What is this bug?
These beetles has been coming into my basement primarily in the evenings. They move quickly and cannot get of its back when turned over, which a lot of them seem to be when I find them. They do not fly. They are about a 1/2 inch long, and can flatten themselves so difficult to pick up. My cat, who is a prolific bug killer, doesn't even like them! Thanks so much for the help.
Montgomery County Maryland
That looks like a type of ground beetle. They are beneficial insects outdoors that hunt down their prey and help to control insect pests.
Here is a page with more about them: https://extension.umd.edu/hgic/topics/predatory-beetles
They sometimes enter our homes (some are attracted to light) through cracks or ill-fitting screens, door sweeps etc. With winter coming, now would be a good time to look for cracks and caulk around them and check where wires and utilities enter the house as well. You could try turning off the lights in your basement during the day and looking for any light leaking near where the wall meets the foundation (if your basement is unfinished.)
Thank you so much for your help, Christine!
You are very welcome. We are happy to help.