Although they are sometimes called "cockroaches of the sea", they are not in the class Insecta and are not insects. Lobsters have two body segments, while an insect has three. The lobster also has eight legs, while insects have six. Lobsters like other crustaceans are arthropods and belong to the subphylum Crustacea. Meaning they have a segmented body, jointed legs and an exoskeleton which they molt at intervals.