Search

The metabolism of ectotherms is temperature-dependent, and the exponential nature of the metabolic rate- temperature relationship means that warmer temperatures are disproportionately affecting the energy balance. T SB a sb (standard met.) temperature deviation from microclimate ambient nest temperature was -3.6 °C in I P. dominula i , -2.4 °C in I P. gallicus i , and -3.3 °C in I P. biglumis i ). The energetic calculations were conducted using temperature-dependent metabolic rate models of the three I Polistes i species, I P. dominula i , I P. gallicus i and I P. biglumis i [[17], [29]], and adequate body temperature models [[4], [17]]. The nest ambient air temperatures in the three habitats were clearly elevated above the meteorological standard ambient temperature recorded by the nearest weather stations (temperature difference, I P. dominula i : 3.6 °C, I P. gallicus i : 2.4 °C, I P. biglumis i : 3.3 °C; Figure 2). [Extracted from the article]

Honeybees need water for different purposes, to maintain the osmotic homeostasis in adults as well as to dilute stored honey and prepare liquid food for the brood. Water is also used for cooling of the hive. Foraging in endothermic insects is energy-intensive and the question arises how much energy bees invest in a resource without any metabolically usable energy. We investigated the energy demand of water collecting bees under natural conditions. The thermoregulation and energetic effort was measured simultaneously in a broad range of experimental ambient temperatures (Ta = 12-40 °C). The thorax temperature as well as the energetic turnover showed a great variability. The mean Tthorax was ranging from ~ 35.7 °C at 12 °C to nearly 42.5 °C at 40 °C. The energy turnover calculated from CO2-release was highest at a Ta of 20 °C with about 60 mW and lowest at 40 °C with about 22 mW per bee. The total costs during collection decreased from 10.4 J at 12 °C to 0.5 J at 40 °C. The energetic effort of the water collectors was comparable with that of 0.5 M sucrose foraging bees. Our investigation strongly supports the hypothesis that the bees’ motivational status determines the energetic performance during foraging. [ABSTRACT FROM AUTHOR]

Vespine wasps ( Vespula sp.) are endowed with a pronounced ability of endothermic heat production. To show how they balance energetics and thermoregulation under variable environmental conditions, we measured the body temperature and respiration of sucrose foragers (1.5 M, unlimited flow) under variable ambient temperature ( T = 20-35 °C) and solar radiation (20-570 W m). Results revealed a graduated balancing of metabolic efforts with thermoregulatory needs. The thoracic temperature in the shade depended on ambient temperature, increasing from ~37 to 39 °C. However, wasps used solar heat gain to regulate their thorax temperature at a rather high level at low T (mean T ~ 39 °C). Only at high T they used solar heat to reduce their metabolic rate remarkably. A high body temperature accelerated the suction speed and shortened foraging time. As the costs of foraging strongly depended on duration, the efficiency could be significantly increased with a high body temperature. Heat gain from solar radiation enabled the wasps to enhance foraging efficiency at high ambient temperature ( T = 30 °C) by up to 63 %. The well-balanced change of economic strategies in response to environmental conditions minimized costs of foraging and optimized energetic efficiency. [ABSTRACT FROM AUTHOR]

Abstract: Endothermic insects like honeybees and some wasps have to cope with an enormous heat loss during foraging because of their small body size in comparison to endotherms like mammals and birds. The enormous costs of thermoregulation call for optimisation. Honeybees and wasps differ in their critical thermal maximum, which enables the bees to kill the wasps by heat. We here demonstrate the benefits of a combined use of body temperature measurement with infrared thermography, and respiratory measurements of energy turnover (O2 consumption or CO2 production via flow-through respirometry) to answer questions of insect ecophysiological research, and we describe calibrations to receive accurate results. To assess the question of what foraging honeybees optimise, their body temperature was compared with their energy turnover. Honeybees foraging from an artificial flower with unlimited sucrose flow increased body surface temperature and energy turnover with profitability of foraging (sucrose content of the food; 0.5 or 1.5mol/L). Costs of thermoregulation, however, were rather independent of ambient temperature (13–30°C). External heat gain by solar radiation was used to increase body temperature. This optimised foraging energetics by increasing suction speed. In determinations of insect respiratory critical thermal limits, the combined use of respiratory measurements and thermography made possible a more conclusive interpretation of respiratory traces. [Copyright &y& Elsevier]