Taxonomic revision of the highly threatened Eumerus tricolor species group (Diptera : Syrphidae) in Southeast Europe, with insights into the conservation of the genus Eumerus

The diversity in the Eumerus tricolor group, the largest group within the genus in Southeast Europe, is investigated. Two new, locally distributed species are described, E. crispus Vujiv & Grkoviv, sp. n. from Serbia and E. nigrorufus Grkoviv & Vujiv, sp. n. from Montenegro. In addition to Southeast European members, one related species E. arctus van Steenis, sp. n. is described from Switzerland. We designate lectotypes for E. ovatus Loew, 1848, E. tarsalis Loew, 1848, E. tricolor (Fabricius, 1798) and E. varius Meigen, 1822. A map of the distribution of members of the E. tricolor group in Southeast Europe is provided. In addition, records from other parts of Europe are listed and an illustrated identification key to the SE European species of the E. tricolor group provided. We also study and discuss the signifi cance of small habitat patches for the preservation of species of Eumerus, because the three species described in this paper are currently known from such patches.Peer reviewe