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Species: Atta sexdens   (Linnaeus, 1758) 

Classification:
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See Also:

Atta sexdens autuorii, Atta sexdens bolchevista, Atta sexdens fuscata, Atta sexdens rubropilosa

Taxonomic History (provided by Barry Bolton, 2014)

Formica sexdens Linnaeus, 1758 PDF: 581 (w.) "AMERICA MERIDIONALI". Neotropic. AntCat AntWiki

Taxonomic history

Mayr, 1865: 82 (q.m.); Wheeler, 1949 PDF: 681 (l.).
Combination in Atta: Fabricius, 1804 PDF: 422; in Atta (Neoatta): Gonçalves, 1942 PDF: 349.
of Atta autuorii, Atta fuscata, Atta piriventris (and its junior synonym Atta lugens), and Atta rubropilosa: Borgmeier, 1959b PDF: 359.

Overview:

Atta sexdens, along with A. cephalotes, is the most widespread member of its genus. Its northern most range is Mexico, and extends through Central America (Panama, Costa Rica, Guatemala, Nicaragua), into South America (Ecuador, Columbia, Peru, Bolivia, Venezuela, Guyana, Brazil, Surinam) and Trinidad and Tobago (Hlldobler & Wilson, 1990; Kempf, 1972; Weber, 1972). The species has a wider tolerance for nest habitats, and is found in closed-canopy-forest, open grassland and disturbed habitats (Solomon, 2007; Weber, 1969). Atta sexdens is a considered a serious pest throughout its range, causing damage to a wide variety of agricultural crops and ornamentals (Cherrett, 1986). 

Distribution:

Global. The northern most range is Mexico, and extends through Central America (Panama, Costa Rica, Guatemala, Nicaragua), into South America (Ecuador, Columbia, Peru, Bolivia, Venezuela, Guyana, Brazil, Surinam) and Trinidad and Tobago.

Paraguay. Alto Paran, Caaguaz, Caazap, Canindey, Central, Concepcin, Cordillera, Guair, Itapa, Misiones, eembuc, Paraguar, San Pedro

Biology:

Threat of introduction
A niche modeling analysis determined that temperature seasonality was the most important variable for predicting its current distribution, while precipitation seasonality was the least important (Solomon, 2007). The modeling also predicts A. sexdens could, should opportunities present themselves, expand its range to western Ecuador and islands in the Lesser Antilles, including Trinidad, and also on Hispaniola and Jamaica. Atta sexdens is a serious pest everywhere it occurs, and has been shown to readily colonize human-altered habitats such as parks and agricultural fields (Solomon, 2007; Weber, 1972; Zanncio et al., 2002). Introduction of this species into habitats outside of its native range could have devastating effects (Hlldobler & Wilson, 1990). A pest risk assessment of unprocessed Eucalyptus concluded the introduction of South American Atta species into the United States was a low probability (Kliejunas et al., 2001).

Identification:

Atta sexdens vs. A. cephalotes
Atta sexdens is highly variable, both within the same colony and across populations. Workers vary in shape, color, sculpture and pubescence (Borgmeier, 1959). Among intercepted attines, the species is most readily confused with A. cephalotes, but can be distinguished by the lack of wooly hairs on the heads of major workers, the duller more opaque integument caused by a dense netting of hexagonal microsculpture, and the 1-2 small teeth or dents on the head anterior to the posterolateral spines. Among other attines, A. sexdens is most readily confused with A. capiguara, but can be separated by the microsculpture netting referred to above (Borgmeier, 1959).

Translated from Borgemeir 1959b
Type locality. - Suriname, Paramaribo.

Workers. - Maxima (Fig. 2; Paramaribo). Length 12 mm. Herzfoermig head, posterior margin strongly bulged. Head width 5 mm, length without mandibles, 4, 2 mm. Rudimentarily ocelli, sometimes absent. Occiput cut. Vertex laterally without tooth, sometimes with tubercles. Occipitalzahn undspitz shortly. Fascias short, with teeth. Eye keels curved inward above, below with a short tooth, also with short ventral tooth. Scape 3, 4 mm. Mandibles with blunt teeth. Thorax length 5, 4 mm. Lower Pronotal zahn strong, slightly curved. The 4 Mesonotal zaehne short, the front conical. Epinotum keeled. Epinotal spines judged longer than the Mesonotal zaehne, but shorter than their mutual distance at the base, straight back. Petiole rounded. Postpetiole keeled, width 1, 3 mm, length 0, 8 mm. Gaster width 3 mm, 5 mm hind tibiae. Mandibles, clypeus and scape shiny. Body dull, densely finely punctate, forehead wrinkled in the middle of something. Protruding hair quite short, in the middle of the forehead, occiput and sides of the head scattered, abundant on the thorax, and gaster Sielchen. Pubescence on sparse, abundant pronotum. Hairy legs diagonally. Reddish brown to dark reddish brown stain. Media (Paramaribo). Length 7 mm. Head width 3 mm. Vertex with very short lateral tooth. Occipital spines just zieml. in length. Thoracic spines pointed, shorter than the front mesonotal spines epinotal spines. Matt. Forehead in the middle with Laengsrunzeln. Long hair on the head and gaster, shorter thorax, scattered pubescence. Rusty brown stain. - Minima (Paramaribo). Length 2, 2 mm. Head width 0.8 mm. Front Mesonotalzaehne very short, so long as the occipital zaehne; ​​rear mesonotal zaehne obsolete; Epinotal zaehne longer. Matt. Hairs on thorax sparse, longer on head and gaster. Wei b c hen (Paramaribo). - Length 19-20 mm. Head width 5 mm, sides converging towards the front, rear edge bulges gently. Occipital zaehne short side vertex with weak swelling or TuberkeI. Ocelli small. Eyes convex. Eye tooth keels obsolete. Fascias with teeth. Without ventral tooth. Scape 3 mm. Mandibles long, with pointed Apikalzahn and 8 blunt teeth. Thorax length 8, 5 mm. Scutellum without a furrow. Epinotum over the base of the short teeth, with swelling. Petiole and blunt postpetiole side with teeth or cusps. Gaster width 7, 5 mm. Front corners poorly marked. Hind tibiae 5 mm. Wing 27 mm. Mandibles, clypeus, scape and legs shiny. Matt body. Prominent short hairs scattered on head, thorax and gaster more abundant. Legs covered with short oblique. Pubescenz spaerJich scatters. Rusty brown color, blacked Gaster.

Males (Paramaribo). - Length 14 mm. Head over the eyes wide ~ 2 mm. Occipital zaehne short and pointed. Eyes strongly convex. Fascias without teeth. Scape 2 mm. Mandibles narrow and short, with Apikalzahn and 7 weak teeth. Thorax length 5, 75 mm. Pronotalzahn triangular shortly. Epinotum unreinforced. Gaster width of 5, 4 mm .. Tibie III, 4, 6 mm. Wing 20 mm. Genitalia (Fig. 14, 23): Stipes slender and pointed, as long as the associate volume, apical membrane with a narrow hairy. Volsellen triangular, slightly curved inwards, tapering apically. Sagittae with strong vertically erect chitinisierten sides, in profile triangular, upper margin bulged. Subgenital concave apically. Matt. Gaster shiny weak. Head, thorax and pedicel thick and long woolly hair, the legs on the ventral side. Gaster, scape pubescent, and short tracks. Wrinkled head. Stain dark brown, legs lighter.

Geographer. Dissemination. - Of all the species of Atta sexdens has the largest distribution: Panama, Colombia, Ecuador, Peru, Bolivia (Guarayos, Trinidad), Venezuela, Guyana. Suriname, B ~ asilien, Paraguay, Argentina (Misiones, Corrientes), 22, 1933, p. 26 [Guatemala], and vol. 10, 1921, p. 146 [Montevideo]. Both figures are re-examined must. In Guatemala, it may also colombica urn, and perhaps in Montevideo urn Acromyrmex sp.

Variation. - Both within the same colony, as in the geograph. Proliferation zone vary the workers in paint, sculpture, gloss and hair, with some soldiers, the head is rubbed as in others he is furnished with hair, never the hair missing shots; in specimens from the south of Brazil the gaster on the sides is Zllweilen shiny ( the smallest workers may be the whole gaster shiny), and sometimes the show occipital lobes front teeth 1-2 on each side; the Epinotaldornen Zllweilen are strongly directed upwards; specimens from S. Catarina show sometimes blackened thorax and pedicel. The females are slightly smaller than the Paramaribo from Brazil, which varies between 27-30 mm Fluegellaenge. Among the males falls on the strong variation of Sagitta, the upper edge (in profile) bulges sometimes deep, sometimes even (d Borgm. In 1950, fig 18-29).

Discussion. - Atta sexdens is capiguara the next, and the soldiers can be easily confused, but differ by the micro-sculpture of the head at sexdens densely netted, so that the tegument is dull, at capiguara extensive to 50dass at high magnification, a certain luster notice is. The females have sexdens schwarzbrauntn Gaster, from the bright-red capiguara Gaster. The males of both species differ in the Sagitta, which are very similar in profile, but in dorsal view appearing Oberraender of capiguara turned inward, and the Seitenwaende are not vertical, but more oblique. Opaciceps of robusta and the soldiers of different sexdens by the scalp and through the smaller entertainments. The mean of sexdens workers are distinguished from robusta, and opaciceps laevigata little. Also, the females and males.

References:

Borgmeier, T. (1959) Revision der Gattung Atta Fabricius (Hymenoptera, Formicidae). Stud. Entomol., (n.s.)2, 321-390.

Cherrett, J.M. (1986) The biology, pest status and control of leaf-cutting ants. Agric. Zool. Rev., 1, 1-27.

Cherrett, J.M. & Peregrine, D.J. (1976) A review of the status of leaf-cutting ants and their control. Ann. Appl. Biol., 84, 124-128.

Hlldobler, B. & Wilson, E.O. (1990) The ants. Harvard University Press, Cambridge, Mass., xii + 732 pp.

Kempf, W.W. (1972) Catlogo abreviado das formigas da regio Neotropical. Stud. Entomol., 15, 3-344.

Kliejunas, J.T., Tkacz, B.M., Burdsall, H.H., Jr., DeNitto, G.A., Eglitis, A., Haugen, D.A. & Wallner, W.E. (2001) Pest risk assessment of the importation into the United States of unprocessed Eucalyptus logs and chips from South America. U.S. Department of Agriculture, Forest Service,

Forest Products Laboratory. Madison, WI, General Technical Report FPL-GTR-124, 134 p.

Solomon, S.E. (2007) Biogeography and evolution of widespread leafcutting ants, Atta spp. (Formicidae, Attini). Ph.D. thesis, The University of Texas at Austin, xi + 95 p.

Taxon Page Author History

On 2012-05-26 09:22:38 Eli Sarnat modified References
On 2012-05-26 09:21:37 Eli Sarnat modified Overview
On 2012-05-26 09:18:35 Eli Sarnat modified Biology
On 2012-05-26 09:16:52 Eli Sarnat modified Overview
On 2012-05-25 16:38:10 Eli Sarnat modified Identification
On 2012-05-25 16:26:07 Eli Sarnat modified Distribution
On 2012-05-25 16:24:32 Eli Sarnat modified Overview
On 2012-05-25 15:33:25 Eli Sarnat modified Identification
On 2011-03-31 23:46:13 Eli Sarnat modified Distribution

Taxonomic Treatment (provided by Plazi)

Borgmeier, T., 1939:
Esta espécie foi descripta pelo seu autor juntamente com cephalotes , sobre material colleccionado por Rolander em Surinam. Como forma typica considero abundante material ( operários , fêmeas , machos) de Paramaribo, Lelydorp, Surinam(Stahel e Geijskes leg.). A mesma forma recebi do dr. N. A. Weber da Guyana Ingleza (Courantyne River, N.° 548, 556). Dou uma figura da cabeça de um operário maior de Paramaribo. Os ninhos desta espécie foram estudados ultimamente por Stahel e Geijskes (1939).

Forel, A., 1911:
[[worker]]. Balem, Est. Sao Paulo (Bieego); Grixas Goyaz, Est. Sao Paulo (v. Ihering).

Wild, A. L., 2007:
Caaguazú , Canindeyú , Central, Cordillera, Misiones, Paraguarí , San Pedro, “ Guañayos ” (Dept. unknown) “Paraguay” (s. loc.) (ALWC, IFML, INBP, LACM, MCSN, MHNG, MZSP, NHMB, NHMW, USNM). Literature records: Alto Paraná , Caaguazú , Caazapá , Canindeyú , Central, Concepción , Cordillera, Guairá , Itapúa , Misiones, Ñeembucú , Paraguarí , San Pedro, “Pto. Itacurí ” (Dept. unknown), “Paraguay” (s. loc.) (Borgmeier 1959b, Emery 1896b, Emery 1906, Fowler 1985, Santschi 1922a).

Forel, A., 1905:
- Caracas.
Sauf la Formica sexguttata , tous ces types du Musee de Copen- hague ont l'etiquette carree verte qui, selon le Dr Meinert, garantit leur authenticite. Ils sont fort bien conserves.
LaFormica rapax F. est un beau Camponotus a longue pubes- cence, long de Jl a 12 millimetres, avec l'abdomen ferrugineux et le reste noir mat. C'est une [[ worker ]] minor-media.

Specimen Habitat Summary

Found most commonly in these habitats: 1 times found in pasture, 1 times found in scrubby forest, 1 times found in tropical moist forest, 1 times found in savanna

Collected most commonly using these methods or in the following microhabitats: 1 times search

Elevations: collected from 100 - 740 meters, 265 meters average

Type specimens: syntype of Atta sexdens fuscata: casent0912496; syntype of Atta sexdens rubropilosa: casent0909449, casent0909450; syntype of Atta vollenweideri piriventris: casent0912497; syntype of Oecodoma abdominalis: casent0900489

(-1 examples)



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