Osmylus (Osmylus) hyalinatus McLachlan, 1875

(Figs 15, 18–19, 24, 27, 30–31, 36, 39–40)

Osmylus hyalinatus McLachlan, 1875, 181.

Other synonyms see Sekimoto & Yoshizawa (2011).

Description of 3rd instar larva. BL 10.8–18.0 (13.3, n = 16) mm.

Coloration. Head light brown, except for black colored stemmata and its surrounding parts; legs light yellow; dorsal side of thorax and abdomen basically light gray to gray; surrounding parts of DPa2 and DPm2 on meso- and metathoraces light brown; ventral side of thorax light yellow; surrounding parts of tubercles from metathorax to 8th abdominal segment yellow; sclerites brown; 9th and 10th abdominal segments and its sclerites light brown, subhyaline.

Head (Fig. 15). Mandiblomaxillary stylets rather short, about 2.0 times as long as head capsule length; ML/ CW 2.3–2.4 (2.3, n = 16). Frontal edge of cranium with 15–20 short setae (n = 6), without pores. Antennae 39 or 40 segmented (n = 2).

Prothorax (Fig. 18): DPc trapezoidal, separated with DM, its setae in middle part long, 1st to 3rd setae from within in posterior margin long. Mesothorax (Figs 18–19): DPm1 present; two short seta bearing on DPm2; DPm2 somewhat wide, its seta on anterior margin long; a seta on DPp1and DPp2 long. Metathorax (Figs 18–19): DAa expanded; DAm2 and DAm3 separated.

First abdominal segment (Fig. 24): DM1 absent; DM2, DPp1, and DPp4 roughly the size of DPp2; a seta on DM2, DPp1, and DPp4 long; DPa present; a seta in dorso-anterior part of LP long. Second to 5th abdominal segment (Fig. 24): DM3 absent; a seta on LA long. Sixth abdominal segment (Fig. 24): VM3 absent; other character states same to 2nd to 5th abdominal segments. Seventh abdominal segment (Fig. 27): VM3 absent. Eighth abdominal segment (Fig. 24): DPp1+DPp2 with a pore on anterior margin. Ninth abdominal segment (Figs 30–31): Dc bearing 7 pairs of long setae in posterior half margin; outer setal row on VPc composed of 2 setae and a pore in exterior margin.

Material examined. 2 exs., Takao-san, Takao-machi, Hachiôji-shi, Tokyo, 23.ii.2011 (collected in 3IL), 2.iv.2011 / 26.iii.2011 (PP), 15.iv.2011 / 7.iv.2011 (EM), S. Matsuno leg. ; 2exs., Morito-gawa, Hayama-machi, Miura-gun, Kanagawa Pref., 24.ii.2011 (collected in 3IL), 15.iv.2011 / 15.iv.2011 (PP), 26.iv.2011 / 27.iv.2011 (EM), S. Matsuno leg. ; 1 ex., (3IL), Kunigami, Bunsui-cho, Niigata Pref., 13.iii.2007, M. Hayashi leg. ; 2 exs., (2 3IL), Shinjô, Daitô-cho, Unnan-shi, Shimane Pref., 8.viii.2007, M. Hayashi leg. ; 2 exs., Hijiri-ko campsite, Kitahiroshima-chô, Yamagata-gun, Hiroshima Pref., 30.iv.2011 (collected in 3IL), 15.v.2011 / 17.v.2011 (PP), 24.v.2011 / 26.v.2011 (EM), S. Matsuno leg.; 5 exs. (1 2IL & 4 3IL), Kanmuri-kôgen, Yoshiwa, Hatsukaichi-shi , Hiroshima Pref., 25.ix.2010, M. Sakamoto leg.; 1 ex., Saragamine, Tôon-shi, Ehime Pref., 12.vi.2009 (collected in 3IL), 7.vii.2009 (PP), 21.vii.2009 (EM), R. Ogawa leg. ; 1 ex. (3IL), same locality, 6.iii.2009, H. Yoshitomi leg.; 2 exs. (3IL), same locality, 26.iii.2009, S. Matsuno leg.; 7 exs. (5 1IL & 2 3IL), same locality, 11.x.2010, S. Matsuno leg.; 1 ex. (3IL), same locality, 26.x.2010, S. Matsuno leg.; 1 ex. (2IL), Omogokei, Kumakôgen-chô, Ehime Pref., 19.viii.2010, S. Matsuno leg. ; 3 exs. (2IL), same locality and collector, 14.ix.2010; 2 exs. (3IL), same locality and collector, 23.xi.2010; 1ex., Omogo-kei, same locality, 7.iii.2011 (collected in 3IL), 8.iv.2011 (PP), 21.iv.2011 (EM), S. Matsuno leg.; 3 exs. (1 2IL & 2 3IL), same locality, 13.xi.2011, S. Matsuno leg.; 2 exs., Komeno-machi, Matsuyama-shi, Ehime Pref., 12.iv.2009 (collected in 3IL), 20.iv.2009 / 21.iv.2009 (PP), 30.iv.2009 / 1.v.2009 (EM), S. Matsuno leg. ; 3 exs. (3IL), Sugesawa-machi, Matsuyama-shi, Ehime Pref., 7.xii.2011, S. Matsuno leg. 3 exs. (2IL), Higashino, Matsuyama-shi , Ehime Pref., 3.xi.2011, S. Matsuno leg.

Remarks. This species is similar to the sympatric species, O. (O.) pryeri, in general appearance (e.g., coloration of body), but clearly differs from it in the shorter mandiblomaxillary stylets (Fig. 36).

Biological notes. This is the most common species in Japan, and collected from ca. 100–1,000 m in altitude. They frequently hide in pockets under waterlogged decayed wood lying in small and shallow streams (Figs 39–40). In some cases, they were collected from under stones or in moss in a stream.

The pupal periods are 10–12 days (10.7 days in average) in a rearing condition of under 22? (n = 3), 9 days under 20? (n = 2), and 11–13 days (12.2 days in average) under 18? (n = 5).

Distribution. Japan (Hokkaidô, Rishiri, Kunashir, Honshû, Shikoku, Kyûshû, Yakushima).