Does she smell like a queen?: Chemoreception of a cuticular hydrocarbon signal in the ant Pachycondyla inversa

Primitive ant societies, with their relatively simple social structure, provide an opportunity to explore the evolution of chemical communication, in particular of mechanisms underlying within-colony discrimination. In the same colony, slight differences in individual odours can be the basis for discrimination between different castes, classes of age and social status. There is some evidence from correlative studies that such inter-individual variation is associated with differences in reproductive status, but direct proof that certain chemical compounds are detected and recognized by ants is still lacking. In the ponerine ant Pachycondyla inversa, fertile queens and, in orphaned colonies, dominant egg-laying workers are characterized by the predominance of a branched hydrocarbon, 3,11-dimethylheptacosane (3,11-diMeC(27)) on the cuticle. Using electroanntennography and gas chromatography with electroantennographic detection, we show that the antennae of P. inversa workers react to this key compound. 3,11-diMeC(27) is correlated with ovarian activity and, because it is detected, is likely to assume the role of a fertility signal reflecting the quality of the sender.