2011 Cicada Invasion is an Opportunity for Scientists

Cicadas swarming a tree in Nashville.

The 2011 cicada invasion is not always an annoyance. For scientists, it’s a precious research opportunity.

Belmont University entomologist Dr. Steve Murphree is an expert on Nashville’s periodical cicadas. He says they are part of the largest emergence group of 13 year cicadas in the nation, called Brood XIX or the Great Southern Brood.

The adult cicadas are currently laying their eggs, which Dr. Murphree says will become the next generation of cicadas.

“Along about the second week of July, those eggs will hatch. They’ll be about an eighth of an inch long with tiny red eyes.”

These small nymphs, as they’re called, will bury themselves underground after they hatch. We won’t see adult cicadas again until 2024.

This means that scientists can only study the adult insects during a window of a few weeks once every 13 years. Dr. Murphree says that in the years between cicada emergences, research potential is limited.

“You can dig them up at other times of the year. If you want to dig up your yard you can find the nymphs, or you can dissect the branches of trees where the eggs have been laid to see how many of them were successful at hatching and how many had died in the egg stage. You can do a little basic research like that.”

Scientists at Vanderbilt are currently studying the effects of cicadas’ noise, which can be as loud as a motorcycle.

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The sheer number of cicadas is overwhelming. Cicadas have the largest population and collective weight of any herbivore in North America. Dr. Murphree says that they come out in such large numbers to protect from predators and guarantee reproduction.

“It’s a good strategy, it’s called predator satiation. Because they come out in such tremendous numbers, the predators are not used to them. And so the generalist predators, even your family dog will eat them, and there are plenty left to mate.”

The cicada’s large population contributes to its inescapably loud noise. The sound can peak at a level of 85 to 88 decibels, which is about at loud as a subway train from 25 feet away.