He is now a very quiet and circumspect young professor. It were indeed a dangerous experiment to wiggle in such a tight suit as now incloses him, so he remains immovable and resigned. A strange process is now going on in his physiology. Hour by hour his outer skin is becoming detached from the under skin, and now he is simply inclosed within its sac. The shell of his former head has been crowded off his face, as it were, and has slid down towards the mouth of the new head within. Shortly after this feature has taken place the imprisoned caterpillar becomes restless to burst his bonds, and a quiet working motion begins, which gradually forces the skin in wrinkles towards the tail of the body, of course drawing it tighter and tighter about the head, and with it the connection from the spiracles at the sides of the body. At last, with one final effort, the skin behind the head ruptures, and discloses the new skin beneath, and through the opening thus made the new head soon appears, and the entire new suit of clothes emerges in a few moments. But though the old clothes are worked off into a little shrunken pellet at the tail, the old head-shell is still retained, being attached to the hairs immediately back of the new head, and thus retained. Five or six times in the life of the caterpillar this same process is performed, each performance leaving its token; so that our "professor" enjoys the unique distinction of being able, in his mature years, to look up to the head he wore when he was a baby or youngster, and make it useful, too, in keeping off the flies as he ponders on the flight of time.
But this is not all our professor's peculiarities. One day, as I came to look at my hump-backed pets, I discovered that most of them had shrunk a full third, and had refused to eat and, what surprised me more, refused to wiggle. A closer examination of the box showed that while they had ignored the lilac leaves, they had been gnawing the pasteboard everywhere in the box, even perforating it with a number of holes. The captives in a thin wooden box were similarly affected, and numbers of holes were to be seen. What did it mean? I had been expecting daily to see my full-grown caterpillars either beginning their cocoons or suspending themselves by their tails in readiness for the chrysalis state. Yet they had done neither. Their time had evidently come, but they were not satisfied with their surroundings, and would seem to wish to escape; and yet, having gnawed their way to liberty, deliberately remained in prison! It was some days before I correctly interpreted their curious contradictory actions, and as I remember it now, my hint came from a spider-web which had spread its catch all beneath a lilac-bush, and upon which I discerned a number of tiny balls of sawdust which had chanced to fall upon it. Looking directly above, among the branches, I soon found a wiggler, not only gnawing the wood but with one-third of its body in a burrow in a twig the size of my finger. I had observed him thus for a few moments when he began to back out, drawing with him a tiny ball of sawdust, which he threw out with a slight wiggle, and soon resumed operations.
Leaving him to his work, I lost no time in taking the hint, and my box was soon criss-crossed with small twigs, and my remaining wigglers soon found themselves at home and littered my box with their chip pellets. The burrow is first made diagonally to the pith, and then follows the centre for about two-thirds of an inch. I remember having about a half-dozen caterpillars thus at work simultaneously. On the morrow, when I opened the box, all signs of caterpillars and burrows had vanished. Though I looked directly upon the spot where yesterday I had surely seen the open tunnel, no vestige of it now appeared, and its whereabouts could only be guessed by the slight rose-colored stain which the caterpillar had left on the bark below. What had happened?
The burrows had been completed in the night, and the caterpillars had retired into them, backward presumably, and then spun over the opening by a disk of silk, which they had finally, or in the process, tinted the exact color of the external surrounding bark. I have frequently exhibited one of these sticks, with its inclosed caterpillar, to curious friends, who were unable to locate, without long and careful scrutiny, the mysterious curtain. The twig, dried in a mild oven so as to kill the inclosed caterpillar, or with its farther side split off for his removal, would serve as an interesting permanent specimen, the delicate disk being otherwise ruptured by the final escape of the moth.
All of mine appeared in the first week of July of the next year. They were small, for the size of the caterpillar, yellowish-white "millers," the fore wings beautifully mottled and banded with brown, and each with three conspicuous round spots of dull red, which feature has secured the insect its specific name of "Trisignata"—Gramatophora trisignata being the name of our professor in learned circles.
His burrowing habits do not seem to be generally known, the only mention of which I have chanced to observe merely alluding to the fact that the "caterpillar has the unusual power of boring very smooth cylindrical holes in solid pine wood." But Professor Wiggler does not bore wood for a pastime, as we have seen.