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

description: Rhyacophila parvicauda sp. nov.
(Figs 6A–6H, 9D)
Diagnosis. The male of R. parvicauda sp. nov. is similar to those of R. inazui sp. nov. and R angulicauda sp. nov. in having a U-shaped apical hinged process of segment X in ventral view, but can be distinguished from the latter two by the shape of the apicodorsal lobe of segment IX given in the diagnosis for R. inazui sp. nov. Additionally, the male genitalia of this species are unique among this species group in having rows of dense spine-like setae along the mesodorsal margin of the apical segment of each inferior appendage (Figs 6A, 6C). Moreover, the apical hinged process of this species is clearly shorter than the other two species, only 1/2 as long as the horizontal part of segment X (Fig. 6A), but those of the other two species are about as long as the horizontal part (Figs 4C, 5A). Regarding the female, R. parvicauda sp. nov. is similar to R. furcicauda sp. nov. in having many brown thick setae on the lateral surface of segment VIII (Fig. 6E), but can be distinguished from the latter by the shape of ventral ridges: In P. parvicauda sp. nov., a ventral ridge of segment VIII is visible posteriorly from the side (arrow in Fig. 6E), but in P. furcicauda sp. nov., the ventral ridge is invisible in lateral view (Fig. 7G).
Adult. Length of each forewing: male 6.4–7.3 mm (mean = 6.7, SD = 0.32, n = 7), female 6.2–6.9 mm (mean = 6.6, n = 2). General morphology and coloration similar to those of R. clemens, but wing venation similar to that of R. inazui sp. nov. (Fig. 4B), root of fork I on each forewing clearly longer than that of fork II.
Male genitalia (Figs 6A–6D). Segment IX dorsal half longer than ventral half in lateral view (Fig. 6A), wide rectangular in dorsal view with small apicodorsal lobe (Fig. 6C). 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. 6B); horizontal part thick, oval in dorsal view (Fig. 6C); apical hinged process U-shaped in ventral view, with pair of short finger-like lobes parallel, 1/2 as long as horizontal part in lateral view, lobes apically rounded, directed posterodorsad (Figs 6A–6D). Anal sclerites composed of two pairs of lobes, each long and rectangular in lateral view, with common internal root (Figs 6B, 6D). Apical band well developed, semi-oval in lateral view, broadly surrounding anus and root of anal sclerites (Figs 6B, 6D). Tergal band connecting ventral part of apical band to dorsum of phallobase (Fig. 6B). Basal segment of each inferior appendage setose, elongate, basal 1/3 narrowest in lateral view (Fig. 6A). Apical segment of each inferior appendage subtriangular in lateral view (Fig. 6A); mesal surface densely covered by long fine setae, with rows of spine-like setae along dorsal margin (Fig. 6C). In phallic apparatus, phallobase short (Fig. 6B); aedeagus narrow tube with sclerotized ventral plate (Fig. 6B); ventral plate horizontal, tongue-shaped with posterior margin truncate in ventral view (Fig. 6D). Parameres absent.
Female genitalia (Figs 6E–6H). Segment VIII annular, dorsal margin almost straight or slightly concave in lateral view (Fig. 6E); pair of ventral ridges widely separated, posterior ends curved posterodosad, visible in lateral view (Figs 6E, 6F); many brown thick setae on lateral surface (Figs 6E, 6F); 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 round in lateral view (Fig. 6G), apparatus long-oval in ventral view (Fig. 6H); processus spermathecae membranous.
Immature stage. Unknown.
Holotype. Male (in alcohol), Mt. Koya-yama primary forests, Oda-cho, Ehime Prefecture, Shikoku, Japan, 33°30’27”N 132°51’39”E, alt. 1100 m, 29.vi.2000, E. Yamamoto (LBM1410012649).
Paratypes. Shikoku: Ehime: 2 males, 1 female, same locality as the holotype, 7.vii.2000, E. Yamamoto & M. Doi (LBM1410012650–1410012652); 1 male, 1 female, same locality as the holotype, 15.vii.2000, E. Yamamoto & M. Doi (SPMN-IS-59791–59795); 3 males, same locality as the holotype, 21.vii.2000, E. Yamamoto & M. Doi (SPMN-IS-59788–59790); 4 males, same locality as the holotype, 29.vii.2000, E. Yamamoto & M. Doi (SPMN-IS-59796–59799); 1 male, Oda-miyama. Oda-cho, 31.v.2001, E. Yamamoto (SPMN-IS-59786); 1 male, same locality, 10.vi.2001, E. Yamamoto (SPMN-IS-59787).
Other specimens examined. Shikoku: Ehime: 1 male, same locality as the holotype, 19.viii.2000, E. Yamamoto & M. Doi (SPMN); 1 female, same locality as the holotype, 20.ix.2000, E. Yamamoto (SPMN). Kochi: 1 male, 1 female, Setogawakeikoku, Tosa-cho, Tosa-gun, 27.v.2004, K. Nio (SPMN).
Etymology. The species name “parvicauda ” (= short tail) is a noun in apposition referring to the short, apical, hinged process of segment X.
Distribution and biology. Rhyacophila parvicauda sp. nov. was collected only from a few small headwater streams in a mountain area of Shikoku (Fig. 9D). This species tends to be distributed at rather higher altitude than R. inazui and R. vesperalis in the same river systems. Adults of this species were collected from late May to August.
Japanese name. Hime-kuremensu-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 69-71, DOI: 10.11646/zootaxa.5447.1.3, http://zenodo.org/record/11119209