Brachypogon biradialis Spinelli, Borkent & Ronderos, 2013, n. sp.

Brachypogon biradialis n. sp.

(Figs. 1–7, 16)

Diagnosis. Female: only species of Brachypogon with the wing exhibiting two elongate radial cells with narrow lumen and cell r3 with a forked intercalary vein. Male: unknown.

Description. Female. Head (Fig. 1) dark brown. Eyes with interfacetal spicules, broadly separated medially. Clypeus with 4–5 pairs of lateral setae. Antenna moniliform; scape with two setae; flagellum entirely dark brown, with 13 flagellomeres; flagellomeres 1–3 slightly broader than long, 4–8 as long as broad, 9–13 slightly longer than broad, AR 0.74–0.80 (0.77, n=4); flagellomere 1 with 1–3 apical sensilla coeloconica. Palpus paler than flagellum; segment 3 short, swollen, with subapical, deep sensory pit; fourth segment with 2 setae; PR 0.92–1.21 (1.10, n=4). Mandible with 5 apical teeth, preceded by 2–3 minute denticles.

Thorax (Fig. 2). Uniformly dark brown. Scutellum with six setae; katepisternum with one slender seta (Fig. 3). Legs entirely dark brown; hind tibial comb with 9 spines; foreleg TR 2.96–3.23 (3.06, n=4), midleg TR 2.30–3.00 (2.72, n=4), hind leg TR 2.14–2.33 (2.26, n=4); tarsomeres 4 subcylindrical; tarsal claws with short internal basal teeth, unequal and longer in foreleg (Fig. 4), small and equal in mid-, hind legs. Wing (Fig. 5) length 0.79–0.89 (0.83, n=4) mm, width 0.37–0.40 (0.38, n=4) mm, CR 0.58 (n=4); two elongate radial cells with narrow lumen, first one slightly longer than second; radial veins thick; costa, R1, R3 with black, stout setae; r3 with forked intercalary vein; distal portion of M2 visible; membrane infuscated, with marginal macrotrichia in r3, m1, m 2 in holotype, more abundant and also few in cua 1 in paratypes. Halter whitish.

Abdomen (Fig. 6). Dark brown. Sternite 8 entire, with broadly V-shaped posteromedian excavation; sternite 9 divided medially, each portion deeply excavated caudomedially; sternite 10 with 2 pairs of setae, anterior pair minute, posterior pair elongate, slender. Two ovoid spermatheca (Fig. 7), both with short, broad neck; unequal in length, measuring 50–56 (53, n=4) by 42–47 (44, n=4) µm, and 45–52 (48, n=4) by 33–45 (40, n=4) µm; rudimentary third spermatheca present.

Male. Unknown.

Distribution. Subantarctic Chile (approximately 38 ºS), Argentina (Somuncurá plateau, in Río Negro province) (Fig. 16). The paratype from 34 km S. Collipulli was collected near a stream in a woodland setting and that from Conguillo National Park was collected from an Araucaria / Nothofagus forest.

Taxonomic discussion. The wing of this species resembles those of species of Borkenthelea Spinelli & Grogan, except for the presence of a forked intercalary vein in cell r3. However, Borkenthelea spp. differs by having eyes contiguous medially, flagellomeres elongated and the katepisternum devoid of setae.

Type material. Holotype female, labeled “ Argentina, Río Negro, Chipauquil (puesto policial), 40º57’41.1’’S, 66º38’20.8’’W, 481m, 4-XII-2006, G. Spinelli, aerial net” (MLP). Paratypes, 3 females from Chile, as follows: 34 km S Collipulli, 23-XII-1984, J.A. Downes, JAD 1678/1/18 (CNCI); nr. Nahuelbuta, 24-XII-1984, J.A. Downes, JAD 1680/1/5 (CNCI); Conguillo National Park, 1150 m, 4/ 5-II-1988, L. Masner, Malaise trap, CD 896 (CNCI).

Derivation of specific epithet. The name biradialis (two radials) refers to the two distinctive narrow radial cells of this species.