The effects of exposure to high temperature on egg survival and rate of development were measured in Heliothis armigera Hübner and H. punctigera Wallengren.
No adverse effect was observed on egg hatch at short exposures ( < 1h ) to temperatures of 44° C and below. 50 % mortality may occur when the eggs of both species are exposed for ca 2 hours to 44° C. High humidity ( 100 % ) significantly influenced egg hatch in both species.
Rate of development increased with exposure time at 35 °C but decreased at temperatures > 35° C. This retardation increased with longer exposures and higher temperatures. Overall H. punctigera eggs required more developmental time and heat units (degree-h) to hatch than H. armigera.
The data could be used to simulate egg survival and development in the field under high summer temperatures conditions.