Butterflies create jet propulsion with clap of wings Afp, Paris Afp, Paris The whimsical, wafting flight of butterflies may not give the impression of top aerodynamic performance, but research published on Wednesday suggests their large flexible wings could be perfectly designed to give them a burst of jet propulsion. Scientists at Lund University in Sweden set out to verify a decades-old theory that insects "clap" their wings together, squeezing out the air between with such force that it thrusts them forward. In their aerodynamic analysis of free-flying butterflies published in the journal Interface, they showed that the clap function does generate a jet of air propulsion.