Taxonomic revision of the Stenodynerus fastidiosissimus species-group in Western Europe and North Africa (Hymenoptera: Vespidae: Eumeninae).

The fastidiosissimus species-group of Stenodynerus de Saussure, 1863 is revised in Western Europe and North Africa, combining morphological data and DNA barcoding. Six species are recognized: S. difficilis (Morawitz, 1867) stat. resurr. (= S. fastidiosissimus auct.), S. fastidiosissimus (de Saussure, 1855), S. laborans (Costa, 1882) stat. resurr., S. montanus Selis, sp. nov., S. muelleri (Dusmet, 1917) (= Stenodynerus gusenleitneri Giordani Soika, 1986 syn. nov.), and S. rufescens Giordani Soika, 1977 stat. nov. Lectotypes are designated for Odynerus fastidiosissimus de Saussure, 1855 and Odynerus insularis Andr, 1883 non Smith, 1859. A key for the identification of members of this species-group is provided. DNA barcodes are published for every species, representing the first available sequences for the fastidiosissimus species-group.