Carebara yamatonis

A relatively common species within Japan.

Identification
Terayama (1996) - This new species is distinguished from Carebara sauteri by the straight outline of mesonotal and propodeal dorsum in profile in major worker (convex in sauteri), angulated posterodorsal corners of propodeum in minor and major workers (rounded in C. sauteri), rnicroreticulation on head in major worker (largely smooth in C. sauteri), and microreticulation on head and pronotum in minor worker (smooth in C. sauteri).

This species was first recorded from Japan by Azuma (1951). Thereafter Japanese myrmecologists have consistently used the name C. sauteri for this relatively common ant. However, C. sauteri was originally described from Taiwan, and morphological comparison between Japanese and Taiwanese specimens suggests that they represent separate species.

Distribution based on Regional Taxon Lists
Palaearctic Region: China, Japan.

Nomenclature

 * . Oligomyrmex yamatonis Terayama, 1996: 23, figs. 48-51 (s.w.) JAPAN.
 * Combination in Carebara: Terayama, 2009: 151.
 * Status as species: Imai, et al. 2003: 131; Lin & Wu, 2003: 65; Terayama, 2009: 151; Guénard & Dunn, 2012: 41.

In 1951, Azuma regarded a Japanese Oligomyrmex (=Carebara) species as sauteri Forel, 1912, which is originally described from Pilam (= Peinan, Taitung Hsien), Taiwan. Thereafter the Japanese myrmecologists applied the name sauteri to this relatively common Japanese species. Recently, a species that is morphologically similar to but apparently different from the Japanese "sauteri" has been collected from the Senkaku Is., the Ryukyus. Unfortunately, the present location of the type specimen of O. sauteri Forel is not known, and is not deposited in the Forel collection of Museum d'Histoire naturelle, Geneve nor in Naturhistorisches Museum, Basel. However, I examined a series of specimens from Taiwan (more than 30 colonies from 10 different localities) which were regarded as O. sauteri judging from the original description and the type locality of O. sauteri. The morphological comparison between the Japanese material and the Taiwanese one indicated that Taiwanese and the Senkaku specimens are conspecific, and that the materials from other parts of Japan belong to a different species. So I regarded the Senkaku population as O. sauteri and the common Japanese form as new to science. Accordingly, most previous records of Carebara sauteri from Japan may concern the present new species.

Worker
Holotype. Major. HL 0.63 mm; HW 0.53 mm; SL 0.28 mm; CI 84; Sl 53; WL 0.53 mm; PL 0.20 mm; PH 0.18 mm; DPW 0.14 mm; TL 2.3 mm.

Head 1.2 x as long as wide, with parallel sides in frontal view; posterior margin concave medially; vertex with a pair of strong tubercles. Mandibles strong, with 5 teeth. Anterior margin of clypeus concave medially with a pair of dull projections. Antennae with 9 segments; scape short, 0.4 x head length; 2nd segment 1.8x as long as wide; 3rd to 7th segments each wider than long; 8th segment 1.3 x as long as wide; apical segment 2.0 x as long as wide. Eyes small, each consisting of 3 facets, and situated at anterior 3/10 of head capsule in lateral view. Ocelli absent.

Alitrunk as in Fig.; pronotum and anterior 1/3 of mesonotal dorsum strongly raised, and the rest of mesonotal dorsum straight in lateral view; metanotum present, but small; propodeal dorsum straight. Posterodorsal corners of propodeum obtusely angulate, without spine; posterior margins carinate, forming a thin lamellar wall.

Petiole 1.1 x as long as high; anterodorsal and posterodorsal corners dully angulate; dorsal margin of node almost straight in lateral view; subpetiolar process small, forming a dull angle. Postpetiole higher than long, with convex dorsal margin in lateral view.

Head coarsely microreticulate; frons and vertex with many longitudinal striae; alitrunk and petiole microreticulate; postpetiole relatively weakly microreticulate; gaster smooth and shining.

Head dark reddish brown; alitrunk and waist reddish brown; gaster and legs brown with a yellowish tinge.

Paratype minors. HL 0.35-0.36 mm; HW 0.30-0.31 mm; SL 0.20 mm; CI 85-86; CI 65-67; WL 0.30-0.31 mm; PW 0.20 mm; PL 0.12-0.13 mm; PH 0.10 mm; DPW 0:08 mm; TL 0.9 mm (n = 5).

Head slightly longer than wide, with subparallel sides and straight posterior margin in frontal view. Mandibles with 5 teeth. Antennae with 9 segments; 3rd to 7th segments each wider than long; 8th segment slightly longer than wide; apical segment 3.0x as long as wide. Eyes small, consisting of a single facet only.

Dorsal outline of promesonotum broadly convex; metanotal groove distinctly incised dorsally; dorsum of petiole broadly convex. Posterior margins of propodeum carinate, forming a thin lamellar wall; its dorsal end angulate, but not forming a distinct spine.

Petiole 1.2x as long as wide; anterodorsal and posterodorsal corners dully angulate; subpetiolar process minute, forming a dull angle. Postpetiole higher than long, with convex dorsal margin in lateral view.

Head, alitrunk, and petiole coarsely microreticulate; postpetiole weakly microreticulate; gaster smooth and subopaque. Body reddish brown; antennae and legs yellowish brown.

Variation. The microreticulation on pronotum and head in the Yaeyama material is weaker than in the Manazuru material. The number of facets of eyes in the major workers vary from 2 to 4.

Females and males. Described and illustrated by Ogata (1991).

Type Material
Holotype. Major worker, Manazuru, Kanagawa Pref., 14.IX.1987, M. Terayama leg. Paratypes. 6 major workers, 25 minor workers, same data as holotype; 10 major workers, 30 minor workers, same locality, 13.V.l995, M. Terayama leg.

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