More than a trillion cicadas are about to invade America after 221 years

Two groups of cicadas, Brood XIII and Brood XIX, appeared at the same time in a double event, causing the number of cicadas across 16 US states to reach trillions.

More than a trillion cicadas could emerge across the midwestern and southeastern United States this spring as two distinct groups emerge together for the first time since 1803 . Brood group XIII and Brood group XIX represent two distinct groups of periodically emerging cicadas ( Magicicada ) with cycles of 17 years and 13 years, respectively. In a rare natural event that occurs every 221 years , these two groups will simultaneously dig through the ground to the surface, starting at the end of April in 16 US states. The double appearance event could lead to the two groups crossing over , Live Science reported on February 6.

Cicadas appear in 13 or 17 year cycles in the US. (Photo: Gene Kritsky/Mount St. Joseph University)

"Under the right circumstances and with the right number of individuals crossing over, it's possible that a new group will start a new cycle," said Floyd Shockley, entomologist and collections manager at the Museum of Natural History. Smithsonian National Nature, said.

Periodic cicadas , which include seven species, spend most of their time underground as pupae and feed on sap that oozes from tree roots. After 13 - 17 years of living without light (depending on the species), the insects will burrow to the ground with their front legs and transform into adult cicadas. Males vibrate the membranes on their sides to create a sound that can be louder than an airplane to attract a mate. After the pair of cicadas have finished mating, the female makes a slit in the branch to lay her eggs inside.

Adult cicadas live for about 3 - 4 weeks and cannot see the eggs hatch until 3 weeks later. Newly hatched pupae burrow into the ground and dig deep burrows to repeat the cycle. The 17-year Brood XIII and the 13-year Brood XIX will briefly overlap along a narrow strip of northern Illinois and eastern Iowa. Brood XIII, also known as the Northern Illinois group , will also emerge in small pockets of Wisconsin and Indiana, while Brood XIX, also known as the Great Southern group , will spread throughout the midwest and southeast. .

The area of ​​overlap is so narrow that cicada populations are probably not much larger in Illinois and Iowa than in other states, according to Gene Kritsky, professor emeritus of biology at Mount St. Joseph in Ohio. More than 1.5 million cicadas can emerge from 0.4 hectares of forest land, but deforestation has stripped away much of the tree canopy these insects need to thrive.

It is likely that cicadas will gather in forests and urban green spaces near where they emerged. This year's double emergence event will end in July. Scientists recommend leaving cicadas alone if possible because they are beneficial to the ecosystem, do not bite or sting, and do not transmit disease.

Cicadas emerge and help loosen the soil as they burrow into the ground. When female cicadas lay eggs, they perform natural pruning, helping the tree produce more flowers and fruit the following year, according to Kritsky. Large numbers of adult cicadas provide food for all types of predators, positively impacting their numbers. After cicadas die, their corpses contribute a large amount of nitrogen and nutrients to the soil.