Worm Observation

Introduction

Earthworms are important for the soil and a lot of fun to study. Few people know there are over 2,000 types of earthworms. Some like to burrow deep in the soil, while others stay near the surface. Do you know what they eat, or what their eating and burrowing habits are? Fill a pot with moist dirt, add a few worms, and observe your worms to find out.

Materials

• Clear plastic pot or deli container, 32 oz or more, at least 12 cm high; like these, available from Amazon.com
• Push pin
• Scissors or nail
• Loose dirt; potting soil works well (enough to fill 1 pot)
• Optional: Water spray bottle (1); like this one, available from Amazon.com. If you do not have one available, you can wring out a wet cloth over the dirt to moisten the soil.
• Newspaper (1 sheet)
• Earthworms (15)
  • Red wigglers (composting worms) can be found locally in a composting pile, or at well-equipped garden stores. You can also purchase them from numerous online vendors, including Amazon.com or Carolina Biological.
  • You can also use other earthworms found in your yard or local bait shop, or buy them from an online vendor, like Carolina Biological. You will need fewer worms if your worms are long (on average more than 7 cm). Note that some species require special care (like refrigerator temperatures.) Make sure you can give your worms the care they need (like storing your pots with worms in a refrigerator).
• Brown paper bag or cardboard box (1)
• Fine-tip permanent marker
• Cutting board
• Knife for cutting food
• Fruit; melon or melon rinds work well. Harder fruits like apples are good, but might take a little more time to start decaying. This will increase the total time to observe what worms do when food is around by a few days. Avoid citrus fruits, as worms do not like these.
• Optional: lab notebook

What Happened?

All earthworms make burrows. Some types make permanent burrows; others make temporary burrows. This is why some of you might have seen burrows change and others might have seen burrows stay the same. All earthworms feed on decaying organic material. This is why the worms were not attracted to the fresh fruit. After a few days, as the fruit starts to decay, the worms like to go and feed and you probably saw worms from the outside of the pot near the decaying fruit. Some might have seen their worms stay around the food, others might have seen them come and go. This depends on the type of worm you are studying

Digging Deeper

There are three types of earthworms: epigeic worms living on the surface of the earth, endogeic worms living in the top layer of the earth, and anecic living deep in the earth. The environment in which earthworms live is linked to their characteristics.

• Epigeic worms live inside and around decaying organic material found at the surface, on which they feed. They are relatively small, quick, and tend to have darker skin. All of these features provide protection against predators. Their burrows are temporary. An example is the red wiggler, a composting worm, often used in composting farms to create rich compost.
• Endogeic worms make semi-permanent burrows in the upper layer of soil. We usually notice them after a heavy rain. Heavy rain saturates the upper layer of the soil, filling the air holes in the soil with water. Worms usually breathe the air in the soil. When there is none available, they come up to find air. These worms are, on average, a little larger than the epigeic worms; they are also slower and are often found in grasslands and farmlands.
• Anecic worms make very deep permanent burrows. They take food (decaying organic matter) from the surface into their burrows. These worms can get long (over 1 m) and big; they have a pale skin color and are quite slow. The bait worm and nightcrawler are anecic worms.

The figure illustrates the three types of earthworms. (Diagram courtesy of the Science Learning Hub. Figure adapted from Fraser and Boag; photos of earthworms copyright Ross Gray.)

For Further Exploration

• Experiment with your worms to find out if they make organic material decompose faster. To do this, prepare two identical pots. Cut up some organic material and hide half of it in one pot, the other half in the other pot. Remember to hide the food against the walls. Add worms to only one pot. Keep both pots in the same environment, water them equally, and observe how fast the food decays and disappears in both pots. Remember to store your pots in a dark place between observations. You can make drawings or pictures of your disappearing food as a record, and make a bar graph of your final data to make the results visual.
• Experiment with different organic materials to see if they disappear at a different rate, or if worms are attracted to one more than the other. Some good options for organic material are moist, shredded newspaper; apple pieces; and straw.
• You can compare habits of different types of worms. To do this, prepare two or more identical pots in a similar way. Host one type of worm in each pot and observe their burrowing and feeding habits.
• Observe what happens after a downpour. Place your pot in a sink or outside on a place that can take some extra watering. Use a watering can to simulate a downpour and observe what happens. Remember to let the water leak out. Worms need a moist environment to thrive, and air to breathe. If all the air holes in the dirt are filled with water, the worm can no longer breathe and will suffocate!
• Check out the project ideas listed in the "Additional Resources" section. These contain some interesting test ideas. Some require an extended observation period; others take less than an hour (once you have the materials).

Related Resources

Project Ideas

Careers