Hundreds of flies on our house - help!

[Dogghound]

Originally Posted by 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...

They dont lay eggs in buildings only hibernate in them, they are parasitic on earthworms and lay their eggs near earthworm burrows in the ground. They are not a health hazard, they just get annoying.

[Jason Green]

Is this not just flies basking though, with some near windows - and some not? I've seen many different Calypterates basking in the last few days; Muscidae, Anthomyiidae, Calliphoridae, etc.

Have a good number been found inside the house? If not, it's equally likely they may be just basking.

Is the wall a darkish colour?

[Jason Green]

Actually, any chance of photographs? You know, one showing their spread and another of an individual.

[Dogghound]

literally hundreds basking? Ive never seen other Calypterates basking in those kind of densities. The only time I find high numbers like this is when they are around a food source.

[Jason Green]

I suppose it would depend on the surface area involved. I have frequently seen tens doing so on bare earth, asphalt sheeting, etc. Quite a lot of Pollenia among them, then of course various Anthomyiids, the odd Tach, etc.