Jumping spider

**Jumping spiders** belong to the family _Salticidae_. These spiders catch their prey by jumping on them.

Species live in many habitats, from leaves lying on the ground, to the tops of trees in the forest, and even way up on Mt. Everest. They are found on every continent in the world except for Antarctica.

At present, 5026 species in 530 genera have been found. They are actually the largest family of spiders, with about 13% of all species.

## Appearance

They are easy to identify because their eye pattern is distinctive. They have eight eyes, two of which are very large, and because their faces form a flat surface, facing where they are going.

## Behaviour

They often hunt high up in bushes, or on vertical walls. To save themselves from falling they do something very much like what climbers do to protect themselves in the mountains. Humans tie a rope to the mountain and attach the other end to the harness they wear. Jumping spiders attach silk from their spinnerets to the thing on which they are standing and then they jump. While they are moving through the air they make silk so that there is always a safety rope trailing out behind them.

Jumping spiders can jump long distances for their size, as much as 16 cm.<sup>p11</sup> When they jump, they use their hind legs. They raise their front legs to be ready to grab their prey.

Many other kinds of spider hunt at night, but jumping spiders depend on their eyes, so they like to come out in the daytime. Often they will find a sunny spot on a wall or tree trunk.

There are however many variations, and many surprising aspects. For one thing, Salticids do not necessarily follow a straight path in approaching prey. They may follow a circuitous course, sometimes even a course that takes the hunter through places where the prey is not visible. Such complex behaviour is hard to reconcile with an organism that has such a tiny brain. Some spiders in species of _Portia_ can take long detours from one bush down to the ground, then up the stem of another bush to capture a prey item on a particular leaf. Such behaviour is the subject of research.

Because they have good vision, jumping spiders can see human beings when they approach. Some jumping spiders may run away from approaching humans, and some do not. But either way a jumping spider will watch a nearby human being. When they do not run away, but do turn to keep watch over a human being, it may seem that they are interested in us. Some of them will even jump from where they are sitting on branches, rocks, etc. onto a person's finger or camera. These spiders only bite to get something to eat or to defend themselves, so if they jump on somebody's hand they will not bite. People might get bitten if they pinch or squeeze a jumping spider.

## Physical capabilities

Jumping spiders are able to climb glass and other very smooth surfaces because besides having two claws on each foot they also have sticky hairs (called _scopulae_) that hold onto the surface.  Many tiny ends on each hair are held to the glass by Van der Waals forces, the force that will make two very flat sheets of glass stick tightly together without any glue.

Jumping spiders are able to see very clearly. Two of their eight eyes are very large and are complicated inside. The eyes cannot move, so the spider will often move its body to look at what it wants to see. However, it can also move the retinas of its two main eyes on the inside of the eye, so the center of the eye's picture can be moved. So the jumping spider has binocular vision.

### Use of silk

Very few kinds of jumping spider make webs; instead they use their silk for their safety rope and also to make a kind of tent where they sleep at night, shed their skins (molt), lay their eggs, and enjoy a long sleep during winter (hibernate). Their silk comes out of their spinnerets (see diagram).