and Observing Earthworms
you find earthworms? They're in garden soil, vacant lots, lawns, parks,
or pastures. A cool, moist fall day or evening is a great time to look
for worms. Humid days before rains, or during rain showers are especially
good for collecting worms. Fall is the best time to sample worms because
most are sexually mature, which helps you tell who's who.
Up the Worms
USDA soil scientist Dr. Dennis Linden tells one way to find worms: First, look
at the soil surface. Castings ("worm poop") are small piles or pellets
of soil, often mixed with some plant litter. Castings are signs that earthworms
are present. When you've found a likely spot for worms, dig a spadeful of soil
and sort through it for earthworms. With experience, you may also find cocoons.
While you are digging, always watch for evidence of large burrows with "slickened" walls.
These may indicate the presence of night crawlers--the larger, deeper-burrowing
Forest ecologist Cindy Hale gives directions for a method that will bring many
of the deeper burrowing earthworms to the surface. How many different kinds
of worms can you find in your study area?
Courtesy Agriculture and Agri-Food Canada, Southern Crop Protection and
Food Research Centre (SCPFRC),
1391 Sandford St., London, Ontario, Canada.
To bring up
off a square of soil about one foot on each side for your "study
area." Use string or boards to make boundaries around
1/4 cup (about 40 grams) of ground yellow mustard seed (this is dry
mustard powder from the spice section in the grocery store) in one
gallon of water. Shake it up well. (Recipe adapted from the SCPFRC)
pour the mustard solution over the soil inside the boundaries of
your study area. Pour it so it soaks into the soil instead of running
off the soil. The worms will start coming up. Don't worry; while
the mustard irritates their skin and makes them escape to the surface,
it does not harm the worms.
up the worms with a forceps and put them right into a pan of fresh
tap water to rinse off the mustard solution. Now you can take them
out of the water, lay them on a wet paper
towel, and use a magnifying glass for a closer look. Explain
that the worms are "breathing" oxygen through their
wet skin, so they must be kept moist at all times. Set out
a few water
misters for students to share. Explain
that worms are fragile animals and can be hurt easily, so they must
be handled with gentleness.
Worms Up Close
NOTE: Students may work in teams of two, with one student assigned
as recorder. After oberving the worms for at least ten minutes, bring the
class back together and ask teams to be ready to share their observations
with the class.
a magnifying glass, count the rings or segments along
the length of a wormís body. These segments help the
worm to twist and wiggle forward or backward with the help
of hair-like structures
called setae (pronounced SET tay).
- If you
place the worm in a plastic cup or on a petri dish, you can see the
underside (ventral side) or the worm. You will be able to
see inside the worm, too. What can you see inside of the earthworm?
Look for the heart and blood vessel. Look for the pulse, indicated
by the vessel alternately swelling and contracting. Which direction
is the blood flowing? How cold you take an earthworm's pulse?
the anterior or head end, which is more pointed and narrow.
You can also place the worm on a rough piece of paper and see which
direction it travels. The head end usually goes forward first.
- On the
head end of the worm, find the clitellum, a whitish,
swollen band that looks like a collar around the wormís
the segments from the head/mouth to the clitellum. This number is
different in different species, so counting segments can help you
know whether your worms are of different species.
for the hair-like bristles called setae around or under the
worm's body. Worms use their setae to help crawl and also to
grip and anchor
themselves firmly in the ground. (Thatís why you see
robins tugging to get worms out of the soil!) Are setae paired?
they spaced around the body? What differences in setae patterns
do you see?
at the worm's shape. Is it cylindrical or flattened?
at the top (dorsal) and belly (ventral) side. Try turning
the worm. A worm turned over will immediately right itself.
the worm's color: brownish, reddish, or gray-blue, or pale or white. Pigmented worm
species live at or near the surface of the soil in organic matter
such as leaf litter or compost piles, but they may also burrow very
deeply and feed at the surface on fresh litter. Nonpigmented worms
live and feed in the soil, not at the surface. The litter-dwelling
species help the soil-dwelling species because they work the organic
matter into the soil where the soil-dwellers can eat it.
the worm's movements on wet and dry surfaces and it s response to
water, touch, and darkness.
After you study and compare the worms, place
them where they can safely get back into the soil.
a large, simple outline of a worm on the chalkboard. Have students
come up and draw, label, or make notes on the drawing to record their
observations. The drawing can show the segments, clitellum, anterior
and posterior ends, the heart and blood vessel, and setae. This
diagram may help you.
- As a
class, discuss how the earthworm's various structures and behaviors
help it to survive in its underground home. After discussing the
observations, introduce the term adaptation and help students
define it (the characteristics and behaviors of an organism that
help it to survive in its environment).
more about earthworms with these recommended Web sites: