Butterflies can look like simple animals with complicated patterns, they softly flit through the air selecting nectar filled flowers for their daily meals, And while these gentile fliers are by no means tough, their wings are more than twice as effective than a bird’s.

That is because birds have thick, rounded wings. The wings of butterflies, and indeed, most insects, have a sharp edge. The sudden cut of of a butterfly’s wing pushes air much like a spoon in coffee. In the case of coffee and creamer, swirls appear around a low pressure center; butterflies use the air in the same way. Their sharp wings swirl the air above their wings making a low pressure vortex. Thus the vortex sucks the butterfly higher and allows the wings to snap back into position with less resistance.

On top of their lift-producing vortexes, once the upstroke has been completed, butterflies have another chance to add more lift. In 1984, Ellington suggested that a quick rotation, like that needed to prepare the wings for the proper angle of attack, could produce more lift. In 1999, The Dickinson group’s Robofly proved this theory true. In the transition from finished-upstroke to beginning-down stroke, butterflies preform a quick change of angle, just enough to add even more lift.

With every beat of its wings, butterflies produce more than enough lift to keep it aloft. This over-lift causes the jerky, tumbling leaf motion associated with butterflies fight. The weird patterns butterflies move in makes catching them, for both birds and humans, more difficult.

Resources

• http://www.zoo.cam.ac.uk/zoostaff/ellington/aerodynamics.html
• http://www.ccmr.cornell.edu/education/ask/index.html?quid=694