The adult house fly measures 6-7 mm, with the female being slightly larger than the male. They are easily identified by the four dark and narrow longitudinal stripes on their thorax. The abdomen is gray or partially yellow and has a dark midline and dark markings on each side. Adults have six legs and a pair of claws utilized for gripping surfaces. Beneath each foot there is a glandular adhesive pad called pulvillusthat allows the insect to hang upside down on smooth surfaces.
The egg measures around 1 mm, is white, elongated, and has rounded ends. They are laid by females individually but are piled in clusters of 75-150 eggs. The optimal temperature for a high egg production ranges from 25 to 30 degrees Celsius, and they must be kept moist in order to hatch. Often, female house flies will lay eggs in close proximity to one another, leading to large masses of flies in different development stages.
Larvae emerge from the egg in warm weather within 8-12 hours. They are 3-9 mm long, have a creamy-white appearance and the shape of a cylinder (tapering towards the head). Moisture is essential for larvae to complete their development, which usually takes 4 to 13 days at optimal temperatures of 12 to 17 degrees Celsius. From the last larval skin the pupal case is formed, measuring about 8 mm and turning from yellow to dark brown as the pupa ages. Pupae complete their development between 2 and 6 days at optimal temperatures of 32-37 degrees Celsius.
The house fly feeds on a large variety of foods rich in organic matter, including excrements and many kinds of sweet liquids or decaying substances. Their mouthparts allow them to ingest only liquid materials (they cannot bite or chew) and are designed to sponge and liquefy a variety of food material. By vomiting saliva and digestive substances onto solid meal, the house fly is able to break down the food and suck everything through a tube leading into the stomach. If the food cannot be dissolved easily, then the fly will store it inside an inner sack called a crop and is then passed between the mouth and crop several times until it’s liquefied.
The lifespan of an adult house fly ranges from 15 to 25 days, but it can live up to 2 months if there is suitable food available (particularly sugar). Females need protein-rich foods in order to produce eggs – access to suitable breeding sites such as human excrement, horse manure, or kitchen waste may extend the reproductive capabilities of flies but is not sufficient for optimal performance. House flies have their sense of smell located in their antennae, which are used to find food. (By measuring the electricity in their smelling cells, researchers have been able to recognize if a certain smell attracts or repels a house fly and help design effective bait traps.) They can also taste food through the many taste hairs located on their legs.
Flies prefer bright sunlight and are usually inactive at night, but may go wandering in artificial light, as well, driven by their insatiable curiosity and exploratory behavior. They live close to humans, in urban or rural areas, usually in regions with a temperate climate. They are most common during the warm season – the optimal temperature for their growth and survival is between 10 and 25 degrees Celsius – but many of them survive the cold of winter, as well, if they manage to find proper shelter. Outside, they rest on grass, shrubs, wires, trash cans, ground, or trees, while indoors, they prefer staying on floors, ceilings, walls, doors.
Seeing large numbers of adult flies are the most common sign of a house fly infestation, but you can also recognize a severe fly problem by the presence of maggots on garbage, manure, and other breeding sites and deposits of saliva and feces on walls, floors, ceilings and other surfaces where flies rest.
Although the fly doesn’t bite, it poses serious risks to human health and comfort, therefore requiring immediate control. The most important direct damage caused by house fly infestations is the annoyance, but the indirect damage is far greater: potential transmission of disease-causing pathogens. Flies pick up these organisms from excrements, garbage, sewage, and other sources of waste and discard them on human and pet food. Salmonella, Campylobacter, Enterococcus, or Chlamydia are some of the most common pathogens associated with the house fly; they are also linked to outbreaks of shigellosis and diarrhea and involved in the transmission of tuberculosis, anthrax, food poisoning, and parasitic worms.
Non-chemical control.Screening, trapping, and other non-chemical control techniques can go a long way in preventing flies’ access on a property. Exclusion methods include putting tight-fitting screen doors on all windows and doors and ensuring there are no openings around gas or water pipes that enter the building. Also, caulking all cracks and holes that may serve as entry points will diminish indoor fly problems. Fly traps are also extremely effective if they are properly baited and placed in strategic locations by a pest control professional. They can be placed both indoors and outdoors; recommended placement areas include entryways, beneath trees, manure and compost piles, and in alleyways. Ultraviolet light traps, sticky fly traps, baited traps, and fly swatters can also be used to control fly populations indoors.
Chemical control.When house fly populations grow out of control, pest control professionals recommend the application of pesticides (adulticides, larvicides) to suppress the growth, although these are most effective in conjunction with other control methods. Inside, home owners can use pyrethrin-based sprays for quick knockdown, while for outdoor infestations, boric acid, powder formulations, and insect growth regulators may be utilized. Exterior applications of synthetic pyrethroids will provide relief to some extent, but their effect will be significantly reduced within a few days form application.
House flies are one of the most mutable species in the world, meaning they have developed resistance to all common classes of insecticides; some of their methods of avoiding toxic residues include metabolic degradation, sequestration of toxins, and reduced cuticle penetrance. Therefore, the best approach to effectively eliminate existing populations and prevent future infestations is a professional management and control program that includes sanitation, exclusion, and chemical control.
Sanitation is the first and most important step in any effective house fly management program. Killing adult flies on the spot may provide some relief, but it’s essential to eliminate all their breeding areas in order to kill their population and prevent future problems.