Strategies of thermoregulation and foraging in two vespid wasps,Dolichovespula maculata andVespula vulgaris

Abstract

D. maculata, the white-faced hornet, stabilized (regulated) thoracic temperature (TTh) over wide ranges of ambient temperature (Ta), whileV. vulgaris, the common yellowjacket, regulatedTTh poorly. The hornets also maintained a higherTTh than the wasps, sometimes heating 38°C aboveTa. Attacking individuals of both species had higherTTh than those either leaving or returning to the nest from foraging. The hornets, who are primarily hunters of live prey, showed peak activity near dawn, and they were as active atTa=2°C as at 20°C. Being able to regulate theirTTh and fly at the lowTa should enhance their ability to capture small insects that are usually torpid at theseTa. The yellowjacket wasps, on the other hand, who are scavengers as well as hunters, did not leave the nest at 2°C; their activity decreased greatly with decreasingTa. Differences in the foraging technique of the two vespids may be related to their different abilities to thermoregulate.