Formica obscuripes

Known as the western thatching ant, Formica obscuripes makes large nest mounds of thatch. This is a temporary social parasite of Formica fusca group ants during their colony founding period. Nest are often located along the edge of meadows and other open areas. Many myrmecophiles and several inquiline ants can be found within these host nests.

Identification
Formica obscuripes ants build nests deep into the soil and create a mound of thatch (twigs, grasses, and other vegetation) that can be more than 1 foot above ground. Nests are normally in an open area exposed to direct sunlight.

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

Habitat
In New Mexico (Mackay and Mackay 2002) - Prairies, sagebrush, mixed deciduous forest up to pinyon-juniper, ponderosa pine-riparian.

Biology
Formica obscuripes twig and earthen mound nests contain a diversity of myrmecophiles including species of Beetles (Cremastocheilus, Haeterius), Fly larvae (Microdon), and many others. Workers feed on a variety of insect prey including caterpillars and tend homopterans for their honeydew.

For New Mexico (Mackay and Mackay 2002) - This species is not common in New Mexico. It nests in thatched mounds or under logs or stones (usually partially covered with thatch). Workers tend aphids. It is polygynous (multiple queens in the nest). This species does not have typical mating flights; instead small numbers leave the nest throughout the season. Dealate females were collected in late June and early July.

Nomenclature

 *  obscuripes. Formica rufa r. obscuripes Forel, 1886b: xxxix (w.) U.S.A. Emery, 1893i: 650 (q.m.); Wheeler, G.C. & Wheeler, J. 1953c: 165 (l.); Hung, 1969: 456 (k.). Raised to species: Creighton, 1950a: 492. Senior synonym of aggerans: Forel, 1914c: 619; Creighton, 1940a: 1; of melanotica: Creighton, 1950a: 492. Material of the unavailable name rubiginosa referred here by Creighton, 1940a: 1. See also: Weber, 1935: 165.
 * aggerans. Formica rufa subsp. aggerans Wheeler, W.M. 1912c: 90 (w.) U.S.A. Wheeler, W.M. 1913f: 430 (q.m.). Junior synonym of obscuripes: Forel, 1914c: 619; Creighton, 1940a: 1.
 * melanotica. Formica rufa subsp. melanotica Creighton, 1940a: 1, fig. 1 (w.q.m.) U.S.A. [First available use of Formica rufa subsp. obscuriventris var. melanotica Emery, 1893i: 650; unavailable name.] Junior synonym of obscuripes: Creighton, 1950a: 492.