Rhyacophila shimamaki 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 : 565-567

Rhyacophila shimamaki Ito & Kuhara sp. nov.

( Figs 1E , 7A–7I )

Rhyacophila sp. 4 : Ito et al. 2010, pp. 56, 81, Hokkaido (Hiyama, Oshima).

Species group and diagnosis. The male of this species resembles that of Rhyacophila crassa Schmid 1970 , species group unknown (Schimid 1970; Hattori 2005), found in Japan (Honshu, Fukushima) ( Fig. 1A , white star), in having a large, sclerotized segment X, well-developed parameres and aedeagus, and thick inferior appendages. However, the male of R. shimamaki is clearly distinguishable from that of R. crassa as follows: Segment X is subtriangular in lateral view, and the aedeagus is serrate apically in R. shimamaki ; segment X is subtrapezoidal in lateral view, and the adeagus is not serrate apically in R. crassa . The species group of this new species, like R. crassa , remains in need of further study.

Adult. Male: Each forewing 7.3–8.2 mm long (mean = 7.9 mm, n = 3) and each hind wing 6.4–7.2 mm (mean = 6.9 mm, n = 3). Female: Each forewing 7.9–8.6 mm (mean = 8.3 mm, n = 4) and 6.9–7.5 mm (mean = 7.1 mm, n = 4). Head dark brown, warts light brown with brown setae, antennae dark brown, palpi light brown. Thorax dark brown dorsally. Legs light 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 sternites VI and VII (or VII) in male and on sternite VI in female (process on sternite VI of male often very small or completely absent).

Male genitalia ( Figs 7A–7D ). Dorsal margin of segment IX (IX) about 1.5 times as long as ventral margin in lateral view. Segment X (X) sclerotized, large, subtriangular, with apices curved ventrad in lateral view, subquadrate with V-shaped incision in middle in dorsal view. Anal sclerites (an sc) just below base of segment X in caudal view, short, wide, sclerotized laterally. Pair of apical bands (ap ba) further below ventral base of segment X strongly sclerotized, round in lateral view; forming pair of scoops with right and left bands joined at middle in caudal view. Aedeagus (ae) narrow basally, gradually broader from basal 1/4, with longitudinal slit in middle of apical 1/3, each half with 8–12 serrate teeth apically. Each paramere (par) slender and longer than aedeagus, with 4–5 spindles apically; long slender mesal branch (me br) arising from basal 1/4.

Basal segment of each inferior appendage (b inf app) thick, 1.5 times as long as apical segment (a inf app), in lateral view with dorsal and ventral margins parallel with each other; apical segment of each inferior appendage (a inf app) thick, with numerous spinules near dorsal and apical margins mesally, round apically in dorsal and lateral views, length 1.4 times as long as basal depth in lateral view.

Female genitalia ( Figs 7E–7I ). Segment VIII (VIII) long, 1.2 times as long as basal height, gradually narrowing posteriorly with convex posteroventral margin in lateral view, rectangular with V-shaped mesal incision on posterior margin in dorsal view, rectangular with very shallowly and widely incised posterior margin in ventral view. Vaginal apparatus long, bag-like with two depressed sclerites mesally; in ventral view, dorsal sclerite large subquadrate with apical incision, ventral one encircling basal 1/2, subtriangular with very shallow incision apically.

Larva. Unknown.

Holotype. Male, Hokkaido, Shiribeshi, Shimamaki-mura , Nagumo-no-sawa, upper reach (42.6470°N, 140.0156°E, 250 m a.s.l.), 20.vi.2007, leg. TI, S ( CBM-ZI 0189177 ).

Paratypes. 1 male, 3 females, same data as holotype ( SPMN-IS) .

Other specimens. Hokkaido, Ishikari: Eniwa-shi, Ichakoppe-zawa , 200–250 m, 1 male, 25–30.vi.2011, leg. TI , S ( TI). Eniwa-shi, Ichakoppe-zawa , tributary, 220 m, 1 male, 26.vi.2011, leg. TI , S ( TI). Chitose-shi, Bifue, Bifue-gawa , near Bifue-no-taki, 1 male, 21.vi.2003, leg. NK , S ( NK). Shiribeshi: Otaru-shi, Okusawa-suigenchi , Shirai-gawa , 1 male, 7.vi.1996, leg. M. Ôhara & Y. Sasaki, M ( NK). Kyôgoku-chô , Kawanishi , Fukidashi-kôen , 1 male, 11.vi.2011, leg. NK S ( NK). Shimamaki-mura , Nagumo-no-sawa, upper reach (type locality), 2 males, 21.v.2007, leg. TI , S ( TI). Iburi: Date-shi, Ôtaki-ku , Toyosato , small spring, 1 male, 2 females, 25.vi.2011, leg. NK , M ( NK); 5 males, 14.vii.2011, leg. NK , M ( NK); 1 male, 31.vii.2011, leg. NK , M ( NK). Date-shi, Ôtaki-ku , Aichi, source of Shiribetsu-gawa , 590 m, 2 males, 25.vi.2011, leg. NK , M ( NK); 1 male, 31.vii.2011, leg. NK , M ( NK). Date-shi, Ôtaki-ku , Aichi, spring near Shiribetsu-gawa , 430 m, 58 males, 39 females, 25.vi.2011, leg. NK , M ( NK); 24 males, 19 females, 14.vii.2011, leg. NK , M ( NK). Sôbetsu-chô, Benkei , small stream, 1 male, 3 females, 25.vi.2011, leg. NK , M ( NK); 1 male, 14.vii.2011, leg. NK , M ( NK). Oshima: Yakumo-chô, small water flow beside Namari-gawa , 3 males, 22.vi.2003, leg. HM , S ( HM). Hakodate-shi, Minami-kayabe-chô, brooklet beside Ôfuna-gawa , 130 m, 1 male, 1.vi.2004, leg. NK , S ( NK). Shiriuchi-chô, Jôrai , 2 males, 18.vi.1976, leg. T . Kumata et al., S ( SPMN-IS); 1 male, 9.vii.1976, leg. T . Kumata et al., S ( SPMN-IS) .

Distribution ( Fig. 1E ). Hokkaido (central and southern area).

Habitat. Adults of this species were collected from springs and small rapid streams in mountain areas.

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

Japanese name. Shimamaki-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 7. Adult of Rhyacophila shimamaki sp. nov. 7A–7D, male: 7A, genitalia, left lateral, omitting left inferior appendage; 7B, same, dorsal, omitting right inferior appendage; 7C, segment X, anal sclerites and apical bands, caudal; 7D, aedeagus and parameres, ventral. 7E–7I, female: 7E, abdominal segments VIII–XI, left lateral; 7F, segment VIII, dorsal; 7G, same, ventral; 7H, vaginal apparatus, left lateral; 7I, 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); me br = mesal branch; par = paramere (paired).