This essay Spiders has a total of 1220 words and 7 pages.
This report deals with testing the toxicity of certain chemicals on
spiders, and determining the toxicity by how it affects itís ability to weave
itís 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
itís 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 spiderís 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 itís 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 spider become the actual silk itself (Lyons,