User blog comment:Plexioth- xD/Monster Hunter 3 Ultimate/@comment-71.173.216.45-20121007000206/@comment-5489419-20121007041121

Well, it isn't just online for the Wii U. There's local multiplayer on the 3DS, too, and that will allow you to fight the Ceadeus Subspecies as well!

You just need to manually find other players near you, or fight the Ceadeus Sub solo.