Zaitzevia elongata Nomura, 1962

(Figs 1H, 10, 19A)

Materials examined. JAPAN: [RYUKYU]: 1 larva, Kawauchi-kawa, Sumiyo-son, Kagoshima Pref., Amami- Ôshima Island, Ryukyu, 29.vi.2008, M. Hayashi leg. 1 larva, Hatsuno, Amami-shi, Amami- ô -shima, 21.ii.2010, Y. Kamite & H. Torikai leg. 1 larva, Mikyô, Amagi-chô, Tokunoshima, 20.vii.2006, Y. Kamite leg. 1 larva, Yaezô, Isen-chô, Tokunoshima, 26.viii.2013, Y. Kamite leg. 4 larvae, Itokina, Isen-chô, Tokunoshima, 19.vii.2006, Y. Kamite leg. 4 larvae, Ishikiru, Amagi-chô, Tokunoshima, 20.vii.2006, Y. Kamite leg. 2 larvae, Genka-gawa, Nagoshi, Okinawa Pref., Okinawa-jima Island, Ryukyu, 8.ii.2019, Y. Kudo leg. 6 larvae, Genka-ôkawa, Genka, Nagoshi, Okinawajima, 16.v.2007, Y. Kamite leg. 1 larva, Onna, Onna-son, Okinawajima, 16.iii.2015, Y. Kamite leg. 2 larvae, Tanna-take-kita, Iheya-son, Iheyajima, 14.iii.2015, Y. Kamite leg. 3 larvae, Kanegusuku, Kumejima-chô, Kumejima, 20.v.2007, Y. Kamite leg. 2 larva, Suhara-gawa, Kumejima-chô, Kumejima, 20.v.2007, 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. 10D; 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. 19A). 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. 10E); with longitudinal ridge on meson; apex notched; ventrally flat, with subpentagonal-shaped operculum, opercular claws, and anal gills.

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

Identification. The larva was identified by association with adult Z. elongata from Amami-Ôshima and Okinawa-jima Islands, because the Zaitzevia fauna of the islands includes only Z. elongata.

Distribution. Amami-Ôshima Is. (type locality), Tokunoshima Is., Okinawa-jima Is., Kume-jima Is., Iheyajima Is.

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