비rood X is upon us. Across the US billions, if not trillions of cicadas have emerged from below the ground, a biblical plague that occurs every 17 연령. Gene Kritsky wouldn’t miss it. “This is special,”그는 말한다. An entomologist at Mount St Joseph University in Cincinnati, Kritsky has studied periodical cicadas for nearly 40 연령. Brood X, the subject of three of his books, holds a particular place in his heart. In the middle of back-to-back interviews during his busiest professional period since 2004 (“It happens, every 17 years”), he found time to share his favourite facts with us.
의 3,400 species of cicadas, just seven are periodical, spending 13 또는 17 years underground before emerging en masse to mate and die. The long life cycles are thought to have evolved in the past 300,000 years as an adaptation to the ice age, with the cicadas living just south of the retreating ice sheets able to surface sooner. 이후 2000, two more periodical species have been discovered in Fiji and India, with eight- and four-year life cycles.
Kritsky says that some people take “cicadations” (vacations) to avoid the swarm. 에 20 연령, he has helped 83 couples pick a date for their weddings. “Though I think a wedding with cicadas is much more romantic,”그는 말한다. “Their mating call is a song of love!”
Only the male cicadas sing, gathered in large numbers in trees. They produce their calls using organs on either side of the body called tymbals, amplifying the sound by their hollow abdomen. “They are screaming at about 96 decibels. That’s louder than the jets flying into Heathrow,” says Kritsky. 과연, prolonged exposure could cause permanent hearing damage. If you can’t reschedule your wedding, you are advised to bring in big speakers – or bagpipes.
Like aphids, bed bugs and all “true bugs” in the insect order Hemiptera, cicadas cannot eat solids (or bite people). “They don’t have chewing mouth-parts,” says Kritsky. 대신, they live off a totally liquid diet of xylem fluid from tree tissue and roots, and release excess fluid through pee. The unexpected squirt from overhead is called “cicada rain” or “honeydew”. It’s not harmful, but some people wear a wide-brimmed hat to avoid it.
Cicadas are thought to have an internal clock, calibrated by environmental cues – such as changes to the flow of fluids in the tree roots. “That’s how they mark the passage of time,” says Kritsky. “What we don’t know is how they remember what year it is.” In Cincinnati in 2007, unseasonably warm temperatures followed by a freeze triggered hundreds of cicadas to emerge a year early.
In the years when a brood is due, the cicadas start to emerge when the soil temperature reaches 18C (65에프) in spring. That is being affected by warming temperatures, says Kritsky. Before 1950 in Cincinnati, Brood X would arrive on about 28 또는 29 할 수있다; now, 평균적으로, it arrives on about 17 할 수있다. The emergence is believed to have started across the US last week.
에 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.
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. 의 위에 9 할 수있다 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. “They are bugs of history,” says Kritsky.
Kritsky puts the “volume” of Brood X at about 1.3 million bugs an acre. 에 2004, the maximum density recorded was 356 a sq metre. The numbers are thought to be a survival strategy to overwhelm predators so that – no matter how many cicadas get eaten – there are still millions left to reproduce.
Few animals aggregate at such a scale, except locusts, bees and some fish. “What’s different is these guys are big,” says Kritsky. The largest are about 2in long, with orange-veined wings and bright red eyes. “These guys are in your face … they’re clumsy.”
에 1970, Dylan was awarded an honorary doctorate from Princeton University, 뉴저지, in the thick of Brood X. He wrote Day of the Locusts about hearing their “high whining trill” from the stage: “The locusts sang, and they were singing for me.”
Female cicadas cannot sing, but indicate interest to males by flicking their wings to make a small sound. 에 2004, David Attenborough mimicked it by snapping his fingers – much to the frustration of a male. Others have described cicadas being attracted to power tools and lawnmowers.
So say those who have tried, Kritsky included. “Because they are sucking on fluid from a root, they’re going to have a very green flavour,”그는 말한다. He first ate them out of curiosity, but stopped after his first Brood X encounter in 1987. “I really like these insects. They got me tenure.”
“I’m just going to tell you this straight,” says Kritsky grimly. The dormant Massospora cicadina fungus resurfaces alongside periodical cicadas, infecting only males. It causes the bug’s abdomen and genitalia to fall off, leaving a mass of fungal matter. It also makes him “extremely sex-driven”, says Kritsky – not to mate (he has been castrated), but to spread the fungus. As well as singing, the infected male will start clicking its wings like a female, to attract more partners. Fewer than 5% of cicadas are reportedly infected, but it is not uncommon for people to eat them for amphetamine in the fungus (a very bad idea, according to scientists).
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. “And that’s where they will be for the next 17 연령,” says Kritsky.
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.
Despite its billions, Brood X is in decline. Destruction and fragmentation of their forest homes since the 1890s means the number of cicadas emerging may one day be no match for their predators. Brood XI has been considered extinct since 1954, and Brood X could go the same way, says Kritsky. More than half the counties in north-west Ohio that recorded Brood X a century ago are silent this year.
Kritsky is hoping to map them this year through a new app, Cicada Safari, which collects reports from the public. In one month it has received 250,000 images of cicadas. With a team of 20 colleagues, Kritsky intends to look through every single one.
This is Kritsky’s third encounter with Brood X. Next time they are reunited, he will be 84. “I’m seeing the grandchildren of what I saw in 1987; I’m going to the same trees as I did 34 years ago.”
The periodic reappearance of cicadas presents an opportunity to reflect on the passage of time. To Kritsky, there’s something comforting about that. “We don’t know when the pandemic will end,”그는 말한다, “but the cicadas came out in May.”