Effect of body size on aggression in the ant, Cataglyphis niger (Hymenoptera; formicidae)

In polymorphic ants, such as Cataglyphis niger, sterile individual workers from the same nest show some degree of variation in size and/or morphology. We studied whether worker size and size difference between opponents had a n effect on aggression during conspecific encounters. Although the capacity to recognize nestmates was shared by all individuals, some patterns of ago nistic behaviors were size related. Escape was mostly displayed by the smal l workers, and threat, associated with ritualized fights, by the large work ers. As game theory predicted, ants of C. niger adjusted their level of agg ression as a function of the size of the opponent. However, only large indi viduals used such assessment strategies, responding with escalation of aggr ession towards small workers and reduction of aggression towards large ones . On the contrary, small individuals behaved in the same manner whatever th e opponent's size. Differences between both morphological castes were discu ssed with reference to the resource holding assessment models. (C) 1999 Wil ey-Liss, Inc.