Odontomachus haematodus, full face view of a worker (click image to enlarge).
Photo courtesy of http://www.antweb.org/

Introduction
Ants in this genus differ from other ponerine ants found in the United States by the unique head shape; peculiar mandibles, which are elongate and inserted near the center of the clypeus (see photo above); the large tapering petiole; and the large size of the workers. Members of this genus are commonly called trap-jaw ants due to their elongate mandibles, which can be opened to 180°, then snapped rapidly together on prey. These ants are amazing in their ability to control and time the mandibular movement. When necessary, an ant can forcibly close the mandibles against a surface or other organism and actually propel itself away for up to several inches! Remarkable behavior. Additionally, they can use the mandibles for much more sensitive movements such as caring for larvae or nest building.

Taxonomic History (from Bolton, 2012)
Described as Formica haematoda Linnaeus, 1758; combined in Odontomachus by Latreille (1804).

Identification
Worker: (from Brown 1976 and MEM specimens). Dark reddish-brown to piceous with antennae and legs yellowish-brown reddish-brown. Length approximately 8.5 mm. Slender pair of acute spines present between metathoracic coxae (difficult to see, may require removal of hind legs from some specimens). Pronotum with transverse striae posteriorly. First gastral tergite shagreened and with fine appressed pubescence separated by at least one-fourth the length of each hair.

Males: (from MEM specimens)
Color yellowish-orange, legs pale yellow. Ocelli not on a conspicuous turret, with each ocellus slightly less wide than the ocelllo-ocular space. Petiole mostly lacking sculpture, smooth.

Workers can be separated from other species in the Southeast by their large size, paired metasternal spines, and transverse striae on the most of the petiole (reduced or lacking posteriorly except at base). Males are yellow with small ocelli that are not raised. A similar species, Odontomachus ruginodis, is much smaller on average, striae completely covers the petiole, lacks metasternal spines, and is confined to southern FL in the US. Males of O. ruginodis are yellowish with a dark brown propodeum and brownish gaster. Workers of other US species do not have transverse striae on the petiole. Basically, if you find a large, dark colored Odontomachus along the Gulf Coast, its probably O. haematodus.

Biology and Economic Importance
Similar to other members of this subfamily, Odontomachus workers have a prominent sting(er), and have the ability to inflict a relatively painful sting.

According to AntWeb data, this species has been collected at the base of a pine tree, in lowland rainforests, grasslands, wet forests, and at port of entries. In southern Alabama, Florida, and Mississippi, this species can be found easily nesting in rotting wood, in soil under rotting wood, and in cavities in trees. This species appears to prefer sandy soils. I have frequently collected Odontomachus haematodus nesting side by side with the introduced Pheidole moerens. This is a very common ant on the Gulf Coast now that appears to replace some Camponotus and Aphaenogaster species in natural settings. If the same types of rotting wood were searched farther north in Alabama or Mississippi, those species would be found instead, but on the coast, they are much less common. Deyrup et al. (1985) noted this species (referred to as O. ruginodis in that paper) occurring in coastal areas in northern Florida. Its distribution does not appear to overlap with O. ruginodis, which is more southern.

Distribution
Because species in this genus have been often misidentified, the distribution of this species is not clearly understood at this time. Brown (1976) reported its distribution as continental South America from Orinoco Delta to Tucuma, Argentina Antweb lists the distribution as India,Neotropical: Argentina, Bolivia, Peru, Ecuador, Guyana, French Guiana, Trinidad & Tobago, Venezuela, Brazil, Surinam, Philippines, Colombia, Panama, Costa Rica, Nicaragua, Honduras, Guatemala, Mexico, Greater Antilles, Lesser Antilles, Bahamas. In the US it has been collected in AL (Baldwin and Mobile Cos.) and MS (Greene and Jackson Cos).

Literature Cited
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.

Bolton, B. 2012. Bolton World Catalog Ants. accessed on October 2012. [Available online: http://www.antweb.org/world.jsp]

Latreille, P. A. 1804. Tableau méthodique des insectes. Pp. 129-200 in: Société de Naturalistes et d'Agriculteurs 1804. Nouveau dictionnaire d'histoire naturelle. Tome 24. Paris: Déterville, 84 + 85 + 238 + 18 + 34 pp. 

Linnaeus, C. 1758. Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. Holmiae [= Stockholm]: L. Salvii, 824 pp.

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