What Eats a Cicada? The Predators That Hunt Them

Practically everything with a mouth eats cicadas. Birds, mammals, reptiles, amphibians, fish, spiders, and even other insects all take advantage of these large, slow-moving, protein-rich insects. Periodical cicadas in particular, which emerge in synchronized broods of billions after years underground, are so defenseless that researchers describe them as lacking toxins, stingers, or biting mouthparts of any kind. The sheer breadth of animals that prey on cicadas is matched only by the staggering volume of cicadas available to be eaten, and that relationship between predator abundance and prey abundance turns out to be the central drama of cicada ecology.

Birds Are the Headline Predators

Birds are the most visible and best-studied cicada predators. During the 2021 emergence of Brood X, one of the largest periodical cicada broods in eastern North America, researchers documented more than 80 bird species opportunistically switching their foraging to include cicadas.¹ That is an extraordinary number. It means the majority of common bird species in the emergence zone abandoned their usual food sources and gorged on cicadas instead. Blue jays, crows, robins, grackles, sparrows, warblers, woodpeckers, and raptors all participated. Even species that typically eat seeds or berries were spotted picking off cicadas.

Studies of 13-year periodical cicadas found a similar pattern. Early emergers in May were eaten heavily by birds, but as emergence ramped up and millions more cicadas appeared, individual birds could not keep pace. At low densities, birds consumed roughly 15 to 40 percent of the standing cicada crop. But where cicada densities exceeded about 24,000 individuals per hectare, birds barely made a dent. Across the entire emergence, avian predators consumed only about 15 percent of the total adult cicada population.² The birds were physically full. They could not eat any more.

Mammals, Reptiles, and Everything Else

The list of mammalian cicada predators reads like a field guide to North American wildlife. Squirrels, raccoons, opossums, skunks, foxes, and domestic dogs and cats all eat cicadas during emergences. Research on apex mammalian predators found that the combination of large body size (cicada bodies can reach 33 millimeters long), superabundance, and a complete lack of chemical or physical defenses makes periodical cicada emergences an extreme resource pulse exploited by mammals, birds, reptiles, and arthropods alike.³

Among the more surprising mammalian predators, brown bears in Japan have been observed digging into the soil to excavate cicada nymphs before they even emerge.⁴ This is a different dynamic than surface predation on adults. The nymphs live underground for years, feeding on root sap, and bears apparently learned to locate and dig them up as a calorie-dense food source. It suggests that cicadas face predation pressure at every life stage, not just during their dramatic above-ground emergences.

Reptiles and amphibians round out the vertebrate predators. Snakes, lizards, turtles, and frogs all eat cicadas when the opportunity arises. Spiders catch them in webs. Predatory wasps, particularly cicada killer wasps (genus Sphecius), are specialized hunters that paralyze cicadas and drag them into burrows to feed their larvae. These wasps are among the few predators that have evolved specifically to exploit cicadas rather than simply taking advantage of an easy meal.

What Happens When Cicadas Fall into Water

Not all cicadas die on land. During mass emergences, huge numbers of cicada bodies end up in streams, ponds, and other water bodies, either blown in by wind or falling from overhanging trees. This creates a significant food pulse for aquatic ecosystems. Researchers studying the Brood X emergence quantified the deposition of cicada detritus into woodland ponds and low-order streams and found that the influx of organic matter reshaped local food webs.⁵ Fish, crayfish, and aquatic invertebrates feast on drowned cicadas. Trout and bass in emergence zones are known to gorge so aggressively on floating cicadas that fly-fishing guides design lures specifically to mimic them during brood years.

The effect is not just about direct consumption. Decomposing cicada bodies release nutrients into the water, boosting algae growth and feeding organisms further down the food chain. A single emergence can temporarily alter the nutrient balance of small forest ponds, with effects that persist for weeks after the last cicada has died.

A Fungal Parasite That Turns Cicadas into Zombies

Among the strangest threats cicadas face is a fungal pathogen called Massospora cicadina, which infects periodical cicadas in a way that looks like something from a horror film. The fungus colonizes the cicada’s abdomen, eventually replacing the rear segments with a mass of fungal spores. Infected cicadas lose their abdomens but continue to fly and behave as if nothing is wrong, effectively becoming spore-dispersal machines for the fungus.

The manipulation goes deeper than simple physical takeover. Researchers found that male cicadas infected with the spore-producing stage of Massospora begin performing wing-flick signals that are normally made only by sexually receptive females. These precisely timed wing-flicks attract uninfected males, who attempt to mate with the infected individuals, spreading spores through close contact. The fungus essentially hijacks the cicada’s sexual signaling system, turning infected males into lures for healthy ones.⁶ Massospora functions at least partly as a sexually transmitted disease, which is unusual among fungal pathogens of insects.

The fungus also has a remarkably flexible life cycle. Its resting spores do not need to wait the full 13 or 17 years between cicada emergences to become infective again. Research showed that spores collected from 17-year cicadas could germinate and infect 13-year cicadas less than a year later, and could even cross species lines between different Magicicada species.⁷ This means the fungus is not locked into the same long cycle as its hosts and can persist in the soil between emergences.

How Cicadas Survive Despite Having So Many Predators

Given that essentially every local predator eats cicadas, it seems like the insects should be wiped out during every emergence. They are not, and the reason is one of the most elegant survival strategies in the animal kingdom: predator satiation. The idea is simple. If you emerge in such overwhelming numbers that every predator in the area gets physically full before they can eat more than a fraction of the population, the majority survive to reproduce.

Field data strongly support this hypothesis. Research on periodical cicada emergences found that each individual cicada’s risk of being captured decreases as overall cicada density increases. Predator populations do not grow in response to the emergence because there is no time to breed more predators in the few weeks that adult cicadas are active. Bird populations were essentially independent of cicada density, meaning the same number of birds were present whether the local cicada count was low or astronomical. And per-bird consumption leveled off rather than increasing with cicada abundance, confirming that the birds were satiated.⁸

This strategy has a cost. It only works at high densities. Cicadas that emerge at the wrong time, in the wrong year, or in areas where local populations have thinned out face dramatically higher per-capita predation because there are not enough bodies to fill up the predators. Researchers have documented that these low-density stragglers suffer near-total predation, which reinforces the evolutionary pressure toward tightly synchronized mass emergence.² The long prime-number cycles of 13 and 17 years may themselves be an adaptation that prevents predators from synchronizing their own population booms with predictable cicada emergences.

There is also a physical vulnerability tied to the satiation strategy. At extremely high densities, cicada nymphs can crowd each other during the molting process as they emerge from the soil and shed their nymphal skins. Researchers have documented a novel form of molting failure in which cicadas physically obstruct one another, a side effect of the same density dependence that protects them from predators.⁹ Being too numerous is, paradoxically, the only defense they have and occasionally their own undoing.

Ripple Effects Through the Food Web

Cicada predation is not just a story about cicadas. When billions of cicadas draw the attention of birds, those birds stop eating whatever they were eating before, and the consequences cascade through the ecosystem. During the 2021 Brood X emergence, the mass switch by more than 80 bird species to cicada foraging released herbivorous insects from their normal predation pressure. Caterpillar densities roughly doubled, and the accumulated leaf damage on host oak trees doubled as well.¹ In other words, the cicadas’ presence indirectly caused more damage to trees, not because the cicadas themselves were feeding on leaves, but because the birds that would normally eat caterpillars were busy eating cicadas instead.

This kind of indirect ecological effect is sometimes called a trophic cascade. It means that cicada emergences reshape forest ecosystems in ways that extend far beyond the obvious spectacle of billions of insects covering every surface. The nutrient pulse from decomposing cicada bodies fertilizes the soil. The temporary release of caterpillars from predation changes the balance between trees and the insects that eat them. And the aquatic nutrient inputs from cicadas falling into streams and ponds alter water chemistry for weeks. A single emergence event, lasting only a few weeks, leaves ecological fingerprints that can be measured months later.

Are Cicadas Safe for the Animals That Eat Them

One reasonable concern, especially for pet owners who watch their dogs enthusiastically crunching cicadas during an emergence, is whether cicadas carry harmful levels of environmental contaminants. After spending over a decade underground feeding on root fluids, cicadas could theoretically accumulate pesticides or heavy metals from the soil. Researchers tested 17-year cicadas from suburban Maryland and found that organochlorine and heavy metal concentrations were well below levels known to be harmful to birds. The cicadas contained metal concentrations similar to or lower than other local invertebrates, with the exception of slightly elevated copper levels compared to earthworms.¹⁰

For pets, the main risk is not toxicity but overindulgence. Dogs that eat large quantities of cicadas can experience gastrointestinal upset simply from the volume of exoskeleton material, which is mostly chitin and not easily digested in large amounts. The cicadas themselves are nutritionally harmless and are actually protein-rich. People eat them too, in many cultures worldwide and increasingly as a novelty in the United States during emergence years. They are typically compared to shrimp or soft-shell crab in texture when prepared fresh, and cicadas are taxonomically related to shellfish closely enough that people with shellfish allergies are sometimes warned to avoid them.

Annual Cicadas Face the Same Predators

Most of the dramatic research focuses on periodical cicadas because their synchronized mass emergences make for spectacular natural events and clean experimental conditions. But annual cicadas, the green-and-black species that show up every summer in most of the United States, face the same roster of predators. Birds, wasps, spiders, and small mammals all eat annual cicadas. The difference is that annual cicada species do not emerge in synchronized masses, so they lack the predator-satiation defense. Instead, they rely on different strategies: camouflage (many annual species are green and blend into foliage), stronger flight ability, and the sheer acoustic confusion of their loud choruses, which can make it harder for predators to zero in on a single individual.

Cicada killer wasps are especially associated with annual cicadas. These large solitary wasps hunt cicadas by stinging them in flight, paralyzing them, and carrying them back to underground burrows where the cicada serves as a live food source for developing wasp larvae. A single wasp may provision its nest with several cicadas over the course of a summer. The wasps are impressive predators, sometimes wrestling with cicadas nearly their own size in midair, but they are not a significant population-level threat. Like birds feeding on periodical cicadas, individual cicada killers can only process so many prey items.

The global picture is much the same. Cicadas exist on every continent except Antarctica, and wherever they live, they occupy a similar ecological niche: large, conspicuous, not particularly fast, and eaten by virtually every local predator. The specific predators change with geography. In Australia, kookaburras and monitor lizards eat cicadas. In tropical Asia, primates and hornbills eat them. In Japan, bears dig up the nymphs. But the fundamental dynamic is constant. Cicadas are near the bottom of a very wide food web, and their survival depends not on evading predators but on producing more offspring than predators can consume.