Stoneflies Are mostly found in cool, well-oxygenated streams. They are sensitive to most of the same pollutants as may-flies except acidity. They may be less numerous than mayflies. The presence of even a few stoneflies in a stream sug-gests that good water quality has been maintained for several months
Perlodidae Patterned Stonefly
source: Nymphs of North American Stonefly Genera; by Kenneth W. Stewart & Bill P. Stark
source: Larvae of the North American Caddisfly Genera; by Glenn B. Wiggins
Hydropsychidae Common Net-Spinner Caddis
Caddisflies May construct a portable case of sand, stones, sticks, or other debris or may spin nets that serve as a retreat and help them to collect and gather food. Many caddisfly larvae are sensitive to pollution, but this family (Hydropsychidae) can be abundant in nutrient-rich environments
Stoneflies Are mostly found in cool, well-oxygenated streams. They are sensitive to most of the same pollutants as may-flies except acidity. They may be less numerous than mayflies. The presence of even a few stoneflies in a stream sug-gests that good water quality has been maintained for several months
source: Nymphs of North American Stonefly Genera; by Kenneth W. Stewart & Bill P. Stark
Perlidae Golden Stonefly
Mayflies Are often the most numerous organisms found in clean streams. They are sensitive to most types of pollution, including low dissolved oxygen, chlorine, ammonia, metals, pesticides, and acidity. Most may-flies are found clinging to the undersides of rocks.
source: Aquatic Entomology; by Arwin Provonsha
Heptageniidae Flat Head Mayfly
Bugs that indicate Good Water Quality
Bugs that indicate Poor Water Quality
A Mayflies—are sen-
sitive to most types of
pollutants
A+ Stoneflies—are
sensitive to most types of
pollutants. The presence
of even a few stoneflies in
a stream suggests good
quality water has been
maintained for several
months.
B Caddisflies—are
sensitive to pollutants,
but some can be toler-
ant
B- Beetles—require a
swift current and ade-
quate supply of oxygen
F Midges—can have a
wide range of tolerances.
The red ones (blood
midges) are extremely tol-
erant to environmental
stress, especially organic
pollution.
C- Crustaceans—can
thrive under conditions of
high organic content and
very low oxygen levels
D Snails—Most snails are
tolerant to a wide range of
stressors. Some snails,
known as lunged snails, can
thrive in poor water quality
and during low flows be-
cause they can breathe at-
mospheric oxygen.
D- Worms—can thrive
under conditions of severe
pollution and very low
oxygen levels, thus are
valuable pollution indica-
tors