Euura ischnocera Liston & Heibo & Prous & Vårdal & Nyman & Vikberg 2017

ischnocera complex

It does not seem possible to distinguish females of this complex morphologically. They display characteristic tendencies in coloration, correlated with host association, but coloration is sometimes highly variable within series reared from the same Salix species, and overlaps broadly in every case with the range of colour pattern in some other segregates. Neither the species differences given by Kopelke (2007a) in the morphology of valvula 3, nor the length of the metatibial spurs were detected in the material examined. Differences in penis valve morphology possibly distinguish the males, according to Kopelke (2007a), but the variability of these characters has not been thoroughly checked. Colour pattern of the males seems to be more stable than that of females. All taxa, as well as E. oblita, but possibly excepting E. plicalapponum, have nearly identical COI barcodes. E. oblita is however not included in the complex, because it is clearly distinguishable by its very long antennae, extremely pale colour pattern in the female, as well as larval morphology. Benson (1958), Zinovjev (1999), and many other authors treated this complex (without E. oblita) as a single species, under the name leucapsis Tischbein. Zinovjev (1999) additionally recorded Salix atrocinerea, S. aurita and S. starkeana as hosts of Phyllocolpa leucapsis auct. [= ischnocera complex], but these hosts are not mentioned by Kopelke (2007a). Salix caprea is probably also used as a host (see under Bionomics of E. prussica and E. cyrnea). Finally, P. leucapsis auct., as well as P. puella [= E. oblita], were recorded as separate species which both have S. fragilis, S. alba, and S. triandra as hosts (Beneš 1968a: 119). Possibly the six nominal species listed below are conspecific, but we retain them provisionally as valid until more complete genetic data is available, and a study of their larval morphology has been made. Adults of this complex are rather abundant in Sweden, but because of the difficulties mentioned above, we are only able to list a few definite records for species based on the material that we have seen.

Euura ischnocera (Thomson, 1863) comb. nov.

Nematus ischnocerus Thomson, 1863: 638. Described: ♀, ♂. Lectotype, ♀, designated by Kopelke (2007a), MZLU [examined]. Type locality: Sweden, Norrland.

Pontania ischnoceros [sic]: Konow (1890).

Phyllocolpa ischnocera (Thomson, 1863): Kopelke (1990b).

Nematus leucostigmus Cameron, 1876c: 308. Described: ♀. Lectotype, ♀, designated by Kopelke (2007a), BMNH [not examined]. Type locality: Scotland, Rannoch. Synonymy by Kopelke (2007a).

Variability. Female: Body length: 3.4–3.9mm. Ratio of length flagellomere 2 / height of eye 0.86-0.93. Male: 3.2– 4.2mm. Female and male: within wider geographic regions, the colour pattern seems very stable, but specimens from the Alps have a much more extensively pale head, pronotum and femora than those from northern Europe. The pterostigma is usually entirely pale, but can be apically more or less darkened. Total number of specimens examined: 14.

Genetic data. COI barcodes of species of this complex, as well as E. oblita, are highly similar, and not useful for identification.

Similar species. Females are most similar to the other segregates with typically extensively dark orbits: E. plicalapponum, E. plicaphylicifolia.

Bionomics. Host plant: Salix myrsinifolia (Kopelke 2007a). Biology: Kopelke (2007a).

Distribution. Central Europe (mainly Alps) and northern Europe, including Scotland (Kopelke 2007a, Liston et al. 2012). Occurrence in Sweden: published records; Västerbotten, Torne Lappmark (Kopelke 2007a).