To consider how some animals, periodical cicadas, survive well in a particular environment due to the species’ life cycle.
The periodical cicadas that emerge in various parts of the United States every 13 or 17 years provide an excellent opportunity for you to engage your students in a discussion about life cycles and how a particular species' life cycle helps it to survive.
It is not difficult for students to grasp the general notion that species depend on one another and on the environment for survival. But their awareness must be supported by knowledge of the kinds of relationships that exist among organisms, the kinds of physical conditions that organisms must cope with, the kinds of environments created by the interaction of organisms with one another and their physical surroundings, and the complexity of such systems. (Benchmarks for Science Literacy, p. 115.) This lesson encourages students to observe the interactions among the cicadas and the other organisms within an environment. Students will be asked to observe some images of cicadas in an interactive and to study how they interact with other organisms in an environment.
Students should explore how various organisms satisfy their needs in the environments in which they are typically found. They can examine the survival needs of different organisms and consider how the conditions in particular habitats can limit what kinds of living things can survive. (Benchmarks for Science Literacy, p. 116.)
While teaching this lesson, it is important for you to be aware of some student misconceptions. Research suggests that upper elementary-school students may not believe food is a scarce resource in ecosystems, thinking that organisms can change their food at will according to the availability of particular sources. Students of all ages think that some populations of organisms are numerous in order to fulfill a demand for food by another population. (Benchmarks for Science Literacy, p. 342.)
Teacher Background Resource: Cicadas come out once a year in specific geographical areas. Most often they are the common cicada. Every 13 or 17 years, some geographical areas are inundated with the periodical cicada. For more information, please visit these websites:
Begin this lesson by asking students if they have heard anything about cicadas, and then specifically the periodical cicadas (the 13- or 17-year cicadas) that are so much in the news these days. Ask students what they know about these insects. Some guiding questions could include:
- Have you heard of some animals called cicadas? If so, what are they?
- What is so special about these insects?
- Why do you think they only come out of the ground once every 13 or 17 years?
- Where are they when they aren't above ground?
- Are cicadas harmful? Can they hurt you?
Once you have finished this discussion, tell students that they will have a chance to learn more about cicadas and how they survive in a particular environment.
In this part of the lesson, students make use of an online interactive to view images of the periodical cicadas and learn more about how their life cycle helps them to survive. Using their Cicadas student esheet, students should go to A Periodical Life Cycle interactive. This interactive leads them through the life cycle of the cicada from the time it is a nymph underground through its transformation into an adult cicada and then its emergence from an egg and back to the ground for another 13- or 17-year span.
As students go through these resources, they should look for answers to these questions:
- When cicadas are still nymphs living underground, what do they use for food?
(Nymphs feed on the sap from tree roots.)
- What kinds of things could negatively affect the cicada nymphs living underground?
(An animal or person could dig up the nymphs. If there is flooding, the nymphs could get washed away.)
- Going further: Periodical cicadas live underground for 13 or 17 years. That's a long time. Life above ground can change dramatically in that time. What are some of the environmental changes that could affect a cicada population living underground? (
Land development. If land is developed for homes or businesses, many nymphs will be destroyed. If trees are removed, once the cicada comes above ground, it may have a difficult time finding a place to lay its eggs.)
- What is one of the first things the cicadas do when they come above ground?
(They find something upright – a blade of grass, a tree, a building – to crawl up on.)
- How does a nymph change into an adult cicada?
(It splits open its shell and crawls out of it as an adult.)
- What changes does the adult cicada go through once it comes out of the shell?
(The adult cicada is white at first and its wings are crumpled up. As it dries off, the cicada's color darkens until it is black and its wings unfold and become an orange-yellow color.)
- What is important about the fact that so many cicadas come out of the ground at the same time? How does this help them to survive?
(The fact that so many cicadas come out of the ground at the same time makes it difficult for predators to significantly reduce the cicada population. The majority of the cicadas survive, allowing the species to survive and reproduce.)
- Where do the female cicadas lay their eggs? Does this also play a part in helping the cicadas survive?
(Female cicadas lay their eggs in the branches of trees, which helps protect the eggs until they hatch, thereby helping the cicadas survive.)
- What are some of the dangers a periodical cicada faces when it is above ground?
(It risks being eaten by predators. Since it is below ground for so many years, when it emerges it may find that there is no longer a habitat (i.e., trees) to support it. Human-made objects, like cars, trucks, bikes, and pesticides could also kill it.)
Students should be prepared to discuss these questions in class.
If you happen to live in an area where the periodical cicadas emerge, you can have your students do a cicada observation activity to help enhance the learning in this lesson. The students, along with their parents, should do the activity at home. Students should use the Cicadas Observation student sheet to help guide them as they observe cicadas. They should also use the student sheet to help them record their observations about how the cicadas behave in their ecosystem.
Now instruct students to do the cicada observation activity as homework. Their student sheet should provide all the information they need to be able to complete this activity at home with the help of their parents. Students should be prepared to share their findings with the class.
As a way to assess student understanding, have students work together in groups to create posters of the life cycle of the periodical cicada. This poster should be sure to explain how the cicada's life cycle helps the species as a whole to survive in a particular environment.
For more lessons about how animals survive in certain environments, see:
For a fun activity that students can do with their parents at home, have students visit the Kids' Cicada Hunt website. This site describes how kids can hunt for and keep cicadas for observation.
Another website dedicated to cicadas and that is appropriate for this age group is the College of Mount St. Joseph's Cicada website. This site provides information about the 17-year cicadas, a FAQ page, a Cicada Calendar, and a place where kids can report a cicada emergence.