Zaitzevia aritai Satô, 1963

Hayashi, Masakazu & Kamite, Yuuki, 2020, Description of larvae of Japanese Macronychini (Coleoptera: Elmidae: Elminae), Zootaxa 4859 (2), pp. 195-227 : 219

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.

Figures

FIGURE 2. Macronychini larvae of Japan. A, Zaitzevia aritai Satô, 1963; B, Zaitzevia yaeyamana Satô, 1963; C, Zaitzevia awana (Kôno, 1934); D, Zaitzevia nitida Nomura, 1963; E, Zaitzevia rivalis Nomura, 1963; F, G, Zaitzevia tsushimana Nomura, 1963; H, Urumaelmis uenoi (Nomura, 1961). Scale bar = 1.0 mm.

FIGURE 11. Zaitzevia aritai Satô, 1963. A, Head and prothorax; B, D, prothorax; C, head and pro- and mesothorax; E–H, last abdominal segment. A, B, E, lateral view; C, D, F, G, dorsal view; H, ventral view.

FIGURE 19. Flat granules and setae on prothorax. A, Zaitzevia elongata Nomura, 1962; B, Zaitzevia aritai Satô, 1963; C, Zaitzevia yaeyamana Satô, 1963; D, Zaitzevia awana (Kôno, 1934); E, Zaitzevia nitida Nomura, 1963; F, Zaitzevia rivalis Nomura, 1963; G, Zaitzevia tsushimana Nomura, 1963; H, Urumaelmis uenoi (Nomura, 1961).