Formica densiventris

Nests are usually found under stones, but may be found in logs and stumps, and under bark. These structures may be partially covered with thatching. Nests may be composed entirely of thatching.

Distribution
Alberta Canada and Western United States.

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

Habitat
In New Mexico (Mackay and Mackay 2002) - Prairies, including disturbed, weedy areas, to semiarid scrub up to pinyon-juniper, ponderosa pine-riparian, Douglas fir, and spruce-fir forests.

Biology
In New Mexico (Mackay and Mackay 2002): brood and reproductives were found in nests in June to August. A dealate female collected on 3 July 1986. Workers are very aggressive when the nest is disturbed. Foragers tend aphids. This is one of the most common Formica spp. in northern New Mexico. It enslaves other Formica spp., including Formica argentea, Formica fusca, and Formica subsericea.

Nevada, Wheeler and Wheeler (1986) - Our 24 records are from 16 localities, which are widely scattered throughout the state north of the Hot Desert; 5,500-10,000 ft. Five records are from the Pinyon-Juniper Biome, 6 from the Coniferous Forest Biome, and 1 is from the ecotone above it. Four nests were in and under rotten wood, 1 was under a stone, 1 was under a stone surmounted by thatch, and 1 was under a prostrate sagebrush trunk. When a populous nest was disturbed the workers moved rapidly and attacked promptly; the bite was annoying. As hosts we found F. argentea, F. fusca, Formica neorufibarbis, and Formica subpolita.

Nomenclature

 *  densiventris. Formica fusca var. densiventris Viereck, 1903: 74 (w.) U.S.A. Cole, 1954a: 90 (m.). Junior synonym of subaenescens: Wheeler, W.M. 1913f: 504. Revived from synonymy as subspecies of fusca: Brown, 1947: 7. Raised to species: Creighton, 1950a: 499. Senior synonym of spicata: Cole, 1954a: 89; Cole, 1955b: 50; of rasilis: Mackay, Lowrie, et al. 1988: 114.
 * rasilis. Formica microgyna var. rasilis Wheeler, W.M. 1903e: 648 (w.q.m.) U.S.A. Subspecies of microgyna: Wheeler, W.M. 1913f: 468. Raised to species: Creighton, 1950a: 506. Junior synonym of densiventris: Mackay, Lowrie, et al. 1988: 114.
 * spicata. Formica rasilis subsp. spicata Creighton, 1950a: 507 (w.q.m.) U.S.A. [First available use of Formica microgyna subsp. rasilis var. spicata Wheeler, W.M. 1913f: 469; unavailable name.] Material of the unavailable name pinetorum referred here by Creighton, 1950a: 507. Junior synonym of densiventris: Cole, 1954a: 89; Cole, 1955b: 50.