Cluster Flies
Key
Features of Cluster Flies
These are dark greyish flies about 8mm long
with yellowish hairs on the back and with overlapping
wings.
Biology
Cluster fly females lay their eggs singly in cracks
in the soil; the larvae emerge in three days and begin
to seek out their food source: earthworms. After burrowing
into the earthworm, the larvae feed for about three
weeks before pupating. The adult Cluster Fly emerges
from its pupa after 12 to 14 days. The adult flies (of
which there 3 to 4 generations per year) feed on flowers.
Distribution
In autumn they congregate in large numbers in upper
rooms or roof spaces of houses to hibernate. The larvae
of one species are parasitic upon certain earthworms,
so this species is more common in rural areas.
Significance
A mass of cluster flies has a characteristic smell.
They are sluggish in flight and are a nuisance in the
house.
Control
Once cluster flies have found their way into buildings
to hibernate they can be difficult to control, due to
their fondness for inaccessible space. It is important
to seal as many openings as possible to stop flies from
entering the building.
Infestations can be controlled through surface sprays
and specialist crack and crevice treatments.
