The Influence of Drought on the Survival of Eggs of Austroicetes cruciata, Sauss. (Orthoptera) in South Australia

Abstract

Drought is the only factor in the environment of the eggs of Austroicetes cruciata that is likely to cause a high mortality rate of the eggs in the field.The eggs may be exposed to drought at various stages of their development. The probability of high mortality due to exposure to drought during the winter is considered to be negligible.The probability of a high mortality rate due to drought when the nymphs are hatching is unimportant. From an analysis of the meteorological records for 50 years, it was estimated that high mortality rates from this cause may occur 12 times in a thousand years at Hawker and less frequently elsewhere in the grasshopper belt.The eggs are exposed to the most severe hazards during the summer. An analysis of the meteorological records shows that severe mortality rates may have occurred as a result of drought in the summer from one to seven times during the 50 years 1891–1940, depending upon the district.