Ormiophasia obscura (Séguy, 1926b)

(Figs 5H, 9H, 11H, 30)

Plagiatormia obscura Séguy, 1926b: 19 (description of male). Holotype male (MNHN), examined. Type locality: Argentina, upper Paraná River, Teyú Cuaré Park, near San Ignacio.

Plagiatormia obscura: Séguy (1927a: 424; catalog). Ormiophasia busckii: Townsend (1931: 82; synonymy of P. obscura with O. busckii); Townsend (1938: 236; catalog); Sabrosky (1953:182; catalog); Tavares (1964: 38; comments on synonymy).

Ormiophasia obscura: Guimarães (1971: 22; catalog).

Type material examined. HOLOTYPE ♂ (Figs 5H, 9H, 11H, 30): “Museum Paris/ Républ. Argentine / Haut Pa- rana/ Teju Cuare, pr. [near to] San Ignacio/ E.R. Wagner [leg.] 1911”/ “Type”/ “ Plagiatormia obscura Seguy / Type/ E. Séguy det. 1925”/ “ P. obscura, 113” (MNHN).

Distribution. Argentina (department of San Ignacio).

Diagnosis. Ormiophasia obscura can be distinguished from other species of Ormiophasia by head with silver pruinosity (Fig. 5H); clypeus of same color as frontoclypeal membrane; wing hyaline (Fig. 30D); and thorax and abdomen brown (Fig. 9H, 11H). Ormiophasia obscura can be confused with O. busckii and O. cruzi because of the brown color of the body and the clypeus of the same color as the frontoclypeal membrane. However, O. obscura has ocellar triangle setulose (bare in O. busckii; Fig. 15 C–D) and does not have the contrast of head pruinosity (Figs 5D, 7D) and weakly infuscated wing (Fig. 21G) of O. cruzi .

Redescription of male. Body length 6.98. Wing length 7.47 mm (n = 1).

Coloration. Head silver-pruinose (Fig. 5H). Frontal vitta and ocellar triangle dark brown. Fronto-orbital plate and lunule brown. Antenna yellowish-orange to brownish-orange. Parafacial, gena, facial ridge, face and mouthparts brown. Occiput brown in upper area, becoming light brownish-yellow in lower area. Thorax silver-pruinose (Figs 9H, 11H). Scutum brown; presutural scutum with three silver-pruinose stripes merged posteriorly after suture. Postpronotal lobe and lateral surface of thorax brown. Scutellum and subscutellum brown. Wing hyaline. Tegula, basicosta, veins, halter and calypteres brown. Legs brown. Abdomen brown at base, becoming dark brown after tergite three; with silver pruinosity.

Head (Figs 5H, 30 A–B). Elliptic in frontal view; ratio of head height/head width 0.75. Ocelli 1.5 times the diameter of dorsal ommatidia. Postocellar setae 2. Frontal vitta entirely obliterated. Frontal setae 8, convergent, posterior ones shorter and weaker. Arista weakly plumose. First flagellomere 2.3 times longer than pedicel. Face 1.4 times wider than facial ridge. Facial ridge 2.1 times wider than parafacial.

Thorax. Basisternum 0.54 times as high as wide (Fig. 30C); median upper margin rounded and long, subrectangular. Prosternal tympanal membrane 0.75 times as high as wide. Proepimeral setae 2, upcurved. Anterodorsal corner of anepisternum with 1 weak seta, about 1/2 length of first notopleural seta; posterior row with 7 setae. Meral setae 8. Wing. Subequal to body length, three times longer than wide. Basicosta subequal in width to tegula. Base of vein R 4+5 with 2 dorsal and 2 ventral setae. Section of vein M between crossvein dm-cu and M 1 straight. Legs. Fore femur with row of 11 dorsal setae from base to apex and row of 14 posteroventral setae from base to apex. Fore tibia with row of 3 equally-spaced anterodorsal setae and 1 preapical seta. Mid femur with 3 posteroventral basal setae.

Terminalia. Not dissected.

Female. Unknown.

Remarks. Due to the lack of examined material from Argentina it is not possible to make any advances in the taxonomy of O. obscura . The holotype male is the only specimen available and its terminalia could not be examined. It is possible, though, to refute the synonymy of O. obscura with O. busckii proposed by Townsend (1931), since O. obscura has a setulose ocellar triangle. Regarding the species of Ormiophasia with distribution closer to O. obscura, O. cruzi extends to Argentina, Misiones, and could be even interpreted morphologically as the same species as O. obscura . The contrast of pruinosity on the head is diagnostic for O. cruzi, but it is more visible in females, which are not known for O. obscura . Thus, the examination of male terminalia of O. obscura would be decisive to resolve this issue, but this necessitates additional material. Furthermore, the diagnostic character assigned to O. obscura by Séguy (1926b: 20) in his key (bend of M rounded) is not reliable, since this character shows intraspecific variation in many Ormiophasia species.