Brachymyrmex coactus

Identification
Jack Longino:

Face smooth, with abundant erect setae; scapes surpass vertex margin by length of first funicular segment; pronotum, mesonotum, and propodeum with dorsal setae; first gastral tergite with abundant erect setae, no appressed pubescence; metanotal groove weakly impressed; color dark brown; large size.

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Bolivia, Brazil , Costa Rica , Guyana, Panama, Paraguay, Peru.

Biology
Jack Longino: This is a mysterious species. It appears to be widespread, occurring in many areas and habitats, but it is rarely collected. The few records suggest it might be more common in mid-elevation sites than in the lowlands. Although many Brachymyrmex might be rare in collections due to their small size and general inconspicuousness, this is not the case for coactus. Brachymyrmex coactus is one of the largest and most conspicuous species in the genus, with a proclivity for foraging or at least moving in dense columns.

At Sirena, in Corcovado National Park, I saw what looked like a colony migration in progress. A slow-moving, double-file column was moving across a trail. The column was more than 20m long, and I could find no clear beginning or end. Workers were carrying mostly pupae, and a few males were travelling with the column. This was the only time I saw coactus at the site, in spite of working there over a two-year period. I found another column, also crossing a trail on the ground, during a trip to the small Cerro Rincón cloud forest, at 700m elevation in the center of the Osa Peninsula.

At Wilson Botanical Garden, a 1200m elevation site in the southern mountains, I observed a dense column on a recent treefall, and I found a nest space with some brood in the base of a bromeliad. Similarly, at a site near Las Alturas in the Cordillera de Talamanca, I found a column on the trunk of a recently felled tree in a small pasture area.

Jenny Jacobs, a student carrying out a project on the leaf litter fauna of the small islands off the northwest coast of Costa Rica, found specimens on Isla San José. John Noyes captured specimens in sweepnet samples from Estación Cacao, at 1100m in the Cordillera de Guanacaste.

Brachymyrmex coactus obviously has some interesting biology. I have never seen isolated foraging workers, only these occasional dense columns. Is the species nomadic? What do they eat?

Nomenclature

 * . Brachymyrmex coactus Mayr, 1887: 523 (w.q.m.) BRAZIL (Santa Catarina).
 * Status as species: Emery, 1888c: 364; Emery, 1890b: 56; Dalla Torre, 1893: 174; von Jhering, 1894: 377; Emery, 1894k: 61; Forel, 1895b: 106; Forel, 1899c: 123; Forel, 1912i: 62; Mann, 1916: 473; Luederwaldt, 1918: 48; Santschi, 1923b: 669; Santschi, 1923c: 272; Emery, 1925b: 41; Borgmeier, 1927c: 141; Kempf, 1972a: 38; Bolton, 1995b: 82; Branstetter & Sáenz, 2012: 255; Fernández & Ortiz-Sepúlveda, 2019: 728; Ortiz-Sepúlveda, et al. 2019: 480 (redescription).
 * Senior synonym of constrictus: Ortiz-Sepúlveda, et al. 2019: 481.
 * Senior synonym of nictitans: Ortiz-Sepúlveda, et al. 2019: 480.
 * Senior synonym of robusta: Ortiz-Sepúlveda, et al. 2019: 481.
 * constrictus. Brachymyrmex constrictus Santschi, 1923b: 671, figs. 5, 38, 61 (w.) BOLIVIA.
 * Status as species: Emery, 1925b: 41; Kempf, 1972a: 38; Bolton, 1995b: 82.
 * Junior synonym of coactus: Ortiz-Sepúlveda, et al. 2019: 480.
 * nictitans. Brachymyrmex coactus var. nictitans Emery, 1906c: 178 (w.) COSTA RICA.
 * Subspecies of coactus: Santschi, 1923b: 670; Emery, 1925b: 41; Kempf, 1972a: 38; Bolton, 1995b: 82.
 * Junior synonym of coactus: Ortiz-Sepúlveda, et al. 2019: 480.
 * robusta. Brachymyrmex coactus var. robusta Santschi, 1923c: 272 (w.) BRAZIL (Santa Catarina).
 * Subspecies of coactus: Emery, 1925b: 41; Borgmeier, 1927c: 141; Kempf, 1972a: 38; Bolton, 1995b: 82.
 * Junior synonym of coactus: Ortiz-Sepúlveda, et al. 2019: 481.

References based on Global Ant Biodiversity Informatics

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 * Alonso L. E., J. Persaud, and A. Williams. 2016. Biodiversity assessment survey of the south Rupununi Savannah, Guyana. BAT Survey Report No.1, 306 pages.
 * 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.
 * Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
 * Drose W., L. R. Podgaiski, C. Fagundes Dias, M. de Souza Mendonca. 2019. Local and regional drivers of ant communities in forest-grassland ecotones in South Brazil: A taxonomic and phylogenetic approach. Plos ONE 14(4): e0215310.
 * Emery C. 1890. Studii sulle formiche della fauna neotropica. Bull. Soc. Entomol. Ital. 22: 38-8
 * Emery C. 1894. Estudios sobre las hormigas de Costa Rica. Anales del Museo Nacional de Costa Rica 1888-1889: 45-64.
 * 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.
 * Forel A. 1912. Formicides néotropiques. Part VI. 5me sous-famille Camponotinae Forel. Mémoires de la Société Entomologique de Belgique. 20: 59-92.
 * INBio Collection (via Gbif)
 * Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
 * Longino J. T. 2013. Ants of Nicargua. Consulted on 18 Jan 2013. https://sites.google.com/site/longinollama/reports/ants-of-nicaragua
 * Longino J. T. L., and M. G. Branstetter. 2018. The truncated bell: an enigmatic but pervasive elevational diversity pattern in Middle American ants. Ecography 41: 1-12.
 * Longino, J.T. 2010. Personal Communication. Longino Collection Database
 * Luederwaldt H. 1918. Notas myrmecologicas. Rev. Mus. Paul. 10: 29-64.
 * Lutinski J. A., B. C. Lopes, and A. B. B.de Morais. 2013. Diversidade de formigas urbanas (Hymenoptera: Formicidae) de dez cidades do sul do Brasil. Biota Neotrop. 13(3): 332-342.
 * 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. 2007. El Género Neotropical Brachymyrmex Mayr (Hymenoptera: Formicidae) en la Argentina. III: Redescripción de las Especies: B. aphidicola Forel, de B. australis Forel y B. constrictus Santschi. Neotropical Entomology 36(5):699-706
 * 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.
 * Rosumek, F.B., M.A. Ulyssea, B.C. Lopes, J. Steiner. 2008. Formigas de solo e de bromélias em uma área de Mata Atlântica, Ilha de Santa Catarina, sul do Brasil: Levantamento de espécies e novos registros. Revista Biotemas 21(4):81-89.
 * Santschi F. 1923. Revue des fourmis du genre Brachymyrmex Mayr. Anales del Museo Nacional de Historia Natural de Buenos Aires 31: 650-678.
 * Santschi F. 1923. Solenopsis et autres fourmis néotropicales. Revue Suisse de Zoologie 30: 245-273.
 * 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.
 * Silva R. R., R. S. Machado Feitosa, and F. Eberhardt. 2007. Reduced ant diversity along a habitat regeneration gradient in the southern Brazilian Atlantic Forest. Forest Ecology and Management 240: 61-69.
 * Silva R.R., and C. R. F. Brandao. 2014. Ecosystem-Wide Morphological Structure of Leaf-Litter Ant Communities along a Tropical Latitudinal Gradient. PLoSONE 9(3): e93049. doi:10.1371/journal.pone.0093049
 * Ulyssea M. A., and C. R. F. Brandao. 2013. Ant species (Hymenoptera, Formicidae) from the seasonally dry tropical forest of northeastern Brazil: a compilation from field surveys in Bahia and literature records. Revista Brasileira de Entomologia 57(2): 217224.
 * Ulyssea M.A., C. E. Cereto, F. B. Rosumek, R. R. Silva, and B. C. Lopes. 2011. Updated list of ant species (Hymenoptera, Formicidae) recorded in Santa Catarina State, southern Brazil, with a discussion of research advances and priorities. Revista Brasileira de Entomologia 55(4): 603-611.
 * Ulysséa M. A., C. R. F. Brandão. 2013. Ant species (Hymenoptera, Formicidae) from the seasonally dry tropical forest of northeastern Brazil: a compilation from field surveys in Bahia and literature records. Revista Brasileira de Entomologia 57(2): 217-224.
 * 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).