Nearly all animals known as worms, including earthworms, are invertebrates, and by definition, invertebrates lack bones. Worm-like lizards, such as Caecilians and Anguis lizards, have reptile skeletons despite their appearance as worms.
Other boneless animals usually referred to as “worms” include nematodes, flatworms, priapulid worms, and a variety of marine worms, including bristleworms, bootlace worms, and arrow worms. Caterpillars, grubs, and maggots are also commonly referred to as “worms,” despite being insect larvae rather than worm-bodied creatures. Worms occupy practically every sort of environment and are an integral element of the global food chain.