Resolving issues in the genus Dioxys (Hymenoptera, Megachilidae, Dioxyini) in the West Palaearctic with a new identification key.

Abstract

The bee genus Dioxys is widely distributed across the Holarctic from the Mediterranean basin to western North America but is species-poor, and individual species can prove challenging to identify. Consequently, there has been a lack of consensus as to how many species actually exist. In the West Palaearctic, the number of species has varied from six to ten, depending on the worker. Due to a previously incorrect assessment of publication dates, Dioxysrotundatus Pérez, 1884, sp. resurr. is restored as the senior synonym of Dioxysmoestus Costa, 1884, syn. nov. The relationship between this species and Dioxysatlanticus Saunders, 1904 is clarified, with the latter restricted to the islands of Gran Canaria and Tenerife (Spain). Dioxysrufipes Morawitz, 1875 is considered part of the West Palaearctic fauna, replacing "D.moestus" sensu Warncke (1977) in the eastern Mediterranean. Dioxysmontanus Heinrich, 1977, sp. resurr. is revalidated from synonymy with Dioxyscinctus (Jurine, 1807). Dioxyspumilus Gerstäcker, 1869 is found to consist of four species, D.pumilus (eastern Mediterranean), Dioxysvaripes De Stefani, 1887, sp. resurr. (western Mediterranean), Dioxyscypriacus Popov, 1944, sp. resurr. (Cyprus), and Dioxyshermonensis sp. nov. (Israel: Mount Hermon). A neotype is designated for D.varipes, and Dioxysfalsificus Engel, 2023, syn. nov. is synonymised with it. This contribution produces a total of 13 species for the West Palaearctic region, and illustrates the degree to which persistent taxonomic problems exist even within small bee genera.