Euura flavescens

155 Euura flavescens (Stephens, 1835) Figs 166, 386 Nematus flavescens Stephens, 1835: 29. Lectotype designated below. Nematus testaceus Thomson, 1871: 153–154. Lectotype designated by Lindqvist (1960c). Synonymy by Cameron (1885). Primary homonym of Nematus testaceus Stephens, 1835 [= Euura miliaris (Panzer, 1797)]. Nematus dilutus Brischke, 1883: 141. Syntypes ♀ ♂, probably destroyed (Blank & Taeger 1998). Type locality: Russia, Kaliningradskaya oblast, Tschernjachovsk [Insterburg]; Poland, Gdansk [Danzig]; Germany, Rheinland-Pfalz, Herrstein, and Sachsen-Anhalt, Halle. Synonymy by Enslin (1913). Pteronidea stichi Enslin, 1913: 321–326. Replacement name for Nematus testaceus Thomson, 1871. Pteronidea fulvescens Lindqvist, 1949: 79. Syn. nov. Pteronidea variegata Lindqvist, 1958: 103–104. Syn. nov. Pteronidea boreophila Lindqvist, 1971b: 12–13. Syn. nov. Diagnosis Females are usually nearly completely pale yellowish like E. dorsata, and at least some E. latibasis and E. seriepunctata, but some specimens of E. flavescens are extensively black. Externally very similar is also E. fuscarima of the E. bipartita group. The best way to identify the species is by examining the lancet. On the dorsobasal part (next to the suture) of the basalmost annulus is a dorsally widening pale area (absent in the other similar species). At least some of the darker specimens (abdomen dorsally mostly black; as in ZMUO.040671, ZMUO.041892, ZMUO.046542, ZMUO.058829, etc.) may belong to a different species, based on nuclear genes. An available name for such specimens might be Pteronidea boreophila. However, based on individual haplotypes of different nuclear genes, the haplotypes from the same specimen tend to group either with E. lienterica or E. flavescens, suggesting an alternative explanation, that these specimens may be of hybrid origin. A similar pattern has been shown for example in Occidozyga Kuhl & Hasselt, 1822 frogs where extensive gene flow can lead to inflated estimates of species numbers (Chan et al. 2021). In such cases standard distance and phylogenetic methods based on concatenated genes mask the reticulate pattern and misleadingly indicate additional distinct lineages (Chan et al. 2021). Based on the lancet structure, we have identified these specimens (as well as the holotype of boreophila) as E. flavescens. Type material examined Lectotype Nematus flavescens, here designated UNITED KINGDOM – England • ♀; London area; 51° N, 0° W; BMNH, B.M.TYPE HYM. 1.631. Lectotype Nematus testaceus SCANDINAVIA • ♀; MZLU, MZLU2017331. Holotype Pteronidea fulvescens RUSSIA – Karelia • ♀; Kenjärvi; 62.126° N, 34.011° E; 4 Jul. 1942; E. Kangas leg.; MZH, http://id.luomus.fi/GL.3500. Notes ~ 8 mm. Best morphological match: DEI-GISHym21140 (~7.0 mm). Holotype Pteronidea variegata FINLAND – Uusimaa • ♀; Helsinki, Munksnäs [Munkkiniemi]; 60.22° N, 24.89° E; 23 Jun. 1932; E. Lindqvist leg.; MZH, http://id.luomus.fi/GL.3559. Holotype Pteronidea boreophila FINLAND – Lapin Lääni • ♀; Kilpisjärvi; 69.04° N, 20.81° E; 8 Jul. 1966; Karvonen leg.; MZH, http://id.luomus.fi/GL.3457. Notes Best morphological match: ZMUO.030845 (somewhat paler and slightly larger). Host plants Several different Salix spp., such as S. caprea L., S. phylicifolia, S. myrsinifolia Salisb. (Kangas 1985) and S. viminalis (Weiffenbach 1985). Genetics COI Based on 27 specimens, maximum within-species distance is 1.82% and the nearest neighbour, diverging by a minimum of 0%, is Euura lienterica. Nuclear Based on 15 specimens, maximum within-species distance is 0.87% (0.63% based on haplotypes of individual females). The nearest neighbour, diverging by a minimum of 0.27%, is Euura lienterica. Distribution and material examined Palaearctic. Specimens studied are from Austria, Belgium, Bulgaria, Estonia, Finland, France, Norway, Russia, Sweden, and the United Kingdom.