Thursday, November 28, 2019

Spiders Essays (1290 words) - Spider Anatomy, Spider,

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

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