There is always a useless bug Pokemon in each generation, that can evolve however much it wants and it will still be pretty stupid. xD (However, it evolves into something cool in Gen V)
In Gen I, it was Weedle/Caterpie.
In Gen II, it was Ledyba/Spinarak
In Gen III, it was Wurmple
In Gen VI, it was Kricketot
In Gen V, it was Sewaddle/Venipede
In Gen VI, as you said, it was Scatterbug
Like what Sempi-dear said, they recycle old ones generation from generation. Take for example the bird Pokemon of each generation, Pidgey, Hoothoot, Taillow, Starly, Pidove and Fletchling. They tend to do this as a start to making new Pokemon for each generation.
Hope I helped. :)
Source: Experience
