The periodic cicadas have one of the strangest survival strategies of any creature on our planet.
The larvae of the cicadas live a slow life underground and only dig themselves up every 17 years.
Then they turn into adult insects that fly up into trees to mate and lay eggs.
About a week later, the insects die.
- They come in such large crowds that it is enough as food for everyone who wants to eat them.
Then there are still enough left for the species to reproduce, says Michael Raupp.
Arouses concern
Many Americans are now looking for signs that the great invasion is near.
Some are curious and may be thinking of trying a recipe for cicada cooked with mushrooms or chocolate.
Others rather describe feelings of disgust or fear - although the insects do not pose a major threat to either humans or most plants.
- They do not kidnap small children and dogs like the monkeys in The Wizard of Oz, says Michael Raupp.