Strumigenys atropos

Identification
Bolton (2000) - In the Malaysian material the hairs fringing the lateral clypeal margins are subequal in size to those on the anterior margin. The species most closely related to atropos is Strumigenys nepalensis, which is also known to occur in Thailand and West Malaysia. Workers of the two separate as follows.

S. atropos: Antenna with 6 segments. Anterior clypeal margin broadly shallowly concave across its entire width. Hairs fringing anterior clypeal margin larger than those fringing lateral margins. Hairs on clypeal dorsum small, almost suborbicular in dorsal view. Dorsum of head in profile without a pair of standing hairs just in front of highest point of vertex. Pronotal dorsum completely smooth and shining. Mesonotum with a single pair of standing hairs. Elongate standing hairs on petiole node recurved, fine and almost flagellate, contrasting with the hairs on the first gastral tergite.

S. nepalensis: Antenna with 4 segments. Anterior clypeal margin transverse. Hairs fringing anterior clypeal margin smaller than those fringing lateral margins. Hairs on clypeal dorsum narrowly spatulate in dorsal view. Dorsum of head in profile with a pair of standing hairs just in front of highest point of vertex. Pronotal dorsum weakly punctate-shagreenate. Mesonotum with three pairs of standing hairs. Elongate standing hairs on petiole node simple, weakly curved, similar to the hairs on the first gastral tergite.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Malaysia. Oriental Region: Thailand.

Nomenclature

 *  atropos. Pyramica atropos Bolton, 2000: 457 (w.) THAILAND. Combination in Strumigenys: Baroni Urbani & De Andrade, 2007: 116

Worker
Holotype. TL 1.6, HL 0.44, HW 0.34, CI 77, ML 0.06, MI 14, SL 0.20, SI 59, PW 0.20, AL 0.44. With mandibles fully closed there is a minute gap between their inner margins just in front of the anterior clypeal margin. Basal dental row of 7 teeth, consisting of alternating slightly taller, more acute teeth and slightly shorter, blunted teeth. Anterior clypeal margin broad and broadly shallowly concave across its entire width. Projecting spoon-shaped hairs that fringe the clypeal margins largest on the anterior margin; minute, closely appressed and inconspicuous laterally. Small appressed hairs on clypeal dorsum broadly scale-like, almost suborbicular. In full-face view dorsolateral margin of head with a continuous row of anteriorly curved spoon-shaped hairs. Similar hairs present all over cephalic dorsum behind clypeus, and dorsum also with a transverse row of 4 elongate slender remiform standing hairs just in front of the occipital margin. These hairs contrast strongly with the otherwise spoon-shaped curved pilosity. Eye very small, of only 1-2 ommatidia in total. Entire dorsum of head behind clypeus finely reticulate-punctate. Dorsal alitrunk glassy smooth everywhere. Pronotal humeral hair elongate and stout, straight to weakly curved. Mesonotum with a single pair of similar but shorter standing hairs. Ground-pilosity of promesonotum of scattered spatulate to narrowly spoon-shaped hairs that are curved toward the midline. Side of alitrunk smooth and shining everywhere. Anterodorsal angle of petiole node in profile with a single pair of long slender back-curved standing hairs that taper to fine apical points. Standing hairs on dorsa of postpetiole and first gastral tergite stouter than the petiolar pair, straighter and tending to be blunted apically. Hairs on dorsal (outer) surfaces of middle and hind tibiae narrowly spatulate, curved toward the apex and closely applied to the surface. Petiole, postpetiole and gaster smooth, the last with basigastral costulae present. Discs of petiole and postpetiole in dorsal view broader than long, the latter completely surrounded by spongiform tissue.

Paratypes. TL 1.6, HL 0.43-0.45, HW 0.33-0.34, CI 76-77, ML 0.06-0.08, MI 14-17, SL 0.20-0.21, SI 59-62, PW 0.20, AL 0.42-0.44 (3 measured).

Type Material
Holotype worker, Thailand: Kaeng Krachan N. P., 17.xi.1985, no. 24 (Lobl & Burckhardt).

Paratypes. 1 worker with same data as holotype; 2 workers with same data hut 19.xi.1985, no. 26 (MHNG, ).