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Arachnida is a large and well-known class of 8-legged arthropods related to crustaceans and insects. Unlike insects, the body is separated into only 2 parts. The cephalothorax, also known as the prosoma, contains the mouth area as well as the chelicerae (pincers or claws used for feeding), pedipalpi (feet used to touch or capture) and 8 legs, four on either side. Arachnids lack antannae. The cephalothorax is partially or completely covered with a protective shield. The second segment is known as the abdomen or opisthosoma, and contains the rest of the body. The abdomen may lack appendages entirely, or it may have specialized appendages, such as the spinneret used to make spiderwebs. Most arachnids breath in through tracheae or book lungs.Most arachnid species are considered to be pests or are thought to be dangerous to humans.some spiders can kill humans, but these occurrences are very rare. Scorpions are also poisonous, and ticks can spread deadly illnesses, such as lyme disease. Arachnids are found throughout the world, from ponds to rainforests to desert to attics. They prefer warmer climates.
There are approx 60 000 species, with many more waiting to be discovered (29).
There are approx 60 000 species, with many more waiting to be discovered (29).