The phylum Arthropoda is comprised of the classes Crustacea, Arachnida, Chilopoda, Diplopoda and Insecta. Arthropods include creatures that live in water, on land and in the air. The phylum Arthropoda gets its name from two Greek words that mean "jointed leg."
The phylum Arthropoda contains all shellfish, spiders, insects, centipedes and millipedes. These creatures are characterized by their jointed legs, segmented bodies and their exoskeletons, which are made out of chitin.The class Insecta, which is in the phylum Arthropoda, contains all insects is by far the most abundant class of creatures found on earth. In fact, the class Insecta is so large that it contains more creatures than all other classes from all other phyla combined.