Monarch Caterpillar Bowel Motions

It can be quite hard to tell which end is which on a monarch caterpillar.  Both ends have antennae and unless you have a macro lens you don't really see their eyes.  

Just as a lesson in anatomy of caterpillars, the end the green stuff comes out of is not the head.  I suppose I was privileged today to have one pass his bowel motion on my hand.  Hmm, I wonder what the deeper meaning was.