Carebara oni

Identification
Terayama (1996) - This species is closely allied to Carebara borealis, but is distinguished from the latter by the combination of the following characteristics: 1) subpetiolar process spine-like in major and minor workers (small obtuse triangle in borealis); 2) posterior margins of propodeum not carinate in major worker (carinate and forming a thin lamellar wall in borealis); 3) eyes situated at anterior 1/3 in minor and major workers (almost midlength in borealis); 4) in lateral view dorsal outline of propodeum convex in minor worker (straight in borealis).

Distribution based on Regional Taxon Lists
Palaearctic Region: Japan.

Nomenclature

 *  oni. Oligomyrmex oni Terayama, 1996: 20, figs. 38-43 (s.w.) JAPAN. Combination in Carebara: Terayama, 2009: 151.

Worker
Holotype. Major. HL 0.80 mm; HW 0.75 mm; SL 0.30 mm; CI 94; SI 40; WL 0.83 mm; PL 0.33 mm; PH 0.25 mm; DPW 0.24 mm; TL 3.5 mm.

Head 1.1 x as long as wide, with parallel sides and very weakly concave posterior margin in frontal view; vertex with a pair of blunt tubercles. Mandibles with 6 strong teeth. Antennae with 9 segments; scape short, 0.4 x head length; 2nd segment longer than wide; 3rd to 7th segments each wider than long; 8th segments 2.3 x as long as wide; apical segments 2.0x as long as wide. Eyes larger than the maximum width of antennal scape, 0.07 mm in diameter, each consisting of about 10 facets, and situated at anterior l/3 of head capsule in lateral view; long erect hairs present on eyes. Anterior ocellus present, 0.05 mm in diameter.

Alitrunk massive; scutellum and metanotum present; mesopleura with a distinct transverse groove at midlength. Propodeal spines tooth-like, with an acute tip; posterior margins of propodeum not carinate.

Petiole longer than wide, with narrowly rounded dorsal margin in lateral view; subpetiolar process low, situated in the anterior portion of petiole, and forming an anteroventral spine. Postpetiole higher than long, with convex dorsal and ventral margins in lateral view.

Head microreticulate with many longitudinal rugae; pronotum, mesonotum and mesopleura smooth and shining in most part; propodeum, petiole and postpetiole microreticulate; gaster smooth and subopaque.

Head blackish brown; alitrunk and gaster reddish brown.

Paratype minors. HL 0.38-0.40 mm; HW 0.35-0.36 mm; SL 0.24-0.25 mm; CI 90-93; SI 68-69; WL 0.38 mm; PL 0.11 mm; PH 0.10 mm; DPW 0.09-0.10 mm; TL 1.0-1.2 mm (n = 5).

Head square, with weakly convex sides and almost straight posterior margin in frontal view. Anterior border of clypeus produced medially. Eyes small, each consisting of 2-3 indistinct facets. Mandibles with 5 teeth. Antennae with 9 segments; 3rd to 7th segments each wider than long; 8th segment slightly wider than long; apical segment 2.4 x as long as wide.

Promesonotal dorsum weakly convex in lateral view; metanotal groove distinctly incised dorsally; dorsum of propodeum convex. Propodeal spines fornting an acute triangle, slightly longer than wide at base; posterior margins of propodeum with a thin lamella.

Petiole longer than high; node with a broadly rounded dorsal margin in lateral view; subpetiolar process low, with a small acute tooth anteriorly.

Head and pronotum smooth and shining in most part; mesopleura and propodeum strongly microreticulate; surface sculpture of waist as in propodeum excepting postpetiolar disc smooth; gaster smooth and subopaque.

Body yellowish brown.

Variation. The tubercles on the vertex of major workers vary in condition from developed to obscure or almost absent. Some major workers have no anterior ocellus.

Type Material
Holotype. Major worker, Mt. Kanna-dake, Okinawa-jima, Okinawa Pref., 9.X.1988, M. Terayama leg. Paratypes. 2 major workers, 5 minor workers, same data as holotype; 1 major worker, 3 minor workers, Okinawa-jima, Okinawa Pref., 19.XI.1975, T. Abe leg.

Etymology
The specific name is the Japanese noun oni, which means a demon who has horns on head.