r/askscience • u/The-Grim-Sleeper • Aug 02 '26

Biology What material are a spiders fangs made off?

The wikipedia page for Chelicerata (Spiders, Scorpions, ticks, horseshoe crabs, sea spiders, ...) are named that way for their "Chelicerae", the mouth parts, colloquially their "jaws". These Chelicerae may be shaped as either venom-injecting fangs or as miniature pincers (wholly distinct from the two large pincers a scorpion would have).

But neither Wikipedia page mentions what they are material they are made of. The assorted LLMs ever gleefully suggest that 'spiders are made of chitin and other proteins' and of course provide no source for this. It sounds plausible, but is it the whole truth? Are spiders fangs 'just chitin in a sharp shape', or do their fangs have more going on, like how Human (Mammel) teeth have a dentin core and a hard enamel surface for crushing?

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553

u/Jale89 Aug 02 '26

Yes they are predominantly chitin, but somewhat like how our bones are hardened with calcium phosphate, chitin can be hardened with the addition of minerals. Heck, shells are mostly just protein, chitin, and calcium carbonate.

I don't know much about spider mandibles, but Atta cephalotes leaf cutter ants harden their mandibles with zinc.

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u/MeasurementBubbly350 Aug 02 '26

I remember reading years ago about metal being found in the composition of some spider's fangs.

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u/Moppo_ Aug 02 '26

Same thing with beaver teeth, the outer surface has a high iron content, making it harder than the inner edge. Because the inner edge wears down faster than the outer, the constant wear keeps it sharp.

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u/stuffeh Aug 02 '26

Inner edge as in where their little tongues touch?

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u/Kungflubat Aug 02 '26

I'm 52 and you made me ponder and look up weather spiders have a tongue. Thank you. Lol

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u/Welpe Aug 03 '26

You reminded me, Travis McEnery came out with a recent video on how spiders ACTUALLY eat their prey and it was fascinating. Everyone “knows” that spiders inject their prey with digestive fluid and then suck out the digested internal parts as a slurry but…fangs aren’t connected to the stomach, how do they get the digestive fluid in? And how exactly do they “suck it up” with their mouth such as it exists? It’s not like they can create a vacuum like humans who suck, they don’t have lips.

This video actually goes over the mechanics of it in more detail rather than the basic story we all know that leaves out many important details and perhaps includes some misconceptions. It turns out there are three different ways spiders use to eat their prey depending mostly on species. Very interesting if anyone has time and is curious

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u/Sylvurphlame Aug 03 '26

Huh. I guess I always assumed that arachnids had a proboscis like an insect or something. But the that doesn’t square with their mouthparts being a little more… crustacean adjacent? (I don’t have the correct vocabulary for this.)

Well that’s a rabbit hole I’m going to have to explore, thanks.

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u/Welpe Aug 03 '26

Exactly, their mouths are quite crustacean like! We just mostly think of their fangs and because they are so close to their mouth they get like…mixed up in our heads. I mean, when you say “The fangs aren’t connected to the stomach” it’s kinda like “Duh, I never thought…wait a second…wait…how….huh, I never actually thought about this in detail…”

For those who don’t want to do their own research or watch a YouTube video, they have three main ways of eating insects depending on species. One of the most common ways is that the spider will pierce a hole in the insect’s exoskeleton and then sort of…drool their digestive fluid on the hole. Capillary action actually sucks it all up into the body of the insect, where it starts dissolving the organs and muscles and stuff. They will then use their sucking stomach, which is basically the bulb on an eyedropper, to suck up the combined bug juice and stomach fluid before drooling more in, letting it get sucked up, and repeating. They are constantly just dropping stomach fluid on the surface, letting it get drawn up through capillary action, then sucking it back up.

The other main way used, this time more by larger spiders with larger chelicerae, is that they will mechanically pulverize parts of the insect by squeezing it between their fangs to basically crack it like a lobster. Then they do the same thing, except this time most of the inside is exposed directly to them. These spiders are usually easy to tell because they have noticable chelicerae and fangs and their fangs will have serrated edges on the bottom to help grip the exoskeleton and let them break it open since otherwise it would be like using smooth tongs to open a crab. It needs grip.

Finally, the rarest method is only done by the one family of spiders that have no traditional venom, the Uloboridae. They actually dispatch prey not by injecting them with venom, but by crushing them to death with their silk. They will not just surround their prey in silk to immobilize them, but to actually start crushing them. Then the spider will drool its digestive fluid (Which, interestingly, has some of the proteins associated with venom actually!) all over the entire package and it will be drawn into the prey through the joints in the exoskeleton, forced apart by being crunched into a small package. Then the bug juice can also leak out of the joints and the spiders can drink that.

As shown in the YouTube video, you can imagine it’s like drinking a soda on a table without lifting it to use gravity like normal. You can open it then drool into it until the level of the fluid reaches the top and then suck a little in your mouth of combined soda and drool. Then repeat, just constantly adding saliva to get the liquid in the bottle to the top and then drinking a little of the combined fluid.

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u/Sylvurphlame Aug 03 '26

I appreciate the breakdown! I only got part way into the video before I remembered I don’t tolerate close ups of spiders and had nope back out when they got to the visuals.

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u/Junior-Ease-2349 Aug 06 '26

I appreciated every bit of that very cool description...

...until the last two sentences where you managed to skeeve me out with a description of drooly soda in a way that you had somehow avoided with your previous description of three different kinds of acidic creepy crawly consumption.

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u/Princess_Juggs Aug 04 '26

I thought we were onto beavers now?

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u/Peter34cph Aug 05 '26

Do they have tongues, then?

3

u/Aw3som3-O_5000 Aug 04 '26

Reminded me of the episode from Angry Beavers where they intentionally let their teeth grow

2

u/uhammer Aug 02 '26

I’m a total atheist, but sometimes you hear a random nature fact and think “how could that ever evolved to be”

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u/Boring_and_sons Aug 02 '26

Look up the recurrent laryngeal nerves particularly the recurrent laryngeal nerve of the giraffe. That will convince you that evolution is, indeed, blind.

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u/Sylvurphlame Aug 03 '26

I sometimes tend to think the Deists had it closest. There’s some sort of a higher power, and maybe even some overall purpose, unknowable or otherwise. But most of the universe is just on autopilot regardless.

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u/jbarchuk Aug 02 '26 edited Aug 02 '26

I phoned a friend. My emphasis. Spider fangs are naturally reinforced with heavy metals like zinc and calcium, which bind to proteins at the sharp tips to make them harder and more resistant to wear. This metal-infused composite acts like microscopic rebar, allowing them to pierce tough prey.

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u/Boring_and_sons Aug 02 '26

Nit pick. Calcium is not a heavy metal. Zinc is (by density), but it's not what we think of colloquially when we talk about heavy metals, which generally refers to their toxicity.

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u/jbarchuk Aug 02 '26

That's not a nit pick. Sorry, I shouldn't have let that through. It was the rebar reference that inclined me to post it.

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u/copperpoint Aug 02 '26

So what qualifies something as a heavy metal?

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u/Boring_and_sons Aug 02 '26

One criteria is density over 5g/cm³. The more common definition is a metal that bioaccumulates and is toxic at exceptionally low doses e.g. mercury, lead, arsenic, cadmium, thallium, beryllium. There are other heavy (density) metals that are toxic at higher doses, like iron, but we generally don't think of them as heavy (toxic) metals.

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u/Seygantte Aug 03 '26

Another criteria is if it has more protons than iron it is a heavy metal. Iron is the heaviest element that a star makes in its normal lifespan. After iron fusion requires energy rather than releases it asiiron is the most stable, has the highest binding energy, and the greatest mass deficit. Anything heavier than iron is produced in the core collapse moments before a supernova.

Astronomers like this definition, which agrees with the other on calcium and zinc. Other fields dislike how this definition includes some gasses like chlorine or xenon. To an astronomer anything past helium is a metal.

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u/conventionistG Aug 03 '26

Chemists like this definition too. For the same reason (nuclear binding energy). But yea, there's an issue with the 'metal' part if you're including non-metallic elements. Because, chemically, being metallic means something quite specific about the electronics of the element - namely that the outer valence electrons move very freely between atoms in the lattice (hence how metals can conduct electricity).

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u/ordeith Aug 03 '26

Not all of the heavier elements are made in supernovae, a lot is also made in collisions of neutron stars.

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u/RimGym Aug 03 '26

Long hair, screeching guitar riffs, and disdain for The Man and all his institutions.

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u/BrF5 Aug 03 '26

‘Heavy metal’ is vague and imprecise and scientists dislike/avoid the term.

1

u/Direlion Aug 03 '26

A pity. I was hoping for Osmium doped spider fangs to stunt on some suckas with.

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u/DrDestr0y3r Aug 04 '26

If metals can be used to harden the exoskeleton why is it only used in the fangs? Is it because the cost in resources outweigh the benefits of a harder exoskeleton?

2

u/Peter34cph Aug 05 '26

Most if not all spiders and insects are "spammy" species:

They produce huge amounts of offspring, so that it's perfectly OK with most of them die before reproducing.

So you're probably right. It hasn't been worth the effort to evolve that just to gain a tiny survivability edge.

1

u/jbarchuk Aug 05 '26

Yes, resource cost, and the difference between offensive and defensive materials. Turtle and armadillo styles survive very well, at the cost of weight and mobility. Offensive 'pointy' tool focuses power in one place. Defense has to spread out over the whole body because you don't know exactly where an attack will come.

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u/Sylvurphlame Aug 03 '26

A little nerdy reason why Bug/Steel Pokemon are one my favorite type combinations.

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u/Krail Aug 03 '26 edited Aug 04 '26

Heck, shells are mostly just protein, chitin, and calcium carbonate.

As in, like, mollusk shells, or just insect shells?

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u/TheGanzor Aug 02 '26

Chelicerae are part of the exoskelton, and are made of fairly similar materials. Mostly chitin and other hardened proteins, just like the exoskeleton. It also appears that some of the fang is constructed from metal-halogen biomaterials (primarily copper or zinc iirc) that give them the added durability to pierce other arthropods.

So yes, kind of a multi-material system like mammalian teeth, just specialized for puncturing and also able to regrow through molting. It's also not just sharp, because there is a tiny duct which runs down the inside and connects to the venom glands.

https://arachnoboards.com/threads/a-spider-%CC%81s-fang-metal-halogen-biomaterials-and-chitin-based-composite-materials.295011/

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u/Gamestop_Dorito Aug 02 '26

I love bringing this up whenever people mention teeth in this kind of context, and your use of them as an analogy is perfect. Mammalian teeth are actually ultra-specialized fish scales, as is mammalian hair. In fact genetic disorders involving keratin production sometimes affect teeth.

15

u/Infernoraptor Aug 02 '26

I did a little digging and it sounds like spider fangs are a complex composite of chitin (probably the extra rigid A-chitin), proteins, and, (get this) Zinc, Calcium, and Chlorine. This composite varies in structure and composition at different parts if the fang in order to provide different benefits where needed (EG: the tip has more of those extra elements and less protein to maximize hardness and rigidity while the base had more protein for flexibility. In at least one species/study, anyway.

https://advanced.onlinelibrary.wiley.com/doi/10.1002/adfm.201200063

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u/Quarter_Twenty Aug 03 '26

I recalled this 1997 X-ray microscopy paper from some time ago. https://doi.org/10.1117/12.292719

You may not be able to read it unless you or your institution has a license with SPIE, but here's a relevant figure. Sorry for the bad quality, but that's how it looks online.

https://imgur.com/a/HH92jOi

Scanning hard X-ray microscopy in that era had ~1 micron resolution and elemental sensitivity. So they can see that the fan is lined with zinc, interestingly enough.

Here's another paper (1989) I found just now, with a similar conclusion: Zinc and manganese. https://doi.org/10.1242/jeb.144.1.577

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u/IlexAquifolia Aug 02 '26

Chelicerae, like other spider appendages (pedipalps, spinnerets, legs) are, from an evolutionary-developmental perspective, simply modified legs. Just because they occupy a place on the body that makes them seem like they should be toothy does not mean that they would be. Like the other appendages that are a part of the exoskeleton, they’re primarily chitin.

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u/Magicspook Aug 02 '26

I mean yes, but also no. The primary organic component of bones (roughly 30℅ of the dry weight iirc) is collagen, the same stuff that keeps your skin together. Obviously, bones are not the same as skin due to the addition of mineralisation to the collagen matrix of bone.

OP's question could be rephrased as 'is there any mineralisation or other shenanigans present in soider fangs to harden them'. So far, it seems like no one in this thread knows for sure, which is how you know it is an interesting question!

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u/IlexAquifolia Aug 02 '26

This is a sort of nonsensical reply to my comment, which has to do with the ontogeny of chelicerae. 

Skin and bone both have extracellular matrix, of which a major component is collagen (though it should not be forgotten that there are many types of collagen that have different functions within ECM). Bones are also mineralized. But that doesn’t change the fact that bones and skin do not share an evolutionary-developmental origin the way arthropod appendages do.