I have new windows and doors, my house is tight. No drafts in the winter, no air leaks felt. How in hell do files still get in? I keep finding dead ones on my porch carpet and sometimes one flying around on a warm day. I can't find where they get in.
Maybe they are newly hatched eggs from last season's flies? If your porch has a door, and you use it, they get it even if you do not notice them at the time.
This might be a plausible source for the flies: maggots or eggs that you brought in from the yard.
Long ago, we had a mountain cabin. Like the house you describe, it was as tight as I could make it. I don't recall ever seeing a fly or even a bug in the cabin. Then, one summer evening, I poured a glass of Jose Cuervo tequilla and went to bed to read and watch TV. There was still a good bit in the glass when I went to sleep. The next morning, when I got up I took the glass into the bathroom to dump out the remains and to rinse it out. What I poured into the sink was at least 3 DOZEN gnats/fruit flies. I'd never seen them before and never saw them afterward.
The theory we cobbled up was that in walking about in the yard, someone in our cabin stepped in "something" that contained the eggs or maggots, and then tracked them into the cabin. They happened to come to maturity on the day or evening I poured the tequila.
FWIW, I followed up with an insect attractant-type of bait. Over
2-3 weeks it was in the cabin, it attracted nothing at all.
I worked extensively with fruit flies as a teacher's aide. My job was to hatch and raise them for student's genetic projects.
I would guarantee you that if you went to the fruit and vegetables in your house right now, that there would be fruit fly eggs on them, ready to hatch out.
The flies you saw at your cabin were probably already there, or just reaching a stage where they could fly. As with the OP, the flies were either already there, or were in a stage ready to hatch out and fly. Without very expensive air filtration systems, or poison, it is very difficult to eliminate flies anywhere, as once you do, more move right in.
I knew a guy who was a "slobsophrenic". That's a crazy slob if you're wondering. He wouldn't take care of his cats beyond throwing some food on the floor for them. The cats would become ill and die under the house. Flies would find any opening from under the house to come up through the walls or any kind of crack in the flooring. It was very strange and disconcerting to see flies come out of nowhere. It's quite possible that you may have had some sort of critter die under your house and it is now a mother ship for maggots.
Even that method is prone to error, as David Hedison found out, flying around the garden and getting stuck in a spider web, waiting for Vincent Price to mercifully swat him after a fly hitched a ride into the transporter chamber and heads got switched. "Help me! Help me!"
formatting link
Bart Simpson's adventure was just as good when they used "The Fly" as the basis for one of their "Treehouse of Horror" episodes. Even Jeff Goldblum's turn at bat was interesting and now the hairs on my back *really* creep me out and I don't like elbow macaroni much after seeing the baboon transport gone horribly wrong.
But seriously, we had a fly problem at work, on the 16th floor of a building without any fly troubles or obvious entry points (sealed windows).
The cause turned out to be a co-worker who brought in a house plant from home that had been sitting outside for a few weeks in the summer, having thousands of eggs laid on it.
I had the same experience, bringing in plants that had been sitting on the front porch. I haven't made that mistake since. I even nuke potting soil in the microwave now, because my little mistake ended up with more flys than you can imagine. Each fly has the same iridescent green markings that suggested they were all hatchlings from the same batch of eggs.
I learned a lot about the life cycle of the common house fly that year, which can go from teeny gnat-sized (still the same shiny green color) to large regular fly to giant old fly in a month. But mostly I learned never to bring in a houseplant from the porch once it's been sitting out there long enough to get covered with fly eggs (about 2 days will do).
Also, when very young, flies are quite small enough to pass through the mesh of the average window screen and then grow so quickly they can't exit the same way.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.