See Swarms of Bugs Descend Like a Summer Snowstorm

Each summer, millions of mayflies rise from the Ebro River, converging on the medieval stone bridge of Tudela, in northeastern Attracted by lamplights along the bridge, the insects swarm the area in a fluttering cloud of white wings.  

 After spending up to a year underwater as larvae, these fragile insectsemerge from the water to mate, lays eggs on an aquatic surface, and die—all in the span of a few hours.Many of the mayflies that gather above the Ebro River end up laying their eggs on asphalt instead of the water—which mirrors the river’s surface because of the light. So most of the eggs never end up hatching. Those that do survive play a very important role—their presence signals to scientists that a river is healthy, and the flying insects themselves provide sustenance for a variety of fish, birds, and small mammals.