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; the large tapering petiole; and the large size of the workers (see photos above) (for a more detailed diagnosis of the genus, see MacGown et al. 2014). 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.
Odontomachus haemtodus is a large, dark colored species native to South America that is now common along the US gulf coast from northern FL to southern LA. Based on large populations, apparent successful competition with native species that nest in the same habitat, and its painful sting, this species shows invasive potential in the US.
Taxonomic History (from Bolton, 2012)
Described as Formica haematoda Linnaeus, 1758; combined in Odontomachus by Latreille (1804).
Worker: (from MEM specimens). HL, 2.32–2.75mm; HW, 1.88–2.16mm; SL, 2.2–2.48mm; EL, 0.46–0.54mm; ML, 1.38–1.56mm; PTH, 1.22–1.38mm; PTL, 0.54–0.60mm; WL, 3.04–3.48mm (n = 10). Entire body generally shiny except where dulled by dense pubescence; concolorous dark reddish-brown to blackish. Head with fine, longitudinal striae covering much of the head in full-face view, striae beginning from frontal lobes and diverging toward posterior corners of head, fading at corners and sides; sides and underside of head lacking sculpture; with numerous, fine, appressed pubescence and scattered elongate, erect setae present (dorsally). Pronotum with somewhat circular concentric striae that become longitudinal near rear margin; appressed pubescence abundant; 5-8 elongate, erect setae present. Mesonotum and propodeum with deep transverse striae; propleuron, mesopleuron, and basalar lobe lacking sculpture; abundant pubescence present dorsally. Metasternum with paired narrowed, elongate, spiniform processes between hind coxae (Fig. 3A). Petiole widest at base, gradually tapering apically to a long spine directed rearward; transverse striae completely surrounding petiole except upper dorso-posteriorly where striae are faint or lacking; subpetiolar process somewhat anvil shaped; appressed pubescence present anteriorly and laterally, but mostly absent posteriorly. Gaster mostly shiny beneath pubescence, lacking striae or other strong sculpture, but weakly shagreened (seen at high magnification); fine, appressed pubescence moderately dense, spaces between hairs usually less than 1/2 the length of a hair; scattered erect, elongate setae present.
Males: (from MEM specimens). HL, 1.00–1.12mm; HW, 1.20–1.30mm; SL, 0.18–0.20mm; EL, 0.62–0.68mm; EW, 0.38–0.40mm; OL, 0.18–0.20mm; OES, 0.20–0.22mm; PTH, 0.90–0.94mm; PTL, 0.50–0.56mm; FWL, 4.95-5.45mm; WL, 2.68–2.83mm (n=5).
Body generally shiny except where obscured by dense pubescence; head, meso- and metasoma yellowish-orange, antenna and legs pale yellowish-orange. Head and body with abundant fine, white pubescence except on anepisternum, where it is mostly absent. Eyes extremely large, maximum diameter of each eye at least 70% of the length of the head in full-face view. Ocelli small to average in size, the length of each ocellus slightly less to approximately the same as the distance between lateral ocellus and eye margin; in full-face view, lateral ocelli do not protrude beyond posterior border of head. Mesosoma: pronotum with faint transverse striae, especially laterally, but mostly appearing to lack sculpture; mesoscutum with faint transversely arcuate striae anteriorly, striae becoming transverse posteriorly; mesoscutellum raised and convex, lacking sculpture; propodeum evenly rounded without obvious declivious face, with strong rugoreticulation; mesopleuron mostly lacking striae or with very faint longitudinal striae. Petiole bluntly rounded apically, with rounded triangular subpetiolar process anteriorly; densely pubescent anteriorly and laterally, but reduced pubescence posteriorly.
Queen: (from MEM specimens). HL, 2.48–2.55mm; HW, 2.14–2.00mm; SL, 2.35–2.36mm; EL, 0.52–0.55mm; ML, 1.56–1.58mm; OL, 0.12–0.13mm; PTH, 1.28–1.62mm; PTL, 0.58–0.66mm; FWL, 6.5mm; WL, 3.56-3.60mm (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. Thus far, the distribution of O. haematodus in the US does not appear to overlap with O. ruginodis, which ranges from Alauchua County, FL to southern FL.
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.
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 Counties).
Funding for the ant work being done by the MEM in Alabama and Mississippi is from several sources including the National Institute of Food and Agriculture, United States Department of Agriculture, under Project No. MIS-012040, the Mississippi Agricultural and Forestry Experiment Station at Mississippi State University, with support from State Project MIS-311080, NSF Grants BSR-9024810 and DFB-9200856, the Tombigbee National Forest (U.S. Forest Service), the Noxubee Wildlife Refuge, Mississippi Natural Heritage Program Research Grant, USDA Forest Service Agreement No. 08-99-07-CCS-010, the William H. Cross Expedition Fund, and primarily by the USDA-ARS Areawide Management of Imported Fire Ant Project. Additionally, special cooperation has been provided by State Parks, National Forests, National Wildlife Refuges, the Natchez Trace Parkway, and from various private landowners in both Alabama and Mississippi.
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.
MacGown, J. A., B. Boudinot, M. Deyrup, and D. M. Sorger. 2014. A review of the Nearctic Odontomachus (Hymenoptera: Formicidae: Ponerinae) with a treatment of the males. Zootaxa 3802 (4):515–552.