House flies (musca domestica) and Bluebottles (calliphora vicina)
House flies are commonly found where people work or live because of the warmer environment and ready supply of food.
Bluebottles (sometimes called blow flies) are also often found in human environments, and are particularly attracted by meat and decaying materials.
Where do they come from?
Eggs are laid in moist or rotting matter - household rubbish, compost or manure and once hatched the flies reach maturity in about two weeks in warmer weather.
Common house flies have a flight range of about five miles and can easily transfer from breeding grounds to homes.
A sudden appearance of many bluebottles in the home normally indicates that a small animal (maybe a mouse or shrew) has died - possibly under the floorboards or up a chimney.
Female bluebottles are easily able to find sources of suitable food and are often found in domestic kitchens.
Cluster fly infestations usually occur in lofts and roof spaces, although they can also be found in sash or casement windows and in unoccupied rooms. Cluster flies are regarded as a pest insect as they tend to 'cluster' in groups of hundreds or even thousands which can be a nuisance, particularly in the spring and autumn months when warmer temperatures cause them to become more active.
Why do flies come indoors?
House flies and bluebottles come indoors looking for food. They are not fussy what sort of food they settle on and are highly active once indoors.
Can they do harm?
House flies can transmit intestinal worms and are also known to be carriers of particular diseases such as gastroenteritis. Bluebottles too, are known to spread diseases. This is partly due to the fact that they are attracted to rotting food and faeces which they may have landed on before landing on your food.
You must cover any open food to avoid contamination by flies landing on it.
You should frequently clean drains, particularly near kitchens, and cover your waste bins to avoid providing ideal breeding conditions.
How do I get rid of them?
The best ways of controlling or avoiding infestations are good hygiene and taking the simple precautions mentioned above.
Insecticidal control using fly sprays ('knock down' sprays) are a good, almost instant, way of dealing with the problem. Flypapers or fly screens can be effective for persistent problems.
Large infestations of flies may be linked to certain agricultural practices and may cause a fly nuisance.