Brachymyrmex coactus

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Brachymyrmex coactus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Myrmelachistini
Genus: Brachymyrmex
Species: B. coactus
Binomial name
Brachymyrmex coactus
Mayr, 1887

Brachymyrmex coactus inbiocri001280743 p 1 high.jpg

Brachymyrmex coactus inbiocri001280743 d 1 high.jpg

Specimen Labels



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 (type locality), Brazil (type locality), Costa Rica (type locality), Guyana, Panama, Paraguay, Peru.

Distribution based on AntMaps


Distribution based on AntWeb specimens

Check data from AntWeb


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?



The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

  • coactus. 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.



  • Bolton, B. 1995b. A new general catalogue of the ants of the world. Cambridge, Mass.: Harvard University Press, 504 pp. (page 82, catalogue)
  • Mayr, G. 1887. Südamerikanische Formiciden. Verh. K-K. Zool.-Bot. Ges. Wien 37: 511-632 (page 523, worker, queen, male described)

References based on Global Ant Biodiversity Informatics

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  • INBio Collection (via Gbif)
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