Rhyacophila angulicauda Kawase 2024, sp. nov.
Creators: name: Kawase, Naoki
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Trichoptera
Rhyacophilidae
Rhyacophila
Rhyacophila angulicauda

description: Rhyacophila angulicauda sp. nov.
(Figs 5A–5I, 9D)
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), root of fork I and II of each forewing approximately same length each other.
Male genitalia (Figs 5A–5D). Segment IX dorsal half longer than ventral half in lateral view (Fig. 5A), trapezoidal in dorsal view; apicodorsal lobe trapezoidal in dorsal view, angular in lateral view, strongly overhanging segment X (Figs 5A, 5C). 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); horizontal part nearly oval and slightly bilobed posteriorly in dorsal view (Fig. 5C); 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); pair of anteroventral corners (of ahp) round, forming sub-oval mounds (Fig. 5D). Anal sclerites composed of two pairs of lobes, each long rectangular in lateral view, with common internal root (Figs 5B, 5D). Apical band well developed, subtriangular with round corners in lateral view, broadly surrounding anus and root of anal sclerites (Figs 5B, 5D). Tergal band connecting base of apical band to dorsum of phallobase (Fig. 5B). Basal segment of each inferior appendage setose, elongate, posterior half gradually thicker in lateral view (Fig. 5A). Apical segment of each inferior appendage subtriangular in lateral view (Fig. 5A), covered with fine setae mesally (Fig. 5C). In phallic apparatus, phallobase short, cup like (Fig. 5B); aedeagus forming narrow tube with sclerotized ventral plate (Figs 5B, 5D); ventral plate horizontal and tongue-shaped with posterior margin truncated or shallowly concave in ventral view (Fig. 5D). Parameres absent.
Female genitalia (Figs 5E–5I). Segment VIII annular, dorsal margin almost straight in lateral view (Figs 5E, 5F); with pair of ventral ridges forming longitudinal narrow bridge, narrowest in anterior 1/4–1/ 3 in ventral view (Fig. 5G); pair of apodemal rods extending into segment VI (Fig. 5E). 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), long oval in ventral view (Fig. 5I); processus spermathecae membranous (Figs 5H, 5I).
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).
Paratypes. Honshu: Kanagawa: 9 males, 3 females, Nishizawa, Nakagawa, Yamakita-machi, 27.v.2020, T. Nozaki (LBM1410012637–1410012648); 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); 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). 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.
description: Published as part of Kawase, Naoki, 2024, Redescription of Rhyacophila clemens Tsuda 1940 (Trichoptera, Rhyacophilidae), with descriptions of five new, allied species from Japan, pp. 55-76 in Zootaxa 5447 (1) on pages 67-69, DOI: 10.11646/zootaxa.5447.1.3, http://zenodo.org/record/11119209