Rhyacophila hattorii Torii, 2021

Torii, Takaaki & Kobayashi, Tohru, 2021, Redescription of Rhyacophila yukii Tsuda 1942 and description of three new Rhyacophila species from Japan (Trichoptera: Rhyacophilidae), Zootaxa 4995 (3), pp. 537-550 : 540-543

Rhyacophila hattorii Torii n. sp.

Figs 2A–2L

Rhyacophila yukii: Schmid 1970 , 197, figs 1–3, male, non Tsuda (1942); Kagaya et al. 1998, pp. 22, 95, list. Hattori 2005, pp. 427, 435, fig. 5, male, female; Inazu & Nishida 2011, p. 176, figs 21, male; Hattori 2018, pp. 487, 495, fig. 5, male, female.

Diagnosis. This new species is similar to other members of the Rhyacophila sibirica Group ( R. transquilla Tsuda 1940 , R. arefini Lukyanchenko 1993 , R. kisoensis Tsuda 1940 , and R. yukii Tsuda 1942 ) in male genitalia, but can be diagnosed easily from them by the following combination of segment X characters: (1) in dorsal view somewhat hexagonal to oval; (2) in lateral view with the upper and lower portions more swollen than the center; (3) in caudal view hexagonal with its dorsal apex incised mesally, elongate downward, ventral apex incised and sclerotized. The female vaginal apparatus of this species is similar to that of R. implicata Arefina 1993 (in Schmid et al. 1993), distributed in Russia. However, it can be distinguished by the posterior process of the vaginal apparatus, which is shorter than that of R. implicata .

Male. Length of each male forewing 7.6–8.5 mm (n = 27). Specimens in alcohol with head, thorax, and wings dark brown; legs yellowish brown, with spurs dark brown. Segments VI and VII with thin spur ventrally.

Male genitalia ( Figs 2A–2F ). Segment IX in lateral view subrectangular, with upper portion longer than lower one, rectangular in dorsal view, twice as wide as long. Segment X in lateral view with upper and lower portions swollen and club-shaped, in dorsal view somewhat hexagonal to oval with its apex incised mesally, in caudal view hexagonal with dorsal apex incised mesally, elongate downward, ventral apex incised and sclerotized. Apical band (a.b.) in lateral view long and narrow, bar shaped. Ventral branch of aedeagus (v.b.a.) in lateral view cylindrical and protruding; aedeagus (aed.) in lateral view curved about 80°, resembling long and narrow spine; ventral lobe of aedeagus (v.l.a.) elongate subelliptical in dorsal view. Basal segment of each inferior appendage (b.i.a.) somewhat trapezoidal in lateral view, in ventral view with its inner and outer margins nearly straight; apical segment of each inferior appendage (a.i.a.) in lateral view with apex depressed obliquely, in ventral view with its inner and outer margins nearly straight, round apically.

Female. Length of each female forewing 7.8–8.8 mm (n = 8).

Female genitalia ( Figs 2G–2J ). Segment VI with thin spur ventrally. Corners of tergum and sternum of segment VII rounded in outline. Segment VIII cone shaped. Segments IX, X, XI ( Fig. 2H ) often retracted into segment VIII or VII and VIII ( Fig. 2G ). Segment IX membranous, trapezoidal, indistinguishable from the intersegmental membrane VIII–X, proximal part slightly wider than distal edge. Segment X cylindrical. Segment XI with pair of cerci (c.). Apodemal rods from segment VIII (ap.r.VIII) extend forward to segment VII. Apodemal rods from segment XI (ap.r.XI) extending forward to segment VI or VII. Posterior process of vaginal apparatus (p.pr.) in dorsal view long elliptical with apex slightly incised ( Fig. 2I ), in lateral view elongate bar shaped ( Fig. 2J ).

Immature stages. Unknown.

Holotype. Male, Hondani, Enzan-Icinose-Takahashi, Kohshu-shi , Yamanashi (35.8432°N, 138.8336°E, 1350 m a.s.l.), 6.vi.1991, T. Nozaki ( SEHU).

Paratypes. 4 males, 3 females, Kawamata-gawa, Ohizumi-cho, Hokuto-shi , Yamanashi, 11.vi.1994, T . Hattori ( SEHU) ; 16 males, same data as holotype ( CBM) .

Other material examined. 4 males, Nippara-gawa, Okutama-machi, Nishiokutama-gun , Tokyo, 5.vi.1991, T . Nozaki; 4 males, Akausagi-yama, Katsuyama-shi , Fukui, 19.vii.2007, T . Ito ( SPMN) ; 10 males, Akausagi-yama, Katsuyama-shi , Fukui, 19.vii.2008, T . Ito ( SPMN) ; 2 females, Abe-toge, Umegashima, Aoi-ku , Shizuoka-shi , Shizuoka, 14.vii.2001, T . Hattori ( SPMN) ; 1 male, 3 females, Abe-toge, Umegashima, Aoi-ku , Shizuoka-shi , Shizuoka, 18.vi.2001, T . Hattori ( SPMN) ; 1 male, Abe-toge, Umegashima, Aoi-ku , Shizuoka-shi , Shizuoka, 6.vi.1999, T . Hattori ( SPMN) ; 1 male, Abe-toge, Umegashima, Aoi-ku , Shizuoka-shi , Shizuoka, 21.vii.1997, T . Hattori ( SPMN) ; 2 females, Kawamata-gawa, Ohizumi-cho, Hokuto-shi , Yamanashi, 11.vi.1994, T . Hattori ( SPMN) ; 1 male, 1 female, Fukazawa-gawa, Heisei-kyo, Minamiarupus-shi , Yamanashi, 6.vii.1997, T . Hattori ( SPMN) ; 1 male, 1 female, Kawamata-gawa, Ohizumi-cho, Hokuto-shi , Yamanashi, 11.vi.1994, T . Hattori ( SPMN) ; 1 male, Ichinoseg-gawa, Sakubadaira-bashi, Enzan-shi , Yamanashi, 22.v.1999, T . Hattori ( SPMN) ; 4 males, 5 females, Ichinoseg-gawa, Sakubadaira-bashi, Enzan-shi , Yamanashi, 22.v.1999, T . Hattori ( SPMN) ; 1 female, Karasu-gawa, Mitsumata, Horigane , Azumino-shi , Nagano, 31.v.1997, T . Hattori ( SPMN) ; 1 female, Udo-gawa, Wasabi-zawa, Ohtokoro , Itoigawa-shi , Niigata, 14.viii.1998, T . Hattori ( SPMN) .

Etymology. The new species is named in memory and honor of the late Mr. Toshio Hattori, a specialist of Trichoptera taxonomy, especially Rhyacophilidae in Japan.

Distribution. Japan (Honshu).

Habitat. The type locality is a small, narrow, mountain stream. The rivers at the other collecting sites varied from 2–10 m wide, with bottoms consisting of boulders of different sizes, pebbles, and leaf litter, and with steep banks. Water was clear, colorless, transparent, and odorless.

Remarks. This species is determined to be the same species as “ R. yukii ” figured by Schmid (1970) ( Figs 2K, 2L ) because the morphology of the male genitalia ( Figs 2A–F ) is identical to that of the species. Schmid (1970) misidentified and figured this species as R. yukii and did not describe any features. From the original description of R. yukii by Tsuda (1942), segment X is “approximately triangular in dorsal view, slightly advanced at the apex, rod-shaped in lateral view, tapered at the apex.” His figures ( Figs 1H, 1I ) show that the morphology of segment X is clearly different from that of R. yukii figured by Schmid (1970) ( Figs 2K, 2L ). Hattori (2005, 2018) reported that the figures by Schmid (1970) depict a species that is different from Tsuda’s R. yukii and that should be named as a new species. The new species name R. hattorii is given to “ R. yukii ” of Schmid (1970).

Japanese name. Hattori-nagare-tobikera.

Figures

FIGURES 1A−1I. Rhyacophila yukii Tsuda 1942, male genitalia (1A−1I): 1A, left lateral; 1B, segment X, dorsal; 1C, segment X, caudal (variation from same locality); 1D, ventral lobe of aedeagus, dorsal; 1E, segment IX and inferior appendages, ventral; 1F, phallic apparatus, left lateral; 1G, caudal; 1H, left lateral, by Tsuda (1942); 1I, dorsal, by Tsuda (1942). Abbreviations: a.b. = apical band; aed. = aedeagus; a.i.a. = apical segment of an inferior appendage (paired); b.i.a. = basal segment of an inferior appendage (paired); d.b.a.= dorsal branch of aedeagus; pht. = phallotheca; v.b.a. = ventral branch of aedeagus; v.l.a. = ventral lobe of aedeagus.

FIGURES 2A−2L. Rhyacophila hattorii new species. 2A−2F, male genitalia: 2A, left lateral; 2B, dorsal; 2C, caudal; 2D, phal- lic apparatus, left lateral; 2E, ventral lobe of aedeagus, dorsal; 2F, inferior appendages, ventral. 2G−2J, female genitalia: 2G, segments VII and VIII, left lateral, with segments IX, X, and XI retracted into segments VII and VIII; 2H, segments VII−XI, left lateral; 2I, vaginal apparatus, ventral; 2J, vaginal apparatus, left lateral. 2K−2L, male genitalia by Schmid: 2K, left lateral, by Schmid (1970) and labelled as “R. yukii”; 2L, dorsal, by Schmid (1970) and labelled as “R. yukii”. Abbreviations: a.b. = apical band; aed. = aedeagus; a.i.a = apical segment of an inferior appendage (paired); ap.r.VIII = apodemal rod from segment VIII (paired); ap.r.XI = apodemal rod from segment XI (paired); b.i.a. = basal segment of an inferior appendage (paired); c. = cercus (paired); pht. = phallotheca; p.pr = posterior process of vaginal apparatus; pr.sp. = processus spermathecae of vaginal apparatus; v.b.a. = ventral branch of aedeagus; v.l.a. = ventral lobe of aedeagus.