Subfamily PONERINAE
Tribe PONERINI

Odontomachus haematodus (Linnaeus) 1758

by Joe A. MacGown, uploaded 21 July 2009, updated 25 November 2013

Odontomachus haematodus, full face view of worker.
(photo by Joe A. MacGown)
Odontomachus haematodus, profile view of worker (photo by Joe A. MacGown)

Odontomachus haematodus, full face view of a worker (photo by Joe A. MacGown)

Odontomachus haematodus, side view of a worker (photo by Joe A. MacGown)
Odontomachus haematodus,ventral view of worker showing mesocoxae and with arrow pointing to metasternal spines. Metacoxae were removed.
(photo by Joe A. MacGown)
Odontomachus haematodus, full face view of a male
(photo by Joe A. MacGown)
Odontomachus haematodus, side view of a male (photo by Joe A. MacGown)
Odontomachus haematodus, side view of a male (photo by Joe A. MacGown)
Odontomachus haematodus foraging in sand dune habitat in Gulf Shores, AL (photo by Joe A. MacGown)
Odontomachus haematodus foraging in sand dune habitat in Gulf Shores, AL (photo by Joe A. MacGown)

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 MEM specimens). HL, 2.32–2.75; HW, 1.88–2.16; SL, 2.2–2.48; EL, 0.46–0.54; ML, 1.38–1.56; PTH, 1.22–1.38; PTL, 0.54–0.60; WL, 3.04–3.48 (n = 10). Dark reddish-brown to piceous with antennae and legs yellowish-brown reddish-brown. Length 8.5–9.5 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). HL, 1.00–1.12; HW, 1.20–1.30; SL, 0.18–0.20; EL, 0.62–0.68; EW, 0.38–0.40; OL, 0.18–0.20; OES, 0.20–0.22; PTH, 0.90–0.94; PTL, 0.50–0.56; FWL, 4.95-5.45; WL, 2.68–2.83 (n=5).  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.

Queen: (from MEM specimens). HL, 2.48–2.55; HW, 2.14–2.00; SL, 2.35–2.36; EL, 0.52–0.55; ML, 1.56–1.58; OL, 0.12–0.13; PTH, 1.28–1.62; PTL, 0.58–0.66; FWL, 6.5; WL, 3.56-3.60 (n=2 except for FWL for which only one individual had wings).  Similar to workers in color and general appearance except with mesosoma developed for wings and with wings present in alate specimens.

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. According to Andy Suarez (Pers. Comm.), O. haematodus was abundant at the Audubon Zoo in downtown New Orleans, LA before Hurricane Katrina hit that region in 2005, and populations continued afterward.

Although this species is often located in habitats with sandy soils, soil type is probably not overly important as it often nests in leaf litter, rotting wood, or in trees, rather than directly in the soil. 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 that appears to replace Camponotus and Aphaenogaster species that nest in rotting wood in natural settings. Searching through similar types of rotting wood 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.

Compared to the native US species, O. haematodus is an aggressive stinger. Upon placing one's hand in leaf litter where a nest is located, workers will immediately sting. The sting is painful, but not long lasting. I have recieved complaints from homeowner's in southern Mississippi of this species biting and stinging them. One homeowner stated, "Ants would latch on with their mandibles and sting repeatedly, lashing out with their abdomens. One ant can sting 4–5 times before you realize it. They are very aggressive."

Alate males and females have been collected from late June through early August.

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.

US Distribution: Alabama (Baldwin, Escambia, and Mobile Cos., Florida (Escambia Co.), Louisiana (Orleans Parish), 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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