A Field Study of Thermoregulation in the Carpenter Bee Xylocopa virginica virginica (Hymenoptera: Anthophoridae)

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Abstract
Thoracic, abdominal, and head temperatures were measured in individual fieldcollected Xylocopa virginica virginica performing a variety of behaviors over a wide range of ambient conditions. The bees were highly endothermic during activity, with thoracic temperatures ( ) that ranged from 31.4 to 48.5 C (at ambient temperatures, , from 15 to 35 C) and a mean thoracic temperature excess ( ) of approximately 16 C under low insolation levels. Linear regressions of on ambient temperature indicate a well-developed thermoregulatory ability (slopes of vs. : male = .25; female = .23). Air temperature, solar radiation, and, in some cases, humidity and wind speed significantly affected body temperatures. Behavior, too, significantly affected body temperatures, apparently in large part because of associated variations in heat production as well as environmental effects on body temperature. Head temperature ( ) appears to be regulated, at least in males, by control of heat transfer to the head from the thorax. During activities requiring high energy expenditure, males regulated and significantly better than females. This may be related to differences in the behavioral requirements of males and females.