Our houseflies seem to show up seasonally, after the heat of the summer andbefore it turns cold. The warm winter we’ve experienced so far this year inNorth Carolina seems to have extended the flies’ season. While ours seem tobe common houseflies, they tend to congregate in our bathrooms and thekitchen. They aren’t as small as the writer Holly describes "bathroomflies". They look very much like the 1/3/04 picture that Jackie sent.While Jackie and her boyfriend were on vacation and returned to full-grownflies, we NEVER see anything less than an adult fly, no immature flies orlarvae. The cycle is that the adult flies show up over a period of two-three days(about 50-80 in number) then die in the next 3-4. We’ll have some peacethen and the cycle resumes, seemingly tied to the outside temperature–nottoo hot or cold. Of possible interest is that they also afflict one of our next door neighbors at about the same time (September-Octoberish) each year,but not the house on the other side of us (same side of street not far from a creek).
Finally, my questions:
1. What would you use to clean the drains in order to kill and eggs/larvae that might be germinating there?
2. What is the lifespan of the type of fly I’ve described?
3. Since they seem to be breeding inside and are drawn to the light, buzzing around the North-facing windows, is the outside temperature just a coincidence?
4. As there is no obvious organic matter that these flies are breeding in, have you any knowledge of something we could spray around the kitchen baseboards that might help control them?
5. Our dogs like to eat the flies. Is this a potential health threat forthem?
I am grateful for any help you can provide.

Dear Heather,
You have such a lucid letter. I hope I can be of some help. Bathroom flies are a totally different species with a different appearance. They breed in drains, but other flies do not. You do seem to have cyclical broods appearing. Finding the food source is the true key to solving the problem. A little bit of ancient history provided by Encyclopaedia Britannica: Spontaneous Generation or Abiogenesis was a theory that stated that fully formed living organisms sometimes arise from non-living matter. Aristotle taught the theory as observed fact. The Italian Redi, in 1668, proved that no maggots were "bred" in meat on which flies were prevented by wire screens from laying their eggs.
The fact is, flies seem to have a way of magically appearing. Flies were also, in the days of the persecutions, associated with witches. There is no magic, they are breeding on something. Adult flies will live for several weeks, but the maturation cycle varies with the temperature. It can be as short as a week in warm temperatures. The dogs can eat the flies without harm. Spraying poisons will help kill the adults, but will make your home toxic. Get to the root of the problem and discover the food source. Could there be something dead in the walls? Potatoes rotting under the sink? They are eating something. Good Luck.

You’re a good man. A good man with bad news. The thought of a dead rodent in the wall had flickered in my mind, but I was able to suppress it before it took hold. Until you wrote. I believe I’ll try the vents first. Perhaps the pantry floor. It would be easier if something smelled. I appreciate your thoughtful reply and bonus history lesson very much.

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