Changing responses to temperature and moisture of diapausing and developing eggs of Allonemobius fasciatus (Orthoptera: Gryllidae)

Abstract

A portion of the Allonemobius fasciatus eggs laid in September averated embryonic diapause when transferred from 20 to 27°C in the first 12 days, but this proportion decreased if the transfer was delayed until day 16 or 20. This response may be explained by the interacting effects of low and high temperatures on the two types of diapause: Incubation at 20°C decreases the incidence of summer diapause during early embryonic stages but increases the incidence of winter diapause at a later stage. The intensity of winter diapause at 20°C was greatly increased by a 5-day exposure to 27°C occurring around the diapause stage. Exposure of eggs in winter diapause to different temperatures indicates that the thermal optimum for diapause development is relatively high (16-11°C) at the beginning and decreases to 6°C later. In the field, diapause development occurred rapidly in autumn but slowly during the winter. A short exposure of eggs to dry conditions (4–6 days) increased the incidence of summer diapause at 30°C but a long exposure (≥ 15 days) terminated summer diapause. In this cricket, the effects of different temperature and moisture conditions on diapause regulation thus change during the course of morphogenetic and diapause development.