Aenictus samungi

Aenictus samungi is a rare species and is known only from the type locality (ca 1100 m a.s.l.). The type series was collected from a foraging column on a forest path in a dry evergreen forest, western Thailand near the Myanmar border; no immature and prey were seen along the column. Workers were fast-running.

Identification
Jaitrong & Ruangsittichai (2018) - A member of the wroughtonii group. Aenictus samungi can be easily distinguished from other wroughtonii group species group by the following characteristics: smallest species of the group (HW 0.31–0.33 mm in A. samungi; HW > 3.7 mm in other members); petiole shorter than high (as long as or longer than high in other members); promesonotum with almost flat or straight dorsal outline (convex and sloping gradually to metanotal groove in other members); antennal scape short only just reaching mid-length of the head (at least two-thirds of the head length or beyond the posterolateral corner of the head in other members). Both Aenictus nuchiti and A. samungi have small bodies and short antennae, but can be easily separated from each other by the different conditions of the propodeum.

This species is also similar to members of the minutulus  group in general appearance and by having a short petiole, short antennal scapes (reaching only to mid-length of the head) and subtriangular mandibles (masticatory margin with a large apical tooth, medium-sized subapical and basal teeth and 2–6 denticles between them). However this species possesses a serrate anterior clypeal margin, the most important characteristic that separates the A. wroughtonii group from the A. minutulus group (anterior clypeal margin without denticles in the A. minutulus group).

Distribution
Western Thailand (Tak Province).

Distribution based on Regional Taxon Lists
Oriental Region: Thailand.

Nomenclature

 *  samungi. Aenictus samungi Jaitrong & Ruangsittichai, 2018: 109, figs. 3, 5 (w.) THAILAND.

Worker
Holotype: HL 0.41; HW 0.31; ML 0.53; PH 0.17; PL 0.12; SL 0.20; TL 1.75; CI 76; PI 143; SI 63. Paratypes (n = 11): HL 0.40–0.43; HW 0.31–0.33; ML 0.51–0.53; PH 0.17–0.18; PL 0.12–0.13; SL 0.20–0.23; TL1.72–1.78; CI 76–80; PI 138–143; SI 63–70.

(holotype and paratypes). Head in full-face view clearly longer than broad, with its sides weakly convex and posterior margin almost straight or feebly concave. Antennal scape short, only slightly extending mid-length of head; antennal segment II (pedicel) clearly longer than each of III–VI; X longer than VII, VIII and IX combined. Frontal carinae fused at level of anterior margin of torulus, extending beyond level of posterior margin of torulus. Clypeus short, with its anterior margin bearing 7 denticles. Mandible subtriangular, with apical tooth large and curved, followed by a medium-sized subapical tooth, 4–5 minute teeth and a medium-sized basal tooth on masticatory margin. Mesosoma in profile almost flat dorsally; metanotal groove distinct. Propodeum in profile with a nearly straight dorsal outline; propodeal junction rounded; propodeal declivity weakly convex, not encircled by a rim. Petiole including subpetiolar process shorter than high, with its dorsal outline convex; subpetiolar process rather developed, with its ventral outline roundly convex, without angle or tooth; postpetiole shorter than petiole and shorter than high, in profile slightly elevated posteriorly.

Head, antennal scape, promesonotum, propodeal dorsum, petiole, postpetiole, gaster, femora and tibiae of legs entirely or extensively smooth and shiny; mesopleuron, metapleuron and lateral face of propodeum superficially reticulate. Antennal flagellum densely finely punctate.

Body with relatively sparse standing hairs mixed with sparse short hairs over surface; longest pronotal hair 0.07–0.08 mm long. Head, mesosoma, waist, gaster, antennae and legs yellowish brown; mandible dark brown.

Type Material
Holotype (THNHM-I-02615, ) and 15 paratype workers (THNHM-I-02616,, , THNHM, ), Thailand, Tak Province, Um Phang District, Thung Yai Wildlife Sanctuary, Yuyi Junction, DEF (dry evergreen forest), 15.44861111°N, 99.04694444°E, ca 1100 m a.s.l., 25.IX.2016, W. Jaitrong leg., TH16-WJT-1069.

Etymology
The species is named after Mr Yuthana Samung (Faculty of Tropical Medicine, Mahidol University, Thailand) who kindly helped us in taking pictures of Thai ants, including the two new species discovered in the present study.