Magicicada septendecim spends the first 17 years of its life underground as a juvenile, feeding on the juices of plant roots - something we can all relate to. They emerge all at once after 17 years, when the soil temperature at about 20cm is above 17.9 degrees C; upon doing so they find a suitable place to molt, mate, lay their eggs, and die.
The synchronization is to starve out and subsequently overwhelm predators, ensuring large amounts of the species can still reproduce.
Sources:
http://magicicada.org/magicicada/m_septendecim/
https://en.wikipedia.org/wiki/Magicicada_septendecim



















