Lasius americanus

This North American species is commonly collected and widespread. They are primarily found in forest habitats but will occasionally occur in bogs and other wetlands. Nests are in soil, in and under rotten logs and stumps, and sometimes in deep leaf litter. (Ellison et al., 2012). This species has only recently (Schär et al. 2018) been recognized as distinct and separate from the morphologically similar Paleoarctic Lasius alienus. North American studies that refer to L. alienus, provided the authors correctly identified this ant, are records of L. americanus.

Identification
Mackay and Mackay (2002) - This is a small, dark brown or black species with relatively large eyes (12-14 ommatidia in maximum diameter). The scape has few (less than 5) or no erect hairs (except at apex). The penultimate tooth is about the same size as the adjacent teeth (other 2 basal teeth).

Ellison et al., (2012) - In New England, the large-eyed Lasius americanus can be confused with either of the other three species in the niger group: Lasius pallitarsis, Lasius neoniger, or Lasius niger. The key feature is that L. americanus lacks erect hairs on its scape and hind tibiae, and is more common in forested habitats. The other three species all have erect hairs on their scapes and hind tibiae, and are more common in open habitats.

Distribution
This North American species is found from southern British Columbia west to Nova Scotia, south to northern Florida and in the mountains of the southwestern United States and Mexico (Ellison et al., 2012).

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

Biology
Wilson (1955) - Over its entire range, this species shows a strong predilection for well shaded woodland, where it nests in rotting logs and stumps and under stones. Among the hundreds of colonies I have encountered in the field in the eastern United States, nearly all conformed to this ecological character. It may happen, however, that at high elevations or at the northern periphery of its range, the species occasionally nests in open situations. At the summit of Grandfather Mountain in North Carolina, for instance, I found a small but vigorous population living under stones in an open blueberry-and-heath "bald". The elevation was 5800 feet, higher by 700 feet than any other collection of the genus made in the course of several field trips in the southern Appalachians.

This species is replaced in nearly every available habitat except woodland by the equally successful and abundant members of the Lasius neoniger complex. Lasius pallitarsis occupies the same types of nesting sites as americanus and probably limits its northward spread. In general, one gains the impression that americanus has been squeezed into relatively narrow ecological ranges by its congeneric competitors, but is nevertheless eminently successful within those ranges.

Records of nuptial flights in this species are too sparse to allow a rigorous comparison with other species, with records ranging from May 30 (Decatur Co., Ga.) to December 4 (Alachua Co., Fla.). Both of these are very exceptional dates, however; the majority of the other records fall in August.

New England
Ellison et al. (2012) - This omnivorous species collects elaiosomes from seeds, live insects and carcasses of dead ones, and tends a wide variety of aphids, scales, and treehoppers, and coccids that feed on plant roots. The colonies can be very large and have many queens, but individual queens disperse and found colonies independently.

Association with Other Insects
This species is a host for the temporary parastites, and.

Nomenclature

 *  americanus. Lasius niger var. americanus Emery, 1893i: 639 (w.q.m.) U.S.A.
 * Wheeler, G.C. & Wheeler, J. 1953c: 147 (l.).
 * As unavailable (infrasubspecific) name: Wheeler, W.M. 1916k: 172; Wheeler, W.M. 1917a: 525; Wheeler, W.M. 1917i: 463; Emery, 1925b: 230; Essig, 1926: 866; Smith, M.R. 1930a: 5; Menozzi, 1932b: 311; Smith, M.R. 1951a: 850.
 * Subspecies of niger: Forel, 1900e: 285; Wheeler, W.M. 1904e: 305; Wheeler, W.M. 1905f: 393; Wheeler, W.M. 1906b: 12; Wheeler, W.M. 1906d: 343; Wheeler, W.M. 1908f: 623; Wheeler, W.M. 1910g: 569; Santschi, 1911d: 7; Wheeler, W.M. 1913c: 116; Wheeler, W.M. 1916m: 592; Cole, 1936a: 37; Dennis, 1938: 295; Wing, 1939: 164; Cole, 1942: 374; Buren, 1944a: 296; Wheeler, G.C. & Wheeler, E.W. 1944: 253.
 * Subspecies of alienus: Creighton, 1950a: 419.
 * Junior synonym of alienus: Wilson, 1955a: 77; Smith, D.R. 1979: 1435.
 * Status as species: Gregg, E.V. 1945: 530; Schar et al., 2018: 6.

Taxonomic Notes
Schar et al. (2018) - Lasius americanus Emery, 1893 was originally described as a subspecies of Lasius niger, and was then raised to species in 1945 by Gregg. Creighton (1950) treated it as a subspecies of Lasius alienus, and then Wilson (1955) finally placed it in synonymy with Lasius alienus. Our results support the species-level status of this taxon as suggested by Gregg (1945). Therefore Lasius americanus is removed from synonymy with Lasius alienus and treated as a full species.