Echinopla tunkuabduljalilii

The holotype of this species was discovered by manual collecting on shrubs near the Bantang River in a lowland secondary dipterocarp forest. The paratypes were found on lower vegetation in an evergreen forest.

Identification
Laciny et al. (2019) - (worker): Predominantly black species with partly yellowish legs; slender and rather small, TL = 5.5 – 5.9 mm. Trunk with extremely fine sculpture, only dorsal part of mesopleura, metapleura, sides of propodeum, and anterior face of petiolar node with coarse punctures. Head much longer than wide (CI = 82 – 85). Palp formula 5, 3. Mesosoma little more than twice as long as pronotal width (MI 209), with sharp, but shallow incision in front of propodeum. Pronotum with tooth-like lateral protrusions, its maximum width at mid-length, narrower than head, if eyes excluded. Propodeum roughly the same length as promesonotum. Petiolar node relatively low, without teeth, with blunt lateral corners. Gaster tergite 1 much longer than wide, without puncturation. Body almost without standing setae (some on clypeus, apices of scapes, and abdominal sterna), but with dense, very short, appressed pubescence.

Echinopla tunkuabduljalilii belongs to the Echinopla mezgeri species group. Hitherto, Echinopla mezgeri from Borneo was the only described species in this group, but at least two further species are known: Echinopla jeenthongi from Thailand and one undescribed species from Java (Seiki Yamane, pers. comm. to HZ). Echinopla mezgeri differs considerably from Echinopla tunkuabduljalilii in surface structures, chiefly by more expanded puncturation on head, mesosoma, petiole, and gaster tergite 1. Specifically the head (dorsally and laterally), the mesonotum, the dorsal surface of the propodeum, and tergite 1 bear a distinct puncturation, which is absent (on propodeum strongly reduced) in Echinopla tunkuabduljalilii. The mesopleura are entirely covered by a coarse puncturation in Echinopla mezgeri, while their ventral part is finely punctured in Echinopla tunkuabduljalilii. On the petiole, a coarse puncturation is developed anteriorly and posteriorly in Echinopla mezgeri, but only anteriorly in Echinopla tunkuabduljalilii. The petiole is distinctly lower in Echinopla tunkuabduljalilii. than in Echinopla mezgeri (PHI 51 vs. 47). The propodeum and first gastral tergite of Echinopla tunkuabduljalilii are comparatively elongated, making the mesosoma (MI 206 vs. 209) and gaster appear more slender compared to Echinopla mezgeri.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Malaysia. Oriental Region: Thailand.

Nomenclature

 *  tunkuabduljalilii. Echinopla tunkuabduljalilii Laciny, Zettel, Maryati & Noor-Izwan, 2019: 251, figs. 1-5 (w.) WEST MALAYSIA.

Worker
Holotype: TL 5.48; HW1 1.15; HW2 1.02; HL 1.35; EL 0.27; SL 1.20; SW 0.15; PML 1.02; PMW 0.96; PpL 0.98; PpW 0.87; PH 0.54; PL 0.53; PW 0.88; GL 1.73; GW 1.29. Indices: CI 85; SI 104; MI 209; PHI 47. Paratypes: TL 5.61 – 5.87; HW1 1.15 – 1.22; HW2 1.02 – 1.04; HL 1.39 – 1.43; EL 0.27 – 0.30; SL 1.13 – 1.22; SW 0.16; PML 1.04 – 1.09; PMW 0.96 – 0.99; PpL 0.93 – 0.98; PpW 0.86 – 0.91; PH 0.53 – 0.56; PL 0.51 – 0.55; PW 0.83 – 0.90; GL 1.67 – 1.80; GW 1.35 – 1.41. Indices: CI 82 – 85; SI 98 – 100; MI 209; PHI 44 – 49.

Structures: Head much longer than wide, anteriorly with subparallel sides, posteriorly roundish, with inconspicuous lobe at middle of posterior margin; surface without punctures, dorsally and laterally dull, ventrally smooth and shiny. Compound eye small, weakly protruding, positioned at mid-length of head. Frons with fine median carina; frontal lobes horizontal, partly covering antennal fossae in dorsal aspect, maximum distance near posterior end equalling half of HW2. Clypeus with median tumescence, surface densely reticulated. Mandibles with coarse punctures; masticatory margin with five teeth. Palp formula 5, 3. Antennal scape long, weakly s-curved, steadily widened from base to apex; antennomeres 8–10 slightly longer than wide. Mesosoma very elongated, subcylindrical, length roughly twice pronotum width; dorsal outline shaped as two weakly convex curves separated by a narrowly impressed mesometanotal suture, forming an hourglass-shape in dorsal view. Propodeum abruptly declivitous and marginally shorter than promesonotum. Dorsal surface chiefly without punctures, only on propodeum with very few dispersed inconspicuous punctures. Mesopleura dorsally, metapleura and sides of propodeum entirely with dense coarse puncturation. Pronotum with pair of tooth-like protrusions, narrower than head excluding eyes. Promesonotal suture indistinct; mesometanotal suture narrow and shallow, but sharply defined; metanotum recognizable as a narrow ovate depression. “Waist” in front of propodeum weakly developed. Legs long; femora slender. Petiole relatively wide and low, with a distinct peduncle; spindle-shaped in dorsal view; anterior surface of node with dense coarse puncturation, posterior surface with some indistinct punctures; lateral corners obtuse, no further dentition. Gaster tergite 1 much longer than wide, completely covering the following tergites in dorsal aspect, without puncturation; hind margin convex, slightly depressed, without serration.

Pilosity: Body with dense, very short, appressed pubescence giving the holotype a dull appearance; the paratypes are more shiny, which is either caused by thinner pubescence or by a different way of preservation; long standing setae restricted to clypeus, apex of scape, and abdominal sterna.

Colour: Trunk dull black, without metallic shimmer (a slight lead-blue tinge visible under strong lighting); apex of abdomen testaceous in holotype. Antennal scape black, funicular segments fading to light brown towards apex. Mandible black, masticatory margin brown; palpi yellow. Legs black, but coxae, trochanters, and bases of all femora light yellowish brown; tarsi pale brown towards apex.

Etymology
Named after the late Almarhum Tunku Abdul Jalil, the fourth son of the current Johor ruler, Sultan Ibrahim Ibni Almarhum Sultan Iskandar; for his strong support towards wildlife conservation in the State of Johor.

References based on Global Ant Biodiversity Informatics

 * Laciny A., H. Zettel, M. Maryati, and A. Noor-Izwan. 2019. A new species of the Echinopla mezgeri group (Insecta: Hymenoptera: Formicidae) from Peninsular Malaysia. Ann. Naturhist. Mus. Wien, B 121: 249-255.