Anisoptera is the first of two volumes on the Odonata in the series Encyclopedia of South American Aquatic Insects. The second will treat the Zygoptera. The Anisoptera volume encompasses the large dragonfly species. A brief review of the biology of the group includes illustrations of the main morphological features as well as explainations of alternative systems for naming the wing veins and other structures.  This will prepare the user of the volume to understand the different names for the same structures that he will encounter in the literature.    The review is then followed by keys to facilitate identification of the adult dragonflies and the known larvae, allowing the user a high probability of identifying his specimens correctly.  In addition to anatomical features, the keys include the known ranges of the species, synonyms, and citations of literature in which more information about each individual species can be obtained.  These citations are compiled in an extensive bibliography, including titles of the original publications in which descriptions of almost all South American species appeared.  Although taxonomic revisions are deliberately avoided, suggestions for additional research are provided where the validity of taxa seems doubtful.  To provide the user with the best possible opportunity to distinguish the species, the keys are richly illustrated with pen and ink drawings of thousands of individual morphological structures arranged in 797 figures.  It is certain that significant changes will occur in the systematics of South American dragonflies in the future, and this book should provide the impetus needed to accelerate the revisional work.  Meanwhile, it will provide a comprehensive overview of the Anisoptera in South America that is otherwise unavailable to most South American scientists because of the great difficulties in obtaining the hundreds of publications from numerous countries in which the descriptions and revisions of the species appeared.  It also provides young entomologists with a basic text for learning what they need to know to work effectively with the Anisoptera of South America and adjacent regions.  Already published within this encyclopedia: -Encyclopedia of South American Aquatic Insects: Collembola ISBN: 0-7923-6704-9-Encyclopedia of South American Aquatic Insects: Ephemeroptera ISBN: 1-4020-0775-2-Encyclopedia of South American Aquatic Insects: Plecoptera ISBN: 1-4020-1520-8 Forthcoming book titles: Forthcoming book titles: -Encyclopedia of South American Aquatic Insects: Odonata - Zygoptera -Encyclopedia of South American Aquatic Insects: Orthoptera-Encyclopedia of South American Aquatic Insects: Heteroptera; -Encyclopedia of South American Aquatic Insects: Neuroptera, including Megaloptera-Encyclopedia of South American Aquatic Insects: Trichoptera-Encyclopedia of South American Aquatic Insects: Lepidoptera-Encyclopedia of South American Aquatic Insects: Coleoptera-Encyclopedia of South American Aquatic Insects: Diptera-Encyclopedia of South American Aquatic Insects: Hymenoptera