Descriptions of two new flightless species of Pseudocsikia Schimmel & Platia (Coleoptera, Elateridae, Dimini) from Taiwan Island, China, with a definition of the formosana species-group.

Two new flightless click beetle species, Pseudocsikiachoui sp. nov. and Pseudocsikiachanjuan sp. nov. , are described and illustrated from Taiwan, China. Their habitus and diagnostic characters are illustrated. The two species most resemble P.formosana , which is endemic to Taiwan, by the strongly protruding pronotal anterior angles accompanied by pits and the shape of aedeagus. They can be all grouped as the P.formosana -species group. A key to the species of the P.formosana -species group and an updated checklist of Chinese Pseudocsikia with supplementary notes on type localities are provided. The discovery of two new species highlights the potential species-richness of the flightless click-beetles on Taiwan Island.