Periodical cicadas are also known as 17-year cicadas or Magicicada septendecim. These insects are famous for emerging from the soil in massive numbers every 17 years. They are also sometimes referred to as "locusts," although they are not true locusts. Periodical cicadas are often confused with annual cicadas, which emerge every year in smaller numbers. Some other synonyms for periodical cicadas include "brood X," "red-eyed cicadas," and "emergent cicadas." These insects are a fascinating natural phenomenon, and their synchronized emergence is an amazing sight to behold. Their distinctive chirping can also be heard for miles around.