Mayfly ID?

[Toby]

I presume its a Mayfly though I get confused with these waterside insects. Found this one tonight in Richmond Pk using a torch

[Endrick]

I'm fairly sure this is a female imago of the Large Dark Olive (Baetis Rhodani). It's quite large with a body of about 1cm although the English ones are a bit smaller than the Scottish ones.

There are very few upwings around at this time of year and the two most common ones are quite different - the other, The March Brown (Rhithrogena Germanica) has mottled wings and is most unlikely to be seen at Richmond park.