The second method of flight, clap and fling, or the Weis-Fogh mechanism, functions differently. In this process, found in very small insects such as thrips and chalcid wasps, the wings clap together above the insect's body and then fling apart. As they fling open, the air gets sucked in and creates a vortex over each wing. This bound vortex then moves across the wing and, in the clap, acts as the starting vortex for the other wing. By this effect, circulation and thus lift are increased to the extent of being higher, in most cases, than the typical leading edge vortex effect. One of the reasons this method is not employed by more insects is the inevitable damage and wear to the wings caused by repeated clapping. It is prevalent, however, among insects that are very small and experience low Reynolds numbers. The mechanism is also employed by the marine mollusc "Limacina helicina", a sea butterfly. Some insects, such as the vegetable leaf miner "Liriomyza sativae" (a dipteran fly), exploit a partial clap and fling, using the mechanism only on the outer part of the wing to increase lift by some 7% when hovering.