Age matters: pheromone profiles of larvae differentially influence foraging behaviour in the honeybee, Apis mellifera

How a colony regulates the division of labour to forage for nutritional resources while accommodating for size and demographic composition is a fundamental question in the sociobiology of social insects. In honeybees, Apis mellifera, young and old larvae produce pheromones that differ in composition. Nurses differentially regulate larval nutrition, feeding young worker larvae a surplus diet that parallels queen larvae in protein composition and food availability, while old larvae are restrictively fed a diet with similar sugar content as queens. The presence of larvae affects division of labour, but it is unknown whether foragers regulate resource collection based on larval age or pheromone production in the nest. We studied how larval age demography and the larval pheromone e-beta ocimene affect foraging activity and foraging load. Our results suggest that workers recognize larval age, probably by detecting changes in the pheromones emitted by larvae as they mature, and adjust the foraging division of labour (pollen versus nectar) to meet the nutritional needs of the colony's brood. For younger larvae, this results in a bias towards pollen collection.