Aquatic entomology has undergone major advances in recent times. For example, aquatic insects are now routinely used to test hypotheses in contemporary ecological theory and to model predictive changes resulting from climate change. Research has also revealed the importance of aquatic insects in the spread of diseases, in the biological assessment of water quality, and in the reconstruction of past environments on earth. Further, it is now accepted that the larvae of aquatic insects play a pivotal role in the breakdown of terrestrial leaf litter and provide an important food source for fishes, both in nature and aquaculture. This book presents these findings together with the background information necessary to understand them, and provides references to classic and more detailed studies in the literature. Only a limited prior knowledge of general ecology or entomology is assumed on the part of the reader. The book will therefore appeal to advanced undergraduate students taking courses in aquatic biology or entomology, as well as to research workers in ecology and pure and applied entomology seeking an overview of this fascinating field of study.