Many structures around the Zion visitor center had these mystery pupae on them.
I don't know what they are.
Whatever was inside has already emerged. I asked a ranger if he knew what they were, and he didn't know either. In my experience with bug ID questions in national parks, the rangers usually know less than I do. They know about the park's history, geology, the plants and the bigger animals, and that's a lot to cover already, but I haven't met an entomologist-ranger yet.