This publication, written by two well-known, highly respected Czech entomologists, provides a summary of knowledge on gall midges, which are small flies from the Diptera order. This book covers their biology, occurrence and distribution in European countries, and their importance in agriculture and forestry. The gall midges forming the family Cecidomyiidae are small flies, usually only two millimeters long. They live in various environments and biotopes. In Europe, about 1800 species of gall midges are known. While the life span of adults is very short (usually only few hours), larvae may live several months, and the soil larvae even several years. The larvae of gall midges are either phytophagous (causing galls on various plants), mycophagous and saprophagous (associated with fungi), zoophagous (predators of other flies and small arthropods) or xylophilous (loving wood and woody material). In this book, the gall midge species for each host plant are described and are arranged alphabetically according to their Latingeneric and species name. Zoophagous, mycophagous and freeliving species of gall midges are always placed at the end of there spective section for specific host plant. An important part of this publication is a collection of black and white and colour photos of galls on plants, and many scanning electron-microphotographs, showing the distinguishing morphological features of larvae, pupae and adult gall midges.