The spider

The body of a spider has two distinct parts. The first part consists of head and breast, called as prosoma or cephalothorax. It is made from a hardened material, called chitin. The second part is the soft abdomen, called opisthosoma. A tiny tube called pedicel connects the cephalothorax and abdomen. The back of a spider is the dorsal side and at the bottom is the ventral side.

The eight legs, the two jaws (chelicera) and the two feelers (palps) are connected to the prosoma. The males have a bulb at the end of their palps. These are filled with semen before copulation and are used to inject the semen into the sexual organs of the female. There are usually eight eyes on the prosoma , but this can vary. For instance, in Europe, spiders with six eyes can be found. Outside of Europe, you may find spiders having no eyes or as many as twelve eyes.

Inside the body there is an extensive nerve system (blue).
The brains are located in the prosoma and the heart at the front upper side of the abdomen (red). The heart beats with a frequency between 30 and 70 beats per minute. When the spider is tensed or exhausted the heartbeat can go up to 200 beats per minute.
The silk making spinners (white) are located at the rear of the abdomen. These are connected to glands that produce different proteins. When these proteins are mixed, it polymerizes to form silk. When pressed through the spinner, the fluid silk produces a thread.
The sexual organ and the egg-producing organ (white) are located between the book lungs (red) and the spinners.

The alimentary canal (yellow) runs through the whole body. At the end of the alimentary canal, is the excretory system. (green).

Cross section of a spider (7)

Ed Nieuwenhuys, January 2006

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