Indicator Value of Freshwater Leeches (Hirudinea) with a Key to the Determination of European Species

For the 33 species of Hirudinea in the fresh waters of Central Europe the following saprobiological data are given: saprobic valency, indicative weight and specific saprobic index. A detailed key is established for determining the 33 species, with a large number of pictures. All the species have a relatively wide range of ecological valency, so that their application for determining the degree of saprobity is meaningful only in connection with different types of indicators.