Rhyacophila furcicauda, 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 : 71-72

Rhyacophila furcicauda sp. nov.

( Figs 7A–7J , 9D )

Rhyacophila sp. 2 ( clemens gr.): Kawase & Morita 2010, 36.

Diagnosis. The male genitalia of R. furcicauda sp. nov. are unique among known species in the R. clemens Species Group in that the apical segment of each inferior appendage is bifurcate ( Fig. 7A ) (those of the other species are not bifurcate). The female genitalia of R. furcicauda sp. nov. are similar to those of R. parvicauda sp. nov. in having thick setae densely on the lateral surface of segment VIII but can be distinguished from the latter by the characters given in the diagnosis for R. parvicauda .

Adult. Length of each forewing: male 6.1–7.2 mm (mean = 6.7, SD = 0.39, n = 8), female 6.7 mm (n = 1). General morphology and coloration similar to those of R. clemens , but wing venation similar to R. inazui ( Fig. 4B ), root of fork I on each forewing clearly longer than that of fork II.

Male genitalia ( Figs 7A–7F ). Segment IX dorsal half longer than ventral half in lateral view ( Fig. 7A ), widely trapezoidal in dorsal view ( Fig. 7D ); apicodorsal lobe extruded posterad, trapezoidal in dorsal view ( Fig. 7D ), angular in lateral view ( Fig. 7A ). 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. 7B ); horizontal part oval in dorsal view ( Fig. 7D ), apically bent upwards in lateral view ( Figs 7A, 7B ); apical hinged process with pair of long finger-like lobes, parallel, directed posterodorsad ( Figs 7A–7D, 7F ), with pair of round anteroventral corners and small protrusion between them ( Fig. 7F ). Anal sclerites composed of two pairs of lobes, each long and rectangular, but apex of each ventral pair obliquely truncate in lateral view; these two pairs of lobes with common internal root ( Fig. 7B ). Apical band well developed, semi-oval in lateral view, broadly surrounding anus and root of anal sclerites ( Figs 7B, 7F ). Tergal band connecting base of apical band to dorsum of phallobase ( Fig. 7B ). Basal segment of each inferior appendage setose, short, thick, nearly rectangular, posterior half gradually thicker in lateral view ( Fig. 7A ). Apical segment of each inferior appendage bifurcate in lateral view ( Figs 7A, 7E ), covered with hair-like setae sparsely laterally, with dense short spine-like setae on posteromesal margin of ventral fork ( Figs 7A, 7D, 7E ). In phallic apparatus, phallobase short; aedeagus forming narrow tube with sclerotized ventral plate ( Figs 7B, 7C ); ventral plate horizontal and long and tongue-shaped, posterior margin with small triangular protrusion apicomesally in ventral view ( Fig. 7F ). Parameres absent.

Female genitalia ( Figs 7G–7J ). Segment VIII annular, dorsal margin almost straight in lateral view ( Fig. 7G ); pair of ventral ridges widely separated anteriorly, running subparallel posteriorly ( Fig. 7H ); with many darkly pigmented and thick setae laterally, with fine pale short setae between ventral ridges ( Figs 7G, 7H ); pair of apodemal rods reaching to posterior end of segment VI. Segment IX membranous, with pair of apodemal rods dorsolaterally, extending into abdominal segment VI. Vaginal apparatus simple; posterior process sclerotized, dorsal margin slightly convex in lateral view ( Fig. 7I ), apparatus oval in ventral view ( Fig. 7J ); processus spermathecae membranous ( Figs 7I, 7J ).

Immature stage. Unknown.

Holotype. Male (in alcohol), Yuzurio-cho, Higashi-ômi-shi, Shiga Pref., Honshu, Japan, 35°4’40” N 136°23’44”E, alt. 370 m, 31.v–26.vi.2009, N. Kawase ( LBM1410012653 ).

Paratypes. Honshu : Mie: 2 males, Okumano, Iga-shi, 9.vi–22.vi.2012, H. Morita ( LBM1410012654– 1410012655 ) . Wakayama: 2 males, Kôya-ryujin Skyline, Ryujin-mura , 28–29.v.2004, (SPMN-IS-59800–59801); 2 males, 1 female, same data, T. Hattori ( LBM1410012656–1410012658 ) .

Other specimens examined. Honshu: Mie: 1 male, Okumano, Iga-shi , 26.v–9.vi.2012, H. Morita (NKa) ; 1 male, Hobo-cho, Kumano-shi , 33°57’N 136°12’E, 31.v.2006, N. Kawase (NKa) . Nara: 1 pupa (male), Kannohgawa, Totsukawa-mura , 11.vi.2005, S. Kobayashi ( SPMN) ; 1 male, Kitozumi, Tenkawa-mura , 22.vii.2021, H. Iketake ( HI) .

Etymology. The species name “furcicauda ” (= fork tail) is a noun in apposition referring to the bifurcate apical segment of each inferior appendage in male genitalia.

Distribution and biology. Rhyacophila furcicauda sp. nov. was collected from only Suzuka Mountains and Kii Mountains in Kinki district, central Japan ( Fig. 9D ). Adults of this species were collected near streamside by sweeping or using a Malaise trap in late May to July.

Japanese name. Nimata-nagare-tobikera.

Figures

FIGURE 4. Rhyacophila inazui sp. nov. 4A, male habitus, left dorsolateral (photographed by K. Inazu); 4B, female right forewing (in alcohol), dorsal; 4C–4H, male genitalia: 4C, left lateral; 4D, segment X and phallic apparatus, left lateral; 4E, dorsal (left inferior appendage omitted); 4F, ventral (left inferior appendage and apical segment of right inferior appendage omitted); 4G1, apical hinged process of segment X, enlarged, ventral; 4G2, ventral plate of aedeagus, enlarged, ventral; 4H, posterodorsal. 4I–4N, female genitalia: 4I, left lateral; 4J, ventral; 4K, segment VIII, left lateral; 4L, same, ventral; 4M, vaginal apparatus, left lateral; 4N, same, ventral. Abbreviation: vr = ventral ridge. Arrows see text.

FIGURE 7. Rhyacophila furcicauda sp. nov. 7A–7F, male genitalia: 7A, left lateral; 7B, segment X and phallic apparatus, left lateral; 7C, same, posterodorsal; 7D, dorsal (left inferior appendage omitted); 7E, apical segment of right inferior appendage, mesal; 7F, segment X and phallic apparatus, ventral. 7G–7J, female genitalia: 7G, segment VIII, left lateral; 7H, same, ventral; 7I, vaginal apparatus, left lateral; 7J, same, ventral. Abbreviation: vr = ventral ridge. Arrows see text.

FIGURE 9. Distributions of species in the Rhyacophila clemens Species Group in Japan.