Billions of cicadas from two broods are expected to emerge in 17 U.S. states in April in an event not seen since 1803.
Brood XIX and XIII cicadas emerge every 13 and 17 years respectively from underground, where they develop.
“The co-emergence of any two broods of different cycles is rare, because the cycles are both prime numbers,” UConn cicada expert John Cooley said.
“Any given 13 and 17-year broods will only co-emerge once every 13 x 17 = 221 years.”
Their simultaneous emergence occurs once every 221 years.
The 1-2 inch bugs will engage in mating before females lay eggs in tree branches and all eventually die.
While their loud noises can be bothersome, cicadas are harmless to humans, pets and most plants.
They provide food for other animals and aerate soil.
Their emergence overlaps in a small area of Illinois and Indiana.
“This summer, some will get a chance to witness a phenomenon rarer — and probably louder — than Halley’s comet,” Cooley said.
“You cannot possibly be unaware that periodical cicadas are out, because they’re out by the millions and millions, and they’re noisy, charismatic, active insects that are just everywhere,” Cooley said.
Young trees may be covered to prevent egg-laying from harming them.
