Rhyacophila koryne, Kawase, 2025

Rhyacophila koryne sp. nov.

( Figs 1E, 1F View FIGURE 1 , 6A–6H View FIGURE 6 , 7A–7E View FIGURE 7 , 16D View FIGURE 16 )

Rhyacophila sp. 3 : Inazu 2008, 66, list; Inazu & Nishida 2011, 177, habitus, male, female.

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

Diagnosis. The male genitalia of R. koryne sp. nov. are slightly similar to those of R. motakanta and R. orthacantha in having the apically bifid, straight apicodorsal lobe of segment IX, but R. koryne sp. nov. is easily distinguished from the latter by the shape of the apicodorsal lobe which is long, club-shaped in lateral view ( Fig. 6C View FIGURE 6 ). On the other hand, the shapes of the apicodorsal lobes of the other two species are short, acute apically (not club-shaped) in lateral view ( Figs 9B, 11B View FIGURES 8–11 ). Female genitalia of this species are very similar to those of R. orthacantha (Figs

7A–7E, 15A–15D), and both species cannot be distinguished from each other in the present study. However, the distributions of both species are clearly allopatric ( Fig. 16D View FIGURE 16 ).

Adult ( Figs 1E, 1F View FIGURE 1 ). Length of each forewing: male 8.6–12.3 mm (mean = 10.8, SD = 0.89, n = 21), female 11.8–13.0 mm (mean = 12.5, SD = 0.52, n = 5). Forewing coloration of R. koryne sp. nov. ( Figs 1E, 1F View FIGURE 1 ) similar to that of R. humerigera sp. nov. Small mesal ventral process on posterior margin of sternites VI and VII in male and sternite VI in female abdomens.

Male genitalia ( Figs 6A–6H View FIGURE 6 ). Segment IX in lateral view, very short ventrally, long dorsally and widely rounded posterolaterally ( Fig. 6C View FIGURE 6 ), subquadrate in dorsal view, with pair of clefts in both sides of apicodorsal lobe ( Fig. 6A View FIGURE 6 ); apicodorsal lobe long triangular with bifid apex in dorsal view ( Fig. 6A View FIGURE 6 ), long club shaped in lateral view ( Fig. 6C View FIGURE 6 ). Segment X long, extending posteroventrad in lateral view ( Fig. 6E View FIGURE 6 ); bilobed apically, each apex blunt in dorsal view ( Fig. 6F View FIGURE 6 ). Pair of anal sclerites fused together, wide, rounded in ventral view ( Fig. 6G View FIGURE 6 ), with pair of dark pigmented protuberances apically, and with long common root basally ( Fig. 6G View FIGURE 6 ). Apical band sclerotized, u-shaped in ventral view, fused with tergal band basally; tergal band wide, flattened, well sclerotized apically, connecting to dorsum of phallotheca anteriorly ( Fig. 6E View FIGURE 6 ). Basal segment of each inferior appendage setose, elongate, basal half slightly thicker ( Figs 6B–6D View FIGURE 6 ). Apical segment of each inferior appendage rounded, right trapezoid in left lateral view ( Fig. 6B View FIGURE 6 ), apical half bearing spinules mesally ( Fig. 6D View FIGURE 6 ). In phallic apparatus, phallotheca near cup-shaped in lateral view ( Fig. 6E View FIGURE 6 ); aedeagus long, almost cylindrical tapering to apex ( Figs 6B, 6E, 6H View FIGURE 6 ); dorsal appendage of phallic apparatus sclerotized, shorter than aedeagus, basal 3/4 fused with aedeagus, apex slightly protruded in middle ( Figs 6E, 6H View FIGURE 6 ). Parameres long cylindrical, tapering to apex, dilated subapically, with a few small spines ventromesally around mid-length ( Figs 6B, 6E View FIGURE 6 ).

Female genitalia ( Figs 7A–7E View FIGURE 7 ). Segment VIII with dorsal cleft excavated to apical 1/4, tiny protrusion usually present mesally ( Fig. 7A View FIGURE 7 ), but occasionally absent, with pair of lateral clefts extending to apical 1/3 ( Fig. 7B View FIGURE 7 ), and posteroventral margin rounded, semicircular ( Fig. 7C View FIGURE 7 ). Intersegmental membrane of segment VIII–X (ismVIII–X) deeply invaginated into segment VIII, slightly sclerotized, dorsally into anterior margin, ventrally into middle part of it, anterior part fixed to interior wall of segment VIII ( Figs 7A–7C View FIGURE 7 ). In vaginal apparatus, posterior process sclerotized, long bottle shape in ventral view ( Fig. 7E View FIGURE 7 ); anterior half slightly curved anteroventrad in lateral view ( Fig. 7D View FIGURE 7 ); processus spermathecae small, long rectangular in lateral view, covered by basal part of posterior process ( Fig. 7D View FIGURE 7 ).

Immature stage. Unknown.

Holotype. Male (in alcohol): Shingo-yuno , Niimi-shi, Okayama Prefecture, Honshu, Japan, 35°00’58” N, 133°19’44” E, alt. 550 m, 1.vi.2013, K. Nojima ( LBM1410012668 View Materials ). GoogleMaps

Paratypes. Honshu : Hyogo : 1 male, 1 female, Amagoike, Takenouchi, Wadayama-cho, Asago-shi , 25.v.2004, K. Inazu ( SPMN) . Okayama: 2 males, 1 female, Uno, Kamo-cho, Tsuyama-shi, 6.v.2013, K. Nojima ( LBM1410012669–1410012671 View Materials ) ; 3 males, 1 female, same data as the holotype ( LBM1410012672–1410012675 View Materials ) GoogleMaps ; 6 males, 1 female, Koshiwata, Kagamino-cho, 9.vi.2013, K. Nojima ( LBM1410012676–1410012682 View Materials ) ; 2 males, Ogaya, Nishi-awakura-son, 12.v.2016, K. Nojima ( LBM1410012683–1410012684 View Materials ) .

Other specimens examined. Honshu: Hyogo: 1 male, Sugawara, Kishida , Shin-onsen-cho, 30.v.2004, K. Inazu (NKa) ; 1 male ( Fig. 1E View FIGURE 1 ), 1 female ( Fig. 1F View FIGURE 1 ), Mihara, Takeno-cho, Toyooka-shi , 9.vi.2009, K. Inazu (NKa) ; 1 female, Kumanami, Muraoka-ku, Kami-cho , 4.vi.2006, K. Inazu (NKa) ; 1 male, Itabami, Nishigouchi, Chikusa-cho , Shisô-shi , 23.v.2016, K. Inazu (NKa) ; 1 female, Mimuro-no-taki, Kouchi, Chikusa-cho, Shisô-shi , 14.vii.2016, K. Inazu (NKa) . Okayama: 6 males, 3 females, Akawase-keikoku, Kami-saibara, Kagamino-cho , 8.vi.2011, K. Nojima (NKa) . Tottori: 1 female, Kachi-gawa, Wakasa-cho , 12.ix.2002, T . Hattori ( SPMN) ; 1 male, Yukawagawa, Yukawa, Nichinan-cho , 11.ix.2008, N. Kuhara (KuN-15026) (NKu) . Shimane: 1 male, Sada-cho, Izumo-shi , 15.ix.1993, H. Nishimoto ( SPMN) .

Distribution and biology. Rhyacophila koryne sp. nov. is distributed in western Honshu ( Fig. 16D View FIGURE 16 ). Adults were collected near mountainous streams in May to September by sweeping or light traps.

Etymology. The species epithet “koryne ” (Greek noun, club) is derived from the shape of the apicodorsal lobe of the segment IX of male genitalia in lateral view.

Japanese name. Maruo-nagare-tobikera.