Ever wonder how those tiny, jumpy flies got onto your bathroom wall? Well, they came out of your sink drain after growing up down in the pipes. A goofy, long “mustache,” fuzzy wings and some aquabatics help them survive in that soggy environment.

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Drain flies are also known as moth flies because they look like miniature moths. One of the most common species of drain fly is Clogmia albipunctata, which has white markings on its dark legs. This is the species we filmed for our video.

Drain flies sneak in from the outside, often through cracks in old pipes. They lay their eggs in the slime inside the pipes. When larvae hatch out of the eggs, they feed on this living slime, which is called a biofilm. It’s made up of bacteria, fungi and other microorganisms that grow on the hair, saliva and bits of food that get washed down a bathroom sink.

---Why do drain flies show up in a house?

Entomologist Greg Curler, who studies drain flies, said they crawl into old buildings through pipes that rusted through, or cracked as the ground shifted. The flies use their antennae to sense the gases coming off the biofilm that has accumulated over time inside the pipes.

“The flies can detect the gas from a very long way,” said Curler, “and are attracted to it.”

---Do drain flies spread bacteria?

Even though they grow up as bacteria-eating larvae down in the pipes below your sink or toilet, the drain flies in your bathroom don’t spread bacteria around. That’s because they’re unlikely to land on you or your toothbrush or food. They’re not looking to eat your food or lay their eggs in it, the way that houseflies and blowflies do. Adult drain flies don’t really eat – they only drink a bit of liquid. And they pretty much stay put. They only fly afar when they need to find a new pipe to lay their eggs in.

---How do you get rid of drain flies?

Drain cleaner might get rid of drain flies temporarily. But the biofilm that attracts drain flies to the inside of pipes is hard to wash away, said Matthew Fields, who studies biofilms at Montana State University.

The microbes in the biofilm produce a sticky slime of proteins and carbohydrates that surrounds and protects them.

“Scrubbing the biofilm is the best way to get rid of it,” said Fields.

Since the insides of pipes where drain flies reproduce are typically out of reach for a good scrub, some biofilm is always there to draw the flies back.

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---+ Shoutout!

🏆Congratulations🏆 to these 5 fans on our Deep Look Community Tab for being the first to correctly answer our GIF challenge! The word we were looking for was "biofilm." This viewer got the exact word:

@Axqu7227

And these fans did not use the specific term, but correctly described the elements of the biofilm:

@sheetals.1912
@jkresinartsandsuppliers6810
@Terra2000Z
@gracechen7393
@pranavr4017

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