Abstract: Sericinus montelus Gray is an ornamental insect with exploitability, which overw inters as diapause pupae, and adults have polymorphism. In this study, the morph ology of diapause and non-diapause pupae and their adults were inve stigated in this butterfly in terms of color, body and wing size, and the length of spine on the 9th abdomen of pupae. Compared with non-diapause pupae, the co l or of diapuase pupae is darker. The faint yellow of antenna terminal is obviousl y different from the body color. The length of spine on the 9th abdomen of 3-day-old diapause pupae is about four times that of 3-day-old non-diapau se pupae. Therefore, non-diapause and diapause pupae can be identified at this s tage. The wingspan and tail length of adults from diapause pupae are significant smaller than those of adults from non-diapause pupae. There are also obvious differences in pattern of abdomen and wing. These differences are consistent wit h the descriptions of the spring form and summer form in this butterfly. The res ults suggest that the seasonal polymorphism of adult is related to diapause in S. montelus.

Key words: Sericinus montelus, dia pause, pupa, adult, polymorphism