The spider

Introduction

Web and silk

The body

Sex and reproduction

The jaws and poison

Spider enemies

Blood circulation, the lungs and moulting

Literature and acknowledgements

The nerve system, sensory organs and legs

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The body

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

The eight legs, the two jaws (chelicerae) 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.

Some spiders have six eyes but most of them have eight eyes located on the front of the prosoma.

The back or top of a spider is called the dorsal side and at the bottom or belly is called the ventral side.
The genitals of the spider (epigynum) are located just behind the legs on the ventral side.

Detail of the spinners of Argiope bruennichi Detail of the epigyne and book lung slits of Araneus diadematus

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).

The spiders shown are two Australian huntsman spiders the Australian wheel web spider Argiope syrmatica and the European wheel web spider Argiope bruennichi

Ed Nieuwenhuys, December 2011
March 23, 2008, November 2006

Next: The jaws and poison

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