Aquatic entomology is the study of insects that live in the water during all or part of their lives. Many flying insects such as dragonflies, damselflies, caddisflies spend their larval youth in a stream, where they are the primary prey of fish. You can tell a lot about the quality of the water in a stream by the species living in it. Aquatic Entomologists sample, count, and identify the BMIs in a stream. Most BMIs thrive in clean water; relatively few tolerate pollution or damage to the habitat. If the quality of the water and habitat is impaired, the species and number of BMIs will tell that story. In a way Aquatic Entomologists help "the bugs" explain what is happening in their environment, so we can improve water quality. "