Why are dead gnats appearing on my bedroom windowsill?

March 4, 2008 7:53 AM

A while ago gnats invaded my windowsill (in NY). I sprayed Raid. They died. I cleaned the area. Now, every day or two dead gnats appear on my windowsill. From where I don't know. No trash, no damp areas I see--only a heater/AC unit--and I've never seen gnats fly out of it. The only plants are in the other room; no gnats around them. Where are they coming from and how do I get rid of them?
posted by shivohum to home & garden (12 comments total)

Is this a bathroom or kitchen window? They could be pupating in the drain then emerging and flying to the window where the Raid is still knocking them out.
posted by Pollomacho at 8:04 AM on March 4

Do you have ventilation ducts, gaps in the wall, storm windows that make an air space between inner and outer windows, etc. where they could be coming from? Also, HVAC units can collect moisure inside, so perhaps that's where they are coming from.
posted by aught at 8:16 AM on March 4

Hrmm, thanks...

This is a bedroom window, a triple-window setup where to pull either of the side windows open, you push them towards the center, and they are right in front of a center window.

I don't see any ventilation ducts or gaps in the wall, either, though maybe they are small and I'm just missing them?

Perhaps there are gnat eggs that I'm missing in the tracks for the windows? I try to clean all the dust there up, but maybe I haven't been successful...
posted by shivohum at 8:24 AM on March 4

How about condensation? I'm assuming the tracks are metal, are they damp at all?
posted by Pollomacho at 8:43 AM on March 4

This may or may not be helpful, but:

I once worked in a small restaurant. A few weeks after we started, we had a gnat infestation. Hundreds of them. We called the exterminator, we scrubbed the place top to bottom, we purchased lidded garbage cans and STILL the gnats came. A couple weeks later we ran out of pickles in the fridge so I went into the stock room to get the extra bucket.

The bucket that had been there when they moved in.

They had been there for 3 years.

It was a bucket of decomposed pickles, literally thick with gnats. Someone had opened it many, many years ago and left it there. Everyone since had just disregarded it. Moral is: Make sure your empty containers are empty. Uuuugggh.
posted by GilloD at 8:50 AM on March 4

I'm assuming the tracks are metal, are they damp at all?

Hrmm, I could check -- it's possible. You think there are eggs there I'm my wet paper towel is not picking up?

GilloD, thanks for the disgusting story! The weird thing is, they're really just on or around the windowsill and the floor underneath. And the floor is clear. They're nowhere else in my room... so it's got to be something in that area, and there are no containers I can see near there.
posted by shivohum at 9:58 AM on March 4

Are you sure they aren't fruit flies? If they are, they could be hatching out of your houseplants. Try putting some gravel around the houseplants, and the fruit flies won't be able to lay eggs in the dirt.
posted by The Light Fantastic at 10:53 AM on March 4

> so it's got to be something in that area, and there are no containers I can see near there

Ok, fullproof then. Bleach is really good at doing one thing - absolutely obliterating DNA. So good hospitals even use it to decon rooms. You can dilute the stuff we can buy to lesson it's whitening power so we can use it as a wash. Run that over anything and everything in the area, from the roof to the floor, and the outside if possible. Decon it, basically.
posted by jwells at 10:56 AM on March 4

I had a problem with midges once accumulating on my bathroom windowsill and in my bathtub. By spraying Raid frequently along the seal of the window, I starting seeing them less and less. The exterminator stated that a nest must have built outside my window, and he stated that eventually they would slowly decrease in population if I kept spraying the seal.
posted by ALongDecember at 10:58 AM on March 4

Do you have a garbage disposal? We had a problem with fruit flies awhile back and we finally figured out that they were coming from the garbage disposal in the kitchen. They seemed to be hatching from the gelatinous goop on the underside of the disposal drain. I used some 409 disinfectant and a new toilet brush to (carefully) clean the underside of the disposal drain. I keep the disposal drain clean and we haven't had any problems since.
posted by braveterry at 1:50 PM on March 4

You seem to think that because you're finding these insects at your window that they must be appearing right near there. That's not necessarily the case. Like all insects they're attracted to light, so even if they're hatching on the entire opposite side of your living space, a window is where you'd most expect to find them -- especially if you've sprayed poison there, so that they die once they come in contact with it.

Like the story above about rotting pickles, I had a similar experience one time, and likewise it was fruit flies. In this case, an old room mate who had since moved out had bought a bag of potatos and tossed it way in the back under the sink. I didn't even know it was there, but a fertilized female fruit fly seems to have found it. I went for weeks with fruit flies all over the place, and then finally noticed the bag one time when I did a concerted search. It was a teeming mass of maggots, and once I tossed it in the dumpster my infestation problem vanished.
posted by Class Goat at 1:57 PM on March 4

Are there actual live gnats bothering you? Otherwise I would highly recommend not spraying any more toxins in your bedroom.

As far as where they come from: potting soil, drains, wet places, rotting fruits or vegetables. You can make a vinegar trap with some vinegar in a glass jar with holes poked in the lid- they crawl in but can't get out.
posted by oneirodynia at 2:32 PM on March 4