Coffin flies are several related species of flies that lay eggs on decaying flesh or fecal matter, and the colloquial name comes from the fact that these insects hatch, grow and breed inside human coffins. Coffin flies are found in households near toilets, garbage cans and food, and these types of flies often make sudden, jerky movements along surfaces such as mirrors and windows.
Coffin flies don't just feed on dead bodies and fecal matter; these insect lay eggs in food, plants, other insects, vertebrate animals, invertebrate animals, fruits, vegetables, curdled milk, shoe polish and paint. Sometimes, these flies infect open wounds on humans, causing a condition known as myiasis, but this usually occurs where hygienic conditions are less than ideal.
Coffin flies belong to the insect family Phoridae, a group of humpbacked flies, similar to fruit flies, that run across surfaces rather than flying. Coffin flies persistently infest cockroaches, bees, crickets, tarantulas, lizards, snakes and hermit crabs. Although coffin flies prefer to lay eggs on decaying flesh, they have been known to attack living organisms.
These types of flies are important to forensic scientists who try to solve murders. When a decomposing corpse has been undiscovered for days, scientists can ascertain the time of death based upon the number and development of flies within the dead body.