Queen and young larval pheromones impact nursing and reproductive physiology of honey bee (Apis mellifera) workers

Several insect pheromones are multifunctional and have both releaser and primer effects. In honey bees (Apis mellifera) the queen mandibular pheromone (QMP) and e-beta-ocimene (eβ), emitted by young larval workers, have such dual effects. There is increasing evidence that these multifunctional pheromones profoundly shape honey bee colony dynamics by influencing cooperative brood care, a fundamental aspect of eusocial insect behavior. Both QMP and eβ have been shown to affect worker physiology and behavior, but it has not yet been determined if these two key pheromones have additive or synergistic effects on: hypopharyngeal gland (HPG) development, actively used in caregiving of larvae, and ovary activation, a component of worker reproductive physiology. Experimental results demonstrate that both QMP and eβ significantly suppress ovary activation compared to controls, but that the larval pheromone is more effective than QMP. The underlying reproductive anatomy (total ovarioles) of workers influenced the effect of eβ on HPG development and ovary activation, so that worker bees with more ovarioles were more likely to develop their HPG and have activated ovaries, providing additional links between caregiving and reproductive physiology in support of the reproductive ground plan hypothesis.