What Do Brown Cicadas Eat? Understanding Their Diet

Cicadas are fascinating insects known for their distinctive sound, often heard during warm summer months. Among the many species of cicadas, brown cicadas are quite common and recognizable due to their earthy coloration and robust bodies. While many people are familiar with their loud mating calls, fewer understand what these insects actually eat. This article delves into the diet of brown cicadas, exploring their feeding habits, the role of their diet in their life cycle, and the impact they have on their environment.

Introduction to Brown Cicadas

Brown cicadas belong to the family Cicadidae and are found in various parts of the world, including North America, Asia, and Europe. Their brown coloration helps them blend into tree bark and soil, providing camouflage from predators. Unlike some brightly colored or patterned insects, brown cicadas rely on their subtle hues and elusive behavior to avoid detection.

These insects are most notable for their unique life cycles, which can span several years underground before they emerge as adults. This extended developmental period is closely tied to their feeding habits.

The Feeding Mechanism of Cicadas

To understand what brown cicadas eat, it’s essential to first learn how they feed. Cicadas have specialized mouthparts designed for piercing and sucking – a structure known as a rostrum or proboscis. This needle-like organ allows them to pierce plant tissues, primarily stems and roots, to access sap.

Unlike chewing insects that consume leaves or other solid plant parts, cicadas rely on liquid nourishment. Their diet is exclusively composed of plant fluids rather than solid plant material or other insects.

What Do Brown Cicadas Eat?

Nymph Stage Diet: Root Sap

The vast majority of a brown cicada’s life is spent underground as a nymph. During this stage, which can last from several years up to 17 years depending on the species, the nymphs feed exclusively on the xylem sap from the roots of plants and trees.

Xylem Sap: This is the watery fluid transported from roots to leaves, rich mainly in water and minerals but low in organic nutrients like sugars.
Root Access: Brown cicada nymphs use their piercing mouthparts to tap into fine roots and extract this nutrient-poor sap.

It may seem surprising that these nymphs survive on such a dilute food source. However, cicadas have evolved unique physiological adaptations to filter out excess water while extracting nutrients efficiently. They process large volumes of xylem sap daily to meet their energy needs.

Adult Stage Diet: Stem and Branch Sap

Once brown cicada nymphs complete their underground development, they emerge from the soil and molt into adults. The adult cicadas climb onto tree trunks or branches where they use their rostrum to feed by piercing stems and branches instead of roots.

Sap Source: Adults mostly feed on phloem sap or sometimes xylem sap found within branches.
Phloem vs Xylem: Phloem sap carries sugars and organic compounds produced through photosynthesis from leaves to other parts of the plant. It is richer in nutrients compared to xylem sap.

Feeding Behavior: Adult brown cicadas often remain stationary or move slowly while feeding for extended periods.

Adult feeding sustains them during their brief reproductive phase which may last only a few weeks. During this time, they focus on mating calls and reproduction rather than growth.

Nutritional Aspects of Brown Cicada Diet

Low Nutrient Intake Requires Adaptations

The primary food sources for brown cicadas are relatively low in nutrients compared to solid plant tissues or animal prey. Both xylem and phloem sap contain water and sugars but lack many proteins and lipids needed for insect development.

To thrive on such a diet:

Large Volume Consumption: Cicadas consume large amounts of sap daily.
Efficient Digestion: They possess symbiotic microorganisms in their gut which help synthesize essential amino acids missing from sap.
Water Processing: Excess water is expelled as droplets through a process called ‘honeydew’ excretion.

Impact on Metabolism

Because sap is watery and low in calories relative to solid foods like leaves or seeds:

Brown cicadas have slower metabolisms during their long nymph stage.
Rapid energy use is reserved for adulthood when activities such as flying and calling demand more energy.

Environmental Impact of Brown Cicada Feeding

While brown cicadas generally do not cause significant damage to healthy trees, their feeding behavior does influence plant health:

Minor Stress on Trees

Piercing roots during nymph feeding may stress young or weakened plants.
Adult feeding on stems can occasionally cause twig dieback if populations are very dense.

However, these impacts are typically minimal because:

Cicadas spread out over a wide area.
Plants usually tolerate low-level sap extraction without permanent harm.

Role in Ecosystems

Brown cicadas also play an important ecological role:

Their excreted honeydew provides food for ants and other insects.
They serve as prey for birds, reptiles, and mammals.
The emergence of large numbers contributes nutrients back into the soil through molted skins and decomposing bodies.

Common Myths About Brown Cicada Diet

There are several misconceptions about what brown cicadas eat:

Myth: “Cicadas chew leaves.”
Fact: Cicadas do not have chewing mouthparts; they feed exclusively by sucking plant sap.
Myth: “Cicadas damage crops by eating fruit.”
Fact: Adults rarely feed on fruit; damage from egg-laying slits can be more relevant than feeding itself.

Myth: “Cicada nymphs eat soil or detritus.”
Fact: Nymphs live underground but feed solely on root sap via piercing mouthparts.

Understanding these facts helps reduce unnecessary fear of cicadas harming plants or crops significantly.

How to Observe Brown Cicada Feeding Behavior

Observing brown cicada feeding can be challenging because:

Nymphs live underground hidden near roots.
Adults often remain still while feeding high up on tree branches.

Still, you can spot adult feeding by looking for:

Stationary brown cicadas clinging to tree bark.
Small puncture marks or darker spots where rostrums pierce stems.
Presence of clear droplets (honeydew) indicating active sap feeding.

Listening for male calling songs often leads you close to feeding adults since calling occurs nearby feeding sites.

Conclusion

Brown cicadas have a unique diet centered around feeding on plant sap at different life stages—root xylem sap during the long underground nymph phase and stem or branch sap during their short adult phase. Though nutritionally limited, this diet supports their development thanks to specialized adaptations like symbiotic gut microbes and efficient water processing.

While brown cicadas’ feeding has minor effects on individual plants, they play valuable roles within ecosystems as prey items and contributors to nutrient cycling. Understanding what brown cicadas eat helps demystify these intriguing insects beyond their noisy reputation and highlights nature’s complex interdependencies.

By recognizing that these insects subsist largely on liquid plant fluids rather than solid vegetation, gardeners and nature enthusiasts can better appreciate the subtle balance between insect survival strategies and healthy plant life.