17-year cicadas emerge en masse in US

Large numbers of cicadas have emerged in the United States after spending 17 years underground. Their loud cries can now be heard in the capital Washington DC and throughout the East Coast and Midwest.

The species is native to the east, south and mid-west regions of the country. The maturation period is 17 years.

Some scientists estimate this year's group could number in the several trillions.

At the park where the Washington Monument is located, the cries were so loud that people could not hear each other speak.

One resident said the cries were noisy but that she gradually got used to them. Another said she has enjoyed the sounds as she can only hear them once every 17 years.

Scientists do not fully understand the reasons behind the 17-year cycle. Some suggest the cicadas come out en masse to increase their chances of survival. This helps them avoid being eaten by birds or getting parasites.

Adult cicadas live for three to four weeks. Experts project their cries to continue through the middle of next month.