Brood X: 17 year cicada swarm in the US could be pushed back by chilly weather

Deafening insects emerge every 17 years and are expected to be seen across swathes of eastern US

An adult cicada. AP Photo

A dirt-covered cicada nymph crawls up from the ground. AP Photo

A dirt covered cicada nymph is seen. AP Photo

A cicada nymph sits on the ground. AP Photo

An adult cicada sheds its nymphal skin on the bark on an oak tree. AP Photo

An adult cicada hangs upside down just after shedding its nymphal skin. AP Photo

An adult cicada rests after shedding its nymphal skin, on the bark of an an oak tree. AP Photo

Residents in Washington, DC, and across much of the eastern US are finding countless holes – each about the size of a penny – appearing in parks and backyards, a clear sign something unusual is afoot.

For the past 17 years, periodical cicada nymphs have been quietly growing underground and feeding on tree sap but now are about to emerge as adults in the billions or even trillions.

The cicadas are expected to emerge in parts of 15 states, from Georgia to Ohio. But the nation's capital is the epicentre of the coming swarm, known as Brood X.

The bugs have a 17-year life cycle, and last appeared in 2004 when George W Bush was president.

According to Cicada Safari, an app created by Mount Saint Joseph University in Cincinnati, Ohio, the insects have already been spotted in several locations across the US.

“We’ve just started seeing adults come out in northern Georgia,” said Gene Kritsky, dean of behavioural and natural sciences at Mount Saint Joseph University.

“We have adults coming out, not massive emergence, just a scattering of here and there in eastern Tennessee. We have a couple of reports now from northern Tennessee."

But an ongoing cold snap in the Washington area may delay the main event.

"This will slow things down for a few days, as long as this unusually cold weather is here," Mr Kritsky told The National.

But insect lovers won't have to wait too much longer.

Entomologists expect this year's swarm to appear by mid-May.

Cicada holes scattered in the soil of a backyard in Washington, DC. Every 17 years, a swarm of periodical cicadas emerges across the eastern US. Willy Lowry / The National

“We’ll start to see an exponential increase in the number of cicadas within the next week or so,” said Floyd Shockley, an entomologist and collections manager at the National Museum of Natural History in Washington.

In many areas of the capital, cicadas will soon be impossible to avoid.

Males emit a mating song that sounds somewhere between a helicopter and TV static. For entomologists, it is a phenomenon only experienced once or twice in their careers.

A close up of a cicada hole in a backyard in Washington, DC. Willy Lowry / The National.

“It’s such an amazing opportunity to study this,” said Mr Shockley.

For those less interested in the creatures, it could be a rough few weeks, with dead bugs piling up on sidewalks and the incessant hum driving many to distraction.