Atta sexdens

Nomenclature

Species: Atta sexdens (Linnaeus, 1758)

Usage: valid
Vernacular name: Leaf Cutting Ant

General description

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 (Hölldobler and Wilson, 1990; Kempf, 1972; Weber, 1972). Atta sexdens is a considered a serious pest throughout its range, causing damage to a wide variety of agricultural crops and ornamentals (Cherrett, 1986). 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). 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; Zanúncio et al., 2002). Introduction of this species into habitats outside of its native range could have devastating effects (Hölldobler and Wilson, 1990; Mikheyev, 2008). 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).

External links

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Risk statement

Atta sexdens is a considered a serious pest throughout its range, causing damage to a wide variety of agricultural crops and ornamentals. 

Diagnostic description

Diagnosis of worker among Antkey species

Antenna 11-segmented. Antennal club indistinct. Antennal scrobe lacking. Posterolateral corners of head spinose. Head with pair of small teeth anterior to posterolateral spines or lacking pair of small teeth anterior to posterolateral spines. Mandibles triangular. Head and body appearing dull, covered by netting of hexagonal microsculpture. Head of major with sparse amount of short and blunt hairs, few of which overlap. Pronotal spines present. Propodeum armed with spines or teeth, dorsum of promesonotum with 2 pairs of spines. Waist 2-segmented.Petiole with a distinct and upright node. First gastral tergite without numerous tubercles. Reddish brown with darker gaster.

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).

The majors of A. sexdens are also distinguished from its two congeners native to the United States (A. mexicana and A. texana) by the petiolar spiracles which are only visible from above in native species (Borgmeier, 1959).

Atta sexdens is distinguished from its close relatives in the genus Acromyrmex by the presence of only three long spines on the mesosomal dorsum, and the absence of tubercles on the mesosomal and gastric dorsum.

Look alikes

Atta cephalotes, Acromyrmex octospinosus

Distribution

Native range. Mexico through Central America (Panama, Costa Rica, Guatemala, Nicaragua), into South America (Ecuador, Columbia, Peru, Bolivia, Venezuela, Guyana, Brazil, Surinam) and Trinidad and Tobago.

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