Posted: 20/06/2014 at 15:32
Edd - I think there are a couple of native moths which have adapted to feed from buddleia; the mullein moth and gothic to name two.
Raddoll520 - it's not quite garden butterfly season yet, July and August are the key moths. if you cut your buddleia down in May it should flower in time for their late-summer emergence. But Edd's right, if you would like to see more butterflies, the best thing to do is grow nettles, which their caterpillars eat.