We are not the same: a chemical heterogeneity between workers in the Yellow-legged hornet

Abstract

Social organisation of eusocial insects requires efficient communication among conspecifics, involving various signals. Among them, Cuticular Hydrocarbons Compounds are used like chemical signals for recognition processes. These semiochemical compounds, which can vary qualitatively and quantitatively, form an individual chemical signature carrying identity of each congeners which contribute to the social cohesion of the colony members. In this study, we analysed the chemical signature of workers of the eusocial and invasive Vespidae species, the Yellow-legged hornet, Vespa velutina nigrithorax. The chemical communication system between hornets’ workers is relatively unknown and their social organisation poorly documented. However, a strong chemical heterogeneity between castes and colonies have been previously identified in the Yellow-legged hornet, suggesting a possible chemical diversity between workers. Our results showed a strong chemical heterogeneity mainly explained by their colonial origin, as previously described, but also by their behaviour at a given time. In this study, four behaviours have been reported in the field and could be assigned to a workers’ sub-caste: animal foragers, builders, defenders and material foragers. A chemical separation of individuals into two groups have been observed, where animal foragers exhibit a clear separation of their chemical profiles compared to their counterparts. Also, animal foragers had more alkenes and fewer branched alkanes than the other workers. This exploratory study demonstrates that workers of this invasive hornet species present different cuticular profiles, probably used in both inter and intra-specific recognition phenomena. This is therefore a first step towards understanding the chemical communication involved in the social organisation of hornet workers.