During the summer, cluster flies go unnoticed as they search for their host, the earthworm. Nailing wood over cracks or caulking them tightly helps reduce the annual buildup of the pest. You can also use the flies' attraction to light to rid your attic of the creatures. Simply open the attic windows on sunny days. The use of a vacuum cleaner is a quick and effective means of reducing a cluster fly population in the home.
Aerosol sprays containing resmethrin or pyrethrins are available for use in homes.
Insect strips or no-pest strips containing Vapona are also helpful. Never use no-pest strips where food is prepared or served, or in bedrooms where children, elderly or sick people spend much time. Use the strips in attics, window frames, spaces around louvers, under eaves and intersections of walls. Look for these materials in the active ingredient list on product labels. Be aware that some spray formulations may stain siding.