Aim of this study was to investigate the presence and distribution of Hydraenidae in relation to selected abiotic parameters in a single, uniform riffle of the Caramagna Stream (northwestern Italy). Six species belonging to the genus ofHydraenaKugelann, 1794 were found (H. andreiniiD'Orchymont, 1934,H. subimpressaRey, 1885,H. assimilisRey, 1885,H. heterogynaBedel, 1898,H. truncataRey, 1884 andH. devilleiGanglbauer, 1901), with evident niche preferences. Our study provided interesting information about ecological requirements of minute moss beetles at small-scale and evidenced that maintaining elevate habitat diversity is essential to preserve high species abundance at local scale. [ABSTRACT FROM AUTHOR]