They're loud. They're sexually aroused. And for one special, cacophonous month up to a trillion of them will engulf suburbs and woodlands across America.
Two cicada "broods" are set for a rare double emergence that last occurred in 1803, when Thomas Jefferson was president and the United States purchased Louisiana from France.
The prospect of another natural wonder just weeks after a total solar eclipse across much of the country has gripped scientists and the public alike.
'Insects of history'
Cicadas comprise a diverse family of over 3,000 insect species found globally, with the majority of their lives spent underground in a larval state.
They emerge as adults to transform and mate, with some species appearing annually and others, known as periodical cicadas, synchronizing their emergence every 13 or 17 years. Mathematicians have long been intrigued by the question of why periodical cicadas follow prime number cycles, despite the lack of a clear evolutionary explanation.
This year's event involves the 13-year Brood XIX, currently emerging in the Carolinas, followed by the 17-year Brood XIII in the Midwest. There could be a small area of overlap in central Illinois.
