The Moulting of the Silkworm and a Histological Study of the Moulting Gland.

Insects during the process of post-embryonic development periodically shed or moult their cuticular covering, and in addition the lining of such internal parts as are of ectodermal origin. The number of moults depends upon the number of growth periods and varies in the different species of insects. In the silkworm Bombyx mori, the species under observation, there are five of these growth periods, or “instars,” in addition to the pupal stage. At the end of each, actual ecdysis takes place. However, sometime before ecdysis takes place, certain glands of ectodermal origin become active and liberate a fluid known as “moulting fluid,” which has an important function in the process of moulting. This fluid assists in the process, and the glands furnishing the fluid are highly important organs physiologically.