Stactobia japonica Iwata 1930

Ito, Tomiko, 2017, The genus Stactobia McLachlan (Trichoptera, Hydroptilidae) in Japan, Zootaxa 4350 (2), pp. 201-233 : 208-213

Stactobia japonica Iwata 1930

( Figs 5 , 6 , 18 )

Stactobia japonica Iwata 1930 , 59, larval syntypes, case, Honshu (Gifu, Nagano). Marshall 1979, 167; Botosaneanu & Nozaki 1996, 54–55, 60, designation of neotype male, habitat, Honshu (Kanagawa, Nagano, Gifu, Shizuoka); Nozaki 1997, 33, 38, Honshu (Kanagawa); Nozaki 2004, 1234, Honshu (Kanagawa); Moriya & Kubota 2012, 135, Honshu (Kanagawa). Lectotype larva, Honshu (Gifu), lectotype by present designation; 2 larvae, paralectotypes, data as for lectotype.

Diagnosis. The final instar larva is distinguished from that of the other species of the S. martynovi Species Group described here by the presence of a pair of small round sclerites ventrolaterally on the prothorax, the prosternite with a pair of transversely wide sclerites near the posterior margin, and a pair of very thin, transversely wide sclerites near the posterior margin of the mesosternite. It is also distinguished from S. distinguenda Botosaneanu & Nozaki , in the S. nielseni Species Group, found in the type locality and unknown in the larval stage, by their sizes because adults and larvae of the S. nielseni Species Group are distinctly smaller, about 2/3 times the size of those of the S. martynovi Species Group in central Japan.

The male of this species is distinguished from other species by the strongly sclerotized, short, curved, and obliquely angled spine of the phallus.

Description (revised following Iwata 1930). Final instar larva ( Figs 6I –6K ). Sclerites dark brown. Head width up to 0.25 mm, body 2.0– 2.5 mm long. Thorax: Setae of tergites of 3 segments about 20–25, 20–25, and 20, respectively; pair of short transversely wide ventral sclerites at middle of posterior margin of prothorax, pair of small round sclerites ventrolaterally on prosternum, pair of very short transversely wide ventral sclerites at posterior edge of mesosternum. Abdominal tergum I with middle dorsal sclerite and pair of small round sclerites dorsolaterally. Other features typical of genus.

Case ( Figs 6L, 6M ). Length 2.0– 2.5 mm. Composed of sandy, dome-shaped dorsal valve and silken, rectangular ventral valve, dorsal valve longer than ventral one, completely sealing larva; nearly rectangular with gently convex lateral margins in dorsal and ventral views. Anterior and posterior hoods relatively small, with median slit at each outer margin. Other features typical of genus.

Male ( Figs 6A–6H ). Antennae each 18-segmented and 0.9–1.0 mm long (n = 5). Length of each forewing and hind wing 1.8–2.0 mm and 1.6–1.7 mm, respectively (n = 5). Tibial spur formula 1, 2, 4.

Genitalia. Tergite VII as long as sternite VII, sternite VII slightly expanded at anterior margin in lateral view, ventral process long with expanded spiny apex. Tergite VIII as long as sternite VIII. Tergite IX with pair of long anterior apodemes, sternite IX reduced. Tergite X semimembranous with weakly sclerotized border dorsolaterally. Subgenital appendages small, round and heavily sclerotized at mesal edges in ventral view. Inferior appendages small, round and heavily sclerotized at mesal edges, with irregularly convex sclerites in lateral and ventral views. Phallus long, almost straight, flattened and roundish apically; internal spine strongly sclerotized, more or less curved, relatively short, about 10–15 times as long as basal width, oblique cleft visible near middle.

Specimens examined. Lectotype, final instar larva, HONSHU, Gifu, Fukuoka-mura (present address Nakatsugawa-shi, boundary of Shimono and Fukuoka), Otohime-taki Fall (35˚34’ 35” N, 137˚27’ 53”E, 375 m a.s.l.), viii.1928, I. Niwa (KUM In 0 77, small vial with lectotype label). Paralectotypes, 2 final instar larvae, same data as lectotype (KUM In 0 77, small vials with paralectotype labels).

Other specimens. HONSHU. Iwate: 32 males, Kitakami-shi, Kiuchi-gawa, small tributary, 330 m a.s.l., 20.vi.1997, TH . Miyagi: 3 males, Sendai-shi, Futakuchi, Natori-gawa, 400–500 m a.s.l., 7–8.vi.1974, TH ; 23 males, same locality, 14.ix.2003, TH ; 4 males, Sendai-shi, Futakuchi, Banji-bashi, 500 m a.s.l., 14.ix.2003, TH. Tochigi: 2 males, Kuroishi-shi, Kinomata-gawa, 7.vi.1998, HN . Saitama: 11 males, Chichibu-shi, Otaki-mura, Kudono-sawa, 20.v.1998, TI & AO . Kanagawa: 5 males, Yamakita-machi, Mts. Tanzawa , Naka-gawa, Shiraishizawa, 700–750 m a.s.l., 2–3.vi.1974, TH ; 1 male, Kiyokawa-mura, Nakatsu-gawa, Nuno-kawa, 22.v.1998, AO; 2 males, Matsuda-machi, Sakawa-gawa, Nakatsu-gawa, 22.v.1998, AO. Toyama: 4 males, Nanto-shi, Taira-mura, Kotani-gawa, 450 m a.s.l., 30.vii.1995, TH . Ishikawa: 1 male, Wajima-shi, Makino-machi, Sosogi, 5 m a.s.l., 10.vi.2011, TH . Yamanashi: 1 male, Oizumu-mura, Kawamata-gawa, Toryu-no-taki, 11.vi.1994, TH ; 4 males, Minobu-cho, Oshiro, 960 m a.s.l., 23.vii.2004, TH; 7 males, Minobu-cho, Oshiro, 460 m a.s.l., 12.vi. 201, TH. Nagano: 2 males, Hakuba-mura, Aoni, 830 m a.s.l., 13.viii.1995, TH . Gifu: 7 males, Nakatsugawa-shi, Tase, Yokokawa-dani, 6.vi.1996, TN (4 males in PTN, 3 males in PTI) ; 3 males, same locality , 21.v.1996 (2 pupae, 1 larva), HN & TN, reared and emerged on 30.v–17.vi.1996, TN ( PTN); 1 larva, same locality , 21.v.1996, HN & TN; 1 male, Kokufu-cho, Utsue-gawa, Shijuhachi-no-taki, 28.v.2001, K. Endo; 1 male, Takayama-shi, Nyukawa, Hirayu Tunnel, 20.ix.1998, HN. Shizuoka: 4 males, Shizuoka-shi, Oi-gawa, Itsuha-zawa, 750 m a.s.l., 25.vi.1994, TH ; 7 males, Shizuoka-shi, Umegashima, Sakasa-gawa, small tributary, 1000 m a.s.l., 16.vii.1995, TH; 8 males, Shizuoka-shi, Umegashima, Abe-toge, 1400 m a.s.l., 6.vii.1997, TH; 1 male, Shizuoka-shi, Umegashima, Onsenue, 1000 m a.s.l., 5.viii.2001, TH; 4 males, same locality, 24.ix.2001, TH ; 4 males, Shizuoka-shi, Kuchisakamoto, 935 m a.s.l., 13.v.2002, TH; 1 male, Shizuoka-shi, Yokosawa, Mitsumine, 1080 m a.s.l., 27.v.2005, TH; 2 males, Shizuoka-shi, Umegashima, Minami-sawa, 780 m a.s.l., 28.vi.2005, TH. Aichi: 1 male, Toei-cho, Shimoda, 14.ix.2013, HN . Nara: 1 male, Kawakami-mura, Takahara-gawa, 850 m a.s.l., TH . Okayama: 2 males, Tsuyamashi, Aba, 13.v.2016, KN ; 13 males, Kagamino-cho, Tominishi-dani, Shiraga-keikoku, 26.vi.2016, KN; 5 males, Nishi-awakura-son, Ogaya, 20.vii.2016, KN; 14 males, same locality, 24.vii.2016, KN. SHIKOKU . Tokushima: 28 males, Tsurugi-cho, Ichiu, Kuwadaira, 900–1140 m a.s.l., 25.ix.2002, TH . Ehime: 2 males, Kuma-kogen-cho, Omogo, Ishizuchi, skyline, small waterfall, 25.v.1999, TI & AO ; 1 male, Uwajima-shi, Nametoke-keikoku, 400– 600 m a.s.l., 23.ix.2002, TH; 1 male, Saijo-shi, Yosakoi-toge, hygropetric zone, 20.v.2008, MT & TI. Kochi: 1 male, Ino-cho, Hongawa, Nago-gawa, 900 m a.s.l., 24.ix.2002, TH ; 1 male, Ino-cho, Hongawa, Terakawa, 5.vi.2004, MT; 8 males, Kami-shi, Monobe, Befu-kyo, 650 m a.s.l., 25.iv.2004, TH; 1 male, Kami-shi, Monobe, Nishikuma-keikoku, 25.iv.2004, MT; 2 males, Kami-shi, Monobe, Shirakami-goe, 3.vii.2004, MT; 30 males, Kami-shi, Monobe, Shiraga-toge, 22.v.2008, MT & TI; 3 males, Okawa-mura, Asatani, small waterfall, 500 m a.s.l., 24.ix.2002, TH. KYUSHU. Fukuoka: 4 males, Hoshuyama-mura, Hoshuyama-gawa, headwater, 8.iv.1997, TN ; 1 male, Soeda-cho, Hikosan, 8.x.1998, AO. Nagasaki: 1 male, Takari-cho, Todoroki-keikoku, 300 m a.s.l., 17.ix.2002, TH . Oita: 3 males, Saeki-shi, Ume, Kuzuha, Nagafuchi-gawa, upper reach, 23.v.1993, NK ; 11 males, Kokonoe-machi, Tano, Naruko-gawa, 900 m a.s.l., 18.ix.2002, TH. Miyazaki: 6 males, Nishimera-son, Omata, 440–450 m a.s.l., 21.ix.2002, TH ; 12 males, Tsuno-cho, Osuzu-yama, 750 m a.s.l., 22.iv.2004, TH.

Distribution ( Fig. 18 ). Honshu (Iwate, Miyagi, Tochigi, Saitama, Kanagawa, Toyama, Ishikawa, Yamanashi, Nagano, Gifu, Shizuoka, Aichi, Nara, Okayama); Shikoku (Tokushima, Ehime, Kochi); Kyushu (Fukuoka, Nagasaki, Oita, Miyazaki). Newly recorded for Shikoku and Kyushu.

Habitat. Adults of this species were collected by the above colleagues and me near falls and very fast-flowing streams.

Japanese name. Kaku-himetobikera.

Remarks ( Fig. 5 ) Stactobia japonica was originally described on the basis of a series of larvae collected from Gifu and Nagano, central Honshu, by Iwata (1930). Botosaneanu & Nozaki (1996) designated a male collected from one of the type localities, Otohime-buchi, Shimono, Fukuoka-cho, Gifu, since they believed that the specimens on which Iwata based the original description were entirely lost. They described the male as this species for the first time ( Botosaneanu & Nozaki 1996).

However, Narita et al. (2001) reported larval specimens of S. japonica among the Trichoptera listed in Iwata’s collection. In March, 2017, I examined the specimens in a bottle labeled “In 0 77, Stactobia japonica ”, now deposited in the Kyoto University Museum. Twenty final instar larvae (16 larvae in cases and 4 larvae without cases) and 2 pupae in cases are preserved in a small vial, which bears a label written in Japanese as “Otohime-taki, Fukuoka-mura, Gifu, VIII.1928, Niwa”. The locality, collector and date agree with the specimen data recorded in Iwata’s paper. Since these larvae must be some of the syntypes of S. japonica , the neotype designated by Botosaneanu & Nozaki (1996) is set aside (International Commission on Zoological Nomenclature 1999, ICZN Art. 75.8).

Although most of the larvae are difficult to study in detail due to their bad condition, being dried up, 3 larvae were in reasonable condition for study. I am designating one of these larvae as the lectotype, and the other 2 as paralectotypes. The taxonomic purpose of this lectotype designation is to assure the correct identity of this distinct species in the context of the present revision of Japanese species of Stactobia . The above diagnosis and description are based primarily on the lectotype. Larvae collected from many localities, including a site near the type locality, conform with the lectotype and paralectotypes, so that the associated adults are described and figured here. The identity of the final instar larva described by Tetsukawa (1965) under the name of S. japonica is uncertain at the species level, because his description is mainly of generic features.

Figures

FIGURE 5. Stactobia japonica Iwata 1930. 5 A – 5 C, lectotype final instar larva and case: 5 A, anterior part of larva, right ventrolateral, ventral sclerites of pro- and mesosterna enclosed in oval lines; 5 B, case, dorsal; 5 C, case, ventral. 5 D, a paraleptotype final instar larva and case, right lateral. Scale bars: 0.1 mm for 5 A; 1.0 mm for 5 B – 5 D.

FIGURE 6. Stactobia japonica Iwata 1930. Male, final instar larva, and case. 6 A – 6 H, male: 6 A, abdominal segments VII – X, left lateral; 6 B, abdominal segments VIII – X, dorsal; 6 C, abdominal segments IX – X, ventral; 6 D, phallus, left lateral; 6 E – 6 H, same, variation. 6 I – 6 K, final instar larva: 6 I, right half of thorax, dorsal; 6 J, pro- and mesosterna, ventral; 6 K, abdominal segments I – III, dorsal. 6 L, 6 M, case: 6 L, dorsal; 6 M, ventral. Specimens: 6 A – 6 D and 6 I – 6 M = Gifu, Fukuoka-cho, Yokokawadani; 6 E = Iwate, Kitagami-shi, 6 F = Miyagi, Sendai-shi; 6 G = Toyama, Nanto-shi; 6 H = Kochi, Kami-shi. Scale bars: 0.1 mm for 6 A; 1.0 mm for 6 L & 6 M.

FIGURE 18. Distributions in Japan of 6 species of Stactobia.