9 Amazing Facts about Spider Silk
For one thing, spiders have four pairs of eyes, and some spider species have the best vision among insects, even better than a dragonfly’s. Spiders also have a tube-shaped heart that pumps blood into their legs, causing these to move. That’s right. Spiders use blood pressure, and not their muscles, to move. All spiders are predators, though they cannot digest solid food, so they have to liquefy their prey before eating it. Also, most spiders are venomous, though few possess venom deadly to humans.
One of the most amazing things about spiders, however, is the fact that they produce silk. They may not be the only creatures to produce silk but boy, they sure know how to use theirs. Just how fascinating is spider silk? Let’s find out.
1. Spider Silk Has a Gazillion Uses.
Well, maybe not a gazillion. Still, the fact remains that while the spider is not the only animal that can produce silk, it is the only animal that can produce different types of silk for different purposes. They can produce fine threads (called gossamer) and thicker threads, as well as both sticky and non-sticky threads.
The most common use spiders have for their silk is to catch prey. Usually, spiders do this by weaving webs of different shapes and sizes. They wait for an insect to fly into the web and get stuck in it. As the poor insect struggles, vibrations are sent along the web, letting the spider know it is time to eat.
There are other ways spiders use silk to catch prey, too. Bolas spiders, for example, use their silk to make something like a fishing line with a sticky blob at the end. They then throw this at insects passing by, snagging them just like fishermen catch fish. For this reason, bolas spiders are also called fishing spiders.
Ogre-faced spiders are also like fishermen. They use their silk to make nets, and then when an insect passes by, they stretch their nets and throw them at the unsuspecting creature, trapping them.
Then, there are the trapdoor spiders, most of which make burrows with entrances made of silk. They hide behind the silk curtain and when prey passes by, disturbing the trip lines along the entrance, they jump out and snare their meal.
In addition to catching prey, spiders use their silk to help them move from place to place. Jumping spiders, for example, use their silk to create a “rope” they can hold on to in case they fall, and other spiders make “balloons” out of their silk, enabling them to “fly” — or parasail — from one place to another.
Spiders also use their silk to communicate with other spiders, leaving silk trails. Males leave these trails to mark their territory, while females lace their silk with pheromones, letting the males know when they are ready to mate. Believe it or not, the pheromones in the silk can also tell a male spider how many exes — previous partners — the female spider has had.
During mating, some male spiders use silk to deliver their packages of sperm to the female. One particular species of spider even uses silk to seal up the female’s reproductive organ so that no other male spider can mate with her after him. Once the female lays eggs, she wraps these in silk in order to protect them until they hatch.
Spiders are not the only ones who make use of spider silk. We do, too. Spider silk is used to create precious cobweb paintings, wherein the canvases are made from mounted spider webs. In the past, spider silk was also used to make bandages and crosshairs for telescopes and rifle sights. Recently, spider silk has an even more amazing use — it is used by scientists as a scaffold for growing human skin cells.
2. Some Spiders Eat Their Silk.
Spider silk is made of protein. It is produced from the spider’s silk glands, which are connected to pairs of movable spinnerets that release the silk. Originally, the silk is in a liquid form but when it comes out, it turns into a rigid fiber, not because of exposure to the air but because the molecular structure of the protein is changed.
Because spider silk is made of protein, it can be eaten by the spider. Some do this, in fact, in order to recover the protein and the energy that they used to make the silk, almost like recycling their webs.
3. Spider Silk Is Stronger Than Steel.
Spider silk may seem thin and frail, but don’t let your eyes deceive you. Darwin’s bark spider silk is the strongest fiber on earth, more durable and elastic than any natural or synthetic fiber, including Kevlar, which is used to make bulletproof vests. It is up to six times stronger than high-grade steel per weight. The only substance found to be stronger than Darwin’s bark spider silk are the teeth of limpets.
The strongest silk belongs to the Darwin’s bark spider. Its silk is ten times tougher than Kevlar and at least two times tougher than any other spider’s silk. Darwin’s bark spiders make their webs over rivers or lakes. That’s how confident they are in the durability of their silk.
4. Spiders Can Make Webs in Different Shapes.
The most common type of spider web is the orb web — the web which looks like a wheel with spokes. In addition to this, there is also the cobweb, or the tangled web, which is a mess of silk often seen at the corners of houses, as well as sheet webs which are flat, and also funnel-shaped webs and triangle webs.
How do spiders make webs? All webs start with a single thread of silk. In the case of orb webs, the spider starts by releasing this thread into the wind and waiting for it to attach to another branch, forming a bridge. The spider then crosses the bridge and releases another thread, forming a V-shape, and then it lowers itself, to form a Y-shape. Once the core of the web is secure, the spider lays out more threads from various anchor points, then from the center to the edges until the web is complete.
Spiders use only the tips of their claws to make webs, so they don’t end up getting stuck.
5. Not All Spiders Spin Webs.
All spiders produce silk, but not all of them spin webs. Tarantulas, for example, actively hunt for prey as they crawl across the ground or climb trees. As we talked about earlier, spiders have many ways of catching prey other than spinning webs.
6. Humans Have Not Been Able to Replicate Spider Silk.
People have been able to replicate many natural substances and fibers, but spider silk is not one of them. The molecular structure of spider silk is simply too complex for us to make. As for spider silk farming, this has not been successful, either. Even though silk can be extracted from spiders, millions of them are needed in order to create just a few feet of silk. Also, spiders are difficult to keep in captivity in large numbers: they need to be kept separate from each other, due to their predatory nature.
7. There Is a Spider That Spins Golden Silk.
Have you ever heard of the story of Rumpelstiltskin, about a miller’s daughter who could spin straw into gold? This is just a fairytale, of course, but there are spiders that can actually produce gold silk. They are the Nephila spiders, or the golden silk orb-weavers.
Indeed, the webs of these spiders shine like gold in the sunlight, ensnaring bees, whereas in the shade, they provide excellent camouflage. The largest piece of cloth made from gold spider silk measures 11 by 4 feet (3.4 by 1.2 meters) and took four years to make!
8. There Is Even a Spider That Spins Its Web Underwater.
The diving bell spider (Argyroneta aquatica) spends its life under the water, creating bell-shaped webs that it fills with air so that it can breathe underwater. It also uses these webs to catch prey, to mate and to raise offspring.
9. Some Spiders Use Their Silk to Create Decoys.
Spiders may be predators, but they also fall prey to other animals such as birds and frogs. Two species of spiders have found ways to use their silk to prevent themselves from getting eaten. The Cyclosa mulmeinensis, for example, creates a replica of itself which it puts in the center of the web, acting as a decoy, while the Celaenia excavata is called the bird dropping spider for a reason — it uses its web to disguise itself as bird poop! Disgusting perhaps, but definitely genius.
What do you know?
Think you remember what you’ve read? Try out the Spider Silk Quiz!