Temperature has a profound effect on the rates of biochemical reactions and thus on the physiology of organisms. With few exceptions, mammals and birds function as endothermic and homeotherms by using internally generated heat to regulate their body temperatures within narrow limits. In contrast, insects exhibit a dizzying diversity of strategies for coping with a variable thermal environment (May 1979, Casey 1981, 1993, Heinrich 1993). Some insects have independently evolved systems of endothermic homeothermy very similar to mammals and birds. Others employ physiological mechanisms or behavioral adaptations to maintain body temperatures within a favorable range. Still others forgo any temperature regulation and instead rely on biochemical adaptations that permit metabolic tolerance of broad temperature fluctuations. Most insects combine one or more of these solutions with a life-history strategy that matches periods of growth and reproduction with seasonally favorable temperatures. Here we survey a variety of responses of swallowtails to their thermal environments.