Key concepts
Have you ever wondered how an animal chooses where to live? With the arrival of spring animals in many areas will be emerging from their winter hiding places to search for a place to live until next winter. One group of critters that can usually be found just about anywhere on land includes the familiar sow bugs and pill bugs. 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 pill bugs or sow bugs, so get ready to build a habitat and do some bug hunting!
You can often find sow bugs and pill bugs in damp, dark places, like the soil under rocks or decaying wood. These insects are both crustaceans (specifically a type called isopods). Other crustaceans include shrimps, lobsters and crabs. This means that sow bugs and pill bugs are more closely related to these animals than to insects like bees and ants. Crustaceans belong to a larger group of animals, called the arthropods, which also includes insects, spiders and others.
Sow bugs and pill bugs breathe with gills, so they need moisture for respiration. But these tiny crustaceans have still had very successful lives on land, as there are now about 5,000 known species of pill bugs and sow bugs living just about anywhere from beaches to deserts. Wherever they go these bugs eat decaying materials, like plants and even dead animals; by following this diet they help recycle nutrients in the soil.
Sow bugs and pill bugs, both of which are also called wood lice, look fairly similar to one another. A pill bug is commonly known as a "roly-poly" for its defensive behavior of rolling up into an armored ball. A sow bug, however, doesn't roll itself up, and has a pair of tail-like structures on the end of its body.

  • Two clean, empty cardboard milk cartons
  • Sharp utility knife
  • Scissors
  • Tape
  • Dry soil
  • Water
  • At least 12 sow bugs or pill bugs (Details for collecting these are given in the activity below.)
  • 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 cut into the cartons and then continue cutting them with the scissors. Discard (recycle) the top parts of the cartons. You should be left with two carton containers with open tops.
  • 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 sow bugs or pill bugs will use to move between the cartons, so make sure these holes line up well between the two cartons.
  • 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 through which any bugs could escape.
  • 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 sow bugs or pill bugs will like this environment?
  • 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 sow bugs or pill bugs will like this environment more than the dry soil one? Your habitat is now ready to do some experimenting.
  • Go outside and collect at least a dozen sow bugs or pill bugs. (Only use one type of bug.) 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 freeze in place when startled, making them harder to spot.
  • Put an equal number of the little crustaceans in each carton (meaning there should be at least six in each). Allow them to explore the cartons while you observe for at least 30 minutes. How many bugs are in each carton over time? Does the carton that most of the bugs are in change over time? What other types of behaviors do you observe?
  • Overall, which environment do the sow bugs or pill bugs seem to prefer, the one with damp or dry soil?
  • Extra: Repeat this activity but compare different environments, such as leaf litter versus soil or small rocks versus small pieces of wood, etcetera. Which environment do the sow bugs or pill bugs prefer in other environmental pairings?
  • Extra: You could try to quantify your results from this activity. To do this, every five minutes you could count how many sow bugs or pill bugs are in each habitat. How do the numbers of these 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 wax worms. (Crickets, mealworms and wax worms can usually be purchased at a local pet store whereas 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 sow bugs or pill bugs end up in the damp soil environment?
Sow bugs and pill bugs are crustaceans, just like shrimps, lobsters and crabs. They breathe with gills, so they need moisture in order to respire. Because of this you should have seen that most of the sow bugs and pill bugs spent more time in the damp rather than the dry soil environment. After about 30 minutes you may have even seen several of the little crustaceans actually dig down into the damp soil and settle in there. The sow bugs or pill bugs that spent time in the container with the dry soil probably only stayed there temporarily before going back to the damp soil. Although sow bugs and pill bugs are amazing in that they're crustaceans that have adapted to live on land, they still need moisture to breathe and survive.
When you are done observing the sow bugs or pill bugs, you may release them where you found them. Be sure to recycle the emptied milk cartons.
More to explore
Suborder Oniscidea—Wood Lice, from BugGuide
Species Oniscus asellus—European Sow Bug, from BugGuide
Fun, Science Activities for You and Your Family, from Science Buddies
What Is Home Sweet Home to a Bug?, from Science Buddies

This activity brought to you in partnership with Science Buddies