DIAPAUSE IN THE EGGS OF GRYLLUS PENNSYLVANICUS BURMEISTER (ORTHOPTERA: GRYLLIDAE)

Abstract

Eggs of Gryllus pennsylvanicus enter diapause after about 100 hours of incubation at 23–26 °C when the embryos are in the postanatrepsis stage. The diapause is obligatory, but the so-called 'intensity' of diapause varies greatly in different eggs. Some hatch 28 days after oviposition while others require 140 days when incubated continuously at 23–26 °C.In eggs exposed to 6–7 °C for varying periods, the effect of cold treatment is to reduce the 'intensity' of diapause. Cold treatment for 90 days or more results in virtually complete termination of diapause. Such eggs require further incubation at 23–26 °C for about 15 days to complete their development.One physiological effect of the cold treatment appears to be that the yolk becomes semifluid, thus possibly allowing its easier assimilation by the embryos so that growth is speeded up, with the result that almost all eggs hatch within a relatively short period of time. It is suggested that non-availability of suitable food for the embryo may be one of the causes of diapause in G. pennsylvanicus.