Black Swallowtail caterpillars

Frost advisory for my area tonight.  The forecast is that the temps will make it down to 36 degrees.  The effects of topography, though, could eat up that four degree difference easily.  I brought some of the plants from the deck inside already but I drove Jormungandr in close so I could wrangle the remaining plant containers onto it's bed and transfer them inside en masse.  The first container I went to pick up was a parsley that I had sitting atop an outside table. My hand froze as I reached for it.  Something was wrong.  Looking closer I saw the plant was positively infested w/ caterpillars.  They each sat at the top of a stalk of parsley and, judging from there only being a stem and no leaf, were eating it.   I brought out my camera, took a picture of them, and left the container where it sat on the table.  I moved all of the other plants inside.  The only ones left out are Yggdrasil, the two cacti, and the parsley plant.  Once that was done I checked on what kind of caterpillars I'd found.   I know what Monarch, Tent (yech), Woolly Bear, and Tussock caterpillars look like but these weren't close to any of them.  Found them on the Internet - Black Swallowtail Butterfly caterpillars!  Another common name for them is Parsley Worms which I can understand based on where I found them.   When they first emerge from the eggs they are black, with rows of white and yellow spots.  Plus, they have a blotch of white on their back to camouflage them as bird droppings.  In subsequent molting acts they lose the white blotch and become increasingly more green.  My problem was what to do w/ them.  I'd like them to make it through the winter but if I bring the plant (and them) inside I'll have black swallowtail butterflies flitting around at Christmas time w/ no where to go.  As usual w/ nature, the best thing turns out to leave them alone.  Late fall broods like this one will move away from the host plant, find a protected place to make a chrysalis, and sleep away the winter.  I can handle that.  I'm very good at doing nothing.  Maybe I'll occasionally check to see if the caterpillars have changed appearance again but I'll leave the parsley plant on the table until the little guys have moved on.