Callibaetis are a must-have for most anglers. These mayflies are prolific in many of the Western Hemisphere's stillwaters including lakes, ponds and slow moving streams. In lakes that are heavily alkaline, these insects can hatch and resemble clouds of smoke. Trout, bass and panfish feast on Callibaetis Mayflies in the nymph, dun and spinner stages. Callibaetis nymphs reside in the weeds on the bottom of still and slow-moving water. Anglers can simulate the nymphs exiting the weeds, swimming up and back to the weeds.