THE CLUSTER FLY

Pollenia rudis

Appearance

A large fly up tp 10mm in length, very "Furry" in appearance with quite obvious golden hairs on its thorax (Tail end)

Biology

The larva (Maggot) lives as a parasite of a certain type of earthworm. (Allolobophora chlorotica)

The eggs are laid on the soil and hatch in about a week .

When the young larva finds a worm it bores into it and develops inside it.

In spring the maggot leaves the worm which is by now almost completely devoured, the maggots then pupate and then turn into adults these flies are then seen sunbathing on south facing walls on houses, buildings ,tree stumps and posts.

In the Autumn they try to enter buildings to over winter and can gather in there thousands , they cluster mainly in lofts, upper rooms and in window casements.

when the weather is cold they are less active but when stimulated by heat, they can become quite active and can cause great concern.

In most years there are two generations but in warm summers there can be up to four. Weather plays a large role in when the flies start to seek out a place to over winter and again in some years it can be as late as December.

There is no known reason at present why some houses are chosen year after year for a winter site for these flies and single houses can be picked out year after year even if they are in a long row of houses, saying that some house will only be targeted the once and never have a problem again.