A source for information on flies
The house fly is one of the most common and recognizable pests in the world. The
adult house fly has reddish eyes and four narrow black stripes on its thorax. The abdomen is gray or yellowish with
irregular dark markings on the sides, and there are distinct vein lines on the wings.
Approximately 1/4-inch in length.
The House fly is a
well-known pest of both indoors and out, and is always found in association with humans or human activity. House
flies have a complete metamorphosis with distinct egg, larvae or maggot, pupal and adult stages. Warm summer
conditions are key for its development, and it can complete its life cycle in as little as 7-10 days. More than 20
generations may occur in subtropical and tropical regions, including Florida.
The female house fly can lay up to 500 eggs in multiple batches over a 3-4 day
period, and it is common for several flies to deposit their eggs close together, leading to large masses of maggots
and pupae. Moisture is required for eggs to hatch; wet, nutrient-rich substances such as fresh animal manure
provide excellent breeding grounds for maggots. The greasy, cream-colored larvae emerge from the egg within 8-20
hours and immediately begin feeding on and developing in the material in which the egg was laid.
Adults tend to live 15 to 25 days, and their longevity is enhanced by the
availability of suitable food, especially sugar. Females need access to suitable proteins in order to produce eggs,
and manure alone is not adequate. House flies have sponging mouthparts so they cannot eat solid food. Instead, they
regurgitate digestive fluids onto food and then sponge up the digested liquid meal.
The House fly is
the most common species on farms and ranches, as it is commonly associated with animal feces. However, it has
adapted well to feeding on garbage, so it is abundant almost anywhere people live. This species breeds primarily in
fresh animal manure and so is most common on and near farms. Lawns where dog manure is left for days can also
become a significant breeding site for house flies. Any building can be plagued by house flies, but those located
near farms and pastures are likely to experience more flies than other structures. House flies rarely breed
indoors, but if they do, the site is usually a trash container that hasn’t been cleaned for a while or possibly
rotting vegetables or fruit in a box in a restaurant storeroom or kitchen.
House flies are inactive at night, and often rest in ceilings, beams, trees, shrubs
and grasses. During the day, house flies favor especially filthy conditions to feed and breed; the most common
being in animal manure, fermenting vegetable and kitchen waste, garbage piles, semi-composted manure piles, and
rotting or decaying organic materials. They tend to be a major nuisance on farms due to their proximity to manure
The potential reproductive capacity of flies is mind-boggling. Scientists have
calculated that a pair of flies beginning reproduction in April may be progenitors, under optiminal conditions and
if all were to live, of 191,010,000,000,000,000,000 flies by August!
Although the house fly does not bite, their control is vital to human health and
comfort all over the world. Due to their attraction to bacteria-laden areas, the potential transmission of
pathogens is a major concern. Pathogenic organisms are picked up by flies from garbage, sewage and other sources of
filth, and then transferred on their mouthparts, through their vomit, feces and contaminated external body parts to
human and animal food.
Among the pathogens commonly transmitted by house flies are Salmonella, Shigella,
Campylobacter, Escherichia, Enterococcus, and many other species that cause illness. These flies are most commonly
linked to outbreaks of diarrhea and shigellosis, but are also involved in transmission of food poisoning, typhoid
fever, dysentery, tuberculosis, anthrax, ophthalmia, and parasitic worms.
The movement of house flies from animal feces to food that will be eaten uncooked by
humans is of particular concern. Also, when consumed by flies, some pathogens can be harbored in the mouthparts or
internal organs for several days, and are then transmitted when flies defecate or regurgitate. In areas where
plumbing is lacking, serious health problems can develop, especially if there are outdoor food markets, hospitals,
or slaughterhouses nearby.
Proper sanitation is the basic step in any fly management practices. Food and
materials on which flies can lay eggs must be removed or destroyed as an egg-laying medium. Pet manure should be
disposed of often, and garbage should be placed in bags and sealed in receptacles with tight-fitting
Around homes and businesses, screening or covering of doors, windows, and trash
containers is useful in denying access of flies to breeding sites. Fly traps may be useful if enough traps are
used, if they are placed correctly, and if they are used both indoors and outdoors.
House flies are attracted to white surfaces and to baits that give off odors.
Indoors, ultraviolet light traps collect the flies inside an inverted cone or kill them with an electrocuting grid.
One trap should be placed for every 30 feet of wall inside buildings, but not placed over or within five feet of
food preparation areas.
In most cases involving house flies around homes, the
problem is twofold: (1) flies are being attracted to the building by trash containers or pet manure and (2)
openings (e.g. doors) exist that are permitting flies to enter. To minimize problems with flies, take the following
• Throw trash away in trash cans in plastic bags. Bags reduce odors associated with
garbage and trash thus attracting fewer flies to the area.
• Locate trash receptacles as far from the building as possible. Those flies that are
attracted to the area will therefore be away from the back door.
• Regularly pick up pet manure from the yard.
• Keep doors and windows closed unless they are equipped with tight-fitting
• Ensure all edges of doors and windows have tight weatherstripping. Flies can
squeeze through amazingly small cracks.