Brachymyrmex oculatus

Identification
Ortiz-Sepulveda et al. (2019) - Brachymyrmex oculatus morphologically resembles B. bruchi and B. patagonicus, because all three species have scapes that surpass the posterior margin of the head, they usually have two erect hairs on the mesonotum, their mesonotum does not bulge dorsally above the pronotum in lateral view, a metanotal groove is absent or narrower than the diameter of the metathoracic spiracles, their gaster has scarce pubescence, and several scattered long erect hairs and their body is brownish. Brachymyrmex oculatus differs from B. bruchi and B. patagonicus, however, by having larger eyes, with a maximal diameter that approximates a third of the length of the head (HL1). They usually have more than 14 ommatidia along their maximal diameter. Whereas B. patagonicus has two erect hairs on the pronotum and B. bruchi usually more than two, the number of erect hairs on the pronotum is variable in B. oculatus.

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina.

Nomenclature

 * . Brachymyrmex oculatus Santschi, 1919f: 55 (w.) ARGENTINA (Buenos Aires).
 * Quirán, et al. 2004: 283 (m.).
 * Status as species: Santschi, 1923b: 660; Emery, 1925b: 43; Kempf, 1972a: 40; Bolton, 1995b: 82; Quirán, et al. 2004: 282 (redescription); Ortiz-Sepúlveda, et al. 2019: 520 (redescription).

Worker
Ortiz-Sepulveda et al. (2019) - Lectotype and paralectotypes (n = 4). HL1 0.45–0.50; HL2 0.35–0.41; HL3 0.11–0.14; HW 0.48–0.58; SL 0.45–0.50; EL 0.15–0.18; WL 0.53–0.61; PnL 0.15–0.17; PnW 0.30–0.39; ML 0.14–0.20; MW 0.23–0.27; Indices CI 106.67–115.15; SI1 86.84–93.75; SI2 122.22– 133.33; OI1 31.25–34.29; OI2 21.88–27.27.

Head. Slightly longer than wide in full face view; posterior cephalic border flat. Dorsum of the head with sparse appressed hairs. Clypeus with a rounded anterior margin and five long, erect hairs of which a single, usually conspicuous hair is near the anterior margin, two hairs are in mediolateral position, and two more near the toruli; other hairs on the clypeus are markedly shorter and appressed or decumbent. Toruli surpassing the posterior clypeal margin in oblique anterodorsal view. The scapes surpass the posterior cephalic margin by a length that is shorter than the maximal diameter of the eye; they have appressed hairs. Ocelli absent. Eyes are positioned on the cephalic midline and usually have more than 14 ommatidia along their maximal diameter.

Mesosoma. Dorsum of the mesosoma with sparse appressed hairs, and typically with two erect hairs on the pronotum and two on the mesonotum; sometimes with additional suberect hairs, mainly on pronotum. The mesonotum is not inflated and does not bulge dorsally above the pronotum in lateral view. Metanotal groove absent or narrower than the diameter of the metathoracic spiracles. Metathoracic spiracles in dorsolateral position, not protruding, and touching the propodeal suture. Dorsum of the propodeum slightly convex and shorter than the propodeal slope. Propodeal spiracles circular, positioned on the posterior propodeal margin, at the middle of the propodeal slope. Legs with scattered appressed hairs. Petiole short and inclined forward.

Gaster. With scattered pubescence and several scattered long erect hairs, mainly at the edges of the segments.

Color and sculpture. Body overall smooth and shiny, with the dorsum of the mesosoma slightly imbricate. Body uniformely brownish.

Type Material
Ortiz-Sepulveda et al. (2019) - Lectotype worker (: USNMENT00758101) and paralectotype workers (NHMB: USNMENT00758101; here designated): six workers [examined]. ARGENTINA: Buenos Aires: Sierra de las Ventanas, Bruch leg.

The specimen at the top of pin NHMB: USNMENT00757132 is here designated as lectotype, whereas the other ants in that pin are paralectotypes.

References based on Global Ant Biodiversity Informatics

 * Cuezzo, F. 1998. Formicidae. Chapter 42 in Morrone J.J., and S. Coscaron (dirs) Biodiversidad de artropodos argentinos: una perspectiva biotaxonomica Ediciones Sur, La Plata. Pages 452-462.
 * Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
 * Ortiz-Sepuvelda C. M., B. Van Bocxlaer, A. D. Meneses, and F. Fernandez. 2019. Molecular and morphological recognition of species boundaries in the neglected ant genus Brachymyrmex (Hymenoptera: Formicidae): toward a taxonomic revision. Organisms Diversity & Evolution https://doi.org/10.1007/s13127-019-00406-2
 * Quiran E. M., J. J. Martínez, and A. O. Bachmann. 2004. The Neotropical genus Brachymyrmex Mayr, 1868 (Hymenoptera: Formicidae) in Argentina. Redescription of the type species, B. patagonicus Mayr,1868; B. bruchi Forel, 1912 and B. oculatus Santschi, 1919. Acta Zool. Mex. Nueva Série 20: 273-285.
 * Santschi F. 1925. Fourmis des provinces argentines de Santa Fe, Catamarca, Santa Cruz, Córdoba et Los Andes. Comunicaciones del Museo Nacional de Historia Natural "Bernardino Rivadavia" 2: 149-168.
 * Vittar, F. 2008. Hormigas (Hymenoptera: Formicidae) de la Mesopotamia Argentina. INSUGEO Miscelania 17(2):447-466
 * Vittar, F., and F. Cuezzo. "Hormigas (Hymenoptera: Formicidae) de la provincia de Santa Fe, Argentina." Revista de la Sociedad Entomológica Argentina (versión On-line ISSN 1851-7471) 67, no. 1-2 (2008).