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- Moths of the Limberlost - 5/25 -


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


Moths of the Limberlost - 5/25

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