Go wanted to catch as many Pokémon as he could and one day while in a forest in the Kanto region, he caught every Bug type Pokémon native to Kanto.
Ash's Pikachu managed to put a swarm of Beedrill in its Electroweb but this Beedrill managed to avoid it and ended up being the one that Go captured.
Beedrill resides at a habitat at the Sakuragi Institute in Vermilion City. It is not the evolved form of
Goh's Weedle or
Goh's Kakuna as they are separate Pokémon.