Difficulty: Challenger (Level 2)

Parts of the United States are about to see a rare event with two types of cicadas emerging at the same time.

The two broods appear together only once every 221 years. More than a trillion of these noisy bugs are set to pop out of the ground later this month.

Young cicadas, called nymphs, mostly emerge at night when the soil is about 17.8 degrees Celsius. They crawl up any hard surfaces they can find and moult to become adult winged cicadas.

Adult cicadas are large insects between 2.5 and 5cm long. They have sturdy bodies, bulging compound eyes and thin, sheet-like wings.

After a few days, adults fly into the tree canopies. Male cicadas sing to attract female cicadas by flicking their wings. The noise is almost as loud as a lawnmower.

After mating, female cicadas lay their eggs into slits they cut in branches. The eggs grow for about six to seven weeks. Once hatched, the nymphs fall out of the trees and burrow underground. These nymphs will spend up to 17 years living underground before they emerge as adults.

Adult cicadas live for just a few weeks and they die after reproducing.