Indomyrma bellae

Zryanin (2012) - At present, this species is only known from the Cat Tien National Park of Southern Vietnam. During three years of research only few speciments of I. bellae were collected. Probably nests are located in rotten wood as in I. dasypyx (single queen was found in big butt of Dipterocarpus sp.). In artificial nest I. dasypyx workers were not attracted to small droplets of diluted honey [Brown, 1986], but Brown noted that these preliminary results should not be taken as conclusive evidence that the ants always ignore sweet substances. In Cat Tien NP five workers of I. bellae were found in perforated plastic container with carbohydrate bait. This may indicate that food spectrum of this genus includes sugars (such as fallen fruits).

Identification
Zryanin (2012) - Weakly defined antennal scrobes, straight masticatory borders of mandibles with 8-9 teeth, 11-merous antennae with 3-merous club, palpal formula 2:2, position of propodeal spiracle close to the margin of propodeal declivity and absence spongiform appendages of the waist segments evidence of belonging a new species to genus Indomyrma. The new species is the second described in this genus and easily recognized from Indomyrma dasypyx by number of ommatidia in worker, 2-3 in former and 8-10 in the latter. In worker and queen I. bellae distinguished from those of I. dasypyx in absence of subacute humeral angles, shape of petiolar node with rounded anterior edge, strong development of torose sculpture on head, alitrunk, petiole and postpetiole, foveolate or punctate sculpture at base of gaster and different character of pilosity (reduction of longer erect and suberect hairs).

Distribution based on Regional Taxon Lists
Oriental Region: Vietnam.

Nomenclature

 *  bellae. Indomyrma bellae Zryanin, 2012: 224, figs. 1-6 (w.q.) VIETNAM.

Worker
(in mm) and indices. Holotype: TL 2.87, HL 0.70, HW 0.57, ML 0.18, SL 0.48, EL 0.03, WL 0.83, PetL 0.28, PpetL 0.17, Gl 0.70, HFL 0.55, HTL 0.38; CI 81, MI 26, SI 85. Paratypes (n=10): TL 2.67-2.87, HL 0.67-0.70, HW 0.55-0.58, ML 0.17-0.18, SL 0.43-0.48, EL 0.03, WL 0.77-0.83, PetL 0.25-0.28, PpetL 0.15-0.17, GL 0.67-0.70, HFL 0.50-0.55, HTL 0.35-0.40; CI 80-83, GL 25-27, SI 79-85.

Habitus as in Fig. 1a. Head 1.20-1.24 times as long as wide, broad behind, narrowed anteriad, with convex sides in full-face view; posterior outline weakly concave, the posterolateral corners with a narrow flange (nuchal groove) as seen from side view. Eyes strongly reduced, consist of 2-3 distinct ommatidia (Fig. 1c), situated a little anterior to midlength of head. Frontal lobes, frontal carinae, clypeal shield and mandibles as in Indomyrma dasypyx. Masticatory borders of mandibles as in Fig. 5, sometimes denticles poorly separated. Palp formula maxillary 2: labial 2 (see Fig. 4). Antennae 11-merous with 3-merous club.

Alitrunk with dorsal surface evenly convex from indistinct anterodorsal pronotal margin to the well distinct metanotal groove. Subacute humeral angles not express. Anterior half of propodeal dorsum is slightly convex. Propodeal teeth longer than wide at base, have upcurved dorsal margins. Propodeal spiracles prominent, situated very close to declivitous margins, directly below tooth bases. Metapleural gland bulla is moderately distinct, with two longitudinal sulci leading forward along lower metapleuron, meatus small and obscure. Propodeal declivity higher than wide, margined above by one or two transverse coste connecting propodeal teeth and by thin lateral margins that merge into the propodal lobes.

Petiole with a short but distinct anterior peduncle and relatively low node without a flanked horizontal area; peduncle with distinct, weakly curved and digitiform subpetiolar process. Viewed from above, petiolar node is elongate oval, with rounded anterior edge. Postpetiole broader than petiole and broader than own length, dorsum and sides strongly rounded.

Gaster broader than deep and first tergum covering more 0.9 of its length in dorsal view. Apical segments forming a small, blunt cone, directed slightly downward as well as caudad.

Sculpture of head, alitrunk, petiole, postpetiole, and gaster as in Fig. 1. Partly sculpture torose (Fig. 1b), i.e. small knobs occur on dorsum of head (particularly towards occiput), alitrunk, nodes of petiole and postpetiole as in Rostromyrmex. Sculpture on lateral and ventral sides of head foveate-reticulate with hairs in the pits. The bottom of pits with very finely rugulose sculpture (Fig. 1c). On dorsum of head foveolar interspaces form 8-9 intermittent vermiculate longitudinal costae, including frontal carinae, between antennal scrobes; middle costae very distinct. Pronotal disc, sides of pronotum and mesonotal dorsum sculpture similar. Mesopleuron and sides of propodeum with irregular sculpture of sparse longitudinal ridges and small knobs. Sculpture of gaster foveolate or punctate, with hairs in the pits; foveolar interspaces predominantly larger than diameter of fovea except the base of first tergum. Small knobs are on the femora, tibia, and scapes of antennas, main sculpture of the appendages finely alveolate. Mandible smooth and shining, with scattered fine punctures.

Pilosity consisting of widely distributed, moderately abundant, short, decumbent and subdecumbent hairs; shorter, denser, fin and more nearly appressed hairs on antennae and legs. Setae fine and sparse on clypeus and mandibles. Longer erect and suberect ahirs on dorsum of head above clypeus shield and alitrunk almost absent (sometimes few hairs). These hairs absent on petiolar node an dorsum of postpetiole; pair of standing hairs on side of peduncle. The longest standing hairs on clypeal shield reach 145 mm, on other parts of body 50-85 mm. Gaster with many of longer hairs, curved sharply caudad.

Color brownish red, appendages and mandibles dull yellow; some parts of cuticle (occiput, mesopleural edges, masticatory borders of mandibles) are darkened.

In the description of Indomyrma dasypyx Brown [1986] characterized only general shape of the sting and suggested structure of gonostylus. Therefore, in present article provides the first detailed picture and description of the skeletal portions of Indomyrma sting apparatus. Spiracular plate: body clearly longer than wide, subrectangular, anterior apodeme wide, has a prominently domelike process. Medial connection membranous. No dorsal notch or posterodorsal lobe. Spiracle small. Quadrate plate: body and apodeme subrectangular, equal in width. Dorsal edge of plate slightly convex, with wide medial and lateral lobes in an acute anterodorsal corner. Anal plate: weakly sclerotized, longer than wide, with 5-6 long setae on terminal edge ( marginal setae the longest). Oblong plate: body posterior arm long and narrow, well sclerotized, strongly curved apodeme moderately long, conoid, rounded at apex. Ventral arm wide, separated by a deep postincision on posterior arm, with elongated well sclerotized furcal arm. Gonostylus long and gradually tapered to an acute apex (as in I. dasypyx), single-segmented, with a marked constriction between own base and posterior arm and setae, dorsoterminal chaeta, companion seta and terminal membrane present. Triangular plate: body thin, with truncate dorsoapical and ventroapical processes; neither dorsal nor medial tubercle present or they are not visible. Lancet: straight, acute, well sclerotized, with distinct ventral ridge and, distally, a dorsal ridge. One elongated lancet valve per lancet. Sting: sting bulb large, slightly arched with distinct basal ridge and anterolateral processes. Valve chamber normal developed, but grade from sting bulb and sting shaft in ventral view. Sting shaft long and slender, without dorsal flange. Furcula: V-shaped in anterior view, lateral arms wrap around sting base; no dorsal arm as in Lordomyrma [see Kugler, 1997]. It looks fused to sting base. According to Kugler [1979], the genus Indomyrma belong to the Lordomyrma (=Promeranoplus) branch in structure of sting apparatus.

Queen
Dealate, paratype: TL 3.34, HL 0.72, HW 0.59, ML 0.22, SL 0.50, EL 0.18, WL 0.98, PetL 0.33, PpetL 0.17, GL 0.92, HFL 0.58, HTL 0.42; CI 84, MI 30, SI 83.

Coarser sculptured, differ from the worker in slightly larger size, much larger eyes (max diameter 179mm), and usual full-queen differences from the workers. The queen has slightly more distinct interfoveolar longitudinal costae on the middorsal head. Nuchal groove is more prominent. Pilosity and color are similar to that of worker; appendages slightly darker.

Type Material
Holotype (worker): Vietnam: Dong Nai: S. Cat Tien N. P., near Bau Sau village, yellow trail, 11°26’N, 107°19’E, 200 m a.s.l., in ferralitic soil from old dipterocarp forest, 24.07.2008, leg. V. Zryanin (BS-353). Paratypes: 4 workers from the same colony to which the holotype belonged; 1 dealate queen from the same locality, in dipterocarp butt, near forest stream, 29.07.2008, leg. V. Zryanin; 2 workers from the same locality, 14.06.2008, leg. V. Zryanin, 5 workers from the same locality, in dipterocarp butt on hill, 26-29.07-2008, leg. A. Tschekanov; 2 workers from the same locality, near forest stream, in leaf litter, 2.05.2010, leg V. Zryanin. The holotype and two paratypes (worker and queen) are deposited in the collection of the Zoological Museum of the Moscow Lomonosov State University, two paratypes are deposited in the collect of the Zoological Institute of the Russian Academy of Sciences, St. Petersburg, one paratype is deposited in the collection of Siberian Zoological Museum, Novosibirsk; other paratypes are in the personal collection of the author.

Etymology
The species is named in honor of the head of the Laboratory for soil zoology and general entomology, Prof. Bella. R. Striganova (A. N. Severtsov Institute of Ecology and Evolution, RAS, Moscow, Russia).