Counting Legs
1Lift a damp log in the woods, and you might find a creature with so many legs that they are hard to count. It might be a centipede, or it might be a millipede. These two animals look a bit alike, but they move, eat, and protect themselves in very different ways. Even their names hold clues about them, if you know a few Greek and Latin word parts.
2Both animals belong to a huge group called arthropods. The word comes from two Greek parts: arthro, which means "joint," and pod, which means "foot." Arthropods have legs that bend at joints, the way your knees do, and a hard covering on the outside of their bodies. Insects, spiders, and crabs are arthropods, too. Insects are sometimes called hexapods, because hexa means "six" and adult insects have six legs. Centipedes and millipedes have far more than six legs, so they are not insects.
3The name centipede comes from Latin. Centi means "hundred," and ped means "foot," so centipede means "hundred feet." The name is not exact, though. Some kinds of centipedes have far fewer than one hundred legs, and some have more. A centipede's long, flat body is made of many sections called segments, with one pair of legs on each segment.
4Millipede means "thousand feet," because milli comes from the Latin word for "thousand." Most millipedes have far fewer legs than that. A millipede's body is usually rounder than a centipede's, and most of its segments have two pairs of legs instead of one.
5Centipedes are fierce hunters, and many of them are very fast. They are carnivores, a word made from the Latin carn, meaning "meat," and vor, meaning "eat." Centipedes catch insects, spiders, and worms. A centipede's first pair of legs is shaped like sharp claws that hold venom, which it uses to catch its prey.
6Millipedes are slow and gentle. Instead of hunting, they munch on dead leaves and rotting wood. By breaking down dead plants, they help turn them into rich soil. A millipede cannot run away quickly, so when it is in danger, it often curls its body into a tight coil. Some millipedes also give off a bad-smelling liquid that makes hungry animals leave them alone.
7Many centipedes and millipedes are nocturnal, from the Latin noct, meaning "night." During the day, they hide in cool, damp places under logs, rocks, and fallen leaves, and they come out after dark. Biologists, scientists who study living things, have found thousands of different kinds. (Bio means "life," and logy means "study of.") So the next time you spot a many-legged creature, take a close look, and remember what its name really means.