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Macroinvertebrate Resources

What Are Benthic Macroinvertebrates?

Benthic macroinvertebrates are animals without a backbone, large enough to be seen with the naked eye, that live on the bottom of stream, lakes, and rivers. They include crustaceans and worms but most are aquatic insects. Beetles, caddisflies, stoneflies, mayflies, hellgrammites, dragonflies, true flies, and some moths are among the groups of insects represented in streams. They are an important link in the food web between the producers (e.g., leaves and algae) and higher consumers such as fish. Benthic macroinvertebrates are one of the most commonly used living water-quality indicators because:

  • They are fairly easy to sample and identify.
  • They are sensitive to pollution and changes in their habitats.
  • They have a relatively long life cycle and so are indicators of water quality over a period of time.
  • They are common in most streams or rivers.

Photo Gallery

Helicopsychidae (snailcase caddisflies)

View more than 50 macroinvertebrate photos by Stroud Water Research Center Entomologist David H. Funk.

Identification Key

Use our dichotomous key to identify an aquatic macroinvertebrate you found in a stream.

Macroinvertebrates.org

Explore this resource for aquatic insect identification to support citizen science identification activities.

3D Printable Designs

Download designs created by Stroud Water Research Center in collaboration with Unionville-Chadds Ford School District.

Leaf Pack Network®

Learn about a simple experiment that uses tree leaves and aquatic macroinvertebrates to determine the health of your local stream.

Taxonomic Certification Program

This Society for Freshwater Science program certifies skilled persons to provide aquatic invertebrate identifications in North America.

Guide Books

The following books are recommended resources. Check your local library; they are also available for purchase from online booksellers.

  • McCafferty, W. P. 1981. Aquatic entomology: the fishermen’s guide and ecologists’ illustrated guide to insects and their relatives. Jones and Bartlett Publishing Company, Boston, Massachusetts.
  • Voshell, J. Reese. 2002. A guide to common freshwater invertebrates of North America. The McDonald & Woodward Publishing Company, Blacksburg, Virginia.

Stream Sampling Protocols and Fact Sheets

Stream Sampling License and Permit Information

Citizens from outside Pennsylvania should consult with the appropriate state agency for permit requirements. Pennsylvania law requires anyone 16 years of age or older collecting aquatic organisms for any reason to have a valid fishing license and follow current Pennsylvania Fish & Boat Commission regulations. High school and undergraduate college students are exempt from the license requirement if their teacher/educator applies for and is issued an Educational Aquatic Field Study Permit. For more information, visit the Pennsylvania Fish & Boat commission website.

Just For Fun

The Pennsylvania Fish and Boat Commission ran a fun Facebook quiz that featured a number of photographs by Stroud Center Entomologist David Funk. Try your hand at the #MysteryMacro Quiz!

Macroinvertebrate News

Online Atlas of Aquatic Insects Aids Water-Quality Monitoring
Online Atlas of Aquatic Insects Aids Water-Quality Monitoring
A new online field guide promises to be an important tool for monitoring water quality and learning how to correctly identify freshwater insects ... Read More
Get Your Freshwater Science Taxonomic Certification
Get Your Freshwater Science Taxonomic Certification
Through the accurate and precise identification of these organisms, you will be better prepared to record taxonomic data for biomonitoring programs ... Read More
Students working on designing a 3-D macroinvertebrate model
Life Lessons in Three Dimensions: Students, Stroud Center, Retired Teacher Collaborate
By creating these teaching tools for other students to learn about freshwater ecosystems, the students developed their own curiosity about their outdoor environment ... Read More
Screenshot of Caddisflies, Engineering an Ecosystem video
Research Reveals Caddisflies are Ecosystem Engineers
Hydropsychid caddisflies spin silk mesh nets that they use to filter feed. These nets are important ecosystem engineering structures in flowing waters ... Read More
Isopoda (aquatic sowbugs)
Test Your Skills With the #MysteryMacro Quiz
Want a fun way to learn about freshwater macroinvertebrates? Check out the Pennsylvania Fish and Boat Commission #MysteryMacro quiz featuring photos by Dave Funk ... Read More
Stroud Science on NPR: Road Salt Boosts Safety But Threatens Fresh Water
Stroud Science on NPR: Road Salt Boosts Safety But Threatens Fresh Water
When StateImpact Pennsylvania wanted to understand how our addiction to road salt is impacting the environment, they came to Stroud Water Research Center ... Read More