Policing in queenless ponerine ants

Potential reproductive conflicts are common in insect societies. One process that can reduce or suppress conflict is policing. We review worker and "queen" policing in queenless ponerine ants. Queenless ants are an important model system for the study of intracolony reproductive conflict. Policing is widespread in queenless ants because workers are totipotent, so that additional potential conflicts occur in comparison to species where workers cannot mate, and these additional conflicts are frequently reduced by policing. Policing is more diverse than suggested by the examples known in other social insects. In almost all species of social Hymenoptera it can include preventing workers from reproducing by killing worker-laid eggs, but in queenless ants it can additionally include immobilisation or mutilation of workers attempting to reproduce by replacing the gamergate (i.e. mated worker with a queen-like role) or by becoming an extra gamergate. Policing by both workers and by the gamergate are important. Policing can be facultative. Depending on the age of the gamergate, workers can prevent her replacement by immobilising challenging workers or they can favour replacement by immobilising the gamergate. The initial definition of policing was inspired by species in which workers retain ovaries but cannot mate. We broaden the definition to include species, such as queenless ants, where females are totipotent, thereby including not only conflict over male production but also over gamergate replacement and gamergate number. Finally, we compare policing with punishment and dominance hierarchy. Policing is not always punishment and it does not necessarily entail dominance relationships.