Strumigenys pilinasis

This forest species will nest under stones, in the soil cover, or in logs.

Identification
Bolton (2000) - A member of the clypeata group. Very closely related to Strumigenys laevinasis but the two usually with quite different clypeal pilosity; see under Strumigenys laevinasis. Despite this statement Brown (1953a, 1964) draws attention to samples from Illinois and North Carolina that appear intermediate between pilinasis and laevinasis. He states that these intermediates can be referred to one or the other of the accepted species but that their actual status remains indeterminate. All material that I have seen has been referable to either one or the other species.

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



Biology
Wesson and Wesson (1939) from their description of the synonymized S. medialis: A colony of about 30 workers and several dealate females taken from a long, decayed, hickory log covered with a tough layer of bark. The log, lying on the edge of some woods, extended from deep shade through a clump of bushes into broken sunlight. There were at least 11 species of ants present, including 5 species of Strumigenys. The S. medialis nest consisted of irregular cavities in the outer rotten portion of the log which appeared to be old galleries o beetle larvae. The colony was transferred to an artificial nest where, as did other species of Strumigenys we have had under observation, they fed on living springtails. In their hunting they were quite inactive, even more so than Strumigenys pulchella; the workers would remain in a crouching position, head close to the substratum, mandibles closed, antennae partially folded, for a great deal of the time. Occasionally some of the dealate females were observed hunting like the workers. Otherwise the hunting methods of this species resembled those of Strumigenys pergandei.

Brown (1964) - Algiers, Louisiana, nest at base of fig tree. Pickle’s Spring, Missouri, forest debris. Arkansas, forest debris. North Carolina, nesting in soil.

Nomenclature

 *  pilinasis. Strumigenys clypeata var. pilinasis Forel, 1901e: 339 (w.) U.S.A. Combination in S. (Cephaloxys): Emery, 1924d: 325; in S. (Trichoscapa): Smith, M.R., 1947f: 587; in Smithistruma: Smith, M.R., 1951a: 827; Brown, 1953g: 60; in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 126. Raised to species: Wesson, L.G. & Wesson, R.G., 1939: 109. Senior synonym of medialis: Smith, M.R. 1951a: 828; Brown, 1953g: 60; of brevisetosa: Brown, 1964a: 197. See also: Bolton, 2000: 106.
 * brevisetosa. Strumigenys (Cephaloxys) clypeata var. brevisetosa Smith, M.R. 1935: 215 (w.) U.S.A. Brown, 1953g: 60 (q.). Combination in S. (Trichoscapa): Smith, M.R., 1947f: 587; Creighton, 1950a: 304; in Smithistruma: Smith, M.R., 1951a: 827; Brown, 1953g: 59. Raised to species: Wesson, L.G. & Wesson, R.G., 1939: 108. Junior synonym of pilinasis: Brown, 1964a: 197. See also: Wilson, 1954: 485.
 * medialis. Strumigenys (Cephaloxys) medialis Wesson, L.G. & Wesson, R.G., 1939: 94, pl. 3, fig. 1 (w.q.) U.S.A. Junior synonym of pilinasis: Smith, M.R. 1951a: 828; Brown, 1953g: 60.

Worker
Bolton (2000) - TL 2.1-2.4, HL 0.60-0.63, HW 0.39-0.41, CI 63-68, ML 0.09-0.12, MI 15-19, SL 0.28-0.34, SI 68-83, PW 0.26-0.29, AL 0.58-0.64 (12 measured).

Teeth of principal dental row of mandible strong and conspicuous; either no diastema between basal lamella and basal tooth, or diastema minute and much shorter than length of basal tooth. Anterior clypeal margin evenly and quite narrowly rounded; line of lateral clypeal margins more or less following line of outer margins of fully closed mandibles. Clypeus in in profile with upper and lower margins distinct, the former almost directly above the latter and the two separated by an obvious groove. Dorsum of clypeus with dense curved narrowly spatulate ground-pilosity; in full-face view hairs close to midline directed anteriorly but those away from midline directed anterolaterally; in profile all hairs curved or arched anteriorly or anterolaterally. Hairs on lateral clypeal margins narrowly spatulate, much longer than those on dorsum, directed anterolaterally; some of the marginal hairs more or less straight, others feebly anteriorly curved. On the anterior clypeal margin hairs nearest the midpoint are often weakly curved away from the midline. Cephalic ground pilosity long and fine, filiform to extremely narrowly spatulate. Hairs on leading edge of scape fine, very narrowly spatulate. Vertex of head near occiptal margin with a transverse row of 4 much longer finer hairs that are usually flagellate (apparently easily lost by abrasion). Dorsolateral margin of head with 1-2 freely projecting flagellate hairs; always with one in apicoscrobal position, frequently with another anterior to it on the upper scrobe margin. Pronotal humerus with a flagellate hair; another pair present on pronotal dorsum and another on mesonotum. Flagellate hairs also occur on waist segments and first gastral tergite; at least one flagellate hair present on dorsal (outer) surface of hind tibia and of basitarsus.

Type Material
Bolton (2000) - Syntype workers, U.S.A. District of Columbia, Washington, bank of Potomac River (A. Forel) [not seen].