I’m Jemma’s hero at the moment. You may be wondering how this happened, but it was really a matter of good timing (and acting). I walked into Jemma’s office this morning and the first thing I saw was a massive spider, at least as big as my hand, sitting in the corner of her ceiling. It was putting finishing touches on its masterpiece: a gigantic cobweb. Clearly, Jemma had just noticed it as well, since she standing by her desk, wielding a rolled up newspaper like a sword and gathering her courage. When she noticed me, she laughed nervously and gestured to the spider. “Not my strong point.”

Now, I’m petrified of spiders, but Jemma didn’t need to know this. “Don’t worry,” I said as I took the newspaper from her. The spider’s multiple eyes seemed to be challenging me to a duel. I was ready to run. But Jemma looked so relieved and she watched me with her sweet smile. With no way out, I took a deep breath and stepped up onto her desk. I reached up and took my best shot. My opponent fell from the ceiling and scampered over my foot. I screamed like a girl (inside) and proceeded to beat the life out of the poor arachnid.

It was all worth it. Jemma was grateful, even though her desk was a mess after my antics. I cleaned up the cobweb for her as well. While trying to get rid of the sticky strands on my hands, I realised that that web was actually a little miracle of nature and that I really didn’t know much about it at all. So I did what I always do and visited the halls of scientific literature.

When you think of silk, you may picture a luxurious evening gown. You may even think of that ancient trade network in Eurasia called the Silk Road. Most likely though, a vivid picture pops into your mind of a younger version of yourself feeding mulberry leaves to a bunch of famished silkworms in a shoebox. In truth, it is not just silkworms that make this strong and stretchy substance that we call silk. Many arthropods (insects and some other creepy crawlies) have the ability to make silk. This includes fleas that use it to make their nests cosy and bees that strengthen the wax of their beloved honeycombs with silk strands.

Silkworms may be fat but they aren’t lazy. They spin an astonishing 800 metres (nearly 900 yards) of silk for a single cocoon. While they’re spinning, their silk glands, which open up onto their lips, account for 20% of their body weight! When they spin faster, the silk becomes stronger, but when they spin slower it becomes stretchier. It seems that they can’t make it super stretchy and super strong all at once. It is on this point that spiders rule.

Spider silk is made from a protein called fibroin, just like silkworm silk. But spider silk is both stronger and stretchier than silkworm silk. This isn’t surprising - silkworm silk has to make a snug and safe cocoon while spider silk needs to trap unsuspecting insects that are flying at great speeds - without breaking. The physics of spider webs is exquisite. Say an unsuspecting fly is buzzing along, minding its own business. While it is moving, it possesses kinetic energy. As it has a fatal collision with a spider’s web, it stops moving and therefore doesn’t have kinetic energy anymore. Energy is never created or destroyed so the kinetic energy has to either be turned into heat energy or elastic energy. If it is turned into elastic energy, the web is deformed, so it will bulge on the other side as the fly lands, just like a trapeze artist falling into a net deforms the net). The kinetic energy picks both options. About 65% of the kinetic energy is turned into heat energy and the rest is turned into elastic energy. It’s vital that so much of the energy is turned into heat, not elastic energy. If all of it became elastic energy, the fly would be very lucky. The web would recoil and bounce back too much - catapaulting the fly off the web again.

Spider silk is lightweight, flexible and five times stronger than steel of the same weight. That’s why biologists have been eyeing spider silk with interest for many years now and engineers have been drooling over it. It could be used for many industrial and medical applications and could even replace nylon in some situations.

There is only one problem: humans haven’t managed to domesticate spiders as they have domesticated silkworms, chickens and cattle. Since farming with spiders isn’t a realistic option, ambitious biotechnologists are opting to produce spider silk without using a spider. They’ve tried sticking genes that carry the code for making spider silk into a range of other living things, like bacteria, yeast and even baby hamster kidney cells. They’ve managed to produce some spider silk protein and then hit another hurdle. Silk protein isn’t so useful if it is not spun into a fibre - something spiders are really good at and humans are still getting the hang of. You see, spiders secrete soluble silk protein from special glands and then turn it into liquid-crystal fibres. If that sounds very complicated to you - that’s because it is. On top of being expert spinners, some spiders are multi-taskers: some species make seven different types of silk all at the same time.

While there is progress in making spider silk, there is also some headway in understanding the stickiness of spider webs. Spiders deposit glue drops on certain strands of their webs. Now, you’ll have noticed that the glue on plasters and other glues don’t do so well when they get wet. Spider webs do the opposite. They need moisture to stay sticky and if they dry out, they lose their stickiness. Spider glue could teach us how to make water-friendly glue which will have a whole bunch of useful applications, including a plaster that sticks tighter to your skin in the shower.

I’m starting to view spiders as really clever engineers now. Maybe I’ll chase them out of the window next time instead of killing them.

Want to dig deeper? See if you can find the answers to these questions:
1. What’s the Silk Road? Where was it, when did it exist and what effect did it have on the history and culture of Eurasia?
2. What other creatures make silk that aren’t mentioned in the article?
3. What are some uses of silk? (The answers may surprise you!)

Feeling creative?
Draw an infographic of a map of Asia and Europe. Illustrate the various things that were traded between the two continents and indicate these on your map. Use your imagination in illustrating the different people groups that live in various regions.

Practical project:
Raise a batch of silkworms on a diet of either mulberry or beetroot leaves (don’t mix their diets - the one or the other). When they start spinning, make a bookmark, heart, star or cross cardboard shape for them to spin on. Place more than one worm on an object to make the silk thicker. If you allow the worms to enclose themselves in their cocoons, you can follow some steps to unwind the cocoon’s thread.

To find out how to, visit: https://www.silkwormshop.com/resource...
This web page has ideas for other projects you can do with your silkworms as well.

Bibliography
1. Beckwith, C. Empires of the silk road: A history of central Eurasia from the Bronze Age to the present. (Princeton University Press, 2009).
2. Sahni, V., Blackledge, T. A. & Dhinojwala, A. A Review on Spider Silk Adhesion. J. Adhes. 87, 595–614 (2011).
3. Gosline, J. M., Guerette, P. A., Ortlepp, C. S. & Savage, K. N. The mechanical design of spider silks. J. Exp. Biol. 202, 3295–3303 (1999).
4. Vollrath, F. & Knight, D. P. Liquid crystalline spinning of spider silk. Nature 410, 541–548 (2001).
5. Lazaris, A. et al. Silk Produced in Mammalian Cells Spider Silk Fibers Spun from Soluble Recombinant. Science 295, 472–476 (2007).