Leptothorax muscorum

Identification
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: Alberta, Canada, Canada, United States. Neotropical Region: Mexico. Palaearctic Region: Andorra, Armenia, Austria, Belgium, Bulgaria, China, Croatia, Czech Republic, Denmark, Finland, France, Georgia, Germany, Greece, Hungary, Iberian Peninsula, Kyrgyzstan, Mongolia, Montenegro, Poland, Russian Federation, Slovenia, Spain, Sweden, 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.

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.

Additional References

 * [[Media:Brown 1955a.pdf|Brown, W. L., Jr. 1955a. The ant Leptothorax muscorum (Nylander) in North America. Entomol. News 66: 43-50 PDF]]