The effect of constant temperature on egg development in the desert locustSchistocerca gregaria(Forsk.)

Abstract

Laboratory studies were conducted on the incubation period of the desert locust,Schistocerca gregaria(Forsk.). When egg-pods were incubated at constant temperature, the duration of the incubation period ranged from 50 days at 19·7°C to 11–12 days at 35–41 °C. The colour of the resulting hatchlings showed dependence on temperature, ranging from grey-white at 41 °C to overall black at 20°C. The minimum temperature at which embryonic development took place was 15·1°C, while the minimum temperature for the hatching sequence was about 20–24°C. The upper lethal limit for embryonic development depended both on temperature and on the duration of exposure of the eggs to that temperature. For example, constant temperatures above 38°C throughout development reduced viability, but exposure to 40°C for six hours each day did not adversely affect development or hatching. Between 15·1 and 35°C the rate of egg development was proportional to temperature; above 35°C the rate appeared to be constant and independent of temperature. Embryonic development was complete when the eggs had experienced 224 degree-days above 15·1°C, except at temperatures in excess of 35°C.