Aenictus rotundicollis

Aenictus rotundicollis is likely sympatric with the similar Aenictus sonchaengi and inhabits lowland rainforests. It is presently only known from Borneo.

Identification
A member of the laeviceps species group. Very similar to Aenictus sonchaengi in having only 2 long standing hairs on the vertex of the head and the dorsally strongly convex promesonotum which forms a high dome. See A. sonchaengi and also identification notes for Aenictus breviceps and Aenictus laeviceps. (Jaitrong and Yamane 2011)

Distribution
Known from Borneo (Sabah, Sarawak, and Brunei).

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

Castes
Known only from the worker caste.

Nomenclature

 *  rotundicollis. Aenictus rotundicollis Jaitrong & Yamane, 2011: 41, figs. 41-43 (w.) BORNEO.

Worker
Measurements. Holotype and paratypes (n = 10): TL 4.15–4.25 mm; HL 0.85–0.90 mm; HW 0.80–0.85 mm; SL 0.68–0.73 mm; ML 1.30–1.35 mm; PL 0.28–0.30 mm, CI 94–95; SI 84–85.

Holotype and paratypes - Head in full-face view rounded, almost as long as broad, with sides strongly convex and posterior margin almost straight or weakly convex; occipital carina complete. Antennal scape relatively short, not reaching posterolateral corner of head; antennal segments II–X each longer than broad; II almost as long as each of III–V; terminal segment (X) almost as long as VII+VIII+IX. Frontal carina short, extending slightly beyond posterior margin of torulus. Anterior margin of clypeus slightly convex, bearing 5–6 denticles. Masticatory margin of mandible with a large apical tooth followed by a medium-sized subapical tooth, 4 denticles, and a small basal tooth; basal margin bearing 2–3 small teeth. Mesosoma relatively stout; promesonotum in profile strongly convex and forming a dome, mesonotum sloping to metanotal groove; propodeum distinctly lower than promesonotum, with its dorsal outline almost straight; propodeal junction roundly angulate; declivity in profile vertical and almost straight, without any trace of dorsal and lateral carinae. Petiole relatively short, almost as long as high and slightly shorter than postpetiole; subpetiolar process well developed and subtriangular, its apex directed downward and backward; postpetiole almost as long as high, dorsum of node more rounded than in petiole.

Entire head smooth and shiny. Sculpture of mandible very fine, not typically striate as seen in other species; the sculpture also covering outer zone, and only apical and masticatory zones smooth. Antennal scape superficially reticulate and shiny. Pronotum smooth and shiny, with its anteriormost portion punctate; mesonotum longitudinally rugulose; mesopleuron, metapleuron and propodeum entirely punctate. Petiole densely punctate; postpetiole shagreened with smooth and shiny interspaces.

Head with a pair of standing hairs on vertex; promesonotum with 2–3 standing hairs. Entire body dark reddishbrown. Typhlatta spot well developed, located anterior to occipital corner.

Type Material
Holotype worker from Malaysia, Sarawak, Niah N.P., 28 I 1993, Sk. Yamane leg. Twenty-one paratype workers, same data as holotype.

Etymology
The specific name is a noun describing the roundly raised promesonotum.