Rhyacophila inazui, Kawase, 2024

Kawase, Naoki, 2024, Redescription of Rhyacophila clemens Tsuda 1940 (Trichoptera, Rhyacophilidae), with descriptions of five new, allied species from Japan, Zootaxa 5447 (1), pp. 55-76 : 64-67

Rhyacophila inazui sp. nov.

( Figs 4A–4N , 9C )

Rhyacophila sp. 2 ( clemens gr.): Inazu 2008, 65, 88, 99, wing markings, flight period; Inazu & Nishida 2011, 176, male. Rhyacophila sp. 1 ( clemens gr.): Kawase & Morita 2010, 36, list.

Rhyacophila sp. ( Clemens gr.): Kawase & Morita 2014, 4, list.

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

Rhyacophila sp. 13: Yamamoto et al. 2021, 70, list.

Diagnosis. Adults of this species are unique in the R. clemens Species Group in having distinct pale yellowish spots along the posterior margin of each forewing ( Figs 4A, 4B ). The male genitalia of R. inazui sp. nov. are very similar to those of R. angulicauda sp. nov. and R. parvicauda sp. nov. in having a U-shaped apical hinged process of segment X in ventral view, but can be distinguished from the latter two by the size of the apicodorsal lobe of segment IX: The apicodorsal lobe of segment IX is indistinct in the present species ( Figs 4C, 4E ), but is large and trapezoidal in R. angulicauda sp. nov. (arrows indicated in Figs 5A, 5C ) and small trapezoidal in R. parvicauda sp. nov. ( Figs 6A, 6C ). The female genitalia of R. inazui sp. nov. are somewhat similar to those of R. angulicauda sp. nov., R. parvicauda sp. nov., and R. furcicauda sp. nov. in having almost straight dorsal margins of segment VIII in lateral view, but can be distinguished from the latter three species by the combination of the following two characteristics: (1) the setae on the lateral surface of segment VIII are hair like ( Figs 4K , 5F ) in R. inazui and R. angulicauda , but thick, spine-like in R. parvicauda and R. furcicauda ( Figs 6E , 7G ); and (2) a pair of ventral ridges extend posterolaterad and can be seen clearly in lateral view in R. inazui and R. parvicauda ( Figs 4K , 6E ) but extend posteroventrad and are invisible in lateral view in R. angulicauda and R. furcicauda ( Figs 5F , 7G ).

Adult ( Figs 4A, 4B ). Length of each forewing: male 6.8–7.8 mm (mean = 7.3, SD = 0.30, n = 17), female 7.8–9.3 mm (mean = 8.2, SD = 0.47, n = 8). General morphology and coloration similar to those of R. clemens , but forewings bearing pale yellowish speckles more densely from base to apical margins ( Fig. 4A ), distinct pale spots visible even in alcohol ( Fig. 4B ). In venation, root of fork I on each forewing clearly longer than that of fork II ( Fig. 4B ).

Male genitalia ( Figs 4C–4H ). Segment IX rectangular in dorsal view with apicodorsal lobe very short ( Fig. 4E ), dorsal half longer than ventral half in lateral view ( Fig. 4C ). 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. 4D ); horizontal part nearly oval in dorsal view with shallow incisions anteriorly and posteriorly in dorsal view ( Fig. 4E ); apical hinged process U-shaped in ventral view, with pair of slender finger-like lobes, directed posterodorsad ( Figs 4C–4F, 4G 1 ), with pair of round anteroventral corners, bearing small median protrusion anteroventrally (arrows in Figs 4F, 4G 1 ). Anal sclerites composed of two pairs of lobes, each long rectangular in lateral view ( Fig. 4D ), but apex of dorsal lobe weakly incised mesally in lateral view, bearing common internal root ( Fig. 4D ). Apical band well developed, semi-oval in lateral view, broadly surrounding anus and base of anal sclerites ( Figs 4D, 4F, 4H ). Tergal band connecting base of apical band to dorsum of phallobase ( Fig. 4D ). Basal segment of each inferior appendage setose, elongate, posterior half gradually thicker in lateral view ( Fig. 4C ). Apical segment of each inferior appendage rounded triangular in lateral view ( Fig. 4C ), covered with hair-like setae mesally ( Fig. 4E ). In phallic apparatus, phallobase short ( Fig. 4D ); aedeagus forming narrow tube with sclerotized ventral plate ( Figs 4D, 4F, 4H ); ventral plate horizontal and tongue-shaped with posterior margin shallowly concave in ventral view ( Fig. 4G 2 ). Parameres absent.

Female genitalia ( Figs 4I–4N ). Segment VIII annular, dorsal margin almost straight in lateral view ( Figs 4I, 4K ), slightly flattened ventrally; with pair of distinct ventral ridges extending posterolaterad in lateral view, gradually separating from anterior to posterior in lateral and ventral views ( Figs 4I–4L ); pair of apodemal rods reaching posterior end of segment VI ( Fig. 4I ). Segment IX membranous, with pair of apodemal rods dorsolaterally extending into abdominal segment VII ( Fig. 4I ). Vaginal apparatus simple; posterior process sclerotized, smooth, rectangular, about three times as long as wide in lateral view ( Fig. 4M ), oval in ventral view ( Fig. 4N ); processus spermathecae membranous ( Figs 4M, 4N ).

Immature stage. Unknown.

Holotype. Male (in alcohol), Amago-ike , Takenouchi , Wadayama-cho , Asago-shi, Hyogo Pref., Honshu, Japan, 35°24’21”N 134°55’13”E, alt. 250 m, 16.iv.2004, K. Inazu ( LBM1410012601 ).

Paratypes. Honshu : Ishikawa : 1 male, Sannomiya , Tsurugi-machi , Hakusan-shi , 20.iv.1986, I. Togashi ( OMNH). Shizuoka : 2 males, Warashina-gawa , Ôma, Shizuoka-shi, 3.iv.1994, T . Hattori (SPMN-IS-59752–59753); 1 male, Utaugenotaki, Kurata, Fujieda-shi, 24.iii.2004, T . Hattori (SPMN-IS-59754). Shiga : 16 males, Sugino, Kinomoto-cho, Nagahama-shi, 12.iv.2012, T . Hattori ( LBM1410012602–1410012617 ). Kyoto : 1 male, Kibune , Kyoto-shi, 11.iv.1990, K. Tanida ( OMNH). Osaka: 1 male & 1 female (couple), same locality, 10.iv.1990, K. Tanida ( OMNH) ; 1 male & 1 female (couple), Ishi-kawa, Takihata-horikoshi , Kawachi-nagano-shi, 20.iv.1987, K. Tanida ( OMNH). Hyogo : 1 male, 2 females, same data as the holotype ( LBM1410012618–1410012620 ). Okayama : 5 males, 4 females, Shiraka-keikoku, Tomi-nishidani, Kaganino-cho, 23.iv.2017, K. Nojima ( LBM1410012621– 1410012629 ) ;

Other specimens examined. Honshu: Shizuoka: 1 male, Nakazawa, Shizuoka-shi, 21.iii.1995, T. Hattori ( SPMN) ; Gifu: 1 female, Sakauchi-sakamoto, Ibigawa-cho , 10–20.iv.2023, N. Kawase (NKa) . Mie: 10 males, 5 females, Kanzan, Suizawa-cho, Yokkaichi-shi , 6–16.iv.2008, H. Morita (NKa) ; 3 males, Miyazuma-kyo, Suizawa-cho, Yokkaichi-shi, 6.iv–16.iv.2009, H. Morita ( SPMN) . Shiga: 16 males, 2 females, Nakanokawachi, Yogo-cho, Nagahama-shi , 26.iv–17.v.2010, N. Kawase (NKa) ; 1 male, Ôkawara, Tsuchiyama-cho, Kôka-shi , 21.iv.2005, N. Kawase (NKa) . Hyogo: 1 male, 1 female, Itoi-gawa, Wadayama-cho, Asago-shi, 5.iv.2002, K. Inazu (in glycerin) ( SPMN) ; 2 males, 2 females, same locality, 6.iv.2004, K. Inazu ( SPMN) ; 5 males, Wakasu, Sayô-cho, 25.iv.1984, H. Nishimoto ( SPMN) . Osaka: 2 males, Takihata, Kawachi-nagano-shi, 25.iv.1985, H. Nishimoto ( SPMN) . Nara: 1 male, Gojyô-shi, 12.iv.1984, H. Nishimoto ( SPMN) . Tottori: 3 males, Wakasa-cho, 24.iv.1984, H. Nishimoto (in glycerin) ( SPMN) ; 3 males, same data (in glycerin) ( SPMN) . Okayama: 1 male, Ombara, Kamisaibara, Kagamino-cho , 13.iv.2019, K. Nojima (NKa) ; 4 males, Ôgaya , Nishi-awakura-son, 7.v.2017, K. Nojima (NKa). Shikoku : Ehime: 1 female, Izugataniyama, Nishidani, Kumakôgen-cho , 1–10.v.2018, E. Yamamoto (NKa) ; 2 males, Namakusa-dani, Odamiyama, Uchiko-cho, 21.iv.2000, E. Yamamoto, T. Ito & A. Ohkawa ( SPMN) ; 10 males, 1 female, same locality, 29.iv.2000, E. Yamamoto ( SPMN) ; 1 male, 3 females, same locality, 21–30.iv.2020, E. Yamamoto (NKa) . Kochi: 1 male, Befu-kyo, Monobe-son, 12.iv.2004, K. Nio ( SPMN) .

Distribution and biology. Rhyacophila inazui sp. nov. is distributed in central to western Honshu and Shikoku ( Fig. 9C ). The adults were collected near mountain streams in spring, late March to early May.

Etymology. This species is dedicated to Mr. Kazuyuki Inazu, who mentioned this species as a possibly undescribed species based on its early flight season and wing color pattern ( Inazu, 2008). The species epithet is a noun in the genitive case.

Japanese name. Inazu-nagare-tobikera.

Figures

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.

FIGURE 4. Rhyacophila inazui sp. nov. 4A, male habitus, left dorsolateral (photographed by K. Inazu); 4B, female right forewing (in alcohol), dorsal; 4C–4H, male genitalia: 4C, left lateral; 4D, segment X and phallic apparatus, left lateral; 4E, dorsal (left inferior appendage omitted); 4F, ventral (left inferior appendage and apical segment of right inferior appendage omitted); 4G1, apical hinged process of segment X, enlarged, ventral; 4G2, ventral plate of aedeagus, enlarged, ventral; 4H, posterodorsal. 4I–4N, female genitalia: 4I, left lateral; 4J, ventral; 4K, segment VIII, left lateral; 4L, same, ventral; 4M, vaginal apparatus, left lateral; 4N, same, ventral. Abbreviation: vr = ventral ridge. Arrows see text.

FIGURE 5. Rhyacophila angulicauda sp. nov. 5A–5D, male genitalia: 5A, left lateral; 5B, segment X and phallic apparatus, left lateral; 5C, dorsal (left inferior appendage omitted); 5D, ventral (left inferior appendage and apex of apical segment of right inferior appendage omitted). 5E–5I, female genitalia: 5E, left lateral; 5F, segment VIII, left lateral; 5G, same, ventral; 5H, vaginal apparatus, left lateral; 5I, same, ventral. Arrows see text.

FIGURE 6. Rhyacophila parvicauda sp. nov. 6A–6D, male genitalia: 6A, left lateral; 6B, segment X and phallic apparatus, left lateral; 6C, dorsal (left inferior appendage omitted); 6D, ventral (left inferior appendage omitted). 6E–6H, female genitalia: 6E, segment VIII, left lateral; 6F, same, ventral; 6G, vaginal apparatus, left lateral; 6H, same, ventral. Abbreviation: vr = ventral ridge.Arrows see text.

FIGURE 7. Rhyacophila furcicauda sp. nov. 7A–7F, male genitalia: 7A, left lateral; 7B, segment X and phallic apparatus, left lateral; 7C, same, posterodorsal; 7D, dorsal (left inferior appendage omitted); 7E, apical segment of right inferior appendage, mesal; 7F, segment X and phallic apparatus, ventral. 7G–7J, female genitalia: 7G, segment VIII, left lateral; 7H, same, ventral; 7I, vaginal apparatus, left lateral; 7J, same, ventral. Abbreviation: vr = ventral ridge. Arrows see text.

FIGURE 9. Distributions of species in the Rhyacophila clemens Species Group in Japan.