The development of a stock of Corcyra cephalonica (Stnt.) from Burma was followed carefully on a diet of wheatfeed, glycerol and yeast at constant temperatures ranging from 15 to 37°C and humidities from 15 to 90% RH. Two other stocks, from Nigeria and Malawi, were also studied under a few conditions. Limits for complete development from egg hatch to adult emergence were about 17 and 35°C at 70% RH. At 15°C, all larvae died early in development, but at 37 -5°C a few managed to pupate. Highest survival and most rapid development occurred at 30-3 2-5 °C and 70% RH. Development was completed in the range 15-80% RH, but few adults emerged at 15% RH and none at 90% RH unless a mouldinhibitor was present in the food. No second-generation larvae were obtained from adults reared and kept at 20°C and 70% RH. Egg period was influenced by temperature but not by humidity in the range 20-80% ,RH. Eggs hatched at temperatures from 175 to 325 C C. Hatch was adversely affected by low humidity, and very few hatched at 20% RH. Considerable variation in the rate of egg hatch between the three stocks may have been due to differences in the length of time each stock had been reared in the laboratory. Cold tolerance of eggs of the Nigerian stock was low. All eggs died at 10°C after a seven-day exposure, and at 15°C, although a few 0-1-day-old eggs exposed for 14 days hatched, none completed development to the adult stage. Although older eggs were slightly more cold-tolerant than younger ones at 10°C, they were less so at 15°C. Adult males tended to emerge earlier and live longer than unmated females. Adults of the recently collected Malawi stock were heavier and lived longer than those of the Burma stock that had been reared in the laboratory for many generations.