Subfamily PONERINAE
Tribe PONERINI

Odontomachus brunneus (Patton, 1894)

 

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

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

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

Odontomachus brunneus, petiole of worker. Note the lack of deep, obvious transverse grooves (click image to enlarge).
Odontomachus brunneus,ventral view of worker. Arrow points to metasternum. Note the lack of spines between the metacocoxal sockets (metacoxae removed)
(click image to enlarge).
Odontomachus brunneus, full face view of a male (click image to enlarge).
Photo courtesy of http://www.antweb.org/
Odontomachus brunneus, side view of a male (click image to enlarge).
Photo courtesy of http://www.antweb.org/
Odontomachus brunneus, side view of a male (click image to enlarge).
Photo courtesy of http://www.antweb.org/
Odontomachus brunneus, foraging on ground at Tall Timbers Research Station, FL (click image to enlarge).
Odontomachus brunneus, brood in colony at Tall Timbers Research Station, FL (click image to enlarge)

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.

This species may be the only native Odontomachus species found along the Gulf Coast, except for O. clarus, which was recently discovered in Louisiana (Adams et al. 2010).

Taxonomic History (from Barry Bolton, 2012)
Described by Patton from Georgia in 1894 as Atta brunnea; Emery moved it to Odontomachus and made it a junior synonym of O. insularis (1895); Brown later revived it from synonymy (1976).

Identification
Worker: (from Patton 1894; Deyrup and Cover 2004; and Deyrup et al. 1985) Concolorous dark brown to blackish-brown with legs and occasionally the head, mesosoma, and posterior portion of gaster (especially underneath) paler. Total length approximately 8.0 mm (length of head + mesosoma _ petiole + gaster). Inner border of mandibles finely serrate; mandibles tridentate apically, and with middle tooth the smallest. Palpi reduced. Tibiae with single spur. Hind femur with fine pubescence at base. Petiolar node produced into a spine that tapers a pic odors ally, faintly rugose at base only; lacking transverse striae. Metasternum lacking paired spines between metacoxae. Mesosoma densely striate dorsally, and head with finer striations dorsally. Pubescence on first gastral tergite extremely fine and dense, almost contiguous, with spaces between hairs less than one-third as wide as length of hairs.

Males: (from Deyrup et al. 1985)
Color yellowish-orange. Ocelli on a conspicuous turret, with each ocellus as wide as the ocelllo-ocular space. Petiole lacking sculpture, smooth.

Workers of this species can be differentiated from other US Odontomachus species by the densely pubescent gaster and lack of transverse striae on the petiole. Males are yellow with raised ocelli.

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.

This species nests in soil and logs in a wide variety of well drained to poorly drained habitats, but especially somewhat moist forests. Foraging may occur during day, but in general, this species is nocturnal.

Distribution
Because species in this genus have been often misidentified, the distribution of this species is not clearly understood at this time. However, in the US, it is clearly only found in the Southeast: AL (Baldwin and Houston Counties), FL (Alachua, Baker, Bay, Bradford, Broward, Citrus, Clay, Collier, Columbia, Dade, De Soto, Duval, Franklin, Gadsden, Gilchrist, Glades, Hamilton, Hernando, Highlands, Hillsborough, Indian River, Jackson, Jefferson, Lake, Lee, Leon, Levy, Liberty, Madison, Marion, Martin, Monroe, Nassau, Okeechobee, Orange, Osceola, Palm Beach, Pasco, Polk, Putnam, Sarasota, St. Lucie, Sumter, Taylor, Volusia, Wakulla, and Walton Counties), and GA (Clinch County).

Literature Cited
Adams, B. J., X. Chen, and L. M. Hooper-Bui. 2010. Odontomachus clarus Roger (Hymenoptera: Formicidae) Reported in Kisatchie National Forest, Louisiana. Midsouth Entomologist 3: 104-105. [Available online: http://midsouthentomologist.org.msstate.edu/pdfs/Vol3_2/Vol3_2_006.pdf]

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

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. and S. Cover. 2004.  A new species of Odontomachus ant (Hymenoptera:  Formicidae) from inland ridges of Florida, with a key to Odontomachus of the United States.  Florida Entomologist 87: 136-144.

Deyrup, M., J. Trager, N. Carlin 1985. The genus Odontomachus in the southeastern United States (Hymenoptera: Formicidae). Entomological News 96:188-195.

Emery, C. 1895d. Beiträge zur Kenntniss der nordamerikanischen Ameisenfauna. (Schluss). Zoologische Jahrbücher. Abteilung für Systematik, Geographie und Biologie der Tiere 8:257-360. [1895-05-11]

Patton, W. H. 1894. Habits of the leaping-ant of southern Georgia. American Naturalist 28:618-619.

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