Queen pheromones are among the most important chemical messages regulating insect societies yet they remain largely undiscovered, hindering research into interesting proximate and ultimate questions. Identifying queen pheromones in multiple species would give new insight into the selective pressures and evolutionary constraints acting on these ubiquitous signals. Here, we present experimental and phylogenetic evidence that 3-methylalkanes, hydrocarbons present on the queen’s cuticle, are a queen pheromone throughout the ant genus Lasius. Phylogenetic analyses of the chemical profile imply that 3-methylalkanes evolve more slowly than other types of hydrocarbons, perhaps due to differential selection or evolutionary constraints. We argue that the sensory ecology of the worker response imposes strong stabilising selection on queen pheromones relative to other hydrocarbons. 3-methylalkanes are also strongly physiologically and genetically coupled with fecundity in at least one Lasius species, which may translate into evolutionary constraints. Our results highlight how honest signalling could minimise evolutionary conflict over reproduction, promoting the evolution and maintenance of eusociality.

Raw CHC dataThe untransformed peak areas, produced by integrating GC-MS output files in Chemstation. The data are grouped by species and caste.Details of phylogenetic analysesPhylogentic reconstructions and Mesquite analyses. See readme file for detials.analysis_files_for_Dryad.zip