Aenictus eguchii

Little is known about the bionomics of A. eguchii. However, judging from the data for the specimens examined this species inhabits lowland primary forests.

Identification
A member of the ceylonicus group. Jaitrong and Yamane (2013) - Aenictus eguchii is most similar in general appearance to Aenictus jawadwipa from Sundaland. However, they differ in some characters. The posteroventral corner of the subpetiolar process is bluntly angulate (not spiniform) in the former, but acutely angulate (spiniform) in the latter. The dorsal outline of the propodeum is straight in the latter but weakly convex in the former. The metapleural gland bulla is more strongly sculptured (puncto-reticulate and opaque) in the former than in the latter (weakly sculptured and shiny). The promesonotum in profile is more distinctly convex in the former than in the latter.

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

Distribution based on Regional Taxon Lists
Oriental Region: Vietnam.

Castes
Known only from the worker caste.

Nomenclature

 *  eguchii. Aenictus eguchii Jaitrong & Wiwatwitaya, 2013: 183, figs. 6A-C (w.) VIETNAM.

Worker
(holotype and paratypes, n = 10). TL 2.20–2.60 mm; HL 0.46–0.58 mm; HW 0.43–0.55 mm; SL 0.30–0.43 mm; ML 0.70–0.85 mm; PL 0.18–0.23 mm; CI 92–96; SI 71–77.

Head in full-face view subrectangular, slightly longer than broad, sides convex and posterior margin almost straight. Antennal scape reaching 2/3 of head length. Frontal carina relatively long, slightly extending beyond the level of posterior margin of torulus. Parafrontal ridge absent. Anterior clypeal margin almost straight, lacking denticles and concealed by curved anterior extension of frontal carina. Masticatory margin of mandible with large acute apical tooth followed by a medium-sized subapical tooth, 2 denticles, and a medium-sized basal tooth; basal margin almost straight. Maximum width of gap between anterior clypeal margin and mandibles about 2.1 times as broad as maximum width of mandible. Promesonotum weakly convex dorsally and sloping gradually to metanotal groove; metanotal groove indistinct; metapleural gland bulla relatively large and transparent, its maximum diameter about 2.8 times as long as distance between propodeal spiracle and metapleural gland bulla. Propodeum in profile with almost straight or feebly concave dorsal outline; propodeal junction angulated, nearly right-angled; declivity of propodeum shallowly concave, and encircled with a rim. Petiole almost as long as high, with its dorsal outline weakly convex; subpetiolar process generally very low, subrectangular with its anteroventral and posteroventral corners angulate, and margin between the corners almost straight. Postpetiole almost as long as petiole, with its dorsal outline convex.

Head including antennal scape entirely smooth and shiny. Promesonotum smooth and shiny except for punctate anteriormost portion; mesopleuron, metapleuron, and propodeum entirely punctate; in addition, mesopleuron with longitudinal rugae. Petiole and postpetiole entirely reticulate except small area on dorsa smooth and shiny. Legs entirely smooth and shiny.

Head and mesosoma dorsally with relatively dense standing hairs; longest pronotal hair 0.20–0.23 mm long. Head, mesosoma, petiole, and postpetiole reddish brown; gaster and legs yellowish brown.

Type Material
Holotype. VIETNAM: Worker from N. Vietnam, Ha Tai Prov., Ba Vi N.P. (ca. 400 m alt.), 12.XI.1999, leg. K. Eguchi, Eg99-VN-126 (VNMN). Paratypes. Seventeen workers, same data as holotype (BMNH, MCZC, SKYC, THNHM).

Etymology
The scientific name is dedicated to Dr. Katsuyuki Eguchi, who donated the type series to us.