Stenelmis aritai M. Satô, 1965

Hayashi, Masakazu, Kamite, Yuuki, Kobayashi, Takuya & Sota, Teiji, 2016, Description of larvae of genera Stenelmis, Ordobrevia and Nomuraelmis (Coleoptera: Elmidae: Elminae) of Japan with their molecular taxonomy, Zootaxa 4178 (4), pp. 451-480 : 464

Stenelmis aritai M. Satô, 1965

( Figs 3 A–C, 9)

Material examined. JAPAN: Okinawa Prefecture: Iriomotejima Is.: 2 exs., Aira-gawa (river), 21.iv.2015, N. Shimura leg. ; Yonagunijima Is.: 3 exs. (dried with an ultrathin coating of gold), Tabaru-gawa (river), 1.ii.2013, YK leg.

Description. Body elongate, gradually narrowing from middle to apex; convex dorsally and flattened ventrally; prominent spiracles on mesothorax and abdominal segments I–VIII; middle longitudinal suture present on thorax and abdominal segments I–VII. Body color entirely black or dark brown but around stemmata white, appendages and legs yellowish brown. Dorsal and ventral surfaces not smooth with minute granules and setae, but last segment smooth on dorsal and ventral surfaces.

Head subquadrate, visible dorsally, well exposed from prothorax; as wide as long; clypeus transverse, with branched setae on front; a pair of developed spines on both sides of clypeus; frons and vertex with granules.

Thorax not serrated on lateral sides; dorsum with granules and brush-like setae, not entirely smooth. Prothorax longer than width, 2.5 times as long as mesothorax; glabrous spots on basal half; with three ventral sclerites, procoxae closed posteriorly; two lateral and 1 postero-medial sclerites; pectinate setae on front and hind margins. Meso- and metathorax transverse, with five ventral sclerites, granulated, each granule with a branched seta.

Abdomen 9-segmented; segments I–VIII transverse, granules with branched setae on dorsal and lateral parts, pleural sclerites presented on segments I–VII; tergal sutures on dorso-lateral area of segments II–VII but short in VII. Last segment (segment IX) more or less shiny, longer than wide, gradually narrowing to apex, without longitudinal ridge; apex with a pair of spines; ventral operculum, opercular claws, and anal gills present.

Habitat. The type locality of the species is a small stream where it is abundant on small rocks and in the gravel of riffles ( Hayashi & Kamite 2015).

Identification. The larva of this species was easily determined because the elmid fauna of Yonagunijima includes only S. aritai ( Hayashi & Kamite 2015) .

Distribution. Ryukyu: Iriomotejima Is. (new record), Yonagunijima Is. (type locality).

Bibliography. Hayashi & Kamite (2015: figs. 1–7).

Figures

FIGURE 3. Larvae of Stenelmis and Ordobrevia of Japan. A – C, S. aritai M. Satô; D – F, S. hayashii M. Satô; G – H, O. gotoi Nomura; I – J, O. maculata (Nomura); K – M, O. foveicollis (Schönfeldt). A, D, G, I, K, dorsal view; B, E, H, J, L, lateral view; C, F, M, ventral view. Scale bars: 1.0 mm.