Brachymyrmex gagates

The type specimens were collected from an epiphytic bromelia (Tillandsia streptophylla) (Wheeler 1934).

Identification
Ortiz-Sepulveda et al. (2019) - Brachymyrmex gagates resembles Brachymyrmex degener and Brachymyrmex gaucho in morphology, because they all have smooth, shiny, and dark brown or black bodies, scapes that surpass the posterior margin of the head, and a gaster with scarce pubescence. Brachymyrmex gagates differs from B. degener by its darker body and by having a mesonotum that is almost circular in dorsal view and that does not bulge above the pronotum in lateral view. It differs from B. gaucho by having a slightly concave posterior cephalic margin, scapes with decumbent hairs, a second segment of the antennal funiculus that is conspicuously shorter than the first antennal segment, and its almost circular mesonotum in dorsal view that does not bulge above the pronotum in lateral view.

Wheeler (1934) - This species seems to be quite distinct from any of those included in Santschi's monograph of Brachymyrmex (1923). It runs to Brachymyrmex incisus in his table, but typical specimens of this form from Panama in my collection show that it differs from gagates in having a narrower head, much less prominent mesonotum, indistinct and unimpressed promesonotal suture, shorter funicular joints, much paler coloration, etc.

Distribution based on Regional Taxon Lists
Neotropical Region: Mexico, Panama.

Nomenclature

 * . Brachymyrmex gagates Wheeler, W.M. 1934g: 206 (w.) MEXICO (Veracruz).
 * Status as species: Kempf, 1972a: 39; Bolton, 1995b: 82; Ortiz-Sepúlveda, et al. 2019: 499 (redescription).

Description
Length 2-2.5 mm.

Head rounded subrectangular and dorsally convex as in the other species of the genus; posterior border straight, with a slight median sinuation. Eyes rather large, flattened, a little behind the middle of the sides and less than twice their length from the anterior corners. Ocelli distinct. Mandibles small, with oblique 5-toothed terminal borders, the median tooth minute. Clypeus large, convex but ecarinate in the middle, its anterior border broadly rounded and projecting, concealing the closed mandibles. Frontal area subtriangular, not very sharply defined; frontal groove represented anteriorly as an indistinct longitudinal ridge but concave just in front of the anterior ocellus. Antennal scapes extending fully one-fourth their length beyond the posterior corners of the head; second funicular joint one and one-half times as long as broad, a little more than half as long as the first joint; joints 3-7 more than one and one-half times as long as broad, terminal joint as long as the two preceding subequal joints together. Thorax with strong and distinctly impressed promesonotal suture, interrupting the dorsal outline, and deep mesoepinotal impression; metaepinotal suture distinct, the prominent metanotal spiracles small, separated by more than five times their diameter. Pronotum broad and rounded, mesonotum less than twice as broad as long, very convex, projecting above the pronotum; metaepinotum slightly longer than broad, trapezoidal, distinctly broader behind than in front; base and declivity of epinotum in profile straight and subequal, the former horizontal, the latter sloping, forming together a rounded but distinct obtuse angle. Petiolar scale small, thin and very narrow, its anterior surface concave above, its posterior surface feebly convex. Gaster voluminous, pointed posteriorly, its large first segment overlying the petiole and provided with a deep groove for its accommodation. Legs stout, fore femora distinctly enlarged and somewhat compressed.

Very shining and very finely and superficially reticulate; basal half of mandibles obscurely striatopunctate; sides of thorax less shining than the dorsal surface; metapleurae subopaque, finely and densely punctate.

Hairs reddish or brownish, pubescence whitish; the former sparse, erect and pointed, in several rows on the gastric segments, absent on the appendages. Pubescence short, distinct, appressed and dilute on the posterior portion of the head; absent on the thorax and abdomen; abundant and subappressed on the appendages, somewhat longer on the antennae than on the legs.

Jet black; clypeus, tips of mandibles and insertions of antennae red; sides of head, antennae and legs dark brown; funiculi sometimes more reddish; tarsal joints beyond the metatarsi pale yellow; trochanters and neck yellowish brown.

Ortiz-Sepulveda et al. (2019) - Lectotype measurements (mm). HL1 0.59; HL2 0.39; HL3 0.18; HW 0.55; SL 0.51; EL 0.16; WL 0.59; PnL 0.18; PnW 0.39; ML 0.16; MW 0.20; Indices CI 93.33; SI1 92.86; SI2 130.00; OI1 28.57; OI2 30.00.

Head. Slightly longer than wide in full face view; posterior cephalic border slightly concave. Dorsum of the head with scattered appresed 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 bear decumbent hairs and surpass the posterior margin of the head by a length smaller than the maximal diameter of the eye. Three ocelli present. Eyes are positioned slightly posteriorly to the cephalic midline and have 10–12 ommatidia along their maximal diameter. Mesosoma. Typically bearing two erect hairs on the pronotum and two on the mesonotum, sometimes with some additional appressed hairs on the dorsum of the mesonotum. The mesonotum is inflated but does not bulge dorsally above the pronotum in lateral view; it is almost circular in dorsal view. Metanotal groove wider than the diameter of the metathoracic spiracles. Metathoracic spiracles in dorsolateral position, protruding slightly, and either just or just not touching the propodeal suture. Dorsum of the propodeum convex and somewhat shorter than the posterior declivity. Propodeal spiracles circular, positioned on the posterior propodeal margin, anterior of the middle of the propodeal slope. Legs have appressed hairs. Petiole short and inclined forward. Gaster. With scattered pubescence and several scattered long erect hairs. Color and sculpture. Head and gaster are smooth and shiny, whereas the dorsum of the mesosoma is slightly imbricate. Body uniformely dark brown, apart from the terminal segments of the tarsus and the hairs, which are lighter.

Type Material
Described from a dozen specimens (No. 607) taken by Dr. Skwarra at Mirador, Vera Cruz, in Tillandsia streptophylla.

Ortiz-Sepulveda et al. (2019) - Lectotype worker (: USNMENT00529454) and paralectotype workers (USNM: USNMENT00529454; : M.C.Z. Cotype 1–321436, M.C.Z. Cotype 4– 621436; here designated): nine workers [examined]. MEXICO: Veracruz: Mirador, 20 Apr. 1929.

The lectotype is the ant at the top of pin USNM: USNMENT00529454, whereas the others on that pin are paralectotypes.

References based on Global Ant Biodiversity Informatics

 * Fernandes, P.R. XXXX. Los hormigas del suelo en Mexico: Diversidad, distribucion e importancia (Hymenoptera: Formicidae).
 * 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
 * Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133