Why don't spiders stick to their webs?
I don't know.
Usually, a spider's web is made up of silk threads which are covered with droplets of glue.
This glue makes the threads sticky.
Now, when an insect flies through the web, the insect normally gets stuck to the sticky threads.
But, a spider does not get stuck because its legs have tiny hair like structures called setae.
When a spider walks on a sticky thread.
The setae gets stuck onto the thread helping the spider to get grip and support to walk.
Now as the point of contact is very less, the glue has very less surface area to stick.
Hence, the spider easily pulls its legs without sticking.
Besides this, a research suggests that certain spider's legs are covered with a special chemical coating.
This coating also helps the legs from sticking to the glue.