Echinopla mezgeri, Zettel, Herbert & Laciny, Alice, 2015

Zettel, Herbert & Laciny, Alice, 2015, Contributions to the taxonomy of the ant genus Echinopla Smith, 1857 (Hymenoptera, Formicidae), Deutsche Entomologische Zeitschrift 62 (1), pp. 101-121 : 111-113

Taxon classification Animalia Hymenoptera Formicidae

Echinopla mezgeri sp. n. Figs 27-30

Type material.

Holotype (worker, NHMW) from Sabah, Danum Valley, Western Trail, T#33, 04°58'N; 117°48'E, 21.VII.2004, leg. D. Mezger (C 003604).

Diagnosis

(worker). Predominantly black species with partly yellowish legs; slender and rather small, TL = 5.3 mm. Trunk with extremely fine sculpture, only meso- and metapleura with coarse punctures. Head much longer than wide (CI = 86). Palp formula 5, 3. Mesosoma about twice as long as pronotal width (MI 205), with sharp, but shallow incision in front of propodeum. Pronotal width smaller than head width, if eyes excluded, with tooth-like lateral corners. Propodeum clearly shorter than promesonotum. Petiolar node stocky, without teeth, with obtuse lateral corners. Gaster tergite 1 much longer than wide, with very dense, extremely fine and shallow puncturation. Body almost without standing setae (some on clypeus and abdominal segments 5 and 6), but with dense, very short, appressed pubescence that gives the species a dull appearance.

Description.

Measurements of holotype worker: TL 5.3; HW1 1.09; HW2 0.98; HL 1.28; EL 0.36; SL 1.11; SW 0.16; HaL not applicable; PML 0.98; PMW 0.89; PpL 0.85; PpW 0.76; PH 0.55; PL 0.51; PW 0.79; GL 1.50; GW 1.22. Indices: CI 86; SI 102; MI 205.

Structures: Head much long than wide, roundish, with convex sides, with inconspicuous lobe at middle of posterior margin; dorsally and laterally with fine punctures that are evanescent close to the midline, and larger only between antennal fossae and eyes; ventral surface 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. Mandibles striate, masticatory margin with five teeth. Palp formula 5, 3. Antennal scape long, weakly s-curved, steadily widened from base to apex; antennomeres 8-10 approximately as long as wide.

Mesosoma very elongated and subcylindrical, length roughly twice pronotum width; dorsal outline shaped as two weakly convex curves separated by a weakly impressed mesometanotal suture. Propodeum abruptly declivitous and distinctly shorter than promesonotum. Dorsal surface smooth on major part of pronotum, relatively finely punctured on posterior parts; meso- and metapleura with coarse punctures. Pronotum with tooth-like angles, narrower than head excluding eyes. Promesonotal suture laterally indicated by a short row of punctures; mesometanotal suture narrow and shallow; metanotum recognizable as a narrow ovate depression. “Waist” in front of propodeum weakly developed. Legs long; femora slender.

Petiole relatively large and stout, with a distinct peduncle; node subtriangular in lateral view, spindle-shaped in dorsal view; surface punctured; lateral teeth obtuse, no further dentition. Gaster tergite 1 much longer than wide, completely covering the following tergites in dorsal aspect, very finely and densely punctured; hind margin convex, slightly depressed, without serration.

Pilosity: Body with dense, very short, appressed pubescence giving the species a dull appearance; long standing setae restricted to clypeus and abdominal segments 6 and 7; a few short oblique setae on other abdominal sternites.

Colour: Trunk dull black, without metallic shimmer; apex of abdomen testaceous. Antenna blackish brown, apex of scape and distal flagellomeres orange brown. Mandible basally black, distally reddish brown; palpi pale yellow. Legs black, but coxae and trochanters yellow, tarsi pale brownish towards apex.

Comparative notes.

Echinopla mezgeri sp. n. is a very peculiar species that resembles Echinopla mistura (Smith, 1860). Echinopla mistura was described by a worker from Bacan Island ( “Bachian”), Moluccas, in a new genus Mesoxena in the subfamily Ponerinae ( Smith 1860), and indeed the strange cylindrical mesosoma and petiole of the specimen have superficial similarities to some ponerines. Donisthorpe (1936) gave a redescription of the type and confirmed its placement in Formicinae, and Brown (1973) synonymized Mesoxena with Echinopla . The damaged type is illustrated by Antweb (2015). Both Echinopla mistura and Echinopla mezgeri sp. n. have an elongated mesosoma and very fine body sculpture, and - in contrast to all congeners - they lack standing setae. However, there are important differences between the two species and it is presently not certain whether they are closely related. The antennal fossae are fully exposed in Echinopla mistura , whereas they are largely covered by the horizontal frontal carinae in Echinopla mezgeri sp. n. The petiole of Echinopla mistura is square in lateral and dorsal aspect, whereas in Echinopla mezgeri sp. n. it is subtriangular in lateral aspect and spindle-shaped in dorsal aspect. In Echinopla mistura the posteriorly flat gaster tergite 1 does not fully cover the following tergites, whereas in Echinopla mezgeri sp. n. it has a downcurved posterior margin and the following segments protrude ventrally. In addition, there are many differences in sculpture, colour of antenna, armature of the pronotum, presence of a metanotal suture, etc. Echinopla mezgeri sp. n. has a palp formula of 5, 3 in contrast to any other species treated here that all have 6, 4, and to Echinopla mistura that has according to Smith (1860) six-segmented maxillary palpi (now lacking in the type).

Etymology.

We dedicate this extraordinary species to Dirk Mezger (Balingen, Germany) who discovered it.