Rhogogaster polaris Lindqvist 1964

Rhogogaster polaris Lindqvist, 1964

(Figs 3e, q, r, 4l, 5d, g, i, k, 6f, o)

Rhogogaster polaris Lindqvist, 1964: 121. Holotype ♂ (MZLU, not examined). Type locality: Norway: Tromsö, Målselva, Kundhaug.

Discussion. Benson (1965) synonymized R. polaris with R. californica (Norton, 1862), but Prous et al. (2014) treated the species as valid. The relationship between the Nearctic R. californica and the Palearctic polaris needs further investigation. Currently, the species are separated only because of their different COI barcodes (about 3 % divergence). Furthermore, the taxa have a different distribution pattern, as polaris seems to be a species with a very restricted northern distribution, whereas californica is widely distributed in the Nearctic realm (Prous et al. 2014). However, the taxonomy of the Nearctic Rhogogaster still needs to be checked, and it is uncertain if the synonymy of Tenthredopsis evansii Harrington, 1889 from Ontario and Tenthredo ripula MacGillivray, 1923a from Oregon with R. californica is really correct. The barcoding data of specimens from various localities in Canada form at least two clusters, and no data are yet available for specimens from California. In line with general patterns of distribution, a Holarctic distribution of the subarctic R. polaris would not be unexpected. At present it seems best to treat the European taxon as a separate species. We have seen males from Norway, Sweden, Finland and eastern Russia (Magadan obl., upper Kolyma river, station Aborigen, ca. 61.983°N, 149.331°E, 15.7.1987, leg. MV). The southernmost confirmed record of polaris is a female from Sweden: Kopparbergs Län: Öje (60.810°N, 13.866°E, 11.06.2013, coll. SDEI, barcoded). Furthermore, a female from Russia (Karelia, Petrozavodsk, ca. 61.837°N, 34.285°E) was examined. However, the separation of the females of polaris and viridis is difficult, and apart from the clear difference in the barcodes, there are only weak differences in coloration. Therefore, whenever possible, records of both species should be based on males or specimens with barcode data. We have seen no males of R. polaris from the more southern parts of the known distribution area. The record of a male from France (Hautes Alpes, Vars, as R. californica; Chevin 1972) requires confirmation. Rhogogaster similis Lindqvist, 1959 is based on a female and fits viridis better than polaris, if the color difference (the darker head) proves to be reliable. Hitherto, polaris specimens which are as dark as the similis type are unknown.