Homeothermic response to reduced ambient temperature in a scarab beetle.

Elephant beetles (Megasoma elephas; Scarabaeidae) weighing from 10 to 35 grams, respond homeothermically when ambient temperature is reduced below about 20 degrees C in the laboratory. This metabolic response is not associated with locomotion or any other overt activity. Warming is initiated when the body temperature reaches an apparent set point of 20 degrees to 22 degrees C. Unlike the case for euthermic birds and mammals, energy metabolism and body temperature in these beetles are conspicuously oscillatory, with a given cycle in oxygen consumption peaking before the corresponding cycle in body temperature.