Periodical Cicadas (a locust-like insect) spend most of their lives living underground. Either once every 13 years or once every 17 years (depending on the brood), they emerge for a month. Numbering in the millions, their “singing” can be as loud as a jet engine. These prime-numbered life cycles help preserve the Cicada’s existence, since potential predators are unlikely to be at peak prevalence during their emergence. (https://bbc.in/2FFSHK4).