6-10mm overall body length

The common cluster flies have reddish eyes and a thorax covered in golden hairs.

Cluster Flies are found in numerous locations, but usually in lofts and roof spaces. South- facing walls often favoured.

Visual sightings of large numbers of adults

There are three main species of fly collectively known as cluster flies. They are Musca autumalis, a small fly of about the same size and colour as the house fly, Pollenia rudis, a larger fly dull brown/grey in colour, and lastly Dasyhora caynella which is about house fly size and shiny green/blue in colour.

Cluster flies, particularly Pollenia rudis are very common occurring throughout Great Britain. The adult flies after hibernation during the winter months, lay their eggs in the earth or in animal dung. Permanent areas of grassland are favourite sites e.g. permanent grazed pasture or parkland as soil cultivation such as ploughing disrupts the flies breeding cycle. The eggs remain in the earth and hatch when soil temperature increases in the spring. The larval stage is parasitic, entering earthworms and feeding upon them until emerging as an adult fly. Cluster flies migrate from outdoors into the lofts of houses and farm buildings during the winter months. Obvious signs of an infestation is a roof space containing a large quantity of lethargic flies and a quantity of dead flies. Unless the loft is used for storage purposes or ~ accessed regularly the flies will hibernate successfully leaving in early spring dependant on the weather.