Five intraspecific raids, involving threePolyergus rufescenscolonies, were recorded in the field during summer 1991. These raids were characterized by violent and prolonged fights and in two cases only were invaders able to pillage some brood. We interpret this phenomenon as a consequence of territorial competition among neighbouring colonies of the European amazon antP. rufescens.These territorial battles could influence the spatial distribution of nests and therefore the success of founding by newly mated queens. The occurrence of intraspecific territorial raids observed for the first time in this obligatory slave-making ant is interpreted as an important factor in the evolution of dulosis.