A centipede is an arthropod with many legs. Centipedes are predators. They hunt during the night; they are nocturnal. Some centipedes are venomous, though none can kill a human that is not allergic. Centipedes are in the class Chilopoda, and related to millipedes, which are not poisonous. As the millipedes, they are segmented. They have between 5 and 173 segments, but only one pair of legs per segment. There may be 8,000 species in the world.