• There are more kinds of insects, more individual insects and a larger
  total mass of insects than all other animals combined.

• Arthropods are invertebrates—they don’t have skeletons inside their bodies. Instead, every arthropod has an exoskeleton—a tough covering on the outside which provides support for muscles and organs.

• Arthropods have jointed legs—in fact, that’s what gives them their name. Arthropod comes from the Greek for "jointed foot."

Besides insects, other arthropods include:

• Arachnids, such as spiders and scorpions

• Crustaceans, such as crabs and lobsters

• Myriapods, such as centipedes and millipedes