Phylum Arthropoda. Phylum Arthropoda includes animals that have been successful in colonizing terrestrial, aquatic, and aerial habitats. It is the largest phylum in the animal kingdom, which includes such familiar forms as lobsters, crabs, spiders, mites, insects, centipedes, and millipedes. The phylum Arthropoda is commonly divided into four subphyla: Chelicerata, Crustacea, Hexapoda, and Myriapoda. Most arthropods are small animals. Only aquatic forms are able to attain substantial sizes, Arthropods are the only invertebrates capable of flight.