Periodical cicadas (Magicicada) are insects known for their synchronized emergence after spending 13 or 17 years developing underground. This prolonged subterranean phase culminates in a massive, coordinated appearance of millions of individuals within a small geographic area. The sheer volume of this emergence is a survival mechanism known as predator satiation. This strategy ensures that while countless cicadas are eaten during this brief, intense period, enough survive to continue the next generation.
Avian Predators
The sudden insect bounty creates a temporary shift in the diet of numerous bird species. Ornithologists have documented over 80 species of birds opportunistically feeding on cicadas, which are easy to catch as they emerge and fly. Common insectivores, such as American crows, robins, blue jays, and grackles, gorge themselves on the insects. Even various raptors, including American kestrels and red-tailed hawks, temporarily add the large insects to their usual diet of rodents and smaller birds.
This temporary diet change among local bird populations has an ecological ripple effect on other prey. For the few weeks of the emergence, many birds switch from hunting other insects, particularly caterpillars, to focusing almost exclusively on the accessible cicadas. This temporary release from predation pressure allows caterpillar populations to flourish. This often leads to an increase in the defoliation of forest trees during the cicada emergence period.
Terrestrial Mammals and Reptiles
The availability of cicadas attracts a wide array of terrestrial vertebrates, many of whom are generalist foragers. Mammals like raccoons and skunks actively dig up the soil to consume the pre-emergent nymphs located just beneath the surface. Squirrels, which are primarily herbivores, readily consume the adults to supplement their usual diet of nuts and seeds.
Cicadas are also consumed by amphibians and reptiles. Ground-dwelling species, including frogs, toads, and turtles, capitalize on the insects that fall to the ground. Even venomous snakes, such as copperheads, prey on the newly emerged or molting insects. Domestic pets also participate in the feeding frenzy, but veterinarians caution that the cicada’s hard, indigestible exoskeleton (chitin) can cause gastrointestinal upset if consumed in large quantities.
Insect and Arachnid Specialists
Among insect predators, the Cicada Killer Wasp (Sphecius speciosus) exhibits one of the most specialized predation strategies. The large, solitary female wasp hunts the adult cicada, often capturing it in mid-air. She delivers a precise sting to the underside of the cicada, injecting venom that paralyzes the insect but does not immediately kill it.
The female wasp transports the cicada, which can be heavier than the wasp itself, back to an underground burrow. She drags the immobilized insect into a nursery cell, where she lays a single egg on its body. Upon hatching, the wasp larva consumes the still-living, paralyzed cicada over approximately two weeks before spinning a cocoon to overwinter. Other invertebrates, such as praying mantises and orb-weaving spiders, also capture and consume the insects.
Ecological Impact of Mass Emergence
The mass die-off of trillions of cicadas creates a pulsed input of nutrients. The decaying bodies of the adult insects are rich in nitrogen, containing approximately six percent nitrogen by dry weight. This nitrogen, along with phosphorus, is rapidly released into the soil and local waterways as the carcasses decompose.
This sudden nutrient pulse increases the availability of soil ammonium and nitrates. This can lead to an increase in the nitrogen content of plant foliage and a temporary boost in the growth of certain understory plants. The synchronized emergence ensures that despite the number of cicadas consumed by predators, the remaining biomass returns a substantial nutrient load to the forest floor, fertilizing the trees that sustained them for over a decade.