The SHELLDER that is latched onto SLOWPOKE's tail is said to feed on the host's left over scraps.
Lives lazily by the sea. If the SHELLDER on its tail comes off, it becomes a SLOWPOKE again.
If the tail-biting SHELLDER is thrown off in a harsh battle, it reverts to being an ordi nary SLOWPOKE.
Naturally dull to begin with, it lost its ability to feel pain due to SHELLDER's seeping poison.
An attached SHELLDER won't let go because of the tasty flavor that oozes out of its tail.
— Pokédex entries (via PokeAPI)