Sawyer, Roy T. (1972). North American freshwater leeches, exclusive of the Piscicolidae, with a key to all species. Illinois Biological Monographs. 46: 1-155.
None. From the introduction: "This monograph is an attempt to revise critically the species of the families Glossiphoniidae, Erpobdellidae, and Hirudinidae, the Piscicolidae having been treated fully by Meyer (1940, 1946a) and Hoffman (1967). This revision entailed examination of 5,000 specimens from over 200 collecting stations in 20 states, although most of the material was from Michigan and Illinois. Hundreds of specimens were examined alive, scores of erpobdellids and hirudinids were dissected, and numerous serial sections and whole mounts were made of the glossiphoniids. Excluding the piscicolids, 40 described species were encountered, plus two new species, and several forms of uncertain taxonomic status were studied. For each species a complete American synonymy has been compiled. The order of presentation in the text follows the chronological order of the original description of the genera and species within each family and genus respectively. In the systematic accounts emphasis has been placed on identification and on a biological as well as morphological definition of each species. Information is also presented on relative abundance, distribution, individual and geographic variation, and biology. To facilitate identification, the species and the more common variants have been illustrated, and the key has employed as many characters as possible. A full bibliography of the primary literature on leeches of the United States and Canada, including references to the piscicolids, is presented to encourage and aid future investigators"