True lateral eye numbers for extant buthids: a new discovery on an old character

This study reports the results of a re-analysis of the number of lateral eyes in extant buthids. Specimens studied were confined mostly to those from China and the adjacent areas. 353 specimens belonging to 20 species (subspecies) and 8 genera were rechecked and found to have 5 pairs of lateral eyes contrary to earlier published works which reported the presence of 3 pairs of lateral eyes only. Combined with reported examples collected through reference investigation including 63 species from 16 genera, our study here shows a total of 79 species from 21 genera of scorpions spanning Asia and Africa had 5 pairs of lateral eyes. Reasons for not observing the presence of the extra lateral eyes are discussed and new protocols for examining specimens including using UV light are proposed to aid lateral eye recognition. Besides, a majority of genera in Buthidae are suggested to be in "Five-eye" model and a re-examination of all previously published taxonomic studies of buthid species is highly recommended.