A female house fly will lay up to 900 eggs in her lifetime, usually in groups of 75 to 100 in a batch. The batches are placed in moist, filthy locations, ideally human or animal waste, and kitchen waste and compost piles. This is why fly control services are often required. The eggs must stay moist and somewhat warm to hatch. The eggs are small, oval-shaped and whitish in color. Seeing clusters of these tiny eggs in your home may not mean infestation, but it will after they hatch and pupate.
Maggots are small, white, worm-like larval flies. They are often found in the places they were hatched: warm, moist, filthy places, so they can feed off the material within that location. Maggots will readily feed off nutrient-rich sources, such as manure. The higher the nutrient value the less they need.
Upon the completion of the larval stage (four to 37 days), in which the maggot will go through three instars, they will find a dry, cool place to form their pupal cocoons. They will travel up to 50 to 150 feet to find a suitable location. If they were laid as eggs within your home, they will most likely pupate within the home. Pupation requires two to 27 days. Pupation cocoons could be yellow or black, depending on the age of the pupae.
Seeing one or two flies does not constitute an infestation; however, seeing several flies, particularly at one time, may be of greater concern. Upon hatching from their pupal cocoons, flies will dry for about one hour. Pupae that have been in your home will often hatch from these cocoons at the same time, causing an infestation of your home. Adults typically live 15 to 25 days, but have been known to live as long as two months. The cycle will keep repeating unless the flies are removed, along with eggs, maggots and ideal breeding locations.