Geographic Variation of Embryonic Diapause in the Migratory Locust, Locusta migratoria L. (Orthoptera, Acrididae), in Japan

Females of Locusta migratoria were collected from 20 locations in Japan and the incidence of diapause in the eggs they produced was examined. Diapause eggs were obtained in autumn in the four main islands of Japan. Nondiapause eggs were obtained in summer in southern Honshu, and in summer and winter in the South-west Islands. Effects of the parental photoperiod on diapause were examined in five populations. The most northern two populations (43°N and 39°N) produced diapause eggs and the most southern population (26°N) produced nondiapause eggs, respectively, between LD 10 : 14 and 16 : 8 hr. The intermediate two populations (35°N and 31°N) produced diapause eggs in short photoperiods (LD 10 : 14 and 12 : 12 hr) and nondiapause eggs in long photoperiods (LD 14 : 10 and 16 : 8 hr). The results showed that schematic voltinisms in this species are univoltine in northern Japan, bivoltine in southern Japan, and multivoltine in the South-west Islands. Genetic control of diapause induction was analyzed by reciprocal crossing of two populations from the bivoltine and multivoltine areas, and a maturnal effect was found to operate.