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Spiders. One of the most diverse organisms on the planet, probably. Just from the top of my head, there are jumping spiders, trap door spiders, *underwater* spiders, giant, bird-eating spiders, leaf-shaped spiders, intelligent spiders, iridescent spiders, vegetarian spiders, dancing spiders, cartwheeling spiders and so on. They never run out of ideas!

And they also never seem to stop being discovered. That makes spider discoveries kinda boring. You can expect multiple species every bloody year, though there are some fascinating ones here and there. But instead, I'm going to look at answering a previously unknown *question*: 

# How do spiders find, make and navigate their sticky webs without getting stuck?

Spiders are essentially blind when it comes to navigating things that come out of their butts, and so I happened across this remarkably convenient study that came out only a few months ago answering my question, focusing specifically on *How Orb-weavers find and grasp silk lines* - the name of the study by William Eberhard.

It turns out that eyes being on the other side of the body to the web is not the only problem for spiders. With the exception of jumping spiders, the arachnids have pretty damn poor eyesight. To make matters worse, they are typically nocturnal, so even if they could see the fine lines of silk - which they can't - they couldn't at night anyway.

To get a good idea of how they do things, we should take a look at a spider's foot:

<center>![](https://steemitimages.com/DQmYpN7ZFPJeVbJ6PNyUeGJjtA32uZEfGyuRjVxxPFiTeCh/image.png)</center>

This actually gives a level of appreciation and understanding as to how they actually do things without getting stuck like their prey. They're not just 'used to it', their feet are uniquely adapted to traverse the sticky silk. 

If you look, you can see the middle tarsal claw closes up and pushes the silk line against the serrated edge of the *serrate accessory setae*, giving them a firm and reliable grip of any individual line. Here's an actual photo:

<center>![](https://steemitimages.com/DQmamjrrCiTeA8EwCYDD6gqBqgHjRccLzQMpkkVeEBCwyJv/image.png)</center>

In a rather gruesome experiment to show this way back in 1757, researchers removed the serrate accessory setae, and found, to no surprise, that spiders had difficulty making webs as well as climbing vertical lines, taking over 5 times the normal duration to do such an otherwise simple task. 

As you can see, this question was more or less answered long ago, but the paper goes on to point out that a spider will never actually see the lines during the construction of the web, so how does one actually find and make things from the silk so blindly?

So far what is known is that the spider uses its legs like a blind man's cane, tapping around to find the line, and then bringing another leg round to grab it and manipulate as it sees fit. Once the second leg has it gripped the fist leg lets go and moves on to feel for the next part. Depending on the awkwardness of the angles, this might require 3 legs to accomplish proper construction maneuvers.

But sometimes, the paper goes on, the angle of the line against any one of the 8 legs just isn't suitable for such an obvious slip in under the tarsal claw. The research goes into great depths hypothesizing ways in which awkward, parallel angles may be overcome, which you can read more about below, but the photos show a whole range of variations of grips from a female Southern House Spider that shows they really have no issue bending legs, lines or rotating their legs on its axis to get the job done:

<center>![](https://steemitimages.com/DQmdWsoJA2CBxMEMg27HFMLZ9dsehBDCPLRZc1qt6pzdmpp/image.png)</center>

# Anti-adhesion surfaces

<div class=pull-left>https://steemitimages.com/DQmZczFWU1YGD54WgrSLmLCBeTkcbEq65gkztnpwF7fXzec/image.png</div>

But there's so much more! I did a little more digging and found that they of course don't just use their feet, so their legs have adapted a few more tools, too. Old evidence explained that spiders avoid sticking to webs by clever behavioural avoidance of the sticky bits as well as an oily coating on its legs, but this came with weak evidence and has since been updated somewhat in a paper from 2012 by *R. D. Briceño*.

Upon further inspection, there are three traits working together; careful skilled movements, a lowered surface area contact by having a dense array of setae (hairs, bristles) on the legs, and a chemical anti-adhesive. 

This picture is a great demonstration of multiple ways the sticky web might interact with the setae on a spider's leg. When withdrawing the leg from the silk, the droplets are dragged to the tip, which allows easy release. The paper compares this to a water droplet going down to the tip of a leaf, giving minimal contact and easy release of the droplet. 

# Conclusion

There's clearly a whole lot more to it than in this post, showing how remarkable such an insignificant part of nature truly is, but I don't want to go into too great depth here and I think the above is a satisfying answer, right? 

It fascinates me that, with eight legs independently working each foot, they can blindly grasp a line with three claws and multiple serrated hairs, release and repeat in order to walk or run up and down its orb at often quite significant speeds. Meanwhile, a three-pronged attack on the silk helps build the web without actually getting stuck in it in the darkness of night, no problem.

They truly are masters of their craft. 

<center>![WhYkkh9.gif](https://steemitimages.com/DQmdEhYBwAGZDsmgdeDywfrba4DRJvaPFToR4HvSKjY8rim/WhYkkh9.gif)</center>

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*Image sources used with permission*

References: 

[How orb weavers find and grasp silk lines](http://www.bioone.org/doi/abs/10.1636/JoA-S-16-057.1)
[Anti Adhesive skills](https://www.researchgate.net/publication/221881111_Spiders_avoid_sticking_to_their_webs_Clever_leg_movements_branched_drip-tip_setae_and_anti-adhesive_surfaces)