Spiders and Their Webs
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Have you ever touched a spider web? Do you remember how hard it was to get the web off of your fingers? As anyone who has ever touched one knows, spider webs are very sticky. Spiders make their webs sticky by putting a special glue on some of the web’s threads. When flies or other bugs get caught in the web, they cannot get out easily. After a bug gets trapped in the web, the spider wraps it in more of its sticky silk. Then, the spider enjoys its meal. But if a spider’s web is so sticky, what keeps the spider itself from getting stuck in it?
One reason why the spider does not get caught in its own web is that not every thread in the web is sticky. Some threads do not have glue on them. The spider knows which threads are safe to walk on and which ones are covered in glue. The spider can easily walk across the entire web without getting stuck in it by only stepping on the dry threads.
When a spider does have to step on the sticky threads to get to a trapped bug, it walks very carefully. A spider will use only the very tips of its legs, just as you or I may walk on our tip toes. Short hairs on a spider’s legs called setae also help keep the spider from getting caught in the glue. These hairs are covered with oils that keep the glue from sticking to the spider’s legs.
Spiders also wash themselves a lot. They always make sure to keep their legs clean, washing them many times a day. Cleaning their legs often removes small pieces of silk or other things that might cause them to get caught in the web. By cleaning themselves so frequently, spiders make it much easier to walk in their webs without getting stuck.