You would have noticed large black flies in house during winter seasons and would have wondered what they are. They are called cluster flies or attic flies. These flies get this name as they live in groups, hard to reach areas like the small crevices of a wall, behind pictures, in furniture hinges, etc. After winter season is over, they move out of the house and live on fruits or flowers.
Though there are no health risks to humans due to their presence inside the house, it can be a cause of irritation to people living in the house because of its bad odor.
How to restrict cluster flies from entering your house
Cluster flies lay eggs in summer. As soon as summer season commences, seal all cracks of the wall, or holes or any such hard to reach gaps with some adhesive. It is advisable not to seal cracks during winter as it may cause the already existing fly in the wall to come out of its place.
Application of insecticide on the exterior of your house before winter just after the eggs hatch and become adult flies will kill them.
Fly lights can be installed in areas like dark spaces like attics, basements, etc. which will draw the flies towards it and kills them.
How to eliminate flies after infestation
Use insecticide on any wall cracks and crevices which you suspect is infected or found flies living. Also look behind curtains, windows frames, behind kitchen baseboards, electrical outlets, Etc.
Identify any walls that have cracks, dust and seal them.
A vacuum cleaner tube can be used to remove clusters of flies in lofts, basements or any other not frequently used spaces.
Keep a pyrethrum spray handy to kill them as soon as you spot them.
Cluster flies are frequently seen in dark spaces like the attic or closets, etc., you can use a residual spray to kill them.