Vespine wasps are known for their high endothermic capacity. Endothermic activity is directly linked to respiration. However, knowledge on wasp respiration is sparse and almost nothing is known about their resting metabolism. We investigated the yellowjackets CO2 production in a flow-through respirometer chamber overnight. Endothermic and behavioral activity was observed by real-time infrared thermography. Most resting wasps were ectothermic or only slightly endothermic (thoracic temperature excess against abdomen < 0.6 C). In the investigated temperature range (Ta = 2.942.4 C) mean CO2 production rate of resting wasps increased steeply according to an exponential function, from 5.658 l g1 min1 at 8.3 C to 8.504 l g1 min1 at 20.2 C, 58.686 l g1 min1 at 35.3 C and 102.84 l g1 min1 at 40 C. The wasps respiratory critical thermal maximum (CTmax), marking the upper edge of their viable temperature range, was 45.3 C. The respiratory CTmax did not differ significantly from the activity CTmax of 44.9 C. CTmax values were considerably below that of honeybees (48.9 and 49.0 C for respiration and activity, respectively). This allows honeybees to kill wasps by heat-balling. Comparison with other arthropods showed that vespine wasps are among the insects with the highest mass-specific resting metabolic rate and the steepest increase of metabolism with ambient temperature.