Vortex provides lift: parasitic wasp
The wings of one parasitic wasp generate lift by clapping together at the top of a stroke and then peeling off, creating a vortex that provides lift.
"As an example, some types of small parasites, Encarsia, make use of a method called 'clap and peel.' In this method, the wings are clapped together at the top of the stroke and then peeled off. The front edges of the wings, where a hard vein is located, separate first, allowing airflow into the pressurised area in between. This flow creates a vortex helping the up-lift force of the wings clapping." (Yahya 2002:30)