This spring and summer, we will see the emergence of trillions of cicadas that we haven’t seen for 17 years. These giant bugs will be everywhere, and their mating hum can reach up to 100 decibels. The Great Eastern Brood, also known as Brood X, has and will spread over one of the largest geographical areas and will be found from Georgia to the Midwest to New York.
What is it?
These large groups of periodical cicadas, a genus of cicada that surface in 13 or 17 year periods, are different from other species of cicada. Only these periodical cicadas, which are separated by the regions and the years they come out, are
called broods. For the 17-year cicada, there are supposed to be 17 different broods, one for each year (Brood X is the tenth brood), but scientists suggest that some might have gone extinct many years ago because not all of them have been observed. For example, Brood X, which we will see this year, last emerged in 2004 and previously in 1987, so we can assume that they will continue with the 17-year cycle. Brood XI would be the cicadas that come out next year, but this group was last seen in 1954, implying that it has gone extinct. While a different brood appears every year, this will be the largest of the 17 broods. They appear in large numbers so that when facing predators, enough will survive to produce offspring.
The reason these cicadas only emerge every 17 years comes from an evolutionary trait that developed 1.8 million years ago. They only appear once the ground temperature is around 68 degrees Fahrenheit, because it is too cold to mate and survive below 68 degrees. Over a million years ago, there was the possibility of unusually cold summers, so the less they came out, the less likely they would encounter a cold summer.
There are many theories for why it is specifically every 17 years. One scientist, Jin Yoshimura, theorizes that the prime-numbered cycles prevent the cicadas from running into the cycles of wasps that eat them as it is hard for predators to predict when they will come out if they appear in prime numbers. Scientists Randel Tom Cox and C. E. Carlton also suggest that prime-numbered cycles also could reduce the chance of mating with different cicadas species.
Do I need to worry?
If you are like me and don’t like bugs, this all might sound like a nightmare, but there is not much harm that these cicadas can do to humans directly. To keep you at ease, here are some things you may want to know: they will not bite you unless they think you are a plant and will not destroy crops. They also do not spread diseases and are not poisonous, but if your pet accidentally eats too many, it could choke on the exoskeleton.
However, cicadas are a danger to trees, especially fruit trees, that are two years old and younger. If you plan on planting a tree, you should wait until after Brood X passes, but if you already have young trees planted there are preventative measures you can take. According to entomologist Mike Raupp, instead of pesticides, you should completely cover the young trees with fine netting (a centimeter or less), so the cicadas can not lay eggs near your trees. Usually after mating, laying eggs, and dying, the new larvae will fall to the ground and burrow into the earth, surviving from the fluids in tree roots until 17 years pass. And the cycle will start all over again.
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