Leptomyrmex fragilis

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Leptomyrmex fragilis
Leptomyrmex fragilis
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Dolichoderinae
Tribe: Leptomyrmecini
Genus: Leptomyrmex
Species: L. fragilis
Binomial name
Leptomyrmex fragilis
(Smith, F., 1859)

Leptomyrmex fragilis side view

Leptomyrmex fragilis top view

Specimen labels

Evolutionary Relationships

Leptomyrmex neotropicus (fossil only)

Leptomyrmex relictus


Leptomyrmex burwelli

Leptomyrmex dolichoscapus


Leptomyrmex mjobergi

Leptomyrmex varians

Leptomyrmex unicolor

Leptomyrmex flavitarsus

Leptomyrmex puberulus

Leptomyrmex darlingtoni

Leptomyrmex fragilis

Leptomyrmex niger

Leptomyrmex erythrocephalus

Leptomyrmex wiburdi

Leptomyrmex cnemidatus

Leptomyrmex nigriventris

Leptomyrmex tibialis

Leptomyrmex geniculatus

Leptomyrmex nigriceps

Leptomyrmex pallens

Leptomyrmex rufithorax

Leptomyrmex rufipes

Leptomyrmex rothneyi

Leptomyrmex ruficeps

Based on Barden et al., 2017. Note only selected Leptomyrmex species are included.

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.


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)

Keys including this Species


Distribution based on Regional Taxon Lists

Indo-Australian Region: Indonesia (type locality), New Guinea.

Distribution based on AntMaps


Distribution based on AntWeb specimens

Check data from AntWeb






The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • 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.

Type Material



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.


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.


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.


  • Baroni Urbani, C.; Wilson, E. O. 1987. The fossil members of the ant tribe Leptomyrmecini (Hymenoptera: Formicidae). Psyche (Camb.) 94: 1-8 (page 2, Senior synonym of gracillimus)
  • Emery, C. 1897c. Formicidarum species novae vel minus cognitae in collectione Musaei Nationalis Hungarici quas in Nova-Guinea, colonia germanica, collegit L. Biró. Természetr. Füz. 20: 571-599 (page 571, male described)
  • Lucky, A. 2011. Molecular phylogeny and biogeography of the spider ants, genus Leptomyrmex Mayr (Hymenoptera: Formicidae). Molecular Phylogenetics and Evolution 59: 281-292.
  • Lucky, A. & Ward, P.S. 2010. Taxonomic revision of the ant genus Leptomyrmex Mayr. Zootaxa 2688: 1-67.
  • Smith, F. 1859a. Catalogue of hymenopterous insects collected by Mr. A. R. Wallace at the islands of Aru and Key. [part]. J. Proc. Linn. Soc. Lond. Zool. 3: 132-158 (page 136, worker described)
  • Stitz, H. 1912. Ameisen aus Ceram und Neu-Guinea. Sitzungsber. Ges. Naturforsch. Freunde Berl. 1912: 498-514 (page 507, Combination in Leptomyrmex)
  • Wheeler, W. M. 1934c. A second revision of the ants of the genus Leptomyrmex Mayr. Bull. Mus. Comp. Zool. 77: 69-118 (page 113, see also)