Formica obtusopilosa

Nests are found under stones or in earthen mounds, similar to those of Myrmecocystus, in fine sandy or loam soils. These ants are very aggressive. Brood was found in nests in June and August, dealate females were found in July. Colonies are probably small, possibly a few hundred workers. One colony also contained workers of F. aserva, Formica argentea, Formica lasioides and Myrmica. (Mackay and Mackay 2002)

Identification
Just approaching medium-sized, the bicolored (black, or darker brown to reddish brown, gaster with lighter colored, yellowish-red alitrunk and head) Formica obtusopilosa workers have a dense gastric pubescence. This species belongs to the sanguinea species group, which is behaviorally differentiated from other Formica species by their slavemaking habitats. They may be found in colonies that contain a mix of conspecific and heterspecific workers. Morphologically the combination of dense gastric pubescence and an indentation in the middle of the clypeus or, more technically, a median concave impression on the anterior border of the clypeus set sanguinea species apart from other North American Formica. Erect light colored hairs (whitish to whitish yellow) that are larger towards their truncate tips differentiate these ants from other sanguinea species.

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

Habitat
In New Mexico (Mackay and Mackay 2002) - Sagebrush scrub through meadows, irrigated plains and pinyon-juniper forests up to aspen forests. Cole (1954) found a nest in dry semi-desert.

Biology
Nests in the soil in open grassy areas. Chambers may be found under stones or there may be a small earthen mound surrounding exposed ground entrances. Colonies can contain up to a few hundred workers.

Nomenclature

 *  obtusopilosa. Formica obtusopilosa Emery, 1893i: 648 (w.) U.S.A. Combination in F. (Raptiformica): Emery, 1925b: 259. Subspecies of sanguinea: Wheeler, W.M. 1901c: 713; Wheeler, W.M. 1913f: 414. Revived status as species: Emery, 1925b: 259; Cole, 1942: 377. Senior synonym of munda: Emery, 1925b: 259; Creighton, 1950a: 465; of alticola: Wilson & Brown, 1955: 128.
 * munda. Formica munda Wheeler, W.M. 1905c: 267 (w.q.) U.S.A. Junior synonym of obtusopilosa: Emery, 1925b: 259; Creighton, 1950a: 465. See also: Wheeler, W.M. 1913f: 416.
 * alticola. Formica munda var. alticola Wheeler, W.M. 1917a: 534 (w.) U.S.A. Combination in F. (Raptiformica): Creighton, 1950a: 466. Subspecies of obtusopilosa: Creighton, 1950a: 466. Junior synonym of obtusopilosa: Wilson & Brown, 1955: 128.