| Leptomyrmex niger|
Collected from rainforest. Nesting habits are unknown.
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)
Keys including this Species
Distribution based on Regional Taxon Lists
Distribution based on specimens
These conspicuous ants are most often encountered individually or as small groups of 2 or 3 foragers on the surface of the ground any time of the day or night. Because of their long legs and thin bodies, they superficially resemble spiders. This is especially true when they are disturbed, as they extend their legs, raise their gasters, and run quickly to escape danger. This has led to their being given the common name "spider ants."
Nests are found in soil or in dead wood, either standing or on the ground, and are often at the base of trees. Colony sizes average a few hundred workers and a single queen. In all but a handful of species, the queen is wingless and worker-like, differing from workers only in being slightly larger and with an enlarged mesosoma. In a few species the queens are fully winged, as they are in most other ants.
When a large source of food is found, workers of Leptomyrmex will return to their nest and recruit additional workers to help utilise the newly found resource. They also use workers as "living storage vessels". These special workers, called repletes, accept liquids from returning foragers who transfer their liquid foods to these selected workers. These special workers continue to accept liquids until their gasters become greatly enlarged and extended. When enlarged, repletes cannot escape the nest and remain inside suspended from the ceiling. They can retain these fluids for extended periods and dispense it on demand when food is in short supply.
Queens have yet to be collected.
The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.
- 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.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
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.
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.
Lucky and Ward (2010):
Syntypes, 2 workers, Papua New Guinea, "New Guinea" [German New Guinea] (Biró) Museo Civico di Storia Naturale, Genoa. One syntype here designated lectotype (CASENT0127396, top specimen).
L. lugubris Syntypes, 2 workers, Papua New Guinea, Morobe: Biolowat (Stevens) Museum of Comparative Zoology
- Emery, C. 1900b. Formicidarum species novae vel minus cognitae in collectione Musaei Nationalis Hungarici quas in Nova-Guinea, colonia germanica, collegit L. Biró. Publicatio secunda. Természetr. Füz. 23: 310-338 (page 333, pl. 8, figs. 3, 4 worker described)
- Karavaiev, V. 1926d. Ameisen aus dem Indo-Australischen Gebiet. Treubia 8: 413-445 (page 430, 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. doi:10.1016/j.ympev.2011.03.004
- Lucky, A. & Ward, P.S. 2010. Taxonomic revision of the ant genus Leptomyrmex Mayr. Zootaxa 2688: 1-67. PDF
- Wheeler, W. M. 1934c. A second revision of the ants of the genus Leptomyrmex Mayr. Bull. Mus. Comp. Zool. 77: 69-118 (page 109, see also)