In view of the sporadic nature of outbreaks of Gryllus bimaculatus Deg., all stages of this cricket were reared in Israel at various temperatures in order to find the effect on its development and fecundity. Eggs were incubated at constant temperatures and also at fluctuating room temperatures. The mean incubation period varied from 7·5 days at 34°C. to 75 days at a mean of 16·4°C.; at 26°C., at which the percentage hatching was greatest, it was 14 days; and the threshold of development was calculated to be about 15°C. For larvae reared at constant temperatures on a diet of bread and fishmeal, the development period varied from about 32 days at 34°C. to 130 days at 22°C.; the threshold was calculated to be 19°C. For adults maintained at constant temperatures, the mean life at temperatures of 26 to 34°C. usually exceeded one month, the preoviposition period varied from 4 days at 34°C. to about 15 at 22°C., and the threshold of reproduction was calculated as 19°C. Of 16 females tested that had been reared and maintained at near optimal temperatures (30–34°C.), more than half gave rise to upwards of 500 larvae each, and two to over 3,000 each. The reproductive capacity was affected by the temperature at which the larva was reared, the number of offspring produced being greatest from pairs of adults reared at 26°, and nil from females reared at 37°C. Light-trap catches during three years showed a peak in midsummer or autumn.