The emergence of cicadas is a natural phenomenon that often sparks concern about their impact on human life. Cicadas are large insects that spend most of their lives underground as nymphs, feeding on tree roots. They are categorized into two groups: annual cicadas, which emerge every year, and periodical cicadas, which emerge simultaneously in massive numbers every 13 or 17 years. After years of development, they emerge as adults for a short, noisy mating season lasting only a few weeks. The sheer numbers of periodical broods, which can reach trillions of individuals, prompt questions about how they interact with people.
Addressing Direct Physical Threats
Cicadas pose virtually no direct physical threat to humans, pets, or wildlife. They do not bite, sting, or carry diseases transmissible to people. The insects lack venom and stingers. Furthermore, cicadas are not blood feeders, which eliminates the risk of them transmitting pathogens like mosquitoes or ticks.
Their mouthparts are designed for piercing plant tissue to suck sap, not for biting flesh. A cicada might occasionally probe human skin if it mistakenly lands on a person and confuses the skin for a plant stem, but their mouthparts are generally incapable of penetrating deeply enough to cause harm. Any sensation from this is typically a harmless, mild pinch or scratch, resulting from an accidental reaction.
The Impact of Auditory Nuisance
The most tangible interaction humans have with cicadas is the intense noise generated by the males. Male cicadas produce their characteristic sound using specialized abdominal structures called tymbals to attract mates. The rapid buckling and unbuckling of these ribbed membranes create a loud, continuous chorus when large groups aggregate.
Cicada choruses can reach significant decibel levels, sometimes measuring between 90 and 100 dB, comparable to a lawnmower or a motorcycle at close range. In some cases, the sound produced by a single species has been recorded as high as 120 dB. Since prolonged exposure to noise above 85 dB is potentially harmful to human hearing, this volume can cause temporary discomfort.
The Centers for Disease Control and Prevention (CDC) notes that due to the short duration of the emergence (typically only a few weeks), the risk of long-term hearing damage is minimal for most people. However, individuals spending extended periods very close to a dense aggregation may experience temporary effects. Simple mitigation strategies include moving away from the loudest chorusing areas or using ear protection if working nearby.
Secondary Health and Environmental Interactions
While cicadas are not directly harmful, their mass emergence creates secondary nuisance issues related to human health and property. After emerging from the ground, the insects molt their exoskeletons, leaving behind shed skins that accumulate in yards and gardens. These discarded exoskeletons are composed of chitin, a protein also found in the shells of crustaceans.
For individuals with shellfish allergies, the Food and Drug Administration (FDA) advises against eating cicadas, as the shared protein structure can trigger an allergic reaction. Beyond ingestion, the sheer volume of decomposing insect bodies and discarded shells creates a clean-up nuisance. This debris may also contribute minor airborne particulate matter that could irritate sensitive respiratory systems.
Cicadas can also impact human property by damaging young trees and valuable shrubs. Female cicadas use an ovipositor to cut small slits into young branches and twigs to lay their eggs. This egg-laying activity can weaken the branches, sometimes causing them to break or wither, a condition known as “flagging.” While mature, established trees are generally unaffected, newly planted or smaller ornamental trees may require protection, such as fine-mesh netting, to prevent structural damage.