Spiders amaze humans for many different reasons. Perhaps you are fascinated by their many different styles of web-building, or maybe you cannot figure out why any animal would need eight legs. But one of the most fascinating aspects of spiders would definitely be their peculiar way of moving, especially when they are moving vertically or upside down. So how can spiders do that? Can all spiders defy gravity in this way?
For a long time science was also ignorant of the reasons behind a spider’s seemingly inexplicable vertical movements, but now science has it figured out. It turns out that spiders are not performing magic tricks for us. Actually their secret to sticking to vertical and other awkward surfaces has to do with the hairs located at the tips of their legs.
A spider’s legs have thousands of tiny hairs that create contact points between their legs and the surfaces that they navigate. The hairs are small and flexible, and some can only be seen with a microscope. Some of their tiny hairs are smooth to the feel, but a microscopic look at those same hairs will reveal that even the smoothest hairs are actually quite rough. These tiny rough hairs of varying sizes allow spiders to attach themselves to just about any surface. If all of a spider’s hairs were rigid, then they would only be able to stick to very few surface types. However, the small hairs located at the end of a spider’s legs are malleable so they can stick to many different surfaces including glass.
Barnacles attach themselves permanently to rocks or the hulls of ships, but spiders can attach themselves to a variety of object temporarily. This type of adhesion, which is demonstrated by spiders, is known as “dynamic attachment”. So you can think of spider adhesion as being about as strong as the adhesive on post it notes.
Have you ever seen a spider fail to climb a particular surface?