Spiders, insects, crustaceans
\- Jointed appendages on a segmented body
\- **Exoskeleton:** skeleton on outside
\- **Mandibles:** chewing mouthparts
\- Metamorphosis: egg → larva → adult
3 subphylum: Chelicerata (spiders, scorpions, ticks), crustacea (shrimp, lobster, crab), Uniramia (centipede, millipede, bees)