Why do they only come back every 17 years?

2024... a year when SpaceX is planning on taking its first commercial trip to mars, also, the next year when we will have the next biggest visit from Cicadas here in Tennessee. These bugs can be such a nuisance, especially when they are so loud you can barely hear yourself think when you're outside! When these bugs come out every 17 years they shed their skin, fly, reproduce, and then die. So, what happens when they disappear again for so long?

Well, these cicadas that come out every 17 years are all adults, and the reason they come out is only to shed their juvenile skin, and then reproduce. After they have completed their reproduction they die. About a week after they appear and the process of reproducing has been finished, the females will lay between 400 and 600 eggs inside tree twigs! Once they have laid their eggs, within the next few days the female will die, as she has completed her purpose. Within the next couple of weeks the eggs will begin to hatch, and the infantile cicadas will drop out of the tree limbs and fall onto the ground. The cicadas that don't get eaten by birds once they drop to the ground will bury into the dirt and begin their young lives under ground. Unlike many bugs that have a very short life span, cicadas actually live for 17 years! However, they spend every single day of their lives (except the few minutes they are above ground after their birth, and the week of life for reproduction before their death) under ground  where they feed on the fluids from roots of shrubs and trees. Cicadas live their whole entire lives under ground except for one week, where they come out of the ground, reproduce, and make that deafening noise we all hate. Although you may hate when they come every 17 years, lets at least all be thankful that they live most of their lives under ground, out of sight, and out of earshot!

Source: “The Periodical Cicada’s Timing.” JW.org, www.jw.org/en/publications/magazines/awake-no4-2016-august/periodical-cicadas/