Dorymyrmex brunneus

A variable and widely ranging species that further taxonomic study may reveal to be a complex of closely related species.

Identification
Cuezzo and Guerrero (2011) - Worker Head slightly longer than wide. Posterior margin of head straight to feebly concave medially. Psammophore with short hairs disposed in a triangle, not reaching the posterior end of hypostome. Promesonotum depressed in lateral view, always lower than the apex of propodeal tubercle. Mesonotal profile with a well-defined dorsal and declivitous face in the posterior end. Metanotal suture well impressed forming a concavity anterior to the propodeum. Queen Maximum diameter of head behind the compound eyes. Posterior margin of head feebly concave medially. Forewing with only one close cubital cell. Male Dark brown. Scape long, reaching the posterior margin of compound eyes. Mandible with only three teeth. Forewing with no discoidal and no cubital cells, hindwing with only two closed cells. Pygostyle poorly developed, paramere stout and covered with long hairs.

The shape of the mesosomal profile was one of the most frequently characters used to separate species of Dorymyrmex but is almost unusable to identify D. brunneus. Local populations of this species have strong differences in the profile of mesosoma and scape length. There are morphological variations among Colombian populations which seem to be stable: only workers with broad head (CI: 90–107) have a strong mesonotal depression making a sort of tubercle at the middle of mesonotum (different from Dorymyrmex biconis), with a deep and wide metanotal groove. Besides, workers have a median ocellus and, sometimes, two tiny lateral ocelli (populations from Boyaca, Colombia). The shape of queen head in frontal view, mandibles with only three teeth in male and the number of closed cells in forewings have proved to be useful to separate D. brunneus from other Dorymyrmex species.

Distribution
Known from Guatemala and from Panama to Argentina.

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Bolivia, Brazil, Colombia, French Guiana, Guatemala, Guyana, Panama, Paraguay, Suriname.

Biology
Cuezzo and Guerrero (2011) - D. brunneus is mainly restricted to arid environments of the Andean region of Colombia, at elevations above 1000 m. Some lowland populations live in dry forests of western Colombia (Valle del Cauca, 400–500 m), savannas in eastern plains (Vichada, 240 m), and in Colombian Amazon basin (Amazonas, 200–300 m).

Like Dorymyrmex biconis, D. brunneus is well adapted to anthropic environments. Most of the specimens studied here have been collected in areas transformed by humans, mainly in open areas with low vegetation (stubble), coffee plantations (shade coffee culture), wooded areas for cattle grazing, and urban areas.

Nomenclature

 *  brunneus. Dorymyrmex pyramicus var. brunnea Forel, 1908c: 385 (w.) ARGENTINA. Gallardo, 1916a: 60 (q.); Cuezzo & Guerrero, 2011: 14 (m.). Combination in D. (Conomyrma): Forel, 1913l: 244; in Conomyrma (Biconomyrma): Kusnezov, 1952g: 430; in Biconomyrma: Kusnezov, 1959: 51; in Dorymyrmex: Shattuck, 1992c: 85. Subspecies of pyramicus: Forel, 1911c: 306; Santschi, 1912e: 531. Raised to species: Santschi, 1929d: 305; Kusnezov, 1952g: 430; Kempf, 1975c: 375.

Worker
Cuezzo and Guerrero (2011) - Lectotype: HL: 0.95; HW: 0.8; EL: 0.23; EW: 0.125; SL: 0.875; WL: 1.175; CI: 84; SI: 92; REL: 24; OI: 54; TLI: 124.

Other material (n = 98): HL: 0.70–1.04; HW: 0.64–0.92; EL: 0.22–0.30; EW: 0.10–0.20; SL: 0.80–1.14; WL: 1.00–1.46; CI: 83–117; SI: 98–129; REL: 24–34; OI: 45–77; TLI: 122–171.

Concolorous dark brown; whitish pubescence covering all body tagma. 0–2 erected setae on the dorsum of pronotum. Head: subquadrate, with lateral margins strongly convex, maximum head width at the compound eye level. Mandibles strongly striate, reddish brown. Compound eyes in central 1/3 of the head as seen in frontal view. Scape long (SI: 92–129), surpassing the posterior margin of head by more than twice its maximum width. Posterior margin of head usually straight but sometimes feebly concave in the middle. Psammophore with a few extremely short hairs disposed in a triangle, the hairs in the top line are near to the foramen magnum and do not reach the oral cavity. Upper setae of psammophore close to the anterior margin of foramen magnum. Mesosoma: promesonotal profile sinuate to straight and, in lateral view, always lower than the apex of propodeal tubercle. Posterior end of mesonotum forming two faces, one dorsal and one declivitous but not conforming a well-developed tubercle. Propodeal tubercle stout, with wide base, and slightly directed dorsally. Declivitous face straight to slightly convex. Metasoma: petiole forward directed, included in a concavity placed in the anterior face of the first gastral segment. Scale apically thin and rounded.

Queen
Cuezzo and Guerrero (2011) - (n = 5): HL: 1.13; HW: 1.15; EL: 0.38; EW: 0.18; IOD: 0.78; SL: 1.1;WL: 2.3.

Color and pubescence as in worker; head: subquadrate, maximum diameter after the compound eyes. Clypeal sides lighter than the rest of the head; scape surpassing the posterior margin of head by more than twice its maximum width; mandibles striated with four teeth and two denticles; posterior margin of head feebly concave medially. Mesosoma: parapsidal furrows well developed, parallel, axilla not divided. A short, incomplete suture divides anepisternum from katepisternum. Forewing with only one closed cubital cell; radial cell long and close. Metasoma: low and stout petiole, apically rounded.

Male
Cuezzo and Guerrero (2011) - (n = 3): HL: 0.58–0.6; HW: 0.58–0.63; EL: 0.28–0.33; EW: 0.15–0.2; SL: 0.25; WL: 1.3–1.38.

Color of the body similar to worker and queen; head: subquadrate with round occipital corner; mandibles thin with only three teeth, the apical more than twice longer than the others. Scape long, reaching the posterior margin of compound eyes. Mesosoma: parapsidal furrows parallel, axilla not divided medially; forewing with one close radial cell and no cubital nor discoidal cell. Hindwing with only two closed cells. Metasoma: petiolar scale low, round, and stout, ventral process round, feebly developed. Pygostyle poorly developed; paramere stout covered with long, erected setae; aedeagus serrate ventrally.

Type Material
Cuezzo and Guerrero (2011) - Lectotypes. 2w, S˜ao Paulo, BRAZIL designed by Kempf 1975: 375.

Etymology
Cuezzo and Guerrero (2011) - The name “brunneus” means dark brown. It is the main color of worker, queen, and male.