Stactobia yona, Ito, 2017

Ito, Tomiko, 2017, The genus Stactobia McLachlan (Trichoptera, Hydroptilidae) in Japan, Zootaxa 4350 (2), pp. 201-233 : 222

Stactobia yona sp. nov.

( Figs 13 , 19 )

Diagnosis. This species belongs to the S. martynovi Species Group. The male of this species is clearly distinguished from other congeneric species by the shape of the phallus which has a long sharp internal spine.

Description. Male ( Figs 13A–13D ). Antennae each 18-segmented and 0.8–0.9 mm long (n = 5). Length of each forewing and hind wing 1.9–2.0 mm and 1.6–1.7 mm, respectively (n = 5). Tibial spur formula 1, 2, 4.

Genitalia. Tergite VII quadrate, sternite VII slightly shorter longitudinally than tergite, ventral process long with apex expanded, spiny. Tergite VIII and sternite VIII subequally large, rectangular. Tergite IX subquadrate with pair of long anterior apodemes, sternite IX reduced. Tergite X semimembranous, quadrate in dorsal view, apically subacute in lateral view, with pair of pale longitudinal sclerites dorsolaterally. Subgenital appendages slender and inferior appendages small and heart-shaped in ventral view. Phallus tubular with slender bar and long flattened spine internally; bar weakly sclerotized, almost 1/2 as long as phallus; spine strongly sclerotized, 10 times as long as basal width, sharply pointed apically.

Final instar larva ( Figs 13E–13G ). Sclerites dark brown. Head up to 0.29 mm wide, body up to 2.0 mm long. Thorax: About 25 setae on each notum; prosternum with pair of very short, transversely wide sclerites and pair of small lateral round sclerites. Abdominal terga each with mid transverse dorsal sclerite and pair of small round dorsolateral sclerites. Other features typical of genus.

Case of larva ( Figs 13H, 13I ). Length 2.2 mm. Composed of silken dome-shaped dorsal valve and silken rectangular ventral valve. Anterior and posterior hoods large, convex, apices each often with small notch at middle. Other features typical of genus.

Type series. Holotype. Male, RYUKYU ISLANDS, Okinawa-jima, Kunigami-son, Aha, Fun-gawa, Tanagagumui, 26˚43’30”N, 128˚17’12”E, 78 m a.s.l., 22.iii.1999, TI & AO (CBM-ZI 166003).

Paratypes. 2 males, same data as holotype (CBM-ZI 166004–166005).

Other specimens. RYUKYU ISLANDS. Okinawa-jima: 2 males, 21 pupae, 5 prepupae, 71 final instar larvae, same data as holotype ; 2 males, Kunigami-son, Yona-gawa, Heigi-bashi, 10.iv.2011, TI; 5 males, same locality, 18.iii.2014, TI. Amami-oshima : 1 male, Uken-son, 24.iii.1997, F. Nishimoto; 1 male, Yamato-son, Materia-no-taki, 25–26.x.2011, TI.

Distribution ( Fig. 19 ). Ryukyu Islands (Amami-oshima, Okinawa-jima).

Habitat. Larvae of this species were collected by AO and me at very fast streams with large stones.

Ethymology. The name “ yona ” is a noun in apposition, coined from the locality where many males were collected.

Japanese name. Yona-kaku-himetobikera.

Figures

FIGURE 13. Stactobia yona sp. nov. Male, final instar larva, and case. 13 A – 13 D, male: 13 A, abdominal segments VII – X, left lateral; 13 B, abdominal segments IX – X, dorsal; 13 C, abdominal segment IX, ventral; 13 D, phallus, ventrolateral. 13 E – 13 G, final instar larva: 13 E, right half of thorax, dorsal; 13 F, pro- and mesosterna, ventral; 13 G, abdominal segments I – III, dorsal. 13 H, 13 I, case: 13 H, dorsal; 13 I, ventral. Specimens: Okinawa-jima, Kunigami-son (type locality). Scale bars: 0.1 mm for 13 A; 1.0 mm for 13 H & 13 I.

FIGURE 19. Distributions in Japan of 7 species of Stactobia.