That's actually just what was left AFTER a wasp picked up the other half of the exploded caterpillar and flew away with it.  ICK!  (But what a great picture that would have been had I been quicker...)

Later, I saw another :

So is this an example of OE spore death?

I checked all my caterpillars for the tell-tale mottled appearance, and none of them had it, from what I could tell.  This one even looks fine, except for the obvious.

Here of some of the ones on the plants:

Don't they look healthy?

(My camera's not great at close-ups.)

I even found a few that had climbed into our Butterfly Bush, hopefully to accomplish their metamorphosis:

Just a few minutes later, this one was in his "j" position:

Does he look okay, or does that green toward his head indicate a problem?

Stay tuned for further developments of this gut-wrenching drama.....

And if you want to see a HAPPY story, check out my friend's experience with Luna Moth babies!