Rank orders and division of labour among unrelated cofounding ant queens

Young, unrelated queens may cooperate in colony founding (pleometrosis) in many species of ants. Whereas the founding queens of many 'advanced' specie s rely completely on body reserves in order to rear their first young, quee ns of the ponerine Pachycondyla 'inversa' forage for food. In founding asso ciations, only one queen specializes in this risky task. Here we show that the division of labour is strongly affected by aggressive interactions betw een cofounding queens: the dominant remains in the nest and guards the broo d, whereas the subordinate is forced to leave and forage. The frequency of queen antagonism increased with the duration since food was last added to t he foraging arena. Egg-laying rates did not differ significantly between ne st-mate queens, but dominant queens destroyed and ate some of the eggs laid by subordinates.