Key to the world fauna of Synchroidae Lacordaire, 1859

(after Nikitsky 1999; Hsiao 2015; Hsiao et al. 2016)

1. Procoxae almost contiguous. North America …………………… Mallodrya subaenea Horn, 1888

– Procoxae distinctly separated ………………………………………………………………………2

2. Pretarsal claws serrate ………………………………………………………………………………3

– Pretarsal claws simple ………………………………………………………………………………4

3. Elytra finely and sparsely punctate in apical two-thirds; sutural stria on elytra strongly marked in apical part. Indonesia (Borneo: South Kalimantan) … Synchroina cuneata (Champion, 1916)

– Elytra densely and coarsely punctate; sutural stria on elytra shallower. Malaysia (Kelantan, Perak, Pahang); Indonesia (West Sumatra, Borneo: South Kalimantan) …………………………………… …………………………………………………………… Synchroina tenuipennis Fairmaire, 1898

4. Pronotum slightly narrowed anteriorly (Fig. 2B), distinctly narrower than elytra at humeri (≤ 0.8 times elytral width at humeri); median lobe of the aedeagus clavate, slender, long, exceeding from the tegmen in natural condition. Mainland China (Sichuan) …………………………………………… …………………………………………… Thescelosynchroa pangu (Hsiao, Li, Liu & Pang, 2016)

– Pronotum strongly narrowed anteriorly (Fig. 2A), nearly as long as elytra at humeri; median lobe of the aedeagus tapered, not extending over the tegmen in natural condition ………………………………5

5. Sides of pronotum almost entirely margined; median part of posterior half of pronotum smooth and impunctate.NorthAmerica ……………………………………… Synchroa punctata Newman, 1838

– Sides of pronotum unmargined or only partially margined; median part of posterior half of pronotum not smooth. Asia …………………………………………………………………………6

6. Lateral margins of pronotum not margined …………………………………………………………7

– Lateral margins of pronotum distinctly margined in posterior one-third or one-fourth ………………8

7. Body and legs blackish-brown; parameres slender, basal part of median lobe gradually narrowed apically. Mainland China (Sichuan, Shaanxi, Gansu) …………… Synchroa chinensis Nikitsky, 1999

– Body and legs reddish to dark brown; parameres stout, basal one-fourth of median lobe subparallel. Taiwan …………………………………………………………… Synchroa formosana Hsiao, 2015

8. Antennae, maxillary palpi blackish-brown; body elongate, slender; prosternal process narrowed apically; aedeagus:parameres stout, wide, with lateral sides subparallel or sinuate.Vietnam; Laos …… ………………………………………………………………… Synchroa elongatula Nikitsky, 1999

– Antennae, legs and maxillary palpi reddish-brown; body stout; prosternal process with long oval apex; aedeagus: parameres slender, with lateral sides gradually narrowed apically ……………… ………………………………………………………………… Synchroa melanotoides Lewis, 1895