Cicada emergence holes are roughly pencil-width openings in soil, typically about half an inch to three-quarters of an inch in diameter, with smooth, rounded edges that look almost drilled. They appear in bare dirt, mulch beds, and thinly grassed areas, usually within a few feet of tree trunks. If you have spotted a cluster of neat, circular holes in your yard and wondered what made them, cicada nymphs tunneling to the surface are one of the most likely explanations, especially during the warmer months. But distinguishing them from the work of other burrowing creatures takes a closer look at some specific details.
Size, Shape, and General Appearance
A single cicada emergence hole is strikingly clean and uniform. The opening is circular, ranging from about 10 to 17 millimeters across, which puts it right around the diameter of a standard wooden pencil or an adult’s index finger. The walls of the tunnel are smooth and slightly compacted, because the nymph has been pushing and packing soil aside with its body and powerful forelegs as it digs upward. Unlike the ragged, irregular burrows left by earthworms or beetle larvae, cicada holes have a finished look, as if someone pressed a dowel into the ground.
The depth of the tunnel beneath each hole varies. Periodical cicada nymphs spend years feeding on tree root sap several inches to a couple of feet underground, and they construct a vertical or near-vertical shaft from their feeding chamber to the surface when soil temperatures hit the right threshold. When you see the hole at the surface, you are looking at the exit point of a tunnel that may extend six inches to more than a foot straight down. Poking a twig into one reveals a surprisingly deep, tidy channel.
Mud Chimneys and Turrets
Not every cicada hole is flush with the ground. In areas with moist or clay-heavy soil, nymphs sometimes construct small turrets of mud pellets around the rim of the hole, stacking them into a chimney-like structure that can rise one to four inches above ground level. These turrets are unmistakable: they look like miniature, slightly lumpy mud volcanoes, about an inch or so wide at the base, tapering to an open top. The purpose of the turret is debated among entomologists, but the leading idea is that nymphs build them as a ventilation shaft, allowing air exchange while they wait just below the surface for conditions to be right for the final push above ground.
Turrets are more common during rainy springs when the soil is saturated. If you see them, they are a strong signal that a large periodical cicada emergence is imminent or already underway. Annual cicadas rarely build prominent turrets, so spotting chimney-topped holes in a year that matches a known periodical brood cycle is a reliable indicator of what is coming.
Where the Holes Tend to Appear
Cicada nymphs feed on the xylem fluid of tree roots, so emergence holes cluster near trees. You will find the highest density of holes within the dripline of deciduous hardwoods like oaks, maples, hickories, and beeches. Conifers attract far fewer cicada nymphs. The holes rarely appear in the middle of an open field with no trees nearby, though they can show up surprisingly far from the nearest trunk if lateral roots extend outward.
Soil type matters too. Nymphs prefer soil that is not too compacted and not too sandy. Well-drained loam and clay-loam soils tend to produce the most emergence holes. Heavily compacted urban lawns, gravel beds, and pavement cracks are less hospitable, though nymphs have been found emerging through surprisingly tough surfaces when no softer option exists. Garden beds with loose mulch or freshly turned soil can see heavy emergence because the nymphs have an easier time tunneling upward.
How Dense Can They Get
During a major periodical cicada emergence, the density of holes can be startling. Researchers have documented counts exceeding 100 holes per square meter in heavily affected areas near mature hardwoods. A single large tree can be surrounded by thousands of exit holes in the soil beneath its canopy. In less favorable spots, or during annual cicada seasons, you might see only a handful of holes scattered across a yard.
This density matters beyond just appearances. A study of Brood X emergence sites found that undisturbed soils riddled with cicada burrows had roughly an 80 percent increase in how quickly water infiltrated the ground compared to nearby soil without burrows. Where burrows were present, the median infiltration rate was about 14 centimeters per hour versus around 8 centimeters per hour in unaffected soil. In urbanized or compacted sites, though, the effect disappeared, likely because human disturbance had already reduced the soil’s capacity to form the open channels that cicada tunnels create.1Hydrological Processes. Influence of the 2021 Brood X cicada emergence on near surface hydrology in forested and urban landscapes
Distinguishing Cicada Holes from Other Yard Holes
Plenty of creatures make holes in soil, and telling them apart saves you from misidentifying (and mistreating) the wrong critter. Here are the most common lookalikes and how they differ:
- Earthworm castings: Earthworm holes tend to be smaller (a few millimeters across) and surrounded by small mounds of granular, pellet-like castings. The hole itself is irregular, not the smooth circle a cicada leaves.
- Ground-nesting bee holes: Solitary bees like mining bees create holes of similar diameter but often produce a small mound of excavated soil next to the entrance, resembling a tiny anthill. The mound is usually fan-shaped or crescent-shaped, not a chimney.
- Vole or mouse burrows: These are larger, typically an inch to an inch and a half across, and often have a worn, trampled look around the entrance from repeated use. Cicada holes are single-use exits; once the nymph leaves, nothing goes back in.
- Japanese beetle grub holes: Grub exit holes are smaller and more ragged than cicada holes, often appearing in clusters in turf. They do not have the smooth, compacted walls that cicada tunnels have.
- Crayfish chimneys: In wet, low-lying areas near waterways, crayfish build mud chimneys that look superficially like cicada turrets. Crayfish chimneys tend to be taller, wider, and located in perpetually damp ground rather than under tree canopies.
The combination of location (near a tree), size (roughly half an inch), smooth circular shape, and timing (late spring to midsummer) makes cicada holes fairly distinctive once you know what to look for.
What You See Around the Holes
The holes themselves are only part of the scene. Cicada nymphs leave behind exuviae, the tan or amber-colored exoskeletons they shed after climbing out of the ground and onto a nearby vertical surface. If you find a cluster of holes and then spot rows of split-backed, hollow shells clinging to tree bark, fence posts, or garden stakes, you can be certain the holes are cicada exits. The exuviae are often the more eye-catching evidence, since they hang around for weeks or months after the emergence.
You might also notice small piles of loose, granular soil near the holes. Nymphs push displaced dirt to the surface as they dig, and in some cases this creates a ring of fine, crumbly soil around the rim. This ring is less prominent than the mounds left by ground-nesting bees but still visible, especially in dark garden soil or mulch.
Periodical Versus Annual Cicada Holes
The holes left by periodical cicadas (the 13-year and 17-year species in the genus Magicicada) and annual or “dog-day” cicadas (genera like Neotibicen and Megatibicen) look similar but differ in a few ways. Periodical cicada nymphs tend to be slightly smaller than annual cicada nymphs at maturity, so their holes average on the smaller end of the size range. Annual cicada holes can occasionally reach close to an inch in diameter because the nymphs are bigger.
The real difference is density and timing. Periodical broods emerge synchronously by the millions, so you see vast numbers of holes appearing within a span of days. Annual cicadas trickle out over weeks, and their holes appear gradually across the summer. If your yard suddenly looks like someone took a hole punch to the soil under every tree in late May, that is almost certainly a periodical brood. If you notice a few new holes each week from June through August, annual cicadas are the more likely source.
Should You Fill or Fix the Holes
The short answer is that you do not need to do anything. Cicada emergence holes are harmless to lawns, gardens, and foundations. They are shallow enough that they do not undermine structural soil, and the tunnels collapse or fill naturally within a few weeks as rain, earthworm activity, and normal soil settling take their course. Filling them by hand with topsoil or compost is unnecessary, but also harmless, so if the appearance bothers you, go ahead.
Some gardeners worry about the holes drying out root zones or allowing pathogens into the soil. In practice, the tunnels actually improve soil aeration and water penetration in the short term. Research on Brood X emergence sites showed a strong positive correlation between the number of burrows at the surface and water infiltration rates in undisturbed soils.1Hydrological Processes. Influence of the 2021 Brood X cicada emergence on near surface hydrology in forested and urban landscapes The tunnels function as temporary channels that help rainwater soak deeper into the soil profile rather than running off. For garden beds and lawns, this is a net benefit, not a problem.
When Holes Appear and How Long They Last
Periodical cicadas emerge when soil temperatures at a depth of about eight inches reach roughly 64°F (18°C), which typically happens in late April through early June depending on latitude. A warm rain in the evening is the classic trigger for a mass emergence, and you can sometimes watch nymphs climbing out of their holes at dusk. Annual cicadas begin emerging somewhat later, often in June or July, and continue sporadically into September.
The holes are most conspicuous during the first week or two after emergence. They stand open, with clean edges, and are easy to spot. Within a few weeks, foot traffic, rain splash, and natural soil movement begin to blur the edges. By late summer, most holes from a spring periodical emergence have closed over or become indistinguishable from the surrounding soil. In heavily mulched beds, the holes can remain visible a bit longer because mulch does not settle and compact the way bare soil does.
Holes as Forecasting Tools
If you are wondering whether a big periodical cicada emergence is headed your way, monitoring for early holes and turrets is one of the best ground-level methods. In the weeks before a mass emergence, nymphs begin constructing their exit tunnels and may create “test” openings that do not quite break the surface. You can sometimes see the soil heaving slightly or notice tiny cracks and dimples in the dirt near tree bases. Once actual open holes appear, emergence is days away at most.
Entomologists and citizen-science projects ask volunteers to report the first sightings of emergence holes and turrets as a way to track the progress of brood emergences across a region. The appearance of mud chimneys, in particular, tends to precede the main wave of adults by several days, giving homeowners and researchers a heads-up. If you see chimneys forming under your oak tree and the calendar lines up with a known brood year, you can expect a lot more holes in the coming nights.
What the Nymphs Look Like When They Come Out
If you happen to be watching at dusk, you may catch a nymph mid-exit. The creature that climbs out of the hole looks nothing like the winged adult cicada you are used to hearing. Nymphs are pale, brownish-tan insects roughly an inch long, with thick, muscular forelegs adapted for digging. Their eyes are dark and bead-like, and they move with a slow, deliberate crawl. They head for the nearest vertical surface, grip it tightly, and then split their exoskeleton down the back to emerge as a soft, white teneral adult. Over the next hour or so, the wings expand and the body darkens. By morning, the adult has hardened and flown off, leaving the empty shell behind and an open hole below.
Seeing the nymphs in person helps cement the connection between the holes in the ground and the deafening chorus in the treetops a few days later. Each hole represents one individual that has spent years underground, and the sheer number of exit tunnels under a single tree is a vivid reminder of the scale of these emergences. Periodical cicada broods can number in the billions across their range, and a well-situated yard can host thousands of exits within a few square meters of soil.
Holes in Unusual Places
While most emergence holes appear in open soil near trees, nymphs occasionally punch through unexpected surfaces. Gardeners have reported holes in potted plants sitting on the ground, through landscape fabric, and even through thin asphalt patches. Nymphs emerging through cracks in driveways or sidewalks leave distinctive evidence: a small pile of fine soil grains pushed up through the crack, sometimes with the shed exoskeleton clinging to the pavement nearby. Indoor emergences are rare but not unheard of, particularly in older homes with crawl spaces or earthen basements. If a tree’s root system extends under a porch or into a basement, a nymph may surface inside the structure, though this is unusual enough to make local news when it happens.
Swimming pools with surrounding decks can also see emergence activity. Nymphs sometimes surface in the gap between concrete deck slabs or through expansion joints. The holes in these cases are less visible because the surrounding material does not hold the clean circular shape the way soft soil does. Instead, you notice the shed exoskeletons and the small piles of expelled dirt more than the hole itself.