Rhyacophila bifue Ito & Kuhara, 2024

Ito, Tomiko, Kuhara, Naotoshi & Malicky, Hans, 2024, Five new species of the genus Rhyacophila Stephens (Trichoptera, Rhyacophilidae) from southwestern Hokkaido, northern Japan, Zootaxa 5536 (4), pp. 551-568 : 557-559

Rhyacophila bifue Ito & Kuhara sp. nov.

( Figs 1D , 3A–3I )

Rhyacophila sp. 3 : Kuhara 2001, p. 17, Hokkaido (Shiribeshi).

Species group and diagnosis. This new species belongs in the Rhyacophila kaltatica Species Group since the males have the dorsal posterior margin of segment IX protruded caudad with several spiny processes, a long depressed segment X, a large anal sclerite and thick inferior appendages with long basal and short apical segments. The male of R. bifue sp. nov. resembles those of R. hamata and two new species described here, R. imakane sp. nov. and R. misago sp. nov. However, the male of R. bifue is clearly distinguished from them by three prominent subtriangular processes on the posterior rugged area of segment IX and the position of the dorsomesal process of each inferior appendage which projects from the apicodorsal edge of the basal segment in R. bifue .

The female of this new species is also similar to those of R. hamata , R. imakane , and R. misago , but is clearly discriminated from them by the shape of abdominal segment VIII; the pair of curved ridges that are present along the posterior margin subapically in R. bifue but absent in those three species.

Adult. Male: Each forewing 6.8–7.1 mm long (mean = 6.9 mm, n = 5) and each hind wing 6.0– 6.2 mm (mean = 6.1 mm, n = 5). Female: Each forewing 7.0– 8.2 mm (mean = 7.5 mm, n = 5) and each hind wing 6.0–7.0 mm (mean = 6.6 mm, n = 5). Head dark brown, warts light brown with brown setae, antennae dark brown, palpi brown. Thorax dark brown dorsally. Legs brown with dark brown spurs. Wings brown with darker veins and fulvous pterostigma. Abdomen with dark brown tergites and light brown sternites, dark pigments scattered dorsally; scent glands of sternite V open on anterolateral-angle mounds well encircled by sutures; small mid-ventral process on each of sternites VI and VII in male and on sternite VI in female.

Male genitalia ( Figs 3A–3D ). Dorsal margin of segment IX (IX) about 3 times as long as ventral margin in lateral view. Rugged posterior area of segment IX (ru po IX) often asymmetrical, with three prominent subtriangular processes. Segment X (X) depressed; wide basally, gradually narrowing with shallow apical incision in dorsal view; in lateral view, slender bar-like, directed ventrocaudad in basal 4/5 and curved dorsocaudad in apical 1/5. Anal sclerite (an sc) strongly sclerotized; wide, subtriangular, with deep longitudinal slit on midline in dorsal view; subrectangular with large subquadrate basoventral process in lateral view. Tergal strap (te st) membranous, long, somewhat undulate in lateral view. Apical band (ap ba) weakly sclerotized, shorter than tergal strap in lateral view. Aedeagus long, slender. Parameres absent.

Basal segment of each inferior appendage (b inf app) long, 2 times as long as apical segment (a inf app), in lateral view with dorsal and ventral margins parallel with each other; dorsomesal process (do me pr) apically on dorsomesal edge of basal segment, sclerotized, directed mesocaudad basally, curved outward at mid-length, gradually narrowing posteriorly, acute apically; apical segment of each inferior appendage round in lateral view, oblong in dorsal and ventral views, apical 2/5 of mesal surface with numerous spinules.

Female genitalia ( Figs 3E–3I ). Segment VIII (VIII) rather short, 0.8 times as long as basal height, gradually narrowing posteriorly in lateral view, nearly parallel sided in dorsal and ventral views; posterior margin slightly incised in ventral view and slightly convex at middle in dorsal view; pair of curved ridges (cu ri) along posterior margin in ventral view.Vaginal apparatus long; processus spermathecae (ps) round in ventral view, semi-membranous; posterior process (pp) sclerotized, long, slightly thickened around middle, 2 times as long as processus spermathecae, subacute apically in lateral view, acute in ventral view.

Larva. Unknown.

Holotype. Male, Hokkaido, Ishikari, Chitose-shi , Bifue , Bifue-no-taki (42.7262°N, 141.1861°E, 500 m a.s.l.), 30.vii.2006, leg. TI & TH, S ( CBM-ZI 0189174 ).

Paratypes. 16 males, 2 females, same data as holotype ( SPMN-IS) .

Other specimens. Hokkaido, Ishikari: Sapporo-shi, Takino, Masumi-no-taki, 1 male, 16.v.1981, leg. TI , S ( TI); 3 males, 1 female, 29.vi.1983, leg. TI , S ( TI). Sapporo-shi, Misumai, Kannon-zawa, 2 males, 30.v.1992, leg. NK , M ( NK); 2 males, 16.vii.1992, NK , M ( NK); 2 males, 2 females, 9.vi.1993, leg. NK , M ( NK); 1 male, 22.vi.1993, leg. NK , M ( NK); 1 male, 21.ix.1993, leg. NK , M ( NK). Eniwa-shi, small tributary of Ichankoppe-zawa , 310 m , 1 male, 25.vi.2003, leg. TI , S ( SPMN-IS); 1 male, 4.vii.2021, leg. TI , S ( TI). Eniwa-shi, Ichankoppe-zawa , 200 m , 2 males, 25.vi.2023, leg. TI , S ( TI). Eniwa-shi, small waterfall beside Moichan-zawa, 1 male, 4.vii.2021, leg. TI , S ( TI); 1 female, 7.ix.2021, leg. TI , S ( TI). Chitose-shi, Bifue, Bifue-no-taki, 2 males, 2 females, 30.vii.2006, leg. TI & TH, S ( TI); 3 males, 1 female, 21.vi.2003, leg. TI et al., S & L ( TI & NK); 32 males, 8 females, 18.vi.2007, leg. TI , S ( TI). Chitose-shi, Shikotsu-kohan, Poropinai, small stream, 7 males, 10 females, 7.vii.1996, leg. YN, M ( NK) ; 20 females, 21.vii.1996, leg. YN, M ( NK) ; 2 males, 5 females, 4.viii.1996, leg. YN, M ( KN) ; 9 females, 18.viii.1996, leg. YN, M ( NK) ; 4 males, 2 females, 18.vi.2007, leg. TI , S ( TI); 4 males, 2 females, 11.vii.1997, leg. TI , M ( SPMN-IS); 1 male, 1 female, 19.iv.1997, leg. TI , M ( NK); 6 males, 14 females, 13.v.1997, leg. TI , M ( NK); 4 males, 7 females, 29.v.1997, leg. TI , M ( NK); 1 male, 3 females, 9.vi.1997, leg. TI , M ( NK); 1 female, 2.vii.1997, leg. TI , M ( NK); 3 females, 11.vii.1997, leg. TI , M ( NK); 1 male, 5.viii.2005, leg. NK , L ( NK). Chitose-shi, Bifue, small stream beside old road, 2 females, 17.vi.2009, leg. NK , M ( NK); 2 males, 1 female, 29.vi.2009, leg. NK , M ( NK). Shiribeshi: Otaru-shi, Okusawa, Ana-taki, 1 male, 26.vii.1995, leg. NK , S ( NK). Otaru-shi, Okusawa-suigenchi, Shirai-sawa, 1 male, 28.vi.1996, leg. M. Ôhara & Y. Sakai, M ( NK) ; 1 male, 29.vii.1996, leg. Y. Sakai & F. Takahashi, M ( NK) ; 1 male, 26.viii.1996, leg. Y. Sakai & F. Takahashi, M ( NK). Rankoshi-chô, Momiji-no-taki , 1 male, 1–7.vii.1990, leg. K. Okazaki, S ( SPMN-IS) ; 1 male, 3 females, 25.vi.1997, leg. TI & AO, S ( SPMN-IS). Kyôgoku-chô, Kawanishi, Fukidashi-kôen, 6 males, 30.vi.1998, leg. TI & AO, S ( SPMN-IS); 2 males, 5.viii.2007, leg. TI , S ( SPMN-IS). Shakotan-chô, small stream near Yobetsu-gawa, 1 female, 25.vi.2003, leg. K. Tojo ( SPMN-IS). Iburi: Tomakomai-shi, Betsubetsu-gawa , 4 males, 22.vi.1997, leg. NK , S ( NK). Date-shi, Ôtaki-ku, Aichi, spring beside Shiribetsu-gawa , 430 m , 9 males, 4 females, 25.vi.2011, leg. NK , M ( NK); 1 male, 14.vii.2011, leg. NK , M ( NK); 1 male, 1 female, 31.vii.2011, leg. NK , M ( NK); 2 males, 13.viii.2011, leg. NK , M ( NK); 1 male, 15.iv.2017, leg. NK , M ( NK).

Distribution ( Fig. 1D , white circles). Hokkaido (central and southwestern areas).

Habitat. Adults of this species were collected in mountain areas beside waterfalls, spring streams, and small fast flowing streams up to several meters wide.

Etymology. The name “ bifue ” is a noun in apposition, coined from the name of the type locality.

Japanese name. Bifue-nagare-tobikera.

Figures

FIGURE 1. Recorded collection sites of Rhyacophila species. 1A, location of Hokkaido and recorded sites of known species discussed in present study. 1B–1E, recorded and collected sites in Hokkaido: 1B, 1C, R. eniwa sp. nov. and R. arefini Lukyanchenko; 1D, R. bifue sp. nov., R. imakane sp. nov., R. misago sp. nov., and R. hamata Hattori & Ohkawa; 1E, R. shimamaki sp. nov.

FIGURE 3. Adult of Rhyacophila bifue sp. nov. 3A–3D, male: 3A, genitalia, left lateral, omitting left inferior appendage; 3B, same, dorsal; 3C, right inferior appendage, dorsal; 3D, same, ventral. 3E–3I, female: 3E, abdominal segments VIII–XI, left lateral; 3F, segment VIII, dorsal; 3G, same, ventral; 3H, vaginal apparatus, left lateral; 3I, same, ventral. Abbreviations: VIII–XI = abdominal segments VIII–XI; a inf app = apical segment of inferior appendage (paired); ae = aedeagus; an sc = anal sclerite (paired); ap ba = apical band (paired); b inf app = basal segment of inferior appendage (paired); cu ri = curved ridge (paired); do me pr = dorsomesal process (paired); pp = posterior process; ps = processus spermathecae; ru po IX = rugged posterior area of segment IX; te st = tergal strap (paired).