Thermoregulation in a hornet nest, vespa orientalis (hymenoptera: Vespinae): The interaction between workers and the pupal brood

Observations and experiments were carried out to assess continuous thermoregulation in the nest of the Oriental hornet Vespa orientalis (Hymenoptera, Vespinae). The temperature of a pupating larva inside a nest without adult hornets was found to be higher by 1°C from the nest temperature in the vicinity of the brood comb. However, the temperature of larvae subjected to diethyl ether anesthesia equaled the ambient temperature. Observations showed that adult worker hornets occasionally warm the pupae from outside their cells and this by blowing warm air through the silk cap, of each cell. Upon artificial warming of combs whose adult population was intentionally removed, the temperature around these combs (at the beginning of the warming process) was lower than that of the silk-encased pupae inside the comb cells. Beyond 31.1°C, the temperature exceeded that of the pupae. The findings suggest that of the normal nest temperature is of 29°C, the pupal temperature is 30ºC, which is apparently optimal for pupal development. Results of the present study prompted construction of a simple model that describes the interaction between the adults and the pupal brood which enables to maintain the latter at a constant temperature.