The present handbook is designed to provide for the first time an up-to-date standard work for Ephemeroptera identification, including last instar larvae (nymphs), subimago (dun), male and female imagines. Recent changes in nomenclature are discussed in detail as well as gaps in current knowledge and probable pitfalls concerning the reliable identification of all taxa known so far from the region. Keys are provided for genera and introductory chapters characterize every family and genus.