ull recognition of the important role that hormones play in the growth, F differentiation, and function of insects was preceded by rather advanced information about identity and action of mammalian hormones. However, extirpation and transplantation of endocrine glands in insects and segmental ligation of larvae gradually yielded knowledge about the location of endo crine cells in insects and led to labeling their hormonal product with appropriate names. The development of relatively sensitive assays permitted the separation of active extracts of the hormones associated with meta morphosis and...