Garden Pests and Diseases: And the greener worm picture, 0 by

wrote:
A caterpillar will eat nothing but the plant you find it on, they will starve unless you give it what it was eating when found. If you want to grow them, plant what they eat, and hope a butterfly comes along to lay eggs. Black Swallowtails eat parsley, Monarchs eat milkweed.

And, yes, they do gobble up the plant. I'm sharing my Rainbow Chard at the moment, hope they leave me some! But I haven't gone looking for what butterfly's larvae it is. Or moth...