Male attraction to short-range multimodal gyne signals in the bumblebees Bombus impatiens

Mating is a crucial event in animal life, with significant implications for individual fitness. Insects have evolved complex mating systems and behaviors, such as pheromone signaling and elaborate courtship rituals, that convey vital information about species identity, mate quality, and receptiveness of prospective mates, thereby enhancing reproductive success. These signals are especially critical in social species where a single female founds a colony following a single event of mating. In this study, we investigate the short-range signals produced by gynes (newly emerged queens) and their role in mating in Bombus impatiens. Mating in bumblebees is facilitated by males marking mating sites with long-range labial gland pheromones, which attract gynes. It is assumed that gynes produce short-range signals necessary to initiate mating. While male bumblebee sex pheromones have been extensively studied across many species, the short-range signals produced by gynes remain poorly understood. Our findings show that males rely on multimodal signals, composed of visual, context-dependent sex pheromones, and likely also vibrational signals produced by gynes. Choice bioassays designed to isolate the different signals produced by gynes indicate that visual cues are essential but not sufficient for successful mating, and compounds from the labial and dufour glands likely play a role in attracting males. Our results also highlight the possible importance of vibrational signals for male attraction. Together, these findings underscore the role of gynes in regulating mating and the significance of context in eliciting male responses and mate selection through various signals.