oyster shell scale. peel the orange and eat the unaffected fruit.

A few drops of Dawn dish soap in water and spray the trees. Safest way to treat fruit trees.

You can scrub them off under running water, with a brush or scrubby sponge before peeling, if you don't like the idea of insect guts smeared on the parts you're going to eat. That's what I do when I encounter scale, mealybugs, etc. on my fruit.

Thanks, everyone! These things rub off easily when I wash the outside of the fruit. Thanks also for the treatment recommendations!

Those black spots (not the scale, for example there’s one in a space about two thirds of the way to the bottom of the picture and another in the group of three scale insects to the right and lower down) make me wonder if you also have fruit fly.