These are the best known of the domestic flies. They are generally gray in color, with the thorax marked with broad dark strips. Often there is some yellow coloring along the sides differentiating them from the face flies. Houseflies are intimately associated with humans and larvae almost always develop in manmade sources of food. These include garbage, animal waste, culled fruits and vegetables, and spilled animal feed.
The adult flies feed on a wide range of liquid waste. Houseflies also can feed on solid foods, such as sugar, by regurgitating and liquefying the food. Houseflies can be serious health threats because they transmit disease organisms. During mild winters houseflies may continue to fly and breed.
These are closely related to houseflies and are hard to identify. The wide separation of the eyes in the male flies and the absence of yellow coloring can often help distinguish face flies. Although similar in appearance, their habits differ greatly from houseflies and they often are more common than houseflies, especially in rural areas.
Face flies pass the winter in the adult stage, often seeking shelter in upper stories of buildings, such as attics, steeples, and little used upper rooms. They become active in spring and females lay eggs in fresh bovine manure less than one day old.
Adult flies may feed on many types of fluids. They are often attracted to the exudations around the eyes, nose, and mouth of cattle. They have been implicated in transmitting pinkeye disease.
Fungus gnats are small dark colored flies that are most often observed collecting around windows, usually during fall and winter. Fungus gnats commonly occur outdoors, where they breed in mushrooms and decaying plant materials. Indoors, fungus gnats infest potting mixes used for houseplants. High organic matter plant mixtures or use of organic fertilizers, such as fish emulsion, can encourage fungus gnat development. Over watering encourages fungus gnats by increasing fungus development.
Fungus gnats cause little, if any, damage to houseplants and are primarily a nuisance problem. Attention to correcting conditions of the breeding area, such as moist potting soil, is the most effective means of controlling infestations.
Fruit flies are among the smallest flies found in homes. They are usually a light brown color and may be marked with bright red eyes. Most often they are found hovering around overly ripe fruit or around fermenting materials, such as leftover beer or soft drinks remaining in opened containers. Fruit flies are best controlled by removing breeding sources.
These are metallic green, blue, or black flies that are common throughout Utah. Blowflies tend to breed on decaying carcasses and dog droppings. Garbage is also used as food for the maggots. Occasionally, blowfly maggots are found in homes wandering off the carcass of a dead rodent or bird present within a home. Adult blowflies may also be attracted to gas leaks.
Cluster flies are one of the most annoying flies found within homes during the cool seasons. They are also serious pests of office buildings, often concentrating in upper stories. The cluster flies are somewhat larger than houseflies and during the period they spend indoors they are semidormant and fly awkwardly.
Habits of cluster flies are very different from other common domestic flies. Immature stages develop as a parasite of earthworms. Eggs are laid in the soil and the maggots enter and feed within the earthworms. Cluster flies do not feed on garbage and animal manure. In late summer, cluster files seek overwintering shelter. Late in the afternoon, they often fly to buildings and rest on areas exposed to the sun. As the sun sets, the flies creep upwardsultimately moving to upper stories. They then seek out cracks and other openings into the building. Once inside the building, the cluster flies may appear in large groups.
Similar to the house fly, however, the stable fly has four dark stripes on the top of the thorax. Their mouths are able to penetrate to suck its hosts blood. Typically laying their eggs in dying grass or hay or dried straw and chicken manure. Mainly eat on dying organic matter. They can cause nasty, pain inflicting bites that can spread disease.