Benthic Macroinvertebrates are
animals that lack a backbone and are generally visible to the
naked eye. They live in the lower areas of streams, under rocks.
They include larval forms of many common insects such as Dragonflies,
Damselflies, and Craneflies.
More
information on benthic Macroinvertebrates can be found on the
following page: http://www.epa.gov/bioindicators/html/invertebrate.html