Spiders

Spiders are perhaps among the most interesting of the smaller hunting animals. They are specially fitted for their task by their power of spinning, Let us think for a while of the common British garden spider and the web it makes.

The spider is a "jointed-footed" animal, only distantly related to insects. The head has simple eyes, a pair of poisonous jaws with which the prey is bitten to death, and a pair of palps or feelers. There are four pairs of walking legs, instead of three pairs as in insects, and each leg ends in tiny claws. On the posterior part of the body there are three pairs of little knobs pierced with fine holes like the "rose" of a watering-can. These are the spinnerets. Hundreds of little tubes lead from these to minute glands from which liquid silk flows out. This liquid passes out through the little tubes to the openings of the spinning organs at the will of the spider, for it requires a muscular contraction to squirt out the fluid. It comes out as a fine spray, but the jets fuse together, and the silk hardens at once into a fine thread. All the spinnerets may be in use at once, or only some of them, so that the thread can be varied in thickness according to the use to which it is to be put.

To make the web the spider first gives out a long thread, makes it fast at one end, and lets it sway in the wind until the other end catches. Having thus made a bridge across the space the web is to occupy, the spider is able to walk along it, and spin the rest of the web at leisure. After the sides of the space are enclosed with lines, the spider lets itself down by a thread to a central point, where it spins a little more silk and then drops to the lowest foundation line, pulling the first ray taut behind it. Climbing up again to the central point, it pays out another ray and pulls it taut to an upper corner. So ray after ray is formed, all meeting in the centre like the spokes of a wheel.

The rays finished and strengthened, a spiral thread is next made from the centre to the circumference. But this is only a temporary rough scaffolding. The spider works back along this to the centre again, laying another and stickier thread, and biting off and rolling up the first as it goes. Then the little ball at the centre is bitten out, and a line is spun from the centre to a hiding-place near, where the spider patiently awaits its victims.

The line acts as a sort of telegraph, for when a fly strikes against the web, the line trembles and the spider immediately lets go, so that the web becomes loose and the fly is hopelessly entangled. Then the spider rushes down on its prey, cuts it out of the web, spins silk threads round it to prevent its escape, and carries it off to the nest. After biting it to death with its poisonous jaws, it slowly sucks the juices from the body of the fly, until nothing is left but a husk. The spider then mends up the web again, and patiently waits for another victim.

There are many other kinds of spiders which make different kinds of webs. Some live in tunnels which they line with silk; others in a mere tube of silk of their own spinning. Specially remarkable are the trap-door spiders which make a nest in the ground, and fit it with a trap-door which swings shut behind the spider, and can be held firmly down from the inside. The trap-door has a silken hinge, and is covered over with particles of earth on the outside, so that it is quite like the ground, and often very difficult to find.

The large spiders, known as tarantulas, whose bite is greatly dreaded even by human beings in the warm countries in which they live, do not spin a snare at all. They live in open burrows and trust to their strength and quickness, and their powerful poison-jaws, to provide them with abundant food.

Another large hairy spider, found in Brazil and some other countries of South America, makes a web so strong that even small birds flying against it are entangled so firmly that they cannot break loose. The spider enmeshes the birds and sucks the juices from their bodies, just as our common spider sucks a fly. This formidable creature has a body more than two inches long, and its legs have as large a spread as a man's hand. It is known as the Mygale or "bird-catching spider."

A traveller quite recently found that in some parts of the world man has turned the spider's fly-catching habits to account for his own comfort. The spider in question is extremely sociable in its habits, and hundreds of them spin their snares close together, so that a tree may be covered with their webs. The inhabitants of the country break off a branch of the tree, and take it into their houses to rid them of flies.

A very interesting point in connection with this story is, that a little beetle is always found living among these spiders. The beetles feed on the hard parts of the insects which the spider has sucked, just as the jackal feeds on the scraps left by the lion. Were it not for these scavengers, the presence of the branch of webs filled with the decaying remains of insects might be unpleasant, but the beetles keep it sweet and clean, and so the dwellers in the house profit by the labour of both spider and beetle.