THE JUMPING SPIDER

As is widely known, spiders construct a web and wait for insects to become trapped. The jumping spider, contrary to others, prefers to go after its prey itself. It makes a nimble leap to reach its prey. It may capture a fly that passes half a metre away from itself in the air by leaping upon it.

The spider makes this amazing leap by its eight feet that work on hydraulic pressure principles, and all of a sudden it descends on its prey and inserts it powerful jaws in it. This leap usually takes place in a convoluted environment of plants. The spider must calculate the most appropriate angle for a successful leap, and consider the speed and direction of its prey.

More interesting is how it saves its own life after catching its prey. The insect could possibly die, because when jumping to catch its prey, it launches itself into the air and so it could easily crash down to the ground from the heights (the spider is usually at the top of a tree).

The spider, however, does not face such an end. The spider thread, which it had secreted just before jumping and which it sticks on the branch it is on, saves it from falling to the ground and keeps him dangling in the air. This thread is so strong that it can hold both the spider and its prey.

Another interesting feature of this spider is that the poison it injects into its prey liquefies its tissues. The food of the spider is nothing else than the liquefied tissues of its prey.

Certainly, the features of this spider are not gifts (!) of coincidence. It is necessary that it should have gained the skill of both jumping and, at the same time, making a thread that will prevent it from falling. If it could not jump, it would starve and die. If it could not make a thread or if its thread were not strong enough, it would crash to the ground. Then the spider must both have a body structure suitable for jumping and a system to secrete a thread strong enough to lift its prey.

Besides that, the spider is not only a mechanism that produces thread and jumps but a complex living organism and must exist with all its features intact at the same time. The development of none of these features can be deferred. For instance, can you think of a spider with an incomplete digestive system?