I have four Tropical Milkweed plants that I've been checking regularly for cats but hadn't seen a single one or any signs of them. When I checked them yesterday, there were six big cats, and all of them look like they're ready to pupate. I thought it was interesting that they all showed up at the same time and look like they're at the same phase. I wish they could tell me how far they traveled.
I have a Common Milkweed plant too. It hasn't had any cats on it either so I borrowed some leaves from that and brought them all inside. Crossing my fingers that I don't get wasps instead of butterflies.