Pill bugs...... roly polies..... potato bugs... whatever you want to call them, somehow there's something less creepy about these guys than other insects.

More loveable, or something.

Maybe it's because they're not insects at all.

Pill bugs are actually crustaceans.

They're more closely related to shrimp and lobsters than crickets or beetles.

Pill bugs even taste like shellfish, if you cook them right.

Some adventurous foragers call them wood shrimp.

As early as 300 million years ago, some intrepid ancestor crawled out of the ocean, sensing there might be more to eat, or less competition, on dry land."

But unlike lobsters, pillbugs can roll up into a perfect little ball for protection.

If you look closely you can see the evidence of where these guys came from.

Like their ocean-dwelling cousins, pill bugs still use gills to breathe.

True insects -- like this cricket -- use a totally different system.

See those tiny holes on this cricket's abdomen?

They're called spiracles.

They lead to a series of tubes that bring fresh air directly to the insect's cells.

But pill bugs don't have any of that.

To survive on land, they had to adapt.

Their gills, called pleopods, are modified to work in air.

Folds in the pleopod gills developed into hollow branched structures, almost like tiny lungs.

In a way, the pillbug is only halfway to becoming a true land animal.

Because... they're still gills.

They need to be kept moist in order to work.

Which is why you usually find pill bugs in moist places, like under damp, rotting logs.

They can't venture too far away.

Sure, pill bugs look like the most ordinary of bugs.

But they're much more than that: evidence that over evolutionary time, species make big, life-changing leaps.

And those stories are written on their bodies.

Hey, while we're on the subject of oddball crustaceans... check out this episode about mantis shrimp.

Their eyes see colors we can't even comprehend.

Their punch is faster than Muhammad Ali's.

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And see you next time.