Aenictus hoelldobleri

The species is so far known to inhabit secondary mixed evergreen broadleaved forests at mid elevations (ca. 300-620 m) where it occurs from young to old successional stages (referred to as Aenictus (ceylonicus group) sp. CN02 in Staab et al. 2014, where more detailed biological information on the habitat can be found). Workers of a foraging column from one colony (MS1647) were observed during daytime (approximately 3pm) to carry pupae of Technomyrmex sp. and ant larvae on the ground. Thus, it is most likely that A. hoelldobleri has a similar life history as other A. ceylonicus group species by living and foraging on the ground and by being a specialized predator of other small ants.

Identification
A member of the ceylonicus group.

Staab (2015) - Aenictus hoelldobleri is most similar to Aenictus henanensis and Aenictus wudangshanensis, two species that also inhabit subtropical broad-leaved forests in China. Aenictus hoelldobleri can easily be distinguished from both species by the shape of the subpetiolar process, which is weakly developed and rounded in A. henanensis (characters for A. hoelldobleri are given in brackets: rectangular- trapezoidal, with a thin lamellae on the ventral outline) and rectangular with a very acute median apex that faces downwards in A. wudangshanensis. Furthermore, A. henanensis has the dorsum of the petiolar node smooth and shiny (finely reticulate) and lacks long, standing hairs on the dorsum of the head (longest hairs 0.15-0.20 mm). Aenictus wudangshanensis also has the mandible in total with 9 teeth/denticles (6-7). The three afore discussed species share with Aenictus thailandianus, Aenictus lifuiae and Aenictus yangi the mandible with six or more teeth/denticles and the relatively small gap between the closed mandibles and the anterior clypeal margin. Aenictus hoelldobleri can be separated from A. thailandianus by the sculpture of the dorsa of promesonotum and postpetiole, which are in A. thailandianus entirely punctate and not shiny (smooth and shiny, at most very finely and superficially reticulate but still smooth and shiny). Aenictus lifuiae and A. yangi differ from A. hoelldobleri by having the dorsum of the mesonotum and the dorsum of the petiole entirely smooth and shiny (finely reticulate). Furthermore, the legs of A. lifuiae are smooth and shiny (legs weakly punctate, most strongly on tibiae, coxae smooth and shiny) and the dentition of the mandible differs by having a large acute apical tooth followed by a series of 6-7 denticles of two sizes, the larger alternating with 1-2 smaller (large acute apical tooth, followed by a medium-sized subapical tooth, 3-4 minute denticles and a medium-sized basal tooth). The dentition of the mandible can also be used to separate A. hoelldobleri from A. yangi, in which the large acute apical tooth is followed by the medium-sized subapical tooth, one denticle, one medium sized tooth, two denticles, and the medium-sized basal tooth. Also, the maximum width of the gap between the anterior clypeal margin and the closed mandibles is in A. yangi at least about as broad as the maximum width of the mandibles (gap clearly smaller than maximum width of mandible).

Key to Aenictus species groups

Distribution
Zhejiang and Jiangxi Provinces, Southeast China.

Distribution based on Regional Taxon Lists
Palaearctic Region: China.

Castes
Known only from the worker caste.

Nomenclature

 * . Aenictus hoelldobleri Staab, 2015: 142, figs. 3D, 4C, 5A-D (w.) CHINA (Jiangxi, Zhejiang).

Worker
Holotype: TL 2.88, HL 0.65, HW 0.57, SL 0.46, ML 0.95, PL 0.25, CI 88, SI 81. Paratypes (n=20 measured): TL 2.34-2.88, HL 0.52- 0.68, HW 0.48-0.60, SL 0.40-0.50, ML 0.83-1.02, PL 0.20-0.25, CI 84-92, SI 75-86.

(Holotype and paratypes). Head in full-face view slightly longer than broad (CI 84-92), sides slightly convex, posterior margin slightly rounded to almost straight, and occipital corners broadly rounded; occipital margin bearing distinct carina. Antennal scape relatively long (SI 75-86), extending well beyond 2/3 of head length but not reaching posterolateral corner of head; antennal segments II-VIII each broader than long, antennal segments IX and X longer than broad; length of segments II-IX continuously rising; terminal segment (X) longer than VIII and IX taken together; last four segments forming indistinct club. Frontal carina long and distinct, surpassing posterior margin of antennal torulus. Clypeus very short, its anterior margin almost straight to feebly concave, with lateral portions bluntly angled. Masticatory margin of mandible with large acute apical tooth, followed by medium-sized subapical tooth, 4 (rarely 3) small denticles, and medium-sized basal tooth; denticles and basal tooth worn out and hard to see in few paratypes; basal margin straight, lacking denticles. Gap between closed mandibles and anterior clypeal margin relatively small, about 0.5-0.6 times as broad as maximum width of mandible. With mesosoma in profile, promesonotum strongly convex, sloping gradually to the weakly developed but distinct metanotal groove; mesopleuron relatively short, demarcated from metapleuron by distinct groove; metapleural gland bulla moderately large, its maximum diameter about 1.3 times as long as distance between propodeal spiracle and most proximate part of metapleural gland bulla. Dorsal outline of propodeum in profile weakly convex, gently sloping posteriorly; propodeal junction angulated, overhanging declivity of propodeum, which is shallowly concave and encircled with thin but distinct rim. Petiole excluding subpetiolar process in profile slightly higher than long; petiolar node with steep anterior face and broadly convex dorsal outline; subpetiolar process developed, its ventral outline trapezoidal and rectangular, its apex on anterior part of process; ventralmost part of subpetiolar process with thin almost transparent lamellae. Postpetiole slightly shorter than petiole, in profile dorsal outline of node convex with small entirely flat area on dorsum; postpetiolar process developed, angulate, pointing anteriorly.

Head entirely smooth and shiny except for finely punctate antennal torulus. Mandible finely striate. Antennal scape entirely punctate. Mesosoma entirely finely reticulate with exception of pronotum and metapleuron; pronotum finely reticulate with large smooth and shiny median area on sides and dorsum; in few larger paratypes pronotal dorsum very finely and superficially reticulate but still smooth and shiny; anterior part of metapleuron smooth and shiny (with very fine and superficial longitudinal rugae in few larger paratypes). Entire petiole, including subpetiolar process, finely reticulate. Postpetiole finely reticulate, with flat surface on dorsum smooth and shiny. Gaster entirely smooth and shiny. Legs weakly punctate, more strongly so on tibiae, coxae smooth and shiny.

Body except sides of mesosoma with abundant standing and decumbent hairs of variable length; length of longest hairs on dorsum of head and pronotum 0.15–0.20 mm. Antennal scapes and legs with abundant decumbent hairs. Antennae, mesosoma, petiole and postpetiole reddish to yellowish brown, gaster and legs yellowish brown.

Type Material
Holotype. Worker from CHINA, Jiangxi Province, near the village Xingangshan, ca. 15 km SE of Wuyuan, 29°4'39"N / 117°55'20"E, 300 m asl, 6.VII.2013, hand collection on ground, leg. Michael Staab, label “MS1647”, deposited in. Paratypes. 20 workers in total, all with the same data as holotype (3 in : CASENT0914931, CASENT0914932, CASENT0914933, 4 in, 10 in IZAS, 3 in ).

Etymology
The species epithet is a patronym in honor of the great German myrmecologist Berthold ‘Bert’ Hölldobler and his invaluable and outstanding contributions to our understanding of ant societies.