He doesn't look upside-down to me. But as they make their sling, they do turn upside-down to make the silk patch their butt will stick to and then they turn back around and continue silking and eventually make their sling. He does look like he's in a position where he might be pupating. And FYI, I can never keep track of the instars either except the final one, generally. But as far as second and third or whatever, I just call them small, medium, and large caterpillars. Makes more sense to me.
