Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
SE U.S. to Paraguay and Bolivia, W. Indies (brunneus in the sense of Brown 1976, which includes ruginodis). Costa Rica (not including ruginodis): one specimen from Braulio Carrillo National Park, 500m elevation.
Face to near margin of vertex striate; first gastral tergite smooth and shining; petiolar node evenly tapered to apex, not dome-shaped as seen from the side, and without a differentiated apical spine; anterior face of petiole largely smooth and shining; lateral face of petiole with feeble transverse rugae near base; posterior face of petiole with feeble transverse rugae near base, largely smooth and shining; pronotal dorsum with striae somewhat curved, but attaining posterior border at oblique angles, not becoming completely transverse; pubescence on first gastral tergum dense, short, fine, giving gaster a wooley appearance; color red brown; measurements (from Brown 1976, including ruginodis): HL 2.00-2.46, HW (measured across temporal prominence) 1.36-1.75, ML 0.92-1.17, eye L 0.32-0.42, CI 68-74, MI 44-51, SI 114-129 (n=17). The Costa Rican specimen has HL 2.5mm.
Brown (1976) had a very broad concept of brunneus, and considered Wheeler's (1905) ruginodis a junior synonym. Deyrup et al. (1985) recognized brunneus and ruginodis as distinct sympatric species in Florida, with brunneus being the clearly native species widespread in the southeastern USA, and ruginodis being restricted to coastal areas of southern Florida, and a possible introduction from the West Indies. With the separation of brunneus and ruginodis, the ranges of both species is now uncertain, because Brown's range for brunneus was a conflation of the two.
In Costa Rica, a similar separation of brunneus and ruginodis appears to occur. I have seen nine different collections of ruginodis from Costa Rica, which closely match specimens I have seen from coastal Florida and Jamaica. The Costa Rican specimens are often from coastal sites, and from open or disturbed inland sites. Thus, it follows a pattern in which species widespread in the caribbean are also found in coastal and anthropogenic habitats on both sides of Costa Rica. Curiously, I have seen a single specimen from Costa Rica that closely matches material of brunneus from the southern USA. This specimen was from a campsite in cleared pasture at the edge of primary rainforest, at 500m elevation in Braulio Carrillo National Park. A possible scenario, consistent with the situation in the southern USA, is that brunneus is a biogeographically older resident adapted to disturbances and to habitats otherwise marginal for most Odontomachus, and ruginodis is a newer and even weedier equivalent, originating in the caribbean, and expanding its range and abundance due to the activities of man (perhaps to the detriment of brunneus).
Atta brunnea Patton 1894:618. Syntype worker: USA, Thomasville, Georgia.
Brown, W. L., Jr. 1976. Contributions toward a reclassification of the Formicidae. Part VI. Ponerinae, tribe Ponerini, subtribe Odontomachiti. Section A. Introduction, subtribal characters. Genus Odontomachus. Studia Entomol. 19:67-171.
Deyrup, M., J. Trager, N. Carlin 1985. The genus Odontomachus in the southeastern United States (Hymenoptera: Formicidae). Entomological News 96:188-195.
Patton, W. H. 1894. Habits of the leaping-ant of southern Georgia. American Naturalist 28:618-619.
Wheeler, W. M. 1905. The ants of the Bahamas, with a list of the known West Indian species. Bull. Am. Mus. Nat. Hist. 21:79-135.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.email@example.com
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