Most cicada nymphs spend their underground years at surprisingly modest depths, with the majority of feeding chambers found between about 7 and 36 centimeters below the surface. That is roughly the depth of a garden trowel blade to a bit past a ruler’s length. Some species dig deeper, and at least one tropical cicada constructs vertical shafts reaching a full meter, but the typical North American periodical cicada lives most of its life in the upper soil horizons where tree roots are densest. What makes their underground existence remarkable is not the depth itself but rather the sheer duration and the slow-motion biological drama playing out in near-total darkness.
Where Nymphs Settle in the Soil
The best field data on burrowing depth comes from studies of periodical cicadas in the midwestern United States, where researchers excavated soil profiles in areas with known populations. Most feeding cells, the small chambers nymphs construct around themselves while attached to a root, were concentrated in the AB soil horizon at depths of 7 to 36 cm.1Soil Science Society of America Journal. Soil Disturbance by the Emergence of Periodical Cicadas That range makes biological sense: it is the zone where most fine tree roots grow and where soil still holds enough moisture and oxygen for an insect to survive for years.
In laboratory settings, nymphs of the smaller species Cicadetta calliope, collected along the Kansas River, constructed sediment-enclosed cells that were 20 to 40 mm long and averaged about 9 mm wide when placed in layered colored sand. These nymphs burrowed immediately after being introduced to the enclosure, excavating air-filled chambers within the substrate.2GeoScienceWorld (PALAIOS). Traces and burrowing behaviors of the cicada nymph Cicadetta calliope: Neoichnology and paleoecological significance of extant soil-dwelling insects Those cell dimensions reflect a small species; periodical cicada nymphs, which are substantially larger, build proportionally bigger chambers. But the general pattern holds: a nymph digs down to root level, constructs a chamber, plugs its mouthparts into a root, and stays put until it is time to molt or relocate to a different feeding site.
The nymphs do not just pick one spot and remain there for the entire 13 or 17 years. They move through the soil periodically, constructing new cells as they grow through successive developmental stages. Each move leaves behind a backfilled tunnel, a pattern that geologists call a meniscate trace, recognizable by the crescent-shaped layers of repacked soil. These tunnels can extend somewhat deeper than the feeding chambers themselves, but the overall lifestyle keeps the nymphs within the root zone.
What They Eat and Why It Takes So Long
A cicada nymph underground is not hibernating or waiting passively. It is feeding, slowly and continuously, on fluid drawn from tree roots. Histological work on tree roots where periodical cicada nymphs had fed showed that the insects’ salivary sheaths, the tiny tubes they push into plant tissue, terminated exclusively in xylem vessels. No salivary sheaths were found in phloem cells.3Ecological Entomology. Xylem feeding by periodical cicada nymphs on tree roots This distinction matters enormously. Phloem sap is sugar-rich and packed with nutrients, which is what aphids tap into. Xylem fluid, by contrast, is extremely dilute, mostly water with trace minerals and amino acids. It is the arboreal equivalent of trying to survive on very weak broth.
This nutritional poverty is thought to be one reason periodical cicadas require such extraordinarily long development times. A nymph sipping xylem for 13 or 17 years is slowly accumulating enough resources to build an adult body, and the diluteness of its food supply means the process cannot be rushed. The nymphs excrete amino acids rather than sugars, another marker of their xylem-feeding habit that distinguishes them from phloem-feeding insects.3Ecological Entomology. Xylem feeding by periodical cicada nymphs on tree roots
Annual cicadas, the ones you hear every summer, also feed on xylem as nymphs but spend only two to five years underground depending on the species. Even their shorter timelines are lengthy compared to most insects, reinforcing how fundamentally challenging xylem feeding is as a survival strategy.
How Soil Conditions Shape Survival
Not all soil is equally hospitable. A study testing how soil compaction affects different cicada species found a stark pattern: as soil density increased, burrowing success dropped across the board. At the highest compaction levels, which mimicked the conditions found in urban and heavily trafficked soils, only one species, Cryptotympana facialis, managed to burrow at all. Nymphs of three other species were essentially shut out, with just a single individual of Platypleura kaempferi succeeding at the tightest compaction.4PubMed Central. Urban soil compaction reduces cicada diversity
This finding has real consequences for cicada diversity in cities. Sidewalks, roads, and construction equipment compress soil far beyond natural levels, and the species that cannot push through packed earth simply vanish from those areas. The research suggests that urban development does not just remove trees, though that matters too. It changes the physical character of the ground in ways that filter out all but the hardiest burrowing species. If you have noticed that city parks tend to produce only one or two cicada species while nearby forests host several, soil compaction is a likely culprit.
Moisture matters as well. Nymphs need soil damp enough to breathe through their cuticle and soft enough to excavate, but not so waterlogged that their chambers flood. Sandy loams and well-drained forest soils tend to support the densest cicada populations, while heavy clay or chronically saturated ground is less favorable.
How They Know When to Come Up
After years underground, nymphs somehow synchronize their emergence, crawling to the surface within days or weeks of each other. Two environmental signals appear to drive this timing: soil temperature and rainfall.
Temperature has long been the leading explanation. When soil at nymph depth warms past a threshold in spring, somewhere around 18°C (64°F) for most periodical cicada broods, the nymphs begin tunneling upward. Researchers studying the thermophysics of this process have focused on how underground cicadas, each experiencing slightly different local soil temperatures, manage to coordinate their emergence into the massive synchronized swarms that periodical cicadas are famous for.5PubMed. How do cicadas emerge together? Thermophysical aspects of their collective decision-making Even small variations in shade, soil type, and depth create a patchwork of thermal microclimates, so the coordination is not as simple as “everyone hits 18°C on the same day.”
Rainfall adds another layer. A study of three cicada species in urban habitats found that precipitation roughly two weeks before emergence was a strong predictor of how many nymphs surfaced. Each additional 100 mm of rain at that two-week lag was associated with roughly double the emergence count in one species, and about 60 percent higher emergence in the other two. Rain one week prior had no detectable effect, and rain three weeks prior showed a smaller but still measurable influence.6PubMed Central. Rainfall Timing as a Key Driver of Cicada Peak Emergence in Urban Habitats The two-week lag suggests the nymphs are responding to the softening and moistening of soil that follows a soaking rain, rather than to the rain itself hitting the surface.
You may have noticed that big cicada emergences often follow warm rainy spells in late spring. That pattern is consistent with these findings: the warmth triggers the upward movement, and the rain loosens the soil enough for mass exit.
What Cicada Tunnels Do to the Ground
When billions of nymphs tunnel to the surface at once, they leave behind a vast network of finger-width holes. These exit tunnels are not trivial. Measurements taken during the 2021 Brood X emergence showed that soils with cicada burrows had roughly 80 percent higher water infiltration rates than nearby soils without them. The median rate in burrowed soils was about 14 cm per hour, versus about 8 cm per hour in unburrowed ground.7Hydrological Processes. Influence of the 2021 Brood X cicada emergence on near surface hydrology in forested and urban landscapes
This effect was strongest in undisturbed forest soils, where there was a clear correlation between the number of surface burrows and the rate at which water soaked in. In urban and disturbed sites, the correlation disappeared, likely because soil compaction and other human impacts collapsed the tunnels or prevented them from forming connected pathways.7Hydrological Processes. Influence of the 2021 Brood X cicada emergence on near surface hydrology in forested and urban landscapes
The practical effect is that a mass cicada emergence acts as a natural aeration event for forest soils. The tunnels channel rainwater deeper into the ground, recharging shallow groundwater and potentially reducing surface runoff. After the holes eventually collapse and fill in, the soil retains some of the improved structure for a while. For forests, this periodic reworking of the upper soil is part of the ecosystem service cicadas provide, even though we usually think of them only as noisy adults.
Do Nymphs Harm the Trees They Feed On?
Given that cicada nymphs spend over a decade sucking xylem from tree roots, you might expect them to seriously damage their host trees. The evidence is more nuanced. A study examining tree ring growth in five midwestern tree species found no detectable effect from root parasitism in the years before emergence. The nymphs apparently draw so little fluid at any given moment that the trees compensate without measurable growth loss.8The American Midland Naturalist. The Effect of Periodical Cicadas on Growth of Five Tree Species in Midwestern Deciduous Forests
The story changes around emergence time. Three of the five species showed reduced growth the year of or the year after a mass emergence. This dip likely reflects the combined stress of root disturbance as billions of nymphs detach and tunnel upward, plus the egg-laying damage adult females inflict on branches. Interestingly, three of the tree species showed a growth boost about five years after an emergence event.8The American Midland Naturalist. The Effect of Periodical Cicadas on Growth of Five Tree Species in Midwestern Deciduous Forests The decomposing bodies of adult cicadas deliver a pulse of nitrogen and other nutrients to the forest floor, and the delayed growth bump may reflect those nutrients cycling back into the soil and eventually reaching the roots.
Young saplings and newly planted trees are more vulnerable than mature specimens. If you plant a tree in a yard shortly before a major emergence, the combined root feeding and branch flagging from egg-laying can set a small tree back considerably. Mature trees, though, ride out the cycle without lasting harm.
The Brazilian Architect and Deeper Burrows
While most cicada nymphs stay within the upper 30 or so centimeters of soil, some tropical species go much deeper. In the Brazilian Atlantic rainforest, nymphs of Guyalna chlorogena construct vertical shafts that reach up to a meter deep. These nymphs are also builders: each shaft is topped by a mud turret, 20 to 40 cm tall, that the nymph extends upward by about 3 cm each night during an active construction phase.9Springer Link / Neotropical Entomology. An Architect Cicada in Brazilian Rainforest: Guyalna chlorogena (Walker)
Each turret is occupied by a single nymph, male or female, and the structures are conspicuous enough that researchers were able to monitor large numbers of them in the field. The purpose of the turrets is still debated, but leading ideas include thermoregulation, gas exchange, and drainage. Tropical soils in rainforest environments can become waterlogged quickly, and a turret chimney rising above ground level would keep the shaft’s opening above pooling rainwater while allowing air circulation down into the tunnel.
This species stands out as an extreme case, but it illustrates a broader principle: cicada burrowing depth and behavior vary with climate, soil, and species. Temperate periodical cicadas in well-drained forest soil have no need to dig a meter down, because suitable roots exist within the first 30 cm. A tropical species dealing with different root architecture, different moisture regimes, and different predator pressures may solve the same survival problems in a very different way.
Built for Digging
Cicada nymphs are anatomically specialized for a life of excavation. Their front legs are heavily modified, with enlarged femora bearing comb-like ridges and robust tibial teeth that work together like miniature shovels or picks. These structures are so distinctive that entomologists can identify cicada nymphs in the fossil record primarily by their leg anatomy.10PubMed Central. Mesozoic evolution of cicadas and their origins of vocalization and root feeding
Fossil nymphs preserved in Cretaceous-era amber show the same basic toolkit: developed femoral combs, strong apical tibial teeth, and the overall limb proportions of an animal built to move through soil. Some fossil specimens resemble the leg structure of modern Cicadidae, while others show the heavier, more plier-like forelegs characteristic of the ancient family Tettigarctidae, which survives today only in Australia.10PubMed Central. Mesozoic evolution of cicadas and their origins of vocalization and root feeding The persistence of this digging body plan across tens of millions of years speaks to how fundamental the underground phase is to cicada biology. These insects did not evolve burrowing as a recent trick; their lineage has been subterranean since dinosaurs walked overhead.
Ancient Traces in Stone
The underground chambers cicada nymphs construct are durable enough to fossilize. Researchers have identified fossil feeding cells attributed to cicada nymphs in deposits ranging from the late Paleozoic through the Cenozoic, with the distinctive meniscate backfill patterns serving as a diagnostic signature.2GeoScienceWorld (PALAIOS). Traces and burrowing behaviors of the cicada nymph Cicadetta calliope: Neoichnology and paleoecological significance of extant soil-dwelling insects A study of modern Cicadetta calliope nymphs and their traces established that these insects are excellent analogs for understanding the meniscate trace fossils that turn up frequently in ancient alluvial soils.
More recently, feeding chambers classified under the trace-fossil genus Feoichnus were described from Maastrichtian-age paleosols in Brazil, dating to the very end of the Cretaceous period, roughly 66 to 72 million years ago. These chambers were elongated, hemispherical, and upwardly concave, with a distinct lining on their inner walls.11Cretaceous Research. Cicada nymph trace fossils from South American Maastrichtian paleosols The lining detail is telling: modern cicada nymphs smooth and reinforce the interior of their cells with a mixture of saliva and fine soil particles, and the fossil chambers show the same feature preserved in stone.
Finding cicada burrows in rocks that formed before the end-Cretaceous extinction event means that these insects were already well established in their underground lifestyle while non-avian dinosaurs still existed. The underground world of cicadas is not just old in evolutionary terms; it is one of the longest-running ecological relationships between insects and plant roots on record. The trees have changed, the continents have shifted, and the soil itself has been remade countless times, but the basic arrangement, a nymph in a chamber on a root, sipping xylem in the dark, has persisted for at least 70 million years.