“It’s not The Planet of the Apes—it’s The Planet of the Arthropods.”

Who are the most successful beings on Earth? It certainly isn’t Man, Ape or any other mammal. The most successful animals on the planet are the arthropods. They have conquered land, sea and air, and make up over three-fourths of all currently known living and fossil organisms. They are the true masters of the Earth!

Various Arthropods Wikipedia Commons

The Phylum Arthropoda got its name from the Greek, arthros (jointed) and poda (foot) and encompasses over 800,000 species, including arachnids (spiders), crustaceans (sea creatures) and insects.  Also, members of this gigantic phylum are Myriapods; centipedes, millipedes, sea spiders, and maybe a host of other organisms yet unidentified.

What do all of these creepy, crawly and flighty creatures have in common?  They are all invertebrate (without a backbone), have symmetrical, segmented bodies, jointed legs, exterior skeletons, a ventral (front) nervous system, highly developed sensory organs and they are cold blooded.

Arthropods have a leg up on all other organsms. They do everything with legs or modified legs. They swim, crawl, jump, and fly, they use legs to sense with (their antennae), to bite and sting with and to chew with (they even chew sideways).  All this and more, is done with legs.
So, with segmented bodies that accommodate environmental changes, with legs that let them walk; with hard, waterproof shells that keep water in or out; and with highly adaptable respiratory systems, arthropods have dominated the animal world.
Arthropods occur in virtually every earthly habitat, from the cold ocean depths to the hottest deserts. They can live through extremes that would kill most vertebrates.
Fun Facts about Arthropods:

• Arthropods crawled onto land about 100 million years before vertebrates did. It’s thought that colonizing land was easier for them for several reasons – including the fact that they had already evolved legs, which they used for walking on the bottom of the sea.
• About 80% of all animal species are arthropods!
• All arthropods undergo metamorphosis – a process where their bodies change radically as they pass from their larval to adult stages. Butterflies are the best-known for entering cocoons as caterpillars and coming out quite different, but all arthropods do something similar!
• When arthropods outgrow their old exoskeleton, they molt – leaving behind their former skin and growing a new one. All arthropods do this at least once in their lives.
• Crustaceans and arachnids – two types of arthropods – have blue blood instead of red blood! Their blood uses a blue copper compound to carry oxygen, instead of the red iron compound used by most other animals.
• An Arthropods’ hard exoskeleton is made of chitin – which is made of a sugar glucose compound! It’s not sweet but it sure is hard!

If all mankind were to disappear, the world would regenerate back to the rich state of equilibrium that existed ten thousand years ago. If insects were to vanish, the environment would collapse into chaos. (E. O. Wilson, The Diversity of Life)