The air over parts of the eastern United States will soon be thick with buzzing cicadas, winged insects that emerge from underground to breed once every 17 years.
An estimated 30 billion (or maybe even more) insects are expected to emerge from the ground in East-Coast sates, from North Carolina up to Connecticut, as soon as the soil temperature hits exactly 17.8 degrees Celsius.
The insects pose no threat to humans, though they may destroy a few young shrubs or trees, reports The Associated Press. “It’s not like these hordes of cicadas suck blood or zombify people,” May Berenbaum, a University of Illinois entomologist told AP.
The last time scientists got to study the cicadas was in 1996. Since then, the insects have been underground, where they feed on roots and go through their various life stages.
The insects, which have red eyes and are about an inch long, will live a couple of weeks above ground — long enough to breed — before they die. Their offspring will burrow underground and will emerge in 17 years, putting their next appearance at 2030.
The mass emergence every 17 years is thought to be an evolutionary method developed to help the insects avoid predators and parasites. Just how the insects tell when 17 years is up remains unknown, though once researcher thinks it could be related to the rate at which trees, and their underground root systems, grow.