1. The reproductive activity in both sexes is completely inhibited during the exposure of adults to 34 °C immediately after feeding. The changes that take place in the reproductive system in males and females during exposure parallel those brought about by starvation or allatectomy.
2. Females exposed for 6 days to 34 °C immediately after feeding, then decapitated and placed at 28 °C, fail to form eggs, while those left with the head intact form mature eggs.
3. The course of oxygen consumption of normal males and females is compared with that of insects placed immediately after feeding at 34 °C and their respiration measured at the same temperature.
4. It seems that the corpus allatum is not active at high temperature, or if active its hormone is ineffective. It is suggested that it is the synthesis of specific adult proteins which is interfered with by high temperature, hence the inhibition of the reproductive activity.