Key to species of Demotina from Vietnam

(with well-developed transverse anterior impression on the pronotum, lateral sides of pronotum not serrate and thickened fore and hind femora)

1. Pronotum widest in basal third, with unevenly rounded sides, forming narrow rounded angle in basal third. Elytra without X- shaped blackish pattern................................................................................. 2

- Pronotum widest slightly behind middle, with rather evenly rounded sides. Elytra with or without X-shaped blackish pattern.................................................................................................... 3

2. Larger (body length 4.4–5.2 mm). Pronotum less transverse, 1.43–1.55 times as wide as long (Figs. 1–2). Aedeagus with roundly truncated apex (Figs 23–24). Northern Vietnam ........................................ D. sapensis sp. nov

- Smaller (body length 2.6–3.4 mm). Pronotum more transverse, 1.6–1.8 times as wide as long (Fig. 4). Apex of aedeagus nar- rower (Figs 27–28). Central Vietnam .............................................. D. vietnamica Eroshkina, 1992

3. Elytra without X-shaped blackish pattern (Fig. 5). Pronotum darker than elytra. Body length 3.3–4.5 mm. Aedeagus with trian- gular apex (Figs 29–30) Central Vietnam ............................................... D. weisei Eroshkina, 1992

- Elytra with X-shaped blackish pattern. Pronotum no darker than elytra. Body length 4.4–5.2 mm ...................... 4

4. Aedeagus apically stretched tongue-like (Figs 25–26). General view as in Fig. 3. Body length 3.9–4.4 mm. Northern Vietnam ......................................................................... D. medvedeviana Moseyko, 2006

- Aedeagus with roundly truncated apex (Figs 21–22). General view as in Fig. 6. Body length 4.4 mm. Northern Vietnam ..................................................................................... D. rufonotata (Pic, 1924)