Acerocnema vanga Chagnon & Sinclair 2021, sp. nov.

Acerocnema vanga sp. nov.

(Figs 7, 8, 13, 18, 22, 26)

urn:lsid:zoobank.org:act: 413C22B3-40E2-455E-B5F2-28638951B664

Type material examined. HOLOTYPE ♂ labelled: “Y. T. British Mts. / 69°13′N 140°05′W / 21–25. VI. 84 320m / G. & M. Wood &/ D. Lafontaine ”; CNC/ 1589605 ”; “ HOLOTYPE / Acerocnema / vanga/ Chagnon & Sinclair [red label]”; “ CNC/ 1589605 ” (CNC). PARATYPES: CANADA. Yukon: same data as holotype (7♀, 13♂, CNC); Firth River [68°50′10.9″N 140°36′00.9″W], 11.vii.1956, R. E. Leech (1♀, CNC); Firth River [68°50′10.9″N 140°36′00.9″W], 14.vii.1956, E.F. Cashman (1♂, CNC); same data except, 17.vii.1956 (1♀, CNC); Herschel Is [69°34′45.7″N 138°54′19.2″W], 7–16.vii.1971, W. R.M. Mason (1♀, CNC); Herschel Is [69°34′45.7″N 138°54′19.2″W], 28–29.vi.1971, D.M. Wood (1♀, CNC). USA. Alaska: Nome Area, mi 17 Kougarok Rd, 64.71°N 163.30°W, 21.vi.2005, MT, J.& R. Skevington (5♂, CNC).

Diagnosis. This species is distinguished by the dark postpedicel in both sexes and scutum without pair of shiny vittae.

Description. Male. Body primary colour black; pleura black; scutum black; entire body pruinose, without shiny scutal vittae. Setae on head yellow.

Head with face and gena yellow; genal width 1/3 eye height; postgena yellow; postocellar triangle brown. Frontal vitta dark yellow, darker than gena; fronto-orbital plate black transitioning to yellow anteriorly; parafacial yellow. Fronto-orbital plate with 3 inclinate frontal setae, 1 proclinate and 1 lateroclinate orbital seta, 1 pair of lateroclinate ocellar setae, 1 pair of short divergent postocellar setae, 1 long yellow inclinate inner vertical seta and 1 lateroclinate outer vertical seta, shorter than inner vertical seta. Vibrissa strong, with 2 short supravibrissal setae and 1–3 short subvibrissal setae, all yellow. Antenna with postpedicel black, about five times as long as pedicel; scape and pedicel black; arista black, bare, not longer than postpediccel. Palpus yellow with pale setulae over surface and slightly flattened at tip.

Thorax with scutal setae dark yellow; acrostichal setae biserial, finer than dorsocentrals; 2 presutural and 3 postsutural dorsocentral setae; 2 posterior postpronotal setae; 1 presutural intra-alar seta; 2 notopleural setae; 1 postsutural intra-alar seta; 2 postsutural supra-alar setae; 2 postalar setae; 2 pairs of scutellar setae. Pleura with 2 dark yellow proepisternal setae; 1 dark yellow proepimeral seta; many dark yellow posterior anepisternal setae and setulae; 1 brown, posterodorsal katepisternal seta; anterior half of anepisternum and anepimeron without setulae; katepisternum with setulae ventrally.

Wings (length 3.6–4 mm) clear, lightly infuscate, R 1 bare; CuA+CuP not meeting wing margin. Halter yellow to white.

Legs entirely yellow, setae yellow. Fore femur with white ventral pile. Fore tibia with 1 preapical anterior seta; 1 anterior seta on apical 1/2. Mid femur with white ventral pile. Mid tibia with 1 preapical anterior, 1 preapical anteroventral, 1 preapical posterior seta; 1 anterodorsal seta on apical 1/2; 1 anterior seta on apical 1/4; 1 posterodorsal seta on apical 3/4. Hind femur with row of anterodorsal setae on apical 1/2. Hind tibia with 2 preapical dorsal setae; 1 preapical ventral seta; 1 dorsal seta on apical 3/4; 1 anterodorsal seta on apical 1/2; 1 ventral seta on apical 1/4. Tarsi with short, white ventral pile.

Abdominal tergites shiny black, with pale setulae over surface. Abdominal sternites black. Sternite 5 enlarged, Y-shaped, large and shiny black, with 2 large, divergent rectangular apical lobes, separated by shallow notch; clothed in fine setae, longest on apex of lobes (Fig. 13).

Terminalia (Figs 7, 8) with epandrium black; surstylus yellow; cercus dorsal section black, ventral section yellow; hypandrium black. Epandrium on dorsal surface of abdomen, surstylus, cercus and tergite 5 all jutting out from ventral surface of abdomen. Surstylus long, L-shaped, with setae on inner long edge and cluster of thick setae at inner apex; inner edge with subapical tooth-like process. Cercus composed of two sclerotized sections connected via membranes: dorsal section formed by bulbous sclerotized oval sclerite, with long setae, setae shorter than in A. merga; ventral section in lateral view comprising rectangular plate with small dorsal lobe and jutting inner digitiform process with file-like lower margin. Pregonite unforked, slender with 2 thick apical setae. Postgonite slightly arched, broader than pregonite with somewhat pointed and rounded apex. Epiphallus not observed.

Female. Very similar to male; terminalia as in generic diagnosis.

Distribution. This species is known only from Yukon and Alaska (Fig. 26).

Etymology. The species name is derived from the Latin vanga (shovel or spade), in reference to the enlarged male sternite 5. The species name is considered a noun in apposition.

Remarks. This new species keys to A. flavifrons Iwasa in Iwasa (2014) on the basis of yellow legs and pruinescent scutum without stripes, but is readily distinguished by the L-shaped surstylus (straight in A. flavifrons (Iwasa 2014, fig. 8)) and postpedicel three times longer than wide (two times longer in A. flavifrons (Iwasa 2014, fig. 6)). In Ozerov (2015), A. vanga sp. nov. keys to A. macrocera, but differs by its yellow palpi (black in A. macrocera). The new species also keys to A. paradoxopyga Stackelberg in Ozerov & Krichosheina (2018) and have apparently similarly shaped surstyli (Stackelberg 1952, fig. 1), but differs by its yellow legs (femora at least partially black in A. paradoxopyga (Ozerov 2015, couplet 5)) and more divergent and shorter, broader lobes of sternite 5 (parallel and narrow in A. paradoxopyga (Stackelberg 1952, fig. 2)).