"Asteroid", what a name for an insect! (So named for one of its food plants, the aster).
They are also called the "Goldenrod Hooded Owlet Moth" (For their other favorite food).
I found a few of these caterpillars while sweeping some wild grassy areas along the side of the road. Small, bright green with yellow and black stripes, they are rather striking when you look up close.
I caught a photo of this one while it was cleaning itself.
I would like to take this opportunity to promote my graduate adviser's book - The Caterpillars of Eastern North America. If you are interested in identifying caterpillars, this is for you! I'd consider it an essential addition to any field guide collection. As any naturalist knows, caterpillars are usually overlooked in butterfly/moth guides. And if caterpillars are shown, they are usually an afterthought for the more showy species. Having a focus on caterpillars and their anatomy and variations is essential. This book has served me quite well so far this summer.