Which macroinvertebrate is an indicator of excellent water quality?

Mayfly larvae are considered excellent indicators of water quality because they are sensitive to pollution and changes in environmental conditions. Their presence in a body of water typically signifies that the water is clean and well-oxygenated. Mayflies require high levels of dissolved oxygen and are often the first species to disappear from an ecosystem when water quality declines. Therefore, a significant population of mayfly larvae strongly implies a healthy aquatic ecosystem.

Dragonfly larvae, caddisfly larvae, and stonefly larvae also serve as indicators of water quality, but they may tolerate a wider range of environmental conditions, including some levels of pollution, compared to mayflies. Therefore, while the presence of these other macroinvertebrates can indicate relatively good water quality, mayfly larvae are the most sensitive and are thus the best indicator of excellent water quality.