Strumigenys abdita

Collected from litter and under a stone S. abdita has been found in forest habitats. It has also been sampled from a lawn.

Identification
Bolton (2000) - A member of the Strumigenys pulchella-group. The main pilosity of this species appears to be easily lost by abrasion. Very few of the specimens examined exhibited the full complement of long hairs, but the dense and very striking pilosity of the dorsal clypeus is always distinct and obvious.

Four species in this group (abdita, Strumigenys creightoni, Strumigenys deyrupi, Strumigenys metazytes) do not have hairs on the anterior or lateral clypeal margins that are recurved or reflexed. Of these creightoni lacks erect hairs on the vertex close to the occipital margin, lacks an apicoscrobal hair, lacks a fine projecting hair at the pronotal humerus, and lacks standing pilosity on the mesonotum. In the other three species filiform or flagellate hairs are present at all these locations.

P. deyrupi separates from both abdita and metazytes as its main pilosity is entirely of long fine flagellate hairs. These occur as a pair on the vertex close to the occipital margin, a pair on the pronotal dorsum (as well as at the humeri), another pair on the mesonotum, and in numbers on the waist segments and especially the first gastral tergite. In both abdita and metazytes the hairs in many or all of these positions are stouter, simple and stiffly filiform, and at most evenly shallowly curved.

Of the last two species abdita is generally larger and its mandibles are usually longer (HL 0.53-0.60, HW 0.40-0.43, MI 17-22) than in metazytes (HL 0.51-0.52, HW 0.36-0.38, MI 16-17). Also, in abdita the anterior clypeal margin is very wide and has abruptly rounded anterolateral angles. The clypeal dorsum has broadly spatulate to spoon-shaped ground-pilosity that is very dense and conspicuous, and is very similar in shape and size to the hairs that fringe the lateral margins. Standing pilosity on the first gastral tergite is usually restricted to an apical and a basal transverse row, though some samples are known which have intermediate hairs present. By comparison metazytes has a short but very shallowly convex anterior clypeal margin that curves evenly into the lateral margins through widely rounded anterolateral angles. Its clypeal dorsum has minute inconspicuous spatulate ground-pilosity that is very much smaller than the large hairs that fringe the lateral margins. Pilosity on its first gastral tergite is more or less evenly distributed over the sclerite.

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



Biology
Wesson and Wesson (1939) - Described from 3 workers found under a board and pieces of slate in a shaded spot in a backyard in Jackson. We did not succeed in locating the colony. It may be noted that of the 4 species of Strumigenys (Strumigenys pergandei, Strumigenys rostrata, Strumigenys reflexa, abdita) found in this yard, 2 were undescribed.

Nomenclature

 *  abdita. Strumigenys (Cephaloxys) abdita Wesson, L.G. & Wesson, R.G., 1939: 106, pl. 3, fig. 6 (w.) U.S.A. Brown, 1953g: 89 (q.); Brown, 1964a: 189 (m.). Combination in S. (Trichoscapa): Smith, M.R., 1947f: 587; Creighton, 1950a: 304; in Smithistruma: Smith, M.R., 1951a: 827; Brown, 1953g: 89; in Pyramica: Bolton, 1999: 1672; in Strumigenys: Baroni Urbani & De Andrade, 2007: 110. See also: Bolton, 2000: 118.

Worker
Length, 2 mm.

Head, exclusive of mandibles, 1.3 times as long as the greatest width across the occipital lobes, 2.4 times as long as the greatest width of the clypeus; sides of anterior portion of head very slightly convergent; clypeus short and broad, the anterior border strongly flattened or truncate but not so as to make the head appear sharply rectangular mandibles rather long and slender, compressed dorso-ventrally, 1/4 - 1/5 the length of the head alone, the internal border nearly straight, the external border straight on the basal half, gently convex on the apical half; mandibles with a pair of large basal teeth partially concealed by the clyeus when the mandibles are closed basal teeth followed by a toothless space 1/3 the length of the portion of the mandibles anterior to them; terminal teeth comprising a compact row of 4 or 5 pair of large acute teeth, the second largest, the rest decreasing somewhat in length anteriorly, meeting and merging with little interruption into the apical series of a number of small teeth on the defleeted tip of the mandibles; antennal scapes slightly angulate basally; first joint as long as the fourth; terminal joint 1 1/4 times as long as the rest of the funiculus. Humeri prominent, broadly angulate; median dorsal carina of thorax obsolescent; prominent lateral carinae present on base of epinotum terminating in the epinotal spines; epinotal spines somewhat longer than broad at the base, acute, flattened; infraspinal lamellae moderately wide dorsally, each suddenly expanding ventrally into a wide, rounded plate; mesoepinotal suture distinct, slightly constricted. Node of petiole in profile rather strongly convex above.

Head, thorax and petiole reticulate-punctate, subopaque, the sculpture on the clypeus decidedly finer than on the rest of the head; frontal area, sides of the mesonotum, meso- and metapleura, dorsum of the postpetiole and gaster smooth and shining, first gastric segment with numerous coarse longitudinal striae on the basal 1/3.

Hairs on the clypeus numerous, moderately long, somewhat irregular, erect, the tips spatulate and curved horizontally, numbering about 30 on the dorsal surface, the border with 10 or 12 .similar hairs curved anteriorly, the whole effect giving the clypeus a woolly appearance when viewed under low magnification. Pilosity of the rest of the head sparser, more curved and narrowly squamose; across the posterior border of the head is a transverse row of 4 evenly spaced, very long, thin, erect hairs; although 1 or 2 of these is sometimes missing, the position of the others is not altered. Antennal scapes with 5 or 6 irregular, moderately long, erect, narrow, squamose hairs on the external border, 4 or 5 similar but much shorter hairs on the dorsal surfaces. Thorax with sparse, moderately long, clavate, subappressed hairs and 1 or 2 much longer erect, thin hairs confined principally to the dorsum of the mesonotum. Node of petiole with numerous rather short, curved, blunt or clavate hairs. Postpetiole and gaster with very few long, slender, nearly straight hairs.

Color ferruginous; gaster darker.

Bolton (2000) - TL 2.1-2.3, HL 0.53-0.60, HW 0.40-0.43, CI 69-75, ML 0.10-0.11, MI 17-22, SL 0.30-0.34, SI 73-80, PW 0.26-0.28, AL 0.58-0.64 (10 measured).

Eye with 4-7 ommatidia in total. Ground-pilosity of clypeus dense and curved, of large broadly spatulate to spoon-shaped hairs that are very conspicuous over the entire surface; those located mid-dorsally are just as obvious as those that fringe the lateral margins. Ground-pilosity spatulate and dense on cephalic dorsum behind clypeus. Behind highest point of vertex cephalic dorsum with 1 (sometimes 2) pairs of erect fine hairs. Apicoscrobal hair usually present and filiform (but 2 samples known where this hair appears naturally absent). Pronotal humeral hair long and fine, filiform to subflagellate. Mesonotum with a single pair of erect fine hairs. Dorsal alitrunk also with 2-4 pairs of shorter spatulate hairs that are suberect to erect. Hairs on first gastral tergite usually restricted to an apical transverse row and another row basally; the sclerite between these rows frequently hairless. Middle and hind basitarsi with 1-2 fine flagellate hairs projecting from their dorsal (outer) surfaces. Basigastral costulae extending about one-quarter the length of the tergite.

Type Material
Bolton (2000) - Syntype workers, U.S .A.: Ohio, Jackson (Wesson & Wesson) [examined].