Stactobia urauchi, Ito, 2017

Ito, Tomiko, 2017, The genus Stactobia McLachlan (Trichoptera, Hydroptilidae) in Japan, Zootaxa 4350 (2), pp. 201-233 : 225

Stactobia urauchi sp. nov.

( Figs 14 , 19 )

Diagnosis. This species belongs to the S. nielseni Species Group. The male of this species is similar to that of Stactobia chichibu in having the inferior appendages in ventral view slender and triangular, but is clearly distinguished from S. chichibu by the presence of a ventral sclerite near the base of the inferior appendages.

Description. Male ( Figs 14A–D ). Antennae each 18-segmented and 0.6–0.7 mm long (n = 5). Length of each forewing and hind wing 1.4–1.6 mm and 1.2–1.4 mm, respectively (n = 5). Tibial spur formula 1, 2, 4.

Genitalia. Tergite VII long and subquadrate, sternite VII longitudinally shorter than tergite, ventral process long with expanded spiny apex. Tergite VIII longitudinally short, sternite VIII twice as long as tergite. Tergite IX subquadrate with pair of long anterior apodemes, sternite IX reduced. Tergite X semimembranous, subquadrate in dorsal view, subacute apically in lateral view, with pair of light longitudinal sclerites dorsolaterally. Subgenital appendages absent. Inferior appendages rectangular, 3 times as long as wide, round apically in lateral view; narrowly triangular, slightly curved mesad in ventral view; represented by pair of slender dorsal arms arising from single anteromesal plate, directed caudad, and with acute apices; transversely wide and longitudinally short ventral sclerite anterior of anteromesal plate of inferior appendages slightly convex at middle, subacute laterally. Phallus tubular with slender bar and 2 spines internally; bar weakly sclerotized, almost 1/3 as long as phallus; spines strongly sclerotized, very short, each 2 times as long as basal width, arranged longitudinally in succession before apex.

Final instar larva ( Figs 14E–14G ). Sclerites dark brown. Head about 0.22 mm wide, body up to 2.0 mm long. Thorax: Setae numbering about 50 on pronotum, 35 on mesonotum, and 20 on metanotum; pair of very short and transversely wide sclerites and pair of small subtriangular lateral sclerites on prosternum and propleura. Abdominal terga I–VIII each with transverse mid dorsal sclerite and dorsolateral pair of small round sclerites. Other features typical of genus.

Case of larva ( Figs 14H, 14I ). Length up to 2.5 mm. Composed of sandy dome-like dorsal valve and silken rectangular ventral valve. Anterior and posterior hoods relatively small, convex, each with tiny notch at middle in most specimens. Other features typical of genus.

Type series. Holotype. Male, RYUKYU ISLANDS, Iriomote-jima: Urauchi-gawa, Kampire-no-taki, 24˚21’ N, 123˚48’ E, 90 m a.s.l., 14.iv.2005, TI & AO (CBM-ZI 166006).

Paratypes. 3 males, same data as holotype (CBM-ZI 166007–166009).

Other specimens. RYUKYU ISLANDS. Iriomote-jima, 2 males, type locality, 29.x.2012, TI ; 3 males, 4 larvae, type locality, 22.iii.2016, TI; 4 males, type locality, 22.x.2016, TI. Ishigaki-jima: 12 males, Mt. Omotodake , small fall along foot path, 20.iii.2016, TI. Yonaguni-jima : 1 male, Nunbaru , 4.iv.2010, N. Shimura.

Distribution ( Fig. 19 ). Ryukyu Islands (Iriomote-jima, Ishigaki-jima, Yonaguni-jima).

Habitat. This species was collected by AO and me at waterfalls and fast flowing streams with large rocks.

Ethymology. The name “ urauchi ” is a noun in apposition, coined from the type locality.

Japanese name. Urauchi-kaku-himetobikera.

Figures

FIGURE 14. Stactobia urauchi sp. nov. Male, final instar larva, and case. 14 A – 14 D, male: 14 A, abdominal segments VII – X, left lateral; 14 B, abdominal segments IX – X, dorsal; 14 C, same, ventral; 14 D, phallus, left lateral. 14 E – 14 G, final instar larva: 14 E, right half of thorax, dorsal; 14 F, pro- and mesosterna, ventral; 14 G, abdominal segments I – III, dorsal. 14 H, 14 I, case: 14 H, dorsal; 14 I, ventral. Specimens: Iriomote-jima, Kampire-no-taki (type locality). Scale bars: 0.1 mm for 14 A; 1.0 mm for 14 H & 14 I.

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