Cicadas: Characteristics, Life Cycle, Habitat, and Interesting Facts
Cicadas are insects belonging to the order Hemiptera and the superfamily Cicadoidea. They are best known for the loud, distinctive calls produced by males of many species during the breeding season. Their sounds can fill forests, gardens, and other outdoor environments, especially during warm weather.
Cicadas have large eyes, broad heads, transparent wings, and specialized mouthparts used to feed on plant fluids. One of their most remarkable characteristics is their life cycle: the young, known as nymphs, typically live underground and feed on fluids from plant roots. Depending on the species, they may remain below the surface for several years before emerging as adults.
What Are Cicadas?
Cicadas are plant-feeding insects found in many parts of the world, particularly in tropical, subtropical, and temperate regions. They belong to the same broad insect order as aphids, leafhoppers, and shield bugs.
There are thousands of described cicada species, varying in size, color, habitat, and behavior. Many have green, brown, black, or gray bodies that help them blend into tree bark and foliage.
Unlike grasshoppers and crickets, cicadas do not produce their characteristic calls by rubbing their legs together. Most singing male cicadas use specialized structures called tymbals, located on the sides of the abdomen, to generate sound.
Physical Characteristics of Cicadas
Cicadas have several distinctive physical features.
- Large compound eyes: Their prominent eyes help them detect movement and navigate their surroundings.
- Transparent wings: Most adult cicadas have two pairs of membranous wings, often marked with visible veins.
- Strong legs: Their legs help them cling to tree trunks, branches, and other surfaces.
- Piercing-sucking mouthparts: A specialized beak, called a rostrum, allows cicadas to draw fluids from plants.
- Tymbals: In many males, these ribbed structures produce sound through rapid deformation and relaxation.
- Exoskeleton: Their external skeleton protects their bodies and provides structural support.
Cicadas vary greatly in size. Some tropical species are relatively large and colorful, while others are small and inconspicuous.
Why Are Cicadas So Loud?
The calls of male cicadas are among the most recognizable sounds of summer in many regions. These sounds are generally associated with communication and reproduction.
How Cicadas Produce Sound
Many male cicadas possess paired tymbals on their abdomen. Muscles rapidly deform these structures, producing repeated clicks that combine into a loud call. The shape of the abdomen and surrounding body structures can help amplify the sound.
The intensity and pattern of a call vary by species. Some cicadas produce continuous buzzing or whining sounds, while others make rhythmic pulses or more complex sequences.
Why Do Cicadas Call?
Cicada calls serve several functions:
- Attracting mates: Males produce species-specific calls that help females locate suitable partners.
- Species recognition: Differences in call patterns help individuals distinguish members of their own species.
- Competition: Males may adjust their calls in response to nearby males.
- Defense: Some cicadas produce sounds when disturbed, although their main calling behavior is often related to reproduction.
Not every cicada species produces loud sounds, and females of most familiar singing species do not generate the same calls as males.
Habitat and Distribution
Cicadas occur on every continent except Antarctica. Most species are associated with woody plants or other vegetation that provides food for both adults and developing nymphs.
Forests and Woodlands
Forests are important habitats for many cicadas. Adults rest on tree trunks and branches, while nymphs develop underground near the roots of suitable plants.
Gardens and Parks
Cicadas commonly inhabit gardens, parks, and residential neighborhoods where trees and shrubs are available. Their calls can be particularly noticeable during periods of warm weather.
Grasslands and Shrublands
Some species occupy shrublands and open landscapes with suitable host plants. Their distribution depends on local vegetation, soil conditions, and climate.
Tropical and Subtropical Regions
Warm regions often support a rich diversity of cicadas. Different species may occupy distinct habitats or emerge at different times of the year.
Underground Habitats
Unlike many insects that spend most of their lives above ground, cicada nymphs develop in the soil. They use their specialized forelegs to move through the earth and reach plant roots from which they obtain food.
The Life Cycle of Cicadas
Cicadas undergo incomplete metamorphosis, developing through three main stages: egg, nymph, and adult.
1. Egg
After mating, females of many species use a specialized structure called an ovipositor to insert eggs into plant tissue, often in small branches or twigs. The exact egg-laying site varies among species.
The eggs hatch after a period determined by the species and environmental conditions.
2. Nymph
After hatching, young cicadas usually move into the soil and begin feeding on fluids from plant roots. Their strong forelegs help them dig through the soil and construct small underground chambers.
Nymphs grow through several developmental stages, shedding their exoskeleton as they increase in size. The underground period varies widely, from relatively short periods in some species to many years in others.
3. Adult Emergence
When development is complete, mature nymphs emerge from the ground, often climbing onto tree trunks, plants, or other surfaces. They then shed their final nymphal exoskeleton, revealing the winged adult.
The discarded exoskeletons can remain attached to trees and other surfaces, making them a familiar sign of cicada emergence.
4. Adult
Adult cicadas mate and reproduce. Many live for several weeks, although their adult lifespan varies by species. After reproduction, adults eventually die, and the next generation begins developing from the eggs.
Why Do Some Cicadas Stay Underground for Years?
One of the most fascinating features of cicada biology is the length of the nymphal stage.
Some species spend only a few years underground, while others have life cycles lasting 13 or 17 years. These exceptionally long cycles are characteristic of certain North American periodical cicadas in the genus Magicicada.
Periodical cicadas emerge in enormous numbers during specific years. Their synchronized emergence may overwhelm predators, allowing enough individuals to survive and reproduce.
However, not all cicadas are periodical. Many species emerge annually, and others appear at different intervals. A cicada heard every summer does not necessarily belong to a species that completes its entire life cycle in one year.
What Do Cicadas Eat?
Cicadas are plant feeders throughout most of their lives.
Nymphs
Underground nymphs use piercing-sucking mouthparts to obtain fluids from plant roots. Their diet consists largely of xylem fluid, a water-rich liquid that transports minerals from roots to other parts of a plant.
Adults
Adult cicadas also feed on plant fluids, commonly from branches and stems. They do not generally chew leaves in the way that grasshoppers do.
Most healthy, established trees tolerate ordinary cicada feeding without serious damage. However, heavy egg-laying by some species can damage young branches and shoots, particularly on small trees and shrubs.
Are Cicadas Harmful to Plants?
Cicadas generally have limited effects on mature, healthy trees, but their impact depends on the species and population density.
Root Feeding
Nymphs obtain fluids from roots, usually without causing major damage to established trees under ordinary conditions. The effects can be more noticeable when plants are young, stressed, or exposed to unusually high insect densities.
Branch Damage
Females of some species cut slits into branches or twigs to lay their eggs. This can cause small branches to wilt, split, or die, a type of damage sometimes called flagging.
Protecting Young Trees
During large periodical cicada emergences, gardeners may protect small or newly planted trees with suitable insect netting. The netting should have openings small enough to prevent cicadas from reaching the branches, and it should be installed and removed at appropriate times.
Chemical control is generally unnecessary for most cicadas. Management decisions should take the species, local conditions, and vulnerability of the plants into account.
Cicadas and Their Role in Ecosystems
Cicadas are important members of many ecosystems.
Food for Wildlife
Adult cicadas and their nymphs provide food for birds, mammals, reptiles, amphibians, and predatory insects. During mass emergences, the sudden abundance of cicadas can provide a major temporary food source.
Nutrient Cycling
When large numbers of cicadas die, their bodies decompose and return nutrients to the soil. This can influence nutrient availability in forests and other habitats.
Effects on Vegetation
Cicada feeding and egg-laying can influence plant growth, particularly when populations are large. These interactions form part of the natural relationship between insects and their host plants.
Ecological Research
Periodical cicadas are valuable subjects for studying insect evolution, predator-prey relationships, synchronized emergence, and the effects of long developmental cycles.
Threats to Cicadas
Cicadas face several environmental pressures, although the severity differs among species.
- Habitat loss: Removing trees and destroying woodland can eliminate feeding and breeding habitats.
- Pesticide exposure: Insecticides may harm cicadas and other non-target insects.
- Climate change: Changes in temperature and rainfall may affect development and emergence timing.
- Soil disturbance: Construction, intensive landscaping, and other activities can damage underground nymphs.
- Loss of host plants: Changes in vegetation can reduce the availability of suitable food sources.
Protecting native trees, maintaining diverse landscapes, and reducing unnecessary pesticide use can help support cicada populations.
Interesting Facts About Cicadas
- They are not locusts: Cicadas and locusts belong to different insect groups.
- Males produce many of the familiar calls: In numerous species, males sing to attract females.
- Their young live underground: Nymphs commonly feed on fluids obtained from plant roots.
- Some species have exceptionally long life cycles: Certain periodical cicadas emerge after 13 or 17 years underground.
- They shed their exoskeletons: The empty nymphal skins often remain attached to tree trunks after adults emerge.
- They do not chew leaves like grasshoppers: Their mouthparts are adapted to sucking plant fluids.
- Some emerge in huge numbers: Periodical cicadas can appear in extraordinary densities during emergence years.
- Their calls are species-specific: Differences in sound patterns help individuals recognize potential mates.
Frequently Asked Questions
What are cicadas known for?
Cicadas are best known for the loud calls produced by males of many species, their transparent wings, and their unusual life cycles.
Why do cicadas make so much noise?
Males generally call to attract females and communicate with members of their species. Their specialized tymbals produce the sound.
What do cicada nymphs eat?
Cicada nymphs usually live underground and feed on fluids from plant roots, primarily xylem fluid.
How long do cicadas live underground?
The underground period varies by species. Some cicadas remain underground for a few years, while certain periodical cicadas spend 13 or 17 years developing before emerging.
Are cicadas dangerous to humans?
Cicadas are generally harmless to people. They do not normally sting or bite humans, although they may fly into people accidentally.
Do cicadas damage trees?
Most cicadas cause little harm to mature, healthy trees. However, heavy feeding or egg-laying can affect young trees and branches, especially during large population emergences.
What is the difference between cicadas and locusts?
Cicadas are sap-feeding insects in the order Hemiptera. Locusts are certain grasshopper species in the order Orthoptera that can form large migratory swarms.
Why do cicadas leave their skins on trees?
The skins are the shed exoskeletons of mature nymphs. After climbing out of the soil, a nymph molts and emerges as a winged adult.
Conclusion
Cicadas are remarkable insects known for their powerful calls, distinctive appearance, and long underground development. Their nymphs typically feed on fluids from plant roots, while adults live above ground and reproduce. Although large populations can occasionally damage young branches, cicadas play valuable roles in food webs and nutrient cycling. Understanding their life cycles and ecological importance helps explain why these noisy insects are such a memorable part of many natural environments.