Moths of the Limberlost | Page 4

direction, even taking the precaution to bake the earth used, because I was very anxious about some rare moths. When they failed to emerge in season I dug them out, only to find that those not moulded had been held fast by the damp, packed earth, and all were ruined. I learned by investigation that pupation takes place in a hole worked out by the caterpillar, so earth must touch these cases only as they lie upon it. The one word 'hole' would have saved all those moths for me.
One writer stated that the tongue cases of some pupae turn over and fasten on the back between the wing shields, and others were strangely silent on the subject. So for ten months I kept some cases lying on their backs with the feet up and photographed them in that position. I had to discover for myself that caterpillars that pupate in the ground change to the moth form with the feet and legs folded around the under side of the thorax, the wings wrap over them, and the tongue case bends UNDER and is fastened between the wings.
For years I could find nothing on the subject of how a moth from a burrowing caterpillar made its appearance. In two recent works I find the statement that the pupa cases come to the surface before the moths leave them, but how the operation is performed is not described or explained. Pupa cases from earth consist of two principal parts: the blunt head and thorax covering, and the ringed abdominal sections. With many feeders there is a long, fragile tongue shield. The head is rounded and immovable of its own volition. The abdominal part is in rings that can be turned and twisted; on the tip are two tiny, needlesharp points, and on each of three rings of the abdominal shield there are in many cases a pair of tiny hooks, very slight projections, yet enough to be of use. Some lepidopterists think the pupa works head first to the surface, pushing with the abdomen. To me this seems impossible. The more one forced the blunt head against the earth the closer it would pack, and the delicate tongue shield surely would break. There is no projection on the head that would loosen or lift the earth.
One prominent lepidopterist I know, believes the moth emerges underground, and works its way to the surface as it fights to escape a cocoon. I consider this an utter impossibility. Remember the earth-encrusted cicada cases you have seen clinging to the trunks of trees, after the insect has reached the surface and abandoned them. Think what would happen to the delicate moth head, wings, and downy covering! I am willing to wager all I possess, that no lepidopterist, or any amateur, ever found a freshly emerged moth from an underground case with the faintest trace of soil on its head or feet, or a particle of down missing; as there unquestionably must be, if it forced its way to freedom through the damp spring earth with its mouth and feet.
The point was settled for me when, while working in my garden, one came through the surface within a few inches of my fingers, working with the tip of the abdomen. It turned, twisted, dug away the dirt, fastened the abdominal tip, pulled up the head, and then bored with the tip again. Later I saw several others emerge in the same way, and then made some experiments that forever convinced me that this is the only manner in which ground pupae possibly could emerge.
One writer I had reason to suppose standard authority stated that caterpillars from Citheronia Regalis eggs emerged in sixteen days. So I boxed some eggs deposited on the eleventh, labelled them due to produce caterpillars on the twenty-seventh and put away the box to be attended on that date. Having occasion to move it on the twentyfourth, I peeped in and found half my caterpillars out and starved, proving that they had been hatched at least thirty-six hours or longer; half the others so feeble they soon became inactive, and the remainder survived and pupated. But if the time specified had been allowed to elapse, every caterpillar would have starved.
One of the books I read preparatory to doing this work asserts concerning spinners: "Most caterpillars make some sort of cocoon or shelter, which may be of pure silk neatly wound, or of silk mixed with hair and all manner of external things--such as pieces of leaf, bark, moss, and lichen, and even grains of earth."
I have had caterpillars spin by the hundred, in boxes containing most of these things, have gathered outdoor cocoons by the peck, and microscopically examined dozens of them, and with the exception of leaf, twig, bark, or some other