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Spiders

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Spiders

Spiders can be found in all environments throughout the entire world, except in the air and sea. (Biology of Spiders, R.Foelix) These invertebrates of the order Aranea are one of the several groups of the Class Arachnida, with about thirty four thousand species.

They range in body size from only a few millimeters in length to almost five inches.

All are carniverous and have four pair of walking legs, one pair of pedipalps, and one pair of chelicerae. (Spiders, W.Shear) Each chelicerae consists of a base and a fang.

The fang folds up inside of a groove in the base until needed when attacking food, then moves out to bite and releases venom from a tiny opening at its end as it penetrates

the prey. (Biology Of Spiders, R.Foelix) They are also used to “chew”, getting digestive juices inside the body of the prey then squeezing out the liquid lunch. The pedipalps are mainly used to catch and rotate the prey while the chelicerae inject it with poison to tear down the tissue.

Later the bases of the pedipalps are used as chewing parts. (The Spider Book,J.Comstock) But in males, these palps are used to transfer sperm into the female. These twleve appendages are attached to a dorsal and a ventral plate, the carapace and sternum which cover the entire prosoma and provide attachment points.

The bodies of spiders consist of two parts, an anterior part called the prosoma and a posterior portion called the opisthsoma. These two portions are held together by a narrow stalk called the pedicel.

This narrow junction allows for the spider to be very limber and acts somewhat as a hinge between the prosoma and opisthosoma. So as a spider moves foward creating a web, it can continue in a straight line throwing its webbing in the direction it chooses.

This is how spiders create their zig-zag web formations. (Biology of Spiders, R.Foelix)

Covering both the prosoma and the opisthosoma is a waxy covering that enables the spider to be a very efficient water conserver. This is one of the characteristics that spiders evolved to adapt to the harsh conditions of terrestrial life. There are eight eyes located in the head region usually in two rows, varying among families. Spiders that

wait for and lunge at its prey will have a row of very large eyes well adapted at detecting the precise distance it is from its prey. Yet those spiders that make webs do ...

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...bush and attack their prey. They too have a large set of eyes on their upper posterior row, above a row of four generally small eyes. Although wolf spiders have well developed eyes, they react mainly to vibrations recieved from beating wings or movement from

insects on the ground. As with the jumping spiders, there are a large pair of fangs that extend down to help assist in seizing prey. The most well known wolf spider is the tarantula. These spiders can reach up to ten inches in their complete lengths. And although lore has it that they are one of the most poisonous spiders, their bites are only painful to humans, not deadly. (Biology of Spiders, R.Foelix)

Though feeding habits vary with spiders their methods of reproduction are all relatively similar, though each species has its own specific ritual. Because spiders are cannabilistic, the much smaller male must be very cautious in approaching a potential mate. If he simply rushes in towards the female, the chances are that he will be seen only as food and consumed. So spider courtship has evolved into a special complex pattern that varies in each species. This variation allows for species recognition, so no gametes are was