An Experiment on the Population of Flies in a Jar

Materials

• This experiment requires an eight-ounce glass jar, and another about three times as large. Each glass jar will contain pieces of peeled ripe banana, or a number of grapes, which have been cut in half, for the flies to feed on. You will also need a cheesecloth to cover the mouth of each jar, and an elastic band to secure it.

Attracting the Flies

• The pieces of ripe fruit will serve as bait in each jar. Place them outdoors if you do not want to attract flies in your house. The larger jar should contain three times more fruit than the smaller one. Cover the jars after enough flies have entered to feed on the fruit. The piece of cheesecloth will prevent more flies from entering the jars and prevent the trapped flies from escaping. Record the exact number of flies in each jar at the start and end of this experiment.

Procedure

• Do not to remove the fabric during the experiment. For the duration of the experiment, place the jars out of direct sunlight and do not interfere with the flies in any way. They will derive nutrients from the fruit and enough air will pass through the cheesecloth to allow the flies to survive without difficulty. Count the number of flies in each jar every day for a 10-day period. Place the jars in the refrigerator briefly to reduce activity before the daily count.

Results

• The larger jar offers more living space and more nutrition and will support a larger population of flies than the smaller. This experiment indicates how fly populations in the wild will grow, depending on the natural resources that are available to them.