Worker task organization in incipient bumble bee nests

Abstract

Bumble bees (Bombus: Apidae) are a long-standing model system for understanding animal behaviour, ecology and evolution. However, how workers in this system are organized to perform fundamental tasks related to brood feeding and food collection remains unclear. Bumble bees undergo dramatically different life stages, across which the social environment, and therefore task organization, changes over time. Queens initiate nests solitarily, and when the first cohort of workers emerge, they help the queen carry out brood-feeding and food collection tasks, whereas the queen transitions to primarily egg laying. Although task organization has been studied in mature colonies, few studies to date have explored how these tasks are organized in young, incipient nests. Here, we explored how food-related tasks, including brood feeding and food collection, are organized by workers in incipient colonies. We found that food-related tasks were nested, in that the majority of workers fed brood, a subset also collected nectar and a smaller subset also collected pollen. These patterns suggest that brood feeding is a task shared by most workers, and that the distinction between pollen collecting versus nonpollen collecting might be the most important axis of division of labour in bumble bee nests, at least at the early nesting stage.