This fly is a nuisance pest that will invade your home in the fall as the temperatures drop at night. The fly lays eggs just under the earth's surface. The larvae hatch out and bore into earthworms until they are ready to pupate. They pupate just under the earth's surface and then emerge as the fly. They do not lay eggs in your home, and they don’t want your food. They are pollen feeders. A Cluster Fly can affect your house from three miles away and in large numbers. No matter what you do, this fly still tries to enter the home. They follow any heat loss in reverse from the structure.
The treatment is to treat the exterior of the home to eliminate them as they try to enter, paying particular attention to cracks and crevices around windows, doors, and eave areas. The whole house gets treated.