GS102, i need 250 -500 words that deal with Earthâ€™s largest phylum is Arthropoda, including centipedes, millipedes, crustaceans, and insects. The insects have shown to be a particularly successful class within the phylum. What biological characteristics have contributed to the success of insects? In many science fiction scenarios, post-apocalyptic Earth is mainly populated with giant insects. Why donâ€™t we see giant insects today?