My milkweed is almost defoliated because the leaves are being devoured by these amazing yellow, black and white striped caterpillars. I took this photo last evening when I was closing up shop downstairs. They "head-butt" when competing for food. Click here for the really interesting article with a video if you want to watch them fight. Plant more milkweed! That is all Monarch caterpillars eat. Really.
Explained here.
