Trophallaxis and aggression in the ponerine ant, Ponera coarctata: Implications for the evolution of liquid food exchange in the hymenoptera

Trophallaxis (i.e. the exchange of alimentary liquid among colony members) plays a major role in the societies of many social Hymenoptera. Food is often not equally distributed among nestmates but instead is directed towards more dominant individuals by means of trophallaxis. Antagonistic behaviour can be associated with the exchange of food, or aggression may trigger the offering of food, even where social food exchange does not normally occur. In orphaned colonies of the ponerine ant, Ponera coarctata, workers interact aggressively at a high frequency. They establish hierarchies soon after the removal of the reproductive queen. One of the consequences of aggression among workers is trophallaxis, which also occurs regularly, although less frequently, in queenright colonies. The connection of trophallaxis and aggression in Ponera coarctata and in many other species of the Hymenoptera is discussed. This study and various other examples show that, besides the nutritional function of trophallaxis, the offering of food may often serve as an appeasement behaviour during aggressive interactions. We speculate that appeasing food offers may have provided the basis for the further evolution and elaboration of trophallaxis in many social Hymenoptera.