Aenictus jarujini

This species is very rare and known only from the type locality (around 1000 m alt.). The specimens were collected from a bivouac under a stone in a disturbed area near a hill-evergreen forest during the dry season.

Identification
A member of the silvestrii species group. A. jarujini is very similar and closely related to Aenictus latifemoratus but the two are easily separated by the following characters: number of antennal segments (9 in A. jarujini; 8 in A. latifemoratus); shape of petiolar node (node subrectangular and relatively low, posteriorly margined with a rim in A. jarujini; node without a distinct rim in A. latifemoratus), condition of subpetiolar process (very low in A. jarujini; well developed and subtriangular in A. latifemoratus); sculpturing on head (strongly macropunctate in posterior dorsal half of head, other regions only weakly macropunctate in A. jarujini; strongly macropunctate or recticulate exten¬sively on dorsum and sides of head in A. latifemoratus).

Key to Aenictus species groups / Key to Aenictus silvestrii group species

Distribution
Northern Thailand

Distribution based on Regional Taxon Lists
Oriental Region: Thailand.

Castes
Known only from the worker caste.

Nomenclature

 *  jarujini. Aenictus jarujini Jaitrong & Yamane, 2010: 329, figs. 1, 2 (w.) THAILAND.

Worker
(n = 20): TL 3.4–3.8 mm; HL 0.83–0.93 mm; HW .70–0.80 mm; SL 0.40–0.47 mm; ML 1.13–1.25 mm; MTL 0.50–0.55 mm; PL 0.25– 0.30 mm; CI 82–89; SI 55–62.

Head in full-face view subrectangular, slightly longer than broad, with feebly convex sides and slightly concave posterior border; occipital margin concave bearing a narrow collar; area between frontal carina and parafrontal ridge depressed. Antenna 9-segmented; scape short, extending to the mid-length of head in full-face view; antennal segment II small, nearly as long as broad; III–V broader than long; VI–VIII nearly as long as broad; the terminal segment (IX) very large, almost as long as VII and VIII combined. Frontal carinae well developed, narrow, often with a longitudinal furrow (fused portion of the carinae) and extending half length of head; seen in proﬁle its dorsal outline straight anteriorly and sloping gradually posteriad. Clypeus short and roundly produced anteriorly, lacking anterior teeth. Mandible with apical tooth large and curved, followed by 10–15 denticles of two sizes, the larger alternating with 2 or 3 smaller; basal margin of mandible lacking denticles. Mesosoma rather robust, seen from above wider anteriorly; posterior half almost parallel-sided; mesonotum laterally margined with ridges; in proﬁle pronotum weakly convex dorsally and promesonotum sloping gradually to metanotal groove; propodeum slightly lower and weakly convex dorsally; mesopleuron not clearly demarcated from metapleuron; upper portion of mesometapleura extensively impressed. Propodeal junction acutely angulated; declivity of propodeum shallowly concave, encircled with a narrow rim. Petiole higher than broad, seen from above almost parallel-sided, anteriorly margined by a transverse carina, while posterior face encircled with a rim similar to that of propodeum; subpeiolar process low and subrectangular; postpetiole similar to petiole in shape and length, but without a well-demarcated posterior face, roundly convex above, impressed near posterior margin, anteroventrally pro-duced as a blunt angle directed downward and forward. Gaster elongate-elliptical, narrowed anteriorly and posteriorly.

Dorsum of head in posterior half with dense macro-punctures (almost reticulate) and micropunctures, and in anterior half with micropunctures and several longitudinal rugulae; sides of head with micropunctures, and sparse and shallow macropunctures. Mandible largely with dense minute punctures, but smooth apically and along masticatory margin. Upper face of antennal scape basally with dense micropunctures and apically much smoother. Dorsal surface of mesosoma weakly and irregularly sculptured, with ill-deﬁned micropunctures, and mat; lateral face of mesosoma densely micropunctate. Petiole dorsally with very superﬁcial reticulum superimposed with dense micropunctures (a condition similar to posterodorsal part of head); postpetiole densely micropunctate. Gaster smooth and shining except for extreme basal portion. Femora and tibiae smooth and shining.

Body with relatively sparse standing hairs mixed with sparse short hairs over the surface; length of the longest pronotal hair approximately 0.20–0.25 mm. Head, mesosoma and waist pale brown; gaster and legs yellow; mandible blackish brown.

Type Material
Holotype. Worker from disturbed area, Haui Nam Dang National Park, Mae Hong Son Province, N. Thai¬land, 7 iii 2008, W. Jaitrong leg., colony WJT08¬HND20. Paratypes. 64 workers, same data as holotype. Type depository. Holotype and some paratypes are deposited in THNHM, and some paratypes in SKYC, BMHN, MCZC, and MZB.

Etymology
The speciﬁc name is dedicated to the late Dr Jarujin Nabhitabhata of the Thailand Natural History Museum, National Science Museum, who was the most excellent specialist in biodiversity sciences in Thailand and helped and inspired many young biologists.