Body temperature regulation in the dragonfly, Arigomphus villosipes (Odonata: Anisoptera: Gomphidae)
Regulation of thoracic muscle temperature has been investigated in a number of dragonfly species but is poorly known in the large and diverse family, Gomphidae. Moreover, temperatures of other body regions have been recorded in very few ectothermic insects. In addition, correlations among multiple components of thermoregulatory behavior have rarely been examined quantitatively. Here I examine thermoregulation in Arigomphus villosipes, a medium-sized gomphid common at the shores of lakes and ponds in the northeastern USA. Measurements of the temperatures of the thorax (Tth), head (Th) and abdomen (Tab), using standard "grab and jab" techniques, indicate that both Tth and Th are relatively independent of air temperature (Ta). It is not clear whether Tth and Th are independently regulated, although some data suggest that they might be. Arigomphus villosipes can warm its thoracic musculature endothermically to maintain high Tth during cool Ta in conditions of low solar radiation intensity. However, regulation is principally behavioral, involving variation in body and wing postures and perhaps in perch substrate choice. Certain of these behaviors are closely associated to form suites of behavior that together are adapted to enhance or inhibit heating, while others are constrained by trade-offs with other functional demands. The former have a significant demonstrable effect on Tth. These combinations of behaviors results in a well-developed capacity for thermoregulation, allowing the insects to expand their activity periods and choice of perches, and probably improving male performance during competitive chases of females prior to mating.
