My post yesterday may make it look like I'm saying, "Oh, no! Everything's wrong because the world's all heating up and stuff!!!" I'm not. I have noticed that our winters have been getting progressively milder - since the 1970's, with a bit more escalation after we entered the 21st century - but flies in January outdoors, well, that's a new one. But I don't actually know why that fly is alive and well and on my window in January.
Maybe houseflies have always done that, and I just never noticed because they chose the office on the other side of the quad, or the office two windows down or maybe they preferred the south windows of the third floor. Or, maybe the flies have a union that managed to lobby for some really cool, er, warm changes. Yes, that's it. I look around me, and everything is set up to support a frigid fly. Modern affluence and heating has gotten to the point that a regular housefly, should it find itself out of doors in the middle of winter, nevertheless will not suffer or die, because there's several hoppers filled with garbage just yards away (there's a couple of supermarkets here), and a few mad dashes in and out of the next door shopping mall helps keep one warm, too. I mean, that last works for humans and sparrows, so I'm sure it works for houseflies.