Long-tailed mayflies (Palingenia longicauda) mate on the surface of the Tisza river near Tiszainoka, Hungary, June 18, 2015. Photo: ReutersLong-tailed mayflies (Palingenia longicauda) mate on the surface of the Tisza river near Tiszainoka,Hungary, June 18, 2015. Photo: ReutersLong-tailed mayflies (Palingenia longicauda) mate on the surface of the Tisza river near Tiszainoka, Hungary, June 18, 2015. Photo: ReutersLong-tailed mayflies (Palingenia longicauda) mate on the surface of the Tisza river near Tiszainoka, Hungary, June 18, 2015. Photo: ReutersLong-tailed mayflies (Palingenia longicauda) mate on the surface of the Tisza river near Tiszainoka, Hungary, June 18, 2015. Photo: Reuters
