A worm is an elongate, soft-bodied, land-dwelling invertebrate. Worm is a common name for various species that belong to different clades of animals--that is they are unrelated to each other. Animals which are commonly called worms include species of annelids, insects (their immature larva stage), and flatworms. Many marine and freshwater species, which are usually seen only by professional biologists, are recognized as "worms". Worms commonly are seen on the sidewalk after a rainstorm, and often die of drying out or being trampled on by humans.