The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
Spence, I dont want to leave ya hanging alone...how about Leptophlebia? The "small pond" is why I say Leptophlebia. Especially if it's about a #14.
This mayfly comes off in my small pond in mid may in New Hampshire.
Though it's built a lot like an ephemerellid, there are too many characters that don't match up, not to mention the wrong habitat.
Kurt, I think the terminal filament in L. johnsoni is reduced,At least in the imago, but I'm not positive on that. Does that character change from sub imago to imago?
Prior to digging the pond I would occassionally see this spinner on window screens, since the pond is in place I now have seen it coming off the the edges of the pond.