Range in size from tiny to large. Named for their single pair of wings, with the former hind wings reduced to little knobs. Have large compound eyes and sucking or piercing mouthparts. Found in most habitats. Larvae, or fly maggots, have liquid diets of dung, fungi or plant matter. Adults are also attracted to moist foods. Predators include other insects, spiders, birds, bats, reptiles, frogs and fish.