Mating system of the European hornet Vespa crabro: male seeking strategies and evidence for the involvement of a sex pheromone.

We describe details of the mate finding strategy of drones of the European hornet, Vespa crabro, and present evidence for the involvement of sex pheromones. Tests were carried out with free flying drones in natural habitats. Males patrolled the nest site itself, as well as nearby nonresource-based sites, without showing territorial behavior. Patrolling was restricted to sunny spots in the vegetation, and thus, the locations changed throughout the day. Drones were attracted to both caged gynes and to dead workers treated with gyne extracts, indicating the presence of a female-produced sex attractant. Treated workers also elicited copulation attempts by the attracted drones. Extracts from gynes, workers, and drones contained exclusively cuticular lipids, and the profile from gynes was much more diverse than that of workers and drones. The most striking differences observed related to the alkenes, monomethyl- and dimethylalkanes. The results provide a lead for potential attracting and copulation-releasing semiochemicals in V. crabro.