Aenictus wiwatwitayai

This species inhabits lowland primary forests. All of Thai specimens were collected from dry evergreen forests.

Identification
A member of the ceylonicus group. Jaitrong and Yamane (2013) – Aenictus wiwatwitayai is similar to Aenictus baliensis, Aenictus longicephalus and Aenictus minipetiolus in having the mandible with more than 4 teeth and smooth and shiny propodeal dorsum. It can be separated from the latter three by the following characteristics: mesosoma almost flat dorsally or feebly convex (strongly convex in the latter); subpetiolar process low, with its anteroventral corner angular, and directed forward and downward (subpetiolar process subrectangular in the latter).

Key to Aenictus species groups / Key to southeastern Asian Aenictus ceylonicus group species

Distribution based on Regional Taxon Lists
Oriental Region: Thailand, Vietnam.

Castes
Known only from the worker caste.

Nomenclature

 *  wiwatwitayai. Aenictus wiwatwitayai Jaitrong & Wiwatwitaya, 2013: 218, figs. 20A-C (w.) THAILAND.

Worker
(holotype and paratypes). Larger workers (n = 10): TL 2.00–2.05 mm; HL 0.45–0.50 mm; HW 0.40–0.45 mm; SL 0.28–0.35 mm; ML 0.63–0.68 mm; PL 0.18–0.20 mm; CI 89–90; SI 69–78. Smaller worker (n = 1): TL 1.80 mm; HL 0.40 mm; HW 0.35 mm; SL 0.20 mm; ML 0.55 mm; PL 0.15 mm; CI 88; SI 57.

Head in full-face view subrectangular, clearly longer than broad, sides convex, posterior margin straight; occipital margin bearing a carina. Antennal scape relatively short, not reaching 2/3 of head length. Frontal carina relatively short, not reaching the level of posterior margin of torulus. Parafrontal ridge feeble and incomplete. Anterior clypeal margin concave, concealed by curved anterior extension of frontal carina. Masticatory margin of mandible with a large acute apical tooth followed by a medium-sized subapical tooth, 2-3 denticles, and a medium-sized basal tooth; basal margin almost straight. Maximum width of gap between anterior clypeal margin and mandibles about 2.4 times as broad as maximum width of mandible. Promesonotum weakly convex or almost straight dorsally and sloping gradually to propodeal junction; metanotal groove indistinct; mesopleuron relatively long, demarcated from metapleuron by an indistinct groove; metapleural gland bulla relatively large, its maximum diameter about 2.2 times as long as distance between propodeal spiracle and metapleural gland bulla. Propodeum in profile with almost straight or feebly convex dorsal outline; propodeal junction nearly right-angled; declivity of propodeum widely and shallowly concave, encircled with a distinct rim. Petiole slightly longer than high, its node low, dorsally convex; subpetiolar process weakly produced below, its anteroventral corner acutely angulate and ventral margin convex. Postpetiole subrectangular, shorter than petiole, with its dorsal outline almost straight.

Head including mandible and antennal scape entirely smooth and shiny. Dorsum of mesosoma smooth and shiny except for anteriormost portion and area in front of propodeal junction punctate; mesopleuron and lateral face of propodeum with relatively irregular longitudinal rugae; metapleuron largely smooth and shiny. Petiole dorsally smooth and shiny, remainder reticulate; postpetiole entirely smooth and shiny.

Head with relatively dense long standing hairs mixed with dense short hairs; mesosoma dorsally with relatively dense decumbent hairs; longest pronotal hair 0.08-0.10 mm long. Head, mesosoma, petiole, and postpetiole reddish brown; gaster and legs yellowish brown.

Smaller worker (a paratype). Similar to the larger worker in general appearance with the following conditions that should be noted: head relatively long and narrow (CI 88); antennal scape very short (SI 57), not reaching half length of head; sculpturation weaker than in the larger worker, entire body smooth and shiny.

Type Material
Holotype. THAILAND: Worker from NE. Thailand, Nakhon Ratchasima Prov., Sakaerat Environmental Research Station, dry evergreen forest, 9.VII.1999, leg. Sk. Yamane, TH99-SKY-05 (THNHM). Paratypes. Nineteen workers, same data as holotype (BMHN, MCZC, SKYC, THNHM).

Etymology
The species is named after Dr. Decha Wiwatwitaya of the Ant Museum, Faculty of Forestry, Kasetsart University, who has guided W. Jaitrong in various ways.