This new checklist covers all recorded UK species. The main list comprises resident, and transitory resident species, species believed to be extinct and immigrants and some species that have probably been imported but have been found in the wild. Also included, in Appendix A, are the adventive species recorded in Britain, which cannot be regarded as part of our fauna, and are probably unlikely to recur, for example those imported from a great distance with produce. Appendix B lists species whose records are either erroneous or unable to be confirmed.