The Year of the Cicadas: 2024 Emergence

The spring and summer of 2024 are set to deliver a biological event of historic proportions. For the first time since 1803, two distinct broods of periodical cicadas—Brood XIII and Brood XIX—will emerge from the ground simultaneously. This rare alignment, occurring once every 221 years, means trillions of insects will surface across the Midwest and Southeastern United States, creating a spectacle that hasn’t been seen since Thomas Jefferson was president.

Understanding the Double Brood Event

Periodical cicadas are distinct from the “annual” cicadas that buzz every summer. These insects spend the vast majority of their lives underground, emerging only after completing a specific 13-year or 17-year life cycle. In 2024, the calendars for two specific groups are overlapping perfectly.

Brood XIII (The Northern Illinois Brood)

This group operates on a 17-year cycle. The last time they emerged was in 2007. Their territory is concentrated in the Midwest. If you live in Northern Illinois, Eastern Iowa, Southern Wisconsin, or a few counties in Northwestern Indiana, you are in the heart of Brood XIII territory.

Brood XIX (The Great Southern Brood)

This group runs on a shorter 13-year cycle. They last appeared in 2011. Brood XIX is geographically massive, covering a wide swath of the Southeastern and Midwestern United States. Residents in Missouri, Southern Illinois, Arkansas, Alabama, Georgia, Tennessee, North Carolina, South Carolina, and parts of Virginia and Maryland will see this emergence.

The Mathematic Rarity

The reason this event is making headlines is the math involved. Because 13 and 17 are prime numbers, they rarely align. The two cycles coincide only once every 221 years. Following the 2024 emergence, these two specific broods will not appear together again until the year 2245.

Where the Cicadas Will Overlap

While both broods are emerging at the same time, they will largely stay in their separate geographic lanes. However, there is a narrow “overlap zone” where residents might see insects from both broods.

The primary convergence point is in Central Illinois, specifically around the Springfield area. Here, the northern range of the 13-year cicadas meets the southern range of the 17-year cicadas. In these specific counties, the density of insects could be staggering. Experts estimate numbers could reach up to 1.5 million cicadas per acre in heavily wooded areas.

The Timeline: When Will They Arrive?

Cicadas do not look at a calendar. Instead, they monitor soil temperature. The emergence is triggered when the soil temperature eight inches beneath the surface reaches exactly 64 degrees Fahrenheit.

  • Late April: Residents in warmer southern states like Georgia and South Carolina will likely see the first signs of Brood XIX.
  • Mid-to-Late May: The emergence will peak in the Midwest, including Illinois and Missouri, as the ground thaws sufficiently.
  • Duration: Once they emerge, the adult cicadas live for approximately four to six weeks. By late June or early July, the event will largely be over, leaving behind only shells and the next generation of eggs.

What to Expect: Noise and Activity

For the uninitiated, a periodical cicada emergence can be a sensory overload. The male cicadas produce a mating call by vibrating a membrane on their abdomen called a tymbal.

  • Decibel Levels: A chorus of cicadas can reach 90 to 100 decibels. This is roughly as loud as a lawnmower, a motorcycle engine, or a jet flyover at 1,000 feet.
  • Visuals: You will see chimney-like mud holes in the ground where the nymphs exit. Shortly after, you will find their molted exoskeletons attached to tree trunks, patio furniture, and brick walls.
  • Flying: Adult cicadas are clumsy fliers. They often bump into people or objects, but this is accidental. They do not have the agility of houseflies or bees.

Impact on Homes and Gardens

While the sheer number of insects can be intimidating, cicadas are generally harmless to property and people. They do not have mandibles to chew leaves like locusts, nor do they sting or bite.

Protecting Young Trees

The biggest risk during an emergence is to young trees and shrubs. Female cicadas cut small slits into branches to lay their eggs. This process, called ovipositing, can weaken or kill small branches. This damage is often called “flagging,” where the leaves at the tip of the branch turn brown and die.

Action Plan:

  • Mature Trees: Do nothing. Established trees can withstand the pruning nature of egg-laying without issue.
  • Saplings: If you have planted fruit trees or ornamentals in the last two to three years, you should protect them. Wrap the canopy in mesh netting with holes smaller than 1⁄4 inch (about 0.6 cm). Secure the netting to the trunk to prevent insects from climbing up from the bottom.
  • Chemicals: Avoid spraying pesticides. They are largely ineffective due to the sheer volume of insects and can harm beneficial pollinators or pets that might eat the cicadas.

Pets and Safety

Dogs and cats are often fascinated by the emerging insects.

  • Toxicity: Cicadas are not toxic. They are safe to eat in small quantities.
  • Indigestion: The insect shells are made of chitin, a fibrous substance that is difficult to digest. If a dog gorges on dozens of cicadas, it may suffer from vomiting or constipation. Monitor your pets while they are outdoors during the peak weeks.

The Ecological Benefit

Despite the noise and the mess, this event provides a massive energy boost to the local ecosystem. The emergence acts as an all-you-can-eat buffet for birds, raccoons, opossums, and fish.

Once the adults die, their bodies decompose on the forest floor. This returns massive amounts of nitrogen and other nutrients to the soil, resulting in a “fertilizer spike” that can boost plant growth in the following years. The exit holes created by the nymphs also serve to aerate the soil naturally, improving water absorption for tree roots.

Frequently Asked Questions

Will the cicadas enter my house?

They do not seek to enter homes. However, they may accidentally fly in through open doors or windows. Ensure your window screens are free of holes to keep them outside.

Can cicadas damage my vegetable garden?

Generally, no. Cicadas are not interested in leafy greens, tomatoes, or flowers. They feed on xylem fluid from woody plants and trees. Your vegetable patch is safe, though you may find them resting on sturdy tomato stakes.

What is the “Zombie Cicada” fungus?

You may hear reports about Massospora cicadina. This is a fungal pathogen that infects periodical cicadas. It causes the posterior of the insect to fall off, replaced by a plug of fungal spores. Interestingly, it causes the insect to become hyperactive and attempt to mate frequently, which spreads the fungus to other cicadas. While gruesome, this fungus is specific to cicadas and does not infect humans or pets.

How do I clean up the shells?

After the emergence, you may have piles of dead insects and shells. These can be swept up or raked. The best disposal method is to add them to your compost pile or bury them in the garden, where they will act as a high-quality organic fertilizer.