Digging as tactics of escape in two bumblebee species with different nesting ecology: Bombus terrestris L. and B. pascuorum Scopoli

Abstract

Hymenoptera respond to confinement by vigorous and persistent escape behavior. In a field study, workers of two bumblebee species, Bombus terrestris L. and B. pascuorum Scop., were tested in glass tubes plugged by soil at the open end, and with their other, closed end oriented towards the-sunlight, so that the bees could alternate between two escape tactics: photopositive behavior and digging behavior. The bees of both species proved to be able to sdve such an escape task, i.e. to dig their way out of the tube almost without exceptions. However, as expected, workers of B. terrestris, a species nesting in underground cavities connected with the outside world by long tunnels, performed better than workers of B. pascuorum, a surface-nesting species. The workers of B. terrestris started to dig earlier, were digging more persistently and more efficiently, and, consequently, escaped out the test tubes earlier than the workers of B. pascuorum. High intraspecific variability in all parameters characterizing digging behavior of the bumblebees was also recorded.