Hepialidae (ghost moths or swifts) are, in terms of diversity and distribution, the most successful group of homoneurous primitive moths. The morphology of Fraus is described in some detail with emphasis on the adult moth, and a new interpretation of hepialid male genitalia is presented. Beyond describing and illustrating a primitive hepialid, these observations are intended to serve as reference for the study of the classification of Hepialoidea and lower Lepidoptera.

In the taxonomic revision, based on more than 3000 specimens, the 25 Fraus species are described and diagnosed. The adult moths, as well as male and female genitalia, are richly illustrated, and distribution maps and flight period diagrams are provided for all species. The biology, behaviour, distribution and phylogeny are summarised and discussed.