Formica planipilis

These ants nest in the soil, usually with some thatching of pine needles, but may also be found nesting in rotten logs and stumps in rocky and gravely soils. Brood and reproductives were found in nests from late June to mid August. Workers forage up into the canopy of pine trees. (Mackay and Mackay 2002)

Identification
The tentorial pit of this species is shallow. The middle and hind tibiae have a double row of bristles on the flexor surface, but each is with few hairs (fewer than 10 hairs in each row). There are a few scattered hairs on the other surfaces of the tibiae. The head of the major is longer than broad; the erect hairs on the mesosoma are short and of about equal length. The hairs on the head are longer and sparser than those on the mesosoma. (Mackay and Mackay 2002) This species is very similar to Formica obscuripes and may be synonymous with it (James Trager, pers. comm.).

Distribution
Canada; Alberta, British Columbia. United States: Washington to North Dakota, south through Nevada, New Mexico, Colorado and Kansas.

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

Habitat
In New Mexico (Mackay and Mackay 2002) - Grasslands, open forests, ponderosa pine forests, often found in riparian areas, popular-spruce forests, up to about 3000 meters elevation.

Biology
Nevada, Wheeler and Wheeler (1986) - Our 46 records are widely scattered throughout the state and represent 29 localities; 4,800-10,200 ft. (75% from 6,000-9,000 ft.). Five records were from the Cool Desert, 3 from the Pinyon-Juniper Biome, and 4 from the Coniferous Forest Biome. F. planipilis makes extensive use of thatch. Most of our nests were typical domes averaging 53 cm in diameter and 28 cm in height; a soil base 76 cm in diameter was recorded in two instances. Nest material: grass culms in pieces 5 cm long, juniper sprays, pine needles. Atypical nests: 1 under log lying on ground, 1 in log, 1 with thatch spread along a log 60 cm in diameter and 1.8 m long, I with thatch surrounding a crack in a rock.

Nest site selected in open areas devoid of cover. Nest begun at the base of some small plant (frequently sagebrush). Extensive use made of thatching. The finished nest consisting of a large mound of collected detritus. (Creighton, 1940)

Nomenclature

 *  planipilis. Formica rufa subsp. planipilis Creighton, 1940a: 9, fig. 1 (w.) U.S.A. Cole, 1956f: 259 (q.). Subspecies of integroides: Creighton, 1950a: 490. Raised to species: Cole, 1956f: 259.