10 or 11
Silcoon and Cascoon.
Beautifly itself does not evolve, but if you have a Wurmple, it will evolve into either a Cascoon or a Silcoon at level 7 (something--nature, I think, determines which one it will evolve into). Silcoon will evolve into Beautifly at level 10 while Cascoon evolves into Dustox at the same level.
Wurmple evolve into Silcoon/Cascoon at level 7. Then, Silcoon/Cascoon evolve into Beautifly/Dustox at level 10.
Wurmple evolves at level 7. Then depending on its personality it will either become silcoon or cascoon.
Find a Wurmple, and evolve it into Silcoon. At level 10, it should be a Beautifly
Silcoon evolves at Level 10.
A Wurmple will evolve into either a Silcoon or a Cascoon at level 7. Then at level 10, it will evolve into a Beautifly (Silcoon) or Dustox (Cascoon).A wurmple will evolve in either silcoon or cascoon depending on its personality value.
Silcoon will evolve at a low level because bug Pokemon evolve quickly.
Silcoon evolves at level 10, as does Cascoon.
Silcoon evolves into a Beautifly at level 10.
Silcoon evolves by training it. When Silcoon reaches level 10, it can evolve into Beautifly.