Whilst out cycling yesterday, I kept going through massive swarms of weird flies. They glided through the air and reminded me of small airbourne jellyfish with hangy legs, until they landed when they looked big and black and mean.

Anyone know what they were?

It's May… mayflies?!

Not mayflies! These things look quite pretty, then ones I saw were a bit erm, scary, in a fly-y kind of way.

sounds like the 'Robber fly' – see pic – I saw loads of those last weekend on Exmoor.

St Marks fly.

Hawthorn flies is my guess , its the time of year for them too .

Perhaps one of these?

crispy bacon – I like the look of yours even less!

knottie – the swarms I saw were always next to clumps of small trees, and google reveals that you're right, and chorlton – that they're sometimes called st marks flies!

so thanks, nice to know what they were, still don't like them!

That robber fly looks **** evil.

conor – just for you

You've got to love them as they're great pollinators of fruit trees. 🙂

ok, I'll respect them for their ability to do something I can't; but love – that's a bit heavy! 😉

Have you seen Avatar? Sounds like the beasties from there ……….

could have been heather flies they fit your discription and float about like jellyfish

IMO reality will always throw up a lot of things a LOT more amazing than the grossly over hyped AVATAR.

STW at its best! A true oracle…

From above info and also more googling I have now found out:

Apparently it is of the bibio family (bibio pomonae) aka heather fly. Apparently the red legs distinguish them from bibio marci. What I saw hanging underneath are it's hind legs which dangle as they fly.

They are big, black and scary!

So not just me that was a bit afraid.

And, Trout, they are very often used to catch… trout. I'm guessing you knew that though!

Thanks all.

How about the lovely Banded Demoiselle.

Ha Ha Nice one Annabananna , we have billions of the buggers on the moors above Ilkley dont taste too good though.