What are these black ants?

For the past while I've noticed at random times, an ant on my wall. Just one every now and then. They look rather large and black. They sting. (one got in my bed once XD) I had a clock on my wall, battery-operated that I had to throw away because it seemed a few had gotten in it. When I would watch them they would go behind the clock so I umed they had a small nest in there. I thought that would take care of the problem, but I just saw another one. I've noticed my electric alarm clock has been making weird crackling noises at time, could they be in there? What kind of ants are these and how can I get rid of them?