SEASONAL-CHANGES IN THE INCIDENCE OF EMBRYONIC DIAPAUSE IN THE BAND-LEGGED GROUND CRICKET, DIANEMOBIUS-NIGROFASCIATUS

The incidence of embryonic diapause in the band-legged ground cricket, Dianemobius nigrofasciatus was examined in regard to egg production b y individual females both in the laboratory and in the field in Osaka, Japan. (1) Females were classified into three types: diapause egg-pro ducers (laid only diapause eggs), nondiapause egg-producers (laid only nondiapause eggs) and mixed egg-producers (laid both diapause and non diapause eggs). (2) The longer the photophase, the smaller was the inc idence of diapause egg-producers, and the larger was that of the nondi apause egg-and mixed egg-producers. The critical day-length was betwee n 13 and 14 hr. (3) The longer the photophase, the smaller was the inc idence of diapause eggs laid by mixed egg-producers. (4) In the field, both nondiapause egg-producers and mixed egg-producers were observed from June to August. In September and October, most of the females wer e diapause egg-producers. The present findings revealed that adults of the overwintered generation occur from June to August and those of th e first generation occur in September and October. The former adult fe males become mixed egg-producers or nondiapause egg-producers under lo ng-day photoperiods, and the latter females become diapause egg-produc ers under short-day photoperiods.