LYCOS RETRIEVER 
Spiders: Abdomens
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The blood of spiders contains many pale blood cells and is slightly bluish in color. The heart, a long, slender tube in the abdomen, pumps the blood to all parts of the body. The blood returns to the heart through open passsages instead of closed tubes, such as those of the human body. If the spider's skin is broken, the blood quickly drains from its body.
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Five species of widow spiders occur in North America. However, the single species occurring in Washington is the western black widow Latrodoctus hesperus. The adult female is a velvety jet black, but males and immatures are striped with white or yellow. The underside of the abdomen of the adult female usually shows two reddish markings, often joined to resemble the shape of an hourglass. The back of the abdomen is usually entirely black, but may be marked with a broken stripe of white, red, or yellow spots.
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Crab spiders (Thomisidae), often hide in flowers and deliver a carefully placed fatal bite to bees, butterflies, and other would-be pollinators that often 2 times its size. The flower spider, Misumena vatia, will change the color of its large abdomen, over several days, to match the color of the flower. Run your mouse over the photo to see the difference.
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Jumping spiders can be identified by their dark hairy body, two large eyes on the front of the head, white spots on top of the abdomen, and generally iridescent mandibles. They are commonly found on walls and fences. They turn like crabs from side to side and catch prey by pouncing on them instead of using webs.
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All spiders have finger-like appendages at the end of their abdomen called spinnerets, which secrete silk during all stages of life. Silk is a fibrous protein that is light and elastic, but it is stronger than steel fibers of the same thickness. Although not all spiders spin webs, all spiders do use silk for many purposes, including capturing prey, rearing young, moving about, and making shelter (see Natural History, below).
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Abdomens