Reproductive division of labour without dominance interactions in the queenless ponerine ant Pachycondyla (= Ophthalmopone) berthoudi

In the queenless ponerine ant Pachycondyla (= Ophthalmopone) berthoudi, a v ariable proportion of the workers in each colony are mated and lay diploid eggs ("gamergates"). Virgin workers do not reproduce. The mechanism of repr oductive regulation was investigated by splitting colonies to create groups of workers containing one, several or no gamergates. In the monogynous gro ups, no aggressive interactions were observed and virgin workers showed no signs of ovarian development. In polygynous groups, aggressive interactions were also not observed and the gamergates rarely interacted with each othe r; again, virgin workers showed no signs of ovary development. The groups w ithout gamergates consisted of a large proportion of callows, with a variab le number having developed ovaries in each. No aggressive interactions were observed and there was no correlation between interindividual behaviours a nd reproductive status. Although the eggs produced in these virgin groups w ere embryonated none hatched. When sterile workers were separated from game rgates by a double mesh screen, several developed their ovaries and laid eg gs. However, when separated by a single mesh antennate screen and allowed t o gamergates, virgin workers remained infertile. Our results suggest that c hemical signals produced by reproductive individuals are important in repro ductive regulation in this species. The absence of any form of behavioural interactions in the regulation of reproduction is unusual for a queenless a nt.