Lomachaeta vianai Casal, 1969

(Figs 13, 14, 19, 20, 55)

Lomachaeta vianai Casal, 1969: 34 . Holotype, ♀, Argentina, Misiones, Dep. Concep. (AMNH, examined). Lomachaeta megomicron Williams & Pitts, 2009: 235 . Holotype, ♂, Argentina, Salta, 8km N La Viña (EMUS, examined), syn. nov.

Diagnosis. MALE. The following combination of characters is diagnostic for L. vianai: the body is black, except the pale yellow T1 apex; the mandible lacks a ventral tooth basally; the gena is weakly carinate; the head and pronotum are areolate; the forewing has its veins encompassing the basal 0.7 × of the wing; the T1 shape is disciform; the T2 disc has dense small punctures; the T2 fringe is composed of thick bristles; and the paramere is virtually straight and has an weak apical setal tuft. Body length 4–6 mm.

FEMALE. The following characters are diagnostic: the head and mesosoma are dark reddish, the metasoma is blackish; the pronotal and propodeal spiracles are scarcely swollen; the head is 1.2 × wider than the mesosoma; the lateral propodeal face has a few complete areolations; the mesosoma is elongate, with the thoracic dorsum nearly as long as wide; the mesosomal dorsum is tightly areolate without subparallel thickened setae; the T1 shape is subdisciform; T2 has dense oblique punctures, mostly subappressed pale yellow setae, and mostly smooth intervals; and the S6 lateral carina is low angular. Body length 2.5–4.5 mm.

Material examined. Type material. Holotype of Lomachaeta vianai, ♀, ARGENTINA, Misiones, Dep. Concepcion, Santa María, X.1956, M.J. Viana (AMNH, Figs 13, 19) ; Holotype of Lomachaeta megamicron, ♂, ARGENTINA, Salta, 8 km N La Viña, 26.X–13.XI.2003, M.E. Irwin & F.D. Parker coll. (EMUS). Other material. ARGENTINA: Salta: 8 km N La Viña, 26.X–13.XI.2003, M.E. Irwin & F.D. Parker (1♂, EMUS, Fig. 55); Chaco Occidental, Los Colorados, 100 km NE Joaquin V. Gonzales, 14.III.1992, B. Bestelmeyer (1♀, MIUP); Pocitos, XI.1978, Fritz (1♂, MIUP). BRAZIL, Goiás, Parque Nacional Chapada dos Veadeiros, A.P. Aguiar and B.F. dos Santos, Yellow Pan Trap: Ponto 1, 13–15.IX.2005 (1♂, UFES); Ponto 3, 19-21.IX.2005 (2♂, UFES); Ponto 6, 9–11.IX.2005 (1♂, UFES); Ponto 10, 9–11.IX.2005 (2♂, UFES); Ponto 15, IX.2005 (1♂, UFES). PARAGUAY: Boquerón, Mariscal Estigarribia, Escuela Agricola, 174m, 21 o 59’45”S 60 o 38’31”W, 5–7.X.2003, B. Garcette, Malaise (1♂, MIUP); Presidente Hayes, Los Pioneros, 22.69014 o S 59.77186 o W, 9–11.X.2003, M. LePonce, Pit Fall Trap (1♀, MIUP, Figs 14, 20) .

Distribution. Argentina (Catamarca, Misiones, and Salta Provinces), Brazil (Goiás), and Paraguay (Boquerón and Presidente Hayes Departments).

Remarks. Previously known from the unique type only, this species is now recognized as a widely distributed species in South America. Although this species is widespread, it is known from only seven localities. The sex association is based on a male and female collected in similar habitats (Chaco Boreal) in Paraguay.