Diaulota decipiens Tasaku, Ono & Maruyama, sp. n.

[Japanese name: Nise-aoki-tsutsumune-umi-hanekakushi]

(Figs. 5B; 6C, E & H; 23A)

Type material. Holotype. Male, “Nippon: Honshû / Okayama-ken / Kurashiki-shi / Ôbatake, Kusumihana / 8. VI. 2003 / leg. Fujitani Y. ” (Fig. 5B) (KUM). Paratypes. Japan: Honshû: Aichi-ken: 4 unsexed, Nishio-shi, Isshiki-chô, Sakushima, 5. V. 2018, M. Asano (KUM); Hyôgo-ken: 1 female, 3 unsexed, Himeji-shi, Matogata-chô, Fukudomari, alt. 0.6 m, 27. V. 2018, R. Wakimura (cYT); 4 males, 4 unsexed, ditto, 2. VI. 2019, R. Wakimura (cYT); Okayama-ken: 1 male, 1 female, 62 unsexed, same data as the holotype (KUM, OMNH, cYT); 6 unsexed, ditto (sea coast), 17. IV. 2015, Y. Senda (HIWA); 3 unsexed, ditto, 24. IV. 2005, Y. & H. Senda (HIWA); 1 unsexed, ditto, 21. III. 2009, O. Yamaji (KUM); 1 male, 3 unsexed, Kasaoka-shi, Is. Manabe-jima, Higa-hama (sea coast), 8. VI. 2014, Y. Senda (HIWA); 8 unsexed, Kasaoka-shi, Is. Kitaki-jima, Kanafuro, 11. X. 2008, O. Yamaji (KUM); 3 males, 2 females, 56 unsexed, Kasaoka-shi, Kasaoka IsIs., Is. Kasaoka-jima (sea coast), 6. IX. 2014, Y. Senda (HIWA); 6 unsexed, Setouchi-shi, Ushimado-chô, Ushimado, 6. V. 2008, O. Yamaji (KUM); 31 unsexed, ditto, 8. VI. 2003, Y. Fujitani (KUM); Hiroshima-ken: 5 unsexed, Hiroshima-shi, Minami-ku, Moto-ujina, 2. I. 2022, M. Shimono (KUM); Yamaguchi-ken: 1 male, 4 unsexed, Iwakuni-shi, Tsuzu, 9. IV. 2022, M. Shimono (KUM); 52 unsexed, Hôfu-shi, Mukô-shima, Tano-ura, 5. VI. 2003, Y. Fujitani (KUM, OMNH, cYT); 10 unsexed, Shimonoseki-shi, Chôfusangen’ya-kaigan, 3. XI. 2012, M. Matsuda (KUM, cYT); 1 unsexed, ditto, 20. I. 2015, M. Matsuda (KUM); 1 unsexed, ditto, 12. II. 2015, M. Matsuda (cYT); 1 unsexed, ditto, 7. IV. 2015, M. Matsuda (KUM); 3 unsexed, ditto, 7. II. 2016, M. Matsuda (KUM). Shikoku: Ehime-ken: 2 females, 1 unsexed, Matsuyama-shi, Katsuoka, Shiraishi-no-hama, (sea coast), 10. V. 2005, Y. Senda (HIWA); 1 male, 1 female, Iyo-shi, Futami-chô, Kushi (sea coast); 1 unsexed, Matsuyama-shi, Hojô-Ôura, 15-16. IV. 2010, M. Maruyama et al. (KUM). Kyûshû: Fukuoka-ken: 1 male, 32 unsexed, Itoshima-shi, Keya-kaigan (on rocky reefs), 21. VII. 2013, N. Tsuji (KUM, OMNH, cYT); 3 unsexed, ditto, 21. VII. 2013, N. Tsuji (cYT); Nagasaki-ken: 1 male, 2 unsexed, Fukue-jima, Gotô-shi, Miiraku-machi, Hamanokuri, Shiraraga-hama (Mouth of Riv.), 1. V. 2019, M. Asano (cYT).

Diagnosis. This species can be distinguished from other species of the genus Diaulota (except for related species D. hokkaidona and D. aokii), by the following characteristics: body small and almost black (Fig. 5B); male head as large as that of female; mentum as long as wide. This species is very similar to D. aokii and D. hokkaidona. Compared to D. aokii, this species differs in the following characteristics: body almost black; apex of apical lobe of median lobe slightly angular in lateral view (Fig. 6E) elytra and abdomen covered with long and thick setae (Fig. 5B). Compared to D. hokkaidona, this species differs in the following characteristics: tarsal formula 4-4-4; apical lobe of median lobe unilobed (Fig. 6E). Also, the distribution of these three species does not overlap so the distribution can also aid in identification. (See the respective distribution).

Description. Body small, robust. Ground color almost black, legs and mouth parts yellowish brown (Fig 5B). Head oval, longer than wide (MHL/MHW=1.16); eyes relatively small; antennae short, about 1.5 times longer than head, segment I longer than II, segment III slightly shorter and narrower than II, segments IV–X widened, segment XI almost semicircular, as long as wide. Labrum with about 20 setae, semicircular, transverse; epipharynx with 6 lateral setae. Mandibles slender, pointed at apex, almost symmetrical, right teeth larger than left one. Lacinia with 7 spines. Mentum with six setae, approximately trapezoidal, anterior margin deeply depressed. Labium: prementum without medial seta; ligula short, unilobed, slightly longer than segment I of labial palpus; palpus with 3 segments, segment I shortest, segment II about 1.2 times longer than I and as wide as I, segment III as long as I and thinner than I and II. Pronotum convex, almost as long as wide, widest around middle. Elytra short, as long as wide, densely covered with long setae. Tarsal formula 4-4-4. Abdomen lateral margin weakly rounded, widest at segments IV and V.

Male: sternite VIII wider than long, apical margin truncate; tergite VIII trapezoidal form, wider than long, apical margin cuspidate at middle; median lobe of aedeagus gently bent, apical lobe unilobed, and angular at apex in lateral view (Fig. 6C); almost parallel, and apical lobe slightly pointed at apex in ventral view; paramere slender, apical lobe narrow rectangle.

Female: sternite VIII wider than long, apical margin weakly rounded; tergite VIII as long as wide, apical margin truncate; spermatheca short, apical part circular, coiled once around base (Fig. 6H).

Measurements. (N = 20): BL, 1.80–2.68 mm; FBL, 0.82–1.01 mm; HW, 0.33–0.38 mm; PL, 0.33–0.43 mm; PW, 0.39–0.47 mm; EW, 0.44–0.50 mm.

Etymology. This Latin name “ decipiens ” means to cheat, deceive, beguile, or mislead in referring to morphological similarity D. aokii.

Habitat. This species was found on rocky beaches with many barnacles and oysters (Nakahama & Kawakami, 2010: as “ D. aokii ”; personal comments from N. Tsuji and Y. Senda).

Distribution. Japan: southern Honshû, Shikoku, Kyûshû (Fig. 23A).