Adult flower flies feed on nectar from flowers and from aphid "honeydew" (see Aphididae).

The larvae of different species feed on different kinds of food. Some feed on decaying, damp plant material, on fungi or on green plants, some on the bulbs of plants in the lily family, some in dung. Many are aquatic and live in shallow freshwater (sometimes in water that seems foul and polluted), some in water-filled treeholes. Some species are scavengers in the nests of ants or wasps. Some of the most amazing are predators on slow-moving, soft-skinned insects like Aphididae. These predators have no eyes and no legs, but they still hunt and eat these little insects.