Formica ravida

This mound building ant in the Formica rufa group nests in open areas and feeds on insects and secretions from homoptera.

Identification
The tentorial pits of this species are shallow. The erect bristles on the tibiae are restricted to two rows on the flexor surface, which extend nearly the entire length of the tibiae. The erect hairs on the gaster are scattered, and do not form an even vestiture when viewed in profile, although the gaster is covered with dense, gray, appressed pubescence. The petiole is narrow in profile with a moderately sharp apex (MacKay & MacKay 2002). There are several short erect hairs coming out of the compound eyes.

Distribution
Western North America.

Distribution based on Regional Taxon Lists
Nearctic Region: Alberta, Canada, Canada, United States.

Habitat
Various; from prairies up to pine forests.

Biology
This ant is a presumed temporary social parasite of other species of Formica in the fusca group. It is a very aggressive ant that readily defends its large mound nests by squirting formic acid. Temnothorax andrei may be occasionally found within this mound nest. Incipient F. ravida nests may be found under logs or stones. In northwestern New Mexico on the Navajo Reservation, this ant was found at 1,492 meters elevation near the San Juan River just outside of Shiprock New Mexico in an open pasture. Deep within these host nests, the inquiline ant, Formicoxenus diversipilosus has been found.

Mackay and Mackay (2002) - Nests are usually in the form of thatched mounds on the sides of logs and stumps. Incipient nests may be found under stones or logs, but usually some thatching is present. These ants are extremely aggressive. Workers fold the gaster under the body and squirt a stream of formic acid several centimeters. This acid is strong enough to cause blistered skin, after repeated contact with these ants.

Nomenclature

 *  ravida. Formica rufa subsp. ravida Creighton, 1940a: 1, fig. 1 (w.q.m.) U.S.A. [First available use of Formica truncicola subsp. integroides var. ravida Wheeler, W.M. 1913f: 560; unavailable name.] Subspecies of obscuripes: Creighton, 1950a: 493. Raised to species: Gregg 1963: 581. Junior synonym of haemorrhoidalis Creighton: Brown, 1965d: 181. [F. haemorrhoidalis Creighton, 1940a: 1, junior primary homonym of F. haemorrhoidalis Latreille, 1802c: 276.] F. ravida designated as first available replacement name and senior synonym of tahoensis: Bolton, 1995b: 202.
 * haemorrhoidalis. Formica rufa subsp. haemorrhoidalis Creighton, 1940a: 1, fig. 1 (w.) U.S.A. [First available use of Formica rufa subsp. integra var. haemorrhoidalis Emery, 1893i: 652 (w.); Wheeler, W.M. 1913f: 441 (q.m.); unavailable name.] [Junior primary homonym of Formica haemorrhoidalis Latreille, 1802c: 276, above.] Replacement name: ravida Creighton, 1940a: 1 (designated first available replacement name by Bolton, 1995b: 202, as haemorrhoidalis Creighton was raised to species and made senior synonym of ravida and tahoensis by Brown, 1965d: 181).
 * tahoensis. Formica rufa subsp. tahoensis Creighton, 1940a: 1, fig. 1 (w.q.) U.S.A. [First available use of Formica truncicola subsp. integroides var. tahoensis Wheeler, W.M. 1917a: 538; unavailable name.] Cole, 1956g: 260 (q.m.). Subspecies of integra: Creighton, 1950a: 488. Junior synonym of haemorrhoidalis: Brown, 1965d: 181; of ravida: Bolton, 1995b: 205.

Type Material
Described from two females and seven workers collected by Mr. W.M. Mann at Elkhorn, Montana. He has also taken six workers at Helena in the same state.

Description
This description is taken from Wheeler, W.M. 1913i under the name Formica truncicola subspecies integroides var ravida which is an unavailable name.

Worker. Length 4-6 mm.

Like the var. haemorrhoidalis Emery in pubescence and sculpture and in lacking erect hairs, except on the gaster, but differing in color. The red of the head, thorax, and petiole is much deeper and not yellowish, the legs, whole of the funiculi, tips of the scapes and the gaster are black and even the largest workers have a large black spot on the pro- and mesonotum. In small workers the red color is darker and more brownish, the whole thorax is blackish and the posterior portion of the head and the whole of the scapes are infuscated. The surface of the body in all of the workers is opaque, the pubescence on the gaster short, dense and dark gray in color; the red anal spot is much restricted.

Female. Lengthe 8.5-9 mm.

Differing from the female of haemorrhoidalis in having the tips of the scapes, the posterior border of the pronotum, three spots on the mesonotum, the whole of the scutellum and metanotum, a few spots on the mesoleurae and the middle and hing legs, including their coxae, black.