Arthropods are invertebrate animals having an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chitin, often mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages. Arthropods are bilaterally symmetrical and their body possesses an external skeleton. 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. Some species have wings. They are an extremely diverse group, with up to 10 million species.
Arthropods are invertebrate animals with a chitinous exoskeleton, segmented bodies, and jointed legs. The phylum Arthropoda contains numerous taxonomic orders in over 20 classes.
Subphylum Hexapoda
Class Insecta (Insects)
Subclass Monocondylia or monochlamydia
Order †Monura
Order Archaeognatha – 350 (Jumping bristletails)
Subclass Dicondylia
Order †Carbotriplurida
Infraclass Thysanura
Order Zygentoma – 370
Infraclass Pterygota
Order †Reculida
Order †Perielytrodea
Order †Eoblattida
Clade Panephemeroptera
Order †Protephemeroptera
Order †Syntonopterodea
Order †Permoplectoptera
Order †Coxoplectoptera
Order Ephemeroptera – 3,000 (Mayflies) Clade Odonataptera Order †Eugeroptera Order †Kukaloptera Order †Argentinoptera Order †Geroptera Order †Eomeganisoptera Order †Meganisoptera Order †Campylopterodea Order †Protanisoptera Order †Triadophlebioptera Order †Protozygoptera Order Odonata – 5,900 (Dragonflies and damselflies) Clade Palaeodictyopteroidea Order †Palaeodictyoptera Order †Archodonata Order †Diaphanopterodea Order †Megasecoptera Clade Polyneoptera Order †Paoliida Order †Protorthoptera (Paraphyletic assemblage of basal and stem polyneopterans) Order †Sheimiodea Order Zoraptera – 28 (Angel insects) Order †Archelytroidea Order †Protelytroptera Order Dermaptera – 1,816 (Earwigs) Order Plecoptera – 2,274 (Stoneflies) Order †Caloblattinidea Order †Alienoptera Order Mantodea – 2,200 (Mantises) Order Blattodea – 3,684–4,000 (Cockroaches and termites) Order Grylloblattodea – 34 (ice-crawlers) Order Mantophasmatodea – 15 (gladiators) Order Phasmatodea – 2,500–3,300 (Stick insects or stick-bugs) Order Embioptera – 200–300 (Webspinners) Order †Chresmododea Order †Cnemidolestida Order †Titanoptera Order †Caloneurodea Order Orthoptera – 24,380 (Grasshoppers, locusts, crickets, etc.) Clade Clareocercaria Order †Hypoperlida Order †Miomoptera Order Psocodea – 11,000 (Lice, bark lice, book lice) Order †Permopsocida Order Hemiptera – 50,000–80,000 (True bugs) Order †Lophioneurida Order Thysanoptera – 5,000 (Thrips) Clade Holometabola Order Hymenoptera – 115,000 (Sawflies, wasps, bees, and ants) Order Strepsiptera – 596 (Twisted-wing parasites) Order Coleoptera – 360,000–400,000 (Beetles) Order †Glosselytrodea Order Raphidioptera – 210 (Snakeflies) Order Megaloptera – 250–300 (Alderflies, dobsonflies, and fishflies) Order Neuroptera – 5,000 (Net-winged insects) Order †Protomecoptera Order †Tarachoptera Order †Permotrichoptera Order Lepidoptera – 174,250 (Butterflies and moths) Order Trichoptera – 12,627 (Caddisfly) Order †Paratrichoptera Order †Protodiptera (Permotipula and Permila) Order Diptera – 152,956 (Flies) Order †Paramecoptera Order Nannomecoptera Order Mecoptera – 481 (Scorpionflies) Order Neomecoptera Order Siphonaptera – 2,525 (Fleas)
Class Entognatha
Order Collembola (Springtails) Order Diplura (Diplurans) Order Protura (Coneheads)
Subphylum Chelicerata
Class Xiphosura
Order Xiphosurida
Class †Eurypterida
Order †Eurypterida
Order †Chasmataspidida
Class Arachnida (Arachnids)
Subclass Acari (Mites) Order Opilioacariformes Order Ixodida (Ticks) Order Holothyrida Order Mesostigmata Order Trombidiformes Order Oribatida (Beetle mites) Order Endeostigmata Subclass Megoperculata Order Amblypygi (Whip spiders) Order Araneae (Spiders) Order †Haptopoda Order Palpigradi (Microwhip scorpions) Order †Uraraneida Order Ricinulei (Hooded tickspiders) Order Schizomida (Short-tailed whip scorpions) Order Uropygi (Thelyphonida s.s., whip scorpions) Order †Trigonotarbida Subclass Dromopoda Order Opiliones (Harvestmen, also known as daddy longlegs) Order †Phalangiotarbida Order Pseudoscorpionida (Pseudoscorpions, or false scorpions) Order Scorpiones (True scorpions) Order Solifugae (Sun spiders or wind scorpions)
Class Pycnogonida
Order Pantopoda (Sea spiders)
Subphylum Myriapoda (Centipedes and millipedes)
