Temperature Regulation of Carpenter Bees (Xylocopa californica) Foraging in the Colorado Desert of Southern California

Abstract

The carpenter bee Xylocopa californica is active during the hot season in the southern California desert. It is endothermic during flight, with a V̇o2 similar to that of bumblebees and sphinx moths. Even when not flying, carpenter bees had V̇o2's an order of magnitude higher than typical insect resting metabolism, due to walking activity and possibly attempts to maintain high body temperature (Tb). Thermal conductance was higher than in moths of similar mass. Free-flying bees kept Tb between 39 and 46 C in air temperatures (Ta) ranging from 20 to 40 C. The maximum tolerable Tb for flight is remarkably high, about 48 C. Calculations of the standard operative temperature (Tes) in paloverde trees frequented by carpenter bees indicate that X. californica is not heat stressed until Ta exceeds 35–38 C, and it should not experience a serious effect on foraging patterns until Ta exceeds 41–42 C.