Homeothermic Response to Reduced Ambient Temperature in a Scarab Beetle

Abstract

Elephant beetles (Megasoma elephas; Scarabaeidae) weighing from 10 to 35 grams, respond homeothermically when ambient temperature is reduced below about 20°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° to 22°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.