Brood X’s cicadas will emerge in a very different world
Brood X’s cicadas are coming of age in a world radically altered from what their ancestors knew.
Not only is it no longer their grandfather or great-grandfather’s planet, it’s a planet some insects could barely recognize – with altered climate and living conditions forcing changes. adaptive for some species, like moths that no longer fly towards bright lights or crickets remixing their love song.
“Brood X’s cicadas, like all periodic cicadas, is a story by Rip Van Winkle,” says Brett Seymoure, postdoctoral fellow at the Living Earth Collaborative at Washington University in St. Louis. “They live underground for 17 years, then arrive in a completely different world due to rapid human-induced environmental change, or HIREC.”
Culture shock of the cicada
Periodic cicadas include seven of the roughly 3,000 species of cicadas – and they tend to get all the press. They only occur in the eastern United States. Unlike most cicadas, periodic cicadas lay eggs that hatch, then their nymphs burrow underground for 13 or 17 years, depending on the species.
Brood X is composed of a few species of the genus Magicicada and is one of the largest groups – containing hundreds of billions of individuals.
“The mating conditions of Brood X’s parents were quite different,” says Seymoure, a behavioral ecologist who studies the effects of lighting on the behavior, physiology and ecology of animals. “And if you think back to when their great-grandparents mated, it was 1970!” It is very interesting to think about this in light of the environmental changes caused by humans.
“Most insect species have several generations in a year and therefore natural selection can select individuals better able to cope with rapid changes,” he says. “In fact, we have seen that some populations of moths are no longer attracted to artificial lights at night.”
Other insects have adapted to environmental changes caused by humans, but most of them have several generations within a year. Grasshoppers and crickets, for example, rely on court songs to find mates – just like cicadas – and they have found ways to deal with noise from traffic or other industrial activities. They literally changed the frequency of their court songs to be more visible against the daily drumbeat of human disturbance.
Can Brood X’s cicadas adapt?
But Brood X cicadas only sample the modern world for a handful of days every 17 years. How can they keep pace?
Adults are above the ground so briefly – and at intervals so far apart – that scientists have trouble observing the behaviors of adults and designing experiments around them. As a result, little is known about how rapid changes in the environment affect periodic cicadas.
“We know that nymphs use soil temperature to determine when to emerge and begin the adult phase (ie find mates). And we know that due to climate change, it seems that some populations are emerging earlier and not waiting to turn 17, ”says Seymoure.
And it’s not just the warming of temperatures.
Light pollution is another powerful anthropogenic stressor on insects. Many insects react to light, whether it’s natural light from a full moon, different types of light bulbs, or the diffuse glow from the sky caused by light pollution in urban areas. Light pollution from artificial light at night is believed to be one of the factors contributing to the global decline in arthropod abundance in recent decades.
“Other species of cicadas are attracted to lights at night,” Seymoure says. “They are the ones who are active at dawn and dusk. On the other hand, periodic cicadas are active during the day and usually begin to mate in the late afternoon, then become inactive. So we don’t know if these cicadas are generally attracted to lights or not, and if there are other effects on their biology from light pollution.
“If there are any,” says Seymoure, “it will be very interesting to see how these bugs deal with lighting conditions that are dozens of times worse than they were in 2004.”
Source: University of Washington at Saint-Louis