Some species of insects are parthenogenetic . The female organism , under certain circumstances , can produce fertile offspring without mating. A complex developmental process is common in insects. This process is called metamorphosis . They contain a ventral nerve cord and a brain.
Excretory organs vary from green glands to Malpighian tubules.
The digestive system is complex and very efficient. They are protostomes and coelomates . The phylum contain the most known species than all the other phyla combined. Lobsters, crayfish , crabs, and shrimp belong to this arthropod class. These organisms contain two body parts the cephalothorax and abdomen .