Physical fights are the usual means of establishing dominance hierarchies in animal societies. This form of dominance behaviour is most strongly expressed in honeybee queens who engage in fights to the death to establish themselves in the colony. Workers can also compete for reproductive dominance resulting in the establishment of stable hierarchies. They do not engage each other physically, but use pheromones that mimic those produced by queens. The dynamics of pheromone production in paired workers suggests that they engage in a pheromonal contest. Because queen pheromones suppress ovary activation, the contest results in the sterility of the loser.