Subfamily PONERINAE
Tribe PONERINI
Odontomachus haematodus (Linnaeus) 1758

trapjaw ant

Author: Joe A. MacGown
Uploaded 21 July 2009, updated 30 May 2014

Odontomachus haematodus, full face view of a worker (AL, Baldwin Co.) (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; 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 (Linnaeus) (Ponerinae), the two-spined trapjaw ant, is a large, dark colored species native to South America that has recently become established along the US gulf coast from northern Florida to southern Louisiana. 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 (Bolton, 2012)
Formica haematoda Linnaeus, 1758: 582 (q.) "AMERICA MERIDIONALI". Neotropic.
Emery, 1899: 5 (l.); Wheeler & Wheeler, 1952: 646 (l.); MacGown, Boudinot, Deyrup & Sorger, 2014: (q.m.). Combination in Odontomachus: Latreille, 1804: 179. Senior synonym of Odontomachus maxillosa: Retzius, 1783: 75;Olivier, 1792: 502; Latreille, 1802: 192; of Odontomachus hirsutiusculus: Roger, 1863: 22; Brown, 1976}: 104; of Odontomachus pallipes and material of the unavailable name Odontomachus bruneipes referred here: Brown, 1976}: 104.

Diagnosis
Odontomachus workers in the US can be easily recognized by their large size; elongate, snapping mandibles that arise from the middle of the anterior  portion of the head, one-segmented petiole that terminates in a spine, and an obvious sting. Workers of O. haematodus can be separated from other species in the Southeast by their large size, paired metasternal spines, and transverse striae on most of the petiole (reduced or lacking posteriorly except at base). Males are yellow with small ocelli that are not raised. A similar species, O. ruginodis, is much smaller on average, striae completely covers the petiole, lacks metasternal spines, and is confined to southern Florida 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, it is probably O. haematodus.

Identification
Worker: Large (TL ≈ 1.0 cm, HL 2.32–2.75 mm, HW 1.88–2.16 mm; SL 2.2–2.48 mm, EL 0.46–0.54 mm, ML 1.38–1.56 mm, PTH 1.22–1.38 mm, PTL 0.54–0.60 mm, MeSL 3.04–3.48 mm). (MEM specimens) (n=10). Entire body dark reddish brown with gaster often darker brownish black and antennae and legs orangish brown. Head longer than wide; anterior corners strongly lobed, forming a deep, triangular depression in middle of posterior border; head somewhat constricted near midpoint, widened anteriorly at eye placement, then narrowing to the straight anterior border of clypeus; 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); eyes large, located at lower third of head at widest point; antenna 12-segmented, lacking club; scape about as long as head, lacking erect setae except apically; frontal lobes close together, expanded to cover antennal insertions; clypeus reduced, anterior border straight; mandibles elongate, thickened, with denticles along inner border and two longer blunt, inward turned, apical teeth. Mesosoma somewhat narrowed; promesonotum distinctly set off from propodeum; 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; with abundant pubescence present dorsally. Metasternum with paired narrowed, elongate, spiniform processes between hind coxae. Waist single-segmented, petiolar node 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.

Queen: Large, slightly larger than worker (HL 2.48–2.55 mm, HW 2.14–2.00 mm, SL 2.35–2.36 mm, EL 0.52–0.55 mm, ML 1.56–1.58 mm, OL 0.12–0.13 mm, PTH 1.28–1.62 mm, PTL 0.58–0.66 mm, FWL 6.5 mm, MeSL 3.56-3.60 mm) ( MEM specimens) (n=2 except for FWL for which only one individual had wings).  Large, slightly larger than worker (HL 2.48–2.55 mm, HW 2.14–2.00 mm, SL 2.35–2.36 mm, EL 0.52–0.55 mm, ML 1.56–1.58 mm, OL 0.12–0.13 mm, PTH 1.28–1.62 mm, PTL 0.58–0.66 mm, FWL 6.5 mm, MeSL 3.56-3.60 mm). Entire body dark reddish brown with gaster often darker brownish black and antennae and legs orangish brown. Head longer than wide; anterior corners strongly lobed, forming a triangular depression in middle of posterior border; head somewhat constricted near midpoint, widened anteriorly at eye placement, then narrowing to the straight anterior border of clypeus; 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); eyes large, located at lower third of head at widest point; three small ocelli present; antenna 12-segmented, lacking club; scape about as long as head, lacking erect setae except apically; frontal lobes close together, expanded to cover antennal insertions; clypeus reduced, anterior border straight; mandibles elongate, thickened, with denticles along inner border and two longer blunt, inward turned, apical teeth. Mesosoma not constricted, in lateral view, somewhat convex dorsally, with numerous short erect, setae dorsally, especially on pronotum; pronotum rounded anteriorly, visible dorsally, with circular concentric striae that become longitudinal near rear margin; mesoscutum with dense, longitudinal striae; mesoscutellum shiny, lacking sculpture; propodeum broadly rounded, with deep transverse striae; mesopleuron, and basalar lobe, shiny, lacking sculpture. Metasternum with paired narrowed, elongate, spiniform processes between hind coxae. Wings with light brownish tint; forewing with closed costal, basal, subasal, two discal, two submarginal, and marginal cells; medial vein extending to wing tip; pterostigma present; hind venation with closed basal and subbasal cells. Waist single-segmented, petiolar node 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; sting present.

Males: Smaller than worker (HL 1.00–1.12 mm, HW 1.20–1.30 mm, SL 0.18–0.20 mm, EL 0.62–0.68 mm, EW 0.38–0.40 mm, OL 0.18–0.20 mm, OES 0.20–0.22mm, PTH 0.90–0.94 mm, PTL 0.50–0.56 mm, FWL 4.95–5.45 mm, MeSL 2.68–2.83 mm) (MEM specimens) (n=5).  Body orangish brown to brown, antennae and legs lighter orange brown. Head slightly wider than long (including eyes), somewhat elliptical, shiny, with numerous appressed, short setae; eyes extremely large, eye length about 70% of the length of the head; 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; antenna 13-segmented, not clubbed, lacking standing erect setae, scape short and rectangular, pedicel short and square, flagellomeres elongate and subequal to one another; mandibles reduced, lacking dentition. Mesosoma thickened, with dense, fine pubescence except on anepisternum; pronotum with faint transverse striae, especially laterally, but mostly lacking 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. Wings with light brownish tint; forewing with closed costal, basal, subasal, two discal, two submarginal, and marginal cells; medial vein extending to wing tip; pterostigma present; hind venation with closed basal and subbasal cells. Waist single segmented; petiole bluntly rounded apically, with rounded triangular subpetiolar process anteriorly; densely pubescent anteriorly and laterally, but reduced pubescence posteriorly. Gaster shiny beneath dense, fine, white pubescence, with a few scattered longer erect setae at sclerite margins; curved, ventrally projecting spine present at apex of last tergite.

Odontomachus workers in the US can be easily recognized by their large size; elongate, snapping mandibles that arise from the middle of the posterior portion of the head, the one-segmented with a petiole that terminates in a spine, and an obvious sting. Workers of O. haematodus 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 Florida 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
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. 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 O. haematodus nesting side by side with the introduced Pheidole moerens. 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. 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. Alate males and females have been collected from late June through early August.

Pest Status
In areas where O. haemtodus colonies are abundant, they may outcompete native ant species for resources, and along the Alabama and Mississippi gulf coast, they appears to replace Camponotus and Aphaenogaster species that nest in rotting wood in natural settings. Compared to native species of Odontomachus in the US, O. haematodus is an aggressive stinger. Upon placing one's hand in leaf litter where a nest is located, workers are quick to 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." I can attest to the veracity of these claims, as I have been stung by this beautiful species on numerous occasions.

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.

Native Range: South America

Nearctic: United States (AntWeb.org and MEM)
Neotropical: Argentina, Bahamas, Bolivia, Brazil, Colombia, Costa Rica, Ecuador, French Guiana, Greater Antilles, Grenada, Guatemala, Guyana, Honduras, Lesser Antilles, Martinique, Mexico, Nicaragua, Panama, Paraguay, Peru, Suriname, Trinidad and Tobago, Venezuela (AntWeb.org, AntWiki.org and Brown 1976).
Oriental: Borneo (AntWeb.org).
Palearctic: China (AntWeb.org).

US Distribution: Alabama (Baldwin, Escambia, and Mobile Cos., Florida (Escambia and Santa Rosa Cos.), Louisiana (Orleans Parish), and Mississippi (Greene and Jackson Counties) [MEM records].

Acknowledgments
Thanks to Ryan J. Whitehouse for help with measuring specimens, comments on descriptions, photography of some specimens, and proofreading. 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 (2001-2014) and USDA-ARS Areawide Management Invasive Ants 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.

Literature Cited

Bolton, B. 2012. Bolton World Catalog Ants. accessed on September 2016.

Brown, W. L., Jr. 1976. Cladarogenys genus nov. Pilot Register of Zoology Card No. 33:1-2.

Emery, C. 1899. Intorno alle larve di alcune formiche. Rendiconti delle Sessioni della Reale Accademia delle Scienze dell'Istituto di Bologna (n.s.)3:93.

Latreille, P. A. 1802. Histoire naturelle des fourmis, et recueil de mémoires et d'observations sur les abeilles, les araignées, les faucheurs, et autres insectes. Paris: Impr. Crapelet (chez T. Barrois), xvi + 445 pp.

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.; Boudinot, B.; Deyrup, M.; Sorger, D. M. 2014. A review of the Nearctic Odontomachus (Hymenoptera: Formicidae: Ponerinae) with a treatment of the males. Zootaxa 3802(4):515-552. 

Olivier, A. G. 1792. Encyclopédie méthodique. Histoire naturelle. Insectes. Tome 6. (pt. 2). Paris: Panckoucke, pp. 369-704.

Retzius, A. J. 1783. Caroli de Geer. Genera et species insectorum e generosissimi auctoris scriptis extraxit, digessit, Latine quoad partem reddidit, et terminologiam insectorum Linneanam addidit. Lipsiae [= Leipzig]: Cruse, 220 pp.

Roger, J. 1863. Verzeichniss der Formiciden-Gattungen und Arten. Berliner Entomologische Zeitschrift 7(Beilage):1-65.

Wheeler, G. C.; Wheeler, J. 1952. The ant larvae of the subfamily Ponerinae - Part II. American Midland Naturalist 48:604-672.

Links

AntWeb
AntCat
AntWiki