Redescription of Rhyacophila clemens Tsuda 1940 (Trichoptera, Rhyacophilidae), with descriptions of five new, allied species from Japan Author Kawase, Naoki text Zootaxa 2024 2024-05-03 5447 1 55 76 http://dx.doi.org/10.11646/zootaxa.5447.1.3 journal article 10.11646/zootaxa.5447.1.3 1175-5326 11119209 3A9842EC-F3D2-4839-9731-AA79A27B25CB Rhyacophila clemens Tsuda 1940 ( Figs 1A–1J , 2A–2K , 9A ) Rhyacophila clemens Tsuda 1940 , 124–125, male ( Kyoto , Nagano ); Tsuda 1948 , 11–12, larva; Ross 1956 , 87, 118, male; Schmid 1970 , 95, 133, list; Tani 1977 , 198, male; Tanida 1985 , 186, larva; Hattori 2005 , 417, 423, 432, male, female, larva; Inazu & Nishida 2011 , 171, male, larva; Nozaki 2016 , 313, 314, male; Hattori 2018 , 477, 483, 492, male, female, larva. Diagnosis. The male of this species is distinguished from those of other Japanese species of the R. clemens Species Group by the combination of the following genitalic characters: The apical hinged process of segment X is Hshaped in ventral view ( Figs 2B, 2C 1 , 2C2 ), and the ventral plate of the aedeagus bears two or more small spines or protrusions posteromesally in ventral view ( Figs 2B, 2D 1 , 2D2 ). Regarding the female, R. clemens is similar to R. vesperalis sp. nov. in having a round bulge on the dorsal margin of segment VIII in lateral view ( Figs 2F, 2H1–2H 3 ), but R. vesperalis can be distinguished from the present species by bearing a pair of dorsolateral protrusions ( Fig. 3G ). Adult ( Figs 1A–1D ). Length of each forewing: male 5.2–7.2 mm (mean = 6.4, SD = 0.55, n = 62), female 6.0– 7.8 mm (mean = 7.3, SD = 0.39, n = 19). Head dark brown, setal warts light brown with brown setae; antennae brown; palpi grayish brown. Thorax dark brown dorsally; pleurites light brown. Legs yellowish brown; spurs and spines grayish brown; tibiae and tarsi covered with brown pubescence. Abdomen with brown tergites, sternites yellowish brown. In fore- and hind wings, base color grayish brown; forewings bearing yellowish white speckles sparsely from base to apical margins, with larger spots on apical end of each cell ( Fig. 1A ), and pale white markings on cross veins r-m , m-cu , and apical end of Cu2 vein; venation complete ( Fig. 1D ), roots of fork I and fork II in each forewing approximately same length; discoidal and median cells open, thyridial cell (TC) closed; cross veins r-m and m-cu present. In abdomen, scent glands of sternite V open on antero-angle mounds well encircled by sutures; small mid ventral process on sternite VII in male, on sternite VI in female ( Figs 2F, 2G ). Male genitalia ( Figs 1G–1J , 2A–2E ). Segment IX (IX) wide trapezoidal in dorsal view, with round apicodorsal lobe (adl) ( Fig. 2A ); dorsal half longer than ventral half in lateral view ( Fig. 1G ). Preanal appendages absent. Segment X (X) reverse L-shaped in lateral view composed of vertical part (vp) and horizontal part (hp) ( Fig. 1H ): vertical part tall in lateral view ( Fig. 1H ); horizontal part widened, sub-rectangular in dorsal view, with posterior margin weakly bilobed ( Fig. 2A ); apical hinged process (ahp) arising from horizontal part apicoventrally ( Fig. 1G–1I , 2A, 2B ), movable at base, H-shaped in ventral view, with pair of finger-like lobes directed posterodorsad, with pair of short mound-like extrusions directed anteroventrad ( Figs. 2B, 2C 1 , 2C2 ). Anal sclerites (as) composed of two pairs of lobes, each long rectangular in lateral view with common internal root ( Fig. 1H ). Apical band (ab) well developed, semi-oval in lateral view, broadly surrounding anus and base of anal sclerites ( Figs 1H, 1I ). Tergal band (tb) almost transparent but with some fine transverse folds, probably elastic ( Figs 1H , 2E ), connecting anteroventral part of apical band to dorsum of phallobase ( Figs 1H, 1J ). Basal segment of each inferior appendage (bsia) elongate, gradually thickened posteriorly in lateral view ( Fig. 1G ). Apical segment of each inferior appendage (asia) subtriangular in lateral view ( Fig. 1G ), densely covered with fine hair-like setae mesally ( Fig. 2A ). In phallic apparatus, phallobase (phb) short, cup-like ( Figs 1H, 1J ); aedeagus (aed) forming narrow tube ( Figs 1H, 1J ) with sclerotized ventral plate (vpl); ventral plate horizontal, tongue-shaped ( Figs 1H–1J ) with longitudinal ridge dorsomesally, posterior margin with two or more small spines or protrusions posteromesally in ventral view ( Figs 2B, 2D 1 , 2D2 ). Parameres absent. FIGURE 1. Rhyacophila clemens Tsuda 1940 . 1A–1J: 1A, male habitus, left dorsolateral (photographed by K. Inazu); 1B, male head and pro-, meso- and metanota, dorsal; 1C, male head, left lateral; 1D, male right wings, dorsal; 1E, lectotype (in glass tube) and labels preserved in INHS; 1F, male right wings, paralectotype (balsam mounted slide) preserved in OMNH; 1G–1J, male genitalia: 1G, left lateral; 1H, segment X and phallic apparatus, left lateral; 1I, same, posterodorsal; 1J, phallic apparatus, left dorsolateral. Abbreviations: I, II, III, IV, V = apical forks I, II, III, IV, V; IX, X = abdominal segments IX, X; A1, A2, A3 = anal veins 1–3; ab = apical band; aed = aedeagus; adl = apicodorsal lobe of segment IX; ahp = apical hinged process of segment X; as = anal sclerite; asia = apical segment of inferior appendage (paired); bsia = basal segment of inferior appendage (paired); C = costa; Cu1, Cu1a, Cu1b = cubital veins 1, 1a, 1b; hp = horizontal part of segment X; M1, M2, M3, M4 = median veins 1–4; m-cu = crossvein between median and cubital veins; phb = phallobase; R1, R2, R3, R4, R5 = radial veins 1–5; r-m = crossvein between radial and median veins; Sc = subcosta; tb = tergal band; TC = thyridial cell; vp = vertical part of segment X; vpl = ventral plate of aedeagus. FIGURE 2. Rhyacophila clemens Tsuda 1940 . 2A–2E, male genitalia: 2A, dorsal (left inferior appendage omitted); 2B, ventral (left inferior appendage and part of right inferior appendage omitted); 2C–2D, variations of apical hinged process of segment X, ventral (2C1, 2C2); variations of ventral plate of aedeagus, ventral (2D1, 2D2) (2C1, 2D1 collected from Hokkaido; 2C2, 2D2 from Ibaraki); 2E, apical band and tergal band, ventral; 2F–2K, female genitalia: 2F, left lateral; 2G, ventral; 2H1–2H3, variations of segment VIII, left lateral (2H1 collected from Hokkaido; 2H2, same Kanagawa; 2H3, same Nagano); 2I, segment VIII, ventral; 2J, vaginal apparatus, left lateral; 2K, same, ventral. Abbreviations: VI, VII, VIII, IX, X, XI = abdominal segments VI, VII, VIII, IX, X, XI; ab = apical band; adl = apicodorsal lobe of segment IX; as = anal sclerite; ahp = apical hinged process of segment X; asia = apical segment of inferior appendage (paired); bsia = basal segment of inferior appendage (paired); hp = horizontal part of segment X; phb = phallobase; pp = posterior process; ps = processus spermathecae; tb = tergal band; vp = vertical part of segment X; vpl = ventral plate of aedeagus; vr = ventral ridge (paired). Arrows see text. Female genitalia ( Figs 2F–2K ). Segment VIII (VIII) annular, bearing dorsal bulge in lateral view (arrows indicated in Figs 2F, 2H1–2H 3 ); with pair of ventral ridges (vr), forming longitudinal bridge, narrow anteriorly, slightly broader posteriorly in ventral view ( Fig. 2I ); pair of apodemal rods reaching posterior end of segment VI ( Fig. 2F ). Segment IX membranous, with pair of apodemal rods dorsolaterally extending into abdominal segment VI ( Fig. 2F ). Vaginal apparatus simple; posterior process (pp) sclerotized, log shaped, long rectangular in lateral view ( Fig. 2J ), long oval with pair of thin longitudinal wrinkles in ventral view ( Fig. 2K ); processus spermathecae (ps) membranous ( Figs 2J, 2K ). Immature stage. Larval stage has been described by Tsuda (1948) , Tanida (1985) , Hattori (2005) , and Inazu & Nishida (2011) . Lectotype . Male (in alcohol, Fig. 1E , deposited in INHS ) (present designation), labelled “Kumogahata, Kyoto / 7. vi.1936 , Tsuda leg.”, “ Rhyacophila sp. No. 106/ 2♂ 2♀ in copula”, “ Rhyacophila / clemens Ts. ”, “ INHS Trichoptera 61337”, and “[ Lectotype ] Male/ Rhyacophila clemens Tsuda, 1940 /designated by N. Kawase , 2024”. Paralectotypes . 2 females (in alcohol, deposited in INHS ) , labelled “ Kumogahata , Kyoto / 7.vi.1936 , Tsuda leg.”, “ Rhyacophila sp. No. 106/ 2♂ 2♀ in copula”, “ Rhyacophila / clemens Ts. ”, “ INHS Trichoptera 61337”, and “[ Paralectotypes ] 2♀ / Rhyacophila clemens Tsuda, 1940 /designated by N. Kawase , 2024” ; 3 males (in alcohol, deposited in INHS ) , labelled, “ Chigonozawa / Nagano , Japan / June 12, 1936 , Tsuda”, “ Rh. clemens ♂ ”, “ INHS Trichoptera 61336”, and “[ Paralectotypes ] 3♂ / Rhyacophila clemens Tsuda, 1940 /designated by N. Kawase , 2024” ; 1 male (pinned, deposited in CNC ) , labelled “ Otakigawa-hontani / Kiso , Nagano , Japan /8-4-39 Coll. Tsuda ”, “ Rhyacophila ♂ ♀ clemens Tsuda ”, “ CNC235664 ” and “ Rhyacophila clemens Tsuda / Paralectotype ♂ / Designated N. Kawase , 2024” ; 1 male (same, in CNC ) , labelled “ Otakigawa-hontani / Kiso , Nagano , Japan /8-4-39/ Tsuda , Coln. ”, “ CNC1409475 ” and “ Rhyacophila clemens Tsuda / Paralectotype ♂ /Designated by N. Kawase , 2024”; male right wings (preparation, Fig. 1F , deposited in OMNH ), labeled “ Rhyacophila clemens n. sp. ”, “ Rhyacophila No. 106 ♂ ” . Other specimens examined. Hokkaido : 1 male , Jôzankei , Sapporo-shi , 30.vi.1974 , T . Hattori ( SPMN ) ; 1male , 1 female , Furubira-cho , 14.vi.1976 , T . Hattori ( SPMN ) ; 8 males , 2 females , Kannon-zawa , Misumai , Sapporo-shi , 3.vii.1992 , N. Kuhara (NKu) ; 1 male , Shisamunai , Chitose-shi , 5.viii.2005 , N. Kuhara (NKu) ; 1 male , same locality, 3.viii.2012 , N. Kuhara (NKu) ; 3 males , 1 female , Bifue , Chitose-shi , 30.vi.2006 , T . Ito & T . Hattori ( SPMN ) ; 2 males , 2 females , Tarumae-gawa , Tomakomai-shi , 9.vi.1996 , N. Kuhara (NKu) ; 6 males , Shirai-sawa , Okusawasuigenchi , Otaru-shi , 29.vii.1996 , Y. Sasaki & F. Takahashi (NKa) ; 13 males , Chihase-gawa , Garô , Shimamakimura , 27.vii.2003 , N. Kuhara (NKu) ; 5 males , Ojironai-gawa , Himekawa , Mori-machi , 3–13.vii.1995 , M. Nakajima (NKa) ; 1 male , 1 female , Shimazaki-gawa , Kasumi-dai , Mori-machi , 24.vi.2003 , N. Kuhara (NKa) ; 5 males , 5 females , Iwafuchi-gawa , Kumaishi-cho , 27.vi–1.viii.1995 , Y. Ito & T . Ito (NKa) ; 10 males , 4 females , Tatenosawa , Iwabe , Fukushima-cho , 21.vi.1995 , N. Kuhara (NKu) ; 3 males , 2 females , Oyobe-gawa , Kamikawa , Matsumaecho , 3.vii.2005 , N. Kuhara (NKu) ; 3 males , Futami-cho , Hakodate-shi , 1.vi.2004 , N. Kuhara (NKu) ; 2 males , Ikusagawa , Nanae-cho , 23.vi.2003 , N. Kuhara (NKu) ; 2 males , Sakurano , Yakumo-cho , 1.vi.2004 , N. Kuhara (NKu) ; 1 male , 1 female , Okusawa , Imakane-cho , 1.vii.2007 , N. Kuhara (NKu) ; 1 female , Saisago-gawa , Hayakawa , Kaminokuni-cho , 2.vii.2005 , N. Kuhara (NKa). Honshu : Aomori : 1 male , Okuse , Towada-shi , 14.vi.2004 , N. Kuhara (NKu) . Iwate : 5 males , 1 female , Ôkawame-cho , Kuji-shi , 12.vi.2004 , N. Kuhara (NKa) ; 1 male , Kadonameiri , Iwaizumi-cho , 12.vii.1997 , N. Kuhara (NKu) ; 2 males , Kadoma , Miyako-shi , 13.vii.1997 , N. Kuhara (NKu) ; 7 males , 1 female , Kuzakai , Miyako-shi , 13.vii.1997 , N. Kuhara (NKu) ; 8 males , 1 female , Naka-zawa , Kamikaai , Kitakami-shi , 2.vii.1995 , T . Hattori ( SPMN ) ; 5 males , Motouchi-gawa , Kitakami-shi , 20.vi.1997 , T . Hattori ( SPMN ) ; 2 males , 1 female , Shitamae , Nishi-waga-machi, 13.vii.1997 , N. Kuhara (NKu) . Miyagi : 1 male , Yokokawa , Shichikashuku-machi , 6.vii.1998 , T . Hattori ( SPMN ) . Akita : 6 males , 1 female , Asahi-gawa , Nibetsu , Akita-shi , 20.vi.1997 , T . Hattori ( SPMN ) ; 1 male (pinned), Kotakizawa , Nakasen , Daisen-shi , 13.vi.2008 , M. Tanaka (MTa) ; 5 males , 5 females , Akamizu-sawa , Sannai , Yokote-shi , 14.vii.1997 , N. Kuhara (NKa) . Yamagata : 1 male , Oshôshizu , Yuza-machi , 9.vi.1998 , H. Nishimoto ( SPMN ) ; 4 males , Kinomezawa , Chôkai-san , Yuza-machi , 9.vi.1998 , H. Nishimoto ( SPMN ) ; 1 male , 1 female , Kanjindai , Nagai-shi , 3.vii.1998 , T . Hattori ( SPMN ) ; 6 males , Hirokawara-gawa , Iide-machi , 3.vii.1998 , T . Hattori ( SPMN ) . Fukushima : 10 males , Kurokawa , Shirakawa-shi, M . Kobayashi ( KPM-NKMK 64270 ) . Ibaraki : 4 males , Yonedaira , Nakadogawa , Takahagi-shi , 29.iv.1998 , N. Kawase (NKa) ; 2 males , Shôbusawa , Yasato , Ishioka-shi , 11–18.v.1997 , N. Kawase (NKa) ; 1 male , Obata , Yasato , Ishioka-shi , 13–20.v.1997 , N. Kawase (NKa) . Tochigi : 1 male , Itamuro , Kuroiso , Nasushiobara-shi , 7.vi.1998 , H. Nishimoto ( SPMN ) ; 1 male , 1 female , Nagai , Yaita-shi , 6.vi.1998 , H. Nishimoto ( SPMN ) ; 5 males , 3 females , Shôjinzawa-yûsui , Yaita-shi , 7.vi.1998 , H. Nishimoto ( SPMN ) ; 1 male , Chûgûshi , Nikkô-shi , 6.vi.1998 , H. Nishimoto ( SPMN ) . Tokyo : 1 male , 1 female (couple), Kotosawa , Mitake , Oume-shi , 24.v.1989 , T . Nozaki (NKa) ; 35 males , 9 females , Kitaaki-gawa , Koiwa , Hinohara-mura , 14.vi.1989 , T . Nozaki (NKa) . Kanagawa : 21 males , 5 females , Nishizawa , Nakagawa , Yamakita-machi , 8.vi.2020 , T . Nozaki (NKa) ; 1 male , same locality, 28.iv.2023 , T . Nozaki (NKa) . Niigata : 5 males , 2 females , Sasagawa , Sado-shi , 12.v.1985 , K. Baba ( KPM-NKMK 84910 ) ; 3 males , Imagawa , Murakami-shi , 24.vi.1956 , K. Baba ( KPM-NKMK 17780 ) ; 1 male , Budo , Murakami-shi , 27.vi.1964 , K. Baba ( KPM-NKMK 18800 ) ; 1 male , same data, K. Baba ( KPM-NKMK 18850 ) ; 1 male , Sanpokumachi , Murakami-shi , 25.ix.1968 , M. Kobayashi ( KPM-NKMK 22270 ) ; 1 male , Kurokawa-mura , Tainai-shi , 11.vii.1964 , K. Baba ( KPM-NKMK 19510 ) ; 2 males , 1 female , same locality, 15.vii.1964 , K. Baba ( KPM-NKMK 19560 ) ; 1 male , 2 females , Ginzan-daira , Yunotani-mura , 2.vii.1999 , T . Hattori ( SPMN ) ; 1 female , Matsunoyamamatsukuchi , Tôkamachi-shi , 24.vi–2.vii.2021 , D. Kato (NKa) ; 1 male , Wasabi-zawa , Ôdokoro , Itoigawa-shi , 14.viii.1998 , T . Hattori ( SPMN ) ; 3 males , Irikon-zawa , Itoigawa-shi , 16.viii.1996 , T . Hattori ( SPMN ) . Toyama : 1 male , Sakai-gawa , Yamazaki , Asahi-machi , 23.ix.2004 , N. Kuhara (NKu) . Fukui : 3 males , Ichijyôdani , Fukui-shi , 30.iv.1998 , H. Nishimoto ( SPMN ) ; 6 males , 2 females , Okuasô , Tsuruga-shi , 19.vi.1994 , T . Hattori ( SPMN ) . Nagano : 6 males , Chigono-sawa , Kisofukushima-machi , 13.vi.1998 , T . Hattori ( SPMN ) ; 5 males , same data (in glycerin) ( SPMN ) ; 2 females , same data (in glycerin) ( SPMN ) . Gifu : 1 female , Iwaimachi , Takayama-shi , 9.vi.2003 , H. Nishimoto ( SPMN ) ; 7 males , 1 female , Namai , Taki-machi , Takayama-shi , 7.vi.2003 , H. Nishimoto ( SPMN ) ; 18 males , 3 females , same locality, 24.vi.2004 , H. Nishimoto ( SPMN ) ; 14 males , 2 females , same locality, 18.vi.2005 , H. Nishimoto ( SPMN ) ; 2 females , Tsukechi-kyo , Shimoure , Tsukechi-cho , 13.v.2002 , H. Nishimoto ( SPMN ) ; 4 males , 1 female , Enbara , Miyama-cho , Yamagata-shi , 5.v.1996 , T . Hattori ( SPMN ) ; 12 males , Nishimaenotani , Tsurumi , Ibigawa-cho , 28–29.v.2002 N. Kawase (NKa) ; 3 males , Ozu , Kuze , Ibigawa-cho , 25.v.2002 , N. Kawase (NKa) ; 2 males , 2 females , Kuze , Ibigawa-cho , 27.v.2004 , H. Nishimoto ( SPMN ) ; 2 males , 1 female , Sakauchigawa , Sakauchi-kawakami , Ibigawa-cho , 7.vi.1998 , T . Hattori ( SPMN ) ; 4 males , 4 females , Hassô-gawa , Sakauchi-kawakami , Ibigawa-cho , 7.vi.1998 , T . Hattori ( SPMN ) ; 1 male , Sakauchi-sakamoto , Ibigawa-cho , 1.vi.2022 , N. Kawase (NKa) . Shizuoka : 1 male , Funabara-gawa , Izu-shi , 18.v.1996 , T . Hattori (in glycerin) ( SPMN ) ; 1 male , 1 female , same locality, 16.vi.1996 , T . Hattori ( SPMN ) ; 4 males , 1 female , Kamifunabara , Izu-shi , 1.iv.2009 , T . Hattori & T . Ito ( SPMN ) ; 1 male , Kazehaya-toge , Izu-shi , 3.vi.2009 , T . Hattori & T . Ito ( SPMN ) ; 1 female , Ôsouri , Nishiizucho , 3.vi.2009 , T . Hattori & T . Ito ( SPMN ) ; 6 males , 5 females , Momosawa-gawa , Nagaizumi-cho , Numazu-shi , 8.iv.1995 , T . Hattori ( SPMN ) ; 1 female , Nagao-gawa , Hirayama , Shizuoka-shi , 27.iv.2006 , T . Hattori ( SPMN ) : 9 males , 1 female , same locality, 8.vi.2006 , T . Hattori ( SPMN ) ; 1 male , Hikage-sawa , Umegashima , Shizuoka-shi , 21.vi.2002 , T . Hattori ( SPMN ) ; 1 male , Minami-sawa , Umegashima , Shizuoka-shi , 28.vi.1997 , T . Hattori ( SPMN ) ; 1 male , 1 female , Kurobe-sawa , Hirano , Shizuoka-shi , 1.vi.1997 , T . Hattori ( SPMN ) ; 3 males , 2 females , same locality, 10.vii.1999 , T . Hattori ( SPMN ) ; 1 female , Yokosawa , Shizuoka-shi , 5.vi.1999 , T . Hattori ( SPMN ) ; 2 males , 6 females , same locality, 9.vi.2001 , T . Hattori ( SPMN ) ; 1 male , 1 female , same locality, 3.v.2002 , T . Hattori ( SPMN ) ; 2 males , same locality, 21.v.2003 , T . Hattori ( SPMN ) ; 3 males , same locality, 21.vi.2003 , T . Hattori ( SPMN ) ; 5 males , Shiraisizawa , Takumi , Shizuoka-shi , 28.v.2001 , T . Hattori ( SPMN ) ; 1 male , 1 female , Yuyama , Shizuoka-shi , 29.iv.1997 , T . Hattori ( SPMN ) ; 8 males , 2 females , Warashina-gawa , Yunoshima , Shizuoka-shi , 11.v.2001 , T . Hattori ( SPMN ) . Mie : 3 males , Inabe-gawa , Fujiwara-cho , Inabe-shi , 21.iii.2001 , F. Nishimoto ( SPMN ) ; 17 males , 4 females , Yamaguchi , Fujiwara-cho , Inabe-shi , 4.vi.2006 , T . Hattori ( SPMN ) ; 1 male , Sakashita , Kameyama-shi , 9.vi.2006 , N. Kawase (NKa) ; 1 male , Kamitage , Misugi-cho , 14.vi.2009 , H. Morita (NKa) ; 13 males , Hachisugawa , Iitaka-cho , 27.v.2004 , T . Hattori ( SPMN ) . Shiga : 4 males , Harikawa , Yogo-cho , Nagahama-shi , 1.vi.2009 , N. Kawase (NKa) ; 3 males , 2 females , Samukaze-gawa , Imazu-cho , Takashima-shi , 19.v.1988 , K. Tanida ( OMNH ) ; 7 males , Kimigahata , Eigenji , Higashi-ômi-shi, 16.v.1993 , K. Tanida ( OMNH ) ; 1 male , Shirakura-dani , Ôkawara , Tsuchiyama-cho , Koka-shi , 17.v.2005 , N. Kawase (NKa) ; 1 male , same locality, 10.viii.2008 , N. Kawase ( LBM1410012584 ) ; 7 males , Ômiya-gawa , Sakamoto-honmachi , Ôtsu-shi , 31.v.1987 , K. Tanida ( OMNH ) ; 4 males , 2 females , Hiyoshi-taisha , Sakamoto , Ôtsu-shi , 24.v.1981 , K. Tanida ( OMNH ) ; 1 male , same locality, 3.v.1987 , K. Tanida ( OMNH ) . Kyoto : 1 male , Kurama , Kyoto-shi , 19.v.1974 , T . Hattori (in glycerin) ( SPMN ) ; 1 female , same data (in glycerin) ( SPMN ) ; 14 males , 1 female , Oku-miya , Kibune , Kyoto-shi , 30.v.1987 , K. Tanida ( OMNH ) ; 2 males , 2 females (2 couples), same data, K. Tanida ( OMNH ) . Osaka : 3 males , 1 female , Takihata , Kawachi-nagano-shi, 10.iv.1990 , K. Tanida ( OMNH ) ; 1 male , 1 female , same locality, 15.v.1984 , Nishida ( SPMN ) ; 1 male , 1 female , same locality, 15.v.1984 , H. Nishimoto ( SPMN ) ; 2 males , 1 female , same locality, 17.v.1985 , H. Nishimoto ( SPMN ) ; 1 male , Izumi-Katsuragi-san, Kisihwada-shi , 22.v.1984 , H. Nishimoto ( SPMN ) . Hyogo : 1 male , 1 female , Amago-ike , Takenouchi , Wadayama-cho , Asago-shi , 7.v.2002 , K. Inazu ( SPMN ) ; 1 male , 1 female , same locality, 1.vi.2004 , K. Inazu (NKa) ; 1 male , 1 female , same locality, 4.vi.2004 , K. Inazu ( LBM1410012585–1410012586 ; 2 males , Kirigataki , Shin-onsen-cho, no collecting date, K. Inazu ( SPMN ) ; 4 males , Ojiro , Mikata , Kami-cho , 21.vi– 11.vii.2015 , S. Fujie ( OMNH ) . Nara : 1 male , Ômataguchi , Higashi-yoshino-mura, 29.v.1988 , K. Tanida ( OMNH ) ; 3 males , Takahara , Kawakami-mura , 27.v.2004 , T . Hattori ( SPMN ) ; 1 male , Sanjyô-gawa , Tenkawa-mura , 15.v.2004 , T . Hattori ( SPMN ) . Wakayama : 1 male , Uigoke , Kanaya , Aritagawa-cho , 26.iv.2004 , T . Hattori ( SPMN ) ; 2 males , Takiwake-no-taki, Takata , Shingû-shi , 20.v.1990 , N. Kuhara (NKu) . Okayama : 2 males , 2 females , Kamisaibaraendô , Kagamino-cho , 14.viii.2011 , K. Nojima (NKa) ; 2 males , Shiraka-keikoku , Tomi-nishidani , Kagamino-cho , 26.vi.2016 , K. Nojima (NKa) ; 2 males , Ôgaya , Nishi-awakura-son, 12.v.2016 , K. Nojima (NKa) ; 3 males , same locality, 20.vii.2016 , K. Nojima ( LBM1410012587–1410012589 ) ; 2 males , Hiruzen-kamifukuda , Maniwa-shi , 5.v.2016 , K. Nojima (NKa) . Remarks . Tsuda (1940) described this species based on 34 males and 16 females collected from several localities in Kyoto and Nagano Prefectures (central Honshu), but he did not designate the holotype . The collection of the late Matsunae Tsuda was believed to have been mostly lost except for microscopic preparations of wings of some species (Tanida personal communication 2023). For this species, only the right wings of a male that was definitely used by Tsuda (1940) are deposited in the Osaka Museum of Natural History (OMNH) ( Fig. 1F ). Although the shape, coloration, and venation of the wings agree well with those of R. clemens described above, they are insufficient for confirming species identity. However, through the course of my study, I noticed that several specimens of R. clemens used by Tsuda (1940) are presently deposited in the Herbert H. Ross collection of the Illinois Natural History Survey in the USA (https://www.gbif.org/occurrence/search?dataset_key=68513375-3aa5- 4f6f-9975-d97d56c21d61&taxon_key=5053001) ( Fig. 1E ). The collection data of these specimens ( 4 males and 2 females ) agree with some of the specimens in the specimen list of Tsuda (1940) and Tsuda’s species number “ Rhyacophila sp. No. 106” labeled in the vial of “INHS Trichoptera 61337” ( Fig. 1E ) corresponds to the number “ Rhyacophila No. 106” on the male wing preparation in OMNH ( Fig. 1F ). These specimens must be some of the syntypes of this species. Furthermore, I found that two pinned male specimens of R. clemens deposited in the Canadian National Collection of Insects, Arachnids & Nematodes in Canada (https://www.cnc.agr.gc.ca/taxonomy/ Specimen.php?id=235664; https://www.cnc.agr.gc.ca/taxonomy/Specimen.php?id=2072494) were also used in the original description. I examined four male and two female specimens (“ INHS Trichoptera 61336 & 61337”) and photographs of male genitalia (“ CNC 235664 ”) kindly provided by Tommy McElrath ( INHS ) and Owen Lonsdale ( CNC ), respectively. The genital morphology of these agreed well with that of R. clemens described above. In order to promote nomenclatural stability and facilitate further identifications of this species, I choose a male in the INHS collection, preserved in ethyl alcohol in a glass vial, as the lectotype with the following five labels: “Kumogahata, Kyoto ; 7.VI.1936 . Tsuda leg.// Rhyacophila sp No. 106; 2♂ 2♀ in copula// Rhyacophila clemens Ts. // INHS ; Trichoptera ; 61337//[ Lectotype ] Male; Rhyacophila clemens Tsuda, 1940 ; designated by N. Kawase , 2024” with the first three labels in Tsuda’s handwriting and the last two labels printed ( Fig. 1E ). This species was also recorded from Iriomote-jima, Ryukyu Archipelago ( Kuranishi 1997 ) and from Taiwan ( Kiss 2013 ; Malicky 2014 ), but I could not examine the specimens used in these studies. Reexamination of these records is necessary since R. clemens was not found from Shikoku and Kyushu, southwestern Japan in the present study ( Fig. 9A ). Distribution and biology. Rhyacophila clemens is one of the common Rhyacophila species of Japan and is broadly distributed from southwestern Hokkaido to western Honshu ( Fig. 9A ). Adults are collected near mountain streams in late April to September. Taira (2023) indicated that this species has a univoltine life cycle. Japanese name . Kuremensu-nagare-tobikera.