I seem to have the same problem. The entire thing was a surprise to me. I didn't realize Butterfly Weed was milkweed, suddenly I've got 10 cats stripping the plants bare. We had a cold front that dropped us to the 60's just as the oldest cats were starting to pupate. One attached to the stone work on the patio and looks normal. Two have attached to another plant and only partially emerged. How long should it take once the skin starts to split? Can you assist in any way without causing damage?
We're warming back up, but it was maybe 80 today. i don't think it was heat related. I'd like to help the last few make it. My boyfriend refuses to drive them to Mexico ourselves.