By Melchisedec
Lancashire,
United Kingdom 
I have scores of these flies skipping about on top of the water in my half-barrel. Does anyone know what they are? I’m afraid it’s not a very good photo. They have a white circle at the tip of the wing.
15 Jul, 2019
Answers
pressed send before I said that the males dance around the females and the white spots are used in the mating rituals.
15 Jul, 2019
Thanks Sbg! I have been wanting to identify them for a week or so. The strange thing is that they’ve all now disappeared! It is very hot, and the barrel is in full sun. I wonder if that’s why? Or perhaps the mating is completed.
16 Jul, 2019
Poecilobothrus nobilitatus the semaphore fly.
the male has the white spots the females don't.
15 Jul, 2019