Ponera tudigong

Ponera tudigong is known from a single location in Tai Lam country park, Hong Kong SAR. The worker and queen were collected in separate pitfall traps 5 meters apart during the same sampling period. Nothing more is known concerning its biology.

Identification
Leong et al. (2019) - Ponera tudigong can be distinguished from the other species in the genus by the following characters:
 * masticatory margin of the mandible with a small denticle and four enlarged teeth (Figure 2, see caste section below), an apomorphic character for this new species
 * petiole relatively thick in lateral view (LPeI 60) with the anterodorsal margin of the node of the petiole projecting slightly forward
 * metanotal groove forming clearly incised suture in dorsal view
 * eyes absent

Specimens were initially recognized as being distinct from the other local Ponera species, Ponera sinensis and Ponera guangxiensis, based on the mandible and shape of its petiole and the absence of eyes, and was later determined to be a new species. It is the only known Ponera species with four mandibular teeth, all other species having either three (most of Ponera species), five (Ponera pentodontos), or seven (Ponera taylori).

Distribution based on Regional Taxon Lists
Palaearctic Region: China.

Biology
Nothing is known about the biology or life history of P. tudigong. Like most species of Ponera, it is likely cryptobiotic and subterranean, as the absence of eyes might suggest. The fact that our specimens were captured in surface pitfall traps may suggest that the species does come to the surface at least occasionally, maybe at night, and possibly to forage or for reproduction purposes, given that a wingless queen was captured in addition to the worker. Of course, soil disturbance during trap emplacement may also be responsible.

Ponera tudigong is known from only a single collection event, despite a significant amount of leaf-litter and pitfall-trap sampling done throughout Hong Kong in recent years. This suggests that the species is indeed quite rare. The habitat it was collected from is a restored secondary forest, and it was collected within one meter of a well-used hiking trail.

Nomenclature

 *  tudigong. Ponera tudigong Pierce, Leong & Guénard, 2019: 12, figs. 2-6 (w.q.) CHINA (Hong Kong).

Worker
(n = 1): ATL 0.43, ATW 0.46, HL 0.59, HW 0.51, MaL 0.29, ML 0.82, PeH 0.39, PeNL 0.23, PeW 0.32, PrW 0.38, SL 0.43, TL 2.3. Indices: ATI 92, CI 85, DPeI 138, LPeI 60, PeI 85, SI 84.

Head. In full face view, head subrectangular (Fig. 3), longer than broad (CI: 85) with shallowly concave occipital margin, and slightly convex lateral margins. Anterior clypeal margin nearly straight, with a low and blunt medial tooth. Eyes absent. Mandibles subtriangular, with a small denticle (t5) and four triangular enlarged teeth (t1 to t4) on the masticatory margin (Fig. 2A). Antennal scapes, when laid back, nearly reaching occipital corners of head; average ratio of the length of antennomeres 7/6:8/6:9/6:10/6 = 1.08: 1.42: 1.92: 2.32. Funicular segments of antennae incrassate, increasing in length and breadth distally. Mesosoma. In profile view, mesosomal dorsum slightly convex. Promesonotal suture and metanotal groove both present and clearly incised. Mesopleuron distinct, separated from mesonotum by a clearly incised promesonotal articulation. In dorsal view, lateral margins of pronotum and mesonotum rounded, lateral margins of propodeum slightly concave. Propodeal corner in lateral view forming a blunt angle. Metasoma. In profile view, petiole sub-rectangular and remarkably thick compared to other species in the genus (LPeI = 59.5), with anterior and posterior margins straight and parallel; anterodorsal corner nearly right-angled, posterodorsal corner blunt; anterodorsal corner higher than posterodorsal corner. Subpetiolar process sub-rectangular in shape, with a large and circular anterior fenestra, extending across the entire ventral margin of the petiole. Posterior portion of subpetiolar process with a well-developed pair of blunted teeth. In dorsal view, petiolar node sub-oval, clearly wider than long (DPeI = 138.1), with a slightly convex anterior margin and slightly concave posterior margin. In dorsal view, abdominal tergum III (= 1st gastral tergum) wider than long (ATI = 91.8), and in profile view with a bluntly rounded anterodorsal corner. Sculpture. Entirety of head punctate, covered by closely and evenly spaced fine puncturing. Mandibles smooth. Sculpturing of mesosoma and metasoma relatively light, ranging from puncticulate to imbricate. Mesosomal and metasomal dorsum nearly smooth. Pilosity. Head and antennae covered by fine golden-colored pubescence. Mandibles with sparse, short, erect to sub-erect filiform hairs. Pilosity of mesosoma consisting of a fine pubescence, similar to that of the head. Fine and sparse pubescence covering each metasomal segment, becoming sparser after the fourth abdominal segment ( = 2nd gastral segment). Short, golden, sub-erect to erect filiform hairs present on all metasomal segments, becoming longer and denser posteriorly from the fifth abdominal segment (= 3rd gastral segment). Color. Coloration of entire body of the individual, excluding the legs, ranging from light to dark reddish-brown. Legs light brown.

Queen
(n = 1): ATL 0.54, ATW 0.54, HL 0.65, HW 0.56, MaL 0.41, ML 1.03, PeH 0.43, PeNL 0.25, PeW 0.35, PrW 0.47, SL 0.48, TL 2.5. Indices: ATI 101, CI 85, DPeI 140, LPeI 59, PeI 75, SI 85.

The description of the queen of Ponera tudigong follows that of the worker caste, with the following differences: Body size larger than that of the worker caste, with large, sub-circular compound eyes, 0.15 mm in diameter, present on the anterior part of the head, roughly one-third the distance to the posterior margin. Three distinct ocelli present on the posterior part of the head. Mandibles similar to worker caste (Fig. 2). Sub-petiolar process of the queen with a subquadrate anterior fenestra, a low and blunt downward-projecting anterior angle, and a downward-projecting square medial tooth. Abdominal tergum III (= 1st gastral tergum) as long as wide (ATI: 101). Sculpturing, coloration, and pilosity of the queen is similar to that of the worker caste, with sculpturing slightly more pronounced.

Etymology
This new species is named in honor of Tudigong (土地公), the lord of the soil and the ground, a widely venerated Chinese deity.

References based on Global Ant Biodiversity Informatics

 * Pierce M. P., C. M. Leong, and B. Guenard. 2019. A new species and new record of the cryptobiotic ant genus Ponera Latreille, 1804 (Hymenoptera, Formicidae) from Hong Kong. ZooKeys 867: 9–21.