How to make the best fruit fly trap

In the research lab I was surrounded by tens of thousands of fruit flies (Drosophila melanogaster for the uninitiated) which were kept carefully stored in plastic test tubes. Not surprisingly, even the most careful maintenance couldn’t keep them all locked away without a few flies escaping. So we had to create our own fruit fly traps for the lab. Luckily, you can make the best fruit fly trap (which is non-toxic, might I add) in less than 5 minutes with household materials.

Materials needed: A cup and dry yeast

fruit fly trap yeast
Baker’s yeast can be purchased at any grocery store or bakery.
fruit fly trap cup

How to create the fly trap

  1. Put some dry yeast powder into a container (or measuring cup) and add about an equal volume of water. Mix with a knife for a few minutes until the yeast is a creamy consistency that spreads like peanut butter.
  2. Take some of the creamy yeast paste on a knife and smear it far back on the inside of a drinking cup. The cup can be glass or plastic.
  3. Place the cup, on its side, in an area where you notice a lot of flies.

How to discard the flies

After setting the fly trap, you should notice that flies will enter the drinking cup and feed on the yeast, sticking around for quite a while. When you see a lot of flies in the trap at once, simply cover the open cup with your hand, walk over to your sink and then submerge the entire trap in water (or uncover with your hand and quickly spray water inside the trap with a faucet). The flies will drown and the yeast paste will dissolve easily.

Yeast powder is extremely cheap so you can set this trap over and over until your fly problem is resolved. This is truly the best fruit fly trap because it’s simple, non-toxic, and completely sustainable. Interestingly, the University of Nebraska-Lincoln also has a good set of instructions for creating homemade fruit fly traps, so check it out.

If you liked this post, you may also be interested in my article on how to distinguish the sexes of Drosophila melanogaster.

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