Harvester ants utilize cuticular hydrocarbons in nestmate recognition

Cuticular hydrocarbons appear to play a role in ant nestmate recognition, b ut few studies have tested this hypothesis experimentally with purified hyd rocarbon extracts. We exposed captive colonies of the harvester ant Pogonom yrmex barbatus to small glass blocks coated with whole cuticular lipid extr acts and the purified hydrocarbon portion of extracts from nestmate and non nestmate workers. As an estimate of agonistic behavior, we measured the pro portion of ants in contact with blocks that flared their mandibles. Blocks coated with cuticular extracts from nonnestmates were contacted by more wor kers in one of two experiments and elicited higher levels of aggression in both experiments than blocks bearing extracts from nestmates. The cuticular hydrocarbon fraction of extracts alone was sufficient to elicit agonistic behavior toward nonnestmates. The results demonstrate that harvester ants c an perceive differences in cuticular hydrocarbon composition, and can use t hose differences in nestmate recognition.