Intelligence in Plants and Animals / Being a New Edition of the Author's Privately Issued "Soul and Immortality."

by Thomas G. Gentry

When we examine the cases of the Basket-worm, hardly any two will be seen to be alike in their ornamentation. So completely is the outside covered, when made upon the arbor-vitæ, which seems to be a favorite food-plant of the species, that the silken envelope is concealed from view. The bits of twigs and leaves are probably protective, and yet one would think that the extremely tough case which covers the caterpillar would be quite sufficient to protect it against all assaults of foes and stress of weather. Nevertheless, this leafy coat of mail, which sometimes wholly covers the sac, must certainly add very much to the protective value of the covering. The caterpillar has a soft, hairless body, and is thus more exposed than many of its neighbors, and nature, it would seem, has favored it far above all of its fellows.

How the worm manages to trim its coat in this manner must seem, to the uninitiated in such matters, wholly inexplicable. To enable the reader to understand the manner of operation, it will be necessary first to explain its mode of feeding. The larva has perfect control of its own movements, notwithstanding the fact that it carries its house upon its back. It can thus thrust its body out of the sac-mouth until nearly the whole of it is exposed, and twist and bend itself in every direction. Specimens have been met with that had dropped from the trees hanging by a thread and squirming, bending and snapping their bodies in the most grotesque ways, while the case spun around like an old-fashioned distaff. Now, when the caterpillar wants to feed it stretches its head and neck out of the case and moves them about until a satisfactory place has been secured, which it clasps with its true legs, three pairs of hard, conical organs armed with sharp claws, and pulls up its body and commences to spin. The spinning-organs are near the mouth, and after several movements of the head, as though smearing the liquid viscid silk upon the leaf, the head is drawn back, drawing out with it a short thread. A similar movement is then made against one side of the mouth of the sac, the process being repeated several times until a stout stay-line is spun by which the larva hangs securely. Now the creature is ready to feed. The behavior, however, varies a great deal. In feeding upon the white pine it secures itself to one leaf by its stay-line, while it reaches to an adjoining leaf which it bites off, and sitting erect, as it were, in its house, comfortably chews off the end which is continually shored upward by the first and second pairs of true legs that stand out free and untrammelled above the sac.

HOUSE-BUILDER MOTH.
Young in House, Winged Male, Young Suspended and Bag-like Female in Longitudinally-Split Cocoon.

But more frequently the worm feeds without separating the leaf from the point of suspension. By making itself fast to the under part of the leaf it is thus enabled to reach the edge, which it gnaws round and round until it has completed its destruction.

So securely does the caterpillar hold on to its house, that one would suppose that its body was lashed to the inside. But no, its body is unhampered, for it can turn itself easily around in its case, and go out at either end, although the head is generally directed upward. It clings to the inside with the hooks upon its hinder feet, and so tenaciously, too, that the writer has never been able to pull one out, being checked by the fear of tearing the creature in two. And now to the mode of attaching the leaf-cuttings to the case. This is always done at or near the mouth of the sac. The Ephemeraform larva is a growing creature, unlike the moth itself, which emerges a perfect insect of full growth. It commences life as a small worm, eats small quantities, and, as may be observed, down towards the foot of the case sews on very small tags. But after it has fastened on these pieces to the mouth, it grows itself, and so also does the case, which it continually stretches and enlarges. Hence the mouth of the case is continually changing, moving upward as the worm feeds, so that the pieces sewed upon the cap of the case thus appear, in an adult caterpillar, precisely as they are seen scattered along the outside from top to bottom. And now, as to how the pieces are put into the case, I shall endeavor to explain. That the worm cuts purposely through the twig which it needs for the case, I feel certain. Of course the outer or detached part drops down. But, while eating, the worm frequently, quite constantly, indeed, spreads its viscid silk along the leaf and so keeps it attached on both sides to the upper rim of the sac, or to its own mouth-parts, and thus the tip of the twig or leaf, instead of falling to the ground when it is severed from the stem, simply drops alongside of the case, to which it is held by the slight filament that attaches it to the sac, or, as happens in many instances, remains attached to the caterpillar’s spinneret. In either case the leaf, twig or stem remains, and, after being drawn up, adjusted and tightened by the worm, adheres tightly. As the creature is forever moving its spinning-tubes around the top of the sac, these fastenings are being continually strengthened, and thus one piece after another is added, and so the basket grows.

While the case of the Basket-worm, and even that part of its body which it chooses to expose to view, are known to the casual observer, yet but few persons have ever seen the mature insect. The female moth is wingless, and never leaves the bag, but makes her way to its lower orifice, and there awaits the attendance of the male. She is not only without wings, but is devoid of legs also, being, in short, nothing more than a yellowish bag of eggs with a ring of soft, pale-brown, silky hair near the tail. The male, on the other hand, has transparent wings and a black body, and is very active on the wing during the warmer portions of the day. After pairing the female deposits her eggs, intermingled with fawn-colored down, within the empty pupa-case, and when this task is completed works her way out of the case, drops exhausted to the ground and dies.

Though a Southern rather than a Northern insect, yet it is found as far north as New Jersey and New York, and occasionally in Massachusetts. It is extremely local in character, abounding in one particular neighborhood and totally unknown a few miles away. Where they occur in abundance they often almost entirely defoliate the trees they attack, but this can be easily prevented by gathering the cases containing the eggs for the next brood during the winter and destroying them. Hand-picking the cases with the worms in them, where their ravages are confined to small trees and shrubbery, will also help to hold them in check. Nature has provided two species of ichneumon for their destruction. One of them, Cryptus inquisitor, is about two-fifths of an inch in length, and the other, Hemiteles thyridopteryx, is nearly one-third of an inch. Five or six of this latter species will sometimes occupy the body of a single caterpillar, and after destroying their victim spin for themselves tough, white, silken cocoons within the bag.

HONEY-PRODUCING CATERPILLARS.

Late in June, growing abundantly in the edges of woods throughout this region, may be seen the Cimicifuga racemosa of botanists, popularly called Rattleweed, or Black Snakeroot. It sends up a stalk, sometimes branching, four or five feet, terminating in a spike or spikes, six to ten inches long, of round, greenish-white buds, which stand upon short stems, and are arranged in rows about the stalk, diminishing in size till they reach the pointed top. The lower buds, when they are about the size of an ordinary pea, open first, and the flowering proceeds by degrees up the spike, so that buds are to be met with throughout a period of from four to six weeks. The flowers emit an intensely sweet odor, which renders them attractive to butterflies and bees.