Jeffery K. Tomberlin, PhD, ABFE
Assistant Professor and Extension Specialist
Texas Cooperative Extension
Carlos Bográn, PhD
Assistant Professor and Extension Specialist
Texas Cooperative Extension
The house fly, Musca domestica, is one of the most common insects associated with people throughout the world. House flies are mostly nuisance pests. However, since they feed and develop on decomposing organic materials they can carry many different organisms that can cause diseases in humans and domestic animals. Suppressing their populations is very important in reducing contagious disease risks and the annoyance they usually cause. The purpose of this publication is to provide basic information on the biology and ecology of the house fly and suggestions on appropriate control methods.
While most winged insects have two pairs of wings, adult flies, including house flies, have only one pair of wings (order Diptera). House flies are approximately ¼-inch long, light grey in color and have four longitudinal black stripes on their back (thorax). Their head is dominated by a pair of large, red-brown compound eyes and sponging mouthparts; they are non-biting flies. Their abdomen typically has a checkered appearance and they are often confused with flesh flies and stable flies. However, flesh flies have only three black stripes on their back, and the tip of their abdomen is typically red, which is not the case in house flies. House flies can be distinguished from stable flies by their mouthparts; stable flies have piercing mouthparts that protrude out in front of their head. Unlike house flies, stable flies are blood-feeders.
Adult house flies live up to three weeks and are active during the warmer portion of the year. Adult females deposit eggs in clusters of 50 to 100; a single female may lay more than 500 eggs in her lifetime. The eggs are deposited in a variety of substrates including moist, rotting, fermenting organic matter, animal manure, accumulated grass clippings, garbage, spilled food and animal feed and soil contaminated with any of these organic materials. House flies are not known to readily colonize decomposing animals. Eggs hatch approximately 12 hours after being laid, and the resulting larvae, or maggots, feed on the decomposing organic material. They will pass through three larval stages (instars). Once they have reached the end of their third instar, the maggots stop feeding, migrate to drier substrates and form pupae (cocoons). Adults emerge from the cocoons in as little as three days and as long as four weeks, depending on current temperatures. The life cycle of the house fly is typically completed in 10 days at 80oF.
Cost effective, long term suppression of house fly populations requires the combination of multiple approaches into an integrated pest management (IPM) strategy. An IPM goal is to avoid or decrease house fly related problems while minimizing potential risks to human health, the environment and non-target organisms including companion animals. Three types of control methods are commonly used to suppress house flies: cultural, biological and chemical control. A simple fly swatter may be the best option to kill a few flies invading a home or retail store. It is important to remove and dispose of dead flies because these may serve as food for other house-invading insects.
Cultural control relies on the modification of the environment to make it unfavorable for house fly reproduction and development. The best cultural control method is sanitation. It is best to frequently clean contaminated surfaces and properly dispose of food and any organic materials that can serve as house fly food or egg-laying substrate. Such organic materials need to be collected and placed in garbage bags that are properly tied in order to prevent access by house fly adults. Most house flies stay within a mile of their birthplace. Removing all food residues and cleaning garbage cans on a weekly basis will reduce their attractiveness to house flies.
House fly numbers in homes and retail businesses can also be reduced by exclusion. Well maintained windows screens and screen doors can minimize house fly access. Retail stores can also install air curtains (powered by air blowers) above their exterior doors to make it harder for flies to gain access. Mechanical doors that open and close automatically can also minimize the chances for house flies to get indoors.
Several types of traps are available to control house flies in homes or retail stores when they have gained access. Sticky traps and ultra-violet light traps do not use toxic chemicals and are a good alternative to the use of insecticides. Traps need to be placed at least 5 feet away from food processing areas to avoid contamination risks and away from windows to avoid attracting more flies into the building. Sticky traps need to be replaced frequently as they loose their effectiveness with time, especially in high dust situations.
Biological control is the use of naturally occurring organisms (natural enemies), such as predators, pathogens, and parasites, to suppress pest populations. Although considered a pest themselves, fire ants are important predators of house fly pupae. Several species of parasitic wasps seek out and kill immature house flies. These parasitic wasps are considered beneficial insects and are not harmful to people or animals. A few species of parasitic wasps are sold commercially as parasitized house fly pupae and are available from insectaries in Texas and other states. However, it is important to know that parasitic wasps may take a long time to work, and they alone can not eliminate a house fly problem. Purchased parasitized pupae should be placed in open containers stored in areas where house fly maggots are present. Containers should be placed in areas that are not accessible to fire ants and other predators of the pupae, as well as out of direct sunlight and rainfall. Biological control should be used in combination with other control methods as part of an integrated pest management program.
Chemical control is the use of insecticides to suppress a pest population. When temperatures are favorable and house fly populations are large, insecticides can be used to quickly bring down pest numbers and increase effectiveness of other control tactics. Chemical control should not be used as the only pest control tactic because this may lead to secondary problems such as development of insecticide resistant fly populations and increased risks of allergies and other health problems, and increased risks of non-target effects. Common house fly insecticides are available as aerosol sprays or in bait formulations. Several products containing pyrethroids (such as cypermethrin, permethrin, tetramethrin and resmethrin) are labeled for house fly control in and around homes. Fly baits, such as QuickBayt® and Golden Malrin®, are usually sugar-based, and they contain a compound that attracts the adult flies. Flies that feed on these baits are killed by the insecticide they ingest. Regardless of the insecticide being used, it is recommended that the user carefully reads and follows the directions on the product label.
The information given herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Cooperative Extension Service is implied.