Effect of Low Temperatures on Development, Hatching and Survival of the Eggs of Aedes aegypti (L)

Abstract

THE resistance of insect eggs to cold can be an important factor governing the survival and distribution of the species. In the case of the eggs of A. aegypti, prolonged exposure to temperatures below 10° C was shown to be lethal1. In order to examine more precisely the effect of storage at a low temperature on embryonal development, ability to hatch and viability of the prolarval stage, eggs at various stages of development were transferred to lower temperatures for periods up to 50 days. Respiration-rate and response to hatching stimulus were examined before and after treatment in the cold. Each batch consisted of eggs laid on filter paper during a period of 12 h. 100 mg of air-dried eggs were placed in microcups, and the oxygen uptake was measured at 30° C in a conventional Warburg apparatus. Respiration was nearly constant during the time of the experiment for 4–6 h. No fluid was added to the cups, in order to prevent hatching. 0.1 ml. of 20 per cent potassium hydroxide was added to the central well. Hatching was induced by lowering the oxygen concentration in the submersion medium2. In order to avoid erratic response, maximum stimulus was applied by adding ascorbic acid (10−3 M final concentration) to the hatching vessels and placing them over pyrogallol in jars which were afterwards evacuated.