Abstract
This is the first part of the taxonomic study on the species group of S. cephalotes SHARP of the genus Stenus LATREILLE, 1797. First, eleven species groups of Stenus that I created in 1988 to 1990 and their related problems are discussed. Second, the species group of S. cephalotes, together with its diagnostic characters and component species are discussed in detail. Eight species (i.e., S. bosatsu NAOMI; S. hagoromo NAOMI; S. intermixtus PUTHZ; S. uneme NAOMI; S. hime NAOMI et PUTHZ; S. kajika NAOMI et PUTHZ; S. satsuki NAOMI et PUTHZ; and S. hotei NAOMI), which have hitherto been regarded as members of the subgenus Hemistenus under a traditional classification of Stenus, are here all considered to belong to the species group of S. cephalotes. Third, ten known species are redescribed in detail; and six new species are described from Japan as follows: S. matobai from Wakayama Pref; S. coffeatus from Kochi Pref; S. hoshinai from Ishikawa Pref; S. ferus from Mie Pref; S. acutatus from Mie Pref; and S. jamesashei from Shiga Pref.
https://ror.org/053se7r61 
