Investigating queen influence on worker behaviour using comparisons of queenless and queenright workers

Abstract

Female eusocial sweat bees are capable of behaving as queens or workers. Relatively few females become queens, and those that do can directly manipulate the reproductive behaviour of other females in the nest. We collected Lasioglossum (Dialictus) laevissimum workers from nests with and without queens (queenright and queenless nests, respectively) to investigate the influence queens exert on worker behaviour via direct manipulation. Overall, very few L. laevissimum workers (17%) had developed ovaries in Ontario, but queenright and queenless workers were equally likely to have developed ovaries and worn mandibles. However, queenless workers were more likely to be mated than queenright workers. These results suggest first, that queens inhibit egg-laying in most, but not all workers, and second, that queen behaviour during the first few days of workers’ adult lives exerts a lasting influence on worker behaviour. We also compared social traits of L. laevissimum and other Dialictus species using principal components analysis. A strong correlation between worker reproduction and male availability suggests that queen manipulation of the worker brood sex ratio has evolved as an indirect mechanism for queens to discourage worker reproduction.