Aenictus subterraneus

Known only from the type locality in a lowland primary forest.

Identification
A member of the minutulus species group. Aenictus subterraneus is most similar in general appearance to Aenictus peguensis (see Aenictus peguensis for details).

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

Castes
Known only from the worker caste.

Nomenclature

 *  subterraneus. Aenictus subterraneus Jaitrong & Hashimoto, 2012: 40, figs. 6A-E, 7 (w.) BORNEO.

Worker
Measurements. Holotype: TL 2.10 mm; HL 0.55 mm; HW 0.48 mm; SL 0.38 mm; ML 0.78 mm; PL 0.18–0 mm; CI 86; SI 79. Paratypes (n = 2): TL 2.10–2.15 mm; HL 0.55–0.58 mm; HW 0.48–0.50 mm; SL 0.38 mm; ML 0.78–0.80 mm; PL 0.18–0.19 mm; CI 86–87; SI 75–79.

Holotype and paratypes - Head in full-face view clearly longer than broad, with sides convex and posterior margin almost straight or feebly concave; occipital margin bearing a carina. Antennal scape reaching midlength of head; antennal segments II–X each longer than broad; II almost as long as each of III–VI; terminal segment clearly longer than broad and almost as long as VII+VIII+IX. Frontal carina short, slightly 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, 7–8 denticles, and a medium-sized basal tooth; basal margin with 4–5 denticles. Promesonotum in profile convex dorsally and sloping gradually to metanotal groove; metanotal groove distinct; metapleural gland bulla relatively small; distance between propodeal spiracle and metapleural gland bulla clearly longer than spiracular diameter (Fig. 6D). Propodeum in profile lower than promesonotum with weakly convex dorsal outline; propodeal junction obtusely angulate; declivity of propodeum shallowly concave, with lateral carinae, but not demarcated basally by a transverse carina. Petiole shorter than high, with petiole in profile its dorsal outline convex; subpetiolar process rather developed, with a sharply pointed lamellate appendage directed downward. Postpetiole clearly shorter than petiole, its dorsal outline slightly elevated posteriorly.

Head including mandible and antennal scape smooth and shiny; basal portion of the scape finely sculptured. Entire pronotum smooth and shiny except for its anteriormost portion punctate; mesothorax, metapleuron, and propodium entirely microreticulate; petiole and postpetiole entirely punctate except dorsal faces smooth and shiny. Legs entirely smooth and shiny.

Head and mesosoma dorsally with relatively sparse standing hairs mixed with sparse short hairs over the surface; longest pronotal hair 0.15–0.18 mm long. Body yellowish-brown, mandible darker than elsewhere; typhlatta spot absent.

Etymology
The specific name refers to the behaviour of this species that was collected from soil.

References based on Global Ant Biodiversity Informatics

 * Jaitong W., and Y. Hashimoto. 2012. Revision of the Aenictus minutulus species group (Hymenoptera: Formicidae: Aenictinae) from Southeast Asia. Zootaxa 3426: 29-44.
 * Jaitrong, W., and Y. Hashimoto. "Revision of the Aenictus minutulus species group (Hymenoptera: Formicidae: Aenictinae) from Southeast Asia." Zootaxa 3426 (2012): 29-44.