By far the most striking caterpillar I have ever chanced upon, this is the larva of Cucullia convexipennis, the Brown Hooded Owlet Moth. The brilliant, contrasting enamel-like colors would look more at home on a piece ceramic. As a rule when an animal boldly advertises its prescence in this fashion it's a warning to a would-be predator that it's toxic. However, I cannot find any resources on the Internet to confirm this supposition.
At close to 50 mm long this is a fifth instar larva and it will be ready to make the change to adulthood soon. It's one of nature's paradoxes that this stunning caterpillar metamorphoses into one of the most nondescript moths imaginable. Here's a link to some images of the adult Brown Hooded Owlet Moth.
The Brown Hooded Owlet Moth's preferred host plant is goldenrod, and they will also eat asters.
The Orange-Humped Mapleworm is another example of a moth which starts out life as colorful caterpillar and transforms into rather mousy moth. This is the adult Symmerista leucitys after making the change.
