Diacamma geometricum

Little has been reported about the biology of .

Identification
Laciny et al. (2015) - Large species (TL 12.8–13.8 mm). Trunk black, without metallic shimmer. Clypeus, mandibles, apex of gaster, and legs dark brown. Trunk strongly striate from genae to gaster tergite 1. Posterior of head longitudinally striate until truncated hind margin; margin narrow. Eyes large, protruding. Clypeus very densely punctured. Mandible with fine striation, in some specimens obliterate. Pronotum transversely-elliptically striate. Propodeum without distinct ridges separating posterior from lateral faces. Petiole stout, node anteriorly rounded, its teeth very long and far apart; subpetiolar process shallowly concave, anterior and posterior corner weakly protruding. Gaster tergite 1 with concentric rugae.

There are some noteworthy morphometric differences between the examined D. tritschleri syntypes (a synonymized species) from Sumatra. While they are of larger overall body-size, both measured syntype specimens possess shorter scapes (SI 157, 158 vs. 162–169) and middle tibiae as well as slightly narrower petioles than their conspecifics from Singapore and Malaysia.

A member of the Diacamma rugosum group. Constituent species are relatively uniform in body structures; most of them have a very coarse striation of mesosoma and gaster, whereas striation on head and gaster tergite 1 is variable among species. Size is usually moderate to large, a metallic shimmer is present in many species. Pilosity and setiferation, the structures of the clypeus and petiole, and last but not least morphometry provide the best differential characteristics.

Distribution
West Malaysia, Singapore, Sumatra.

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

Nomenclature

 *  geometricum. Ponera geometrica Smith, F. 1857a: 67 (w.) SINGAPORE. Wheeler, W.M. 1919e: 54 (m.); Emery, 1899c: 5 (l.). Combination in Diacamma: Mayr, 1862: 718. Subspecies of rugosum: Emery, 1897b: 154; Emery, 1901g: 566; Wheeler, W.M. 1909d: 338; Emery, 1911d: 66; Wheeler, W.M. 1919e: 54; Wheeler, W.M. 1921c: 529; Wheeler, W.M. 1924b: 242; Wheeler, W.M. 1927d: 1; Wheeler, W.M. 1928c: 5; Karaviev, 1935a: 62 (redescription); Yasumatsu, 1940a: 67. Junior synonym of rugosum: Wilson, 1958d: 368. Status as species: Roger, 1860: 301; Mayr, 1862: 718; Mayr, 1863: 407; Roger, 1863b: 16; Mayr, 1886c: 358; Emery, 1887b: 435; Dalla Torre, 1893: 28; Santschi, 1932b: 14; Donisthorpe, 1932c: 448; Radchenko, 1993a: 80; Laciny, Pal & Zettel, 2015: 102 (redescription). Senior synonym of tritschleri: Laciny, Pal & Zettel, 2015: 102.

Worker
Laciny et al. (2015) - syntypes (n = 2): TL 13.30, 13.63; HW 2.35; HL 3.03, 3.07; EL 0.70, 0.71; SL 3.72, 3.68; PH 1.89, 1.87; PL 1.26, 1.24; PW 1.13, 1.15; SpD 1.19, 1.24; SpL 0.64, 0.60; WL 4.70; MTL 2.84, 2.80. Indices: CI 77; SI 158, 157; PI 67, 66; SpDI 107, 109; SpLI 58, 53; EI 29, 30. Non-type material (n = 5): TL 12.78–13.76; HW 2.12–2.25; HL 2.80–3.03; EL 0.64–0.71; SL 3.55–3.72; PH 1.83–2.04; PL 1.20–1.35; PW 1.28–1.39; SpD 1.09–1.33; SpL 0.59–0.71; WL 4.43–4.73; MTL 2.84–3.00. Indices: CI 73–76; SI 162–169; PI 63–67; SpDI 86–105; SpLI 46–55; EI 28–31.

Structures: Head moderately elongate; in front of eyes sides subparallel, behind eyes moderately curved towards relatively wide hind margin. Eyes relatively large and protruding. Very coarse rugae present from genae to gaster tergite 1. Posterior of eyes longitudinal rugae reaching occipital margin that ends in small, blunt teeth. Clypeus entirely covered with very dense puncturation, medially approximately rectangularly protruded; tip often slightly rounded. Mandibles with coarse punctures and more or less strongly developed striation. Pronotum with transverse-elliptical rugae. Rugae on mesopleura and propodeum sides more or less oblique. Posterior face and lateral faces of propodeum not separated by ridges, ventrally with blunt edge. Petiole appearing moderately stout in dorsal aspect, its sides anteriorly converging; spines very long and distant; subpetiolar process shallowly concave, laterally carinate, anterior and posterior corners weakly protruding, posterior one varying from obtuse to slightly acute; ventral outline with short, dense pilosity. Gaster tergite 1 with coarse, concentric, semi-circular or semi-elliptical rugae; along posterior margin coarsely punctured. Gaster tergite 2 with very fine and dense puncturation, slightly shiny.

Pilosity: Standing setae on trunk long and numerous, on mesosoma shorter than on head and gaster. Short appressed pilosity almost uniformly developed, relatively dense, but thin; only on hind margin of pronotum, on mesonotum and dorsum of propodeum more distinct. Standing setae on legs about as long as those on mesosoma, setae on scape short.

Colour: Trunk black; clypeus in some specimens brown; on gaster posterior margins of tergites and apex pale brown. Antennae blackish. Mandibles and legs dark brown; forecoxa black; tarsi infuscated.

Type Material
Laciny et al. (2015) - Holotype, Singapore (CASENT0901342).

Ponera geometrica

Holotype worker in. Labelled “SING 3” (= Singapore) and with a Donisthorpe type-label.