In a rare event, a trillion cicadas from two different broods are expected to begin appearing in the Midwest and Southeast regions of the United States by the end of April.
This is the first time since 1803 that Brood XIX, or the Great Southern Brood, and Brood XIII, or the Northern Illinois Brood, will emerge together in an event known as dual emergence.
Thomas Jefferson was president the last time the 17-year cycle of the Northern Illinois Brood aligned with the 13-year period of the Great Southern Brood. After this spring, it would be 221 years before the groups, geographically side by side, reappeared together.
A roughly 16-state area will be the center stage for these seasonal cicadas, which differ from those that appear annually in smaller numbers.
Forests, including urban green spaces, are more likely to see higher numbers of cicadas than agricultural regions. To put into perspective how many of these bugs can come out, a trillion cicadas, each just over an inch long, would cover 15,782,828 miles if they were placed end to end, says Floyd W. Shockley, an entomologist and collections manager at the Smithsonian National Museum of Natural History.
“That cicada train will reach the moon and back 33 times,” said Dr. Shockley.
When do the cicadas come out?
The first cicadas are expected to start emerging in late April. Temperature determines when they emerge, said Gene Kritsky, a retired biology professor at Mount St. Joseph University in Cincinnati, and the author of several books on cicadas, including “A Tale of Two Broods.”
Professor Kritsky says the soil first needs to reach 64 degrees Fahrenheit, about six inches deep, and “then you get a nice soaking rain, and that’s when they really germinate,” he said.
They will use their forelegs to tunnel out of the ground, their red eyes looking for a place where they can peacefully finish maturing. A few days after they emerge and molt, the males begin humming in an effort to find a mate, a slow build. crescendo of noise which as a chorus may stronger than the plane.
Where are they going?
The first waves of cicadas will appear in northern Louisiana, southern Arkansas, Alabama, Mississippi, northern Georgia, and as far west as South Carolina, Professor Kritsky said.
They then appear in central North Carolina, eastern Tennessee and northern Arkansas, followed by southern Missouri, southern Illinois and western Kentucky. Eventually, he said, cicadas will appear throughout central and northern Missouri and Illinois, northwestern Indiana, southern Wisconsin and eastern Iowa.
How long does dual emergence last?
The Midwest and Southeast should be buzzing for about six weeks.
In most cases, Dr. Shockley, the cicadas, which live for about a month, will die not far from where they appeared.
Are cicadas dangerous?
Cicadas do not bite or sting, nor do they carry any disease. But because they are “poor fliers and even worse landers,” cicadas often end up on sidewalks and city streets, where they can be disturbed by people or vehicles and “may make things smooth.”
“In urban areas, there will be enough numbers to require the removal of their bodies,” said Dr. Shockley. “But instead of throwing in the trash or cleaning street sweepers, people should consider them basically free fertilizer for plants in their gardens and natural areas.”
If you have a dog that likes to eat them, it’s not a good idea to let them swallow the insects because it can lead to intestinal blockage, says Professor Kritsky.
How do I get rid of cicadas?
The short answer is: You don’t want to. If you have delicate plants that you want to protect, then use a special net created for that purpose.
Bugs are beneficial to the environment, acting as the tree’s natural gardeners. The holes they leave when they emerge from the soil help aerate the soil and allow rainwater to seep into the subsoil and nourish tree roots in the hot summer months. The cracks they make in trees can cause some branches to break, and leaves to turn brown in a process called “flagging,” which is a type of natural pruning. When the branch grows back, the fruits it bears are likely to be larger. When they die, the decaying bodies of the cicadas provide nutrients that the trees need.
John R. Cooley, a professor of biology at the University of Connecticut, says his best advice for people living in dual emergence regions is to let the bugs go.
“The forest is where they live,” he said. “They are part of the forest. Don’t try to kill them. Don’t try to spray insecticide, all kinds of things. That will only disappear because there are more than you can possibly kill with insecticide. You will kill everyone.”
