It might be a gyspy moth.

Until those in the know chime in, an image search yielded the Eastern Tent Caterpillar Moth that looks similar (to this layperson, anyway!).

Did the cocoon look like these (described on one site as yellowish, silky)?

Not a Gypsy moth.

Likely the Eastern Tent, but possibly the more widespread Forest Tent, where did the potting bench kit originate?

The cocoon looked similar to the one in javiwas's picture, but with less silk around it, at least when I found it - it may have originally had a lot of silk attaching it to something.

The potting bench was made by Gronomics in East Bethel, Minnesota. I'll start looking up moths, see if I can ID it.

Sherry

Considering it came from a cocoon, unless the bench is hiding another cocoon, you don't have to worry about spreading a pest since they need two to tango.

Yes, that occurred to me, too, after I posted about it. But, after looking through moth pictures, I agree it's just an eastern tent caterpillar, which I see here all the time. The moths must be here, too, duh, I guess I just haven't noticed them. I did notice that the cocoon seemed big in relation to the size of the moth, and it left a big, obvious hole in the cocoon where it emerged. My promethea moths appear to have emerged without making a hole in their cocoons! I've kept ALL the cocoons, since I can't be sure one might not still have a pupa in it! :)

Sherry