On my way into work earlier in the week I noticed two large mayflies who'd been spent, laying on the asphalt. I stopped and carried them into work so I could take them home and inspect them. At first I thought that they may have been either a brown or a green drake (the big Eastern ones you hear about) but after consulting with some of the local guys on another forum, the consensus seems the be that they are indeed Hexegenia limbata. I waited a few days to take these pictures and the bodies are kind of shriveled and dry, but you can still see how big these things are. This was a real treat for me b/c I've never seen a mayfly this big. I'll bet if you pitted a hex and a salmonfly in a cage match you'd have a good fight on your hands. (insert sarcastic smilie b/c I can only attach 4 images.....)
Anyway, hope you enjoy the pictures and maybe they'll help you tie up some good imitations. These were about 1.5 inches long before they shriveled. You can click on any picture to see the full album.