Key Concepts
Animals, environments, crustaceans, adaptations

Introduction

Have you ever wondered how an animal chooses what type of environment to live in? With the arrival of spring, in many areas flowers will be blooming and animals will be emerging from their winter hiding places and searching for a place to live until next winter. One group of critters that can usually be found just about anywhere on land includes sowbugs and pillbugs. As they come out to enjoy the warmer weather, what type of environment do you think they’ll seek? In this science activity, you’ll answer part of this question using your own local pillbugs or sowbugs, so get ready to build a habitat and do some bug hunting!

This activity is not appropriate for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.

Background

You can often find sowbugs and pillbugs in damp, dark places, like the soil under rocks or decaying wood. Sowbugs and pillbugs are both crustaceans (specifically a type called isopods). Other crustaceans include shrimp, lobsters and crabs. This means that sowbugs and pillbugs are more closely related to lobsters and shrimp than to insects like bees and ants. Crustaceans belong to a larger group of animals, called the arthropods, which includes insects, spiders and others.

Sowbugs and pillbugs breathe with gills, so they need moisture to breathe. But these tiny crustaceans have still had very successful lives on land, as there are now about 5,000 known species of pillbugs and sowbugs living just about anywhere from beaches to deserts. Wherever they go, sowbugs and pillbugs eat decaying materials, like plants and even dead animals, and by following this diet they help recycle nutrients in the soil.

Sowbugs and pillbugs, which are also called woodlice, look fairly similar to each other. Pillbugs are commonly known as “roly-polies” for their defensive behavior of rolling up into an armored ball. But sowbugs don’t roll themselves up, and have a pair of tail-like structures on the end of their body. 

Materials

  • Two clean, empty cardboard milk cartons
  • Sharp utility knife
  • Scissors
  • Tape
  • Dry soil
  • Water
  • At least 12 sowbugs or pillbugs. Details for collecting these are given in the activity.

Preparation

  1. Carefully use the utility knife and scissors to cut the tops of the two milk cartons completely off at least four inches up from their bottoms. Have an adult use the utility knife to start cutting the cartons, and then continue cutting the cartons with the scissors. Discard (i.e., recycle) the top parts of the cartons. You should be left with two carton containers with open tops.
  2. About one inch up on each carton bottom, cut out rectangles that run the length of the side of the carton and that are between one to two inches tall. These will be the “doors” that the sowbugs or pillbugs will use to move between the cartons, so make sure these holes line up well between the two cartons.
  3. Turn the carton bottoms so that their rectangular door holes line up and then tape the two cartons together. Make sure there are no gaps that any bugs could escape through.
  4. Remove any large pieces of wood or rocks from the dry soil you’ll be using. Put dry soil into one carton until it just reaches the bottom of the hole you made (or is about one inch deep). Smooth out the surface of the soil so it is flat. Do you think the sowbugs or pillbugs will like this environment?
  5. Put the same amount of dry soil into the other carton and then mix in a little water until the soil has a cookie dough consistency. Smooth out the surface so that it’s flat, but do not press down hard because you don’t want to compact the soil. Do you think the sowbugs or pillbugs will like this environment more than the dry soil one? Your habitat is now ready to do some experimenting. 

Procedure

  1. Go outside and collect at least a dozen sowbugs or pillbugs. To find them, look under stones, decaying wood, old leaves, in gardens in the soil near plants and along house foundations and basements. You may need to look closely because they’re small, can blend in well with their surroundings and might stop moving when startled. 
  2. Put an equal number of the little crustaceans in each carton (meaning there should be at least six in each carton). Allow them to explore the cartons while you observe for at least 30 minutes. How many bugs are in each carton over time? Does which carton most of the bugs are in change over time? What other types of behaviors do you observe? 
  3. Overall, which environment do the sowbugs or pillbugs seem to prefer, the one with damp soil or the one with dry soil? 

Extra: Repeat this activity but compare different environments, such as leaf litter vs. soil, or small rocks vs. small pieces of wood, etc. Which environment do the sowbugs or pillbugs prefer in other environment pairings?

Extra: You could try to quantify your results from this activity. To do this, every five minutes you could count how many sowbugs or pillbugs are in each habitat. How do the numbers of crustaceans in each environment change over time?

Extra: You could do similar activities with other small, common animals, such as crickets, earwigs, ants, slugs, snails, mealworms and waxworms. (Crickets, mealworms and waxworms can usually be purchased at a local pet store, while the other animals may be found locally by looking under rocks, garden plants, rotting logs and leaf litter.) What type(s) of environments do these other animals prefer? If the animal you’re using might be able to escape from the containers, be sure to secure a lid to them!

 

Observations and Results

Did most of the sowbugs or pillbugs end up in the damp soil environment? 

Sowbugs and pillbugs are crustaceans, just like shrimp, lobsters and crabs. They breathe with gills, so they need moisture in order to breathe. Because of this, you should have seen that most of the sowbugs and pillbugs spent more time in the damp soil environment than the dry soil environment. After 30 minutes of being in the habitat, you may have even seen several of the little crustaceans actually dig down into the damp soil, and settle in there. The sowbugs or pillbugs that spent time in the container with the dry soil probably only stayed there temporarily before going back to the damp soil. While sowbugs and pillbugs are amazing in that they’re crustaceans that have adapted to live on land, they still need moisture to breathe and survive.

Cleanup

  1. When you are done observing the sowbugs or pillbugs, you may release them where you found them (and recycle the emptied milk cartons).

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Credits

Teisha Rowland, PhD, Science Buddies

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Key Concepts
Animals, environments, crustaceans, adaptations
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