Cluster fly

(Pollenia rudis)

(Pollenia rudis)

During the summer months, cluster flies are present outside and pose no real nuisance. Once the temperature starts to decrease, the flies often enter buildings looking for a place to hibernate; this is usually in roof spaces where they are able to gain entry. If the area in which they are hibernating begins to warm up, the flies can sometimes emerge early and become a nuisance to the occupants.

Life cycle:

Complete metamorphosis

Egg Eggs are laid loosely in areas such as damp soil or rotting leaves. The egg hatches after around 7 days.
Larva Larvae actively seek earthworms to act as a host, during which time they bore into the body of the host worm and develop through the instar, feeding on the worm. Once reaching the final stage before pupation, and close to the earthworm’s death, the larva bores out again in order to pupate in the soil.
Pupa  The pupae is the final stage before metamorphosis into the adult form. This stage is largely controlled by the weather. It is thought that in the UK there could be between two and four generations per year.
Adult  The adult flies are around 6 mm in size, with red eyes and yellow-gold hairs covering the thorax. They feed on nectar from gardens and wild flowers.


Commonly found in Europe and the UK, the flies are often attracted to human dwellings when looking for a place to hibernate, usually in the colder months. They can often be found in cracks and crevices in houses, such as in exposed beams, window ledges and door frames.

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BPCA (2015) The British Pest Manual: A reference manual for the management of environmental health pests and pests of the food industry, 2015 edn., Derby: BPCA.