Where 13-Year Periodical Cicadas Spend Their Underground Phase

Periodical cicadas are among nature’s most fascinating insects, known for their extraordinary life cycles and synchronized emergences. One of the most well-known types is the 13-year periodical cicada, which spends the vast majority of its life underground before emerging in overwhelming numbers for a brief but spectacular aboveground phase. But where exactly do these cicadas spend those long 13 years beneath the surface? In this article, we will explore the underground habitat of 13-year periodical cicadas, how they survive, and what makes this subterranean phase crucial to their lifecycle.

The Life Cycle of 13-Year Periodical Cicadas

Periodical cicadas belong to the genus Magicicada, which includes species with either 13- or 17-year life cycles. The 13-year varieties are primarily found in the southern United States, while the 17-year cicadas dominate northern regions. Despite differences in cycle length, their life stages are quite similar:

Egg Stage: Adult females lay eggs in small slits they cut into tree branches.

Nymph Stage: After hatching, nymphs drop to the ground and burrow underground.
Underground Development: Nymphs feed on xylem fluids from tree roots while developing through several instars (growth stages).
Emergence: After 13 years, the mature nymphs tunnel to the surface to molt into adult cicadas.

Adult Stage: Adults live aboveground for about 4-6 weeks to mate and lay eggs, completing the cycle.

The underground stage constitutes roughly 99% of their lifespan and is essential for growth and maturation.

The Underground Habitat: Where Do They Live?

Depth and Location

Once hatched, cicada nymphs immediately burrow into the soil, usually within a few feet of the tree where they were born. Most periodical cicada nymphs reside at depths ranging from 8 to 24 inches (20 to 60 cm) below ground, although some reports indicate occasional presence down to around 30 inches (75 cm). The exact depth depends on several factors including soil type, moisture levels, root availability, and temperature.

Because the nymphs feed on tree roots by inserting their piercing-sucking mouthparts into xylem vessels, their underground location is tightly linked to where suitable host trees grow. Common hosts include oaks (Quercus spp.), hickories (Carya spp.), maples (Acer spp.), and various other deciduous trees native to their range.

Soil Preferences

The type of soil influences how easily nymphs can burrow and access roots. Loamy or sandy soils that drain well are preferred since heavy clay or waterlogged soils can impede movement and increase mortality risks.

Loamy Soil: Provides balance between nutrient retention and drainage.

Sandy Soil: Easier for digging but may require proximity to roots for sufficient nutrition.
Clay Soil: Less favorable due to hardness and poor aeration.

Root Zone Dependency

Periodical cicadas rely exclusively on tree roots for sustenance during their underground phase. By tapping into fine feeder roots closer to the surface, they get steady amounts of xylem fluid containing water and minimal nutrients. This fluid supports them through slow development as they molt multiple times over the years.

Interestingly, different species of Magicicada may prefer different tree species or root zones based on local availability. This root dependency means that healthy forests with diverse tree populations provide optimal habitats.

How Do Cicadas Survive Underground for So Long?

Spending over a decade underground may seem like a daunting survival challenge for any insect. Yet periodical cicadas have evolved remarkable adaptations that enable them to thrive during this extended subterranean phase.

Slow Growth and Metabolism

Cicada nymphs grow very slowly compared to many other insects. Their metabolism is extremely low while underground, conserving energy over time.

They molt about five times during development.
Each instar stage can last several years.
Feeding on nutrient-poor xylem fluid means energy intake is limited.

This slow metabolic rate allows them to survive on scarce resources without exhausting their energy reserves quickly.

Protection from Predators

Being underground shields nymphs from many aboveground predators such as birds or mammals. Soil acts as a barrier against environmental extremes like temperature fluctuations and storms as well.

However, some predators can still reach them underground, like moles or certain parasitic wasps, but overall predation is significantly reduced compared to aboveground life.

Temperature Regulation

Soil temperature remains more stable than surface air temperatures throughout seasons. This stability allows nymphs to avoid extreme cold or heat that could be fatal.

In winter months, nymphs enter a state similar to dormancy but can still feed minimally from roots when available during warmer spells.

Water Availability

Because they feed on xylem sap drawn from tree roots transporting water, nymphs have consistent access to hydration even during dry periods.

This water intake helps maintain physiological processes necessary for survival throughout their long developmental period.

The Final Year: Preparing for Emergence

As the 13th year approaches completion, mature nymphs prepare to emerge. They sense environmental cues such as soil temperature reaching approximately 64degF (18degC), signaling spring’s arrival.

At this point:

Nymphs tunnel upward through soil toward the surface.
They usually emerge at night or early morning when conditions are humid.
Once aboveground, they find nearby vegetation or vertical surfaces on which to molt into adults.

The emergence often occurs en masse involving thousands or millions of individuals across large geographic areas , a phenomenon known as a “brood.” This synchronized emergence overwhelms predators by sheer numbers, increasing individual survival chances during mating.

Environmental Impact of Underground Cicadas

The prolonged underground presence of periodical cicadas plays an ecological role beyond just individual survival:

Soil Aeration: Their tunneling activities help aerate soil layers improving nutrient cycling.

Root Pruning: Feeding can prune weaker tree roots stimulating new root growth in some cases.
Nutrient Input: When adults die after mating season aboveground, their decomposing bodies add nutrients back into forest soils.
Food Web Contribution: Cicada nymphs serve as prey for subterranean animals contributing energy flow within ecosystems.

Conclusion

The underground phase of 13-year periodical cicadas is a marvel of evolutionary adaptation involving a delicate balance between soil environment, host tree availability, and biological survival strategies. These insects spend most of their lives hidden beneath our feet at depths generally between 8 to 24 inches in well-drained soils rich with tree roots , feeding slowly on xylem fluids until they reach maturity after thirteen years.

Their ability to remain protected yet sustained underground allows them to emerge spectacularly in massive broods that have fascinated humans for centuries. Understanding where these cicadas live below ground not only sheds light on their fascinating life history but also highlights the interconnectedness between soil ecosystems and forest health crucial for sustaining biodiversity.

Next time you witness a mass emergence of periodical cicadas filling warm spring air with buzzing chorus sounds , remember these insects spent over a decade quietly thriving beneath your feet before appearing suddenly in one grand finale celebration of life!