List of Arachnids

All spiders are arachnids. All arachnids are not spiders. The class of arachnids contains 11 orders, including acari (mites and ticks), araneae (spiders) and scorpiones (scorpions). Arachnid species number in the hundreds of thousands; with the exception of mites, all live by sucking the life out of their prey. Arachnids possess four pairs of jointed legs. Most arachnids breathe through gill-like tissue on the sides of their bodies. Many species have expandable bodies to allow for large feedings; most grow by shedding their skins.

  1. Smallest Arachnids

    • The smallest arachnids fall into the species found in the order acari. The largest members of this order such as ticks measure less than 10 millimeters long. The smallest members of this order aren't visible to the human eye; entire families of the Honeybee Tracheal Mite can live inside of an insect or on a single human hair. All acari are parasites: they live off of a host and give nothing to the host in return.

    Largest Arachnids

    • The largest arachnids are found in India, where Giant Black Scorpions can grow to a foot in length and weigh several ounces. Mature Emperor Scorpions, found in Africa, reach 6 to 8 inches, head to stinger. Residents of the desert southwest United States may stumble across Desert Hairy Scorpions; at 4 to 6 inches in length, these scorpions are about half the size of Indian scorpions. Among spiders, tarantulas lead the pack, with many being as big as Desert Hairy Scorpions.

    Deadliest Arachnids

    • The bite of the Brown Recluse Spider, regarded by many as deadly, holds little lethal danger; treated quickly and appropriately, the spider's venom causes sickness but not death. Left untreated, however, a Brown Recluse bite can result in significant tissue damage and, rarely, death. Scorpions head the list of deadliest arachnids. More people die from scorpion stings each year than from snake bites, although only around 25 species produce lethal venom. Scorpion stingers retain their venom and ability to puncture skin even after the scorpion dies.

    Newly Discovered Arachnid

    • In the fall of 2010, a team of researchers and Yosemite National Park employees discovered a new arachnid species: the Yosemite Cave Pseudoscorpion. Pseudoscorpions look like scorpions but have neither tails nor stingers. Its amber body and red-tinged legs distinguish the Yosemite Cave Psuedoscorpion from the other nearly 3,000 species of pseudoscorpions.Blind and accustomed to temperatures in the 50s, this arachnid species lives out its days underground, munching on mites and flies.