Agonistic interactions and exploitation of limited food sources in Blattella germanica (L.)

The importance of size asymmetries between contestants that engage in agonistic interactions at a limited food source were investigated. Rates of agonistic interactions at the experimental food sources were not density-dependent. Most of the interactions concerned dyads either of the same developmental stage or of close developmental stages. Larvae interacted more frequently with an animal of the same developmental stage whereas adults interacted more frequently with an adult of the other sex or with a large, instar 6, larva. According to the composition of the feeding group, the number of acts initiated per individual per unit time varied with developmental stage. A factorial analysis of correspondence, followed by a cluster analysis, enabled us to define three categories of interacting groups according to group structure. Feeding group structure influenced the level of individual aggression, particularly in adults. We show how a slight change in group structure modified intensity and direction of aggressiveness, particularly in males and in females.