Talk about a rude awakening. Brood X cicadas are coming aged in world that’s drastically altered from the one their ancestors knew.
Not only is that this not their grandfather’s or great-grandfather’s planet, it’s one that some bugs might barely recognize — with a changed climate and living conditions that are forcing adaptive changes for a few species, like moths that not fly to bright lights or crickets remixing their love song.
“Brood X cicadas, like all periodical cicadas, are a Rip Van Winkle story,” said Brett Seymoure, the Grossman Family Postdoctoral Fellow with the Living Earth Collaborative at Washington University in St. Louis. “They live underground for 17 years, then come up to a totally different world thanks to human-induced rapid environmental change.”
Periodical cicadas comprise seven of the roughly 3,000 species of cicadas — and that they tend to urge all the press. They only occur in eastern US. Unlike most cicadas, periodical cicadas lay eggs that hatch then their nymphs burrow underground for either 13 or 17 years, depend on the species. Brood X is formed from a couple of species within the genus Magicicada and is one among the most important groups — containing many billions of individuals.
“The mating conditions that Brood X’s parents had were quite different,” said Seymoure, a behavioral ecologist in Arts & Sciences who studies the consequences of lighting on animal behavior, physiology and ecology. “And if you think that back to when their great-grandparents mated, it had been 1970! this is often very interesting to believe in light of artificial environmental change.
“Most insect species have several generations in one year and thus survival can select for individual’ that are better ready to deal with rapid changes,” he said. “In fact, we’ve seen that some populations of moths are not any longer interested in artificial lights in the dark .”
Other insects have adapted to human-caused environmental change, but most of them have several generations in one year. Grasshoppers and crickets, for instance , believe courtship songs to seek out mates — a bit like cicadas — and they’ve found ways to deal-with-noise from traffic or other industrial activity. They’ve literally changed the frequency of their courtship songs to be more conspicuous against the daily drum of human disturbance.
But Brood X cicadas only sample the modern-world for less than a couple of days every 17 years. How can they keep up?
Adults are above ground so briefly — and at intervals that are such wide stretches apart — that scientists struggle with observing adult behaviors and designing experiments around them. As a result, there’s little known about how rapid changes within the environment affect periodical cicadas.
“We do know that nymphs use ground temperature to work out when to emerge and start the adult phase (i.e. find mates). and that we know that thanks to global climate change , it seems that some populations are emerging earlier and not waiting the 17 years,” Seymoure said.
‘Bugged’ by light
And it’s not only warming temperatures.
Light pollution is another powerful human-induced stressor on insects. Many bugs respond-to-light — whether it’s natural light from the complete moon, differing types of light bulbs, or diffuse sky-glow caused by light pollution in urban areas. Light pollution from artificial light in the dark is assumed to be one factor contributing to global declines in arthropod abundance over the previous couple of decades.
“Other species of cicadas are allure in lights in the dark ,” Seymoure said. “They’re those that are active at dawn and dusk. On the opposite hand, periodical cicadas are active during the day and typically begin copulating in late afternoon then become inactive. So we don’t know if these cicadas are generally interested in lights or not, and if there are the other effects on their biology from light pollution.
“If there are,” Seymoure said, “it are going to be very interesting to ascertain how these bugs handle the light-conditions that are tens of times worse than they were in 2004.”
The findings are reported on Washington University in St. Louis