The reproductive system of a Diacamma species from Malaysia is described. Intact colonies have no queens. Instead one mated worker (gamergate) reproduces. Only a few workers (2%) have weakly developed ovaries. Newly emerged workers possess thoracic appendages, called gemmae, but only one worker retains them, mates and becomes a gamergate. All other individuals are mutilated mostly by already mutilated workers. After the gamergate has been removed this mutilation-behavior continues for at least 24 h. After three days no more mutilation occurs.
Groups of workers without gamergate start to fight about one week after the gamergate was removed and one worker reaches the alpha-position and becomes the sole egg layer. When workers emerge in already established groups they are not mutilated. Workers, which were isolated one week earlier than the rest of the group, and thus already escaped inhibition by the gamergate, had a higher chance to obtain the alpha-position.
To test factors that might influence worker-dominance, juvenile hormone titer was measured. Juvenile hormone was not detectable in gamergates and alpha-workers but the amounts of juvenile hormone in non-reproductive workers increased with age. This is discussed with regard to the situation found in honeybees.