Fruit flies and related species (Diptera: Drosophilidae and other families)
Fruit flies are a common nuisance in Michigan homes, even in the winter. They develop in ripe fruit, fungi, or moist areas where fruit or vegetables are stored or discarded, and probably in any wet, decaying vegetation. Fruit fly maggots feed primarily on the decaying matter and fungi occurring in these areas. They can reproduce very quickly at warm temperatures. These flies are very common visitors in our home during the summer and fall months when they are attracted to ripe fruit or vegetables, fermenting liquids and garbage pails kept indoors. They are small enough to pass through window screens. If possible, these foods should be placed in the refrigerator. Keep garbage stored in tightly sealed bags and remove it from the house as quickly as possible.
If you continue to see these flies during the cold months when insects are not active outdoors, one of two things may be happening:
1) The flies entered the home in the fall seeking a nice, protected spot to spend the winter, and because the home is heated, they remain active and find their way into to the living area.
2) They are coming from larvae which are developing in some forgotten vegetable or organic matter in the home.
If the latter is true, the best method of control is to locate where the maggots are feeding and remove the food source. If the flies are simply overwintering or hibernating in wall voids, attics, cracks and crevices found throughout the house, there is not much that can be done during the winter other than to spray the flies with any household aerosol insecticide containing pyrethrins (like Raid). Anything that can be done to prevent the flies from entering the home by sealing or caulking around windows, doors, and other possible points of entry will help reduce the number of flies seen in the winter. Be sure to read and follow all the instructions and safety precautions found on the pesticide label before using any pesticide. If you have additional questions, please feel free to call me at (517) 353-9386.