Primer effects of a brood pheromone on honeybee behavioural development

Primer pheromones are thought to act in a variety of vertebrates and invert ebrates but only a few have been chemically identified. We report that a bl end of ten fatty-acid esters found on the cuticles elf honeybee larvae, alr eady known as a kairomone, releaser pheromone and primer pheromone, also ac t as a primer pheromone in the regulation of division of labour among adult workers. Bees in colonies receiving brood pheromone initiated foraging at significantly older ages than did bees in control colonies in five out of f ive trials. Laboratory and additional field tests also showed that exposure to brood pheromone significantly depressed blood titres of juvenile hormon e. Brood pheromone exerted more consistent effects on age at first foraging than on juvenile hormone, suggesting that the primer effects of this phero mone may occur via other, unknown, mechanisms besides juvenile hormone. The se results bring the number of social factors known to influence honeybee d ivision of labour to three: worker-worker interactions, queen mandibular ph eromone and brood pheromone.