10
Dustox doesn't evolve.
The Pokemon cascoon will evolve into Dustox at level 10 =D
at level 85
It evolves into Dustox.
It evolves into Dustox at lv. 10
It evolves at level 10, into Dustox.
Wurmple evolve into Silcoon/Cascoon at level 7. Then, Silcoon/Cascoon evolve into Beautifly/Dustox at level 10.
Obviously cascoon evolve into a dustox because silcoon evolve into a beautiful!!
Cascoon evolves into Dustox at level 10
The first stage of Dustox is Wurmple. Then, depending on its personality, (I don't know which personality gives you which. O.o), you will get Silcoon or Cascoon. Silcoon will evolve into Beautifly at level 10 and Cascoon will evolve into Dustox at level 10 as well. -Hope this helps!;)
Dustox doesn't evolve into any other Pokemon.
Level it up. At level 7 it'll evolve into silcoon. At level 10, it'll evolve into beautifly. OR, it might be at level 7 and you'll get a cascoon and then at level 10 dustox.