Social signals in the cuticular chemical profile of Odontomachus trap-jaw ants

The cuticular chemical profile of insects is a primary means of communication. Mate choice for many solitary insects is based on sex-dimorphism, while for eusocial insects this profile provides information through which colonies members are identified and individual fertility status is assessed. Profiles of queens and workers have been described for many species, however comparisons of fertility signals between closely related species are rare. We compare the cuticular chemical profiles of four species of Odontomachus ants, O. brunneus, O, ruginodis, O. relictus, and O. haematodus, and focus on identifying the fertility signals and dimorphism between sexes. We also present experimental data from two of these species that show that fertility signals are interpreted as such by workers only when they are within the context of a complete profile. Our results provide unique insights into how these eusocial chemical signals evolve and point to the potential origin of these signals from their solitary insect ancestors.