Spiders are air breathing arthropods
They also have over 100 different varieties. 
They are the largest order of arachnids
They say that the daddy long legs has one of the most potent venoms, however it is harmless to humans because it's pincers are too brittle to pierce human skin.
cephalothorax. Unlike most arthropods, spiders have no extensor muscles in their limbs and instead extend them by hydraulic pressure.
Their abdomens bear appendages that have been modified into spinnerets that extrude silk from up to six types of glands. Spider webs vary widely in size, shape and the amount of sticky thread used. It now appears that the spiral orb web may be one of the earliest forms, and spiders that produce tangled cobwebs are more abundant and diverse than orb-web spiders. Spider-like arachnids with silk-
Spider
Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs able to inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all orders of organisms. 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. , at least 48,200 spider species, and 120 families have been recorded by taxonomists. However, there has been dissension within the scientific community as