Leptomyrmex niger

Collected from rainforest. Nesting habits are unknown.

Identification
L. niger is one of three unicolorous black species found in New Guinea. Lacking dense pubescence, it is unlikely to be confused with the stout and hairy Leptomyrmex flavitarsus. Superficially, L. niger resembles Leptomyrmex melanoticus, but can be distinguished by its lack of a narrow and conical ‘neck’ and relatively stout head (CI 0.57–0.69 vs 0.53–0.56 in L. melanoticus). The elongate eyes (EL 0.38–0.47 mm) are generally larger than the small, round eyes of L. melanoticus (EL 0.36–0.39). Antennal scapes of L. niger are relatively shorter (SI 2.96–3.89) than those of L. melanoticus (SI 4.02–4.05). Additionally, the junction of the dorsal and declivitous faces of the propodeum is distinctly angular, unlike in L. melanoticus where the dorsal face gradually rounds into the declivitous face. (Lucky and Ward 2010)

Key to New Guinean Leptomyrmex Species

Distribution based on Regional Taxon Lists
Indo-Australian Region: New Guinea.

Castes
Queens have yet to be collected.

Nomenclature

 *  niger. Leptomyrmex niger Emery, 1900c: 333, pl. 8, figs. 3, 4 (w.) NEW GUINEA. Karavaiev, 1926d: 430 (m.). Senior synonym of lugubris: Lucky & Ward, 2010: 40. See also: Wheeler, W.M. 1934c: 109.
 * lugubris. Leptomyrmex lugubris Wheeler, W.M. 1934c: 110, fig. 14 (w.) NEW GUINEA. Junior synonym of niger: Lucky & Ward, 2010: 40.

Worker
Lucky and Ward (2010) – measurements (n = 11) HL 1.76–1.89, HW 1.01–1.25, MFC 0.18–0.33, IOD 0.55–0.62, SL 3.62–3.94, EL 0.38–0.47, WL 3.16–3.58, PW 0.90–1.00, DPW 0.31–0.39, HTL 3.25–4.45, HTWmin 0.09–0.14, HTWmax 0.16–0.23, CI 0.57–0.69, SI 2.96–3.89, OI 0.11–0.14, HTC 0.50–0.81.

Small and slender (HL 1.76–1.89; HW 1.01–1.25) with head, excluding mandibles, less than twice as long as broad (CI 0.57–0.69) and widest just posterior to eyes. Sides of head straight and subparallel, tapering anteriorly to slightly concave genae, rounded posterior to eyes, gently tapering to flat postocular margin. Approximately 20 teeth and denticles interspersed on masticatory margin of mandible. Anterior clypeal margin flat to slightly concave. Eyes positioned slightly posterior to midline of head, relatively large, oblong, hairless and reaching lateral margins of head. Antennae slender and slightly compressed. Scapes surpassing posterior margin of head by nearly 3/5 their length.

Pronotum with anterior portion dorsoventrally flattened, posterior portion domed. Propodeum with a longitudinal impression, dorsal face 1.5 times length of declivitous face, faces meeting at a distinct (not broad and rounded) angle. Dorsal face of propodeum concave in profile at anterior end. Petiole nearly twice as long as broad, node triangular in profile. Dorsal surface of node with longitudinal impression, anterior face of node much shorter and more rounded than flat posterior face, the two meeting at a rounded angle. Ventral surface flat to weakly concave.Gaster elongate-elliptical. Legs very slender, compressed.

Surface very finely shagreened and shining. Mandibles shining with a row of coarse punctures along margin. Pubescence yellow, mostly limited to head and gaster. Pilosity confined to clypeus, venter and gaster with irregular row of ~4 dark bristles on hind tibiae. Generally black throughout, but portions of mandibles, tarsi, joints and antennal funiculus pale yellow.

Male
Lucky and Ward (2010) – measurements (n = 2) HL 1.52–1.65, HW 1.06–1.10, SL 0.39–0.41, EL 0.63–0.68, HTL 4.80–5.14, CI 0.64–0.72, SI 0.35–0.39, SI2 1.00–1.24.

Type Material
Lucky and Ward (2010):

Syntypes, 2 workers, Papua New Guinea, "New Guinea" [German New Guinea] (Biró). One syntype here designated lectotype (CASENT0127396, top specimen).

L. lugubris Syntypes, 2 workers, Papua New Guinea, Morobe: Biolowat (Stevens)