Zaitzeviaria ovata (Nomura, 1959)

(Figs 1D, 6, 18E, 20C)

Materials examined. JAPAN: [HONSHU]: 7 larvae, Miyama-gawa, Manda, Izumo-shi, Shimane Pref., Honshu, 23.xii.2017, M. Hayashi leg. 2 larvae, Inu-dani, Nishihayashigi, Izumo-shi, Shimane Pref., Honshu, 20.i.2018, M. Hayashi leg.

Description. Body length of mature larva ca. 3.0 mm in expanded specimen.

Body elongate, narrowing from thorax to apex; convex dorsally and flattened ventrally; subtriangular in cross section; spiracles on mesothorax and abdominal segments I–VIII. Body color light brown to brown, and appendages yellowish brown. Dorsal and ventral surfaces not smooth with minute flat granules (Fig. 6D: 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 simple long setae (Fig. 18E). Prothorax wider than long, 2 times as long as mesothorax; with glabrous areas on basal half; 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 coarse and minute granules; pleural sclerites on segments I–VII. Last segment (segment IX) longer than wide, gradually narrowing to apex; tergal surface with minute granules and coarse granules sparsely; without ridge on both sides (Fig. 6E); with longitudinal ridge on meson; apex truncate and slightly dentate; ventrally flat, with subpentagonal-shaped operculum, opercular claws, and anal gills.

Habitat. Headwaters to upper stream reaches; larvae live in the gravel and/or sand substrate.

Identification. The larva was identified by mitochondrial DNA sequences (Hayashi & Sota 2010).

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

Bibliography. Hayashi & Sota (2010: fig. 13).