The Spiders And Their Spider Relatives

I'm sure that it's fear of spiders that drives my fascination with them. Apparently, my interest is one that has been around for a lot of people since early times, it's even well established in myth and literature. In the old Greek mythology the maiden Arachnewas so proud of her spinning and weaving that she challenged Athena to a contest. The goddess easily vanquished the girl and then, to punish her for her conceit, turned Arachne into a spider and condemned her to spin forever.

Today, Arachne is the Greek word for spider and Arachnida is the name of the order of spiders, scorpions, harvestmen, mites and other less well-known creatures. Strangely enough, many members of this order do not spin.

The other insects, with nearly a million different kinds, might dominate the land if the arachnids were not pitted against them. From time immemorial spiders and their clan have killed and eaten insects of all kinds and sizes. One female black widow spider is reported to have destroyed two hundred and fifty house flies, thirty-three fruit flies, two crickets and one other spider during its lifetime. On the other hand, some insects do destroy spiders.

More than sixty thousand different species of arachnids are known and they live about us in vast numbers. An Englishman once calculated that there were two million, two hundred and sixty-five spiders on a single acre in an undisturbed grassy area. He also deducted that in England and Wales the average number of spiders per acre is more than fifty thousand. Those numbers are far surpassed by the mites, which are probably the most abundant of all land animals.

The arachnids live in almost every conceivable place, from the icy wastes of the Arctic to the steaming jungles of the tropics, from the glaciers of the highest mountains to the arid depths of Death Valley. Although some mites abound in fresh and salt water, for the most part arachnids are land animals. They vary in size from mites so small that dozens can live in a breathing tube of a honeybee to bulk Amazonian tarantulas with hairy legs spanning ten inches.

The arachnids are often confused with insects by uninformed people. However, they are easily distinguishable when you know what to look for. arachnids do not have an antennae, or feelers, that are the badge of all insects. Four pairs of walking legs are present in typical arachnids, whereas in insects there are only three pairs.

The typical insect chews up and swallows its plant or animal food or sucks juices through a wonderfully devised beak or tongue. The arachnid has no true jaws, and no need for them, since it has a most unusual way of feeding. The feeding method of spiders will serve as an example. Their food consists largely of living insects which are trapped in webs or capture in the chase.

The front legs and leg like growths called "pedipalpi" hold the prey, while the spider's sharp fangs are thrust into it. Near the end of the fang is a tiny opening through which venom flows into the wound if it is necessary to quiet the victim. The fangs crush the insect at the same time a strong digestive fluid from the mouth glands is poured over the area.

This liquie breaks down and predigests the body of the insect, so that it can be sucked into the spider's very small mouth opening. Solid material cannot be taken through the mouth, but even large and tough animals can be converted by pre-digestion to liquid form.

The body of the arachnid is divided into two principal parts, the cephalothorax (a united head and thorax) and the abdomen. The cephalothorax bears three kinds of appendages. Frist comes the pair of strong fangs, called the "chelicerae." Behind them is a pair of "pedipalpi," often spined, used for grasping. Then come four pairs of walking legs.

The abdomen is joined broadly to the cephalothorax in some groups. However in the spiders and some others there is a very narrow waist between.

A sting or a lash may be present in the tip of the abdomen. In the spiders the abdomen bears the spinning organs. The openings to the breathing organs, the anal opening, and the reproductive pores are on the under side of the abdomen.

The arachnids' sense of sight is poor except in a few spiders, but their sense of touch is very strongly developed. They do not smell or hear in the way that many other animals do. However, even with limited equipment they have prospered and developed many remarkable habits.