Benthic macroinvertebrates (also known as "benthos") are small animals living among stones, logs, sediments
and aquatic plants on the bottom of streams, rivers and lakes. They are large enough to see with the naked
eye (macro) and have no backbone (invertebrate). Insects comprise the largest diversity of the these
organisms and include mayflies, stoneflies, caddisflies, beetles, midges, crane flies, dragonflies and
others. Non-insect members of the benthic macroinvertebrate community are snails, clams, aquatic worms and
crayfish. To date, the WAB has collected and identified 538 different kinds (mostly Genus level
identifications) of benthos from 6,202 stations on 5,530 different streams throughout West Virginia. The WAB
has found the diversity of some benthos to be especially high, including mayflies (49 genera) and stoneflies
(43 genera). Some benthic genera are fairly common throughout the state, while others are limited in their
distribution to just a few areas. The most commonly encountered benthos is the midge Polypedilum (Family
Chironomidae), found at 81% of collection stations. The caddisfly Cheumatopsyche (Family Hydropsychidae) and
mayfly Baetis (Family Baetidae) have been found at 77% and 72% of the stations, respectively. The net-winged
midge Blepharicera (Family Blephariceridae) is not common, found at only 1.2% of all collection stations.
This sensitive organism is restricted to the steeper streams in the higher mountains of the state, where
oxygen rich water cascades over waterfalls and tumbles through small rapids and riffles.