In the core series games
If held by an Beedrill (or is present in the player's Bag)PE, allows it to Mega Evolve into Mega Beedrill if its Trainer has a Key Stone. Each Trainer can only Mega Evolve one Pokémon per battle.
Unaffected by item negating effects (such as Embargo and Klutz). Item manipulating effects (such as Trick and Fling) cannot give Beedrill a Beedrillite or remove a Beedrillite from Beedrill.
Outside of battle
If held by an Beedrill, allows it to Mega Evolve into Mega Beedrill when it performs a Spectacular Talent during a Pokémon Contest Spectacular while its Trainer has a Key Stone. Beedrill will remain a Mega Beedrill until the Talent Round ends.
Pokémon holding Beedrillite in Pokémon Omega Ruby and Alpha Sapphire cannot be traded to Pokémon X and Y.
| One of a variety of mysterious Mega Stones. Have Beedrill hold it, and this stone will enable it to Mega Evolve during battle.
|| One of a variety of mysterious Mega Stones. This stone will enable Beedrill to Mega Evolve during battle.
In the manga
In the Pokémon Adventures manga
In Omega Alpha Adventure 20, Giovanni was revealed to have obtained a Beedrillite. He used it to Mega Evolve his Beedrill as part of his explanation that the meteoroid threatening to destroy the world may be housing a Pokémon inside of it.
In other languages
|| 大針蜂進化石 Dàzhēnfēng Jìnhuà Shí
|| 大針蜂進化石 / 大针蜂进化石 Daaihjāmfūng Jeunfa Sehk
|| 독침붕나이트 Tokchimbungnite