Filth Fly

What Are They?

The term filth fly applies to several species of fly that can live off of filth like rotting garbage and manure.

Many species fall into this category:

Filth flies almost exclusively live in close proximity to humans, as their proliferation depends on our environment. Refuse bins and excrement from farm animals provide ample breeding grounds for the insect.

Filth flies thrive in warm temperatures and can be found anywhere from tropical environments to temperate regions.

Because of their abilities to carry and transmit enteric disease, filth flies can also be referred to as Typhoid flies.


Adult filth flies range in size and are typically categorized into two groups: large filth flies and small filth flies.

Large Flies
Large varieties usually measure between a quarter of an inch to half an inch in length.

Common species classified as large filth flies include the house fly, the flesh fly, and the stable fly.

Small Flies
Small filth flies are usually about an eighth of an inch in length and include fruit flies, drain flies, and phorid flies. In most cases, female filth flies tend to be larger than males.

Most filth flies have dark gray or black bodies. Some exhibit several darker stripes running along the lengths of their bodies. A few species have shiny, metallic abdomens and thoraxes.

Filth flies have large compound eyes that encompass most of the head. Male filth flies typically have conjoined eyes, whereas females have a noticeable space between the two.

A pair of veiny, membranous wings extends from the thorax and grants the insect flight. A second pair of club-like appendages are positioned behind the wings to halt flight.

What Attracts Them?

Filth flies originally needed animal excrement or rotting animal carcasses for food and harborage. The highly adaptable insects have since been able to survive solely on rotting organic materials, which humans provide in abundant supply.

Any environment humans live in can accommodate the proliferation of filth flies.

In rural areas, the insects typically live in animal manure, which remains their preferred breeding source.

Filth flies in suburban settings may breed or seek harborage in piles of decaying yard clippings, dumpsters, trash piles, and waste bins. Even recycling centers are common breeding environments for filth flies.

In nature, filth flies serve as valuable scavengers that help break down dead animals and organic waste. However, when infesting homes and restaurants, filth flies serve as a nuisance and a health concern.

What Food Do They Eat?

Adult filth flies subsist on liquid diets. Equipped with sponging mouthparts, filth flies are not capable of biting and chewing food. Instead, the fly secretes a mixture of saliva and digestive juices to liquefy solid food. The fly then ingests the food by sucking the liquid substance through its tube-like mouthparts.

During this process, the fly can leave bacteria from its stomach as well as those on its tarsi on the food source, thereby contaminating anything on which it lands.

Sugar & Sweet Food
Filth flies usually prefer to feed on sugary substances, grease, rotting vegetables, and decaying animal carcasses.

Life Cycle & Reproduction

Like any fly in the order Diptera, the filth fly experiences a four-stage life cycle that begins with the egg stage. During warm conditions, female filth flies lay eggs in animal excrement or decaying organic matter. Female filth flies lay about 100 to 200 eggs at a time, and egg sites must be moist in order for the eggs to hatch. Under the right conditions, eggs hatch in about 12 hours.

Small, pale-white larvae (maggots) emerge from the eggs and consume the decaying material around them. After about five days of development (sensitive to environmental conditions), larvae burrow to dryer areas to transform into pupa.

The final development stage before reaching adulthood, the pupal stage may last several days or several weeks (sensitive to environmental conditions).

When adult filth flies emerge from their pupal cases, their wings quickly harden and they are able to fly. Female flies emerge functionally reproductive and can begin laying eggs about a week after emerging from the pupal case.

Environmental factors like temperature and moisture often affect the rate at which generations spawn. Tropical regions may experience over 20 generations of filth flies in a year. Milder climates generally lend toward 10 to 12 generations of flies annually. Adult filth flies usually live from two weeks to a month. When temperatures drop as winter approaches, all adults die off and larvae and pupae overwinter in manure or protected environments.


The filth fly is a disease-bearing insect that can spread a number of harmful pathogens to humans. Over 100 different pathogens have been found on filth flies, and some of the most common organisms the pests spread include Salmonella, cholera, E. coli, hepatitis, typhoid fever, tuberculosis, and anthrax. Individuals usually develop food poisoning and dysentery from eating food contaminated by filth flies.

As mechanical transmitters of disease, filth flies physically carry disease-causing pathogens from one location to another. The insects initially pick up pathogens from the rotting food waste, feces, and dead animal carcasses they feed on and use as breeding grounds. After that, anything a filth fly lands on is likely to be contaminated by the pathogens the insect has picked up. Filth flies can also contaminate food with their internal bacteria when they defecate or leave behind salivary fluid from feeding.

Signs of Infestation

Filth fly infestation is easy to detect because the insects remain out in the open when active. Even when resting, the insects can usually be found clinging to walls or ceilings. Finding flies inside the home is the main indication of an infestation.

One or two flies around the residence may be incidental, but seeing a number of the pests at once typically indicates that they are breeding inside.

Filth flies in the home will most likely concentrate around areas where organic material may be present. Trash bins with organic waste are the main draw for filth flies. The insects may also be attracted to food that is left uncovered.

Pet droppings will also attract filth flies around the home.


The best ways to prevent a filth fly infestation is too keep the residence clean and to regularly take out the trash. Trash containing rotting organic materials should be taken out as soon as possible. Keeping doors and windows closed will reduce the flies’ abilities to enter the home.

Inside the Home
If flies have found a way inside and have begun breeding, then pest control methods are necessary.

Learn about getting flies out of the home.