Temperatures of the thorax head and abdomen (T of A. junius were investigated in free-flying individuals in the field, during endothermic warming, and during heating of the thorax with an external heat source. Field data show that is well-regulated and is strongly elevated and closely coupled to variation in Ta(j is consistent with previous suggestions that heat is pumped via hemolymph circulation from thorax to abdomen during periods of heat stress. During wingshivering in the laboratory, rises in parallel with T while T does not rise during warming of Tth but often increases by several degrees after peak Tth is reached. External heating experiments suggested that is coupled to by an active process that requires an intact circuit for hemolymph circulation but can be controlled in part independently of circulation between the thorax and abdomen.