Tetraponera difficilis

Identification
Ward (2001) - Workers of this species can be distinguished from those of others in the nigra-group by the combination of intermediate eye size (REL2 0.44-0.48), sparse pilosity (CSC 2-4, MSC 0-5), and the structure of the mesopropodeal impression: open anteriorly, with a pit-shaped depression posteriorly. The shiny, puncticulate integument and relatively slender petiole are also characteristic. Workers show modest variation in size, shape of the petiole, amounts of standing pilosity, and color of the appendages. More striking is the variability of the appressed pubescence on the gaster. In most workers the appressed hairs occur in moderate to high density on the gaster, sufficient to dull the lustre of the underlying integument. But in some individuals from Borneo and the Philippines the hairs are short, sparse, and separated by more than their lengths, and the gaster is correspondingly shinier. Finally, while the legs are only moderately long in most workers (LHT/HL 0.67-0.77; LHT/HW 0.77-0.88), they are unusually long in one worker examined from Danum Valley, Sabah (leg. H. Okido) (LHT/HL 0.80, LHT/HW 0.90).

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia, Malaysia, Philippines, Singapore. Oriental Region: Thailand.

Nomenclature

 *  difficilis. Sima difficilis Emery, 1900d: 677 (w.) INDONESIA (Sumatra). Wheeler, W.M. 1919e: 144 (q.). Combination in Tetraponera: Wheeler, W.M. 1919e: 65. Senior synonym of dilatata, nitens, stipitum: Ward, 2001: 628.
 * stipitum. Sima stipitum Forel, 1912n: 54 (w.) SINGAPORE. Combination in S. (Tetraponera): Emery, 1921f: 27; in Tetraponera: Chapman & Capco, 1951: 82. Junior synonym of difficilis: Ward, 2001: 628.
 * nitens. Sima nitens Stitz, 1925: 117 (w.q.) PHILIPPINES. Combination in Tetraponera: Chapman & Capco, 1951: 81. Junior synonym of difficilis: Ward, 2001: 628.
 * dilatata. Sima (Tetraponera) dilatata Karavaiev, 1933c: 267, fig. 15 (w.) INDONESIA (Prinsen I.). Combination in Tetraponera: Chapman & Capco, 1951: 80. Junior synonym of difficilis: Ward, 2001: 628.

Worker
Ward (2001) - HW 0.82-0.99, HL 0.90-1.22, LHT 0.66-0.84, CI 0.81-0.90, FCI 0.11-0.15, REL 0.38-0.44, REL2 0.44-0.48, SI 0.55-0.62, SI3 1.15-1.32, FI 0.43-0.51, PLI 0.57-0.63, PWI 0.44-0.51, PDI 0.97-1.12, LHT/HW 0.77-0.90, CSC 2-4, MSC 2-5.

Medium-sized species; clypeus short, its anteromedial margin weakly convex and even with, or protruding only slightly beyond the level of, the anterolateral clypeal margin; frontal carinae moderately well separated, the distance between them exceeding basal scape width; eye relatively modest in size, scape notably longer than eye (SI3 > 1.14); pro femur relatively slender, FI usually <0.48 in all but largest workers; lateral pronotal margins present, blunt-edged; mesopropodeal impression consisting of two sections: anteriorly, an open transverse, strip of integument with varying density of longitudinal rugulae or carinulae; posteriorly, a pit-shaped depression defined by flanking lateral ridges that decline anteriorly, usually rather suddenly and at a point marked by a weak denticle, visible on the profile of the mesosoma; propodeum usually about as high as wide, and somewhat depressed below the level of the promesonotum; dorsal face of propodeum rounding gradually and continously into the declivitous face; petiole with short but well differentiated anterior peduncle and with relatively slender node (PL/HL 0.54-0.61); posteroventral petiolar teeth lacking; in profile petiole typically as illustrated, with the node rather broadly and evenly rounded, its anterior face only slightly steeper than its gently declining posterior face; petiole about twice as long as wide (see PWI values); postpetiole about as long as, or slightly longer than, wide; metabasitarsal sulcus prominent, occurring in a darkened patch of raised cuticle and occupying more than half the length of the basitarsus. Integument smooth and shiny, with scattered fine punctures, mostly ≤0.010 mm in diameter, and separated by several to many diameters, leaving conspicuous shiny interspaces, especially on the side of the mesosoma; lower malar area with coarser punctures and weak longitudinal rugulae. Standing pilosity scarce, present on gaster and apex of head, and on the following dorsal surfaces: posterior half of head (2-4, usually 2), pronotum (2-5), petiole (0-5), and postpetiole (0-5); with head in full-face view, standing hairs absent from sides of head, except for one or two near the mandibular insertions; short appressed pubescence scattered over body, generally somewhat inconspicuous; appressed hairs on abdominal tergite IV (first gastric tergite) varying considerably in density, from very dense (hairs overlapping extensively) to sparse (hairs separated by more than their lengths). Body black to dark brownish-black; appendages varying from dark brown to light yellowish-brown (antennae, protibia and tarsi usually the lightest in color).

Type Material
Ward (2001) - Syntypes, 2 workers, Benculen, Sumatra, Indonesia (E. Modigliani).