Leptomyrmex cnemidatus

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Leptomyrmex cnemidatus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Dolichoderinae
Genus: Leptomyrmex
Species: L. cnemidatus
Binomial name
Leptomyrmex cnemidatus
Wheeler, W.M., 1915

Leptomyrmex cnemidatus side view

Leptomyrmex cnemidatus top view

Specimen labels

Synonyms
Evolutionary Relationships
Leptomyrmex
Neotropical

Leptomyrmex neotropicus (fossil only)



Leptomyrmex relictus



Australasian
Micro-Leptomyrmex

Leptomyrmex burwelli



Leptomyrmex dolichoscapus



Macro-Leptomyrmex


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.

L. cnemidatus has been recorded in wet sclerophyll, dry sclerophyll, rainforest and semi-evergreen vine thicket. Nests occur in or under rocks and logs, or in holes in the ground.

Identification

Throughout the major part of its range in northeastern New South Wales and southeastern Queensland, Leptomyrmex cnemidatus can be distinguished from congeners by the combination of head shape (elongate, with rounded postocular margin and long scapes: CI 0.59–0.63; SI 2.94–3.12), coloration (orange, with gaster and distal portions of the femora black) and size (HW 1.20–1.39 mm; WL 3.79–4.32 mm). These characters separate it from sympatric species with which it might be confused, including Leptomyrmex nigriventris (considerably larger: HW 1.49–1.76 mm; WL 4.32–4.98 mm; legs unicolorous orange), Leptomyrmex rothneyi (postocular margin of head con¬stricted and projecting; head and pronotum spotted or mottled), Leptomyrmex rufipes (postocular margin of head con¬stricted and projecting), Leptomyrmex tibialis (considerably larger and head broader: HW 1.68–1.96 mm; WL 4.51–5.13 mm; CI 0.71–0.79), Leptomyrmex varians (legs, including coxae, black) and L. wiburdi (head broad, scapes shorter: CI 0.66–0.70; SI 2.29–2.64).

In some portions of its range, L. cnemidatus can be difficult to distinguish from its sister species, Leptomyrmex erythrocephalus. In the Blue Mountains these species maintain morphological and color differences in sympatry, and north of Sydney L. cnemidatus occurs within 100km of the coast whereas L. erythrocephalus is found in inland, more than 100km from the coast. In the Sydney region, however, L. cnemidatus becomes variable in coloration and can be difficult to distinguish from its sister species. This area of confusion may represent a recent contact zone where the two species are introgressing, or it may be that in this region complete divergence has never occurred. Study of this scenario on the population level will be needed to gain insight into the status of these two species in this area. In general, L. cnemidatus is the smaller of the two species, and can be identified by the presence of 2–4 black setae on the clypeus (L. erythrocephalus has 0–2 black setae). If only 2 setae are present, then these are separated by less than 0.25 mm, whereas L. erythrocephalus possesses 0-2 setae and the hairs are separated by more than 0.25mm.

Identification Keys including this Taxon

Distribution

Distribution based on Regional Taxon Lists

Australasian Region: Australia (type locality).


Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

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.

Castes

Nomenclature

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

  • cnemidatus. Leptomyrmex erythrocephalus var. cnemidatus Wheeler, W.M. 1915d: 268 (w.) AUSTRALIA. Wheeler, W.M. 1934c: 92 (m.). Subspecies of erythrocephalus: Wheeler, W.M. 1934c: 92. Raised to species: Lucky & Ward, 2010: 26. Senior synonym of brunneiceps, venustus: Lucky & Ward, 2010: 26.
  • brunneiceps. Leptomyrmex erythrocephalus subsp. brunneiceps Wheeler, W.M. 1934c: 88 (w.) AUSTRALIA. Junior synonym of cnemidatus: Lucky & Ward, 2010: 26.
  • venustus. Leptomyrmex erythrocephalus subsp. venustus Wheeler, W.M. 1934c: 87, fig. 5 (w., ergatoid q.) AUSTRALIA. Junior synonym of cnemidatus: Lucky & Ward, 2010: 26.

Type Material

  • Leptomyrmex erythrocephalus brunneiceps: Syntype, 4 workers, Mt. Wilson, New South Wales, Australia, Museum of Comparative Zoology.
  • Leptomyrmex erythrocephalus brunneiceps: Syntype, 2 workers, Mt. Wilson, New South Wales, Australia, National Museum of Natural History.
  • Leptomyrmex erythrocephalus brunneiceps: Syntype, 3 workers, Mt. Wilson, New South Wales, Australia.
  • Leptomyrmex erythrocephalus brunneiceps: Syntype, 2 workers, Wentworth Falls, New South Wales, Australia.
  • Leptomyrmex erythrocephalus cnemidatus: Holotype, worker, New South Wales, Australia, Museum of Comparative Zoology.
  • Leptomyrmex erythrocephalus venustus: Syntype, 6 workers, 1 queen, Mt. Tomah, New South Wales, Australia, Museum of Comparative Zoology.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

Lucky and Ward (2010) - measurements (n = 9) HL 1.99–2.29, HW 1.20–1.39, MFC 0.23–0.30, IOD 0.68–0.80, SL 3.64–4.18, EL 0.40–0.48, WL 3.79–4.32, PW 1.07–1.25, DPW 0.37–0.50, HTL 4.44–5.08, HTWmin 0.12–0.17, HTWmax 0.27–0.31, CI 0.59–0.63, SI 2.94–3.12, OI 0.10–0.14, HTC 0.41–0.60.

Medium to small species (HW 1.20–1.39 mm; WL 3.79–4.32 mm) with head, excluding mandibles, less than twice as long as broad (CI 0.59–0.63). Head widest at eye level, sides of head subparallel, narrowing anteriorly, genae straight. Head posterior to eyes rounding and gently narrowing to flat posterior margin. Mas¬ticatory margin of mandible with approximately 7 teeth and 15 denticles interspersed. Anterior clypeal margin weakly concave medially. Eyes positioned approximately at midline of head, relatively small and hairless, reaching but not surpassing lateral margin of head. Antennae not compressed, scapes surpassing the posterior margin of head by about 3/5 of their length. Pronotum long and slender. Propodeal declivity about 1/3 as long as dorsal face, the latter bearing a transverse impression at anterior end. Propodeal angle rounded. Petiole in profile slightly bulbous, median longitudinal impression on anterior, dorsal and posterior faces. Posterior face of petiole concave, ventral face convex. Gaster elliptical. Femora and tibiae compressed. Whole body, includ¬ing mandibles, subopaque, finely and densely shagreened. Mandibles with a row of coarse punctures along margin. Short, whitish pubescence covering surface, lending pruinose appearance. Pilosity confined to mandi¬bles and clypeus and venter. Ventral face of fore, mid and hind tibia with irregular row of short dark bristles.

Typical color pattern consisting of rufotestaceous head and mesosoma, with gaster and distal portions of femora black. Variation from this color pattern is common; in the area of sympatry with Leptomyrmex erythrocephalus (Sydney region) the central portion of clypeus, excluding the anterior margin, presents 2–4 black setae (sometimes abraded—look for black setal base); if only 2 setae are present, these are separated by less than 0.25 mm.

Queen

Lucky and Ward (2010) - Head broader than in worker, the posterior border slightly impressed medially. Three ocelli deeply set into head in triangular formation, the anteriormost one largest, the posterior two smaller. Anterior clypeal margin nearly flat. Pronotum, mesonotum and propodeum voluminous, convex. Dorsal face of propodeum convex, thus lacking transverse impression. Petiole broader than high, with distinct medial impression. Gaster glo¬bose, larger than in worker. Scapes, femora and tibiae broad, robust.

Surface of body dull and opaque, appearing dusty. Pilosity longer on the clypeus; pubescence on gaster longer and yellowish. Queen coloration similar to that of worker.

Male

Lucky and Ward (2010) - (n = 5) HL 1.37–1.55, HW 1.02–1.11, SL 0.44–0.50, EL 0.55–0.68, HTL 3.84–4.34, CI 0.70–0.78, SI 0.42–0.45, SI2 0.91–1.02.

Wheeler (1934) - Head decidedly longer than its transverse diameter through the eyes, which are very large and prominent, with sinuate mesial and external orbits. Ocelli large. Posterior portion of head subtrapezoidal, with rather straight lateral and posterior borders. Cheeks very short, concave, not more than one-third as long as the eyes. Mandibles with blunt tips, the angle between the internal and longer masticatory border broadly rounded, the latter without any traces of denticles. Clypeus flattened, its anterior border straight in the middle, sinuate on each side. Antennae somewhat shorter than the body; scapes subcylindrical, fully three times as long as broad, slightly stouter than the filiform funiculus; first funicular joint it little longer than broad, second joint about three times as long as broad; joints 3-5 much longer, each of them constricted and bent, the fourth near the base, the two others near the apex; remaining joints gradually decreasing in length to the tip. Pronotum produced and narrowed anteriorly; mesonotum subelliptical, somewhat longer than broad, strongly convex dorsally and overarching the pronotum anteriorly; scutellum nearly twice as broad as long, convex in the middle, depressed and narrowed on each side; mesosterna very long and convex; epinotum very long, from above one and three-fourths times as long as broad, as broad behind as in front, the sides slightly concave in the middle. Base of epinotum in profile very long and sloping, with two sinuate, transverse impressions, the declivity very short, rounded and not distinctly marked off from the base. Petiole evenly convex dorsally and ventrally. Gaster narrowed at the base, enlarged toward the tip. Genitalia extruded; squamulae large, convex, smooth and shining; stipites rather large, with broadly excised posterior border; volsellae boot-shaped. Legs very long, middle tibiae strongly bowed. Wings long (8 mm.); pterostigmal appendage well-developed, pedunculate and sausage-shaped; basal third of cubitus absent.

Shagreened, the thorax more coarsely than the head and gaster, subopaque, except the epinotum and gaster which are distinctly shining.

Hairs absent, except on the ventral surface of the gaster where they are black, coarse and stiff, and on the mandibles and stipites, where they are fine, short, abundant and white. Pubescence very fine, short, white and appressed, visible on the pleurae, epinotum, gaster and appendages and sufficiently abundant to produce a pruinose effect.

Brownish testaceous or brown; epinotum, gaster, mesopleurae and femora dark brown; tibiae, tarsi and genital valves yellow; veins and membranes of wings yellowish; palpi brownish.

References

  • 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.