Zaitzevia aritai Satô, 1963

(Figs 2A, 11, 19B)

Materials examined. JAPAN: [RYUKYU]: 4 larvae, Shirahama-rindô, Taketomi-chô, Okinawa Pref., Iriomotejima, Ryukyu, 4.iii.2018, Y. Ishida & R. Morimoto 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 brown, and appendages light brown. Dorsal and ventral surfaces entirely not smooth with flat granules (Fig. 11D; 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. 19B). 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. 11E); with longitudinal ridge on meson; apex notched; ventrally flat, with subpentagonal-shaped operculum, opercular claws, and anal gills.

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

Identification. The larva was identified by association with adult Z. aritai from Shirahama-rindô, Iriomotejima Island. Two species of Zaitzevia occur on the island but only Z. aritai occurs within the locality.

Distribution. Yaeyama Islands: Iriomote-jima Is. (type locality), Ishigaki-jima Is.

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