The Megalopterans represent an old insect group and one not extremely speciose, having approximately 275 described species. Neotropical and Indomalayan biogeographic areas probably hold the most species, whereas Nearctic and Australian species are the most well studied. The aquatic larvae are medium-to-large predaceous insects found in a wide variety of habitats, including habitats as unique as pitcher plants. Many species have long lived larvae (up to 5 years). This long residence time in the aquatic environment, coupled with their large size, makes megalopterans important consumers in stream and river trophic webs. Additionally, the insects often make suitable attachment sites for a wide diversity of ectosymbiotic organisms. The egg, pupa, and adults stages are short-lived and terrestrial.