Mate choice in the bumble bee Bombus impatiens: The role of gyne-produced signals in attracting males

Insect mating is often regulated by various signals conveying information about mate species, quality, and receptiveness. In most bumble bee species, queens mate once while males can mate multiple times, and therefore it is predicted that females will be choosy and males will show high variation in sexual traits. Indeed, bumble bee males have been shown to mark mating sites with pheromones from their labial glands, yet attracted queens may not always mate. Thus, male signals are not the only barrier for mating success. Our study examines the signals produced by gynes and their role in short-range attraction and mating behavior in Bombus impatiens. We propose that males rely on multimodal signaling, consisting of context-dependent sex pheromones produced by gynes. We first show that males are attracted to live gynes over workers only under ambient light, suggesting that males combine visual information with additional signals. Then, we show that males are not attracted to the visual signals alone and are only partially attracted to chemicals originated from the gynes’ CHCs, Dufour, labial and mandibular glands. We also show that vibrational signals produced by gynes are likely to play a role in the attraction of males. Bioassays involving chemical, visual, and vibrational signals suggest the involvement of chemicals produced in the Dufour, labial and the mandibular glands of gynes in either attracting or repelling conspecific males. These results demonstrate the role of virgin queen’s in stimulating mating, and the importance of context for eliciting mate response and choice via chemical signals.