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What To Do About Cluster Flies (Polleniarudis)

WHAT ARE CLUSTER FLIES?


Cluster Flies are a common pest species in the UK. They are mainly a pest in rural locations, but we have dealt with them in towns and cities over the years. They are mainly a rural pest because of their life cycle, which is a pretty gruesome, yet amazing life cycle to say the least.


They are a parasitic pest species of fly that live in and on Earthworms. The larval stage (Maggot) of the Cluster Fly lives inside Earthworms from Spring until the end of the Summer.


At the end of the summer the adult Cluster Flies leave their hosts, killing the poor EarthWorm in the process!


In the Winter, after feeding in fields and grasslands they would usually start to 'cluster' together (hence the name Cluster Flies) in hollowed out trunks of trees, under bark, holes in walls, etc. But in the modern world Cluster Flies have realised that there are much safer harborages to be found! These new safe Cluster Fly overwintering places are in homes, caravans, etc.


HOW DO I KNOW IF I'VE GOT A CLUSTER FLY INFESTATION?


In late Summer or Autumn you may notice tens or even thousands of Cluster flies sunning themselves before they crawl into lofts or even holes in window frames!

They may reemerge if temperatures fluctuate, but as average temperatures drop, they will take up more permanent residence inside.


This process will happen again in the spring as they start to wake up to carry out their life cycle again for another year.


Amazingly the offspring from these flies will nearly always come back to the same overwintering place, but usually in bigger numbers!


HOW DO I KNOW I'VE GOT CLUSTER FLIES?


As mentioned in the previous chapter, you may notice cluster flies sunning themselves on the side of your house. This will nearly always be on a south-easterly facing wall, and preferably a white or reflectively coloured wall.


You may also notice the flies inside bedroom windows, this is where they have found a way in, but cant get back out, as they get confused by the glass in the window. If they can find a way back out to sunbathe they will usually leave a calling card in the form of brown fecal matter around the window frames.


You may also see them up in the loft, especially if there is a light up there, as cluster flies will be drawn to this on warmer days thinking its daylight.

Sometimes you will also notice a strange pungent smell! This is caused by pheromones (chemical smell signals) that are designed to tell other Cluster Flies where the best place to cluster is.


WHAT CAN YOU DO?


Very little. The task of proofing your house to keep them out would never be viable and very likely to be impossible, as one tiny hole missed would render the operation futile.


Repointing around window frames may help, but they nearly always find another clustering site not too far away, like your loft.


You could use a normal fly spray, this will kill all the Cluster Flies that it touches, but it won't affect the ones hiding away from the spray.


Old fashioned fly papers can have a small effect on the population, but highly unlikely to stop further infestations, or to have any effect at all.


You could also wait for a very cold day and try to hoover them up while they are docile, but again it's not very effective.


WHAT WE CAN DO AGAINST THE CLUSTER FLY INFESTATION.


We have numerous ways to deal with large numbers of cluster flies. We will come out and give you the options that are best suited to your requirements. We must also look for evidence of bats at your house, as the use of insecticides is highly restricted in those circumstances. If this is an issue we will take you through your options on how to get rid of cluster flies.


Contact Pest Interceptors today for expert advice and pest control services.

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