Have I discovered a new bug?!
The diameter of the ball on top looks like mabe 1.5 mm. When not walking it retreats to some extent under it’s ball. When it walks, viewed from above it looks as though it is riding on wheels, so perfectly smooth is its motion. I found it in a canyon in Los Angeles. Thank you very much.
This is a Debris Carrying Lacewing Larva. Some Lacewings carry debris, including the carcasses of prey, as protection and camouflage.