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Healthy Stream Critters (Cadettes & Seniors)
This activity can be done in conjunction with the Streamwalk. Be sure to observe the Streamwalk tips and Safety-Wise Manual before conducting this activity.
There's a whole world of life in rivers and streams. Living alongside fish, amphibians, reptiles, and wildlife are macroinvertebrates—creatures that are large (macro) enough to be seen with the naked eye, and that lack a backbone (invertebrate). Aquatic insects, clams, snails, crayfish, worms and leeches are all macroinvertebrates. Some, like snails, live their whole lives in the water; others, like dragonflies, leave the water as adults to feed and reproduce. In streams, most macroinvertebrates live under or attached to submerged rocks, logs, and plants. Like all living things, they need oxygen to breathe, water of the right temperature to thrive and reproduce in, suitable habitat, and the right kind of food. When these requirements aren't met, these creatures will sicken and die.
Scientists and trained volunteers study macroinvertebrates to learn more about stream quality. The basic principle behind the study of macroinvertebrates is that some are more sensitive to pollution than others, so if you find lots of macroinvertebrates that can't tolerate pollution, you've found a pretty clean stream. On the other hand, if you find only macroinvertebrates that can live in polluted conditions, your stream may have a problem. Below are a few examples of macroinvertebrates that live in clean streams.
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Description: The stonefly has six legs with strong claws, and their antennae are often long and easily seen. They have two hair-like tails and a smooth abdomen, their eyes are often big and widely separated, and many have strong color patterns. Size: Stoneflies are .5 to 1.5 inches long |
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Description: Caddisfies have three pairs of segmented legs and two back hooks. Some have fluffy gill tufts on their abdomen and no tails. Their antennae are not visible, and they have rounded bodies and tiny eyes. Size: Caddiflies grow up to 1.5 inches. |
To see full color photos of these stream critters, check out the
Missouri Streams Teams Home Page at
www.rollanet.org/~streams/macroinv 
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Description: Mayflies can be brown, tan or mottled in color, and many have plate-like or feathery gills on their abdomen. They have six jointed legs, two long and delicate antennae, and three hair-like tails. Size: Bodies of mayflies are .25 to 1 inch long. |
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Description: The Dobson fly is dark brown, has six legs, large pinching jaws and eight pairs of feelers on the lower half of their bodies with gill tufts below them. They have short antennae and two pairs of hooks at the end of the abdomen that anchor them to the stream bottom. Size: Dobsonflies can reach up to 4 inches long. |
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Description: Small oval body covered with tiny hairs. One pair of tiny antennae and 6 legs. Walks very slowly on the bottom; does not swim! Size: Riffle beetles are about 1/4 inch. |
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Getting Started in Volunteer Monitoring Monitoring macroinvertebrates requires training in safety considerations,
field methods, bug identification, and analysis of results. Troops
interested in macroinvertebrate or other forms of stream monitoring
should get in touch with a local program that trains volunteers
in these activities. There are currently over 770 volunteer monitoring
programs around the country, plus several that are national in
scope. Check out EPA's National Directory of Volunteer Environmental
Monitoring Programs to find a group near you that may help train
your troop. (Call 1-800-490-9198 and ask for EPA publication 841-B-98-009.)
EPA's Adopt Your Watershed web page at www.epa.gov/adopt
can also link you up with volunteer groups in your watershed.
Also check the resource list on pages 40-41. Two national organizations that can also help you get started are: the Izaak Walton League of America's Save Our Streams program (for macroinvertebrate monitoring training and kits) at 1-800-BUG-IWLA; and EARTH FORCE (for low-cost water quality monitoring kits to test for pH, dissolved oxygen, and other substances in the water) at 1-800-23-FORCE. |
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