Behavioural patterns of Bombus terrestris L. (Hymenoptera Apidae) workers in captive colonies

In bumblebee societies with great plasticity in division of labour and no age-based polyethism, the existenceof a social hierarchy among workers has been recognized during all periods of colony development. This study,performed on three caged “mature” colonies of Bombus terrestris, aimed to identify and compare the behaviouralpatterns of the workers obtained by means of focal animal sampling performed during 25 hours on three randomlyselected workers for each colony. Results showed that the workers devoted most of the time to non-task behaviours,about 30% to task activities and little time to social interactions (5%) and aggressive acts (5%). From thecomparisons among colonies, differences in the stage of colony development were detected and it emerged that, atthe moment of the recordings, no colony had actually reached the initiation of the competition phase, although oneof them was probably the closest to this point.