The work is divided into two parts: a catalogue and an atlas. In the catalogue, the Irish caddisfly (Trichoptera) fauna is reviewed. A checklist of the 149 valid species is presented. Detailed information is provided on the Irish and European distributions along with data on ecology, flight periods and taxonomy. Sections listing published and unpublished records are included. There is a comprehensive bibliography. In addition, there are accounts of the history of Irish caddisfly studies, identification and recording. The atlas contains full page maps showing the Irish distribution of each species with 10 km square records plotted using longitude and latitude. The maps are based on an analysis of some 20,000 records, both published and unpublished.