Stenopygium nubeculum Becker, 1922

(Figs 1–8, 17)

Stenopygium nubeculum Becker, 1922: 75; Robinson 1970: 40.52 (catalog); Brooks 2005: 109 (review); Yang et al. 2006: 202 (catalog).

Examined material. Bolivia, Cochabamba, 105 km E Cochabamba at Rio Carmen Mayo, 17°8ʹ47ʺS 65°43ʹ55ʺW, 1800 m, FIT, 8–12.ii.1999, F. Génier, 99-058 (3♀, CNC); idem, low cloud forest, 1–6.ii.1999, 99-025 (1♀, CNC); idem, 17°8ʹ51.24ʺS 65°43ʹ50.40ʺW, 1750 m, FIT, 1–6.ii.1999, R. S. Hanley (3♂, 1♀, CNC); Santa Cruz, 32.8 km NW Comarapa, Kara Huasi, Yungas de la Siberia, 17°49ʹ20ʺS 64°42ʹ31ʺW, 2400 m, Yungas, FIT, 28–30.i.1999, F. Génier, 99-107 (1♀, CNC). Ecuador, Loja, Zamora [4°01′04.0″S 79°11′30.2″W], 1800 m, 26.xi.1970, L.E. Peña col. (7♂, 6♀, MZUSP); idem, 1200 m, 25.xi.1970 (6♂, 4♀, MZUSP; 6♂, 6♀, INPA; 4♂, 2♀, NMNH); idem, 1900 m (3♂, MZUSP); Papallacta (Quito Baeza) [0°22′41.0″S 78°08′37.2″W], 2600 m, 12.i.1971 (4♂, MZUSP); idem, 3000 m, 12–14.i.1971 (1♂, MZUSP); Napo, Baeza [0°27′59.2″S 77°53′27.4″W], 1900 m, 9.ii.1983, Masner & Sharkey (2♂, CNC); idem, ii.1983 (2♂, CNC); Tandapi [0°24′48.1″S 78°47′51.3″W] 40 km SW Quito, 1300–1500 m, 15–21.vi.1965, Pena (38♂, 28♀, CNC).

Distribution. Bolivia, Peru (Yang et al. 2006) and Ecuador * (Fig. 17).

Remarks. Specimens of Stenopygium nubeculum are relatively rare in collections. Before the present study, only the type series of the species was known, from Mapiri, Bolivia [15°18′22.4″S 68°13′24.8″W] (at elevations above 2,000 m) and Callanga, Peru [12°27′52.8″S 71°58′19.5″W] (1,200 m). Additionally, all 128 specimens listed here were collected above 1,000 meters, which may indicate habitat preference for higher altitudes in this species.

The female terminalia of S. nubeculum, illustrated here for the first time (Figs 7–8), is very similar to that of S. punctipennis, differing only in the number of spines of the acanthophorite (six in S. nubeculum, five in S. punctipennis), and this corroborates the small clade in Dolichopodinae formed by Cheiromyia Dyte, Stenopygium Becker, Pelastoneurus Loew, Platyopsis Parent and the Nearctic and Neotropical species of Paraclius Loew. This clade is supported by the fusion in the anterior portion of tergite 8 to sternite 8 in females (Fig. 8) (Brooks 2005; Capellari & Amorim 2009).

As pointed out by Brooks (2005), the relationships between Stenopygium, Pelastoneurus and Platyopsis remain uncertain and inconclusive. We found species of Pelastoneurus that share diagnostic characters with Stenopygium, such as a bulging clypeus of length equal to that of the face, also present in an unidentified species (Fig. 15) collected in the same locations in Ecuador from which S. nubeculum specimens were collected. This feature is also shared with several other New World species of Pelastoneurus (Brooks 2005). The long, thin cercus of S. nubeculum is also shared with an unidentified species of Pelastoneurus from Brazil (Fig. 16). However, all species of Pelastoneurus mentioned here have the dorsal and ventral microtrichia of the arista-like stylus longer than lateral microtrichia (Fig. 15), five pairs of dorsocentral setae and absence of wrinkles in the phallus. Future studies of the Andean fauna of Dolichopodinae may help to resolve the relationships between these genera, which are still poorly characterized.