This Butterfly Boudoir or Roost is made to the butterfly trust specifications, so that you can put sugar water or honey water onto the sponge (or see butterflies food for a specially formulated food we sell) which attract the butterflies. The slot represents a crack in bark that the butterflies would naturally roost or hibernate in, once they crawl in there are branches fastened in there that has rough bark, and they can climb on to them and roost over night some species will hibernate. Cost £20.00 + £5.96 postage added at checkout.