After 17 years underground, billions of periodical cicadas – a species of flying cicadas – prepare to surface in the United States, with the goal of mating after completing their maturation cycle. As a love claim, they emit a deafening noise, comparable in decibels to that produced by a powerful motorcycle. The phenomenon, which is scheduled to begin at the end of the week, will be especially noticeable on the east coast of the United States, from Tennessee to New York.
The insects are part of a group called in English Brood X (Generation X) —also known as “the great generation of the East” – although only the males stridulate or screech in search of a female. This sound is the mating song, for which they flex a drum-like organ called a timpani. After 17 years feeding and growing underground, the chorus of billions of cicadas chirping in unison will put a peculiar soundtrack to parks and gardens in the coming days.
“An invasion is coming. This spring, billions of cicadas will emerge from the ground”, warns the Twitter account of the National Mall, or National Esplanade, the vast expanse of Washington gardens where some of the most iconic monuments are located, which will be taken at assault by the noisy insects.
The US Environmental Protection Agency (EPA) has launched a campaign on social networks so that the population does not spray insecticides since they can affect other living beings. “Cicadas are harmless. They are a nutritious food source for other animals. Ignore them. They will not be here forever,” says the government agency. Periodical cicadas, which do not bite or attack humans, typically live for just over a month on the surface.
Periodical cicadas are intriguing because of their long maturation and the accuracy with which they surface every 17 years. According to Daniel Gruner, an associate professor of Entomology at the University of Maryland, studies have shown that they can perceive time cycles because they are connected to the roots of trees. Root fluid movement slows down in winter and speeds up during the growing season. “However, we do not know how they keep track of the years one after another” until completing 17, continues Gruner, who points out that the timing is imperfect, since there are some that are ahead.
The expert clarifies that the use of pesticides is not justified as a hypothetical remedy because cicadas “are not pests, they do not bite or transmit pathogens, nor do they damage crops or property.” Spraying, he adds, only increases health risks for humans and other animals.
The entomologist at the University of Connecticut John Cooley argues that instead of waiting for their arrival in fear, their hatching is an opportunity to enlighten ourselves: “We can learn more about our forests; understanding how they work is key to living in them sustainably”.
Although they have not yet appeared en masse, it is not uncommon to find some exoskeletons already in the entrances of houses or to hear the click when they are crushed during a distracted walk through Washington. Two of the factors that make them emerge from the subsoil are humidity and warm temperatures. The ideal heat condition is an earth at 18 degrees. “We have had a cold wave and that seems to have slowed down the process a lot,” says Cooley, who foresees that the final hatching should take place next week.
Active reproductive cycle
Cicadas spend most of their lives underground feeding on tree roots, before tunneling to the surface. Once outside, generally in green areas, they head en masse towards the trees. Females lay between 400 and 600 eggs on thin branches that they pierce with a series of punctures.
The invasion of these insects will be a great feast for spiders and other predators, such as mice, birds or snakes. According to the people who have tried them, they taste similar to tofu. There are several subspecies of periodical cicadas, with different life cycles and swarm volumes. The generation that is now emerging on the east coast, the Brood X, is the longest-lived and one of those that is hatching en masse.
The phenomenon usually lasts about 40 days. Considering that the buzz that a swarm of males emits to attract females can reach 90 decibels, the presence of these insects alters the daily life of citizens. The ear will be exposed to sounds as loud (and annoying) as those of a construction.
According to the Centers for Disease Control and Prevention (CDC), 50 minutes of exposure to the sound of a motorcycle can damage hearing. Many citizens decide to stay in their homes during this particular phenomenon, but this will be the first time that it has occurred after 14 months of movement limitations due to the coronavirus, so it is unknown whether the desire to go outdoors or the annoyance presence will be able to increase.
Within a month of being on the surface, they die. If the buzzes of the males take effect on the females, they will have mated and will have left huge amounts of eggs in the branches of the trees. In late summer or early fall, a new generation will head underground to feed on tree roots. Gruner argues: “We should enjoy this event for the amazing natural spectacle that it is, before they go underground for another 17 years.”