Echinopla charernsomi

The holotype and one paratype were collected from a shrub/tree in a dry evergreen forest. No nest was found but it is possible this is an arboreal or twig nesting species (Lubertazzi, Nov 2022; W. Jaitrong, pers. comm.).

Identification
Tanansathaporn et al. (2018) - A member of the Echinopla mezgeri group.

Medium-sized, HW 1.40–1.56 mm, head in full-face view broader than long; eye relatively large, moderately convex; dorsum of mesosoma distinctly laterally marginate along its length, armed with numerous teeth; in dorsal view mesosoma with waist-like incision in front of propodeum; promesonotal suture present, narrow and shallow; metanotal groove distinct, deeply impressed; in posterior aspect, dorsal margin of petiole with numerous teeth; lateral margin of petiole with 3-4 large teeth; first gastral tergite globose, its posterior margin without denticles. Dorsa of head, mesosoma and first gastral tergite finely, longitudinally striate; lateral face of pronotum irregularly reticulate-punctate; mesopleuron punctate; lateral face of propodeum irregularly rugose. Dorsa of head, mesosoma, petiole, and first gastral tergite with dense black and long hairs mixed with dense pubescence. Body black; trochanters and tip of gaster reddish brown.

Similar to Echinopla striata and Echinopla lineata by having a longitudinal striation on the dorsal body surface. However, E. charernsomi can be distinguished from E. striata by much smaller size (HW 1.40–1.60 mm in E. charernsomi, HW 1.72–1.85 mm in E. striata), a irregularly reticulatepunctate lateral face of propodeum (smooth and shiny in E. striata), and yellowish brown trochanters (black to dark brown in E. striata). Echinopla charernsomi is separated from E. lineata by the smaller body size (HW 1.40–1.60 mm in E. charernsomi; HW 1.58–1.75 mm in E. lineata) and a punctate and reticulatepunctate sculpturing on the lateral face of the mesosoma (in E. lineata, entirely striate).

Distribution
Nakhon Ratchasima, Nakhon Nayok and Tak provinces, Thailand.

Distribution based on Regional Taxon Lists
Oriental Region: Thailand.

Nomenclature

 *  charernsomi. Echinopla charernsomi Tanansathaporn & Jaitrong, 2018: 3, figs. 1-3 (w.) THAILAND.

Worker
Holotype: TL 5.32, HL 1.28, HW 1.60, SL 1.32, ED 0.28, PW 1.52, MSL 1.96, PL 0.52, PH 0.48, DPW 1.40, GW 1.72, CI 125, EI 18, SI 83, LPI 92, DPI 292. Paratypes (n = 2): TL 4.72–5.28, HL 1.12–1.16, HW 1.40–1.56, SL1.20–1.28, ED 0.28, PW 1.28–1.52, MSL 1.84–1.96, PL 0.56–0.64, PH 0.52– 0.56, DPW 1.24–1.48, GW 1.52–1.80, CI 130–134, EI 18–19, SI 82–84, LPI 88–91, DPI 226–231.

Worker. Head in full-face view trapezoidal, narrowed anteriorly and broader than long, lateral margin weakly convex, posterior margin moderately convex, posterolateral corner roundly convex. Eye relatively large, moderately convex, located close to posterior corner of head. Frontal lobe obliquely elevated, in full-face view covering antennal fossa only in part. Mandible short, subrectangular, and its masticatory margin armed with five teeth. Clypeus broad, anterior margin almost straight. Frontal carina short, not surpassing level of anterior margin of eye. Antennae 12-segmented; scape moderately long and slender, one third of scape length extending beyond posterior margin of head; funicular segments, each longer than broad; antennal segment II slightly narrower and longer than each of III–XI; terminal segment (XII) almost as long as X and XI combined.

Mesosoma stout, dorsum of mesosoma distinctly marginate at sides along entire length, length roughly 1.3 times pronotum width; propodeum slightly larger than promesonotum. In profile dorsal outline of promesonotum weakly convex, while propodeum strongly convex; both promesonotum and propodeum meeting at deep and broad incision, the metanotal groove; promesonotal suture present, narrow and shallow; mesopleuron flat, not clearly demarcated from metapleuron. In dorsal view mesosoma with waist-like incision in front of propodeum; pronotum trapezoidal or subrectangular, anterior margin convex, posterior margin concave, lateral margin straight; pronotum narrower than head; mesonotum clearly shorter and narrower than pronotum; propodeum more or less subglobose, as broad as pronotum, and longer than mesonotum; anterior and lateral margins of mesosoma armed with numerous teeth. Legs relatively long; femora flat, seen from posterior aspect broad at base then gradually narrowed to apex.

Petiole in profile longer than high, and narrowed dorsally. In dorsal view petiole transverse, about as broad as propodeum, each side with strong posteriorly bent spine; anterior face much narrower than posterior face. In posterior aspect dorsal margin with 12-13 denticles; lateral margin with 3-4 large teeth.

First gastral tergite in dorsal view globose, covering remaining tergites, slightly broader than long, posterior margin roundly convex without denticles.

Dorsum and lateral face of head finely, longitudinally striate; antennal scape superficially reticulate with smooth and shiny interspaces; mandible roughly and irregularly rugose. Dorsa of pronotum, mesonotum and propodeum longitudinally striate; lateral face of pronotum irregularly reticulate-punctate; mesopleuron punctate; lateral face of propodeum irregularly rugose; legs reticulate with smooth and shiny interspaces. First gastral tergite densely, finely, longitudinally striate.

Dorsa of head, mesosoma, petiole, and first gastral tergite with dense erect long hairs mixed with dense pubescence. Scape and legs with sub erect long hairs mixed with sparse pubescence.

Entire body black; apex of mandible, antennal segments X-XII, trochanters, and tip of gaster reddish brown; eye grayish brown.

Type Material
Holotype – worker (THNHM-I-01365), NE Thailand: Nakhon Ratchasima province, Wang Nam Khiao district, Sakaerat Environmental Research Station, 14.5097°N, 101.9319°E, 17.VIII 2009, leg. W. Jaitrong. Paratypes: one worker (THNHM-I-01366), same data as holotype (THNHM); one worker (THNHM-I-01367), Central Thailand: Nakhon Nayok province, Muang Nakhon Nayok, Hin Tang subdistrict, 14.4372°N, 101.3758°E, dry evergreen forest, 25.III 2000, leg. W. Jaitrong (THNHM).

Etymology
The species epithet is dedicated to Dr. Kosol Charernsom of Kasetsart University, who is the most excellent specialist in biodiversity sciences in Thailand and helped and inspired many young taxonomists.

References based on Global Ant Biodiversity Informatics

 * Tanansathaporn S., H. Zettel, N. Pinkaew, M. Kongmee, S. Waengsothorn, and W. Jaitrong. 2018. Two new species of the genus Echinopla Smith, 1857 (Hymenoptera: Formicidae: Formicinae) from Thailand. Far Eastern Entomologist 370: 1-11.