Each summer, millions of mayflies rise from the Ebro River, converging on the medieval stone bridge of Tudela, in northeastern Spain.
Attracted by lamplights along the bridge, the insects swarm the area in a fluttering cloud of white wings. (See amazing swarm pictures from National Geographic magazine.)
After spending up to a year underwater as larvae, these fragile insects emerge 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. (Also see “Swarming Locusts Descend on Egypt.”)
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.
The tiny mayfly is a “true wonder of nature,” says Greg Hoover, an entomologist at Pennsylvania State University.
Photographer Juan Antonio Martínez captured ethereal moments of the 2015 swarm, which first appeared in the Spanish edition of National Geographic magazine.
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