ROLE OF FAMILIARITY IN STRUCTURING MALE-MALE SOCIAL INTERACTIONS IN THE COCKROACH GROMPHADORHINA-PORTENTOSA (DICTYOPTERA, BLABERIDAE)

We examined the influence of prior social experience on the outcome of agonistic interactions between male Madagascar hissing cockroaches, G romphadorhina portentosa (Schaum). Males were placed randomly in pairs and allowed to form stable dominance-subordinance associations (origi nal pairs). Two types of social conditions were then examined. Treatme nt pairs were composed of either familiar males (the males were re-pai red with the same male that they had interacted with previously) or un familiar individuals (males were paired with a male that they had not interacted with previously). Males in familiar pairs maintained their rank during subsequent interactions. However, males in unfamiliar pair s lost their rank, indicating that familiarity of the opponent and not past experience of winning or losing an encounter determined the outc ome of interactions. We also compared the behavior of individual males in the treatment groups with their behavior in the original pairings. Previously dominant males decreased their levels of aggression and hi ssed less when interacting with unfamiliar opponents. Previously subor dinate males were more aggressive and hissed more in unfamiliar pairs. As a result, overall levels of behavior displayed in pairs of males d id not differ. Aggression and hissing appear to be important in the ma intenance, rather than the establishment, of relationships between G. portentosa males. We also discuss the possibility that agonistic hissi ng functions in individual discrimination rather than as a status cue.