Arachnids differ from insects in that they have 8 legs insteadof 6 (which insects have). Arachnids' mouthparts have 2 appendages calledpedipalps. In scorpions and whip scorpions, pedipalps are claws. The malespider uses pedipalps in mating.
Some arachnids are noted for their architecture. Spiders spin unique webs spunfrom spinnerets located in the spiders' abdomen.
Some arachnids, such as certain spiders and scorpions, have venom they use to disable and kill prey.
The black widow and the brown recluse spiders' venom can be fatal to humans.