Leptomyrmex fragilis

Leptomyrmex fragilis has been recorded in rainforest, including lowland secondary and primary rainforest, montane rainforest and native gardens. Nests occur in the soil and in logs.

Identification
L. fragilis is the most commonly encountered Leptomyrmex species in New Guinea. Distinctively slender (HW 0.94–1.05 mm; PW 0.85–0.96 mm; DPW 0.27–0.33 mm), yellow and virtually hairless, it is unlikely to be confused with the one other pale species found in New Guinea, Leptomyrmex puberulus, which is stout and hairy, notably on the pronotum, head and eyes. Closely related to L. fragilis is the entirely black Leptomyrmex melanoticus, which may be a melanic form of L. fragilis. Although no intermediate color forms are currently known, future collections may reveal these sister species to be mere color variants within a single species. (Lucky and Ward 2010)

Key to New Guinean Leptomyrmex Species

Distribution based on Regional Taxon Lists
Indo-Australian Region: Indonesia, Papua New Guinea, Philippines.

Nomenclature

 *  fragilis. Formica fragilis Smith, F. 1859a: 136 (w.) INDONESIA (Aru I.). Emery, 1897d: 571 (m.); Stitz, 1912: 507 (m.); Lucvky & Ward, 2010: 36 (ergatoid q.). Combination in Leptomyrmex: Emery, 1897d: 571. Senior synonym of gracillimus: Baroni Urbani & Wilson, 1987: 2; of femoratus, maculatus, wheeleri: Lucky & Ward, 2010: 34. See also: Wheeler, W.M. 1934c: 113.
 * femorata. Leptomyrmex fragilis var. femorata Santschi, 1932b: 17, fig. 3 (w.) NEW GUINEA. Subspecies of fragilis: Wheeler, W.M. 1934c: 113. Junior synonym of fragilis: Lucky & Ward, 2010: 34.
 * gracillimus. Leptomyrmex gracillimus Wheeler, W.M. 1934c: 115, fig. 16 (w.) NEW GUINEA. Junior synonym of fragilis: Baroni Urbani & Wilson, 1987: 2.
 * maculata. Leptomyrmex fragilis var. maculata Stitz, 1938: 108 (w.) NEW GUINEA. Junior synonym of fragilis: Lucky & Ward, 2010: 34.
 * wheeleri. Leptomyrmex wheeleri Donisthorpe, 1948d: 600 (w.m.) NEW GUINEA. Junior synonym of fragilis: Lucky & Ward, 2010: 34.

Worker
Lucky and Ward (2010) – measurements (n = 10) HL 1.74–1.98, HW 0.94–1.05, MFC 0.17–0.21, IOD 0.53–0.64, SL 3.96–4.61, EL 0.34–0.40, WL 3.21–4.04, PW 0.85–0.96, DPW 0.27–0.33, HTL 4.41–5.02, HTWmin 0.11–0.15, HTWmax 0.16–0.21, CI 0.51–0.58, SI 3.92–4.73, OI 0.12–0.16, HTC 0.55–0.74.

Small, slender species (HW 0.94–1.05 mm; WL 3.21–4.04 mm) with elongate head (CI 0.51–0.58), excluding mandibles, nearly twice as long as broad, widest at eyes. Sides of head straight; gently tapering anteriorly, posteriorly narrowing abruptly to a conical neck-like constriction. Approximately 15 teeth and denticles interspersed on masticatory margin of mandible. Anterior clypeal margin weakly concave. Eyes posi¬tioned at midline of head, relatively small, round, hairless, not surpassing lateral margins of head. Antennae slender, not compressed, scapes surpassing posterior margin of head by 3/5 their length.

Pronotum slender, distinctly elongated anteriorly. Propodeum with dorsal face 1.5 times the length of declivitous face, both faces concave, and meeting at rounded angle. Petiolar node triangular in profile, dorsal face rounded and bearing a longitudinal impression. Ventral surface of petiole weakly concave. Gaster long and slender, legs very long and slender (HTL 4.41–5.02 mm), not compressed (HTC 0.55–0.74).

Surface very finely shagreened and shining. Pubescence yellow, moderately dense on head and gaster. Pilosity confined to clypeus, venter and gaster. Head, thorax and usually gaster rufotestaceous. Femora and tibiae ranging from pale to dark brown, tarsi white. While generally rufotestaceous throughout, some variants with dark spots laterally on the gaster, or with gaster entirely black.

Queen
Lucky and Ward (2010) – Head broader than in worker. Three ocelli deeply set into head in triangular formation, the anteriormost one largest, the posterior two smaller. Pronotum, mesonotum and propodeum voluminous, convex. The ante¬rior portion of the mesonotum with a distinctly raised medial bump. Dorsal face of propodeum broadly con¬vex. Petiole broader than high, with distinct medial impression. Gaster globose, larger than in worker. Scapes, femora and tibiae broad, distinctly robust.

Surface of body appearing velvety, shagreened. Queen coloration similar to that of worker; gaster may be unicolorous pale or portions may be black.

Male
Lucky and Ward (2010) – measurements (n = 3) HL 1.41–1.58, HW 1.01–1.04, SL 0.34–0.39, EL 0.58–0.65, HTL 4.74–5.26, CI 0.64–0.73, SI 0.34–0.38, SI2 1.09–1.15.