on without obstruction of any kind. According to A. Schenck, the gall-nuts of the rose are adapted to the shelter and support of the larvæ of more than two hundred species of flies, and those of the oak are also the home of numerous varieties. Malpighi, who died near the end of the seventeenth century, remarked that there was no part of the plant on which galls did not arise. The roots, runners, stalks, leaf-stems, leaves, buds, flower-stems, flowers, and fruit, all are made to serve as the nest or place of transformation for the young of one or more species of insect; but only the aphis lives upon them permanently.
Another very frequently observed means of securing young insect broods is by envelopes formed, sometimes with great apparent skill, by rollings or foldings of the leaf. Some weevils have the art of cutting out patterns of leaves, and, without wholly severing their attachment, rolling them up into a scroll, within which they deposit their eggs; and they do the whole with such mathematical accuracy that their constructions have been made the subjects of formal monographs, like those of Drs. Heis and Debey on the funnel-rollers. Specimens of these scrolls are familiar enough, as they have been observed on the hazel, beech, hornbeam, alder, birch, aspen, and vine, where the operations of the insects are in some seasons attended with injury to the crop. The caterpillars of many butterflies and moths are also sheltered in the same manner; while other caterpillars associate themselves together and spin webs for their nests, in the air between the leaves and twigs of trees. Nests of this kind are frequently found on fruit-trees and shrubbery, and afford a very good degree of protection to their inhabitants against late frosts, storms, birds, and parasites. The nest of the procession-spinner serves, curiously, only as a resting-place for the insect in the larval state, though it finally becomes the common home of the pupæ. The caterpillars, to satisfy their hunger, are accustomed to leave the nest in a kind of orderly procession, climbing up the stem of the tree to wander all over the crown of the foliage, and, after they have done their work, to return again in procession to their nest. They are avoided by man on account of the irritation produced by the sting of their hairs, and are for the same reason safe against all birds but the cuckoo. A carnivorous beetle, the Calosoma sycophanta, also despises their fortress and their weapons, and breaks voraciously into their communities, like a wolf into a sheep-fold. We must remember here, the consummate architectural skill with which honey-bees build up their combs of waxen cells closely joined one to another. Their whole manner of life and their professional division of labor, in which they remind us of civilized human life, provoke the query, Whence the mechanical and technical skill and the intelligence of these little creatures?
A considerable number of our insects are burrowers, and during the period of their larval development excavate, under the epidermis of the leaves and other green parts of plants, passages, small at first,
