Binhon atrum Pic, 1922, an enigmatic genus and species described in the family Dascillidae based on a single female from Vietnam, is illustrated, diagnosed and formally synonymised with Plastocerus thoracicus Fleutiaux, 1918 (Elateridae: Plastocerinae). The species is recorded from China (Guangxi, Yunnan) for the first time. The taxonomic history of the genus Plastocerus Schaum, 1852 (not Plastocerus LeConte, 1853) with emphasis on its synonyms, is briefly summarised.