Is it a last instar caterpillar? If not, could it just be molting/between instars?
Sherry

I'm not sure. All I know is it looks just like this:

http://www.ipm.iastate.edu/ipm/hortnews/node/2576

Also, all it does is try to escape from it's container. Could we possibly chat about this over the phone?? If you don't mind, send me an e-mail with your phone number at someguy00273952@yahoo.com.

Imperial moths wander and wander a lot before making their pupa, so just keep it in the enclosed space you've given it. In nature they go underground to make their pupa, but it'll go under the leaves and do the same thing - be sure it has several inches of leaves. It's normal for it to want to stay on the move for a while before burrowing and pupating - it'll settle down soon. A friend found one wandering around just like yours and gave it to me, but I can't remember how long it took for it to settle down and make the pupa.
Congrats on your find!
Sherry

P.S.
If the info I gave you isn't enough, let me know, and I'll e-mail you my phone number.
Sherry

What I would do:

1) Put about 8" of good, moist topsoil in a 5-10 gallon bucket.

2) Lay various hostplants in there, including pine (not fir or the other conifer that escapes my memory right now)

3) Put the cat in the bucket

4) Go back in a couple hours. If it is still wandering around, I'd say it wants a hostplant you don't have. My very first imperial was a 5th instar that starved itself to death because it wanted only pitch pine and I was no longer had access to pitch pine.

KC, from the looks of it in the picture, I'm pretty sure it's through eating and ready to pupate.
But it won't hurt to add host plant leaves.
Sherry

I did not notice there was link to a picture. I was posting at 7:55 and had to be somewhere at 8, but it was an EMERGENCY so I made time.

From the pic, it does not look bright green so I agree that it is done eating.

What Sherry wrote will work. What I wrote will work. Putting layers of paper towels in a bucket will work. But be aware that the caterpillar is probably not going to pupate for 10+ days. It will become unable to move. It will shrink considerably. That is the way it happens so don't be discouraged by the poor appearance.

Overwintering is the tricky part. I'm batting way less than 50% the last few years. It is very discouraging.