Calambus C. G. Thomson 1859

Key to the known species of Calambus C.G. Thomson, 1859 of the Palaearctic region

1. Punctation of pronotum sparse and fine, intervals between punctures on average more than 1–2 diameters of one puncture. Male antenna more weakly serrated, antennomeres 5 to 10 at least 1.4–1.5 times as long as wide....................... 2

- Punctation of pronotum dense and coarse, intervals between punctures on average equal to 1–2 diameters of one puncture or less. Male antenna more strongly serrated, antennomeres 5 to 10 less than 1.4 times as long as wide.................... 7

2. Hind angles of pronotum strongly elongate and slender, 2 times longer than wide. Head and thorax black; elytra brown. Body length 7.9 mm. China: Yunnan........................................................... C. angulatus sp. nov.

- Hind angles of pronotum short and broadened, about as long as wide............................................. 3

3. Punctation of pronotum denser, intervals between punctures equal to 1–3 diameters of one puncture. Head and thorax usually black, rarely brown or dark brown; elytra usually black, with yellow-reddish patch on each elytron near base; rarely elytra entirely black or yellow-reddish. Body length 6.5–8.8 mm. Europe, Turkey, Western Siberia...................................................................................................... C. bipustulatus (Linnaeus, 1767)

- Punctation of pronotum sparser, intervals between punctures equal to 2–5 diameters of one puncture.................... 4

4. Antenna longer, reaching hind angles of pronotum. Body black or brown; elytra with yellowish-brown patch on each elytron near base. Body length 7–8 mm. Russia: Primorsky Krai................................. C. jureceki Stepanov, 1930

- Antenna shorter, not reaching hind angles of pronotum. Body from black to brown; elytra without patches............... 5

5. Antenna more strongly serrated, antennomere 4 almost triangular, less than 1.5 times as long as wide. Pronotum narrower, longer than wide. Body black. Body length 6.5–9 mm. Japan: Honshu, Shikoku, Tsushima...... C. japonicus (Fleutiaux, 1902)

- Antenna less strongly serrated, antennomere 4 almost conical, more than 2 times longer than wide. Pronotum wider, slightly wider than long....................................................................................... 6

6. Antenna slightly shorter, antennomeres 5–10 more expanded and shorter, less than 1.5 times as long as wide. Pronotum and elytra less convex. Body from blackish brown to brown. Body length 7.3–8.6 mm. Russia: Sakhalin, Kuril Islands; Japan: Hokkaido............................................................................ C. kusuii Ôhira, 1994

- Antenna slightly longer, antennomeres 5–10 narrower and longer, at least 1.5 times as long as wide. Pronotum and elytra more convex. Body from blackish brown to brown. Body length 7–9.5 mm. Japan: Hokkaido, Honshu, Shikoku, Kyushu; records for Russia (Sakhalin, Kuril Islands) apparently based on misidentifications...................... C. mundulus (Lewis, 1879)

7. Punctation of pronotum simple; basal median impression of pronotum wide and long. Scutellum tongue-shaped. Elytral striae more convex. Body blackish brown, sometimes pale brown. Body length 8–10 mm. Russia: from Western Siberia to Sakhalin........................................................................... C. ussuriensis (Denisova, 1948)

- Punctation of pronotum umbilicate; basal median impression of pronotum narrow and short. Scutellum elongate oviform. Elytral striae less convex. Body black; pronotum reddish brown laterally; elytra yellowish laterally. Body length 8–10 mm. China: Yunnan.......................................................... C. yunnanensis Schimmel & Tarnawski, 2017