Every Ant Tells a Story - And Scientists Explain Their Stories Here
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Temporal range: 20.43–0 Ma
Early Miocene – Recent
Trachymyrmex septentrionalis
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Trachymyrmex
Forel, 1893
Type species
Atta septentrionalis, now Trachymyrmex septentrionalis
49 species
1 fossil species
(Species Checklist)

Trachymyrmex septentrionalis casent0003337 profile 1.jpg

Trachymyrmex septentrionalis

Trachymyrmex septentrionalis casent0003337 dorsal 1.jpg

Specimen Label

Evolutionary Relationships

Cyatta (1 species), Kalathomyrmex (1 species)

  (4 species)

  (2 species)

  (23 species)

  (21 species)

  (4 species)

  (49 species)

  (11 species)

  (1 species)

  (49 species)

  (49 species)

  (63 species)

  (19 species)

Based on Ward et al. (2014), Blaimer et al. (2018) and Li et al. (2018).

A genus of fungus growing ants. Trachymyrmex is mostly Neotropical, occurring in the Nearctic region mostly in the southern parts of Florida, Texas and Arizona, except for one species. Trachymyrmex septentrionalis that occurs up to New York in the North, Illinois, Texas, and Louisiana in the west, and south to Florida and the West Indies. Long Island and Staten Island in New York are the northernmost records for an attine ant. (Mayhé-Nunes & Brandão 2002)

At a Glance • Fungus Grower  



Mayhé-Nunes & Brandão (2002) - The most clear feature to distinguish the monomorphic Trachymyrmex from other attine cognate genera is the always present mesosomal projections on the dorsum of pronotum and/or mesonotum, surmounted by secondary tubercles or minute teeth, that in some species are transformed in small blunt hillocks. All species of Atta lack dorsal projections on the pronotum, and show in addition a strong variation of total body length amongst workers of the same colony. Acromyrmex and Mycetosoritis, the probable closest genera to Trachymyrmex, share with most Trachymyrmex the tuberculated dorsal surface of the first gastric tergite. There are some Trachymyrmex species that look very similar to Acromyrmex workers, which are, nonetheless, almost as polymorphic as in Atta. On the other hand, Trachymyrmex differs from the enigmatic Mycetosoritis by their relatively shallow antennal scrobes (deeply impressed in Mycetosoritis) only comparable to the scrobes found in the Strigatus group of Cyphomyrmex. Most Cyphomyrmex of the Rimosus group have the frontal lobes very expanded laterally, clearly surpassing two thirds of the head width. although two species of this group, Cyphomyrmex longiscapus and Cyphomyrmex foxi show weakly expanded frontal lobes while, in the strigatus group, Mycetophylax lectus and Mycetophylax bruchi present extremely expanded frontal lobes.

The extremely homogeneous Sericomyrmex differs from the strikingly heterogeneous Trachymyrmex in the females by having heart-shaped head, broadest posteriorly, broader than long, lacking any trace of occipital tooth and supraocular tumulus; the preocular carina fades out before or at the level of posterior orbit of eye; the frontal lobes are always triangular and inconspicuously expanded laterad, the interfrontal width about one half of head width as measured across the eyes; the antenna! scapes are relatively short, never quite reaching the occipital border in full-face view when laid back over the head as much as possible; thorax compact; piligerous tubercles practically absent.

Trachymyrmex species groups

Keys including this Genus


Keys to Species in this Genus


Distribution and Richness based on AntMaps





Species Uncertain

  • Trachymyrmex sp.1: n = 6, 2n = 12, karyotype = 12M (Panama) (Murakami et al., 1998).
  • Trachymyrmex sp.2: 2n = 18, karyotype = 18M (Panama) (Murakami et al., 1998).
  • Trachymyrmex: 2n = 22, karyotype = 18M+4SM (Brazil) (Barros et al., 2013).
  • Trachymyrmex: n = 9, 2n = 18, karyotype = 16M+2SM (Brazil) (Barros et al., 2014) (as Trachymyrmex fuscus)."

All Karyotype Records for Genus

Explore Karyotype Data: All, Drilldown
Taxon Haploid Diploid Karyotype Locality Source Notes
Trachymyrmex 18 18M Panama Murakami et al., 1998
Trachymyrmex 22 18M+4SM Brazil Barros et al., 2013
Trachymyrmex 6 12 12M Panama Murakami et al., 1998
Trachymyrmex 9 18 16M+2SM Brazil Barros et al., 2014 as ''Trachymyrmex fuscus''
Trachymyrmex relictus 10 20 20M Brazil Barros et al., 2013
Trachymyrmex septentrionalis 10 20 20M Panama Murakami et al., 1998


The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • TRACHYMYRMEX [Myrmicinae: Attini]
    • Trachymyrmex Forel, 1893e: 600 [as subgenus of Atta]. Type-species: Atta septentrionalis, by subsequent designation of Wheeler, W.M. 1911f: 174.
    • Trachymyrmex subgenus of Cyphomyrmex: Emery, 1913b: 251; Emery, 1924d: 344.
    • Trachymyrmex subgenus of Acromyrmex: Forel, 1917: 247.
    • Trachymyrmex raised to genus: Gallardo, 1916b: 242; Wheeler, W.M. 1916c: 11; Wheeler, W.M. 1922a: 669; Borgmeier, 1950b: 384; Kempf, 1972a: 252.

Kempf was in the process of revising Trachymyrmex at the time of his death. Brandao and Mayhe-Nunes subsequently used Kemp's manuscripts when revising the genus in a series of papers that focused on individual species groups.


Mayhé-Nunes & Brandão (2002) - Dorsal mesosomal spines multidentate or multituberculate, often transformed into small blunt hillocks, bristling with secondary tubercles. Frontal carinae strongly diverging caudad reaching or nearly reaching the lateral angles of the occiput, forming laterad a sometimes shallow but always present scrobe for part of the scapes. Inter frontal width close to or less than 2/3 of the head Width (including eyes). Worker caste monomorphic or nearly so, size Variation slight; major workers absent.


  • Ashmead, W. H. 1905c. A skeleton of a new arrangement of the families, subfamilies, tribes and genera of the ants, or the superfamily Formicoidea. Can. Entomol. 37: 381-384 (page 384, Trachymyrmex in Cryptoceridae, Attinae)
  • Bolton, B. 2003. Synopsis and Classification of Formicidae. Mem. Am. Entomol. Inst. 71: 370pp (page 201, Trachymyrmex as genus)
  • Borgmeier, T. 1923. Catalogo systematico e synonymico das formigas do Brasil. 1 parte. Subfam. Dorylinae, Cerapachyinae, Ponerinae, Dolichoderinae. Arch. Mus. Nac. (Rio J.) 24: 33-103 (page 128, Trachymyrmex as genus)
  • Borgmeier, T. 1950b. Bemerkungen zu Dr. Creighton's Werk "The ants of North America". Rev. Entomol. (Rio J.) 21: 381-386 (page 384, Trachymyrmex as genus)
  • Donisthorpe, H. 1943h. A list of the type-species of the genera and subgenera of the Formicidae. [concl.]. Ann. Mag. Nat. Hist. 11(10): 721-737 (page 733, Trachymyrmex subgenus of Cyphomyrmex)
  • Emery, C. 1895l. Die Gattung Dorylus Fab. und die systematische Eintheilung der Formiciden. Zool. Jahrb. Abt. Syst. Geogr. Biol. Tiere 8: 685-778 (page 770, Trachymyrmex in Myrmicinae, Attini; Trachymyrmex as subgenus of Atta)
  • Emery, C. 1913c. Études sur les Myrmicinae. [V-VII.]. Ann. Soc. Entomol. Belg. 57: 250-262 (page 251, Trachymyrmex subgenus of Cyphomyrmex; Trachymyrmex in Myrmicinae, Attini)
  • Emery, C. 1922c. Hymenoptera. Fam. Formicidae. Subfam. Myrmicinae. [part]. Genera Insectorum 174B: 95-206 (page 344, Trachymyrmex subgenus of Cyphomyrmex; Trachymyrmex in Myrmicinae, Attini)
  • Forel, A. 1893h. Note sur les Attini. Ann. Soc. Entomol. Belg. 37: 586-607 (page 600, Trachymyrmex as subgenus of Atta)
  • Forel, A. 1899d. Formicidae. [part]. Biol. Cent.-Am. Hym. 3: 25-56 (page 30, Trachymyrmex as subgenus of Atta)
  • Forel, A. 1917. Cadre synoptique actuel de la faune universelle des fourmis. Bull. Soc. Vaudoise Sci. Nat. 51: 229-253 (page 247, Trachymyrmex subgenus of Acromyrmex; Trachymyrmex in Myrmicinae, Attini)
  • Gallardo, A. 1916c. Notas acerca de la hormiga Trachymyrmex pruinosus Emery. An. Mus. Nac. Hist. Nat. B. Aires 28: 241-252 (page 242, Trachymyrmex raised to genus)
  • Gallardo, A. 1916e. Notes systématiques et éthologiques sur les fourmis attines de la République Argentine. An. Mus. Nac. Hist. Nat. B. Aires 28: 317-344 (page 318, Trachymyrmex as genus)
  • Kempf, W. W. 1972b. Catálogo abreviado das formigas da regia~o Neotropical. Stud. Entomol. 15: 3-344 (page 252, Trachymyrmex as genus)
  • Kusnezov, N. 1964 [1963]. Zoogeografía de las hormigas en Sudamérica. Acta Zool. Lilloana 19: 25-186 (page 63, Trachymyrmex as genus)
  • Rabeling C, Cover SP, Mueller UG & Johnson RA. 2007. A review of the North American species of the fungus-gardening ant genus Trachymyrmex (Hymenoptera: Formicidae). Zootaxa 1664:1-54. PDF
  • Mayhé-Nunes, A. J. and Brandão, C. 2002. Revisionary studies on the attine ant genus Trachymyrmex Forel. Part 1: definition of the genus and the opulentus group (Hymenoptera: Formicidae). Sociobiology. 40:667-698. PDF
  • Mayhé-Nunes, A. J. and Brandão, C. R. F. 2005. Revisionary studies on the attine ant genus Trachymyrmex Forel. Part 2: the Iheringi group (Hymenoptera: Formicidae). Sociobiology. 45(2):271-305. PDF
  • Mayhé-Nunes, A. J.; Brandão, C. R. F. 2007. Revisionary studies on the attine ant genus Trachymyrmex Forel. Part 3: The Jamaicensis group (Hymenoptera: Formicidae). Zootaxa. 1444:1-21. PDF
  • Wheeler, W. M. 1907d. The fungus-growing ants of North America. Bull. Am. Mus. Nat. Hist. 23: 669-807 (page 670, Trachymyrmex as subgenus of Atta)
  • Wheeler, W. M. 1910b. Ants: their structure, development and behavior. New York: Columbia University Press, xxv + 663 pp. (page 141, Trachymyrmex as subgenus of Atta)
  • Wheeler, W. M. 1911g. A list of the type species of the genera and subgenera of Formicidae. Ann. N. Y. Acad. Sci. 21: 157-175 (page 174, Type-species: Atta septentrionalis, by subsequent designation)
  • Wheeler, W. M. 1916c. Ants collected in British Guiana by the expedition of the American Museum of Natural History during 1911. Bull. Am. Mus. Nat. Hist. 35: 1-14 (page 11, Trachymyrmex as genus)
  • Wheeler, W. M. 1922i. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. VII. Keys to the genera and subgenera of ants. Bull. Am. Mus. Nat. Hist. 45: 631-710 (page 669, Trachymyrmex as genus; Trachymyrmex in Myrmicinae, Attini)