Sorry What ― Caterpillar Legs Aren't Really Legs

That's our day ruined.
Douglas Rissing via Getty Images

Hi, hello. I hope you’re having a good day. Are you? Because I was, until I found out about caterpillar’s non-legs.

We’ve already written about the fact that the specks on the outside of strawberries aren’t actually seeds, and revealed that the nub on the end of a banana isn’t what you might think.

And now, after reading a paper published earlier this month in Science Advances, it seems that caterpillar’s legs aren’t actually legs (what?). So, we thought we’d share how they move, and what the ‘legs’ actually are instead.

Instead of legs, caterpillars have what are known as “prolegs”

Unlike the real legs they’ll go on to develop in their adult butterfly form, caterpillars have what scientists call “prolegs.”

In fact, the stubs that contain what will become the caterpillar’s “real” legs as a butterfly (the thoracic legs) aren’t even used as legs ― instead, they’re all bunched in the caterpillar’s face.

What looks like legs to us are the six “prolegs” beneath that. These are sort of nubs that don’t actually propel the critter forward ― instead, they’re just sort of accessories to the whole moving apparatus.

Instead of being a propulsion device, caterpillars’ leg-like appendages (am I saying that? OK) are closer to anchors. The creature propels itself forward by contracting the muscles of its main body and then thrusting itself forwards.

Their “legs” have a barbed pad called a crochet on their pads, which sticks to leaves and twigs to ensure they don’t fall off (huh!).

Scientists weren’t sure whether the “prolegs” of caterpillars came from a now-defunct real leg, were a modified real leg, or are their own special thing.

So, the paper was researched and published ― and researchers found that the genes responsible for a caterpillar’s little faux legs are the same ones that create legs in crustaceans.


Well, the prolegs of caterpillars are “novel,” researchers say. But they are “likely derived from an old endite [crustacean leg node] GRN [gene regulatory network].”

So, if you ever get a chance to get up close and personal with a caterpillar’s legs, enjoy them while you can ― they’re the only creature that’s literally walking on lies.

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