Periodical cicadas facts for kids

Quick facts for kids Periodical cicada
A Magicicada septendecim cicada in Munich (2015)
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hemiptera
Family:	Cicadidae
Subfamily:	Cicadettinae
Genus:	Magicicada W. T. Davis, 1925
Type species
Magicicada septendecim (Linnaeus, 1758)

Magicicada is a group of special insects called periodical cicadas found in eastern North America. There are seven different kinds, and they are famous for appearing only every 13 or 17 years. Even though some people call them "locusts," they are not. Cicadas are actually "true bugs," while locusts are a type of grasshopper.

These cicadas spend almost all their lives underground as young insects called nymphs. They feed on the sap from the roots of deciduous trees. After 13 or 17 years, depending on their type, the mature nymphs dig their way out of the ground. This happens between late April and early June, and they all come out at the same time in huge numbers!

Once above ground, the adult cicadas live for only about four to six weeks. During this short time, the males sing loudly to attract mates. After mating, the females lay their eggs in the branches of trees. Within two months of coming out, the adult cicadas die. Their babies then hatch and burrow underground, starting the 13- or 17-year cycle all over again.

What Do Periodical Cicadas Look Like?

Adult periodical cicadas have bright red eyes and a black body. Their wings are clear with orange veins. The underside of their body can be black, orange, or a mix of both, depending on the specific kind of cicada.

These adult cicadas are usually about 2.4 to 3.3 centimeters (about 1 inch) long. This makes them a bit smaller than the "annual cicadas" you might see every summer. Female cicadas are a little bigger than the males.

Male Magicicada cicadas gather in large groups and sing together to attract females. Each type of cicada has its own special song. Some sound like "weeeee-whoa," while others make buzzing and ticking noises.

Cicadas cannot sting, and they usually don't bite. They have mouthparts that are like tiny straws, which they use to drink sap from plants. As nymphs, they use these to get water and food from tree roots underground. As adults, they drink from plant stems. If you hold an adult cicada, it might poke you with its mouthpart, which can hurt a little, but it's not dangerous. Cicadas are not venomous or poisonous, and they don't spread diseases.

Periodical cicadas don't usually harm old, strong trees. However, if you're planting new trees or bushes, it's a good idea to wait until after the cicadas have emerged and gone. Young plants can be covered with a fine net (with holes smaller than 1 cm or 3/8 inch) to protect them when the females are laying eggs.

There's also a special fungus called Massospora cicadina that only infects 13- and 17-year cicadas. This fungus replaces the end of the cicada's body with spores, making the cicada unable to have babies. Eventually, the cicada dies.

The Amazing Life Cycle of Cicadas

How a periodical cicada changes from a young nymph to an adult

Almost all cicadas spend many years underground as young insects before they come out for a short adult life of a few weeks. What makes the seven periodical cicada species so special is that all the cicadas in one area come out at the exact same time, in the same year. This is amazing because their lives underground are so long—13 or 17 years! No other cicada species in the world (out of about 3,000 kinds) does this.

Other cicadas, often called "annual cicadas," have some adults emerge every summer. Their life cycles are usually shorter, from two to ten years.

The young periodical cicada nymphs live underground, usually within 60 centimeters (2 feet) of the surface. They feed on the sap from plant roots. As they grow, they go through five stages underground. The main difference between the 13-year and 17-year cycles is how long it takes for one of these stages to develop. As they get older, the nymphs dig deeper to find bigger roots to feed on.

A Magicicada cicada shedding its skin

In late April to early June of the year they are due to emerge, the mature nymphs build tunnels to the surface. They wait for the soil to reach a certain warm temperature. Sometimes, the nymphs even build mud towers, a few inches tall, above the ground. No one is quite sure why they do this.

The nymphs usually come out on a spring evening when the soil temperature about 20 centimeters (8 inches) deep is above 17.9°C (64.2°F). In the southern United States, this is usually in late April or early May. In the far north, it's late May to early June.

After emerging, the nymphs shed their old skin (molt). They might do this in the grass or climb up trees or other surfaces to find a good spot. After this final molt, they spend about six days in the trees, waiting for their new outer shell to become hard. When they first come out of their old skin, they are soft and off-white, but they turn dark within an hour.

A Magicicada cicada in the final stage of molting, before its new body hardens. You can see its old skin next to it.

Adult periodical cicadas live for only a few weeks. By mid-July, they have all died. Their short adult lives have one main purpose: to have babies. The males "sing" a special mating song using special body parts called tymbals. Groups of singing males form loud "choruses" that attract females. Males fly from tree to tree, singing and looking for females. Most mating happens in these "chorus" trees.

Female cicadas respond to the males' calls by flicking their wings, which tells the males they are ready to mate. The sound of a large group of singing males can be very loud, reaching up to 100 decibels! Besides their main "calling" songs, males also make a special "courtship" song when they get close to a female.

Magicicada egg slits (circled in red)

Both male and female cicadas can mate many times, but most females seem to mate only once. After mating, the female cuts V-shaped slits in the bark of young twigs. She lays about 20 eggs in each slit, laying 600 or more eggs in total. After about 6–10 weeks, the eggs hatch. The tiny nymphs drop to the ground, dig in, and start their 13- or 17-year journey underground.

How Cicadas Survive: Overwhelming Predators

Holes where cicadas emerged from the ground

The nymphs come out of the ground in incredibly large numbers, sometimes more than 1.5 million cicadas per acre (over 370 per square meter)! This mass emergence is a survival trick called "predator satiation." For the first week after they emerge, periodical cicadas are easy prey for animals like reptiles, birds, squirrels, cats, dogs, and other small and large mammals.

Scientists believe that by coming out all at once in such huge numbers, the cicadas simply overwhelm their predators. There are so many cicadas that predators can eat all they want, but still, most of the cicadas survive and can reproduce.

Another interesting idea is why their life cycles are prime numbers (13 and 17 years). This might be a way to avoid predators that also have regular life cycles. For example, if a predator had a 3-year life cycle, it would be hard for them to match up perfectly with a 13- or 17-year cicada emergence. This means that when cicadas emerge, some of their predators might be too young to take full advantage of the sudden food supply.

Some scientists also think that the prime-numbered cycles help prevent different groups of cicadas from mixing and mating. This could have been important when conditions were very tough, like after the Ice Age.

This idea about prime numbers and avoiding mixing has been supported by computer models. It's now the most accepted explanation for why these insects have such long and mathematically unique survival strategies.

Impact on Other Animals and Plants

The huge numbers of cicadas can affect other animals and plants. For example, trees might grow less the year before a cicada emergence because the growing nymphs are feeding more on their roots. Moles, which eat cicada nymphs, do very well the year before an emergence but then have fewer babies the next year because their food source decreases.

Wild turkey populations also benefit. They get a lot of extra food by eating adult cicadas on the ground at the end of their lives. When uneaten cicadas die and decompose, they add nutrients back into the forest soil.

However, cicadas can also have a negative impact. Eastern gray squirrel populations have been affected because female cicadas laying eggs in tree branches can damage the upcoming nut crops that squirrels rely on.

Cicada Broods

Periodical cicadas are grouped into "broods" based on the year they emerge. For example, in 2014, the 13-year Brood XXII came out in Louisiana, and the 17-year Brood III emerged in western Illinois and eastern Iowa.

Back in 1898, a scientist named Charles Lester Marlatt gave Roman numerals to 30 different cicada broods. He named 17-year broods I through XVII and 13-year broods XVIII through XXX.

However, many of these broods have never been seen. Also, two of Marlatt's broods (XI and XXI) used to exist but are now extinct. We still use Marlatt's numbering system because it's helpful, even though only 15 broods are known to be alive today.

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  A Brood XIII periodical cicada nymph before its final molt

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  A newly molted Brood XIII periodical cicada

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  Many Magicicada cicadas (newly molted adults and old skins) on plants

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  An adult Brood X periodical cicada (Magicicada septendecim) in Princeton, New Jersey (June 2004)

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  A Brood X cicada laying eggs in a tree branch near Baltimore, Maryland (May 26, 2021)

Where Do Cicada Broods Live?

USDA Forest Service map of periodical cicada brood locations by county and timing of next emergence (as of 2013)

The 17-year periodical cicadas are found in the Eastern, upper Midwestern, and Great Plains states of the U.S. The 13-year cicadas live in the Southern and Mississippi Valley states. Sometimes, their areas overlap a little. For example, Brood IV (17-year) and Brood XIX (13-year) overlap in parts of Missouri and Oklahoma. They last emerged together in 1998 and will again in 2219.

Scientists at the University of Connecticut are currently creating new maps of where all the cicada broods live. They are using information from scientists and volunteers who report where they see cicadas.

Different Types of Magicicada Species

There are seven known species of Magicicada: three have a 17-year life cycle, and four have a 13-year life cycle. These species are also grouped into three main types: the Decim group, the Cassini group, and the Decula group. This is because each 17-year species is very similar to one or more of the 13-year species.

17-year cycle				Species group	13-year cycle
Image	Scientific name	Common Name	Distribution		Image	Scientific name	Common Name	Distribution
	M. septendecim (Linnaeus, 1758)	17-year locust, Pharaoh cicada	Canada, United States	Decim		M. tredecim (Walsh & Riley, 1868)		southeastern United States
						M. neotredecim Marshall & Cooley, 2000		United States
	M. cassinii (Fisher, 1852)	17-year cicada, dwarf periodical cicada	United States	Cassini		M. tredecassini Alexander & Moore, 1962		United States
	M. septendecula Alexander & Moore, 1962		United States	Decula		M. tredecula Alexander & Moore, 1962		United States

A Look Back: History of Cicada Sightings

The first known report of a huge cicada emergence was in 1633 by William Bradford, the governor of the Plymouth Colony. He wrote about "Flies" that were like wasps or bumblebees. They came out of holes in the ground, ate plants, and made a loud noise that made the woods ring. The Native Americans told him that sickness would follow, and it did.

Later, in 1749, a Swedish scientist named Pehr Kalm visited Pennsylvania and New Jersey. He saw a massive cicada emergence. He wrote that people believed these insects appeared in huge numbers every 17 years. He also found old records, including one from Benjamin Franklin, that showed large numbers of cicadas in 1715 and 1732. Kalm himself didn't hear any cicadas in 1750 in the same places where he heard many in 1749.

Based on Kalm's report and a cicada he provided, Carl Linnaeus named the insect Cicada septendecim in 1758.

In 1775, Thomas Jefferson wrote in his "Garden Book" about the 17-year cycle of Brood II. He remembered "great locust years" in 1724, 1741, and 1758. He noted that the insects had emerged again at his home, Monticello, in 1775. He also wrote that the females lay their eggs in small tree twigs.

In 1777, both a 13-year and a 17-year brood emerged at the same time in the St. Louis area. This happened again in 1998.

In 1800, Benjamin Banneker, a scientist, wrote that he remembered "great locust years" in 1749, 1766, and 1783. He correctly predicted that Brood X would appear again in 1800, 17 years after its last appearance to him.

Can You Eat Cicadas?

Yes, Magicicada cicadas can be eaten if they are cooked! Native Americans used to roast them in hot ovens until they were brown.

In 1907, scientist C. L. Marlatt wrote that eating cicadas is mostly just an interesting idea. He said they don't appear often enough to be a regular food. He also noted that most people don't like the idea of eating insects. However, he believed that cicadas, if collected at the right time and cooked well, could be a tasty food. He pointed out that cicada nymphs eat only clean plant matter, which makes them a cleaner food source than, for example, oysters, which live in muddy river bottoms.

Images for kids

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  A Brood X Magicicada with a fungus infection in Bethesda, Maryland (May 31, 2021)

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  Mud turrets made by emerging Brood X Magicicada nymphs in Potomac, Maryland (June 30, 2021)