MARSH FLY

any of several hundred insect species of the family Sciomyzidae (order Diptera), notable because the larval phase preys parasitically on slugs, snails, and other mollusks. These medium-sized flies occur worldwide; about 500 species are known, each associated with certain types of host, usually found in marshy habitats. Eggs are commonly laid on the host animal. After the larva matures it may pupate inside the shell of an eaten snail. Adult flies, varied in form, often have a yellowish or brown body and dappled wings.