Chemical Strategies of the Beetle Metoecus Paradoxus, Social Parasite of the Wasp Vespula Vulgaris.

The parasitoid beetle Metoecus paradoxus frequently parasitizes colonies of the common wasp, Vespula vulgaris. It penetrates a host colony as a larva that attaches itself onto a foraging wasp's body and, once inside the nest, it feeds on a wasp larva inside a brood cell and then pupates. Avoiding detection by the wasp host is crucial when the beetle emerges. Here, we tested whether adult M. paradoxus beetles avoid detection by mimicking the cuticular hydrocarbon profile of their host. The beetles appear to be chemically adapted to their main host species, the common wasp, because they share more hydrocarbon compounds with it than they do with the related German wasp, V. germanica. In addition, aggression tests showed that adult beetles were attacked less by common wasp workers than by German wasp workers. Our results further indicated that the host-specific compounds were, at least partially, produced through recycling of the prey's hydrocarbons, and were not acquired through contact with the adult host. Moreover, the chemical profile of the beetles shows overproduction of the wasp queen pheromone, nonacosane (n-C29), suggesting that beetles might mimic the queen's pheromonal bouquet.