LABEL FAMILIARITY AND DISCRIMINATORY ABILITY OF ANTS REARED IN MIXED GROUPS

The discriminatory ability of the ant Manica rubida was tested using m ixed species groups composed of M. rubida and Formica selysi. We recor ded the response of M. rubida reared in homospecific or heterospecific groups towards postpharyngeal glandular secretions (applied on a nest mate) of F. selysi that originated from various home-or heterospecific groups. The reaction of the ants depended largely on the source of th e scent applied, and tends to suggest a hierarchical system for deciph ering the odour. The ants exhibited a diminishing degree of aggression that corresponded to an increase in the degree of odour familiarity. The most aggressive encounters were manifested when M. rubida ants fro m homospecific colonies were exposed to the glandular secretions of E selysi ants from homospecific colonies. A lesser degree of reaction wa s noted when M. rubida from mixed species were tested with similar ali en secretions. At the other extreme, heterospecific M. rubida ants exp osed to a completely familiar signal (that of E selysi nestmates) did not elicit any overt aggression. Intermediate reactions occurred when the secretion was only partially familiar. The introduction of complet ely alien elements e.g., the occurrence of alkenes and alkadienes char acteristic to F. selysi but barely present in M. rubida from homospeci fic colonies, appeared to elicite the highest aggression. On the other hand, in M. rubida from heterospecific groups, all the signal element s were familiar but the overall composition deviated from the aquired template. We hypothesize that the deciphering of the odour may be hier archical and that the template to which the odour is compared is acqui red. Moreover, since the odour is dynamic, template plasticity must fo llow. Acquisition of the template is not a permanent event, but has to be reinforced via constant perception of nestmates' odours.