It's some type of scale insect. There are numerous different species, in different colors, sizes, etc... Someone else might know the exact name of that one since you posted such nice pictures.

While seldom killing any plant, scale insects are horrendous pests on my potted indoor fruit trees and other plants, but don't seem to ever be a problem on things outside, maybe due to naturally occurring predatory insects and such.

Looks like Florida wax scale.

Here is a link that might be useful: Florida wax scale