蜘蛛綱

蜘蛛綱 (Arachnid) 又叫蛛形綱，節肢動物門中嘅其中一綱。大約有 65,000-73,000 個物種，包括咗蜘蛛、蠍子、牛痺、蟎等等。

蜘蛛綱同昆蟲係好易分－蜘蛛綱嘅物種有 8 隻腳，昆蟲淨係得嗰 6 隻。

蜘蛛綱嘅品種大部份食肉，有啲蜘蛛綱嘅物種係有毒，有啲對人畜有害。

分類 
 Trigonotarbida - extinct
 Amblypygi - "blunt rump" tailless whip scorpions with front legs modified into whip-like sensory structures as long as 25 cm or more
 Araneae - spiders (40,000 species)
 Mesothelae - very rare, basal spiders, with abdomen segmented and spinnerets median
 Opisthothelae - spiders with abdomen unsegmented and spinnerets located posteriorly
 Araneomorphae - most common spiders
 Mygalomorphae - tarantulas and tarantula-like spiders
 Phalangiotarbida - extinct
 Opiliones - phalangids, harvestmen or daddy-long-legs (6,300 species)
 Palpigradi - microwhip scorpions
 Pseudoscorpionida - pseudoscorpions
 Ricinulei - ricinuleids, hooded tickspiders
 Schizomida - "split middle" whip scorpions with divided exoskeletons
 Scorpiones - scorpions (2,000 species)
 Solifugae - solpugids, windscorpions, sun spiders or camel spiders (900 species)
 Haptopoda - extinct
 Uropygi - whip scorpions, with first legs modified as whip-like sensory organs and with a long thin tail at end of abdomen (100 species)
 Acarina - mites and ticks (30,000 species)
 Acariformes
 Sarcoptiformes
 Trombidiformes
 Opilioacariformes
 Parasitiformes - holothyrans, ticks and mesostigmatic mites

蜘蛛綱大約有 110,000 品種，可能有好多未有人發現嘅。