Individuality and colonial identity in ants: the emergence of the social representation concept

Abstract

Colonial identity in social insects is based on nestmate recognition, which is mediated through cuticular substances. Although this is considered to be distinct from kin recognition, it is possible that through evolution the signal mediating kinship was replaced by the signal mediating “nestmateship”. Cuticular hydrocarbons in Cataglyphis niger are responsible for modifying the ant’s aggressive behavior and are considered to have a similar function in other ants species. In ants, the postpharyngeal gland (PPG) serves as a storage organ for these cues and functions as a “gestalt” organ, with the gestalt being permanently updated. Its content is constantly being exchanged with nestmates through trophallaxis and allogrooming. We hypothesize that already in the primitive ponerine ants the PPG evolved as a gestalt organ even without trophallaxis. We discuss two alternative primary selective pressures for the evolution of trophallaxis: facilitating food exchange versus exchanging recognition cues. Callow workers seem to be characterized by a “cuticular chemical insignificance” followed by a “chemical integration” period when they acquire the gestalt of the colony and learn the associated template. We hypothesize that the template has evolved from a simple personal chemical reference in primitive species with small colonies to an internal representation of the colonial identity in larger colonies.