Leptothorax muscorum

Wheeler and Wheeler (1986) - This small ant "is one of the very few truly boreal-alpine members of its family. It is known from a very wide area in the northern Palearctic" (Brown, 1955:43). "Of all ants occurring in North America, Leptothorax muscorum is the species best able to survive in extreme Arctic-alpine conditions. Throughout boreal and alpine North America within the limits of the timbered areas, L. muscorum is found in company with Camponotus herculeanus (Linnaeus) and Formica neorufibarbis Emery, the two dominant ants of the region" (Brown, 1955:47). Brown (p. 49) reported L. muscorum from an island at the mouth of the Mackenzie River, lat. 69°32'N, long. 133°47'W, which "seems to be the northernmost record for ants in the Western Hemisphere."

Identification
This is apparently a species complex and is in need of clarification. 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. The anterior face of the petiole is weakly con-cave, and meets the dorsum in an angle, the posterior face is convex and rounded. The dorsum and sides of the mesosoma, petiole and post-petiole are completely covered with punctate-granulose sculpture. There are numerous short (0.01mm), blunt-tipped hairs. (Mackay and Mackay 2002)

Pale brown to brown with antennal clubs and head often slightly darker. Propodeal spines short but distinct. General appearance more slender than Leptothorax acervorum. Head striate, alitrunk rugose and gaster smooth. Appendage hairs few and adpressed. Clypeus in some Scandinavian series have a distinct median concavity as described for Leptothorax gredleri Mayr (Buschinger, 1966) but they are not otherwise different from the typical species. Length: 2.4-3.2 mm (Collingwood 1979).

Distribution
Appenines to Central Scandinavia and Pyrenees to Urals, not found in British Isles but common in continental Europe (Collingwood 1979). Northern North America.

Distribution based on Regional Taxon Lists
Nearctic Region: Canada, United States. Neotropical Region: Mexico. Palaearctic Region: Andorra, Armenia, Austria, Belarus, Belgium, Bulgaria, China, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Georgia, Germany, Greece, Hungary, Iberian Peninsula, Kyrgyzstan, Latvia, Liechtenstein, Lithuania, Luxembourg, Mongolia, Montenegro, Netherlands, Norway, Poland, Republic of Moldova, Romania, Russian Federation, Slovakia, Slovenia, Spain, Sweden, Switzerland, Ukraine.

Biology
This species is similar to Leptothorax acervorum but is smaller and more slender. In Scandinavia, it is restricted to sheltered valleys in woodland areas where it nests in stony banks, tree stumps or under bark. Its habits are similar to those of L. acervorum with small colonies having one or occasionally two queens. Males and alate queens are found in July and August.

Colonies of this species are found in dead Beargrass stems in Montana.

Colorado - Gregg (1963) reported this ant in Colorado from dry tundra and a variety of forest types; 5,345-12,000 ft.

New Mexico - This is one of the most common Leptothorax spp. in northern New Mexico. It nests in rotten logs (usually ponderosa pine) throughout the area. Logs may range from 15 cm to 1 m in diameter. Nests may also be located below stones. Brood and reproductives were found in the nests in July and August and nests may contain more than one queen. It shares nests with Myrmica fracticornis, Myrmica emeryana (=Myrmica latifrons) and Tapinoma sessile. (Mackay and Mackay 2002)

Nevada, Wheeler and Wheeler (1986) - We have 25 records from 18 localities 6,400-11,000 ft. Four records were in the Alpine Biome, 14 were in the Coniferous Forest. In the Alpine 1 nest was under a stone and 1 in dead wood; in the Coniferous Forest 7 nests were in and under rotten wood and 2 were in and under loose bark on dead trunks.

Nomenclature

 *  muscorum. Myrmica muscorum Nylander, 1846b: 1054 (w.q.m.) FINLAND. Combination in Leptothorax: Mayr, 1855: 439; in L. (Mychothorax): Forel, 1915d: 26. Subspecies of acervorum: Forel, 1874: 84. Status as species: André, 1883a: 294; Ruzsky, 1905b: 616. Senior synonym of canadensis, kincaidi, septentrionalis, yankee (and its junior synonyms obscurus, sordidus): Brown, 1955a: 47; of betulae, fagi, flavescens: Radchenko, 1995a: 25. Current subspecies: nominal plus uvicensis. See also: Buschinger, 1966b: 165; Baroni Urbani, 1971c: 99; Kutter, 1977c: 130; Collingwood, 1979: 72; Smith, D.R. 1979: 1397; Loiselle, Francoeur, et al. 1990: 323; Kupyanskaya, 1990: 139; Atanassov & Dlussky, 1992: 132; Radchenko, 2007: 31.
 * flavescens. Leptothorax muscorum var. flavescens Ruzsky, 1896: 72 (w.) RUSSIA. [First available use of Leptothorax acervorum subsp. muscorum var. flavescens Ruzsky, 1895: 26; unavailable name.] Subspecies of muscorum: Ruzsky, 1905b: 621. Junior synonym of muscorum: Radchenko, 1995a: 25.
 * canadensis. Leptothorax canadensis Provancher, 1887: 245 (w.q.m.) CANADA. Wheeler, G.C. & Wheeler, J. 1955b: 21 (l.). Combination in L. (Mychothorax): Emery, 1924d: 261; in L. (Leptothorax): Wheeler, G.C. & Wheeler, J. 1955b: 21. Subspecies of acervorum: André, 1887: 295; Wheeler, W.M. 1903c: 225. Status as species: Emery, 1895c: 318; Creighton, 1950a: 274. Material of the unavailable name convivialis referred here by Creighton, 1950a: 276. Junior synonym of muscorum: Brown, 1955a: 47.
 * obscurus. Leptothorax canadensis subsp. obscurus Viereck, 1903: 72 (w.) U.S.A. Junior synonym of yankee: Creighton, 1950a: 277.
 * yankee. Leptothorax (Leptothorax) canadensis var. yankee Emery, 1895c: 319 (w.q.) U.S.A. Wheeler, W.M. 1917a: 513 (m.); Wheeler, G.C. & Wheeler, J. 1955b: 21 (l.). Subspecies of canadensis and senior synonym of obscurus, sordidus: Creighton, 1950a: 277. Junior synonym of muscorum: Brown, 1955a: 47.
 * betulae. Leptothorax muscorum var. betulae Ruzsky, 1916: 6 (w.) RUSSIA. Subspecies of muscorum: Ruzsky, 1936: 94. Junior synonym of muscorum: Radchenko, 1995a: 25.
 * fagi. Leptothorax (Mychothorax) muscorum var. fagi Ruzsky, 1905b: 619, fig. 151 (w.) CAUCASUS. Junior synonym of muscorum: Radchenko, 1995a: 25.
 * septentrionalis. Leptothorax (Mychothorax) muscorum var. septentrionalis Wheeler, W.M. 1917a: 511 (w.q.m.) CANADA. Material of the unavailable name calderoni referred here by Creighton, 1950a: 276. Junior synonym of muscorum: Brown, 1955a: 47.
 * sordidus. Leptothorax muscorum var. sordidus Wheeler, W.M. 1903c: 224, pl. 12, fig. 2 (w.) U.S.A. Junior synonym of yankee: Creighton, 1950a: 277.
 * kincaidi. Leptothorax yankee var. kincaidi Pergande, 1900: 520 (w.q.) U.S.A. Junior synonym of muscorum: Brown, 1955a: 47.