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Abstract: 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 (T a =2.9–42.4°C) mean CO2 production rate of resting wasps increased steeply according to an exponential function, from 5.658μlg−1 min−1 at 8.3°C to 8.504μlg−1 min−1 at 20.2°C, 58.686μlg−1 min−1 at 35.3°C and 102.84μlg−1 min−1 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. [Copyright &y& Elsevier]

Abstract: A comparison of the thermoregulation of water foraging wasps (Vespula vulgaris, Polistes dominulus) under special consideration of ambient temperature and solar radiation was conducted. The body surface temperature of living and dead wasps was measured by infrared thermography under natural conditions in their environment without disturbing the insects’ behaviour. The body temperature of both of them was positively correlated with T a and solar radiation. At moderate T a (22–28°C) the regression lines revealed mean thorax temperatures (T th) of 35.5–37.5°C in Vespula, and of 28.6–33.7°C in Polistes. At high T a (30–39°C) T th was 37.2–40.6°C in Vespula and 37.0–40.8°C in Polistes. The thorax temperature excess (T th–T a) increased at moderate T a by 1.9°C (Vespula) and 4.4°C (Polistes) per kW−1 m−2. At high T a it increased by 4.0°C per kW−1 m−2 in both wasps. A comparison of the living water foraging Vespula and Polistes with dead wasps revealed a great difference in their thermoregulatory behaviour. At moderate T a (22–28°C) Vespula exhibited distinct endothermy in contrast to Polistes, which showed only a weak endothermic activity. At high T a (30–39°C) Vespula reduced their active heat production, and Polistes were always ectothermic. Both species exhibited an increasing cooling effort with increasing insolation and ambient temperature. [Copyright &y& Elsevier]