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This question originally appeared on Quora. It was answered by Rahul Kandalam.

The birth and death of Periodical Cicadas is by far the best and rarest natural phenomenon that occurs on our planet earth. Cicadas are spectacular insects often making dramatic and sudden appearances.

A cicada:

In East coast of North America, in the dry forests, this phenomenon occurs  once every 17 years.

The nymphs of Cicadas come out from the ground (often at night) and there will be billions of them (yes,  billions!) marching towards the nearest tree and they start climbing the trees. This is the biggest insect emergence that occur on the planet. They reach the top and shed their skin and come out in their winged forms. This transformation takes one full night and they are ready to fly the next morning. 

They swarm the forest the next day and their sounds fill the air. They fly, some rest on leaves and some on the ground. Some fall in the water.

This is once-in-a-lifetime lucky feast for the carnivores. Be it the turtles in the water, be it the birds, be it the cats or other animals in the wild. The cicadas are so much in number that all the animals fill their stomach overwhelmingly. The cicadas keep coming and the survived cicadas begin the process of mating and lay eggs that ultimately fall on the ground. This is the job of cicadas literally (laying eggs surviving all the odds). 

In just a few days, all the cicadas die and they fall to the ground too. The forest goes silent. The cicadas here will not be heard again for another seventeen years! (The picture below shows the dead cicadas).

Having fed the predators, the cicadas leave one  last gift for the forest when they die. The nutrients that cicadas have taken for seventeen years (while underground) are all given back at once (when they die). This brings an excellent growth for the trees. This is regarded as the single largest dose of fertilizer in the nature.

Such a designer the nature is, in protecting itself and its dependents. OTOH, we are destroying the nature and ultimately the humanity, in the name of development.