Key to larvae of species of Japanese Stenelmis, Ordobrevia, Nomuraelmis, and related genera

1. Procoxal cavities not closed posteriorly, without sclerite.................................... Other genera of Elmidae

- Procoxal cavities closed posteriorly, with sclerite(s) (Figs 5 B, 6B)............................................. 2

2. Body flat, slightly convex dorsally and flattened ventrally; meso- and metathorax and abdominal segments I–VIII with blade- like lateral projections on both sides................................................... Leptelmis gracilis Sharp

- Body elongate, semi-cylindrical, gradually narrowing from middle to apex; convex dorsally and flattened ventrally...... 3

3. Last abdominal segment with large flat slope on dorsum; body color dark brown dorsally and cream ventrally, with light spots on head, pro- and mesothorax, dark spots on side of each abdominal segments I–VII.... .. Graphelmis shirahatai (Nomura)

- Last abdominal segment semi-conical without flat slope on dorsum (Figs 5 E, 6E).................................. 4

4. Body surface entirely smooth (Figs 2 A–C, 3D–J)............................................................ 5

- Boby surface entirely or partly not smooth................................................................. 8

5. Body color entirely cream-colored, but with dark band on basal and apical margins in all segments (Figs 2 A, B).......................................................................................... Stenelmis vulgaris Nomura

- Body color entirely orange (Fig. 3 D–J).................................................................... 6

6. One or two teeth on apico-lateral margin of abdominal tergites I–VIII (Fig. 11 H); Scale-like setae on apical margins of thorax and abdominal segments I–VIII (Fig. 11 C)............................................. Ordobrevia gotoi Nomura

- Three to five teeth on apico-lateral margine of abdominal tergites I–VIII (Figs 10 H, 12H)........................... 7

7. Prothorax with long brush-like setae (Figs 12 A, G); brush-like setae on apical margins of thorax and abdominal tergites I–VIII........................................................................... Ordobrevia maculata (Nomura)

- Prothorax with short brush-like setae (Figs 10 A, G); scale-like setae on apical margins of thorax and abdominal tergites I–VIII............................................................................... Stenelmis hayashii M. Satô

8. Ventral surface of abdominal segments I–VIII not smooth (Figs 2 K, 4I, 7D)...................................... 9

- Ventral surface of abdominal segments I–VIII smooth (Figs 3 M, 4C, 13D)....................................... 11

9. Ventral surface of last segment not smooth (Figs 4 I, L, 15F), apical spines of last segment slightly sharpened (Fig. 15 H)............................................................................. Nomuraelmis amamiensis M. Satô

- Ventral surface of last segment smooth (Figs 4 F, 13F, 14F), apical spines of last segment clarity sharpened (Fig. 14 E).... 10

10. Apical spines of last abdominal segment large (Figs 6 E, 7E, 9E)................................................................................. Stenelmis nipponica Nomura, Stenelmis hisamatsui M. Satô, Stenelmis aritai M. Satô

- Apical spines of last abdominal segment small (Fig. 8 E)................................. Stenelmis ishiharai M. Satô

11. Blunt spines on tergite of last abdominal segment in middle area (Fig. 13 E)........... Ordobrevia foveicollis (Schönfeldt)

- Sharp spines on tergite of last abdominal segment (Fig. 14 E)........................ Ordobrevia amamiensis (Nomura)