By definition, ectotherms are largely dependent on environmental sources of heat for thermoregulation, but some ectotherms raise their body temperatures by producing metabolic heat. For example, the powerful flight muscles of many insects must reach 35°C–40°C before the insects can fly, and they must maintain these high temperatures during flight. Such insects warm up to fly by contracting their flight muscles isometrically in a manner similar to shivering in mammals. The heat-producing ability of insect muscle can be quite remarkable. An impressive case is a species of scarab beetle that lives mostly underground in mountains north of Los Angeles, California. These beetles come aboveground to mate, with the males flying in search of females. They undertake this mating ritual only at night, in winter, during snowstorms.

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Honey bees regulate temperature as a group. They live in large colonies consisting mostly of female worker bees that maintain the hive and rear the larval offspring of the single queen bee. During winter, worker bees cluster around the brood (eggs and larvae). They adjust their individual metabolic heat production and density of clustering so that the brood temperature remains remarkably constant, at about 34°C, even as the outside air temperature drops below freezing.