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