Large gatherings of butterflies are common alongside the Iguazu River on the Brazil-Argentina border. When the river flow gets lower, the rocky riverbanks become exposed, retaining water in small ponds very rich in salts. This attracts butterflies of several species, mainly of the Pieridae family. Butterflies absorb and concentrate the salts in their bodies, pumping out the excess water.
Photograph by Daniel Pinheiro #nature #photography