Rhyacophila humerigera, Kawase, 2025

Rhyacophila humerigera sp. nov.

( Figs 1C, 1D View FIGURE 1 , 4A–4G View FIGURE 4 , 5A–5E View FIGURE 5 , 16D View FIGURE 16 )

Rhyacophila sp. 2 : Tanaka 2012, 20–22, male; Tanaka 2014, 38, list.

Rhyacophila sp. : Tanaka 2022, 34, list.

Rhyacophila sp. aff. motakanta Schmid 1970 View in CoL : Aoya & Tanaka 2023, 26, list.

Diagnosis. The male genitalia of R. humerigera sp. nov. are somewhat similar to those of R. koryne sp. nov., R. motakanta and R. orthacantha in having the apically bifid apicodorsal lobe of segment IX. The difference is, however, considerable. R. humerigera sp. nov. bears a pair of lateral shoulders in the middle of the apicodorsal lobe ( Figs 4A, 4 View FIGURE 4 Aa), whereas other three species bear the simple, short apicodorsal lobe without such a pair of shoulders. Regarding the female genitalia, R. humerigera sp. nov. is similar to R. motakanta Schmid 1970 and R. lambakanta Schmid 1970 in bearing a medium-sized dorsal and a pair of lateral clefts in segment VIII ( Figs 5A–5C View FIGURE 5 , 13A–13B, 14A–14B View FIGURES 12–15 ), but this species can be distinguished from the latter by the shape of the posterior processes of the vaginal apparatus: In R. humerigera , the apical part of the posterior process is simply round ( Figs 5D, 5E View FIGURE 5 ), but in R. motakanta , the apical part of that decreases abruptly in width and height (arrows in figs 13C, 13D); in R. humerigera , the vaginal apparatus bends approximately 45 degrees in lateral view ( Fig. 5D View FIGURE 5 ), but in R. lambakanta , it bends 90 degrees in the middle in lateral view (arrows in fig. 14D).

Adult ( Figs 1C, 1D View FIGURE 1 ). Length of each forewing: male 8.2–10.4 mm (mean = 9.3, SD = 0.77, n = 14), female 10.0–11.3 mm (mean =10.7, SD = 0.50, n = 5). General morphology of R. humerigera sp. nov. similar to those of R. geranos sp. nov., but forewings of this species with many brown reticulations all over ( Figs 1C, 1D View FIGURE 1 ). In abdomen, small mid ventral process on posterior margin of sternites VI and VII in male, on that of sternite VI in female.

Male genitalia ( Figs 4A–4G View FIGURE 4 ). Segment IX (IX) in lateral view, very short ventrally, long dorsally, widely rounded posterolaterally ( Fig. 4C View FIGURE 4 ); subquadrate in dorsal view, with pair of clefts in both sides of apicodorsal lobe ( Fig. 4A View FIGURE 4 ). In dorsal view, apicodorsal lobe (adl) long, extending posterad, bifid apically, with pair of pointed shoulders laterally ( Fig. 4A View FIGURE 4 ) ( three specimens in Iwate Prefecture bear pair of rounded shoulders laterally ( Fig. 4 View FIGURE 4 Aa)); in lateral view apicodorsal lobe like sharp claws ( Fig. 4C View FIGURE 4 ). Segment X (X) long, straight, extending posteroventrad in lateral view ( Figs 4C, 4D View FIGURE 4 ); bilobed apically in dorsal view, each apex round ( Fig. 4E View FIGURE 4 ). Pair of anal sclerites (as) fused together, wide, round in ventral view, with pair of dark pigmented protuberances apically ( Fig. 4F View FIGURE 4 ), and with long common root basally.Apical band (ab) sclerotized, u-shaped in ventral view and fused with tergal band basally ( Fig. 4F View FIGURE 4 ); tergal band (tb) wide, flattened, well sclerotized apically, connecting to dorsum of phallotheca anteriorly ( Fig. 4D View FIGURE 4 ). Basal segment of each inferior appendage setose, elongate, basal half slightly thicker ( Figs 4B, 4C View FIGURE 4 ). Apical segment of each inferior appendage rounded, right trapezoid in left lateral view ( Fig. 4C View FIGURE 4 ), apical half bearing spinules mesally. In phallic apparatus, phallotheca (pht) cup-shaped in lateral view ( Fig. 4D View FIGURE 4 ); aedeagus (aed) long, almost cylindrical, tapering to apex ( Figs 4D, 4G View FIGURE 4 ); dorsal appendage of phallic apparatus (dap) sclerotized, shorter than aedeagus, basal 3/4 fused with aedeagus, apical margin slightly rounded, protruded mesally ( Figs 4D, 4G View FIGURE 4 ). Pair of parameres (par) long cylindrical, each tapering to apex, dilated subapically, bearing many small spines ventrally around mid-length ( Figs 4B, 4D View FIGURE 4 ).

Female genitalia ( Figs 5A–5E View FIGURE 5 ). Segment VIII (VIII) with dorsal cleft (dc) wide and deep in dorsal view ( Fig. 5A View FIGURE 5 ), with pair of deep lateral clefts (lc) extending to middle part of segment ( Fig. 5B View FIGURE 5 ), and with posteroventral margin rounded, semicircular ( Fig. 5C View FIGURE 5 ). Intersegmental membrane of segment VIII–X (ismVIII–X) deeply invaginated into segment VIII, slightly sclerotized, dorsally into anterior margin, ventrally into middle part of segment VIII, anterior part fixed to interior wall of segment VIII ( Figs 5A–5C View FIGURE 5 ). In vaginal apparatus, posterior process (pp) sclerotized, long bottle shape in ventral view ( Fig. 5E View FIGURE 5 ), anterior half curved ventrad ( Fig. 5D View FIGURE 5 ); processus spermathecae (ps) small, long oval in lateral view, covered by basal part of posterior process ( Fig. 5D View FIGURE 5 ).

Immature stage. Unknown.

Holotype. Male (in alcohol): Shibukuro-gawa , Tazawako-tamagawa , Senboku-shi, Akita Prefecture, Honshu, Japan, 39°56’20” N 140°42’22” E, alt. 485 m, 18–25.vi.2018, K. Aoya ( LBM1410012663 View Materials ). GoogleMaps

Paratypes. Honshu : Iwate : 1 male (pinned), 1 female (pinned, fig. 1D), Seiren-no-taki, Uchikawame, Hanamaki-shi , 10.viii.1994, T. Hattori ( SPMN) ; 1 male, 1 female, tributary Tobetsu-gawa, Yamagata-cho, Kuji-shi , 12.vi.2004, N. Kuhara ( LBM1410012664–1410012665 View Materials ) . Akita: 2 males (pinned, fig. 1C), Toroko, Hachimantai, Kazuno-shi, 4.vii.2019, M. Ookura ( SPMN) ; 1 male, type locality, 28.ix–5.x.2018, K. Aoya ( LBM1410012666 View Materials ) ; 1 male, type locality, 5–13.x.2018, K. Aoya ( LBM1410012667 View Materials ) .

Other specimens examined. Honshu: Aomori: 1 male, 1 female, Akaishi-gawa, Komori-machi, Ajigasawamachi , 6.vi.1982, M. Kobayashi ( KPM-NKMK71010 ) ; 1male, Sasanai-gawa, Iwasaki, Fukaura-machi , 7.vi.1982, M. Kobayashi ( KPM-NKMK71080 ) . Iwate: 4 males, 1 female, Matsukusa, Kuzakai, Miyako-shi , 12.vii.1997, N. Kuhara (KuN-14991) (NKa) ; 1 male, 3 females, same data, N. Kuhara (KuN-14995) (NKa) ; 6 males, Oyama-gawa, Kadoma, Miyako-shi , 13.vii.1997, N. Kuhara (KuN-14982) (NKu) . Akita: 1 male (pinned), Koirikawa, Hachimori, Happou-cho , 14.vi.2019, M. Ookura (MTa) ; 1 male (pinned), Numanosawa, Tazawako, Senboku-shi , 24.ix.2013, M. Tanaka (MTa) ; 1 male (pinned), Kotaki-zawa, Nakasen, Daisen-shi , 13.vii.2010, M. Tanaka (MTa) .

Distribution and biology. Rhyacophila humerigera sp. nov. is distributed in northern part of Tohoku District in Honshu ( Fig. 16D View FIGURE 16 ). Adults were collected near mountain streams in June to October by sweeping, Malaise traps or light traps.

Etymology. The Latin species epithet “humerigera ” (Latin adjective, with a pair of shoulders) is derived from the shape of the apicodorsal lobe of the segment IX in male genitalia: a pair of shoulders on both sides of the apicodorsal lobe.

Japanese name. Kadoo-nagare-tobikera.