Leptothorax crassipilis

These ants nest in the soil, under stones or rarely in logs and stumps, in sandy loam to rocky loam soils. Brood and reproductives were found in nests from June to August, flights occurred in August. Most nest females are found simply under the stone, one gyne was at a depth of about 10-cm in the soil. This species may be polygynous, as one nest contained 2 dealate females. Colonies were found together with Myrmica hamulata, Camponotus vicinus, Formica lasioides and Formica occulta. (Mackay and Mackay 2002)

Identification
The clypeus of the worker is depressed in the middle and is without a medial carina, although several lateral carinae are present. The propodeal spines are well developed, and thickened at the bases. The anterior face of the petiole meets the dorsum in an angle, the posterior face is convex and rounded. The dorsum of the postpetiole is completely covered with punctate-granulose sculpture. The mesosoma has heavy and dense sculpture. There are numerous long (most over 0.1 mm), pointed (occasionally blunt) tipped hairs. (Mackay and Mackay 2002)

Distribution
United States: Wyoming south to New Mexico, west to Nevada and Arizona. South into Mexico.

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

Habitat
Oak woodland, deciduous forests, ponderosa pine-riparian, Chihuahua pine, Douglas fir, spruce and fir forests, grasslands, subalpine fir, moist, shaded slopes as well as grassy, level, riparian areas. (Mackay and Mackay 2002)

Nomenclature

 *  crassipilis. Leptothorax (Mychothorax) acervorum subsp. crassipilis Wheeler, W.M. 1917a: 513 (w.q.m.) U.S.A. Raised to species: Creighton, 1950a: 278. See also: Loiselle, Francoeur, Fischer & Buschinger, 1990: 329.