Brachymyrmex musculus

Nothing is known about the biology of .

Identification
Ortiz-Sepulveda et al. (2019) - Brachymyrmex musculus morphologically resembles Brachymyrmex bruchi, Brachymyrmex patagonicus, and Brachymyrmex oculatus, because all four species have scapes that surpass the posterior margin of the head, a mesonotum that does not bulge dorsally above the pronotum in lateral view, a gaster with scattered pubescence and a brownish body. However, B. musculus differs from the three other species by having a metanotal groove that is wider than the diameter of the metathoracic spiracles.

Brachymyrmex tristis differs from B. musculus by having dense decumbent hairs on the head and the dorsum of the mesosoma, a mesonotum that bulges dorsally above the pronotum, and metathoracic spiracles that protrude slightly.

Distribution
This species was for decades thought to be invasive in Florida and the gulf coast of the United States. All such references to B. musculum are now deemed to be Brachymyrmex patagonicus (MacGown et al. 2007).

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Colombia, Costa Rica, Mexico, Paraguay, Venezuela.

Nomenclature

 * . Brachymyrmex tristis r. musculus Forel, 1899c: 124 (w.) COSTA RICA.
 * Forel, 1901c: 135 (q.).
 * Status as species: Forel, 1901c: 135; Santschi, 1923b: 673; Emery, 1925b: 43; Menozzi, 1927c: 268; Kempf, 1972a: 40; Bolton, 1995b: 82; Deyrup, et al. 2000: 301; Deyrup, 2003: 44; MacGown & Forster, 2005: 65; Fernández & Ortiz-Sepúlveda, 2019: 728; Ortiz-Sepúlveda, et al. 2019: 514 (redescription).

Worker
Ortiz-Sepulveda et al. (2019) - Lectotype and paralectotype (n = 5). HL1 0.43–0.48; HL2 0.30–0.33; HL3 0.10–0.11; HW 0.39– 0.42; SL 0.39–0.42; EL 0.10–0.12; WL 0.42–0.46; PnL 0.11; PnW 0.25–0.29; ML 0.08–0.10; MW 0.18–0.20; Indices CI 87.16–91.26; SI1 98.92–100.00; SI2 117.65–136.76; OI1 23.16–30.00; OI2 21.10–23.81. Additional material examined (n = 3) HL1 0.48–0.51; HL2 0.33–0.37; HL3 0.10–0.12; HW 0.44– 0.47; SL 0.43–0.47; EL 0.12–0.14; WL 0.35–0.51; PnL 0.10– 0.14; PnW 0.30–0.32; ML 0.10–0.12; MW 0.19–0.20; Indices CI 89.09–92.59; SI1 97.87–102.04; SI2 125.00–131.58; OI1 26.00–30.61; OI2 21.15–24.07.

Head. Slightly longer than wide in full face view; posterior cephalic margin slightly concave. Dorsum of the head has sparse appressed hairs. Clypeus with the medial anterior margin somewhat forming a lip 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 are 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 with a length up to the maximal diameter of the eye; with appressed hairs. Three ocelli are present but inconspicuous. Eyes are positioned on the cephalic midline with 9–11 ommatidia along their maximal diameter.

Mesosoma. Typically with two erect hairs on the pronotum and two on the mesonotum; sometimes with additional suberect hairs mainly on the pronotum. The mesonotum is not inflated and does not bulge dorsally above the pronotum in lateral view. Metanotal groove wider than the diameter of the metathoracic spiracles. Metathoracic spiracles in dorsolateral position, not protruding, and close to the propodeal suture. Dorsum of the propodeum convex and shorter than the posterior 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 several scattered long erect hairs.

Color and sculpture. Body overall smooth and shiny, except for the sometimes slightly imbricate sculpture on the dorsum of the mesosoma. Body typically brownish; however, the bulbi of the antennae are whitish, and the antenna and legs, especially the tarsi, are somewhat lighter in color than the body.

Type Material
Ortiz-Sepulveda et al. (2019) - Brachymyrmex tristis r. musculus Forel, 1899: 124 (w.). Lectotype worker (: USNMENT00757155) and paralectotype workers (MHNG: USNMENT00757153– 00757155; USNMENT00758113–00758115; : USNMENT00757152; here designated): 16 workers [examined]: COSTA RICA: Pittier; Forel (1901a: 135) (q.).

Determination Clarifications
United States - Prior to 2007 in states along the Gulf coast Brachymyrmex patagonicus was incorrectly identified as B. musculum (MacGown et al. 2007).

References based on Global Ant Biodiversity Informatics

 * Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
 * Fernandes, P.R. XXXX. Los hormigas del suelo en Mexico: Diversidad, distribucion e importancia (Hymenoptera: Formicidae).
 * Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
 * Forster J.A. 2005. The Ants (hymenoptera: Formicidae) of Alabama. Master of Science, Auburn University. 242 pages.
 * Hernandez, F. Varela and G. Castano-Meneses. 2010. Checklist, Biological Notes and Distribution of Ants (Hymenoptera: Formicidae) from Barranca de Metztitlán Biosphere Reserve, Hidalgo, Mexico. Sociobiology 56(2):397-434
 * Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
 * Maes, J.-M. and W.P. MacKay. 1993. Catalogo de las hormigas (Hymenoptera: Formicidae) de Nicaragua. Revista Nicaraguense de Entomologia 23.
 * 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
 * Perfecto I., and J. Vandermeer. 1996. Microclimatic changes and the indirect loss of ant diversity in a tropical agroecosystem. Oecologia 108: 577-582.
 * Rivas-Arancibia, S. P., H. Carrillo-Ruiz, A. Bonilla-Arce, D. M. Figueroa-Castro, and A. R. Andres-Hernandez. 2014. Effect of disturbance on the ant community in a semiarid region of central Mexico. Applied Ecology and Environmental Research 12: 703-716.
 * Valenzuela-González J., Quiroz-Robledo L. y Martínez-Tlapa D. 2008. Capítulo 8. Hormigas (Insecta: Hymenoptera: Formicidae). En: Manson R., Hernández-Ortiz V., Gallina S y K. Mehltreter (eds) Agroecosistemas cafetaleros de Veracruz: biodiversidad, manejo y conservación.Instituto de Ecología A.C.-Instituto Nacional de Ecología (INE-SEMARNAT). P.107-121. ISBN 970-709-112-6.
 * Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133