If you are too fastidious to read this chapter, it will be your
permanent loss, for it contains the life history, the evolution of
one of the most amazingly complicated and delicately beautiful
creatures in existence. There are moths that come into the world,
accomplish the functions that perpetuate their kind, and go out,
without having taken any nourishment. There are others that feed
and live for a season. Some fly in the morning, others in the glare
of noon, more in the evening, and the most important class of big,
exquisitely lovely ones only at night. This explains why so many
people never have seen them, and it is a great pity, for the nocturnal,
non-feeding moths are birdlike in size, flower-like in rare and
complicated colouring, and of downy, silent wing.
The moths that fly by day and feed are of the Sphinginae group,
Celeus and Carolina, or Choerocampinae, which includes the
exquisite Deilephila Lineata, and its cousins; also Sphingidae,
which cover the clear-winged Hemaris diffinis and Thysbe. Among
those that fly at night only and take no food are the members of
what is called the Attacine group, comprising our largest and
commonest moth, Cecropia; also its near relative Gloveri, smaller
than Cecropia and of lovely rosy wine-colour; Angulifera, the male
greyish brown, the female yellowish red; Promethea, the male
resembling a monster Mourning Cloak butterfly and the female
bearing exquisite red-wine flushings; Cynthia, beautiful in shades
of olive green, sprinkled with black, crossed by bands of pinkish
lilac and bearing crescents partly yellow, the remainder transparent.
There are also the deep yellow Io, pale blue-green Luna, and
Polyphemus, brown with pink bands of the Saturniidae; and light
yellow, red-brown and grey Regalis, and lavender and yellow
Imperialis of the Ceratocampidae, and their relatives. Modest
and lovely Modesta belongs with the Smerinthinae group; and there
are others, feeders and non-feeders, forming a list too long to
incorporate, for I have not mentioned the Catocalae family, the
fore-wings of which resemble those of several members of the
Sphinginae, in colour, and when they take flight, the back ones
flash out colours that run the gamut from palest to deepest reds,
yellows, and browns, crossed by wide circling bands of black; with
these, occasionally the black so predominates that it appears as
if the wing were black and the bands of other colour. All of them
are so exquisitely beautiful that neither the most exacting
descriptions, nor photographs from life, nor water colours faithfully
copied from living subjects can do them justice. They must be seen
alive, newly emerged, down intact, colours at their most brilliant
shadings, to be appreciated fully. With the exception of feeding
or refraining from eating, the life processes of all these are
very similar.
Moths are divided into three parts, the head, thorax, and abdomen,
with the different organs of each. The head carries the source of
sight, scent, and the mouth parts, if the moth feeds, while the
location of the ears is not yet settled definitely. Some
scientists place hearing in the antennae, others in a little organ
on each side the base of the abdomen. Packard writes: "The eyes
are large and globose and vary in the distance apart in different
families": but fails to tell what I want to know most: the range
and sharpness of their vision. Another writer states that the eyes
are so incomplete in development that a moth only can distinguish
light from darkness and cannot discern your approach at over five feet.
This accords with my experience with Cecropia, Polyphemus,
Regalis, and Imperialis. Luna either can see better, hear acutely,
or is naturally of more active habit. It is difficult to capture
by hand in daytime; and Promethea acts as if its vision were even
clearer. This may be the case, as it flies earlier in the day
than any of the others named, being almost impossible to take by
hand unless it is bound to a given spot by sex attraction.
Unquestionably the day fliers that feed--the Sphinginae and
Choerocampinae groups--have fairly good vision, as also the little
"Clear-wings" tribe, for they fly straight to the nectar-giving
flowers and fruits they like best to feed upon, and it is extra
good luck if you capture one by hand or even with a net. It must
be remembered that all of them see and go to a bright light at
night from long distances.
Holland writes: "The eyes of moths are often greatly developed,"
but makes no definite statements as to their range of vision, until
he reaches the Catocalae family, of which he records: "The hind
wings are, however, most brilliantly coloured. In some species
they are banded with pink, in others with crimson; still others have
markings of yellow, orange, or snowy white on a background of jet
black. These colours are distinctive of the species to a greater
or less extent. They are only displayed at night. The conclusion
is irresistibly forced upon us that the eyes of these creatures are
capable of discriminating these colours in the darkness. We cannot
do it. No human eye in the blackness of the night can distinguish
red from orange or crimson from yellow. The human eye is the greatest
of all anatomical marvels, and the most wonderful piece of animal
mechanism in the world, but not all of power is lodged within it.
There are other allied mechanisms which have the power of responding
to certain forms of radiant energy to a degree which it does not possess."
This conclusion is not "irresistibly forced" upon me. I do believe,
know in fact, that all day-flying, feeding moths have keener sight
and longer range of vision than non-feeders; but I do not believe
the differing branches of the Catocalae group, or moths of any family,
locate each other "in the blackness of night," by seeing markings
distinctly. I can think of no proof that moths, butterflies or any
insects recognize or appreciate colour. Male moths mate with females
of their kind distinctly different from them in colour, and male
butterflies pair with albinos of their species, when these differ
widely from the usual colouring.
A few moths are also provided with small simple eyes called ocelli;
these are placed on top of the head and are so covered with down
they cannot be distinguished save by experts. Mueller believes
that these are for the perception of objects close to a moth while
the compound eyes see farther, but he does not prove it.
If the moth does not feed, the mouth parts are scarcely developed.
If a feeder, it has a long tongue that can be coiled in a cleft in
the face between the palpi, which Packard thinks were originally
the feelers. This tongue is formed of two grooved parts so
fastened together as to make a tube through which it takes flower
and fruit nectar and the juices of decaying animal matter.
What are thought by some to be small organs of touch lie on either
side the face, but the exact use of these is yet under discussion,
It is wofully difficult to learn some of these things.
In my experience the antennae, are the most sensitive, and
therefore the most important organs of the head--to me. In the
Attacine group these stand out like delicately cut tiny fern
fronds or feathers, always being broader and more prominent on the
male. Other families are very similar and again they differ
widely. You will find moths having pointed hair-like antennae;
others heaviest at the tip in club shape, or they may be of even
proportion but flat, or round, or a feathered shaft so fine as to
be unnoticed as it lies pressed against the face. Some writers say
the antennae are the seat of scent, touch, and hearing. I had not
thought nature so impoverished in evolving her forms as to overwork
one delicate little organ for three distinct purposes. The
antennae are situated close where the nose is, in almost every
form of life, and I would prefer to believe that they are the
organs of scent and feeling. I know a moth suffers most over any
injury to them; but one takes flight no quicker or more precipitately
at a touch on the antennae than on the head, wing, leg, or abdomen.
We are safe in laying down a law that antennae are homologous organs
and used for identical purposes on all forms of life carrying them.
The short antennae of grasshoppers appear to be organs of scent.
The long hair-fine ones of katydids and crickets may be also, but
repeatedly I have seen these used to explore the way ahead over leaves
and limbs, the insect feeling its path and stepping where a touch
assures it there is safe footing. Katydids, crickets, and
grasshoppers all have antennae, and all of these have ears definitely
located; hence their feelers are not for auricular purposes.
According to my logic those of the moth cannot be either. I am quite
sure that primarily they serve the purpose of a nose, as they
are too short in most cases to be of much use as 'feelers,' although
that is undoubtedly their secondary office. If this be true, it
explains the larger organs ofthe male. The female emerges from
winter quarters so weighted with carrying from two to six hundred
eggs, that she usually remains and develops where she is. This
throws the business of finding her location on the male. He is
compelled to take wing and hunt until he discovers her; hence his
need of more acute sense of scent and touch. The organ that is
used most is the one that develops in the evolution of any form
of life.
I can well believe that the antennae are most important to a moth,
for a broken one means a spoiled study for me. It starts the
moth tremulously shivering, aimlessly beating, crazy, in fact,
and there is no hope of it posing for a picture. Doctor Clemens
records that Cecropia could neither, walk nor fly, but wheeled in
a senseless, manner when deprived of its antennae. This makes
me sure that they are the seat of highest sensibility, for I
have known in one or two cases of chloroformed moths reviving and
without struggle or apparent discomfort, depositing eggs in a
circle around them, while impaled to a setting board with a pin
thrust through the thorax where it of necessity must have passed
through or very close the nervous cord and heart.
The moth is covered completely with silken down like tiny scales,
coloured and marked according to species, and so lightly attached
that it adheres to the cocoon on emergence and clings to the
fingers at the lightest touch. From the examination of specimens
I have taken that had disfigured themselves, it appears that a moth
rubbed bare of down would seem as if covered with thinly cut, highly
polished horn, fastened together in divisions. This is called
'chitine' by scientists.
The thorax bears four wings, and six legs, each having five joints
and ending in tiny claws. The wings are many-veined membranous
sacs, covered with scales that are coloured according to species
and arranged to form characteristic family markings. They are a
framework usually of twelve hollow tubes or veins that are so
connected with the respiratory organs as to be pneumatic. These
tubes support double membranes covered above and below with down.
At the bases of the wings lie their nerves. The fore-wings each
have a heavy rib running from the base and gradually decreasing
to the tip. This is called the costa. Its purpose is to bear
the brunt of air-pressure in flight. On account of being compelled
to fly so much more than the females, the back wings of the males
of many species have developed a secondary rib that fits under
and supports the front, also causing both to work together with
the same impulse to flight. A stiff bunch of bristles serves the
same purpose in most females, while some have a lobe extending
from the fore-wing. As long as the costa remains unbroken to
preserve balance, a moth that has become entangled in bushes
or suffered rough treatment from birds can fly with badly
damaged wing surfaces.
In some species, notably the Attacine group and all non-feeding,
night-flying moths, the legs are short, closely covered with long
down of the most delicate colours of the moth, and sometimes
decorated with different shades. Luna has beautiful lavender legs,
Imperialis yellow, and Regalis red-brown. The day-flying, feeding
group have longer, slenderer legs, covered with shorter down, and
carry more elaborate markings. This provision is to enable them
to cling firmly to flower or twig while feeding, to help them to
lift the body higher, and walk dextrously in searching for food.
It is also noticeable that these moths have, for their size,
comparatively much longer, slenderer wings than the non-feeders,
and they can turn them back and fold them together in the fly
position, thus enabling them to force their way into nectar-bearing
flowers of trumpet shape.
The abdomen is velvet soft to the touch, and divided into rings
called segments, these being so joined that this member can be
turned and twisted at will. In all cases the last ring contains
the sex organs. The large abdomen of the female carries several
hundred embryo eggs, and that of the male the seminal fluid.
Much has been written of moths being able to produce odours that
attract the sexes, and that are so objectionable as to protect
them from birds, mice, and bats. Some believe there are scent
glands in a few species under the wing scales. I have critically
examined scores of wings as to colour markings, but never
noticed or smelled these. On some, tufts of bristlelike hairs can
be thrust out, that give a discernible odour; but that this
carries any distance or is a large factor in attracting the sexes
I do not believe so firmly, after years of practical experience, as
I did in the days when I had most of my moth history from books.
I have seen this theory confounded so often in practice.
In June of 1911, close six o'clock in the evening, I sat on the
front veranda of the Cabin, in company with my family, and
watched three moths sail past us and around the corner, before
I remembered that on the screen of the music-room window to the
east there was a solitary female Promethea moth, that day emerged
from a cocoon sent me by Professor Rowley. I hurried to the room
and found five male moths fluttering before the screen or clinging
to the wild grape and sweet brier vines covering it. I opened the
adjoining window and picked up three of the handsomest with my
fingers, placing them inside the screen. Then I returned to
the veranda.
Moths kept coming. We began studying the conditions. The
female had emerged in the diningroom on the west side of the
cabin. On account of the intense heat of the afternoon sun, that
side of the building had been tightly closed all day. At four
o'clock the moth was placed on the east window, because it was
sheltered with vines. How soon the first male found her, I do not
know. There was quite a stiff evening breeze blowing from the
west, so that any odour from her would have been carried on east.
We sat there and watched and counted six more moths, every one of
which came down wind from the west, flying high, above the
treetops in fact, and from the direction of a little tree-filled
plot called Studabaker's woods. Some of them we could distinguish
almost a block away coming straight toward the Cabin, and sailing
around the eastern corner with the precision of hounds on a hot trail.
How they knew, the Almighty knows; I do not pretend to; but
that there was odour distilled by that one female, practically
imperceptible to us (she merely smelled like a moth), yet of such
strength as to penetrate screen, vines, and roses and reach her
kind a block away, against considerable breeze, I never shall
believe.
The fact is, that moths smell like other moths of the same species,
and within a reasonable radius they undoubtedly attract each
other. In the same manner birds carry a birdlike odour, and
snakes, frogs, fish, bees, and all animals have a scent peculiar
to themselves. No dog mistakes the odour of a cat for that of
another dog. A cow does not follow the scent of horses to find
other cattle. No moth hunts a dragon-fly, a butterfly, or in my
experience, even a moth of another species in its search for a
mate. How male moths work the miracles I have seen them accomplish
in locating females, I cannot explain. As the result of acts we
see them perform, we credit some forms of life with much keener
scent than others, and many with having the power more highly
developed than people. The only standard by which we can determine
the effect that the odour of one insect, bird, or animal has upon
another is by the effect it has upon us. That a male moth can
smell a female a block away, against the wind, when I can detect
only a faint musky odour within a foot of her, I do not credit.
Primarily the business of moths is to meet, mate, and deposit
eggs that will produce more moths. This is all of life with those
that do not take food. That they add the completing touch and
most beautiful form of life to a few exquisite May and June nights
is their extra good fortune, not any part of the affair of living.
With moths that feed and live after reproduction, mating and egg
placing comes first. In all cases the rule is much, the same. The
moths emerge, dry their wings, and reach full development the
first day. In freedom, the females being weighted with eggs seldom
attempt to fly. They remain where they are, thrust out the egg
placer from the last ring of the abdomen and wait. By ten o'clock
the males, in such numbers as to amaze a watcher, find them
and remain until almost morning. Broad antennae, slenderer
abdomen, and the claspers used in holding the female in mating,
smaller wings and more brilliant markings are the signs by which
the male can be told in most cases. In several of the Attacine
group, notably Promethea, the male and female differ widely in
markings and colour. Among the other non-feeders the difference
is slight. The male Regalis has the longest, most gracefully
curved abdomen and the most prominent claspers of any moth I ever
examined; but the antennae are so delicate and closely pressed
against the face most of the time as to be concealed until
especially examined. I have noticed that among the moths bearing
large, outstanding antennae, the claspers are less prominent than
with those having small, inconspicuous head parts. A fine pair of
antennae, carried forward as by a big, fully developed Cecropia,
are as ornamental to the moth as splendidly branching antlers are
to the head of a deer.
The female now begins egg placing. This requires time, as one of
these big night moths deposits from three hundred and fifty to
over six hundred eggs. These lie in embryonic state in the abdomen
of the female. At her maturity they ripen rapidly. When they
are ready to deposit, she is forced to place them whether she has
mated or not. In case a mate has found her, a small pouch near
the end of her abdomen is filled with a fluid that touches each
egg in passing and renders it fertile. The eggs differ with species
and are placed according to family characteristics. They may be
pure white, pearl-coloured, grey, greenish, or yellow. There are
round, flat, and oblong eggs. These are placed differently in
freedom and captivity. A moth in a natural location glues her eggs,
often one at a time, on the under or upper side of leaves. Sometimes
she dots several in a row, or again makes a number of rows, like a
little beaded mat. One authority I have consulted states that
"The eggs are always laid by the female in a state of freedom upon
the food-plant which is most congenial to the larvae." This has not
'always' been the case in my experience. I have found eggs on
stone walls, boards, fences, outbuildings, and on the bark of dead
trees and stumps as well as living, even on the ground. This also,
has been the case with the women who wrote "Caterpillars and their
Moths", the most invaluable work on the subject ever compiled.
A captive moth feels and resents her limitations. I cannot force
one to mate even in a large box. I must free her in the conservatory,
in a room, or put her on an outside window br door screen. Under
these conditions one will place her eggs more nearly as in freedom;
but this makes them difficult to find and preserve. Placed in a
box and forced by nature to deposit her eggs, as a rule, she will
remain in one spot and heap them up until she is forced to move to
make room for more. One big female Regalis of the last chapter
of this book placed them a thimbleful at a time; but the little
caterpillars came rolling out in all directions when due. In my
experience, they finish in four or five nights, although I have
read of moths having lived and placed eggs for ten, some species
being said to have deposited over a thousand. Seven days is
usually the limit of life for these big night moths with me;
they merely grow inactive and sluggish until the very last, when
almost invariably they are seized with a muscular attack, in which
they beat themselves to rags and fringes, as if resisting the
overcoming lethargy. It is because of this that I have been forced
to resort to the gasoline bottle a few times when I found it impossible
to paint from the living moth; but I do not put one to sleep unless
I am compelled.
I never have been able to induce a female to mate after confinement
had driven her to begin depositing her eggs, not even under the
most favourable conditions I could offer, although others record
that they have been so fortunate. Repeatedly I have experimented
with males and females of different species, but with no success.
I have not seem a polygamous moth; but have read of experiences
with them.
Sometimes the eggs have a smooth surface, again they may be
ridged or like hammered brass or silver. The shells are very
thin and break easily. At one side a place can be detected where
the fertilizing fluid enters. The coming caterpillar begins to
develop at once and emerges in from six to thirty days, with the
exception of a few eggs placed in the fall that produce during the
following spring. The length of the egg period differs with
species and somewhat with the same moths, according to suitable or
unfavourable placing, and climatic conditions. Do not accept the
experience of any one if you have eggs you very much desire to
be productive of the caterpillars of rare moths; after six days
take a peep every day if you would be on the safe side. With many
species the shells are transparent, and for the last few days
before emergence the growth of the little caterpillars can be
watched through them.
When matured they break or eat a hole in their shells and emerge,
seeming much too large for the space they occupied. Family
characteristics show at once. Many of them immediately turn and
eat their shells as if starving; others are more deliberate. Some
grace around for a time as if exercising and then return and eat
their shells; others walk briskly away and do not dine on
shell for the first meal. Usually all of them rest close
twenty-four hours before beginning on leaves. Once they commence
feeding in favourable conditions they eat enormously and grow so
rapidly they soon become too large for their skins to hold them
another instant; so they pause and stop eating for a day or two
while new skin forms. Then the old is discarded and eaten for a
first meal, with the exception of the face covering. At the same
time the outer skin is cast the intestinal lining is thrown off,
and practically a new caterpillar, often bearing different markings,
begins to feed again.
These moults occur from four to six times in the development of the
caterpillar; at each it emerges larger, brighter, often with
other changes of colour, and eats more voraciously as it grows.
With me, in handling caterpillars about which I am anxious,
their moulting time is critical. I lost many until I learned to
clean their boxes thoroughly the instant they stopped eating and
leave them alone until they exhibited hunger signs again. They
eat greedily of the leaves preferred by each species, doing best
when the foliage is washed and drops of water left for them to
drink as they would find dew and rain out of doors. Professor
Thomson, of the chair of Natural History of the University of
Aberdeen, makes this statement in his "Biology of the Seasons",
"Another feature in the life of caterpillars is their enormous
appetite. Some of them seem never to stop eating, and a species
of Polyphemus is said to eat eighty-six thousand times its own
weight in a day." I notice Doctor Thomson does not say that he
knows this, but uses the convenient phrase, "it is said." This
is an utter impossibility. The skin of no living creature will
contain eighty-six thousand times its own weight in a day. I
have raised enough caterpillars to know that if one ate three
times its own weight in a day it would have performed a
skin-stretching feat. Long after writing this, but before the
manuscript left my hands, I found that the origin of this statement
lies in a table compiled by Trouvelot, in which he estimates that
a Polyphemus caterpillar ten days old weighs one half grain, or
ten times its original weight; at twenty days three grains, or
sixty times its first weight; and so on until at fifty-six days
it weighs two hundred and seven grains, or four thousand one hundred
and forty times its first weight. To this he adds one half ounce
of water and concludes: "So the food taken by a single silkworm in
fifty-six days equals in weight eighty-six thousand times the
primitive weight of the worm." This is a far cry from eating
eighty-six thousand times its own weight in a day and upholds in
part my contention in the first chapter, that people attempting to
write upon these subjects "are not always rightly informed."
When the feeding period is finished in freedom, the caterpillar,
if hairless, must be ready to evolve from its interior, the
principal part of the winter quarters characteristic of its species
while changing to the moth form, and in the case of non-feeders,
sustenance for the lifetime of the moth also. Similar to the moth,
the caterpillar is made up of three parts, head, thorax, and abdomen,
with the organs and appendages of each. Immediately after moulting
the head appears very large, and seems much too heavy for the size
of the body. At the end of a feeding period and just previous to
another moult the body has grown until the head is almost lost from
sight, and it now seems small and insignificant; so that the appearance
of a caterpillar depends on whether you examine it before or after
moulting.
The head is made up of rings or segments, the same as the body, but
they are so closely set that it seems to be a flat, round, or
pointed formation with discernible rings on the face before casting
time. The eyes are of so simple form that they are supposed only
to distinguish light from darkness. The complicated mouth is at
the lower part of the head. It carries a heavy pair of cutters
with which the caterpillar bites off large pieces of leaf, a first
pair of grinders with which it macerates the food, and a second
pair that join in forming the under lip. There is also the tube that
connects with the silk glands and ends in the spinneret. Through
this tube a fluid is forced that by movements of the head the
caterpillar attaches where it will and draws into fine threads that
at once harden in silk. This organism is sufficiently developed
for use in a newly emerged caterpillar, for it can spin threads by
which to drop from leaf to leaf or to guide it back to a starting
point.
The thorax is covered by the first three rings behind the head,
and on it are six legs, two on each segment. The remainder of the
caterpillar is abdominal and carries small pro-legs with which to
help it cling to twigs and leaves, and the heavy anal props that
support the vent. By using these and several of the pro-legs
immediately before them, the caterpillar can cling and erect the
front part of the body so that it can strike from side to side
when disturbed. In the case of caterpillars that have a horn, as
Celeus, or sets of them as Regalis, in this attitude they really
appear quite formidable, and often I have seen them drive away
small birds, while many people flee shrieking.
There are little tubes that carry air to the trachea, as
caterpillars have no lungs and can live with a very small amount
of air.
The skin may be rough, granulated, or soft and fine as silk, and
in almost every instance of exquisite colour: bluish green,
greenish blue, wonderful yellows and from pale to deep wine red,
many species having oblique touches of contrasting colours on the
abdominal rings. Others are marked with small projections of
bright colours from which tufts of hair or bristles may grow. In
some, as Io, these bristles are charged with an irritating acid
that will sting for an hour after coming in contact with the skin,
but does no permanent injury. On a few there are what seem to be
small pockets of acid that can be ejected with a jerk, and on some
a sort of filament that is supposed to distil a disagreeable odour.
As the caterpillar only uses these when disturbed, it is safe to
presume that they are placed for defence, but as in the case of
moths I doubt their efficacy.
Some lepidopterists have thought the sex of a moth could be
regulated by the amount of food given the caterpillar; but with
my numerous other doubts I include this. It is all of a piece
with any attempt at sex regulation. I regard it as morally certain
that sex goes back to the ovary and that the egg produced yields a
male or female caterpillar in the beginning. I am becoming convinced
that caterpillars recognize sex in each other, basing the theory
on the facts that in half a dozen instances I have found cocoons,
spun only a few inches apart. One pair brought to me as interwoven.
Two of these are shown in the following chapter. In all cases a male
and female emerged within a few minutes of each other and mated as
soon as possible. If a single pair of these cocoons ever had produced
two of a kind, it would give rise to doubts. When all of them proved
to be male and female that paired, it seems to me to furnish
conclusive evidence that the caterpillars knew what they were
doing, and spun in the same place for the purpose of appearing
together.
At maturity, usually near five weeks, the full-fed caterpillar
rests a day, empties the intestines, and races around searching for
a suitable place to locate winter quarters. With burrowing
caterpillars that winter in pupa cases, soft earth or rotting wood
is found and entered by working their way with the heads and
closing it with the hind parts. At the desired depth they push in
all directions with such force that a hollow larger, but shaped as
a hen's egg, is worked out; usually this is six or more inches below
the surface. So compactly is the earth forced back, that fall rains,
winter's alternate freezing and thawing, always a mellowing process,
and spring downpours do not break up the big ball, often larger than
a quart bowl, that surrounds the case of the pupa. It has been
thought by some and recorded, that this ball is held in place by
spinning or an acid ejected by the caterpillar. I never have
heard of any one else who has had my luck in lifting these earth
balls intact, opening, and photographing them and their contents.
I have examined them repeatedly and carefully. I can find not the
slightest trace of spinning or adhesion other than by force.
With one of these balls lifted and divided, we decided what
happened underground by detaining a caterpillar on the surface and
forcing it to transform before us, for this change is not optional.
When the time comes the pupa must evolve. So the caterpillar lies
on the earth, gradually growing shorter, the skin appearing dry
and the horns drooping. There never is a trace of spinning or acid
ejected in the sand buckets. When the change is completed there
begins a violent twisting and squirming. The caterpillar skin opens
in a straight line just behind the head on the back, and by working
with the pointed abdomen the pupa case emerges. The cast skin
rapidly darkens, and as I never have found a trace of it in an
opened earth ball in the spring, I suppose it disintegrates
rapidly, or what is more possible, is eaten by small borers that
swarm through the top six inches of the earth's crust.
The pupa is thickly coated with a sticky substance that seems to
serve the double purpose of facilitating its exit from the
caterpillar skin and to dry over it in a glossy waterproof
coating. At first the pupa is brownish green and flattened, but as
it dries it rapidly darkens in colour and assumes the shape of a
perfect specimen. Concerning this stage of the evolution of a moth
the doctors disagree.
The emergence I have watched repeatedly, studied photographically,
and recorded in the tabulated records from which I wrote the
following life histories. At time to appear I believe the pupa
bores its way with the sharp point of the abdomen; at least I
have seen Celeus, and Carolina, Regalis and Imperialis coming
through the surface, abdomen tip first. Once free, they press
with the feet against the wing shields, burst them away and leave
the case at the thorax. Each moth I ever have seen emerge has been
wet and the empty case damp inside. I have poured three large
drops of pinkish liquid the consistency of thin cream from the abdominal
rings of a Regalis case. Undoubtedly this liquid is ejected by
the moth to enable it to break loose from and leave the case with
its delicate down intact. The furry scales of its covering are so
loosely set that any violent struggle with dry down would disfigure
the moth.
Among Cecropia and its Attacine cousins, also Luna, Polyphemus, and
all other spinners the process is practically the same, save that
it is much more elaborate; most of all with Cecropia, that spins
the largest cocoon I ever have seen, and it varies its work more
than any of the others. Lengthwise of a slender twig it spins a
long, slim cocoon; on a board or wall, roomier and wider at the
bottom, and inside hollow trees, and under bridges, big baggy
quarters of exquisite reddish tan colours that do not fade as do
those exposed to the weather. The typical cocoon of the species
is that spun on a fence or outbuilding, not the slender work on
the alders or the elaborate quarters of the bridge. On a board
the process is to cover the space required with a fine spinning
that glues firmly to the wood. Then the worker takes a firm grip
with the anal props and lateral feet and begins drawing out long
threads that start at the top, reach down one side, across the
bottom and back to the top again, where each thread is cut and
another begun. As long as the caterpillar can be seen through
its work, it remains in the same position and throws the head
back and around to carry the threads. I never thought of
counting these movements while watching a working spinner, but
some one who has, estimates that Polyphemus, that spins a cocoon
not one fourth the size of Cecropia, moves the head a quarter
of a million times in guiding the silk thread. When a thin webbing
is spun and securely attached all around the edges it is pushed
out in the middle and gummed all over the inside with a liquid glue
that oozes through, coalesces and hardens in a waterproof covering.
Then a big nest of crinkly silk threads averaging from three to
four inches in length are spun, running from the top down one side,
up the other, and the cut ends drawn closely together. One writer
states that this silk has no commercial value; while Packard thinks
it has. I attach greater weight to his opinion. Next comes the
inner case. For this the caterpillar loosens its hold and completely
surrounds itself with a small case of compact work. This in turn is
saturated with the glue and forms in a thick, tough case, rough on
the outside, the top not so solidly spun as the other walls;
inside dark brown and worn so smooth it seems as if oiled, from the
turning of the caterpillar. In this little chamber close the
length and circumference of an average sized woman's two top joints
of the first finger, the caterpillar transforms to the pupa stage,
crowding its cast skin in a wad at the bottom.
At time for emergence the moth bursts the pupa case, which is
extremely thin and papery compared with the cases of burrowing
species. We know by the wet moth that liquid is ejected, although
we cannot see the wet spot on the top of the inner case of Cecropia
as we can with Polyphemus, that does not spin the loose outer case
and silk nest. From here on the moths emerge according to species.
Some work with their mouths and fore feet. Some have rough
projections on the top of the head, and others little sawlike
arrangements at the bases of the wings. In whatever manner they
free themselves, all of them are wet when they leave their quarters.
Sometimes the gathered silk ends comb sufficient down from an
emerging Cecropia to leave a terra cotta rim around the opening
from which it came; but I never saw one lose enough at this time
to disfigure it. On very rare occasions a deformed moth appears.
I had a Cecropia with one wing no larger than my thumb nail, and
it never developed. This is caused by the moth sustaining an injury
to the wing in emergence. If the membrane is slightly punctured
the liquid forced into the wing for its development escapes and
there is no enlargement.
Also, in rare instances, a moth is unable to escape at all and is
lost if it is not assisted; but this is precarious business and
should not be attempted unless you are positive the moth will die
if you do not interfere. The struggle it takes to emerge is a part
of the life process of the moth and quickens its circulation and
develops its strength for the affairs of life afterward. If the
feet have a steady pull to drag forth the body, they will be
strong enough to bear its weight while the wings dry and develop.
All lepidopterists mention the wet condition of the moths when they
emerge. Some explain that an acid is ejected to soften the pupa
case so that the moth can cut its way out; others go a step
farther and state that the acid is from the mouth. I am extremely
curious about this. I want to know just what this acid is and
where it comes from. I know of no part of the thorax provided with
a receptacle for the amount of liquid used to flood a case, dampen
a moth, and leave several drops in the shell.
As soon as a moth can find a suitable place to cling after it is
out, it hangs by the feet and dries the wings and down. Long
before it is dry if you try to move a moth or cause disturbance,
it will eject several copious jets of a spray from the abdomen
that appears, smells and tastes precisely like the liquid found in
the abandoned case. If protected from the lightest touch it will
do the same. It appeals to me that this liquid is abdominal,
partly thrown off to assist the moth in emergence; something
very like that bath of birth which accompanies and facilitates
human entrance into the world. It helps the struggling moth in
separating from the case, wets the down so that it will pass the
small opening, reduces the large abdomen so that it will escape the
exit, and softens the case and silk where the moth is working.
With either male or female the increase in size is so rapid that
neither could be returned to their cases five minutes after they
have left them.
It is generally supposed that the spray thrown by a developing
moth is for the purpose of attracting others of its kind. I have
my doubts. With moths that have been sheltered and not even
touched by a breath of wind, this spray is thrown very frequently
before the moth is entirely dry, long before it is able to fly
and before the ovipositor is thrust out. According to my sense of
smell there is very little odour to the spray and what there is
would be dissipated hours before night and time for the moths to
fly and seek mates. I do not think that the spray thrown so soon
after escape from cocoon or case is to attract the sexes, any farther
than that much of it in one place on something that it would saturate
might leave a general 'mothy' odour. Some lepidopterists think this
spray a means of defence; if this is true I fail to see why it should
be thrown when there is nothing disturbing the moth.
Many of the spinning moths use leaves for their outer foundation.
Some appear as if snugly rolled in a leaf and hanging from a twig,
but examination will prove that the stem is silk covered to hold
the case when the leaf loosens. This is the rule with all
Promethea cocoons I ever have seen. Polyphemus selects a cluster
of leaves very frequently thorn, and weaves its cocoon against
three, drawing them together and spinning a support the length of
the stems, so that when the leaf is ready to fall the cocoon is
safely anchored. When the winter winds have beaten the edges from
the leaves, the cocoon appears as if it were brown, having three
ribs with veins running from them, and of triangular shape.
Angulifera spins against the leaves but provides no support and so
drops to the ground. Luna spins a comparatively thin white case,
among the leaves under the shelter of logs and stumps. Io spins so
slightly in confinement that the pupa case and cast skin show
through. I never have found a pupa out of doors, but this is a
ground caterpillar.
Sometimes the caterpillar has been stung and bad an egg placed in
its skin by a parasite, before pupation. In such case the pupa
is destroyed by the developing fly. Throughout one winter I was
puzzled by the light weight of what appeared to be a good Polyphemus
cocoon, and at time for emergence amazed by the tearing and
scratching inside the cocoon, until what I think was an Ophion
fly appeared. It was honey yellow, had antennae long as its
extremely long body, the abdomen of which was curved and the
segments set together so as to appear notched. The wings were
transparent and the insect it seems is especially designed to
attack Polyphemus caterpillars and help check a progress that
otherwise might become devastating.
Among the moths that do not feed, the year of their evolution is
divided into about seven days for the life of the moth, from
fifteen to thirty for the eggs, from five to six weeks for the
caterpillar and the remainder of the time in the pupa stage. The
rule differs with feeding moths only in that after mating and egg
placing they take food and live several months, often until quite
heavy frosts have fallen.
One can admire to fullest extent the complicated organism, wondrous
colouring, and miraculous life processes in the evolution of a
moth, but that is all. Their faces express nothing; their
attitudes tell no story. There is the marvellous instinct through
which the males locate the opposite sex of their species; but one
cannot see instinct in the face of any creature; it must develop
in acts. There is no part of their lives that makes such pictures
of mother-love as birds and animals afford. The male finds a mate
and disappears. The female places her eggs and goes out before her
caterpillars break their shells. The caterpillar transforms to the
moth without its consent, the matter in one upbuilding the other.
The entire process is utterly devoid of sentiment, attachment or
volition on the part of the creatures involved. They work out a
law as inevitable as that which swings suns, moons, and planets
in their courses. They are the most fragile and beautiful result
of natural law with which I am acquainted.