This is the “wheel bug.” While it resembles something out of a horror movie, it is actually one of the “good’ insects. The semi-circle crest of this bug resembles half of a cog wheel, hence the name. It is a member of the Assassin bug family and they feed on soft-bodied insects such as caterpillars, moths, aphids, and leafhoppers.
Do not pick them up, they can bite. Just leave them alone and let them feed on some of our nuisance insect pests.