For one of our class trips we went to a farm where they go only native plants, as well as do restoration work. In one of the greenhouses we found a bunch of these guys of different instars (instar is the technical term for the stages of molting for larvae)

You probably already know that caterpillars use eyespots to scare away potential predators. However, these guys have an extra trick up their sleeves. The problem is that when the caterpillar is very small, the eyespots are not big enough to scare away predators. So, they use another type of mimicry. The early instars of this caterpillar are splotchy brown and white, which makes them look like pieces of bird poo! After a few molts it will turn green, to give it more of a "snake" look, to complement the big-scary eyespots (example here: http://www.furaffinity.net/view/1753804/).

It's hard to get a good, focused shot of its head, because my camera keeps focusing on the eyespots XD