Deafening invasion of Brood XIII to hit Midwest

Naturalists expect the invasion to begin as early as today and certainly by next week. In large swaths of the Midwest, from northern Illinois into parts of Wisconsin, Michigan and Indiana, Brood XIII will emerge from the earth to fill the air with a sound as deafening and grating as a petrol-powered chainsaw.

It is a remarkable rite of nature that happens only in the eastern half of North America. Brood XIII is the horror-film name given to billions of "periodical cicadas" which have been dormant in the ground for a full 17 years, and this week will answer the call to surface and mate, noisily.

The clatter of the much more common annual cicada, or "dog day" cicadas, is as much a part of summer in the US as lemonade and baseball. But periodical cicadas are different because of their extended dormancy. And when they surface they do so in overwhelming numbers.

"Periodical cicadas are dormant longer than any insect in the world," said Richard Grantham, entomologist at Oklahoma State University. "The adults emerge, they never feed, they have a big orgy, and they die." Any day now, the nymphs of Brood XIII will burst from the soil, scale the nearest vertical surface, usually a tree trunk, and shed their skins to sprout the adult cicada's wings. The last such mass emergence of periodical cicadas in the Midwest occurred in 2004. Those cicadas belonged to Brood X.

With as many as 1.5 million of the red-eyed insects crowding a single acre, they are hard to miss, not least because of the accompanying racket from the mating call of the males. Fortunately, they do little serious damage other than rattling the eardrums and stripping smaller shrubs. Moreover, it is usually all over within 30 days when the adults die.

By then the mating is done and the females will have laid their eggs in twigs and leaves. A little later the eggs will hatch and the new nymphs will migrate down back into the soil where they will remain, sucking sap from tree roots, until their time arrives to resurface. Brood XIII will not be back until 2024.

This year's onslaught is coming a week or two earlier than usual - another sign, scientists say, of higher temperatures thanks to carbon emissions. "Global warming right now is basically accepted as a non-controversial fact, and... things will start to change as a result of that," confirmed Dan Summers, an authority on cicadas at the Field Museum of Chicago.

Midwesterners, meanwhile, can do nothing about the intrusion aside from covering their ears. "People want to control everything," says Ron Wolford of the University of Illinois. "I like it when nature says, 'You may be planning your wedding, but you know what? You're going to have to put up with us - we only do this every 17 years.' I tell people to sit back and enjoy and don't get so ruffled about it."

The cicadas are good news, however, for birds and even pets who feast on the sudden bounty which is particularly high in protein. "They're going to have quite a meal. It's going to be like Thanksgiving for them," said Tom Tiddens of the Botanic Garden in Chicago.

According to Mr Grantham, they are pretty nifty snack for humans, too. "You'd probably want to take the wings and legs off of them," he said. "But they'd have lots of protein."

Jenna Jadin, an entomologist from Maryland, has even produced a brochure for preparing them, called Cicada-Licious: Cooking and Enjoying Periodical Cicada. She notes that we already enjoy crayfish, crabs and shrimps of the same arthropod family, "So popping a big juicy beetle, cricket, or cicada into your mouth is only a step away."

Seventeen years of dormancy seems the norm for periodical cicadas, and scientists have speculated that the prime number of years spent in the soil represents an attempt by the insects to make it harder for potential predators to mimic their cycles.