Fight between virgin queens (Apis mellifera) is initiated by contact to the dorsal abdominal surface

To determine the nature of the stimuli involved in queen recognition, we videotaped fighting behaviour between young virgin queens and developed a bioassay. The results of the bioassay were as follows: ( 1) Under illumination with red light, the queens responded with stinging behaviour (stB.); thus, lack of visual stimuli did not play an essential role in releasing stB. ( 2) Tethered queens, narcotised queens, and dead queens were stung, demonstrating that movement was not essential for releasing stB. ( 3) Reduced contact between queens by placing a single screen between them reduced the stinging response, while queens separated by a double screen, blocking direct contact, had no stinging response. ( 4) StB. was released when queens were in contact with isolated queen abdomens or dorsal abdominal integuments. ( 5) Workers fitted with queen dorsal abdominal integument released stB. ( 6) Fifteen day old queen pupae released stB. We hypothesize that the pheromone triggering fighting behaviour is located on the queen's abdominal tergites, which is the location of the tergite glands.