Zaitzevia nitida Nomura, 1963

(Figs 2D, 14, 19E)

Materials examined. JAPAN: [HONSHU]: 2 larvae, Hirose, Ibigawa-cho, Gifu Pref., 12.vi.2005, Y. Kamite leg. 1 larva, Mandokoro-chô, Higashiômi-shi, Shiga Pref., 28.iv.2013, Y. Kamite leg.

Description. Body length of mature larva ca. 4.0 mm in expanded specimen.

Body elongate, narrowing from thorax to apex; convex dorsally and flattened ventrally; semicircular in cross section; spiracles on mesothorax and abdominal segments I–VIII. Body color black or dark brown, and appendages orange colored. Dorsal and ventral surfaces entirely not smooth with flat granules (Fig. 14D; Kodada et al. 2016: 583) and various types of setae.

Head visible from above, well exposed from prothorax; as wide as long; clypeus transverse, setose; without a pair of spines on both sides of clypeus (frontal tooth); vertex rugose with brush-like setae; eyes large but lens of stemmata absent. Antenna with three antennomeres; antennomere 1 shorter than antennomere 2, with short branched setae; antennomere 2 with long sensorial appendage; antennomere 3 short with small sensorial appendage. Maxillae and labium forming a unit (maxillolabial unit). Maxilla with three palpomeres; cardo small; stipes large; galea and lacinia separate, setose apically. Labium narrow with two palpomeres; ligula short and transverse; mentum long; submentum short and transverse.

Thorax not serrated on lateral sides; dorsum entirely not smooth with granules and flat brush-like setae (Fig. 19E). Prothorax wider than long, 2 times as long as mesothorax; with glabrous smooth area on dorsum; with seven ventral sclerites (one between coxae, two anteromedial, two anterolateral, and two posterolateral), procoxae not closed posteriorly; flat feather-like setae on hind margins. Meso- and metathorax transverse; metathorax slightly longer than mesothorax. Meso- and metathorax with five ventral sclerites (one large anteromedial, two anterolateral, and two posterolateral).

Abdomen 9-segmented; segments I–VIII transverse, dorsal surface entirely not smooth with granules; pleural sclerites on segments I–VII. Last segment (segment IX) longer than wide, gradually narrowing to apex; tergal surface with minute and coarse granules; with ridge on both sides (Fig. 14E); with longitudinal ridge on meson; apex notched; ventrally flat, with subpentagonal-shaped operculum, opercular claws, and anal gills.

Habitat. Middle to lower stream reaches; larvae live in the gravel substrate.

Identification. The larva was identified by association with adult Z. nitida from the middle stream in Gifu Prefecture. In the area, the middle to lower stream is populated by Z. nitida only.

Distribution. Hokkaido, Honshu (type locality), Shikoku, Kyushu, Sado Is.

Bibliography. The larva of this species is described here for the first time.