Although outwardly still, and although all the former activity appears to have been exchanged for a state of dull repose, changes of active kind, and of marvelous extent, are meanwhile proceeding within the cocoon or pupa-case. The elements of the caterpillar’s form are being gradually disintegrated or broken down, and built up anew in the form and image of the adult butterfly. Old textures and garments are being exchanged for new ones; particle by particle the outward and inward structures of the larva are being replaced by others proper to the mature being; and in due course, and after a longer or shorter period, the cocoon is ruptured, and the perfect form emerges--a bright and beautiful creature, furnished with wings and active senses, and rejoicing in the exercise of its new-born functions amid the sunlight and the flowers. Such is an outline of the familiar process by which the larva or caterpillar of the butterfly becomes transformed or developed, to form the “imago” or perfect and adult form. And if we review the stages exemplified in the process, we shall be able to detect in each an obvious harmony and correspondence both with the preceding and with the succeeding stage. Thus we find that the life of the perfect and mature insect is at the best of a comparatively short and transient nature, and its energies are directed chiefly to reproduction--to the deposition of eggs, from which new individuals will, in due course, be reproduced. The larval stage, on the contrary, is devoted to nutrition; to the laying up, as it were, of a store of nourishment, sufficient to last throughout the lifetime of the being, and to sustain it while its adult functions are being performed. Indeed, the entire lifetime of the higher insect may be divided into, or comprised within, two distinct periods. The first of these latter is the nutritive period, represented by the caterpillar-state, when the nutrition of the body is mainly provided for; and the second period, no less defined than the first, is included in the life of the perfect form, which is devoted to reproducing the species. This last we might therefore term the reproductive period of insect-life.