These larvae are about a quarter inch long and almost transparent. They feed on microscopic organisms, particularly crustaceans such as water fleas. Adult phantom midges do not feed on blood.

The dark patches seen in the thorax (at left) and near the end of the abdomen are air sacs that allow the larva to stay in deep water where there is little dissolved oxygen. Phantom midge larvae have a diurnal migration pattern (to the surface at night) that follows their food supply and allows them to recharge their air sacs.