What are Arthropods?

Arthropods have no backbones but they have an exoskeleton which means external skeleton which is hard, a segmented body and jointed attachments called appendages. Arthropods have limbs with joints which allow them to move. Their body cavity contains the nervous system, circulatory system, reproductive system and digestive system. The different types of Arthropod are 

The world's biggest Arthropod, the Japanese Spider Crab

• The Trilobites - this is a group of marine animals that have gone extinct.
• The Chelicerates which includes spiders, mites and scorpions, and other similar creatures. 
• The Myriapods ("many feet") which comprise millipedes and centipedes.
• The biggest group of Arthropods is the Hexapods ("6 legs"), which include insects. 
• Fifthly is the Crustaceans, which mostly live in water. These include lobsters, crabs, crayfish, shrimp and barnacles, and includes all the world's biggest arthropods.

Trilobites

The largest of these extinct marine arthropods is a specimen of Isotelus rex from Manitoba. It is over 70 cm in length.

Crustuceans

The Japanese Spider Crab is a crustacean of the class Malacostraca, is the largest arthropod in the world. However, the American Lobster, Homarus americanus, another crustacean is heavier than the Japanese Spider Crab. The Japanese Spider Crab weighs about 20kg and  American Lobster weighs up to 22kg. The Coconut Crab, Birgus latro, also a crustacean, is the largest land arthropod and the largest land invertebrate. 

Chelicerates

The world's biggest spider, the Giant Bird-Eating Spider

Myriapods

Myriapods include millipedes and centipedes. The biggest centipede is the Amazon Giant Centipede, Scolopendra gigantea. It has a body size of 33 cm (13 inches). The biggest millipede is bigger though - the African Giant Black Millipede can grow to 38.6cm (15.2 in). Imagine one of those crawling through your backyard! 

Hexapods

The heaviest insect at larva stage is the goliath beetle, Goliathus goliatus. It is at least 115g. The largest adult insect is the Little Barrier Island Giant Weta, Deinacrida heteracantha. The heaviest ever recorded was a pregnant female weighing about 71g (2.5 oz). These are both shorter than the stick insect Phobaeticus Chani which lives in the rainforests on the island of Borneo. The biggest insect ever is the dragonfly Meganeura Monyi which died out long ago. It has a wingspan of more than 75cm - almost the size of a crow! Can you imagine yourself catching this gigantic drangonfly with a net? However, the largest living species of dragonfly is still very big - Megaloprepus caeruleata, measuring 19cm across the wings, with a body length of over 12cm. The largest cockroach is the giant burrowing cockroach, Macropanesthia rhinoceros. This cockroach as long as  8.3 cm and a weight of 36 g.  The largest and the heaviest ants are the female ants Dorylus helvolus.  It has a length of 5 cm. The largest bee is the Indonesian resin bee, Megachile pluto. This female bee can be 3.8cm long, with a 6.3cm wingspan. The largest wasp is the spider wasp, Tarantula Hawk.  It is about 6.8 cm long with a wingspan of 11.6cm.

The largest termite is the African species Macrotermes bellicosus.  The larvae of this termite can be as long as 10.6cm. The largest butterfly is Queen Alexandra's birdwing,  Ornithoptera alexandrae. The largest moth is the Atlas moth, Attacus atlas. Both of these species have bodies longer than 8cm, a wingspan of 28cm and weigh of 12g. The  largest praying mantis is the Chinese mantis, Tenodera aridifolia. The female mantis can be as long as 10.6cm. The largest flea is the Hystrichopsylla schefferi, which can reach a length of 1.2cm. You can find this kind of flea in the fur of the Mountain Beaver. What an unlucky beaver he must be!  

The world's largest Arthropods

• The longest ever arthropod was most likely the Sea Scorpion, Jaekelopterus rhenaniae, or if not, then the Sea Scorpion Pterygotus, or possibly even the myriapod Arthropleura. This last one was, in any case, the biggest arthropod ever to live on land.
• The biggest living arthropod is the Japanese Spider Crab, and the heaviest is  the American Lobster - these are both Crustaceans.
• The biggest living land arthropod is also a crustacean - the Coconut Crab.