There are green caterpillars feasting on my dill plants. I googled them and discovered that they will grow into gorgeous black swallowtail butterflies. I can’t kill them now, those butterflies are so pretty. They have done a fair amount of damage to the dill, though.
We always plant extra dill and parsley for the caterpillars, and we plant milkweed specifically for it to be eaten by the monarch caterpillars. Last year we had a stinkbug invasion, and they killed quite a few of my caterpillars, so I moved them inside. I even bought screened enclosures for the two sets of caterpillars, and had to harvest milkweed and dill/parsley for them each morning and afternoon. It was a lot of work, but seeing them emerge from the chrysalises was fascinating. If you watch the caterpillars, you might see where they go to make their chrysalises. Then you can keep an eye on them to watch them turn into butterflies. Enjoy your swallowtails!