Locomotion by Tandem and Parallel Wings : A Note on the Flight of Dragonflies and Beetles

A two-dimensional analysis was carried out on the locomotion by tandem and parallel wings in relation to the free flight of dragonflies and beetles, remarking the mutual interference between fore and hind wings. The results obtained are summarized as follows : In the case of tandem wings, (1) High thrust and propulsive efficiency can be achieved when the forewing oscillates with a definite phase lag behind the hindwing, as in the case of real dragonflies, (2) Somewhat smaller amplitude of hindwing leads to optimum condition for work sharing of two wings, (3) The hard forewing does not serve for the thrust and propulsive efficiency, whereas the hard hindwing does for the augmentation of them ; In the case of parallel wings, (4) The hard wing placed near the soft wing acts nearly as an infinite plate, as for the ground effect, increasing both thrust and propulsive efficiency.