Odontomachus brunneus

Identification
Deyrup and Trager (1985) - Worker: gaster densely covered with fine, almost contiguous appressed hairs; striations of pronotum not transverse posteriorly; petiolar node faintly rugose at extreme base only; inner side of hind femur at base finely pubescent; color piceous in n. Florida, body (except gaster) frequently lighter in s. Florida. Male: each ocellus as wide as the ocello-ocular space, ocelli on a conspicuous turret: petiole smooth; head and body entirely yellowish orange.

Distribution
Occurs in xeric areas in Mexico, southwestern US, Florida (Deyrup and Trager 1985). It also has a wide range in the remainder of the neotropics but the limits of its distribution are presently unclear.

This taxon was described from U.S.A.

Biology
In Florida Deyrup and Trager (1985) found that brunneus occurred in wet areas such as hammocks and ditches. Males were found to fly in the spring.

Deyrup and Cover (2004) - Odontomachus brunneus occurs in both well-drained and poorly drained habitats; nests may be in soil or in rotten wood. This species was studied by Van Pelt (1958) at the Welaka Reserve (now Welaka State Forest) in Putnam Co., Florida. Van Pelt found many colonies, which occurred in all the terrestrial habitats in the area, including flatwoods, mesic forest, swamp forest, upland scrub and sandhill. Nests were in various microhabitats, including deep leaf litter, fallen logs, at the bases of trees, and open or sparsely covered sandy areas. At the Archbold Biological Station, brunneus occurs in moist habitats, including flatwoods, bayheads, the edges of seasonal ponds, and elevated tussocks or fallen pines within seasonal ponds. It has not been found in the more elevated upland areas of the Station, which are occupied by Odontomachus relictus. This distribution gives the impression that there is some competitive displacement based on differential adaptation to moisture conditions, but the evidence remains circumstantial. It may be relevant that in parts of its range devoid of relictus, where brunneus occurs in dry, upland areas individuals never achieve the large size and dark color seen in some specimens from wet areas. Nobody knows, however, whether the smaller, paler individuals represent stressed individuals in suboptimal conditions, or whether they represent an adaptive phenotypic response in a robust population.

Workers of brunneus sometimes emerge to forage on cloudy days, but are generally nocturnal. The formidable jaws of brunneus are not used as assertively as one might expect, and there is fragmentary evidence that brunneus is sensitive to chemical defenses. Prey are approached tentatively, and the ant recoils immediately after striking the prey (Brown 1976). There may be a delay before the prey is picked up and carried away; Brown (1976) suggested that these ants react to chemical defenses, which are allowed to dissipate before the prey is retrieved. Alex Wild, while a student at the Archbold Biological Station, twice observed brunneus retreating hastily when confronted by aroused workers of Dorymyrmex bureni (Trager) (unpublished natural history notes on file at the Archbold Biological Station). Dorymyrmex bureni is much smaller than O. brunneus, but can release large quantities of defensive chemicals that are pungent to the human nose. Van Pelt (1958) reported accumulations of brunneus head capsules in the nests of Formica archboldi Smith, and suggested the possibility that brunneus is a regular part of the diet of F. archboldi. If this is the case, it is more likely that the brunneus are subdued by chemical means than by mandible-to-mandible combat.

Nesting Biology
Cerquera and Tschinkel (2010) - O. brunneus excavates simple nests, each consisting of a single, vertical shaft connecting more or less horizontal, simple chambers. Nests contained between 11 and 177 workers, from 2 to 17 chambers, and 28 to 340 cm2 of chamber floor space and reached a maximum depth of 18 to 184 cm. All components of nest size increased simultaneously during nest enlargement, number of chambers, mean chamber size, and nest depth, making the nest shape (proportions) relatively size-independent. Regardless of nest size, all nests had approximately 2 cm2 of chamber floor space per worker. Chambers were closer together near the top and the bottom of the nest than in the middle, and total chamber area was greater near the bottom. Colonies occasionally incorporated cavities made by other animals into their nests.

Nomenclature

 *  brunneus. Atta brunnea Patton, 1894: 618 (w.) U.S.A. Deyrup, Trager & Carlin, 1985: 191 (m.). Combination in Odontomachus: Emery, 1895c: 268. Junior synonym of insularis: Emery, 1895c: 268. Revived from synonymy and senior synonym of fuscus Stitz, 1925: Brown, 1976a: 103. See also: Brown, 1976a: 139.
 * fuscus. Odontomachus haematodes var. fuscus Stitz, 1925: 115, fig. 2 (w.) CUBA. [Unresolved junior primary homonym of fuscus Stitz, 1916, above. Note that the proposed replacement name repetita Baroni Urbani, 1971b: 361 is unavailable.] Junior synonym of brunneus: Brown, 1976a: 103.

Additional References

 * Cerquera LM, Tschinkel WR. 2010. The nest architecture of the ant Odontomachus brunneus. Journal of Insect Science 10:64


 * 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.