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are the pedipalps, which in many species resemble miniature legs. These can be used to assist in the manipulation of food, but in males are modified and important in mating. Beneath the prosoma are attached the four pairs of legs which so readily allow spiders to be recognized by human beings. They are jointed in the samemanner as those of insects, and the various sections have the same hard- ened cuticle as the rest of the spider’s body. Were it not for the fact that, between the joints, the cuticle is soft and flexible, move- ment would be somewhat restricted. As it is, with all six joints in the leg operating at a slightly different angle, a great deal of free- dom of movement is achieved, and the neces- sary muscles are attached to the inside walls. At the tip of the last leg segment, known as the tarsus, are claws, three of which are found in most web-building spiders (other species have only two). The upper surface of the prosoma is pro- tected by a hardened plate known as the carapace. The same degree of strengthen- ing and hardening is not found in the cuti- cle of the abdomen, which is comparatively soft and allows for considerable expansion. The upper surface of the abdomen is often attractively colored, with markings some- times hinting at the segmented ancestry of spiders. Toward the front of the abdomen on the under surface are openings both to the respiratory system and to the reproductive system. Internally, the abdomen harbors the vital organs of the digestive, circulatory, reproductive, and excretory systems; respi- ration is facilitated by book lungs. This is the only way the primitive mygalomorphs breathe, but in more advanced spiders, a tra- cheal system of tubes has developed along the lines of that seen in insects. At the tip of the abdomen are the spinnerets used in the production and deployment of silk. The main problem with having a hard exo- skeleton is that it restricts the ability to grow freely. Like insect larvae and nymphs, young spiders overcome this problem by periodi- cally molting. As with insects, the onset of this process is marked by a cessation in feed- ing. The first stage in molting occurs when the sides of the prosoma split below the car- apace. The process is encouraged by move- ments of the spider’s body and rhythmic

their daily lives. Sensory hairs are usually present over the entire body, as are special structures known as slit organs. Both types of sense organs are linked to the nervous system whose brain is also found in the pro- soma. They help the spider orient itself in its environment and detect prey or potential danger. The mouth is also situated at the front of the spider’s prosoma. The most notable appendages here are the pair of chelicerae which carry the all-important fangs; the fangs oppose one another in most species except in the primitive mygalomorphs, whose fangs thrust downwards. Adjacent to the chelicerae

Attractive but deadly, the Australian black widow spider has entered folk mythology on account of its bite, which can be fatal to humans.

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