Strumigenys pilinasis

This forest species will nest under stones, in the soil cover, or in logs. An inhabitant of the soil cover and upper soil layers, often utilizing such shelters as are afforded by small chips and twigs lying on, or wood partly buried in, the soil (Brown 1953).

Strumigenys pilinasis is a common eastern North American litter-dwelling ant that has been collected in contiguous states between Connecticut and Florida and west to eastern Texas and Oklahoma. Of 9,013 databased records of Nearctic Strumigenys, in a database maintained by the Booher (2019), S. pilinasis ranked fourth with 646 specimen records. In two studies of Strumigenys found nesting in empty fallen nuts in forests near Washington D.C. (near lectotype collection), S. pilinasis was by far the most common species (Duffield & Alpert 2011, Booher et al. 2017).

Identification
Strumigenys pilinasis is one of the most easily diagnosed Nearctic Strumigenys and can be distinguished from all other North American species by the unique clypeal pilosity. Strumigenys pilinasis is the only species with simple coarse hairs extending from the lateral border of clypeus that are strongly J-shaped. These hairs, although variable, have several to many inclined anteriorly at their bases, strongly curved along their mid-length, and directed posteriorly at their apices. These hairs are simple and coarse to extremely narrowly expanded, always more cylindrical than spatulate along their entire length (Booher, 2019).

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

Biology
Wesson and Wesson (1939) from their description of the synonymized S. manni: 32 workers obtained by sifting dirt and humus in a small cedar grove (western Pike County, Ohio) located on the gently sloping base of a hill. Mingled with the cedars were a few small oaks and an occasional maple sapling. The soil was a black clay from 5 to 8 cm deep above the limestone bed rock. The ground was shaded by cedar and small oak trees and was covered with a rather thick, loose humus abounding with springtails.

Nomenclature

 *  pilinasis. Strumigenys clypeata var. pilinasis Forel, 1901e: 339 (w.) U.S.A. (District of Columbia).
 * Combination in S. (Cephaloxys): Emery, 1924d: 325.
 * Combination in S. (Trichoscapa): Smith, M.R. 1947f: 587.
 * Combination in Smithistruma (Smithistruma): Smith, M.R. 1951a: 828; Brown, 1953g: 60.
 * Combination in Pyramica: Bolton, 1999: 1673.
 * Combination in Strumigenys: Baroni Urbani & De Andrade, 2007: 126.
 * Subspecies of clypeata: Wheeler, W.M. 1908a: 148 (in key); Wheeler, W.M. 1910g: 568; Emery, 1924d: 325; Smith, M.R. 1931a: 19; Smith, M.R. 1931c: 700 (redescription).
 * Status as species: Wesson, L.G. & Wesson, R.G. 1939: 109 (in key); Smith, M.R. 1947f: 587; Creighton, 1950a: 307; Smith, M.R. 1951a: 828; Brown, 1953g: 60 (redescription); Smith, M.R. 1958c: 136; Brown, 1964a: 197; Smith, D.R. 1979: 1407; DuBois & LaBerge, 1988: 141; Mackay & Anderson, 1993: 388; Bolton, 1995b: 384; Bolton, 2000: 106 (redescription); Deyrup, 2003: 47; Coovert, 2005: 97; MacGown & Forster, 2005: 68; MacGown, et al. 2005: 288; Deyrup, 2017: 136; Booher, 2019: 403.
 * Senior synonym of manni: Booher, 2019: 403.
 * Senior synonym of ohioensis: Booher, 2019: 403.
 * manni. Strumigenys (Cephaloxys) manni Wesson, L.G. & Wesson, R.G. 1939: 97, pl. 3, fig. 3 (w.) U.S.A. (Ohio).
 * Combination in S. (Trichoscapa): Smith, M.R. 1947f: 587.
 * Status as species: Creighton, 1950a: 306.
 * Junior synonym of ohioensis: Smith, M.R. 1951a: 828; Brown, 1953g: 87; Bolton, 2000: 109.
 * Junior synonym of pilinasis: Booher, 2019: 403.
 * ohioensis. Strumigenys ohioensis Kennedy & Schramm, 1933: 98, figs. 1, 2 (w.) U.S.A. (Ohio).
 * Brown, 1953g: 87 (q.m.).
 * Combination in S. (Cephaloxys): Wesson, L.G. & Wesson, R.G., 1939: 108.
 * Combination in S. (Trichoscapa): Smith, M.R. 1947f: 587.
 * Combination in Smithistruma (Smithistruma): Smith, M.R. 1951a: 828; Brown, 1953g: 87.
 * Combination in Pyramica: Bolton, 1999: 1673.
 * Combination in Strumigenys: Baroni Urbani & De Andrade, 2007: 125.
 * Status as species: Wesson, L.G. & Wesson, R.G. 1939: 109 (in key); Smith, M.R. 1947f: 587; Creighton, 1950a: 308; Smith, M.R. 1951a: 828; Brown, 1953g: 87 (redescription); Smith, M.R. 1958c: 136; Brown, 1964a: 196; Smith, D.R. 1979: 1407; DuBois & LaBerge, 1988: 141; Deyrup, et al. 1989: 98; Mackay & Anderson, 1993: 388; Bolton, 1995b: 385; Bolton, 2000: 109 (redescription); Deyrup, 2003: 47; Coovert, 2005: 95; MacGown & Forster, 2005: 68; MacGown, et al. 2005: 287; Deyrup, 2017: 135.
 * Junior synonym of pilinasis: Booher, 2019: 403.

Taxonomic Notes
Booher (2019): Kennedy and Schramm provided an inaccurate illustration of S. ohioensis. They described and illustrated hairs projecting from the lateral borders of the clypeus that were relatively short and directed anteriorly, when in fact these hairs are variable and several to many are strongly J-shaped—being inclined anteriorly at their bases, strongly curved along their mid-length, and point posteriorly at their apices. In 1939, Wesson & Wesson described S. manni (new junior synonym S. pilinasis) and it was the first description to accurately describe the key and unique distinguishing character of this species, the J-shaped clypeal pilosity. However, Wesson & Wesson did not realize S. manni was synonymous with S. ohioensis because they did not examine the type specimens of S. ohioensis and only relied on the original description and illustrative work (Kennedy and Schramm 1933). Brown (1953) provided greater detail and a full accounting of this set of events when he listed S. manni as a junior synonym of S. ohioensis, but Brown did not examine the S. pilinasis holotype (Brown 1953).