If you live on the East Coast of the United States, you might not realize that for the past 17 years, you’ve been walking, eating, and sleeping above a hidden world of insects called cicadas. These fascinating creatures spend most of their lives underground, and every 17 years, they come out in huge numbers to do three things: shed their skin, find a mate, and then die.
Cicadas are divided into groups called broods, and they have different cycles for when they emerge. Some broods come out every 13 years, while others, like the ones on the East Coast, appear every 17 years. During their long time underground, cicadas feed on the juices from plant roots. When it’s time to come out, they dig their way to the surface and live for just a few weeks.
When cicadas emerge, they are hard to miss. There are billions of them, and they make a lot of noise! The male cicadas sing loudly to attract female cicadas, and their combined songs can be as loud as a chainsaw. In fact, if you’re using a chainsaw or a lawn mower, male cicadas might come closer, thinking the noise is from other cicadas.
Cicadas don’t come out alone; they bring along a host of predators and parasites. One interesting parasite is a fungus called Massospora. This fungus infects cicadas by getting inside their bodies and eating them from the inside. When the fungus is ready, it bursts out of the cicada, spreading its spores to other cicadas nearby.
Scientists can predict when cicadas will appear, but they still don’t fully understand why cicadas have 13- and 17-year cycles. One advantage of emerging all at once is that there are so many cicadas that predators can’t eat them all, so some survive to reproduce. Also, because cicadas come out every 13 or 17 years, which is longer than the lifespan of many predators, these animals don’t learn to depend on cicadas for food.
Why cicadas prefer 13 and 17 years instead of other numbers like 16, 18, or 12 is still a mystery. It might be random, or maybe cicadas like prime numbers for some reason.
After mating, cicadas gradually die off, and their loud calls fade away. The eggs they lay will start the cycle all over again. The new generation will burrow into the ground, feed on plant juices, and wait for their turn to emerge and fill the air with their songs. In 17 years, they’ll be ready. Will you be ready to see them?
Draw and label the life cycle of a cicada, from its time underground to its emergence and eventual death. Use arrows to show the progression and include details about each stage. This will help you visualize the unique 17-year cycle of cicadas.
Listen to recordings of cicada songs and compare them to other loud sounds like a chainsaw or lawn mower. Discuss why cicadas might be attracted to these noises. Try to mimic the sound using instruments or household items and see how close you can get to the real thing.
Choose a specific brood of cicadas and research when and where they are expected to emerge next. Create a short presentation or poster that includes a map, timeline, and interesting facts about your chosen brood.
In groups, role-play the interactions between cicadas, their predators, and parasites like the Massospora fungus. Discuss how these relationships affect the cicada population and the ecosystem as a whole.
Investigate why cicadas might prefer 13- and 17-year cycles. Explore the concept of prime numbers and discuss their significance. Create a chart showing other prime numbers and hypothesize why cicadas might have evolved to use these specific cycles.
If you live on the East Coast of the United States, you’ve spent the last 17 years of your life walking, eating, and sleeping above a dormant population of insects known as cicadas. Every 17 years, billions of them emerge from the ground to do three things: molt, mate, and die. There are 15 different broods of cicadas, grouped by their emergence cycles. Some of these broods follow a 13-year cycle, while others follow a 17-year cycle.
Cicadas live underground for most of their lives, feeding on the juices of plant roots. When it’s time to emerge, the adults burrow their way to the surface, where they will live for just a few weeks. During this time, their presence is unmistakable. There will be billions of them, and they are quite loud. Male cicadas gather to call for female mates, and their collective chorus can reach up to 100 decibels—comparable to the sound of a chainsaw. Interestingly, if you are using a chainsaw or a lawn mower, male cicadas may be attracted to you, mistaking the noise for their own.
Like many aspects of nature, cicadas do not emerge alone; they come with a variety of predators and parasites. One notable example is the fungus Massospora, which infects cicadas by burrowing into their abdomen and consuming them from within. When the spores of this fungus rupture, they burst out of the still-living cicada, effectively turning it into a vehicle for spreading spores to other cicadas nearby.
While we can predict when cicadas will emerge and fade away, the reasons behind their specific life cycles remain uncertain. There are advantages to having an entire species emerge simultaneously; the sheer number of cicadas can overwhelm predators, ensuring that some will survive to reproduce. Additionally, since cicadas emerge every 13 or 17 years—longer than the lifespan of many of their predators—these animals do not learn to rely on cicadas as a food source.
The question of why cicadas have 13- and 17-year cycles, rather than 16, 18, or 12, remains unanswered. It could be a matter of chance, or perhaps cicadas have a preference for prime numbers.
Eventually, the cicadas will mate and gradually die off, their calls fading into the distance. The eggs they lay will initiate the cycle once more, with their offspring burrowing into the earth, feeding on plant juices, and waiting for their turn to emerge and fill the air with their songs. In 17 years, they will be ready. Will you?
Cicadas – Insects known for their loud buzzing sounds, often found in trees during the summer. – Example sentence: Cicadas are fascinating insects that spend most of their lives underground before emerging to sing in the trees.
Broods – Groups of cicadas that emerge at the same time, often in large numbers. – Example sentence: The periodical cicada broods appear every 13 or 17 years, creating a spectacular natural event.
Emerge – To come out from a hidden or enclosed space, such as cicadas coming out from the ground. – Example sentence: After spending years underground, the cicadas finally emerge to mate and lay eggs.
Predators – Animals that hunt and eat other animals for food. – Example sentence: Birds are common predators of cicadas, often feasting on them when they emerge.
Parasites – Organisms that live on or in a host organism and get their food from or at the expense of their host. – Example sentence: Some parasites can infect cicadas, affecting their behavior and life cycle.
Fungus – A type of organism that includes molds, yeasts, and mushrooms, which can decompose organic material. – Example sentence: The fungus Massospora infects cicadas, altering their behavior and spreading its spores.
Massospora – A type of fungus that specifically infects cicadas, affecting their behavior and reproduction. – Example sentence: Massospora is a fungus that causes infected cicadas to behave in unusual ways, helping the fungus spread.
Cycles – Regularly repeating sequences of events in nature, such as the life cycle of cicadas. – Example sentence: The life cycles of cicadas are synchronized with the seasons, allowing them to emerge in large numbers.
Reproduce – To produce offspring or new individuals, ensuring the continuation of a species. – Example sentence: Cicadas reproduce by laying eggs in tree branches, which eventually hatch into nymphs that burrow underground.
Underground – Beneath the surface of the ground, where cicada nymphs live for most of their lives. – Example sentence: Cicada nymphs spend several years underground, feeding on tree roots before they are ready to emerge.
