|Abstract||This further volume in a series on the Lepidoptera of Great Britain and Ireland includes a review (by M. Rothschild, pp. 9-62) of British aposematic Lepidoptera (including an annotated list of toxic secondary plant substances sequestered and stored by 15 species, and a similar list of defensive substances synthesized by 20 species). A systematic section beginning with a key to the families of Ditrysia (a suborder that includes the bulk of the Lepidoptera) and continuing with accounts of the species in 15 families forms the major part of the book. Keys to species within families are provided, together with illustrations of important characters for recognition. General notes are provided on aspects of the families such as their biology, food-plants, immature stages and distribution, and the information on genera and species includes further notes on such aspects. Distribution maps of species are provided, and the adults are illustrated in colour. Many of the species dealt with are of economic importance, especially in the families Cossidae, Tineidae, Lyonetiidae, Gracillariidae and Sesiidae.