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A source for information on flies

Phorid Fly  Phoridae spp.

Phorid flies are yellowish-brown with a small head and large black eyes. They have veined wings and an arched thorax, earning them the nickname “humpbacked fly”. They resemble Fruit flies in appearance, but they lack their prominent red eye color.

Phorid flies are minute, and are usually 1/16-1/8-inch long.

Phorid flies reproduce in moist areas where food and water are present. Eggs are often laid directly on decaying material, and hatch within 24 hours. Their entire life cycle lasts about 25 days or more, depending on temperature, food, and moisture available. Females are very attracted to odors of decaying animal remains and readily lay eggs on or near it.

However, larvae do not initiate wounds or attack healthy animals or humans. Adults have sponging mouthparts and are often confused with fruit flies and fungus gnats due to their small size, breeding habits, and flight pattern. Phorid flies may run rapidly across windows, TV screens, tables, and walls in short, jerky movements, appearing reluctant to fly.

Phorid flies can breed in more types of materials than any other structure-infesting fly. They can become a nuisance in hospitals, food establishments, or homes. They can also be found outdoors in decaying organic matter such as vegetation, animal feces, carcasses of animals, decaying insects and nests of ants, termites, bees and wasps. In nature, they are typically associated with dead animals and heavily decaying vegetation. In mausoleums, they are known as “coffin flies” because they breed inside bodies stored in the crypts and coffins. In buildings, they may found breeding in drains, trash containers, dumpsters, rotting produce, recycle bins, grease traps, garbage disposals, crawlspaces, and any site where moist organic matter can accumulate for five days or longer. Phorid flies have also been found to breed in poorly stored meats, damaged containers of moist foods, and organic-based glues and paints.

Larvae have also been found feeding in sour milk, decaying plants, open animal and human wounds, decaying animal and human (cadaver) flesh, feces, laboratory culture media, clogged drains, mausoleum crypts, human tissue at hospitals, plant soil, garbage cans and disposals, etc.

Interesting Fact:
The Phorid fly has been utilized as a biological control agent in the eradication of fire ants. They “parasitize” fire ants by depositing eggs that hatch into larvae and pupate inside the fire ant’s head capsule.

Adult flies use chemical cues to locate fire ants, which they attack and lay an egg in the ant’s thorax. The maggot hatching from the egg then migrates to the ant’s head. As the fly pupates, it releases enzymes that cause the head to fall off, killing the ant.

Health Concerns:
Since Phorid flies originate in filthy conditions, there is a possibility of transmitting certain diseases. This is of particular concern since they often turn up in burn units, operating rooms and pathology labs where sterility is of extreme importance. It is important to locate and eliminate the larval breeding source; concentrations of adult flies and decaying odors are good indicators of nearby breeding grounds.

The Phorid fly Larvae develop in moist areas where organic material and standing water are present. Phorid larvae also develop in animal matter. The entire life cycle lasts 25 days or more, depending on the environmental conditions and the availability of food.

Though electrocuting devices and sticky traps help minimize Phorid fly populations, other steps are necessary in order to eradicate them. Start by eliminating or reducing moisture sources and avoid accumulation of wet organic matter in and around structures, as they are preferred breeding grounds. Seal cracks and crevices to prevent entry, and dispose of garbage and old bird and insect nests. The key to controlling phorid flies is finding the breeding sites and removing them by proper cleaning practices. Phorid flies, like other types of small flies, can be difficult to totally eliminate because they can breed in such small amounts of organic matter. A number of breeding sites can be found and eliminated while others may easily be overlooked. The inspection needs to focus on finding all sites where moist organic matter has accumulated and then removing that matter completely.

On occasion, drain line breaks under slabs or in crawlspaces can result in huge phorid fly populations in homes, restaurants, or other buildings. Drain breaks beneath a slab floor will require the expertise of a plumber to diagnose. If flies are found to be breeding under the slab, the slab will need to be broken open and the drain line repaired. If the wet, contaminated soil is not removed and replaced with fresh, dry soil, the phorid fly problem will persist.

Indoors, thoroughly clean drain pipes and traps with a stiff-bristled brush. It even helps to remove the trap and use a “snake” in clogged rains to clean pipes of all buildup, which can serve as a food source for larvae. Bleach may be poured into the pipes after a thorough cleaning, followed by a careful flushing with boiling water.

"Riley Pest Management is a small company with a big heart that will go the extra mile to take care of an issue for you no matter when it happens. They have proven to be a very good friend to non-profits."

-- Duggan Cooley, former CEO- RCS

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