'Sure looks like a MW tussock moth cat to me, Lisa. It probably came from a long distance away. The RA and your coneflowers are beautiful! Sherry

I don't kill them. I just let them have their share. I don't bring them in, mind you, and I think a lot of them are "wasp food". They don't eat that much so as to decimate your plants. Kenna likes them, too. She calls them her "fur balls". They are pretty cats, and so-so moths. It's just up to you. I leave em alone and let them have some milkweed, too. If you have any cynanchum laeve (milkweed vine), you could move them to that as well. They will eat eggs and tiny Monarch larvae by accident. Susan

Maybe the Milkweed Tussock moth caterpillar, Euchaetes egle? Take a look at the attached image and see if it matches up with what you've been seeing. It doesn't fit real well with your description, but is the only other gregarious milkweed caterpillar that I can think of right off the bat. ;-) Here is a link that might be useful:

Wow, fantastic photos. I've often wondered what these little guys look like; now I have an excellent reference. I agree, Sherry, they do look like the pull toys for dogs! :-) I've read these little cats can decimate wild milkweed. I often wonder if they are another reason the little wild 'Red Ring' milkweed is having such a time surviving in the wild. Mary