Thorp and Covich's Freshwater Invertebrates: Keys to Nearctic Fauna, Fourth Edition presents a comprehensive revision and expansion of this trusted professional reference manual and educational textbook—from a single North American tome into a developing multivolume series covering inland water invertebrates of the world. Readers familiar with the first three editions will welcome this new volume. The series, now entitled Thorp and Covich’s Freshwater Invertebrates, (edited by J.H. Thorp), began with Volume I: Ecology and General Biology, (edited by J.H. Thorp and D.C. Rogers). It now continues in Volume II with taxonomic coverage of inland water invertebrates of the Nearctic zoogeographic region. As in previous editions, all volumes of the fourth edition are designed for multiple uses and levels of expertise by professionals in universities, government agencies, and private companies, as well as by undergraduate and graduate students.