How many sections are arthropods divided into?

The three main classes of arthropods are: insects (cockroachs, ants, flies, bees, beetles, butterflies), crustaceans (crabs, lobsters, shrimps, barnacles) and arachnids (scorpions, Spiders, mites). Other classes are onychophorans (velvet worms), diplopods (millipedes) and chilopods (centipedes).