**6. Conclusions**

The alien species *V. v. nigrithorax*, since its accidental introduction in France, has now successfully colonized several European countries. In the areas in which it has settled, it has become clear that it has a negative effect on *A. mellifera*, documented by the numerous losses of beehives reported by beekeepers. Hornets concentrate their predation activity on the honey bee colonies as they provide an abundant and continuous source of food. *V. v. nigrithorax*, however, hunts numerous other insects present in the environment and, among them, wild bees, attacking them while they are on the flowers intent on collecting nectar and pollen. This activity removes from the environment insects that play a very important ecosystem role. In fact, by visiting cultivated and spontaneous plants, wild pollinators guarantee not only the production of seeds and fruits of economic interest, but also the biodiversity of spontaneous plants.

Recent studies have shown that in Europe, and on other continents, pollinating insects and honey bees are in decline due to a combination of multiple factors. There is no doubt that the accidental introduction of the invasive predator *V. v. nigrithorax* can aggravate the situation. In fact, the Asian yellow-legged hornet has widely contributed to the decrease in the colonies of honey bees, weakening them to such an extent that they collapse and are more susceptible to parasites, viruses, and fungi.

Given the fundamental role of natural pollinators, studies are currently under way to ascertain the real effects of *V. v. nigrithorax* on wild bee populations and, more generally, on the environment in the newly introduced areas.

The introduction of an invasive exotic species, as well as causing damage to the ecosystem and biodiversity, can also generate a grea<sup>t</sup> deal of damage to the economy. *V. v. nigrithorax* has a negative impact, particularly on agriculture. The disappearance of beehives leads to the loss of honey bee products, putting the beekeeping industry in the position to be out of the market due to lack of production and/or rising of production costs. This type of economic impact is currently the most studied and can be easily expressed in monetary values.

The reduction in production yields of crops, as a result of the reduction of pollinators in general, is not quantifiable at the moment.

**Author Contributions:** Conceptualization, D.L. and A.M.; validation, S.L. and L.C.; literature investigation, D.L., A.M. and M.P.; data curation, D.L., S.L. and L.C.; writing—Original draft preparation, D.L.; writing—Review and editing, D.L. and S.L.; visualization, D.L. and L.C.; supervision, M.P.; project administration, S.L.; funding acquisition, M.P. All authors have read and agreed to the published version of the manuscript.

**Funding:** The paper was published thanks to University of Turin funds but should be considered as an After-LIFE product of the LIFE14 NAT/IT/001128 STOPVESPA funded by the European Commission.

**Conflicts of Interest:** The authors declare no conflict of interest, the absence of any personal circumstances or interest that may be perceived as inappropriately influencing the representation or interpretation of reported research results. The funder had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
