Long-tailed mayflies mate on the surface of the Tisza river near Tiszakurt

Long-tailed mayflies (Palingenia longicauda) mate on the surface of the Tisza river near Tiszakurt, Hungary June 14, 2016. Millions of these short-lived mayflies engage in a frantic rush to mate and reproduce before they perish in just a few hours during "Tiszaviragzas" or Tisza blooming season from late spring to early summer every year. REUTERS/Laszlo Balogh

Long-tailed mayflies (Palingenia longicauda) mate on the surface of the Tisza river near Tiszakurt, Hungary June 14, 2016. Millions of these short-lived mayflies engage in a frantic rush to mate and reproduce before they perish in just a few hours during «Tiszaviragzas» or Tisza blooming season from late spring to early summer every year. REUTERS/Laszlo Balogh