Figures 5, 17, 18C
Nematus dahlbomi Thomson, 1871: 134–135. Described: syntypes, ♀. Published type locality: Lappland. Lectotype (examined)
designation by Lindqvist (1954). Amauronematus dahlbomi: Konow, 1890. Nematus dahlbomii: de Dalla Torre, 1894; misspelling. Pontopristia dahlbomi: Lindqvist, 1961. Nematus (Pontopristia) dahlbomi: Zhelohovcev, 1988. Amauronematus (Pontopristia) dahlbomi: Liston, 1995. Euura dahlbomi: Goulet & Bennett, 2021. Pontopristia lapponica Malaise, 1921: 14. Described: syntypes, 8♀, 2♁. Published type locality [as comment under P. romani,
p. 14]: Vassijaure, Lappland [Sweden, Vassijaure]. Lectotype designated below. Synonymy with suavis var. fusca by Conde
(1938). Synonymy with dahlbomi by Lindqvist (1961). Pontopristia suavis var. fusca Malaise, 1921: 12–13. Described: syntypes, 7♀, 2♁ (?NHRS, not located). Published type locality:
Vassijaure, Lapland [Sweden, Vassijaure]. Synonymy with N. dahlbomi by Lindqvist (1954).
Diagnosis. Female: The lancet of this species is highly distinctive, with marginal serrulae developed only on the first and second annuli and the apical half of the lamnium, and some ctenidia visible on the basal annular sutures (Fig. 17A–B).
Male: So far, this is the only amentorum group male, apart from that of E. amentorum, with a pale fore wing costa and stigma (Fig. 5G). The male of E. amentorum differs in its very long extension of pseudoceps (Fig. 18A), and paler colouration of head and body (Fig. 3E–F). The penis valve strongly resembles those of E. freyja (Fig. 18 E–F) and E. microphyes (Fig. 18D), but E. dahlbomi has edge of paravalva below the valvispina less strongly downward-deflected.
Description. Female (Fig. 5A). Length 3.5–4.0 mm. Black. Pale are more or less mandibles, palps, labrum, tibiae, apices of femora. Cerci pale. Wing veins including fore wing pterostigma pale.
Head (Fig. 5B). In dorsal view moderately contracted behind eyes, and length posterior of eye about 0.50–0.60 × length of eye. Mostly dull with coriaceous sculpture except for labrum. Upper head densely setose; setae pale, about 0.7 × as long as anterior ocellus diameter. Clypeus slightly emarginate medially. Labrum apically rounded. Antenna 0.94–1.0 × as long as fore wing costa.
Thorax. Pronotum, mesoscutum and tegula densely punctate with small shiny interspaces; vestiture similar to upper head, adpressed. Lateral mesoscutal lobe approximately 1.60 × as long as greatest width. Mesoscutellum as broad as long, without longitudinal median furrow; with few, extremely weak punctures; smooth and shiny. Upper half of mesepisternum usually smooth, shiny (Fig. 5C); with small ventral glabrous patch; setae about 0.5 × as long as diameter of anterior ocellus.
Abdomen. Valvulae 3 in lateral view (Fig. 5F) clearly orientated upwards; tapering to the narrowly rounded tip. In dorsal view (Fig. 5E) subparallel-sided, gently widened before tip, 1.0–1.1 × as wide as narrowest distal width of metatibia. Cercus reaches approximately to the tip of valvulae 3. Lancet (Fig. 17A–B): 16–19 annular sutures; strongly curved (lower edge concave); approximately basal half of lamnium without marginal serrulae, distal half with rather flat serrulae; basal annular sutures with ctenidial teeth; a lobe present at anterior of tangium.
Male [based on 4 specimens]. Length 3.7 mm. As female, except: Antenna 1.2–1.3 × as long as fore wing costa. Abdomen black except for pale cerci, and more or less sternum 9. Tergum 8: tergal hollows narrow, fully sclerotised. Procidentia subrectangular, projecting clearly beyond posterior tergal edge by slightly less than its distal width, becoming a narrow carina (without the sculpture of the adjacent areas) towards anterior. Penis valve (Fig. 18C): Valvispina short, basally narrow; edge of paravalva below the valvispina only slightly downward-deflected; lobe on paravalva below valvispina small or absent.
Variability. Upper half of mesepisternum sometimes with coriaceous sculpture, dull (Fig. 5D).