I was able to identify this quite easily as the Green Saddleback Caterpillar, Acharia stimulea. Fortunately I didn't touch it! Those hairs contain venom which give rise to a stinging, swollen rash and sometimes nausea. Still, it is an amazing looking thing! It gives rise to a dark brown, near black moth. It seems they will eat almost anything, most of which I have growing in my yard. Apples, Dogwood, sunflower, viburnum, blueberry, cherry, and some others. I am amazed I am not overrun with them!