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The relation between the respiratory activity of resting honeybees and ambient temperature (T(a)) was investigated in the range of 5-40 degrees C. Bees were kept in a temperature controlled flow through respirometer chamber where their locomotor and endothermic activity, as well as abdominal ventilatory movements was recorded by infrared thermography. Surprisingly, true resting bees were often weakly endothermic (thorax surface up to 2.8 degrees C warmer than abdomen) at a T(a) of 14-30 degrees C. Above 33 degrees C many bees cooled their body via evaporation from their mouthparts. A novel mathematical model allows description of the relationship of resting (standard) metabolic rate and temperature across the entire functional temperature range of bees. In chill coma (<11 degrees C) bees were ectothermic and CO(2) release was mostly continuous. CO(2) release rate (nls(-1)) decreased from 9.3 at 9.7 degrees C to 5.4 at 5 degrees C. At a T(a) of >11 degrees C CO(2) was released discontinuously. In the bees' active temperature range mean CO(2) production rate (nls(-1)) increased sigmoidally (10.6 at 14.1 degrees C, 24.1 at 26.5 degrees C, and 55.2 at 38.1 degrees C), coming to a halt towards the upper lethal temperature. This was primarily accomplished by an exponential increase in gas exchange frequency (0.54 and 3.1 breaths min(-1) at 14.1 and 38.1 degrees C) but not in released CO(2) volume per respiratory cycle (1487 and 1083 nl cycle(-1) at 14.1 and 38.1 degrees C). Emission of CO(2) bursts was mostly (98%) accompanied by abdominal ventilation movements even in small CO(2) bursts. Larger bursts coincided with a longer duration of active ventilation. An increased amount of CO(2) expelled per unit time of ventilation indicates a higher efficiency of ventilation at high ambient temperatures.

We investigated the respiration patterns of wasps (Vespula sp.) in their viable temperature range (2.9–42.4°C) by measuring CO2 production and locomotor and endothermic activity. Wasps showed cycles of an interburst–burst type at low ambient temperatures (T a <5°C) or typical discontinuous gas exchange patterns with closed, flutter and open phases. At high T a of >31°C, CO2 emission became cyclic. With rising T a they enhanced CO2-emission primarily by an exponential increase in respiration frequency, from 2.6mHz at 4.7°C to 74mHz at 39.7°C. In the same range of T a CO2 release per cycle decreased from 38.9 to 26.4μlg−1 cycle−1. A comparison of wasps with other insects showed that they are among the insects with a low respiratory frequency at a given resting metabolic rate (RMR), and a relatively flat increase of respiratory frequency with RMR. CO2 emission was always accompanied by abdominal respiration movements in all open phases and in 71.4% of the flutter phases, often accompanied by body movements. Results suggest that resting wasps gain their highly efficient gas exchange to a considerable extent via the length and type of respiration movements. [ABSTRACT FROM AUTHOR]

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]