Phorid Fly Facts

Characteristics

The little house fly is somewhat smaller (3.5-6 mm or 0.14-0.24 inch) than the common housefly, which certainly helps explain the name. It is slender, and the median vein in the wing is straight. Fannia at rest hold their wings over the back more than the house fly does, creating a narrower V-shape to the wing outline.

Where found

The phorid fly is found throughout the United States and worldwide. The greatest variety are found in the tropics.

Habitat

The sweet smell of home. Larvae breed in a variety of moist decaying organic matter, including dung, fungi, and decaying plant material. Breeding material can include the moist organic film lining drain pipes, the moist residue in the bottom of trash receptacles, in elevator pits, garbage disposals, and faulty septic systems.

Food

Breathe easy. Your round kernels are safe! But watch the mac and cheese. The merchant grain beetle cannot attack round kernels. Its flat body form lets it crawl through very small cracks and into imperfectly sealed packages. It is commonly found in oilseed products like nuts and cereal products, rolled oats, rice flour, cake mixes, macaroni, and cookies.

Biology

Females lay their eggs close to the larval food, with 1-100 being laid at one time and up to 749 in her lifetime. The developmental time (egg to adult) varies from 12 to 28 days, depending on temperature and larval food sources. Phorid flies can often be identified by their escape habit of running rapidly across a surface rather than taking to the wing. This behavior is a source of one of their alternate names: scuttle fly. They are a diverse and successful group of insects. Approximately 4,000 species are known.

Fun fact, but not for fire ants: They are close, but they're not friends. Phorid flies represent a new and hopeful means to control fire ant populations in the southern United States, where fire ants were accidentally introduced in the 1930s. The genus Pseudacteon, or ant-decapitating fly, of which 110 species have been documented, is a parasitoid of the ant in South America.

Members of Pseudacteon reproduce by laying eggs in the thorax of the ant. The first instar larvae migrate to the head. The larvae develop by feeding on the hemolymph, muscle tissue, and nervous tissue in the head. Eventually, the larvae completely devour the fire ant's brain, causing it to do nothing but wander aimlessly for approximately two weeks. After about two to four weeks, they cause the ant's head to fall off by releasing an enzyme that dissolves the membrane attaching the ant's head to its body. The fly pupates in the detached head capsule, requiring a further two weeks before emerging. Various species of Phoridae have been introduced throughout the U. S. Southeast, starting with Travis, Brazos, and Dallas counties in Texas, as well as Mobile, Alabama, where the ants first entered North America.

Damage

"I see dead people." Several species of phorid flies breed in human corpses and are commonly referred to as coffin flies when they become problems in morgues, mortuaries and mausoleums. Adults can be found on flowers or on larval food materials, which consist of moist decaying organic matter. Because they frequent such unsanitary places, they may transport various disease-causing organisms to food materials. Phorid flies are of great concern in health-care facilities because of their unsanitary habits, and because larvae have been found in the open wounds of patients.

Good riddance

The key to control is finding and eliminating all of the breeding sites. Don't stop until all potential sources have been inspected and eliminated.