Echinopla circulus

Nothing is known about the biology of .

Identification
Zettel and Laciny (2015) - A member of the Echinopla melanarctos group. Worker: Predominantly black species with yellowish legs (but tarsi black); relatively large, TL = 6.4– 7.6 mm. Surface of head and mesosoma with numerous pedestals, each bearing one long standing black seta and a ring of short pale hairs directed horizontally. Gaster tergite 1 with similar pedestals at base, but their height strongly reduced towards posterior margin, so that they appear as low dimples; additionally with strong, circular ridges. Head wider than long (CI = 115–124). Mesosoma about one fourth longer than pronotal width (MI 124–132), with narrow, sharp and deep incision in front of propodeum. Pronotal width slightly less than head width, if eyes excluded. Propodeum slightly shorter than promesonotum. Petiole node almost smooth, anteriorly with transverse ridge, dorsally with four small teeth between the lateral spines, without teeth laterally below lateral spine. Setae on dorsal surface, legs and scape abundant, long and mostly black.

Echinopla circulus is very similar to Echinopla pallipes, but clearly differs in the structure of gaster tergite 1. A less conspicuous difference is found in the frontal lobes that are parallel in E. pallipes, but anteriorly slightly converging in E. circulus. On average E. circulus is larger than E. pallipes (HW1 2.04–2.29 in E. circulus sp. n., 1.85–2.02 in E. pallipes including an aberrantly large worker from Gunung Mulu).

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

Castes
Known only from the worker caste.

Nomenclature

 *  circulus. Echinopla circulus Zettel & Laciny, 2015: 111, figs. 21-25 (w.) MALAYSIA.

Worker
Holotype: TL 7.6; HW1 2.29; HW2 2.07; HL 1.89; EL 0.31; SL 1.78; SW 0.20; HaL 0.55; PML 1.30; PMW 1.98; PpL 1.2; PpW 1.63; PH 0.63; PL 0.53; PW 1.11; GL 2,28; GW 2.38. Indices: CI 121; SI 78; MI 126.

Paratypes: TL 6.4–7.8; HW1 2.04–2.23; HW2 1.80–2.07; HL 1.67–1.93; EL 0.29– 0.31; SL 1.57–1.83; SW 0.18–0.21; HaL 0.46–0.58; PML 1.09–1.47; PMW 1.63–1.98; PpL 0.96–1.15; PpW 1.41–1.65; PH 0.55–0.62; PL 0.45–0.51; PW 0.90–1.06; GL 1.96–2.41; GW 2.12–2.32. Indices: CI 116–124; SI 77–84; MI 124–132.

Structures: Head wider than long, roundish, with convex sides; frons, vertex and tempora rugose-tuberculate, the high “pedestals” connected by low ridges; antennal scrobes, part of genae, and clypeus longitudinally rugose; ventral surface smooth and shiny. Ventrolateral ridge forming a distinct angle below eye. Compound eye small, but strongly protruding, positioned distinctly behind mid-length of head on a small socket. Frons with long median carina; frontal lobes obliquely elevated, completely covering antennal fossae in dorsal aspect; margins anteriorly slightly converging, their maximum distance near posterior end, distinctly greater than half of HW2. Clypeus subapically with transverse carina; median carina indistinct among longitudinal rugae. Mandibles striate, masticatory margin with five teeth. Antennal scape moderately long, weakly s-curved, steadily widened from base to apex; antennomeres 8–10 slightly longer than wide.

Mesosoma very stout, length roughly 1.3 times pronotum width, dorsal outline regularly convex; propodeum distinctly shorter than promesonotum. Dorsal surface rugose-tuberculate as on vertex; sides irregularly rugose; posterior-most part of propodeum smooth and shiny. Pronotum rounded, distinctly narrower than head excluding eyes. Promesonotal and mesometanotal suture sharp, narrow and (laterally) deep, but both inconspicuous between “pedestals”; promesonotal suture evanescent in medial third. “Waist” in front of propodeum hardly developed. Legs moderately long; femora basally stout, strongly narrowed towards apex.

Petiole small, node square, without dorsal crest; surface smooth; lateral teeth moderately long, directed straight towards sides; dorsally between lateral teeth with two pairs of small denticles; anterior face of node separated from dorsal summit by a fine ridge that is medially evanescent; below strongly developed lateral teeth without further dentition. Gaster tergite 1 wider than long, completely covering the following tergites; hind margin convex, without serration; surface anteriorly with pedestals that are basally almost as high as those on mesosoma, but gradually becoming lower towards hind margin where they are only low tubercles; between these structures with coarse rugae that are more or less arranged in circles.

Pilosity: Trunk dorsally with very long, mostly black, but in some areas pale, standing setae that arise from the apices of tubercles. Short, pale pilosity rather inconspicuous (more conspicuous only on dorsum of mesosoma), often arranged in subapical rings of horizontally projecting hairs on pedestals. Scape also with very long standing setae. Legs without appressed pilosity, but all parts with numerous, black or white, oblique setae of varying length. Femora with rows of setae on flexor and extensor sides. Longest setae on middle and hind tibiae as long as those on scape.

Colour: Trunk black, without metallic shimmer; apex of abdomen testaceous. Antenna black or very dark brown, extreme base of scape and apex of last antennomere pale. Mandible basally black, distally brown; other mouthparts yellowish to testaceous. Legs chiefly testaceous; forecoxa black (but anteriorly testaceous in the specimen from the Crocker Range); tarsi partly infuscated.

Type Material
Holotype (worker, ) from Borneo, Sarawak, Kelabit Highlands, Bareo – Arur Dalam, ca. 1000 m a.s.l., 26.II.1993, leg. M.A. Jäch (14); 4 paratypes (workers, NHMW, ) same locality, leg. H. Zettel (11); 1 paratype (worker, NHMW) from Borneo, Sabah, Crocker Range National Park, Mawer Waterfall area, undergrowth, 17.VI.1996, unknown collector; 2 paratypes (workers, ) from Borneo, Sabah, Poring Hot Spring, 7.I.1998, leg. A. Malsch (8257).

Etymology
From the Latin circulus for a small circle and referring to the concentric rugae on gaster tergite 1; used as a noun in apposition.

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.