2012年9月19日 星期三

Spiders - What Kind of Animals Are They?


Spider exists everywhere from the tropics to Antarctica. They are not insects. Unlike insects they are made of two different parts that are connected to each other with a small stalk. The two parts are the head part and the abdomen part. On the head part there is eight eyes and four appendages. On the first two appendages are there is a fang that is linked to the poison gland. The spiders use these two fangs to immobilize its prey or to protect itself.

Below there is two other appendages that is used as a mouth. Below there are eight legs. There are four on each side of the spider. The abdomen parts of the spider's body are mostly for storing food. But this part also makes the spider silk and the lungs are located here.

The silk is produced in a special gland in the abdomen part. The silk can be extremely strong. Most spiders use silk to catch their prey. Most spider use the silk in a web the trap insects. But there are other methods as well. The webs adhesive properties only work for about two days. Then the spider eats up the silk and builds a new web. The size for spiders can differ a lot. Most spiders are small. But the body of some spiders can be up to 9 cm. And then they have legs as well. So they could be very large.

After the spider has immobilized the prey with its venom they then crush their prey with their teeth. They then spit up an enzyme from there stomach that will break up the tissue of their pray and the tissue will become a liquid food for the spider. The spider will then filter the food through its hair in the mouth and suck the food into the stomach. This is done by making an under pressure in the stomach by using the muscles around the stomach.

In a satisfied spider a very large part of the abdominal part of the body are made up of liquid food that is stored in the spider. The spider is because of this able to survive very long time without any food.

There are over 34,000 different known species in the world. Some large spiders can give a painful bite, but they are usually not so harmful. Other spiders do have a dangerous venom but their teeth are too weak to penetrate the human skin. But of the 34,000 species of spiders there are only about 200 that could be hazardous to humans. These both have a poison that are hazardous and have a bite that can penetrate the human skin. The most known of these are the black widow spider, the brown recluse spider and the funnel web spider.

The black widow spider is the most venomous spider in North America but as it only injects a very small amount of venom it is not very often people die. Brown recluse spider could give very bad wounds. They are more serious for kids. The funnel web spider is very dangerous but so far only 13 deaths are known.




Robert L J Bloom is the author and can provide additional information about pictures of spider bites from many types of spiders. He also provides more information about black widow spiders.





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