Taxonomy and systematics of three species of the genus Eumerus Meigen, 1822 (Diptera: Syrphidae) new to southeastern Europe

The genus Eumerus Meigen (Diptera: Syrphidae) is considered one of the most species-rich hoverfly genera. Here, we present two new species, E. montanum Grković, Radenković et Vujić sp. nov. (Montenegro, Greece) and E. rubrum Grković et Vujić sp. nov. (Greece), and one species, E. uncipes Rondani, 1850, recorded for the first time in southeastern Europe. The species are members of three different taxon groups, respectively E. strigatus sensu Speight et al. (2013), E. tricolor sensu Chroni et al. (2017) and E. clavatus as defined here. Diagnostic characters for each of the three taxon groups and descriptions of the two new species are provided. In addition, we employed morphological and molecular data for available taxa of the E. strigatus taxon group in order to corroborate their taxonomical status and systematic position. Finally, we discuss the diversity of these taxon groups (E. clavatus, E. strigatus and E. tricolor) and give a detailed overview of the differences between closely-related species.