Mandibular gland secretions of two parasitoid wasps (Hymenoptera: Ichneumonidae)

Males of Rhyssa persuasoria and Megarhyssa nortoni nortoni exhibit marked aggregation behavior prior to and during the emergence of females from host trees, and this has been linked with the secretion of an odorous liquid from the mandibular glands. The volatile components of these secretions were examined by combined gas chromatography-mass spectrometry. While both species contained 6-methylhept-5-en-2-one, M. nortoni nortoni was characterized by a series of alkyl spiroacetals and R. persuasoria contained 3-hydroxy-3-methylbutan-2-one. The same spiroacetals have previously been isolated from the mandibular glands of other Hymenoptera and have been directly associated with aggregation behavior in some species. The chemical and behavioral aspects of the two species are discussed.