Diurnal and Seasonal Changes in Thermal Preference of Single, Isolated Bees and Small Groups of Bees (Apis mellifera L.)

Abstract

The aim of the present study was: to compare thermoregulatory behaviour of single honeybee workers and groups of 3–15 bees over their annual activity period and to check out whether the annual fluctuations of ambient temperature selection are correlated with phases of the colony development. Thermal behaviour of both single workers and groups of bees was recorded, using a video camera, in a thermal gradient system. Thermal preferences of the insects were tested seasonally in spring (May/June), summer (July/August) and autumn (September–November). Both single bees and small groups of bees changed their thermal behaviour in daily cycle. The season of the year had distinct effect on temperature preferences of both single honeybee workers or small groups of bees. In single honeybee workers the lowest ambient temperatures were preferred in late spring (the swarming phase) while the highest temperatures were selected during the summer (the colony growing phase). There were significant seasonal changes in ambient temperature selected by groups of honeybee workers. Groups of honeybee workers tended to prefer the lowest temperatures in late spring and the highest temperatures were selected during the summer. The day-night differences exhibited by small groups of bees in our experiments are likely to represent behavioural responses of the honeybee colony. In our experiments we proved an influence of the season of the year on the honeybees’ thermal behaviour, which might be connected with seasonal shifts of temperature regulated by the honeybee colony.