Chelaner lacunosus

The ant is apparently very rare, having been recorded in the SWBP on two occasions from Eneabba and once in Cape Arid National Park. Elsewhere in WA it has been found in Queen Victoria Spring Nature Reserve. There is also one record from SA.

Identification
Heterick (2001) - A member of the falcatum group. The Western Australian specimen of Chelaner lacunasum is distinct from the Pinnaroo material, being much darker, and with reduced propodeal denticles. Nonetheless, this worker shares several characters that are considered diagnostic for the species: 1, overall sculpture; 2, conformation of the clypeus; 3, shape of the anterior promesonotum and nodes; 4, presence of erect and suberect setae on the alitrunk; 5, bevelled appearance of the propodeal declivity; and 6, acutely angled metapleural lobes. Chelaner lacunosum differs from other members of the falcatum-group in terms of the pilosity and sculpture of its alitrunk.

Heterick (2009) - Workers depart from the usual predominantly glabrous appearance found in most other members of its species group, in that the body surfaces are covered with many short, erect setae.

Distribution
WA, SA.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Biology
Heterick (2001) - Like other members of the C. falcatum-group, C. lacunosum is known from a limited number of specimens (here, five workers), but this may give a misleading picture of its actual abundance. The region around the Great Australian Bight has sparse human settlement, and the ant fauna of the Australian mainland between the coastal towns of  Esperance (Western Australia) and Ceduna (South Australia) is almost unknown.

Nomenclature

 *  lacunosum. Monomorium lacunosum Heterick, 2001: 382, figs. 25, 58 (w.) AUSTRALIA.
 * Combination in Chelaner: Sparks et al., 2019: 232.

Worker
Holotype. HML 1.66; HL 0.60; HW 0.48; CeI 81; SL 0.37; SI 76; PW 0.39. Others. HML 1.62-1.72; HL 0.56-0.60; HW 0.47-0.49; Cel 80-88; SL 0.34-0.38; SI 70-79; PW 0.37-0.39 (4 measured).

As for the worker of Chelaner falcatum, but with the following apomorphies.

Head. Frons of head capsule longitudinally striate and reticulate with combination of incurved decumbent and subdecumbent setulae and erect and suberect setae. Compound eyes circular or subcircular; (viewed laterally) compound eyes set posterior of midline of head capsule; eye moderate, eye width 0.5-I.5x greatest width of antennal scape. Anteromedial clypeal margin straight or slightly emarginate, median clypeal carinae not produced as teeth or denticles. Longest lateral anterior clypeal setae long, extending beyond dorsal margin of closed mandibles. Posteromedial clypeal margin level with posterior surface of antennal fossae. Frontal lobes parallel, sinuate. Venter of head capsule without elongate, basket-shaped setae. Palp formula 2,3. Maximum number of mandibular teeth and denticles: five; mandibles (viewed from front) triangular and smooth, with piliferous punctures; apical and basal mandibular margins meeting in tooth or denticle.

Alitrunk. Promesonotal sculpture present in form of microreticulation and rugosity over entire promesonotum; erect and suberect promesonotal setae greater than 10. Mesonotal suture absent. Metanotal groove absent. Propodeal sculpture present as uniform rugosity, with well defined costulae on declivitous face of propodeum; propodeal processes present on posterior propodeal angles as small denticles or sharp flanges; lobes present and produced apically so as to form acute angled, sharp projections. Declivitous face of propodeum longitudinally concave between its lateral margins. Erect and suberect propodeal setae greater than 10; propodeal setulae decumbent and subdecumbent.

Petiole and postpetiole. Petiolar node cuboidal; sculpture present; petiolar node rugose. Ratio of greatest node breadth (viewed from front) to greatest node width (viewed in profile) near 4:3 to near 1:1. Anteroventral process always present as pronounced spur. Height ratio of petiole to postpetiole near 1:1 to near 4:3; height-length ratio of postpetiole near 2:1. Sculpture present; postpetiole rugose.

Gaster. Pilosity of first gastral tergite consisting of combination of appressed setulae and longer, erect and suberect setae.

General characters. Colour tawny yellow to yellow-orange; or, alitrunk, petiole, postpetiole, and appendages russet, head and gaster chocolate. Worker caste monomorphic.

Type Material
Holotype. Worker (top point), South Australia, 25 km SSW Pinnaroo 35°28'S, 140°47'E, 24.x.l983, J.D. Gnomon & J. C. Cradle, ANIC berlesate no. 890 mallee and heath litter. Paratypes. South Australia: I + 2 workers with same data as holotype (ANIC and ).



Etymology
Latin: “pitted”.