Callibaetis nymphs can be found in most stillwaters. They are usually abundant around weedbeds and are most active in the morning hours until noon. Per 3. Sizes: 10, 12, 14. Colors: (048)Gray, (412)Peacock, (561)Olive/Peacock. Cancer and Reproductive Harm- www.P65Warnings.ca.gov. Type: Flies.