We are not 100% sure on the ID for this beetle, but we do know for certain that it is a female …and she is almost ready to lay eggs. There is a similar looking one on Bug Guide that you can compare it to. The abdomen of a gravid (pregnant) female enlarges by stretching of membranes between the abdominal segments, making the wing cases (elytra) look like they’ve shrunk. Photo by Molly Baylor on 6/20/20 in Missoula, MT.