Some Effects of the British Climate and Constant Temperatures on the Life-cycle of Ephestia cautella (Walker)

Abstract

The effect of temperature on the life-cycle of Ephestia cautella (Wlk.) has been investigated, with emphasis on the effects of constant low temperatures and of the variable conditions of the English winter. The humidity was never low enough to have any effect on survival.The total life-cycle (egg laid to adult) takes about 64 days at 20°C. and about 41–45 days at 25°C. on a wheatfeed-glycerine mixture.The lowest temperatures at which the major changes in the life-cycle can be completed are:— hatching, 10° to 13°C; pupation, 8·5°C; and the change to adult, 10° to 13°C.Large larvae are more resistant to cold than smaller larvae or eggs. The shortest exposures necessary to prevent large larvae from becoming adult are about one day at –1°C., five days at 0°C, 32 days at 5°C., or 83 days at 10°C.Pupae can become adult at slightly lower temperatures than large larvae and also they can survive slightly longer exposures at – 1°C.Adult moths live for a mean of 18 days at about 10°C. Below this temperature adult life is shortened by cold, until at – 1°C. moths survive for only one or two days. Adult life is also shortened at temperatures above 10°C., presumably by increased metabolism. At 35°C. adults live about three days. Copulation is infrequent at 13°C. and below, and few fertile eggs are laid at these temperatures. The highest number of eggs are laid at temperatures between 20°C. and 33°C.