The Wurmple were caught at the Hoenn Battle Frontier with Taillow's help. Goh caught three, hoping that at least one of them would evolve into Silcoon.[1]
All of the Wurmple evolved into Cascoon while battling Taillow in an attempt to defend itself, much to Goh's dismay.[2]
During a rainstorm Goh's Golurk unitentionally created, all the Cascoon evolved into Dustox in spite of the chaos around them under the protection of all their friends in the area, dispelling the rainstorm with Sunny Day and saving the day.[3]
These Dustox are Goh's first Pokémon to fully evolve while under his ownership.
These 3 Dustox are the second group of multiple Pokémon of the same species to be owned by a main character. The first is Ash's 30 Tauros, caught over 1,000 episodes prior.