Mostly aquatic or semiaquatic. Deuterophlebiidae- mountain midges, body with 7 pairs of broad ventrolateral prolegs, antennae forked, on rocks in rapid current. Nymphomyiidae- body with 8 pairs of slender prolegs, in rapid current among bryophytes in the eastern Canada and adjacent Usa. Chaoboridae- phantom midges, thoracic segments fused and wide, antennae prehensile, no prolegs, limnetic and littoral predators. Chironomidae- midges, also Tendipedidae, prothorax with proleg, body smooth, apneustic.
Most families are terrestrial, but some are partially aquatic or semiaquatic.
Stratiomyidae- soldier flies, body flattened, integument tough.