Monarch Caterpillar The head end has longer horns. Who knew? A monarch caterpillar feeds on Butterfly weed in August. I was surprised to see that they were eating the flowers, not just the leaves! A Monarch Caterpillar Common Milkweed plays host to an entire community of insects. Here is the monarch caterpillar and a newly emerging butterfly. Monarch butterfly Share this:PinterestFacebookTwitterLike Loading... Related