Two cicada broods emerge together for first time in 221 years
Billions of cicadas from two different broods are set to emerge from underground in an ultra-rare synchronised event not seen for 221 years.
Brood XIII emerges every 17 years, and Brood XIX has a 13-year cycle.
Both broods last aligned in 1803, when Thomas Jefferson was the US president.
The next time is set for 2245.
It’s uncommon but not unheard of for two broods to appear at the same time, but these two are so geographically close that they may overlap and interbreed in some of the woods and fields in Illinois –a potentially exciting rarity for entomologists.
Cicadas do not bite but emit sounds between 80 and 100 decibels, the equivalent to a low flying airplane or a lawn mower.
Scientists believe that huge and synchronised arrival provides protection against predators.
There are more than 3,000 species of cicadas worldwide, but only nine are periodical, and seven of those are found in North America.
In India, a periodical species of the genus Chremistica emerges every four years, while in Fiji, a periodical species of the genus Raiataena emerges every eight years.
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