Myrmecina nitidiuscula

This species was collected from leaf litter in a secondary forest in Sumatra, Indonesia.

Identification
Myrmecina nitidiuscula is easily distinguished from other named species of Myrmecina known from Sundaland by the combination of the following characteristics:
 * rather smooth and shiny head with ventrolateral area (temple + gena) of head smooth
 * triangular propodeal spine pointing posteriad and with very broad base
 * short and broad mid- and hind-tibiae

Distribution
Known from Sumatra.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Indonesia.

Nomenclature

 *  nitidiuscula. Myrmecina nitidiuscula Satria & Yamane, 2019: 188, figs. 2C, 5, 6 (w.q.) INDONESIA.

Worker
Holotype and paratypes (n = 4): HL 0.65−0.67 mm, HW 0.72−0.74 mm, MDL 0.35−0.38 mm, EL 0.15−0.16 mm, SL 0.58−0.59 mm, WL 0.87−0.93 mm, PNW 0.50−0.52 mm, PSL 0.14−0.15 mm, PTH 0.21 mm, PTL 0.18−0.22 mm, CI 110, MDI 53−56, SI 78−80, PTHI 116.

Relatively small (HL 0.65−0.68 mm, HW 0.72−0.75 mm, WL 0.87−0.93 mm). Head in frontal view rectangular, slightly shorter than broad, with posterior margin slightly concave; lateral sides of head evenly convex. Clypeus consisting of short dorsal disc and steep anterior slope; its anterior margin almost straight, with small median tooth and a pair of weak lateral processes. Eye relatively large (EL 0.15−0.16 mm; 34−35 ommatidia), breaking outer margin of head by 1/5 length of eye in profile. Mandible triangular; masticatory margin with large apical tooth, followed by two relatively large teeth, 3–4 small denticles, diastema and low but broad basal tooth. Antenna 12-segmented, with 3-segmented club; apical segment slightly longer than segments 10 and 11 combined; scape relatively short, not surpassing posterolateral corner of head. Mesosoma in lateral view short and stout, with dorsal outline roundly convex; anterior ventrolateral portion of pronotum weakly angulate, without anterior process; mesonotum completely fused with pronotum; anteroventral corner of mesopleuron angulate; mesopleuron not differentiated from metapleuron. Propodeum in dorsal view weakly separated from mesonotum but without distinct metanotal groove; propodeal spine in profile triangular, apically blunt but pointing posteriad, with very broad base; dorsum with a pair of barely recognized denticles anteriorly; declivity steep, with transverse carina connecting propodeal spines; flat posteriormost portion of propodeum laterally margined by wall (part of propodeal lobe). Petiole in dorsal view as broad as long, in lateral view consisting of flat to weakly concave dorsal face and gently sloping anterior face; ventral outline of petiole straight, with longitudinal median keel that is posteriorly angulate; postpetiole in dorsal view much broader than long, shorter but broader than petiole, in profile dorsally shallowly convex, with ventral margin almost straight; sternopostpetiolar process absent. Gaster in dorsal view almost circular; first gastral tergite without distinct antero-lateral angle. Mid- and hind tibiae very broad and short, 2.5 as long as broad.

Head superficially sculptured with scattered shallow punctures but generally smooth and shiny; frontal lobe, area between eye and frontal lobe, and area close to mandible more strongly sculptured; ventrolateral surface of head (temple + gena) smooth and shiny; mandible smooth, with dorsobasal portion irregularly sculptured; antennal scape superficially sculptured and shiny. Mesosoma, petiole and postpetiole with coarse irregular longitudinal sculpture; anterior protruding portion (neck) of pronotum transversely rugose. Gaster smooth and shiny.

Body including legs covered with abundant long erect setae; clypeus with a pair of very long setae and a few short setae on disc and a pair of long setae arising around base of anterior tooth; antennal scape with suberect to erect setae, some of which are longer than scape width.

For color pattern see Figures of worker; mesosoma reddish brown; head and gaster blackish brown with apex of gaster orange. Clypeus, mandible, and antenna pale reddish brown. All legs yellowish brown.

Queen
Paratype (n = 1): HL 0.68 mm, HW 0.75 mm, MDL 0.37 mm, EL 0.19 mm, OED 0.28 mm, SL 0.58 mm, WL 0.97 mm, PNW 0.60 mm, PSL 0.16 mm, PTH 0.21 mm, PTL 0.20 mm, CI 110, MDI 54, SI 77, PTHI 105.

Differing from worker only in structure of eye and in structure and surface texture of mesosoma as follows: size of eye and number of ommatidia greater than in worker (EL 0.19 mm; 67 ommatidia), but each ommatidium similar in size in both; mesosoma in dorsal view with mesoscutum large, broad and roundly convex anteriorly; notaular lines absent; parapsidal lines weakly impressed, shorter than half of mesoscutum length; metanotum medially produced anteriad, dividing mesoscutellum into two triangular sections; propodeum separated from metanotum by deep groove; mesosoma in profile forming single dome; mesonotum and metanotum higher than pronotum and propodeum; mesopleuron demarcated from pronotum and metapleuron, divided into dorsal and ventral sections by deep groove; separation of metapleuron from lateral face of propodeum incomplete; dorsum of pronotum transversely striate; mesoscutelum smooth and shiny, with posteromedian portion coarsely longitudinally rugose; ventral section of mesopleuron smooth and shiny; other parts rugose to irregularly sculptured.

Type Material

 * Holotype. Worker, Indonesia, Sumatra, Aceh, Leuser Ecosystem, Putri Betung, 21.IX.2012, R. Satria Leg., individual code: SEMUT20180326B (MZB).
 * Paratypes. Two workers (SEMUT20180808A, SEMUT20180808B), same data as for holotype (RSC); 2 workers (SKYUSI-FOR004–005), same locality, but alt. >1100 m, good forest, 20.IX.2012, Yamane & Syaukani leg. (SKYC); 1 dealate queen (SEMUT20181112), same locality, but alt. 850 m, plantation, 19.IX.2012, Yamane & Syaukani (RSC).

Etymology
The species epithet relates to the extensively shiny dorsum of the head.

References based on Global Ant Biodiversity Informatics

 * Satria R., and S. Yamane. 2019. Two new species of the ant genus Myrmecina (Hymenoptera: Formicidae: Myrmicinae) from Sumatra. Zoosystematica Rossica 28: 183–193.