GO IN DEPTH

Spider Webs

Spider Webs Photo Credit: Peter Miller. Licensed under CC BY-NC-ND 2.0 (https://creativecommons.org/licenses/by-nc-nd/2.0/) via flickr (https://www.flickr.com/photos/pmillera4/27457901631/).

A listener asks: Can spiders get caught in the webs of other spiders?


Transcript

A spider’s tangled web. I’m Bob Hirshon and this is Science Update.

Science Update listener Christopher Bender of Spartanburg, South Carolina, wrote to ask whether spiders can get caught in the webs of other spiders. We asked Jonathan Coddington, an arachnologist at the Smithsonian Institution.

Coddington
The short answer is yes: any spider could get stuck in any other spider’s web or even in its own web. They don’t have any special immunity to sticky silk.

But if a web-spinning spider were to get caught, it might free itself by secreting an enzyme in its saliva that is powerful enough to cut the silk of another spider’s web. In its own web, a spider avoids touching its sticky silk; it also coats the tips of its legs with oil to prevent entanglement. If  you have a science question, give us a call at 1-800-WHYISIT. If we use it on the air, we’ll send you a Science Update mug. I’m Bob Hirshon, for AAAS, the science society.


Making Sense of the Research

Many people react to spiders in much the same way as a First Fairy in Shakespeare's A Midsummer Night's Dream: "Weaving spiders, come not here / Hence, you long-legged spinners, hence!"

Despite many people's wariness when it comes to spiders, they are quite amazing creatures and many provide useful services in terms of keeping down the insect population. In fact, researchers Martin Nyffeler of the University of Basel and Klaus Birkhofer of Lund University in Sweden and the Brandenburg University of Technology Cottbus-Senftenberg in Germany have estimated that spiders consume between 400-800 million tons of food each year. That food consists mainly of insects, little non-insect bugs called springtails, and even small vertebrates. This amount is equal to the mass of all humans on Earth. Their research appeared in the journal The Science of Nature, March 14, 2017.

How do they go about doing that? Spiders have many methods they use to catch prey. The most common method is for them to spin a web, which is sticky so that anything that gets into it will be trapped there. Since the web is sticky, though, how do spiders avoid getting caught in their own webs?

Two of the ways spiders avoid getting caught in there own webs are explained in the Science Update broadcast. Spiders spin both sticky and non-sticky silk. So, when they walk on their webs, they try to avoid the sticky silk. Scientists also are investigating whether spiders produce an oily chemical that they can use to coat the tips of their legs to prevent getting stuck to the web or to help free themselves if they do get caught.

A third method for avoiding getting caught in a web or for freeing themselves that is not discussed, though, is that web-spinning spiders have extra sets of claws on their feet. All spiders have two claws on their feet; web-spinning ones have three. These claws are used to grasp threads and provide traction as the spider moves along.

Now try and answer these questions:

  1. How much food, including insects, do spiders consumer each year?
  2. Do you think this provides a benefit to an ecosystem? Why or why not?
  3. How do spiders avoid getting entangled in their webs?
  4. If a spider does find itself caught, what can it do to free itself?

You can learn more about spiders by listening to the Spider Web Sites Science Update. This feature talks about the complex social structure established by spiders.

You also can watch the Spider Genes Put a New Spin on Arachnids’ Potent Venoms video from Science Magazine.


Going Further


For Educators

This Science Update would be a good way to talk with students about the various survival strategies that organisms use. The webs spiders use are ingenious ways for them to catch prey without expending too much energy.

In addition, you could have your students consider the spider web itself and how it is an engineering wonder. Engineers have been studying the properties of the silk spiders use to help develop materials that can be used by humans. This is an instance of biomimicry and you can help your students explore that concept with the Death-Defying Cockroaches lesson.


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Organisms in Motion: Practical Applications of Biological Research
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Periodical Cicada Survival
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Fish Tricks
6-8 | Hands-On

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