This fuzzy moth has wings, but it will never fly.

Why?

Because we humans made it that way.

It’s a domestic silk moth.

It looks  almost nothing like its wild cousin.

For five thousand years humans have bred silk  moths, changing the course of their evolution   to be their own unique species.

All  because we covet their shimmering threads.

The silkworm – this moth’s caterpillar – spits  out an extraordinary fiber.

It’s ideal for making   everything from satiny sheets to  glamorous gowns to terrible ties.

But we don’t just love it for its looks.

Silk is one of nature’s strongest fibers.

The thread is thinner than a human hair,   but for its weight, it’s five  times stronger than steel.

The silkworm begins its life  snuggled in a tiny, translucent egg.

The hungry caterpillar nibbles its way out.

It’s  raised on a farm where it can chomp and chomp   and chomp.

Here they’re feasting  on ground-up mulberry leaves.

Each larva starts out smaller than the date on  a penny, and in just a few weeks it’s as long   as your finger.

Now, this plump caterpillar  can get to work on its next phase of life:   making its cocoon.

It secretes a  liquid from a spinneret on its head.

As soon as the solution touches the  air, it becomes a pliable fiber.

What we know as “silk” is a long, unbroken  strand constructed primarily from two proteins.

The inside is fibroin –  it's the structural center.

The outside is sericin – the  glue binding it all together.

The larva spins raw silk for  two to three days straight.

The end result is a single strand of silk, up to  ten city blocks long.

This tiny shelter maintains   just the right humidity and temperature for  the caterpillar to transform into a moth.

Once the cushy casing is complete,  farmers harvest the raw silk.

For most silkworms in captivity,  this is where their journey ends.

They die when manufacturers boil,  steam, or dry them out in the sun.

Silk harvesters unspool the single  thread of silk that makes up   each cocoon.

If they were to let the moth  hatch, it would break the valuable thread.

It takes up to two thousand unbroken  cocoons to make one silk dress.

However a few lucky pupae are  allowed to continue developing,   and become moths, so they can  spawn the next generation.

After centuries under our watch  these industrious weavers can’t fly,   and their camouflage is gone, so they wouldn’t  last long in the wild.

They can hardly move.

Once outside the cocoon, a flightless male must  seek out a female quickly because they only have   a few days to live.

So they now rely on us  to make sure they find a mate and reproduce.

Silk production is a multi-billion  dollar global industry.

And it's not just for fashion and luxury.

Silk fabric is a natural insulator  yet it also allows air flow.

Silk is used in modern medicine  to stitch together wounds,   stabilize bones, and even replace  tendons inside our bodies.

And so, our relationship with the  humble silkworm continues – as it has   for millennia – at least until we figure  out how to make silk as well as it can.