The Lyons Share

I went a quick walk around Woods Mill at lunch today and saw half a dozen or more of these little mayflies on the bridge by the stream restoration. They were looking like they had very recently emerged and I thought it odd that they were six months too late (or too early). Basically as far away from May as you can get. It wasn't until I looked a little closer that I realised it had something really strange going on with its head. Are these the eyes? Bob Edgar told me that some male mayflies can have their eyes extended upwards and this is known as being 'turbinate'. It seems so strange as they don't seem to look like a typical compound eye. Here is a close up. I can't get it to species but it has highlighted a blind spot for me. With only around 50 species in the UK, this is surely not a difficult group. It looks like I'll be ordering the FBA key.

08/11/2011 UPDATE:  Patrick Roper thinks it's the Pond Olive Cloeon dipterum (also one of the three species Bob suggested and the one I thought looked most likely from a Google search). However, I prefer the Turbinator.