Influence de la température d'élevage sur la fertilité des pontes de Schistocerca gregaria

Thermal conditions, within the range of ambient temperature that permits normal development, colour changes, and the behaviour characterizing sexual maturity of Schistocerca, may influence the fertility of pods estimated as the percentage of viable eggs yielding hoppers. When the insects are kept at 20°C during the night, and from 33 to 42°C during the day, the percentage of hatching is normal and rather constant during the whole parental life. When the diurnal temperature is 30°C, the rate of hatching decreases steadily as the adults grow older. At 28°C, all the pods are sterile from the beginning of the reproductive period.Interbreeding of adults reared at different diurnal temperatures shows that the males are mainly responsible for the sterility of the pods laid at 28°C; under these conditions, copulation occurs but there is no fertilization. Perturbations arising from this low temperature persist since the males do not recover their ability to fertilize females when transferred to a warmer environment.Females too are responsive to thermal conditions, but the functional disturbances provoked by a low temperature are not as serious as in the case of males and they do not last so long. A number of females bred at 28°C can be fertilized. When fertilization does occur, the percentage of hatching depends on the temperature existing at the time of laying and, especially, on the previous thermal conditions. When there is no fertilization, parthenogenetic reproduction can occur with a frequency that increases with a rise in external temperature from 28 to 36°C.