Effects of Photoperiod and Temperature on the Maculation of the Fall Webworm Moth, Hyphantria cunea DRURY (Lepidoptera: Arctiidae)

Abstract

Hyphantria cunea has two generations per year in Japan, and there is seasonal polyphenism in the maculation of male forewings. The male moths emerging from diapause pupae of the over-wintering generation are conspicuously maculated, while those from non-diapausing pupae of the summer generation are pure white. Our experiments showed that black spots were formed by combined effects of low temperature during the pupal stage and short day-length during the larval stage and further that the former was more important than photoperiod. Concerning the relation between diapause and the formation of the maculation, short day-length during the larval stage was likely to cause an increase in the black spots only under the low temperature treatment during the pupal stage. Temperature in the larval stage was not responsible for the appearance of speckles.