While photographing a Wooley croton (Croton capitatus) I grabbed a stem to position it and immediately felt a PAINFUL sting on my fingers. Puzzled, I looked for a paper wasp or honeybee and finally focused on this well camouflaged critter on the croton stem.

Now the BEAUTY of iNat! @sambiology, @cullen, @kueda @loarie
I sat down tonight to enter this painful observation... when my dashboard opened, there on the screen was an observation of an identical bristly green caterpillar by @ericisley.
http://www.inaturalist.org/observations/4423970
That saved me a lot of "page flipping" and "googling".

See:
http://www.inaturalist.org/taxa/82279-Automeris-io
"As the larvae develop, they will lose their orange color and will turn bright green and urticating, having many spines. These stinging spines have a very painful venom that is released with the slightest touch; a condition known as erucism. The green caterpillars have two lateral stripes, the upper one being bright red and the lower one being white."

Yup... I believe that is it!!!