Phorid Flies

What Are They?

  • Also known as the humpbacked fly, coffin fly, and scuttle fly due to the physical appearance and certain behavioral tendencies of the insect.
  • A common pest in food preparation facilities, phorid flies pose particularly serious problems in hospitals, nursing homes, and other settings associated with healthcare and medical treatment.
  • Also invades and infest hotels, restaurants, and even private residences
  • Though small in stature relative to other fly species, phorid flies have the ability to carry and spread germs and bacteria from the unsanitary places in which the insects tend to live and breed.

What Do They Look Like?

dead phorid fly
phorid fly
phorid fly side view


Typically ranging in length from about 1/16 to 1/8 of an inch.


The adult phorid fly is characterized by a rounded and elevated thorax, which makes the insect appear to have a humped back. The distinctively shaped thorax also leads many people to refer to phorid flies as humpbacked flies.


Generally black or brownish-yellow in color, phorid flies each boast a single pair of light brown wings.

Before maturing into winged adults, phorid flies complete a larval phase of development (maggots) in which the insects are whitish in color, slender and tapered at the head, and about four or five millimeters long.

Where Do They Live?

Commonly associated with moist and decaying organic matter, phorid flies reside and breed in a variety of unsanitary settings. In fact, some experts believe the insects vary in preferred breeding sites more than any other fly species.

Phorid flies are known to breed in:

  • animal carcasses
  • garbage
  • decaying plants
  • dirty trash containers
  • dormant garbage disposals
  • piles of feces
  • drain pipes
  • the overly saturated soil of potted plants
  • glue or paint

Its small size enables the insect to locate traces of moist organic material accessible only through cracks in countertops or floors.


Because phorid flies are also known to infest coffins containing human corpses buried underground, the insects are sometimes called coffin flies. Unlike other fly species, phorid flies run rapidly and erratically instead of taking flight immediately when disturbed. The erratic movement of the insects often prompts the use of the alternative common name ‘scuttle flies’ for phorid flies.

What Do They Eat?

In addition to using decaying organic matter as a breeding site, phorid flies (larva) use the same material as a food source. The pest insects feed on substances like feces and sewage, decomposing fruits and vegetables, rotting meat, and the carcasses of dead animals. Phorid flies also consume fungi as well as the organic debris that accumulates in soiled trash receptacles and drains.

Life Cycle & Reproduction

The enormous reproductive potential of phorid flies enables the insects to produce large populations of offspring quickly and efficiently.  Phorid flies reproduce rapidly, with adult females capable of laying 40 eggs within 12 hours and roughly 500 eggs over the course of a lifetime.


After mating, females lay approximately 40 eggs over the course of 12 hours. Smooth and elongated, phorid fly eggs are typically found within the immediate vicinity of moist, decaying organic material.


Upon hatching, phorid fly larvae are virtually transparent or colourless. The body of each larva is tapered and narrows from the posterior end toward the head. Slender and legless, undeveloped phorid flies resemble tiny worms during the larval stage of the life cycle. As they mature, the larvae turn whitish in colour and grow to a length of about 4.5 mm.

Larvae hatch from the eggs in one to three days and feed on the surrounding organic matter. After a week or two, larvae move to drier environments and pupate, changing in color from white to yellowish-brown.

The larvae of some phorid flies even parasitize other animals. Depending on the particular species, parasitic types of phorid flies lay eggs in the nests of ants, bees, termites, and wasps as well as on the bodies of live beetles, caterpillars, and millipedes. After emerging from the eggs, the newly hatched larvae feed on the occupants of the nest or the living animal upon which they were deposited. All phorid flies spend about 8 to 16 days in the larval phase of development, depending on the temperature of the environment.


Phorid flies spend varying lengths of time as pupae, depending on the temperature of the surrounding environment. Overall, the phorid fly life cycle takes a minimum of about two weeks and as long as seven weeks to complete.

How Long Do They Live?

Heavily affected by environmental climate, the lifespan of an adult phorid fly is roughly eight days.

Problems Caused by Phorid Flies

Phorid flies are capable of entering indoor structures undetected and breeding wherever enough moisture and organic material accumulates. The pest insects tend to breed in undetectable locations such as areas moistened by broken drain pipes underneath the floor. Unsightly and bothersome, phorid fly infestations often catch homeowners unaware due to the rapid rate at which the insects reproduce.


In addition to reducing the aesthetic appeal of the indoor environments they infest, phorid flies can negatively affect the health of humans by spreading bacteria and disease organisms from unsanitary breeding sites to food preparation surfaces.

Signs of Infestation

Because phorid fly infestations often prove difficult to locate within an indoor setting, witnessing large numbers of the insects emerging all of a sudden, frequently serves as the first, and possibly only, noticeable sign of an infestation problem.

Phorid flies regularly emerge from dirty trash containers, cracks in the floor, and areas where fruits and vegetables are stored. The unsanitary insects commonly infest grimy drains in sinks and floors, as well. Attracted to light, phorid flies often gravitate toward windows, lamps, and other sources of illumination.


Effectively preventing phorid fly infestations primarily involves cleaning or removing the types of locations in which the insects prefer to breed.

Homeowners and residents should:

  • regularly clean trash cans and recycling bins
  • immediately discard spoiled food
  • promptly fix leaky plumbing


Getting rid of the organic buildup that accumulates on the walls of drains is another important step in phorid fly prevention.


Homeowners as well as business owners of food handling facilities should also repair cracks and crevices in the floors to prevent food debris and moisture from accumulating, fermenting, and creating ideal breeding grounds for phorid flies.

Learn how to manage a sudden fly infestation.