Mathematical Insects

My wife is always asking why prime numbers are such a big deal. I've given her a few answers, but now I'm going to tell her to ask the cicadas.

That's right, Chicagoland is now eagerly awaiting the emergence of 17-year cicadas, a beady-eyed bug which shows up in huge swarms - once every 17 years. There's a similar group with 13 year pattern.

Basically it's an arithmetic trick to starve out predators and parasites:

For example, if the cicada has a life cycle of 17 years and its parasite has a life cycle of 5 years, then they will only meet every (17x 5) = 85 years, which is the least common multiple of the two numbers. This enables the periodical cicada to escape from the natural population control, and this also accounts for the astounding population density of the cicada – it can get as high as 1.5 million cicadas per acre!

Cicadas time their slumbers
To coincide with prime numbers.

With combinatorial math
They carve out a cyclical path
Escaping their enemies' wrath.