How to Create a Fool-Proof Gnat Trap




I was so frustrated from swatting at gnats every day in my house. I had them go up my nose, in my mouth and eyes, and actually bite me so hard once that I yelled. We didn't keep much, if any, food out on the counter, so the gnats even resorted to getting in our diaper pail! Talk about disgusting - poop-fed gnats going in your eyes and biting you. It doesn't get much worse than that. Even my two year old son started mimicking my swatting and trying to catch them out of the air with a loud clap. I tried several iterations of this trap, and finally hit the jackpot with the one in this instructable.

You'll have some fun when you notice gnats on the fruit. Give the plastic a flip and the gnat will fly into the corner between the bowl and the plastic. If you get good enough, you can smash them without putting a finger hole in the plastic!

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Step 1: Gather Your Gear

What's needed:

 - A serving bowl or large salad bowl. I chose a 9 inch salad bowl, about 2 1/2 inches deep.
 - A small fruit cup, shorter in height than the large bowl. This is very important.
 - Fresh fruit, approximately 1/4 cup. I have used banana with great success, but used grapes for this instruction
 - 2 cups of water
 - Liquid dish soap
 - Cellophane wrap (I used Saran Wrap)
 - Serrated knife
 - Food coloring (optional)

Step 2: Put Water in the Large Bowl

In the large bowl, put approximately 2 cups of water, such that there is at least 1 inch of water in the bowl. You can add a drop or two of food coloring now if you desire.

Step 3: Add Fruit to the Small Bowl

Cut up some fresh fruit for your enemy to dine on. Bananas are best but I'm out, so I'm giving grapes a try. DO NOT add water to the small bowl; this will cause the fruit to rot much too quickly.

Step 4: Place the Small Bowl Into the Large Bowl

Step 5: Add Some Soap

Put two or three drops of liquid dish soap in the water. This breaks the surface tension of the water, allowing the gnats to sink to the bottom instead of float for hours.

Step 6: Cover the Bowls With Cellophane

It's important here to make sure the plastic wrap is perfectly sealed around the edge of the large bowl, or the gnats will just come in, get a snack, lay some eggs, and fly out of your trap.

Step 7: Poke Some Holes in the Plastic

With the tip of the serrated knife, poke some holes about as large as a pencil lead (old school, not today's mechanical leads). This will allow the gnat to enter the trap, but the plastic will have a sort of tunnel effect, capitalizing on the gnat's poor flying accuracy and keeping him in the trap. I poke holes about 1 1/2 to 2 inches apart, and be sure not to poke any above the edge of the smaller bowl or they might get lucky and fly directly up and out. Poke 5 or six right above the fruit cup.

Step 8: Set the Bowl in a Gnat-frequented Area

The kitchen counter near the fruit bowl works best. There is no alternative to gnat control like putting the fruit away and taking out the garbage every night. We still had a problem, but this killed around 40 gnats in two or three days. I recommend changing the fruit every three days or you'll have a hairy beast to clean up.

Step 9: Count the Dead

In less than 5 days, there are 49 dead gnats in my trap. There were no hatches on the fruit, but I think it was important to let the fresh fruit get a little ripe so the smell attracted them. Even now there are gnats we see around that we know will find their way to the kitchen counter and into the trap.

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    14 Discussions


    2 years ago

    In my case i use this repellent

    Repel 100 Insect Repellent, 4 oz. Pump Spray. It is a very good
    repeller as i know. So i think bette t use any repeller than trap, but
    traps good to.

    Btw, thanks for idea)


    2 years ago

    "Poke 5 or six right above the fruit cup."

    You want them to get to the fruit?


    3 years ago

    contradictory info. You say be sure not to poke holes over the smaller fruitcup, then you say poke 5-6 holes over the smaller fuit cup. Which is it?

    1 reply

    3 years ago

    I came back to this post just to say this worked. I was blown away!! We got rid of the pests in 3 days! Thank you so much!!


    3 years ago

    I like this idea! What I have always done is take a small water bottle and cut off the top of he bottle (it will look like an upside down funnel when it comes off the bottle). Add an inch or so of vinegar to the bottom of the bottle. Turn the top upside down to create a funnel and place it on the top of the bottle. Tape it in place being sure to close any gaps. Place the whole thing where you see fruit flies and/or gnats. See how many you can catch with this!

    1 reply

    Reply 3 years ago

    Sounds like a new Instructable to me! ;)


    5 years ago on Introduction

    Nicely done, however, I think it might be important to note that those are, in fact, fruit flies, and this method (the bait at least) won't work with gnats (like the ones that hang around potted plants) because they aren't eating, or laying their eggs there (Believe me, I've tried)
    One other thing that might be helpful, flying insects (excluding beetles) can't fly if their wings get wet, though I find it most successful with oils or rubbing alcohol. It can be hard to kill just one, at least with your hands, but it isn't too hard to spray the nasty little buggers with a spray bottle (it's important not to use an aerosol bottle, because insects (like flies) can feel the movement of the air and avoid your death ray).
    But pretty much, you can hit them more easily in mid air with a mist of liquid, they they plummet to the earth, where they have a MUCH harder time getting away, so you can smoosh them. OR if you use rubbing alcohol, at least with small insects, one spray will at least send them down and mostly incapacitate most movement, and generally a second should send them to the afterlife. I think it actually causes them to shrivel up, because their cells burst or something. But I do know it works. Better yet, this stuff won't leave residue (besides a dead insect carcass). It evaporates super quickly and is generally safe on surfaces as long as you don't soak them (even small amounts on live plants can be okay)


    6 years ago on Introduction

    so, make sure the fruit bowl is shorter than the water bowl i presume?
    otherwise, the plastic wrap would seal it off.

    in a few days, you have a bowl full of dead gnats, and a bunch of hatching baby gnats on the fruit?

    2 replies

    Reply 6 years ago on Introduction

    You're correct about the smaller bowl being shorter. It doesn't have to be much shorter, just the height of a gnat. :) I haven't seen any hatches on the fruit yet, just a bunch of dead ones in the water. Check out my update picture at the end, just added.


    Reply 6 years ago on Introduction

    It doesnt seem like the smaller bowl is sealed off, so yeah i think it would make sense to assume the smaller one is shorter than the larger one. And the idea of the plastic wrap is like how a fly cant seem to fly out a window properly. They just miss and miss because theres no accuracy in their flight. So they will just fly around get really tired and fall down into the soapy water, sink and die.

    Im assuming the plastic wrap doesnt quite seal off the smaller bowl. Id imagine the same lack of accuracy would apply. Assuming the bowl is anywhere from a centimeter or so from the top of the smaller bowl, it would give the smell of the fruit causing the flies to find it, but make it difficult to actually get to and lay eggs.