17-year cicadas are emerging in large numbers from underground in Eastern USA (Credit: Futureman1199 /CC BY-SA -3.0 Creativecommons.org)

As if the COVID-19 pandemic has not been difficult enough, 2020 has another "trick" in store for the residents of Southwest Virginia, parts of North Carolina, and West Virginia. This one will come in the form of millions and millions of noisy cicadas who are gradually emerging from their 17-year underground hibernation to spend the final few weeks of their lives mating and breeding. Dubbed Brood IX, the alien-like insects are expected to peak in mid-June, with as many as 1.5 million specimens emerging per acre. The visit, however, will be short-lived, and most will be gone by July.

Cicadas spend most of their lives underground in their nymph stage and only emerge above ground for a few weeks to mate and breed (Credit: cicadamania.com)

Unlike annual cicadas, who often show up like uninvited guests at summer barbecues, periodical cicadas spend most of their lives underground in an immature "nymph" stage, sucking sap from tree roots. They emerge in their adult state as black, shrimp-sized alien-like bugs, with red, beady eyes and transparent wings every 13 or 17 years to reproduce, and die soon after.

While researchers do not know the reason for the odd number of years the bugs spend underground, they have a theory. They speculate that if the insects came out after an even number of years, say 16, they would make predictable prey for predators with two, four, and eight-year lifespans. However since 13 and 17 are both prime numbers, any predator that might depend on the insects would have to match that lifespan. As to how the cicadas know when to emerge? That's a well-kept secret known only to the bugs!

The alien-like insects can be annoying due to their loud mating calls (Credit: James St. John / CC BY-SA 2.0/ creativecommons.org)

Even though they are not dangerous, the clouds of millions of cicadas can be a little daunting and even a nuisance since they seem to appear everywhere. Additionally, the constant drone of male cicadas, which sing at 120 decibels, about the range of the human pain threshold, to attract females, can be annoying,

"It's like a loud, loud humming noise, like millions of grasshoppers all at once," Virginia farmer Debbie Noonkester told As It Happens host Carol Off. "Then they've got this weird shriek every once in a while ... and it's a just really, really strange sound."

Noise aside, Noonkester has another reason for disliking the insects. They cause significant damage to her young blueberries, blackberries, peaches, and apple trees. That's because, within days after their emergence, female cicadas begin to seek pencil-width twigs or vines in which to lay their eggs. The slits they create to place the eggs often cuts off the food supply causing the branch to wither. While mature trees can withstand the damage, young fruit or nursery trees often become stunted or even die. The orchard farmer says she lost 500 trees during the previous cicada visit, 17 years ago.

The cicadas lay their eggs inside slits created in thin twigs, which often kills young plants (Credit: lorax/ CC BY-SA 3.0/ creativecommons.org)

The eggs hatch by the end of the summer, and the immature cicadas drop down to burrow into the soil, where they spend the next 17 years feeding on the plants' roots. Their work completed, the parents die and end up as a once-in-a-lifetime treat for cats, dogs, birds, squirrels, rats, and even humans. In case you are curious, the high protein bugs taste like "cold canned asparagus."

Annoying and destructive as they may be, Virginia Tech entomologist Doug Pfeiffer believes the cicadas' rare and brief visit should be appreciated. The expert says, "This insect is really fascinating, and if you don't have fruit trees or grapevines to protect, you can enjoy this phenomenon while it lasts."

Resources: nbcnews.com, www.pubs.ext.vt.edu, npr.org,sciencenetlinks.com