Highly specific responses to queen pheromone in three Lasius ant species

Queen pheromones mediate the reproductive division of labor in social insect colonies and provide novel opportunities for investigating the evolution of animal communication. Previous work found that queens in the ant genus Lasius produce several 3-methylalkanes in greater relative amounts than workers do. At least one of these (3-MeC₃₁) is a queen pheromone that regulates worker sterility in two Lasius species, although there are indications that other 3-methylalkanes might also function as queen pheromones. Here, we presented workers from three Lasius species with four different 3-methylalkanes, and measured the effect on worker ovary development. In all three species, only 3-MeC₃₁ showed clear evidence of inhibiting worker fecundity. Our results suggest that worker ants can discriminate homologous hydrocarbons that differ in chain length and only treat specific homologs as queen pheromones. These results provide insight into the conflicting selective pressures on cuticular hydrocarbons arising from their multiple roles in signaling and adaptation to the abiotic environment.