Crustacea and myropedia are two other classes of arthropod that are not arachnids. Arachnids are arthropods that live on land, have two tagmata, eight legs, two pedipalps and no antennae. Insects have three tagmata, six legs, no pedipalps and two antennae. Good luck with the other classes of arthropod. read more
As nouns the difference between arthropod and arachnid is that arthropod is an invertebrate animal of the phylum arthropoda , characterized by a chitinous exoskeleton and multiple jointed appendages while arachnid is any of the eight-legged creatures, including spiders and scorpions, of the class arachnida . read more