Stactobia semele Malicky & Chantaramongkol 2007

Ito, Tomiko, 2017, The genus Stactobia McLachlan (Trichoptera, Hydroptilidae) in Japan, Zootaxa 4350 (2), pp. 201-233 : 230-232

Stactobia semele Malicky & Chantaramongkol 2007

( Figs 17 , 19 )

Stactobia semele Malicky & Chantaramongkol 2007, 1044 , 1090, holotype male, Taiwan.

Diagnosis. This species belongs to the S. martynovi Species Group and is distinguished from congeneric species by the shape and position of the internal spine of the phallus.

Description. Male. Antennae each 18-segmented and 0.6–0.7 mm long (n = 5). Length of each forewing and hind wing 1.5–1.7 mm and 1.3–1.5 mm, respectively (n = 5). Tibial spur formula 1, 2, 4.

Genitalia ( Fig 17A–17D ). Tergite VII subquadrate, almost as long as sternite VII, ventral process with expanded spiny apex. Tergite and sternite VIII subequally long and longer than those of segment VII. Tergite IX subquadrate with pair of long anterior apodemes, sternite IX reduced. Tergite X semimembranous, weakly sclerotized dorsolaterally, subquadrate with large triangular excision medially in dorsal view. Subgenital appendages slender with round mesal edges. Inferior appendages roundish, in ventral view with small heart-shaped sclerites. Phallus tubular with internal slender spine at half length, subacute apically; spine almost straight, slightly curved at apex, 15–18 times as long as basal width.

Final instar larva ( Figs 17E–G ). Sclerites dark brown. Head about 0.29 mm wide, body up to 2.0 mm long. Thorax: About 25, 20, and 15 setae on pro-, meso- and metanota, respectively; pair of very short and transversely wide sclerites posteriorly on each of pro- and mesosterna. Abdominal terga each with middorsal sclerite and pair of small round sclerites dorsolaterally. Other features typical of genus.

Case ( Figs 17H, 17I ). Length 2.2 mm. Composed of dome-like dorsal valve and smaller rectangular ventral valve. Anterior and posterior hoods each convex apically with tiny notch at middle. Made of silk, with sand grains scattered on dorsal valve and hoods. Other features typical of genus.

Specimens examined. RYUKYU ISLANDS. Iriomote-jima: 11 males, Omijya-gawa, Omijya-bashi, 13.iv.2005, TI; 5 males, same locality, 30.ix.2013, TI ; 9 males, 11 final instar larvae, same locality, 22.iii.2016, TI ; 1 male, Omijya-gawa, Tage-no-taki, 22.iii.2016, TI; 1 male, Aira-gawa, middle reach, 21.iii.2016, TI; 1 male, Yuchin-gawa, small fall, 23.iii.2016, TI.

Distribution ( Fig. 19 ). Ryukyu Islands (Iriomote-jima), Taiwan. Newly recorded for Japan.

Habitat. Larvae of this species were collected by me from very fast streams with large rocks.

Japanese name. Taiwan-kaku-himetobikera.

Remarks. The final instar larva and its case is described here for the first time.

Figures

FIGURE 17. Stactobia semele Malicky & Chantaramongkol. Male, final instar larva, and case. 17 A – 17 D, male: 17 A, abdominal segments VII – X, left lateral; 17 B, abdominal segments IX – X, dorsal; 17 C, abdominal segment IX, ventral; 17 D, phallus, left lateral. 17 E – 17 G, final instar larva: 17 E, right half of thorax, dorsal; 17 F, pro- and mesosterna, ventral; 17 G, abdominal segments I – III, dorsal. 17 H, 17 I, case: 17 H, dorsal; 17 I, ventral. Specimens: Iriomote-jima, Omijya-gawa. Scale bars: 0.1 mm for 17 A; 1.0 mm for 17 H & 17 I.

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