Euura dolichura (Thomson, 1871)

Liston, Andrew D., Heibo, Erik, Prous, Marko, Vårdal, Hege, Nyman, Tommi & Vikberg, Veli, 2017, North European gall-inducing Euura sawflies (Hymenoptera, Tenthredinidae, Nematinae), Zootaxa 4302 (1), pp. 1-115 : 69-70

E. dolichura group

= Pontania Costa, 1852 , in part

Diagnosis. Adult. In lateral view right mandible gradually tapering, left one with swollen base and thin, blade-like apex. Vein 2r-m normally present in both fore wings. Supraclypeal area densely setose. Antenna moderately long: ♀ about as long, or slightly longer, than costa of fore wing; ♂ longer than costa of fore wing. Cercus long: about 6× as long as basal width and reaching back to apex of valvula 3. Lancet: not tapering very strongly from base to apex; slightly sinuate. Medial annular sutures straight and nearly vertical; medial and basal annuli with more or less clearly developed serrulae. Antennal hollow entirely pilose and dull. Penis valve ventrally without small spines; base of valvispina ventrally clearly divided from lobe on which it arises by an incision, or at least a right-angled deflection.

Larva. Third abdominal segment with 4 dorsal annulets. Suranal plate with widely separated pseudocerci.

Gall. In leaves. Only developed above the leaf-blade. Usually elongate ("sausage-shaped"), rarely globose; often occurring in pairs, one on each side of the midrib.

Phenology. All species strictly univoltine.

Notes. A number of Salix species in addition to those mentioned below have been recorded in northern Europe as hosts of this group in earlier literature. They may represent misidentifications, as yet unrecognised galler species, or secondary hosts of the nominal species listed below. Examples of such unclarified records from Sweden are Pontania femoralis on S. cinerea in Uppland ( Wahlgren 1951) and Pontania femoralis on S. polaris in Torne Lappmark (Vassijaure) ( Palm 1923) . Other dolichura group / host plant species combinations mentioned in the literature from other parts of northern Europe, and which might occur in Sweden, are from Salix arbuscula ( Benson 1958, Kopelke 2003a, Trail 1889), S. aurita ( Benson 1935) , S. cinerea (Zinovjev 1999) , S. hastata (Zinovjev 1999) , S. herbacea (Zinovjev 1999) , S. lanata ( Benson 1958) , S. myrsinites ( Benson 1954) , and S. viminalis (Zinovjev 1999) .

Although Kopelke (1994) stated that the species of this group are strictly monophagous, Beneš (2015a: 146) noted that a female reared from a gall on Salix myrsinites ( Slovakia, High Tatra Mts) oviposited (in captivity) both on S. retusa and S. purpurea , on which galls and larvae subsequently developed. A further case in the dolichura group of successful development of galls on an atypical host was mentioned by Zinovjev (1999: 211). According to Zinovjev (1999), the species of this group studied by Kopelke (1986) "might be associated with entire willow sections rather than particular species" and they "may just appear to be monophagous: in particular regions, host plants of these sawflies are the only representatives of their sections". This may be the case in Europe, where each of the nominal species recognised by Kopelke (1986, 1994), as well as the two European taxa added by Vikberg & Zinovjev (2014), has a recorded host that following Skvortsov (1999) belongs to a Section of Salix different from Sections used by any other European dolichura group segregate.

Kopelke (1994: 130) illustrated more or less different shapes of the clypeus in seven species of the dolichura group, including four species that occur in Scandinavia. We were unable to find consistent differences in this character between series of reared specimens of these species. Perhaps the shape of the emargination is variable. In any case, the perception of the shape of the emargination and the proportions of the parts of the clypeus lateral to this is greatly altered both by the angle at which it is viewed and by distortion in dried specimens.

Vikberg & Zinovjev (2014) stated that the ratio of the length of the lamnium of the lancet to head width can be used as an aid to identification of females of the dolichura group. They plotted this relationship for a few individuals of five Palaearctic nominal species, and the ranges of these ratios mostly did not overlap. However, the ratios of three of the most widespread northern European nominal taxa were not included: E. dolichura , E. glaucae and E. nigricantis . Once these are included, large overlaps occur between several species. The character is therefore of limited practical value for identification.

On external morphological characters, most nominal species in this group are scarcely distinguishable. The shape of the metatarsal claws was mentioned by Vikberg & Malinen (2012) as a character that might be of potential use in recognising some species: in particular to distinguish the male of E. dolichura from the others. It may be possible to separate virilis , only potentially occurring in Scandinavia, from those definitely known there by its more extensively pale coloration. On the other hand, two other nominal taxa ( E. elaeagnocola ( Kopelke, 1994) comb. nov., transferred from Pontania , and E. helveticae (Kopelke, 1994)) that are at present only known from Central Europe, share the paler colour pattern of virilis . Furthermore, some specimens of E. femoralis from the British Isles are also very pale ( Vikberg & Malinen 2012). One might therefore question whether these differences are of taxonomic significance. They might simply represent clinal variability, recognised in many other sawfly species, with more southern populations tending to be paler.

Based on COI and Cytb sequences, genetic differences among species within the group are in many cases very small (Nyman et al. 2007), and barcode data at BOLD for 15 specimens under the names virilis , dolichura , glaucae , nigricantis and lapponicola can hardly be interpreted, because it is frequently not clear how the samples were identified and in what sense the names were used.

Euura bigallae ( Vikberg & Zinovjev, 2014) comb. nov.

Pontania bigallae Vikberg & Zinovjev, 2014: 4 –7. Described: ♀, ♂, larva, gall, recorded hosts: Salix caprea and S. starkeana ssp. cinerascens . Holotype, ♀, FMNH [examined]. Type locality: Finland, Kainuu ( Kn ): Hyrynsalmi.

Variability. Female: Body length: 3.4–4.4mm. Male: 3.3–3.7mm. Total number of specimens examined: 3.

Genetic data. None available.

Bionomics. Host plants: Salix caprea and Salix starkeana ssp. cinerascens ( Vikberg & Zinovjev 2014) and hybrids of these ( Kokkonen 2000). Biology: Kokkonen (2000: as species P1; undescribed sp. of the dolichura group), Vikberg & Zinovjev (2014). The galls of this species are unique in the West Palaearctic: round, paired galls developed only above the leaf blade.

Distribution. Definite records so far were only from Norway, Finland and northern Russia, but possibly occurs also in Central Europe ( Vikberg & Zinovjev 2014). Occurrence in Sweden: material examined; Västerbotten.