arachnids number of legs
Spiders are found worldwide on every continent except for Antarctica, and have become established in nearly every habitat with the exceptions of air and sea colonization. As of November 2015, at least 45,700 spider species, and 114 families have been recorded by taxonomists. Although most spiders live for at most two years, tarantulas and other mygalomorph spiders can live up to 25 years in captivity. While the venom of a few species is dangerous to humans, scientists are now researching the use of spider venom in medicine and as non-polluting pesticides. Spiders occur in a large range of sizes. The smallest, Patu digua from Colombia, are less than 0.37 mm (0.015 in) in body length. The largest and heaviest spiders occur among tarantulas, which can have body lengths up to 90 mm (3.5 in) and leg spans up to 250 mm (9.8 in). Scorpions are in the Order Scorpiones, spiders are in the Order Araneae, ticks and mites are in the Order Acari. The creatures most correctly called daddy-longlegs are in their own separate Order which is Opiliones. Common names for this Order are 1) daddy-longlegs, 2) harvestmen and 3) opilionids. They are characterized by having one basic body segment which shows segmentation on the posterior portion, at most 2 eyes and all 8 legs attach to the pill-like body segment. Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other orders of organisms. Arachnids are a Class (Arachnida) of joint-legged Invertebrate Animals in the subphylum Chelicerata. All Arachnids have multiple legs and look like Insects, the only difference is that Insects have six leg and Arachnids have 8 legs. They are largely terrestrial and solitary Animal, gathering only for mating. 1 The Larvae of Mites and Ricinulei have only six legs; the fourth pair appears when they moult into nymphs. However, there are also adult mites with six, or even four legs.  Segmented Body - The chief external feature of Arachnids is the division of the body into two parts called the 'Prosoma' and the 'Opisthosoma'. The 'Prosoma' is composed of a united head and Thorax. The Prosoma anchors the Chelicerae (pincers), Pedipalps (mouth parts) and four pairs of legs. Presence of 8 Legs - Almost all Adult Arachnids have 8 legs. Arachnids also have two further 'Pairs of Appendages' that have become adapted for feeding, defence, and sensory perception. The first pair, the 'Chelicerae', serve in feeding and defence. Because these arachnids are spiders, they have 2 body basic body parts (cephalothorax and abdomen), have 8 eyes most often clumped together in the front of the body, the abdomen shows no evidence of segmentation, have 8 legs all attached to the front most body part (the cephalothorax) and make webs out of silk. 1 However, there are also adult mites with six, or even four legs.  Segmented Body - The chief external feature of Arachnids is the division of the body into two parts called the 'Prosoma' and the 'Opisthosoma'. The 'Prosoma' is composed of a united head and Thorax.
8