The Order Decapoda have five pair of walking legs, and include the familiar crabs, lobsters, and crayfish. The first pair of appendages are usually modified as antennae . Crustaceans have two pair of antennae. Another set of anterior appendages are modified as mandibles, which function in grasping, biting, and chewing food. Male crayfish also use one pair of legs as a copulatory organ.
All crustaceans share a common type of larva called a nauplius larva.
They are one of the few successful terrestrial crustaceans. They feed on decaying vegetation in the leaf litter. Subphylum Uniramia - centipedes, millipedes, insects Uniramians have a single pair of antennae, and uniramous appendages . They probably evolved from oligochaete worms. Centipedes dwell in damp places under old logs and stones.