Acromyrmex crassispinus

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Acromyrmex crassispinus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Acromyrmex
Species: A. crassispinus
Binomial name
Acromyrmex crassispinus
(Forel, 1909)

Acromyrmex crassispinus casent0173793 profile 1.jpg

Acromyrmex crassispinus casent0173793 dorsal 1.jpg

Specimen labels


Acromyrmex crassispinus is the most common leaf-cutting ant species in southern Brazil (Rando & Forti, 2005).



Latitudinal Distribution Pattern

Latitudinal Range: -20.8961° to -31.632389°.

Tropical South

Distribution based on Regional Taxon Lists

Neotropical Region: Argentina, Brazil, Paraguay (type locality).

Distribution based on AntMaps


Distribution based on AntWeb specimens

Check data from AntWeb

Countries Occupied

Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species.

Estimated Abundance

Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species.


Explore-icon.png Explore Fungus Growing 
For additional details see Fungus growing ants.

A handful of ant species (approx. 275 out of the known 15,000 species) have developed the ability to cultivate fungus within their nests. In most species the fungus is used as the sole food source for the larvae and is an important resource for the adults as well. Additionally, in a limited number of cases, the fungus is used to construct part of the nest structure but is not as a food source.

These fungus-feeding species are limited to North and South America, extending from the pine barrens of New Jersey, United States, in the north (Trachymyrmex septentrionalis) to the cold deserts in Argentina in the south (several species of Acromyrmex). Species that use fungi in nest construction are known from Europe and Africa (a few species in the genera Crematogaster, Lasius).

The details of fungal cultivation are rich and complex. First, a wide variety of materials are used as substrate for fungus cultivating. The so-called lower genera include species that prefer dead vegetation, seeds, flowers, fruits, insect corpses, and feces, which are collected in the vicinity of their nests. The higher genera include non leaf-cutting species that collect mostly fallen leaflets, fruit, and flowers, as well as the leafcutters that collect fresh leaves from shrubs and trees. Second, while the majority of fungi that are farmed by fungus-feeding ants belong to the family Lepiotaceae, mostly the genera Leucoagaricus and Leucocoprinus, other fungi are also involved. Some species utilise fungi in the family Tricholomataceae while a few others cultivate yeast. The fungi used by the higher genera no longer produce spores. Their fungi produce nutritious and swollen hyphal tips (gongylidia) that grow in bundles called staphylae, to specifically feed the ants. Finally, colony size varies tremendously among these ants. Lower taxa mostly live in inconspicuous nests with 100–1000 individuals and relatively small fungus gardens. Higher taxa, in contrast, live in colonies made of 5–10 million ants that live and work within hundreds of interconnected fungus-bearing chambers in huge subterranean nests. Some colonies are so large, they can be seen from satellite photos, measuring up to 600 m3.

Based on these habits, and taking phylogenetic information into consideration, these ants can be divided into six biologically distinct agricultural systems (with a list of genera involved in each category):

Nest Construction

A limited number of species that use fungi in the construction of their nests.

Lower Agriculture

Practiced by species in the majority of fungus-feeding genera, including those thought to retain more primitive features, which cultivate a wide range of fungal species in the tribe Leucocoprineae.

Coral Fungus Agriculture

Practiced by species in the Apterostigma pilosum species-group, which cultivate fungi within the Pterulaceae.

Yeast Agriculture

Practiced by species within the Cyphomyrmex rimosus species-group, which cultivate a distinct clade of leucocoprineaceous fungi derived from the lower attine fungi.

Generalized Higher Agriculture

Practiced by species in several genera of non-leaf-cutting "higher attine" ants, which cultivate a distinct clade of leucocoprineaceous fungi separately derived from the lower attine fungi.

Leaf-Cutter Agriculture

A subdivision of higher attine agriculture practiced by species within several ecologically dominant genera, which cultivate a single highly derived species of higher attine fungus.

Note that the farming habits of Mycetagroicus (4 species) are unknown. Also, while species of Pseudoatta (2 species) are closely related to the fungus-feeding genus Acromyrmex, they are social parasites, living in the nests of their hosts and are not actively involved in fungus growing. ‎

Nickele and Reis Filho (2015) studied the population dynamics of this species in São Mateus do Sul city (25°58’56,33”S, 50°23’49,26”W, alt. 766 m) state of Parana, Brazil. They worked in recently-planted Pinus taeda plantations (clear cut June-July, 2007 and replanted August, 2007). Initially the plantations contained no colonies of Acromyrmex crassispinus and within a few years the developing canopy created enough shade that none of the incipient colonies initially found, and studied, remained. The initial open nature of the tree plantation was a good area for the initiation of incipient nests, despite the subsequent poor nature of the site over a longer time frame.

The presence of A. crassispinus nests was observed from 15 months after planting (Spring/2008), where there was one nest per hectare, on average. Nest density rose to 26 nests per hectare at 30 months after planting (Summer/2010), then declined through time, Fifty-four months after planting, the forest canopy closed and at 72 months after planting, there was only 0.33 nests per hectare, on average. The few nests observed after 54 months after planting were located near tree gaps in the middle of planting.

In the spring of 2009, winged male or female ants were not observed in the nests sampled. In the spring of 2010, winged ants were observed in 50, 20, 20 and 10% of the nests sampled in September, October, November and December, respectively). Males emerge earlier than females. In several nests, while males were already adult, females were still in the pupal stage. Reproductives only occurred in the largest sized nests sampled. The presence of reproductive ants in sampled colonies only from the spring of 2010 (three years after planting) suggests the first nuptial flight of an A. crassispinus colony also occurs after the third year of the colony foundation.

Barrera et al. (2015) studied the diversity of leaf cutting ants along a forest-edge-agriculture habitat gradient. Their study site, in Chaco Serrano of Central Argentina, had forest remnants of various sizes within an agriculture area with wheat, soy and maize. A. crassispinus was the most common species (42% of the 162 colonies sampled). This species was especially abundant in the forest interior and nest abundance here was positively correlated with the size of the forest remnant (12 sites, from 0.42 ha to > 1,000 ha forest area). Along the forest edge it was slightly less abundant than Acromyrmex lundii and Amoimyrmex striatus. A few colonies of Acromyrmex heyeri and Amoimyrmex silvestrii were also found along the forest edge.

Nickele et al., (2009) found this species prefers to nest in open areas.


Nickele et al. (2015) studied this species in Paraná, Brazil, both in the field and lab, to elucidate details of their leaf transport. Some of their findings: In Acromyrmex crassispinus cutting and carrying of fragments were clearly separated activities performed by distinct worker groups differing in body size. Cutters were larger than carriers. In addition, the behavior of foragers of differed significantly according to variation in trail distances. On short trails (1 m), cutters frequently transported the fragments directly to the nest, whereas on long trails (more than 10 m), most cutters transferred the fragments to other workers. Transport chains (fragments found on the trail or directly received from nestmates are transported consecutively by different carriers) happened more frequently when workers harvested plants far from the nest. Transfer was mostly indirect, in other words, fragments were dropped on the ground and collected by outgoing workers that turned back and returned to the nest. Direct fragment transfers between workers were not observed under laboratory conditions. It was observed only on long trails in the field. Lopes et al. (2003) also did not observe direct fragment transfers for this species under laboratory conditions. These results demonstrate that Acromyrmex species display both division of labor between cutters and carriers, and task partitioning during leaf transport, with trail lengths showing marked effects on the likelihood of sequential transport. Furthermore, the results of this study provide support for the hypothesis that the behavioral response of transferring fragments in Acromyrmex species would have been selected for because of its positive effect on the information flow between workers.

Association with Other Organisms

Explore-icon.png Explore: Show all Associate data or Search these data. See also a list of all data tables or learn how data is managed.
  • This species is a host for the nematode Panagrolaimus sp. (a parasite) (Quevillon, 2018) (multiple encounter modes; indirect transmission; transmission outside nest).
  • This species is a host for the phorid fly Myrmosicarius crudelis (a parasitoid) (Quevillon, 2018) (encounter mode primary; direct transmission; transmission outside nest).



Images from AntWeb

Acromyrmex crassispinus casent0173794 head 1.jpgAcromyrmex crassispinus casent0173794 profile 1.jpgAcromyrmex crassispinus casent0173794 dorsal 1.jpgAcromyrmex crassispinus casent0173794 label 1.jpg
Worker. Specimen code casent0173794. Photographer April Nobile, uploaded by California Academy of Sciences. Owned by ALWC, Alex L. Wild Collection.


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

  • crassispinus. Atta (Acromyrmex) mesonotalis var. crassispina Forel, 1909a: 257 (w.) PARAGUAY.
    • Santschi, 1925a: 374 (q.).
    • Combination in Acromyrmex: Emery, 1924d: 349.
    • Subspecies of mesonotalis: Forel, 1914e: 11; Emery, 1924d: 349.
    • Status as species: Santschi, 1925a: 374; Santschi, 1925d: 241; Borgmeier, 1927c: 131; Gonçalves, 1961: 138; Kempf, 1972a: 12; Cherrett & Cherrett, 1989: 50; Bolton, 1995b: 55; Wild, 2007b: 30.
    • Senior synonym of atratus: Gonçalves, 1961: 139; Kempf, 1972a: 12; Bolton, 1995b: 55.
    • Senior synonym of diabolica: Gonçalves, 1961: 139; Kempf, 1972a: 12; Bolton, 1995b: 55.
    • Senior synonym of insularis: Gonçalves, 1961: 139; Kempf, 1972a: 12; Bolton, 1995b: 55.
    • Senior synonym of mediocris: Gonçalves, 1961: 139; Kempf, 1972a: 12; Bolton, 1995b: 55.
    • Senior synonym of rusticus: Gonçalves, 1961: 139; Kempf, 1972a: 12; Bolton, 1995b: 55.
    • Material of the unavailable name rufescens referred here by Gonçalves, 1961: 139; Kempf, 1972a: 12; Bolton, 1995b: 55.
  • atratus. Acromyrmex hispidus st. atratus Santschi, 1925a: 376 (w.q.) ARGENTINA (Córdoba), BRAZIL (Rio Grande do Sul).
    • Subspecies of hispidus: Borgmeier, 1927c: 132; Santschi, 1929d: 304.
    • Junior synonym of crassispinus: Gonçalves, 1961: 139; Kempf, 1972a: 12; Bolton, 1995b: 54.
  • diabolica. Acromyrmex nigrosetosa var. diabolica Santschi, 1922b: 362 (w.) BRAZIL (Santa Catarina).
    • Santschi, 1925d: 240 (m.).
    • Subspecies of crassispinus: Santschi, 1925a: 375.
    • Status as species: Santschi, 1925d: 240; Borgmeier, 1927c: 131.
    • Junior synonym of crassispinus: Gonçalves, 1961: 139; Kempf, 1972a: 12; Bolton, 1995b: 55.
  • insularis. Acromyrmex aspersus var. insularis Santschi, 1925d: 242 (w.) BRAZIL (São Paulo: Victoria I., San Sebastião Is).
    • Subspecies of aspersus: Borgmeier, 1927c: 129.
    • Junior synonym of crassispinus: Gonçalves, 1961: 139; Kempf, 1972a: 12; Bolton, 1995b: 55.
  • mediocris. Acromyrmex diabolicus var. mediocris Santschi, 1925d: 241 (w.) BRAZIL (Paraná; in text as Oarana).
    • Subspecies of diabolicus: Borgmeier, 1927c: 131.
    • Junior synonym of crassispinus: Gonçalves, 1961: 139; Kempf, 1972a: 12; Bolton, 1995b: 56.
  • rusticus. Acromyrmex crassispinus st. rusticus Santschi, 1925a: 375 (w.q.) BRAZIL (Santa Catarina).
    • Subspecies of crassispinus: Borgmeier, 1927c: 131.
    • Junior synonym of crassispinus: Gonçalves, 1961: 139; Kempf, 1972a: 12; Bolton, 1995b: 57.



  • 2n = 38 (Brazil) (Fadini & Pompolo, 1996).
  • 2n = 38, karyotype = 12M + 20SM + 4ST + 2A (Brazil) (de Castro et al., 2020).


References based on Global Ant Biodiversity Informatics

  • 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.
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  • Diehl-Fleig E. 2014. Termites and Ants from Rio Grande do Sul, Brazil. Sociobiology (in Press).
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  • Klingenberg, C. and C.R.F. Brandao. 2005. The type specimens of fungus growing ants, Attini (Hymenoptera, Formicidae, Myrmicinae) deposited in the Museu de Zoologia da Universidade de Sao Paulo, Brazil. Papeis Avulsos de Zoologia 45(4):41-50
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  • Mentone T. O., E. A. Diniz, C. B. Munhae, O. C. Bueno, and M. S. C. Morini. 2011. Composition of ant fauna (Hymenoptera: Formicidae) at litter in areas of semi-deciduous forest and Eucalyptus spp., in Southeastern Brazil. Biota Neotrop. 11(2):
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  • Oliveira Mentone T. de, E. A. Diniz, C. de Bortoli Munhae, O. Correa Bueno and M. S. de Castro Morini. 2012. Composition of ant fauna (Hymenoptera: Formicidae) at litter in areas of semi-deciduous forest and Eucalyptus spp., in Southeastern Brazil. Biota Neotrop 11(2): 237-246.
  • Osorio Rosado J. L, M. G. de Goncalves, W. Drose, E. J. Ely e Silva, R. F. Kruger, and A. Enimar Loeck. 2013. Effect of climatic variables and vine crops on the epigeic ant fauna (Hymenoptera: Formicidae) in the Campanha region, state of Rio Grande do Sul, Brazil. J Insect Conserv 17: 1113-1123.
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  • Passos, L. and P.S. Oliveira. 2003. Interactions between ants, fruits and seeds in a restinga forest in south-eastern Brazil. Journal of Tropical Ecology 19(3):261-270.
  • Rodrigues, A., M. Bacci, Jr., U.G. Mueller, A. Ortiz and F.C. Pagnocca. 2008. Microfungal “Weeds” in the Leafcutter Ant Symbiosis. Microbial Ecology 56:604-614
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  • Rosado J. L. O., M. G. de Gonçalves, W. Dröse, E. J. E. e Silva, R. F. Krüger, R. M. Feitosa, and A. E. Loeck. 2012. Epigeic ants (Hymenoptera: Formicidae) in vineyards and grassland areas in the Campanha region, state of Rio Grande do Sul, Brazil. Check List, Journal of species lists and distribution 8(6): 1184-1189.
  • Santos Rando J. S., and L. C. Forti. 2005. Occurrence of ants Acromyrmex Mayr, 1865 in some cities of Brasil. Maringá 27(2): 129-133.
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  • Santschi F. 1925. Nouveaux Formicides brésiliens et autres. Bulletin et Annales de la Société Entomologique de Belgique 65: 221-247.
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  • Santschi F. 1929. Nouvelles fourmis de la République Argentine et du Brésil. Anales de la Sociedad Cientifica Argentina. 107: 273-316.
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  • de Souza D. R., S. G. dos Santos, C. de B. Munhae, and M. S. de C. Morini. 2012. Diversity of Epigeal Ants (Hymenoptera: Formicidae) in Urban Areas of Alto Tietê. Sociobiology 59(3): 703-117.