This is the caterpillar of the Yellow-collared Scape Moth. The adult moths are abundant throughout our area in late summer and fall. I have seen several of the caterpillars feeding on spike-rush at Oakes Quarry in Fairborn. 

This caterpillar looks like such a harmless bit of white fluff, doesn't he? But if you see something like this, DON'T touch it. This is a Black-waved Flannel Moth caterpillar--one of the worst stinging caterpillars around. Photographed at Oak Openings near Toledo, Ohio. 

This is a Clear Dagger moth caterpillar. Note the yellow markings on the top of his head. I found him waiting on my doorstep when I got home from the store one day. 

This is a Hag Moth caterpillar, also known as a "Monkey Slug". These caterpillars wave their "arms" like an octopus when moving. This is another one of the stinging caterpillars you want to avoid touching. Photographed at Twin Creek MetroPark.