Tyrannomyrmex rex

This species is known from two specimens, the holotype worker collected from a litter sample in peninsular Malaysia and a second specimen from Singapore. The Singapore specimen was collected in December 2012 in MacRitchie Reservoir, Singapore (N 01°20’30’’, E 103°49’43’’), during a biodiversity survey of the ants from Singapore. It was found in a selectively logged primary forest not exploited for decades, comprising primary forest species at an intermediate stage of regeneration. While the plant species composition was that of a primary forest, it lacked large emergent trees present in adjacent unlogged primary forest. The site was located near an old growth primary forest (Jacquemin et al., 2015).

Identification
Fernández (2003) - Tyrannomyrmex possesses a unique combination of traits which separate it from other myrmicines: modified setae along the internal border of the mandibles and mandibles with two teeth, apical and subapical, with the rest of the masticatory border lacking teeth. The modified setae are reminiscent of some of the Adelomyrmex (Fernández, 2003), but in Tyrannomyrmex the setae are thick, nonspatulate, and cylindric.

The antennal club is not easily-defined. At first glance it appears to be 2-segmented, but the last segments under careful examination might also be interpreted as 3-segmented.

Key to Tyrannomyrmex species.

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

Castes
Known only from the worker caste.

Nomenclature

 *  rex. Tyrannomyrmex rex Fernández, 2003a: 3, figs. 1,2 (w.) WEST MALAYSIA.

Worker
HW 0.60 HL 0.80 EL 0.06 SL 0.64 PrW 0.49 WL 1.06 PL 0.43 PPL 0.29 PW 0.29 PPW 0.31 GL 0.92 TL 3.75 CI 75 SI 106.

Head in full face view longer than wide, with rounded posterolateral corners, and slightly concave posterior margin; sides slightly convex, slightly narrowing anteriorly. Basal mandibular border separated from masticatory border by distinct angle, masticatory border mostly edentate except for two apical teeth, ventral border of masticatory margin with row of thick, modified setae. Palp formula 2,2 in situ count. Anterior margin of clypeus convex, nearly angular medially; posteriorly clypeus projects narrowly between frontal lobes; median portion of clypeus raised and convex in lateral view, not modified as a flattened area and devoid of any carinae. Frontal lobes short and approximate. Antennae 11-segmented, with ill-defined 3-segmented club, the apical segment largest; scapes longer than head width, slightly incrassate subapically. Scape, when placed back, fails to reach the vertex margin by less than its maximum diameter. Eyes small, with a few ill-defined facets (about 6–7), situated slightly anterior to midlength of sides of head. Mesosoma forming a single broad and continuous convexity in lateral view, devoid of any grooves; propodeum armed with two small triangular teeth, propodeal spiracle round and at distance from propodeal margin equivalent to three diameters. Metapleural lobes broad, more or less rounded. Metapleural gland orifice not seen at 120X. Petiole large and prominent, campaniform in lateral view, in dorsal view the node longer than wide; postpetiole more or less as long as wide. Body shining and heavily foveolate, except for the smooth gaster. Most head foveae dense, about 70% of the eye size; those of mesosoma scattered and smaller in size. Body lacking pilosity, except for numerous small erect hairs arising from the cephalic foveae and anterior pronotal region; a few erect hairs on propleura and forecoxa; anterior margin of clypeus with long erect hairs, including a distinct medial seta. Dorsum of mandible, scape and flagellomeres with several erect hairs. Inner ventral margin of masticatory border of mandibles with modified thick, cylindric and transparent setae. Body light brown in color.

Type Material
Holotype worker: Malaysia, Negri Sembilan; Pasoh Forest Reserve, litter sample, xi.1994, M. Brendell, M. Jackson & S. Lewis legg No. 312.