[MUSIC PLAYING] NARRATOR: Sometimes to get where you want in life, you need to go all out.

Fleas need to get off the ground and onto someone they can exploit.

That's bad news if you've got fur or feathers.

There are more than 2,000 flea species, each partial to its own kind of creature.

But the one you'll most likely cross paths with is the cat flea.

Fleas are one of nature's greatest jumpers, taking a gigantic leap almost too fast to comprehend.

They're small and narrow, like a little sesame seed with legs.

Their fly ancestors lost their wings millions of years ago to help them slip through fur with ease.

Fleas are tough to get rid of.

Stiff backwards facing hairs catch on fur when you try to pick them out.

Try to squish one?

Nope.

They're flexible bodies are armored with rugged plates called sclerites.

Adult fleas only eat one thing--blood.

This cat flea prefers cat blood.

But in a pinch, it will latch on you too.

They lay eggs that drop from the cat's body into its bedding.

A few days later, they hatch.

And worm-like larvae wiggle out.

The hungry larvae scavenge for food.

Their favorite meal comes from Mom and Dad-- adult flea poop.

That's just semi-digested blood.

Now who could turn that down?

The larva curls up in a cocoon it makes from whatever dirt, sand, or other materials it finds nearby.

A few days later... violà, all grown up.

Now this hungry flea needs a warm body to call home.

Its jump is super fast, 100 times faster than the blink of an eye.

But it takes more than muscle to move that fast.

The flea can compress itself like a spring thanks to a rubbery protein called resilin in its legs and body.

First, the flea pulls in its oversized rear legs and locks them in place.

It squeezes and flattens its body, squishing the resilin and building up energy for the jump.

Then... it releases the energy all at once.

The flea tumbles through the air, legs extended.

With a lot of effort and a little luck, it will land on its target, and the whole incredibly itchy cycle will begin again.

(Lauren) Hi, Deep peeps, Lauren here.

You may have noticed a different but familiar voice on our episode today.

My good friend and fellow science reporter Laura Klivans is back to take over for me as the new official Deep Look host.

Here's a playlist of our ten Deep Look episodes she's already hosted.

(Laura) Thanks, Lauren, I'm thrilled to be back.

If you miss Lauren's voice, you can follow her now over at NPR, where she's the new climate science reporter.

Link is in the description.

Thanks.