INTERINDIVIDUAL DISTANCES IN MIXED-SPECIES GROUPS OF ANTS - AN ESTIMATION OF COHESION IN SOCIAL-GROUPS

Spatial organization was estimated in mixed-species groups of ants wit h interindividual distance measures as a function of: (1) the age of t he workers when associated; and (2) the presence of the brood. Workers of Manica rubida (Myrmicinae) and Formica selysi (Formicinae) were re ared in single-species groups (control) or in artificial, mixed-specie s groups, created 5 h, 12 h or 22 h after emergence, with or without b rood. By recording the location of each individual in the nest during the 10 days following the creation of the groups, we evaluated the spa tial organization and the interindividual distances between homocoloni al or allospecific workers, and between workers and homocolonial or al lospecific brood. The cohesion of the group, depend on the age of the workers when associated: the younger the individuals are when the grou ps are created, the smaller are the interindividual distances. Moreove r, homocolonial individuals aggregated with brood, when present, which improves the overall cohesion of the group. However, in mixed groups, both species associated preferentially with members of their own spec ies. This suggests that newly-emerged ants do not depend totally on th e odors of their nestmates to construct their recognition template and that they also possess an innate, specific template.