♪ (host) It can start as an itch, maybe a tickle on your scalp.

It's head lice-- tiny and tenacious.

Thanks to millions of years of evolution, these suckers are not easy to get rid of.

You might end up in a salon, but not the kind for haircuts.

Young lice are so small, they're almost impossible to see with the naked eye.

Our scalp is their buffet.

They feed on our blood.

You can see it inside this adult louse-- it's that brownish stuff that's moving.

The secret to their success?

Their claws, called tarsal claws, and this little part, called a spine-- a pair on each of its six legs.

They've evolved to fit perfectly around a human hair.

They make lice into speedy little acrobats, using our hair like a tightrope.

They can't jump or fly, but they get around.

Say two kids-- one blonde, one brunette-- touch heads.

The louse just scoots right over.

It's been one long game of hopscotch, from human head to human head.

And it has to be us; our head lice can't live on other animals.

In fact, other primates have their own species of lice, adapted to their unique hair.

Birds have lice that hide in their feathers-- ooh, cozy.

And we all want them gone.

Common insecticides won't kill our head lice anymore-- they've become resistant to them.

Even their eggs have serious staying power, glued to individual strands of hair.

But lice do have a weakness.

They can't survive away from our moist, warm scalp.

Head lice cannot even live on other hairy parts of our body.

So if you or a professional painstakingly comb them out, they'll starve and die within hours.

Okay, it's not fun, but it's just a temporary encounter with a tiny hitchhiker that is biologically destined just for you.

Anyone else feeling itchy?

Here at Deep Look, we think all critters, even the less lovable ones, like mosquitoes and ticks, deserve their moment in the spotlight.

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