The reproductive potential of workers in slave-making ants

Colonies of slave-making ants have been used repeatedly to test sex allocation theory. It was suggested that workers of slave-making ants are more strongly selected to reproduce than workers of related, non-parasitic species, because they are incapable of manipulating sex allocation and the sexualization of larvae in their colonies. I show here that in slave-making Formicoxenini, worker ovaries on average consist of significantly more ovarioles than in non-parasitic Leptothorax species. Similarly, whereas in most Leptothorax species, workers form reproductive hierarchies and lay eggs only in orphaned colonies, slave-maker workers show antagonistic interactions already in the presence of the queen and at least in some species have been observed ovipositing in queen-right colonies. The significance of these results is discussed.