Basic Spider Information
Spiders are found almost everywhere in the world - from the poles to the hottest deserts. To many people a spider is just a spider, but there are many different types of spider and some don't even look like spiders. Some spiders build webs, others dont. Some spiders are big others are tiny. Some spiders have deadly venom, most spiders have venom that is harmless to humans and some have no venom at all.
Spiders are not insects, they differ in severeal respects:
- They have eight legs instead of six.
- They have two body segments instead of three.
- The have eight simple eyes instead of two compound eyes.
- They have no antennae.
- They never have wings.
- They are never herbivores.
Spiders are in fact Arachnids.
Spiders are almost as variable in colour, shape and behavior as their insect counterparts.
Above is a picture I drew of a female Araneus diadematus. It is labeled to show the names of parts of the spiders anatomy.
Cephalothorax - also known as the prosoma, this is the spiders head. All of the spider's limbs are connected to this part. It contains the central nervous system, venom glands and part of the spider's digestive system. On the outside of the cephalothorax are eight simple eyes and jaws called chelicerae.
Abdomen - this is the spider's body. It contains most of the spider's digestive system, the spider's heart, breathing organs called book lungs, silk glands and the ovaries in females. In the abdomen are a number of different silk glands that produce different kinds of silk - some sticky, some not, some rigid, some stretchy. The silk is secreted from organs called spinnerets which are located at the tip of the abdomen. When a female spider is full of eggs, her abdomen will become quite large.
Palp - the palps are like small legs that are attatched to the spiders face. The perform a similar role to insects antennae. They also have another important function - mating. In male spiders the palps have a swollen bulb like attatchment which is used to place sperm in the female's genital opening. It is easy to tell a male spider because it will have these swollen palps. Arachnologist use the intricate sttructure of the male's palps to tell what species they belong to as their structure depends of the species.
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