Every year from late spring to early summer, an incredible natural spectacle transforms Hungary's Tisza River. Millions of long-tailed mayflies, or Palingenia longicauda, rise in huge clouds from the river, flutter on the surface of the water, mate and perish, all in just a few hours. The unique event which lasts for three to four days, is frequently referred to as “blooming of the Tisza”, and is amongst the most fascinating natural phenomena in European rivers. By Kaushik