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That's awesome what you are doing! I am still waiting for Monarchs to arrive this summer (I am in the northeast). There is lots of milkweed and I find myself looking for eggs/little ones when I am out walking. I haven't ever calculated my 'success rate' (egg to butterfly) but I would like to think it is better than in the wild.
My sense is that lots of other critters eat the butterfly eggs. I would bring them in as soon as you see them. My experience with milkweed is in the NE where it grows wild. I have never seen a plant fully eaten down to stems so I cannot give advice on this. I would say that it is quite robust and forms perennial plots up here, so give it time and it should keep growing. Cannot remember comment about paper towels. Is it where they form their chrysalises? I think I have used a wide mouth canning jar with a paper towel as the cover. Sometimes they formed chrysalises on the paper towels which made it easy to transfer them to a butterfly tent/cage. I let them go almost immediately. They take a few hours to be able to fly and as soon as they can I let them go. Hope this helps. Good luck.
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