The Response of Male Bumblebees to a Putative Queen Pheromone

Queen pheromones are chemical signals produced by the dominant reproductive female in many species of eusocial insects. These pheromones are vital for maintaining a reproductive division of labor. Two evolutionary scenarios may describe the origin of queen pheromones. Sensory exploitation describes a scenario where the pheromone is produced to take advantage of a preexisting sensory bias in a population. An alternative scenario is that the recipient of the pheromone has an adapted response to a preexisting chemical signal. There is a growing body of evidence that cuticular hydrocarbons that act as queen pheromones are co-opted from ancient fertility signals that existed in solitary ancestral species of modern social Hymenoptera. In many species of Hymenoptera, similar cuticular hydrocarbons have also been identified as sex pheromones. I tested the hypothesis that a putative queen pheromone identified in Bombus impatiens originated from a sex pheromone present in an ancestral species with an experiment designed to identify primer and releaser effects of queen pheromones on males. Although behavioral (releaser) results were inconclusive, future analyses of the collected samples may reveal neural or reproductive physiological (primer) responses to the pheromone. This experiment will serve as a foundation from which to design additional studies concerning the evolution of chemical social signals