Abnormal amount of mosquitoes showing up in our house

September 4, 2020 9:05 AM

Twice now in the past two years of living in this house, we've had a sudden overnight influx of mosquitoes in one area of the house, like a swarm just hatched somewhere. I feel like something weird is happening and don't know where to look.

We moved into our home two years ago(central TX). Last summer, I woke up one morning, went into our little half-bath in the bedroom, and there was probably 15-20 mosquitoes flying in there. I quickly shut the door, then proceeded to smash all of them. It was a blood bath. The weirdest thing is that the door was not closed before I went in, yet somehow they haven't gotten to the rest of the house, which makes me think they all just hatched. I found a few more in the following days, but not many.

Fast forward to last week, when we started seeing more and more mosquitoes in the kitchen. I get bit a lot normally, so I'm very cautious of keeping doors closed in the summer time. We also have a yard treatment every month, so mosquitoes is not something we normally have in the house. One day there was one, then two the next day, then the next evening we killed probably 8 in the kitchen, seeing them mostly on the ceiling, which makes me suspect the vent. Our kitchen is not enclosed, so I can't just shut the door this time, but this past week, we've continued to see a few mosquitoes every night in the living/dining space.

It is driving me mad. I've kept camphor oil in the bedroom so luckily it has not been an issue when I'm sleeping, but every time I'm on the couch, they come to bite me, then I try to kill them and I miss, and it's a frustrating battle of searching and then losing them.

Does anyone have suggestions on what might be happening? Both times have happened so quickly and focused on one location that it makes me think it's not any of the usual issues. Could it be something in the vents? How would I check? Please help my sanity.

posted by monologish to Home & Garden (14 answers total)

Both of those rooms have drains. If it is a modern house those drains should be vented to outside by code. Most drains are protected by a loop seal to keep sewer gasses from coming back up into the house. It might be possible for mosquitoes to be coming down the vents and laying eggs in the water that forms the loop seals. If that is the case I would expect you to be able to find an even mix of male and female mosquitoes. If they are coming in seeking to bite you would expect to find a much higher percentage of females. If you don't use drains much perhaps treating them with BT could help.
posted by The Violet Cypher at 9:19 AM on September 4, 2020 [4 favorites]

Is it possible you've got standing water somewhere? Someplace they could be breeding? That'd be the first thing I'd go hunting for. If not inside, then immediately close to doors/windows outdoors - roof gutters are the first place I'd check.
posted by jquinby at 9:21 AM on September 4, 2020 [2 favorites]

Do you have a crawl space? We had a problem like that and it was water pooling under the house.
posted by nzero at 9:27 AM on September 4, 2020 [2 favorites]

Response by poster: Some additional info: all drains are used at least once a day. we have two cats that go in and out. house was built in 66, on slab. backyard is xeriscaped with a lot of plants, no intentional standing water element. there is a rain collecting double barrel system on the side of the house that is mostly left alone.
posted by monologish at 9:33 AM on September 4, 2020

Not very helpful in identifying the issue but those electric tennis racket bug zappers are very effective, especially indoors.
posted by raccoon409 at 9:45 AM on September 4, 2020 [2 favorites]

two main thoughts:

Rain collection barrels are notorious for breeding mosquitoes. There's products you can use (a mosquito dunk) to kill them if you see anything in there.

The second is that mosquitoes really like light. They move toward lights in the nighttime. Do either rooms have lights ever left on or anything like that?
posted by bbqturtle at 9:54 AM on September 4, 2020 [1 favorite]

Any air gap at all in the rain barrels will cause them to become mosquito breeding tanks. You can easily find out if this is the case, as the water will be teeming with larvae.

Pouring a small amount of vegetable oil (say, half a cup) on top of the water is one way to create a barrier on the water's surface.
posted by pipeski at 9:55 AM on September 4, 2020 [1 favorite]

Any rain collection tank ought to have insect screening over the overflow outlet. Has yours been damaged?
posted by flabdablet at 10:35 AM on September 4, 2020

My roof gutters drain poorly. Mosquitoes will breed up there and then lurk by my front door. (How do they know?) I have to periodically climb onto the roof and throw some mosquito dunks into the standing water.
posted by gnutron at 11:26 AM on September 4, 2020

Is the a gap under the slab? Could a drain pipe be leaking, creating a breeding environment under the house?
posted by Midnight Skulker at 12:44 PM on September 4, 2020 [1 favorite]

Mosquitoes will quite happily breed in potted plants if they're kept moist. But they may very well be hitching a ride on the cats.
posted by aspersioncast at 2:27 PM on September 4, 2020

Definitely check indoor potted plants for standing water. This has happened to me before.
posted by gatorbiddy at 9:45 PM on September 4, 2020

As a bonus you'll get to find out which of your potted plants, if any, you've been overwatering.
posted by flabdablet at 10:49 PM on September 4, 2020

Cover your drains when not actively using them
posted by Jacqueline at 3:00 PM on September 5, 2020