Virgin queen attraction toward males in honey bees

Abstract

Although the honeybee is a crucial agricultural agent and a prominent scientific model organism, crucial aspects of its reproductive behaviour are still unknown. During the mating season, honeybee males, the drones, gather in congregations 10–40 m above ground. Converging evidence suggests that drones emit a pheromone that can attract other drones, thereby increasing the size of the congregation. Virgin queens join the vicinity of the congregation after it has formed, and mate with as many as 20 males in mid-air. It is still unclear which sensory cues help virgin queens find drone congregations in the first place. Beside visual cues for long-range orientation, queens may use olfactory cues. We thus tested virgin queens’ olfactory orientation on a walking simulator in which they have full control over odour stimulation. We show that sexually-mature virgin queens are attracted to the odour bouquet from a group of living drones. They are not attracted to the bouquet from a group of workers. In addition, non-sexually receptive females (workers) of the same age are not attracted to the drone odour bouquet. Interpreted in the context of mating, these results may suggest that virgin queens use volatile olfactory cues from the drones to find the congregations.

Marked interspecific differences in the neuroanatomy of the male olfactory system of honey bees (genus Apis)

“…One cannot exclude, however, that secondary components of the queen pheromonal blend may have played a role during speciation in these species, together with other reproductive isolation processes. Additionally, more and more data in A. mellifera point to the use by drones of drone‐produced pheromones in the formation of the congregations (Bastin, Cholé, Lafon, & Sandoz, ; Brandstaetter, Bastin, & Sandoz, ; Gerig, ; Lensky, Cassier, Notkin, Delorme‐Joulie, & Levinsohn, ; Villar, Wolfson, Hefetz, & Grozinger, ). These cues may also be used by virgin queens to find the congregations (Bastin, Savarit, Lafon, & Sandoz, ).…”

Age-specific olfactory attraction between Western honey bee drones (Apis mellifera) and its chemical basis

“…In the context of mating, volatile stimuli seem more adequate than low-volatility compounds for supporting the formation of a drone congregation high in the air. This putative substance needs to attract other drones (but also virgin queens, see [ 45 ]) from long distances, given that drones travel up to 15 km to find a congregation area [ 72 ]. Our results thus point to the production of one or more attractive volatile molecules by sexually mature drones, which do not occur, or in too small quantities in younger drones to support mutual attraction.…”

“…Because turning the ball is an easy task for the bee, we can evaluate whether it preferred to receive odour stimulation or not. As shown by a previous experiment testing workers with an appetitively learned odorant (supplementary material in [ 45 ]), attraction can be measured by the time spent and the distance walked by the insect in the odour quadrant relative to the other quadrants.…”

“…To evaluate the effect of drone maturation on their mutual olfactory attraction, the behavioural experiments were carried out with three groups of drones: 2–3 day-old drones (N = 59), 7–8 day-old drones (N = 46) and 12–15 day-old drones (N = 39). To ensure that the results reflected the behaviour of fit, well-positioned and closed-loop aware drones, three selection criteria were used [ 45 ]: 1) Mobility: unfit drones, i.e. individuals that walked less than 200 mm during the first 5 min, were excluded; 2) Lateral bias: drones that turned more than 7200° (i.e.…”

“…We could show that drones captured when flying out of the hive are indeed attracted to the odour bouquet from other drones [ 44 ]. Interestingly, virgin queens are also attracted to such drones’ odour bouquet in this setup [ 45 ]. These results confirmed that drones produce an attractive odour substance.…”