Periodical cicadas are unusual insects. They live for a long time—13 or 17 years—but they only spend about four weeks of that long life as adults! Two kinds of periodical cicadas can be found in the United States. One has a life cycle of 13 years and is generally found in the southeastern United States. The other kind has a 17-year life cycle and is more commonly found in the northeastern part of the country. Periodical cicadas live underground for most of their lives and emerge only at the end of their 13- or 17-year life cycles. Because there are various periodical cicada populations, called broods, emerging at different intervals, some kind of periodical cicada can usually be found somewhere in the United States. But by far the largest emergence of periodical cicadas is the famous Brood X, which last emerged from its 17-year cycle in 2004.
View A Periodical Cicada Calendar in the media player above to see a slide show of a periodical cicada life cycle.
Defending Against Predators
With predators always on the lookout for a meal, prey must constantly avoid being eaten. To do this, prey utilize a variety of survival strategies that add to the chances of survival for the species. Some of these are defense mechanisms which can give the prey an advantage against enemies.
Some of these defense mechanisms involve camouflage or protective coloration. Some animals employ warning coloration, conspicuous markings that make it easily recognizable and warn would-be predators that it is poisonous, foul-tasting, or dangerous in some way. Similarly, some prey use mimicry, the advantageous resemblance of one species to another, often unrelated, species that is undesirable to its prey. Camouflage, or cryptic coloration, allows an organism to match or blend into its background, thus hiding it from predators and/or prey.
Some animals use chemical defenses to repel or inhibit potential predators. A good example of this is the skunk. This strategy is also commonly employed by arthropods, amphibians, and snakes. Various types of plants also use chemical defenses that range from those that cause them to taste bad to some that cause indigestion to some that can even kill their predators.
Physical defenses are also quite useful to prey animals. Some have physical features that make an animal an undesirable meal, such as a porcupine’s quills or a turtle’s shell. Physical attributes that give an animal an advantage over prey, such as speed, are also useful for survival.
And some organisms utilize a survival strategy called predator satiation. This involves timing mating and reproduction so that a maximum number of offspring are produced in a short period of time. When food is so abundant, predators are satiated and that allows a greater percentage of young to survive. Examples of organisms that use this strategy include wildebeest, caribou, many plants, and the periodical cicada.
To learn more about predator satiation and periodical cicadas, go to the Science Update Cicada Cycles on prime numbers.
Periodical cicadas are apparently very tasty. While there are no predators that prey only on the periodical cicadas, there are plenty of animals that feast on them when they emerge because they’re so abundant and so easy to catch. This includes birds, rodents, snakes, lizards, and fish. Mammals like opossums, raccoons, domestic pets—cats and dogs—will eat them. And yet because of their overwhelming numbers, even though a lot of them are eaten, enough survive to carry on. Ecologists call that strategy predator satiation. Basically it means that there’s safety in numbers, so to speak. The insects emerge in such prodigious quantities that predators cannot possibly eat them all. The strategy depends on timing. If the cicadas didn’t emerge all at once, or if they came out over an extended period of time, they could be wiped out by predators before they had a chance to reproduce. This ensures the survival of another generation.
Using what you've learned about periodical cicadas and prey defense strategies in this lesson, answer these questions (you can write your answers on the Periodical Cicada and Prey student sheet).
- What does the cicada eat for most of its life?
- About how long does the periodical cicada spend as an adult?
- How long do periodical cicadas live underground?
- Why does the periodical cicada emerge from the ground?
- Which is more vulnerable to prey, an adult cicada or an underground nymph? Why?
- The emergence of the periodical cicada in such large numbers is an example of which defense strategy? How does it help the periodical cicada?
- What is another defense strategy described in this lesson? How does it work.
- Where does the female cicada lay its eggs?
- What happens to the eggs?
This esheet is a part of the Cicada Emergence lesson.