I've never come across one myself, but I believe that is an "Unexpected Cycnia" moth, Cycnia collaris, (apparently the same as Cycnia inopinatus). This reference says, "food plants are various milkweeds, especially butterfly weed and whorled milkweed, but common milkweed, not so much."

Thank you! I love that name. Maybe they were unusual even when they were discovered years ago.

You may have helped me id the fuzzy dirty white caterpillars too. When I was looking up info on cycnia collaris, I came across cycnia tenera. The moths look a lot alike but their caterpillars are very different. So far I've only found that cycnia tenera feed on dogbane which I don't have. Pretty sure the ones I saw were on asclepias tuberosa. Next summer I will pay more attention to where I find them.

I believe this is a Cycnia tenera caterpillar I saw on swamp milkweed (9/21/25):

And I'm pretty sure this is an adult C. tenera (photo from last summer, 7/14/24):

Here's a helpful guide to some of the critters that eat milkweed: Milkweed Specialist Insects of New England

I think that's it. I saw several of those on a. tuberosa (I think).