2nd Place: Multimodal signaling by queens regulates mating behavior in the bumble bee Bombus impatiens

Insect mating is often regulated by sex pheromones that convey information about mate species, quality, and receptiveness. These signals are released from exocrine glands and elicit response in conspecifics. In bumble bees, sex pheromones in males have been investigated intensively but the queen pheromones or their glandular source remained poorly studied. Bumble bee males mark mating sites with labial gland secretions, however, the male’s signaling alone has not been found to stimulate mating behavior. Our study examines signals produced by the virgin queens and their role in short range attraction and mating behavior in Bombus impatiens. We propose that males rely on multimodal signaling, combining both visual and chemical signals produced in the queens’ Dufour’s and labial glands. Using a 2-choice bioassay, we show that males are attracted to both live and dead queens over workers but are not attracted to dummy queens that were stripped from their chemical odors, or to the chemical signals alone. We further show that this attraction does not occur under red light (a spectrum that the bees cannot see), suggesting males are relying on a combination of visual and chemical signals, but not on visual or chemical signals alone. Current experiments aim to identify the source of the pheromone by testing male attraction to the total secretion and selected compounds produced in the Dufour’s and labial glands. These results demonstrate the role of virgin queens in stimulating mating behavior. Furthermore, our study models the importance of multimodal signal bioassays for sex pheromone identification.