This Dustox is a Bug/Poison-type Pokémon owned by Jessie.
Dustox was caught during Jessie's travels through Hoenn. Jessie caught Dustox on her way through Petalburg Woods as a Wurmple. It later evolved into a Cascoon and then into a Dustox and became Jessie's main contest Pokémon during her Hoenn and Kanto contests. In Crossing Paths, Dustox was released during the Dustox Crossing to mate with a special colored Dustox and has not been seen since.
Jessie's Dustox has something in common with Ash's Butterfree; both Pokémon were released by their trainers in order to have a relationship with another of their kind and also mated with their own species of a different color.
Dustox is the first Pokémon to have its PokéBall shattered on screen by its trainer.
Although Jessie was initially disappointed she didn't have a Beautifly she appreciated her Dustox and has even called her Dustox dear and when she'd summon her for battle she would call her "My dear Dustox".