Gagne's introductory chapters include biographical sketches of those individuals who have contributed most to our knowledge of Neotropical gall midges. He also discusses classification and distribution, external anatomy and biology, and techniques for collecting, rearing, and preparing specimens for study. The heart of the book comprises two chapters. The first presents the midges themselves: identification keys to the genera, a synopsis of each genus and higher taxon, and a list of all known species from South America. The second includes keys and descriptions of galls and other damage caused by the midges, with known hosts.