House flies are not only annoying when they buzz past your head while you are watching television, they can also be a health hazard when there are too many of them around. Knowing whether you have a few rogue flies that came in through a hole in a screen or whether you have a fly infestation on your hands will help you determine how to best handle the situation.
One of the most noticeable signs that you potentially have an infestation of flies is seeing a lot of flies buzzing around. Though you may have large numbers of flies in certain areas, such as close to dustbins in the sweltering summer heat, an infestation will be signified by more than normal amounts of flies. Swarming flies is also a good sign that you may have a much larger problem on your hands.
Fly infestations occur when something rotted, which then bred maggots, which then hatched into flies. The pungent and distinct smell of maggots is another indicator a fly infestation has happened or is underway. The smell emanates from the rotting food the maggots feed off of. You should look in corners, under dustbins and other areas where something may have died or rotted. Flies breed by laying eggs when they land. The eggs hatch in a mere 24 hours which produces larvae or maggots. After a few days, the maggots hatch into flies. You can squash a potential fly infestation by finding larvae before the flies hatch, which occurs in approximately three days.
You will hear the buzzing of numerous flies if you listen closely. This sign works well in more cavernous areas such as garages and sheds. Since you will typically find flies gathering around waste, listen around areas where garbage is. Though you can more easily hear adult flies, if you listen very closely you can hear a mound of maggots moving around as well. You may need to get uncomfortably close to an area with a dead animal, rotten trash or other source of smell to find the maggots by listening for them. The sound is similar to a light rustling, as they are squirming inside their casings; this, when multiplied by thousands, can be heard with an unaided human ear.
If you suspect a fly infestation, one way to get a jump on the problem is to have insecticide sprayed into corners where flies would typically breed, such as garages, sheds and trash storage areas. You can also hang fly strips from the ceilings of the same areas. If you notice a large quantity of flies caught on the fly traps or laying dead in the corners where the insecticide was sprayed, you may have found evidence of an infestation.