath the larval cuticula, its cells are generating
a new pupal cuticula. As long as the latter is soft and
plastic the cell growth may proceed, but when the cutic-
[ 297 ]
INSECTS
ular substance begins to harden, growth ceases, and the
external form of the insect will henceforth show no further
change in its structural features.
The propupa of the moth remains for several days a
soft-skinned creature (Fig. 159 C) inside the cuticula of
the larva, during which time its body contracts in size and
its wings, legs, antennae, and maxille lengthen. The wings
are flattened against the sides of the body, and the other
appendages are applied close to the under surface. Then
a gluelike substance is exuded from the body wall, which
fixes the members in their positions and soon dries into a
hard coating or glaze over the body and appendages, giving
to the whole a shell-like covering. In this way the soft
propupa (C) becomes a chrysalis (D). Finally, the old
caterpillar skin splits along the back of the first two body
segments, over the top of the head, and down the right side
of the facial triangle. The pupa now quickly wriggles out
of the enclosing skin and pushes the latter over the rear
extremity of its body into the end of the cocoon, where it
remains as a shriveled mass, the last evidence of the
caterpillar.
The pupa, or chrysalis, of the tent caterpillar (Fig.
159 D) is much smaller than the propupa (C), and its
length is only about one-third that of the original cater-
pillar (A). The color of the chrysalis is at first bright
green on the fore parts, yellowish on the abdomen, and
usually more or less brown on the back. Soon, however,
the color darkens until the front parts and the wings are
purplish black, and the abdomen purplish brown. Though
the covering of the chrysalis is hard and rigid, the creature
is still capable of a very active wriggling of the abdomen,
for three of its intersegmental rings remain flexible. By
this provision the pupa is able to divest itself of the larval
skin. The pupe of some species of moths push them-
selves partly out of the cocoon just before the time of
transformation to the moth, and when the latter emerges
[ 298 ]
tHE CATERPIELAKR AND THE MOTH
it leaves the pupal skin projecting from the mouth of the
cocoon (Plate 12).
Concurrent with the remodeling in the external form of
the insect, other changes have been taking place within the
body. The first of the complicated metamorphic processes
that affect the inner organs occurs in the stomach, where,
as we have already observed, the inner wall is cast off at
about the time that the caterpillar begins the spinning of
its cocoon. This shedding of the stomach lining 1s quite a
different thing from the molting of an external cuticula,
for the stomach wall is a cellular tissue. Evaheemere.
wherever other cell layers are discarded, as in the case of
the epidermis, the cells are absorbed info the body cavity.
A new stomach wall is generated usually from groups of
small cells that originally lay outside the old wall and were
retained when the latter was cast off. These cells, as do
the imaginal discs of the epidermis, form a new lining.to
the stomach and give a new shape to this organ, which in
the adult insect may be quite different from that of the
larva. The shedding of the stomach wall is not necessarily
a part of the metamorphosis, for in some insects and in
certain other related animals, it is said, the stomach
epithelium as well as the cuticular lining is shed and
renewed with each molt of the body wall.
The parts of the alimentary canal that lie before and
behind the stomach, that 1s, the oesophagus and crop
(Fig. 154, Oe, Cr) and the intestine (Jw), formed in the
embryo as ingrowths of the body wall, are regenerated
from groups of cells in their walls in the same manner as is
the epidermis itself, the old cells being absorbed into the
body. The cuticular linings of these parts are shed with
the cuticula of the body wall at the time of the molt. The
complete alimentary canal of the moth is very different
from that of the caterpillar, as will be shown in the next
section of this chapter (Fig. 164).
The walls of the Malpighian tubules are said to be
regenerated in some insects, but the tubules do not change
[ 299 |
INSECTS
much in form in the moth, and they continue their ex-
cretory function during the pupal stage. The silk glands
of the caterpillar are greatly reduced in size, and their
ducts, as a consequence of the suppression of the spinneret,
open at the base of the labium within the entrance to the
mouth.
Internal organs that have not been specially modified
in their development for the purposes of the larva, in-
cluding usually the nervous system, the heart, the respira-
tory tubes, and the reproductive organs, suffer little if any
disintegration in their tissues; they simply grow to the
mature form, which may be much more elaborate than
that of the larva, by a resumption of the ordinary processes
of development. The nervous system, and particularly
the tracheal system, however, in some insects undergo
much reconstruction between the larval and the adult
stages.
A most important part of the reconstruction between
the larva and the adult has to do with the muscle system.
Since, in its two active stages, the insect leads usually
two very different lives, the mechanism of locomotion is
likely to be radically different in the larva and in the
adult; and in such cases the transformation of the insect
will involve particularly a thorough reorganization of the
musculature. Most larvae have acquired an elaborate
system of special muscles for their own use because they
have adopted a wormlike mode of progression. On the
other hand, the adults have need of certain muscles, par-
ticularly those of the wings, which would be only an en-
cumbrance toa larva. Consequently, muscles needed only
by the adult are suppressed in the larval stage, and the
special muscles of the larva must be cleared away during
the pupal stage. The metamorphosis in the muscle sys-
tem, therefore, varies much in different insects according
to the mechanical difference between the larva and the
adult.
The purely larval muscles that are to be discarded when
[ 300 J
THe CATERPILLAR AND THE MOTH
their purpose has been accomplished go into a state of dis-
solution during the pupal period. The débris of their
tissues is thrown into the blood, from which it is later ab-
sorbed as nutriment by the newly forming organs. The
caterpillar has a very elaborate system of muscles forming
a complicated network of fibers against the inner surface
of the body wall, some running longitudinally, others
transversely, and still others obliquely. Most of the
transverse and oblique fibers are not retained in the moth,
and 1f specimens of those muscles are examined during the
early part of the pupal period they are seen to have a weak
and abnormal appearance; the structure typical of healthy
muscle tissue is obscure or indistinctly evident in them,
and in places they are covered with groups of free oval
cells. These cells are probably phagocytes.
A phagocyte is a blood corpuscle that destroys foreign
proteid bodies in the blood, or any unhealthy tissue of the
body. It is not probable anes the insect phagocytes are
the active cause of the destruction of the larval tissues, but
they do engulf and digest particles of the degenerating
tissues. They are present in large numbers in some insects
during metamorphosis, and are scarce or lacking in others.
The decadent state of the larval tissues that have passed
their period of activity lays them open to the attack of
the phagocytes, but these tissues will go into dissolution
by the solvent powers of the blood alone. Active, healthy
tissues are always immune from phagocytes.
Some of the larval muscles may go over intact to the
adult stage, and others may require only a remodeling
or an addition of fibers to make them serviceable for the
purposes of the adult. The adult muscles that are com-
pletely suppressed during the larval stage appear to be
generated anew during the pupal stage. There 1s a dif-
ference of opinion among investigators as to how the new
muscles are developed, but it is probable that they take
their origin from the same tissues that built up the larval
muscles.
[ 301 |
INSEGES
The development of the internal organs proceeds with-
out interruption from the beginning of the propupal period
until the adult organs are completed at the end of the pupal
stage. The external parts, however, do not make a con-
tinuous growth. After reaching a certain stage of de-
velopment, the form of the body wall and of the append-
ages is fixed by the hardening of the new cuticula on
their outer surfaces. In this stage, therefore, they must
remain, and the half-mature form attained is that char-
acteristic of the pupa. The final development of the body
wall and the appendages of the adult is accomplished by
a second separation of the epidermis from the cuticula,
which allows the cellular layers, now protected by the
pupal cuticula, to go through a second period of growth
during the pupal stage. This pupal period of growth at
last results in the perfection of the external characters
of the adult, which are in turn fixed by the formation of
the adult cuticula. In the meantime, the new muscles
that are to be retained have become anchored at their
ends into the new cuticula, and the mechanism of the
adult insect is ready for action. The perfect insect,
cramped within the pupal shell, has now only to await
the proper time for its emergence.
Through the whole period of metamorphosis, the insect
must depend on its internal resources for food materials.
Oxygen it can obtain by the usual method, for its respira-
tory system remains functional; but in the matter of
food it is in a state of complete blockade. The pupa has
two sources of nourishment: first, the food reserves stored
in the cells of the fat-body; second, the materials resulting
from the breaking down of the larval tissues, which are
scattered in the blood and eventually absorbed.
The fat cells, at the beginning of metamorphosis in some
insects, give up most of their stored fat and glycogen; and
they now become filled with small granules of proteid
matter. The proteid granules are probably elaborated in
the fat cells from the absorbed detritus of the larval
[ 302 ]
ak CAtERPIEPAR AND THE MOTH
organs by means of enzymes produced in the nuclei of the
cells. The fat cells thus take on the function of a stomach,
converting the materials dissolved in the blood into forms
that the growing tissues can assimilate. During this time
the masses of fat tissue that compose the fat-body of the
Fic. 160. Bodies in the blood of a young pupa of the tent caterpillar
a, a free fat cell, containing large oily fat globules, and small proteid granules;
4, ¢, fat cells in dissolution; d, free proteid granules in the blood, and e, fat
globules liberated from the disintegrating fat cells; f, blood corpuscles
larva have broken up into free cells, and these cells,
vacuolated with oil globules and later charged with pro-
teid granules, now fill the blood.
The interior of the moth pupa, or chrysalis, shortly
after the larval skin is shed, contains a thick, yellow,
creamy liquid. In it there may be discovered, however,
the alimentary tract, the nervous system, and the tracheal
tubes, the latter filled with air; but all these parts are so
soft and delicate that they can scarcely be studied by
ordinary methods of dissection.
The creamy pulp of the pupa’s body, when examined
under the microscope, is seen to consist of a clear, pale,
amber-yellowish liquid full of small bodies of various
sizes (Fig. 160), which give it the opaque appearance and
thick consistency. The liquid medium is the blood, or
body lymph. The largest bodies in it are free fat cells ee
smaller ones are probably blood corpuscles (f); and the
[ 303 |
INSECTS
finest matter consists of great quantities of minute grains
(d) floating about separately or adhering in irregular
masses. Besides these elements there are many droplets
of oil (e), recognizable by their smooth spherical outlines
and golden-brown color. The fat cells are mostly irregu-
larly ovoid or elliptical in shape; their protoplasm i is filled
with large and small o1l globules, and contains also masses
of fine granules like those floating free in the blood. These
granules are the protoplasmic substances formed within the
fat cells. Many of the cells have irregular or broken out-
lines (6, c), as if their outer walls had been partly dis-
solved, and the contents of such cells appear to be escap-
ing from them. In fact, many are clearly in a state of dis-
solution, discharging both their oil globules and their pro-
teid elec into the blood; and it 1s clear that the
similar matter scattered so profusely through the blood
liquid has come from fat cells that have already disin-
tegrated. All these materials will gradually be consumed
in the building of the tissues of the adult, the organs of
which are now in process of formation.
In Chapter IV we learned that every animal consists of
a body, or soma, formed of cells that are differentiated
from the germ cells usually at an early stage of develop-
ment. The function of the soma is to give the germ
cells the best chance of accomplishing their purpose. An
insect that goes through two active forms during its life, a
larval and an adult form, differs from other animals in
having a double soma. The entire organism, of course, is
not double, for, as we have just seen in the study of the
caterpillar, many of the more vital organs are continuous
from the larva to the adult; but there is a group of organs
which, after reaching a definite form of development in
the larval stage, at the end of this stage virtually die and
go into dissolution, while a new set of tissues develops
into new organs or into new tissues replacing those that
have been lost. The groups of somatic cells that-form the
tissues and organs that undergo a metamorphosis, there-
[ 304 ]
hh CATERPILLAR AND THE MOTH
fore, are differentiated in the embryo into two sets of cells,
one set of which will form the special organs of the larva,
while those of the other will remain dormant during the
larval life to form the adult organs when the larval cells
have completed their functions. The cells of the second
set carry the hereditary influences that will cause them to
develop into the original, or ancestral, form of the species;
the cells of the first set produce the temporary larval
form, which may retain certain primitive characters from
the embryonic stage, but which does not represent an
ancestral form in the evolution of the species.
An extreme case of anything is always more easily
understood when we can trace it back to something simple,
or link it up with something familiar. The metamorphosis
of insects appears to be one of the great mysteries of
nature, but reduced to its simplest terms it becomes only
an exaggerated case of a temporary growth in certain
groups of cells to form something of use to the young,
which disappears by resorption when the occasion for its
use is past. Innumerable simple cases of this kind might
be cited from insects; but there is a familiar case of well-
developed metamorphosis even in our own growth,
namely, the temporary development of the milk teeth and
their later substitution by the adult teeth. If a similar
process of double growth from the somatic cells had been
carried to other organs, we ourselves should have a meta-
morphosis entirely comparable with that of insects.
THe Morty
For three weeks or a little longer the processes of re-
construction go on within the pupa of the tent caterpillar,
and then the creature that was a caterpillar breaks through
its coverings and appears in the form and costume of a
moth (Fig. 159 J). The pupal shell splits open on the
forward part of the back (E) to allow the moth to emerge,
but the latter then only finds itself face to face with the
wall of the cocoon. It has left behind its cutting instru-
[ 305 ]
INSECTS
ments, the mandibles, with its discarded overalls; but it
has turned chemist and needs no tools. The glands that
furnished the silk for the larva have shrunken in size and
have taken on a new function; they now secrete a clear
liquid that oozes out of the mouth of the moth and acts
as a solvent on the adhesive surfaces of the cocoon threads.
The strands thus moistened are soon loosened from one
another sufficiently to allow the moth to poke its head
through the cocoon wall and force a hole large enough to
permit of its escape. The liquid from the mouth of the
moth turns the silk of the cocoon brown, and the lips of
the emergence hole are always stained the same color—
evidence that it is this liquid that softens the silk—and
the frayed edges of the hole left in the cocoon of the tent
caterpillar show many loose ends of threads broken by
the moth in its exit.
The most conspicuous features of the moth (Fig. 161)
are its furry covering of hairlike scales and its wings.
The wings are short when the insect first emerges from
its cocoon (Fig. 159 J), but they quickly expand to normal
length and are then folded over the back (Fig. 161 A).
The colors of the moths of the tent caterpillar are various
shades of reddish-brown with two pale bands obliquely
crossing the wings (Plate 14 G, H). The female moth
(Plate 14 H, Fig. 161 B) is somewhat larger than the male,
her body being a little over three-fourths of an inch in
length, and the expanded wings one and three-fourths
inches across.
The tent caterpillars perform so thoroughly their duty
of eating that the moths have little need of more food.
Consequently the moths are not encumbered with imple-
ments of feeding. The mandibles, which were such large
and important organs in the caterpillar (Fig. 152, Md)
but which shrank to a rudimentary condition in the pro-
pupa (Fig. 19 H, Md), are gone entirely in the moth
(Fig. 162). The maxillae, which were fairly long lobes
in the propupa (Fig. 159 H, Mx), have likewise been
[ 306 ]
THe CATERPIELAR-AND THE MOTH
reduced to mere rudiments in the adult, where they appear
as two insignificant though movable knobs (Fig. 162,
Mx). The median part of the labium has been reduced
to almost nothing in the moth; but the labial palpi
(LéP/p) are long and three-segmented, and when normally
covered with hairlike scales they form two conspicuous
feathery brushes that project in front of the face.
The mouth parts of the tent caterpillar moth are not
typical of these organs of moths and butterflies in gen-
Fie. 161. Moths of the tent caterpillar, Afalacosoma americana. (A little greater
than natural size)
eral, for most of these insects are provided with a long
proboscis by means of which they are able to feed on
liquids. Everyone is familiar with the large humming-
bird moths, or hawk moths, that are to be seen on summer
evenings as they dart foun flower to flower, thrusting
into each corolla a long tube uncoiled from heneath the
head; and we have all seen the sunlight-loving butterflies
carelessly flitting over the flower beds, alighting here and
there on attractive blooms to sip the sweet liquid from
the nectar cups.
Moths and_ butterflies carry the proboscis tightly
coiled, like a tiny watch spring (Fig. 163 A, Prd), be-
neath the head and just behind the mouth. It can be
unwound and extended (B, Prd) whenever the insect
wants to extract a drop of nectar from the depths of a
[ 307 |
INSECTS
Fic. 162. Facial view of the head of
the tent caterpillar moth, with cover-
ing scales removed, and antennae cut
off near their bases
Ant, base of antenna; EZ, compound
eye; Ld, labium; L4P/p, labial palpus;
Lm, labrum; Mth, mouth; Mx, maxilla
flower corolla, or when it
would merely take a drink
of water or other liquid.
The proboscis consists of the
greatly lengthened maxillae
firmly attached to each other
by dovetailed grooves and
ridges. The inner face of
each maxilla is hollowed in
the form of a groove run-
ning its entire length, and
the two grooves apposed
between the united maxillae
are converted into a central
channel of the proboscis.
The two blades of the pro-
boscis spring from the sides
of the mouth. The first
part of the alimentary canal just back of the mouth 1s
transformed into a bulblike sucking apparatus. The
Fic. 163. Head and mouth parts of the peach borer moth
A, side view. B, three-quarter facial view. zt, basal part of antenna; EZ,
compound eye; LéP/p, labial palpus; O, ocellus; Pr, proboscis
| 308 |
THE CATERPILLAR AND THE MOTH
upper wall of the structure is ordinarily collapsed into
the cavity of the bulb, but it 1s capable of being lifted by
strong muscles inserted upon it from the walls of the
head. The alternate opening and closing of the bulb
sucks the liquid food up through the tube of the pro-
boscis and forces it back into the gullet. The moths and
butterflies are thus sucking insects, as are the aphids and
cicadas, but they are not provided with piercing organs,
though some species have a rasp at the end of the pro-
boscis which is said to enable them to obtain juices from
soft-skinned fruits.
With the tent caterpillar, it is interesting to note, the
maxillae are much longer in the pupa (Fig. 1§9 I, Mx)
than they are in either the caterpillar or the adult moth
(Fig. 162, Mx), as if nature had intended the tent cater-
pillar moth to have a proboscis like that of other moths,
but had then changed her mind. The real meaning of
this is that the moths of the present-day tent cater-
pillars are descended from ancestors that had a functional
proboscis in the adult stage like that of other moths, and
that the reduction of the proboscis of the modern moths
has taken place in times so recent that the organ has not
yet been suppressed to the same degree in the pupa.
The alimentary tract of the tent caterpillar moth 1s
very different from that of the caterpillar. In the cater-
pillar, the organ consists of three principal parts (Fig.
164 A), the first comprising the oesophagus (Qe) and the
crop (Cr), the second being the stomach, or ventriculus
(Vent), and the third the intestine (Jz). In an adult moth
that is almost mature, but which is still inside the pupal
shell (B), the oesophagus has become a long narrow tube
(Oe) at the rear end of which the crop forms a small sac
(Cr) projecting upward, which may contain a bubble of
gas. The stomach has contracted to a pear-shaped bag
with very thin transparent walls, and is usually filled
with a dark-brown liquid. The intestine has changed
radically in form, for it now consists of a long, slender,
[ 309 |
INSECTS
tubular part, the small intestine (Jt), and of a great
terminal receptacle, the rectum (Rect), filled with a mass
of soft orange-colored matter. In the fully-matured insect
(C), after it has escaped from the cocoon, still further
Cr Vent Int
Fic. 164. Transformation in the form of the alimentary canal
of the tent caterpillar from the larva to the adult moth
A, alimentary canal of the caterpillar. B, the same of the pupa.
C, the same of the moth
Cr, crop; Int, intestine; Ma/, Malpighian tubules (not shown full
length); Oe, oesophagus; Rect, rectum; SJnt, small intestine; Vent,
ventriculus
alterations have taken place. The crop sac (Cr) is now
greatly distended into a spherical vesicle tensely filled
with gas—air, probably, that the moth has swallowed,
perhaps to aid it in breaking the pupal shell, for there are
sometimes small bubbles also in the tubular oesophagus.
[ 310]
it CATERPILUAR SAND THE MOTH
The stomach is contracted to a mere remnant of its
former size (A, Vent), and its walls are thrown into thick
corrugations. The intestine (SJvt) is about the same as
in the earlier stage of the moth (B).
Since the moth of the tent caterpillar probably eats
nothing, it has little use for a stomach. The intestine,
however, must serve as an outlet for the Malpighian
tubules (Ma/), since the latter remain functional through
the pupal stage. The secretion of the tubules contains
great numbers of minute spherical crystals, which accumu-
late in the rectal sac (Rect) where they form the orange-
colored mass contained in this organ and discharged as
soon as the moth leaves the cocoon.
Most of the male moths of the tent caterpillar emerge
from the cocoons several days in advance of the females.
At this time their bodies contain an abundance of fat
which fills the cells of the fat tissue as droplets of oil.
This fat is probably an energy-forming reserve which the
male moth inherits from the caterpillar, for the internal
reproductive organs are not yet fully developed and do
not become functional until about the time the females
are out of their cocoons.
The bodies of the female tent caterpillar moths, on the
other hand, contain little or no fat tissue; but each female
is fully matured when she emerges from the cocoon, and
her ovaries are full of ripe eggs ready to be laid as soon as
the fertilizing element is received from the male (Fig. 165,
Ov). The spermatozoa will be stored in a special recep-
tacle, the spermatheca (Spm), which is connected with the
exit duct of the ovaries (/g) by a short tube. Each egg
is then fertilized as it issues from the oviduct. The ma-
terial that will form the covering of the eggs when laid 1s
a clear, brown liquid contained in two great sacs (Fig.
165, Res) that open into the end of the median oviduct
(Vg). Each sac is the reservoir of a long tubular gland
(C/G/). The liquid must be somehow mixed with air
when it is discharged over the eggs to give the egg covering
[311]
INSECTS
its frothy texture. It soon sets into a jellylike substance,
then becomes firm and elastic like soft rubber, and finally
turns dry and brittle.
The date of the egg laying depends on the latitude of
the region the moths inhabit, varying from the middle
th OV
Ov... \ \ < A Ov Q.
Res
PDO
/ / é ‘ \
Spm Bepx Dov Ayige Joy! Aussi
Fic. 165. The female reproductive organs of the moth of the tent caterpillar,
as seen from the left side
a, external opening of the bursa copulatrix; 47, anus; 4, opening of the vagina;
Bcpx, bursa copulatrix; C/G/, colleterial glands, which form the substance of the
egg covering; Dov, duct of the left ovary; Ov, left ovary, full of ripe eggs; ov, ov,
upper ends of the ovarian tu bules; Rect, rectum; Kes, reservoirs of the colleterial
glands (C/G/); Spm, spermatheca, a sac for the storage of the spermatozoa; #/,
terminal strand of the ovary; Vg, vagina
of May in the southern States to the end of June or later
in the north. While the eggs will not hatch until the fol-
lowing spring, they nevertheless begin to develop at
once, and within six weeks young caterpillars may be
found fully formed within them (Fig. 166 B). Each little
caterpillar has its head against the top of the shell and its
body bent U-shaped, with the tail end turned a little to
one side. The long hairs of the body are all turned for-
ward and form a thin cushion about the poor creature,
which for crimes yet uncommitted is sentenced to eight
[312]
THE CATERPILLAR AND THE. MOTH
months’ solitary confinement in this most inhuman posi-
tion. Yet, if artificially liberated, the prisoner takes
no advantage of the freedom offered. Though it can
move a little, it remains coiled (A) and will fold up again
if forcibly straightened, thus asserting that it is more com-
fortable than it looks.
It is surprising that these infant caterpillars can remain
inactive in their eggshells all through the summer, when
the warmth spurs the vitality of other species and speeds
them up to their most rapid growth and development.
External conditions
in general appear to
have much to do with
regulating the lives of
insects, and if the tent
caterpillars in_ their
eggs seem to give
proof that the crea-
tures are not entirely
the slaves of environ-
Fic. 166. The young tent caterpillar fully
formed within the egg by the middle of
ment, the truth is summer
probably that all in- A, the young caterpillar removed from the
: egg. B, the caterpillar in natural position
sects are not gov- Ain ine eas
erned by the same
conditions. We have seen that some of the grasshoppers
and some of the aphids will not complete their develop-
ment except after being subjected to freezing tempera-
tures, and so it probably is with the tent caterpillars—
it is not warmth, but a period of cold that furnishes the
condition necessary to the final completion of their de-
velopment. Whatever may,.be the secret source of their
patience, however, the young tent caterpillars will bide
their time through all the heat of summer, the cold of
winter, and not till the buds of the cherry or apple leaves
are ready to open the following spring will they awake
and gnaw through the inclosing shells against which their
faces have been pressing all this while.
[313]
CHAPTERS
MOSQUITOES AND FLIES
THOUGHTFUL persons are much given to pondering on
what is to be the outcome of our present age of intensive
mechanical development. Thinking, the writer holds, 1s
all right as a means of diverting the mind from other
things, but those who make a practice or a profession of
it should follow the example of that famous thinker of
Rodin’s, who has consistently preserved a most com-
mendable silence as to the nature of his thoughts. We
can all admire thinking in the abstract; it is the expression
of thoughts that disturbs us. So it is that we are troubled
when the philosophers. warn us that the development of
mechanical proficiency is not synonymous with advance-
ment of true civilization. However, it is not for an
entomologist to enter into a discussion of such matters,
because an observer untrained in the study of human
affairs is as likely as not to get the impression that only a
very small percentage of the present human population
of the world is devoted to efficiency in things mechanical
or otherwise.
There is no better piece of advice for general observance
than that which admonishes the cobbler to stick to his
last, and the maxim certainly implies that the entomolo-
gist should confine himself to his insects. However, we
can not help but remark how often parallelisms are to be
discovered between things in the insect world and affairs
in the human world. So, now, when we look to the insects
for evidence of the effect of mechanical perfection, we
observe with somewhat of a shock that those very insect
[314]
MOSQUITOES AND FLIES
species which unquestionably have gone farthest along
the road of mechanical efficiency have produced little else
commendable. In this class we would place the mos-
quitoes and the flies; and who will say that either mosqui-
toes or flies have added anything to the comfort or enjoy-
ment of the other creatures of the world?
Reviewing briefly the esthetic contributions of the
major groups of insects, we find that the grasshoppers
have produced a tribe of musicians; the sucking bugs have
evolved the cicada; the beetles have given us the scarab,
the glow-worm, and the firefly; the moths and butterflies
have enriched the world with elegance and beauty; to the
order of the wasps we are indebted for the honeybee.
But, as for the flies, they have generated only a great
multitude of flies, amongst which are included some of
our most obnoxious insect pests.
However, in nature study we do not criticize; we derive
our satisfaction from merely knowing things as they are.
If our subject 1 is mosquitoes and flies, we look for that
which is of interest in the lives and structure of these
insects.
FLies IN GENERAL
The mosquitoes and the flies belong to tne same ento-
mological order. That which distinguishes them ae
pally as an order of insects is the possession of only one
pair of wings (Fig. 167). Entomologists, for this reason,
call the mosquitoes and flies and all related insects the
Diptera, a word that signifies by its Greek components
‘two wings.” Since nearly all other winged insects have
four wings, it is most probable that the ancestors of the
winged insects, including the Diptera, had likewise two
pairs of wings. The Diptera, therefore, are insects that
have become specialized primarily during their evolution
by the /oss of one pair of wings.
We shall now proceed to show that the evolution of a
two-winged condition from one of four wings has been a
[315 ]
INSECES
progress toward greater efficiency in the mechanism of
flight, and that the acme in this line has been attained by
the flies and mosquitoes. The truth of this contention
will become apparent when we compare the relative
development of the wings and the manner or effective-
ness of flight in the several principal orders of insects.
Fic. 167. A robber fly, showing the typical structure of any
member of the order Diptera
The flies are two-winged insects, the hind wings being reduced
to a pair of knobbed stalks, the halteres (H/)
It is most probable that when insects first acquired
wings the two pairs were alike in both size and form.
The termites (Fig. 168 A) afford a good example of in-
sects in which the two pairs of wings are still almost
identical. Though the termites are poor flyers, their weak-
ness of flight is not necessarily to be attributed to the
form of the wings, because their wing muscles are partially
degenerate. The dragonflies (Fig. 58) are particularly
strong flyers, and with them the two pairs of wings are
but little different in size and form; but the dragonflies
[ 316 |
MOSQUITOES AND FLIES
are provided with sets of highly developed wing muscles
which are much more effective than those of other insects.
From these examples, therefore, we can not well judge
of the mechanical efficiency of two pairs of equal wings
moved by the equipment of muscles possessed by most
Fic. 168. Evolution of the wings of insects
A, wings of a termite, approximately the same in size and shape. B, wings
of a katydid, the hind wings are the principal organs of flight. C, wings of
a beetle, the fore wings changed to protective shells, elytra (Z/), covering the
hind wings. D, wings of a hawk moth, united by the spine (f), which is
held in a hook on under surface of fore wing. E, wings of the honeybee,
held together by hooks (4) on edge of hind wing. F, wing of a blowfly,
and the rudimentary hind wing, or halter (H/)
eau
INSECTS
insects; but it is evident that the majority of insects
have found it more advantageous to have the fore and
hind wings different in one way or another.
In the grasshoppers, it was observed (Fig. 63), the hind
wings are expanded into broad membranous fans, while
the fore wings are slenderer and of a leathery texture.
The same is true of the roaches (Fig. aye the katydids
(Fig. 168 B), and the crickets, except in special cases where
the fore wings are enlarged in the male to form musical
organs (Fig. 39). In all these insects the hind wings are
the principal organs of flight. When not in use they are
folded over the body beneath the fore wings, which latter
serve then as protective coverings for the more delicate
hind wings. In the beetles (Figs. 137, 1 168 C) the hind
wings are much larger than the fore wings, and, as with
the grasshoppers and their kind, they take the chief part
in the function of flight. The beetles, however, have
carried the idea of converting the fore wings into pro-
tective shields for the hind wings a little farther than have
the grasshoppers; with them the fore wings are usually
hard, shell-like flaps that fit together in a straight line over
the back (Fig. 137A), forming a case that completely
conceals, ordinarily, the membranous hind wings folded
beneath them. Neither the grasshoppers nor the beetles
are swift or particularly efficient flyers, but they appear to
demonstrate that the ordinary insect mechanism of flight
is more effective with one pair of wings than with two.
The butterflies and the moths use both pairs of wings
in flight; but with these insects, it is to be noted, the front
wings are always the larger (Fig. 168 D). The butterflies,
with four broad wings, Aly well in their way and are ca-
pable of long-sustained flight, though they are compara-
tively slow goers. Some of the moths do much better
in the matter of speed, but it is found that the faster flying
species have the fore wings highly developed at the ex-
pense of the hind wings; and that the two wings on each
side, furthermore, are yoked together in such a manner as
[318 ]
ee
MOSQUITOES AND FLIES
to insure their acting as a single wing (D). The moths
clearly show, therefore, as do the grasshoppers and the
beetles, the efficiency of a single pair of flight organs as
opposed to two. The moths, however, have attacked
from a different angle the problem of converting their in-
herited equipment of four wings into a two-wing mecha-
nism—instead of suppressing the flight function in one pair
of wings, they have given a mechanical unity to the two
wings of each side, thus attaining functionally a two-
winged condition.
The wasps (Fig. 133) and bees, likewise, have evolved
a two-winged machine from a four-wing mechanism on the
principle of uniting the two wings on each side. The bees
have adopted a particularly efficient method of securing
the wings to each other, for each hind wing is fastened to
the wing in front of it by a series of small hooklets on its
anterior vein that grasp a marginal thickening on the rear
edge of the front wing (Fig. 168 E). Moreover, the bees
have so highly perfected the unity in the design of the
wings that only on close inspection ‘is it to be seen that
there are actually two wings on each side of the body.
Finally, the flies, including all members of the order
Diptera, have boldly executed the master stroke by com-
pletely eliminating the second pair of wings from the
mechanism of flight. The flies are literally two- winged
insects (Figs. 167, 168 F). Remnants of the hind wings,
it is true, persist in the form of a pair of small stalks,
each with a swelling at the end, projecting from behind
the bases of the wings (Figs. 167, 168 F, H/). These
stalks are known as “‘balancers,” or Aa/teres, and in their
structure they preserve certain features that show them
to be rudiments of wings.
The giving over of the function of flight to the front
pair of wings has necessarily involved a reconstruction in
the entire framework and musculature of the thorax, and a
study of the fly thorax gives a most interesting and in-
structive lesson in the possibilities of adaptive evolution,
[319 ]
INSECTS
showing how a primitive ancestral mechanism may be
entirely remodeled to serve in a new capacity. If the flies
had been specially “created,” and not evolved, their
structure could have been much more directly fitted to
their needs.
It is not only in the matter of wings and the method of
flight that the flies show they are highly evolved insects;
Fic. 169. The black horsefly, Tabanus atratus
A, the entire fly. B, facial view of the head and mouth parts. mt, antenna;
E, E, compound eyes; Lé, labium; Lm, labrum; Md, mandible; Mx, maxilla;
MxP/p, maxillary palpus
they are equally specialized in the structure of their mouth
parts and in their manner of feeding. The flies subsist on
liquid food. Those species that can satisfy their wants
from liquids freely accessible have the mouth parts formed
for sucking only. Unfortunately, however, as we all too
well know, there are many species that demand, and usu-
ally obtain, the fresh blood of mammals, including that
of man, and such species have most efficient organs for
piercing the skin of their victims.
The most familiar examples of flies that “bite” are the
mosquitoes and horseflies. The horseflies (Fig. 169 A),
some of which are called also gadflies and deer flies, belong
to the family Tabanidae. An examination of the head of
[ 320]
MOSQUITOES AND FLIES
the common large black horsefly (Fig. 169 B) will show
the nature of the feeding organs with which these flies are
equipped. Projecting downward from the lower part of
the head are a number of appendages; these are the mouth
parts. They correspond in number and in relative posi-
tion with the mouth appendages of the grasshopper (Fig.
66), but they differ from the latter very much in form
because they are adapted to quite a different manner of
feeding. The horsefly does not truly bite; it pierces the
skin of its victim and sucks up the exuding blood.
By spreading apart the various pieces that compose the
group of mouth parts of the horsefly, it will be seen that
there are nine of them in all. Three are median in posi-
tion, and therefore single, but the remaining six occur in
duplicate on the two sides, forming thus three sets of
paired structures. The large club-shaped pieces, how-
ever, that lie at the sides of the others, are attached at
their bases to the second paired organs and constitute a
part of the latter, so that there are really only two sets of
paired organs. The anteriormost single piece is the
labrum (Fig. 169 B, Lm); the first paired organs are the
mandibles (Md); the second are the maxillae (Mx); the
second median piece is the hypopharynx (not seen in
Fig. 169 B); and the large, unpaired, hindmost organ is the
labium (Zé). The lateral club-shaped pieces are the palpi
of the maxillae (MxP/p).
The labrum is a strong, broad appendage projecting
downward from the lower edge of the face (Figs. 169 B,
170 A, Lm). Its extremity is tapering, but the tip is
blunt; its under surface is traversed by a median groove
extending from the tip to the base but closed normally
by the hypopharynx (Fig. 170 D, Hphy), which fits against
the under side of the labrum and converts the groove into
a tube. The upper end of this tube leads directly into the
mouth, a small aperture situated between the base of the
labrum and the base of the hypopharynx and opening into
a large, stiff-walled, bulblike structure (Fig. 170 A, Pmp)
[ 321]
INSECTS
which is the mouth cavity. The anterior wall of the bulb
is ordinarily collapsed, but it can be lifted by a set of strong
muscles (Mc/) arising on the front wall of the head (C/p).
This bulb is the sucking pump of the fly, and it will be
A B
Fic. 170. Mouth parts of a horsefly, Tabanus atratus
A, the labrum (Zm) and mouth pump (Pmp), with dilator muscles
of the pump (Mc/) arising on the clypeal plate (C/p) of the head
wall. The mouth is behind the base of the labrum
B, the left mandible
C, the left maxilla, consisting of a long piercing blade (Zc), and a
large palpus (P/p)
D, the labium (Zé) terminating in the large labella (La), and the
hypopharynx (HpAy) showing the salivary duct (S/D) and its
syringe (Syr), discharging into a channel of the hypopharynx (Hphy)
that opens at the tip of the latter
seen that it is very similar to that of the cicada (Fig. 122,
Pmp). In the fly, however, the liquid food is drawn up to
the mouth through the labro-hypopharyngeal tube instead
of through a channel between the appressed maxillae.
The mandibles of the horsefly (Fig. 170 B, Md) are long,
bladelike appendages, very sharp pointed, thickened on
[ 322]
MOSQUITOES AND FLIES
the outer edges and thin on the knifelike inner edges.
They appear to be cutting organs, for each is articulated
to the lower rim of the head by its expanded base in such
a manner that it can swing sidewise a little but can not be
protruded and retracted as can the corresponding organ
of the cicada. The maxillae (C) are slender stylets, each
supported on a basal plate attached to the head; this plate
carries also the large, two-segmented palpus (P/p). The
maxillae are probably the principal piercing tools of the
horsefly’s mouth-part equipment.
The median hypopharynx (Fig. 170 D, Hphy) is a
tapering blade somewhat hollowed above, normally ap-
pressed, as just observed, against the under surface of the
labrum to form the floor of the food canal. The hypo-
pharynx itself is traversed by a narrow tube which is a
continuation from the salivary duct (S/D). The latter,
however, Just before it enters the base of the hypopharynx,
is enlarged to form an injection syringe (Syr). The
salivary syringe in structure 1s a small replica of the mouth
pump (A, Pmp), and its muscles arise on the back of the
latter. The saliva of the fly is injected into the wound
from the tip of the hypopharynx. By reason of this fact,
the bite of a fly may be the source of infection to the
victim, for it is evident that the injection of saliva affords
a means for the transfer of internal disease parasites from
one animal to another.
Behind all the parts thus far described is the median
labium (Fig. 170 D, Zé), a much larger organ than any of
the others, consisting of a thick basal stalk and two great
terminal lobes (La). The soft, membranous under sur-
faces of the lobes, which are known as the /ade//a, are
marked by the dark lines of many parallel, thick-walled
grooves extending crosswise. These grooves may be
channels for collecting the blood that exudes from the
wound, or they may also distribute the saliva as it issues
from the tip of the hypopharynx between the ends of the
labella. The effect of the saliva of the horsefly on the
[ 323 ]
INSECTS
blood is not known, but the saliva of some flies is said to
prevent coagulation of the blood.
Some of the smaller horseflies will give us an unsolicited
sample of their biting powers, and in shaded places along
roads they often make themselves most vexatious to the
foot traveler just when he would like to sit down and enjoy
a quiet rest. To horses, cattle, and wild mammals, how-
ever, these flies are extremely annoying pests, and, where
abundant, they must make the lives of animals almost
unendurable; for the sole means of protection the latter
have against the painful bites of the flies is a swish of the
tail, which only drives the insects to make a fresh attack
on some other spot.
There is another family of “biting” flies, known as the
robber flies, or Asilidae (Fig. 167), the members of which
attack other insects. They are strong flyers and take their
victims on the wing, even bees falling prey to them. The
robber flies have no mandibles, and the strong, sharp-
pointed hypopharynx appears to be the chief piercing
implement. The saliva of the fly injected into the wound
dissolves the muscles of the victim, and the predigested
solution is then completely sucked out.
As was shown in Chapter VIII, on metamorphosis, ~
whenever the adult form of an insect is highly specialized
for a particular kind of life, it is usually found that the
young is also specialized but in a way of its own to adapt
it to a manner of living quite different from that of its
parent. This principle is particularly true of the flies, for,
if the adult flies are to be regarded as in general the most
highly evolved in structure of all the adult insects, there
can be no doubt that the young fly is the most highly
specialized of all the insect larvae.
The flies belong to that large group of insects which do
not have external wings in the larval stage, but with the
flies the suppression of the body appendages includes also
the legs, so that their larvae are not only wingless but
legless as well (Fig. 171). The legs, however, as the wings,
[ 324 ]
MOSQUITOES AND FLIES
are represented by internal buds, which, when they enter
the period of growth during the early stage of metamor-
phosis, are turned inside out to form the legs of the adult
fly.
The lack of legs gives a cylindrical simplicity of form
to most fly larvae, which not only makes these insects look
like worms, but has caused many of them to live the life of
Fic. 171. Structure of a fly larva, or maggot
An, anus; 4Sp, anterior spiracle; DTra, dorsal tracheal trunk; LTra, lateral
tracheal trunks; mh, mouth hooks; PSp, posterior spiracle
a worm and to adopt the ways of a worm. In compensa-
tion for the loss of legs, the fly larvae are provided with an
intricate system of muscle fibers lying against the inner
surface of the body wall, which enables them to stretch
and contract and to make all manner of contortionistic
twists.
At first thought it seems remarkable that a soft-bodied,
wormlike creature can stretch itself by muscular contrac-
tion. It must be remembered, however, that the body of
the larva is filled with soft tissues, many of which are but
loosely anchored, and that the spaces between the organs
are filled with a body liquid. The creature is, therefore,
capable of performing movements by making use of its
structure as a hydraulic mechanism; a contraction of the
rear part of the body, for example, drives the body liquid
and the soft movable organs forward, and thus extends the
anterior parts of the body. A contraction of the length-
wise muscles then pulls up the rear parts, when the move-
[325 ]
INSECTS
ment of extension may be repeated. In this fashion the
soft, legless larva moves forward; or, by a reversal of the
process when occasion demands, it goes backward.
A special feature in the construction of fly larvae is the
arrangement of their breathing apertures, which 1s cor-
related with the manner of breathing. In most insects, as
we have learned (Fig. 70), there is a row of breathing pores,
or spiracles, along each side of the body, which open into
Fic. 172. Rat-tailed maggots, larvae of the drone fly, which live
submerged in water or mud and breathe at the surface through a
long, tail-like respiratory tube
Upper figure, resting beneath a small floating object; lower,
feeding in mud at the bottom
lateral tracheal trunks. In the fly larva, however, these
spiracles are closed and are not opened for respiration until
the final change of the pupa to the adult.
The fly larva is provided with one or two pairs of
special breathing organs situated at the ends of the body.
Some species have a pair of these organs at each end of the
body (Fig. 171, 4Sp, PSp), and some a pair at the pos-
terior end only. The anterior organs, when present (Fig.
171, 4Sp), consist of perforated lobes on the first body
segment, the pores of which communicate with the an-
terior ends of a pair of large dorsal tracheal trunks (DTra).
The posterior organs (Pp) consist of a pair of spiracles on
the rear end of the body, which open into the posterior
ends of the dorsal tracheae. By means of this respiratory
arrangement, the fly larva can live submerged in water,
[ 326 |
MOSQUITOES AND FLIES
or buried in mud or any other soft medium, so long as it
keeps one end of the body out for breathing.
The rat-tailed maggot (Fig. 172), which is the larva of
a large fly that looks like a drone bee, has taken a special
advantage of its respiratory system; for the rear end of its
body, bearing the posterior spiracles, is drawn out into a
long, slender tube. The creature, which lives in foul water
or in mud, can by this contrivance hide itself beneath a
floating object and breathe through its tail, the tip of
which may come to the surface of the water at a point
some distance away. The end of the tail is provided with
a circlet of radiating hairs surrounding the spiracles,
which keeps the tip of the tail afloat and prevents the
water from entering the breathing apertures.
The great disparity of structure between the larva of a
fly and the adult necessarily involves much reconstruc-
tion during the period of transformation, and probably
the inner processes of metamorphosis are more intensive
in the more highly specialized Diptera than in any other
group of insects.
The pupa of an insect, as we have seen in Chapter VIII
(page 254), is very evidently a preliminary stage of the
adult, the larval characters being usually discarded with
the last molt of the larva. The pupa of most flies, however,
while it has the general structure of the adult fly (Fig.
182 A, F), retains the special respiratory scheme of the
larva and at least a part of the larval breathing organs.
The fact that the larvae breathe through special spiracles
located on the back suggests that the primitive fly larvae
lived in water or in soft mud, and that it was through an
adaptation to such an environment that the lateral
spiracles were closed and the special dorsal spiracles de-
veloped. The retention by many fly pupae of the larval
method of breathing and of at least a part of the larval
respiratory organs, though their habitat would not seem
necessarily to demand it, suggests, furthermore, that the
[ 327]
INSECTS
pupae of the ancestors of such species lived in the same
medium as the larvae...
If our supposition is correct, we may see a reason for the
apparent exception in the flies to the general rule that the
pupa presents the adult structure and discards the pecu-
larly larval characters. The pupae of some flies whose
Fic. 173. Larva (A) and pupa (B) of a horsefly, Tabanus puncti-
fer (about 1% times natural size)
An, anus; H, head; PSp, posterior spiracle; Sp, spiracle
larvae live in the water, however, revert at once to the
adult system of lateral spiracles (Fig. 173 B, Sp). With
such species, the larva comes out of the water just before
pupation time and transforms in some place where
breathing is possible by the ordinary respiratory organs.
This is the general rule with other insects whose larvae
are aquatic.
The order of the Diptera is a large one, and we might
go on indefinitely describing interesting things about flies
in general. Such a course, however, would soon fill a larger
book than this; hence, since we are already in the last
chapter, a more practical plan will be to select for special
consideration a few species that have become closely as-
sociated with the welfare of man or of his domesticated
animals. Such species include the mosquitoes, the house
fly, the blowfly, the stable fly, the tsetse fly, the flesh flies,
and related forms.
[ 328 ]
MOSQUITOES AND FLIES
Mosquitoes
The mosquitoes, perhaps more than any other noxious
insect, impel us to ask the impertinent question, why
pests were made to annoy us. It would be well enough to
answer that they were given as a test of the efficiency of
our science in learning how to control them, if it were not
for the other creatures, the wild animals, whose existence
must be at times a continual torment from the bites of
insects and from the diseases transmitted by them. Such
creatures must endure their tortures without hope of relief,
and there is ample evidence of the suffering that insects
cause them.
In earlier and more primitive days the rainwater barrel
and the town watering trough took the place of the course
in nature study in our present-day schools. While the
lessons of the water barrel and the trough were perhaps
not exact or thoroughly scientific, we at least got our
learning from them at first hand. We all knew then what
“wigglers” and “horsehair snakes’’ were; and we knew
that the former turned into mosquitoes as surely as we
believed that the latter came from horsehairs. Modern
nature study has set us upon the road to more exact
science, but the aquarium can never hold the mysteries
of the old horse trough or the marvels of the rainwater
barrel.
The supposed ancestry of the horsehair snake 1s now an
exploded myth, but the advance of science has unfortu-
nately not altered the fact that wigglers turn into mos-
quitoes, except in so far as the spread of applied sanita-
tion has brought it about that fewer of them than for-
merly succeed in doing so. And now, as we leave the
homely objects of our first acquaintance with “wigglers”’
for the more convenient apparatus of the laboratory, we
will call the creatures mosquito larvae, since that is what
they are.
The rainwater barrel never told us how those wiggling
[ 329 ]
INSECTS
mosquito larvae got into it—that was the charm of the
barrel; we could believe that we stood face to face with the
great mystery of the origin of life. Now, of course, we
understand that it is a very simple matter for a female
Fic. 174. Life stages of a mosquito, Culex quinquefasciatus
A, the adult female. B, head of an adult male. C, a floating egg raft, with
four eggs shown separately and more enlarged. D, a young larva suspended
at the surface of the water. E, full-grown larva. F, the pupa resting against
the surface film of the water
[ 330 ]
MOSQUITOES AND FLIES
mosquito to lay her eggs upon the surface of the water,
and that the larvae come from the eggs.
There are many species of mosquitoes, but, from the
standpoint of human interest, most of them are included
in three groups. First there are the “ordinary” mos-
quitoes, species of the genus Cu/ex or of related genera;
second, the yellow-fever mosquito, 4édes aegypti; and
third, the malaria-carrying mosquitoes, which belong to
the genus Anopheles.
The common Culex mosquitoes (Fig. 174 A) lay their
eggs in small, flat masses (C) that float on the surface of
the water. Each egg stands on end and is stuck close to
its neighbors in such a manner that the entire egg mass
has the form of a miniature raft. Sometimes the eggs
toward the margin of the raft stand a little higher, giving
the mass a hollowed surface that perhaps decreases the
chance of accidental submergence, though the raft 1s
buoyed up from below by a film of air beneath the eggs.
Almost any body of quiet water is acceptable to the
Culex mosquito as a receptacle for her eggs, whether it be
a natural pond, a pool of rainwater, or water standing in
a barrel, a bucket, or a neglected tin can. Each egg raft
contains two or three hundred eggs and sometimes more,
but the largest raft seldom exceeds a fourth of an inch in
longest diameter. The eggs hatch in a very short time,
usually in less than twenty-four hours, though the in-
cubation period may be prolonged in cool weather. The
young mosquito larvae come out of the lower ends of the
eggs, and at once begin an active life in the water.
The body of the young mosquito larva is slender and
the head proportionately large (Fig. 174 D). As the
creature becomes older, however, the thoracic region of
the body swells out until it becomes as large as the head, or
finally a little larger (E). The head bears a pair of lateral
eyes (Fig. 175, 4), a pair of short antennae (4zf), and, on
the ventral surface in front of the mouth, a pair of large
brushes of hairs curved inward (a). From the sides of
[331]
INSECTS
the body segments project laterally groups of long hairs,
some of which are branched in certain species. The rear
end of the body appears to be forked, being divided into an
upper and a lower branch. The
upper branch (c), however, is
really a long tube projecting dor-
sally and backward from the next
to the last segment. The lower
branch is the true terminal seg-
ment of the body and bears the
anal opening of the alimentary
canal at its extremity. On the end
of this segment four long, trans-
parent flaps project laterally (d),
two groups of long hairs are situ-
ated dorsally, and a fan of hairs
ventrally (Fig. 174 E).
The principal characteristic of
the mosquito larva is the speciali-
zation of its respiratory system.
The larva breathes through a
single large aperture situated on
the end of the dorsal tube that
ae oe ofa projects from the next to the last
ulex mosquito larva J s ins
Ae lipnoceHma brdchee Op segment of the body (Fig. 175,
abdomen; dnt, antenna; 6, PSp). This orifice opens by two
eye; c, respiratory tube; d,
terminal shea Eithead. © Unniehaispinacles into two wide
PSp, posterior spiracle; tracheal trunks (Tra) that extend
Th, thorax; Tra, dorsa - : 5
eaeheaieeace forward in the body and give off
branches to all the internal organs.
The mosquito larva, therefore, can breathe only when the
tip of its respiratory tube projects above the surface of the
water, and, though an aquatic creature, 1t can be drowned
by long submergence. Yet the provision for breathing at
the surface has a distinct advantage: it renders the
mosquito larva independent of the aeration of the water
it inhabits, and allows a large number of larvae to thrive
[ 332]
MOSQUITOES AND FLIES
in a small quantity of water, provided the latter contains
sufficient food material.
The tip of the respiratory tube is furnished with five
small lobes arranged like the points of a star about the
central breathing hole. When the larva is below the sur-
face, the points close over the aperture and prevent the
ingress of water into the tracheae; but as soon as the tip
of the tube comes above the surface, its points spread
art. Not only is the breathing aperture thus exposed,
but the larva is enabled to remain indefinitely suspended
from the surface film (Figs. 174 D, 181 B). In this posi-
tion, with its head hanging downward, it feeds from a
current of water swept toward its mouth by the vibration
of the mouth brushes. Particles suspended in the water
are caught on the brushes and then taken into the mouth.
Any kind of organic matter among these particles con-
stitutes the food of the larva. Larvae of Culex mos-
quitoes, however, feed also at the bottom of the water,
where food material may be more abundant.
The body of the mosquito larva has apparently about
the same density as water; when inactive below the sur-
face, some larvae slowly sink, and others rise. But the
mosquito larva is an energetic swimmer and can project
itself in any direction through the water by snapping the
rear half of its body from side to side, which characteristic
performance has given it the popular name of “‘wiggler.”
The larva can also propel itself through the water with
considerable speed without any motion of the body. This
movement is produced by the action of the mouth brushes.
Likewise, while hanging at the top of the water, the larva
can in the same manner swing itself about on its point of
suspension, or glide rapidly across the surface.
The larvae of Culex mosquitoes reach maturity in about
a week after hatching, during the middle of summer; but
the larval period is prolonged during the cooler seasons of
spring and fall. The larva passes through three stages,
and then becomes a pupa.
[333 |
INSECIS
The mosquito pupa (Fig. 174 F) also lives in the water,
but is quite a different looking creature from the larva.
The thorax, the head, the head appendages, the legs, and
the wings are all compressed into a large oval mass from
Fic. 176. Mouth parts of a female mosquito, Fodlotia digitata
A, the head with the proboscis (Pré) in natural position. B, the
mouth parts separated, showing the component pieces of the
proboscis
Ant, antenna; Z, compound eye; Hph/y, hypopharynx; Zé, labium;
Lm, lJabrum; Md, mandibles; Mx, maxillae; MxPlp, Pip, max-
illary palpi; Pré, proboscis
which the slender abdomen hangs downward. The pupa,
owing to air sacs in the thorax, is lighter than water and,
when quiet, it rises to the surface where it floats with the
back of the thorax against the surface film. The pupa has
lost the respiratory tube and the posterior spiracles of the
larva, but has acquired two large, trumpetlike breathing
tubes of its own that arise from the anterior part of the
[ 334]
MOSQUITOES AND FLIES
thorax, the mouths of which open above the water when
the pupa comes in contact with the surface. The pupa, of
course, does not feed, but it is almost as active as the larva,
for it must avoid its enemies. When disturbed it rapidly
swims downward by quick movements of the abdomen,
the extremity of which is provided with two large swim-
ming flaps. The duration of the pupal stage in midsummer
is about two days.
The adult mosquito issues from the pupal skin through a
split in the back of the latter. We now see why the pupa
is made lighter than .
water—it must float
at the surface in order
to allow the adult to
escape into the air.
The full-fledged
mosquito (Fig. 174 A)
has the general fea-
tures of any other --~
two-winged fly, but
It is distinguished
from nearly all other
flies by the presence
of scales on its wings
and on parts of its ’
head, body, and ap-
pendages. The mouth Fic. 177. Aédes atropalpus, male, a mosquito re-
lated to the yellow fever mosquito and similar to
parts of the adult nen peaence
mosquito are of the
piercing and sucking type, and are similar in structure to
those of the horsefly, except that the individual pieces are
longer and slenderer, and together constitute a beak,
or proboscis, extending forward and downward from the
head (Fig. 176 A, Pré). The male and the female mos-
quitoes are readily distinguishable by the character of the
antennae, these organs in the male being large and
feathery (Fig. 174 B), while those of the female are
[335]
INSEGYS
threadlike and provided with comparatively few short
hairs (A). The sexes differ also in the mouth parts, for,
as in the horseflies, the males lack mandibles.
The mouth parts of the mosquito, in the natural posi-
tion, do not appear as separate pieces, as do those of the
horsefly. The various elements, except the palpi, are com-
pressed into a beak that projects forward and downward
from the lower part of the head (Fig. 176 A, Prd). The
length of the beak varies in different kinds OF mosquitoes ;
it Is particularly long in the large South American species
shown in Figure 176.
When the beak of the female mosquito is dissected
(Fig. 176 B), the same equipment of parts is revealed as is
poseeseed by the female horsefly (Fig. 169 B), namely, a
labrum (Lm), two mandibles ( Ma), two maxillae (Mw), a
hypopharynx (Hphy), and a labium (14). It is the labium
that forms most of the visible part of the beak, the other
pieces being concealed within a deep groove in its upper
surface.
The /aérum (Fig. 176 B, Lm) is a long median blade,
concave below, terminating in a hard: sharp point; it is
probably the principal piercing tool of the mosquito’s
outfit. The mandibles of the mosquito (Md) are very
slender, delicate bristles; those of the species figured are
so weak that it would seem they can be of little use to the
insect. The manillae (Mx) are thin, flat organs with
thickened bases, each terminating in a sharp point armed
on its outer edge with a row of backward-pointing, saw-
like teeth which probably serve to keep the mouth
parts fixed in the puncture as the ee labrum is
thrust deeper into the flesh. The pa/pi (MxP/p) arise
from the bases of the maxillae. The Aypopharynx (Hphy)
is a slender blade with a median rib which is traversed by
the channel of the salivary duct. Its upper surface is con-
cave and, in the natural position, is closed against the
concave lower side of the labrum, the two apposed pieces
thus forming between them a tube which leads up to the
[ 336 |
MOSQUITOES AND FLIES
mouth opening. The saliva of the mosquito is injected
into the wound from the tip of the hypopharynx, and the
blood of the victim is sucked up to the mouth through the
labro-hypopharyngeal tube. The labium (Ld) serves
> SESy9
AS
Fic. 178. Mosquito larvae
A, Aédes atropalpus. B, Anopheles punctipennis, the
malaria mosquito larva
c, respiratory tube; d, terminal lobes; e, stellate groups
of hairs that hold the larva at the surface of the water
(fig. 181 A); f, spiracular area; PSp, spiracle
principally as a sheath for the other organs. It ends in
two small lateral lobes, the labella, between which pro-
jects a weak, median tonguelike process. When the mos-
quito pierces its victim the base of the labium bends back-
ward as the other bristlelike members of the group of
mouth parts sink into the wound.
Mosquitoes of both sexes are said to feed on the sap of
[ 337 ]
INSECTS
plants, which they extract by puncturing the plant tissues;
they will also feed on the exuding juices of fruit, or on any
soft vegetable matter. The females, however, are notort-
ous for their propensity for animal blood, and they by no
means limit their quest for this article of food to human
beings. The male mosquitoes, apparently, very rarely
depart from a vegetarian diet. The pain from the bite of
a female mosquito and the subsequent irritation and
swelling prob&bly result from the injection of the secre-
tion from the salivary glands of the insect into the wound.
It is said that the saliva of the mosquito prevents coagula-
tion of the blood.
Because of the short time necessary for the completion
of the life cycle from egg to adult during summer, there
are many generations of mosquitoes from spring to fall.
The winter is passed both in the adult and in the larval
stage. Fertile females may survive cold weather in pro-
tected places; and larvae found in large numbers, frozen
solid in the ice of ponds, have become active on being
thawed out, and capable of development when given a
sufficient degree of warmth.
The yellow-fever mosquito, now known as dédes aegypti
but at the time of the discovery of its relation to yellow
fever generally called Stegomyia fasciata, is similar in its
habits. during the larval and pupal stages to the Culex
mosquitoes. It lays its eggs singly, however, and they
float unattached on the surface of the water. The adult
mosquito may be identified by its decorative markings.
On the back of the thorax is a lyrelike design in white ona
black ground; the joints of the legs are ringed with white;
the black abdomen is conspicuously cross-banded en
white on the basal half of each segment. The male has
large plumose antennae and long maxillary palpi. The
female has a strong beak, but small palpi, and her an-
tennae are of the short- Kenaee form usual with female
mosquitoes. The species of 4édes shown in Figure 177
much resembles the yellow-fever mosquito, but it is a
[ 338 ]
MOSQUITOES AND FLIES
more northern one common about Washington, D. C.,
where it breeds in rock pools along the Potomac River.
The larva of Aédes (Fig. 178 A) resembles a Culex larva,
but it feeds more habitually at the bottom of the water
and may spend long periods below without coming to the
Fic. 179. Mosquito pupae in natural position resting against the under
surface of the water
A, dédes atropalpus. B, Anopheles punctipennis
surface for air. In its search for food it noses about in the
refuse at the bottom of the water and voraciously con-
sumes dead insects and small crustaceans. The pupa like-
wise (Fig. 179 A) does not differ materially from a Culex
pupa. When quiet it floats at the surface of the water
with the entire back of its thorax against the surface film
and the tips of its breathing tubes above the surface.
Probably no mosquito pupa hangs suspended from its
respiratory tubes in the manner in which the pupae of
various species are often figured.
Aédes aegypti is the only known natural carrier of the
virus of yellow fever from one person to another. The
disease can be taken only from the bite of a mosquito of
this species that has become infected by previous feeding
on the blood of a yellow-fever patient. The organism
that produces yellow fever is perhaps not yet definitely
known, though strong evidence has been adduced to show
[ 339 ]
[INSECTS
that it is one of the minute, non-filterable organisms
called spirochetes. The virus will not develop in the
mosquitoes at a temperature below 68° F., and dédes
aegypti will not breed
in latitudes much be-
yond the _ possible
range of yellow fever.
Yellow fever, there-
fore, 1s a disease ordi-
narily confined to the
tropics and warmer
parts of the temper-
abel, Zones. Sedson=
al outbreaks of it
that have occurred in
northern cities have
been caused probably
by local infestations
of infected mosqui-
toes brought in on
Fic. 180. The female malaria mosquito, ships from poniihe
Anopheles punctipennis southern port.
The malaria mos-
quitoes belong to the genus dzopheles, a genus repre-
sented by species in most temperate and tropical regions
of the world, which are prevalent wherever malaria oc-
curs. Our most common malaria species is Anopheles
punctipennis (Fig. 180), characterized by a pair of dull
white spots on the edges of the wings. The Anopheles
females lay their eggs singly on the surface of the water,
where they float, each buoyed up by an air jacket about
its middle.
The larvae of Anopheles (Fig. 178 B) differ conspicu-
ously from those of Culex and Aédes both in structure and
habits. Instead of a respiratory tube projecting from near
the end of the body, as in Culex (Figs. 174 E, 175), there
is a concave disc (Fig. 178 B, f) on the back of the next to
[ 340 |
MOSQUITOES AND FLIES
the last segment, in which the posterior spiracles (P. Sp)
are located. The larva floats in a horizontal Grae just
below the surface film of the water (Fig. 181 A), from
which it is suspended by a series of floats (Fig. 178 B, e)
consisting of starlike groups of short hairs arranged in
pairs along the back. The spreading tips of the hairs pro-
Fic. 181. Feeding positions of Anopheles and Culex mosquito larvae
A, Anopheles larva suspended horizontally beneath the surface film, and feeding
at the surface with its head inverted. B, Culex larva hanging from the respira-
tory tube
ject slightly above the water surface and keep the larva
afloat. In the floating position, the respiratory disc
breaks through the surface film, and its raised edges leave
a dry area surrounding the spiracles. The long hairs that
project from the sides of the thorax and the first three
body segments are mostly pee and plumose.
The Anopheles larva (Fig. 1 A) feeds habitually at
the top of the water. When Tee it shoots rapidly
across the surface in any direction, but goes downward
reluctantly. In order to feed in its horizontal position,
it turns its head completely upside down and with its
mouth brushes creates a surface current toward its mouth.
The pupa of Anopheles (Fig. 179 B) is not essentially
[341]
INSECES
different from that of Culex or Aédes. Its most distinc-
tive character is in the shape of the respiratory tubes,
which are very broad at the ends.
The parasite of malaria is not a bacterium but a micro-
scopic protozoan animal named Plasmodium. There are
several species or varieties that correspond with the differ-
ent varieties of the disease. The malaria Plasmodium has
a complicated life cycle and is able to complete its life only
when it can spend a part of it in the body of a mosquito
and the other part in some vertebrate animal. In the
human body the malaria parasites live in the red corpus-
cles of the blood. Here they multiply by asexual repro-
duction, producing for a while many other asexual gener-
ations. Eventually, however, certain individuals are
formed that, if taken into the stomach of an Anopheles
mosquito, develop there into males and females. In the
stomach of the mosquito, these sexual individuals unite
in pairs, and the resulting zygofes, as they are called,
penetrate into the cells of the stomach wall. Here they
live for a while and multiply into a great number of small
spindle-shaped creatures, which go through the stomach
wall into the body cavity of the mosquito and at last col-
lect in the salivary glands. If now the mosquito, with its
salivary glands full of the Plasmodium parasites in this
stage, bites some other animal, the parasites are almost
sure to be injected into the wound with the saliva. If
they are not at once destroyed by the white blood cor-
puscles, they will quickly enter the red blood corpuscles,
and the victim will soon show symptoms of malaria.
Tue House Fiy anp Some or Irs RELATIONS
Our familiar domestic pest, the house fly, may be taken
as the type of a large group of flies, and in particular of
those belonging to the family Muscidae, which is named
from its best known member, Musca domestica, the house
fly—musca being the Latin er for fly.
The house fly (Fig. 182 A), though ee a domes-
[342]
MOSQUITOES AND FLIES
tic pest to people that live indoors, is intimately associated
with the stable. Its favorite breeding place is the manure
pile. Here the female fly lays her eggs (B), and here the
larvae, or maggots (C), live until they are ready for trans-
formation. It is estimated that fully ninety-five per
cent of our house flies have been bred in horse manure.
A few may come from garbage cans, or from heaps of
vegetable refuse, but such sources of fly infestation are
comparatively unimportant. Measures of fly control are
directed chiefly to preventing the access of flies to stable
manure and the destruction of maggots living in it.
The eggs of the house fly (Fig. 182 B) are small, white,
elongate-oval objects, about one twenty-fifth of an inch
in length, each slightly curved on one side and concave on
the other. The female fly begins to lay eggs in about ten
days after having transformed to the adult form, and she
deposits from 75 to 150 eggs at a single laying. She re-
peats the laying, however, at intervals during her short
productive period of about twenty days, and in all may
deposit over 2,000 eggs. Each egg hatches in twenty-four
hours or less.
The larva of the house fly, in common with that of many
other related flies, is a particularly wormlike creature, and
is commonly called a maggot (Fig. 182 D). Its slender
white body is segmented, but, in external appearance, it
is legless and headless. On a flat area at the rear end of
the body are located two large spiracles (PS), which
the novice might mistake for eyes. The tapering end of
the body is the head end, but the true head of the maggot
is withdrawn entirely into the body. From the aperture
where the head has disappeared, which serves the maggot
as a mouth, two clawlike hooks project (mh), and these
hooks are both j jaws and grasping organs to the maggot.
The larva sheds its skin twice during the active part of its
life, which is very short, usually only two or three weeks.
Then it crawls off to a secluded place, generally in the earth
beneath its manure pile, where it enters a resting condi-
[343 ]
INSECTS
tion. Its skin now hardens and contracts until the
creature takes on the form of a small, hard-shelled, oval
capsule, called a puparium (Fig. 182 E).
Fic. 182. The house fly, Musca domestica
A, the adult fly (514 times natural size). B, the house fly egg (greatly magnified).
C, larvae, or maggots, in manure. D, a larva (more enlarged). E, the puparium,
or, hardened larval skin which becomes a case in which the larva changes to a
pupa. F, the pupa
| 344 |
MOSQUITOES AND BETES
Within the puparium, the larva sheds another skin, and
then transforms to the pupa. The pupa (Fig. 182 F) 1s
thus protected during its transformation to the adult by
the puparial skin of the larva, which serves in place of a
cocoon. When the adult is fully formed, it pushes off a
circular cap from the anterior end of its case, and the fly
emerges. The length of the entire cycle from egg to adult
varies according to temperature conditions, but it 1s
usually from twelve to fourteen days. The adult flies are
short-lived in summer, thirty days, or not more than two
months, being their usual span of life. In cooler weather,
however, when their activities are suppressed, they live
longer, and a few survive the winter in protected places.
One of the essential differences between flies of the
house fly type and the mosquitoes and horseflies is in the
structure of the mouth parts. The house fly lacks mandi-
bles and maxillae, but it retains the median members of
the normal group of mouth-part pieces, which are the
labrum, the hypopharynx, and the labium. These parts
are combined to form a sucking proboscis that 1s ordi-
narily folded beneath the head, but which is extended
downward when in use (Fig. 183 A, Pré).
The labium (Fig. 183 B, Ld) is the principal component
of the proboscis of the house fly, and its terminal lobes, or
labella (Za), are particularly well developed. From the
base of the labium there projects forward a pair of palps
(P/p), which are probably the palpi of the maxillae,
though those organs are otherwise lacking. The anterior
surface of the labium is deeply concave, but its trough-
like hollow is closed by the labrum (Lm). Against the
labial wall of the inclosed channel lies the hypopharynx
(Hphy). When the lobes of the labium are spread out, the
anterior cleft between them is closed except for a small
central aperture (a). This opening becomes the func-
tional mouth of the fly, though the true mouth is situated,
as in other insects, between the bases of the labrum and
the hypopharynx, and opens into a large sucking pump
[345 |
INSECHS
having the same essential structure as that of the horse-
fly (Fig. 170 A).
The house fly has no piercing organs; it subsists en-
tirely on a liquid diet. The food liquid enters the aper-
ture between the labella, and is drawn up to the true
> Peb
Fic. 183. Head and mouth parts of the house fly
A, lateral view of the head with the proboscis (Pré) extended. Ant,
antenna; £, compound eye; La, labella, terminal lobes of the pro-
boscis; P/p, maxillary palpi (the maxillae are lacking); Pré, pro-
boscis
B, the proboscis of the fly, as seen in three-quarter front view and
from below. The proboscis consists of the thick labium (Ld), ending
in the labellar lobes (La), between which is a small pore (a) leading
into the food canal (FC) of the proboscis. The food canal contains
the hypopharynx (HpAy), and is closed in front by the labrum (Lm)
mouth through the food canal in the labium between the
labrum and the hypopharynx. The fly, however, is not
dependent on natural liquids; it can dissolve soluble sub-
stances, such as sugar, by means of its saliva. The
saliva is ejected from the tip of the hypopharynx, and
probably spreads over the food through the channels of
the labial lobes. These same channels, perhaps, also
collect the food solution and convey it to the Jabellar
aperture.
[ 346 J
MOSQUITOES AND FLIES
During recent years we have become so well educated
concerning the ways of the house fly, its disgusting habits
of promiscuous feeding, now in the garbage can or some-
where worse, and next at our table or on the baby’s face,
and we have learned so much about its menace as a pos-
sible carrier of disease, that it is scarcely necessary to en-
large here upon the fly’s undesirability as a domestic
companion.
The most serious accusation against the house fly 1s
that, owing to the many kinds of places it frequents with-
out regard to sanitary conditions, and to its indiscriminate
feeding habits, there is always a chance of its feet, body,
mouth parts, and alimentary canal being contaminated
with the germs of disease, particularly those of typhoid
fever, tuberculosis, and dysentery. It has been demon-
strated that flies can carry germs about with them which
will grow when given a proper
medium, and likewise that
flies een at large may be
covered with bacteria, a
single fly sometimes being
loaded with millions of them.
The wisdom of sanitary
measures for the protection
of food from contamination
by flies can not, therefore,
be questioned.
There is one form of insect
siete - : /
villainy, however, of which Prb
the house fly is not guilty;
the structure of its mouth Fic. 184. Head of the stable fly,
. - Stomoxys calcitrans
parts clears it of all accusa- ;
‘i itien Ant, antenna; P/p, maxillary pal-
tions of biting. And yet we pus; Prd, proboscis
hear it often asserted by per-
sons of unquestioned veracity that they have been bitten
by house flies. The case is one of mistaken identification
and not of imagination on the part of the plaintiff; the
[ 347 |
INSECTS
insect that inflicts the bite is not the house fly, but another
species closely resembling the common domestic fly in gen-
eral appearance, though a little smaller. If the culprit is
caught, there may be seen projecting from its head a long,
hard, tapering beak (Fig. 184, Prd), an organ quite differ-
ent from any part of the mouth equipment of the true
house fly (Fig. 183). This biting fly 1s, in fact, the stable
fiy, a species known to entomologists as Stomoxys calct-
trans. It belongs to the same family as the house fly, and
while it sometimes comes about houses, it is particularly
a pest of horses and cattle.
The stable fly lives in most parts of the inhabited world.
Both sexes have blood-sucking habits, and probably feed
on any kind of warm-blooded animal, though the species
is most familiar as a frequenter of stables and as a pest
of domestic stock. The stable fly breeds mostly in fer-
menting vegetable matter, the larvae being found prin-
cipally under piles of wet straw, hay, alfalfa, grain, weeds,
or any vegetable refuse.
Cattle are afflicted by another pestiferous fly called
the horn fly, or Haematobia irritans. The species gets its
common name from the fact that it is usually observed
about the bases of the horns of cattle, where great numbers
of individuals often assemble. But the horns of the
animals are merely convenient resting places. Haematobia
is a biting fly like Stomoxys, and, because of its greater
numbers, it often becomes a most serious pest of cattle.
Through irritation and annoyance during feeding, it may
cause loss of flesh in grazing stock, and a reduction of milk
in dairy cows. The horn fly resembles the stable fly, but is
smaller, being about one-half the size of the house fly. It
breeds mostly in fresh manure of cattle dropped in the
fields.
Of all the biting flies there is none to compare with
the tsetse fly of Africa (Fig. 185). Not only is this fly an
intolerable nuisance to men and animals because of the
severity of its bite, but it is a deadly menace by reason of
[348 ]
MOSQUITOES AND FLIES
its being the carrier of the parasite of African sleeping
sickness of man, and that of the related disease called
nagana in horses and cattle.
African sleeping sickness is caused by a protozoan para-
site of the genus Trypanosoma that lives in the blood and
other body liquids. Trypanosomes are active, one-celled
organisms having one end of the body prolonged into a
tail, or flagellum. They are found as parasites in many
vertebrate animals, but most of them do not produce dis-
ease conditions. There are at least three African species,
however, whose presence in the blood of their hosts means
almost certain death. Two cause the sleeping sickness in
man, and the other produces nagana in horses, mules, and
cattle. The two human species have different distribu-
tions and produce each a distinct variety of the disease.
One is confined to the tropical
parts of Africa, the other 1s
more southern. The southern
form of the disease is said to be
much more severe than the
tropical form, claiming its vic-
tims in a matter of months,
while the other may drag along
for years. The sleeping sick- +
ness and nagana trypanosomes
are entirely dependent in nature
on the tsetse flies for their
means of transport from one
person or from one animal to
another. Fic. 185. A tsetse fly, Glossina
Miireveserseity (Hip) 18c) isa PUSH mae (eheet Ave Smee
larger relation of the horn fly
and the stable fly, having the same type of beak and an
insatiable appetite for blood. The tsetse fly genus is
Glossina. There are two species particularly concerned
with the transportation of sleeping sickness, corresponding
with the two species of trypanosomes that cause the two
[349 ]
INSECTS
forms of the disease. One is Glossina palpalis (Fig. 185),
distributor of the tropical variety of the disease; the other
is Glossina morsitans, carrier both of the southern variety
of sleeping sickness and of nagana.
The stable fly, the horn fly, and the tsetse fly, we have
said, belong to the same family as the house fly, namely,
the Muscidae; and yet they appear to have mouth parts of
a very different type. The differences, however, are of a
superficial nature. All the muscid flies, biting and non-
biting, have the same mouth-part pieces, which are the
labrum (Figs. 183 B, 186 C, Lm), the hypopharynx
(Hphy), and the labium (Z4). They lack mandibles and
maxillae, though the maxillary palps (P/p) are retained.
In the biting species, the labium is drawn out into a long,
slender rod (Fig. 186 C, Ld), and its terminal lobes, the
labella (La), are reduced to a pair of small, sharp-edged
plates armed on their inner surfaces with teeth and ridges.
In the natural position, the deflected edges of the labrum
(Fig. 186 B, Lm) are held securely within the hollow of the
upper surface of the labium (L4), the two parts thus in-
closing between them a large food canal (FC) at the bot-
tom of which lies the slender hypopharynx (Hpf/y), con-
taining the exit tube of the salivary duct.
The biting muscids, therefore, have a strong, rigid,
beaklike proboscis formed of the same pieces that com-
pose the sucking proboscis of the house fly (compare
Fig. 183 A with Figs. 184 and 186 A), but the labium 1s so
modified that it becomes an effective piercing organ. When
one of these flies bites, it sinks the entire beak into the flesh
of its victims. The tsetse fly is said to spread its front legs
apart when it alights for the purpose of feeding, and to
insert its beak by several quick downward thrusts of the
head and thorax. The insect then quickly fills itself with
blood, with which it may become so distended that it can
scarcely fly. The bulb at the base of the tsetse fly’s
labium (Fig. 186 C, 4) is no part of the sucking apparatus;
it is merely an enlargement for the accommodation of
[ 350]
MOSQUITOES AND: FLIES
muscles. The true sucking organ lies within the head
(Pmp), and does not differ in structure from that of other
flies.
While our indictment of the flies has applied thus far
only to the insects in the mature form, there are species
which, though entirely innocent of any criminality in their
Fic. 186. Head and mouth parts of the tsetse fly, Glossina
A, lateral view of the head and proboscis (Pré) of Glossina palpalis,
male
B, cross-section of the proboscis of Glossina fusca (from Vogel),
showing the food canal (FC) inclosed by the labrum (Zm) and
labium (Zé), and containing the tubular hypopharynx (HpAy)
through which the saliva is injected into the wound
C, mouth parts of Glossina palpalis, with the parts of the proboscis
separated. 4, basal swelling of the labium; La, the labella, or
terminal lobes of the labium used for cutting into the skin of the
victim; Lé, labium; Lm, labrum; P/p, maxillary palpus (the
maxillae are lacking); Pmp, mouth pump
[351]
INSECTS
adult behavior, are, however, most obnoxious creatures
during their larval stages. The ordinary blowflies, which
are related to the house fly, lay their eggs in the bodies of
dead animals, where the larvae speedily hatch and feed
on the putrefying flesh. Another kind of blowfly deposits
living larvae instead of eggs. These flies may be regarded
as beneficial in that their larvae are scavengers. But some
of their relations appear to have taken a diabolical hint
from their habits, for they make a practice of depositing
their eggs in open wounds, sores, or in the nostrils of living
animals, including man. The larvae burrow into the tis-
sues of the victims and cause extreme annoyance, suffer-
ing, and even death. A notable species of this class of
pests is the screw worm. Infestation by fly larvae, or
maggots, is called myiasis.
Well-known cases of animal myiasis are that of the bot-
fly in horses and of the ox warble in cattle. The flies of
both these species lay their eggs on the outside of the
animals. The young larvae of the botfly are licked off
and swallowed, and then live until full-grown in the
stomach of the host. The young ox-warble larva burrows
into the flesh of its host and lives in the body tissues until
mature, when it bores through the skin on the back of the
afficted beast, drops out, and completes its transforma-
tion in the ground.
Not only animals but plants as well are subject to in-
ternal parasitism by fly larvae. Garden crops are at-
tacked by leaf maggots and root maggots; orchardists in
the northern States have to contend against the apple
maggot, which is a relation of the olive fly of southern
Europe and of the destructive fruit flies of tropical coun-
tries. That notorious scourge of wheat fields, the Hessian
fly, is a second or third cousin of the mosquito, and it is in
its larva form that it makes all the trouble.
The special attention that has been given to pestiferous
flies must make it appear that the Diptera are a most
undesirable order of insects. As a matter of fact, however,
(3524
MOSQUITOES AND FLIES
there are thousands of species of flies that do not affect us
in any injurious way; while, furthermore, there are
species, and many of them, that render us a positive serv-
ice by the fact that their larvae live as parasites in the
bodies of other injurious insects and bring about the de-
struction of large numbers of the latter.
Scientifically, the Diptera are most interesting insects,
because they illustrate more abundantly than do the
members of any other order the steps by which nature has
achieved evolution in animal forms. An entomologist
would say that the Diptera are highly specialized insects;
and as evidence of this statement he would point out that
the flies have developed the mechanical possibilities of
the common insect mechanism to the highest general level
of efficiency attained by any insect and that they have
carried out many lines of special modification, giving a
great variety of new uses for structures originally limited
to one mode of action. But when we say that any animal
has developed to this or that point of perfection, we do not
mean just what we say, for the creature itself has been
the passive subject of influences working upon it or within
it. A fundamental study of biology in the future will
consist of an attempt to discover the forces that bring
about evolution in living things.
[353 ]
INDEX
A
Acrididae, 28
Aédes, adult, 338
larva, 339
pupa, 339
Aédes aegypti, 331, 339, 340
carrier of yellow fever, 339
Aesop and the cicada, 183
Agile meadow grasshopper, 53
Alimentary canal, tog
Amblycorypha oblongifolia, 39
habits, 40
song, 41
Ame collective, 143
American cockroach, 79
Anabrus simplex, 54
Ancient insects, 77
Angular-winged katydids, 41-43
Annual cicadas, 184
song, 184
Anopheles, 331, 340
punctipennis, see Malaria mos-
quitoes
Antennae, 12
Aphids, 152
apple, 157, 162
birth, 164
cornicles, 174
eggs, 157
feeding, 153
garden, I71, 172
hatching, 159-161
mouth parts, 153
parasites, 178
predators, 175
stem mothers, 162
wing production, 164-166
young, 162
Aphis, 153
apple-grain, 170
green apple, 162
rosy apple, 168
Aphis-lion, 176
Arthropoda, 26
Asilidae, 324
Australian cockroach, 79
B
Beetles, blister, 22-25
lady, 175, 230
May, 230
YOUN E2317
Behavior, 126
Black cricket, 60
in New England, 60
rivalry of males, 62
song, 60-63
Black-horned tree cricket, 67
antennal marks, 67
attraction of female by male,
68, 69
song, 68
Blatella germanica, see German
roach
Blood of insects, 112
Blowflies, 352
Botflies, 352
Brain, 117, 118
Broad-winged tree cricket, 65
antennal marks, 67
song, 64
Bush crickets, 69
song, 70
Bush katydids, 38
song, 39
[355]
INDEX
Cc
Camel crickets, 55
Cantharidin, 23
Carboniferous dragonflies, 95
insects, 86, 89, 90
plants, 87, 88
Caterpillar, 262
alimentary canal, 289, 290
celery, 229
jaws, 286
life, 262
nature, 228
silk glands, 287
press, 288
spinneret, 286
spinning of cocoon, 282, 283
structure, 237
tent, 262-293
transformation to moth, 293-305
Caterpillar and moth, 262
Cecropia moth, 228, 229
Cellulose, digestion of, by ter-
mites, 137
Chitin 256
Chloealtis conspersa, 30
musical apparatus, 30
song, 30, 31
Chrysalides, 251
Cicadas, 182
annual, 184
periodical, 184-225
Cicadidae, 182
Circotettix carlingianus, 32
verruculatus, 32
Cockroaches, 79
Collembola, 247
Common meadow grasshopper, 52
song, 53
Coneheads, 50
Conocephalus fasciatus, 54
song, 54
Corn-root aphis, 172
Coulee cricket, 54
Cricket family, 55
Crickets, 55
bush, 69
camel, 55
European, 55
field, 58
foot, 55
mole, 58
musical organs, 56, 57
tree, 63
Croton bug, see German roach
Culex, 331
eggs, 331
food, 337, 338
larva, 331
male and female, 335
mouth parts, 335-337
D
Deer flies, 320
Diapheromera femorata, 7\
Digestion, 110
Diptera, 315
Double soma, 304
Dragonflies, 95
adult, 233
Carboniferous, 95
young, 233
18
Ears of grasshoppers, 30
of katydids, 36
Egg laying of cicada, 212
Eggs of aphids, 157, 158
of cicada, 212
Culex mosquito, 331
grasshopper, 5, 6, 7
house fly, 343
roaches, 8a, 81
tent caterpillar, 262
Enzymes, I11
Epicauta vittata, 22
European house cricket, 55
[ 356]
INDEX
F
Fat-body, 260, 292
Field crickets, 58
Flies, 314
horn fly, 348
horsefly, 320-324
house fly, 342-347
in general, 315
larva, 325
pupa, 327
stable fly, 348, 350
tsetse fly, 348
young, 231
Food exchange by termites, 144
Foot of cricket, 55
of grasshopper, 32
katydid, 32
Fork-tailed bush katydid, 39
song; 39
Four-spotted tree cricket, 67
G
Gadflies, 320
Ganglia, 118
Garden aphids, 171, 172
Genus, defined, 27
German roach, 79
egg case, 81
hatching, 81, 82
Germ cells, 100, 103, 124, 304
Glossina, see Tsetse fly
palpalis, 350
morsitans, 350
Grasshopper, 1
adults, 17
cousins, 26
definition, 2
destruction of eggs by blister
beetles, 23, 24
devastation by, 18
ears, 30
egg laying, 4, 5
egg-pod, 5
eggs, 6, 7
Grasshopper, growth, 13, 14
hatching, 8, 9
head, 12
males and females, 3
migration, 18
molting, 14-16
ovipositor, 4
parasite, Ig, 20
songs, 30, 31
spiracles, 13
wings, 29
young, I, 8, 11
Grasshopper family, 28
Grasshopper’s cousins, 26
Green apple aphis, 162-168
Green bugs, 152
Gryllus, 58, 60
assimilis, see Black cricket
domesticus, 55, 60
H
Handsome meadow grasshopper,
54
song, 54
Halteres, 319
Heart, 112
Hexapoda, see Insecta
Histoblast, 259
Histogenesis, 260
Histolysis, 259
Honey dew, 155
Hormones, 119
Horsefly, 320
larva, 325
mouth parts, 321-323
pupa, 325
sucking pump, 322
House centipede, 82, 83
House fly, 342
breeding places, 343
eggs, 343
larva, 343
mode of feeding, 346
mouth parts, 345, 346
[357]
INDEX
House fly, pupa, 345 Larva of Culex, 331, 332, 333
puparium, 344 of flies, 325
unsanitary habits, 347 ; house fly, 343
Hypermetamorphosis, 250 mosquitoes, 329
Hyperparasite, 181 wasps and bees, 252
Hypopharynx, 108 Leaf insect, 71, 72, 73
Legs of insects, 107
I Lepisma, 93
Imaginal discs, 259 Life of a caterpillar, 262
Imago, defined, 259 Locustidae, 32
Insecta, 28 Locusts, 2
Intestine, 110 seventeen-year, 182
Luna moth, 228, 230
J
Jumping bush cricket, 69 M
song, 70 Machilis, 93
June bugs, 230 Maggots, 252
Malacosoma americana, see Tent
K caterpillar
Katydid, 43 Malaria mosquitoes, 340
habits, 46 adult, 340
musical instruments, 47, 48 eggs, 340
song, 44, 48, 49 larva, 340, 341
true, 43 upa, 341
Katydid family, 32 Nile ae 342
Katydids, 32 Malpighian tubules, 116
angular-winged, 41 Mandibles, 107
bush, 38 Mantids, 73
ears, 36— Mantis, praying, 73-76
musical instruments, 34-36 eggs, 75, 76
round-headed, 37 Maxillae, 108
Pichon gs May beetles, 230
King termite, 134 een a
Meadow grasshoppers, 52-54
1e Mecostethus gracilis, 31
Labium, 108 Metabolism of pupa, 260
Labrum, 108 Metamorphosis, 14, 226
Lady-beetles, 175, 230 complete, 245
Ladybird beetles, 175, 230 defined, 22
Larva, characters, 246 diagram, 243
definition, 245 incomplete, 245
nature, 249 of tent caterpillar, 297, 299-304
of Aédes, 339 Microcentrum retinerve, 41, 43
Anopheles, 340, 341 song, 43
[358]
INDEX
Microcentrum rhombifolium, 41,
42, 43
song, 41, 42, 43
Mole cricket, 58
song, 58
Molting of grasshopper, 14, 16
Mormon cricket, 54
Mosquitoes, 329
adult, 330, 335, 338
Aédes, 331
Anopheles, 331, 340
common, 331
Culex, 331
larvae, 329
malaria, 331, 340
Stegomyia, 338
yellow fever, 338
young, 239
Moth of tent caterpillar, 305
characters, 306, 307
egg laying, 312
emergence from pupa, 305, 306
mouth parts, 306, 307
proboscis, 307, 308
reproductive organs, 311
Moths, Cecropia, 228
celery, 229
Luna, 228, 230
Promethea, 228
tent caterpillar, 305
Mouth parts, 12, 107
Musca domestica, see House fly
Muscidae, 342
Musical instruments of cicada,
207-209
of crickets, 56, 57
grasshoppers, 30, 31
Insects, 33, 34
katydids, 34, 35, 36
Myiasis, 352
N
Nagana, 349
Narrow-winged tree cricket, 66,
67
Narrow-winged tree cricket, an-
tennal marks, 66, 67
song, 67
Nemobius vittatus, 58
song, 58, 59
Neoconocephalus ensiger, 50
song, 51
retusus, 50
robustus, §1
song, $1
Neocurtilla hexadactyla, 57
Neoxabia bipunctata, 6g
Nervous system, 117
Nymph, defined, 245
O
Oecanthus angustipennts, see Nar-
row-winged tree cricket
latipennis, see Broad-winged
tree cricket
nigricornis, See
tree cricket
nigricornis quadripunctatus, 68
niveus, see Snowy tree cricket
Oesophagus, 110
Orchelimum agile, 53
laticauda, 54
vulgare, §2, 53
Oriental roach, 79, 80
Origin of insect wings, 91, 92
Orocharis saltator, 70
Ovaries, 122
Ovipositor, 4, 123
Ox warble, 352
If
Paleodictyoptera, 90, 92
Parasites, defined, 179
of aphids, 177-179
grasshopper, 19, 20
Parthenogenesis, 162
Periodical cicada, 182
abdomen, 205
adults, 199
Black-horned
[359]
INDEX
Periodical cicada, air chamber, 205
broods, 215-217
death of adults, 214
digging methods, 199, 191
egg laying, 212-214
eggs, 212, 219
food, 200
front leg of nymph, 190
hatching of eggs, 217-223
head of adult, 201
huts, turrets, 192
mouth parts, 201-205
musical instruments, 199, 207-
212
nymphal chambers, 187-189
stages, 186, 187
nymphs, 185-193, 223-2265
Ovipositor, 199
races, 215
salivary pump, 204
song of large variety, 210, 211
of small variety, 211, 212
sucking mechanism, 203
transformation, 193-199
two varieties, 199
young nymphs, 223-225
Phagocytes, 259, 301
Phaneroptera, 38
Pharynx, 110
Phylloxera, 172
Phylum, 26
Physiology of tent caterpillar, 283
Plant lice, 152
Plasmodium, 342
Proboscis of moth, 307, 308
Promethea moth, 228, 229
Propupa of tent caterpillar, 296-
298
Protoplasm, 100
Pterophylla camellifolia, see Katy-
did
Pupa, 250, 253, 254
added stage in metamorphosis,
a
Pupa, definition, 245
of flies, 327
house fly, 345
mosquitoes, 334, 339, 341
tent caterpillar, 298
reason for, 257
Puparium, 252
of house fly, 344
Q
Queen termite, 134, 149
R
Rat-tailed maggot, 327
Reproduction, 102
Reproductive organs, 122
Respiration, 114
Reticulitermes, 136
life history, 136-141
Rhadophorinae, 55
Roaches, 77, 80
and other ancient insects, 77
eggs, 80, 81
Robber flies, 324
Rocky Mountain locust, 17, 18,
19
Rosy apple aphis, 168-170
Round-headed katydids, 37
Amblycorypha oblongifolia, 39
angular-winged, 41
fork-tailed bush, 39
Microcentrum, 41, 43
Phaneroptera, 38
Scudderia, 38, 39
S
Sarcophaga kellv1, 19-21
Scudderia, 38
furcata, see Fork-tailed bush
katydid
Segments of body, 12
Sense organs, 121
[ 360 |
INDEX
Seventeen-year locust, see Periodi-
cal cicada
Shield-bearers, 54
Sleeping sickness, 349
Slender meadow grasshopper, 54
Snowy tree cricket, 65
antennal marks, 66
musical instruments, 57
song, 66
Soldiers of termites, 131
Soma, 104, 304
Somatic cells, 104
Song of insects, 33, 34
of cicada, 210-212
crickets, 58, 60, 62-70
grasshoppers, 30, 31
katydids, 39, 41, 42, 43, 44,
47, 48, 49, 51, 535 54
Spiracles, 13, 114.
Spirochetes, 340
Stagmomantis carolina, 73
Stimulus, 106
Stomach, 109
Stridulation, 33
Striped ground cricket, 58-60
song, 58, $9
Syrphid flies, 177
Jarvae feeding on aphids, 176,
177
Sword-bearing conehead, 50
song, $1
1
Tabanidae, 320
Tent caterpillar, 262
behavior on leafless tree, 278,
279
cocoon, 282
egg, 263
egg mass, 263, 264
epidermis, 295
fat-body, 292
feeding habits, 270, 272, 273,
276
Tent caterpillar, general external
form, 285, 286
head, 284, 285
internal organs, 289-291
jaws, 286
jumping from trees, 280, 281
manner of feeding, 277
metamorphosis, 293
molts, 275
moth, 305
newly-hatched, 265
prepupal stage, 295
propupa, 296, 297
pupa, 298
silk glands, 286
press, 288
spinneret, 286
spinning cocoon, 282, 283
structure and physiology, 283
tents, 270
weaving tent, 272, 273
young, 262
in egg, 312, 313
Termites, 125
Ame collective, 143
Gastessainiaia)t42
community life, 134
destruction by, 129
digestion of cellulose, 137
egg laying, 150, 151
food exchange, 144
fungus grown for food, 148
king, 134
life history, 136-141
males and females, 133
nests aboveground, 148
in trees, 148
underground, 147
queen, 134, 149
Reticulitermes, 136
short-winged form, 133, 140
soldiers, 131
tropical termites, 146
winged form, 133
[ 361 ]
INDEX
Termites, wingless males and
females, 140
workers, 131
young, 136
Testes, 122
Tettigoniidae, 32
Thorax, 12
Thysanura, 247
Tracheae, 114
Tree crickets, 63
antennal marks, 66, 67
attraction of males for females,
68, 69
black-horned, 67
broad-winged, 65
four-spotted, 67
musical organs, 56, 57
narrow-winged, 67
Neoxabia, 69
Oecanthus, 65-68
snowy, 65
song, 65, 66, 67
two-spotted, 69
Triungulins, 23
Tropisms, 121
True katydid, 43
Trypanosoma, 349
Tsetse fly, 348, 349, 350
mouth parts, 350, 351
Two-spotted tree cricket, 69
song, 69
Ww
Walking stick, 72
Walking stick insects, 71
Wasps and bees, larvae, 230, 238,
252
Ways and means of living, 99
White ants, 128
White grubs, 230
Wings, 83, 84
evolution, 315
of bees, 319
beetles, 318
butterflies and moths, 318
dragonflies, 316
flies, 319
grasshoppers, 318
roaches, 83, 84, 318
termites, 146, 316
wasps, 319
origin, 91, 92
Wigglers, 230, 329
Woolly aphis, 172
x
Xiphidium, 54
Mf
Yellow fever, 339
Yellow fever mosquito, 331, 339,
340
[ 362 ]
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