Arachnid and that there may be up to 600,000 in total. Arachnid Arachnids () are a class (Arachnida) of joint-legged invertebrate animals (arthropods), in the subphylum Chelicerata. Almost all adult arachnids have eight legs, although the front pair of legs in some species has converted to a sensory function, while in other species, different appendages can grow large enough to take on the appearance of extra pairs of legs. The term is derived from the Greek word ("aráchnē"), from the myth of the hubristic human weaver Arachne who was turned into a spider. Spiders are the largest order in the class,
Threatened arthropods and other animals that prey upon arthropods. This includes enormous numbers of mammals, avafauna, fishes, reptiles and amphibians; in addition, arthropods constitute the bulk of faunal pollinators, so that the survival of crops as well as millions of natural flora species depend on robust and biologically diverse arthropod populations. The survival of diverse arthropods is essential to propagation of higher animals on the food chain, e.g. those species who prey upon the insectivores and other taxa that consume arthropods. Even if constant arthropod total biomass results after certain arthropod extinctions, the ecosystem stability is compromised by reduction in species numbers.