ARTHROPODS OF THE WORLD
Although all of the more than 1 million insect species are arthropods, many other animals are also members of this large phylum. One other category is the arachnids, including scorpions, spiders, ticks, and mites.

The features all arthropods have in common begin with their segmented body that contains jointed appendages ("arthro" means "jointed" and "pod" refers to "foot").

All arthropods have a hard exoskeleton that provides support and protection over their entire body and appendages. As the animal grows, it outgrows its own exoskeleton, sheds or molts the old one, and grows a new, larger one.

Many arthropods also have hearing organs and antennae that provide the senses of taste and touch. Their nervous system consists of a 'brain' (cerebral ganglia) and a ventral nerve cord with ganglia. Arthropods' compound eyes contain numerous light-sensitive areas that form an image and can detect movement.

In addition, arthropods have a tubular heart with many chambers that pump hemolymph (a fluid that is somewhat analogous to blood) throughout the body's small and large spaces.