You can find one in a room or pokemon locator
Cascoon is a Bug type pokemon.
Horsea and Cascoon are extremely rare, but Horsea can be found on Misty's map, Drake's map, Wallace's map, and the Underwater map. But you can only get it like 1/100 chance, maybe even less. Cascoon, you have to get a Wurmple and hope with all your strength that it will be a Cascoon. Usually it is a Silcoon, but you can still get it hopefully. *Edit* Ermm... Horsea and Cascoon are really common and its not a 1% Chance -New009
A easy way to train Your Cascoon is as follows. First out it at the first spot of your party. Then go to a place with strong Pokemon. Send out your Cascoon then swap it out with your strongest. Defeat the other Pokemon and your Cascoon will get a lot of exp. points.
You can find Cascoon in Pokemon Platinum at Route 205 North, Eterna Forest.
in pokemon diamond a cascoon evolves at lvl 27
Cascoon evolves into Dustox at level 10
To evolve a cascoon, it must gain levels. To gain a level with a cascoon, either attack with it, or if impossible, place it as your active pokemon and switch out at the start of the battle. If you have a EXP share, give the cascoon that and battle with a different pokemon.
Maybe... Cascoon?
Cascoon is #268 in the national pokedex, and it is a Bug type Pokemon.
lv10, Cascoon evolve into Beautifly.
Cascoon can be found in the Petalburg Woods or evolved from Wurmple at Level 10.
In eterna forest.