I fish central New Jersey and pretty much every year at this time in the late afternoon I see a very large white mayfly emerging. I never see it in any numbers, maybe just 1 or 2. It's usually climbing for altitude though not very swiftly I am thinking maybe a size 12? A local fly shop said probably a Cahill but this one seems larger and looks white plus other than one here or there, there is never any abundance. In fact, when I do see one my reaction is WOW, what is THAT?? If anyone has any suggestions I'd be happy to know. Thanks.