As part of its ongoing efforts to promote every single Pokémon out there, The Pokémon Company has shared special content dedicated to Appletun:
Did you know? Eating a sweet apple caused its evolution. A nectarous scent wafts from its body, luring in the bug Pokémon it preys on. Its body is covered in sweet nectar, and the skin on its back is especially yummy. Children used to have it as a snack.
Source: The Pokémon Company