In a honeybee colony, brood stimulates development of hypopharyngeal glands of nurse bees. A chemical signal, a blend of 10 fatty acid esters, has been identified on larval cuticle. We demonstrate that the blend of 10 esters, ethyl oleate, and methyl palmitate stimulates the protein synthesis of hypopharyngeal glands of nurses. Thus, in Apis mellifera the chemical signal from the brood acts as a primer pheromone in addition to its previously shown role as a releaser pheromone.