The effects of temperature and moisture on the inception of diapause in eggs of the Australian plague locust,Chortoicetes terminifera Walker (Orthoptera: Acrididae)

Chortoicetes terminifera lays a mixture of diapause and non-diapause eggs during the autumn months of March and April. Diapause eggs cease development in late anatrepsis when kept in moist soil at 32.5°C. These conditions favour rapid embryogenesis and hatching in non-diapause eggs. Significant reductions in the incidence of diapause were obtained when newly-laid eggs were kept for 40 days at either 15.5°C or 32.5°C in conditions that prevented the uptake of water. In eggs held for a similar period in moist soil at 15.5°C, diapause was virtually eliminated. These eggs did not develop to the stage at which water uptake occurs. It is suggested that the inception of diapause is dependent upon the occurrence of warm, moist conditions at the time of laying and that these requirements are an integral part of the overall inductive process, which also involves the temperature and photoperiod at which the parent insects are reared. A flow-diagram illustrating the development of diapause eggs in relation to temperature and moisture is discussed in relation to the survival of the species.