Acromyrmex

Acromyrmex
Acromyrmex versicolor
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Attini
Genus:	Acromyrmex Mayr, 1865
Type species
Formica hystrix, now Acromyrmex hystrix
Subgenera
Acromyrmex Mayr, 1865 Moellerius Forel, 1893
Diversity
55 species (Species Checklist, Species by Country) Acromyrmex versicolor Specimen Label

Evolutionary Relationships

Neoattina Cyatta (1 species), Kalathomyrmex (1 species) Mycetarotes   (4 species) Mycetosoritis   (2 species) Cyphomyrmex   (23 species) Mycetophylax   (21 species) Mycetagroicus   (4 species) Mycetomoellerius   (30 species) Sericomyrmex   (11 species) Xerolitor   (1 species) Paratrachymyrmex   (9 species) Trachymyrmex   (9 species) Amoimyrmex   (3 species) Acromyrmex   (55 species) Atta   (20 species)

Based on Ward et al. (2014), Blaimer et al. (2018), Li et al. (2018) and Cristiano et al. (2020).

A genus of fungus growing ants. Primarily a Neotropical group, Acromyrmex occurs from the southern USA south to southern South America. They cultivate fungus within their nests and, like Atta, they are true leaf-cutters. Most Acromyrmex inhabit tropical forests, grasslands, and disturbed areas. Acromyrmex versicolor is atypical in that it is found in dry desert areas of the southwestern USA and northern Mexico.

At a Glance

• Fungus Grower

 

Photo Gallery

• 

  Acromyrmex worker covered in Pseudonocardia. These leafcutter ants use this bacteria to fight invasive fungus, that attack their fungus gardens. Photo by João Pedro Sá Medeiros.

Identification

The genus Acromyrmex occupies a morphological "middle ground" between the highly polymorphic genus Atta and the monomorphic genus Trachymyrmex. Acromyrmex is separated from Atta by the presence of 3 pairs of spines or teeth on the promesonotum (only 2 pairs in Atta), and from Trachymyrmex by the presence of spines or teeth on the promesonotum (rather than tubercles), by the absence of shallow antennal scrobes (often present in Trachymyrmex), and its polymorphic worker caste (monomorphic in Trachymyrmex).

See images of species within this genus

Keys including this Genus

• Key to North American Genera of Myrmicinae

 

Biology

Longino (Ants of Costa Rica) - Acromyrmex species are true leaf cutters. Compared to Atta, they have a greater predilection for flowers and fruits. Their colonies are smaller (thousands of workers rather than millions), and foraging columns are usually single file and sparse. Their nests are usually in pre-formed cavities, and they do little excavating of their own.

Morphologically they are sandwiched between Atta and Trachymyrmex. Atta have very large colonies, strong worker size polymorphism, and a smooth gastral dorsum. Trachymyrmex have smaller colonies, usually smaller monomorphic workers, and a tuberculate gastral dorsum. Acromyrmex have intermediate colony sizes, strong worker polymorphism (but the major workers are not as highly differentiated as Atta majors), and the gaster is tuberculate. Single workers of Acromyrmex can be difficult to differentiate from Trachymyrmex in a key.

In Costa Rica there are few species of Acromyrmex. In lowland and seasonally dry habitats there are usually one or two forms of the Acromyrmex octospinosus species complex. In moist to wet montane areas Acromyrmex coronatus dominates.

Schultz et al. (1998) have discovered cryptic species in the A. octospinosus complex in Panama, and one should expect similar complexity to occur in Costa Rica. I recognize three species in the complex in Costa Rica (octospinosus, Acromyrmex echinatior, Acromyrmex volcanus), but the morphological basis for the distinctions is slight and some concentrated research on the group could easily redraw the species boundaries.

There is a large literature on Acromyrmex that is not reviewed or cited here.

Association with Other Organisms

Species Uncertain

• An unknown species is a host for the histerid beetle Euspilotus latimanus (a myrmecophile) in Brazil (Arriagada, 1987; Lackner, 2014).

All Associate Records for Genus

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Taxon	Relationship	Associate Type	Associate Taxon	Associate Relationship	Locality	Source	Notes
Acromyrmex	host	histerid beetle	Euspilotus latimanus	myrmecophile	Brazil	Arriagada, 1987; Lackner, 2014
Acromyrmex ambiguus	host	diapriid wasp	Gymnopria lucens	parasite	Brazil, Uruguay	Loiacono, 1987; Gonzalez et al., 2016
Acromyrmex ambiguus	host	histerid beetle	Euspilotus myrmecophilus	myrmecophile	Argentina, Brazil, Uruguay	Lackner, 2014; Lackner & Arriagada, 2020
Acromyrmex ameliae	inquiline	ant	Acromyrmex subterraneus	host
Acromyrmex balzani	host	ant	Pseudoatta argentina	workerless inquiline			Needs confirmation
Acromyrmex charruanus	inquiline	ant	Acromyrmex heyeri	host
Acromyrmex echinatior	host	ant	Acromyrmex insinuator	inquiline
Acromyrmex fowleri	workerless inquiline	ant	Acromyrmex rugosus	host
Acromyrmex heyeri	host	ant	Acromyrmex charruanus	workerless inquiline
Acromyrmex heyeri	host	ant	Pseudoatta argentina	workerless inquiline
Acromyrmex insinuator	inquiline	ant	Acromyrmex echinatior	host
Acromyrmex insinuator	inquiline	ant	Acromyrmex octospinosus	host
Acromyrmex lobicornis	host	diapriid wasp	Szelenyiopria pampeana	parasite	Argentina	Loiacono, 2013; Gonzalez et al., 2016
Acromyrmex lobicornis	host	diapriid wasp	Trichopria formicans	parasite	Argentina	Loiacono, 2013; Gonzalez et al., 2016
Acromyrmex lundii	host	ant	Pseudoatta argentina	workerless inquiline
Acromyrmex lundii	host	diapriid wasp	Bruchopria hexatoma	parasite	Argentina	Loiacono, 2013; Gonzalez et al., 2016
Acromyrmex lundii	host	diapriid wasp	Doliopria myrmecobia	parasite	Argentina	Loiacono, 2013; Gonzalez et al., 2016
Acromyrmex lundii	host	histerid beetle	Euspilotus myrmecophilus	myrmecophile	Argentina, Brazil, Uruguay	Lackner, 2014; Lackner & Arriagada, 2020
Acromyrmex octospinosus	host	ant	Acromyrmex insinuator	inquiline			not able to reproduce in ''Acromyrmex octospinosus'' colonies
Acromyrmex subterraneus	host	ant	Acromyrmex ameliae	workerless inquiline
Acromyrmex subterraneus	host	fungus	Aspergillus flavus	pathogen		Sales & Toledo, 2020
Acromyrmex subterraneus	host	fungus	Metarhizium anisopliae	pathogen		Sales & Toledo, 2020

Morphology

Worker Morphology

• Antennal segment count: 11
• Antennal club: gradual
• Palp formula: 4,2
• Total dental count: 8-11
• Spur formula: 0, 0
• Eyes: present
• Scrobes: absent
• Caste: polymorphic

Karyotype

All Karyotype Records for Genus

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Taxon	Haploid	Diploid	Karyotype	Locality	Source	Notes
Acromyrmex ambiguus		38	14M + 12SM + 8ST + 4A	Brazil	de Castro et al., 2020
Acromyrmex ambiguus		38	2M+6SM+16ST+14A	Uruguay	Goñi et al., 1984
Acromyrmex ameliae		36		Brazil	Cardoso et al. 2018; de Castro et al., 2020
Acromyrmex aspersus		38	8M+10SM+16ST+4A	Brazil	Teixeira et al., 2017
Acromyrmex balzani		38	12M+10SM+14ST+2A	Brazil	Barros et al., 2016
Acromyrmex balzani		38	12M+10SM+14ST+2A	French Guiana	Aguiar et al., 2020
Acromyrmex coronatus	19	38	12M+8SM+16ST+2A	Brazil	Barros et al., 2016
Acromyrmex crassispinus		38		Brazil	Fadini & Pompolo, 1996
Acromyrmex crassispinus		38	12M + 20SM + 4ST + 2A	Brazil	de Castro et al., 2020
Acromyrmex disciger		38	10M+12SM+14ST+2A	Brazil	Barros et al., 2016
Acromyrmex echinatior		38	8M+6SM+14ST+10A	Brazil	Barros et al., 2016
Acromyrmex heyeri		38	2M+6SM+16ST+14A	Brazil; Uruguay	Goni et al., 1983; SantosColares et al., 1997
Acromyrmex hispidus		38	2M+6SM+16ST+14A	Uruguay	Goni et al., 1983
Acromyrmex lundii		38	10M + 14SM + 10ST + 4A	Brazil	de Castro et al., 2020
Acromyrmex niger		38	12M+14SM+10ST+2A	Brazil	Barros et al., 2016
Acromyrmex nigrosetosus		38	12M + 14SM + 10ST + 2A	Brazil	de Castro et al., 2020
Acromyrmex rugosus		38	16M+12SM+8ST+2A	Brazil	Barros et al., 2016
Acromyrmex subterraneus		38		Brazil	Fadini & Pompolo, 1996
Acromyrmex subterraneus		38	14M + 18SM + 4ST + 2A	Brazil	de Castro et al., 2020
Acromyrmex subterraneus molestans		38	10M+10SM+16ST+2A	Brazil	Fadini & Pompolo, 1996; Teixeira et al., 2017

Nomenclature

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

• ACROMYRMEX [Myrmicinae: Attini]
  • Acromyrmex Mayr, 1865: 83 [as subgenus of Atta]. Type-species: Formica hystrix, by monotypy.
  • Acromyrmex raised to genus: Emery, 1913b: 251.
  • Subgenera of Acromyrmex: nominal plus Moellerius.

References

• Arriagada, G. 1987. Notas sininimicas y datos distribucionales de Saprininae neotropicales. Revista Chilena de Entomologia 15: 61–70.
• 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, Acromyrmex in Cryptoceridae, Attinae)
• Bolton, B. 2003. Synopsis and Classification of Formicidae. Mem. Am. Entomol. Inst. 71: 370pp (page 197, Acromyrmex as genus of Attini)
• Cherrett, J. M.; Cherrett, F. J. 1989. A bibliography of the leaf-cutting ants, Atta spp. and Acromyrmex spp., up to 1975. Overseas Dev. Nat. Resour. Inst. Bull. 14: 1-58 (page 1, Bibliography 1. Subgenera of Acromyrmex:nominal plus Moellerius)
• Cristiano, M.P., Cardoso, D.C., Sandoval‐Gómez, V.E., Simões‐Gomes, F.C. 2020. Amoimyrmex Cristiano, Cardoso, Sandoval, gen. nov. (Hymenoptera: Formicidae): a new genus of leaf‐cutting ants revealed by multilocus molecular phylogenetic and morphological analyses. Austral Entomology 59, 643–676 (doi:10.1111/aen.12493).
• Dalla Torre, K. W. von. 1893. Catalogus Hymenopterorum hucusque descriptorum systematicus et synonymicus. Vol. 7. Formicidae (Heterogyna). Leipzig: W. Engelmann, 289 pp. (page 151, Acromyrmex as subgenus of Atta)
• 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, Acromyrmex in Myrmicinae, Attini; Acromyrmex as subgenus of Atta)
• Emery, C. 1905f. Revisione delle specie del genere Atta appartenenti ai sottogeneri Moellerius e Acromyrmex. Mem. R. Accad. Sci. Ist. Bologna (6)2:39-54 (page 39, Acromyrmex as subgenus of Atta)
• Emery, C. 1913c. Études sur les Myrmicinae. [V-VII.]. Ann. Soc. Entomol. Belg. 57: 250-262 (page 251, Acromyrmex raised to genus; Acromyrmex in Myrmicinae, Attini)
• Emery, C. 1914e. Intorno alla classificazione dei Myrmicinae. Rend. Sess. R. Accad. Sci. Ist. Bologna Cl. Sci. Fis. (n.s.) 18: 29-42 (page 42, Acromyrmex in Myrmicinae, Attini)
• Emery, C. 1924f [1922]. Hymenoptera. Fam. Formicidae. Subfam. Myrmicinae. [concl.]. Genera Insectorum 174C: 207-397 (page 347, Acromyrmex in Myrmicinae, Attini; Acromyrmex as genus)
• Forel, A. 1885a [1884]. Études myrmécologiques en 1884 avec une description des organes sensoriels des antennes. Bull. Soc. Vaudoise Sci. Nat. 20: 316-380 (page 354, Acromyrmex as subgenus of Atta)
• Forel, A. 1893b. Sur la classification de la famille des Formicides, avec remarques synonymiques. Ann. Soc. Entomol. Belg. 37: 161-167 (page 163, Acromyrmex as subgenus of Atta)
• Forel, A. 1899d. Formicidae. [part]. Biol. Cent.-Am. Hym. 3: 25-56 (page 30, Acromyrmex as subgenus of Atta)
• Forel, A. 1913c. Fourmis de Nigérie. Rev. Zool. Afr. (Bruss.) 2: 352-353 (page 251, Acromyrmex divided into subgenera Acromyrmex Mayr and Moellerius Forel)
• Forel, A. 1917. Cadre synoptique actuel de la faune universelle des fourmis. Bull. Soc. Vaudoise Sci. Nat. 51: 229-253 (page 247, Acromyrmex in Myrmicinae, Attini; Acromyrmex as genus)
• Fowler, H. G. 1988b. Taxa of the neotropical grass-cutting ants, Acromyrmex (Hymenoptera: Formicidae: Attini). Científica (Jaboticabal) 16: 281-295 (page 284, Partial revision of genus)
• Gonçalves, C. R. 1961. O genero Acromyrmex no Brasil (Hym. Formicidae). Stud. Entomol. 4: 113-180 (page 113, Revision of Brazilian fauna)
• Lackner, T. 2014. Phylogeny of the Saprininae reveals interesting ecological shifts in the history of the subfamily (Coleoptera: Histeridae). Zoological Journal of the Linnean Society 172: 521–555.
• Mayr, G. 1865. Formicidae. In: Reise der Österreichischen Fregatte "Novara" um die Erde in den Jahren 1857, 1858, 1859. Zoologischer Theil. Bd. II. Abt. 1. Wien: K. Gerold's Sohn, 119 pp. (page 83, Acromyrmex as subgenus of Atta)
• Mueller, U.G., Schultz, T.R., Currie, C.R., Adams, R.M.M., Malloch, D. 2001. The origin of the attine ant-fungus mutualism. The Quarterly Review of Biology 76, 169-197.
• Santschi, F. 1925a. Revision du genre Acromyrmex Mayr. Rev. Suisse Zool. 31: 355-398 (page 355, 388, Key to species (out of date); Acromyrmex as genus)
• Wheeler, W. M. 1907d. The fungus-growing ants of North America. Bull. Am. Mus. Nat. Hist. 23: 669-807 (page 670, Acromyrmex as subgenus of Atta)
• Wheeler, W. M. 1910b. Ants: their structure, development and behavior. New York: Columbia University Press, xxv + 663 pp. (page 141, Acromyrmex as subgenus of Atta)
• 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, Acromyrmex in Myrmicinae, Attini)