Purdue University
Agricultural Extension Service
Entomology Department
E-35

Cluster Flies

The cluster fly (Pollenia rudis). sometimes called the attic fly, is a familiar pest in many homes. The flies are somewhat sluggish and make their appearance during the fall and winter and become especially active and noticeable on sunshiny, mild days of early spring. They buzz around rooms and frequently collect in large numbers at windows, especially in rooms which are not frequently used. Cluster flies are slightly larger than house flies and may be recognized by the short golden hairs on their thorax which is the part of the body to which the legs and wings are attached. Although they do no damage, their appearance in homes is a considerable annoyance.

Cluster flies have a peculiar life cycle. The maggots or larval stages are parasites within the bodies of earthworms. When the adult flies emerge in late summer and early fall, they seek places of protection to spend the winter which in many cases is within the walls, attics, and basements of homes. Screens afford no protection since the flies may crawl in through small openings seemingly too small to permit entrance.

Control Difficult

Complete control of cluster flies is difficult since the over-wintering pests are concealed in walls, window casings, possibly attics and other inaccessible places. From these locations, they select warm days to enter the house itself through any openings they can find. It is not difficult to kill the flies as they enter but more will likely make their appearance later on.

Recommended Control

1.	Close all openings through which the flies enter rooms. A favorite place is the pulley openings through which the weight cords run.

2. Use a 2 or 3 gallon compressed air sprayer and apply a chlordane spray to thoroughly wet the surfaces in attics, basements, closets, store rooms and other areas where the flies frequently are seen. Use a 45 percent chlordane emulsion diluted at the rate of 1 pint in 3 gallons of water. For smaller areas, use a standard 2 percent chlordane solution. Do not apply these heavy residual sprays in bedrooms or in papered or other well furnished rooms.

3.	Paint all window sashes and casings with a 10 percent DDT solution or a 2 percent chlordane solution and repeat as necessary.

4.	To kill flies as they enter rooms, use a high grade pyrethrum fly spray or a pyrethrum or chlordane aerosol. If an aerosol bomb is used, the application should
be made throughout the home. These chemicals, when used in this manner, provide little or no residual protection.

Department of Entomology

COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS
State of Indiana, Purdue University and the United States Department of Agriculture Cooperating
L. E. Hoffman, Director, Lafayette, Indiana
Issued in furtherance of the Acts of May 8 and June 30, 1914.

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