Ponera japonica

Ponera japonica is found in forested habitats, as are most Ponera, but is unusual in also nesting in open sites.

Identification
Taylor (1967) - The relatively large size, the tendency to develop a median clypeal denticle, the large eyes, the relatively long scapes, and the broad petiolar node, mark japonica as the most primitive species of its group. Total length of workers around 2.5 mm. Body color brown  to  blackish  brown. Scapes not  reaching median posterior border of head, failing to do so by at least 1/5 maximum scape thickness.

Leong et al. (2019) - Worker: This species is characterized by a short antennal scape; a posterior margin of head convex; a petiolar node in dorsal view arched with a straight posterior margin; and a petiolar node in lateral view with a straight and slightly sloping posterior margin. Ponera japonica presents similarities with Ponera incerta, Ponera tenuis, Ponera pianmana, Ponera taiyangshen, and Ponera yuhuang, however the following differences are noted. The median clypeal tooth is distinct and developed in Ponera japonica, but indistinct in Ponera incerta. Ponera japonica has a five segmented club, but four segmented club in Ponera tenuis. The posterior margin of the petiolar node in lateral view is straight in Ponera japonica, but slightly convex in Ponera pianmana. Ponera japonica presents a blunter posterodorsal corner of the petiolar node in lateral view than in Ponera taiyangshen; with also the posterior margin of the petiolar node straight in Ponera japonica, but slightly convex in Ponera taiyangshen. Ponera japonica also presents a subpetiolar teeth, which is absent in Ponera yuhuang.

Distribution
Widespread in the Orient and Indonesia.

Distribution based on Regional Taxon Lists
Palaearctic Region: China, Democratic Peoples Republic of Korea, Japan, Republic of Korea, Russian Federation.

Biology
Taylor (1967) - Detailed information is given by Hayashida (1957, 1960), concerning the ecology of japonica (erroneously identified as Ponera scabra). It is not uncommon, though sparsely distributed, in the vicinity of Sapporo, on the Ishikari Plain of Hokkaido, an area once extensively forested but now largely urban or cultivated. Of 28 ant species collected there it was 18th in abundance (18 or 1.3% of 1491 colonies taken in a total of 43 hours collecting, divided equally between 8 habitat types). P. japonica apparently has fairly broad habitat preferences and was taken in the following situations: (1) arid sparsely vegetated sand dunes or river sides (50% of the 18 colonies); (2) dry sparsely vegetated, disturbed cropfields or roadsides (6% of colonies); (3) rather humid pastures and meadows with dense grass and herb cover and loamy clay soil (22 % of colonies); (4) humid woods or forests with low insolation, loamy soils and abundant decaying matter lying on the ground (22% of colonies). It was not taken at the sea shore, in peat bogs, or on the margins of wood lots. The general parameters of habitat preference were given as low light intensity, and moderate moisture conditions (Hayashida 1957). Foraging is restricted to the ground layer, as usual in Ponera.

In woods and grasslands nests were in or under humus and other debris, but in more open habitats japonica was found nesting among the roots of grasses or in exposed soil, even where it was sandy. If debris or stones were available in open habitats nests were usually constructed beneath them. In the arid sand dunes or dry river beds about 75% of colonies were under stones.

P. japonica nests under stones and in the soil, especially in the humus layer. Okamoto (1972) reported that larvae do not spin cocoons and the pupae are thus naked. It is found from low-lying to mountainous sites.

Nomenclature

 *  japonica. Ponera japonica Wheeler, W.M. 1906c: 306 (w.q.) JAPAN. Imai, Brown, et al. 1984: 67 (k.). Senior synonym of crocea: Taylor, 1967a: 76. See also: Kupyanskaya, 1990: 86.
 * crocea. Ponera japonica var. crocea Santschi, 1941: 273 (w.) JAPAN. [Unresolved junior primary homonym of crocea Roger, 1860: 288, above.] Junior synonym of japonica: Taylor, 1967a: 76.

Description
Leong et al. (2019) - Workers (n=5) HL 0.50–0.58; HW 0.41–0.47; SL 0.32–0.38; A06L 0.02; A07L 0.03; A08L 0.05; A09L 0.06; A10L 0.08; PrW 0.30–0.36; WL 0.69–0.76; PeH 0.31–0.35; PeNL 0.16–0.19; PeW 0.24–0.28; ATL 0.33–0.39; ATW 0.39–0.47; CI 79–83, SI 78–86, PeI 80–84, LPeI 51–56, DPeI 143–154, ATI 82–86.

Head. In full-face view, head subrectangular and distinctly longer than broad (CI: 79–83), with concave posterior margin, slightly convex lateral margins, and rounded posterolateral corners. Eye small; composed of a total of 4 to 6 indistinct facets. Anterior clypeal margin with blunt medial tooth. Masticatory margin of mandible with a series of about 11 indistinct denticles, and three large teeth on the apical part. Antennal scape, when laid backward, with a remaining distance of about 12–14% of the scape length to the posterolateral corner; average ratio of the length of antennomeres 7/6:8/6:9/6:10/6 = 1.18: 2.11: 2.93: 4.06 (n=5).

Mesosoma. Mesosomal dorsum in lateral view convex. Pronotum in dorsal view with acutely convex anterior margin and slightly convex lateral margins. Metanotal groove thin and clearly incised. Lateral mesopleural suture distinctly incised. Propodeal dorsum in dorsal view broad with straight lateral margins. Propodeal dorsum and declivity forming approximatively a 125 degree angle. Metasoma. Petiolar node in dorsal view thick and arched, with well convex anterior margin, and straight posterior margin. Petiolar node in lateral view moderately thick and trapezoidal, with straight anterior and posterior margins, and convex dorsal margin. Subpetiolar process with medium-sized and oval fenestra, blunt anteroventral corner, slightly concave ventral margin, and posteroventral corner concave with small teeth. Third abdominal tergum distinctly broader than long (ATI: 82–86), with slightly convex anterior margin, and straight posterior margin.

Sculpture. Head densely punctate. Mandible sparsely punctate. Propodeum evenly punctate. Mesonotum and propodeal dorsum scatteredly punctate. Mesopleuron with weakly striate lower portion and scatteredly punctate upper portion. Metapleuron with weakly striate lower portion, but with smooth upper portion. Propodeal declivity smooth and shining. Petiolar node sparsely punctate, with smooth posterior face, dorsum with few superficial punctures. The third and fourth abdominal segments densely punctate, other segments smooth and shining with few punctures.

Pubescence. Head with dense short hairs. Mesosoma with evenly distributed short hairs; lower metapleuron with few short hairs, but glabrous in upper portion. Dorsal and ventral faces of head, anterior margin of clypeus, sides of mandibles, dorsum of petiolar node, gastral sterna and posterior half of gastral terga with many long erect hairs. Subpetiolar process with a few long erect hairs.

Color. Body color brown. Mandible, clypeus, antennae, legs, and apex of gaster yellowish orange.

Queen
Taylor (1967) - Two Japanese syntypes have the following dimensions: HL 0.65 mm; HW 0.53 mm; SL 0.45 mm; CI 81; SI 85; PW 0.46 mm; PNL 0.22 mm; PH 0.43 mm; DPW 0.33-0.34 mm; PNI 72-74; maximum diameter of compound eye 0.15 mm; ocular index 28; palpal formula: Maxillary 2: Labial 2 (1 inspected).

Type Material
Wheeler, as usual, designated no holotype from his original series of P. japonica. A worker ( collection) with the measurements given below is here designated lectotype and is so labeled. Four additional syntype workers in the MCZ collection and 8 in the, along with 2 queens (one in each of these collections) have been designated and labeled as paralectotypes. Yamanaka, Suruga (West slope, Hakone Mts), Japan (Syntypes examined- MCZ, AMNH).