Spatial variation of the aggressive response towards conspecifics in the ant Crematogaster scutellaris (hymenoptera: formicidae)

In this study we investigated the relationship between spatial distance and intraspecific aggression in the Mediterranean tree-nesting ant Crematogaster scutellaris. Aggression tests were carried out in the field confronting group of workers (20 from each nest) collected from pairs of nests located at increasing distances one from the other (5, 10, 20, 40 and 80 meters). For each distance, 6 replicate tests, using different pairs of tests, were carried out. The probability of aggression and the time of the first aggressive event were recorded and modelled as a function of the distance between two nests using generalised linear models. Results showed that both the probability of aggression and the time of first attack were correlated to spatial distance in a complex way, having their maximum at intermediate distances between nests. The observed relationship cannot be simply interpreted according to the “dear enemy” or the “nasty neighbour” effects and contains elements in favour of both.