In A Nutshell
We’ve long thought that spiders excrete some sort of oily substance that negates the sticky effects of their webs, allowing them to walk across the silken strands. That’s only part of the answer to the question of why they don’t stick to their own webs, though. Spiders can spin both sticky and non-sticky web strands, and they also have complicated, bristle-like structures on their feet that help keep them from sticking even if they do accidentally walk on the sticky parts.
The Whole Bushel
Some people love them and some people hate them, but either way, spiders are still one of the high-tech wonders of the animal kingdom. For a long time, we’ve wondered just how they keep from getting caught in their own webs; the point of a web for many spiders is to capture their prey, after all—what makes spiders different?
The answer is a complicated one, and it turns out that scientists’ guesses have only been a part of it.
It’s long been thought that spiders secrete an oily substance that counteracts the stickiness of the webs and keeps them from getting caught in their own traps. Researchers at the Natural History Museum in Bern, Switzerland tested spiders’ legs under a couple of different conditions to see how adhesive they were. Legs that were just wet or dry didn’t stick to the webs, but legs that were treated with solvents or cleaners would stick, as the spider’s protective, oily coating was removed.
The structure of a spider’s foot has something to do with it, too. With relatively recent advancements in magnification and video, scientists have been able to get a close-up look at how spiders walk (and those that aren’t spider fans, definitely shouldn’t watch).
Spiders have tiny, tiny claws on the ends of their feet, and the feet and claws are covered with little bristly hairs. These can be moved independently, and when the spider walks it can adjust these little claws so they’re walking at an angle that minimizes how much of their feet touches the sticky secretions on the web. The bristles on the claws help stabilize them and keep them from sliding across the silk.
Sticking to their webs isn’t something that spiders have to worry about all the time, either. Spiders have both sticky and non-sticky strands in their webs. This means that they usually don’t need to worry about getting caught in it at all. In fact, spiders that spin round webs all do the same thing. It’s only the circular threads that they smear with a sticky substance to try to catch their prey; the outermost threads and the spoke-like, radial threads aren’t sticky at all, giving them an easy way to get around without having to worry about getting stuck.
And those that are sticky, often aren’t completely sticky. Most spiders will only place little droplets of their glue on the web, making it easier for them to avoid but still impossible for a flying insect to dodge.
In spite of their delicate appearance, the strands of a spider web are ridiculously strong. Comparatively, if we were to construct our own webs similar in strength and elasticity to a spider’s web, it would have to be made from rubber and steel.
Creating webs isn’t the only thing spiders do with their silk, either. Some are known to use silk production in mating rituals, while others use silk to build little spider shelters. Silk is used to wrap and protect spider eggs, and when the eggs hatch, the babies can use pieces of silk to glide away from both the nest and their millions of newly hatched siblings.
Show Me The Proof
Popular Science: FYI: Why Don’t Spiders Get Trapped In Their Own Webs?
Library of Congress: How do spiders avoid getting tangled in their own webs?
Natural History Museum of Los Angeles County: Spider biology