Time of day: Late evening through dusk
Current speed: All speeds, but best in fast water
Substrate: Everything from boulders to weeds to leaf drift to silt
Environmental tolerance: Very tolerant of high temperature and slow water
Trout appear to be aware of this phenomenon, for their stomachs will often be crammed with as many as 100 to 200 immature nymphs a week before the hatches will begin for the season.