Rhyacophila angulicauda, Kawase, 2024

Kawase, Naoki, 2024, Redescription of Rhyacophila clemens Tsuda 1940 (Trichoptera, Rhyacophilidae), with descriptions of five new, allied species from Japan, Zootaxa 5447 (1), pp. 55-76 : 67-69

publication ID	https://doi.org/ 10.11646/zootaxa.5447.1.3
publication LSID	lsid:zoobank.org:pub:3A9842EC-F3D2-4839-9731-AA79A27B25CB
DOI	https://doi.org/10.5281/zenodo.11123318
persistent identifier	https://treatment.plazi.org/id/385587AA-F73A-116B-FF4C-C6A3FD04A4D4
treatment provided by	Plazi
scientific name	Rhyacophila angulicauda
status	sp. nov.

Treatment

Rhyacophila angulicauda sp. nov.

( Figs 5A–5I View FIGURE 5 , 9D View FIGURE 9 )

Diagnosis. The male of R. angulicauda sp. nov. is very similar to those of R. inazui sp. nov. and R parvicauda sp. nov. in having a U-shaped apical hinged process of segment X in ventral view, but can be easily distinguished from the latter two species by the shape of the apicodorsal lobe of segment IX given in the diagnosis for R. inazui sp. nov. The female of R. angulicauda is similar to those of R. inazui sp. nov., R. parvicauda sp. nov., and P. furcicauda sp. nov. in having an almost straight dorsal margin of segment VIII in lateral view, but can be distinguished from the latter three by the characters of segment VIII as indicated in the diagnosis for R. inazui sp. nov.

Adult. Length of each forewing: male 6.0– 7.6 mm (mean = 6.8, SD = 0.46, n = 27), female 6.9–9.1 mm (mean = 8.0, SD = 0.54, n = 13). General morphology and coloration similar to those of R. clemens . In venation, this species also similar to R. clemens ( Fig. 1D View FIGURE 1 ), root of fork I and II of each forewing approximately same length each other.

Male genitalia ( Figs 5A–5D View FIGURE 5 ). Segment IX dorsal half longer than ventral half in lateral view ( Fig. 5A View FIGURE 5 ), trapezoidal in dorsal view; apicodorsal lobe trapezoidal in dorsal view, angular in lateral view, strongly overhanging segment X ( Figs 5A, 5C View FIGURE 5 ). Preanal appendages absent. Segment X reverse L-shaped in lateral view composed of vertical part and horizontal part: vertical part tall in lateral view ( Fig. 5B View FIGURE 5 ); horizontal part nearly oval and slightly bilobed posteriorly in dorsal view ( Fig. 5C View FIGURE 5 ); apical hinged process U-shaped in ventral view, with pair of thick finger-like lobes parallel to each other, each apex round, directed posterodorsad ( Figs 5B–5D View FIGURE 5 ); pair of anteroventral corners (of ahp) round, forming sub-oval mounds ( Fig. 5D View FIGURE 5 ). Anal sclerites composed of two pairs of lobes, each long rectangular in lateral view, with common internal root ( Figs 5B, 5D View FIGURE 5 ). Apical band well developed, subtriangular with round corners in lateral view, broadly surrounding anus and root of anal sclerites ( Figs 5B, 5D View FIGURE 5 ). Tergal band connecting base of apical band to dorsum of phallobase ( Fig. 5B View FIGURE 5 ). Basal segment of each inferior appendage setose, elongate, posterior half gradually thicker in lateral view ( Fig. 5A View FIGURE 5 ). Apical segment of each inferior appendage subtriangular in lateral view ( Fig. 5A View FIGURE 5 ), covered with fine setae mesally ( Fig. 5C View FIGURE 5 ). In phallic apparatus, phallobase short, cup like ( Fig. 5B View FIGURE 5 ); aedeagus forming narrow tube with sclerotized ventral plate ( Figs 5B, 5D View FIGURE 5 ); ventral plate horizontal and tongue-shaped with posterior margin truncated or shallowly concave in ventral view ( Fig. 5D View FIGURE 5 ). Parameres absent.

Female genitalia ( Figs 5E–5I View FIGURE 5 ). Segment VIII annular, dorsal margin almost straight in lateral view ( Figs 5E, 5F View FIGURE 5 ); with pair of ventral ridges forming longitudinal narrow bridge, narrowest in anterior 1/4–1/ 3 in ventral view ( Fig. 5G View FIGURE 5 ); pair of apodemal rods extending into segment VI ( Fig. 5E View FIGURE 5 ). Segment IX membranous, with pair of apodemal rods dorsolaterally, extending into abdominal segment VI. Vaginal apparatus simple; posterior process sclerotized, jackknife-shaped, dorsal margin slightly convex in lateral view ( Fig. 5H View FIGURE 5 ), long oval in ventral view ( Fig. 5I View FIGURE 5 ); processus spermathecae membranous ( Figs 5H, 5I View FIGURE 5 ).

Immature stage. Unknown.

Holotype. Male (in alcohol), Abe-tôge (alt. 1400 m), Umegashima , Shizuoka-shi, Shizuoka Pref., Honshu, Japan, 35°18’46”–55”N 138°21’4”–19”E, alt. 1400 m, 21.vi.2007, T. Hattori ( LBM1410012630 View Materials ).

Paratypes. Honshu: Kanagawa : 9 males, 3 females, Nishizawa, Nakagawa, Yamakita-machi, 27.v.2020, T. Nozaki ( LBM1410012637–1410012648 View Materials ) ; 3 males, 1 female, same locality, 28.iv.2023, T. Nozaki ( OMNH). Shizuoka : 2 males, same data as the holotype (SPMN-IS-59778–59779) ; 1 male, 1 female, same locality as the holotype, 21.vii.1997, T. Hattori (SPMN-IS-59755–59756) ; 2 males, 4 females, same locality as the holotype, 6.vi.1999, T. Hattori ( LBM1410012631–1410012636 View Materials ) ; 2 males, 1 female, same locality as the holotype, 10.vii.1999, T. Hattori (SPMN-IS-59780–59782) ; 2 males, same locality as the holotype, 14.vii.2001, T. Hattori (SPMN-IS-59757–59758) ; 2 males, 1 female, Nishi-hikagesawa, Umegashima, Shizuoka-shi, 28.v.2014, T. hattori & T. Nozaki (SPMN-IS-59783–59785) ; 12 males, 7 females, Minami-sawa, Umegashima, Shizuoka-shi, 2.vi.1996, T. Hattori (SPMN-IS-59759–59777) .

Other specimens examined. Honshu: Tokyo: 4 males, Nippara-gawa, Okutama-machi , 5.vi.1991, T . Kagaya & T . Nozaki (NKa) . Kanagawa: 4 males, Sokozawa, Sagamihara-shi , 9.iv.1984, T . Nozaki (NKa) ; 5 males, Shiomizu-gawa, Kiyokawa-mura , 5.vi.1994, T . Hattori ( SPMN) ; 1 female, Shiraishizawa, Yamakita-machi , 26.iv.1984, T . Nozaki ; 1 female, same locality, 2–3.vi.1984, T . Nozaki (NKa) ; 25 males, 5 females, Nishizawa, Nakagawa , Yamakita-machi, 8.vi.2020, T . Nozaki (NKa) . Niigata: 7 males, 1 female, Wasabi-zawa , Ôdokoro, Itoigawa-shi, 14.viii.1998, T . Hattori ( SPMN) . Yamanashi: 1 male, 1 female, Doryu-no-taki, Nishi-ide , Ôizumicho, Hokuto-shi, 30.v.1997, T . Hattori ( SPMN) ; 7 males, 1 female, Goasawa, Komukawa , Asahi-machi, Nirasakishi, 18.viii.1996, T . Hattori ( SPMN) ; 9 males, Hondani, Ichinose, Enzan-shi , 6.vii.1991, T . Nozaki (NKa) . Nagano: 1 male, 2 females, Oguro-gawa , Ina, Ina-shi, 17.vi.1996, T . Hattori ( SPMN) ; 2 females, Sonohara-gawa, Achi-mura , 20.vi.1994, T . Hattori ( SPMN) . Gifu: 1 male, Kurumishima, Asahi-cho, Takayama-shi , 16.vii.2012, H. Iketake ( HI) . Shizuoka: 9 males, 2 females, Hikage-sawa , Umegashima, Shizuoka-shi, 21.vi.2002, T . Hattori ( SPMN) ; 1 female, Nishi-hikagezawa, Umegashima, Shizuoka-shi , 16.vii.1995, T . Hattori ( SPMN) ; 6 males, 1 female, Minami-sawa, Umegashima , Shizuoka-shi, 28.vi.1997, T . Hattori ( SPMN) ; 15 males, 1 female, same locality, 4.v.1999, T . Hattori ( SPMN) ; 2 males, same localiy, 8.ix.2001, T . Hattori ( SPMN) ; 2 males, Ikawa-tôge, Umegashima, Shizuoka-shi , 29.iv.1998, T . Hattori ( SPMN) ; 3 males, same locality, 26.vi.2001, T . Hattori ( SPMN) ; 3 males, 2 females, Nigorikawa, Umegashima , Shizuoka-shi, 9.vi.2002, T . Hattori ( SPMN) ; 3 males, Yokosawa, Shizuoka-shi , 4.vi.2001, T . Hattori ( SPMN) ; 1 female, same data (in glycerin) ( SPMN) ; 1 female, same locality, 9.vi.2001, T . Hattori (in glycerin) ( SPMN) ; 1 male, same locality, 21.v.2003, T . Hattori (in glycerin) ( SPMN) ;

Etymology. The Latin species epithet “angulicauda ” (= angle tail) is a noun in apposition referring to the shape of apicodorsal lobe of segment IX in male genitalia of this species.

Distribution and biology. Rhyacophila angulicauda sp. nov. is distributed only in central Honshu, Japan ( Fig. 9D View FIGURE 9 ). Adults were collected near mountainous streams from April to August. In some localities, adults of this species and R. clemens were collected at the same time, but this species tends to be distributed at higher altitudes than R. clemens in the same river system.

Japanese name. Kakuo-nagare-tobikera.