Rhyacophila vesperalis Kawase 2024, sp. nov.

Rhyacophila vesperalis sp. nov.

(Figs 3A–3K, 9B)

Rhyacophila clemens: Kobayashi 1959, 343, list; Gyotoku & Nozaki 1992, 14, list. Misidentifications.

Rhyacophila clemens (variation) : Hattori 2005, 423 (4d’ & 4e’ in Fig. 10), male & female; Hattori 2018, 483 (4d’ & 4e’ in Fig. 11), male & female.

Rhyacophila sp. F : Nojima 2017, 111, list.

Rhyacophila sp. 14 : Yamamoto et al. 2021, 70, list.

Diagnosis. The male and female of this species are readily distinguishable from those of other Japanese species of this species group by the following genital characters: In the male, the apical hinged process of segment X bears a pair of long anteroventral longitudinal ridges (arrows in Figs 3D, 3E 1); and in the female, segment VIII bears a pair of lateral flanges posterolaterally like short wings (arrows in Figs 3G, 3H). Additionally, the male of this species is somewhat similar to R. kumgangsanica Kumanski 1990, a Korean species (Fig. 8), but can be easily distinguished from the latter by the following character: The shape of each apical segment of the inferior appendage is subtriangular in R. vesperalis (Fig. 3A) but subrectangular in R. kumgangsanica (Fig. 8A) in lateral view.

Adult. Length of each forewing: male 5.6–7.2 mm (mean = 6.5, SD = 0.48, n = 29), female 6.8–8.6 mm (mean = 7.8, SD = 0.53, n = 14). General morphology and coloration similar to those of R. clemens, wing venation of this species also similar to that of R. clemens (Fig. 1D).

Male genitalia (Figs 3A–3E). Segment IX almost rectangular in dorsal view with tiny apicodorsal lobe (Fig. 3C), dorsal half longer than ventral half in lateral view (Fig. 3A). Preanal appendages absent. Segment X reverse L-shaped in lateral view composed of vertical part and horizontal part: vertical part tall in lateral view (Fig. 3B); horizontal part sub-oval in lateral view (Fig. 3A), sub-rectangular in dorsal view with posterior margin bilobed (Fig. 3C); apical hinged process arising from horizontal part apicoventrally, with pair of long finger-like lobes posteriorly, with pair of anteroventral longitudinal ridges (arrows indicated in Figs 3D, 3E 1). Anal sclerites composed of two pairs of lobes, with common internal root (Fig. 3B), each long rectangular in lateral view, but apex of each ventral pair rather pointed ventrally (Fig. 3B). Apical band well developed, semi-oval in lateral view, broadly surrounding anus and base of anal sclerites (Figs 3B, 3D). Tergal band connected anteroventral part of apical band to dorsum of phallobase. Basal segment of each inferior appendage setose, elongate, posterior half gradually thicker in lateral view (Fig. 3A). Apical segment of each inferior appendage subtriangular in lateral view (Fig. 3A), densely covered with fine hair-like setae mesally (Fig. 3C). In phallic apparatus, phallobase short, cup-like (Fig. 3B); aedeagus forming narrow tube with sclerotized ventral plate (Figs 3B, 3D); ventral plate tongue like with posterior margin roundly concave and tiny protrusion mesally in ventral view (Figs 3D, 3E 2). Parameres absent.

Female genitalia (Figs 3F–3K). Segment VIII annular, bearing slightly angular dorsal bulge in lateral view; pair of posterolateral flanges like short wing (arrows in Figs 3G, 3H); with pair of ventral ridges closest in anterior 1/4–1/ 3 in ventral view (Fig. 3I); pair of apodemal rods reaching to middle of segment VI (Fig. 3F). Segment IX membranous, with pair of apodemal rods dorsolaterally extending to abdominal segment VI or more deeply (Fig. 3F). Vaginal apparatus simple; posterior process sclerotized, approximately three times as long as wide, dorsal margin round in lateral view (Fig. 3J), long oval with pair of thin longitudinal wrinkles in ventral view; processus spermathecae membranous (Fig. 3K).

Immature stage. Unknown.

Holotype. Male (in alcohol), Odamiyama-hontani, Nakagawa, Uchiko-cho, 33°32’14”N 132°52’29”E, alt. 990 m, 10–20.iv.2021, E. Yamamoto, Ehime, Shikoku, JAPAN (LBM1410012590).

Paratypes. Shikoku: Ehime: 1 male, 1 female, same locality as the holotype, 19.v.2000, E. Yamamoto (LBM1410012591–1410012592); 1 male, same locality as the holotype, 10.v.2001, E.Yamamoto (SPMN-IS-59744); 4 males, 2 females, same locality as the holotype, 21.v.2001, E. Yamamoto (SPMN-IS-59745–59750); 3 males, 1 female, same locality as the holotype, 31.v.2001, E. Yamamoto (SPMN-IS-59737–59740); 2 males, 1 female, same locality as the holotype, 10.vi.2001, E. Yamamoto (SPMN-IS-59741–59743); 2 males, 3 females, Namakusadani, Odamiyama, Nakagawa, Uchiko-cho, 11–20.vi.2020, E. Yamamoto (LBM1410012596–1410012600); 1 male, 2 females, same locality as the holotype, 11–20.vi.2021, E. Yamamoto (LBM1410012593–1410012595); 7 males, 5 females, Odamiyama-hônomata, Nakagawa, Uchiko-cho, 33°32’40”N 132°51’11”E, alt. 925 m, 21–30.vi.2018, E. Yamamoto (OMNH); Tokushima: 1 female, Kônose-kyo, Kitokitagawa, Naka-cho, 6.v.2009, T. Torii (SPMN-IS-59751).

Other specimens examined. Honshu: Tottori: 1 male, Wakamatsu-gawa, Yukawa, Nichinan-cho, 15.ix.2002, T. Hattori (SPMN). Shimane: 1 male, Takezaki-oidani, Okuizumo-cho, 19.v.1992, N. Nishimura (NKa). Okayama: 10 males, Shingô-yuno, Niimi-shi, 1.vi.2013, K. Nojima (NKa). Hiroshima: 1 male, Hosomi-dani, Yoshiwa, Hatsukaichi-shi, 7.vi.2004, I. Mori (SPMN); 2 males, same locality, 7.vi–19.vii.2004, I. Mori (SPMN). Yamaguchi: 1 male, Jiyoshi, Toyota-cho, Shimonoseki-shi, 22.v.1996, T. Hattori (SPMN). Shikoku: Kagawa: 2 males, 1 female, Koujigawa, Shionoe-cho, Takamatsu-shi, 23.v.2000, E. Yamamoto (SPMN). Ehime: 1 female, Teppô-ishikawa Camp-village, Omogo-mura, 22–23.v.1999, A. Ohkawa & T. Ito (in glycerin) (SPMN); 1 female, same data (SPMN); 1 male, Jiyoshi-tôge, Yanadani, Kumakôgen-cho, 23.ix.2002, T. Hattori (in glycerin) (SPMN); 2 males, 5 females, Odamiyama-Tarô-dani, Uchiko-cho, 20.v.2000, E. Yamamoto (SPMN); 1 male, 2 females, Odamiyama-Namakusadani, Uchiko-cho, 26.vii.1998, E. Yamamoto (SPMN); 1 male, same locality, 29.v.1999, E. Yamamoto (in glycerin) (SPMN); 4 males, 1 female, same locality, 21.vi.1999, E. Yamamoto (NKa); 6 males, 4 females, same locality, 5.vi.2000, E. Yamamoto (SPMN); 5 males, 4 females, same locality, 16.vi.2000, E. Yamamoto (SPMN); 1 female, same locality, 29.vi.2000, E. Yamamoto (SPMN); 2 males, same locality, 8.vii.2000, E. Yamamoto (SPMN); 3 males, 1 female, same locality, 16.vii.2000, E. Yamamoto (SPMN); 2 males, 1 female, Oda-koyayama, Oda-cho, 29.v.2000, E. Yamamoto & M. Doi (SPMN); 2 males, 1 female, same locality, 22.vi.2000, E. Yamamoto & M. Doi (SPMN); 3 males, 4 females, same locality, 29.vi.2000, E. Yamamoto & M. Doi (SPMN); 3 females, same locality, 7.vii.2000, E. Yamamoto & M. Doi (SPMN); 3 males, 1 female, same locality, 15.vii.2000, E. Yamamoto & M. Doi (SPMN); 2 males, 1 female, same locality, 21.vii.2000, E. Yamamoto & M. Doi (SPMN); 3 males, 1 female, Oda-cho, 20.ix.2000, E. Yamamoto (SPMN). Kochi: 1 pupa (male), Befu-kyo, Monobe-son, Kami-shi, 25.iv.2004, T. Hattori (SPMN); 1 male, Nishikawa-keikoku, Umaji-mura, 24.iv.2004, K. Nio (SPMN); 1 male, Uramasa-dani, Aki-shi, 25.iv.2004, K. Nio (SPMN); 1 male, Shiraidani-keikoku, Hongawa, Ino-cho, 23.v.2002, K. Nio (SPMN); 1 male, same locality, 1.vii.2005, M. Takai (SPMN); 1 female, Teragawa, Hongawa, Ino-cho, 26.v.1999, A. Ohkawa & T. Ito (SPMN); 1 female, Nagatani-keikoku, Sakawa-cho, 7.iv.2004, K. Nio (SPMN); 1 male (pinned), Yahazu, Higashi-tsuno-mura, 10.x.1988, T. Nozaki (NKa); 1 female, Irazuyama, Higashitsuno-mura, 8.v.2004, M. Takai (SPMN); 1 male, Tsunoyama-kaitaku, Higashitsuno-mura, 8.v.2004, M. Takai (SPMN); 2 males, Tengu-shinrinkôen, Higashitsuno-mura, 23.v.2004, M. Takai (SPMN). Kyushu: Fukuoka: 1 male, Yoshii-machi, Ukiha-gun, 5.iv.1956, N. Gyotoku (KPM-NKMK12420); 1 male, Mishike, Imogawa, Ukiha-machi, Ukiha-shi, 13.v.1986, T. Nozaki; 1 male, Dôbaru, Kokuraminami-ku, Kitakyushu-shi, 22.v.1996, T. Hattori (in glycerin) (SPMN); 1 male, same locality, 17.iv.2004, T. Hattori (SPMN); 1 female, same data (in glycerin) (SPMN); 2 males, 1 female, Uchigaso-keikoku, Hata, Nôgata-shi, 5.v.1997, T. Hattori (SPMN). Kumamoto: 11 males, 1 female, Kakizakoiwaoku, Izumi-mura, 24.v.1996, T. Hattori (SPMN); 6 males, same data (in glycerin) (SPMN); 6 females, same data (in glycerin) (SPMN). Oita: 1 male, Shinyabakei, Yabakei-machi, 7.v.1997, T. Hattori (SPMN); 1 female, Shimizubakuen, Mori, Kusu-machi, 18.iv.2004, T. Hattori (SPMN); 2 males, Nakatsue-mura, 10.v.1997, H. Nishimoto (SPMN). Miyazaki: 4 males, 1 female, Torinosu-dani, Saigôyamasanga, Misato-cho, 27.v.2018, D. Nakano (NKu). Kagoshima: 3 males (pinned), Natsunokawauchi, Kamou-machi, Aira-shi, 23.iii.1989, T. Nozaki (NKa); 3 males, 1 female, Kogihara, Ôkuchi-shi, 20–21.iv.2004, T. Hattori (SPMN).

Etymology. The Latin species epithet “vesperalis ” (= western) is an adjective referring to the broad distribution of this species in western Japan.

Distribution and biology. Rhyacphila vesperalis sp. nov. is distributed in western Honshu, Shikoku and Kyushu (Fig. 9B). Adults were collected near mountainous streams in April to September.

Japanese name. Nishi-kuremensu-nagare-tobikera.

Remarks. Although Hattori (2005) provided precise illustrations of the apical hinged process of the male segment X and the shape of the female segment VIII of specimens from western Japan and considered these to represent geographical variations of R. clemens (Hattori 2005: 4 d’ & 4e’ in Fig. 10), the examination of a large number of specimens in the present study revealed that the male and female genitalia illustrated by Hattori actually correspond to those of R. vesperalis sp. nov. described above. The distributions of R. clemens and R. vesperalis sp. nov. are allopatric except in Okayama Prefecture of western Honshu (Figs 9A, 9B), but the differences between these two species in male and female genitalia are stable even in Okayama Prefecture.