Leptothorax canadensis

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 concave, and meets the dorsum in an angle, the posterior face is convex and rounded. The dorsum and sides of the mesosoma, petiole and postpetiole are completely covered with punctate-granulose sculpture. There are numerous short (0.01mm), blunt-tipped hairs. (Mackay and Mackay 2002)

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

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

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."

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.

This species is a host for the slave-making species (Beibl et al., 2005; de la Mora et al., 2021).

Nomenclature

 *  canadensis. Leptothorax canadensis Provancher, 1887: 245 (w.q.m.) CANADA.
 * Wheeler, G.C. & Wheeler, J. 1955b: 21 (l.).
 * Combination in L. (Mychothorax): Ruzsky, 1904a: 288; Emery, 1924d: 261;
 * combination in L. (Leptothorax): Wheeler, G.C. & Wheeler, J. 1955b: 21.
 * Subspecies of acervorum: André, 1887: 295; Dalla Torre, 1893: 123; Wheeler, W.M. 1903c: 225; Wheeler, W.M. 1906b: 8; Wheeler, W.M. 1908f: 621; Wheeler, W.M. 1910g: 566; Forel, 1914c: 617; Wheeler, W.M. 1916m: 588; Wheeler, W.M. 1917a: 511; Wheeler, W.M. 1917e: 18; Emery, 1924d: 261; Cole, 1936a: 36; Wing, 1939: 162; Cole, 1942: 369; Wheeler, G.C. & Wheeler, E.W. 1944: 247; Buren, 1944a: 288; Smith, M.R. 1951a: 820.
 * Junior synonym of muscorum: Brown, 1955a: 47.
 * Status as species: Emery, 1895c: 318; Wheeler, W.M. in Viereck, 1903: 73; Creighton, 1950a: 274; Cole, 1953d: 27; Cole, 1954d: 240; Schar et al., 2018: 6.
 * Senior synonym of Leptothorax canadensis kincaidi: Schär et al., 2018: 6.
 * Senior synonym of Leptothorax canadensis obscurus: Schär et al., 2018: 6.
 * Senior synonym of Leptothorax muscorum septentrionalis: Schär et al., 2018: 6.
 * Senior synonym of Leptothorax muscorum sordidus: Schär et al., 2018: 6.
 * Senior synonym of Leptothorax canadensis yankee: Schär et al., 2018: 6.
 * Material of the unavailable name convivialis referred here by Creighton, 1950a: 276.
 * obscurus. Leptothorax canadensis subsp. obscurus Viereck, 1903: 72 (w.) U.S.A.
 * Junior synonym of yankee: Creighton, 1950a: 277.
 * Junior synonym of canadensis: Schar et al., 2018: 6.
 * 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.
 * Junior synonym of canadensis: Schar et al., 2018: 6.
 * 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.
 * Junior synonym of canadensis: Schar et al., 2018: 6.
 * 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.
 * Junior synonym of canadensis: Schar et al., 2018: 6.
 * kincaidi. Leptothorax yankee var. kincaidi Pergande, 1900: 520 (w.q.) U.S.A.
 * Junior synonym of muscorum: Brown, 1955a: 47.
 * Junior synonym of canadensis: Schar et al., 2018: 6.

Taxonomic Notes
Schar et al. (2018): Leptothorax canadensis Provancher, 1887 stat. nov. was considered a subspecies of ''Le. acervorum by Andre (1887), a full species by Emery (1895) and a junior synonym of Le. muscorum'' by Brown (1955). Our findings support the hypothesis of ''Le. canadensis representing a full species, and it is therefore removed from synonymy with Le. muscorum''. The following junior synonyms should be moved from ''Le. muscorum to Le. canadensis: Leptothorax canadensis obscurus Viereck, 1903, Leptothorax canadensis yankee Emery, 1895, Leptothorax muscorum septentrionalis Wheeler, 1917, Leptothorax muscorum sordidus Wheeler, 1903, and Leptothorax yankee kincaidi'' Pergande, 1900. However, the North American members of the genus Leptothorax are a difficult species complex whose taxonomy remains unresolved.

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