...this morning I transferred the cocoon from the small spice jar to a large tomato sauce jar. Thanks again for your help Charley!

...the cocoon is still attached to the building and doesn't seem to have changed at all. I don't know when exactly it was made, but something is telling me that maybe it's dead? It was there all summer and even a little before that. I think Polyphemus overwinter and then emerge, so I'm not sure what's going on with this one. Maybe it's not a Polyphemus? Not sure. I've been contemplating carefully removing it from the building and giving it a closer examination (although I probably shouldn't).

PS: So does yours look just like this one?

Polyphemus, like other saturniids, overwinter in their cocoons and emerge in the spring. If this has been there since this past spring, that is a little suspicious... it suggests that it has already overwintered once and didn't survive. Or maybe it was parasitized, as seems to be the case with saturniid cocoons more often than not. I do agree with the ID--the size and shape are just right. If you do remove it, you can shake it gently to get a clue as to what's inside: a rattle indicates a viable (or at least not parasitized) pupa, and no rattle indicates a parasitized cocoon or one that has already eclosed.

Do parasites enter, or lay eggs in, the caterpillar before it enters it's cocoon stage? ...or do they bore their way into the cocoon after? It might seem like a silly question, but I'm pretty unfamiliar with Lepodoptera.

I was really hoping to see a Polyphemus eclose (is that the right word?). They are sooo beautiful and I've never seen one in real life before. I think I will try to remove it tomorrow and do like you said and shake it a little. Thanks again, Charlie! You are always a great help. :)

It depends on the species. There are some parasitoids that attack larvae/pupae once the cocoon has been made, but I think it's most common for them to oviposit on or in the caterpillar, with the larvae waiting until the cocoon is made to finish feeding. There are some wasps that even oviposit in moth eggs but let the caterpillar pupate before killing it.

Yup, "eclose" is used in the same way as "hatch" but is applied to pupae and cocoons as well as eggs.

I finally went out today and removed the cocoon from the wall. It really took some work! I couldn't believe how plastered down it was. It was quite heavier than I expected, also. It did actually rattle, too! It was a muffled sort of rattle...just as I would imagine a whole pupa inside a silken case might make (if I had x-ray goggles to see through the cocoon wall). Also, there aren't any holes or tears or anything in the cocoon. It seems to be in perfect shape...so whatever was originally in there, is still there.

I'd keep it in some kind of container until late spring and see if something emerges. I can't think of anything other than a polyphemus that it could be. If nothing has happened by late spring / early summer, I'd cut it open and see what's going on in there.

Sounds good. I put it in an old spice jar and will go ahead and wait. :)

Those moths are so beautiful! And large! I checked out some of their cocoons here on BugGuide and they DO look the same. I really, REALLY hope I get to see the adult emerge from it. Do you remember about how long it took your dresser specimen to emerge? Do you think I have a chance of catching it in the process if I check on it every day? I don't know much about lepidopterans.