Comparative thermoregulation of sympatric endothermic and ectothermic cicadas (Homoptera: Cicadidae: Tibicen winnemanna and Tibicen chloromerus).

Measurements of body temperature in the field demonstrated that endothermic cicadas regulate body temperature by behavioral mechanisms as well as by endogenous heat production. Regression analysis suggests both endothermic and ectothermic species are thermoregulating. Body temperature of endothermically active cicadas without access to exogenous heat is approximately the same as the body temperature of basking cicadas. Tibicen winnemanna (Davis) raises body temperature in the field with the heat produced in flight or through the activation of the flight musculature without the act of flight. T. chloromerus (Walker) uses solar radiation to elevate body temperature to the level necessary for activity. The thermal responses of each species are related to its activity patterns with minimum flight temperature and shade-seeking temperatures significantly lower in the endothermic T. winnemanna. Heat torpor temperature appears to be related to the environment rather than behavior pattern. Endothermy in cicadas may serve to uncouple reproductive behavior from environmental constraints; to circumvent possible thermoregulatory problems; to permit the utilization of habitats unavailable to strictly ectothermic cicadas; to reduce predation; to optimize broadcast coverage and sound transmission; and to decrease possible acoustic interference.