Osmia (Melanosmia) ephippiata Smith, 1879

Proshchalykin, Maxim Yu. & Müller, Andreas, 2019, Additional records of osmiine bees (Hymenoptera: Megachilidae: Osmiini) from Siberia, Zootaxa 4563 (1), pp. 163-174 : 169

Osmia (Melanosmia) ephippiata Smith, 1879

Material examined. Russia. Irkutsk Province. ♀, Angara River [Natural History Museum, London], holotype of O. ephippiata Smith.

Distribution in Siberia. Irkutsk Prov.

General distribution. Russia (Siberia).

Remark. The female type of Osmia ephippiata Smith, 1879 is a morphologically anomalous specimen, whose mandibles are conjoined with each other and with the underside of the clypeus. This anomaly makes it impossible to assess the species-specific mandibular dentation and clypeal margin, both of which are decisive taxonomic characters in Osmia species of the subgenus Melanosmia (e.g. Tkalců 1983; Haeseler 1999; Müller 2002; Rightmyer et al. 2010; Johansson & Paukkunen 2017). Aside from this anomaly, the type of O. ephippiata closely corresponds morphologically to O. maritima Friese, 1885 . It differs from European specimens of O. maritima only by the predominantly black rather than predominantly yellowish-brown pilosity of tergum 1. However, the proportion of dark and bright hairs on tergum 1 appears to be a variable trait in O. maritima , which is exemplified by female specimens from Tyva and Altai Republics in southern Siberia, whose tergum 1 is covered with a mixture of black and yellowish-brown hairs. This suggests that in O. maritima all intergradations exist between a completely dark haired and a completely bright haired tergum 1. Thus, O. ephippiata might be a senior synonym of O. maritima . In fact, the type locality of O. ephippiata (“Angara River”, Irkutsk Province) falls within the known distribution range of O. maritima . However, in contrast to the males, females of numerous O. ( Melanosmia ) species are morphologically very close to each other, so that it cannot be excluded that O. ephippiata is a valid species not distinguishable from O. maritima in the female sex. Therefore, we refrain from synonymizing O. maritima with O. ephippiata in the present study and regard the latter name as a nomen dubium as it cannot be assigned with certainty to a given taxon based on morphological characters.