Abstract
The South American species of the water beetle genus Hydraena Kugelann, 1794, are revised, based on the study and databas-ing of 2,418 specimens. New collection records are provided for 14 previously described species, and 54 new species are described. The South American fauna now comprises 82 species, only three of which are also known to be present outside of South America. Two new species groups are described, and several new species complexes are diagnosed. A neotype is designated for Hydraena paraguayensis Janssens. High resolution digital images of the holotypes of new species are presented, as are images of the primary types of 18 previously described species (online versions in color).
NSTL