The fire ant Solenopsis invicta has emerged as a model for such studies because a fundamental social trait is under the control of a supergene. In the monogyne social form, colonies always contain a single queen while in the polygyne social form, colonies contain many (sometimes hundreds) queens. These two social forms also differ in a host of colony- and individual-level traits, many of which relate to their different strategies of colony founding. In previous work we showed that all these differences are due to a supergene in which recombination between the variants is completely suppressed. The sequencing of haploid males further demonstrated that the same genomic region also influences social organisation in the four most closely-related species. To get a better understanding of the evolution of the supergene we will first generate a high quality genome of the non-recombining region of S. invicta to identify inversions and other rearrangements. The second aim is to identify the semiochemical that allow workers to discriminate between queens of the monogyne and polygyne forms. Our preliminary data indicate that the semiochemicals responsible for discrimination include piperidine alkaloids (which are the most abundant compounds in the volatile polar fraction) and unsaturated cuticular hydrocarobons. We therefore propose to conduct recognition assays with reconstructed blend of synthetic compounds with the aim to test if they are as effective as reference extracts from monogyne and polygyne queens. The information generated by these studies will fill a critical gap in the map between genotype and complex phenotype in S. invicta by identifying the specific semiochemicals involved in mediating an important social polymorphism.