Comparing the nest chemical profile of Vespa velutina and Vespa crabro: a potential tool to detect invasive hornet species

In the fight against invasive alien species, timely reporting is essential to monitor their spread and face the invasion. This is particularly evident in the case of Vespa velutina nigrithorax, an invasive hornet species with a significant ecological, economic, and public health impact. V. velutina colony reports are often late or dubious, as they are represented by the discovery of abandoned nests found in late autumn or winter when the colony has completed its cycle. Abandoned colonies of V. velutina might be in some cases misidentified with nests of the native European hornet Vespa crabro. Verifying whether a nest belongs to V. velutina could be fundamental for monitoring its presence and expansion. Thus, a reliable method to correctly assign an abandoned nest to its exact species would be important for the management of this invasive threat. In these hornets, the nest material is characterized by a blend of chemical compounds that reflects its inhabitants and could be used for species identification. Here, by using gas-chromatography coupled with mass-spectrometry, we investigated the differences between the chemical signature of V. velutina and V. crabro nests, characterizing for the first time the nest chemical profile of the latter. Among the identified 43 compounds, two compounds were unique to V. crabro, and another two were found only in V. velutina nests. These discriminant compounds provide a diagnostic tool for the species identification of abandoned hornet nests, especially when uncertain reports come from areas on the invasion front or not yet invaded.