Embryonic Diapause and Life Cycle in the Migratory Locust, Locusta migratoria L. (Orthoptera: Acrididae), in Kyoto

Conditions for induction and completion of embryonic diapause by Locusta migratoria were identified in laboratory experiments, and the life cycle was studied by field observations in Kyoto, Japan. Afield survey showed that hoppers appeared from May to September and that adults appeared from June to December. Females collected in the field laid nondiapause eggs in June and July and diapause eggs from September to November. In the laboratory, females laid nondiapause and diapause eggs in long and short photoperiods, respectively; the critical photoperiod at 30°C was between 13.5L-10.5D and 14L-10D. When the photoperiod to which females were exposed was changed either from long to short or short to long, the percent diapause eggs produced changed according to the shift. Oviposition was suppressed in some females exposed to long photoperiods. Embryonic diapause tended to be prevented when eggs destined for diapause were incubated at high temperatures. Embryonic diapause was completed at 25°C after eggs were kept at 5°C for 4 months or at 15°C for 2 months. L. migratoria seemed to be mostly bivoltine but partly univoltine in Kyoto.