I have had 3 bumble bees in my house recently, two very much alive and one dead. The third one seemed to appear out of nowhere then I noticed a small hole in the ceiling where a cable used to run, perhaps they had overwintered there? The two live ones I was able to release hoping they will not succumb to the cold. I don't know what variety of bumble bee they were but they had little if any yellow markings and were about two inches long.