What to Expect When You’re Expecting a Cicada Double Emergence
Even if you’ve never heard of cicadas, you’ve heard them.
A few species of these noisy bugs make a limited appearance every summer across the United States. But this year, they’ll be preceded by TRILLIONS of rarely-seen periodical relatives for a family reunion that hasn’t happened in 221 years.
Learn more about what you can expect from the May/June 2024 emergence of two periodical cicada broods: Brood XIX (the 13-year Great Southern Brood) and Brood XIII (the 17-year Northern Illinois Brood).
What is a cicada?
Cicadas are two-inch-long, big-eyed, big-winged insects with LOUD songs and dramatic life cycles.
They hatch from eggs laid in the branches of trees or shrubs and burrow underground as juvenile “nymphs.” After spending their youth underground drinking sap from tree roots, they then return aboveground to shed their exoskeletons and become adults, mate, lay hundreds more eggs, and die within a month.
The sound they make— which can be as loud as a jackhammer when a whole chorus of cicadas is singing together— is a love song. Male cicadas vibrate a membrane on their abdomens called a thymbal, and the sound attracts females to come and mate. Each species of cicada has its own signature song.
While most cicada species spend 2-5 years underground and emerge in relatively small numbers every year, only 7 species of cicadas in the United States emerge together as broods on strict 13 or 17-year schedules.
In 2024, two periodical broods—Brood XIX (the 13-year Great Southern Brood) and Brood XIII (the 17-year Northern Illinois Brood)—will emerge together in a one-in-two-and-a-half-human-lifetimes, overlapping event.
Who will see the cicada double emergence in 2024?
If you live in the United States, chances are you have seen and will see annual cicadas, like the big green “dog day” cicadas that emerge in late summer
Periodical cicadas have a more limited range across the Eastern United States, and occupy smaller stretches as broods:
- Brood XIX (the 13-year Great Southern Brood) will appear across the Southeast.
- Brood XIII (the 17-year Northern Illinois Brood) will appear across a small area of the Midwest.
- BOTH Brood XIII and Brood XIX will overlap in limited areas of Iowa and Illinois.
Since both annual and periodical cicadas wait until the ground reaches 64 degrees Fahrenheit to emerge, ETAs for these bugs will vary from state to state based on climate. In general, most of the periodical cicadas are expected to appear between May and June.
Even though this year is a rare double emergence, you won’t see double the amount of periodical cicadas— there’s a very small overlap of the two broods’ ranges. This year will be rare in that you’ll be able to see periodical cicadas around Chicago at the same time you’ll be able to see them in Southern Illinois, but the amount of cicadas present in any given area will be standard for a regular 17- or 13-year cicada emergence. (But even a regular emergence still means a LOT of bugs!)
When was the last time these two periodical cicada broods emerged at the same time? 221 years ago, in 1803:
- 37 years before English paleontologist Richard Owen coined the word “dinosaur.”
- 56 years before Charles Darwin published “On the Origin of the Species.”
- 90 years before the World’s Columbian Exposition, the event that started the Field Museum’s collection.
- The year President Thomas Jefferson signed the Louisiana Purchase.
- The next time a 13-year brood and 17-year brood simultaneously emerge will be 2245.
Why do periodical cicadas spend so much more time underground than annual cicadas?
Scientists think periodical cicadas have adapted to spend so much of their lives under the surface to avoid predators.
When they’re underground, they’re hard to find; when they’re above ground, they appear in such large numbers that while some will be eaten, others will live long enough to reproduce and ensure the continuance of their 13 or 17-year cycle.
Where can I learn more about cicadas?
We’re celebrating cicadas throughout May and June at the Field Museum— check out insect pinning, taste testing, and learning resources on our events page.
