hello miracle grower, congratulations! You are now a butterfly gardener as well as a herb gardener. If the catipillar is yellow and black, chances are its a black swallowtail, or what the uninformed refer to a a parsley worm. You are so lucky. Yes, the catipillar will devour your dill, but just think of the good your doing in sharing your dill with the butterflies. I always plant a few extra dill,parsley or fennel just to share. In the future, if you like, the catipillars are easy to move from one plant to another, they don't sting, although when you touch them, what looks like little orange horns appear. Harmless. Good luck.