Mesembrinella semiflava Aldrich, 1925

(Figs 47–48, 137–138, 211, 254, 297, 341, 383, 426, 466)

Mesembrinella semiflava Aldrich, 1925: 14. Holotype male (USNM), examined photographically. Type locality: La Suiza de Turrialba, Costa Rica.

Huascaromusca semiflava: Kosmann et al. (2013: 77); Wolff & Kosmann (2016: 867); Wolff et al. (2017: 253); Marinho et al. (2017: tab. 1).

Mesembrinella semiflava: Cerretti et al. (2017: tab. 2).

Diagnosis. A medium-sized fly averaging 10.6 mm (9–12/5) in length; ppn with 2x 2 setae; subcostal sclerite bare; outer posthumeral seta absent; wing hyaline; T1+2 and anterior third or more of T3 yellow-orange; femora orange; katepisternum 2:1, often with a second small seta posteriorly.

Redescription. Male. Head. Frons 0.043 (0.04–0.05/3) of head width at narrowest. Fronto-orbital silvery when viewed from above, pale orange when viewed from below; frontal setae ascending about halfway to vertex; frontal vitta orange, obliterated about 40% of distance to vertex; parafacial slender, silvery when viewed from above, orange below; gena pale orange with silvery tomentum and with a few dark setae anteriorly, with pale fine setae posteriorly; postgena yellowish with pale tomentum and golden setae; occiput with shiny black upper edge, remainder with silvery tomentum and fine tan setae; median occipital sclerite shiny black; antenna: pedicel and first flagellomere yellow-orange, arista brown; palpus typical; ocellar triangle medium-sized, anterior ocellus 1.5x size of posterior ocelli; supravibrissal setae weak, clustered at base of facial ridge.

Thorax with whitish tomentose stripes; pleura all orange; chaetotaxy: ac 0:1, dc 2:3, ia 0, ph 0, ppn 2x 2, kat 2:1 [may have an extra weak posterior seta; this condition is variable but fairly common], horizontal portion of meral setae composed of only a couple of setae, 1 pair converging ap, sa absent, 1 lat, 1 stout bas, 1 weak pb, 1 disc; subscutellum weakly developed; spiracles small, yellow-orange; legs: trochanters and femora orange, tibiae and tarsi brown. Wing hyaline, faintly yellowish, slightly darker yellow along costa; subcostal sclerite bare; basicosta yellow, tegula orange; section IV 0.14 of section III; disc of both calypters pale yellow; rim of upper calypter dark with pale setae, rim of lower calypter pale with long golden setae.

Abdomen. T1+2 yellow-orange, anterior 2/3 of T3 yellow-orange, rear 1/3 of T3 darker, often with inverted V pattern mid-dorsally; T4–5 shiny blue-purple with whitish tomentum; T1+2 with cluster of stout lateral marginal setae and single seta posteriorly; T3 with lateral marginal seta; T4–5 each with row of marginal setae; disc of T5 with mid-dorsal horizontal row of stout setae, rest of disc with sparse, fine setae. Terminalia in lateral view with surstylus straight, parallel-sided, cercus with apical hook (Fig. 47); in posterior view, cerci broad at base, tapering to tip (Fig. 48); phallus in lateral view with short stout epiphallus (Fig. 137); in dorsal view, hypophallic lobes slightly expanded with coarse serrations (Fig. 138). T6, STS7+8, pre- and postgonite, ejaculatory sclerite and ST6 as in Fig. 211; ST2–5 as in Fig. 254.

Female. Similar to male except frons 0.194 (0.18–0.20/5) of head width at narrowest and abdomen lacking arrow-like mid-dorsal black area on T3 (found in some males), that area orange. T6 of OV shape; T7 continuous, narrowed midway; T8 thinned and translucent midway; epiproct bilobed (Fig. 297); ST6–8 and hypoproct as in Fig. 341; spermathecae filiform (Fig. 383); ST1–5 as in Fig. 426.

Type material examined. HOLOTYPE ♂ (Costa Rica, Cartago; USNM; examined photographically: Fig. 466), labeled: COSTA RICA / La Suiza ’23 [= 1923] / Pab. Schild; 16 III [apparently day and month]; AL Melander / Collection / 1961; USNMENT / 01295434; Mesembrinella / semiflava / Ald ..

PARATYPE: Costa Rica. 1 ♀, La Suiza, Pablo Schild, 28.ii.1923, paratype 26799 (USNM).

Additional material examined. Costa Rica, Cartago. 1 ♂*, Quebrada Segunda, P.N. Tapanti, 1250 m, iii.1992, L_N_194000 560000, G. Mora (INBIO); 1 ♀ ♦ (TLW286), Turrialba P.N., Barbilla Cerro Tigre, 1400 m, 16.iv.2002, B. Hernández (INBIO); 1 ♀ ♦ (TLW287), Pejibaye Estación, Biológica Copal Sendero Garvula, Cima 1090 m, 8.iv.2005, B. Gambon (INBIO). Heredia. 1 ♀ *, Sarapiqui P.N., Braulio Carillo Send. El Saino al Rio Peje, 400–500 m, 18.ix.2005, M. Ballestero, A. Peraza (INBIO). Puntarenas. 1 ♂*, 1 ♂, San Vito, Rio Jaba, 8°46ʹN 82°57ʹW, 1100 m, 24.i.1998, D.M. Wood (CNC); 1 ♀, Est. Altamira Sendero al Rio Platanillal, 1100 m, 21.ii–16iii. 1972, R. Villalobos (INBIO). Ecuador, Pichincha. 1 ♀, Maguipucuna Biol. Res., 0.12°N 78°. 63°W, 24–25.ii.1996, P. Hibbs (LACM).

Distribution. Costa Rica, Ecuador.

Remarks. Three specimens were extracted; the DNA recovered was of too low quality to obtain good barcodes, therefore they were not included in the NJ analysis.