Rotundicephala koheii Tasaku, Ono & Maruyama 2023, sp. n.

Rotundicephala koheii Tasaku, Ono & Maruyama, sp. n.

[Japanese name: Sawada-umi-hanekakushi]

(Figs. 1C; 2G; 14D; 15E, F & I; 16; 25A & B)

Type material. Holotype. Male, “Kanaya, Futtsu-shi, / Chiba-ken / 9. IV. 2007 / Hiroki ONO leg.” (Fig. 14D) (KUM). Paratypes. Japan: Honshû: Chiba-ken: 1 male, 1 female, 23 unsexed, same data as holotype, 9. IV. 2007, H. Ono (KUM); 3 unsexed, Tateyama-shi, Sunosaki, Sunosaki-kaigan, 15. VI. 2007, H. Ono (KUM); 1 unsexed, ditto, 15. IV. 2008, H. Ono (KUM); 1 unsexed, ditto, 12. II. 2009, H. Ono (KUM); 2 unsexed, Shirahamamachi, Nemoto, 1. IV. 2005, H. Ono (cHO); 1 unsexed, ditto, 26. III. 2007, H. Ono (cHO); 1 unsexed, ditto, 18. IV. 2008, H. Ono (cHO); Tôkyô-to: 1 male, Izu-ôshima, Okada, Noda-hama, 15. VII. 2022, Y. Tasaku (cYT); Kanagawa-ken: 1 male, 23 unsexed, Manazuru-machi, Manazuru-misaki, 15. IV. 2003, M. Maruyama (KUM); 5 unsexed, Yokosuka-shi, Wada-naga-hama (Nahama), 24. III. 2007, I. Kawashima (KUM); 1 unsexed, ditto, 1. IV. 2007, I. Kawashima (KUM); 1 male, 5 unsexed, ditto, 20. IV. 2007, M. Asano (KUM); 1 unsexed (abdomen lost), Manazuru Pen. Banbaura-kaigan, 5. V. 2002, S. Arai (KUM); 1 male, Yokosuka-shi, Nagai, Arasaki-kôen, 24. IX. 2021, K. Chiyoda (cYT); Shizuoka-ken: 1 unsexed, Shimoda-shi, Taraimisaki, 21. IV. 2003, M. Moriguchi (KUM); 2 unsexed, Shimoda-shi, Tsumeki-zaki, 21. VI. 2003, M. Maruyama (KUM).

Diagnosis. This species similar to R. pacifica comb. n. and previously confused (e.g., Sawada, 1971;Ahn, 1996) (we call them as the R. pacifica species-complex) but, can be distinguished by the combination of the following characteristics: head and pronotum slightly convex (Fig. 14D); segments IV–IX of antennae as long as wide (Fig. 15I). Also, this species can be easily distinguished from R. koreana comb. n. by the short antennae not reaching elytra.

Description. Body small, robust, shining (Fig. 14D). Ground color reddish blown, abdominal segments VI–VII usually almost black, legs and month parts slightly paler.

Head slightly convex, almost circular, as long as wide (MHL/MHW = 0.95) (Fig. 1C); eyes small; antennae almost as long as head and pronotum combined, segments IV–X as long as wide, segment XI oval and longer than X (Fig. 15I). Labrum transverse, anterior margin rounded, with about 20 setae; epipharynx with 6 lateral setae (Fig. 16A). Mandibles almost symmetric, right median tooth larger than left one (Fig. 16E). Mentum almost trapeziform, anterior margin deeply emarginated with about 15 setae (Fig. 16B). Pronotum convex, as long as wide. Tarsal formula 3-3-4. Abdomen oblong oval.

Male: apical lobe of median lobe bent almost at right angle (Fig. 15E).

Female: spermatheca short, coiled one time at base (Fig. 15F).

Measurements. (N = 20): BL, 1.87–2.63 mm; FBL, 0.82–1.01 mm; HW, 0.34–0.42 mm; PL, 0.37–0.43 mm; PW, 0.34–0.40 mm; EW, 0.34–0.42 mm.

Etymology. This species is named after Dr. Kohei Sawada, who contributed greatly to the elucidation of the Japanese coastal Staphylinidae fauna.

Habitat. This species is found from the crevices of rock and around the holdfast of seeweeds (e.g., Monostroma nitidum Wittrock) on the intertidal zones (Fig. 25B).

Distribution. Japan: central Honshû (Fig. 25A).