Echinopla subtilis

The type specimens were collected via foggoing from a lower montane mixed dipterocarp forest, > 650 m a.s.l., on Aporusa sp.

Identification
Zettel and Laciny (2015) - (worker). Predominantly black, medium -sized, slender species, TL = 6.1–6.8. Dorsal surface of head and mesonotum with irregularly winding deep impressions, laterally with smaller fractions, tending to become polyporous. Head wider than long (CI = 106–115). Maxillary palpi exceptionally long. Mesosoma about one half longer than wide (MI = 151–156). Pronotum much narrower than head, laterally rounded. Propodeum much shorter than promesonotum; promesonotal suture distinct, medially forming an angle; metanotal suture straight, sharp and deep. Petiole polyporous, longer than high, with irregularly tuberculated dorsal crest and 1–2 teeth below prominent lateral spines. Gaster tergite 1 and visible hind margins of the following tergites 2–4 with very fine, dense puncturation, appearing matt. Setae on dorsal surface white, relatively short.

Echinopla subtilis strongly differs from all hitherto described congeners by its sculpture. The dorsal surface of the head and mesosoma has irregularly winding deep impressions; they are best seen in the centre of the face where the pilosity is reduced. The gaster tergite 1 appears dull due to a very fine and dense puncturation and a relatively dense, appressed pilosity. In contrast to all aforementioned species it does not fully cover the following tergites; this character is shared with the following species that are related to Echinopla lineata and Echinopla striata.

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

Castes
Known only from the worker caste.

Nomenclature

 *  subtilis. Echinopla subtilis Zettel & Laciny, 2015: 115, figs. 31-34 (w.) MALAYSIA.

Worker
Holotype: TL 6.1; HW1 1.52; HW2 1.41; HL 1.33; EL 0.36; SL 1.45; SW 0.17; HaL 0.17; PML 1.04; PMW 1.20; PpL 0.76; PpW 0.91; PH 0.49; PL 0.55; PW 1.00; GL 1.72; GW 1.61. Indices: CI 115; SI 95; MI 151.

Paratype: TL 6.8; HW1 1.65; HW2 1.57; HL 1.57; EL 0.38; SL 1.52; SW 0.18; HaL 0.17; PML 1.13; PMW 1.28; PpL 0.87; PpW 1.00; PH 0.50; PL 0.62; PW 1.08; GL 1.72; GW 1.63. Indices: CI 106; SI 92; MI 156.

Structures: Head slightly wider than long, with convex sides and almost straight hind margin; dorsally with irregularly winding deep impressions, laterally and on clypeus with smaller fractions, tending to become polyporous; ventral surface smooth and shiny. Compound eye slightly protruding, positioned behind midlength of head. Frons with low median carina subdivided by a narrow impression; frontal lobes chiefly horizontally oriented, in full-face view covering most of antennal fossae, maximum distance of margins clearly smaller than half of HW2. Clypeus with low median carina, anterior almost straight (weakly convex). Mandibles striate, masticatory margin with five teeth. Palpi very long. Antennal scape relatively long, weakly s-curved, steadily widened from base to apex; all antennomeres longer than wide.

Mesosoma moderately slender, length slightly more than 1.5 times pronotum width; propodeum much shorter than promesonotum. Dorsal outline of promesonotum and propodeum almost forming a straight line (anteriorly and posteriorly slightly downcurved), interrupted by the incision of a sharp, narrow metanotal groove. Promesonotal suture complete medially forming a blunt angle. Surface as on head, but less conspicuous due to dense pilosity. Few small tubercles along dorsal margins, almost absent from mesonotum. Pronotum anterolaterally rounded, much narrower than head. “Waist” in front of propodeum well developed in dorsal aspect. Legs comparatively long and slender.

Petiole, longer than high, slender subtriangular in lateral, slightly transverse in dorsal aspect; surface sculpture polyporous; dorsal apex bluntly crested, with irregularly set tubercles; below moderately long, apically blunt lateral teeth with one or two smaller teeth. Gaster tergite 1 and visible hind margins of the following tergites 2–4 with very fine, dense puncturation, appearing mat. Gaster tergite 1 slightly longer than wide, with evenly convex, unmodified hind margin; insertions of setae appearing as small punctures.

Pilosity: Trunk dorsally and laterally with very dense, appressed white pilosity, but almost absent from centre of face. Dorsal surface with relatively short whitish standing setae, slightly longer on clypeus, propodeum and anterior part of gaster tergite 1. White standing setae on scape, femora, tibiae, and first tarsomeres relatively long.

Colour: Black, without metallic shimmer, mesosoma appearing grey by whitish pilosity. Gaster of holotype dark brown. Gaster tergites 2–4 with narrow whitish hind margin. Mandible basally black, distally reddish. Other mouthparts pale yellow. Apex of last antennomere, apices of middle and hind coxa, trochanters, and distal parts of tarsi orange coloured.

Type Material
Holotype (worker, ) from Sabah, Poring Spring, lower montane mixed dipterocarp forest, > 650 m a.s.l., on Aporusa sp., 13.IV.1992, fogging, leg. A. Floren (A62/F1); paratype (worker, NHMW), same locality and collection data, except 9.II.1993, leg. A. Floren (A51/F5).

Etymology
The Latin adjective subtilis (= fine, subtle) refers to the fine sculpture of gaster tergite 1.

References based on Global Ant Biodiversity Informatics

 * Zettel H., and A. Laciny. 2015. Contributions to the taxonomy of the ant genus Echinopla Smith, 1857 (Hymenoptera, Formicidae). Deutsche Entomologische Zeitschrift 62(1): 101-121.