I think all butterflies eat nectar for the energy to fly. So, to keep them in a riparium would require that the plants there all be blooming, with flowers that attract butterflies. Otherwise they just starve. Then, of course, they do fly, so the riparium would have to be screened in to keep their range down to just the riparium. Assuming all of this works out, those butterflies would lay eggs and the eggs would hatch into the larva stage - caterpillars, which would eat the plants.
I don't think this is a winner.