Where Can I Find A Vespiquen In Pokemon Platinum?

There are two ways here. One is to slather honey on a tree and hope you get a GIRL combee and evolve it at level 21. (maybe). Two is to go to the pokemon league and the first elite four person, Aaron will have Vespiquen. The second option is for your pokedex.

Hope this helped!!

You can't find it you just need to evolve combee but only female

You have to slather a tree with honey if you find a combee it has to be a girl so it can evolve into vespiquen