Microptila orienthula Kjaerandsen and Ito

(Figs 1, 4 A, 5)

Microptila orienthula Kjaerandsen and Ito 2009, 177–180, male, female, Japan (Hokkaido, Honshu); Nishimoto and Nishimoto 2014, 63, Japan (Honshu).

Male. Length of each forewing and hind wing 1.6–2.2 mm and 1.4–1.8 mm, respectively (n = 4). Antennae each 19-segmented and 0.6–0.9 mm long (n = 4).

Genitalia (Figs. 1 B–1G). Segment IX (IX) annular, dorsally with deep and wide triangular excision at anterior margin, posterior margin with shallow and wide concavity, transverse tergal bridge very narrow, dorsal midline about 1/10 as long as segment IX in dorsal view (Fig. 1 C); in ventral view (Fig. 1 D) anteroventral margin with shallow triangular concavity, posteroventral margin with deep wide concavity. Tergite X (t X) quadrate with large median triangular concavity caudally in dorsal view (Fig. 1 C), semimembranous and transparent, lateral margins lightly sclerotized. Subgenital plate (sg plate) semimembranous with slightly sclerotized lateral margins, twice as long as tergite X (Figs. 1 B, 1C), long ovate with tiny U- or V-shaped excavation caudally in dorsal view (Fig. 1 E). Inferior appendages (inf app) well developed, setose, without any branches, each with basal 2/3 stout, tapered in distal 1/3 (Figs. 1 B, 1D), apex in ventral view incurved and acute (Fig. 1 D), in ventromesal view (Fig. 1 F) basal 2/ 3 with longitudinal setose ridge mesally and apical 1/3 triangular with strongly sclerotized dorsomesal edge. Phallus elongate, with slender titillator (ti) arising near apical 1/3, wrapped around phallus 1.5 times (Fig. 1 G).

Female. Length of each forewing and hind wing 1.3–1.8 mm and 1.3–1.6 mm, respectively (n = 4). Antennae each 18-segmented and 0.4–0.6 mm long (n = 4).

Abdominal segments I–VII densely covered with long thick setae. Segment VII (VII) tergite and sternite fused laterally, conical in ventral view (Fig. 1 H). Segment VIII (VIII) almost as long as segment VII, often withdrawn into segment VII, ventroposterior margin slightly protruded in some specimens (Figs. 1 H–1J).

Specimens examined. Type specimens: 3 males, 2 females, Japan, Hokkaido, Shiriuchi-cho, hygropetric zone beside Idesu-gawa, 12.vii.2008, T. Ito (CBM-ZI 135131–135135, on slides).

Additional records (other than those of Kjaerandsen and Ito 2009): Japan, Honshu, Niigata: 42 males, 12 females, Itoigawa-shi, Kotaki-gawa, 300–400 m above sea level (a.s.l.), 14.viii.1998, T. Hattori . Toyama: 3 males, Nanto-shi, Taira-mura, Nashidani-gawa, 450 m a.s.l., 30.vii.1995, T. Hattori . Shizuoka: 10 males, 2 females, Shizuoka-shi, Nyujima, 400 m a.s.l., hygropetric zone, 5.vii.1989, T. Hattori ; 10 males, same locality, 11.vi.1999, T. Hattori; 2 males, same locality, 18.vi.2001, T. Hattori; 18 males, 2 females, Shizuoka-shi, Yugashima, 400 m a.s.l., hygropetric zone, 30.viii.2005, T. Hattori ; 3 males, 1 female, Shizuoka-shi, Akazawa, hygropetric zone, 2.ix.2009, T. Hattori; 1 male, same locality, 19.ix.2013, T. Hattori & T. Ito; 9 males, 4 females, Hamamatsu-shi, Komyo-san, 29.viii.2009, T. Torii. Aichi: 5 males, 2 females, Shinshiro-shi, Horai, 4.viii.1998, H. Nishimoto . Shiga: 2 males, Higashi-omi-shi, Eigenji, Kanzaki-gawa, hygropetric zone near Kazakoshi-bashi, 9.ix.2014, T. Ito; 8 males, 1 female, same locality, 11.vi.2016, T. Ito. Shikoku, Kochi: 2 males, Tosa-shimizu-shi, Akasho, small stream, 21.v.1999, T. Ito & A. Ohkawa. Kyushu, Nagasaki: 1 male, Isahaya-shi, Korai-cho, Todoroki-kyo, 18.ix.2000, A. Ohkawa. Yakushima: 1 male, 2 females, Nagata, Hamanaka, Nakano-bashi, 30.viii.1986, Y. Takemon; 1 female, unnamed tributary of Miyanoura-gawa, 10.v.2006, T. Ito.

Remarks. The males of this species are distinguished from other congeneric species by the large, stout inferior appendages and long oval subgenital plate with tiny U- or V-shaped excavation apically.

Habitat (Fig. 4 A). Adults of this species were collected from hygropetric zones and fast flowing streams with large rocks.

Distribution (Fig. 5). Japan (Hokkaido, Honshu, Shikoku, Kyushu, Yakushima). New to Shikoku, Kyushu and Yakushima.

Japanese name. Mikuro-himetobikera.