Phorid Flies

Adult Phorid flies are often seen in bathrooms, basements near floor drains, or near potted plants.

You may see Phorid flies scurrying across your television or computer monitor, and across surfaces in your bathroom or laundry.

Adult Phorid fly are tiny insects, about 1/16” to 1/8” in length.

Phorid flies are yellowish-brown or black in color

The thorax is dramatically arched, giving the Phorid fly its common nickname of “humpbacked fly”.

Phorid flies have a small head, a short, narrowed abdomen, and large legs with a hind femur laterally flattened (adapted for jumping).

A unique identifying feature of adult Phorid flies is the presence of two distinctive veins near the front of the wing, terminating about halfway before the wing tip.

Phorid flies are well known for their habit of scuttling in a fast run instead of immediately taking off when disturbed, hence another of their nicknames, “scuttle flies”.

Phorid fly larvae are dirty white and about 3/32” in length.

Phorid fly larvae are elongated, almost cylindrical, slightly flattened and tapered at the anterior (front) end.

The puparium (a rigid outer shell formed from the larval skin that covers the pupae of most flies) is boat-shaped, about 1/8” in length, light brown and slightly translucent.

Eggs are very small (1/32”) and opaque-white.

Phorid flies do not bite.

However, because Phorid flies come from leaking sewer lines, rotting produce or dead animals, the risk of disease transmission is a concern.

Phorid flies pose an even greater risk in hospitals and nursing homes because there are documented cases of Phorid fly larvae feeding on necrotic flesh associated with wounds of patients.

Phorid flies are frequently found outdoors around flowers and moist decaying matter.

Adult Phorid flies are attracted to light. Therefore, in summer, deck and patio lights will attract them to doorways and windows.

Once inside, Phorid flies will breed wherever moisture and organic matter are available.

Also known as “sewer flies,” Phorid flies are often linked with clogged drains and damaged sewer lines that are in or close to your house or building.

When searching for Phorid fly breeding sources, look  for moist, decaying organic matter such as rotting bags of potatoes, onions or other stored tubers; recycling bins and  rarely cleaned garbage cans; beneath and behind refrigerators and other large appliances;  tiny amounts of organic debris can also be found under the legs or feet of appliances, tables and cabinets.

Floor drains and all small cracks and crevices at floor level should be inspected and if necessary, thoroughly cleaned.

If no obvious food source or breeding grounds can be located, the Phorid flies may be coming from an unknown broken sewer or septic line, or cracked septic tank. A professional plumber may need to be called to inspect.

Phorid flies feed on feces, sewage, fungi, and decomposing fruits and vegetables, rotting meat, and the carcasses of dead animals.

Phorid flies go through a complete metamorphosis, which has four stages: egg, larva, pupa and adult.

A mated female Phorid fly can lay up to 750 eggs in her lifetime; and as many as 100 tiny eggs at a time, but more typically about 40 eggs in a 12-hour period.

The eggs are usually laid in or on suitable larval food places such as decaying materials, feces, or dead animals.

Eggs hatch within 24 hours.

Phorid fly larvae go through three larval instars lasting 8-16 days.

Pupae stage last 14 days.

Newly emerged adult Phorid flies mate and repeat the life cycle.

The life cycle from egg to adult is short and may complete in 14 days, but may take up to 37 days, depending on temperature, moisture and food availability

There are approximately 4,000 known species of Phorid flies (Diptera: Phoridae) distributed worldwide.

Phorid flies are known to be common pests of mausoleums, mortuaries and funeral homes, where they are often referred to as “coffin flies.”

Phorid fly larvae are capable of breeding inside crypts, which are otherwise inaccessible.

Moreover, Phorid fly larvae can dig in the ground and thrive on buried human bodies.

On the positive side, Phorid flies can be beneficial as multiple species of Pseudacteon Phorid flies are currently known to be biological control agents of red imported fire ants.

Phorid flies are strong fliers; with the help of wind, adults are capable of traveling up to 6 miles in a 24-hour period.

The family of phorid flies (Phoridae) includes species belonging to the genus Pseudacteon, which are known to parasite fire ants (Disney, 1994).