Hundreds of flies on our house - help!

[guyfm]

Hello,

Can anyone help us, or give some advice. Every day we have literally hundreds of flies (they look like smaller, non-shiny bluebottles) all over the front & side of our house. They sit in the sun all day and then slope off as the sun moves...

None of our neighbours seem to have them, so I can't put it all down to being in the countryside and surrounded by fields & farms.

Really grateful for any suggestions, or possible solutions.

Thanks,
Sian

[Wild-Woman]

I can only imagine they're doing what you have already said and that is sun-bathing. Perhaps your neighbours house does not benefit from the sun as much as yours and so the flies stay put, where they are warm. It has been unseasonably warm and a lot of insects have hung on for longer than normal. I should think that with the onset of any frosts and a general drop in temperature would see the flies disappearing naturally.

[The Woodman]

Hi Sian

They might be Cluster Flies. These are now congregating for their winter hibernation inside the roof voids of selected properties. If they are, they are harmless and will disperse in the spring. Some attics can have thousands of them and the easiest way of ridding them is with a vacuum and releasing them outdoors.

I the spring, some folks see good numbers awaking and trying to get out through windows which can be a bit disturbing. Simplest thing is to open the window and let them out.

I have to check a large property on Monday morning which has had a brown long eared bat roost during the summer months. The owner wants the flies "treated" and I have to make sure there are no bats present before the company sprays.

There are many other species enjoying the last of the sun's warmth on south facing surfaces, however.

I don't know why these flies are attracted to certain properties but can only guess the conditions in the roof are to their liking.

Welcome to WAB, too.

[Dogghound]

They sound like cluster flies to me. Clusterflies migrate and group up in buildings, entering through small cracks and gaps into the wall cavity and roof void where they hibernate for the winter then leave in the spring. It is possible that you house is warmer than others in your area. It could be south facing, or you may have higherheating temperatures, more shelter etc. They often bask in the sun on warm days during the hibernation period. They dont breed in buildings and dont carry any significant problems. They are parasitic on earthworms.

I would personally leave them, however there are load of insecticides which you could use. I would not recomend plugging up gaps incase other wildlife is in them such as bats. You also need to be careful when you start using chemicals. Any gap needs to be thoroughly checked before you do anything to it.

I had to do a roof inspection for bats earlier this week and had hundred flying out at me (flies not bats).


EDIT. Cross post with woodman/wild woman.

[thunder]

Worth pointing out that 'treating' cluster flies with insecticides will not stop the flies congregating in future years. Nobody is quite sure what attracts cluster flies to one particular house. There is some suggestion that pheromones may play a part, so the flies just follow the scent of last year's cluster. Perhaps a good spraying with a powerful aftershave may work better than insecticide.

henrya

[Jason Green]

...solutions?

[thunder]

Originally Posted by Jason Green

...solutions?

1) Learn to live with them.
2) Change the micro-climate of the roof space in which they congregate so that the conditions are no longer to their liking. Such as make it slightly warmer, by installing some very low power heating in the roof space to raise the temperature by a couple of degrees. Or possibly make it colder by increasing air flow with, say extra air bricks, or more insulation at loft floor level. You may have to experiment to find what works.

henrya

[Jason Green]

I meant, solutions to what.

As far as I can see, the OP is talking about flies landing on the house, basking in the sun. There's no solution to that. Well, short of preventing the house's exposure to sunlight!

As for roofs and clusterflies, whilst this may be the right ID for the insects landing on the house there's no real corrolation between a specific genus (Pollenia) and absorbing heat from a warm wall. We have no reason to suspect the loft is involved.

[Dogghound]

Originally Posted by Jason Green

I meant, solutions to what.

As far as I can see, the OP is talking about flies landing on the house, basking in the sun. There's no solution to that. Well, short of preventing the house's exposure to sunlight!

As for roofs and clusterflies, whilst this may be the right ID for the insects landing on the house there's no real corrolation between a specific genus (Pollenia) and absorbing heat from a warm wall. We have no reason to suspect the loft is involved.

Its highly likely Jason, it would be pointless giving advice on something less likely i.e. Fanniidae. If they are Pollenia they will almost certainly be roosting/hibernating within that house, as that is how they behave.

[guyfm]

Thanks for all the replies, everyone. They do gather around the eaves over our downstairs bay windows which we have discovered are not sealed/finished so I suppose that would be a perfect egg-laying spot for them...

Sian