Arthropod Behavior: Response of the Pill Bugs

Pill bugs are members of the Arthropod phylum. All arthropods are invertebrates with jointed appendages and hard external skeletons made of chitin. A pill bug is a small animal that can roll up into a ball when threatened. Pill bugs live in dark environments, and they breathe with gills. Because they eat dead organic matter, pill bugs play important roles in ecosystems. In this activity you will see whether pill bugs show a preference for dry or moist environments.

Materials

Petri dish

Crayon

Scissors

Filter paper (such as from a coffee filter)

Spray bottle of water

Five pill bugs (handle carefully; release after the activity is done)

Activity

1. Fold the piece of filter paper in half and cut it into two equal parts. You may have to trim the pieces a little to get the right fit in the petri dish.
2. Use a crayon and draw a bold line on the filter paper down the center so that the petri dish is divided into two equal halves.
3. Thoroughly wet one half of the filter paper. Place this half on one side of the line in the dish.
4. Place the dry piece of filter paper in the other half of the dish. You should be able to see the line you drew down the center of the dish. If not, trim the pieces of filter paper.
5. Place the five pill bugs on the center line.
6. Over the next few minutes, see which side the pill bugs move toward.

Follow-Up Questions

1. Did the pill bugs seem to prefer a wet or dry environment? Why do you think this was the case?
2. Pill bugs are members of the subphylum Crustacea. Do you think most crustaceans prefer this type of environment? If you were to go outside and hunt for pill bugs, where might you look?

Answers

1. Pill bugs prefer moist environments. They need moisture to survive, since they have gills for respiration.
2. Yes. When hunting for pill bugs, it is best to look in dark areas with lots of moisture, such as under rocks.

Extension

See if pill bugs prefer light or dark conditions. Use aluminum foil to cover up one side of the petri dish and see if the pill bugs move toward the light or the dark. Remember to use either all wet or all dry filter paper in the bottom of the dish so that you are testing only one variable.