I've only assumed that Jeff is a male. My eyesight is not good enough for me to be able to sex a fly. If she's female, well, we live in an age when names go unisex seemingly at random, so a female Jeff can't be all that surprising. Somehow I don't think the fly would care in any case. If Jeff is female, though, I ought to be seeing maggots eventually. Female flies begin laying eggs at about four days old, the Internets tell me, and continue to lay them the rest of their lives, which can be from fifteen to thirty days. Maggots emerge from eggs within eight to twenty hours of their being laid. I haven't noticed any maggots in the house so far, and Jeff has been living with me for a week, so maybe he is a male after all. I certainly hope so.
If Jeff was a middle-aged fly when he moved in, he might be dead within a week or so. If he was younger, he might be with me into September. I've given up hope that I'll be able to swat him, or even to coax him out a window. Many flies will head straight for a window when they find themselves trapped indoors, and if you open both window and screen they will scoot right outside at the first opportunity. Jeff is either a homebody, or perhaps agoraphobic, or he is uncommonly stupid, even for a fly, as he hasn't gotten anywhere near a window for the entire time he's been in the house, as far as I know. He sure is adept at escaping the flyswatter, though.
This is for you, Jeff.
And stay off of my watermelon!