The study of blackflies has come of age--the blackfly is now recognized as a carrier of major endemic diseases; its larval stages are seen to play a major role in the ecology of rivers and streams; and blackfly chromosomes have proved unusually amenable material for cytogenetical studies. The expanded interest in the blackfly has greatly increased the scientific literature about them--literature that is extremely technical, highly specialized, and often of little help to non-specialists. This work bridges the gap between specialists and those whose work brings them in contact with the blackfly, but who need information at a more general level. It synthesizes present knowledge about the natural history of the fly family Simuliidae, covering taxonomic background, elements of larval structure and life in water, adult fly structure, migration, mating, biting and bloodsucking, human diseases, and natural enemies of larval and adult flies. Over 1200 bibliographic citations, a glossary of technical terms, and numerous figures, tables and illustrations are included.