Species-specific volatile substances in the venom sac of hover wasps

Analyses of the volatile compounds in the venom sacs of seven species of stenogastrine wasps, belonging to three different genera, have revealed a mixture of linear alkanes and alkenes, with a chain length ranging from C(11 )to C-17 in all the species. Among conspecifics, the composition of the mixture was consistent, while clear differences have been found between different species. Venom glands of some species also contained oxygenated compounds and, in one species, some pyrazines. Most of these compounds were found to be species-specific but were not always found in every individual of a species. In the genus Parischnogaster, P jacobsoni and P. mellyi showed the presence of some spiroacetals that were not found in P. alternata and P. striatula. The possible functions of the venom sac volatiles in the biology of the Stenogastrinae are discussed.