This spring, billions of bugs from two different broods of red-eyed, high-decibel periodical cicadas are expected to emerge together — and possibly interbreed — in the middle of the country for the first time since 1803.
Brood XIII cicadas, mostly concentrated in Illinois, Iowa and Wisconsin, come out of the ground every 17 years. Their Brood XIX cousins emerge every 13 years and are spread across the Midwest and Southeast. Between them, they represent all seven known species of periodical cicadas.
It’s uncommon but not unheard of for two broods to appear at the same time, said Floyd Shockley, entomology collections manager at the National Museum of Natural History and the Smithsonian’s resident cicada expert, in an email.
But these two are so geographically close that they may overlap and interbreed in some of the woods and fields near Springfield, Ill., a potentially exciting rarity for entomologists.
“And what will be the cycle of the new cicadas? We will have to wait to see,” Shockley said. The hybrid XIII/XIX offspring could form a new brood or a add a new branch to an existing brood. “Population genetics in these guys is wild so we will only know in 13 years what is happening with those hybrids.”
Adding to the mystery is the fact that it will be impossible to figure out this year whether the two broods overlap at all, or if so, how much, because the bugs are nearly identical except for the length of their life cycles, according to the University of Connecticut’s Cicada Project.
The project’s observation data from 13 and 17 years ago indicate that the two breeds may be a bit too far apart to intermingle. Cicadas don’t tend to travel too far from where they emerge.
Periodical cicada nymphs spend years underground growing and feeding off fluid from the roots of plants. When their time to emerge arrives, they tunnel upward, wait for the soil temperature to reach about 64 degrees and then crawl to the surface, en masse, within a few weeks.
The D.C. region experienced an enormous Brood X emergence in 2021.
Once aboveground, the plump nymphs inch their way up the nearest vertical surface — a tree, a fence post, a person standing very still — where they molt one last time, spread their wings and spend the last weeks of their lives desperately trying to mate.
The males develop their signature sound, a loud high-pitched, high-decibel buzz that ideally will attract females. The noise can be overwhelming, but other than that, cicadas are not harmful to humans.
After a few weeks, they will die, also en masse, leaving behind a smelly mess and billions of eggs containing the next generation.