The identification keys presented here include a key to the genera of European Syrphidae and Microdontidae and keys to the species of various genera. They do not comprise a comprehensive set of keys to the identification of European syrphid species. While every effort has been made to ensure that each key is as self-contained and accurate as possible it is not suggested that these keys be used in isolation from other literature on identification of European syrphids. In the StN Species Accounts volume (Speight, 2012) information is given for each species on identification literature, sources of figures of the male terminalia, sources of coloured illustrations of the adult fly etc., together with suggestions (where appropriate) of additional features to use for identification purposes. That information is not repeated here. A genus for which an StN key to the European species exists is indicated in the generic key following the name of the genus, by the phrase “see StN key to European species”. Various syrphid genera are represented in Europe by no more than one species. For these, the generic key provides a mechanism for identification to species level and the name of the European species is given in the generic key, following the name of the genus. This volume is presented in two sections, an English section and a French section. The key to European syrphid genera appears only in the English section. But all of the keys to the species of individual genera appear in both sections. Each key is dated, to show when it was most recently updated. The keys to the species of individual genera are presented in alphabetical order of the genera they cover, under Microdontidae and Syrphidae. No grouping is made of genera in subfamilies or tribes. For further information on the known European species in each genus the StN Species Accounts volume (Speight, 2012) should be consulted. There is unfortunately no standard set of English-language terms used for morphological features in taxonomic literature on Syrphidae. Contrasting accounts are provided by Thompson (1999) and Speight (1987). Part 3 of the present volume presents a Glossary of the terms used for morphological features in the StN keys, together with figures showing those features
