A contribution to the knowledge of the genus Thyreus Panzer in the West and Central Palaearctic (Hymenoptera, Apidae), with two new species, taxonomic updates, host relationships, and a key to European species

Thyreus Panzer, 1806, is a moderately sized bee genus containing about 115 species with an Old World distribution matching that of their principal hosts, bees of the genus Amegilla Friese, 1897. The Palaearctic fauna was revised during the mid-20 th century but has received relatively little attention since then. New collections, examination of museum specimens, and DNA barcoding have improved our understanding of this genus in the West and Central Palaearctic. The previously unknown sexes of T. parthenope Lieftinck, 1968, T. picaron Lieftinck, 1968, and T. priesneri Lieftinck, 1968, are identified and clarified. New host data are presented for Thyreus hellenicus Lieftinck, 1968, in Greece, where it parasitises Anthophora (Paramegilla) superans Walker, 1871 = Anthophora (Paramegilla) inclyta Walker, 1871 syn. nov. (= Anthophora dubia Eversmann, 1852 sensu auctorum). A lectotype is designated for Thyreus truncatus (Pérez, 1884), and its range and status are discussed. New records are presented to resolve the distributional ranges of confused or poorly studied species, along with new host data. Thyreus praevalens (Kohl, 1905) is newly reported for Europe from Greece. Specimens previously referred to as “ T. picaron ” in Central Asia do not belong to that species and are newly described as Thyreus jansseni Wood, sp. nov. (Kyrgyzstan and Afghanistan). A further new species in the scutellaris group is described, Thyreus impressus Wood, sp. nov. (Kyrgyzstan). A modified and updated identification key to the 12 European members of the genus is presented, with the aim of stimulating work on this challenging bee genus.