Cicada Holes: Understanding the Mysterious ‘Cicada Chimneys’ in Your Yard

Subtle yard mounds hint at a massive underground awakening well before the first chorus.

By Medha deb

Created on Sep 25, 2025

Subtle yard mounds hint at a massive underground awakening well before the first chorus.

Why You Might Notice Strange Holes (and Mounds) in the Ground Before Cicadas Arrive

Each spring and early summer, residents across much of the Eastern United States experience a remarkable natural event: the mass emergence of periodical cicadas. These insects make headlines for their numbers—up to 1.5 million per acre during big emergences in places like Maryland, Indiana, and Pennsylvania. Their sudden appearance and thunderous mating calls are legendary. However, before you witness swarms of winged adults, you may first notice peculiar signs in your yard: small mud mounds with a central hole—commonly called cicada chimneys. These formations are the earliest evidence that a brood of cicadas is about to breach the surface after years underground.

What Is a Cicada Chimney?

A cicada chimney is a short, mud-built mound that forms above a hole in the ground, often appearing a few weeks before the cicada nymphs themselves emerge. But what exactly are these structures, and why do cicadas build them?

Cicada chimneys or mud chimneys are exit tunnels created by developing cicada nymphs.

They form over the holes where cicadas plan to surface as adults.

The mud structure provides a pathway out for cicadas, especially in wet soil conditions, helping them avoid water or mud sliding into their exit tunnel.

These chimneys typically start to appear as the weather gets warmer—usually late spring to early summer.

Expert entomologists explain that the primary reason for building a chimney is to maintain an open, breathable passage to the surface. In drier soil, you may see only a simple hole without the chimney.

Cicada Life Cycle: Why Chimneys Form

To understand cicada chimneys, it’s essential to know the mysterious life cycle of these insects.

Eggs: Female cicadas lay their eggs in the branches of trees using a tube-like structure called an ovipositor.

Nymphs: When the eggs hatch, the nymphs drop to the ground and burrow into the soil, feeding on the sap from tree roots. They stay underground for 13 or 17 years, depending on the species.

Emergence: As the soil temperature rises (around 64°F/18°C at about eight inches depth), nymphs begin to move to the surface. In wetter conditions, they construct mud chimneys above their exit tunnels to protect themselves from mud and water ingress.

Adult: After emerging, the nymphs climb nearby trees or structures, shed their outer shell (exuvia), and become noisy, flying adults.

This process is particularly visible during mass emergences of periodical broods, such as Brood X, with vast numbers of synchronized cicadas surfacing simultaneously.

What Do Cicada Chimneys and Holes Look Like?

Cicada chimneys have several distinctive features that set them apart from other ground holes made by insects or small animals:

Size: Typically, chimneys are about 2–3 inches high and 1–2 inches wide. The hole at the center measures about ½ inch wide.

Shape: The mound is usually rounded or chimney-like, sometimes called a turret, and may be domed or loosely built, depending on soil moisture.

Material: Cicada chimneys are made of mud, not just loose dirt.

The look of the chimney depends on the soil conditions. When the soil is moist, cicada nymphs tend to build more pronounced chimneys as they push mud upwards while excavating their exit gallery. In drier regions or during dry spells, the hole may be all that is visible.

Comparison: Cicada Chimneys vs. Other Yard Holes
Feature	Cicada Chimney	Ant Hill	Wasp or Bee Hole
Opening Size	~1/2 inch	Very small	Varies, usually small
Material	Mud mound	Dirt, mixed with plant debris	Loose soil or sand
Shape	Chimney or turret-shaped	Low, spread-out mound	No mound, or slight lip
Associated Insect	Cicada	Ant	Ground bee/wasp

Why Do Cicada Chimneys Form?

Cicada chimneys are ingenious adaptations that help cicadas successfully transition from their underground to above-ground life:

Preventing Cave-ins: The chimney keeps mud or water from sliding into the hole, ensuring the nymph can breathe and move freely during its approach to the surface.

Moisture Management: In wet or heavy soils, the structure provides an essential escape route. In dry soils, only a simple opening may be present.

Breathing Room: The open tunnel allows for gas exchange while the nymph waits for ideal emergence conditions.

Clue for Observers: For humans, spotting these chimneys is a reliable sign that cicada emergence is imminent in your area.

Are Cicada Chimneys Unsafe for People or Pets?

The appearance of cicada chimneys in your yard is not a cause for alarm. Experts confirm that:

The mud structures themselves cannot harm humans or pets.

Cicadas are not venomous, poisonous, or aggressive.

They do not sting or bite, and they do not create lasting damage to lawns or mature trees.

The only potential impact is superficial holes left behind after the emergence, which can be easily managed with regular yard care.

What Should You Do if You Find Cicada Chimneys?

Let Nature Take Its Course: The best response is usually to observe and leave the structures undisturbed. Cicadas are important for the ecosystem, acting as food sources for many animals and providing soil aeration through their tunneling.

No Need for Removal: They do not damage your garden or property in a significant, long-term way, so there’s usually no need to destroy or remove the chimneys.

Yard Maintenance: After cicadas have finished emerging, simply fill any visible holes with soil as part of your regular lawn care routine.

The Ecological Importance of Cicadas

Cicada emergence events are more than just a spectacle—they play a meaningful role in local ecosystems:

References

Author

medha deb

Medha Deb is an editor with a master's degree in Applied Linguistics from the University of Hyderabad. She believes that her qualification has helped her develop a deep understanding of language and its application in various contexts.

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