Flies as a group are part of an insect order known as Diptera (meaning two-wing) and there are over 120,000 species of them in the world. While many of these species can end up in the home, including fruit flies, drain flies, and blow flies, only one species occurs so often in domiciles that it is called the housefly. Houseflies are pests for their annoying habit of buzzing around you but they are also fairly dirty creatures (some estimates say they carry up to 65 different diseases) and can pose a health risk.
If you are trying to identify what fly you are looking at, house flies are about 1/8th of an inch to 1/4th of an inch long and have 4 dark stripes on the back of their abdomen (Figure 1). House flies exhibit complete metamorphosis, going from egg, to maggot, to pupae, to adult in about 1-3 weeks (Figure 2). Females seek out decaying organic matter in which to lay their eggs. Some of their favorite egg laying sites includes grass clippings, animal excrement, and garbage. When dealing with these flies you can locate the adults just about anywhere in the home but especially around lights and windows. You may also find symptoms of a fly infestation such as fly spots, white colored specks from the fly’s mouth juices, on windows and walls. You may find more than just the adult in the home as well. Maggots can be found in garbage cans or wandering on the ground and pupal cases often accumulate on the ground near garbage cans.
If you are dealing with a fly issue, control must be approached in an integrated pest management mindset.
- Your first step will be to limit breeding site availability. This will discourage females from entering your home and will suppress local populations. Be sure to place garbage in a garbage can that has a closable lid which fits tightly. You can try to rake glass clippings out of piles to discourage egg laying in them.
- Next you will want to focus on exclusion. Flies enter homes through holes in screens, open doors, or openings in caulking. Be sure that screens are affixed properly and are not damaged. If you like to leave your door open in spring/summer be sure you have a screen door that closes completely and has no holes. You should routinely check caulking around the home for holes and reseal when you find openings.
- Sticky fly traps and fly swatters are the cheapest and best control methods for flies in the house. Chemical control is typically not recommended or feasible for flies. They spend too much time in the air and not settled down where we make our applications. If you are dealing with an extreme infestation, you should contact a pest control professional to help you knock down the fly population and determine where they are emerging from.