The cocoon I discovered last fall, hanging from a branch of a hazelnut hung on all winter. I came across it again the other day and finally remembered to do some research to see what type of creature made it. I believe it is the cocoon of a Promethea or Polyphemus Moth. Both are in the silk moth family. I do have a dead, ragged specimen of one of these moths found here a few years ago.
I'm really intrigued by how the leaf is wrapped with silk to form the cocoon. It looks like an embossed pattern. It is also impressive how it has survived this long. When I first came across it late last fall, it already had the opening on top, so I am not sure when the moth emerged. I hope this summer and fall will bring new opportunities to see a cocoon in the construction stages.