What do you call these flies?

[flobadob]

They look a bit like some sort of a spaceship. They have a part that drops down below them like an arm. I used to think they were called mayflies but having googled that I realised that they are not.

[Count-A-Strong]

For the second time today:
St Marks flies

[tinpotLizzie]

Probably Craneflies (Daddy Longlegs). They lay their eggs in grass & they hatch out in warm, wet weather - the present weather conditions are perfect!
If you see a flock of Starlings all over grassland it usually means that the Daddy Longlegs are hatching!!

[welshlibranr]

I think they are St Mark's flies, apparently they are only around for a short time, ans should be gone by about mid May!...........hope so, we've had swarms of them!.......so annoying!........