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The arachnids include spiders, mites, ticks, scorpions, and a variety of lesser-known groups. Though famous for having eight legs, they have an even greater number of appendages – 12 in all. Arachnids do not have mandibles (the equivalent of jaws for an insect), but rather a modified pair of leg-like appendages called chelicerae. Behind those is another pair of appendages called pedipalps – these four limbs are used to capture prey and break it into small pieces before it is eaten with the arachnid’s sucking mouthparts or pharynx. Eight walking legs propelled these creatures through an evolutionary leap – the arachnids were the first arthropods to move into terrestrial environments.
There are around 102,000 described species of arachnid, but only 33 of them have been evaluated by the IUCN. Of those 33, 19 are listed as threatened – 58 percent. Many charismatic species of tarantula are suffering from uncontrolled collecting for the pet trade. Endangered cave-dwelling arachnids, such as the Kauai Cave wolf spider of Hawaii and the little-known Tooth Cave pseudoscorpion of Texas, are often limited to just one or two caves, making them very vulnerable to disturbance, habitat destruction, or tourism. The blind Kauai Cave wolf spider feeds on the Kauai Cave amphipod, which is also endangered. Only twelve arachnid species are listed as Endangered in the United States – if the IUCN average for endangerment holds for all arachnids generally, there are many more U.S. arachnid species in need of legal protection.