The recently printed 4th volume covers three insect groups: The Diplura (Author: E. Christian, Vienna), the Symphyta (Author: W. Schedl, Innsbruck) and the Auchenorrhyncha (Author: W.E. Holzinger, Graz). The Austrian dipluran fauna currently comprises 18 species and one subspecies, belonging to 2 families. The taxonomy of subterranean populations of the Plusiocampa strouhali group is not yet resolved. More distinct species are listed in the Symphyta: currently recorded in Austria are 714 species belonging to 12 families. Nearly 12 species may be regarded as questionable. There is also a large number of Auchenorrhyncha (cicada), namely 626 species. In addition, 32 species have unclear taxonomical status. It is assumed that due to their habitat requirements perhaps a further 40 species will live in Austria. So the number of cicada species in Austria might be at least 670.