Strumigenys bimarginata

Described from a single worker found under a piece of bark lying on the ground in a somewhat open, grassy spot in rather brushy cut-over woods. A dealated female belonging to this species was found about 15 cm. distant in some thin, vegetable debris. (Wesson and Wesson 1939)

Identification
Bolton (2000) - A member of the clypeata group. Only two species exhibit a bicarinate clypeal margin that is clearly visible in full-face view: bimarginata and Strumigenys filirrhina. Their different clypeal and cephalic pilosities distinguish the two species (development of the clypeus is discussed in the group treatment).

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



Biology
Brown (1964) - Two workers were taken in Andropogon sod (S. talpa came from the same sod sample) at Red Hills State Park, Illinois (Smith and Stannard leg.). It has previously been recorded from southern Illinois and southern Ohio.

Nomenclature

 *  bimarginata. Strumigenys (Cephaloxys) bimarginata Wesson, L.G. & Wesson, R.G., 1939: 95, pl. 3, fig. 2 (w.q.) U.S.A. Combination in S. (Trichoscapa): Smith, M.R., 1947f: 587; Creighton, 1950a: 304; in Smithistruma: Smith, M.R., 1951a: 827; Brown, 1953g: 62; in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 116. See also: Bolton, 2000: 103.

Worker
Length, 1.7 mm.

Head, exclusive of mandibles, 3.3 times the greatest width of the clypeus, 5.7 times the length of the exposed portion of the closed mandibles. Viewed anteriorly, the sides of the head anterior to the antennal insertions are straight, converging, their projections lying along the exterior border of the closed mandibles; clypeus rather narrow but evenly rounded, not acute, flattened dorsally; clypeus viewed from the side with its edge broadly and deeply grooved along the entire lateral and anterior borders, thus giving the clypeus the appearance of having 2 margins, a thin but narrow upper margin and a thicker broader lower margin which projects beyond the upper margin and is visible when the clypeus is viewed anteriorly. Mandibles rather slender and elongate, the exterior border straight basally, feebly convex apically; basal tooth stout, partially concealed by the clypeus when the mandibles are closed; succeeding toothless space very short; apical teeth comprising 7 or 8 large irregular teeth which decrease in size anteriorly to merge into the apical series of numerous small teeth. Antennal scapes broadly curved basally, not angulate, fourth funicular joint slightly longer than the first; terminal joint slightly longer than the remainder of the funiculus. Sides of head posterior to the antennal insertions suddenly expanding to a broadly circular border so that that portion of the head appears subglobose when viewed anteriorly. Posterior border narrowly and rather deeply excised. Thorax essentially as in Strumigenys clypeata; mesoepinotal suture distinct but not constricted; median longitudinal carina prominent, especially on the basal surface of the epinotum. Petiole, postpetiole and gaster as in S. clypeata.

Head, thorax and petiole densely reticulate-punctate, subopaque; vertex of head with 8 or 10 broken irregular longitudinal rugae. Mandibles, clypeus, sides of mesonotum, meso- and metapleura, dorsum of the postpetiole and gaster smooth and shining; basal ¼ of the first gastric segment with numerous coarse longitudinal striae.

Hairs on clypeus sparse, long, erect, more numerous on the edges, each hair being fairly straight at the base, curved and slightly enlarged on the apical 1/3, ¼ to ½ the width of the clypeus; hairs on vertex numerous, shorter, erect, clavate, curved anteriorly; antennal scapes with numerous hairs similar to those on the vertex but less clavate, curved toward the tips of the scapes; hairs on the thorax, petiole and postpetiole numerous, variable, those on the thoracic dorsum being rather long, slightly clavate, appressed, those on the petiole and postpetiole averaging longer, more erect and not clavate; gaster with sparse, long, slender, erect hairs. Spongiform processes as in S. clypeata and related species.

Color ferruginous; mandibles, antennae and legs slightly lighter; gaster darker.

Bolton (2000) - TL 2.2-2.4, HL 0.58-0.61, HW 0.34-0.36, CI 62-65, ML 0.10, MI 18-22, SL 0.27-0.29, SI 76-78, PW 0.23-0.25, AL 0.52-0.55 (2 measured). Clypeus in full-face view distinctly bimarginate around its entire anterior and lateral borders; the two margins concentric, the outer (lower) margin in this view projects out beyond the inner (upper) margin. In profile the upper and lower margins seen to be separated by a marked concave peripheral groove or gutter. Hairs on clypeal margins long and fine, slightly flattened, splayed or even weakly forked apically, may be weakly curved away from the midline or somewhat posteriorly. Clypeal dorsum with all hairs more or less erect, fairly short and curved, flattened, splayed or weakly forked apically, some may curve posteriorly; no long flagellate hairs on clypeus. Flagellate hairs absent from dorsolateral margins of head; without a flagellate pair posteriorly on the cephalic dorsum. Cephalic ground-pilosity narrowly spatulate, with flattened and splayed apices, curved anteriorly or weakly anteromedially. Flagellate hairs present at pronotal h umerus, on pronotal and mesonotal dorsa, on hind basitarsus and on first gastral tergite where thay are very long, mostly longer than the petiolar peduncle.

Type Material
Bolton (2000) - Syntype worker and queen, U. S. A.: Ohio, Adams County, Cedar Mills (Wesson & Wesson) [examined].