Houseflies of Horror
August 25, 2010 3:42 PM   Subscribe

Is there anyway to trace the source of massive amounts of houseflies infiltrating my kitchen? It is a disgusting mystery.

My kitchen is first (ground) floor, my living room is upstairs. The construction is new, the windows are all well screened. Everything is super clean. The rubbish is kept outside and the garbage kept in the freezer until dump day. Dry food stuffs are kept in the fridge. No food is kept in the open. Every time I go downstairs, there are at least 15 flies on the screens. They are very, very slow and easily killed. They almost seem to want it.
I have a downvent on my JenAir range, 2 air con floor vents (in and out), one floor heating vent. There are no flies upstairs, no smell of rot or death. I suspect they are coming from outside, but for the life of me I can't figure it out. Any clues?
posted by Pennyblack to Home & Garden (22 answers total) 4 users marked this as a favorite
Is this new and sudden, or an ongoing issue? We had housefly infestations almost every year in my house... apparently it's a certain type of housefly, but I can't remember what right now. They were just living in the crawlspace and coming through the vents and everyone told us there was nothing to be done about it, but they always went away after a couple weeks.
posted by brainmouse at 3:46 PM on August 25, 2010

Several years ago a friend of mine lived in a cheap summer sublet apartment. There were hoards of flies all over the place; it was disgusting. After some investigation, she found the dead mouse carcasses. It sounds like you keep the place pretty unappealing to rodents, though, so I don't know what's going on with your place. My first thought, though, is hidden dead things.
posted by phunniemee at 3:48 PM on August 25, 2010

(I will just note this happened to me once--I went down to my basement and found tens of huge, fat, slow houseflies on every window. It only happened once, dwindling over a few days. At the time I thought maybe I had left a trash bag open or something, but they never came back once I got all of them.)
posted by maxwelton at 3:48 PM on August 25, 2010

They may be coming from inside.

Long, long time ago I shared an apartment with another guy. He eventually moved out, and I stayed there alone. I started noticing fruit flies in my kitchen, more and more of them. I went and bought a "No Pest strip" (you could still buy them then) and that killed them -- but every time I cleaned up the dead ones, next day there'd be more dead ones.

Eventually I figured out what had happened. My roommate had bought a bag of potatoes and stuck it way back under the sink, in a place I hadn't even realized existed. He'd forgotten about it and left it there. I never knew it was there in the first place.

But a fertilized female fruit fly found it, and laid her eggs there. They were probably fifty generations along by the time I located it and that bag was... well, probably I shouldn't describe it. Once I carried it out and tossed it in the dumpster, the fly problem ceased.

I bet your flies are breeding on something organic that you've forgotten about (or never knew, because it was left by the previous tenant), hidden somewhere you don't usually look.
posted by Chocolate Pickle at 3:50 PM on August 25, 2010 [3 favorites]

You need to determine whether they are true houseflies or blowflies (aka bluebottles). Blowflies are unmistakably iridescent blue-green on the thorax. They breed from carrion.

Last year we experienced a blowfly infestation in our apartment and it was the stuff of nightmares. As phunniemee mentions, a dead mouse can be the culprit, and frequently the thing is so tiny that it might die inside the wall with no detectable odor, but with enough fuel for a hundred blowflies over several days.

If it is blowflies, you can take heart that they only hatch from FRESH carrion. As a result, they are somewhat self-limiting. Get fly strips and use a vacuum cleaner to kill them en masse and wait 3-5 days for the number to taper off. If they don't go away on their own in a week, call the pros.
posted by overeducated_alligator at 3:54 PM on August 25, 2010 [2 favorites]

Is there any bloody/organic garbage in your bathrooms that you have forgotten about?
posted by bread-eater at 4:22 PM on August 25, 2010

Just chipping in and saying it happened to me too - one day our apartment was invaded by really fat and healthy looking flies. Never seen such happy looking ones. I had the same thoughts as you did: all organic rubbish thrown out, every corner cleaned, nothing the flies could possibly be hatching from... eventually figured out some perpetually careless roomate had, after returning from shopping, somehow placed a packet of raw chicken meat in a sheltered corner somewhere (wrapped in paper, wrapped in plastic, beneath some other stuff, in a corner we rarely went to) instead of the freezer...

So yeah... it's probably something, somewhere, you haven't looked yet.
posted by xdvesper at 4:23 PM on August 25, 2010

Do you keep houseplants, and if so do you keep the soil very wet?
posted by palacewalls at 4:24 PM on August 25, 2010 [1 favorite]

I came in to say animal carcass in the walls. Get an exterminator. When I lived in Miami, I had this problem and it turned out that there was a massive, massive rat in the walls (It was a citrus rat, which was somehow supposed to make me less skeeved out.).
posted by notjustfoxybrown at 4:26 PM on August 25, 2010

I once brought in some house plants that had spent the summer outside. All of a sudden, big house flies all over the place. Presumably, eggs had been laid in some of their soil. Anything like that?
posted by zadcat at 4:35 PM on August 25, 2010

Make sure your drains are clear of any refuse.
posted by Civil_Disobedient at 4:36 PM on August 25, 2010

Anecdote: we came back from a vacation about a month ago to find a bunch of big fat slow flies in our house. They all congregated on one side of the house, in the basement or the kitchen. No garbage out, nothing smelled bizarre, we kept the food well sealed and all that. (We don't have any plants, so that ruled that out.)

My husband went searching and found a bird carcass in the attic. It did not have any flies around it, but he threw it out and within a day or two the flies went away.
posted by Lucinda at 5:21 PM on August 25, 2010

We had a rat in our basement once and my landlord set out traps, but we never saw it again or found the body. Then there was a brief period where the basement smelled like dead fish, but it cleared up after a couple of days and since we never found the rat's carcass, we didn't really investigate it very much.

A couple of weeks later, there were dozens of flies congregating on the basement windows. They looked like carpeting. It was truly horrifying. But even more horrifying was when I sprayed them all with insecticide. Nothing can prepare you for the awful, awful sound of dozens of flies all dying at once, buzzing their last against a concrete floor. *shudder* Stuff of nightmares.
posted by starvingartist at 5:27 PM on August 25, 2010

Response by poster: Thanks everyone! No houseplants, no hidden rotten food. Tonight I'm going to cover all the vents and see what happens in the morning. These are big sluggish flies which obviously appear after they have all grown up and fed well. I'm thinking something is dead under the house and the flies are finding their way in through vents, electrics or plumbing.
posted by Pennyblack at 5:52 PM on August 25, 2010

Best answer: Could they be cluster flies? We used to get these esp at this time of year. More common in rural locations , nothing to do with garbage.
posted by canoehead at 6:34 PM on August 25, 2010 [1 favorite]

This is very weird - I had the exact same thing happen. Scads of flies coming out of nowhere, all very slow and not really caring about my desire to kill them.

As I recall, they were proper houseflies - not the green ones, and not horseflies.
posted by Earl the Polliwog at 6:36 PM on August 25, 2010

Do people in the rest of your neighborhood have trash barrels that don't close all the way (I.E. too much trash inside to close properly?) We used to have terrible problems in the summer with flies until our area started recycling and we all got recycling bins to go with our trash cans. Now everyone's garbage stays covered and this year our fly problem was almost nonexistent.
posted by St. Alia of the Bunnies at 7:09 PM on August 25, 2010

I had a friend once with a simulate problem and found that a window air-conditioning unit wasn't draining, and flies somehow started to breed in there. Had to throw the whole thing out.
posted by Dee Xtrovert at 7:12 PM on August 25, 2010

Response by poster: Canoehead, I think you've got it. I am in a very rural area and we do have tons of worms in our lawns. The kitchen is very low to the ground and 2 steps below the kitchen is a converted garage which is even lower. The 2 ground floor rooms are open plan. Those buggers are getting in somehow. They are the biggest, dumbest, slowest flies I have ever seen. I can actually pluck them off the screen with a paper towel pinched in my fingers. I also made the mistake of checking my ceiling light covers. Wow. It is a wonder any light got through. I guess I'll just have to keep killing them and hoping they goes away soon. When I lived in England we had a flying ant problem. Every year, middle of June, our living room wall became black with them. They were more disgusting than flies because their wings fell off and they became wriggly wormy things. Horrible, horrible. I guess I'll be thankful my flies are not flying ants.
posted by Pennyblack at 8:06 PM on August 25, 2010

We had cluster flies last year, yech. We bought one of these, affixed it to the kitchen window, and they were all gone within about 48 hours. An added plus is that you cannot see inside it, so there are no disgusting fly carcasses on view.
posted by Oriole Adams at 12:03 AM on August 26, 2010 [1 favorite]

May I suggest you add "flies" to the tags? I was thinking I'd have to keep this in mind in case I ever have a similar problem, but knew I'd never remember "Cluster Flies" — and if searching by tags, I'd probably search for "flies."
posted by taz at 6:32 AM on August 26, 2010

Yeah, they're definitely cluster flies. My dad runs a holiday cottage up a Scottish glen, and they hibernate inside the windowframes. Or they did, until he bought pretty much the same thing as Oriole Adams. (Added bonus: said box is both environmentally friendly and, according to the manufacturers, good for two years.)
posted by Len at 9:50 AM on August 26, 2010

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