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Information On Spiders

 

Spider Information

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The Spider (arthropod)

Though there are many spiders left to be found in the rain forest, some 30,000 have been recognized. You can find spiders all over the planet. In caves, on mountains, in the deserts, and the marshes.

Spiders are not insects. Insects have 6 legs, while the spider has 8 legs.

Even though the spider is an enormous benefit to mankind, man's attitude towards them remains ambivalent. In warmer countries, where lack of doors and windows may make the entry of spiders into human habitations easy, such visitors are accepted as part of everyday life and are sometimes welcomed, since they hunt and eat such as cockroaches and other less wanted pests.

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Crab Spider: (tibellous olongus) feeding on a moth.

All spiders are carnivorousand feed almost exclusively upon prey which they have caught themselves, although some species take advantage of food which has been taken by other spiders and one family feeds upon other spiders.

The arthropods can be considered the most successful animals on earth in terms of variety and numbers of individuals. Present estimates are that there may be in excess of twenty million different species.

The first fossil Arachnids occur in rocks estimated to be 350 million years old, where they are represented by some early scorpions, but the earliest spiders are recorded from rocks only 300 million years old.

The reproduction system of the spider is relatively simple. The male has a number of testes lying on the floor of the abdomen from which tubes lead to the genital opening in the center of the epigastric furrow. The female has two ovaries from which the oviduct passes to a single uterus and vagina, which opens through the genital pore to the exterior. The female has a least one pair of spermathecae, sacs in which sperms from the male are stored until they are required for fertilization of the eggs at a later date.

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Lynx Spider: Peucetia sp. Most spiders live for only one season, with the males having shorter lives than the females, since once mated they are of no further use and die. Some wolf and jumping spiders which hatch in the spring or early summer of one year may survive until the fall of the next year. The Tegenaria, the common house spider, and the Pholcus, daddy-longlegs, can live longer, maybe because of the buffer from the extremes of climate by the protection of their human habitations.

Although silk production is not unique to the spiders, it is an important ability that plays a major part in their everyday life. Spiders manufacture several different kinds of silk form the silk glands in the abdomen. Seven different glands have been identified, although no single family has been found to have all seven of these glands. Each gland produces a different kind of silk used for different uses. The aciniform glands are used to produce the silk used for wrapping prey. The cylindrical glands are used to make the egg- sac. The cribellar glands are found only in the cribellate spiders and are used to produce the web in which to trap prey.

Silk is a protein produced by the silk glands in the form of a liquid. The silk hardens as it leaves the spinneret. It id believed that this hardening is brought on by the spider pulling on the silk as it is produced, the more it is pulled, the stronger it becomes. To the naked eye, most silk appears to be a single thread, but this is not the case. The strands that are visible consist of numerous strands. The finest strands are about 1/1000000 of an inch in diameter.

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Crab Spider: Thomaisus onustus

As with many arthropods, spiders are able to regenerate lost appendages during their developmental stages, although the closer the spider is to maturity, the less likely it is that the lost appendage will assume its normal size and form. Once a spider is adult, this ability is lost.

The Future of the Spider

Man can obviously play a role in the success of most living organisms, including the spiders. Agricultural expansion, depletion of marshlands, destruction of forests, open woodlands used for the raising of animals for food, land erosion, flora destruction, all of these aid in the demise of the spider. However, spiders and their prey are far better equipped for survival in the long term than man. It is certain that long after man finally disappears from the earth, spiders will still be laying traps for their prey.

 


 


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