Aenictus glabratus

The type series was collected by sifting from the leaf litter in a lowland rainforest in Malay Peninsula.

Identification
A member of the silvestrii species group. A. glabratus is a distinct species in having the head almost smooth and shiny and the body much paler (clear yellow or yellowish brown) and smaller than in the other species of the A. silvestrii-group.

Key to Aenictus species groups / Key to Aenictus silvestrii group species

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

Castes
Known only from the worker caste.

Nomenclature

 *  glabratus. Aenictus glabratus Jaitrong & Nur-Zati, 2010: 450, figs. 1-3 (w.) WEST MALAYSIA.

Worker
Measurements. Holotype and paratypes (n = 7): TL (total length) 2.85- 2.95 mm; HL (head length) 0.63-0.65 mm; HW (head width) 0.48-0.53 mm; SL (scape length) 0.33-0.38 mm; ML (mesosomal length) 0.83-0.85 Jaitrong, W. & A.M. Nur-Zati — A New Species of Aenictus From Malay Peninsula 451 mm; MTL (maximum length of mid tibia) 0.30-0.38 mm; PL (petiole length) 0.20-0.23 mm; CI (cephalic index = HW/HL × 100) 76-81; SI (scape index = SL/HW × 100) 67-71.

(holotype and paratypes). Head in full-face view rectangular, distinctly longer than broad, with almost parallel sides; posterior margin of head almost straight but weakly sinuate; occipital margin concave bearing a carina. Antenna 9-segmented; scape short, extending to the midlength of head in full-face view; antennal segment II longer than III and IV; V-IX, each longer than broader; terminal segment (IX) very large, almost as long as VI, VII and VIII combined. Frontal carinae short extending less than half length of head, very poorly developed in posterior half. Clypeus short and roundly produced anteriorly, lacking teeth on anterior margin. Mandible with apical tooth large, followed by 10-12 denticles of two sizes, the larger alternating with 1-3 smaller; basal margin of mandible with 1-2 denticles near basal angle.

With mesosoma seen in proile promesonotum weakly convex dorsally and sloping gradually to metanotal groove; propodeum slightly lower and weakly convex dorsally; mesopleuron not clearly demarcated from metapleuron. Propodeal junction angulated; declivity of propodeum shallowly concave, encircled with a rim.

Petiole almost as long as high, anteriorly margined by a transverse carina, while posterior lacking it; subpeiolar process subtriangular, its apex directed downward; postpetiole slightly smaller than petiole, roundly convex dorsally, anteroventrally produced as a blunt angle directed downward and forward. Gaster elongate-elliptical, narrowed anteriorly and posteriorly. Head entirely smooth and shiny except anteriormost portion of head in pro"le where short irregular longitudinal rugae are present; area around antennal sockets with dense punctures; upper face of antennal scape basally with dense micropunctures and apically much smoother; mandible largely with dense minute punctures, but smooth apically and along masticatory margin. Dorsal surface of mesosoma weakly and irregularly corrugated but shiny; anteriormost portion of pronotum punctate; sides of pronotum smooth and shiny; mesopleuron, metapleuron and sides of proprodeum densely punctate. Gaster smooth and shiny except for extreme basal portion. Femora and tibiae smooth and shiny.

Body with relatively sparse standing hairs mixed with sparse short hairs over the surface; length of the longest pronotal hair approximately 0.13–0.15 mm. Head, mesosoma and waist yellowish brown; gaster and legs clear yellow; mandible dark brown.

Type Material
Holotype. Worker from Selangor, Semangkok Forest Reserve. (550 m alt.), Malaysia, Nur-Zati et al. leg., 21 XI 2007, WSM0167.03. Paratypes. Six workers, same data as holotype. Type depository. The holotype and one paratype are deposited in the Forest Research Institute Malaysia (Malaysia) and some paratypes in the Natural History Museum, London, (U.K.), SKY collection at Kagoshima University (Japan), the Natural History Museum of the National Science Museum (Thailand).

Etymology
The species epithet “glabratus” is a Latin word meaning smooth. This refers to the smooth and shiny head of this species, while the head is entirely sculptured in the other species of the A. silvestrii-group.