Arachnids are arthropods in the class Arachnida of the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, harvestmen, camel spiders, whip spiders and vinegaroons.
"Arachnida" from Ernst Haeckel's Kunstformen der Natur, 1904
Courtship behavior of Thelyphonus sp.
Hubbardia pentapeltis (Schizomida)
Fossil Goniotarbus angulatus (Phalangiotarbida)
Arthropods are invertebrates in the phylum Arthropoda. They possess an exoskeleton with a cuticle made of chitin, often mineralised with calcium carbonate, a body with differentiated (metameric) segments, and paired jointed appendages. In order to keep growing, they must go through stages of moulting, a process by which they shed their exoskeleton to reveal a new one. They are an extremely diverse group, with up to 10 million species.
Protaetia cuprea (copper chafer). Beetles are the most diverse order of arthropods.
Cicada climbing out of its exuviae while attached to tree
Long bristles (setae) of a Tliltocatl albopilosus tarantula
Head of a wasp with three ocelli (center), and compound eyes at the left and right