Sucrose-response thresholds and the expression of behavioural tasks by middle-aged honeybee workers

Task assignment and division of labour in social groups persist as a key issue in the evolution of behaviour. Previous studies have argued that honeybees, Apis mellifera, display a pollen foraging syndrome that plays an important role in structuring the temporal division of labour within their colonies. Bees with low-sucrose-response thresholds early in life forage earlier and are more likely to be pollen-biased foragers than those that have higher thresholds early in life. We tested the hypothesis that sucrose-response thresholds are consistently expressed by bees performing a cluster of tasks—guarding, fanning and undertaking—that are typical of middle-aged bees. These three task groups show mean response thresholds that do not differ significantly from those of pollen foragers collected from the same colonies. However, a substantial percentage of undertakers do not respond in the bioassay, a feature that this group shares with nectar foragers. Notably, whereas mean colony response threshold varies among colonies, the ordination of response thresholds among tasks varies little among colonies. Sucrose-response thresholds for pollen and nectar foragers in our study were consistent with published results for these task groups. Our results support the hypothesis that task and sucrose-response thresholds are entwined and suggest the further hypothesis that fanning and guarding are associated with pollen collection.