Why do spiders hang upside down?

Although many people may be afraid of spiders, they are indeed very helpful to us, because they eat harmful insects.

They eat grasshoppers and locusts which destroy crops. Spiders also eat flies and mosquitoes which carry diseases. 

Spiders mostly feed on insects but some capture and eat tadpoles, small frogs, small fish and mice. 

Most females are larger and stronger than the males and occasionally they eat the males!

Spiders can live anywhere they can find food, like fields, woods, swamps, caves and deserts. One kind of spider spends most of its life underwater!

Another kind lives near the top of Mount Everest, the world's highest mountain.

And as we know, some live in houses, barns, and other buildings. Others live on the outside of buildings, on walls, windscreens and corners of doors and windows. 

Many spider species have also found it more convenient to literally turn their world upside down, as they spend most of their lives hanging suspended by their legs, and walk by swinging under the influence of gravity. 

All spiders spin silk but some don't spin webs. Bolas spiders spin a single line with a sticky end. Any insect near, gets trapped when the spider swings the sticky line near them. 

Web-spinning spiders, like hunting spiders, live in caves, in grass or shrubs, or in trees. They cannot catch food by hunting because of their poor vision. 

Instead, they spin webs to trap insects. 

A web-spinning spider does not become caught in its own web. When walking across the web, it grasps the silk lines with a special hooked claw on each foot.

So how does the spider manage to stay upside down? 

Well, scientists believe they have solved this mystery. Their secret to hanging upside down, is down to small hairs at the end of their legs. 

These thousands of tiny hairs create multiple contact points between the spider and the surface that increase the spider’s ability to hang on.

The spider’s system is very much like that of a Post-It note, as temporary attachment systems, like hairy adhesive pads, can be used multiple times, and adhere strongly enough to hold the animal, but the contact can be loosened very quickly and effortlessly.

In fact, you can hang a weight of double the spider on its body, while it is sitting upside down on a smooth glass pane, and it won’t fall off!

In smaller spiders this relation is even higher, because those have a higher foot pad area relative to their volume.