Observations on the ecology of the Australian field cricket, Gryllulus commodus Walker, in the field.

Gryllulus commodus has one generation each year, the active stages being present in summer and autumn and the eggs in winter and spring. Crickets are found in abundance only in areas where the soil is heavy black clay. This affords shelter from desiccation to the eggs, which lose water very rapidly if exposed to dry conditions. Also in these areas there may be an abundance of food for the nymphs and adults, in the form of sown permanent pasture. Where either shelter for the eggs or food for the active stages is lacking the numbers of crickets tend to be lower. Certain aspects of the behaviour and physiology of G. commodus which are important in relation to the survival and multiplication of the species are discussed. The relative chanses in the abundance of crickets in the south-eastern districts of South Australia were determined by a survey method during the period 1949-52. Evidence is presented that differences In the abundance of crickets from year to year are mainly attributable to differences in the amount and distribution of rainfall during the winter and spring, which result in differential survival of the eggs. The history of cricket outbreaks in South Australia is traced and it is concluded that, if present trends in agricultural practices continue, future outbreaks will tend to be more severe and more widespread, although probably not more frequent.