The fluttery flight of butterflies has so far been somewhat of a mystery to researchers, given their unusually large and broad wings relative to their body size. Now researchers have studied the aerodynamics of butterflies in a wind tunnel. The results suggest that butterflies use a highly effective clap technique, therefore making use of their unique wings. This helps them rapidly take off when escaping predators.
Source: Butterfly wing clap explains mystery of flight — ScienceDaily