23. Experiments on the Sterility of Ephestia kühniella Z. (Lepidoptera, Phycitidz), in Relation to High Temperature (30° C.)

1 Cultures of Ephestia kühniella were reared at 30° C. and 23° C. These were mainly related stocks, and the emergence of adults from the two types of culture overlapped sufficiently to enable the high temperature moths to be paired with those reared at the lower temperature. 2 The effect of temperature on the longevity and the number of eggs laid was determined by placing alternate females (from both types of cultures) at 23° C. and 30° C. immediately after pairing. The percentage of eggs hatching was also determined. 3 Males reared at 30° C. were impotent when young, i. e., aged two days or less, but a small percentage of them (5 per cent.) attained potency as they aged. 4 Females reared at 30° C. and aged two days or less gave as high a percentage of successful pairings with males reared at 23° C. as did females reared at 23° C., irrespective of the temperature at which the eggs were laid. 5 Older females reared at 30° C. gave no successful pairings with males reared at 23° C. when the eggs were laid at 30° C., but gave a moderate percentage (64 per cent.) of successful pairings when the eggs were laid at 23° C. The conclusion drawn was that a temperature of 30° C. had a sterilizing effect on the females. 6 When young females reared at 30° C. were paired with males reared at 23° C. a smaller percentage of eggs hatched when these were laid at 30° C. than when they were laid at 23° C. This indicated that potent sperm may be weakened by exposure to the higher temperature. The possibility that the effect observed was due at least in part to a higher degree of abortion of the fertilized eggs when these were laid at 30° C. could not be excluded. 7 The number of eggs laid was greater and the longevity was less in females reared at 30° C. which received potent sperm than in those receiving impotent sperm. 8 The longevity of females, whether they were impregnated with potent or impotent sperm, was determined by the temperature at which they were kept after emergence, and not by the temperature at which they were reared. 9 Among females reared at 30° C. and receiving potent sperm the number of eggs was independent of the temperature at which they were laid. 10 Among females receiving impotent sperm the number of eggs laid was directly proportional to the longevity, which itself depended on the temperature at which the females were kept after pairing.