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

Our dichotomous key helps you identify aquatic macroinvertebrates you found in a stream.

Discovery Tank

A macroinvertebrate touch tank with bubblers and ice packs to keep the animals alive.

Not everyone can access a stream to learn about aquatic life, but with a discovery tank, the stream can come to them!

Leaf Pack Network®

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

Rock Pack Experiment

The Rock Pack Experiment combines STEM topics in stream ecosystems through the world of the net-spinning caddisfly.

Monitor My Watershed

Monitor My Watershed Browse Sites page.

View macroinvertebrate data from the Leaf Pack Network and Rock Pack Experiment. Help resources are available here.

Water Quality Mobile App

Log and share data collected in the field and interpret it through learning pop-ups. Available for Apple and Android devices.

3D Printable Designs

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

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

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

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.
Still from mayfly egg hatching video.
Mayfly Eggs Hatching a Minute After Being Laid
This ovoviviparous mayfly holds her eggs internally until embryonic development is complete after which she lays them in water and they hatch immediately.
An entomologist sorts samples seated at a table in the Susquehanna River.
Monitoring the Health of the Susquehanna
An article in an area newspaper chronicled Stroud Water Research Center’s annual sampling of the Susquehanna River near Mehoopany, Pennsylvania. Stroud Center studies have shown that the river's health has
Screenshot of midge video.
Mystery Midge with “Kite Tail” Eggs
Stroud Center entomologist David Funk documented the unusual behavior of an orthoclad midge species at Lake Umbagog on the Maine/New Hampshire border: Adult females fly over the lake and extrude
Mayfly rearing syste.
Could Rising Temps Be Killing Mayflies, Threatening Streams? Scientists Investigate.
When mayfly populations decline, it's a warning that something has gone wrong. But what? Stroud Center scientists and their colleagues are investigating.
Maria Scarborough with U.S. Sens. Chris Coons and Sheldon Whitehouse at the Stroud Center table at a bioblitz.
Stroud Team Helps Discover Species Diversity in State and National Parks
Stroud Center entomologists, interns, and educators joined citizen scientists and others for the National Park Service Centennial BioBlitz.