Spiders Essay

This essay has a total of 1291 words and 7 pages.

Spiders



Spiders
This report deals with testing the toxicity of certain chemicals on spiders,
and determining the toxicity by how it affects it’s ability to weave it’s web. This
report contains research on the four chemicals (benzedrine, chloral hydrate, caffeine, and
alcohol) as wellas the spiders and their webs.

Spiders are of course found in the class Arachnidia, which also contain mites, scorpions,
and other arthropods. The order which spiders are classified under is called Araneae, a
word of Latin origin. Most spiders are land dwelling, but some can be aquatic. Those that
are aquatic spend most of their lives in or around water. Spiders can live in a vast
amount of different places around the world. Jumping spiders have been collected on Mt.
Everest at a height of 22,000 feet, the highest elevation at which any animal has been
collected (Orkin, Insect Zoo 1).

Adult species vary greatly in size, which is a contributing factor in the prey they
choose, and also the way they catch this prey. Spiders range from less than three
hundredths of an inch to more than 10 inches. All spiders are carnivorous in their eating
habits, insects being first on their menu. Spiders usually catch live animals because the
movement of the prey attracts its attention. Some spiders have poor vision, and rather
depend on the movement of it’s web to locate an insect. (Orkin, Insect Zoo 2). The prey
is usually wrapped in silk before the spider injects the venom to kill it. Yet the larger
the spiders, the larger its prey. Some spiders have been known to kill vertebrate
animals, such as fishing spiders, who thrive on small fish, or bird spiders, feeding on
small birds from South America, as well as a variety of lizards. Some species have even
been known to attack snakes. When food is scarce, mainly during winter months,


spiders have no trouble have no trouble with food, most can go months without eating.
A spider’s structure is irregular when compared to other animals, yet similar to those of
other arachnids. An arachnid is of course classified on the number of it’s legs, which
happens to be eight. Spiders have two main body regions: the cephalothorax and the
abdomen . The cephalothorax consists of the head and the thorax, which are fused
together. Insects have three main body regions, a head, thorax, and abdomen. Other
arachnids have those two regions connected through a broad waist. All spiders also have
simple eyes, lacking compound eyes only found in insects. Spiders can have many pairs of
eyes however, this number often reaches four. Spiders do not have
an antenna either. (Orkin, Insect Zoo 6)

Many spiders secrete a fluid in their posterior abdomens which is later extruded as a
silk. This fibrous protein is used to weave webs, snares, shelters, and/or egg sacs. A
spider uses fingerlike spinnerets to disperse this silk. Most spin more than one kind of
silk to customize its web, or to just fit its purpose. For example, the spider makes some
parts of its web not sticky so that it can run across it and not get caught. Another
source says that spiders first lay down a type of silk known as “dry thread”, with which
they weave a “dry spiral. Once this is completed, the spider lays down a sticky spiral of
thread and goes on to eat the dry one. The sticky spiral must be replaced every couple
days because it loses its “stickiness.”

Some scientists suggest that the pattern of an orb web (most common type of web used by
spiders) is designed to attracted insects. These webs are thought to produce patterns
that resemble those reflected by numerous flowers in UV light. Since insects only see in
UV light, they might as well fly into a trap (Lyons, Spider Silk 1).

Spider silk has been recognized for centuries as a high quality fiber. A few pairs of
stockings and gloves have been made from the silk as early as the 16th century. Various
attempts have been made to produce it commercially, yet have failed. New efforts are
currently under


construction as more people are finding new ways to use a strong, elastic fiber. A few of
these ideas are bulletproof vests, or replacement tissues for tendons and ligaments.
Advanced techniques, such as molecular biology are being used to determine the exact
composition of spider silk, and the changes it undergoes as the liquid proteins inside the
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