This Eastern Black Swallowtail (Papilio polyxenes) caterpiller is biting through the stem below the Queen Anne's Lace (Daucus carota) flower. After the flower drooped, the caterpillar climbed down and ate most of the bloom for it's meal. Then it repeated the process on a much smaller bloom the next day. I assume that this is a behavior that prevents the plant from sending bad tasting chemicals to the injury site just as a Monarch caterpillar will do on Milkweed.