Thermal investigations on social insects

Abstract

So cial in sects (honey-and bum ble bees, wasps, hor nets, ants and ter mites) are in ter est ing in many as pects, among them the en er getic ad van tages of so cial life and con quer ing of un fa vour able ter ri to ries. Own in ves ti ga tions and data from lit er a ture deal with the en ergy me tab o lism of these in sects (ex cept ter mites because of ex per i men tal dif fi cul ties), with lo co mo tor ac tiv i ties, en ergy bal ances of for ag ing, en ergy sav ing by in su la tion of wasp nests com pared with the af ford to con struct the wooden en ve lope, bee clus ter strat egy for sur viv ing at low temper a tures, and rear ing of brood.The en ergy and heat flow data were ob tained by in di rect and isoperibol di rect cal o rim e try, bomb cal o rim e try, ex per i ments with a cus tomer con structed car ou sel flight cal o rim e ter, ther mom e try, and false col our thermography.

Viability of thermal imaging in detecting nests of the invasive hornet Vespa velutina

“…The increase of the environmental temperature during the day may limit nest detectability, due to the higher air temperature and the presence of sunrays on the foliage of the trees. Moreover, V. velutina is predominantly diurnal (Perrard et al ., 2009; Poidatz et al ., 2018); since nest temperature is positively correlated with the number of individuals inside the nest (Schmolz & Lamprecht, 2004), it can be assumed that the difference in temperature between the nest and its surroundings ( TDI ) is at its maximum before sunrise, when all the hornets are inside the nest and the environmental temperature of the surroundings reach its minimum. On the contrary, detectability decreases after sunrise, when the environmental temperature reaches values similar to the inside temperature of hornet's nests (Martin, 1990).…”

“…It is well known that social insects are able to control the temperature of their nests in order to ensure a favourable environment for themselves and their brood through social homeostasis (Schmolz & Lamprecht, 2004), and honeybees, wasps and hornets are no exceptions (Kastberger & Stachl, 2003; Kovac & Stabentheiner, 2012). Several species of hornets tend to maintain the nest temperature around 28–30 °C by altering their own metabolism, helped by the insulating properties of the nest envelope (Stabentheiner & Schmaranzer, 1987; Martin, 1990).…”

“…Unlike honeybees, wasp and hornet colonies have an annual development cycle which starts from a solitary founder queen and then the number of workers increases during the season. Therefore, a colony in its early stage displays a limited ability for thermoregulation and only large colonies are able to maintain an optimum temperature (Martin, 1990; Schmolz & Lamprecht, 2004). Assuming that this is also true for V. velutina , the fully grown developed nests are the most suited to be revealed by thermography.…”