I imagine you would know it was a Green Drake if you saw one, assuming you saw one like I saw. I don't know what size it would equate to, but it probably had a 3" wing span. I've seen a lot of different hatches, and this bug absolutely dwarfed anything I had seen before. It seemed like it was at least twice as big as any other bug I have seen hatch on the Davidson. I'm sure I'm not remembering it as accurate as it actually was, but I'm pretty sure I don't have any dries in my box that would equate to the size of the bug. It was big.