As you've surely seen, the East Coast is preparing for a pending cicada invasion. And by "preparing," I mean "hyperventilating in front of a computer screen." Sure, everything happening remotely close to New York always gets blown out or proportion—that big gray cloud you just Instagrammed is going to release water, which is called "rain"; everyone will be fine—but, I mean, there are going to be a lot of cicadas, like multiple-hundreds per person. Despite the pending invasion of these mutating alien-shrimp pods, you're all probably going to be fine. Probably. To get the low-down on what the upcoming cicada onslaught will be like, I exchanged some emails with Dr. Angie Shelton, a biology professor at Indiana University. Here's what she said.
I've seen reports that cicadas are going to outnumber humans 600-1, maybe more. That's a lot of cicadas! Right?
In 1962, Henry Dybas and Dwight Davis estimated areas with the highest density of cicadas had > 300 cicadas per square yard. This is equivalent to 100 to 193 pounds of cicadas per acre, which is similar to the weight of cattle that can be raised on an acre of land. I'm not sure how this relates to the weight of humans.
Cicadas occur throughout most of the world, but the periodical cicadas that emerge only every 13 to 17 years in huge numbers are restricted to eastern North America. Other species of cicadas live underground for several years, but some adults emerge every year and these annual cicadas occur later in summer and are in much lower numbers.
How long will the invasion last?
The adult cicadas will be around for four to six weeks. By mid-June they should be gone, although piles of dead insects may remain. In mid-summer their tiny eggs will hatch in the tree branches where they were laid, fall to the ground, and burrow down to tree roots where they will spend the next 17 years.
They're coming east, basically, for the sole purpose of mating. Why do they need to go somewhere to, um, do that?
They are actually already in the ground beneath your feet, just waiting for the soil to warm up to precisely the right temperature to complete their development. Cicadas don't move far from where they emerge from the ground. Different broods emerge in different parts of the country in different years. This is a map of where upcoming cicada broods will be.
Once the soil reaches a certain temperature, all the cicadas in that part of the country will emerge synchronously within about two weeks of each other. All they do during the adult portion of their life is sing, mate, and lay eggs. The loud "singing" is primarily from males that gather in groups, called “leks,” where they sing to attract the best females. This noise can be impressively loud, up to 90 decibels, can exceed OSHA noise safety standards, and make it virtually impossible to have a conversation outdoors. On the up side, cicadas only sing during the day, making it possible to sleep at night.
So, people are freaking out about this. I mean, they're pretty scary-looking, but cicadas can't actually hurt people, right?
Cicadas are completely harmless. They look weird (you might too if you lived underground for 17 years), but they do not bite, are not poisonous, and will not attack. If they seem to fly into people it's simply because there are so many of them and they are not very graceful fliers.
Cicadas are a great food source for many animals. Mole populations are often larger the year following a cicada emergence because the abundance of big bugs provide lots of food and can result in more baby moles. Many dogs enjoy eating cicadas and may eat so many they make themselves sick.
During every emergence, some people decide to try eating cicadas. They are reported to taste a bit like a nutty-flavored shellfish. They are a good source of low-fat protein, however, they can cause allergic reactions, particularly in people allergic to shellfish (both are arthropods).
What do people have to look forward to, then? How will they know they're in the midst of the cicada invasion?
If you live in or visit an area with a lot of large trees with the Brood II range, which extends from Connecticut to northern Virginia, chances are you'll know when the emergence happens. There will be a loud buzzing sound during the day and you'll see lots of enormous bugs flying around.
There has to be some kind of environmental fall-out from so many cicadas being in a relatively small area, though, doesn’t there?
Aside from possibly more moles in yards next year, cicadas have few negative effects. Some small tree branches may die, but this has been shown to have no long-term negative effects on trees and may actually be beneficial, similar to pruning. The dead cicada bodies also provide a large pulse of nutrients that can fertilize forests and yards.
Any more insect invasions we need to worry about in the near future?
Cicadas are probably the least problematic insect "invasion." They occur regularly every 17 or 13 years throughout eastern U.S. forests. More problematic insect invasions are usually species that are new to North America, such as the hemlock wooly adelgid, which kills hemlock trees, and the emerald ash borer (which kills ash trees). Those insects have far greater environmental effects, but are small and isolated to certain tree species and are rarely noticed by people until the trees have died.