These insects, the Tisza mayflies look like pixies dancing above the Tisza river. Wondrous scene! They are so rare, as I know, they can be found only at the Tisza river in Europe and their swarm lasts only one day. Actually more days, because the swarm doesn't happen in the very same time along the river, which is almost 1,500 km long with its oxbows. Enjoy the vision!