Rhyacophila kangae Park & Nozaki, 2021

Nozaki, Takao & Park, Sun-Jin, 2021, Two new species of the genus Rhyacophila Pictet (Trichoptera, Rhyacophilidae) from Korea and Japan, Zootaxa 5067 (1), pp. 97-105 : 98-99

Rhyacophila kangae Park & Nozaki sp. nov.

( Figs 1 , 4 , 9 )

Rhyacophila sp. 3 : Kang 2020, 232–233, male (photographs), Korea.

Diagnosis. This species belongs to the Rhyacophila nigrocephala Species Group ( Ross 1956). The male genitalia are similar to those of R. confissa and R. vicina , but the male of R. kangae sp. nov. is distinguishable from those of the latter two species by the shape of the complex of preanal appendages and apicodorsal lobe of segment IX: In dorsal aspect, the two lobes are widely separated from each other, forming a large U-shape in R. kangae sp. nov. ( Fig. 1B ), but they form a narrow slit in R. confissa and R. vicina ( Figs. 2B, 3B ). Furthermore, the male of R. kangae sp. nov. bears large compound eyes in proportion to its head width when compared with those of R. confissa and R. vicina : 0.37–0.45 in R. kangae , but 0.23–0.31 in R. confissa and R. vicina ( Figs. 1F a b, 2C, 3C ). The female genitalia are similar to those of R. confissa and R. vicina but can be distinguished by the shape of the vaginal apparatus: In ventral aspect, the posterior process of the vaginal apparatus is long and rectangular in R. kangae sp. nov. ( Fig. 4F ), but that of R. confissa bears an 8-shaped unpigmented part apicoventrally ( Fig. 6B ), and that of R. vicina is constricted at 2/5 from the posterior apex ( Fig. 7B ). The male and female of R. kangae sp. nov. are also similar to those of a Japanese species, R. yamamotoi sp. nov., but they are distinguished by the characters given in the diagnosis for that species, below.

Adult. Specimens in alcohol mostly dark brown, but tibiae and tarsi of all legs light brown. Forewings each 12.2–13.5 mm in male (n = 6), 13–14.8 mm in female (n = 2). Ratio of width of eye to distance between eyes (a/b in Fig. 1F ) 0.37–0.45 in male (n = 6), 0.25–0.33 in female (n = 6).

Male genitalia. Segment IX (IX) longitudinally short in lateral aspect ( Fig. 1A ), ventral half longer than dorsum; membranous along midline in dorsal aspect ( Fig. 1B ). Complex of pair of preanal appendages and apicodorsal lobe of segment IX (com.) bilobed from about basal 2/5, widely separated, large, U-shaped in dorsal aspect ( Fig. 1B ); each lobe finger-like in lateral aspect ( Fig. 1A ), with 3 tiny teeth apicomesally (2 dorsal, 1 ventral, inset for Fig. 1A ). Anal sclerites (a.s.) fused basally, bilobed apically, each round apex with minute black denticles dorsally. Apical band (a.b.) long, curved posterad, dorsal margin connected to base of anal sclerite; ventral margin connected to base of sagittal appendage (s.a.) of tergal band ( Fig. 1A ); sagittal appendage trapezoidal in dorsal and ventral aspects ( Fig. 1C ). Basal segment of each inferior appendage (i.a.) thick in lateral aspect ( Fig. 1A ); posteromesal angle triangular, directed mesad in dorsal aspect ( Fig. 1B ); mesal face with ridged tendon (t.i.a.) along midline, extending to phallotheca (pha.) ( Figs 1A, 1D ). Distal segment of each inferior appendage bilobed, dorsal lobe club-like in lateral aspect ( Figs 1A, 1D ), ventral lobe semicircular in lateral aspect, both lobes with minute spines apicomesally. In phallic apparatus ( Fig. 1E ), aedeagus (ae.) bottle-shaped in dorsal and ventral aspects; parameres (para.) slender, club-like, apices curve laterad, and with tiny spines.

Female genitalia. Segment VIII (VIII) annular, but semi-membranous along dorsal and ventral midlines, with pair of dorsal weakly sclerotized extensions ( Fig. 4C ); pair of apodemal rods reaching posterior end of segment VI. Segment IX (IX) membranous, with pair of strongly sclerotized bands dorsolaterally extending into segment VI as apodemal rods ( Fig. 4B , ap. IX); fused with segment X (X) ventrally, pair of ventrolateral sclerotized bands extending to segment X ( Fig. 4B ). Segment X slender, with pair of strongly sclerotized bands dorsolaterally; fused with segment XI (XI) ( Fig. 4B ). In vaginal apparatus, processus spermathecae (p.s.) claw-like in lateral aspect ( Fig. 4E ), semicircular in ventral aspect ( Fig. 4F ); posterior process (p.p.) long rectangular in ventral aspect, more than 3 times longer than anterior width, face-down and saucer-shaped in lateral aspect ( Fig. 4E ).

Immature stages. Unknown.

Holotype. Male (in alcohol), Bangtaecheon Stream , Jindong-ri , Girin-myeon , Inje-gun, Gangwon-do, Korea, 38.024°N, 128.472°E, alt. 690 m, 23.v.2018, MS. Kang (net sweeping) ( NIBR0000935610 ).

Paratypes. 1 male, 1 female, same data as the holotype ( NIBR0000935608–0000935609 ) ; 4 males, 1 female, Samil River , Sanae-myeon , Hwacheon-gun, Gangwon-do, Korea, 10.vi.2014, T . Ito (net sweeping) ( CBM-ZI 0180236–0180240 ) .

Other specimens examined. KOREA: 2 males, 4 females, Gyebangsan , Gangwon-do, 11.vi.2014, T. Ito (net sweeping) (1 male, 2 females: SJP; 1 male, 2 females: TN) .

Etymology. This species is dedicated to Ms. Mi-Sook Kang, who gifted us valuable specimens and information concerning Korean caddisflies, including this species.

Distribution. The Korean Peninsula (Gangwon-do, South Korea).

Remarks. This species was found in Gangwon-do, South Korea, where both R. confissa and R. vicina are distributed ( Fig. 9 ). One of the sites where R. confissa was collected in this study is only 1.4 km from the type locality of R. kangae sp. nov. in the same stream (Bangtaecheon Stream). Although the genitalic morphology of the new species is similar to those of R. confissa and R. vicina , the differences in diagnostic characters described above are stable.

The male of R. kangae sp. nov. bears large compound eyes in proportion to its head width when compared with those of males of R. confissa and R. vicina , and also with those of females of these three species. The sexual dimorphism in the size of compound eyes observed in this new species suggests that the mating behavior of this species may differ from that of R. confissa and R. vicina .

Figures

FIGURE 9. Distributions of 4 Rhyacophila species in East Asia. Distribution areas of R. confissa and R. vicina are cited from Ivanov (2011), Park & Kong (2020), and Yang et al. (2016).

FIGURES 1–3. Rhyacophila spp., male. 1A–1F, Rhyacophila kangae sp. nov. 1A–1E, genitalia: 1A, left lateral, apicomesal part of complex of preanal appendages and apicodorsal lobe of segment IX enlarged; 1B, dorsal; 1C, upper part, ventral; 1D, left inferior appendage, mesal; 1E, phallic apparatus, dorsal. 1F, head, dorsal (a, b: see text). 2A–2C, Rhyacophila confissa Botosaneanu 1970: 2A, genitalia, left lateral; 2B, same, dorsal, anal sclerite enlarged; 2C, head, dorsal. 3A–3C, Rhyacophila vicina Botosaneanu 1970: 3A, genitalia, left lateral; 3B, same, dorsal, anal sclerite enlarged; 3C, head, dorsal. Abbreviations: a.b. = apical band, ae. = aedeagus, a.s. = anal sclerite, com = complex of preanal appendages and apicodorsal lobe of segment IX, i.a. = inferior appendage (paired), para. = paramere (paired), pha. = phallotheca, s.a. = sagittal appendage, t.b. = tergal band, t.i.a., = tendon of inferior appendage (paired), IX = segment IX.

FIGURE 4–7. Rhyacophila spp., female. 4A–4F, Rhyacophila kangae sp. nov.: 4A, head, dorsal; 4B, abdominal segments VIII to XI, left lateral, 4C, abdominal segment VIII, dorsal; 4D, same, ventral; 4E, vaginal apparatus, left lateral; 4F, same, ventral. 5A–5E, Rhyacophila yamamotoi sp. nov.: 5A, head dorsal; 5B, abdominal segment VIII, left lateral; 5C, same, dorsal; 5D, same, ventral; 5E, vaginal apparatus, left lateral; 5F, same, ventral. 6A, 6B, Rhyacophila confissa Botosaneanu 1970: 6A, vaginal apparatus, left lateral; 6B, same, ventral. 7A, 7B, Rhyacophila vicina Botosaneanu 1970: 7A, vaginal apparatus, left lateral; 7B, same, ventral. Abbreviations: ap.VIII = apodemal rod of abdominal segment VIII (paired); ap.IX = apodemal rod of abdominal segment IX (paired); p.p. = posterior process; p.s. = processus spermathecae; VIII, IX, X, XI = abdominal segments VIII, IX, X, XI.