Houseflies are more than just annoying pests. Although they don't bite, houseflies can carry diseases, and those diseases can be transmitted to humans when flies land on and contaminate food. Chemical insecticides are available to handle fly infestations, but insecticide-resistant strains of flies are developing in response to these treatments. For an environmentally friendly, nontoxic way to handle a fly problem, use homemade traps instead of chemicals. Your traps will only be effective if you also take steps to prevent additional flies from entering your home.
Cut the top off the soda bottle, using scissors. Cut below the tapered top portion of the bottleneck. Coat the inside bottom of the bottle with corn syrup. Place a piece of overripe banana or raw meat in the bottom of the bottle.
Invert the top of the bottle and insert it into the bottom section of the bottle. Hold the cut edge of the bottle top level with the cut edge of the bottle bottom. Paperclip the two pieces together if you plan to stand the trap on the floor, table or counter. Place the trap in the desired location.
Punch a hole through both layers of plastic on one side of the bottle, using a hole punch or sharp knife. Make another hole opposite the first. Tie each end of a length of string to one of the holes, creating a loop handle. Use the string to hang the trap in the desired location.
Discard the trap and replace it with a new one when the corn syrup is full of dead flies or the bait begins to smell rancid.