1. The effect on moulting of exposing 1st-, 2nd-, 3rd- and 4th-stage larvae of Rhodnius to 36.5° C. immediately after feeding was studied. After transfer to normal temperature (28° C.) moulting is delayed; the duration of the delay is directly proportional to the period of exposure to high temperature.
2. Unfed larvae exposed to high temperature exhibit delayed moulting when placed at normal temperature after feeding, and prolonged exposure also inhibits micturition which normally occurs directly after feeding.
3. Since the Malpighian tubules appear to function normally, it is suggested that the inhibition of the mechanisms responsible for emptying the rectum results in the cessation of micturition.
4. The harmful effects on moulting of heat-treatment of unfed larvae can be eliminated by placing the exposed insects at normal temperature for an appropriate period before feeding.
5. Exposure to high temperature either before or after feeding results in the decrease and malformation of the sensory bristles and plaques in the next larval stage.