This lesson helps students identify common macroinvertebrates and how to evaluate a creek based on biological indicators.

Grades: 3 +

Indoors or Outdoors

Time: 20 - 40 min.

Materials for each group:


  • Language Arts
  • Science


  • Scientific Processes
    6.4(a),  7.4(a),  8.4(a)
  • Scientific Concepts
    6.10(c),  7.12(b)
  • Reading/Vocabulary
    6.9(b),  7.9(b),  8.9(b)


  • Macroinvertebrate
  • Larva
  • Nymph
  • Pollution



Aquatic Ecology

"Bug Picking"
in the field

macroinvertebrate study:
Elementary Level

Have you ever noticed the many small animals such as crayfish, snails, and insects living under the rocks, around plant roots, and in the sediment at the bottom of creeks, rivers, ponds, and lakes? Some of these small aquatic animals (benthic invertebrates) are very sensitive to changes in the water and will die if there is not enough water or if the water becomes polluted. By looking for and recognizing the different types of aquatic animals living in aquatic environments, you can begin investigating the ability of those environments to support aquatic animals such as fish and amphibians which also helps us determine whether it is suitable for use by people, too.


Safe footwear for wading, forceps (tweezers), magnifiers, aquatic nets, pipettes, Bug Picking Data Sheet, pencils and shallow pans for holding specimens


  1. Wade into shallow water, turning over rocks, looking carefully on the under sides of the rocks for aquatic benthic invertebrates. If you are in an area with a sandy or muddy bottom, use a fine mesh net, holding it so that the net is pulled upstream along the bottom, catching leaf litter. Use magnifiers to find the tiny animals in the leaf litter and on the rocks. Use forceps to gently pick up the invertebrates and place them in the shallow pans with water. Replace rocks in their original positions.
  2. Begin to divide the invertebrates according to different types or groups based on similar physical features. (Water in the pans will keep them alive while you take data.)
  3. On the data sheet, put a tally mark next to the picture that matches each aquatic animal you find. Gently return the aquatic animals to the water.
  4. Look at the data you gathered. To determine if your water might be polluted, answer these questions or circle the correct response.

Did you find animals that are pollution-sensitive? (Group 1)

1-3 species
More than 3 species

Did you find animals that are somewhat-sensitive? (Group 2)

1-3 species
More than 3 species

Did you find animals that are pollution-tolerant? (Group 3)

1-3 species
More than 3 species

Conclusions: (Remember that the data you are taking will not give conclusive evidence of clean or polluted water, but might indicate the need for further investigation.)

  1. What conclusion can you draw if you found species in Group3, but not in Groups 1 or 2?
  2. What conclusion can you draw if you found several different species in each of the groups?
  3. What could be happening upstream, on land around the water upstream, or in your present location to affect the water quality where you are sampling?

This water appears to be (circle one):

Not Polluted


Cherry, Lynne. A River Ran Wild
Furtado and Gilroy, Biomonitoring Guide,   Colorado River Watch Network, January 1995.
Cummins, K.  &  Merrit, R. Aquatic Insects of North America, Kendall/Hunt Publishing Company,  1996.
EPA,  "Rapid Bioassessemnt Protocols for Use in Streams and Rivers", May 1998.
EPA,  "Volunteer Stream Monitoring:  A Methods Manual", November 1997
McCafferty, Patrick W. Aquatic Entomology, Jones and Bartlett Publishers,  1983.
Save Our Streams, The Izaak Walton League of America,  1401 Wilson Blvd., Level B  Arlington, Virgina 22209.
(Publishes an excellent key)
Sobel, David. Beyond Ecophobia: Reclaiming the Heart in Nature Education, 1996.
Texas Commission on Environmental Quality, WET Instruction Handbook,  2004.
Texas Parks and Wildlife,  "Junior and Master Angler Education Program."
Texas Parks and Wildlife,  "Clean Creek, Polluted Creek"  Video produced by Texas Parks and Wildlife Department,  1994.

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