Ants and many other social insects use cuticular hydrocarbons as a chemical signature of their social group. Not only colonies differ in this chemical signature, which provides a label of identity, but even within a colony, some individuals, like the queen, have distinctive chemical profiles, which allow specific recognition. Gamergates, workers that for different reasons escape the queen's dominance and start laying eggs, also have a distinctive chemical profile. The identification of the receptors responsible for detecting these cuticular hydrocarbons has remained elusive until now. Here, the authors describe a family of olfactory receptors in the ant Harpegnathos saltator, which act as cuticular-hydrocarbon detectors and specialize in different signals (queen, gamergate, etc.), thus providing a peripheral basis for social recognition. The nine-exon subfamily of olfactory receptors is particularly expanded in this and other ant species. Using the elegant possibility of transgenically expressing the ant olfactory receptors in Drosophila melanogaster neurons, the authors characterized through electrophysiological recordings the response of 22 of these nine-exon olfactory receptors when stimulated with a significant battery of cuticular hydrocarbons. They show that they respond to compounds of several castes and to individual hydrocarbons that can be found in these compounds. Several of these receptors are specific for queen signals, others for gamergate signals and others for a more general colony signature. Thus, global identity could emerge from an across-fiber pattern signal provided by the joint contribution of several of these receptors. The interesting question that remains open, given that the analyses described remain at the peripheral level, is where these nine-exon olfactory receptors send their axons at the central level, as in other insects, information is sent to the primary olfactory center in the brain, the antennal lobe. Yet, as antennal lobes are built from glomeruli, which receive the contribution of a single receptor-neuron class, one could ask if glomeruli receiving the signals of these nine-exon receptors are located in a particular area of the antennal lobe, which would be dedicated to social recognition. Calcium imaging recordings of antennal lobe activity, upon stimulation of the nine-exon receptors with the compounds assayed in this paper, could provide the answer to this question.