Also known as blow flies, green bottle flies are larger than common houseflies and are bright blue-green in color. They feed on waste material, exposed food and decomposing plants and animals. They don't usually enter a house just because of lights. When you find large numbers of green bottle flies in your house, it usually means that you have feeding and breeding sites suitable for them. You can get rid of the flies by eliminating these sites.
Take out the garbage at least once a week and clean the area where you usually place your garbage can. Flies sometimes lay eggs in meat and vegetable scraps in your garbage, especially in the summer. The maggots and pupae then develop in the trash and other dark, secluded places. Vacuum any fly maggots and pupae, then discard the bag.
Hire a plumber to check your sewer pipes, especially if you see the green bottle flies near plumbing. There may be a break in your sewer pipes, allowing sewage to seep beneath the pipe. Flies can then access the sewage and use it as a feeding and breeding site.
Remove all decomposing animal remains from the house and bury them at least 12 inches deep. Alternatively, place them in a garbage bag, tie the bag tightly and discard it. According to the University of Nebraska-Lincoln, the dead animal is often a mouse in a forgotten mouse trap or one that died in an unknown location after eating mouse poison.
Place fly strip traps near windows during the day. These sticky traps catch the green bottle flies that are attracted by the light from windows. This kills the flies without introducing chemicals into the house.
Use a flyswatter to kill any green bottle flies you see.
Spray the green bottle flies with insecticides that contain pyrethrins.