Aenictus minimus, Jaitrong, Weeyawat & Hashimoto, Yoshiaki, 2012

Jaitrong, Weeyawat & Hashimoto, Yoshiaki, 2012, Revision of the Aenictus minutulus species group (Hymenoptera: Formicidae: Aenictinae) from Southeast Asia, Zootaxa 3426 (1), pp. 29-44 : 34-36

Aenictus minimus sp. nov.

( Figs 3 A–E, 7)

Types. Holotype worker from N. Vietnam, Thai Nguyen, Na Hau Village, My Yen Comm. Forest, 8.XI.2001, Sk. Yamane leg., VN 01-SKY-29 ( VNMN). Four paratype workers, same data as holotype ( SKYC, THNHM).

Measurements. Holotype: TL 2.15 mm; HL 0.50 mm; HW 0.44 mm; SL 0.28 mm; ML 0.66 mm; PL 0.15 mm; CI 88; SI 63.

Paratypes (n = 4): TL 1.80–2.15 mm; HL 0.45–0.50 mm; HW 0.35–0.44 mm; SL 0.23–0.28 mm; ML 0.55–0.66 mm; PL 0.14–0.15 mm; CI 78–88; SI 63–64.

Description of worker (holotype and paratypes). Head in full-face view subrectangular, clearly longer than broad, with feebly convex sides and shallowly concave posterior margin. Antennal scape reaching midlength of head in larger workers (not reaching midlength of head in smaller workers); antennal segment II longer than broad and almost as long as III+IV; III–VIII each broader than long; terminal segment distinctly longer than broad, 2.1 times as long as broad and longer than VII+VIII+IX. Frontal carina very short, not extending beyond the level of posterior margin of torulus. Masticatory margin of mandible with a large apical tooth followed by a medium-sized subapical tooth, 3–4 denticles, and a medium-sized basal tooth; basal margin with 1–2 small denticles next to basal tooth and followed by a larger denticle. Mesosoma in profile almost flat dorsally; metanotal groove indistinct or almost absent; metapleural gland bulla relatively large and transparent; distance between propodeal spiracle and metapleural gland bulla shorter than spiracular diameter ( Fig. 3 D). Propodeum in profile with straight dorsal outline; propodeal junction right-angled in larger workers (roundly convex in smaller workers); declivity of propodeum shallowly concave, with lateral carinae, but not demarcated basally by a transverse carina. Petiole slightly shorter than high, with its dorsal outline convex, slightly elevated posteriorly; subpetiolar process large, rectangular; anterior and posterior corners each acutely angulate. Postpetiole slightly shorter than petiole, its dorsal outline convex.

Head including mandible and antennal scape smooth and shiny; entire mesosoma smooth and shiny except mesopleuron, upper portions of metapleuron, and area between propodeal spiracle and metapleural gland bulla that are superficially reticulate. Petiole and postpetiole entirely smooth and shiny. Legs entirely smooth and shiny.

Head and mesosoma dorsally with relatively dense standing hairs mixed with sparse short hairs over the surface; longest pronotal hair 0.07–0.08 mm long. Ground color yellow; typhlatta spot absent.

Etymology. The species epithet “ minimus ” is a Latin word meaning minimum. This refers to this species being the smallest within this species group.

Distribution. Vietnam ( Fig. 7 ).

Bionomics. So far A. minimus is known only from the type locality. The type series was collected from a disturbed forest in the daytime.

Remarks. Aenictus minimus is most similar in general appearance to A. changmaianus and A. minutulus (see under A. changmaianus for details).

Figures

FIGURE 3. Aenictus minimus sp. nov. (holotype). A, Head in full-face view; B, body in dorsal view; C, body in profile; D, propodeal junction, petiole and postpetiole in profile; E, mandible.

FIGURE 7. Distribution of the Aenictus minutulus group.