Role of cuticular lipids in nestmate recognition of the European hornet Vespa crabro L. (Hymenoptera, Vespidae)

Summary:

In order to elucidate nestmate recognition in the European hornet Vespa crabro L. (Hymenoptera, Vespidae) the behavioral response of workers towards dead nestmates and non-nestmates was tested in a bioassay. The testing arena was integrated in a socially and physically intact nest, in an effort to ensure natural behavior of the extremely sensitive wasps. The hornets responded to dead non-nestmates with aggressive behavior, whereas dead nestmates were tolerated or ignored. Solvent extraction of non-nestmate dummies resulted in significant decrease of agonistic behavior of the responding workers. Their behavior towards extracted non-nestmate dummies was no longer statistically distinguishable from the behavior towards nestmate dummies treated in the same way. Treatment of extracted nestmate dummies with cuticular extracts of non-nestmates induced aggressive behavior in the responding workers, whereas treatment of the extracted non-nestmate dummies with cuticular extracts of nestmates lead to a significant decrease of agonistic behavior, when compared with untreated non-nestmates. ¶A statistical comparison of the two colonies with regard to the chemical composition of the cuticular extracts revealed that relative peak areas of 5 monoenes, 4 methyl branched alkanes, 1 terpenoid ester, and 2 n-alkanes differed significantly. The chemical analysis of the Dufour's gland revealed that all 16 compounds identified in the gland were also present in the cuticular extracts. ¶The results strongly indicate that particular mixtures of cuticular lipids play an important role in nestmate recognition of V. crabro.