By Jonny Lupsha, Wondrium Staff Writer
Billions of cicadas are emerging across the eastern United States. For the first time in 17 years, a brood of the flying insects will sing, mate, and die off in a mass four- to six-week breeding event. Insects took flight 400 million years ago.
If you haven’t already heard it—literally—the 17-year cycle of cicada mating has returned. Throughout the eastern United States, billions of the flying insects are having a party that begins with males singing a mating song to the females. Once the females answer the call, they’ll select a tree that will house her eggs for the next 17 years and insert them into it.
Four to six weeks later, the adults will die. Unfortunately, this will leave Americans on the East Coast cleaning up, walking on, and driving over billions of cicada corpses.
This noisy affair will invade the eardrums of Americans from northeast Texas to Cape Cod. It may be a nuisance, but it owes to many paleontological wonders. In his video series Major Transitions in Evolution, Dr. Anthony Martin, Professor of Practice in the Department of Environmental Studies at Emory University, explained why insects are so populous. It began 400 million years ago in the Devonian period.
A Plague of Insects
“Flight was a major evolutionary innovation in insects, and flying insects in particular changed terrestrial ecosystems in really significant ways,” Dr. Martin said. “Recent DNA analyses show the closest living relatives of insects are this group of crustaceans known as remipedes. This means insects are actually more closely related to crustaceans than to myriapods like millipedes and centipedes.”
According to Dr. Martin, insects must have evolved from six-legged terrestrial arthropods. Their evolutionary success owes to a number of factors. First, insects have very high reproductive rates. Given the right species and conditions, this can literally result in several generations per year. Second, insects have incredible numbers of offspring. Combining that with the high reproductive rates, insects are guaranteed a large genetic variability.
“As a result, insects show really rapid responses in their populations to any sort of selection pressures,” Dr. Martin said. “Just ask scientists at chemical companies that manufacture pesticides. They frequently change their formulae because the pesticide-resistant insects are adapting so rapidly.”
He said this is an example of what he’d call “unnatural selection.” Humans, by attempting to control pest populations, have unwittingly selected in favor of better-adapted insects, which then go on to reproduce larger numbers of pesticide-resistant offspring. This is analogous to one public concern about the medical industry—that is, as humans combat disease, only the weaker diseases will die off, leading to the proliferation of “super diseases.”
At the same time, insects’ early ability to fly gave them an edge over many other of Earth’s creatures.
“Knowing how modern dragonflies are such fantastic predators today, meganeura and these other giant dragonflies of the Carboniferous period must’ve been the scariest things in the air, giving good reason even for small vertebrates to be afraid of an attack from above,” Dr. Martin said. “Also keeping in mind that flying vertebrates hadn’t evolved yet, these insects, once evolved, ruled the skies.”