Hey Rox, it sounds very similar to this thing I had a run-in with a few months ago. I returned home one afternoon to find this perfectly circular hole about 1 inch in diameter drilled into one of my porch colums. There was sawdust all on the floor beneath it. At first I thought someone had done this as a mean prank, but then I heard "buzzing" coming from the hole. Well, I got my can of bug killer and began spraying in the hole. In a little bit, this huge bug comes "drunkily" flying out and crashes to the ground. It was about 3 to 4 inches in length and also had the stripes on its back. It was the meanest looking thing I'd ever seen. Well, to make a long story short, I did some research and found that it was a Carpenter Bee. I had heard of Carpenter Ants but never bees.
It might just be that this is your mystery bug also.
Johnny
