Energetics and thermoregulation of foraging wasps and bees

The body temperature and the respiration of bees and wasps foraging for sucrose solution on artificial flowers were investigated in a previous project. However, investigations on the foraging energetics of these insects on natural sources in their natural environment have not been done. Therefore, for the first time we will measure the temperature and the respiration of the animals during foraging of nectar and other food in the field. Foraging honeybees and wasps there have two thermal strategies. Honeybees and vespine wasps are heterothermic insects which are ectothermic during many duties inside their nest, but heat up their thorax considerably (become endothermic) before they start foraging. This ensures proper function of their flight muscles and a high mobility. In the endothermic state their energy turnover increases with a decreasing ambient temperature and an increasing activity. By contrast, polistine wasps are hardly endothermic, i.e. they do not exhibit a strong pre-flight warm-up above the ambient level. Their energy turnover is supposed to increase with increasing ambient temperatures. These different strategies will be investigated and compared with regard to the energetic investment and use of external heat (sun) during foraging. Honeybees and wasps forage nectar from flowering plants and sweet juices from fruits. During this activity their body temperature will be measured thermographicaly by means of an infrared camera, without disturbing them. Simultaneously the surrounding air will be sucked off and the consumed O 2 and the emitted CO 2 will be measured. The same will be done when the insects collect water from a barrel. This investigation will be of special interest, because the water provides no gain in energy, but it is nevertheless essential and they therefore invest a lot of energy in this task. To assess the level of the active metabolic rate of foraging insects it is necessary to know the basal metabolic rate. For honeybees the so called "resting metabolism" is already known, but for the wasps it has to be determined. Therefore, they will have to stay overnight in a measuring chamber, where their respiration and body temperature will be measured. The hornet (Vespa crabro) is the biggest native wasp. Like in other wasps very little is known about their thermoregulation during foraging and other duties. The question is whether this species, which is of twice the body size and has a weight about five times greater than other wasps, must have a warmer thorax to be fit to fly. Therefore, their body temperature will be measured at the nest entrance (during take off and landing) and during foraging for food, water and pulb and be compared with that of bees and other wasps. This project will provide the empirical basis for the development of a general qantitative (thermodynamik) model of individual thermoregulation and energetics of foraging wasps and bees.

The body temperature and the respiration of bees and wasps foraging for sucrose solution on artificial flowers were investigated in a previous project. However, investigations on the foraging energetics of these insects on natural sources in their natural environment have not been done. Therefore, for the first time we will measure the temperature and the respiration of the animals during foraging of nectar and other food in the field. Foraging honeybees and wasps there have two thermal strategies. Honeybees and vespine wasps are heterothermic insects which are ectothermic during many duties inside their nest, but heat up their thorax considerably (become endothermic) before they start foraging. This ensures proper function of their flight muscles and a high mobility. In the endothermic state their energy turnover increases with a decreasing ambient temperature and an increasing activity. By contrast, polistine wasps are hardly endothermic, i.e. they do not exhibit a strong pre-flight warm-up above the ambient level. Their energy turnover is supposed to increase with increasing ambient temperatures. These different strategies will be investigated and compared with regard to the energetic investment and use of external heat (sun) during foraging. Honeybees and wasps forage nectar from flowering plants and sweet juices from fruits. During this activity their body temperature will be measured thermographicaly by means of an infrared camera, without disturbing them. Simultaneously the surrounding air will be sucked off and the consumed O 2 and the emitted CO 2 will be measured. The same will be done when the insects collect water from a barrel. This investigation will be of special interest, because the water provides no gain in energy, but it is nevertheless essential and they therefore invest a lot of energy in this task. To assess the level of the active metabolic rate of foraging insects it is necessary to know the basal metabolic rate. For honeybees the so called "resting metabolism" is already known, but for the wasps it has to be determined. Therefore, they will have to stay overnight in a measuring chamber, where their respiration and body temperature will be measured. The hornet (Vespa crabro) is the biggest native wasp. Like in other wasps very little is known about their thermoregulation during foraging and other duties. The question is whether this species, which is of twice the body size and has a weight about five times greater than other wasps, must have a warmer thorax to be fit to fly. Therefore, their body temperature will be measured at the nest entrance (during take off and landing) and during foraging for food, water and pulb and be compared with that of bees and other wasps. This project will provide the empirical basis for the development of a general qantitative (thermodynamik) model of individual thermoregulation and energetics of foraging wasps and bees.