As you have now doubt already heard, once every 17 years, trillions of cicadas emerge from beneath the ground in the US. But here are some remarkable facts that you may not know...
Not all cicadas are equal: Of the 3,400 species of cicadas, just seven are periodical, spending 13 or 17 years underground before emerging en masse to mate and die. That's why they're sex-mad.
The X in Brood X means 10: In 1898, broods were assigned a Roman numeral based on their location and the calendar year when they emerge. Numbers 1-17 denote 17-year cicadas while 18-30 follow a 13-year cycle.
Historically significant: Brood X is the largest brood of the 17-year cicadas, spread over 15 US states from Indiana to New York. Its prevalence in cities means it has been written about for centuries. On 9 May 1715, a minister at Pennsylvania’s oldest church wrote in his journal that “some singular flies came out of the ground”; this was the first historical record of Brood X. Every emergence since has been documented – this is the 19th.
Taste like asaparagus: So say those who have tried.
Circadian rhythm: Cicadas are thought to have an internal clock, calibrated by environmental cues - such as changes to the flow of fluids in the tree roots. But nobody has yet figured out how they know what year it is.
Ecologically good news: Male cicadas die after mating; the female lays 500 eggs in tree branches, then also dies. The ant-like nymphs hatch six to 10 weeks later, drop to the ground and burrow underground as fast as they can to evade predators. They will settle about eight to 12 inches beneath the surface, feeding on a tree root. They stay there for 17 years. Every stage of the cicada life cycle has benefits for regional ecology, from turning over the soil, providing natural pruning for trees, boosting predator populations and returning nutrients to the soil through their rotting bodies.