Odontomachus ruginodis

A fairly widespread species that occurs from Florida (where it might be introduced) south through the Caribbean and into northern South America. It is ground-nesting and found in both disturbed and natural habitats.

Identification
Deyrup and Trager (1985) - Worker: gastral hairs, pronotal striation, inner side of hind femur approximately as in Odontomachus clarus; petiole conspicuously transversely striate on sides and back; color reddish brown to piceous gaster black. Male: each ocellus less than two-thirds as wide as ocello-ocular space, ocelli not on a turret; petiole strongly rugose laterally; propodeum and lateral pronotal spot black, remainder of thorax and head yellow, gaster brown.

The conspicuous striae on the posterior face of the petiole distinguish workers of this species from the similar Odontomachus clarus and Odontomachus relictus, but there are additional species with petiolar striae (e.g., Odontomachus bauri Emery) outside the U.S (Deyrup and Cover 2004).

Identification Keys including this Taxon

 * Key to US Odontomachus species

Distribution
This species occurs sporadically through southern and central Florida, at least as far north as Orlando, and also in the West Indies. Its distribution in South and Central America is unclear because it has been confused with Odontomachus brunneus. Its ability to thrive in disturbed habitats should allow it to invade mainland Neotropical areas, if it is not already present. It is probable that this species will be distributed by commerce to disturbed areas in the Southwest. (Deyrup and Cover 2004)

In the United States, Deyrup (1991) speculated that this was introduced into Florida as it was patchily distributed and had a predilection for disturbed habitats. However, MacGown et al. (2014) stated that the status of Odontomachus ruginodis as an exotic species is unclear. The Florida populations may be recent arrivals from Antillean populations, as evidenced by the frequent collection in disturbed areas, such as near homes, rather than in natural habitats. Indeed, Puerto Rican populations of O. ruginodis show a preference for forests that are at least 25 years old (Osorio-Pérez et al. 2007), and males of Nearctic O. ruginodis more-closely resemble those of the Antilles rather than of the mainland Neotropics. During the past 20 years, this species appears to have been steadily expanding its range northward in Florida.

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Bahamas, Barbados, Bermuda, Costa Rica, Dominican Republic, Ecuador, Galapagos Islands, Greater Antilles, Grenada, Guadeloupe, Guatemala, Haiti, Honduras, Mexico, Panama, Puerto Rico.



Biology
Deyrup & Cover (2004); Deyrup, Davis & Cover (2000) - In Florida, this species occurs in disturbed areas, including urban and suburban habitats and in both wet and dry areas. It occurs along the beaches in the tropical part of the state, as well as in open woods, including mangrove areas. It has not yet been found inland in natural habitats. In Puerto Rico it differs from another sympatric species (perhaps Odontomachus bauri) in its preference for open, sunny areas, especially river bottoms (see below).

The defensive mandible-snapping behavior of ruginodis was studied by Carlin and Gladstein (1989). When a nest is attacked by other ants, the ruginodis workers rush out, snapping at anything that seems a threat. Enemy ants may be dismembered or knocked out of the way by the mandibular strikes. If the mandibles hit a solid object, the ruginodis may itself be flung into the air for a distance of several centimeters. This does not seem to be an escape mechanism, as the worker, upon landing, immediately charges back into the fray. The nest entrance is usually guarded by a single worker, who stands with cocked mandibles near the entrance. If an intruder approaches within striking distance, the mandibles snap shut, responding to signals from the antennae and long sensory hairs at the bases of the mandibles. The heavy apices of the mandibles do not slice into the intruder, but knock it away a distance of about one to fourteen centimeters. Carlin and Gladstein call this the “bouncer defense.”

Males have been collected from early May through June (MacGown et al., 2014).

Puerto Rico
Wheeler (1908): ...found only in open, sunny places in the sandy soil of river bottoms. It is smaller than ..Odontomachus haematodus.., has a paler head, and the petiole is less acuminate above, with a shorter spine.

Nomenclature

 *  ruginodis. Odontomachus haematodus var. ruginodis Smith, M.R. 1937: 828 (w.q.) BAHAMAS. [First available use of Odontomachus haematodes subsp. insularis var. ruginodis Wheeler, W.M. 1905b: 82; unavailable name.] Deyrup, Trager & Carlin, 1985: 192 (m.). Raised to species: Wilson, 1964b: 4. Junior synonym of brunneus: Brown, 1976a: 103. Revived from synonymy: Deyrup, Trager & Carlin, 1985: 192.

Description
To this variety I assign a small form of O. haematodes, which in color and pilosity resembles specimens of insularis taken in Florida (Lake Worth, Enterprise, Biscayne Bay, etc.). In the worker the head, antennae, and legs are dark red, the thorax nearly black. The upper surface of the head and thorax is opaque and strongly sculptured. The petiole, which is sharply and transversely rugose on its anterior and posterior surfaces, is narrow, decidedly convex behind, with rounded sides, and passes rather gradually into the spine.

This variety was taken only on New Providence Island at Nassau (Queen's Staircase and Fort Charlotte) and a neighboring key, Hog Island. Specimens of the very same form have been sent to me from Havana, Cuba, by Mr. C. F. Baker. Florida specimens of insularis, like those of the next variety to be described, have only faint traces of the transverse rugae on the petiole.

In Nassau I found the variety ruginodis nesting under stones in small colonies of often not more than a dozen individuals. In the moat of old Fort Charlotte several isolated females were seen starting their colonies. In this phase the petiole is much broader and much more rugose than in the worker.