Cicadas pose no direct physical danger to humans or pets. They do not bite, sting, or carry venom, and they are not venomous or poisonous. The real risks are indirect and mostly minor: dogs gorging on too many cicadas can get an upset stomach, people with shellfish allergies may react to eating them, and the sheer surprise of a large, buzzing insect flying into a car has caused a handful of genuine accidents. For the vast majority of people and animals, a cicada emergence is loud and strange but entirely harmless.
Why Cicadas Cannot Hurt You Physically
Cicadas belong to the order Hemiptera, the “true bugs,” and they feed exclusively on plant fluids. Their mouthparts are a thin, straw-like structure designed to pierce tree roots and branches, not skin. They have no stinger, no mandibles capable of breaking human skin, and no venom glands. If a cicada lands on your arm and probes with its mouthpart, you might feel a slight prick, but it is not a bite in any defensive or predatory sense. The insect simply mistakes you for a tree.
They also do not transmit diseases to people. Unlike mosquitoes or ticks, cicadas are not vectors for any known pathogen that infects humans or domestic animals. Their underground lifecycle, spent sucking xylem fluid from roots for years at a stretch, does not bring them into contact with the kinds of microorganisms that cause human illness.
The Panic Factor Is the Biggest Human Hazard
The closest cicadas come to injuring people is through startling them. Periodical cicadas emerge in enormous numbers, fly clumsily, and make a tremendous racket. A case analysis from emergency departments documented incidents where passengers leaped from moving vehicles after cicadas flew in through open windows.1Western Journal of Emergency Medicine. Clinical Insights and Case Analysis of Disorders Attributed to Cicadas in the Emergency Department That kind of reflexive panic, not any property of the insect itself, is what sends people to the hospital.
If you are driving during a heavy emergence, keeping windows up or using screens is the simplest precaution. Cyclists and motorcyclists in emergence zones sometimes wear face shields or glasses to avoid a startled swerve when a cicada hits them at speed. The insects are large enough that a collision at highway speed can sting, but the impact is no different from any other large beetle or moth.
Noise and Its Effects on People
A chorus of male cicadas can be genuinely loud. Some species produce calls exceeding 90 decibels at close range, comparable to a lawnmower or a loud motorcycle. Research on how insect sounds affect human perception found that cicada vocalizations, with calling frequencies above 1,000 Hz and amplitudes greater than 30 Hz, tend to divert attention and reduce engagement, likely because people associate the sound with the discomfort of relentless summer chorusing.2Nature Publishing Group. Empirical study on the effect of single insect sounds on human perception based on pressure and engagement indicators
Sustained exposure to very loud cicada choruses could theoretically contribute to temporary hearing discomfort, especially if you spend hours working directly beneath a heavily populated tree. Wearing earplugs or noise-canceling headphones during peak daytime chorusing is a reasonable step if the noise bothers you. For most people, the annoyance fades within the few weeks the adults are active aboveground.
Are Cicadas Safe for Dogs and Cats to Eat?
Dogs, in particular, find cicadas irresistible. The insects are big, slow, crunchy, and abundant. A dog snapping up a few cicadas is in no danger at all. Cicadas are not toxic, and many wild birds and mammals feast on them with no ill effects. A study in Science found that more than 80 bird species opportunistically switched their diets to include cicadas during the 2021 Brood X emergence.3PubMed. Periodical cicadas disrupt trophic dynamics through community-level shifts in avian foraging If the local bird population can gorge on cicadas without harm, the occasional snack is not going to hurt your dog.
The problem is quantity. A dog that eats dozens of cicadas in a single outing can end up with vomiting, diarrhea, or a temporary intestinal blockage from all those exoskeletons, which are tough and not easily digested. This is the same kind of gastrointestinal upset that happens when a dog eats too much of anything unfamiliar and fibrous. It usually resolves on its own within a day, but a dog that seems lethargic, refuses food, or keeps vomiting for more than 24 hours after a cicada binge is worth a vet visit.
Cats are less likely to overindulge because they tend to bat at things rather than swallow them whole, but the same rules apply: a few are fine, a feast could cause stomach trouble. Small dogs are at slightly higher risk simply because their digestive tract is shorter and a mass of exoskeleton takes up proportionally more space.
Allergic Reactions When Eating Cicadas
Eating cicadas has a long culinary history. Archaeological and etymological evidence from Oaxaca, Mexico, suggests that cicada consumption likely has pre-Hispanic roots, with cicadas serving as a protein source during the dry season alongside the guaje pods of their host trees. In many cultures across Asia, Africa, and the Americas, cicadas remain a normal food item.
The allergy concern is real, though. Cicadas are arthropods, and their muscle tissue contains proteins structurally similar to those found in shrimp, crab, and other crustaceans. A proteomic study of cicada nymphs directly detected the pan-allergens tropomyosin and arginine kinase, both well-known triggers in shellfish allergy. The researchers found high sequence similarity and close evolutionary relationships between these cicada allergens and their counterparts in silkworm and crustaceans, meaning the immune system of someone allergic to shrimp could mistake cicada protein for shrimp protein.4Food Chemistry. Mining allergens in Cryptotympana atrata nymphs: integrating proteomics and homology-based bioinformatics The same study’s modeling predicted several additional potential allergens in cicada tissue, including peroxidase and carboxylesterase.
If you have a known allergy to shellfish, shrimp, or silkworm products, you should treat cicadas as a potential trigger. This applies equally to your pets: dogs with known food allergies, particularly to shellfish-based ingredients in commercial pet food, may also react. The cross-reactivity is not guaranteed for every allergic individual, but treating it as a serious possibility is the sensible approach.
Contaminants in Cicadas
Periodical cicada nymphs spend 13 or 17 years underground, feeding on root xylem. During that time, they can accumulate whatever is in the soil. This raises a fair question: do cicadas pick up enough heavy metals or pesticide residues to be harmful?
The evidence is reassuring for normal circumstances. A study measuring organochlorine and heavy metal concentrations in 17-year cicadas from Maryland found levels well below those known to be harmful to birds. Cicadas contained metal concentrations similar to or lower than other local invertebrates, with the exception that they carried somewhat more copper than earthworms.5PubMed. Organochlorines and heavy metals in 17-year cicadas pose no apparent dietary threat to birds Copper and lead levels at one site were elevated, but that site had received sewage plant effluent from river flooding, a specific contamination source rather than a general pattern.
A separate study confirmed the mechanism behind accumulation: metal concentrations in nymphal exoskeletons track soil metal concentrations, with chalcophile elements binding to sulfur-containing groups in the keratin-rich shell.6Science of The Total Environment. Influence of soil chemistry on metal and bioessential element concentrations in nymphal and adult periodical cicadas (Magicicada spp.) In plain terms, if the soil is clean, the cicadas are clean. If you live near a Superfund site, an old industrial area, or land with known heavy pesticide history, eating large quantities of locally emerging cicadas would be less advisable. For most suburban and rural yards, contaminant levels are not a practical concern.
The Fungus That Makes Cicadas Behave Strangely
One of the stranger aspects of cicada biology involves a parasitic fungus called Massospora. Infected cicadas lose the rear portion of their abdomen, which gets replaced by a chalky mass of fungal spores, yet they continue to fly around and attempt to mate, spreading spores to healthy individuals. Researchers discovered that Massospora produces psychoactive compounds during infection: cathinone, an amphetamine previously known only from plants, and psilocybin, a tryptamine previously known only from certain mushrooms.7PubMed Central. Psychoactive plant- and mushroom-associated alkaloids from two behavior modifying cicada pathogens These chemicals appear to be part of how the fungus manipulates its host’s behavior, keeping the cicada active and social even as its body is destroyed.
This sounds alarming, but it is not a human health risk. You can tell an infected cicada by the white or yellow chalky plug where its abdomen should be. The quantities of cathinone and psilocybin in a single infected insect are trace amounts, far too small to have any pharmacological effect on a person or a pet. Still, the visible fungal infection is a good reason to inspect any cicada you intend to eat and discard ones that look obviously diseased. Dogs will not make that distinction, but a dog eating a few Massospora-infected cicadas is not going to experience anything beyond possible mild stomach upset from the fungal material.
Damage to Trees and Gardens
While cicadas are harmless to people and pets in a direct sense, they can genuinely damage young trees. The harm comes not from the nymphs feeding underground, which is typically too diffuse to injure a healthy tree, but from the adult females laying eggs. Female periodical cicadas use a saw-like ovipositor to slice into pencil-thin branches and deposit eggs inside. The slits weaken the branch, and the portion beyond the cut often wilts and dies, a phenomenon called flagging because the dead brown tips resemble tiny flags drooping from the canopy.
Research on Brood X damage to ornamental trees found that cicadas oviposited in 69 of 84 species and cultivars tested, and the egg-laying wounds caused branch wilting and death in about a third of those species.8Environmental Entomology. Damage to Ornamental Trees and Shrubs Resulting from Oviposition by Periodical Cicada Mature trees handle this without lasting harm because they have thousands of branches and can afford to lose some tips. Young trees, especially newly planted ornamentals and fruit trees with thin trunks and few branches, can be set back severely or even killed if most of their new growth is damaged.
How to Protect Young Trees
The single most effective protection for young trees is physical netting. Multiple studies have compared netting to insecticide treatments and consistently found netting superior. One trial on nonbearing apple trees found that green, tubular, one-centimeter-mesh netting excluded cicadas entirely and was the most effective treatment tested.9Journal of Economic Entomology. Effects and Control of Periodical Cicada (Homoptera: Cicadidae) Oviposition Injury on Nonbearing Apple Trees A separate comparison of netting versus imidacloprid, a systemic neonicotinoid insecticide, found that netted trees sustained very little injury while unprotected trees were heavily damaged; the insecticide did not provide reliable protection.10Journal of Economic Entomology. Comparison of Exclusion and Imidacloprid for Reduction of Oviposition Damage to Young Trees by Periodical Cicadas (Hemiptera: Cicadidae)
Practical advice for a homeowner expecting a periodical brood emergence:
- Net early: Drape fine mesh netting (about one centimeter or smaller) over any tree you planted in the past two to three years, securing it at the trunk before adults begin emerging.
- Delay new planting: If a brood is due next spring, wait until the following year to plant new fruit or ornamental trees.
- Skip the sprays: Insecticides have not shown reliable results against oviposition damage, and broad-spectrum sprays kill beneficial insects along with cicadas.
- Leave mature trees alone: Flagging on a large oak or maple looks dramatic but almost never threatens the tree’s long-term health.
How Cicada Emergences Ripple Through Ecosystems
Periodical cicada emergences are among the most dramatic resource pulses in temperate forests. When billions of cicadas surface simultaneously, they swamp every predator in the area with more food than could possibly be consumed. The research on Brood X documented a striking cascade: as over 80 bird species switched to eating cicadas, they stopped hunting caterpillars and other herbivorous insects. Released from that predation pressure, caterpillar densities roughly doubled, and so did the leaf damage on host oak trees.3PubMed. Periodical cicadas disrupt trophic dynamics through community-level shifts in avian foraging
For a homeowner, this can mean more caterpillars chewing on your garden during and just after a cicada year. The effect is temporary, usually resolving within weeks as bird foraging patterns return to normal and cicada adults die off. But it is a good reminder that the ecological consequences of an emergence extend well beyond the insects themselves. Your oak tree might lose more leaves to caterpillars than usual, your garden might see an uptick in leaf-chewing pests, and insect-eating birds might temporarily ignore the feeders you set out for them.
Cicadas as Food for Humans
In parts of the world, people have been eating cicadas for centuries. In Oaxaca, Mexico, archaeological and etymological evidence points to cicada consumption with pre-Hispanic roots, where cicadas and their host plant’s seed pods together provided protein during the dry season. Across East Asia and parts of sub-Saharan Africa, cicadas are collected, roasted, fried, or ground into flour as a normal component of the diet.
For someone curious about trying cicadas during an emergence, a few practical points are worth knowing. Newly emerged adults, called tenerals, are considered the best for eating because their exoskeleton has not yet hardened, making them softer and milder in flavor. Collect them early in the morning when they are still pale and sluggish on tree trunks. Avoid cicadas from areas treated with pesticides or near busy roadways where exhaust particulates settle on the ground. As discussed above, anyone with a shellfish allergy should avoid them entirely. Cook them before eating; roasting, sautéing, or boiling kills any surface bacteria and makes the texture more palatable. The protein content is substantial, and the flavor is often compared to nuts or shrimp depending on preparation.
For pets, you do not need to worry about “allowing” them to eat a few. The concern is exclusively about volume. If your dog is scooping up cicadas by the mouthful on every walk, shorter leash outings through the worst emergence zones and a firm “leave it” command are your best tools. Most dogs lose interest once the novelty wears off or the emergence winds down.