Brachymyrmex santschii

This is a common, distinctive species that occurs in cloud forest leaf litter. It appears to have a narrow elevational range. In the Monteverde area it occurs frequently in Winkler samples from the cloud forest, but has not been collected just below the cloud forest in the Peñas Blancas Valley, in spite of intensive collecting there. On the Barva transect, intensive sampling by Project ALAS produced numerous collections from the 1070m site, but none from the 2000m and 500m sites.

Identification
Ortiz-Sepulveda et al. (2019) - Brachymyrmex santschii morphologically resembles Brachymyrmex iridescens, because both species have the head and the mesosoma with strongly alveolate sculpture. However, they can be distinguished from one another because B. santschii has a metanotal groove that is wider than the diameter of the metathoracic spiracles, scapes that surpass the posterior margin of the head, and a gaster with scattered pubescence.

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

Nomenclature

 * . Brachymyrmex santschii Menozzi, 1927d: 338, fig. 5 (w.) COSTA RICA.
 * Ortiz-Sepúlveda, et al. 2019: 529 (w.-q. intercaste)
 * Status as species: Kempf, 1972a: 41; Bolton, 1995b: 82; Ortiz-Sepúlveda, et al. 2019: 527 (redescription).

Worker
Ortiz-Sepulveda et al. (2019) - (n = 4). HL1 0.40–0.44; HL2 0.29–0.30; HL3 0.08–0.10; HW 0.37– 0.40; SL 0.39–0.42; EL 0.09–0.11; PnL 0.11–0.13; PnW 0.24–0.28; ML 0.09; MW 0.13–0.17; Indices CI 89.80– 91.82; SI1 102.27–109.76; SI2 136.36–138.24; OI1 24.39– 26.84; OI2 20.00–24.44.

Head. Longer than wide in full face view; posterior cephalic margin flat or slightly concave. Dorsum of the head with subdecumbent 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 margin of the head by a length approximately equal to the maximal diameter of the eye; they bear appressed hairs. Three conspicuous ocelli are present. Eyes are positioned on the cephalic midline and have 8–9 ommatidia along their maximal diameter.

Mesosoma. Dorsum subsinusoidal in lateral view. Without erect hairs, but with decumbent hairs on the promesonotum. The mesonotum is variable, typically not or weakly inflated, and not or slightly bulging dorsally above the pronotum in lateral view. Metanotal groove wider than the diameter of the metathoracic spiracles. Metathoracic spiracles in dorsal position, not protruding and not touching any sutures. 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 appressed hairs. Petiole short and inclined forward.

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

Color and sculpture. Head and dorsum of the mesosoma finely alveolate, those parts that are not sculptured, including the gaster, are smooth and shiny. The body is brownish, but sometimes the antennae, tarsi, and articulations of the legs are more yellowish. Intercaste description. The morphology of the putative worker-queen intercaste differs from that of the worker by its larger body size, the eyes that have around ten ommatidia along their maximal diameter, its strongly expanded mesonotum, the absence of a metanotal groove, the dorsolateral position of the metathoracic spiracles, the less convex dorsum of the propodeum, and a markedly expanded gaster with dense pubescence.

Type Material
COSTA RICA: San José.

Ortiz-Sepulveda et al. (2019) - We do not designate a lectotype here, as we have not studied the type series, which would be deposited at the German Entomological Institute in Berlin-Dahlem.

References based on Global Ant Biodiversity Informatics

 * Favretto M. A., E. Bortolon dos Santos, and C. J. Geuster. 2013. Entomofauna from West of Santa Catarina State, South of Brazil. EntomoBrasilis 6 (1): 42-63.
 * Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
 * Longino J. T., and R. K. Colwell. 2011. Density compensation, species composition, and richness of ants on a neotropical elevational gradient. Ecosphere 2(3): 16pp.
 * Longino J. et al. ADMAC project. Accessed on March 24th 2017 at https://sites.google.com/site/admacsite/
 * 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
 * Rosa da Silva R. 1999. Formigas (Hymenoptera: Formicidae) do oeste de Santa Catarina: historico das coletas e lista atualizada das especies do Estado de Santa Catarina. Biotemas 12(2): 75-100.