Mesembrinella mexicana Whitworth & Yusseff-Vanegas 2019, sp. nov.

Mesembrinella mexicana Whitworth, sp. nov.

(Figs 27–28, 117–118, 201, 245, 289, 333, 376, 418, 458, 488)

Diagnosis. A small bluish fly averaging 9.2mm (8–10/5) in length. Calypters white, including discs, rims and setal fringe vs. discs light tan, rims and setal fringe dark in M. spicata; anterior spiracle yellowish vs. anterior spiracle brown in M. spicata; male with short projections from rear of ST5 (Fig. 245) vs. male with long projections in M. spicata (Figs. 12, 246); epandrium, cerci and surstyli distinctive (Figs 27–28) vs. epandrium, cerci and surstyli in M. spicata as in Figs 29, 30; females sometimes with disc of T5 with three or four stout setae (suggesting the aeneiventris species-group); female, T4 with at least a partial row of marginal setae dorsally.

Description. Male. Frons broad, 0.126 (0.120 –0.130 /5) of head width at narrowest; about twice the width of parafacial at level of lunule. Fronto-orbital from faint grayish to faint yellowish, frontal setae ascending about 25% of distance to vertex; frontal vitta with lower 1/3 yellow and upper 2/3 black; parafacial and gena bright yellow-gold, setae on gena typical; postgena with silvery tomentum and fine yellow-gold setae; occiput with silvery tomentum and fine yellow setae, median occipital sclerite with pale tomentum; pedicel and first flagellomere bright yellow, arista with brown base and black tip; palpus typical; eye with median facets not larger than lateral facets; ocellar triangle large, ocelli small and similar in size; supravibrissal setae short and in double row ascending about 1/4 of distance to antennal base.

Thorax. Dorsum with faint, pale tomentum and tomentose stripes; chaetotaxy: ac 2:1, dc 2:3, ph 1, ia 0, ppn 3x 3, kat 1:1, meral setae with horizonal portion of inverted L consisting of only one seta, 1 pair converging ap, 1 lat, 1 stout bas, 1 weak pb, 1 disc; subscutellum prominently developed; anterior spiracle yellow, posterior spiracle light brown; legs entirely brown except joint between femora and tibiae yellowish. Wing hyaline; subcostal sclerite with pubescence only; basicosta orange, tegula brown; section IV 0.165 of section III; calypters pale; rim of upper calypter sometimes faintly darkened.

Abdomen entirely blue with pale tomentum; T1+2–4 with a pair of lateral seta on each segment; no row of stout setae on the posterior margin of T4 or T5 or on disc of T5, disc with only fine setae. Terminalia in lateral view with a tiny surstylus and cercus at the posterior end of a large epandrium (Fig. 27), in posterior view as in Fig. 28; phallus in lateral view with short stout epiphallus and large basiphallus extending ventrally (Fig. 117); in dorsal view anterior half very broad (Fig 118); pre- and postgonite, ejaculatory sclerites, and hypandrium as in Fig. 201; ST2–5 very broad (Fig. 245), progressively wider to the rear like in M. spicata, ST5 exceptionally large with pair of pointed posterior projections, about half the length of those in M. spicata.

Female [only two known]. Similar to male except frons 0.255 (0.25–0.26/2) of head width at narrowest, rows of stout setae on posterior margin of T4 and T5, and several (3 or 4) stout discal setae in horizontal row on T5, which would suggest placement in the aeneiventris species-group. T6 of RV shape; T7 with two well separated sclerites (Fig. 289); ST6–8 and hypoproct as in Fig. 333; spermathecae filiform, as in Fig. 376; ST1–5 as in Fig. 418.

Type material. HOLOTYPE ♂ (Mexico, Oaxaca; CNC; Fig. 458), labeled: MEXICO Oax [= Oaxaca] 1 km N / Portillo del Rayon / ca Km 188 1400m / 25.VII.92 D.M.Wood; HOLOTYPE / Mesembrinella / mexicana / T.L. Whitworth.

ALLOTYPE ♀ ♦ (TLW407): Mexico, Oaxaca. 1 km N Portillo del Rayon, ca km 188, 1400 m, 25.vii.1992, D.M. Wood (CNC).

PARATYPES: Mexico, Oaxaca. 1 ♂♦* (TLW395), 2 ♂♂♦ (TLW346, 397), 8 ♂♂, 1 ♀ ♦* (TLW406), 1 km N Portillo del Rayon, ca km 188, 1400 m, 25.vii.1992, D.M. Wood (CNC).

Distribution. Mexico.

Remarks. Six specimens (TLW 377, TLW 395–397, TLW 406–407) were barcoded, and all sequences clustered together near M. guaramacalensis sp. nov. (Fig. 488). All type specimens were collected in the same location on the same day.

Etymology. The species is named after its country of origin, Mexico.