A midge fly is a small, two-winged fly that superficially resembles a mosquito. They are found on practically every land area outside permanently arid deserts and the frigid zones. Midge flies are commonly known as "blind mosquitoes" because they are mosquito-like in appearance but do not bite. They are harmless, with small mouthparts that are not elongated into a piercing structure for blood feeding. Most midges, apart from the gall midges, are aquatic during the larval stage. As larvae, most midges live at the bottoms of ponds, lakes, and other aquatic habitats, and some species live in other types of moist places. Midges are important food for aquatic animals, especially trout and young salmon. Some midges, such as many Phlebotominae (sand fly) and Simuliidae (black fly), are vectors of various diseases. However, midges are also important as prey for insectivores, such as various frogs and swallows, and others are important as detritivores, forming part of various nutrient cycles.