Seasonal variation in embryonic diapause of the striped ground cricket, Allonemobius fasciatus

ABSTRACT. The incidence and intensity of embryonic diapause in the striped ground cricket, Allonemobius fasciatus DeGeer (Gryllidae), is influenced by the date of oviposition and the incubation temperature. At 20C, embryos develop normally until the end of the appendage-formation stage when diapause occurs. The intensity of 'winter' diapause at this stage is greatest in eggs laid early in the season. Incubation at higher temperature induces a different and earlier 'summer' diapause. The higher the temperature the earlier the stage at which this developmental suppression is imposed. At 27 and 30C, some individuals develop without any interruption and hatch within 20 days. The proportion of these fast-developing eggs is low in summer but increases towards the end of the laying season. In nature, this species is univoltine and precocious hatching before winter is unlikely.
When embryos diapausing at an early stage at 27C are transferred to low temperatures, they resume development and enter winter diapause. The time required to reach the winter-diapause stage after transfer is inversely related to the temperature (30-30C). At 30C, sunmer diapause is neither induced nor maintained.