Chelaner petiolatus

Monomorium petiolatum is a cryptic forager in rainforest ground litter (Heterick 2001).

Identification
This species has a remarkably long petiolar peduncle, and this feature, combined with the glossy, shining cuticle, gives the ant the appearance of a glasswork creation when viewed under a microscope. The long peduncle also distinguishes it from other members of the kilianii-group, except for Monomorium shattucki (which, however, has a conspicuous petiolar node).

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  petiolatum. Monomorium petiolatum Heterick, 2001: 388, figs. 29, 80 (w.) AUSTRALIA.

Worker
Holotype. HML 2.02; HL 0.62; HW 0.51; Cel 81; SL 0.57; SI 114; PW 0.37. Others. HML 2.04-2.29; HL 0.59-0.65; HW 0.50-0.57; CeI 80-88; SL 0.56-0.59; SI 104-111; PW 0.30-0.40 (13 measured).

As for the worker of Monomorium kiliani, but with the following apomorphies.

Head. Head square or rectangular; vertex convex. (Viewed laterally) compound eyes set at midline of head capsule. Anteromedial clypeal margin straight or slightly emarginate, median clypeal carinae not produced as teeth or denticles. Posteromedial clypeal margin level with posterior surface of antennal fossae. Anterior tentorial pits equidistant between mandibular insertions and antennal fossae. Palp formula 2,2. Maximum number of mandibular teeth and denticles: four; mandibles (viewed from front) triangular and smooth, with piliferous punctures.

Alitrunk. Promesonotal setulae appressed. Mesonotal suture absent. Metanotal groove present as feebly impressed furrow between promesonotum and propodeum. Dorsal propodeal face gently convex, or sloping posteriad with wedge-shaped flattening or shallow depression that is widest between propodeal angles. Propodeal setulae absent.

Petiole and postpetiole. Petiolar spiracle lateral and positioned in pedicel well anteriad of petiolar node. Petiolar node conical, dorsally rounded. Ratio of greatest node breadth (viewed from front) to greatest node width (viewed in profile) near 1:1. Height ratio of petiole to postpetiole near 1:1 to near 4:3; height-length ratio of postpetiole near 3:4 to near 1:2.

Gaster. Pilosity of first gastral tergite consisting entirely of well-spaced erect and suberect setae.

General characters. Colour shining orange: head gaster, and legs often lighter in colour. Worker caste monomorphic.

Type Material
Holotype. Worker, Queensland, Mt Tyson 2 km SW Tully l7°55'S, 145°54'E, 7.v.1983, D. K. Yeates, QM berlesate no. 588, rainforest, 650m, sieved litter. Paratypes. Queensland: 3x3 workers, Table Mtn., Cape Tribulation 16°09'S, 145°26'E, 24.iv.1983, G. B. Monteith & D. Cook, QM berlesate no. 542, rainforest, 320m, sieved litter, ANIC ants vial no. 40.211 (ANIC,, ); 3x2 workers, same collection data as preceding paratypes, QM berlesate no. 540 (ANIC, BMNH, MCZ); 3 workers, Queensland, banks of Daintree R., 8.viii.1975, B. B. Lowery, RF., in rotten wood, Chelaner (ANIC).



Etymology
Latin: “little stalk” (referring to the petiolar peduncle).