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
This taxon was described from the United States. It is also found in Canada. This ant is found in British Colombia, Alberta,  Washington State, Oregon, Idaho, northern California and Montana, Wyoming, Colorado to North Dakota, South Dakota and South to Arizona and New Mexico.

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.

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.

Additional References

 * [[Media:Cole 1932.pdf|Cole, A. C. Jr. 1932. The Thatching Ant, Formica Obscuripes Forel Psyche Volume 39 (1932), Issue 1-2, Pages 30-33 PDF]]