Balling behaviour in the honey bee in response to exogenous queen mandibular gland pheromone

Honey bee (Apis mellifera) colonies generally respond to the introduction of a foreign queen by aggressively surrounding or 'balling' the new queen. We explored the role of queen mandibular gland pheromone (QMP) in initiating balling behaviour. The addition of a synthetic blend of QMP to the abdomen of worker bees initiated balling behaviour of these workers when re-introduced into their own colony. There was a positive, dose-dependent relationship between the number of balls formed, time to ball formation and size of balls formed. When the QMP dose was below that normally found on a queen, 10(-3) queen equivalents, it resulted in significantly slower ball formation and smaller bail diameter. The acid components of the five-component QMP elicited balling behaviour while the aromatic components did not, but the full blend elicited the strongest response. Stinging behaviour was the most prevalent and persistent factor preceding the formation of balls. We concur with others who have proposed that a 'marking' pheromone is released when an aggressive worker flexes her abdomen, and that the release of this pheromone causes ball formation. There were no obvious changes in resident queen behaviour while balling of QMP-treated workers was occurring. We conclude that queen mandibular gland pheromone is a significant signal in foreign queen recognition and the initiation of balling behaviour.