Hydroptila tokoyo Ito & Sasaki, 2023

Ito, Tomiko, Sasaki, Tetsuro, Takahashi, Chicaco, Sugawara, Hirotaka & Hayashi, Fumio, 2023, The family Hydroptilidae Curtis (Trichoptera) in the Ogasawara Islands, northwestern Pacific, with particular reference to adaptive radiation in the oceanic islands, Zootaxa 5231 (2), pp. 141-164 : 154-157

Hydroptila tokoyo Ito & Sasaki sp. nov.

( Figs 9H–9K , 10E )

Diagnosis. The male of this species is similar to that of H. ogasawaraensis , but is distinguished from the latter by the length of the phallic apparatus, the presence of lateral plates of segment X, and the shape of inferior appendages; the anterior end of the phallic apparatus extends from abdominal segment VII when retracted, the lateral plates are absent, and the inferior appendages are without lateral humps in H. ogasawaraensis ( Figs 9A–9D ); the phallic apparatus extends from abdominal segment III when retracted, a pair of lateral plates is present, and each inferior appendage has a lateral hump in H. tokoyo ( Figs 9H–9L ).

Male. Head, thorax, wing color, tibial spurs, processes of sternites V and VII are as for H. demersa . Forewings each 2.0– 2.1 mm in length and hind wings each 1.8–2.0 mm (n = 2). Antennae each 27–29-segmented, length 1.0– 1.2 mm long (n = 2).

Male genitalia ( Figs 9H–9L ). Segment IX (IX) annular, its transverse tergal bridge narrow, its midline 1/3 as long as segment; with deep subquadrate margin dorsally; small, sclerotized, subrectangular, dark and setose plate (dsp IX) at posterodorsal margin, covered with very fine setae; deep and broad subtriangular excision on anterior margin ventrally. Dorsal plate (dp) semi-membranous, blunt apically in dorsal view, subtriangular in lateral view. Lateral plates (lp) subtriangular in lateral view, apically directed caudoventrad. Subgenital plate (sp) slightly sclerotized, gradually tapered, directed caudoventrad, with very small hook subapicoventrally. Inferior appendages (ia) thick, directed caudad, each with irregularly shaped lateral hump (lh) at basal 2/5 and hooked caudodorsad apically. Phallic apparatus very long, almost straight, anterior end extending from middle of segment III when retracted, with slender titillator at 4/5 length.

Female, larva and case. Unknown.

Holotype. Male , Japan, Ogasawara Islands , Chichi-jima : Tokoyo-gawa,Tokoyo-no-taki Waterfall (N27.0574, E142.2058, 30 m above sea level), 2.iii.2020, TI & CT, S ( CBM-ZI 0184761 ).

Paratypes. 1 male, same data as holotype ( CBM-ZI 0184762 ) .

Other specimens. Chichi-jima: 1 male, same data as holotype ; 1 male, type locality, 16.iv.2019, TI & CT, S ; 1 pupa (male), a tributary of Tokoyo-gawa, upper reach, 19.iv.2022, TI & TS, H .

Distribution ( Fig. 1C ). Japan (Ogasawara Islands: Chichi-jima).

Habitat and remarks ( Figs 10E, 10F ). The males were collected from Tokoyo-no-taki Waterfall, covered with bryophytes and algae ( Fig. 10E ). Many Hydroptila larvae were there ( Fig. 10F ), but they couldn’t be identified at species level morphologically, since two species ( H. tokoyo and H. ogasawaraensis ) have been detected there by both morphological examination of males and DNA analyses of larvae.

Japanese name. Tokoyo-hime-tobikera.

Figures

FIGURE 1. Location of the Ogasawara (Bonin) Islands in the northwestern Pacific (1A) and collecting sites of the six species of Hydroptila on Ani-jima (1B), Chichi-jima (1C), and Haha-jima (1D).

FIGURE 9. Adults of Hydroptila ogasawaraensis Ito 2011 (in Ito et al. 2011) and H. tokoyo sp. nov. Hydroptila ogasawaraensis (type specimens) (9A–9G): 9A, male abdominal segments I–X, left lateral; 9B, male genitalia, left lateral, with enlarged figure of apex of subgenital plate; 9C, same, dorsal; 9D, same, ventral; 9E, phallic apparatus, left lateral; 9F, female abdominal segments VIII–X, ventral; 9G, vaginal apparatus, ventral. Male of H. tokoyo sp. nov. (9H–9L): 9H, abdominal segments I–X, left lateral; 9I, genitalia, left lateral, with enlarged figure of apex of subgenital plate; 9J, same, dorsal; 9K, same, ventral; 9L, phallic apparatus, left lateral, with enlargement of apical 1/3. Abbreviations: VIII–X = abdominal segments VIII–X; dp = dorsal plate; dsp IX = dark and setose plate of segment IX; ia = inferior appendage (paired); lh = lateral hump; lp = lateral plate; pa = phallic apparatus; sp = subgenital plate.

FIGURE 10. Habitats (type localities) and immature stages of Hydroptila spp. H. ogasawaraensis Ito 2011 (in Ito et al. 2011, 10A–10D): 10A, habitat, larvae found on rock in region enclosed by dashed oval; 10B, other part of habitat; 10C, habitus of larva in case in field, dorsal; 10D, habitus of larva in case in alcohol, right lateral. H. spp., possibly H. ogasawaraensis or H. tokoyo n. sp., Tokoyo-no-taki (type locality of H. tokoyo) (10E, 10F): 10E, habitat; 10F, habitus of larva in case in alcohol, left lateral. Scale bars, 1 mm.