Stactobiella tshistjakovi

Stactobiella tshistjakovi (Arefina & Morse 2002)

(Figs 1, 6)

Stactobia tshistjakovi Arefina & Morse in Arefina et al. 2002, 103–104, male, Russian Far East (Khasansky); Arefina & Armitage 2003, 17, Russian Far East (Sakhalin).

Stactobiella tshistjakovi: Arefina 2004, 209; Ito et al. 2010, 57, Japan (Hokkaido); Ito 2013, 51, 80, Japan (Hokkaido); Potikha & Vshivkova 2016, 364, Russian Far East (Primorye); Ito 2017, 40, Japan (Hokkaido); Ito 2018, 508, 511, Japan (Hokkaido).

Revised description. Adult. Wings brown, some light brown patterning in forewings, but often indistinct in alcohol; light brown dots absent in hind wings. Wing length: males (n=5), forewings each 1.8–2.0 mm and hind wings each 1.6–1.8 mm; females (n=5), forewings each 2.0– 2.2 mm and hind wings each 1.8–1.9 mm. Antennae brown; in male (n=5), each 18-segmented, 0.8–1.1 mm long; in female (n=5), each 18-segmented, 0.6–0.7 mm long. Short ventral process on abdominal segment VII in male and on VI in female.

Male (Figs 1 A–1F). Segment IX smaller than segment VIII, with pair of long anterior apodemes. Segment X membranous, subquadrate with pair of heavily sclerotized hook-shaped rods near ventral edges internally. Subgenital plate bar-like, arising from above bases of inferior appendages, directed caudad, subacute apically. Inferior appendages narrowly triangular in ventral view, without any humps or branches, each with 4 long setae near base, curved mesad and with 2 fine setae subapically. Aedeagus divided at basal 3/5, semi-membranous at apical 1/5, beak-like apically; paramere arising at basal 3/5, directed caudad, slightly shorter than aedeagus.

Female (Figs 1G, 1H). Tergite and sternite of segment VII fused laterally. Segments VIII–X without any surface sclerites. Segment VIII with about 20 marginal setae. Vaginal apparatus long lozenge-shaped in ventral view, mushroom-shaped in lateral view.

Specimens examined. Russia, central Sakhalin: 7 males, 12 km from Tymovskoye Town, 6.viii.2001, B. Martin & N. Minakawa. Japan, Hokkaido: 4 males, 30 females, Horokanai-cho, Shumarinai, Shumarinai-gawa, small tributary, 7.vii–3.viii.2016, T. Ito, Malaise trap & light pan trap; 6 males, 33 females, Shibecha-cho, Shirarutoro-etoro-gawa, Tomi-bashi, 25.vii.2008, T. Ito, light trap; 17 females, same locality, 16.vii.2009, T. Ito, light trap; 1 male, 5 females, same locality, 28.vii.2012, T. Ito, light trap; 10 males, 15 females, Shibecha-cho, Shirarutoro-etoro-gawa, 17 m above sea level, 16.vii.2009, T. Ito, light trap; 1 female, Eniwa-shi, Ichankoppe-zawa, 200 m above sea level, 15.vii.2000, T. Ito, light trap; 2 males, 2 females, Otaru-shi, Okusawa-suigenchi, 29.vii.1996, Y. Sasaki & F. Takahashi, (mounted on slide by N. Kuhara; deposited in personal collection of N. Kuhara); 5 males, Kuromatsunai-cho, Utasai-gawa, tributary, 100 m above sea level., 16.vii.2005, N. Kuhara (deposited in personal collection of N. Kuhara); 1 male, Nanae-cho, Onuma-choshi-guchi, 23.vi.2003, T. Ito, net sweeping. Honshu, Iwate: 1 male, Oshu-shi, Koromogawa-ku, Omori, Misawa-gawa, Tatsumi-bashi, 19.vi.2017, T. Ito, light pan trap. Shiga: 6 males, 1 female, Higashi-omi-shi, Kanzaki-gawa, Kazakoshi-dani, 29.v.2015, T. Ito, light trap.

Remarks. The male of this species is distinguished from those of congeneric species by the hook-shaped rods of segment X, the almost straight form of the subgenital plate, the narrowly triangular inferior appendages with beak-like apices and the distallybifurcate aedeagus with a straight paramere. The female is described for the first time.

Distribution (Fig. 6). Russian Far East (Primorye, Sakhalin), Japan (Hokkaido, Honshu). New to Honshu.

Habitat. Adults of this species were collected beside small stony streams.

Japanese name. Sawa-himetobikera.