The ephydrids (“shore flies”) are among the less common true flies in our fresh waters. Their larvae have a maggot-like body with a velvety surface texture, and at the end of the abdomen there are two respiratory siphons or (rarely) two black hooks. There is no visible head. Some species have caterpillar-like pseudopods along the underside of the body.
Ephydrid larvae are found in many stream types including algae-covered streambeds, and some species are common in geothermally heated waters.
Ephydrid larvae are thought to graze on stream biofilms (algae and other microorganisms on submerged surfaces).
Some ephydrids can be found in polluted or low oxygen waters and as a result they have relatively low tolerance values of 4 (hard bottom sites) and 1.4 (soft bottom sites).