House Flies

Flies are a common problem in homes at certain times of the year.

Flies are a common problem in homes at certain times of the year. Flies that occur in the summer are usually either house flies or blow flies. Flies that occur in the fall, winter and spring are often cluster flies, especially in homes that are located in the country. Two other flies that will over winter in country homes are face flies, and black blow flies.

House Flies

House flies occur mainly in the summer, except in places such as farms, where they can live year round in heated buildings. Starting each spring, house fly populations are low and gradually increase through the summer peaking in the fall just before frost. Under ideal summer conditions, house flies can go from egg to adult in 7 days. This is why garages that have garbage bins can become filled with flies and maggots in a very short time. The cold weather in the fall and early winter will kill off most of the house fly population.

Face Flies

Face flies are pests of farm animals such as cattle and horses. Face flies closely resemble house flies and are difficult to tell apart. They breed in cattle dung and feed on the secretions around the faces of cattle and horses and other large animals.

Black Blow Flies


Black blow flies are also common around farms, breeding in carrion, manure and other decaying organic matter. Unlike most species of blow flies which occur over the warmest parts of the summer, black blow flies are most numerous in the cooler weather of the spring and fall.

Houses or other structures that are located on or near farms are more likely to have face flies and black blow flies as well as cluster flies. Depending on the year and type of farm, this can result in large numbers of flies emerging inside the house in the fall and again in the spring.

Treatment of House Flies

The best treatment for house flies is to make sure window screens fit tightly and keep screen doors closed. House flies will often follow you in as you go in through an outside door. Keep garbage and recycling material in bins with tightly fitting lids. Aerosol fly sprays with pyrethrins will help to temporarily know down heavy numbers. Cluster fly type treatments will not work to eliminate summer house fly problems.

The treatment that we provide for cluster flies will also work on over wintering face flies and black blow flies. Many of our customers on farms have been telling us for years that the number of flies are greatly reduced in their homes following our spring treatment. This is not due to the continuing action of the insecticide as the residual life of insecticides today, due to environmental concerns is short, about 30 days for most permethrin formulations. Rather it is the reduction in the numbers of the over wintering fly population which results in fewer flies that will be breeding in the vicinity of the home.