Minor Insect Orders

A number of insect orders are infrequently collected in freshwater habitats and have relatively low richness of aquatic species; however, these taxa may be locally abundant and can play important roles in freshwater food webs. The two families of Megaloptera, Corydalidae (fishflies and dobsonflies) and Sialidae (alderflies), have fully aquatic, predatory larvae. Larval corydalids, known as hellgrammites, are large, long-lived, and especially diverse in streams of Indomalaya and the Neotropics; larval sialids are smaller, found in a variety of lotic and lentic habitats, and have high diversity in the Holarctic. Aquatic Neuroptera include the cosmopolitan family Sisyridae (spongillaflies), whose larvae are obligate predators of freshwaters sponges, and Nevrorthidae, exclusively found in mountain streams of Indomalaya, Australasia, and the Palearctic. Additionally, several taxa of Osymidae are water-dependent and occasionally collected in aquatic samples. Five insect orders that are often considered fully terrestrial are known to have aquatic representatives: Blattodea, Hymenoptera, Lepidoptera, Mecoptera, and Orthoptera. A number of species of Blattodea (cockroaches) in the family Blaberidae are aquatic or amphibious in habitats such as phytotelmata and streams. Many species of Hymenoptera (wasps) are endoparasitoids of aquatic invertebrates; additionally, adult Pompilidae (spider wasps) in the genus Anoplius dive underwater to prey upon semiaquatic spiders. Four different taxa of Lepidoptera (moths) have aquatic or amphibious larval stages (caterpillars) that consume aquatic plants, including the speciose subfamily Acentropinae (=Nymphulinae). One relict family of Mecoptera (scorpionflies), Nannochoristidae, has stream-dwelling larvae. Finally, a diverse fauna of aquatic and water-dependent Orthoptera (grasshoppers) are known, with the greatest richness in Indomalaya and the Neotropics. Future ecological investigations of the minor aquatic insect orders will undoubtedly uncover additional taxa with aquatic life stages.