Dichopygina perfecta

Dichopygina perfecta (Pettey, 1918) (Figs 2–6)

Neosciara perfecta Pettey, 1918: 325, 341, figs 30, 61. Type locality: USA, Maryland, Montgomery Co., Plummers Island.

Bradysia perfecta (Pettey, 1918): Stone & Laffoon, 1965: 234.

Corynoptera perfecta (Pettey, 1918): Steffan, 1966: 49, 54.

Dichopygina perfecta (Pettey, 1918): Mohrig et al., 2013: 200–201, fig. 28.

Material examined. Canada. 1♂, New Brunswick, Fundy National Park, Devil`s Halfacre Road (45°35'22″N, 64°57' 20″W; elev. 61 m), 21 May 2013, leg. Shirley Butland (CNFDK107-14) (BIOG); 1♂, New Brunswick, Kouchibouguac National Park, Near Park Compound, behind Research House (46°46'15″N, 65°00'23″W; elev. 61m), malaise trap, 26 August 2013, leg. Bernard Martin (CNKOS809-14) (BIOG). Finland. 2♂, Lapland, Rovaniemi, Sorvanulkki, herb-rich, old-growth boreal forest, malaise trap, 28 July 2014, leg. Jukka Salmela (SCILA010-16, SCILA009-16) (BIOG).

Diagnosis. The morphological differences between D. perfecta and D. bernhardi are hereby confirmed. The gonostylus of D. perfecta has almost equal 7–9 thin and straight subapical megasetae in one group, whereas D. bernhardi has 10–13 megasetae at the apical half of the gonostylus and the basalmost megasetae longer than others. In addition, the tegmen of D. perfecta is equally rounded, while it is flatter in D. bernhardi.

Redescription. Colour. Thorax bright brown; abdomen, hypopygium brown; legs yellow; wing hyaline or slightly darkened. Antenna unicolour and yellowish brown.

Head. Eye bridge 2–3 facets wide. Antennal setae fine, dense, shorter than segment width. Length/width of flagellomere 4 of antenna 1.40–1.80; transition of basal part to neck pronounced (Fig. 3). Neck length/segment width 0.30–0.40. Maxillary palpus bright and 3-segmented; basal segment with 1 bristles; 2nd segment short, oval; 3rd segment as long as basal segment; sensillae present.

Thorax. Notum brown. Thoracic setae weak, white. Posterior pronotum bare. Mesothoracic sclerites bare. Wings (Fig. 4). Length 1.6–1.9 mm. bM, r-m bare; R 1/ R 0.60–0.80; c/w 0.63–0.72. Membrane without macrotrichia; venation weak, with faint stM; M-fork of normal shape; R 1 ending clearly before base of M-fork. Halter bright. Legs. Foretibia with dense patch of setae and curved margin; claws untoothed. Hind coxa of same colour as femora. Hind tibia 0.80–0.90 mm; Tibial spurs of equal length. Abdomen. Abdominal setae weak, sparse. Tergal setae white; sternal setae white.

Hypopygium (Fig. 5). Hypopygium 0.5–0.7 times as long as wide. Base of gonocoxites with normal, weak hairs; gonocoxites narrowly separated; inner margin of gonocoxites U-shaped; inner membrane of hypopygium bare; gonostylus elongate, narrowed and curved (Fig. 2); 1.1–1.5 times longer than wide; inner margin straight, or concave in ventral view; apical part of gonostylus tapered. Apical tooth without internal structure, shorter than subapical megasetae; 1.1–1.7 times longer than broad. Awl-like setae absent. Innerside of gonostylus with 7–9 thin and straight subapical megasetae in one group. Position of basalmost megaseta 55–67% from apex. Whiplash-hair absent. Tegmen 0.6–0.7 times as long as broad; equally rounded; without special structures; central process absent (Fig. 6). Aeadeagal apical structure and teeth absent.

Remarks. The species is firstly recorded in Finland and Canada.

Distribution. Finland, Canada, USA (Mohrig et al., 2013).