Other common worms include roundworms and flatworms . Some animals are also called worms , but do not belong to this group . Invertebrate animals commonly called `` worms '' include annelids ( earthworms ) , nematodes ( roundworms ) , flatworms , marine polychaete worms ( bristle worms ) , marine nemertean worms ( `` bootlace worms '' ) , marine Chaetognatha ( arrow worms ) and insect larvae such as caterpillars , grubs , and maggots .