Here’s Mentzelia (or Nuttallia) nuda, a biennial that’s common in sandy places on the Great Plains. The flowers open in the late afternoon.
I tried to take a picture at 10 p.m. last night but discovered that taking pictures of a flower you can’t see is not very productive. I knew where it was, sort of, but not exactly, and in the process also discovered that using the flash to help find the flower does not result in a clear picture. When I finally got a fairly acceptable picture, I noticed there was a gigantic earwig right in the middle of the flower.
This one is certified earwig-free.