Aenictus duengkaei

This species has been known only from eastern Thailand. The type series was collected from soil in a lowland dry evergreen forest (ca. 200 m), while the other colony (WJT04-E50) was collected from soil in an agricultural area. Thus, this species inhabits both primary and disturbed forests. (Jaitrong & Yamane 2012)

Identification
A member of the javanus species group. Aenictus duengkaei is similar to Aenictus piercei in terms of body size and coloration. Furthermore, the propodeal declivity is not margined basally with a carina in both species. However, A. duengkaei is easily separated from the latter by the condition of the mandible that has a distinct denticle on the basal margin, while the denticle is lacking in A. piercei. (Jaitrong & Yamane 2012)

Distribution based on Regional Taxon Lists
Oriental Region: Thailand.

Castes
Known only from the worker caste.

Nomenclature

 *  duengkaei. Aenictus duengkaei Jaitrong & Yamane, 2012: 55, figs. 2, 7A (w.) THAILAND.

Worker
Holotype: TL 1.90 mm; HL 0.43 mm; HW 0.38 mm; SL 0.20 mm; ML 0.58 mm; PL 0.15 mm; CI 88; SI 53.

Larger workers (paratypes, n = 5): TL 1.80-1.90 mm; HL 0.43-0.45 mm; HW 0.36-0.38 mm; SL 0.19-0.20 mm; ML 0.53-0.58 mm; PL 0.14-0.15 mm; CI 83-88; SI 52-53. Smaller workers (paratypes, n = 3): TL 1.50-1.55 mm; HL 0.40-0.43 mm; HW 0.25-0.28 mm; SL 0.15-0.16 mm; ML 0.45-0.48 mm; PL 0.10-0.13 mm; CI 63-65; SI 59-60.

Head in full-face view distinctly longer than broad and subrectangular, with sides weakly convex or almost parallel, and posterior margin clearly concave; seen in profile occipital corner of head rounded. Antennal scape very short, not reaching midlength of head; antennal segment II clearly longer than each of III-VI; III-VI shorter than broad; terminal segment longer than VII+VIII+IX and about 1.6 times as long as broad. Anterior margin of clypeus bearing 5-7 denticles. Masticatory margin of mandible with 3 acute teeth including a large apical tooth; basal margin with 1-2 denticles behind large basal tooth. Mesosoma seen in profile almost flat dorsally; propodeal junction angulate; declivity of propodeum almost flat, with blunt lateral carinae, but not demarcated basally by a transverse carina. Petiole round almost as long as high; subpetiolar process well developed, subrectangular, its ventral border almost straight and longer than posterior border; postpetiole slightly smaller than petiole and its dorsal outline roundly convex.

Head and antennal scape smooth and shiny; mandible extensively smooth but narrow zone along basal margin sculptured. Dorsal and lateral face of pronotum smooth and shiny except for anteriormost portion microreticulate; mesonotum smooth and shiny; mesopleuron superficially shagreened with smooth and shiny interspaces; metapleuron and propodeum shiny but microreticulate. Petiole entirely microreticulate but its dorsal face with a small area that is smooth (in larger specimens this area weakly sculptured). Postpetiolar node almost smooth and shiny.

Head with relatively sparse standing hairs; mesosoma dorsally with relatively dense standing hairs mixed with sparse short hairs over the surface; longest pronotal hairs 0.07-0.10 mm long. Head, gaster and legs yellowish brown; mesosoma, petiole and postpetiole reddish brown; mandible darker than elsewhere.

Type Material
Holotype worker from E. Thailand, Chacheongsao Prov., Khao Ang Reu Nai, dry evergreen forest, 22.VIII.2003, Sk. Yamane leg., TH03-SKY-79. Twelve paratype workers, same data as holotype.

Etymology
The specific name is dedicated to Dr. Prateep Duengkae of the Faculty of Forestry, Kasetsart University, who helped us in collecting material in eastern Thailand.