On Wed, 29 Jul 2020 14:40:12 +0100, John Rumm wrote:

I think they suggest you stick some bait in the try to attract them...
(must admit ours tends to get lots of moths etc, but blue bottles ignore
it)

Not all species of fly are attracted to UV, round here is it small 2
- 3 mm "floaters" that ignore it. Blue bottles don't but when they
get zapped they explode spreading bits of fly over a couple of
feet...

We did have an invasion of the same species of "house fly" last week,
dozen or more of the things just suddenly appeared. Next day we found
the well decomposed remains of a blackbird hidden near the door that
we had left open for longer than normal before we noticed the flys...

--
Cheers
Dave.