Dear Dr. Universe: How do spiders make silk? Also, sometimes spiders hang down from the ceiling, when they climb back up, where does the silk go? –Johnny, 8, Pullman, WA

Dear Johnny,

Spiders can do some amazing things with their sticky, stretchy, and super-strong silk. Us cats are pretty curious about these little silk-spinning machines, too.

Besides chasing spiders around, I’ve watched them use silk to build webs, catch bugs, and protect their young spiderlings.

Some spiders will even eat their own web. Imagine if you could build your own house and eat it, too.

Spiders have lots of jobs to do and eating their web is one way they can get a bit of energy. It’s also a good back-up meal in case they don’t catch any bugs. After all, their silk is made up of protein.

Screen Shot 2016-04-04 at 9.05.13 AMInside their abdomens, spiders have a liquid made of watery proteins. They also have special, nozzle-like organs called spinnerets. Along with some chemical reactions in the abdomen, spinnerets help spiders transform those watery proteins into silky strands.

That’s what I found out from my friend Beverly Gerdeman, an entomologist at Washington State University. Like you, she’s also very curious about bugs and spiders.

Gerdeman explained that spiders have two or more spinnerets. The exact number depends on the kind of spider you are.

While it might look like spiders make just one strand of silk, they actually make a whole bunch of strands spun together like a rope.

The silk is extremely flexible and can stretch up to four times its original length. And even though it’s lightweight, for it’s size, it’s actually stronger than steel. It’s a great material for building things.

Not all spiders build webs, but a lot of them do. Different spiders can also spin out silk in different thicknesses for different jobs.

Some spiders will use the silk to go “fishing” for bugs, wrap cocoons around their young, and even travel long distances.

A lot of young spiders, for example, can throw up a line of silk and wait for a draft of air to carry it away. Then, they can control their movement using their legs and silk—much like your friendly, neighborhood Spiderman.

It helps them move their population around. Some pilots have reported seeing spiders drifting along more than 10,000 feet up in the air.

Spiders may throw up a line of silk to help them travel, but as you observed, they also drop their lines down.

I’m not a scaredy cat, but I admit I get a little surprised to see a spider in front of my nose.

Sometimes, the spiders will climb back up their line really fast. The silk doesn’t go back into the spinneret, though. It likely just gets knocked away in the breeze or the spider pulls it back up for a snack. Mm, protein.

Once they eat their web, some spiders will recycle it back into their abdomen, so they can keep on spinning.

Sincerely,
Dr. Universe

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