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My conception of legs was recently shattered upon learning that the stubby appendages that a caterpillar uses to walk are not, in fact, legs, but rather fat nubs of flesh called prolegs that have no genetic relation to the larva's real legs, which are skinny and clustered by its face. This discovery sent me into a bit of a philosophical tailspin. What was a leg, if not an appendage made for walking? How many fake legs had I seen before and never questioned, utterly bereft of a framework by which to discern which were fake and which were real? I had a lot of learning to do!

Luckily, we here at Defector are heavily invested in legs, so we have prepared a leg quiz for anyone looking to test their leg smarts. The answers are directly below the photos, so if you really want to test yourself, scroll slowly and stop as soon as you reach the caption.

Let's start off easy. Are these legs real?

A close-up of three leg-like appendages of a green caterpillar with orange and black spots
Credit: Didier Descouens, CC by-sa 4.0, via Wikimedia Commons

If you guessed fake, you are correct.

What about these legs, are they real?

A close-up of two thoracic legs on a green caterpillar
Credit: Didier Descouens, CC by-sa 4.0, via Wikimedia Commons

These legs are real, very real!

Are these legs real?

A close-up of two sets of thoracic legs on a velvetbean caterpillar
Credit: USGS Bee Inventory and Monitoring Lab, croppedUSGS Bee Inventory and Monitoring Lab, CC by 2.0

There are few things more real in the universe than these legs, which are some of the truest I've seen.

Are these gams real or fake?

A zoomed-in photo of the stubby leg-like appendages of a velvetbean caterpillar
Credit: USGS Bee Inventory and Monitoring Lab, croppedUSGS Bee Inventory and Monitoring Lab, CC by 2.0

I could spot these chubby phonies from a mile away!

Think you've got the hang of it now? Think this game is for babies? Well, what about these needly boys?

A close-up of the comb-like legs of a grey count caterpillar
Credit: Sanjay Kumar, CC by-sa 4.0, via Wikimedia Commons

Fake! I honestly don't even know if these fake appendages are prolegs or some other appendage, but, legs or not, they are certainly not real.

Or what about these slimy stubs?

a close-up of two nubs of the gelatinous covering of a jewel caterpillar of the species Acraga Coa
Credit: Ángel Eduardo López García, CC by-sa 4.0, via Wikimedia Commons Ángel Eduardo López García

These legs are the fakest legs we've seen yet, which is to say they're not real legs and also not fake legs. They're not legs at all, but one of many gelatinous spikes studding the tough outer covering of a beautiful jewel caterpillar, in this case the caterpillar of the Cheeto-colored tropical jewel moth Acraga coa. The spines might feel like Jell-O when you squish them, but please don't take a bite.

And what, uhh, about these?

A screenshot of two of the furry orange arms of the monkey slug caterpillar
Credit: cropped from Greg Dwyer, CC by-sa 2.5, via Wikimedia Commons.

These are not just fake legs, they're actually fake arms. This is the monkey slug caterpillar, which will grow up into a hag moth (some of the best common names I've ever encountered). Each monkey slug caterpillar has nine pairs of these curly, hairy arms, which are more accurately called tubercules, protruding from its main body. The monkey slug's real fake legs, meaning its prolegs, are reduced to suction cups. (If you'd like to see the vaguely unsettling belly of a monkey slug caterpillar, suction-cup legs and all, click here.)

What do we have here, caterpillar legs?

A zoomed-in shot of the orange warts of a pipevine swallowtail caterpillar
Credit: Katja Schulz, CC by 2.0, via Wikimedia Commons, cropped

Psych! These are not legs, real or fake. These are fleshy, tentacle-like projections called dorsal warts. These particular dorsal warts stick out of the back of a pipevine swallowtail caterpillar. Isn't that fun?

Is this leg real or fake?

A screenshot of the pseudopodia of an amoeba
Credit: Smallrex, CC by-sa 4.0, via Wikimedia CommonsSmallRex

This is obviously not a caterpillar but an amoeba, which is displaying the temporary leg-like projection of its membrane called a pseudopod. Remember how in high school you learned about amoebas eating by extending their body around their food and then connecting their body back together again? That's the logic behind their fake legs, too. An inspiration to caterpillars everywhere!

Okay, going back to basics...are these caterpillar legs real or fake?

A close-up of the stubby prolegs of a sawfly larva of the species Abia sericea
Francesco Canu, CC by-sa 4.0, via Wikimedia Commons

Tricked you again! These are indeed fake legs but they do not belong to a caterpillar! These are the prolegs of the larva of Abia sericea, which is a species of sawfly, an insect inside the order Hymenoptera, which contains ants, bees, and wasps. Many larval sawflies look just like caterpillars and can only be distinguished by sawfly larvae's lack of crochets, which are the velcro-like tips of each of a caterpillar's fake legs. Butterflies and moths aren't the only ones with beautiful and voracious larvae.

Lots of leg-looking things here, but I want you to focus on the curved fangs right below the face of this handsome house centipede. Are these jaws or legs?

Closeup of a house centipede found in a dormitory in Charlottesville, Virginia.
Credit: Kevincollins123, CC by-sa 3.0, via Wikimedia Commons

Centipedes are famous for being basically all-leg, and these curved pincers are no exception. These highly modified legs are called forcipules, and they function like fangs, able to inject venom into prey. In some ways, forcipules are the philosophical opposite of prolegs—once legs, but now functioning as not-legs, as opposed to "legs" that were never legs but now are used for everything a leg should do (walk). It makes one wonder, which has the stronger claim to the title of leg? A leg that has eschewed the purpose of its forebearers, now steadfast in the realm of Mouth? Or a leg that has, through some grand evolutionary avenue, come to embody the quintessential notion of leg in form and function? Which leg can stay? Which leg must go?

Now on to these legs. Real or fake?

A close-up shot of the legs of a sculpture of Heimlich the caterpillar from A Bug's life
Credit: sfgamchick, CC BY-NC-ND 2.0, via Flickr

So you can probably guess these legs are fake, but not in the way you might think. These are fake real legs, meaning fictionalized representations of the thoracic real legs of Heimlich the German caterpillar who works as a clown in the movie A Bug's Life. Pixar chose to render Heimlich's thoracic legs with mitten-like hands, which are certainly cute, but as-of-yet unseen in a real caterpillar. However, Heimlich does in fact walk on three sets of prolegs, which are more accurately rendered as stubby little appendages. You might consider the legs pictured above even a further degree away from realness, as they are not a screenshot of the movie itself but a photo taken of Heimlich's Chew Chew Train, a now-shuttered slow-moving ride at Disney California Adventure that once reminded kids to eat their foods and vegetables: a shadow of a shadow in the cave, an allegory of an allegory. Realness is fleeting, and so are we.

Final question: What's up with this leg, or, for that matter, this foot? It's gotta be fake, right?

A sketch of DeSantis's foot inside of a humongous black boot, showing a pointed toe and a lifted heel.
Photo by Scott Olson/Getty Images, Illustration by Chris Thompson

The mystery of this suspect appendage remains unknown, even to science. But it seems clear that no leg is faker than this; a protrusion that defies all anatomical logic, in person and in shadow. If we were to unsheath the signified (the pant and boot) from the signifier ("leg"), what would be revealed? Some fleshed appendage? A leg molded only from Jell-O? A proleg? The unknowable void? Whatever lies underneath, let it stay encased in Boot; I do not wish to see it!

So how'd you do?

0–3 correct: Have you even seen a leg? The first four were basically freebies! Go back to leg school!

3–6 correct: Good for a neophyte. You have proven you know a perfectly acceptable, not-weird amount about legs.

6–9 correct: What are you, some kind of leg enthusiast? I'm impressed!

9–12 correct: What are you, some kind of leg freak? I'm unsettled!

13 correct: Ron DeSantis you are NOT welcome here, skitter back to your burrow!

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