Spying some Canada Thistle, I looked for signs of tortoise beetle feeding behaviour. Then I looked for the insects themselves. I saw more of the fecally-protected larvae than the adults, and was about to give up when I looked at a goat's beard plant next to the thistles and there was this lone adult. These beetles are introduced from Europe and have been used to help control the non-native and invasive Canada Thistle. Thanks to Tom Murray for help with the species ID.