CHAPTER XVI.

SOCIAL CATERPILLARS.

Move in regular files-form Nests lined with silk-"The Processionary" The Leaf-rolling-The Leaf-bending-The Leaf-mining Caterpillar..

THE caterpillars described in the last chapter are hermits, which lead a solitary life: there are, however, other tribes which spend either a part or the whole of their vermicular life in society. The perfect insect deposits all its eggs on the same leaf or plant, and the caterpillars proceeding from these eggs are: disclosed about the same time, and frequently live together until they assume a different form. The goldtailed moth (Arctia Chrysorrhea) is one of those insects which lay eggs productive of social cater pillars. They deposit their eggs in a cover formed of hair plucked from their own body. The moment one of these caterpillars is evolved, it seeks its food! on the leaf on which the Author of nature had taught the parent insect to deposit it: a second soon joins the first-born; and a third speedily follows the se cond: thus a row of caterpillars parallel to each other may be seen reaching nearly across the leaf: a second row then begins to form itself; which, when it has extended across the leaf, is succeeded by a third. The whole of the upper surface of the leaf becomes thus entirely covered, except a small space left open for the first rank to feed upon. The heads of each rank

being generally in the same line, they all advance simultaneously; and their progress has very much the appearance of a regular military movement; as may be seen by the annexed figure.

They eat only the upper membrane of the leaf; leaving the larger nervures and the under skin untouched. The parts which they do not consume, are wanted in order to construct a habitation to protect them against the inclemencies of the weather, and conceal them from their natural enemies. As soon as they have satisfied the calls of appetite, some of the young caterpillars set about tying the leaf, which having been already rendered thin and supple, is easily made to assume a concave shape. The threads used in joining the edges of the leaf, so as to give it a cuplike shape, are so many, that they form a little silken roof under which the caterpillars feed. The exposure, however, to the light and heat does not seem to be agreeable to them; they therefore add to the thin silken roof threads in such quantities, that a perfectly white and impervious web is made. These, after all, are but temporary sheds hastily formed, until the insects have had time to construct a more complete and du

rable fabric. After the lapse of a few days they commence the erection of their new abode, which is a silken tent, sufficiently capacious to contain the whole community, and so closely woven, as to afford them, during the whole of the winter, a complete shelter both from wind and rain. They lay the foundation of their new edifice, by covering a shoot with silk, and carefully nibbling away all the leaf-buds, so as to prevent them from growing in the spring: they thus secure their abode from the destruction which would ensue from the sprouting of the branches. They then inclose, in a double covering of silk, one or two leaves at the end of the shoot; these leaves being thus brought together are worked into the form of a vault: the nest of these caterpillars may very commonly be observed attached to our fruit-trees in the autumn, when the fall of the leaves discloses them to view. By an inexperienced eye, one of these nests might be mistaken for the web of a spider: indeed, when deserted by the caterpillars, they not unfrequently become the abode

of this insect. These nests vary in shape; some being round, others flat.

They differ also in extent: in proportion as they become enlarged, either in length, breadth, or capacity, a greater number of leaves, little shoots, and even branches, are comprised within the limits of the tent. The irregularity of their shape arises from the additional webs which from time to time it becomes necessary to form. These additional webs divide the interior of the nest into irregular compartments; each of them capable of containing a number of caterpillars. If a section of these nests be examined with a microscope, the cells may be distinctly perceived; some of them containing caterpillars; others excrements;

and others both. The difficulty is to comprehend how these insects find ingress and egress, in such an apparent labyrinth. But in each web, doors or holes may be perceived, which, in adding new webs to old ones, they carefully avoid obliterating.

Into these nests, which they have been taught to spin of a texture sufficiently strong to protect them during the space of eight months, from the sun, the rain, and the storms, they retire during a part of the night, as well as during that perilous period in which they un

dergo their metamorphosis. So tender are they, that they find it necessary not only to line their tent with the softest silk, but also to carpet with the same material all the roads and approaches which lead to this habitation. Having lived together till the beginning of summer, they then separate, and undergo their usual metamorphosis.

There is a very singular species of caterpillar which fixes its residence on the oak. It is a stranger to this country, although well known in France. From six hundred to eight hundred individuals frequently dwell together in the same nest: the external form of these habitations presents nothing very striking; it resembles the large knots formed on the tree itself.

In

order to accommodate this great number of caterpillars, its dimensions must of course be considerable. Some of them measure eighteen or twenty inches in length, five or six in breadth, and four in depth. Each is a simple pocket without partitions; the sides being composed of several layers of a greyish coloured silk, which assimilates so well with the natural hue of the oak, as completely to deceive the eyes.

When the glow of day begins to soften, and the sun is about to set, these insects quit their habitation in order to proceed in search of food-the twilight and the night constituting the period of their activity. Their movements are conducted with wonderful regularity. A single caterpillar first goes out of the nest, and is immediately followed by others, which form a sort of procession: the leader is succeeded by two moving abreast; that rank by a third, composed of three abreast; and so on till sometimes the last row contains twenty ranged side by side: the ranks are so compact, that the tail of one row is touched by the