Page 100 - For Men of Understanding

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 spi-
der 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 neces-
sary 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 suit-
able 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?