This was on a milkweed which is also covered with aphids. 4-5mm long. Moved fast. Six legs. My first impression was an albino ladybug larva with parasites stuck to its back—it's not, just saying that is sort of how it looked, but pointy on its rear end.

Tried a google image search and got case bearing moth larva. It's not that.

It was really hard to photo without a macro lens. This is the best I could do. Any ideas?

It looks like a Lacewing larva.
https://entomology.ca.uky.edu/...
http://blogs.ifas.ufl.edu/clay...

Looks like a lacewing larvae.

Wow, you guys tied six minutes after I posted. Fabulous! I have a ton of lacewing eggs and was just wondering how long it will take them to hatch. They are all over a dill patch right next to the aphid-infested milkweed. And what I thought were parasites on its back?
One cool fact about the green lacewing larvae is that it is often called a "trash bug" because of its practice of placing the emptied exoskeletons of its prey on its back. These pile up over time and seems pretty cool to me that this helpful critter shows off the work that its doing in the garden. Brown lacewing larvae eat aphids as well but don't accumulate the trophies of their kills.
Here's another picture. Hard to see, but...


How cool is that? Thanks for the articles, Danita

Edit: oops, forgot this

for the acorn.

I've found a few of the smaller larvae when they have a ton of junk on their backs. I think people call them junk bugs.

I watched one a couple weeks ago stop after finding a piece of something that it liked, grab it, throw it on its back, and pat it down.

I found a video of one "on the move"
https://www.youtube.com/watch?...

They all look different, it just depends on what they've found and who they've eaten.

That's hilarious! I was describing exactly that to my daughter a couple of hours ago while we were out for brunch. She is so politely tolerant of my plant and insect behavior conversation during meals!