Cluster Fly : Pollenia
the most common cluster fly. It
is about the same size as a house fly and easily identified by its
large, reddish eyes, the thorax covered with yellow-gold hairs and its
habit of folding its wings over its back when resting.
adult flies lay their eggs on damp soil, rotting leaves etc., and the
emerging larvae seek out and develop inside earthworms.
They pupate in the soil and the merging adult flies feed on
nectar of flowers. In warm
weather, up to four generations of flies may be produced.
In late summer, large number of flies can ‘cluster’ as
explained above, often giving off a sickly-sweet smell.
Green Cluster Fly :
Dasyphora cyanella resembles
the common greenbottle fly. The
larvae grow in dung and the adults cluster in the same manner, often in
association with the common Cluster Fly.
Autumn Fly :
Musca autumnalis resembles
a small house fly. The
larvae develop in cow dung etc., and are commonly associated with
flies are primarily a nuisance insect when they invade the living areas
of buildings, however the large number of dead flies that can accumulate
in the hibernating areas can provide food for Carpet Beetles.
carpet beetle infestations in historic collections have been shown to
originate in cluster fly debris on window sills, loft areas etc., where
they have not been cleaned up regularly.
cluster flies develop in the surrounding countryside and may fly half a
mile to hibernate, controlling the sources is impossible.
up windows, cracks etc., and underlining roof slates etc., to deny
access is the only effective measure to prevent the flies entering a
building. However, it is
often not possible or practicable.
In severe cases, insecticide can be sprayed around the edges of
window to kill insects before they get in.
cluster flies are found in a building, vacuuming them up and destroying
the bag is often effective for small numbers.
Large accumulations normally need professional treatment using
insecticidal smokes or fogs. In
severe cases, external walls can be sprayed with insecticide to kill
landing flies before they enter.
is important that dead cluster flies are removed by vacuuming regularly
as they can attract other pest insects.