Hydroptila nagahama 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 : 157-160

Hydroptila nagahama Ito & Sasaki sp. nov.

( Figs 11H–11N , 12C–12H )

Diagnosis. The male of this species resembles that of Hydroptila ishiura sp. nov. in having a narrow transverse tergal bridge of segment IX and an almost straight phallic apparatus, but it is clearly distinguished from the latter by the forms of inferior appendages and absence of a subgenital plate or lateral processes: The inferior appendages are narrowly triangular in H. ishiura ( Figs 6B, 6D ), but the inferior appendages are each subquadrate with a strongly sclerotized, large claw and three stout spines on its caudodorsal margin in this species ( Figs 11I, 11K ).

Adult ( Figs 11H–11N , 12E ). Head, thorax, wing color, tibial spurs, processes of sternites V and VII same as for H. ishiura . Forewings each 2.0 mm in length and hind wings each 1.8 mm in male (n = 2); forewings each 2.0 mm in length and hind wings each 1.8–1.9 mm in female (n = 2). Antennae each 28-segmented, length 1.1 mm in male (n = 2); each 25-segmented, length 0.9–1.0 mm in female (n = 2).

Male genitalia ( Figs 11H–11L ). Segment IX (IX) annular, rather long, about 2.2 times longer than height, transverse tergal bridge narrow, on midline about 1/6 as long as segment, with transverse dark and setose plate (dsp IX) not projecting and with deep and wide circular excisions at anterior margins dorsally and ventrally. Dorsal plate (dp) semi-membranous, trapezoidal with mesal concavity at caudal margin in dorsal view; thick and triangular with subacute apex, longer than inferior appendages and curved ventrad in lateral view. Inferior appendages (ia) subquadrate with strongly sclerotized, large claw ventromesally, thick spine caudoventrally, and three thick spines caudodorsally. Phallic apparatus long, almost straight, anterior end extending from middle of segment VI when retracted, without titillator. Lateral processes and subgenital plate absent.

Female genitalia ( Figs 11M, 11N ). Segment VIII relatively short, with no distinct tergite or sternite: 2–3 pairs of marginal setae on each of dorsum and venter, pair of transverse bands near ventral margin; ventral margin slightly projecting caudad at middle. Vaginal apparatus depressed, thin in lateral view, elongate-oval in ventral view.

Final instar larva and case ( Figs 12G, 12H ). The final instar larva and case of this species are very similar to those of H. ishiura , H. ogasawaraensis , and H. hahajima , and could not be discriminated from those of the latter three species.

Holotype. Male , Japan, Ogasawara Islands , Haha-jima: Nagahama (N26.6736, E142.1502, 130 m above sea level), 12.iv.2022, TI & TS, L ( CBM-ZI 0184766 ).

Paratypes. 1 male, 2 females, same data as holotype ( CBM-ZI 0184767–0184769 ) .

Other specimens. Haha-jima: 8 females, 4 pupae (1 male, 3 females), 81 larvae, type locality, 28.ii.2020, TI et al., L & H ; 1 male, type locality, 21.xii.2021, TS & Y. Kaga, L; 1 larva, Iguma-dani, 29.ii.2020, TI et al., H ( Table 1 ) .

Distribution ( Fig. 1D ). Japan (Ogasawara Islands: Haha-jima).

Habitat ( Figs 12C, 12D, 12F ). Larvae and pupae were found on surfaces of hard rocks and in small concavities of hygropetric habitat in small mountain streams, respectively.

Etymology. The species epithet refers to the name of the type locality.

Japanese name. Nagahama-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 6. Adults of Hydroptila ishiura sp. nov. Male (6A–6E): 6A, abdominal segments I–X, left lateral; 6B, genitalia, left lateral; 6C, same, dorsal; 6D, same, ventral; 6E, phallic apparatus, left lateral. Female (6F, 6G): 6F, abdominal segments VIII–X, ventral; 6G, vaginal apparatus, ventral. Abbreviations: VIII–X = abdominal segments VIII–X; dp = dorsal plate; dsp IX = dark and setose plate of segment IX; ia = inferior appendage (paired); lp = lateral process (paired); pa = phallic apparatus; sp = subgenital plate.

FIGURE 11. Adults of Hydroptila hahajima sp. nov. and H. nagahama sp. nov. Adults of H. hahajima (11A–11G): 11A, male abdominal segments I–X, left lateral; 11B, male genitalia, left lateral; 11C, same, dorsal; 11D, same, ventral; 11E, phallic apparatus, left lateral; 11F, female abdominal segments VIII–X, ventral; 11G, vaginal apparatus, ventral.Adults of H. nagahama (11H–11N): 11H, male abdominal segments I–X, left lateral; 11I, male genitalia, left lateral; 11J, same, dorsal; 11K, same, ventral; 11L, phallic apparatus, left lateral; 11M, female abdominal segments VIII–X, ventral; 11N, vaginal apparatus, ventral. Abbreviations: VIII–X = abdominal segments VIII–X; ch = curled hook (paired); dp = dorsal plate; dsp IX = dark and setose plate of segment IX; ia = inferior appendage (paired); pa = phallic apparatus; lp = lateral process; sp = subgenital plate.

FIGURE 12. Habitats of type localities, adult and immature stages of Hydroptila hahajima sp. nov. and H. nagahama sp. nov. H. hahajima (12A, 12B): 12A, habitat; 12B, larva in case in alcohol, left lateral. H. nagahama (12C–12H): 12C, 12D, habitat; 12E, adult on light trap sheet; 12F, three pupae in crack on rock surface; 12G, larva in case in field; 12H, larva in case in alcohol. Scale bars, 1 mm.