There are four main species of fly collectively known as cluster flies. They are:
The Autumn Fly
The Common Cluster Fly
The Green Cluster Fly
The Yellow Swarming Fly
Cluster flies are very common indeed. The adult cluster fly hibernates during the
winter season in roof spaces. The flies lay eggs in the earth and also in animal
dung. As the temperature climbs in late spring, the eggs will hatch.
The larval stage is parasitic, entering earthworms and feeding on them until the
larva emerges as an adult cluster fly. There may be two to four generations of flies
in one year.
Cluster flies migrate from the outside conditions into the lofts of house and farm
buildings during the winter season. Obvious signs of an infestation include large
quantities of lethargic/dead flies around windows. Once in roof spaces the flies
will stay in hibernation until sapring.
Small infestations behind curtains and around windows can be simply removed with
a vacuum cleaner.
For a larger problem in areas such as loft spaces, treatment is best carried out
by a qualified pest control technician after the first winter frosts. This usually
ensures that all of the hibernating flies are in the treatment area, resulting in
a more cost effective solution. Pestforce usually treats this problem with an insecticide
space spray, will quickly eradicate any cluster flies present.