If male, Burmy can evolve into Mothim once it reaches level 20. If female, Burmy can evolve into Wormadam once it reaches level 20.
Its cloak is based on what location it most recently battled in. If it battled in a grassy area, it will have the grass cloak. If it battled at a beach or in a cave, it will have the sandy cloak. If it fought in a building, it will have the trash cloak. Once a (female) Burmy evolves into Wormadam, its cloak becomes part of its skin, and decides the Wormadam's second type.