Leptogenys leleji

No data on the prey specialization of L. leleji are available. However, the shape of its cranio-mandibular system closely resembles that of the actual specialists on terrestrial isopods. Rare occurrence of this species (only three specimens were collected within a month of intensive sampling) indicates a small colony size and therefore a solitary hunting as in other specialists on isopods. Hence, it is possible to assume a similar prey specialization in L. leleji that can explain its similarity with the congeners from other zoogeographical realms in the shape of craniomandibular system. (Zyranin 2016)

Identification
Zyranin (2016) - This species is well distinguished from the other Vietnamese and Oriental congeners with a set of the following characters in the worker: cephalic capsule wider than long; anterior clypeal margin fringed with narrow translucent lamella; mandibles linear, a large gap formed between clypeus and mandible when fully closed; basal flagellar (third antennal) segment elongate; dorsum of body with standing hairs; propodeum with lateral teeth, posterior apex of petiole in profile drawn out into a tooth.

Distribution based on Regional Taxon Lists
Oriental Region: Vietnam.

Biology
Zyranin (2016) - The prey specialization in Leptogenys is associated with significant changes of the cranio-mandibular system [Dlussky, Fedoseeva, 1988] and may be responsible for most of morphological diversity within the genus [Schmidt, 2013]. The characteristic prey of many representatives of Leptogenys are the oniscoid isopods as have been reported for the species from the New World, Africa, New Guinea, etc. [Dejean, Evraerts, 1997 and the references cited therein; Lattke, 2011]. These terrestrial crustaceans frequently constitute an important part of the soil fauna, but they are well protected from predators. In particular, they are able to roll themselves up or secrete adhesive proteinaceous compound as a defense mechanism against ants [Deslippe et al., 1995 cit. ex Lattke, 2011]. Thus, isopod-hunting Leptogenys species usually have curved, elongate, and narrow mandibles. The ants hunt isopods solitarily as a rule, and their hunting success positively correlates with the length of their mandibles [Dejean, Evraerts, 1997]. The lengthening of mandible is accompanied by a broadening of the anterior margin of the cephalic capsule, displacement of the compound eyes dorsolaterally on the head, certain changes in the shape of the clypeus. In general, these ants are characterized by the large body size of workers and small colony size (few dozen workers per family) [Lattke, 2011]. Most likely such morphological traits occurred independently in different species groups with the similar levels of social organization as a result of prey specialization.

Nomenclature

 *  leleji. Leptogenys leleji Zryanin, 2016: 51, figs 1–5 (w.q.) VIETNAM.

Worker
Holotype. HL 2.18, LCM 1.45, HW 2.13, ML 1.88, EL 0.40, SL 2.10, PW 1.41, WL 3.70, PNH 1.08, PNL 1.34, PNW 0.83; CI 98, SI 99, LNI 81, DNI 62.

Habitus of worker as in Fig. 1. Head in full-face view markedly wider anteriorly than posteriorly, lateral and posterior margins forming continuous convexity, occipital carina distinct. Clypeus triangularly produced, with a blunt apex; anterior clypeal margin fringed with narrow translucent lamella, without peg-like setae medially; median longitudinal carina of clypeus sharp. Eyes large, weakly convex, placed dorsolaterally on head, their greatest diameter greater than maximal width of scape. Frontal groove shallow, extending to the level of posterior margin of eye. Mandibles long, feebly curved near bases, with only apical tooth and distinct crest along basal margin; blades in full-face view generally same width from the base to apex; a large gap formed between clypeus and mandible when fully closed; basal groove indistinct. Palp formula: maxillary 4, labial 4. Antennal scape relatively short (SI 99). Basal flagellar (third antennal) segment elongate, markedly longer than neighboring antennal segments (the lengths of the segments 2–4: 0.35 mm, 0.53 mm, 0.38 mm).

Mesosoma (alitrunk) with deep and wide, transversally striate metanotal groove that divides dorsal outline of mesosoma into two distinct convexities in lateral view. Mesonotum wider than long, with markedly median impression on posterior half; anteroventral mesopleural carina well-developed, forming small angular lobe anteriorly; epicnemial carina projected anteriorly into distinct laminate and angulate epicnemial process; anapleural sulcus divides mesopleuron into smaller anepisternum and larger katepisternum; mesometapleural suture well impressed. Metapleural-propodeal suture developed as ridge that extends from propodeal spiracle and broadened toward metathoracic spiracle; propodeal spiracle slit-like; bulla of metathoracic spiracle convex. Propodeum armed with triangular tooth at the level of spiracle; propodeal declivity with carina uniting apices of these teeth; area anteriad to the carina concave in cross-section, with mostly smooth and shining surface; area posteriad to the carina depressed as a broad transverse sulcus. Apex of protibia without setae; first protarsal segment with comb of stout setae opposite strigil; meso- and metatibial apex each with two apical spurs and several setae; posterior metacoxal swelling well developed; tarsal claws pectinate.

Petiole with convex anterior margin, and straight ascending dorsal margin in lateral view; both margins joined by convexity; dorsal margin ends in blunt pointed tooth that projects beyond posterior margin by almost one-fifth node length, tooth forms approximately 30-degree angle with longitudinal axis. Posterior margin of petiole in lateral view straight but not sinuate; posterior face flat and sharply margined laterally. Node longer than wide in dorsal view, its anterior margin little more than half of posterior margin; cross-section of petiolar node at mid-length with convex sides. Subpetiolar process shaped as sub-rectangular tubercle with gentle posterior slope. Anterior and dorsal margins of first gastral (third abdominal) segment joined through a continuous convexity; constriction between first and second gastral segments well marked. Prora shaped as sharp, ventrally directed lobe at anteroventral angle of first gastral segment. Pygidium with indistinct median carina, hypopygium with a row of small setae close to base of sting.

Cephalic dorsum between and behind eyes mostly smooth and shining, with shallow piligerous punctae; malar space and frontal area striate; clypeus with fine longitudinal to oblique striae, which are more pronounced antero-medially. Antennae covered with dense piligerous punctulae. Dorsal surface of mandible with fine striation. Propleuron and pronotal dorsum sulcate; mesopleuron mostly smooth and shining, katepisternum scrobiculate along mesometapleural suture; metapleuron sulcate to scrobiculate; dorsum of propodeum with irregular fovea and median sulcus; metanotal groove with cross-ribs. Petiole scrobiculate, with rimose posterior face. Gaster smooth and shining.

Body with abundant suberect to erect hairs; apressed pubescence present on cephalic dorsum, antennae and legs. Longest hairs present on median lobe of clypeus.

Body colour mostly black to dark brown, with blue reflection of smooth surfaces. Antennae, mandibles, and legs mostly brown. Gastral apex and edges of last sclerites, base and apex of scape, crest on basal margin of mandible, last segments of tarsus dull yellow.

Queen
(ergatoid) (n=2): HL 2.31–2.35, LCM 1.50–1.51, HW 2.23–2.35, ML 1.93–2.07, EL 0.45–0.46, SL 2.31–2.36, PW 1.49–1.55, WL 4.06–4.10, PNH 1.20–1.21, PNL 1.39–1.41, PNW 0.95–1.02; CI 96–100, SI 101–104, LNI 85–87, DNI 68–72.

Ergatoid queen is very similar to the worker except for the following features: body bigger, dorsal propodeal margin more convex compare to the worker, petiole broader than in the worker in dorsal view and gaster more voluminous. In addition, hairs on dorsum of body are more abundant and appendages are darker than in worker.

Type Material
Holotype, worker: Vietnam, Lam Dong Province, Lac Duong District, Bi Dup-Nui Ba Nature Reserve, near Long Lanh village, 12°10' N, 108°40' E, 1450 m a.s.l., 28.III.2008, leg. V. Zryanin (BD8). Paratypes: 2 ergatoid queens, same locality, 26.III and 23.IV.2008, leg. V. Zryanin (BD1, BD77). The holotype and one paratype are deposited in the collection of the Zoological Institute of the Russian Academy of Sciences (St. Petersburg), one paratype is deposited in the collection of the Zoological Museum of the Moscow Lomonosov State University.

Etymology
The species is named in honor of the head of the Laboratory of Entomology (Institute of Biology and Soil Science, Vladivostok, Russia), Prof. Arkadiy S. Lelej, the authority of fauna and taxonomy of Hymenoptera.

References based on Global Ant Biodiversity Informatics

 * Zryanin V. A. 2016. remarkable new species of Leptogenys Roger, 1861 (Hymenoptera: Formicidae) from Vietnam. Euroasian Entomologicl Journal 15(1): 50-54.