Open-brood pheromone is just like it sounds, a pheromone given off by uncapped brood. Actually, at least two types of pheromone are released by open brood and together they allow the brood to regulate and control the actions of the nurse bees. Sounds backwards, but it’s true: the brood controls the workers.
For example, brood ester pheromone (BEP) increases protein production in workers, inhibits worker ovaries, and regulates the capping of brood cells. Another brood pheromone called E-β-ocimene, regulates the activities of workers, managing the nurse-to-forager ratio. According to a recent paper by Maisonnasse, Alban et al., “The production of two different types of pheromones by the larvae, gives a powerful signal to adjust all workers for colony tasks, especially larval care.”
In comparison, BEP is produced by larvae that are four to five days old and is disseminated by larva-to-bee and bee-to-bee contact. E-β-Ocimene is produced by larvae that are newly hatched to about three days old and is volatile, disseminated quickly throughout the nest atmosphere.
From a practical standpoint, open brood can be used to suppress worker ovaries in a colony that has become queenless. After a colony loses the queen, the amount of open brood soon decreases and then disappears. Without open-brood pheromone to suppress the worker ovaries, some of the workers will begin to lay unfertilized eggs which will mature into drones.
The addition of a frame of open brood every week can effectively suppress the worker ovaries until a new queen can be introduced. Some beekeepers have even been able to reverse a laying worker colony by adding open brood for several weeks. Eventually, after the worker ovaries are suppressed, the colony can raise a new queen from the introduced larvae.
Chemical communication in a beehive is complex and surprising, but learning to use the information can be a real trip.