Factors influencing dominance behaviour in queenless bumblebee workers (Bombus terrestris)

ABSTRACT. The establishment of a dominance order within seventy eight groups of four callow workers was investigated. The dominant worker establishes its position by means of overt aggression. Aggression starts 20—40 h after confinement. Dominance order becomes established within 2 days of removal from the colony. Once established, the dominance order is maintained by dominant-subordinate interactions.
The dominant worker starts ovipositing at an age of about 6 days. Subordinates rarely lay eggs. In 25% of the groups the dominant worker is superseded by another worker before any oviposition occurs. Once the dominance order is established, the dominant worker inhibits endocrine activity in subordinates.
Differences in body size and in endocrine activity are thought to be responsible for the ranking of workers in the dominance hierarchy. Ranking seems to depend more on the activity of the corpora allata (CA) than on the activity of the ovaries. Ovariectomized workers do not differ from control workers in the performance of dominance behaviour. Dominant ovariectomized workers do not construct egg cells, but they do defend these if they are present.