The Oriental Intruders in the Checklist: First European Records of Two Non-Native Eumerus Species (Diptera: Syrphidae) with Taxonomic Revisions of the European Fauna

The hoverfly genus Eumerus includes both vital native pollinators and potential agricultural pests, yet taxonomic ambiguities and missing distribution data hinder effective conservation and pest management. To resolve questionable taxa and compile an updated European inventory, we examined historical type specimens, reviewed literature, and evaluated species descriptions. We designate a lectotype for Eumerus alpinus Rondani, 1857, establish four new synonymies (Eumerus aurofinis Grković, Vujić, & Radenković, 2015, is a junior synonym of E. rusticus Sack, 1932; E. lasiops Rondani, 1857, is a junior synonym of E. barbarus (Coquebert, 1804); E. alpinus Rondani, 1857, is a junior synonym of E. olivaceus Loew, 1848; E. nebrodesius Rondani, 1868, is a junior synonym of E. amoenus Loew, 1848; exclude four doubtful taxa; and record two non-native Asian species (E. aurifrons (Wiedemann, 1824) and E. figurans Walker, 1859) in Europe for the first time. The updated checklist comprises 81 valid European species. Biogeographical analysis reveals peak species richness in the Mediterranean (65 species), whereas Macaronesia exhibits the highest rate of localised endemism at 75% (9 of 12 recorded species), followed by the Mediterranean (28%) and Pannonian (25%) regions. With over 60% of assessed native European Eumerus species threatened according to the IUCN Red List, this updated taxonomic framework provides an essential baseline for monitoring non-native pest introductions and guiding targeted conservation strategies for vulnerable endemic pollinators.