This is a nymph form of the Wheel Bug (Arilus cristatus), which I found perched on an almost-blooming thistle in my “wildflower meadow.” The nymphs appear in mid-June, and when they molt they will emerge brilliant coral with the characteristic wheel-shaped ridge on the back. About twenty minutes after molting, the Wheel Bug will turn from pink to grey.
Wheel Bugs, which are members of the Assassin Bug family, are incredibly beneficial to have in your garden as they prey on all sorts of pests including members of the dreaded stink bug family (harlequin bugs, squash bugs, brown marmorated stink bugs, etc.), which really decimate my garden. However, you don’t want to get bitten by an Assassin Bug—it is supposedly ten times more painful than a bee sting. So give these guys a wide berth when you find them, but definitely keep them around!