Duration: 30 to 40 minutes
Vocabulary: dragonfly, mosquito, predator, prey, pest,
Summary: Students act out the predator/prey relationship between dragonflies and mosquitoes and learn why wetlands are important in this relationship.
Objectives: Students understand how wetlands are very important in mosquito/pest control, as wetlands contain natural predators for these animals.
Materials: 10 small plastic containers, 3 large mats (carpet squares, piece of tarp, trash bag cut open, etc), whistle
Wetlands are a very important habitat—one that we are losing quickly and need to protect. Some people do not like wetlands because they believe them to be breeding grounds for mosquitoes, and otherwise useless. Truthfully, wetlands contain many natural predators of mosquitoes and have balanced ecosystems, while otherwise mosquitoes can reproduce in any small amount of water, like that sitting in an old tire, a container under a deck, a soda can beside the road, etc. etc.
Dragonflies are a natural predator of mosquitoes. A dragonfly’s life begins when an egg is laid in the water. The dragonfly larva hatches, and swims around the water eating mosquito larvae. They can stay in this stage for anywhere from 2 months to 5 years, depending on the species. Eventually, larva climb up a plant out of the water and shed their skin to become an adult dragonfly. Dragonflies can reproduce and lay eggs in ponds, lakes, or streams, but wetlands are an especially ideal environment.
Warm Up: Ask students if a mosquito has ever bitten them. Explain that mosquitoes are considered pests because they can be harmful to humans. Ask if they have ever used a chemical spray to protect themselves from mosquito bits.
Explain that there are some natural ways to get rid of mosquitoes, and one is to have a healthy population of dragonflies around to eat them. In order to have dragonflies, though, we need healthy bodies of water where they can live and reproduce.
Divide students up into groups. 1 student will be a dragonfly, and 3 will be mosquitoes to start. Lay the 3 mats on the ground spaced widely apart. Then, put the 10 small containers of water relatively close together. Explain to the students that the mats represent wetlands, which there are not very many of, and the small containers represent anything lying around that collects water, like an old tire, a bucket left outside, or a water bottle thrown beside the road.
Explain that the mosquitoes can reproduce in any small container of water, while the dragonflies need the wetlands. They will be playing a game of ‘tag,’ but with some special rules. The dragonflies can tag the mosquitoes “out,” in which case they are eaten and have to go sit down, but whenever you blow the whistle they have to run back to a wetland (if they are a dragonfly) or a container of water (if they are a mosquito). When they do this, send in one more dragonfly or mosquito for each person, as this will count as them reproducing. For example, after the first time you blow the whistle there will be 2 dragonflies and 6 mosquitoes. Next there will be 4 dragonflies and 12 mosquitoes, and then however many other students are left. Note: students who got out can be sent in again after a whistle is blown if there are no students left.
The students should see that there are more mosquitoes than dragonflies. But what will happen when the wetland habitat is destroyed?
Start the game over, but explain to the students that you are a foreman who is going to build a mall over the wetlands. As the game goes on, remove one of the mats, and then a second mat. Now, all of the dragonflies have only one place to visit to reproduce, while the mosquitoes still have ten.
Now it is even harder to keep up with the mosquitoes!
Ask students to name a natural predator of mosquitoes. Ask them to explain why wetlands are important, and what might happen if they are destroyed.
Have students make posters asking people to save wetlands, or to be careful with leaving containers around that can fill with water and be a home to mosquito larva.
Ask students if there are any other variations of the game they could try.