Worker Policing in the Honey Bee: Basic Facts and Ideas

Hymenopteran societies are non-clonal. As a result, there is potential conflict among individuals or groups of individuals over reproduction. One area of conflict is male production. In most eusocial Hymenoptera, workers cannot mate but retain functional ovaries. Hence, workers can manipulate their colony's male production simply by laying eggs. Individual workers should gain from causing the colony to rear their sons because a worker is more related to her own sons (0.5) than to the queen's sons (0.25). However, in the honey bee male production by workers in queenright colonies is rare—only one adult male in a thousand is a worker's son. The rarity of workers' sons is due to worker policing—workers kill eggs laid by other workers. Workers discriminate between queen-laid and worker-laid eggs by means of an egg-marking pheromone which marks the queen-laid eggs. Over evolutionary time, worker policing has probably resulted in selection for reduced numbers of workers to have activated ovaries. In a queenright colony, only one worker bee in 10,000 has fullyactivated ovaries. Worker policing is effective because the costs of policing are low. The eggmarking pheromone makes the potentially costly error of killing queen-laid eggs quite rare. Because eggs are held in open cells it is not costly to check them. In occasional "anarchistic" queenright honey bee colonies many workers have activated ovaries and large numbers of workers' sons are reared. Eggs laid by anarchistic workers are removed from cells much more slowly. Thus an important aspect of the anarchistic syndrome is suggested to be chemical mimicking of queen-laid eggs. Anarchistic colonies are very rare, but the reason for this rarity is currently unknown. One possibility is that anarchistic colonies have increased mortality. Another possibility is that the component traits of the anarchistic syndrome, ovary activation and chemical mimicking, are individually costly and so are selected against when rare. Although human and insect societies are very different they share one basic similarity. Conflicts occur in both because resources are limited and interests vary. Worker policing tends to unite the workers in a honey bee colony because it removes most of the benefit of selfishly laying eggs. Policing in human societies can also reduce the benefit from selfish strategies. However, human society can also align selfish and collective interests in ways that insect societies cannot. For example, by making it possible for individuals to learn trades and professions needed by society but which also enable the individual to make a reasonable