In C. elegans, various defective phenotypes PE859 during the development, which were casused by Ras pathway mutations, led the discovery of basic components and the framework of the RTK/Ras/MAPK signaling pathway. Also in D. melanogaster, mutants related to Ras were studied and provided basic information on the function of Ras, after the identification of three Ras homologues. Such studies revealed the importance of epithelial growth factor receptors and their downstream Ras pathways for various developmental events of Drosophila ranging from cell fate determination during embryogenesis to the control of cell apoptosis. Imaginal disc proliferation and appendage differentiation during larvae/pupae stages, cell fate determination during embryogenesis, polarization of body axes during oogensis and the control of cell apoptosis were intensively studied for Ras. Thus, we can acquire a lot of information on D. melanogaster Ras. On the other hand, in relation to Ras of other insect species, there are few reports of the characteristics and the mode of action. Furthermore, ras cDNA sequences of insects except for D. melanogaster have not been reported, although several cDNA sequences have been predicted from the genome data of some insect species. During the growth of insects, the timing of developmental events, such as molting and metamorphosis, is strictly regulated by two peripheral hormones, juvenile hormone and 20hydroxyecdysone. Recently, in relation to the body size determination of D. melanogaster, it was indicated that the secretion of ecdysone, the precursor of 20E, was regulated by the Ras signaling pathway. Similarly, functional links between ecdysone and small GTPases during the development of Drosohila have begun to be reported. These reports suggest that the modes of action of 20E, and probably JH, are closely associated with the Ras function during insect development. Hydroxynorketamine However, such relations shown so far are indirect, and the precise mode of such interactions is ambiguous.It is well known that the effects of peripheral hormones, especially the roles of 20E in the metamorphosis and function of JH, are not clear in Drosophila.