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 among the fastest moving arthropod predators that cannot fly. 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.