We, the residents of the Northeastern United States are going to be invaded very soon and we will be outnumbered 600 to one by the invaders when it happens. Cicadas are coming top the Northeast in hordes by the billions and will be invading our region. 30 billion of them is the rough estimate of how many will be blanketing the Northeastern States. Why are they coming here? The following quote from an AP story states their mission very clearly:

They're looking for just one thing: sex. And they've been waiting quite a long time.

 

Yep. That's why.