An alarm pheromone in the venom gland of Vespa velutina : evidence revisited from the European invasive population
Résumé
Alarm pheromones are major communication signals in animals and major semiochemicals
in the colony organisation of social insects. We investigated the composition of
venom in Vespa velutina, an invasive hornet species accidentally introduced into Europe a
decade ago. Crushed venom glands were applied to seven wild V. velutina nests and induced
aggressive responses of workers in all the colonies tested. Then, solvent extracts or headspace
Solid Phase Micro Extraction (SPME) were analysed and quantified by gas chromatography
coupled with either flame ionization detector or a mass spectrometer, and checked retention
times to Kovats indices and Linear retention indices (LRI). We compared our results to those
obtained in the same species from its native area in a previous study. Nonan-2-one and the 4,
8-dimethylnon-7-en-2-one were found in large amount in the venom gland. Five other molecules
including the heptan-2-one, non-8-en-2-one, undecan-2-one and two unknown molecules
were also found. Similar compounds were globally found, however, one unknown compound
was present in our European population but absent in native area ones and should be identify.
Although pheromones are thought to be species-specific, our results suggest that their composition
may vary within species due to population history, thus questioning its value as a taxonomic
tool. Although our results are preliminary, we also recommend carefully considering the
origin of the Vespa velutina individuals chosen to develop pheromone-based methods (attractants
or mating disruption) for pest management.