It is the caterpillar of Giant Leopard Moth, Ecpantheria scribonia. A beautiful, large (about 2-3") moth that is white with black spots. They are completely harmless and do not bite, their only means of defense is to curl into a ball sticking their stiff, bristly outward to deter an attack. In some regions people keep them and their relative the fuzzy bear (A caterpillar that is black with a single brown stripe) as pets. The fuzzy bear turns into the Isabelle tiger moth.