Cluster Flies 

Cluster fly are not to be confused with the common housefly. They are slightly larger, dark grey and non-metallic in colour.

In autumn they search out places to hibernate and may be seen in large numbers (in lofts) clustering together hence the name cluster flies.

Cluster flies can be troublesome in autumn and in spring when they come out of hibernation. A ULV or smoke treatment can achieve a vast knock down, but complete control is almost impossible, as they may return to the same building year after year.