January 06, 1999
I.The first sub-topic
1.Detail of the external anatomy
2.Detail of the sensory organs
B.Circulation and locomotion
1.Detail of the circulitary system
2.Detail of the respiratory system
II.The second sub-topic
A.Digestion, Venom, and Spider Silk
1.Detail of the digestive system
2.Details of venom and spider silk
Conclusion: Spiders are a very special unique and complexed Arachnids
January 06, 1999
The word spider came from an Old English verb spinnan.Spinnan means ?to
spin.?People in Eroupe see spiders with distaste, in African and in American cultures
spiders are respected.
Spiders are the most abundant and distinctive of all earthly predators. Most of the
time they are not dangerous to us, spiders eat almost always insects and are found in
places from the Tundras all the way to the low forrests They play abig job in taking care
of the insect population, even the ones that can give us diseases.
Even though insects and spiders belong to the group called, Arthopoda, they look
so different from each other so they are put into different classes. The Insects and the
Arachnids. Scientists think that these two classes split up thousands of years ago.
Spiders come in different sizes, some of them are only 0.1 centimeter long,and
some of the are more than 4 inches long. They have two body parts and eight legs. The
spiders head and thorax are one body part. The thorax is the chest area of a spider. The
abdomen or the stomache is the second body part Each leg has seven sections, and on
the tips of many spiders legs are two tiny claws. Spiders that make a web use these claws
and their notched hairs, to walk on their webs without sticking to them.
Like insects, spiders have a body shell called an exoskeleton. This shell covers the
body and the legs and keeps the spider from drying out. Much like our skin is to us. And
to support the spider like our bones support us. Spiders even have a skelton inside called
the internal skeleton. This is where the muscles attach.
Unlike insects, spiders don’t have antennaes. They do have two things near their
mouths these are called pedipalps. They are used by spiders to handle their food. The
palps of a baby male spider look like boxing gloves. When they grow up the palps are
used for breeding.
Spiders have eight eyes in two groups and some spiders can see images. Others
can’t and they have to rely on feel like those on webs. Web weaving spiders eat, breed,
and lay their eggs from silk threads.
The main part of a spiders senses are two types of hair. The tiny ones have nerves.
When these hairs are bent they send information to the brain and may cause it to run
away or get ready to attack. They also sense touch, vibration and air flow.
The second type of hair are the even tinier one these keep an eye out for pressure
changes in the air.
Curculation and Locomotion
Spiders have an open circulatory system this means that they have no blood
vessels or arteries. Instead, the blood oozes between the spiders flesh, and collects in
little pockets on the underside of the body.
A good circulation is very important to the spiders legs. When spiders don’t get
enough water, their legs fold up and they can’t move them.
Spiders have different kind of respitory systems. Some have a tubular tracheae,
some have book lungs, and others have both. They first spiders to live had one or two
pairpairs of book lungs. The spiders now days have one pair of book lungs and a pair of
Spiders are th only animal to digest their food on the out side of their bodies. The
gut of the spider is behind its stomach, and part of it goes into the front legs. This lets the
spiders to live for days without eating.
Almost all spiders have venom glands. Most spider venoms are not harmful to us,
but the black black widow and the brown recluse spiders will poisen us.
What makes a spider a spider? They can spin a web. All spiders, even baby ones,
have silk glands and spinning organs called spinnerets. The silk glands push the web out
and the spinnerets weave the web.
First reference. The Comptons Interactive Enclopedia CD ROM.
Additional reference.The Discovery Channel On-Line on the internet.