Aenictus yangi

Aenictus yangi is only known from Xishuangbanna in southern Yunnan. The type locality is a tropical lowland rainforest situated at an elevation of around 550 m. The new species was only collected twice, both times through leaf litter extraction. As for most Aenictus we strongly suspect that A. yangi has a more hypogaeic lifestyle and might be more abundant in the soil stratum. (Lui et al, 2015)

Identification
A member of the ceylonicus group.

Lui et al. (2015) - Aenictus yangi differs from other South East Asian members of the A. ceylonicus group by the following combination of characters: head in full-face view distinctly longer than broad (CI 82–90); masticatory margin of mandible with seven teeth/denticles; antennal scapes relatively long (SI 76–86); metanotal groove noticeably present but weak; propodeal junction noticeably angulate with distinct tooth; subpetiolar process relatively elongate, subrectangular, and slightly projecting anteroventrally; propodeum laterally mostly smooth and shiny, weakly irregularly rugulose at base, and weakly reticulate-punctate near propodeal junction; petiole and postpetiole mostly smooth and shiny with lower portions reticulate-punctate.

The identification of A. yangi within the A. ceylonicus species group can be determined using the Key to southeastern Asian Aenictus ceylonicus group species. This ant is morphologically most similar to Aenictus baliensis (Bali), Aenictus longicephalus (Lombok), Aenictus minipetiolus (Lombok), and Aenictus wiwatwitayai (Thailand). A. yangi can be separated from these by the development of the metanotal groove, the shape of the propodeum and the subpetiolar process, and the sculpture on the mesosoma and waist segments. Aenictus yangi can be easily separated from Aenictus brevipodus (Thailand), and Aenictus formosensis (Taiwan) by the number of mandibular teeth, shape of the head, the shape and punctate of petiole and postpetiole, and the shape of subpetiolar process.

Key to Aenictus species groups

Distribution based on Regional Taxon Lists
Palaearctic Region: China.

Castes
Known only from the worker caste.

Nomenclature

 *  yangi. Aenictus yangi Liu, Hita Garcia, Peng & Economo, 2015: 38, figs. 3A, 4A-D (w.) CHINA.

Worker
TL 2.21–2.60; HL 0.51–0.57; HW 0.43–0.50; SL 0.33–0.42; ML 0.69–0.87; PL 0.17–0.20; CI 82–90; SI 76–86.

Head in full-face view distinctly longer than broad (CI 82– 90), sides convex, posterior head margin straight to very weakly convex; occipital margin bearing a distinct carina. Antennal scapes relatively long (SI 76–86), extending beyond 2/3 of head length but not reaching posterior head margin. Frontal carinae relatively short and indistinct, reaching the level of posterior margin of torulus. Parafrontal ridges absent. Anterior clypeal margin weakly to moderately concave, not concealed by curved anterior extension of frontal carina. Masticatory margin of mandible with large acute apical tooth followed by one medium-sized subapical tooth, one small denticle, one medium-sized tooth, two smaller denticles, and medium-sized basal tooth, reaching total of seven teeth/denticles; basal margin straight. Maximum width of gap between anterior clypeal margin and mandibles about 1.0 to 1.4 times broader than maximum width of mandible. Promesonotum convex dorsally and sloping gradually to metanotal groove; metanotal groove noticeably present but weak; mesopleuron relatively long, clearly demarcated from metapleuron by weak groove; metapleural gland bulla relatively large, its maximum diameter about 1.7 to 2.1 times longer than distance between propodeal spiracle and metapleural gland bulla. Propodeum in profile with feebly convex dorsal outline; propodeal junction noticeably angulate with distinct tooth; declivity of propodeum moderately concave and encircled by strongly developed rim. Petiole in profile higher than long, its dorsal outline strongly convex; subpetiolar process relatively elongate, subrectangular, and slightly projecting anteroventrally. Postpetiole slightly smaller than petiole, its dorsal outline strongly convex. Head including antennal scape entirely smooth and shiny. Mandibles predominantly unsculptured, smooth and shiny with weak, superficial striation basally. Promesonotum entirely smooth and shiny; mesopleuron and metanotal groove irregularly rugulose; propodeum laterally mostly smooth and shiny, weakly irregularly rugulose at base, and weakly reticulate-punctate near propodeal junction. Petiolar node and postpetiole mostly smooth and shiny with lower portions reticulate-punctate. Head and mesosoma dorsally with abundant erect to subdecumbent hairs. Head, mesosoma, and gaster usually reddish brown, always distinctly darker than yellow to light yellowish brown mandibles, antennae, petiole, postpetiole, and legs.

Type Material

 * Paratypes, 14 pinned workers, China, Yunnan, Xishuangbanna, Man Sai village, 21°51'34.4"N, 101°16'39.6"E, 680m, young rain forest, leaf litter, 12.IIV.2013 (B. Blanchard, B. Guénard & C. Liu) (: CASENT0717204; : CASENT0735506; CASENT0735508; HLMD: CASENT0735507; ISAS: CASENT0717203; CASENT0735495; CASENT0735496; CASENT0735498; : CASENT0735505; : CASENT0735504; : CASENT0735501; : CASENT0735500; : CASENT0735499; : CASENT0735497).
 * Paratypes, 14 pinned workers, China, Yunnan, Xishuangbanna, Man Sai village, 21°51'34.4"N, 101°16'39.6"E, 680m, young rain forest, leaf litter, 12.IIV.2013 (B. Blanchard, B. Guénard & C. Liu) (: CASENT0717204; : CASENT0735506; CASENT0735508; HLMD: CASENT0735507; ISAS: CASENT0717203; CASENT0735495; CASENT0735496; CASENT0735498; : CASENT0735505; : CASENT0735504; : CASENT0735501; : CASENT0735500; : CASENT0735499; : CASENT0735497).

Etymology
The new species is dedicated to Da-Rong Yang from the Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences. We want to thank him for his great support of the first author’s studies in the area.