Stactobia chichibu, Ito, 2017

Ito, Tomiko, 2017, The genus Stactobia McLachlan (Trichoptera, Hydroptilidae) in Japan, Zootaxa 4350 (2), pp. 201-233 : 219-222

Stactobia chichibu sp. nov.

( Figs 12 , 19 )

Diagnosis. This species belongs to the S. nielseni Species Group. The male of this species is somewhat similar to that of S tactobia risiana Schmid 1959 , described from Pakistan, in having thin triangular inferior appendages in ventral view, but clearly differs from S. risiana by the shape of the dorsal arms of the inferior appendages: A slender bar is present in this species, but absent in S. risiana .

Description. Male ( Figs 12A–12E ). 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 1.2–1.3 mm, respectively (n = 5). Tibial spur formula 1, 2, 4.

Genitalia. Tergite VII as long as sternite VII, ventral process long with expanded spiny apex. Tergite VIII longitudinally short, sternite VIII long, 1.5 times as long as tergite VIII. Tergite IX with pair of long anterior apodemes, sternite IX reduced. Tergite X semimembranous, weakly sclerotized dorsolaterally; basal 1/3 broad and tapered, apical 2/3 subrectangular in dorsal view, subacute apically in lateral view. Subgenital appendages absent. Inferior appendages slender, triangular, slightly curved mesad in ventral view; slender dorsal arms arising from anterodorsal edges, directed caudad, apices round in lateral view and acute in ventral view. Phallus long, almost straight, rounded apically; slender bar and 2 spines apically; spines strongly sclerotized, very short, 1.5 times as long as basal width, slightly curved, directed caudad.

Final instar larva ( Figs 12F–12H ). Sclerites dark brown. Head 0.22 mm wide, body 1.9 mm long (n = 1). Thorax: Setae of nota numbering about 35, 30, and 30, respectively; very short, transversely wide sclerite ventrally on prosternum. Abdominal tergum I with transverse mid dorsal sclerite and pair of small round sclerites dorsolaterally. Other features typical of genus.

Case of larva ( Figs 12I, 12J ). Length up to 2.2 mm. Composed of sandy, dome-like dorsal valve and silken rectangular ventral valve. Anterior and posterior hoods gently convex at middle, nearly semicircular in outline, without middle slit or notch or projection. Other features typical of genus.

Type series. Holotype. Male, HONSHU, Saitama, Chichibu-shi, Otaki, Tochimoto, small stream, 35˚56’ N, 138˚51’ E, 670 m a.s.l., 19.v.1998 (larva), reared and emerged until 19.vi.1998, TI & AO (CBM-ZI 165999).

Paratypes. 3 males, same data as holotype (CBM-ZI 166000–166002).

Other specimens. HONSHU. Saitama: 4 males, same data as holotype ; 1 pupa, 1 larva, type locality, 19.v.1998, TI & AO. Yamanashi: 1 male, Minobu-cho, Ohjiro, seep, 430 m a.s.l., 23.viii.2009, TN ( PTN) ; 1 male, Minobu-cho, Ojiro, 960 m a.s.l., 23.viii.2009, TH; 2 males, Minobu-cho, Ojiro, 460 m a.s.l., 12.vi.2010, TH. Shizuoka: 1 male, Shizuoka-shi, Nyujima, hygropetric zone, 11.vii.1999, TH ; 2 males, same locality, 28.vii.2005, TH. SHIKOKU . Tokushima: 5 males, Naka-cho, Konose-kyo, hygropetric zone, 22.v.2008, MT & TI . Kochi: 9 males, Yuzuhara-cho, Ushiro-betto, 15.v.2010, MT.

Distribution ( Fig.19 ). Honshu (Saitama, Yamanashi, Shizuoka); Shikoku (Tokushima, Kochi).

Habitat. Larvae of this species were collected by the colleagues above and me in hygropetric zone and seep habitats.

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

Japanese name. Chichibu-kaku-himetobikera.

Figures

FIGURE 12. Stactobia chichibu sp. nov. Male, final instar larva, and case. 12 A – 12 E, male: 12 A, abdominal segments VII – X, left lateral; 12 B, abdominal segments IX – X, dorsal; 12 C, same, ventral; 12 D, left inferior appendage, left dorsolateral; 12 E, phallus, left ventrolateral. 12 F – 12 H, final instar larva: 12 F, right half of thorax, dorsal; 12 G, pro- and mesosterna, ventral; 12 H, abdominal segments I – III, dorsal. 12 I, 12 J, case: 12 I, dorsal; 12 J, ventral. Specimens: Saitama, Chichibu-shi (type locality). Scale bars: 0.1 mm for 12 A; 1.0 mm for 12 I & 12 J.

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