These tiny insects are sensitive to pollution. Even small amounts will kill a population, so seeing a healthy number of Small Minnow Mayflies means the water is clean. A stream that sees a fast decline in this insect's population may be experiencing some form of chemical pollution.
Small Minnow Mayflies look very much like other Mayflies. Their abdomen is tipped with the two long, thin filaments. Two sets of wings allow the Small Minnow Mayfly to fly, though the second set - the hind wings - are much smaller than the first set. Wings are clear, but may be patterned with opaque black patches around the edges.
These Mayflies are active during the warm months of the year and range throughout the western parts of North America. This particular species produces multiple generations per year and will appear more so during the early and middle hours of the day.