Abstract
The flapping of a dragonfly, Pantara flavescense, horizontally flying in a field was observed with a high speed video camera. As a result, it was clarified that a frequency of the flapping with maximum amplitude in the observation was the same order as one of the flapping in a wind tunnel. Also, it was observed that vortices regularly occurred every one cycle by flapping with large amplitude in the wind tunnel and diverged downstream with combining each other. The flow upstream of the dragonfly flapping was induced in three forms of curved flow lines into the region around the body. Furthermore, wakes were generated in horizontal, downward and upward directions according to these forms.
